Image forming apparatus

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an image forming apparatus provided with a recording apparatus for recording an image on a sheet, and a sheet feeding apparatus detachably mounted on the recording apparatus for automatically feeding sheets in succession, and more particularly to a guide member for defining a conveying path of the sheet.

2. Related Background Art

There have conventionally been proposed various image forming apparatuses for forming an image on a sheet.

Among such apparatuses, there has been proposed an apparatus provided with a recording apparatus for image recording (hereinafter called “printer”) and an auto sheet feeder (hereinafter referred to as “ASF”) detachably mounted on a sheet feeding port of the printer, wherein, through such sheet feeding port:

sheets are manually fed one by one when the ASF is not mounted; and

sheets are automatically fed in succession when the ASF is mounted (see the Japanese Patent Application Laid-Open No. 6-183582).

In the image forming apparatus of the above-described type, the printer is provided with a guide member for guiding the sheet in case of sheet feeding with manual insert, while the ASF is provided with a guide member for guiding the sheet in case of automatic sheet feeding. These guide members are provided in approximately the same position in the transverse direction of the sheet, such that the image recording position in the transverse direction of the sheet (namely the position of image formation on the sheet, in the transverse or width direction thereof) remains the same in the sheet feeding with manual insert and in the automatic sheet feeding.

In the image forming apparatus of the above-described type, however, if the guide member of the printer is positioned at the inner side of the sheet compared to the guide member of the ASF because of the dimensional tolerance at the manufacture thereof, the guide member of the printer becomes an obstacle for the automatically fed sheets and may induce skewing or jamming of the sheet or damage to the sheet end.

Such drawback can be resolved by precisely assembling the image forming apparatus with highly precise parts, but such assembling is difficult and the use of the highly precise parts results in an increased cost.

Furthermore, even if the guide member of the printer and that of the ASF are provided in substantially the same position in the transverse direction of the sheet, a sheet eventually skewed will interfere with the guide member of the printer, thus inducing skew or jamming of the sheet or damage to the sheet end.

SUMMARY OF THE INVENTION

In consideration of the foregoing, an object of the present invention is to provide an image forming apparatus for preventing skewing or jamming of a sheet or damage to an end of the sheet.

Another object of the present invention is to provide an inexpensive image forming apparatus.

Still another object of the present invention is to provide an image forming apparatus for matching an image recording position in a transverse direction of the sheet, regardless of whether a sheet feeding apparatus is used or not.

The above-mentioned objects can be attained, according to the present invention, by an image forming apparatus provided with a recording apparatus having a feeding port for feeding a sheet and recording an image on the sheet fed from the feeding port, and a sheet feeding apparatus detachably mountable on the feeding port and automatically feeding the sheets in succession to the recording apparatus.

In the present invention, the recording apparatus includes a first guide member for guiding an edge of the sheet in the transverse direction of the sheet.

The sheet feeding apparatus includes a second guide member for guiding the edge of the sheet in the transverse direction of the sheet.

The second guide member is disposed and displaced toward an inner side of the sheet with respect to the first guide member.

In such a case, the image recording position in the transverse direction of the sheet is preferably displaced, in case the sheet is fed by the sheet feeding apparatus, toward the inner side of the sheet, in comparison with the case in which the sheet is not fed by the sheet feeding apparatus, by an amount substantially equal to the amount of displacement between the first guide member and the second guide member.

There may also be provided mode discrimination means for discriminating whether the sheet feeding is executed by the sheet feeding apparatus, and the image recording position in the transversal direction of the sheet may be displaced according to the result of discrimination by the mode discrimination means.

In such case, the recording apparatus and the sheet feeding apparatus may be respectively provided with connectors allowing mutual electrical connection, and the mode discrimination means may electrically detect the connection state of the connectors.

On the other hand, the recording apparatus may be provided, together with the first guide member, with a third guide member for guiding an edge of the sheet in the transverse direction thereof, while a conveying path of the sheet when the sheet feeding apparatus is connected to the recording apparatus is disposed to make a detour to avoid the third guide member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2

are perspective views showing embodiments of the present invention;

FIGS. 3 and 4

are cross-sectional views showing embodiments of the present invention;

FIGS. 5 and 6

are perspective views showing embodiments of the present invention;

FIG. 7

is a schematic plan view showing an embodiment of the present invention;

FIG. 8

is a cross-sectional view showing an embodiment of the present invention;

FIGS. 9 and 10

are perspective views showing embodiments of the present invention;

FIG. 11

is a perspective view showing an arrangement of parts relating to a printer mounting and dismounting mechanism of the ASF of the present invention;

FIG. 12

is a perspective view showing an arrangement of parts, associated with the mounting and dismounting mechanism of the ASF, of a printer to be connected with the ASF of the present invention;

FIGS. 13

,

14

,

15

,

16

,

17

and

18

are cross-sectional views seen from the left hand side and showing the mounting and dismounting mechanism of the printer and the ASF of the present invention;

FIG. 19

is a perspective view showing the arrangement of parts and relationship of forces in symbols, relating to the mounting and dismounting mechanism of the printer and the ASF of the present invention;

FIGS. 20

,

21

,

22

and

23

are plan views showing the mounting and dismounting mechanism of the printer and the ASF of the present invention;

FIG. 24

is a block diagram showing a connection of a printer

101

and an ASF

1

of the present invention;

FIG. 25

is a schematic cross-sectional view showing the printer

101

and the ASF

1

of the present invention in a connected state;

FIG. 26

is a schematic view showing the connection between a connector

117

and an ASF connector

44

;

FIGS. 27 and 28

are schematic views showing the connection and the operating direction of a driving mechanism of the ASF

1

;

FIG. 29

is a flowchart showing the control sequence for the sheet feeding operation in a printer control unit

202

in a first embodiment;

FIG. 30

is a flowchart showing the main control sequence of an ASF control unit

201

;

FIG. 31

is a sub flowchart C

2

for controlling a sheet feeding operation by the ASF control unit

201

in the first embodiment;

FIG. 32

is a sub flowchart C

3

for controlling an initializing operation by the ASF control unit

201

;

FIG. 33

is a sub flowchart C

1

for controlling a device discriminating operation in the printer control unit

202

;

FIG. 34

is a flowchart for controlling the sheet feeding operation by the printer control unit

202

in a second embodiment;

FIG. 35

is a sub flowchart C

2

for controlling the sheet feeding operation by the ASF control unit

201

in the second embodiment;

FIG. 36

is a schematic cross-sectional view showing a state after completion of a step S

22

in the sheet feeding operation;

FIG. 37

is a timing chart showing the outline of the operation flow of the printer

101

and the ASF

1

in the second embodiment; and

FIG. 38

is a chart showing the content of a drive table T for a sheet feeding motor

27

.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now the present invention will be described in detail by preferred embodiments thereof, with reference to the attached drawings.

[First Embodiment]

FIG. 1

is a perspective view showing a printer mounted to an ASF constituting a first embodiment of the present invention;

FIG. 2

is a view showing the mode of mounting of the printer to the ASF;

FIG. 3

is a cross-sectional view of the ASF; and

FIG. 4

is a cross-sectional view of the ASF in a state in which the printer is mounted.

As shown in

FIGS. 1

to

4

, the image forming apparatus

100

is provided with a printer (recording apparatus)

101

for recording an image on a sheet, and an ASF (automatic sheet feeding apparatus)

1

for automatically feeding sheets in succession to the printer

101

. The printer

101

is provided with a sheet feeding port (feeding port)

101

A (cf.

FIG. 5

) for feeding the sheets, and the ASF

1

is so constructed as to be detachably mounted to the feeding port

101

A. The printer

101

and the ASF

1

are respectively provided with connectors

117

,

44

capable of mutual electrical connection, as will be explained later.

The above-mentioned printer

101

is a so-called mobile printer, which is compact, portable and is provided with a battery. In the present embodiment, the printer

101

is not provided with the ASF, so that the printer

101

alone can only achieve a sheet feeding in manual insert. Such configuration allows compactization, simplification and low cost in the printer

101

, optimum for the mobile printer. However, the present invention is naturally applicable even if the printer

101

is provided with a compact ASF.

Such compact, portable printer

101

is assumed to be particularly used outdoors, in an automobile or in a customer's office at the visit of a salesman. In such situations, the number of the required recording sheets is relatively small, so that the manual insert sheet feeding or the simple internal ASF of a low capacity is presumed to be enough, but, if the printer

101

is used in the ordinary office environment, there may be encountered a requirement of printing the various sheets of a relatively large quantity.

The ASF

1

separated from the printer

101

is suitable for such requirement. The ASF

1

has a so-called desk-top form which is commonly found on the desk of the ordinary office environment, and the printer

101

, when fitted to the ASF

1

, can have the character of a desk-top printer. The ASF can automatically feed various recording media, not only ordinary paper but also postcards, envelopes, plastic films, fabrics etc. owing to the configuration to be explained later.

Thus the present embodiment can provide an extremely valuable printer, in which a printer which is compact and mobile when used singly can also be used as a desk-top printer of high performance by being mounted to the ASF of the present invention. The ASF

1

functions also as so-called docking station, serving as a storage box for the printer

101

when it is not used, and also adding the automatic sheet feeding function when the printer is mounted.

The ASF

1

of the present invention can stably stand by itself when the printer

101

is not mounted, and can separate the printer

101

while supporting the sheets. Thus, the stand-by state for the operation of the desk-top printer can be attained by simply mounting the separated printer

101

to the self-standing ASF

1

. Consequently, there can be provided a docking station extremely convenient for use by the user.

In order to use the printer

101

both as the mobile printer and the desk top printer, it is important that the mounting and dismounting operations of the ASF

1

and the printer

101

can be easily achieved, because, for a user who carries the printer

101

without the ASF

1

almost everyday and combines the printer

101

with the ASF

1

whenever returning to his office, a complicated or time-taking operation of mounting and dismounting will be cumbersome.

In the present embodiment, as shown in

FIG. 3

, the ASF

1

is provided at the front face thereof with an aperture

1

A, for accommodating the printer

101

. The printer

101

is also provided with a substantially horizontal sheet passing path, and is so constructed as to be pushed into the front aperture

1

A of the ASF

1

with the sheet feeding side of the printer

101

being moved substantially horizontally toward the ASF

1

whereby a sheet path as will be explained latter is formed.

Thus, in the present embodiment, the printer

101

having the horizontal path is pushed substantially horizontally into the ASF

1

and is mounted thereto. When the printer

101

is pushed substantially horizontally into the ASF

1

, the printer

101

is automatically fixed thereto (method of mutual fixation when the printer

101

is mounted to the ASF

1

being explained later in detail). In order to separate the printer

101

from the ASF

1

, it is merely necessary to push a lever

40

provided on the upper face of the ASF

1

, whereby the printer

101

is unlocked from the ASF

1

and is pushed out toward the front side of the ASF

1

.

Such configuration allows the user to achieve extremely easily mounting and dismounting of the printer

101

and the ASF

1

, whereby the printer can be used as the mobile printer and also as the desk-top printer.

In the present embodiment, in order to facilitate the mounting and dismounting operations, the ASF

1

is provided at the front side thereof with a table portion

45

c

. In case of mounting the printer

101

to the ASF

1

, the printer

101

is at first placed on the table portion

45

c

. In this operation, the user grasps, with one hand, the top and bottom faces of the printer

101

at the approximate center portion of the front (a sheet discharging side) thereof and places the printer

101

in such a manner that the rear side (a sheet feeding side) of the printer

101

is lightly positioned on the table portion

45

c

. (Otherwise the user may hold both ends of the printer

101

with both hands.)

Then the printer

101

placed on the table portion

45

c

is pushed deeper with a hand, whereby the lateral faces of the printer

101

are guided, by printer side guide portions

45

a

provided at both ends of the table portion

45

c

, to a positioning boss (to be explained later), which is thus fitted with a positioning hole (to be explained later) of the printer

101

and the positioning is achieved. In this operation, the user is only required to place the printer

101

at the approximate center of the table portion

45

c

and to press in the printer

101

, and any precise positioning operation is not required.

The table portion

45

c

is provided, at both lateral portions, with printer sliding areas

45

b

on which the bottom face of the printer slides. The printer

101

is provided, on the bottom face thereof, with plural rubber feet (not shown), in order that the printer

101

is less easily moved by the external force when the printer

101

is singly used for example on a desk.

However, in mounting the printer

101

to the ASF

1

, there will be required a large pressing force and the pressing operation of the printer

101

will become difficult if the rubber feet are in contact with the table portion

45

c

. Consequently, the printer sliding portions

45

b

are formed with a step difference larger than the height of the rubber feet, in order that the rubber feet do not come into contact with the table portion

45

c.

On the other hand, the upper case

47

of the ASF is provided with an eaves portion

47

a

substantially parallel to the table portion

45

c

, and forms, in cooperation with the table portion

45

c

, a pocket for accommodating the printer

101

. The pocket thus formed indicates to the user, by its form, the direction of substantially parallel pushing of the printer

101

toward the ASF

1

, and the user can push the printer

101

only in such direction.

This pushing direction coincides with the connection direction of the connectors to be explained later for electrically connecting the printer

101

and the ASF

1

, and the connectors are mutually connected in the course of pushing the printer

101

into the ASF

1

. Such configuration improves operability by eliminating other separate operations for connecting the connectors, and prevents destruction of the connectors resulting from abnormal interference thereof caused by pushing from a different direction.

Also, if the front portion (sheet discharging side) of the printer

101

receives an upward force after the printer

101

is mounted to the ASF

1

, the eaves portion

47

a

prevents that the printer

101

is lifted upwards with respect to the ASF

1

to cause destruction of the mounting portion or release of the mounting.

Also in the present embodiment, the eaves portion

47

a

shows a largest protruding amount at both ends and has a recessed eaves portion

47

b

at the center. Such recessed eaves portion

47

b

avoids covering of an operation unit, such as a power switch, provided on the top face of the printer

101

. The effect of preventing the above-mentioned upward lifting motion of the printer can be sufficiently obtained in case the clearance between the eaves portion

47

a

and the top face of the printer is within a range of 0.5 to 2 mm, but the desired effect cannot be obtained if the clearance is excessively large.

In the present embodiment, the depth L

1

of the printer

101

, the depth L

2

of the table portion

45

c

and the depth L

3

of the eaves portion

47

a

shown in

FIG. 4

satisfy the following relation:

L

1

/

2

≲

L

2

≲

L

1

−15 mm

The printer

101

can be stabilized when it is mounted in the ASF

1

, by selecting the depth L

2

of the table portion

45

c

larger than a half (L

1

/

2

) of the depth L

1

of the printer. Such relationship need only be satisfied in a part of the table portion

45

c

but not in the entire area of the table portion

45

c

.

If L

1

/

2

≳L

2

, the printer

101

protrudes significantly from the ASF

1

in the mounted state, and the entire apparatus becomes very unstable, as the rear part thereof may be lifted for example by a downward external force applied to such protruding portion.

On the other hand, a finger inserting space can be secured under the front side of the printer

101

by selecting the depth L

2

of the table portion

45

c

smaller, by at least 15 mm, than the depth L

1

of the printer

101

. Thus the user can hold the top and bottom faces of the printer

101

with a hand, in mounting and dismounting the printer

101

. (Naturally the user may hold the printer with both hands.) Such relationship need not be satisfied over the entire width of the table portion

45

c

but a recess or recesses may be formed at the central portion or at the end portions so as to satisfy the above-mentioned relationship.

Furthermore, as a space is provided under the front face of the printer

101

, there can be realized a design without a large height in the visual impression. The thickness (height) of the table portion

45

c

is preferably at least about 10 mm in order that the user can insert a finger under the printer

101

.

The present embodiment further satisfies the following relationship:

L

1

/

4

≲L

3

≲L

1

/

2

It is found possible to prevent the upward lifting the printer

101

and there can be obtained sufficient effect for limiting the pressing direction of the printer

101

if the depth L

3

of the eaves portion

47

a

is equal to or more than ¼ of the depth L

1

of the printer

101

. It is also found, if the depth L

3

of the eaves portion

47

a

exceeds ½ of the depth L

1

of the printer

101

, the pushing amount of the printer

101

is excessively large with respect to the depth of the printer

101

and the feeling for operation becomes unsatisfactory.

Also, the large eaves portion

47

a

results in visual disadvantages that the entire apparatus appears larger and oppressive to the user. It may also interfere with the manipulation of the printer

101

on the top face of the printer

101

, so that the depth L

3

of the eaves portion

47

a

preferably does not exceed ½ of the depth of the printer

101

. The protruding amount within the above-mentioned range can maintain a sufficient strength in thus protruding eaves portion

47

a

, thus providing sufficient toughness in the entire apparatus.

The configuration of the table portion

45

c

and the eaves portion

47

a

under the above-mentioned conditions allows a form capable of fully exhibiting the effects such as extremely good operability, limitation of the pressing direction and prevention of the upward lifting of the printer

101

.

Between the table portion

45

c

and the eaves portion

47

a

there are laterally formed large apertures, as the height of the printer side guide portions

45

a

need only be larger than the clearance between the eaves portion

47

a

and the top face of the printer

101

. Such a large aperture avoids interference with a power supply cord, an interface connector or an infrared communication unit eventually provided on the lateral faces of the printer

101

. Thus, the printer

101

with the power supply cord or the interface connector mounted thereon may be mounted to or detached from the ASF

1

.

Below there will be explained the connectors

117

,

44

for enabling mutual electrical connection of the printer

101

and the ASF

1

, and connector covers

119

,

59

for protecting these connectors.

The printer

101

and the ASF

1

are respectively provided with detachable and attachable connectors

117

,

44

, which are electrically connected for exchanging the power supply or the control signals. (In the following description, the connector

117

at the side of the printer

101

will be referred to as “printer connector

117

”, while the connector

44

of the ASF

1

will be referred to as “ASF connector

44

”.

The printer connector

117

is provided, as shown in

FIG. 5

, in the upper part of a face opposed to the ASF

1

on the mounting operation of the printer

101

to the ASF

1

, and the ASF connector

44

is provided, as shown in

FIG. 11

, in a position opposed to the printer connector

117

when the printer

101

is mounted.

The printer

101

and the ASF

1

are respectively provided with connector covers

119

,

59

detachably mountable on the connectors

117

,

44

. (In the following description, the connector cover for protecting the printer connector

117

will be referred to as “printer connector cover

119

”, while the connector cover for protecting the ASF connector

44

will be referred to as “ASF connector cover

59

”. See

FIGS. 5 and 4

respectively for the printer connector cover

119

and the ASF connector cover

59

). When the printer

101

and the ASF

1

are mutually separated, the connector covers

119

,

59

are respectively fitted on the connectors

117

,

44

for protecting the same. Thus the connectors

117

,

44

are protected from dust deposition, whereby the conductivity in the connected state can be satisfactorily maintained. It is also rendered possible to prevent application of excessive large static electricity to the internal electrical circuits through the connectors

117

,

44

, thereby preventing destruction of such electrical circuits. Furthermore, such detachable connector covers

119

,

59

allows to achieve a lower cost and space saving, and are particularly suitable for an ultra compact printer such as the mobile printer.

On the other hand, on the upper face of the table portion

45

c

of the ASF

1

(namely the surface on which the printer

101

rests), there are provided connector cover storage areas

45

d

,

45

e

for storing the connector covers

119

,

59

detached from the connectors

117

,

44

, whereby, in the mutually connected state of the printer

101

and the ASF

1

, the connector covers

119

,

59

detached from the connectors

117

,

44

are placed in such storage areas

45

d

,

45

e

(cf. FIG.

4

). The storage areas

45

d

,

45

e

are composed of projections corresponding to the dimensions of the connectors, within the thickness of the table portion

45

c.

The connector covers

119

,

59

stored in the storage areas

45

d

,

45

e

are supported between the printer

101

and the ASF

1

, thus being protected from being lost. Such configuration is also preferable from an aesthetic standpoint as the connector covers

119

,

59

become no longer visible from the outside. Furthermore, in detaching the printer

101

from the ASF

1

, the connector covers

119

,

59

stored in the storage areas

45

d

,

45

e

become easily visible so that the user does not forget fitting of the connector covers

119

,

59

on the connectors

117

,

44

.

With respect to the present embodiment relating to the connector covers, the present invention is applicable to the printer and the ASF even when they are for example a notebook personal computer and a station therefor.

Furthermore, the printer connector

117

and the ASF connector

44

of the present embodiment are both protected by the connector covers

119

,

59

, but either of the connectors

117

,

44

may be protected by a connector cover.

Furthermore, the connector cover storage areas are provided, in the present embodiment, on the upper face of the table portion

45

c

of the ASF

1

, but they may be provided in another part of the ASF

1

. Also, the connector cover storage areas may be provided in the printer

101

instead of the ASF

1

.

Below there will be outlined how the recording sheet is fed and recorded in a state where the printer

101

is mounted to the ASF

1

(details being given later).

FIG. 4

is a cross-sectional view showing a state in which the printer

101

is mounted to the ASF

1

, wherein a pressure plate

26

is provided for setting a predetermined number of sheets to be explained later. The pressure plate

26

is rotatably supported at an end thereof by an ASF chassis

11

and is clockwise biased, by a pressure plate spring

13

, toward a pickup rubber member

23

, wound around a pickup roller

19

.

At the sheet setting, the pressure plate

26

is displaced and retained in a direction separated from the pickup rubber member

23

, by means of a cam to be explained later. In such state, a predetermined clearance is maintained between the pickup rubber member

23

and the pressure plate

26

, and the sheets are inserted and set in such clearance.

The leading end of the sheet impinges on and is defined in position by a bank sheet

37

, composed of a plastic film, provided on a bank

36

. A major portion of a trailing end of the sheet is supported by an ASF sheet feeding tray

2

, which is rotatably supported at an end thereof by an upper case

47

and is supported at a certain angle in a sheet supporting state.

When the ASF

1

receives a sheet feeding command from the printer

101

, the pickup roller

19

starts clockwise rotation and the cam at the same time releases the pressure plate

26

from the supported state. Thus, the pressure plate

26

comes into contact with the pickup rubber member

23

whereby the sheet starts to move by the surface friction of the pickup rubber member

23

. A sheet is then separated by the bank sheet

37

and is transported in an ASF sheet path

58

(cf.

FIG. 3

) formed by the bank

36

and a positioning base

39

.

Thereafter, the sheet is conveyed from an ASF sheet discharge portion

56

(cf.

FIG. 3

) to a sheet path, formed by a platen

105

and a bottom surface of a battery

107

in the printer and constituting a manual insertion port in the printer

101

alone.

When a sheet end sensor

108

detects the sheet conveyed in the above-mentioned sheet path, the printer

101

recognizes the sheet conveyance from the ASF

1

, and a leading end of the sheet impinges on a nip between an LF roller

109

and a pinch roller

110

. Also in response to the information from the sheet end sensor

108

of the printer

101

, the ASF

1

transmits, at a predetermined timing, a response signal indicating the completion of sheet feeding to the printer.

In this state the sheet is pressed, by the rigidity thereof, toward the nip between the LF roller

109

and the pinch roller

110

, thereby achieving so-called registration of the leaving end of the sheet. Upon receiving the response signal indicating the completion of the sheet feeding from the ASF

1

, the printer

101

rotates the LF roller

109

at a predetermined timing, thereby advancing the sheet toward a recording unit provided with a head

115

. Thus, the sheet is advanced by a predetermined manner and the head

115

executes the recording on the sheet surface. Subsequently, the sheet is conveyed between a discharging roller

112

and a spur

111

and is discharged.

In the present embodiment, the sheet path is formed in the above-described manner when the printer

101

is mounted to the ASF

1

, and the mounting direction of the connectors

44

,

117

is substantially parallel to the direction of such sheet path of the printer

101

.

In the case the sheet conveyed from the ASF

1

to the printer

101

and present over the ASF

1

and the printer

101

is jammed in any part, it becomes necessary to separate the printer

101

from the ASF

1

. The substantially parallel configuration of the sheet path and the connecting direction of the connectors enables mutual separations of the sheet path and the connection of the connectors in such situation.

If the sheet path is perpendicular to the connecting direction of the connectors, the sheet has to be moved in a direction of a thickness of the sheet for separating the printer

101

in the connecting direction of the connectors, whereby the sheet may be broken or the broken sheet may remain in the apparatus. Furthermore, if the sheet is thick enough and cannot be easily broken, the separation itself of the printer

101

becomes impossible.

However, in the configuration of the present embodiment in which the sheet path is substantially parallel to the connecting direction of the connectors, the printer

101

can be separated in the case of a sheet jamming by a movement along the sheet, whereby the sheet jamming can be extremely easily handled without the sheet breaking or without a broken sheet remaining in the apparatus.

Below there will be explained the method of guiding the conveyed sheet (method of positioning the sheet in the transverse direction thereof).

In the present embodiment, as the ASF

1

is so constructed as to be detachably mountable on the sheet feeding port of the printer

101

, there can be achieved both:

sheet feeding without the ASF

1

; and

automatic feeding of sheets in succession with the mounted ASF

1

.

Thus, there can be enabled both the manual insert sheet feeding and the automatic sheet feeding, and the apparatus can be made more compact in comparison with a configuration having a manual insert sheet feeding port and an automatic sheet feeding port separately.

The printer

101

is provided, as shown in

FIG. 5

, with a sheet feeding tray

116

, which is pivotably supported at an end thereof and is rendered openable and closable. The sheet feeding tray

116

constitutes the sheet path and stabilizes the sheet feeding operation, in case of sheet feeding in manual insertion without the mounting of the ASF

1

. The sheet feeding tray

116

(or sheet path) is supported substantially horizontally in case of the manual insert sheet feeding.

At one end of the upper face of the sheet feeding tray

116

, there is perpendicularly formed a reference guide (third guide member)

116

a

parallel to the edge thereof, and, at the other end of the upper face, there is provided a right edge guide

122

which is slidably movable in the transverse direction of the sheet. These guides

116

a

,

122

guide both lateral edges of the manually inserted and fed sheet. These guides

116

a

,

122

have a substantially same shape (seen in the transverse direction of the sheet).

On the other hand, the ASF

1

is provided, as shown in

FIG. 4

, with a reference guide accommodating portion

36

b

, formed by a reference guide guiding portion

36

c

positioned thereabove. When the printer

101

is pressed into the ASF

1

, the reference guide

116

a

of the printer is pressed downwards by the guiding portion

36

c

and is rotated further downwards, and is accommodated, together with the right edge guide

122

, in the accommodating portion

36

b

. Above the reference guide accommodating portion

36

b

, there is formed a sheet path for automatic sheet feeding so as to make a detour to avoid the reference guide (third guide member)

116

a

. In the present embodiment, as the sheet feeding tray

116

is accommodated, in a downward rotated state, in the reference guide accommodating portion

36

b

, the sheet path on the automatic sheet feeding can be formed horizontally (particularly in the vicinity of the accommodating portion

36

b

), like the sheet path on the manual insert sheet feeding, there avoiding drawbacks (such as a backward tension on the sheet) resulting from an unnaturally shaped sheet path. The reference guide accommodating portion

36

b

is so formed as to accommodate the right edge guide

122

in any sliding position. On the automatic sheet feeding, a lateral edge of the sheet in the transverse direction thereof is guided by a sheet reference guide (second guide member)

26

b

of the ASF.

If the sheet automatically fed by the ASF

1

is guided both by the guide

26

b

of the ASF and the guide

116

a

of the printer, and if the guide

116

a

of the printer is eventually positioned at the inner side of the sheet than the guide

26

b

of the ASF because of the dimensional tolerance in the manufacture, the guide

116

a

of the printer constitutes an obstacle for the automatically fed sheet, resulting in skewed sheet advancement, damage to the sheet end or sheet jamming.

However, the present embodiment can avoid such drawbacks since the sheet automatically fed by the ASF

1

is guided solely by the guide

26

b

of the ASF.

Also, it is not necessary to precisely form the guide

26

b

of the ASF and the guide

116

a

of the printer or to employ precisely formed parts therefor in order to avoid such drawbacks, so that there can be avoided an increase in the cost resulting therefrom.

Furthermore, even if the sheet is somewhat skewed, the sheet can be protected from interference with the guide

116

a

of the printer, whereby skewed sheet advancement, damage to the sheet end or sheet jamming resulting from such interference can be avoided.

In the printer, the sheet is guided by the guide (third guide member)

116

a

of the sheet feeding tray

116

, but it is also possible to provide the interior of the printer with a similar guide (first guide member

124

) in a same position in the transverse direction of the sheet to guide a lateral edge of the manually inserted and fed sheet

200

with the guide

116

a

on the sheet feeding tray and such internal guide. The skewed sheet advancement can be further prevented by defining the sheet conveying direction with a longer section along the sheet conveying direction.

In the case the guide (first guide member

124

) is provided in the interior of the printer, the sheet reference guide (second guide member)

26

b

of the ASF can be formed, as shown in

FIG. 7

, at a position displaced, by a predetermined amount t, toward the inner side of the sheet (namely toward the recording position by the head). Thus, in case of automatic sheet feeding, the sheet can be prevented from interference with the internal guide of the printer, whereby skewed sheet advancement, damage to the sheet end or sheet jamming resulting from such interference can be avoided. The displacement amount t is determined to be equal to or more than the positioning tolerance between the printer

101

and the ASF

1

in the transverse direction of the sheet. In consideration of eventual skewed sheet feeding from the ASF, the displacement amount t may be, for example, about 0.6 mm.

Furthermore, in the case the guide of the ASF is displaced by t from that of the printer as explained above, the image recording position on the sheet in the transverse direction of the sheet in the case of sheet feeding by the ASF

1

(namely in case of automatic sheet feeding) may be displaced by an amount approximately equal to t (amount of displacement between the first and second guide members), in comparison with a case where the sheet feeding is not executed by the ASF

1

(namely in case of sheet feeding in manual insert). In this manner, the image is recorded in the same position regardless of the automatic or manual insert sheet feeding, thereby avoiding a drawback resulting from the difference in the image recording position (for example difference in the image recording position on a pre-printed sheet).

In the case the recording position is automatically displaced according to whether the sheet feeding is executed or not by the ASF, there may be provided mode discrimination means for discriminating whether the sheet feeding is executed by the ASF

1

, and the recording position may be displaced according to the result of discrimination by the mode discrimination means. Such mode discrimination means can be composed, for example, of:

means for electrically detecting the connection state of the printer connector

117

and the ASF connector

44

; or

a switch or a sensor provided on the printer for exclusively detecting the presence or absence of the ASF

1

(namely detecting the automatic/manual insert sheet feeding).

The amount of displacement between the guides of the ASF and of the printer and the amount of displacement in the recording position between the automatic and manual insert sheet feedings need not be exactly same, but have to be selected same in such a level that an ordinary person observes that “the image is recorded in a same recording position regardless whether the sheet is automatically fed or manually inserted and fed”.

Below there will be explained an ASF sheet feeding tray

2

for supporting the stacked sheets.

As shown in

FIGS. 1

to

4

, the ASF sheet feeding tray

2

is supported at an end thereof by the upper case

47

of the ASF and is rendered rotatable about the supporting portion. Thus, the ASF sheet feeding tray

2

is opened with a predetermined angle when supporting sheets and can be closed, as shown in

FIG. 8

, in the absence of the stacked sheets thereon.

Such configuration is not for using the mobile printer

101

as the desk-top printer in combination with the ASF

1

but indicates that the printer

101

is very compact and portable even in a state mounted in the ASF

1

.

In order to enable such use, the ASF sheet feeding tray

2

needs to be closed, as far as possible in a form along the external form of the ASF

1

mounted with the printer. For this reason, the ASF sheet feeding tray

2

is composed of a thin plate.

Also in the present embodiment, the sheet feeding tray

2

is so shaped as to cover, in the closed state, the operation unit of the printer

101

as shown in

FIG. 9

, in order to prevent the function of the printer

101

caused by an unexpected manipulation of the operation unit when the ASF

1

is carried with the closed sheet feeding tray

2

and with the printer

101

mounted therein. Furthermore, the sheet feeding tray

2

preferably engages with an arbitrary portion of the upper case

47

of the ASF

1

, in order to prevent unexpected opening of the tray

2

when the ASF is carried.

On the other hand, in case of feeding an envelope E in the longitudinal position as shown in

FIG. 10

, the tab E

1

of the envelope E is usually positioned at the left hand side, and the ASF

1

of the present embodiment receives a strong resistance at the tab side (left side) for example by the swelling of the tab portion by moisture, whereby the envelope E receives a clockwise rotating force.

In the present embodiment, in order to prevent such clockwise rotation of the envelope E, the ASF sheet feeding tray

2

is provided, at an upstream position in the sheet feeding direction, with an ASF sheet feeding tray side guide

2

a

(hereinafter simply referred to as side guide). Thus, when the envelope E is set in the longitudinally oblong position on the ASF

1

, a right edge of a trailing end of the envelope lies along the side guide

2

a

and is prevented from the clockwise rotation.

The envelope in the longitudinally oblong position is subjected to a resistance of the tab portion E

1

at the timing of feeding the envelope E, particularly in the present embodiment when the envelope E proceeds over the bank sheet

37

and when a leading end of the envelope E is lifted immediately thereafter along the inclined surface of the bank

36

. After these situations the resistance of the envelope tab E

1

becomes smaller so that the clockwise rotation is not generated even without the side guide

2

a.

For these reasons, in the present embodiment, the side guide

2

a

is provided in a part in the vicinity of a trailing end of the envelope E for preventing the clockwise rotation of the envelope E, but not in the entire longitudinal range of the envelope. The side guide

2

a

is so shaped, when the ASF sheet feeding tray

2

is closed, as to be accommodated in a step difference G formed between the upper case

47

of the ASF and the printer

101

(cf. FIG.

8

), whereby, when the sheet feeding tray

2

is closed, the side guide

2

a

does not interfere with other portions and the portability is not deteriorated as the sheet feeding tray

2

can be accommodated in a form matching the external shape of the ASF.

The side guide

2

a

can be effective if the height thereof is equal to or more than the thickness of the stacked sheets such as the envelopes, and a step difference at least equal to the thickness of the stacked sheets is formed between the upper case

47

of the ASF and the printer

101

.

Furthermore, the configuration of the present embodiment is effective for preventing not only the clockwise rotation of the envelope in the longitudinal feeding but also eventual clockwise rotation of any other sheet of a length comparable to that of the envelope, caused by any reason. The side guide

2

a

, being integral with the ASF sheet feeding tray

2

, can also be very inexpensive in cost. The side guide

2

a

may also be so formed as to be accommodated, in the closed state, in a recess formed in the printer

101

or the ASF

1

, instead of the step difference G mentioned above.

Below there will be explained a mounting and dismounting mechanism of the ASF

1

and the printer

101

.

FIG. 11

is a perspective view showing the mounting and dismounting mechanism of the ASF

1

;

FIG. 12

is a perspective view showing the mounting and dismounting mechanism of the printer

101

; and

FIG. 13

is a cross-sectional view showing the mounting and dismounting mechanism of the ASF

1

.

As shown in

FIG. 11

, the ASF

1

is provided with a positioning base

39

which is provided with two positioning bosses

39

d

,

39

e

. On the other hand, the printer

101

is provided, as shown in

FIG. 12

, with a board holder

118

so positioned as to oppose to the positioning base

39

and provided with a positioning hole

118

a

opposed to a first positioning boss

39

d

and a positioning oblong hole

118

b

opposed to a second positioning boss

39

e

. In connecting the printer

101

with the ASF

1

, before the connection is made between the ASF connector

44

and the printer connector

117

, the bosses

39

d

,

39

e

are fitted with the positioning holes

118

a

,

118

b

(oblong hole) to define the relative position of the printer

101

and the ASF

1

in the x and z directions. Thus the ASF connector

44

and the printer connector

117

can be exactly connected without damage by the misalignment of the connectors. Also, the sheet path of the ASF

1

can be exactly connected with the sheet path in the printer

101

.

On the other hand, the ASF

1

is provided, as shown in

FIG. 11

, with a horizontal printer sliding portion

45

b

for defining the moving direction of the printer

101

on the connecting operation. Also, there are provided hooks

16

,

17

(more exactly hook claws

16

a

,

17

a

of the hooks

16

,

17

) so as to be protrudable upwards from the printer slidable portion

45

b

. These hooks

16

,

17

(in the following they are distinguished if necessary as a left hook

16

and a right hook

17

) are both fixed on a hook shaft

18

as shown in FIG.

13

and are rotatably mounted on the chassis

11

so as to rotate integrally. Between the hook

16

and the ASF base

45

, there is provided a hook spring

3

, composed of a compressed coil spring, to bias the hooks

16

,

17

upwards (namely in a direction that they engage with hook fixing holes

103

y

,

103

z

to be explained in the following).

On the other hand, the base

103

of the printer

101

is provided with, as shown in

FIG. 12

, hook fixing holes

103

y

,

103

z

in positions corresponding to the claws

16

a

,

17

a

of the hooks

16

,

17

when the ASF

1

is mounted, and the engagement of the claws

16

a

,

17

a

with the fixing holes

103

y

,

103

z

defines the relative position of the ASF

1

and the printer

101

in the y direction.

On the other hand, on the positioning base

39

of the ASF, there is fixed, as shown in

FIG. 13

, a lever shaft

42

supporting a push lever

40

so as to be movable in directions

40

A and

40

B and rotatable in a direction

40

C. Between the push lever

40

and the chassis

11

there is provided a push lever spring

7

for clockwise biasing the push lever

40

. Between the push lever

40

and the left hook

16

there is provided a connecting spring

9

so as to maintain the upper face of the left hook

16

and the lower end

40

d

of the push lever

40

in constant contact (engagement).

Furthermore, the push lever

40

is provided with a boss

40

c

for limiting the rotation thereof, and the positioning base

39

is provided with slide faces

39

a

,

39

b

,

39

c

for impinging on the boss

40

c

. The slide faces

39

a

,

39

b

,

39

c

are represented by chain lines in order to clarify the configuration. In the above-described configuration, the rotation of the push lever

40

about the lever shaft

42

is limited by impingement of the boss

40

c

of the push lever

40

against the guide face

39

a.

In the foregoing description, the hooks

16

,

17

and the push lever

40

are provided on the ASF

1

while the hook fixing holes

103

y

,

103

z

are provided on the printer

101

, but it is also possible to provide the printer

101

with the hooks and a push lever and the ASF

1

with the hook fixing holes. Also, there are provided two hooks

16

,

17

and the corresponding fixing holes

103

y

,

103

z

, but such number is not restrictive and there may be provided three or more hooks and the corresponding fixing holes. Furthermore, the hooks

16

,

17

do not need to be rotatable as explained in the foregoing but they only need to be displaceable. Furthermore, the hooks

16

,

17

are so formed as to rotate integrally by fixing on the hook shaft

18

, but it is also possible to press the hooks

16

,

17

by the lever shaft

42

and to achieve integral rotation by such configuration.

Thereafter, popup members

43

a

,

43

b

provided on the ASF

1

press an upper part

102

a

of the printer

101

in the sheet feeding side thereof in a direction

43

A (y direction) to release the connection between the connectors

117

,

44

. The popup members

43

a

,

43

b

are biased by an elastic member (not shown), in the direction

43

A (y direction) and are rendered slidable in the y direction.

The biasing force for the popup members

43

a

,

43

b

is selected at a suitable level, because such biasing force, functioning as a repulsive force in mounting the printer

101

to the ASF

1

, renders such mounting impossible if it is excessively strong (for example at a level with which the ASF

1

is not moved by the biasing force at the mounting of the printer

101

thereto).

However, the force required for detaching the connectors may exceed the biasing force of the popup members

43

a

,

43

b

, and, in such case, the connection between the connectors cannot be released solely by the popup members

43

a

,

43

b

. For this reason, in the present embodiment, a protruding portion

40

b

of the push lever

40

protrudes in the y direction by a movement of the push lever

40

in a direction of the arrow

40

A.

The protruding portion

40

b

of the push lever

40

presses a lower (or central) portion

102

b

of the printer

101

at the sheet feeding side thereof, thereby releasing the connection between the connectors

44

,

117

. It is thus rendered possible, for the user, to easily extract the printer

101

in the y direction from the ASF

1

.

Now there will be explained, with reference to

FIGS. 14

to

16

, the operations in connecting the printer

101

and the ASF

1

and the functions of such operations.

FIG. 14

is a view showing a state in which the printer

101

is rested on the printer sliding portion

45

b

;

FIG. 15

is a view showing a state in which the printer

101

is pressed in; and

FIG. 16

is a view showing a state in which the printer

101

is connected to the ASF

1

.

At first referring to

FIG. 14

, as the printer

101

is pressed in a direction indicated by the arrow A along the printer sliding portion

45

b

of the ASF base

45

, the hooks

16

,

17

are rotated clockwise and the claws

16

a

,

17

a

are pressed downwards in a direction indicated by the arrow

16

A (hook

17

and claw

17

a

being omitted in FIG.

15

). In this operation, the push lever

40

is moved downwards through the connecting spring

9

. The printer

101

is pressed further in this state and, the bosses

39

d

,

39

e

of the ASF engage with the positioning holes

118

a

,

118

b

(oblong hole) of the printer to define the relative position in the x and z directions. Thereafter, the ASF connector

44

and the printer connector

117

are mutually connected.

When the hook fixing holes

103

y

,

103

z

reach the positions of the claws

16

a

,

17

a

, they are moved counterclockwise (in a direction indicated by the arrow

16

B) by the biasing force of the hook spring

3

, whereby the fixing holes

103

y

,

103

z

respectively engage with the claws

16

a

,

17

a

. Also the push lever

40

, already moved downwards, is pushed up to the normal position by the hook spring

3

, through the hooks

16

,

17

. In this manner the connection between the printer

101

and the ASF

1

is completed. As the hooks

16

,

17

are so constructed as to rotate integrally, they do not rotate unless both claws

16

a

,

17

a

match and engage with the fixing holes

103

y

,

103

z

and the push lever is not pushed up. Consequently, for example if the printer

101

is mounted in an inclined state to the ASF

1

, the push lever

40

is not pushed up to the normal position, and the user can easily know whether the printer

101

is properly mounted to the ASF

1

, by observing the state of the push lever

40

.

Furthermore, if the height of the claws

16

a

,

17

a

in a state engaging with the fixing holes

103

y

,

103

z

is selected substantially same as or somewhat higher than the height of the hook shaft

18

(constituting the rotary center of the hooks

16

,

17

), the hooks

16

,

17

do not rotate under the application of a force in an opposite direction (or in a direction opposite to the direction indicated by the arrow A) to the printer

101

, whereby the printer

101

can be protected from detachment from the ASF

1

.

Below there will be explained the operations in separating the printer

101

and the ASF

1

and the functions of such operations.

For separating the printer

101

and the ASF

1

, a push portion

40

a

of the push lever

40

is pressed down (in the direction indicated by the arrow

40

A) as shown in FIG.

17

. The push lever

40

, of which boss

40

c

is sandwiched between guide faces

39

a

,

39

b

formed on the positioning base

39

, is incapable of rotation about the lever shaft

42

until the end of the guide face

39

b

and descends in the direction indicated by the arrow

40

A. Thus, the hooks

16

,

17

integrally rotate in a downward direction indicated by the arrow

16

A about the hook shaft

18

whereby the claws

16

a

,

17

a

are disengaged from the fixing holes

103

y

,

103

z

. In the present embodiment, as the hooks

16

,

17

are so constructed as to rotate integrally, the manipulation of the push lever

40

allows for simultaneous disengagement of both claws

16

a

,

17

a

thereby achieving a simple separating operation. Also, in disengaging the claws

16

a

,

17

a

from the fixing holes

103

y

,

103

z

, it is not necessary to unmovably hold the image forming apparatus

100

itself, and a simple separating operation is realized by merely depressing the push lever

40

with one hand.

When the claws are disengaged as explained above, the popup members

43

a

,

43

b

, shown by broken lines in

FIGS. 16 and 17

, push the upper portion

102

a

of the printer

101

in the sheet feeding side thereof, thereby pushing out the printer

101

in a direction indicated by the arrow B. At the same time, the ASF connector

44

and the printer connector

117

are mutually disengaged.

A state shown in

FIG. 15

is reached when the user terminates the depression of the push lever

40

in the direction indicated by the arrow

40

A. In this state, the connectors

44

,

117

are disconnected and the hook

16

and the printer

101

are disengaged, whereby the user can easily remove the printer

101

from the ASF

1

.

However, if the force required for disengaging the connectors exceeds the pushing force of the popup member

43

a

,

43

b

as explained in the foregoing, the state shown in

FIG. 15

is not reached because the printer

101

does not move when the hook

16

is disengaged from the printer

101

, so that the user cannot remove the printer

101

from the ASF

1

.

Consequently, in the present embodiment, there is added the above-described pushing function by the user.

FIG. 17

shows a state in which the printer

101

does not move even after the hook

16

is disengaged from the printer

101

. In this state, the (left) hook

16

is disengaged from the fixing hole

103

y

while the boss

40

c

of the push lever

40

is released from the limitation in the moving direction by the guide face

39

b

of the positioning base

39

.

Also the lever shaft

42

is pressed to the upper end face of a sliding hole

40

e

of the push lever

40

, thereby limiting the downward movement of the (left) hook

16

. Furthermore, as a contact face

40

d

of the push lever

40

with the (left) hook

16

is formed as an arc around the lever shaft

42

, the position of the (left) hook

16

does not change by the rotation of the push lever

40

.

If the user continues to depress the push portion

40

a

of the push lever

40

, it rotates in a direction indicated by the arrow

40

D about the lever shaft

42

, and such rotation brings the protruding portion

40

b

of the push lever

40

in contact with the lower portion

102

b

of the printer

101

in the sheet feeding side thereof while the (left) hook

16

is disengaged from the printer

101

, whereby the printer

101

is pushed out in a direction indicated by the arrow B.

If the push lever

40

continues to be depressed thereafter, a contact face

40

f

of the push lever

40

impinges on a stopper portion

39

f

of the positioning base

39

as shown in

FIG. 18

, whereupon the rotation of the push lever

40

is limited. The push-out (shifting) amount of the printer

101

by the push lever

40

is so selected as to release the engagement between the (left) hook

16

and the printer

101

and the engagement between the connectors.

After the printer

101

is thus pushed out, the user terminates the depression of the push portion

40

a

of the push lever

40

, whereupon the (left) hook

16

is elevated in a direction indicated by the arrow

16

B by the function of the hook spring

3

. At the same time the push lever

40

is pushed up by the (left) hook

16

, whereby the boss

40

c

of the push lever

40

impinges on the guide face

39

c

of the positioning base

39

and the push lever

40

rotates thereafter in a direction indicated by the arrow

40

E by the tension of the spring

7

. When the boss

40

c

of the push lever

40

impinges on the guide face

39

a

of the positioning base

39

, the push lever

40

is limited in rotation and is elevated in a direction indicated by the arrow

40

B by the force of the hook spring

3

.

Thus, the connectors are eventually disconnected as shown in

FIG. 15

, while the (left) hook

16

is disengaged from the printer

101

, and the user can easily remove the printer

101

from the ASF

1

.

In the present embodiment, as explained in the foregoing, the push lever

40

is depressed substantially vertically in detaching the printer

101

from the ASF

1

, so that a vertical force is applied to the ASF itself. For this reason, the ASF

1

is not displaced when the printer

101

is pushed out substantially horizontally. Also, since the printer

101

is pushed out substantially horizontally, there will not result a failure in the detachment, caused by the movement of the printer

101

in the mounting direction by the weight thereof.

FIG. 19

is a view showing the arrangement of the push lever

40

, the popup members

43

a

,

43

b

, the positioning bosses

39

d

,

39

e

, the (left) hook

16

, the (right) hook

17

, and the ASF connector

44

and the relationship of forces thereof, and

FIG. 20

is a partial cross-sectional view of the upper face of the ASF

1

.

As shown in

FIGS. 19 and 20

, the positioning bosses

39

d

,

39

e

of the printer

101

and the hooks

16

,

17

are provided in the vicinity of both ends of the printer

101

in the width thereof. The ASF connector

44

is positioned between the positioning bosses

39

d

,

39

e

, close to the second positioning boss

39

e

. The push lever

40

and the second popup member

43

b

are positioned farther, than the ASF connector

44

, from the first positioning boss

39

d.

In the above-described configuration, the detachment of the printer

101

from the ASF

1

is achieved by the depression of the push lever

40

in the direction indicated by the arrow

40

A as explained in the foregoing, whereupon the hooks

16

,

17

are disengaged from the fixing holes

103

y

,

103

z

(cf.

FIG. 14

) while the protruding portion

40

b

of the push lever

40

impinges on and pushes out the printer

101

. In this manner there can be achieved disconnection of the connectors and disengagement of the hooks

16

,

17

from the fixing holes

103

y

,

103

z.

The popup members

43

a

,

43

b

are auxiliary members for reducing the force required for depressing the push lever

40

by the user, and are slidably biased, by an elastic member (not shown), at a predetermined position.

In the present embodiment, the printer

101

is pushed out, while sliding on the printer sliding portion

45

b

by rotation about the positioning boss

39

d

or

39

e.

The positioning hole

118

a

at the side of the first positioning boss constituting the center of rotation is formed as a circular hole while the positioning hole

118

b

at the side of the second positioning boss is formed as an oblong hole (cf. FIG.

12

), so that, in case of detaching the printer

101

from the ASF

1

by rotation about the first positioning boss

39

d

starting from the state shown in

FIG. 20

, there is reached a positional relationship between the printer

101

and the ASF

1

as shown in FIG.

21

.

In such state, however, the printer

101

cannot be moved by the pushing force of the first popup member

43

a

alone, because of the sticking engagement between the first positioning boss

39

d

and the positioning hole

118

a

. Also, in case the user forcedly remove the printer

101

from the ASF

1

, there may result deformation or destruction of the first positioning boss

39

d

.

Therefore, in order to avoid such sticking engagement, the present embodiment adopts a configuration in which, before the printer

101

is pushed out by the push lever

40

and the second popup member

43

b

, the engaging position between the first positioning boss

39

d

, constituting the center of rotation of the printer

101

, and the positioning hole

118

a

is displaced toward the connector disengaging direction by the pushing force of the first popup member

43

a.

More specifically, in the dimensional relationship shown in

FIG. 19

, the force required to push out the printer

101

by the pushing force of the first popup member

43

a

by rotation about the first positioning boss

39

d

is represented by:

F

1

≳(

X

1

/

X

2

)×

P

1

+

P

2

wherein F

1

is the printer pushing force of the first popup member

43

a

, P

1

is the force required for detaching the connectors, P

2

is the frictional force between the printer

101

and the printer sliding portion

45

b

of the ASF

1

, X

1

is the distance from the second positioning boss

39

e

constituting the center of rotation to the connector

44

, and X

2

is the distance from the second positioning boss

39

e

constituting the center of rotation to the first popup member

43

a.

As will be apparent from the foregoing relation, the pushing force F

1

of the first popup member

43

a

can be made smaller as the distance between the first popup member

43

a

and the ASF connector

44

becomes larger or as the ratio X

1

/X

2

becomes smaller. In consideration of the aforementioned fact that the pushing force F

1

of the first popup member

43

a

functions as a repulsive force in mounting the printer

101

to the ASF

1

and a fact that the force required for disconnecting the connectors is generally within a range of 1 to 2 kgf, the ratio X

1

/X

2

is advantageously selected at 0.5 or smaller.

On the other hand, in the present embodiment, the claw of the (right) hook

17

is formed lower than that of the (left) hook

16

, whereby the (right) hook

17

is disengaged from the fixing hole

103

z

(cf.

FIG. 12

) earlier than the disengagement of the (left) hook

16

from the fixing hole

103

y.

Therefore, at the moment when the (right) hook

17

is disengaged from the fixing hole

103

z

of the printer

101

, the printer

101

rotates about the second positioning boss

39

e

by the pushing force of the first popup member

43

a

, whereby the engaging position between the first positioning boss

39

d

and the positioning hole

118

a

moves toward the connector disengaging side as shown in FIG.

22

.

Subsequently the (left) hook

16

is disengaged from the fixing hole

103

y

of the printer

101

whereupon the printer

101

is pushed out by the push lever

40

and the second popup member

43

b

. Thus it is rendered possible to detach the printer

101

from the ASF

1

in a state shown in

FIG. 23

without the sticking engagement between the first positioning boss

39

d

and the positioning hole

118

a.

If the push lever

40

and the second popup member

43

b

are provided between the ASF connector

44

and the first positioning boss

39

d

constituting the center of rotation of the printer

101

, and if the connectors has a large connecting force, the connector

44

becomes the center of rotation of the printer

101

whereby a sticking engagement is generated between the first positioning boss

39

d

and the circular positioning hole

118

a

of the printer

101

, eventually resulting in deformation and/or destruction of the boss

39

d.

Based on these facts, the push lever

40

and the second popup member

43

b

have to be positioned farther, than the ASF connector

44

, from the first positioning boss

39

d

constituting the center of rotation of the printer

101

.

[Control Unit]

FIG. 24

is a block diagram of a main control unit for the printer and a control unit for the external ASF of the present invention.

A main control unit

202

for controlling the printer

101

is provided on a main body board

123

shown in

FIG. 4

, and is provided with a microcomputer in which a CPU

203

, a ROM

204

, and a RAM

205

are connected through buses.

In the recording operation by the printer

101

, the main control unit

202

drives a carriage motor

121

through a motor driver

208

and also drives a recording head

115

mounted on a carriage (not shown) connected to the carriage motor

121

through a head driver

210

according to a main control program stored in the ROM

204

, thereby effecting recording of a line.

Subsequently the main control unit

202

advances the sheet by driving a sheet feeding motor

120

through a motor driver

206

, and then repeats the driving of the carriage motor

121

and the recording head

115

, thereby completing the recording on the sheet. The connector

117

functions as a bothway communication port capable of transmitting command signals from the CPU

203

of the main control unit to the exterior and receiving response signals from the exterior into the CPU

203

, and is also capable of power supply to the exterior as will be explained later. A sheet end sensor

108

is provided in the printer body and has an optical or mechanical switch. When the sheet

200

is inserted into the printer main body, the output voltage of the sheet end sensor

108

changes from a LOW state to a HIGH state. A sheet discharge sensor

113

similar in configuration to the sheet end sensor

108

outputs a voltage of a HIGH state if the sheet

200

after recording remains in the printer body.

The output voltages of the sheet end sensor

108

and the sheet discharge sensor

113

can be monitored by the CPU

203

, and the output voltage of the sheet end sensor

108

can be directly outputted to the exterior through the connector

117

.

The ASF control unit

201

for controlling an external ASF

1

is provided, as in the main control unit

202

, with a microcomputer in which a CPU

213

, a ROM

214

and a RAM

215

are connected through buses. The CPU

213

controls a sheet feeding motor

27

through a motor driver

216

, based on an ASF control program stored in the ROM

214

. The ASF connector

44

functions as a bothway communication port for receiving signals from external equipment such as the printer

101

and transmitting signals from the CPU

213

of the ASF control unit.

[Communication Port]

FIG. 26

is a schematic view showing the detailed configuration of the connector

117

and the ASF connector

44

mentioned above. The connector

117

and the ASF connector

44

are respectively provided with eight ports

117

a

to

117

h

and

44

a

to

44

h

, and ports having a same alphabetical suffix are mutually connected electrically when the printer

101

is mounted to the ASF

1

.

In the ASF side, there are provided a ground (GND) line

44

a

; a 5 V power supply line

44

b

for signals; a 24 V power supply line

44

e

for driving the sheet feeding motor

27

; a transmission port

44

f

for transmitting signals to the printer; a reception port

44

g

for receiving signals from the printer; and a line

44

h

for receiving the output voltage of the sheet end sensor

108

provided in the printer body. Ports

44

c

and

44

d

are mutually short circuited, whereby the printer

101

can easily identify, utilizing ports

117

c

and

117

d

, connection of an external equipment.

[Separating and Conveying Mechanisms of ASF]

FIG. 25

is a cross-sectional view showing a state in which the external ASF of the present invention is mounted on the printer body.

A sheet feeding roller

19

for feeding the sheet

200

is fitted with a sheet feeding rubber member

23

, and, when the sheet feeding roller

19

is rotated, the sheet

200

is conveyed, by the frictional force of the sheet feeding rubber member

23

.

A pressure plate

26

for supporting the stacked sheets

200

is pivotably supported by the ASF chassis

11

at the upstream end in the sheet conveying direction. The pressure plate

26

is biased toward the sheet feeding rubber member

23

by a pressure plate spring

13

. But, in the initial state, the sheet feeding rubber member

23

and the pressure plate

26

are mutually separated because cam portions

19

c

provided on both ends of the sheet feeding roller

19

engage with cam portions

26

a

provided on both ends of the pressure plate

26

, whereby the sheets

200

can be smoothly set. A bank

36

is provided with an impingement face

36

a

in the extension of the sheet conveying direction of the pressure plate

26

, and the sheets

200

are set in such a manner that the front end thereof impinges on the impingement face

36

a

. The impingement face

36

a

is provided with a bank sheet

37

constituting a sheet separating member. The bank sheet

37

is composed of an elastic member such as a plastic sheet, and serves to separate the sheets one by one, utilizing an elastic force generated by bending.

[Conveying and Printing Mechanisms of the Printer]

In the following there will be explained, with reference to

FIG. 25

, a conveying mechanism and a printing mechanism in the printer.

An LF roller

109

for conveying the sheet

200

is composed of a metal pipe and a film of a material with a high friction coefficient such as urethane resin formed on the metal pipe. The LF roller

109

is rotated by the sheet feeding motor

120

shown in FIG.

24

and pinches and conveys the sheet

200

in cooperation with a pinch roller

110

.

A recording head

115

for recording image information on the sheet

200

conveyed by the LF roller

109

is mounted on a carriage (not shown), capable of reciprocating motion along the longitudinal direction of the LF roller

109

. The recording head

115

is driven together with the carriage by the carriage motor

121

shown in

FIG. 24

, and is capable of a reciprocating motion in the transverse direction of the sheet (a direction perpendicular to the plane of the drawing).

Spurs

111

and sheet discharge rollers

112

are positioned in two sets at the downstream side of the LF roller

109

and the recording head

115

, for conveying the sheet

200

after the recording. The sheet discharge rollers

112

are linked with the LF roller

109

through transmission members (not shown) and are rotated by the LF roller

109

so as to convey the sheet

200

in a direction the same as the conveying direction of the LF roller

109

.

Also the sheet end sensor

108

is provided in the sheet path of the upstream side in the sheet conveying direction with respect to the LF roller

109

while the sheet discharge sensor

113

is positioned between the two sets of sheet discharge rollers, and each sensor changes the output voltage from the LOW state to the HIGH state in response to the passing of the sheet

200

.

[Driving Mechanism of ASF]

FIGS. 27 and 28

show the driving mechanism of the external ASF of the present invention.

There are provided a sheet feeding motor

27

composed of a stepping motor capable of forward and reverse rotation; an idle gear

28

meshing with a motor gear

27

a

of the sheet feeding motor

27

; an ASF double gear

29

having two gears different in diameter and meshing with the idle gear

28

; a forward rotating planet gear

31

meshing with the smaller one of the above-mentioned double gear and rotating around the double gear; a reverse rotating sun gear

33

having two gears different in diameter and meshing with the smaller one of the above-mentioned double gear

29

; and a reverse rotating plane gear

35

meshing with the smaller gear of the above-mentioned reverse rotating sun gear

33

and rotating around the reverse rotating sun gear. A sheet feeding roller gear

19

a

provided on the shaft end of the sheet feeding roller

19

has a toothless portion

19

b

. The sheet feeding roller gear

19

a

is positioned on the rotating trajectory of the forward rotating planet gear

31

and the reverse rotating planet gear

35

so as to mesh with these gears.

In the following there will be explained the functions of these gears. Referring to

FIG. 27

, when the sheet feeding motor

27

rotates in a direction indicated by the arrow b (reverse rotation), the gears rotate respectively in directions indicated by arrows. More specifically, through the idle gear

28

and the ASF double gear

29

, the reverse rotating planet gear

35

moves about the reverse rotating sun gear

33

from a broken-lined position in

FIG. 27

to a solid-line position as indicated by an arrow, and meshes with the sheet feeding roller gear

19

a

, thereby rotating the sheet feeding roller

19

in a direction indicated by an arrow (namely in a direction to advance the sheet

200

on the pressure plate

26

toward the printer

101

). The sheet feeding roller gear

19

a

, rotating by meshing with the reverse rotating planet gears

35

, is released from the meshing when the toothless portion

19

b

reaches a position opposed to the reverse rotating planet gear

35

, whereby it is no longer rotated by the reverse rotation of the sheet feeding motor

27

.

In this operation, the forward rotating planet gear

31

moves from a broken-lined position in

FIG. 27

to a solid-line position in a direction indicated by the arrow and is stopped therein by impinging on a stopper (not shown), so that it does not influence the rotation of the sheet feeding roller

19

.

Then, referring to

FIG. 28

, when the sheet feeding motor

27

rotates in a direction indicated by the arrow f (forward rotation), the gears rotate respectively in directions indicated by arrows. More specifically, through the idle gear

28

and the ASF double gear

29

, the forward rotating planet gear

31

moves about the ASF double gear

29

from a broken-lined position in

FIG. 28

to a solid-line position as indicated by an arrow, and meshes with the sheet feeding roller gear

19

a

, thereby rotating the sheet feeding roller

19

in a direction indicated by an arrow in

FIG. 28

(namely in a direction to advance the sheet

200

on the pressure plate

26

toward the printer

101

). The sheet feeding roller gear

19

a

, rotating by meshing with the forward rotating planet gear

31

, is released from the meshing when the toothless portion

19

b

reaches a position opposed to the forward rotating planet gear

31

, whereby it is no longer rotated by the forward rotation of the sheet feeding motor

27

.

In this operation, the reverse rotating planet gear

33

moves from a broken-lined position in

FIG. 28

to a solid-line position and is stopped therein by impinging on a stopper (not shown), so that it does not influence the rotation of the sheet feeding roller

19

.

In a position where the toothless portion

19

b

of the sheet feeding roller gear

19

a

is opposed to the forward rotating planet gear

31

, the cam portion

19

c

of the sheet feeding roller engages with the cam portion

26

a

of the pressure plate

26

as in the initial state, thereby separating the pressure plate

26

from the sheet feeding rubber member

23

.

Consequently, when the sheet feeding motor

27

is continuously rotated in the forward direction, the cam portion

19

c

of the sheet feeding roller

19

engages with the cam portion

26

a

of the pressure plate

26

whereby the sheet feeding roller

19

terminates rotation in a phase the same as in the initial state where the pressure plate

26

is separated from the sheet feeding rubber member

23

, and the forward rotating planet gear

33

and the reverse rotating planet gear

35

thereafter rotate idly in the solid-lined positions in

FIG. 28

whereby the mechanism is stabilized in a state not transmitting the rotation to the sheet feeding roller

19

.

As explained in the foregoing, the sheet feeding roller

19

rotates only in a direction for advancing the sheet

200

toward the printer

101

regardless whether the sheet feeding motor

27

is rotated in the forward (normal) or reverse direction, and never rotates in the opposite direction.

[Sheet Feeding Operation and Recording Operation (in the Printer)]

In the following there will be explained a series of operations for feeding, conveying and recording the sheet

200

and thereafter discharging the sheet

200

, to be executed by the printer and the ASF of the present invention.

In response to a recording command received from an external information device such as a computer, the printer

101

executes at first a sheet feeding operation and then a recording operation.

FIG. 29

is a flowchart showing the control sequence in case the printer

101

executes a sheet feeding operation. At first the main control unit

202

of the printer

101

executes a sub flow C

1

of which details will be explained later with reference to FIG.

33

. The sub flow C

1

is to discriminate, a type of the external device mounted to the printer, through the ports

117

f

,

117

g

shown in FIG.

26

.

Then the sequence proceeds to a step S

1

, and, if the result of the sub flow C

1

indicates that the ASF is mounted to the printer

101

, the sequence proceeds to a step S

2

as the sheet feeding is to be executed by the ASF. In a step S

2

, the main control unit

202

transmits an initializing command signal to the ASF, and the sequence proceeds to a step S

3

.

If a response signal indicating the completion of initialization in the ASF is not received in the step S

3

, the sequence repeats the step S

3

. Upon receiving such response signal, the sequence proceeds to a step S

4

in which the main control unit

202

transmits a sheet feed command signal and a sheet type signal indicating the kind of the sheet (such as ordinary paper, coated paper, postcard, glossy film etc.) to the ASF, and the sequence proceeds to a step S

5

.

The sequence proceeds to a step S

8

if the response signal is not received from the ASF in the step S

5

, but repeats the step S

5

if a predetermined limit time t

2

has not elapsed. If a step S

8

identifies that the limit time t

2

has elapsed, the sequence proceeds to a step S

9

in which the main control unit

202

issues a sheet feeding error and terminates the sheet feeding operation. If a step S

5

receives a response signal from the ASF, indicating the completion of the sheet feeding, the sequence proceeds to a step S

7

. A step S

7

executes so-called head feeding operation for the sheet

200

(an operation for feeding a leading end of a sheet to an initial position), whereby the main control unit

202

drives the sheet feeding motor

120

to rotate the LF roller

109

by a predetermined amount R

3

in the sheet conveying direction in the recording operation (forward (normal) rotation), thereby terminating the sheet feeding operation. The predetermined amount R

3

is so selected that the leading end of the sheet

200

does not reach the detecting area of the sheet discharge sensor

113

but reaches a position directly under the recording head

115

. Consequently, when the printer

101

starts recording on the sheet

200

, it need not be reversed toward the upstream side in the conveying direction, so that the trailing end of the sheet

200

does not collide with the internal components of the ASF and that the sheet

200

can be protected from creasing or misfeeding.

Also if the step S

5

receives a response signal from the ASF, indicating a sheet feeding error, the sequence proceeds to a step S

9

in which the main control unit

202

issues a sheet feeding error and terminates the sheet feeding operation.

If, in the step S

1

, the result of the sub flow C

1

indicates that the ASF is not mounted on the printer

101

, the sequence proceeds to a step S

10

as the sheet feeding is to be executed by manual insert.

If the user does not insert a sheet in the step S

10

, the sheet is not detected and the sheet end sensor

108

provides a low output voltage, whereupon the sequence repeats the step S

10

. When the user inserts the sheet

200

in the printer

101

to impinge the sheet

200

on the LF roller

109

, the sheet end sensor

108

releases a High output voltage, indicating the sheet detection, whereupon the sequence proceeds to a step S

11

. In the step S

11

, the main control unit

202

drives the sheet feeding motor

120

through the sheet feeding motor driver

206

, so as to rotate the LF roller

109

normally by a predetermined amount R

4

(in the forward direction for conveying the sheet in the conveying direction in the recording operation). The predetermined amount R

4

is so selected that the leading end of the sheet

200

reaches the detection area of the sheet discharge sensor

113

. Then a step S

12

identifies that the sheet feeding is successful if the sheet discharge sensor

113

detects the sheet

200

, and the sequence proceeds to a step S

13

. In the step S

13

, the main control unit

202

drives the sheet feeding motor

120

through the sheet feeding motor driver

206

, so as to rotate the LF roller

109

reversely by a predetermined amount R

5

(in the reverse direction for conveying the sheet in a direction opposite to the conveying direction in the recording operation). The predetermined amount R

5

is so selected that the sheet

200

conveyed to the detection area of the sheet discharge sensor

113

is returned to the recording start position and that the leading end of the sheet

200

does not come out of the nip between the LF roller

109

and the pinch roller

110

.

In the step S

12

, if the sheet discharge sensor

113

does not detect the sheet

200

, for example if the sheet

200

does not impinge strongly enough on the LF roller

109

and is not pinched between the LF roller

109

and the pinch roller

110

or if the leading end of the sheet

200

does not reach the detection area of the sheet discharge sensor

113

even after sheet conveyance by the amount R

4

because of a skewed impingement of the sheet

200

on the LF roller

109

, the main control unit

202

identifies a failure in the sheet feeding in manual insert and the sequence proceeds to a step S

14

. In the step S

14

, the main control unit

202

drives the sheet feeding motor

120

through the sheet feeding motor driver

206

so as to rotate the LF roller

109

reversely by a predetermined amount R

6

. The predetermined amount R

6

is so selected that the leading end of the sheet

200

, conveyed to the detection area of the sheet discharge sensor

113

, can satisfactorily escape from the nip between the LF roller

109

and the pinch roller

110

.

Thus, in the manual insert operation, the successful feeding can be securely confirmed by discriminating whether the sheet discharge sensor

113

detects the sheet

200

, and, in case of a failure in the sheet feeding, the sheet

200

is returned to a position where it is not pinched by the LF roller

109

whereby the sheet

200

can be easily removed and manually inserted anew.

In contrast to the ASF sheet feeding, there are no mechanical components colliding with the returning sheet

200

in case of manual insert, so that the returning conveyance thereof does not result in creasing or misfeeding.

After the completion of the sheet feeding operation by the above-described sheet feeding control sequence, the printer

101

executes the recording operation. The main control unit

202

drives the carriage motor

121

through the motor driver

208

and the recording head

115

, mounted on the carriage (not shown) connected to the carriage motor

121

, through the head driver

210

, thereby affecting recording of a line. Subsequently the main control unit

202

drives the sheet feeding motor

120

through the motor driver

206

to advance the sheet

200

by a line, and then repeats the driving of the carriage motor

121

and the recording head

115

, thereby completing the recording on the sheet. After completion of the recording, the main control unit

202

drives the sheet feeding motor

120

, thereby rotating the LF roller

109

normally. Thus, the sheet discharge roller

112

is driven to discharge the sheet

200

from the printer

101

.

[Sheet Feeding Operation (in the ASF)]

FIG. 30

is a flowchart showing the main control sequence of the ASF which can be externally attached to the printer of the present invention. The control unit

201

of the ASF

1

of the present invention is normally in a stand-by state when connected to the printer

101

, and repeats a step S

37

, if a command signal is not received from the printer

101

, until the command signal is received. When a command signal from the printer

101

is received through the serial receiving port

44

g

shown in

FIG. 26

, the sequence proceeds to following sub flows or steps according to the content of the command signal. If the command signal from the printer

101

is a “sheet feed command” or an “initializing command”, the sequence respectively proceeds to a sub flow C

2

for controlling the ASF sheet feeding operation or a sub flow C

3

for controlling the initializing operation, and, after the completion of each sub flow, the sequence returns to the step S

37

to enter the stand-by state. If the command signal from the printer

101

is a “type of device discriminating command”, the sequence proceeds to a step S

6

for transmitting an ID code indicating the type of the ASF

1

itself to the printer

101

through the serial transmitting port

44

f

, and then proceeds to the step S

37

for entering the stand-by state.

Among the two sub flows mentioned above, the sub flow C

2

for controlling the ASF sheet feeding operation will be explained in the following, and the sub flow C

3

for controlling the initializing operation will be explained later.

FIG. 31

is a flowchart showing the sub flow C

2

for controlling the sheet feeding operation in the ASF

1

.

At first in a step S

15

, the ASF control unit

201

reads a driving table T for the sheet feeding motor

27

optimum for the sheet type to be fed, from the ROM

214

to the CPU

213

, based on the sheet type information received together with the sheet feeding command signal from the printer

101

. The driving table T contains information such as the drive speed of the sheet feeding motor

27

composed of a pulse motor, a registration pulse number P

5

for rotating the sheet feeding roller

19

by an optimum amount according to the sheet type for registering operation in a step S

22

to be explained later etc., and plural tables are prepared according to the characteristics of anticipated sheets.

After reading the driving table T, the sequence proceeds to a step S

16

in which the ASF control unit

201

sets “0” as the initial value for variables INIT, n and Pc. These variables are stored in the RAM

215

. The variable INIT is a flag indicating whether the rotating phase of the sheet feeding roller

19

is in an initial position; n is a rotation number counter indicating the number of rotations of the sheet feeding roller

19

after the start of the sheet feeding flow C

2

; and Pc is a pulse number counter indicating the number of pulses given to the sheet feeding motor

27

for driving in the reverse direction.

In a next step S

17

, the ASF control unit

201

drives, through the sheet feeding motor driver

216

, the sheet feeding motor

19

by one pulse in the reverse direction. A next step S

18

increases the value of the pulse number counter Pc by 1, and, in a next step S

19

, the ASF control unit

201

compares the value of the pulse number counter Pc with a permitted pulse number Pmax.

The permitted pulse number Pmax is the total pulse number from the start of reverse rotation of the sheet feeding motor

27

to the end of rotation of the sheet feeding roller to a position where the toothless portion

19

b

of the sheet feeding roller gear comes opposed to the reverse rotation planet gear

35

as explained in FIG.

27

. Since the condition Pc<Pmax is satisfied immediately after the start of sheet feeding, the sequence proceeds to a step S

20

, in which the ASF control unit

201

confirms the output voltage of the sheet end sensor

108

in the printer

101

through the port

44

h

shown in FIG.

26

. As the sheet

200

does not reach the interior of the printer

101

immediately after the start of sheet feeding, the sheet end sensor

108

provides a LOW output voltage, so that the sequence returns to the step S

17

. Through the repetition of the steps S

17

through S

20

, the reverse rotation planet gear

35

shown in

FIG. 27

moves from the broke-lined position to the solid-lined position and meshes with the sheet feeding roller gear

19

a

, whereby the sheet feeding roller

19

starts rotation. When the sheet feeding roller

19

starts rotation from the initial phase state, the sheet feeding roller cam

19

c

and the pressure plate cam

26

a

are disengaged whereby the pressure plate

26

is lifted upwards by the pressure plate spring

13

and the sheets

200

stacked on the pressure plate

26

are brought into pressure contact with the sheet feeding rubber member

23

. In this operation,the leading end of the sheets

200

, impinging on the impinging face

36

a

of the bank

36

, is also lifted upwards and is maintained in contact with the approximate center of the bank sheet

37

.

The steps S

17

through S

20

are further repeated to continue the reverse rotation of the sheet feeding motor

27

, whereby the sheet feeding roller

19

is rotated to initiate the conveyance of the sheet

200

by the frictional force of the sheet feeding rubber member

23

. The leading end of the sheet

200

is separated from the underlying sheets by a repulsive force generated by bending the elastic bank sheet

37

, whereby only one sheet is advanced.

However, the relationship Pc<Pmax no longer stands when the reverse rotation of the sheet feeding motor

27

is continued until the value of the pulse number counter Pc reaches a certain magnitude, whereupon the sequence branches to a step S

24

from step S

19

. In the step S

24

, the ASF control unit

201

drives the sheet feeding motor

27

in the forward direction by a predetermined pulse number P

4

, which is enough for rotating the sheet feeding roller

19

to the initial position by the forward rotating planet gear

31

. Thus, by the execution of the step S

24

, the sheet feeding roller

19

rotates to a phase of one exact rotation from the initial position, wherein the toothless portion

19

b

of the sheet feeding roller gear reaches a position opposed to the forward rotating planet gear

31

so that the sheet feeding roller gear is disengaged and stopped. Then, a step S

25

returns the pulse number counter Pc to “0” and increases the value of the rotation number counter n by “1”. As n=1 in this state in a next step S

26

, the sequence returns to the step S

17

to start the reverse rotation of the sheet feeding motor

27

again.

The ASF control unit

201

repeats the steps S

17

through S

20

as explained in the foregoing whereby the sheet feeding roller

19

starts a twice rotation and the sheet

200

is further conveyed. When the leading end of the sheet

200

reaches the sheet end sensor

108

in the printer

101

, the sheet end sensor

108

generates a HIGH output voltage whereby the sequence proceeds from S

20

to S

21

. In the step S

21

, the ASF control unit

201

compares a sum of the value of the pulse number counter Pc and the registration pulse number P

5

in the read driving table T, with the permitted pulse number Pmax. If Pc+P

5

≲Pmax, the sequence proceeds to a step S

22

since, in case the sheet feeding motor

27

is further driven in the reverse direction by P

5

pulses, the reverse drive is not released in the course of the drive.

On the other hand, if Pc+P

5

>Pmax, the sequence proceeds to a step S

24

since, by further driving the sheet feeding motor

27

in the reverse direction by P

5

pulses, the toothless portion

19

b

of the sheet feeding roller gear comes opposed to the reverse rotation planet gear

35

in the course of such drive whereby the driving transmission to the sheet feeding roller

19

is interrupted. The step S

24

again drives the sheet feeding motor normally by P

4

pulses to return the sheet feeding roller

19

to the initial position. Then a step S

25

sets “0” for Pc and n+1 for n, and the sequence proceeds to a step S

26

. In this state there stands n=2 because the sheet end sensor

108

normally detects the sheet

200

in the twice rotation of the sheet feeding roller, so that the sequence returns to the step S

17

. At this time, as the sheet end sensor

108

has generated a HIGH output voltage and the pulse number counter Pc has just been reset, the sequence proceeds from the step S

17

to S

18

→S

19

→S

20

→S

21

and S

22

because there is now satisfied a relation Pc+P

5

≲Pmax.

The step S

22

executes so-called registering operation. The ASF control unit

201

drives the sheet feeding motor

27

reversely by the pulse number PS in the read driving table T, thereby rotating the sheet feeding roller

19

. In this operation, the leading end of the sheet

200

is further advanced into the printer

101

from the position detected by the sheet end sensor

108

, and is stopped by impinging on the nip formed between the stopped LF roller

109

and the pinch roller

110

, but the trailing portion of the sheet

200

is further advanced by the sheet feeding roller

19

. Consequently, the leading end of the sheet

200

is aligned parallel to the nip formed between the LF roller

109

and the pinch roller

110

.

In a next step S

23

, the ASF control unit

201

transmits a signal indicating the completion of sheet feeding to the printer

101

through the serial transmitting port

44

f

shown in

FIG. 26

, whereupon the sequence is completed.

In case no sheet is present on the pressure plate

26

, the sheet end sensor

108

does not generate the HIGH output voltage regardless of the number of rotations of the sheet feeding roller

19

.

Therefore, the ASF control unit

201

repeats twice a sequence of executing a loop of S

17

→S

18

→S

19

→S

20

→S

17

by a predetermined number of times and then returning to S

17

through S

19

→S

24

→S

25

→S

26

, and, upon reaching the step S

26

for the third time, the rotation number counter of the sheet feeding roller

19

becomes n=3 and the sequence then proceeds to a step S

27

for transmitting a sheet feeding error signal to the printer

101

, whereupon the sequence is terminated.

[Other Operations (Printer and ASF)]

FIG. 32

is a flowchart of a sub flow C

3

for controlling the initializing operation of the ASF

1

. Upon receiving an initializing command signal from the printer

101

, the ASF control unit

201

proceeds to a step S

28

for confirming the value of a flag INIT indicating whether the rotational phase of the sheet feeding roller

19

is in an initial position. If INIT=1 indicating that the sheet feeding roller

19

is already in the initial position, the sequence proceeds to a step S

31

for transmitting an initialization completion signal to the printer

101

, whereupon the sequence is terminated. If INIT=0, the sequence proceeds to a step S

29

for driving the sheet feeding motor

27

normally by a predetermined pulse number P

0

, which is selected to be sufficient for rotating the sheet feeding roller gear until the toothless portion

19

b

thereof reaches a position opposed to the forward rotating planet gear

31

thereby rotating the sheet feeding roller

19

to the initial position from any rotational phase. Thus, the step S

29

rotates the sheet feeding roller

19

to the initial position, and the pressure plate

26

and the sheet feeding rubber member

23

are mutually separated to enable smooth setting of the sheets

200

.

A next step S

30

sets “1” as the flag INIT in order to indicate that the sheet feeding roller is in the initial position. Then a step S

31

transmits an initialization completion signal to the printer

101

, and the sequence is terminated.

FIG. 33

is a flowchart showing a sub flow C

1

for discriminating, through ports

117

f

,

117

g

shown in

FIG. 26

, the type of the device externally connected to the printer. At first, in a step S

32

, the main control unit

202

transmits a device type discrimination command signal to the external device through the port

117

g

. If a response signal from the external device is not received through the port

117

f

in a step S

33

, the sequence proceeds to a step S

35

, and if a predetermined limit time t

1

has not elapsed, the sequence returns to the step S

33

. If the limit time t

1

has elapsed in the step S

35

, the sequence proceeds to a step S

36

for discriminating that the external device is absent, whereupon the sequence is terminated.

If a response signal is received from the external device in the step S

33

, the sequence proceeds to a step S

34

, in which the main control unit

202

reads a partial code ID indicating the type of the mounted device from the received response signal, whereupon the sequence is terminated.

[Second Embodiment]

FIGS. 34 and 35

show a second embodiment of the control sequence in the printer of the present invention and the external ASF which can be mounted to the printer. Parts or operations equivalent in function or shape to those in the first embodiment will be represented by the same numbers or symbols and will not be explained further.

In the first embodiment, as shown in

FIG. 31

, the ASF control unit

201

drives the sheet feeding motor reversely by P

5

pulses in the step S

22

, and then transmits the sheet feeding completion signal to the printer

101

in the step S

23

. In such case, however, the sheet feeding roller

19

is not returned to the initial position, so that the sheet feeding roller

19

remains in contact with the sheets

200

as shown in FIG.

36

. If the leading end aligning operation or the recording operation is executed in the printer in this state simply by the LF roller

109

alone, the sheet feeding roller

19

generates a backward tension to deteriorate the accuracy of conveyance of the sheet

200

.

The second embodiment is to avoid such drawback.

As shown in

FIG. 35

, after the registering operation in the step S

22

, the ASF control unit

201

proceeds to a step S

38

for driving the sheet feeding motor

27

normally (forwardly) by a predetermined pulse number P

6

, which is selected sufficient for rotating the sheet feeding roller

19

to the initial position by the forward rotating planet gear

31

. Simultaneous with the start of forward rotation of the sheet feeding motor

27

, there is activated a counter for measuring a time elapsed from the start of drive, and, after the elapse of a predetermined time t

3

, the sequence proceeds to a step S

39

to transmit a synchronous driving request signal to the printer

101

. The predetermine time t

3

is selected slightly longer than the time from the start of rotation of the sheet feeding motor

27

in the step S

38

to the start of rotation of the sheet feeding roller

19

by the movement of the forward rotating planet gear

31

to the meshing position with the sheet feeding roller gear

19

a.

Also, in the step S

38

, the drive speed of the sheet feeding motor

27

is so selected that the peripheral speed of the sheet feeding rubber member

23

mounted on the sheet feeding roller

19

is slightly larger than that of the LF roller

109

rotating in the step S

7

in the printer.

Upon completion of the step S

38

, the sheet feeding roller

19

is rotated to a phase the same as in the initial position, and the sequence proceeds to a step S

40

, in which the ASF control unit

201

sets, in the INIT flag, a value “1” indicating that the rotational phase of the sheet feeding roller

19

is in the initial state, and the sequence is terminated.

On the other hand, the main control unit

202

of the printer, upon receiving the synchronous driving request signal transmitted by the ASF control unit

201

in the above-mentioned step S

39

, proceeds from the step S

5

in

FIG. 34

to a step S

7

for starting the forward (normal) rotation of the LF roller

109

.

FIG. 37

is a timing chart outlining the operations of the printer

101

and the ASF

1

of the present embodiment in the course of time.

When the printer starts the sheet feeding operation, at first a device type discrimination command signal is transmitted to the ASF (S

32

). The ASF transmits an ID signal, indicating its own device type code to the printer (S

37

). Then the printer transmits an initializing command signal to the ASF (S

2

). The ASF, if not in the initialized state, executes initialization by rotating the sheet feeding roller (S

29

), and transmits an initialization completion signal to the printer (S

31

). Then the printer transmits a sheet feeding command signal to the ASF (S

4

).

The ASF reads an optimum driving table T based on the sheet type information transmitted together with the sheet feeding command signal (S

15

, omitted in

FIG. 37

) and drives the sheet feeding motor based on the sheet feeding operation control flow C

2

, thereby rotating the sheet feeding roller (S

18

). When the sheet end sensor provided in the printer detects a sheet and generates a HIGH output voltage, the ASF further rotates the sheet feeding roller by a rotation amount R

1

based on the aforementioned pulse number P

5

, thereby achieving so-called registering operation (S

22

). After the registration, the ASF further rotates the sheet feeding roller by a rotation amount R

3

to a position the same as the initial position (S

38

), and, after the elapse of a time t

3

from the start of driving of the sheet feeding motor, transmits a synchronous driving request signal to the printer (S

39

).

Upon receiving the synchronous driving request signal from the ASF, the printer rotates the LF roller by a rotation amount R

3

, thereby executing so-called leading end feeding operation for feeding a leading end of the sheet to an initial position (S

7

).

In the present embodiments, as will be apparent from the foregoing description, the sheet feeding roller

19

starts rotation in a state after the completion of the step S

22

as shown in

FIG. 36

, and the LF roller

109

starts rotation slightly later, and the peripheral speed of the sheet feeding rubber member

23

is slightly larger than that of the LF roller

109

. Consequently, when the LF roller

109

starts rotation for the leading end feeding operation in the step S

7

, there is not generated a backward tension on the sheet

200

because the sheet feeding rubber member

23

maintained in contact therewith starts rotation slightly earlier, and the backward tension resulting from the difference in the peripheral speed is also not generated since the peripheral speed of the sheet feeding rubber member

23

is slightly larger than that of the LF roller

109

. Consequently, the accuracy of transportation of the sheet

200

is stabilized in the leading end feeding operation.

If the time t

3

is excessively small, the LF roller

109

may start rotation before the driving force of the sheet feeding motor

27

is transmitted to the sheet feeding roller

19

, while, if the time t

3

is excessively large, the sheet feeding roller

19

rotates by a large amount before the LF roller

109

starts rotation whereby the sheet

200

may be deformed on the way or may become not parallel to the nip formed by the LF roller

109

and the pinch roller

110

. Based on experimental results, the optimum range of time t

3

in the present embodiment is 10 ms to 100 ms. Also if the peripheral speed of the sheet feeding rubber member

23

mounted on the sheet feeding roller

19

is not fast enough with respect to the peripheral speed of the LF roller

109

, there may be generated a backward tension when the sheet feeding rubber member

23

causes slippage depending on the type of the sheet

200

or on the environmental conditions, while the sheet

200

may be deformed in case the peripheral speed of the sheet feeding rubber member

23

is too fast. Based on experimental results, the optimum value of the peripheral speed of the sheet feeding rubber member

23

in the step S

38

of the present embodiment is 5 to 50% faster than the peripheral speed of the LF roller

109

in the step S

7

.

Also in the present embodiment, a signal corresponding to the “sheet feeding completion signal” in the first embodiment is named as the “synchronous driving request signal” because of the difference in the meaning of operation, but the actual signal may be identical with the “sheet feeding completion signal”. Consequently the sheet feeding control flow is basically same in the first and second embodiments (FIGS.

29

and

34

). Stated differently, the printer shown in the first embodiment can be used in combination with either of the ASF's shown in the first and second embodiments.

In the following there will be explained, with reference to

FIG. 38

, the content of the plural driving tables T in the second embodiment.

For example, if the sheet type information received by the ASF

1

indicates an ordinary paper, the ASF control unit

201

selects a driving table T

1

. For the ordinary paper, the driving speed is set at a middle speed, because the registering operation in the step S

22

receives a low resistance. Also, as the possibility of skew feed is low during sheet feeding, the amount of pressing to the LF roller

109

need not be large so that the registration pulse number P

5

is selected small.

In case the sheet type information received by the ASF

1

indicates an envelope, the ASF control unit

201

selects a driving table T

3

. As the envelope shows a high resistance in feeding, particularly in the registering operation in the step S

22

, the drive speed is selected lower in comparison with the case of ordinary paper, thereby securing a large torque, in order to prevent the sheet feeding motor

27

from stepping out of the synchronization. On the other hand, as the envelope tends to cause a skew feed in the course of feeding in comparison with other sheet types, the registration pulse number P

5

in the step S

22

is selected at a middle value, which is larger than in the table T

1

for the ordinary paper. Thus, the leading end of the envelope is pressed by a larger amount to the LF roller

109

, and the leading end of the envelope can be more securely registered.

Also, in case the sheet type information indicates glossy paper, the ASF control unit

201

selects a driving table T

4

. The glossy paper shows a large resistance in the registering operation, but tends to generate less skewing. For this reason, in the driving table T

4

, the driving speed is selected low while the registration pulse number P

5

is selected small as in the ordinary paper.

In case the sheet type information indicates a postcard, the ASF control unit

201

selects a driving table T

2

. Since the postcard does not show a large resistance in the registering operation, the driving speed in the registering operation is selected at a middle value as in the ordinary paper.

On the other hand, if the LF roller

109

of the printer and the sheet feeding roller

19

of the ASF rotate simultaneously in the state shown in

FIG. 37

, a rigid sheet such as a postcard is not easily deformed in the course of conveyance, so that the sheet feeding roller

19

of the larger peripheral speed may forcedly press in the postcard against the frictional force of the LF roller

109

, whereby the leading end of the postcard may be conveyed in excess of the rotation amount R

3

of the LF roller and the obtained print may become improper. In order to avoid such situation, in the driving table T

2

, the registration pulse number P

5

in the step S

22

is selected as large as possible. More specifically, it is set as a variable, represented by P

5

=Pmax−Pc and determined by the driving pulse number for the reverse rotation of the sheet feeding motor

27

required until the detection of the sheet

200

by the sheet end sensor

108

. Thus, regardless of when the sheet

200

is detected by the sheet end sensor

108

, the total pulse number of the reverse rotation of the sheet feeding motor

27

becomes Pmax at the end of execution of the step S

22

. Stated differently, the toothless portion

19

b

of the sheet feeding roller gear

19

a

securely rotates to a position of disengagement opposed the reverse rotating planet gear

35

. Therefore, after the end of the step S

22

, the rotational phase of the sheet feeding roller

19

is significantly advanced from the initial position, and, if the sheet feeding roller

19

rotates in the step S

40

, the phase thereof promptly returns to the initial position. Consequently the postcards stacked on the pressure plate

26

are promptly separated from the sheet feeding rubber member

23

immediately after the start of the synchronous drive of the LF roller

109

and the sheet feeding roller

19

, so that the sheet feeding roller

19

no longer presses in the postcard against the frictional force of the LF roller

109

.

Also in case the sheet type information received by the ASF

1

from the printer

101

indicates a sheet type for which the ASF

1

is not prepared or does not indicate the sheet type, the ASF control unit

201

selects a driving table T

5

. The driving table T

5

of the present embodiment has values the same as those in the driving table T

2

for the postcard, but it is naturally possible, depending on the contemplated conditions, to provide the table T

5

with values the same as those of the table for other sheet types or with values completely different from those of other tables.

According to the present invention, as explained in the foregoing, the second guide member of the sheet feeding apparatus is disposed and displaced toward an inner side of the sheet, with respect to the first guide member of the recording apparatus, so that the automatically fed sheet can be prevented from interfering with the first guide member, and there can therefore be avoided a skew feed of the sheet, damage to the sheet end or sheet jamming resulting from such interference.

Also, as there is not required a strict relative positional relationship between the first and second guide members, it is not necessary to employ highly precise parts and it is rendered possible to avoid an increase in the cost.

Furthermore, even if the sheet generates skewing of a certain extent, it can be prevented from interfering with the first guide member, and there can therefore be avoided the skew feed of the sheet, damage to the sheet end or sheet jamming resulting from such interference.

Also, by displacing the image recording position in the transverse direction of the sheet in the case of automatic sheet feeding toward the inner side of the sheet, in comparison with that in the case of manual insert sheet feeding, by an amount approximately equal to the displacement amount between the first and second guide members, it is rendered possible to record the image in a same position regardless of whether the sheet feeding is executing automatically or in manual insert, thereby avoiding a drawback resulting from the difference in the recording position (for example difference in the recording position on the preprinted sheet).

Number	Name	Date
5005025	Miyakawa et al.	Apr 1991
5065158	Nojima et al.	Nov 1991
5170184	Hanabusa et al.	Dec 1992
5238235	Nitta et al.	Aug 1993
5291224	Asano et al.	Mar 1994
5379998	Nakagawa	Jan 1995
5480247	Saikawa et al.	Jan 1996
5506606	Saikawa et al.	Apr 1996
5524874	Tojima	Jun 1996
5531431	Saito et al.	Jul 1996
5610636	Hanabusa et al.	Mar 1997
5636929	Asano et al.	Jun 1997
5697716	Akahane	Dec 1997
5733055	Hiramatsu et al.	Mar 1998
5823522	Fujiwara et al.	Oct 1998
5847719	Yamaguchi et al.	Dec 1998
5877783	Iwasaki et al.	Mar 1999
5892523	Tanaka et al.	Apr 1999

Number	Date	Country
403128828	May 1991	JP
404049144	Feb 1992	JP
6-183582	Jul 1994	JP

Image forming apparatus

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (1)

US Referenced Citations (18)

Foreign Referenced Citations (3)