Z-fold print media handling system

FIELD OF THE INVENTION

The present invention relates generally to printing mechanisms, and more particularly to a system for handling accordion-fold or Z-fold print media, such as for printing banners and the like, using an inkjet printing mechanism without needing a bulky and noisy tractor-feed mechanism.

BACKGROUND OF THE INVENTION

Inkjet printing mechanisms use cartridges, often called “pens,” which shoot drops of liquid colorant, referred to generally herein as “ink,” onto a page. Each pen has a printhead formed with very small nozzles through which the ink drops are fired. To print an image, the printhead is propelled back and forth across the page, shooting drops of ink in a desired pattern as it moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as those using piezoelectric or thermal printhead technology. For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481, both assigned to the present assignee, Hewlett-Packard Company. In a thermal system, a barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heater elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor. By selectively energizing the resistors as the printhead moves across the page, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart or text).

To clean and protect the printhead, typically a “service station” mechanism is mounted within the printer chassis so the printhead can be moved over the station for maintenance. For storage, or during non-printing periods, the service stations usually include a capping system which hermetically seals the printhead nozzles from contaminants and drying. Some caps are also designed to facilitate priming, such as by being connected to a pumping unit that draws a vacuum on the printhead. During operation, clogs in the printhead are periodically cleared by firing a number of drops of ink through each of the nozzles in a process known as “spitting,” with the waste ink being collected in a “spittoon” reservoir portion of the service station. After spitting, uncapping, or occasionally during printing, most service stations have an elastomeric wiper that wipes the printhead surface to remove ink residue, as well as any paper dust or other debris that has collected on the printhead.

To print an image, the printhead is scanned back and forth across a printzone above the sheet, with the pen shooting drops of ink as it moves. By selectively energizing the resistors as the printhead moves across the sheet, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart or text). The nozzles are typically arranged in linear arrays usually located side-by-side on the printhead, parallel to one another, and perpendicular to the scanning direction, with the length of the nozzle arrays defining a print swath or band. That is, if all the nozzles of one array were continually fired as the printhead made one complete traverse through the printzone, a band or swath of ink would appear on the sheet. The width of this band is known as the “swath width” of the pen, the maximum pattern of ink which can be laid down in a single pass. The media is moved through the printzone, typically one swath width at a time, although some print schemes move the media incrementally by for instance, halves or quarters of a swath width for each printhead pass to obtain a shingled drop placement which enhances the appearance of the final image.

The picking and movement of print media through the printzone of an inkjet printing mechanism is the subject addressed herein. The print media, may be any type of substantially flat material, such as plain paper, specialty paper, card-stock, fabric, transparencies, foils, mylar, etc., but the most common type of medium is paper. For convenience, we will discuss printing on paper as a representative example of these various types of print media. The media may be supplied to the printing mechanism in a variety of different configurations. For instance, in desktop inkjet printers, paper is typically supplied in a stack of cut-sheets, such as letter size, legal size, or A-4 size paper, which are placed in an input tray. Typically, sheets are sequentially pulled from the top of the stack and printed on, after which they are deposited in an output tray. Other types of inkjet printing mechanisms feed the paper from a continuous roll, such as an inkjet plotter. Upon completion of plotting an image or drawing on a portion of the continuous roll, the plotter has a severing mechanism to cut the newly printed sheet from the remainder of the roll.

It would be desirable to have an inkjet printing mechanism which can print on both Z-fold media and conventional cut-sheets of media A Z-fold or accordion folded stack of media has each sequential sheet joined to the adjacent sheet along a fold, with the sheets being bent back onto one another into a Z-shape when viewed from the side. Along each side, conventional Z-fold paper has border extensions with a series of evenly-spaced holes therethrough which are engaged by sprockets of a tractor-feed mechanism on the printer to advance the media through the printzone. Typically Z-fold paper came supplied in a letter sized stack, with perforations along the folds at the top and bottom of each sheet to assist in separating the sheets upon completion of the print job. The border extensions with the tractor feed holes are also joined to the side edges of the media at perforations, which enables separation of the borders from the sheet upon completion of the print job. Unfortunately, the tractor-feed mechanisms were very expensive to build, and often noisy in operation. Furthermore, most of these tractor-fed printers were bulky, increasing the overall size or “footprint” of the printer, so excessive desk top space in the work environment was occupied by these earlier printers.

Yet it would be desirable to use Z-fold paper in a conventional cut-sheet inkjet printing mechanism without a costly tractor-feed. Z-fold media is particularly useful for printing banners, extended graphs, continuous scrolls or outlines of text, and a variety of other images, such as artwork and the like. The versatility of an inkjet printing mechanism would be greatly enhanced if it could feed not only cut-sheets of paper but also Z-fold media. Unfortunately, conventional inkjet printing mechanisms are unable to feed a Z-fold stack of paper from a cut-sheet input tray. By tearing the border extensions off of a Z-fold paper stack, the Z-fold paper will fit in the input tray, but conventional inkjet printing mechanisms are unable to pick the Z-fold media from the tray. Because the Z-fold sheets are physically attached to one another, often the conventional printer tries to pick the entire stack all at once, leading to a significant paper jam. This problem is often encountered in cut-sheet media feeding, and is known in the art as a “multiple pick,” where several sheets are picked from the input tray all at once.

For cut-sheet media, this multiple pick problem is often remedied by using a friction separator pad at the edge of the input tray, where media begins to enter the feed zone. The media drive rollers feed the sheet through the feed zone. If the second sheet from the top of the stack moves with the first sheet, the second sheet is driven over a friction separator pad. The coefficient of friction of the friction separator pad to the media is higher than the coefficient of friction between the two media sheets. Thus, the second sheet stops on the separator pad and does not continue to be fed through the mechanism. This prevents a multiple pick. Unfortunately, this conventional manner of preventing multiple picks with cut-sheet media does not work with a Z-fold stack of media because the sheets are all attached, and the first sheet pulls in the second sheet, the third sheet, etc.

For cut-sheet media, sheets left on the separator pad are pushed off the separator pad by a kicker. As the first sheet moves through the feed zone, the trailing edge of the first sheet eventually passes across the feed zone entrance. This trailing edge releases or activates the kicker which pushes the second sheet off of the separator pad and back into the input tray. Without a kicker, the number of multiple picks would increase. For instance, if this partially fed second sheet was not kicked back and the operator added more media on top of the existing media in the input tray, then a multiple pick usually occurs near this remaining partially fed sheet and the new media which has been loaded on top of it. Thus, kickers play an important role in preventing multiple picks when using cut-sheet media. Unfortunately, this conventional kicker method of pushing media off the friction separator pad is totally ineffective to prevent Z-fold media multiple picks. Since the kicker is not mechanically activated until the trailing edge of the last sheet passes through the feed zone entrance, any multiple picks of the Z-fold stack have already occurred when the kicker is finally activated. Thus, the kicker has no function in Z-fold media picking.

Other solutions were also tried to feed Z-fold media. An earlier system tested by the inventors used a hinged guide wall that was elevated by a user when feeding Z-fold paper. Unfortunately, this system was extremely cumbersome. This system required removal of the output tray, and an elaborate threading scheme to insert the leading edge of the Z-fold stack into the media pick area. This loading technique was complex and not very “user friendly.” It required a good degree of manual dexterity to thread the media, and it was not intuitive or easy to remember. Most users want to see their image printed, and they do not want to be bothered by elaborate and time-consuming media loading schemes.

Thus, a need exists for a versatile, compact and economical inkjet system mechanism, capable of feeding both cut-sheets of media and Z-fold media, which is quiet and easy to use.

SUMMARY OF THE INVENTION

According to one aspect of the invention, a method of printing on a Z-fold media from an input of an inkjet printing mechanism is provided. The printing mechanism has an inkjet printhead that prints on media in a printzone. The Z-fold media includes a first sheet that defines a leading edge and a subsequent second sheet. The second sheet is attached to the first sheet in a Z-fold arrangement, with a first surface of the first sheet in contact with a first surface of the second sheet. The method includes the step of incrementally advancing the leading edge of the Z-fold media from the input toward the printzone in a series of forward steps through frictional engagement with a second surface of the first sheet, which is opposite the first surface of the first sheet. Each of these forward steps of the series is separated in time by a pause. In a separating step, the first surface of the first sheet of Z-fold media is separated from the first surface of the second sheet during said advancing step. After the separating step, in a moving step, the Z-fold media is moved into the printzone to receive ink ejected from the printhead.

According to another aspect of the invention, a method is provided for printing on either cut-sheet media or on Z-fold media when loaded in an input of an inkjet printing mechanism, where the printing mechanism has an inkjet printhead that prints on media in a printzone. The method includes the step of adjusting a printhead to media spacing, defined by a distance between the printhead and media when in the printzone for printing, to a cut-sheet spacing for printing on cut-sheet media or to a Z-fold spacing for printing on Z-fold media. In a monitoring step, the printhead to media spacing is monitored to determine whether the printhead to media spacing is at the cut-sheet spacing or at the Z-fold spacing. In an advancing step, the loaded media is advanced from the input to the printzone to receive ink ejected from the printhead.

According to a further aspect of the invention, a method is provided for printing on this Z-fold media in an inkjet printing mechanism, including the step of advancing the leading edge of the Z-fold media from the input toward the printzone through frictional engagement of a roller member with a second surface of the first sheet which is opposite the first surface of the first sheet. During the advancing step, the first sheet and the second sheet are simultaneously bent around the roller member in a bending step. During the bending step, in a separating step, the first surface of the first sheet is separated from the first surface of the second sheet. After the separating step, the Z-fold media is moved into the printzone to receive ink ejected from the printhead in a moving step. In the illustrated embodiment, a series of other steps are performed before printing to separate the Z-fold sheets of media, and to prevent fold failures, a significant problem encountered during development of the claimed invention.

According to an additional aspect of the invention, a method is provided for inkjet printing on this Z-fold media, where the Z-fold media also has a last sheet defining a trailing edge and having an outer surface. The method includes the step of advancing the leading edge of the Z-fold media from the input toward the printzone through frictional engagement of a roller member with a second surface of the first sheet which is opposite the first surface of the first sheet. During the advancing step, in a gripping step, the outer surface of the last sheet is gripped with a first friction member located at the input. During the gripping step, the first surface of the first sheet is separated from the first surface of the second sheet by pulling the first sheet with the roller member toward the printzone in a separating step. After the separating step, the Z-fold media is moved into the printzone to receive ink ejected from the printhead in a moving step.

According to still another aspect of the invention, an inkjet printing mechanism is provided for printing on either cut-sheet media, or on Z-fold media, which may use the method steps described above. In particular, a media selection monitoring mechanism is provided to monitor which type of media, cut-sheet or Z-fold has been selected by an operator. The printing mechanism has a controller that includes a monitoring portion responsive to the media selection monitoring mechanism to determine whether the printhead to media spacing has been adjusted for cut-sheet media or for Z-fold media.

An overall goal of present invention is to provide a Z-fold media handling system for an inkjet printing mechanism which is also capable of feeding conventional cut-sheets of media.

A further goal of present invention is to provide an inkjet printing mechanism capable of using both Z-fold and cut-sheet media which is easy to use, economical, and provided in a compact inkjet printing mechanism.

Another goal of present invention is to provide a method of picking and feeding Z-fold media using an inkjet printing mechanism that is also capable of printing on cut-sheet media, without inducing fold failures in the Z-fold media.

An additional goal of the present invention is to provide an economical method of operating an inkjet printing mechanism which optimizes the print quality of an image when printed on either Z-fold or cut-sheet media, and which operates quietly, with minimal user intervention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a fragmented perspective view of one form of an inkjet printing mechanism, here an inkjet printer, including one form of a Z-fold media handling system of the present invention.

FIGS. 2-3

are adjoining portions of a flow chart illustrating one form of a method of operating the Z-fold media handling system of

FIG. 1

, including an initial loading step, followed by steps

1

through

9

, and ending with a printing step.

FIG. 4

is an enlarged side elevational, sectional view of the components of the Z-fold media handling system of FIG.

1

.

FIGS. 5-13

are fragmented, sectional, side elevational views of the Z-fold media handling system of

FIG. 1

, showing various stages of operation according to the flow chart of

FIGS. 2 and 3

, as follows:

FIG. 5

shows the initial loading of a Z-fold stack of media;

FIG. 6

shows a first step;

FIG. 7

shows a second step;

FIG. 8

shows a third step;

FIG. 9

shows both a fourth step and a sixth step;

FIG. 10

shows a fifth step;

FIG. 11

shows a seventh step;

FIG. 12

shows an eighth step; and

FIG. 13

shows a ninth step.

FIG. 14

is a fragmented perspective view of the inkjet printer of

FIG. 1

, with several components removed to show the operation of the media select lever.

FIGS. 15 and 16

are fragmented, sectional, side elevational views taken along lines

15

—

15

of

FIG. 14

, with

FIG. 15

showing the printhead-to-media spacing adjusted for Z-fold media, and

FIG. 16

showing the printhead-to-media spacing adjusted for cut-sheet media.

FIGS. 17-19

are perspective views of a feedback portion of the Z-fold media handling system of

FIG. 1

, showing various stages of operation as follows:

FIG. 17

shows a rest state before the feedback routine begins;

FIG. 18

shows the beginning of the feedback routine; and

FIG. 19

shows the end of the feedback routine.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1

illustrates an embodiment of an inkjet printing mechanism, here shown as an inkjet printer

20

, constructed in accordance with the present invention, which may be used for printing for business reports, correspondence, desktop publishing, artwork, and the like, in an industrial, office, home or other environment A variety of inkjet printing mechanisms are commercially available. For instance, some of the printing mechanisms that may embody the present invention include plotters, portable printing units, copiers, cameras, video printers, and facsimile machines, to name a few. For convenience the concepts of the present invention are illustrated in the environment of an inkjet printer

20

.

While it is apparent that the printer components may vary from model to model, the typical inkjet printer

20

includes a chassis

22

surrounded by a housing or casing enclosure

24

, typically of a plastic material. Sheets of print media are fed through a printzone

25

by an adaptive print media handling system

26

, constructed in accordance with the present invention for feeding both cut-sheet and Z-fold stacks of media. The print media may be any type of suitable sheet material, such as paper, card-stock, transparencies, mylar, and the like, but for convenience, the illustrated embodiment is described using paper as the print medium. The print media handling system

26

has a feed or input tray

28

for storing sheets of paper before printing. A series of motor-driven paper drive rollers described in detail below (items

90

FIGS. 4-16

) may be used to move the print media from tray

28

into the printzone

25

for printing. After printing, the sheet then lands on a pair of retractable output drying wing members

30

, shown extended to receive the printed sheet. The wings

30

momentarily hold the newly printed sheet above any previously printed sheets still drying in an output tray portion

32

before retracting to the sides to drop the newly printed sheet into the output tray

32

. The media handling system

26

may include a series of adjustment mechanisms for accommodating different sizes of print media, including letter, legal, A-4, envelopes, etc., such as an envelope feed slot

34

, and a sliding length adjustment lever

35

.

The printer

20

also has a printer controller, illustrated schematically as a microprocessor

36

, that receives instructions from a host device, typically a computer, such as a personal computer (not shown). Indeed, many of the printer controller functions may be performed by the host computer, by the electronics on board the printer, or by interactions therebetween. As used herein, the term “printer controller

36

” encompasses these functions, whether performed by the host computer, the printer, an intermediary device therebetween, or by a combined interaction of such elements. The printer controller

36

may also operate in response to user inputs provided through a key pad

38

located on the exterior of the casing

24

. A monitor coupled to the computer host may be used to display visual information to an operator, such as the printer status or a particular program being run on the host computer. Personal computers, their input devices, such as a keyboard and/or a mouse device, and monitors are all well known to those skilled in the art.

A inkjet printhead carriage

40

is slideably supported by a guide rod

42

for travel back and forth across the printzone

25

when driven by a carriage propulsion system, here shown as including an endless belt

44

coupled to a carriage drive DC motor

46

. The carriage propulsion system may also have a position feedback system, such as a conventional optical encoder system, which communicates carriage position signals to the controller

36

. For instance, an optical encoder reader may be mounted to carriage

40

to read an encoder strip

47

extending along the path of carriage travel. The carriage drive motor

46

then operates in response to control signals received from the printer controller

36

. One suitable carriage system is shown in U.S. Pat. No. 4,907,018, assigned to the present assignee, the Hewlett-Packard Company.

The carriage

40

is also propelled along guide rod

38

into a servicing region, as indicated generally by arrow

48

, located within the interior of the casing

24

. The servicing region

48

may house a conventional service station (not shown), which may provide various conventional printhead servicing functions as described in the Background portion above. A variety of different mechanisms may be used to selectively bring printhead caps, wipers and primers (if used) into contact with the printheads, such as translating or rotary devices, which may be motor driven, or operated through engagement with the carriage

40

. For instance, suitable translating or floating sled types of service station operating mechanisms are shown in U.S. Pat. Nos. 4,853,717 and 5,155,497, both assigned to the present assignee, Hewlett-Packard Company. A rotary type of servicing mechanism is commercially available in the DeskJet® 820C and 870C color inkjet printers, sold by the Hewlett-Packard Company.

In the printzone

25

, the media sheet receives ink from an inkjet cartridge, such as a black ink cartridge

50

and/or a color ink cartridge

52

. The cartridges

50

and

52

are also often called “pens” by those in the art. The illustrated color pen

52

is a tri-color pen, although in some embodiments, a set of discrete monochrome pens may be used. While the color pen

52

may contain a pigment based ink, for the purposes of illustration, pen

52

is described as containing three dye based ink colors, such as cyan, yellow and magenta The black ink pen

50

is illustrated herein as containing a pigment based ink. It is apparent that other types of inks may also be used in pens

50

,

52

, such as paraffin based inks, as well as hybrid or composite inks having both dye and pigment characteristics.

The illustrated pens

50

,

52

each include reservoirs for storing a supply of ink. The pens

50

,

52

have printheads

54

,

56

respectively, each of which has an orifice plate with a plurality of nozzles formed therethrough in a manner well known to those skilled in the art. The illustrated printheads

54

,

56

are thermal inkjet printheads, although other types of printheads may be used, such as piezoelectric printheads. The printheads

54

,

56

typically include a substrate layer having a plurality of resistors which are associated with the nozzles. Upon energizing a selected resistor, a bubble of gas is formed to eject a droplet of ink from the nozzle and onto media in the printzone

25

. The printhead resistors are selectively energized in response to enabling or firing command control signals, which may be delivered by a conventional multi-conductor strip

58

from the controller

36

to the printhead carriage

40

, and through conventional interconnects between the carriage and pens

50

,

52

to the printheads

54

,

56

.

Z-Fold Print Media

Handling System

FIGS. 2 and 3

together form a flow chart

60

which illustrates one manner of operating the Z-fold media handling system

26

in accordance with the present invention. The method starts with the user loading media into the input tray

28

as an initial step, followed by Steps

1

through

9

, which are assigned item numbers

64

,

66

,

68

,

70

,

72

,

74

,

76

,

78

and

80

respectively, with the final step of beginning the print job being indicated as item number

82

. In flow chart

60

, the first through the ninth steps

64

-

80

together define one form of a Z-fold media feeding routine

84

in accordance with the present invention.

To accomplish the Z-fold feeding routine

84

, the Z-fold media handling system

26

, shown in detail in

FIG. 4

, may be used, although it is apparent that other inkjet printing mechanisms may be used to implement the illustrated method

84

.

FIG. 5

shows the initial step

62

, where a stack of Z-fold media

85

is loaded into the input feed tray

28

. The Z-fold stack

85

includes an upper or first sheet

86

, which has a leading edge

88

. The other end of the first sheet

86

is attached at a fold to a second sheet

89

of stack

85

, etc., for the desired number of sheets in the stack. Usually the sheets are connected together with a series of perforations along the folds, which allow the sheets to be easily torn apart by hand to separate the sheets of one print job from the remainder of the Z-fold supply. The trailing edge of the Z-fold stack

85

may be located at either end of the input feed tray

28

, that is adjacent the length adjuster

35

, or at the opposite end of the feed tray

28

.

In

FIG. 4

, the Z-fold media handling system

26

is shown as including a drive roller

90

, which may be a single roller or several discrete rollers, preferably three or four such rollers

90

(see FIG.

14

), and a lower pinch roller

91

preferably adjacent each of the drive rollers

90

. The drive rollers

90

may be mounted along a common shaft

92

, which may be coupled to a conventional drive motor and gear assembly, such as a stepper motor assembly

93

(see FIG.

1

). In response to instructions received from controller

36

via a control signal, the stepper motor

93

incrementally advances the drive rollers

90

to pull a sheet of media into the printzone

25

where it receives ink selectively ejected from pens

50

,

52

. Each incremental advance of the drive motor

93

is referred to in the art as a “step,” which is not to be confused with the various stages or “steps”

64

-

80

of the Z-fold media feed routine

84

. It is apparent that other types of media drive motors may also be used, such as an encoded DC (direct current) drive motor to incrementally advance the media The concepts illustrated herein may be applied to these different types of motors with various modifications that are within the capabilities of those skilled in the art. For instance, when using a DC motor, an encoder feed back system may be used to determine the relative degree of travel of the media through the printer, rather than counting motor steps.

A media sensor

94

may be mounted along the upper periphery of the drive roller

90

. The media sensor

94

provides feed-back to the controller

36

as to when the media leading edge

88

has passed through a feed path

95

from under a media guide

96

and into contact with an upper pinch roller or rollers

98

. The upper pinch rollers

98

assist to guide the media downwardly into the printzone

25

, as indicated by the dashed line

86

′ in

FIGS. 4 and 5

.

The Z-fold media handling system

26

includes a raiseable pressure or lift plate

100

, which lays along a portion of the underside of the input tray

28

, and is pivoted to the chassis

22

at a pair of pivot attachment points

102

. As shown in

FIG. 5

, the stack of media

85

is loaded into printer

20

to overlay the pressure plate

100

, with the stack pushed forward until the leading edge

88

of the top sheet

86

, as well as the edges of each sheet in the stack under edge

88

, are in contact with a loading wall

104

. As best shown in

FIG. 4

, the pressure plate

100

carries a first friction member, such as a cork pad

105

located along an upper surface of the pressure plate

100

, adjacent the loading wall

104

. A second friction member, here, a friction separator pad member

106

, is mounted on the chassis

22

along a portion of the loading wall

104

, preferably adjacent a conventional kicker member

107

. The kicker

107

normally is spring-biased into a kicking position, which is also the rest state of the kicker. As a sheet of media passes over kicker

107

from the feed tray

28

to the printzone

25

, the spring (not shown) is stressed and the kicker is pushed into a feed position within a recess in the loading wall

104

. The kicker

107

is shown pivoted outwardly in

FIG. 4

into the kicking position to push cut-sheets of media back into the input tray

28

.

In a conventional cut-sheet feeding system, the media feed path

95

begins at the input tray

28

where the pressure plate

100

raises to bring a single sheet of cut media into contact with the drive rollers

90

. The drive rollers

90

then pull the single sheet of cut media through the feed zone entrance

108

, between the drive rollers

90

and lower pinch rollers

91

. The rollers

90

continue to pull the sheet under guide

96

, past the media sensor

94

, under the upper pinch rollers

98

, then downwardly as indicated by dashed line

86

′ into the printzone

25

. In the printzone

25

, the media sheet is supported by a media support member, such as a platen member or pivot assembly

109

, preferably with a reverse-bowed concave tensioning between the pinch rollers

98

and the pivot

109

, which provides a desired printhead to media spacing between the printheads

54

,

56

and the sheet of media in the printzone

25

.

After each pass of the carriage

40

across the printzone

25

, the media is then advanced by continuing to turn the drive rollers

90

in a forward or loading direction, here defined in

FIGS. 5-13

as being a counterclockwise direction indicated by curved arrow

111

. The media sheet is incrementally advanced through the printzone

25

until the entire image has been printed through consecutive passes of the printheads

54

,

56

over the media. Upon completion of the print job, the printed sheet is ejected onto the output wings

30

, where it dries momentarily before being lowered onto the output tray

32

. When printing on a stack of Z-fold media

85

, advantageously this same feed path

95

, from the entrance

108

to the output on wings

30

, is used with the illustrated media handling system

26

.

When printing on a series of consecutive cut-sheets, the kicker

107

is activated between sheets, as well as after the trailing edge of the last sheet passes over the kicker, whether this last sheet is cut-sheet media or the end of a Z-fold banner print job. Typically the body of the sheet of media, between the leading and trailing edges, holds the kicker in the feed position within its storage recess in the loading wall

104

. When the trailing edge passes over the kicker, the kicker is released to travel to the kicking position. When released, the kicker

107

rotates out, of its storage recess and pushes the remainder of the cut-sheet stack back into the input tray

28

to prevent a multiple pick.

The separator pad

106

also plays a major roll in preventing cut-sheet double picks, which are a commonly occurring subset of the multiple pick phenomenon. In a double pick scenario, two sheets of media are advanced by the drive rollers

90

toward the feed path entrance

108

. The lower sheet encounters the high-friction separator pad

106

. The separator pad

106

grips the lower sheet while the drive rollers

90

continue to advance the upper sheet toward the feed path entrance

108

. Since the coefficient of friction between the upper and lower sheets of media is less than the coefficients between the upper sheet and drive rollers

90

, and between the lower sheet and the separator pad

106

, the upper and lower sheets are pulled apart The upper sheet continues through the feed path

95

to the printzone

25

, with the trailing edge of the upper sheet activating the kicker

107

, which then pushes the lower sheet back into the input tray

28

.

Thus, in a cut-sheet media feed system, sheet-to-sheet media separation basically occurs on the separator pad

106

. The portion of method

84

for sheet-to-sheet separation of Z-fold media is quite different from the cut-sheet separation scheme. Here, the term “separation” refers to the relative sliding apart of adjacent sheets in the input tray

28

, with an initial goal in Z-fold feeding being forward movement of the leading edge

88

toward the feed path

95

, while leaving the remainder of the stack

85

in the input tray

28

. In the Z-fold feeding routine

84

, sheet-to-sheet separation is primarily accomplished before the Z-fold media encounters the high friction separator pad

106

on the way toward the printzone

25

for printing. In the Z-fold scheme, the friction member on the pressure plate

100

, here the cork pad

105

, is primarily responsible for sheet-to-sheet separation, as described in further detail below. Thus, in the Z-fold routine, the majority of the sheet-to-sheet separation action occurs upstream (at pad

105

) from the location (at pad

106

) of the conventional separation action for cut-sheet media. Indeed, one of the primary functional goals used in implementing routine

84

is to keep the media stack

85

off of the separator pad

106

, although the leading edge

88

is allowed to travel back and forth over the separator pad

106

during different stages of the routine, as described below.

FIG. 5

shows the completion of the initial operator involvement at step

62

, where the Z-fold stack of media

85

has been loaded into feed tray

28

and pushed against the loading wall

104

. At this stage, the operator also moves a media select or “banner” lever

110

, located under the input tray

28

, to the right as shown in FIG.

1

. To assist the operator in remembering which way to move the lever

110

for cut-sheet and Z-fold banner-type media, the lever advantageously has a Z-fold icon appearing on right side of the lever

110

, and a cut-sheet icon appearing on the left side. Thus, to return to normal cut-sheet feeding, the operator moves the lever

110

to the left. It is apparent that the lever

110

may be located in a variety of other locations, although by placing it at the input tray

28

it is readily apparent to the operator while loading media, making it more likely that the operator will remember to move the lever when changing types of media Indeed, the operation of the media select lever

110

may be totally eliminated in some embodiments, having the selection occur at a host computer which then communicates with the printer controller

36

to shift to the desired type of media. Such a selection from the host computer may be made manually by an operator, or it may be automatically transmitted to the printer controller

36

depending on the size and type of image being printed. In the illustrated embodiment, the media select lever

110

operates to adjust the printhead-to-media spacing, as described further below with respect to

FIGS. 14-16

.

The Z-fold media handling system

26

and method

84

will now be described with respect to flow chart

60

in

FIGS. 2 and 3

, and the illustrated printer

20

in

FIGS. 4-13

. After the Z-fold media stack

85

has been loaded into the input tray

28

(FIG.

5

), and the media select lever

110

moved to the Z-fold position, the operator may then initiate a print job from a host computer, as indicated by arrow

62

′ in flow chart

60

.

As shown in

FIG. 6

, the first step

64

comprises a registering step to indicate to the controller

36

where the leading edge

88

of the banner paper

85

is located. In the first step

64

, with the lift plate

100

elevated and the pivot

109

lowered to their pick positions, the drive rollers

90

rotate in the forward direction

111

to move the leading edge

88

of the first media sheet

86

through the feed path

95

and into contact with media sensor

94

. Sometimes only the first sheet

86

is pulled into the printzone, but other times, particularly if the Z-fold stack is only a few sheets thick, the entire stack

85

is pulled into the feed path

95

. Even if the entire stack

85

is pulled through, sensor

94

still registers the location of the leading edge. While pulling of the entire stack

85

through feed path

95

may at first blush seem like a malfunction, quite to the contrary, it is an advantage in beginning sheet-to-sheet separation in the media stack

85

because it creates a relative motion between adjacent sheets. When bending the whole stack

85

around the drive rollers

90

, the angular velocity of the sheets is the same, but the surface velocity of adjacent sheets changes as they are pulled around the drive rollers

90

. That is, the inner-most first sheet

86

has a lesser distance to travel around rollers

90

than the second sheet

89

, the second sheet has a lesser distance to travel than the third sheet, etc., so these adjacent sheets begin to separate from one another during such an initial Z-fold multiple pick. Using conventional plain Z-fold paper, these multiple Z-fold picks of the entire stack are believed to occur about 20% of the time, whereas, if the stack is pressed together, for instance, manually, then this Z-fold multiple pick may occur at a frequency of about 80%.

At the end of the first step

64

, the media sensor

94

relays information on the location of the leading edge

88

back to the controller

36

. Once this initial position of the Z-fold leading edge

88

is registered by the controller

36

, the second step

66

, as well as the remaining steps

68

-

80

, may be performed reliably. That is, upon finding the leading edge

88

, the controller

36

then starts counting the number of motor steps in routine

84

from a zero reference corresponding to the location of the leading edge at the sensor

94

. Each motor step corresponds to an incremental move of the media, here, approximately equal to 0.085 millimeters ({fraction (1/300)} inch). Upon completion of the first step

64

, a signal

64

′ is communicated to initiate the second step

66

.

In

FIG. 7

, the second step

66

comprising an unloading step is shown as the drive rollers

90

rotate in a backwards or unloading direction (counterclockwise in the FIGS.

4

-

13

), as indicated by curved arrow

112

. Preferably, the drive rollers

90

rotate backwards at a normal speed. Several relative media movement speeds are used here to described the illustrated embodiment of the Z-fold feed routine

84

. As used herein, a “fast speed” is as fast as the drive motor

93

can go without damaging the media or at a speed which is typically limited by the efficiency of the particular motor selected for a given implementation. In the illustrated embodiment, this fast speed is on the order of 12.2 centimeters per second (4.8 inches per second), compared to a normal speed of around 8.4 centimeters per second (3.3 inches per second). From the development work conducted by the inventors, it appears that the faster this “fast” speed is, the better the Z-fold pick routine

84

will perform. In later steps, the speed of the drive rollers

90

is described as a “slow speed,” such as when moving the media forward. Here, the relative degree of “slow” for the best performance the inventors found to be as slow as possible. For instance, the illustrated motor

93

has a slow speed of about 2.0 centimeters per second (0.8 inches per second). It is apparent that there may be other practical limits on the fastest “fast” speed and on the slowest “slow” speed as improvements in motor performance standards are made, but these practical limits will become apparent to those skilled in the art when practicing the concepts illustrated herein. For instance, “too slow” may be the point where throughput performance is severely degraded for minimal benefits in sheet-to-sheet separation; whereas “too fast” may be the point where the media is crumpled, rather than merely pushed backwards.

In the second step

66

, this backward motion of the drive rollers

90

, preferably at a normal speed, here 8.4 centimeters per second (3.3 inches per second), pushes the remainder of the Z-fold stack

85

rearwardly in an unloading motion from the feed path entrance

108

and against the length adjuster

35

at the front of the printer. Indeed, preferably the stack

85

actually moves the length adjuster

35

outwardly away from the printer chassis

22

, as indicated by arrow

114

, from the initial position shown in dashed lines to the final position shown in solid lines in FIG.

7

. For example, for conventional letter size Z-fold media

85

, the length adjuster

35

is moved approximately 1.514 3.0 millimeters in the direction indicated by arrow

114

. Using a conventional stepper motor assembly

93

of the type typically employed in the inkjet printer

20

, the motor

93

moves back-wards a certain number of steps to propel the drive rollers

90

in the unloading direction

112

. The number of steps selected is not only dependent upon the type of motor

93

, but also the diameter of the drive rollers

90

and the configuration of any other components between the input tray

28

and the printzone

25

. In the illustrated embodiment for printer

20

, in the second step

66

, the stepper motor moves backwards a number of steps selected from the range of 1000-1200, with an optimal number of steps for printer

20

being on the order of 1100 steps. It is apparent to those skilled in the art that the number of steps noted herein for practicing method

84

are given by way of illustration only with respect to the printer

20

embodiment, and that the number of steps will vary for different printing mechanism designs. In the illustrated embodiment, one step of the stepper motor

93

is approximately equal to 0.085 millimeters ({fraction (1/300)} inch). This rearward motion of the Z-fold stack

85

moves the media off of the friction separator pad

106

at the top portion of the loading wall

104

. In the illustrated embodiment, the leading edge

88

of the Z-fold stack

85

is moved approximately 1.5-3.0 millimeters away from the loading wall

104

during the second step

66

. Upon completion of the second step

66

, a signal

66

′ is generated to initiate the third step

68

.

Before discussing the remainder of the steps

68

-

80

, it may be helpful to insert Table 1 which lists the direction of motion of rollers

90

, along with the speed and number of steps of the stepper motor

93

which may be used to accomplish the desired Z-fold media pick routine

84

using the illustrated printer

20

. These values are given by way of example only, and they may vary between different types of printing mechanisms; however, the exact selection of motor speed and steps is believed to be within the level of ordinary skill in the art, once the manner of conducting pick routine

84

is understood with reference to the illustrated embodiment. Indeed, using a single speed throughout may even be suitable in some embodiments, although the illustrated embodiment is preferred, particularly when using inkjet printer

20

.

TABLE 1

Illustrated Drive Roller Directions,

Drive Motor Speeds and Distances by Method Step

Method

Roller

Motor

Range of

Optimum

Step

Direction

Speed

Motor Steps

Motor Steps

1

Forward

Normal

Until Leading

Until Leading

Edge is Found

Edge is Found

2

Backward

Normal

1000-1200

1100

3

Forward

Slow

150-250

200

4

Backward

Fast

150-250

200

5

Forward

Slow Stutter

5-15 Repeated

8 Repeated 20

Steps

15-25 Times

Times

6

Backward

Fast

100-180

140

7

Forward

Slow

750-900

830

8

Backward

Normal

400-600

500

9

Forward

Normal

Until Leading

Until Leading

Edge is Found

Edge is Found

In

FIG. 8

, the third step

68

is a separating step where the Z-fold stack

85

is again moved forward by rotating drive rollers

90

in the counterclockwise direction of arrow

111

with the lift plate

100

elevated to a pick position. Preferably, this forward motion of drive rollers

90

is performed slowly for a number of motor steps selected according to Table 1, here approximately 200 steps. This slow forward motion of the drive roller

90

begins to separate the first page

86

from the balance of the media stack

85

, using the friction generated by the cork friction member

105

on pressure plate

100

on the outer surface of the last sheet of the stack

85

. That is, the cork pad

105

holds the stack

85

in place in the feed tray

28

, while the elastomeric surface on the drive rollers

90

pulls the leading edge

88

of the top sheet

86

onto the separator pad

106

and away from the remainder of stack

85

to accomplish sheet-to-sheet separation. Here, the remainder of the stack

85

may remain on the cork friction pad

105

(solid lines in FIG.

8

), or the stack

85

may land on the separator pad

106

(dashed lines in FIG.

8

). Note in these steps, that the pressure plate

100

remains in a raised position with the cork friction pad

105

located adjacent a central one of the drive rollers

90

(see FIG.

14

).

Upon completion of the third step

68

, a signal

68

′ is issued to initiate the fourth step

70

. The fourth step

70

comprises a stack pushing back step. As shown in

FIG. 9

, as the remainder of the stack

85

begins to approach the feed zone entrance

108

, the drive rollers

90

have stopped and reversed in direction to rotate backward as indicated by arrow

112

at a fast speed (see Table 1), for preferably

200

motor steps.

FIG. 9

shows the completion of this backwards travel of the stack

85

. If the stack

85

is tightly compacted and acting as a single sheet, together the third and fourth steps

68

,

70

(

FIGS. 8 and 9

) aid in sheet-to-sheet separation by driving the stack

85

over the friction separator pad

106

. That is, if the bottom sheet also rides up on the separator pad

106

in the third step

68

, this bottom sheet is momentarily gripped by the pad

106

as the drive rollers

90

begin first pushing the top sheets backwards (arrow

112

) in the fourth step

70

. During the fourth step

70

, the entire stack

85

is eventually pushed off of the separator pad

106

, as shown in FIG.

9

. Upon completion of this pushing back of the media stack

85

, a signal

70

′ is generated to initiate the fifth step

72

.

The fifth step

72

is illustrated in

FIG. 10

, where preferably a series of motor steps are initiated to continue separating the first media sheet

86

from the remainder of the stack

85

. In the fifth step

72

, a series of stopping and starting motions are performed, preferably 20 times, where the media drive rollers

90

are moved forward preferably at a slow pace as indicated in Table 1, typically for a very small duration of steps, on the order of 8 steps for each forward motion. Preferably, between each of the 20 forward slow steps, the motion of the drive roller

90

is paused or rested briefly for a short duration, for instance on the order of 50 milliseconds. This stopping and starting action of the fifth step

72

leads to a stuttering action of the drive roller, that is, the printer

20

sounds like it is stuttering, hence, the fifth step is referred to herein as a “stuttering step.” This stuttering step

72

takes advantage of the difference between the effects of static friction and dynamic friction to separate the top sheet from stack

85

. That is, static friction generated between the sheet

86

and roller

90

during the pause between the forward steps tends to be greater than the dynamic friction in the media handling system

26

. Thus, the static friction generated during the pause provides a greater force to pull the top sheet away from the remainder of the sheets in the stack than if only a continual pulling action was provided by driving the rollers at a constant speed. This initial tugging action at the beginning of each stuttering forward step facilitates the separating operation to draw the initial sheet of media

86

into the feed path entrance

108

.

Upon completion of the fifth step

72

, a signal

72

′ is generated to initiate the sixth step

74

, which shown in FIG.

9

. The sixth step

74

is basically a repeat of the fourth step

70

, which moves the balance of the Z-fold stack

85

away from the feed zone entrance

108

.

FIG. 9

shows the drive roller

90

rotating backward again, as indicated by arrow

112

, at a fast speed selected according to Table 1. In the sixth step

74

, preferably the drive motor

93

is moved

140

steps. This rearward or backing up motion of the remainder of stack

85

then facilitates operation of the next step. Indeed, together the fifth and sixth steps

72

,

74

together act as the last opportunity to aid in sheet-to-sheet separation, similar to the pair of early separation steps, the third and fourth steps

68

and

70

. Upon completion of the sixth step

74

, a signal

74

′ is issued to initiate the seventh step

76

.

Before continuing with a discussion of the remainder of the steps, it is worth mentioning one of the major hurtles the inventors encountered while developing the illustrated Z-fold handling routine

84

. During developmental work on method

84

, in addition to the multiple pick problem, another feed failure mode was encountered, one which may be called a “fold failure.” In a fold failure, the Z-fold media folded over on itself in the area where the pages are connected together. Fold failures typically occurred during printing. While printing, the Z-fold paper is metered through the feed path

95

and a natural paper loop

116

(shown in dashed lines in

FIG. 13

) is created in the input tray. The size of loop

116

continues to get smaller as the loop approaches the feed zone entrance

108

. As loop

116

passed along the perforations between joining sheets along the loading wall

104

, occasionally the pick rollers

90

would grab the loop

116

before the media could unfurl, that is, before the media could straighten for feeding through the entrance

108

. In grasping loop

116

, the drive rollers

90

folded and flattened the loop, leaving a triple thick media region for about 0.5-1.5 centimeters across the width of the sheet, creating this “fold failure.” After passing through the narrow feed path

95

and under both sets of pinch rollers

91

and

98

, this triple folded region typically held its folded configuration as it passed under the printheads

54

,

56

. When unfolded by the operator, an unprinted band (a white band when printing on white media) appeared in the image at the location of the fold, often ruining the final image and requiring a total reprint of the image.

These fold failures usually occurred where the second page was attached to the third page, where the fourth page was attached to the fifth page, etc. Fold failures normally do not occur with cut-sheet media. When Z-fold media is picked and fed through the feed zone and a multiple pick has not occurred, fold failures started when the front edge of stack

85

was on top of the friction separator pad

106

instead of being butted against the loading wall

104

of the input tray

28

. Thus, the goal in preventing not only multiple picks, but also to prevent fold failures, is to keep the balance of the stack

85

away from the separator pad

106

. This is accomplished in part by using the cork friction pad

105

on the pressure plate

100

to hold the bottom of the stack

85

in place, while the drive rollers

90

push and pull the top sheets of the stack. This pushing and pulling of the top sheet

86

while holding the bottom of the stack still, separates the top sheet

86

for feeding into the path entrance

108

, while the pushing backwards action (arrow

112

) keeps the stack

85

off of the separator pad

106

. By pushing the stack

85

backward away from the separator pad

106

, fold failures are avoided.

Moving ahead to

FIG. 11

where the completion of the seventh step

76

is shown, the drive rollers

90

have again been rotated in the forward direction

111

at a slow pace, selected according to Table 1, preferably for an optimal duration of

830

steps of motor

93

. This slow forward motion of the seventh step

76

continues to separate the top sheet

86

from the remainder of the Z-fold stack

85

. Also during this seventh step

76

, the leading edge

88

begins to move through the media feed-path

95

past the separator pad

106

and past the lower pinch rollers

94

. In

FIG. 11

, the leading edge

88

is shown as being under guide

96

, although during any particular feed operation, the leading edge

88

may end up at any location in feed path

95

between the lower pinch rollers

91

and the upper pinch rollers

98

(for

FIG. 12

, too). By this stage of operation, the majority of the time the stack

85

now stays off of the separator pad

105

, as shown in

FIG. 11

, although occasionally during some pick routines the stack

85

may creep up onto the separator pad

106

. Upon completion of the seventh step

76

, a signal

76

′ is generated to initiate the eighth step

78

.

The eighth step

78

is illustrated in

FIG. 12

, where several actions occur together. For one, the drive rollers

90

rotate in the backwards direction

112

at a normal speed according to Table 1, preferably for approximately 500 steps of motor

93

. Concurrently with this backward motion of the drive rollers

90

, the printhead carriage

40

releases a media pick clutch

130

(see FIGS.

17

-

19

), which allows the pivot

109

and pressure plate

100

to move to media feed positions. Preferably, the first sheet

86

is grasped between the drive rollers

90

and the lower pinch rollers

91

while the pressure plate

100

is lowered. As shown in

FIG. 12

, the pivot

109

has raised upwardly from the pick position to a preferred printhead-to-media spacing for printing on Z-fold paper. In

FIG. 12

, the pressure plate

100

has dropped to a feed position, so the front edges of the sheets in stack

85

are resting against the loading wall

104

. The rearward motion of the drive rollers

90

pushes the leading edge

88

backwards to prevent the remainder of the Z-fold stack

85

from lurching forward onto the separator pad

106

, which advantageously also avoids fold failures at the feed path entrance

108

. Upon completion of the eighth step

78

, a signal

78

′ is generated to initiate the ninth step

80

.

As shown in

FIG. 13

, during the ninth step

80

the drive rollers

90

rotate in a forward direction

111

to deliver the leading edge

88

,

88

′ of the Z-fold stack

85

into the printzone

25

. The lift plate

100

has been lowered to allow loop

116

to freely feed the remainder of the Z-fold stack through the feed path

95

and then into the printzone

25

to receive ink ejected from the printheads

54

,

56

, as indicated by the dashed line

86

′. Upon delivery of the first sheet of media

86

to the printzone

25

, the ninth step

80

issues a signal

80

′ to the printer controller

36

, which then performs step

82

, which is beginning the print job. In step

82

, the forward motion

111

of the drive rollers continues at a pace determined by the printer controller

36

to print a selected image with optimum quality on the Z-fold sheet

85

. Depending upon the print modes selected, the sheet

85

may be moved forwardly through the printzone

25

a full swath width, or at some incremental value thereof, for each pass of the printheads

54

,

56

across the printzone. During the print job

82

, no further backward motion (direction

112

) of rollers

90

is performed because once started, the Z-fold stack

85

has been found to feed well from the input tray

28

without incurring multiple pick type jams or fold failures. While the rollers

90

could rotate backward during printing, it is believed that such motion may lead to print defects, so only forward motion

111

is used during the printing step

82

.

Turning now to

FIGS. 14-17

, as mentioned briefly above, the media selector lever

110

may be used to adjust the printhead-to-media spacing, a spacing which is known in the art as “pen-to-paper spacing,” since the most common media used is paper. Preferably, the pen-to-paper spacing or “PPS” is increased when printing with Z-fold media to dimension A as shown in

FIG. 15

, over the PPS used for printing cut-sheet media, shown as dimension A′ in

FIG. 16

(A′<A). This increased PPS prevents the upwardly projecting folded perforations or “tents”

118

(

FIG. 15

) in the Z-fold media

85

, as well as any bulges beside downwardly projecting valleys in the folded perforations, from hitting the printheads

54

,

56

during printing. Any such contact of the printheads

54

,

56

with the media

85

could lead to a smeared image, or worse yet, printhead damage for instance, from media fibers being rammed into the printhead nozzles. A preferred manner of accomplishing this PPS adjustment using lever

110

is shown in

FIGS. 14-16

.

In

FIG. 14

, the banner selection lever

110

is shown in solid lines moved to the right in the Z-fold media position to lower the pivot

109

and increase the PPS dimension A to accommodate the Z-fold tents

118

. The cut-sheet position of the banner lever

110

is shown in dashed lines in FIG.

14

. The illustrated media handling system

26

includes a lifter shaft assembly

120

which is pivoted to the chassis

22

along a pivot axis

122

. The lifter shaft assembly

120

has a lower foot portion

124

and an upper leg portion

125

which are biased by a torsional coil spring

126

to pivot in a clockwise direction

128

around axis

122

toward a cut-sheet or rest position shown in

FIG. 16. A

clutch mechanism, such as a clutch disk member

130

is mounted for limited rotation around the drive roller shaft

92

to raise and lower the pivot

109

with respect to the printheads

54

,

56

. That is, counterclockwise rotation (arrow

139

) of the clutch disk

130

rotates the lifter shaft lower foot

124

upwardly in a counterclockwise direction, causing the distal end of foot

124

to push against the under surface of the pressure plate

100

to raise the pressure plate to the media pick and feed positions shown in

FIGS. 6-13

. As described further below with respect to

FIGS. 17-19

, the clutch disk

130

is selectively coupled to the drive motor

93

through operation of the printhead carriage

40

, so the clutch disk may be driven by the motor

93

. The clutch disk

130

defines a clutch pocket

132

which has an edge that is selectively engaged by an upper surface of the leg portion

125

of the lifter shaft assembly

120

.

The banner lever

110

is pivoted near a mid-span point to the chassis

22

at a pivot post

134

. The banner lever

110

has a wedge-shaped head

135

at the distal end of the lever which engages an undersurface of the lifter shaft assembly foot

124

. As shown in

FIGS. 14 and 15

, when an operator moves the banner select lever

110

to the right (Z-fold position), the wedge shaped head

135

moves toward the left and under the lifter shaft foot

124

to elevate foot

124

. Elevating foot

124

pivots the assembly

120

in a counterclockwise direction

136

around axis

122

, so the upper surface of the lifter shaft leg

125

pushes on the edge of the clutch pocket

132

, which rotates the clutch disk member

130

in a clockwise direction

138

. This clockwise rotation

138

of the clutch disk

130

drops the pivot

109

away from the printheads

54

,

56

to lower the media and increase the PPS to dimension A. The additional clearance provided by the larger PPS dimension A for Z-fold prevents printhead crashes with the Z-fold tents

118

or with any bulges adjacent downwardly projecting Z-fold valleys, which are simply folds in a direction opposite to those of the tents

118

.

When the operator decides to return to printing on cut-sheet media, the banner select lever

110

is moved to the left, which moves the wedge-shaped lever head

135

to the right, as indicated in dashed lines in FIG.

14

. In this cut-sheet position, the lever head

135

resides in a recess underneath the lifter shaft foot

124

. Moving the selector lever

110

to the cut sheet position allows the lifter shaft assembly

120

to rotate in the clockwise direction

128

(

FIG. 16

) under the force of the torsional coil spring

126

to the cut-sheet position, where a clutch disk stop

140

comes to rest against a conventional cut-sheet spacing adjuster

141

. Preferably, the cut-sheet spacing adjuster

141

is adjustable with respect to the chassis

22

to set the cut-sheet PPS dimension A′ to a desired level during factory assembly of printer

20

. This downward rotation

128

of the lifter shaft assembly

120

allows the edge of the clutch pocket

132

to ride along the upper surface of the lifter shaft leg

125

, which rotates the clutch disk

130

in a counterclockwise direction

139

under the force of a return spring

142

. The return spring

142

, shown schematically in

FIGS. 15 and 16

, couples the clutch disk

130

and pivot

109

to the chassis

12

to rotate the pivot

109

upwardly to close the PPS dimension A back to a cut-sheet spacing, indicated as dimension A′ (FIGS.

16

and

18

).

To provide feedback to the controller

36

as to what position the media select lever is currently adjusted, a variety of different mechanisms may be used, such as limit switches, and optical or electromagnetic sensors. However, these devices increase the overall number of parts used to make the printer

20

, as well as increasing the assembly cost. Additionally, these devices increase the complexity of the controller

36

, which also adds to the cost of the printer

20

.

FIGS. 17-19

show a banner lever position detection system

150

in accordance with the present invention for determining the position of the banner lever

110

, with the lifter shaft assembly

120

omitted for clarity in these views. This lever detection scheme

150

uses the optical positional feedback system already installed on the printhead carriage

40

. This banner lever position detection system

150

places a physical bump or ridge

152

on the clutch disk

130

. As mentioned briefly above, the printhead carriage

40

is used to alter positions of the pivot

109

and pressure plate

100

between a media pick position (in the first step

64

, and in FIGS.

6

-

11

), and a cut-sheet feed position (

FIG. 16

) or a Z-fold banner feed position (the eighth and ninth steps

78

,

80

, and in

FIGS. 12

,

13

and

15

).

FIGS. 17-19

show how this is accomplished.

At the beginning of the first step

64

, the printhead carriage

40

moves to the far left (as shown in FIGS.

1

and

17

-

19

) and hits a shoulder portion

154

of a clutch actuator mechanism, such as an actuator or arm

155

. The actuator arm

155

also has a head portion

156

, opposite the shoulder

154

. When the carriage

40

pushes the actuator

155

to the far left (FIGS.

18

and

19

), the head

156

pulls a flexible wall portion

158

of clutch

130

into contact with a portion of a bull gear

160

of the stepper motor and gear assembly

93

(see FIG.

1

). The bull gear

160

periphery has media drive teeth

162

formed thereon which are coupled to the stepper motor to pick and feed media. The bull gear

160

also has a face adjacent the clutch

130

with a series of clutch drive teeth

164

formed thereon. The clutch flexible wall

158

of clutch

130

has an outboard surface with teeth (not shown) formed thereon to engage the clutch drive teeth

164

of the bull gear

160

when the carriage

40

moves the actuator

155

to an initial engaged position at the far left of the printer

20

, as shown in FIG.

18

.

Opposite the geared surface of the flexible wall

158

, an inboard surface of wall

158

has a cammed surface or cam

165

formed thereon. The cam

165

has a contour comprising first and second cam portions, here, shown as thick and thin portions

166

and

168

, respectively of wall

158

. The first and second cam portions are separated by a clutch cam feature, such as a clutch bump or ridge, here illustrated as shoulder

152

which joins together the thick and thin portions

166

and

168

. An under surface of the actuator head

156

advantageously serves as a cam follower that rides along a cam surface

165

.

During the media pick routine

84

, the controller

36

monitors the position of the printhead carriage

40

using the encoder strip

47

(FIG.

1

), which provides an indication of when the carriage

40

moves. Of particular interest is when the actuator head

156

slides down the clutch bump shoulder

152

on the clutch disk

130

. How long, i.e., how many steps of the media drive stepper motor

93

are required to reach the clutch bump shoulder

152

, indicates the initial position of the pivot.

109

. By counting the number of motor steps, from the initial position of the pivot

109

, which is adjusted by the operator's positioning of the media select lever

110

, the controller

36

may determine whether the pivot

109

is in the Z-fold printing position (

FIG. 15

, PPS dimension A) or in the cut-sheet printing position (

FIG. 16

, PPS dimension A′). If reading this for the first time, it takes a few moments to figure out this unique inventive concept, as several components are now acting together. While carriage-activated media drive clutch mechanisms have been used in the past, for example as described in U.S. Pat. No. 5,000,594, assigned to the present assignee, Hewlett-Packard Company, this is the first time the inventors are aware of that such a mechanism has been used to provide media-to-printhead spacing information to the controller

36

.

To initiate a media pick (for either Z-fold or cut-sheet media), the carriage

40

pushes on the clutch actuator

155

to engage the flexible wall

158

of clutch

130

with the drive roller bull gear

160

. While the carriage

40

is still pushing on the clutch actuator

155

to keep the gears on the flexible clutch wall

158

engaged with the bull gear face gears

164

, the controller

36

starts the media drive motor

93

turning to move the media drive rollers

90

. The controller then keeps track of the number of motor steps during the first step

64

of method

84

, looking for two points, (1) when the pressure plate

100

raises to pick position, and (2) when the actuator

155

encounters the cam feature or clutch bump

152

. For the illustrated printer

20

, after about

340

steps of this stage of operation, the actuator arm

155

has a locking face

170

which falls into a lock position adjacent a latch surface

172

of the clutch disk flexible wall

158

(FIG.

19

), which through the operation of the lifter shaft assembly

120

(see

FIGS. 15-16

) also raises the pressure plate

100

to the media pick position. During the first portion of this stage of the media pick operation (for both Z-fold and cut-sheet media), from the first step of drive motor

93

up to about step

240

, the controller

36

monitors the position of the carriage

40

through the encoder

47

, while counting the number of media advance steps taken by motor

93

. As the actuator head

156

slides along the clutch disk cam surface

165

, it finally slides down the clutch bump shoulder

152

, causing the carriage

40

to move further to the left, with this change in carriage position being detected by the controller

36

using the encoder strip

47

and the conventional encoder reader mounted on the carriage

40

. For example, the parameter monitored by the controller

36

may be the number of steps that the media drive motor

93

makes from the start position until the change in the position of the printhead carriage

40

as it slides over the clutch bump feature

152

. It is apparent that other parameters may be used to detect this change in carriage position, such as time of rotation, rate of change of carriage location or motor rotation, threshold levels for distances, degrees of rotation, etc., any of which reflects this difference in the angular position of the pivot

109

by monitoring the rotation of the drive motor

93

from a starting position to an ending position defined by the contour of clutch disk cam surface.

The two cases to be distinguished are positions of the pivot

109

for Z-fold media (

FIG. 15

) and for cut-sheet media (FIG.

16

). In

FIG. 15

, the pivot

109

is rotated downwardly (PPS=dimension A) for Z-fold media prior to the initiation of a pick cycle because the operator has moved the media selector lever

110

to the right, which corresponds to the Z-fold banner position. This downward position of the pivot

109

, which is coupled to the clutch

130

by the carriage

40

, begins at a position indicated in FIG.

15

and in dashed lines in

FIG. 18

, which is lower than the pivot (and clutch) starting positions for cut-sheet media, as indicated in FIG.

16

and in solid lines in FIG.

18

. During the pick cycle, the number of media drive motor steps it takes to detect the change in carriage position caused by traveling over the clutch bump

152

will be fewer for Z-fold media than when the media selector lever

110

is moved to the left for cut-sheet media and the pivot

109

is raised to the cut-sheet position of FIG.

16

.

The number of steps of the drive motor

93

are correlated to correspond to the distance of travel, and provide an indication to the controller

36

of the position of the media select lever

110

. For example, about 180 motor steps indicate a cut-sheet position, whereas about 100 motor steps indicate that the lever

110

is in the banner position. The controller

36

may use this information to supply a message to the host computer, which may respond by instructing the operator to move the lever

110

to a desired position corresponding to the type of media selected in the printer set-up program.

Thus, a variety of advantages are realized using the Z-fold media handling system

26

and routine

84

described herein. One of the most significant advantages is the ability to easily print on Z-fold media using the same inkjet printer one uses to print on conventional cut-sheet media. Furthermore, the mechanism employed is quiet and does not need a bulky tractor drive mechanism to feed the Z-fold media. As a further advantage, while the media stack

85

has been shown with the free end of the uppermost sheet loaded in the input tray against wall

104

, the system

26

also functions as described above if the free end of this uppermost sheet is located adjacent the length adjuster

35

. When loaded with free end of the uppermost sheet against the length adjuster

35

, this uppermost sheet is pulled through the feed path

95

underneath the next sheet down in the stack, that is, the uppermost sheet travels between the drive rollers

90

and this next sheet down. In this case, no printing occurs on this uppermost sheet because when in the printzone

25

, the sheet that was uppermost in the stack

85

is then underneath what was the next sheet in the stack. Here, the edges where the uppermost sheet joins the next down sheet serves as the leading edge

88

. Thus, this next sheet down serves as the first sheet

86

to receive ink, whereas the uppermost sheet serves as a blank leader sheet, which is typically detached from the printed banner then discarded or recycled.

Additionally, this system

26

and routine

84

are accomplished without significantly impacting the cost of the printer mechanism

20

, for example by using the carriage encoder strip

47

along with a slight modification to the clutch disk

130

, to monitor the media select lever's position. Placement of the media select lever

110

near the media input tray

28

enhances the ease of switching between types of media, since the icons on the lever

110

provide a quick reminder to the user that the lever needs to be adjusted. Furthermore, providing the lever

10

in a color which contrasts with the color of the balance of the printer enclosure

24

draws user attention to the lever as a component which needs to be adjusted prior to printing.

Number	Name	Date	Kind
4923188	Neir	May 1990	A
5226742	Pintar et al.	Jul 1993	A
5269613	Olson et al.	Dec 1993	A
5305020	Gibbons et al.	Apr 1994	A
5391008	Hattori	Feb 1995	A
5772339	Yamaguchi	Jun 1998	A
5819666	Ishikawa et al.	Oct 1998	A
5838338	Olson	Nov 1998	A

	Number	Date	Country
Parent	09/318673	May 1999	US
Child	09/615689		US

Z-fold print media handling system

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Disclaimer

Abstract

Description

Claims

CROSS REFERENCE TO RELATED APPLICATION(S)

US Referenced Citations (8)

Foreign Referenced Citations (1)

Continuations (1)