Electronic apparatus capable of feeding sheets from a front side, and sheet feeding device for use therewith

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electronic apparatus, such as a word processor, a personal computer or the like.
2. Description of the Related Art
In some of conventional so-called laptop or notebook-size electronic apparatuses, such as word processors, personal computers or the like, in which a display unit for displaying an image using a liquid crystal or the like is provided so as to be openable/closable with respect to the main body of the apparatus by rotating, a recording unit for recording the image displayed on the display unit is incorporated in the apparatus. The recording unit is generally disposed at the rear side of the main body of the apparatus. Accordingly, a sheet is supplied in a state in which the display unit is closed, or by the user going to the rear side of the apparatus. When continuously supplying sheets, a separate sheet feeding device (an automatic sheet feeding device (ASF)) is mounted on the electronic apparatus only when necessary, in order to make the apparatus compact.
In the above-described conventional approach, the display unit must be closed and opened, or the operator must stand up and go to the rear side of the apparatus, whenever supplying a sheet or mounting the sheet-feeding device, making operation of the apparatus cumbersome.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electronic apparatus having an excellent operability by arranging the apparatus to allow the operator to supply a sheet from the front side of the apparatus.
According to one aspect, the present invention, which achieves the above-described object, relates to an electronic apparatus having an inlet for manually inserting a sheet in the vicinity of the rotational axis of a display unit rotatably provided with respect to a main body of the apparatus. The electronic apparatus includes a sheet feeding device, capable of continuously feeding sheets, provided so as to be detachable with respect to the inlet.
In one embodiment, the display unit makes a keyboard, provided in the main body of the apparatus, inoperable by covering the keyboard in a closed state, and makes the keyboard operable in an opened state. The sheet feeding device covers a portion of the keyboard when being mounted, and setting of feeding control of the sheet feeding device can be input through an uncovered portion of the keyboard.
According to the above-described configuration, the inlet is provided in the vicinity of the rotational axis of the display unit so that a sheet can be manually inserted from the front side of the apparatus. In addition, since the sheet feeding device can be mounted on the inlet, the sheet feeding device can be mounted from the front side of the apparatus. Accordingly, the operation of the apparatus and the sheet-feeding operation can be performed from the front side of the apparatus, thereby improving the operability of the apparatus.
While a portion of the keyboard is covered when mounting the sheet feeding device from the front side of the apparatus, setting of feeding control can be input through uncovered keys of the keyboard, thereby improving the operability of the apparatus.
According to another aspect, the present invention relates to a sheet feeding device, capable of continuously feeding sheets, provided so as to be detachable with respect to an inlet, provided in the vicinity of the rotational axis of a display unit which is rotatable with respect to a main body of an apparatus. The sheet feeding device includes sheet supporting means for supporting sheets, positioning means for positioning the sheets while regulating end portions of the sheets in the direction of the width, and feeding means obliquely disposed so as to generate a feeding force for feeding the sheets supported by the sheet supporting means in a direction of the positioning means and a feeding force for feeding the sheets toward the positioning means, and separation means for individually separating the sheets fed by the feeding means.
According to still another aspect, the present invention relates to a sheet feeding device, capable of continuously feeding sheets, provided so as to be detachable with respect to an inlet, provided in the vicinity of the rotational axis of a display unit provided so as to be rotatable with respect to a main body of an apparatus. The display unit includes conveying means for conveying a sheet manually inserted from the aperture and the sheets fed from the sheet feeding device. The sheet feeding device includes sheet supporting means for supporting sheets, positioning means for positioning the sheets while regulating end portions of the sheets in the direction of the width, feeding means obliquely disposed so as to generate a feeding force to feed the sheets supported by the sheet supporting means in a direction of the positioning means and a feeding force for feeding the sheets in a predetermined direction different from the direction of the positioning means, and control means for driving the feeding means until the trailing edge of a sheet fed by the feeding means passes through the feeding means even after the sheet has been conveyed by the conveying means.
The foregoing and other objects, advantages and features of the present invention will become more apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a word processor, serving as an electronic apparatus, according to an embodiment of the present invention;
FIG. 2 is a vertical cross-sectional view of the word processor shown in FIG. 1;
FIG. 3 is a plan view of the word processor shown in FIG. 1;
FIG. 4 is a partially cross-sectional side view illustrating a state in which a sheet feeding device is mounted on the word processor;
FIG. 5 is a perspective view illustrating the state in which the sheet feeding device is mounted on the word processor;
FIG. 6 is a perspective view illustrating an example of the sheet feeding device;
FIG. 7 is a perspective view illustrating electrical connection between the word processor and the sheet feeding device;
FIG. 8 is a plan view of the sheet feeding device;
FIG. 9 is a plan view illustrating the positional relationship between members of the sheet feeding device;
FIG. 10 is a plan view illustrating a state of the sheet feeding device before feeding a sheet;
FIG. 11 is a plan view illustrating a state of the sheet feeding device in which oblique movement of a sheet is corrected after starting the feeding of the sheet;
FIG. 12 is a perspective view illustrating a separation mechanism of the sheet feeding device;
FIGS. 13(a) and 13(b) are vertical cross-sectional views illustrating the separation mechanism of the sheet feeding device;
FIGS. 14(a) and 14(b) are plan views illustrating the separation mechanism of the sheet feeding device;
FIGS. 15(a) through 15(c) are cross-sectional views illustrating a sheet feeding state by a sheet feeding roller of the sheet feeding device;
FIGS. 16(a) and 16(b) are diagrams illustrating feeding control of a sheet from the sheet feeding device to a recording unit;
FIGS. 17(a) through 17(c) are diagrams illustrating a state in which oblique movement of a sheet fed from the sheet feeding device is corrected;
FIG. 18 is a block diagram of control means provided in the word processor;
FIG. 19 is a flowchart illustrating an example of sheet-feeding control;
FIG. 20 is a graph illustrating the relationship between the number of revolutions and the torque of a motor provided in the sheet feeding device;
FIG. 21 is a perspective view illustrating another example of the sheet feeding device;
FIG. 22 is a flowchart illustrating another example of sheet-feeding control;
FIGS. 23(a) and 23(b) are perspective views illustrating other examples of the sheet feeding roller provided in the sheet feeding device;
FIG. 24 is a perspective view illustrating the sheet feeding device having another separation mechanism;
FIG. 25 is a perspective view illustrating the separation mechanism shown in FIG. 24;
FIGS. 26(a) and 26(b) are cross-sectional views of the other separation mechanism shown in FIG. 24;
FIGS. 27(a) through 27(d) are front views of the separation mechanism shown in FIG. 24;
FIG. 28 is a cross-sectional view illustrating another example of the relationship between the sheet feeding roller and an elastic member of the sheet feeding device;
FIG. 29 is a flowchart illustrating still another example of sheet-feeding control;
FIG. 30 is a plan view illustrating still another example of the separation mechanism;
FIG. 31 is a front view of the separation mechanism shown in FIG. 30;
FIG. 32 is a perspective view illustrating another example of the elastic member for pressing a sheet against the sheet feeding roller;
FIG. 33 is an exploded perspective view illustrating an example of a cluch mechanism provided between the sheet feeding roller and the motor; and
FIGS. 34(a) and 34(b) are perspective views illustrating the operation of the clutch mechanism shown in FIG. 33.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred embodiment of the present invention will now be described in detail with reference to the drawings.
A description will be provided of the configuration of a word processor WP, serving as an electronic apparatus, to which the present invention is applied, with reference to FIGS. 1 through 5. FIG. 1 is an external perspective view of the word processor WP. FIG. 2 is a vertical cross-sectional view of the word processor WP shown in FIG. 1. FIGS. 3, 4 and 5 are a plan view, a side view and a perspective view of the word processor WP in a state in which a sheet feeding device (to be described later) is mounted thereon, respectively.
In FIGS. 1 and 2, there are shown a keyboard 1 for inputting information, a display unit 2, using a liquid crystal or the like, for displaying the information, a sheet processing unit 3 for recording the information on a fed sheet 5. In the present embodiment, the sheet processing unit 3 comprises a recording unit for recording the information on the sheet 5. Reference numeral 4 represents an inlet or aperture for inserting the sheet 5 into the recording unit 3. As shown in FIG. 1, when a sheet feeding device 6 (to be described later) is not mounted, the sheet 5 is manually inserted directly into recording unit 3 through the aperture 4.
The word processor WP is a so-called laptop type. In the word processor WP, a cover 2a including the display unit 2 is provided so as to be rotatable around a rotation shaft 2b relative to a main body 1a of the apparatus. As shown in FIG. 1, when the cover 2a is opened, the keyboard 1 can be operated. A power supply S, a substrate P and the like are incorporated within the main body 1a.
The aperture 4 is provided at the side of the main body 1a. When the cover 2a is opened, the aperture 4 is exposed to the outside, so that the sheet 5 can be inserted therein from the operational side of the keyboard 1. The recording unit 3 includes conveying rollers 21 and 22 for conveying the sheet 5 inserted from the aperture 4, and a recording head 23 for performing recording on the conveyed sheet 5. These units will be described in detail later on. After recording by the recording unit 3, the sheet 5 is discharged to a side opposite to the aperture 4 (the rear side of the main body 1a).
FIGS. 3 through 5 illustrate a state in which the sheet feeding device 6 is mounted on the word processor WP. The sheet feeding device 6 is mounted close to the center of the aperture 4. When manually inserting the sheet 5, the sheet 5 is inserted making the left end of the aperture 4 a reference position (as indicated by one-dot chain lines in FIG. 3). The sheet 5 fed from the sheet feeding device 6 has a reference position close to the center. Hence, a reference position for starting recording in the recording unit 3 differs between the manually fed sheet and the sheet fed from the sheet feeding device 6. When the sheet feeding device 6 is mounted, the mounting is detected by detection means (not shown), and the recording operation of the recording unit 3 is controlled based on the detection.
When the sheet feeding device 6 is mounted, a portion of the keyboard 1 is hidden by the sheet feeding device 6. However, since keys for setting recording conditions, such as the number of copies, printing conditions and the like, are arranged at a portion A shown in FIG. 3, the recording conditions can be input even after the sheet feeding device 6 has been mounted. Also when manually inserting a sheet, the keys in the portion A are used, so that recording conditions can be set by inputting through these keys after manually inserting the sheet.
As shown in FIGS. 4 and 5, the sheet feeding device 6 is mounted by causing recesses at distal ends of arms 7a (to be described later) to engage a mounting shaft Y provided on the main body 1a, and legs 7z to contact a horizontal surface in front of the aperture 4.
Sheet feeding device
Next, a description will be provided of the configuration of the sheet feeding device 6 with reference to FIG. 6.
The sheet feeding device 6 includes a lower case 7, serving as sheet accommodating means S, an upper case 8 and an upper cover 13. The lower case 7 includes the arms 7a for connecting the sheet feeding device 6 to the recording unit 3 by engaging therewith, a reference surface (a central portion in the lateral direction) 7b, provided at a sheet accommodating surface, for accommodating and supporting sheets 5, and serving as reference height when mounting sheets, supporting surfaces (two side portions in the lateral direction) 7c whose height is more or less below that of the reference surface 7b, an aperture 7d for feeding a separated sheet 5, and an inclined portion 7e, serving as separation means for separating the sheets 5, all provided as one body. The reference surface 7b and the supporting surfaces 7c are connected with continuous inclined surfaces.
The upper case 8 covers a feeding motor 12, serving as a driving source, and a gear train. Reference numeral 9 represents a sheet feeding roller, serving as feeding means for feeding the sheet 5. A gear 10 is formed at one end of the sheet feeding roller 9 at the side of the feeding motor 12 as one body with the sheet feeding roller 9. The sheet feeding roller 9 includes a shaft 9b whose two end portions are supported on the lower case 7, and cylindrical roller units 9a, made of a hard rubber or the like, provided at two locations on the shaft 9b at a predetermined interval. In the present embodiment, the width of the roller units 9a is 8 mm, and the distance between the centers of the roller units 9a is 35 mm.
The height of the surface of the sheet feeding roller 9 in contact with the sheet 5 is equal to or higher than the reference surface 7b. A worm gear 11 is mounted on the feeding motor 12. In the present embodiment, a DC motor is used as the feeding motor 12.
When the sheet feeding device 6 is mounted, electric power is supplied from the power supply S provided in the main body 1a of the word processor WP to the feeding motor 12. As shown in FIG. 7, metallic armatures 61 connected to the feeding motor 12 via cords 60 are provided at front-end portions of the sheet feeding device 6, and metallic armatures 62 connected to the power supply S via a CPU (central processing unit, to be described later, are provided at the main body 1a so as to face the metallic armatures 61. When the sheet feeding device 6 is mounted on the main body la, the metallic armatures 61 contact the metallic armatures 62, so that the sheet feeding device 6 is electrically connected to the main body la. The metallic armatures 62 provided at the main body 1a act as springs, so that the metallic armatures 61 and the metallic armatures 62 elastically contact.
Sheet-feeding control of the sheet feeding device 6 is performed by turning on/off electric power supply to the feeding motor 12 by a motor driver 35 of the CPU unit provided in the word processor WP. Accordingly, control means for performing sheet-feeding control is not provided at the sheet feeding device 6.
As shown in FIG. 6, a spring 14, serving as contact means for contacting the sheet 5 to the sheet feeding roller 9 is provided on the upper cover 13, so that the sheet 5 contacts the sheet feeding roller 9 by being pressed thereagainst. An end portion 14a of the spring 14 contacts the sheet 5. Although in the present embodiment, a leaf spring is used as the contact means, any other elastic member, such as a coil spring, a sponge, a piece of rubber or the like, may also be used.
FIG. 8 is a diagram illustrating the configuration of the sheet feeding device 6.
In FIG. 8, the sheet feeding roller 9 is disposed so as to have an angle .alpha. with respect to a direction orthogonal to the sheet feeding direction (a direction indicated by an arrow A) of the recording unit 3. Although in the present embodiment, the angle .alpha. is set to 5.degree., the angle is not limited to this value. Oblique movement can also be prevented by performing oblique-movement-preventing processing (to be described later), provided that the angle .alpha. is between the range of 0.degree.<.alpha..ltoreq.45.degree..
A front side wall 7s (see FIG. 6), side plates 7f and 7g are formed as one body on the lower case 7. The side plate 7f is formed so as to coincide with the recording reference position of the recording device 3, and functions as positioning means for positioning one side (one end portion in the direction of the width) of the sheets 5. The sheet 5 is fed so that the one side thereof moves along the side plate 7f. The side plate 7g is formed at a position having a certain amount of clearance with the ther side of the sheet 5 set along the side plate 7f. This is for facilitating setting of the sheet 5 on the lower case 7, and for accommodating variations in the size of sheets, and changes in the size of sheets due to changes in the ambient temperature and humidity. In the present embodiment, the clearance is set to 2 mm.
FIG. 9 is a diagram illustrating the positional relationship among respective units of the sheet feeding device 6. As described above, the sheet feeding roller 9 comprises the two roller units 9a and the shaft 9b, and is disposed so that the center line between the two roller units 9a is shifted to a position closer to the reference side plate 7f by .beta. from the center position of the sheet 5 when the sheet 5 is aligned along the side plate 7f. The center of the reference surface 7b and the inclined portion 7e (see FIG. 12), serving as separation means, provided at the front side wall 7s is also situated at a position shifted to the side plate 7f by .beta., and is located at a substantially central portion when the sheet 5 is aligned along the side plate 7f. In FIG. 9, the contact position between the spring 14 shown in FIG. 6 and the sheet 5 is provided at a side upstream from the roller units 9a of the sheet feeding roller 9 in the sheet-feeding direction indicated by the arrow A, and at a position where the spring 14 does not contact the sheet feeding roller 9 when the sheet 5 is absent.
In the present embodiment, the inclined portion 7e for sheet separation is provided at the same position as the center of the roller units 9a in the lateral direction of the sheet 5. However, the inclined portion 7e may be provided at any other position, provided that as indicated by hatching, a portion of the sloped portion 7e is present within a range of extension of the position pressed by the spring 14 in the sheet-feeding direction or in a direction orthogonal to the sheet feeding roller 9. If the abovedescribed distance .beta. is set within the range of 0.ltoreq..beta..ltoreq.W/4, where W is the width of the sheet 5, oblique movement of the sheet 5 can be prevented by performing oblique-movement-preventing processing (to be described below).
Processing to prevent oblique movement of the sheet
Next, a description will be provided of processing to prevent oblique movement of the sheet by the sheet feeding device 6 with reference to FIGS. 10 and 11.
By setting the sheet 5 on the reference surface 7b and closing the upper cover 13, the spring 14 can press the sheet 5 against the sheet feeding roller 9. Thereafter, by driving the feeding motor 12, the sheet 5 can be fed. If, as shown in FIG. 10, the sheet 5 is obliquely positioned, when feeding of the sheet 5 begins by driving the feeding motor 12, the sheet 5 is conveyed by the sheet feeding roller 9 in a direction B because the sheet 5 is obliquely disposed. If the sheet 5 is conveyed in this state, a corner of the sheet 5 contacts the side plate 7f, and the sheet 5 rotates around a contact position D in a direction C. If the sheet 5 is further conveyed, the sheet 5 is fed while one side thereof moves along the side plate 7f in a direction A, as shown in FIG. 11. Accordingly, irrespective of the state in which the sheet 5 is set within the lower case 7, the sheet 5 is fed along the reference side plate 7f without obliquely moving.
Separation mechanism
Next, a description will be provided of a separation mechanism of the sheet 5 with reference to FIGS. 12, 13 and 14.
FIG. 12 is a perspective view illustrating a separation portion.
In FIG. 12, as described above, the inclined portion (separation means) 7e for sheet separation is formed in the aperture 7d. Regulation members 7h are formed as one body on the side plates 7f and 7g on either side of the aperture 7d.
The regulation members 7h function as regulation means for regulating the passage of the sheet 5 by controlling the degree of curvature of the sheet 5 along its leading edge. Each of the regulation members 7h has an inclined surface to guide the sides of the leading edge of the sheet 5 to the aperture 7d.
When feeding a sheet 5 in a downwardly-convex curled state, as shown in FIG. 14(b), due to storage conditions or environmental conditions, the sheet 5 is in some cases fed while a side portion of the sheet 5 at the side of the side plate 7f moves in a direction opposite to the sheet-accommodating surface, because the feeding direction of the sheet feeding roller 9a is the direction B shown in FIG. 10. In such a case, if the amount of floating of the sheet 5 at the side of the side plate 7f is great, deviations in the sheet-feeding position and the recording position may occur. The regulation members 7h are provided in order to regulate such movement of the sheet 5 in the direction of the thickness.
Next, a description will be provided of a manner in which the sheet 5 is separated at the inclined portion 7e, serving as the separation means.
When the sheet feeding roller 9 rotates, the lowermost sheet 5 of the sheets mounted on the lower case 7 is fed, and the leading edge of the fed sheet 5 contacts the inclined portion 7e. The inclined portion 7e generates a drag to downwardly press the sheet 5 against the feeding force of the sheet feeding roller 9a. As a result, the sheet 5 is bent, and the lowermost sheet 5 is separated from the inclined portion 7e.
Although in the present embodiment, the regulation members 7h are provided so as to regulate two end portions of the sheet 5, the regulation member 7h may be provided only on the side plate 7f so as to regulate at least a side of the sheet 5 at the side of the side plate 7f, serving as the recording reference position.
Although in the present embodiment, an inclined surface is formed on the regulation member 7h, a curved surface or a surface having a circular cross section may also be formed.
FIG. 13(a) is a cross-sectional view of the inclined portion 7e for sheet separation. The reference surface 7b and a gap e for passing the sheet 5 is formed in the vicinity of the inclined portion 7e. The slope of the inclined portion 7e has an angle .gamma. with respect to the reference surface 7b. In the present embodiment, the angle .gamma. is set to 60.degree.. The angle .gamma. may have any other value within the range of 30.degree.-80.degree..
In the present embodiment, the height h1 of the slope formed on the inclined portion 7e is set to be at least the maximum expected height of curl of the sheet 5 contacting the inclined portion 7e. In the present embodiment, the value of the height h1 is set to 9 mm.
FIG. 13(b) is a cross-sectional view of the regulation member 7h. The regulation member 7h is separated by a gap having an interval X from the supporting surface 7c. The angle made by the slope of the regulation member 7h and the supporting surface 7c is the angle .gamma. of the inclined portion 7e for sheet separation. The interval X provides the amount of floating of the sheet 5 from the supporting surface 7c allowed for ordinary feeding and recording. In the present embodiment, X=2 mm.
As in the case of the height h1, the height h2 of the slope formed on the regulation member 7h is set to be at least the estimated height of curl of the sheet 5 contacting the regulation member 7h, more specifically, at least the height of floating of the sheet 5 from the reference surface 7b. In the present embodiment, since the height of floating has a maximum value when feeding a single sheet, the height in this case is set as the height of floating of the sheet 5. The height h2 of the slope of the regulation member 7h is set to a value higher than the height h1 assuming that the height of curl of the sheet 5 produced in the regulation member 7h is higher than the height h1. In the present embodiment, the height h2 is set to 12 mm.
In the present embodiment, the angle .gamma. between the slopes of the inclined portion 7e and the regulation member 7h, and the reference surface 7b and the supporting surface 7c, respectively, equals 60.degree.. If the angle .gamma. is less than 30.degree., there is the possibility that the leading edges of the second sheet and/or subsequent sheets enter the gap e together with the first sheet while the first sheet is fed. Hence, it is desirable that the angle .gamma. is at least 30.degree.. The inclined portion 7e and the regulation member 7h make the same angle .gamma. with the reference surface 7b and the supporting surface 7c, respectively. However, since the gap X between the regulation member 7h and the supporting surface 7c is much greater than the thickness of the sheet 5, there is less possibility that the leading edges of the second and/or subsequent sheets will enter the gap X. Hence, the angle made by the regulation member 7h and the supporting surface 7c may be different from the angle made by the sloped portion 7e and the reference surface 7b, or may be less than 30.degree.. Although in the present embodiment, the heights h1 and h2 of the slopes provided in the inclined portion 7e and the regulation member 7h, respectively, are arranged to be h2>h1, the relationship between the heights h1 and h2 is not limited to this relationship, but may be set in accordance with an estimated curled state of the sheet 5. For example, the relationship may be set to h1=h2.
FIG. 10 illustrates a manner in which the sheet 5 is fed from the sheet feeding device 6.
FIGS. 14(a) and 14(b) illustrate a state before starting the feeding operation, as seen from the front side. The sheet 5 is not always flat depending on environmental conditions, such as the ambient temperature and humidity, and conditions of use. For example, upwardly convex curl and downwardly convex curve may occur, as shown in FIGS. 14(a) and 14(b), respectively.
The heights h1 and h2 of the slope provided in the inclined portion 7e for sheet separation and the regulation member 7h, respectively, are set to values greater than the height of curl of the sheet 5 contacting the respective members. Hence, even if the sheet 5 is curled, end portions of the sheet 5 contact the slopes of the inclined portion 7e and the regulation member 7h, and the sheet 5 is guided to the gap e formed for passing the sheet 5. The height h2 is set to be equal to or greater than the height hi so that the sheet 5 is normally fed even in the above-described curled states.
The supporting surface 7c is made to be lower than the reference surface 7b and the upper surface of the roller units 9a of the sheet feeding roller 9 in order to reduce the force required for the spring 14, because a large force is needed for pressing the sheet 5, in which upwardly convex curl has been produced as shown in FIG. 14(a), against the sheet feeding roller 9 to a flat state by the spring 14 (see FIG. 6).
At that time, since the sheet feeding roller 9 has the two roller units 9a at the predetermined interval, the sheet 5 can contact the sheet feeding roller 9 with excellent balance even in a curled state, so that the sheet 5 can be precisely fed. For example, when the sheet 5 is in an upwardly-convex curled state, the roller units 9a can contact the sheet 5 at portions where the height of curl is the same, because, as shown in FIG. 9, the roller units 9a of the sheet feeding roller 9 are disposed across the center of the sheet 5 in the lateral direction. Also in the case of downwardly convex curl, the sheet feeding roller 9 can feed the sheet 5 while contacting it with excellent balance, because the roller units 9a contact the sheet 5 across the apex of the curl.
FIG. 15(a) is a cross-sectional view illustrating the positional relationship between the spring 14, for contacting the sheet 5 to the sheet feeding roller 9 while pressing the sheet 5, and the sheet feeding roller 9. A portion where the spring 14 presses against the roller units 9a of the sheet feeding roller 9 is always positioned at an upstream side (the right side in FIG. 15(a)) from the center of rotation of the sheet feeding roller 9 irrespective of the number of mounted sheets to be separated and fed. When only a single sheet is present, the portion is situated at a position more upstream by .delta.. Thus, the sheet 5 is always pressed against the sheet feeding roller 9 by the spring 14. Hence, when a leading-edge portion of the lowermost sheet 5 passes through the inclined portion 7e, entrance of sheets mounted on the lowermost sheet into the gap e is prevented, the sheet 5 can be easily bent at the inclined portion 7e for sheet separation, and therefore feeding of a plurality of sheets is prevented (see FIG. 15(b)). A leading-end portion 14a of the spring 14 is configured so as not to contact the roller units 9a of the sheet feeding roller 9 even if the sheet is absent (see FIG. 15(c)).
The positional relationship between the sheet feeding device and the recording unit
FIGS. 16(a) and 16(b) are schematic diagrams illustrating the arrangement of the sheet feeding device 6 and the recording unit 3. In FIG. 16(a), reference numeral 20 represents a sheet detection sensor for detecting the presence of a sheet within the recording unit 3. Reference numeral 21 represents a conveying roller, and reference numeral 22 represents a pinch roller driven by the conveying roller 21 by a spring or the like (not shown). The conveying roller 21 and the pinch roller 22 constitute conveying means. Reference numeral 23 represents a recording head (recording means) for forming an image on the sheet.
In FIG. 16(a), when the set sheet 5 has been fed by the sheet feeding roller 9 toward the conveying roller 21 of the recording unit 3 by a distance M1, the leading edge of the sheet 5 is detected by the sheet detection sensor 20. When the sheet 5 has been further fed by a distance M2, the leading edge of the sheet 5 reaches a so-called nip portion where the conveying roller 21 contacts the pinch roller 22. Thereafter, the sheet 5 is conveyed by the conveying roller 21, as illustrated in FIG. 16(b). The leading edge of the sheet 5 passing through the nip portion between the conveying roller 21 and the pinch roller 22 is further conveyed by a distance M3. The distance M3 is adopted in consideration of a blank portion from the leading edge of the sheet 5 to a position where printing is actually performed, i.e., a so-called upper margin M4. The sheet feeding roller 9 is disposed at a position where the trailing edge of the sheet 5 passes while the leading edge of the sheet 5 is conveyed by the distance M3. That is, as shown in FIG. 16(b), the length L of the sheet is less than the position Z of the roller. Since the value of the upper margin M4 differs depending on images to be recorded, the value of the position Z of the roller may be determined from the minimum value of the upper margin M4.
Positional relationship between the sheet feeding roller and the sheet
Next, a description will be provided of the positional relationship between the sheet feeding roller 9 and the trailing edge of the sheet 5 with reference to FIGS. 17(a) through 17(c).
In FIGS. 17(a) through 17(c), the sheet 5 is fed in a direction A by the rotation of the sheet feeding roller 9 in a direction D.
As described above, the sheet feeding roller 9 has two roller units 9a, and is obliquely disposed with respect to a direction orthogonal to the sheet-feeding direction (the direction A). Accordingly, in a state shown in FIG. 17(a), the two roller units 9a contact the sheet 5. When the sheet 5 is further fed and assumes a state shown in FIG. 17(b), the trailing edge of the sheet 5 is detached from one of the roller units 9a. When the sheet 5 is further fed and assumes a state shown in FIG. 17(c), the trailing edge of the sheet 5 is also detached from the other roller unit 9a. FIG. 17(c) illustrates the position where the trailing edge of the sheet 5 passes through the sheet feeding roller 9 when the sheet 5 is conveyed by the distance M3, as shown in FIG. 16(b).
In FIGS. 17(a) through 17(c), the next sheet to be fed contacts the upper surface of the sheet 5 being fed, and the spring 14 for pressing the sheets against the sheet feeding roller 9 presses the sheets from above. Accordingly, in the state shown in FIG. 17(b), the next sheet contacts the roller unit 9a, that has been detached from the trailing edge of the sheet 5 being fed, at a point E. Feeding of the next sheet in the direction A is prevented by the resistance of the separation portion (inclined portion 7e), and this resistance prevents the rotation of the sheet feeding roller 9 thereon.
Usually, when the sheet feeding roller 9 is disposed in a direction orthogonal to the sheet-feeding direction, and a slippable mechanism, such as a one-way clutch or the like, is provided for the sheet feeding roller 9, i.e., when the sheet-feeding direction coincides with the direction in which the sheet is actually fed, the drive of the sheet feeding roller 9 is stopped in the state shown in FIG. 17(a), and the sheet 5 is drawn by the conveying roller 21 of the recording unit 3. In such an approach, however, if the sheet feeding roller 9 is obliquely disposed with respect to the direction orthogonal to the sheet-feeding direction, frictional load at the point E prevents the rotation of the sheet feeding roller 9. Hence, a large conveying force capable of conveying the sheet 5 against the frictional load is needed for the recording unit 3.
The conveying force of the recording unit 3, i.e., the driving force of the conveying roller 21, can be reduced by driving the sheet feeding roller 9 until the the state shown in FIG. 17(c) is provided, i.e., the trailing edge of the sheet 5 completely passes through the sheet feeding roller 9
Feeding force
Even when the sheet 5 has been fed by the sheet feeding roller 9 and reached the conveying roller 21 of the recording unit 3, the sheet feeding roller 9 must be rotated for an additional period to ensure the leading edge of the sheet 5 is present at the nip portion between the conveying roller 21 and the pinch roller 22.
If the feeding force of the sheet feeding roller 9 is greater than the stiffness of the sheet 5, the sheet 5 is bent. The stiffness of the sheet 5 changes depending on the ambient temperature and humidity. In particular, a large feeding force is needed for assuredly bending a thick sheet, such as a post card or the like.
In the present embodiment, the feeding force is set to a value smaller than the minimum stiffness of the sheet, so that slip is always produced between the sheet 5 and the sheet feeding roller 9 without bending the sheet 5. The feeding force can be appropriately set by adjusting the pressing force (sheet-feeding pressure) to press the sheet 5 against the sheet feeding roller 9, i.e., the spring force of the spring 14 for pressing the sheet 5 against the sheet feeding roller 9. The spring force may be set so as to satisfy the following relational expressions (1)-(3):
FB<FK (1)
FN.sub.min <FK<FN.sub.max (2)
FK<FZ (3),
where FN.sub.max and FN.sub.min are the maximum value and the minimum value of the pushing force to push the sheet 5 into the nip portion between the conveying roller 21 and the pinch roller 22, respectively, FB is a force necessary to separate the sheets by the separation means, FZ is the buckling force of the sheet, and FK is the feeding force of the sheet by the sheet feeding roller 9. If the pushing force exceeds the value FN.sub.max, the leading edge of the sheet does not stop at and enters the nip portion, so that positioning of the leading edge of the sheet cannot be exactly performed. If the pushing force is less than the value FN.sub.min, the leading edge of the sheet cannot be grasped by the nip portion when the conveying roller 21 starts to feed the sheet while rotating, thereby causing a failure in feeding.
The spring force of the spring 14 for pressing the sheet 5 against the sheet feeding roller 9 is set so as to satisfy the relational expressions (1)-(3). The same effects may be obtained by appropriately selecting the coefficient of friction of the roller units 9a of the sheet feeding roller 9.
Control means
Next, a description will be provided of control means for performing driving control of the sheet feeding device 6, and the recording unit 3 using the sheet feeding device 6, with reference to a block diagram shown in FIG. 18.
In the block diagram shown in FIG. 18, only the connections between respective units are shown, and detailed control lines are omitted.
In FIG. 18, a CPU 30 includes control means for reading programs and various kinds of data from a ROM (read-only memory) 31 (to be described later), or from a floppy-disk drive 32 and the like. The CPU performs necessary calculations and determinations, and performs various kinds of controls.
The ROM 31 stores various kinds of programs to be used by the CPU 30, and various kinds of data necessary for recording, such as character codes, dot patterns (to perform the function of a character generator (CG)) and the like.
A RAM (random access memory) 33 functions as a read/write memory, and includes, inter alia, (i) a working area for temporarily storing data being accessed and results of calculations, (ii) a buffer area for storing various kinds of data input from the keyboard 1, the external interface unit 47, and the floppy-disk drive 32, etc., and (iii) a text area for preserving documents. A CPU unit 100 is connected to the recording unit 3 via a recording-head driver 34, a motor driver 35 and a detection unit 36.
The recording-head driver 34 drives the recording head 23 provided in the recording unit 3 under the control of the CPU 30. The motor driver 35 drives a conveying motor (not shown), serving as a driving source for, inter alia, the conveying roller 21, a carriage motor (not shown) for moving the recording head 23 in a direction orthogonal to the conveying direction of the sheet 5, and the feeding motor 12.
The detection unit 36 transmits detection information from the sheet detection sensor 20 provided in the recording unit 3, a temperature/humidity detection sensor for detecting the temperature and humidity within the device, and the like, to the CPU 30. A power supply 38 controls the supply of a power supply V.sub.H for driving the recording head 23, a power supply V.sub.M for driving the conveying motor, the carriage motor, the feeding motor 12 and the like, a power supply FDD for driving the floppy-disk driver 32, and a power supply V.sub.CC for other logic circuits.
A controller 39 transfers data to be recorded by the recording head 23, changes the voltage and current of the driving power supply V.sub.H, and performs various kinds of controls by the control of the CPU 30. The keyboard 1 for inputting various kinds of data necessary for recording and editing is connected to the CPU unit 100 via a keyboard connector (KBC) 40.
The display unit 2, including an LCD (liquid-crystal display), for displaying data and various kinds of information input from the keyboard 1 is connected to the CPU unit 100 via an LCD connector (LCDC) 41. A CRT or any other device may be used instead of the LCD for the display unit 2. The floppy-disk drive 32 is also connected to the CPU 100 via a floppy-disk-drive connector (FDDC) 42. A hard-disk drive, an external RAM or the like may be connected instead of the floppy-disk drive. Interfaces, such as an RS232C 44, a Centronix 45, a modem 46 and the like, for performing control of the recording unit 3 and communication with an external apparatus by an external control device, can be connected to the CPU unit 100 via interface connectors (IFC) 43.
Control operation
Next, a description will be provided of control procedures for performing driving control of the sheet feeding device 6, and the recording unit 3 using the sheet feeding device 6, with reference to a flowchart shown in FIG. 19.
When a recording command has been received and a sheet-feeding operation has been started (step S1), the feeding motor 12, such as a DC motor, is turned on (step S2), and feeding of the lowermost sheet 5 contacting the roller units 9a of the sheet feeding roller 9 is started.
When the sheet 5 has been fed by the distance M1 shown in FIG. 16(a), the sheet detection sensor 20 is turned on (step S3), the drive (reverse drive) of the conveying motor of the recording unit 3 in a direction reverse to the sheet-feeding direction by a predetermined amount N1 steps at a predetermined speed F1 pps is started (step S4). In the present embodiment, a stepping motor is adopted as the conveying motor.
When the sheet 5 has been further fed from the position corresponding to the sheet detection sensor 20 by the distance M2 by the sheet feeding device 6, the sheet 5 contacts the conveying roller 21 driven in a direction opposite to the sheet-feeding direction by the conveying motor. By further driving the feeding motor 12 for a predetermined time period, the leading edge of the sheet 5 can assuredly contact the conveying roller 21 along the nip portion between the conveying roller 21 and the pinch roller 22 while producing slip between the sheet 5 and the sheet feeding roller 9. Thus, oblique movement of the sheet 5 is corrected. Although oblique movement of the sheet 5 is corrected when the sheet 5 is fed from the sheet feeding device 6, the sheet 5 may be obliquely fed to the recording unit 3 depending on accuracy when mounting the sheet feeding device 6 on the word processor WP. The above-described operation is performed in order to assuredly correct such oblique movement.
Thereafter, the conveying motor is (forwardly) driven in the sheet-feeding direction by a predetermined amount N2 steps at a predetermined speed F2 pps by switching the drive of the conveying motor (step S5). At that time, the sheet 5 is conveyed by the conveying roller 21 of the recording unit 3 while being fed by the sheet feeding roller 9 driven by the feeding motor 12 of the sheet feeding device 6. When switching the direction of revolution or changing the speed of revolution of the conveying motor, the revolution of the conveying motor is stopped for 0.1 second.
The feeding motor 12 is turned off after driving the conveying motor by N2 steps (step S6). The fed distance of the sheet 5 by the drive of the feeding motor 12 and the conveying motor is the distance necessary to detach the trailing edge of the sheet 5 is detached from the roller units 9a of the sheet feeding roller 9. The feeding motor 12 is not turned off when the conveying motor has started the drive in the sheet-feeding direction. If the feeding motor 12 is turned off immediately when the leading edge of the sheet 5 has reached the conveying roller 21, a failure in sheet conveyance may occur because the leading edge of the sheet 5 may not have entered the nip portion between the conveying roller 21 and the pinch roller 22. In addition, as described above, if it is intended to convey the sheet 5 only by the conveying roller 21 in a state in which the trailing edge of the sheet 5 reaches the sheet feeding roller 9, a large conveying force is needed for the conveying roller 21.
After turning off the feeding motor 12, the conveying motor is further (forwardly) driven in the sheet-feeding direction by a predetermined amount N3 steps at a predetermined speed F3 pps (step S7), and the sheet 5 is conveyed to a position to start recording. The distance M3 shown in FIG. 16(b) corresponds to the drive of (N2+N3) steps of the conveying motor.
When the sheet 5 has been conveyed to the position to start recording, a recording operation is started (step S8).
The predetermined speed F1 pps when driving the conveying motor in a direction opposite to the sheet-feeding direction is set to a value equal to or less than the speed F3 pps in step S7 in order to prevent fluttering of the leading edge of the sheet 5. The speed F2 pps of the conveying motor driven together with the feeding motor 12 is set to a value equal to or less than the revolution speed of the feeding motor 12, and equal to or less than the above-described speed F1 pps.
F2 pps.ltoreq.F1 pps.ltoreq.F3 pps
The revolution speed corresponding to F2 pps.ltoreq.the speed of revolutions of the feeding motor.
If the revolution speed of the feeding motor 12 is set to a value less than the revolution speed of the conveying motor, load at the sheet feeding roller 9 (a resistive force against sheet conveyance) increases, so that a desired amount of feeding may not be achieved. If the desired amount of feeding is not achieved, there is the possibility that the sheet 5 does not reach an ordinary position to start recording, and therefore, in the worst case, recording is performed while the sheet is absent. In order to prevent the occurrence of such a case, the conveying force at the recording unit 3 (the driving force of the conveying roller 21) must be increased, thereby causing an increase in the cost and the size of the sheet feeding device 6.
In step S3, if the sheet detection sensor 20 is not turned on after the feeding motor 12 has been turned on, the drive of the feeding motor 12 is continued within a predetermined time period. After the lapse of the predetermined time period, it is determined that the sheet to be fed is absent, and the absence of the sheet is reported after stopping the sheet-feeding operation. In the present embodiment, the predetermined time period is set to 5 seconds. As shown in FIG. 15(c), the spring 14 is disposed at a position where the roller units 9a of the sheet feeding roller 9 are absent, i.e., where the spring 14 does not contact the roller units 9a, in order that the spring 14 and the sheet feeding roller 9 are not damaged even if there are no sheets to be fed in the sheet feeding device 6.
Recording means
As described above, the recording means (the recording head 23) records an ink image on a recording sheet conveyed by the conveying means. An ink-jet recording method is favorably used for the recording means in the present apparatus.
Ink-jet recording means includes liquid-discharging ports for discharging an ink liquid for recording as flying droplets, a liquid channel communicating with the liquid-discharging ports, and discharging-energy generation means, provided at a portion of the liquid channel, for providing discharging energy for forcing the ink liquid through the liquid channel. The discharging-energy generation means is driven to discharge ink liquid droplets in accordance with an image signal to record an image.
Pressure-energy generation means, for example, an electromechanical transducer, such as a piezoelectric element or the like; electromagnetic-energy generation means for heating an ink liquid by projecting an electromagnetic wave, such as a laser or the like, and discharging ink droplets generated by the heating; thermal-energy generation means for discharging ink droplets by heating an ink liquid using an electrothermal transducer, or the like is used as the discharging-energy generation means.
Among these approaches, a method in which ink droplets are discharged using the thermal-energy generation means using an electrothermal transducer is preferable, because liquid-discharging ports can be arranged at high density, so that high-resolution recording can be performed and a small-size recording head can be provided. In this method, film boiling produced in the ink by thermal energy provided by the electrothermal transducer is utilized, and the ink is discharged from the discharging ports.
Next, a description will be provided of another embodiment of the sheet feeding device 6 with reference to FIG. 20.
In the above-described embodiment, by driving the sheet feeding roller 9 for a predetermined time period after the sheet 5 fed by the sheet feeding roller 9 has reached the conveying roller 21 of the main body, slip is produced between the sheet 5 and the sheet feeding roller 9. However, the present invention is not limited to such an approach. For example, in the present embodiment, a DC motor is adopted as the feeding motor 12. As shown in FIG. 20, a DC motor has characteristics in which the number of revolutions of the motor is inversely proportional to the load torque, and the revolution of the motor stops when the torque exceeds a predetermined value. The present embodiment utilizes such characteristics.
In FIG. 20, if the torque of the feeding motor 12 necessary for feeding the sheet in a usual manner equals TT, the number of revolutions of the feeding motor 12 at that time equals RT, and the sheet feeding roller 9 rotates at the number of rotations obtained from the number RT by taking into consideration of the reduction ratio of a drive transmission mechanism and the transmission efficiency. As the value of the torque TT increases, the number of revolutions decreases. When the value of the torque equals TM, the number of revolutions equals 0. The torque TM is called a starting torque. The motor can rotate when the value of the load is less than the starting torque. The value of the starting torque can be freely set by changing the diameter of the wire and the number of turns of the coil within the motor.
Accordingly, the starting torque is set so that the number of revolutions of the feeding motor 12 becomes 0 before the sheet 5 is bent when driving the sheet feeding roller 9 for a predetermined time period after the sheet 5 fed by the sheet feeding roller 9 has reached the conveying roller 21 of the main body.
That is, if the value of a force necessary to bend the sheet 5 converted into the value of the motor torque is represented by TS, the torque TM may be set so that the relationship of TS>TM holds. At that time, although the number of revolutions of the feeding motor 12 equals 0, since the sheet 5 is brought in contact with the conveying roller 21 by a feeding force generated from the torque TM, the leading edge of the sheet 5 can be assuredly aligned with the conveying roller 21. The above-described relational expressions (1) and (2) must also be satisfied.
The feeding motor 12, serving as a driving source for the sheet feeding roller 9 functioning in the above-described manner, acts as feeding-force providing means K as the spring 14 in the above-described embodiment.
Next, a description will be provided of still another embodiment of the sheet feeding device 6 with reference to FIG. 21.
In the above-described embodiments, slip is produced between the sheet 5 and the sheet feeding roller 9 when driving the sheet feeding roller 9 for a predetermined time period after the sheet 5 fed by the sheet feeding roller 9 has reached the conveying roller 21 of the main body, or the starting torque of the DC motor, serving as the feeding motor 12, is set to such a small value that the sheet 5 is not bent. The same effects may also be obtained by providing, as shown in FIG. 21, a frictional member 50, such as a felt or the like, functioning as a torque limiter between a pedestal 9c provided at one end portion of the sheet feeding roller 9 and one end portion 10a of the worm gear, and by driving the frictional member 50 in the axial direction of the sheet feeding roller 9 by a spring (not shown).
The force of the spring for driving the frictional member 50 is set to a value greater than the driving force of the feeding motor 12 transmitted to the sheet feeding roller 9 for feeding the sheet 5, and smaller than a force necessary to bend the sheet 5 when driving the sheet feeding roller 9 for a predetermined time period after the sheet 5 has reached the conveying roller 21 of the main body. That is, the spring force to set the limit value of the torque limiter may satisfy the above-described relational expressions (1)-(3).
In this case, the feeding motor 12 is not necessarily a DC motor, but any other motor, such as a stepping motor or the like, may also be used.
The frictional member 50 functioning in the above-described manner acts as feeding-force providing means as the spring 14 and the feeding motor 12 in the above-described embodiments.
In addition to the operations of the sheet feeding device 6 and the recording unit 3 shown in FIG. 19, a control method as shown in FIG. 22 is preferable.
In FIG. 22, when a recording command has been received and a feeding operation has been started (step S10), counting of a time T1 by a timer is started (step S11), and the DC motor, serving as the feeding motor 12, is turned on (step S12) to feed the sheet 5.
The sheet 5 is fed until the leading edge of the sheet 5 passes through the sheet detection sensor 20. When the sheet 5 has been fed by the distance M1 shown in FIG. 16(a), the sheet detection sensor (PE sensor) 20 is turned on (step S13), and the counting of the time T1 by the timer is terminated and the count value T1 is stored, and counting of a time T2 by the timer is newly started (step S14). The feeding speed (V0) is calculated from the stored time T1 and the fed distance M1 (step S15). A DC motor is adopted as the motor for rotatably driving the sheet feeding roller 9. When a plurality of sheets are individually fed, the pressing force of the spring 14 for pressing the sheets 5 against the sheet feeding roller 9 changes depending on the number of remaining sheets, and the rotation speed of the sheet feeding roller 9 changes due to changes in the pressing force. The feeding speed is calculated in order to more precisely estimate the time when the leading edge of the sheet 5 reaches the conveying roller 21 of the recording unit 3.
When the feeding speed (V0) has been calculated, the time (TT) required for feeding the sheet 5 for the distance M2 shown in FIG. 16(a) is calculated from the value V0 (step S16). Thereafter, as in the case of FIG. 19, the (reverse) drive of the conveying motor in a direction opposite to the sheet-feeding direction at a predetermined speed F1 pps is started (step S17). The feeding motor 12 feeds the sheet 5 until the count value T2 by the timer equals the value TT. when the value T2 coincides with the value TT (step S18), the drive of the conveying motor of the recording unit 3 in the reverse direction is stopped (step S19), and the conveying motor is (forwardly) driven in the sheet-feeding direction by a predetermined amount N2 steps at a predetermined speed F2 pps (step S20). In the present embodiment, a stepping motor is adopted as the conveying motor. As described above, when switching the direction of revolution, or changing the revolution speed, as will be described below, of the conveying motor, the revolution of the conveying motor is stopped for 0.1 second.
When the conveying motor has been driven by the N2 steps, the drive of the feeding motor 12 is stopped (step S21). Thereafter, the conveying motor is (forwardly) driven by a predetermined amount N3 steps at a predetermined speed F3 pps (step S22) to feed the sheet 5 to the position to start recording. As in the case of FIG. 19, the sheet 5 is fed by the drive of the conveying motor and the feeding motor until the trailing edge of the sheet 5 is detached from the sheet feeding roller 9. Also as in the case of FIG. 19, the sheet 5 is fed to the conveying roller 21 rotatably driven in a direction opposite to the sheet-feeding direction, and both the conveying roller 21 rotatably driven in the sheet-feeding direction and the sheet feeding roller 9 are rotated.
If the PE sensor 20 is not turned on after the feeding motor 12 has been turned on in step S13, the feeding motor remains to be turned on if the time elapsed after the feeding motor 12 has been turned on is within a predetermined time period. After the lapse of the predetermined time period (step S24), it is determined that a sheet to be fed is absent, and the absence of the sheet is reported after stopping the feeding operation (step S25).
In the above-described embodiments, the sheet feeding roller 9 comprises the shaft 9b and the two roller units 9a, made of a hard rubber or the like, fitted on the shaft 9b at the predetermined interval. However, the configuration of the sheet feeding roller 9 is not limited to such a configuration, but may have the following configuration.
FIGS. 23(a) and 23(b) illustrate examples of the configuration of the sheet feeding roller 9. The sheet feeding roller 9 shown in FIG. 23(a) comprises a roller unit 15a, made of a hard rubber or the like and formed as one body so as to contact a sheet to be fed at two portions, fitted on a shaft 15b. As in the case of FIG. 23(a), in the sheet feeding roller 9 shown in FIG. 23(b), a roller unit 16a is formed as one body, and portions of the roller unit 16a in contact with a sheet to be fed are connected with a curved surface. In each of the roller units 15a and 16a shown in FIGS. 23(a) and 23(b), respectively, the diameter of a portion between portions in contact with a sheet to be fed is formed to be smaller than the diameter of the portions in contact with the sheet, so that the sheet feeding roller 9 contacts the sheet at two portions at a predetermined interval. In such configurations, since each of the roller units 15a and 16a is formed as one body, the interval between two portions in contact with the sheet can be precisely provided.
Next, a description will be provided of another separation mechanism with reference to FIGS. 24 through 27(d). FIGS. 24 and 25 are perspective views illustrating a separation unit. In FIGS. 24 and 25, a gap member 7e' for forming a gap C for separation is provided in an aperture 7d. A guide member 7h', provided in the vicinity of the gap member 7e', for facilitating entrance of the leading edge of the sheet 5 into the gap C, and similar guide members 7h, provided at two sides of the aperture 7d, are formed as one body. The guide members 7h also function as regulation means for regulating the movement of the sheet 5 in the direction of the thickness at side portions of the sheet 5, and regulate floating of the sheet 5 at the above-described side plate 7f, providing the feeding reference position or the recording reference position.
When feeding the sheet 5 in a downwardly convex state as shown in FIG. 27(b) due to stocking conditions of the sheet 5 and environmental conditions, since the feeding direction of the sheet feeding roller 9 equals the direction B shown in FIG. 10, a side-end portion of the sheet 5 at the side of the side plate 7f moves in a direction opposite to the accommodating surface for the sheet 5, and, in some cases, floats. In such a case, if the amount of floating of the sheet 5 is great, the feeding position may become different from the recording position. However, since the regulation members 7h for regulating the movement of the sheet 5 in the direction of the thickness is provided, precise feeding can be performed.
As in the above-described embodiments, the gap member 7e' is provided at a position shifted from the center line of the sheet 5 in the lateral direction toward the side plate 7f by a distance .beta.. That position is asymmetrical with respect to the center line of the sheet 5 in the lateral direction at an arbitrary position of the sheet placed in the sheet accommodating portion of the lower case 7. Hence, when the sheet 5 is fed again while turning the sheet 5 upside down, the portion of the sheet 5 in contact with the gap member 7e' differs from the initial portion.
Accordingly, even if an end portion of the sheet 5 is raised due to contact with the gap member 7e' when refeeding the sheet 5 while turning the sheet 5 upside down, the raised portion does not contact the gap member 7e'. As a result, the sheet 5 can be smoothly fed.
As described above, the gap member 7e' for separation is provided at a position where it does not contact two corner portions of the sheet 5. Gaps Ch formed by the guide members 7h are present at portions corresponding to the two corner portions of the sheet 5. However, as can be seen from FIGS. 26(a) and 26(b), since the gaps Ch are wider than the gap C for separation, the corner portions of the sheet 5 are not raised.
Although in the present embodiment, the guide members 7h, serving as the regulation means, are provided so as to regulate two side-end portions of the sheet 5, only a single guide member 7h may be provided at one side so as to regulate a side-end portion of the sheet 5 at the side of the side plate 7f, providing the feeding reference position.
FIG. 26(a) is a cross-sectional view of the guide member 7h'. In FIG. 26(a), the gap C formed between the reference surface 7b and the gap member 7e' has a size X which is somewhat greater than the thickness of the sheet 5, in order to form a gap for separating the sheet 5. An inclined surface of the guide member 7h' is formed continuously and as one body with the gap member 7e' for separation at the gap C. The inclined surface makes an angle .gamma. with the reference surface 7b. In the present embodiment, the angle .gamma. is set to 60.degree..
In the present embodiment, surface formed on the inclined surface formed on the guide member 7h' is greater than the maximum estimated height of curl of the sheet 5 at a portion where the guide member 7h' contacts the sheet 5.
FIG. 26(b) is a cross-sectional view of the guide member 7h. In FIG. 26(b), the gap Ch between the guide member 7h and the supporting surface 7c has a value Y which is greater than the value X, and the angle made by the inclined surface of the guide member 7h and the supporting surface 7c has the same value .gamma. as in the case of the guide member 7h'.
As in the case of the above-described height h1, the height h2 of the inclined surface formed on the guide member 7h is set to a value greater than the height of curl of the sheet 5 estimated at a portion where the sheet 5 contacts the guide member 7h, more specifically, the height of floating of the sheet 5 from the reference surface 7c. In the present embodiment, since the height of curl has a maximum value when a single sheet 5 is present, the height of floating of the sheet in such a case is adopted as the above-described height of floating. The height h2 of the inclined surface of the guide member 7h is set to a value greater than the above-described height h1, assuming that the height of curl of the sheet at the guide member 7h is greater than the value h1.
In the present embodiment, the angle .gamma. made by the inclined surfaces of the guide members 7h' and 7h, and the reference surface 7b and the supporting surface 7c, respectively, equals 60.degree.. If the angle .gamma. is less than 30.degree., there is the possibility that the second sheet and/or subsequent sheets could enter the gap member 7e' together with the first sheet while the first sheet is being fed. Hence, it is desirable to make the angle .gamma. equal to or greater than 30.degree.. In the above-described embodiment, the inclined surfaces of the guide members 7h' and 7h make the same angle .gamma. with the reference surface 7b and the supporting surface 7c, respectively. However, since the gap Ch between the guide member 7h and the supporting surface 7c is considerably greater than the thickness of the sheet 5, there is less possibility that the leading edges of the second and/or subsequent sheets will enter the gap Ch. Hence, the angle between the inclined surface of the guide member 7h and the supporting surface 7c may have a value different from the above-described value .gamma., for example, a value less than 30.degree.. Although in the present embodiment, the heights of the inclined surfaces of the guide members 7h' and 7h are set so as to be h2>h1, any other relationship between the heights h1 and h2 may be adopted in accordance with the state of curl of the sheet 5, for example, as h1=h2.
FIGS. 27(a) through 27(d) illustrate the function of the above-described guide members 7h' and 7h. FIGS. 27(a) and 27(b) illustrate states before starting a feeding operation, as seen from the front side. The sheet 5 is not always flat depending on environmental conditions, such as the ambient temperature and himidity, conditions of use, and the like. Upwardly convex curl may be produced in the sheet 5 as shown in FIG. 27(a), or downwardly convex curl may be produced in the sheet 5 as shown in FIG. 27(b).
FIGS. 27(c) and 27(d) illustrate states in which the sheet 5 is passing through the above-described gaps.
As described above, the heights h1 and h2 of the inclined surfaces of the guide members 7h' and 7h are greater than the height of curl of the sheet 5 at contact portions with the guide members 7h' and 7h. Hence, even if the sheet 5 is curled, end portions of the sheet 5 contact the inclined surfaces of the guide members 7h' and 7h, and the sheet 5 is guided into the gaps C and Ch. The gap Ch between the guide member 7h and the supporting surface 7c is set to be greater than the gap C between the guide member 7h' and the reference surface 7b, and the height h2 is set to be equal to or greater than the height h1, in order to normally feed even the curled sheet 5.
The height of the supporting surface 7c is set to be lower than heights of the reference surface 7b and the upper surface of the sheet feeding roller 9 for the following reason. That is, when it is intended to press the sheet 5 having upwardly convex curve as shown in FIG. 27(a) against the sheet feeding roller 9 by the spring 14, a large force is needed for the spring 14 to press the sheet 5 to a flat state. The force needed for the spring 14 is reduced by lowering the supporting surface 7c.
FIG. 28 is a cross-sectional view illustrating the positional relationship between the sheet feeding roller 9 and the spring 14, serving as contact means for contacting the sheet 5 to the sheet feeding roller 9. Portions where the spring 14 contacts and presses the roller units 9a of the sheet feeding roller 9 are always situated at a side downstream from the center of rotation of the sheet feeding roller 9 irrespective of the number of mounted sheets 5 to be separated and fed, and at a side more downstream by .delta. when only a single sheet is present. Thus, the sheet 5 is conveyed so as to always contact the reference surface 7b while being pressed at a side downstream from the sheet feeding roller 9. When the leading edge of the sheet 5 enters the gap formed by the gap member 7e, the leading edge of the sheet 5 is pressed so as not to float and easily enter the gap C.
Next, a description will be provided of another embodiment of control procedures for controlling the drive of the sheet feeding device 6 and the recording unit 3 with reference to a flowchart shown in FIG. 29.
In the above-described embodiment of the control procedures, oblique movement of the sheet 5 is prevented by contacting the sheet 5 to the conveying roller 21 by rotating the conveying roller 21 in the reverse direction. In the present embodiment, however, oblique movement of the sheet 5 is prevented by stopping the conveying roller 21.
In FIG. 29, when a recording command has been received and a feeding operation has been started (step S1), counting of a time T1 by a timer is started (step S2), and the DC motor, serving as the feeding motor 12, is turned on (step S3) to feed the sheet 5.
The sheet 5 is fed until the leading edge of the sheet 5 passes through the sheet detection sensor 20. When the sheet 5 has been fed by the distance M1 shown in FIG. 16(a), the sheet detection sensor (PE sensor) 20 is turned on (step S4), and the counting of the time T1 by the timer is terminated and the count value T1 is stored, and counting of a time T2 by the timer is newly started (step S5).
The feeding speed (V0) is calculated from the stored time T1 and the fed distance M1 (step S6). When a plurality of sheets 5 are set and are individually fed, the pressing force of the spring 14 for pressing the sheets 5 against the sheet feeding roller 9 changes depending on the number of remaining sheets, whereby a force necessary to rotatably drive the sheet feeding roller 9 changes. Since the DC motor is adopted as the sheet feeding motor 12, serving as a driving source to rotatably drive the sheet feeding motor 9, the rotation speed of the sheet feeding roller 9 changes as the force necessary to rotatably drive the sheet feeding roller 9 changes. Accordingly, by calculating the feeding speed (V0), the time when the leading edge of the sheet 5 reaches the conveying roller 21 of the recording unit 3 can be more precisely estimated.
When the feeding speed (V0) has been calculated, the time (TT) required for feeding the sheet 5 for the distance M2 shown in FIG. 16(a) is calculated from the value V0 (step S7). The feeding motor 12 feeds the sheet 5 until the count value T2 by the timer equals the value TT. When the value T2 coincides with the value TT (step S8), the conveying motor of the recording unit 3 is driven by a predetermined amount N1 steps (step S9). In the present embodiment, a stepping motor is adopted as the conveying motor.
When the conveying motor has been driven by N1 steps, the drive of the feeding motor 12 is stopped (step S10). Thereafter, the conveying motor is driven by a predetermined number of steps, N2 steps (step S11).
As described above, the feeding motor 12 is stopped after driving the conveying motor by N1 steps. If the feeding motor 12 is stopped immediately when the leading edge of the sheet 5 has reached the conveying roller 21, there is the possibility that the sheet 5 would not assuredly enter the conveying roller 21, thereby causing a failure in conveyance of the sheet 5. Accordingly, the sheet 5 is fed by the feeding motor 12 until the sheet assuredly enters the conveying roller 21. Then, the conveying motor is driven by N2 steps in order to convey the sheet 5 to the position to start recording, i.e., the distance M3 shown in FIG. 16(b). Accordingly, the relationship of M3=N1+N2 holds.
When the sheet 5 has been conveyed to the position to start recording in step S11, recording is actually started (step S12).
If the sheet detection sensor 20 is not turned on in step S4 after the feeding motor 12 has been turned on, the feeding motor 12 remains on if the time elapsed after the feeding motor 12 has been turned on is within a predetermined time period. After the lapse of the predetermined time period, if the sheet detection sensor is not turned on, the absence of the sheet is reported after stopping the feeding operation (step S14). In the present embodiment, the predetermined time period is set to 5 seconds. When the sheets 5 are not present, the spring 14 directly contacts the sheet feeding roller 9, as shown in FIG. 28. Accordingly, a roller 14a is provided at the distal end of the spring 14 so as not to damage the sheet feeding roller 9 and the spring 14.
In the above-described embodiments, only a single gap member 7e for separation has been illustrated. However, the number of the gap member 7e is not limited to only one. For example, as shown in FIGS. 30 and 31, the present invention can also be applied to a configuration in which two gap members 7j and 7k for separation are provided.
In FIG. 30, roller units 9a of a sheet feeding roller 9, a reference surface 7b provided on a lower case 7 for accommodating sheets 5, a reference surface 7c provided at a position lower than the reference surface 7b, a side plate 7f, serving as a recording reference position, and a spring 14, serving as contact means, have the same configuration as in the above-described embodiments. A gap provided by the gap member 7j has the same configuration as the above-described gap formed by the gap member 7e'. That is, the gap is provided within a range where the sheet 5 is pressed by the spring 14 in the lateral direction, and is situated at a position shifted from the center line of the sheet 5, when a side of the sheet 5 is aligned along the side plate 7f, to the side plate 7f by a distance .beta.. The other gap member 7k is situated at a position further from the side plate 7f than the gap member 7j.
FIG. 31 is front view of the configuration shown in FIG. 30. The interval of a gap C formed between the gap member 7j and the reference surface 7b equals X shown in FIG. 26(a), and the interval of the gap C formed between the gap member 7k and the reference surface 7c also equals X.
As in the above-described embodiments, guide members for guiding the leading edge of the sheet 5 into the gap C are provided at the gap members 7j and 7k as one body therewith, and the heights of continuous inclined surfaces for guiding the sheets, provided on the guide members 7j and 7k, from the reference surfaces 7b and 7c equal h1 and h2, respectively. The heights h1 and h2 correspond to the estimated heights of curl of the sheet 5 at respective positions. In the present embodiment, the height of curl of a single sheet is adopted as the height of curl of the sheet 5. Since the sheet 5 is pressed by the spring 14 in the vicinity of the gap member 7j, the height of curl is estimated to be greater at the gap member 7k. Hence, it is arranged to be h2>h1.
Gaps having a height h3 from the reference surface 7b are provided at two sides of the gap members 7j and 7k, and regulation members 7h for regulating the direction of the thickness of the sheet 5 are provided. A continuous inclined surface for guiding the sheet 5 into the gap is provided on the regulation member 7h, the height of the inclined surface equals h3. The size of a gap Ch formed by the regulation member 7h equals Y shown in FIG. 26(b), which is greater than the size X of the gap formed by the gap members 7k and 7j. Since the height h3 is a gap at two end portions of the sheet 5, the height h3 is set to be greater than the height h2 of the inclined surface of the gap member 7k so as not to hinder the passage of the sheet 5 even if the sheet 5 is curled.
The heights h1 and h2 of the inclined surfaces and the height h3 of the gap at the two sides may be appropriately set in accordance with the kind of sheets to be used, environmental conditions and the like, for example, as h1=h2=h3.
When providing two gap members in the above-described manner, in general, the two gap members are worn differently depending on states of contact with sheets. Accordingly, even if one of the two members is worn earlier, the other is less worn, so that feeding of a plurality of sheets at a time can be prevented as much as possible.
Although in the above-described embodiments, the spring 14 is used as contact means for contacting the sheet 5 to the sheet feeding roller 9, the present invention can also be applied to a configuration in which contact means is fixedly provided and a pressing member is provided on the sheet feeding roller.
Although in the above-described embodiments, a roller is provided on the elastic member and the sheet is pressed against the sheet feeding roller, the present invention can also be applied to a configuration in which, as shown in FIG. 32, an end portion of an elastic member 50 does not contact a sheet feeding roller. Also in this case, the contact position between the sheet and the elastic member is situated at a side downstream from the sheet feeding roller 9a in the sheet-feeding direction.
In the above-described embodiments, load when conveying the sheet 5 by the conveying roller 21 is reduced by driving the sheet feeding roller 9 until the trailing edge of the sheet 5 fed from the sheet feeding roller 9 passes through the sheet feeding roller 9. The same object can be achieved by using the following clutch mechanism.
The clutch mechanism will be described with reference to FIGS. 33 through 34(b). A projection 9c is formed at one end of the sheet feeding roller 9. When the shaft 9b of the sheet feeding roller 9 is inserted into a hole in the center of rotation of the gear 10, the projection 9c engages a projection 10a formed on the gear 10. The worm gear 11 mounted on the feeding motor 12 meshes with the gear 10.
When the gear 10 is rotated by the feeding motor 12 in a direction E shown in FIG. 34(a), the projection 10a contacts the projection 9c, so that the sheet feeding roller 9 is rotated in the same direction E. When the sheet 5 has been fed from the sheet feeding device 6 to the recording unit 3 in this state, and the sheet 5 has reached the conveying roller 21 of the recording unit 3, the drive of the feeding motor 12 is stopped, and then the sheet 5 is conveyed by the conveying roller 21.
When the sheet 5 is conveyed by the conveying roller 21, the sheet feeding roller 9 is also rotated in a direction F shown in FIG. 34(b). When the sheet feeding roller 9 has been rotated in the direction F, the projection 9c separates from the projection 10a. Hence, the gear 10 stops rotation, and only the sheet feeding roller 9 rotates until the projection 9c again contacts the projection 10a after the sheet feeding roller 9 has completed about one rotation.
If the feeding motor 12 and the sheet feeding roller 9 are connected by the worm gear 11, the gear 10 cannot be rotated even if it is intended to rotate it from the side of the sheet feeding roller 9. Hence, the sheet 5 cannot be conveyed by the feeding roller 21 of the recording unit 3 unless the above-described clutch mechanism is used. Even if the worm gear 11 is not used, if the sheet feeding roller 9 is rotated at the same time the sheet 5 is conveyed by the conveying roller 21 of the recording unit 3, a body having large inertia including a gear train from the sheet feeding roller 9 to the feeding motor 12 must be rotated at the same time. Hence, a large conveying force is required for the conveying roller 21 of the recording unit 3. Accordingly, the above-described clutch mechanism is effective. Since the clutch mechanism of the present embodiment is obtained by the combination of the projections 9c and 10a, the configuration is simple, and therefore the production cost is low.
Although an ink-jet method is most suitable as the recording method of the recording unit 3, the present invention is not limited to this recording method, but any other recording method, such as a thermal transfer method, an impact transfer method, an electrophotographic method or the like may be used.
The individual components shown in outline or designated by blocks in the drawings are all well known in the electronic apparatus arts and their specific construction and operation are not critical to the operation or the best mode for carrying out the invention.
While the present invention has been described with respect to what is presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Number	Date	Country
6-004055	Jan 1994	JPX
6-261331	Sep 1994	JPX
6-280041	Oct 1994	JPX
6-280623	Nov 1994	JPX
6-280624	Nov 1994	JPX

Number	Name	Date
4699534	Asakura et al.	Oct 1987
5219155	Kanome	Jun 1993
5672019	Hirmatsu et al.	Sep 1997

Electronic apparatus capable of feeding sheets from a front side, and sheet feeding device for use therewith

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