Printer

Abstract

In order to prevent the paper feed direction from greatly varying due to swinging of a retard roller in the allowable range of the insertion depth of a paper tray with respect to a body of a printer, a printer (100) is provided with a pickup roller (81) and a feed roller (82) fixed to a body, and a paper tray (20) detachably mounted thereto, the printer (100) having a retard roller (84) that is in contact with the feed roller (82) in a state in which the paper tray (20) is mounted, and sandwiches and conveys the stored paper (S) with the feed roller (82). The retard roller (84) has: a base member (84d) fixed to the lower part of the front part of the paper tray (20); a roller member (84b) that is in contact with the feed roller (82); and a swing arm member (84a) that rotatably supports the roller member (84b) at the upper end part thereof, is provided so that the lower end part thereof can rotate forward and backward with respect to the base member (84d), is disposed in a posture extending in the height direction (H), and swings forward when the roller member (84b) is pressed by the feed roller (82).

Description

printer

[0001] The present invention relates to a printer.

[0002] The printer is equipped with a pull-out paper tray that holds a stack of paper sheets (hereinafter referred to as paper) cut to a specified size. The printer's main body is equipped with a pickup roller and a feed roller that rotate in contact with the topmost sheet of paper stored in the paper tray, sending the sheet into the paper feed path.

[0003] When the pickup roller and feed rollers are used to feed out the paper, a double feed may occur in which the second sheet of paper stacked directly below the top sheet (the sheet placed next to the top sheet) is fed out together with the top sheet while overlapping it due to static electricity, etc. If a double feed occurs, there is a risk that paper jams may occur in the path of subsequent sheets or that printing may become misaligned in the printing section.

[0004] To prevent this, a retard roller is positioned opposite the feed roller, and the paper is sandwiched between the feed roller and the retard roller for feeding. In this case, the torque of the feed roller is applied to the top sheet of paper that is in contact with the feed roller, so the top sheet of paper is fed. Because the retard roller is applied with a torque in the opposite direction to the feed direction of the feed roller, the second sheet of paper that has advanced on top of the top sheet of paper is stopped by the torque of the retard roller and separated from the top sheet of paper, thereby eliminating the double feed (see, for example, Patent Document 1).

[0005] Patent No. 6035312

[0006] Here, the pressure at which the feed roller and the retard roller come into contact needs to be within a predetermined range, but in printers where the feed roller is located in the printer body and the retard roller is located in the paper tray, the pressure at which the feed roller and the retard roller come into contact will vary depending on the depth to which the paper tray is inserted into the body, so it is desirable that the depth to which the paper tray is inserted into the body be constant.

[0007] However, even if the insertion depth of the paper tray into the main body varies slightly due to manufacturing errors or handling of the printer, the printer will still operate normally. In other words, even if the insertion depth of the paper tray into the main body is small, as long as the small depth is within a certain range, the printer will operate normally in the same way as if the insertion depth were specified.

[0008] For this reason, the retard roller is configured so that the contact pressure does not fluctuate significantly even if the contact position with the feed roller changes and the angle of oscillation changes. Furthermore, the printer is required to prevent the direction of the common tangent at the contact position between the feed roller and the retard roller from fluctuating significantly due to oscillation of the retard roller within the allowable range of insertion depth of the paper tray into the main body (the range in which the printer operates normally).

[0009] The present invention has been developed in consideration of the above circumstances, and aims to provide a printer in which the direction of the common tangent between the feed roller and the retard roller does not fluctuate significantly due to the oscillation of the retard roller within the allowable range of the insertion depth of the paper tray into the main body.

[0010] The present invention is a printer comprising a feed roller fixed to the printer body, and a paper tray containing a large number of sheets of paper that is removably attached to the printer body, and a retard rotor that contacts the feed roller when the paper tray is attached to the printer body and transports the paper contained in the paper tray by sandwiching it between the feed roller and the feed roller, and the retard roller has a base member fixed to the lower front part of the paper tray, a roller member that contacts the feed roller, and a swing arm member that rotatably supports the roller member at its upper end and has a lower end that is rotatable back and forth relative to the base member, is arranged in a vertically extending position, and swings forward when the roller member comes into contact with the feed roller.

[0011] The printer according to the present invention prevents the direction of the common tangent to the feed roller and the retard roller from fluctuating significantly due to oscillation of the retard roller within the allowable range of insertion depth of the paper tray into the main body.

[0012] 4A is a cross-sectional view of a vertical plane passing through the center of the width direction W of a dye-sublimation thermal printer (hereinafter referred to as the printer) and along the front-to-rear direction L. FIG. 4B is a perspective view showing a paper tray. FIG. 4C is a simplified schematic representation of FIG. 1. FIG. 4D is a partial cross-sectional view (part 1) corresponding to FIG. 1 for explaining the structure and operation of a pickup roller, a feed roller, and a retard roller. FIG. 4E is a partial cross-sectional view (part 2) corresponding to FIG. 1 for explaining the structure and operation of a pickup roller, a feed roller, and a retard roller. FIG. 4F is a perspective view showing the interior of a retard roller. FIG. 4G is a perspective view (part 1) explaining a configuration for generating a torque difference in the retard roller. FIG. 4G is a cross-sectional view (part 2) explaining a configuration for generating a torque difference in the retard roller, corresponding to FIG. 4A, for explaining the structure and operation of a comparative example in which a roller member of a retard roller is swung up and down by a swing arm member extending rearward in the front-to-rear direction from in front of the roller member, with the axis at the front end of the swing arm member as a rotation fulcrum. 10 is a cross-sectional view equivalent to FIG. 4B illustrating the structure and operation of a comparative example in which a roller member of a retard roller is swung up and down by a swing arm member extending rearward in the front-to-rear direction from in front of the roller member, with the axis of the front end of the swing arm member as a rotation fulcrum. FIG. 11 is a perspective view showing the positional relationship between a paper tray and a paper guide. FIG. 12 is a plan view showing the positional relationship between a paper tray and a paper guide. FIG. 13 is a cross-sectional view showing a vertical cross section taken along line A-A in FIG. 10. FIG. 14 is a cross-sectional view showing a vertical cross section taken along line B-B in FIG. 10. FIG. 15 is a cross-sectional view showing a vertical cross section taken along line C-C in FIG. 10. FIG. 16 is a cross-sectional view showing a vertical cross section taken along line D-D in FIG. 10.

[0013] Hereinafter, an embodiment of a printer according to the present invention will be described as follows with reference to the drawings.

[0014] [Overall Configuration of Printer] FIG. 1 is a cross-sectional view of a dye-sublimation thermal printer 100 (hereinafter referred to as printer 100) taken along a vertical plane passing through the center of the width direction W and along the front-rear direction L.

[0015] The illustrated printer 100 is one embodiment of a printer according to the present invention. The printer 100 can accommodate both sheets of paper S (hereinafter simply referred to as paper S) that have been pre-cut to a predetermined size, and roll paper R (hereinafter simply referred to as paper R), which is a single long, strip-shaped sheet of paper wound into a roll, and can selectively print and output onto either paper S or R.

[0016] The printer 100 comprises a case 10, a paper tray 20, a printing unit 30, a cutter unit 40, a creasing unit 50, a roll paper storage unit 60, a conveying means 70, a control unit 90, and a conveying path P.

[0017] <Case> The case 10 is an exterior cover that houses the printing unit 30, cutting unit 40, creasing unit 50, roll paper compartment 60, transport means 70, control unit 90, and transport path P. The case 10, printing unit 30, cutting unit 40, creasing unit 50, roll paper compartment 60, transport means 70, control unit 90, and transport path P form the main body of the printer 100. As will be described later, the paper tray 20 is detachable from the main body of the printer 100. An outlet 15 for discharging printed sheets S and R is formed in the front panel that covers the front of the case 10 in the length direction L.

[0018] <Paper Tray> FIG. 2 is a perspective view showing the paper tray 20. The paper tray 20 stores a large number of sheets S stacked in the thickness direction. The paper tray 20 is removably attached to the main body of the printer 100 in a drawer-type manner. Specifically, the paper tray 20 is located at the bottom of the printer 100, and can be removed from the main body of the printer 100 by pulling it forward in the front-to-rear direction L, as shown by the outline arrow in FIG. 1. When removed from the main body of the printer 100, the paper tray 20 is attached to the main body of the printer 100 as shown in FIG. 1. The detailed structure of the paper tray 20 will be described later.

[0019] <Roll Paper Compartment> The roll paper compartment 60 is formed above the paper tray 20, on the front side in the front-to-rear direction L. The roll paper compartment 60 is the section that accommodates roll paper R. In Figure 1, the roll paper compartment 60 accommodates roll paper R with the axis of the roll paper R parallel to the width direction W of the printer 100, and with the paper wound counterclockwise from the center toward the outer periphery. The roll paper R accommodated in the roll paper compartment 60 rotates counterclockwise as shown by pulling out the bottom end of the roll paper R to the right in Figure 1 and unwinding it.

[0020] <Printing Unit> The printing unit 30 is located behind the roll paper compartment 60 in the front-to-rear direction L. Under the control of the control unit 90, the printing unit 30 prints on the sheets S and R passing through a section of the transport path P that rises in a substantially vertical direction behind the roll paper compartment 60 (printing path P3, described below).

[0021] The printing unit 30 includes a thermal head 31, an ink ribbon 32, and a platen roller 33. A sublimation dye is applied to the ink ribbon 32. The ink ribbon 32 is fed from a feed roll 32a to a take-up roll 32b in synchronization with the transport of the papers S and R, and the sublimation dye of the ink ribbon 32 is diffused and transferred onto the papers S and R by the heat of the thermal head 31 in contact with the ink ribbon 32, thereby performing printing.

[0022] The platen roller 33 is disposed on the opposite side of the ink ribbon 32 and thermal head 31 across the sheets S and R conveyed along a print path P3, which will be described later. The platen roller 33 presses the sheets S and R against the ink ribbon 32.

[0023] <Cutter Unit> The cutter unit 40 is located in front of the roll paper compartment 60. The cutter unit 40 operates under the control of the control unit 90. The cutter unit 40 cuts the paper R in the width direction W as it passes through the portion of the transport path P that extends forward from above the roll paper compartment 60 (the discharge path P9, described below). As described above, the cutter unit 40 cuts the paper R, which is roll paper, to a predetermined length, but it can also cut off unnecessary edges of the paper S, which is sheets.

[0024] <Creasing Unit> The creasing unit 50 is located behind the roll paper compartment 60 in the front-to-rear direction L and between the printing unit 30 and the paper tray 20 in the height direction H. The creasing unit 50 operates under the control of the control unit 90. The creasing unit 50 forms creases, which are depressions extending along the width direction W, in the paper S that passes through a portion of the transport path P that extends in the front-to-rear direction L below the roll paper compartment 60 (the creasing path P7, described below). As described above, the creasing unit 50 forms creases in the paper S, which is a sheet of paper. However, it may also form creases in the paper R, which is a roll of paper, by controlling the cutting and transport.

[0025] <Conveying Path> Figure 3 is a schematic diagram that simplifies Figure 1 to clarify the conveying path P. The conveying path P is the path along which the sheets S and R are conveyed by the conveying unit 70, and is indicated by a dashed line in Figure 3. The symbol Q shown next to the conveying path P indicates the forward direction in which the sheet S is conveyed from the paper tray 20 toward the discharge outlet 15 and the forward direction in which the sheet R is conveyed from the roll paper compartment 60 toward the discharge outlet 15, and the symbol -Q indicates the reverse direction that is opposite to the forward direction Q.

[0026] The transport path P has a sheet feeding path P1, a sheet feeding path P2, a printing path P3, a waiting path P4, a printing lower path P5, a reversing waiting path P6, a creasing path P7, a roll paper feeding path P8, and a discharge path P9.

[0027] The sheet feeding path P1 (hereinafter simply referred to as the feeding path P1) is a transport path along which the sheets S stored in the paper tray 20 are fed one by one. The feeding path P1 is formed by extending diagonally upward and forward from the front end of the paper tray 20. The means for feeding the sheets S from the paper tray 20 to the feeding path P1 are a pickup roller 81 and a feed roller 82 provided in the main body of the printer 100, but a retard roller 84 provided in the paper tray 20 is also used to prevent double feeding of the sheets S.

[0028] When the sheet S is fed out, the hopper 21a of the sheet tray 20 is raised, and the operation of feeding out the sheet S will be described later together with the structure of the retard roller 84.

[0029] The sheet paper feed path P2 (hereinafter simply referred to as the paper feed path P2) is a transport path that continues from the payout path P1, extends upward from the front end of the payout path P1, then folds back and downward in the space formed in front of the roll paper storage section 60, extends rearward through the space between the roll paper storage section 60 and the paper tray 20, and is further formed to a position that rises upward behind the roll paper storage section 60.

[0030] Printing path P3 continues from the front end of paper feed path P2, rising upward along the rear of roll paper compartment 60, and then extending forward to the upper front of roll paper compartment 60. The platen roller 33 and thermal head 31 of printing unit 30 described above are positioned opposite each other with printing path P3 in between.

[0031] The standby path P4 follows the printing path P3 and extends from the front end of the printing path P3 to the upper front part of the roll paper storage section 60, and then extends downward in front of the roll paper storage section 60 in a concentric circle with the outer periphery of the roll paper storage section 60 to a position just before it hits the paper feed path P2.

[0032] The downstream printing path P5 is formed to follow the printing path P3, extending diagonally downward and forward from the rear end of the printing path P3 and passing outside the paper feed path P2 behind the roll paper compartment 60.

[0033] The reversal standby path P6 is continuous with the downstream printing path P5, extending forward in the front-to-rear direction L from the front end of the downstream printing path P5 through the space between the paper feed path P2 and the paper tray 20, with its front end connected to the rear end of the paper feed path P2. The downward-facing side of the paper S passing through the reversal standby path P6 has already been printed, and by being transported again along the paper feed path P2 from the reversal standby path P6, the upward-facing side of the paper S in the reversal standby path P6 becomes the target for printing in the printing unit 30 when the paper S next passes through the printing path P3. Therefore, the reversal standby path P6 and the paper feed path P2 form a reversal path that reverses the front and back sides of the paper S.

[0034] The creasing path P7 is formed following the reversing standby path P6, extending from the rear end of the reversing standby path P6 above the paper tray 20 toward the rear in the front-rear direction L. The creasing section 50 is disposed on the creasing path P7.

[0035] The roll paper feed path P8 extends rearward from approximately the bottom of the roll paper compartment 60, rises upward at the rear of the roll paper compartment 60, and is formed to the rear end of the print path P3.

[0036] The discharge path P9 is formed following the print path P3, from the front end of the print path P3 above the roll paper compartment 60 and extending forward in the front-to-rear direction L to the discharge opening 15. The cutter unit 40 is formed in the discharge path P9.

[0037] <Conveying Means> The conveying means 70 is provided on the conveying path P. The conveying means 70 operates under the control of the control unit 90. The conveying means 70 conveys the sheets S and R along the conveying path P, and also switches the conveying path P to which the sheets should be sent. The conveying means 70 is mainly composed of a drive roller driven by a motor (not shown) controlled by the control unit 90, a driven roller having no driving force, and switching members 71, 72, and 73 that switch the conveying path P.

[0038] Of the conveying means 70, illustrations and descriptions are omitted for a pair of rollers consisting of a normal drive roller and driven roller that sandwich and feed the sheets S and R. The conveying means 70 includes a pickup roller 81, a feed roller 82, and a retard roller 84, which will be described later. The pickup roller 81, the feed roller 82, and the retard roller 84 will be described later.

[0039] The switching member 71 is provided at the front end of the printing path P3. The switching member 71 switches between sending the sheets S and R sent in the forward direction Q on the printing path P3 to the waiting path P4 for printing on the sheets S and R, or sending the sheets S and R to the discharge path P9 for discharge. The switching of the transport path by the switching member 71 is controlled by the control unit 90.

[0040] The switching member 72 is located at the rear end of the printing path P3. The switching member 72 acts as a switching valve that returns paper S sent in the reverse direction -Q along the printing path P3 to the downstream printing path P5 without accidentally entering the roll paper feed path P8. The switching member 72 is biased by a spring toward the side that blocks the roll paper feed path P8.

[0041] As a result, when the printed paper is a sheet of paper S, the switching member 72 sends the paper S sent in the reverse direction −Q on the printing path P3 to the printing downstream path P5.

[0042] On the other hand, if the printed paper is roll paper R, the switching member 72 is biased by a spring in a direction that blocks the roll paper feed path P8, but because paper R is a continuous piece, even if the leading edge of the paper R reaches the printing path P3, the portion that continues to the rolled paper R stored in the roll paper compartment 60 pushes the switching member 72 apart against the bias of the spring, opening the path to the roll paper feed path P8. Therefore, when paper R that has been sent in the reverse direction -Q along the printing path P3 is rewound into the roll paper feed path P8, the switching member 72 can rewind the paper R into the roll paper feed path P8 without any hindrance.

[0043] The switching member 73 is provided at the rear end of the downstream printing path P5. The switching member 73 functions as a switching valve to ensure that the sheet S, when sent to the reverse waiting path P6, is sent to the creasing path P7 without being returned to the downstream printing path P5 when the sheet S is transported in the reverse direction −Q.

[0044] The switching member 73 biases the sheet S by a spring in the direction that sends the sheet S to the creasing path P7. After printing, the sheet S is placed up to its rear end in the reversing standby path P6, but while printing is being performed, the rear end of the sheet S remains in the lower printing path P5. In other words, during printing, the sheet S is not sent all the way to the reversing standby path P6, and its rear end remains in the lower printing path P5.

[0045] Thereafter, for printing of the second color and thereafter, the paper S is sent in the reverse direction −Q through the downstream print path P5 and returned to the standby path P4 again. The printer 100 then repeats the above-described printing operation to perform multi-color printing and coating.

[0046] In this way, the paper S in the middle of multi-color printing is positioned across the reverse waiting path P6 and the printing downstream path P5, and the paper S in this state presses the switching member 73 against the spring force to the side that allows the paper S to pass through the printing downstream path P5, thereby switching the side that sends the paper S to the printing downstream path P5.

[0047] <Control Unit> The control unit 90 is disposed above the paper tray 20 and behind the printing unit 30. The control unit 90 controls the operations of the printing unit 30, the cutter unit 40, the creasing unit 50, and the conveying means 70.

[0048] [Outline of Printer Operation] <For Paper S (Sheets S)> The printer 100 operates as follows for paper S passing through the above-described transport path P. First, paper S stored in the paper tray 20 is fed in the forward direction Q through a feed path P1, then sent in the forward direction Q through a paper feed path P2, then sent in the forward direction Q through a print path P3, and then sent in the forward direction Q through a standby path P4.

[0049] The paper S is then fed in the reverse direction -Q through the waiting path P4, and then fed in the reverse direction -Q through the printing path P3, while being printed on one side (the side facing the thermal head 31) in the printing unit 30. When multicolor printing is performed on the paper S in the printing unit 30, or when coating is performed after printing, the paper S is repeatedly fed in the forward direction Q and the reverse direction -Q through the printing path P3 and the waiting path P4.

[0050] The paper S printed in the printing unit 30 is then sent in the forward direction Q (corresponding to the reverse direction −Q in the printing path P3) through the printing downstream path P5, then sent in the forward direction Q through the reversing standby path P6, then sent in the forward direction Q through the paper feed path P2, and then sent in the forward direction Q through the printing path P3. As described above, the paper S is turned over as it passes through the reversing standby path P6 and the paper feed path P2.

[0051] When the printer 100 finishes printing only one side of the paper S, the paper S is then sent in the forward direction Q along the discharge path P9 and is discharged from the discharge port 15 to the outside of the printer 100, where the printing is completed.

[0052] When the printer 100 prints on both sides of the paper S, the paper S is fed in the forward direction Q through the print path P3 and then fed in the forward direction Q through the waiting path P4.

[0053] The paper S is then fed in the reverse direction -Q through the waiting path P4, and then fed in the reverse direction -Q through the printing path P3, while being printed on the other side (the side facing the thermal head 31) in the printing unit 30. When multicolor printing is performed on the paper S in the printing unit 30, or when coating is performed after printing, the paper S is repeatedly fed in the forward direction Q and the reverse direction -Q through the printing path P3 and the waiting path P4.

[0054] The paper S printed in the printing unit 30 is then sent in the forward direction Q through the printing downstream path P5, then sent in the forward direction Q through the reversal waiting path P6, then sent in the forward direction Q through the paper feed path P2, then sent in the forward direction Q through the printing path P3, then sent in the forward direction Q through the discharge path P9, and is then discharged outside the printer 100 from the discharge outlet 15.

[0055] When creasing is performed on the printed sheet S, in the case of single-sided printing, when the sheet S after single-sided printing is in the reversal waiting path P6, it is sent in the reverse direction -Q through the reversal waiting path P6, and then sent in the reverse direction -Q through the creasing path P7, where it is creasing in the creasing section 50.

[0056] When creasing is performed on the printed sheet S, in the case of double-sided printing, when the sheet S after double-sided printing is in the reversal waiting path P6, it is sent in the reverse direction -Q through the reversal waiting path P6, and then sent in the reverse direction -Q through the creasing path P7, where it is creasing in the creasing section 50.

[0057] <For Paper R (Roll Paper R)> The printer 100 operates as follows for paper R passing through the above-described transport path P. First, paper R stored in the roll paper compartment 60 is unwound in the forward direction Q along the roll paper feed path P8. As the roll paper R is unwound, it is unwound from the roll.

[0058] The paper R is then fed in the forward direction Q through the print path P3, and then fed in the forward direction Q through the standby path P4.

[0059] The paper R is then returned in the reverse direction −Q through the waiting path P4, and then returned in the reverse direction −Q through the printing path P3, while being printed on one side (the side facing the thermal head 31) in the printing unit 30. When the paper R is returned in the reverse direction −Q, it is rewound onto the roll.

[0060] When the printing unit 30 performs multicolor printing on the paper R or when coating after printing, the paper R is repeatedly fed in the forward direction Q and the reverse direction −Q through the printing path P3 and the waiting path P4.

[0061] The paper R printed in the printing unit 30 is then sent in the forward direction Q along the printing path P3, and then sent in the forward direction Q along the discharge path P9, where it is cut to a predetermined length by the cutter unit 40, and the printed paper R separated from the roll by the cutting is discharged outside the printer 100 through the discharge outlet 15, completing the process.

[0062] The portion of the paper R that has been cut off and connected to the roll is rewound onto the roll in the roll paper storage section 60, and is returned in the reverse direction -Q through the discharge path P9, printing path P3, and roll paper feed path P8.

[0063] [Retard roller and paper tray] Figures 4A and 4B are partial cross-sectional views equivalent to Figure 1 to explain the structure and function of the pickup roller 81, feed roller 82, and retard roller 84, Figure 5 is a perspective view showing the retard roller 84, Figure 6 is a cross-sectional view showing the inside of the retard roller 84, and Figures 7A and 7B are exploded perspective views explaining the configuration that generates a torque difference in the retard roller.

[0064] Note that Figure 4A shows the state in which the paper tray 20 is attached to the main body of the printer 100 in the normal position (reference position) in the front-to-back direction L, and Figure 4B shows the state in which the paper tray 20 is attached to a position closer to the reference position (a position forward in the front-to-back direction L from the reference position).

[0065] 7A shows the retard roller 84 as viewed from below on the outside in the width direction W, and FIG. 7B shows the retard roller 84 as viewed from above on the inside in the width direction W.

[0066] The pickup roller 81 and the feed roller 82 are fixed to the main body of the printer 100 via an arm 83. When the paper tray 20 is attached to the main body of the printer 100, the pickup roller 81 and the feed roller 82 are disposed above the paper tray 20 and near where the front panel 22 of the paper tray 20 is formed in the front-rear direction L, that is, at a position above and corresponding to the front of the paper tray 20.

[0067] The pickup roller 81 and the feed roller 82 are integrally formed by an arm 83. The arm 83 positions the pickup roller 81 behind the feed roller 82 in the front-to-rear direction L. The arm 83 is also positioned at an angle overall so that the pickup roller 81 is lower in the height direction H than the feed roller 82, but the arm 83 can rotate coaxially with the rotation axis of the feed roller 82, and is biased by a spring in a direction that presses the pickup roller 81 against the sheets S stored in the paper tray 20.

[0068] The pickup roller 81 and the feed roller 82 are driven by a single motor, so that the pickup roller 81 and the feed roller 82 rotate and stop in synchronization and rotate in the same direction when rotating.

[0069] <Details of the paper tray> As shown in Figure 2, the paper tray 20 is formed in a thin box shape (tray) without a top plate, and is made up of a bottom plate 21 on which the paper S is stacked, side plates 24 and 25 that rise on both sides of the width direction W in the thickness direction of the paper S (height direction H of the printer 100), a rear plate 23 that rises on the rear side in the front-to-rear direction L, and a front plate 22 that rises on the front side in the front-to-rear direction L.

[0070] The front portion 21a of the bottom plate 21 is formed so as to be able to swing upward around the rear end of the front portion 21a as an axis C3. In other words, the front portion 21a functions as a hopper that lifts up the front portion of the paper S placed on the bottom plate 21 when tilted upward. Hereinafter, this front portion 21a will be referred to as the hopper 21a. The hopper 21a is moved up and down by the drive of a motor (not shown) provided in the main body of the printer 100. The motor that moves the hopper 21a up and down is driven under the control of the control unit 90.

[0071] The paper tray 20 has an inclined plate 27 that extends diagonally upward and forward from the upper end of the front plate 22. That is, the inclined plate 27 is inclined downward toward the rear. An opening 27d is formed in the center of the inclined plate 27 in the width direction W. The inclined plate 27 will be described in more detail below.

[0072] The paper tray 20 has a front cover member 26 that is connected to the inclined plate 27 and to portions of the side plates 24, 25 that extend forward beyond the front plate 22. The front cover member 26 is formed to extend in the width direction W forward of the front plate 22. The front cover member 26 is formed to extend outward beyond the side plates 24, 25 in the width direction W.

[0073] The paper tray 20, which has been pulled out forward in the front-to-back direction L from the main body of the printer 100, is attached to the main body of the printer 100 as shown in Fig. 1 by pushing the front cover member 26 rearward (opposite the direction indicated by the outline arrow in Fig. 1) into a space formed at the bottom of the printer 100 and extending in the front-to-back direction L. When the paper tray 20 is attached to the main body of the printer 100, the front cover member 26, together with the case 10, forms the front surface of the printer 100 in the front-to-back direction L.

[0074] The paper tray 20 is equipped with a retard roller 84 shown in Fig. 2. The retard roller 84 is disposed in a space in front of the paper tray 20, which is formed between the front plate 22 and the front cover member 26. A portion of the retard roller 84 protrudes above the surface of the inclined plate 27 through an opening 27d formed in the inclined plate 27.

[0075] When paper S is being fed from the paper tray 20, the hopper 21a of the paper tray 20 is lifted upward and assumes an inclined position (shown by the dotted line in Figure 2) by a plate 19 (see Figures 1, 4A, and 4B) provided in the main body of the printer 100 and operated under the control of the control unit 90, which pushes the hopper 21a up through an opening 20A (see Figure 1) formed on the underside of the paper tray 20.

[0076] The hopper 21a is configured to tilt upward so that, regardless of the number of sheets of paper S stored in the paper tray 20, the topmost sheet of paper S lifted by the hopper 21a strikes the pickup roller 81, lifting the pickup roller 81, as shown in Figures 4A and 4B, and the extension of the leading edge of the sheet S strikes the rear end of the inclined plate 27 without coming into contact with the feed roller 82.

[0077] 2, the retard roller 84 provided on the paper tray 20 faces the inside of the paper tray 20 through the opening 27d of the inclined plate 27 of the paper tray 20. Then, as shown in FIG. 4A, when the paper tray 20 is installed in the normal position in the main body of the printer 100, the retard roller 84 is positioned so as to come into contact with the feed roller 82 fixed to the main body of the printer 100.

[0078] <Retard roller> (Configuration) The retard roller 84 is a driven roller and is not driven, but the paper S is sandwiched between the driven feed roller 82 and the non-driven retard roller 84, and the paper S is transported to the feed path P1 by driving the feed roller 82.

[0079] More specifically, as shown in FIG. 5, the retard roller 84 includes a base member 84d, two swing arm members 84a, a roller member 84b, and two coil springs 84c.

[0080] 4A, the base member 84d is disposed in the front space between the front plate 22 and the front cover member 26, and is fixed to the lower part of the paper tray 20. The base member 84d has a vertical wall 84k extending upward in the height direction H from the front part thereof.

[0081] The roller member 84b is a substantially cylindrical roller that comes into contact with the feed roller 82. The detailed structure of the roller member 84b will be described later, but when the roller member 84b rotates around the axis C2, it generates a torque in the opposite direction (a torque counter to the direction of rotation) to brake the rotation.

[0082] The swing arm member 84a is a long, narrow plate-like member that supports the roller member 84b on the base member 84d. The swing arm member 84a is disposed with its longitudinal direction aligned with the height direction H of the printer 100. The swing arm members 84a are disposed at both ends of the axis C2 of the roller member 84b, which is disposed with its axis C2 aligned with the width direction W of the printer 100, so as to be perpendicular to the axis C2.

[0083] The swing arm member 84a supports the roller member 84b at one end (upper end) on the upper side in the longitudinal direction so as to be rotatable about axis C2, and at one end (lower end) on the lower side in the longitudinal direction, is supported by the base member 84d so as to be rotatable about axis C1 parallel to axis C2. As a result, the swing arm member 84a is supported so as to be swingable back and forth about axis C1 relative to the base member 84d, as shown by the black arrow in Figure 5, and swings the roller member 84b back and forth.

[0084] The coil spring 84c is disposed between the swing arm member 84a and the vertical wall 84k in the front-to-rear direction L, with one end in contact with the swing arm member 84a and the other end in contact with the vertical wall 84k. As a result, the coil spring 84c presses the swing arm member 84a rearward within its swingable range.

[0085] Therefore, when there is no obstacle restricting the position of the roller member 84b, the retard roller 84 is biased by the elastic force of the coil spring 84c and is positioned at the rear of the swingable range. On the other hand, when there is a member or the like against which the roller member 84b abuts in front, the swing arm member 84a swings to compress the coil spring 84c, and the retard roller 84 is displaced forward within the swingable range.

[0086] (Basic Action of Retard Roller to Eliminate Double Feeding) The retard roller 84 configured as described above operates together with the feed roller 82 as follows.

[0087] As shown in Figure 4A, the paper tray 20 containing the paper S is attached to the main body of the printer 100 at a reference position in the front-to-rear direction L. At this time, the feed roller 82 fixed to the main body of the printer 100 abuts against the upper rear portion of the roller member 84b of the retard roller 84 of the paper tray 20, and the roller member 84b is pressed downward and forward.

[0088] As a result, the swing arm member 84a supporting the roller member 84b is pushed forward within the swing range, and the coil spring 84c is elastically deformed by the pushing load, causing the retard roller 84 to be in a state in which the swing arm member 84a is displaced forward within the swing range.

[0089] Then, under the control of the control unit 90, the hopper 21a is lifted, and the topmost sheet S of the sheets S (hereinafter referred to as the topmost sheet S) is pressed against the pickup roller 81.

[0090] Next, under the control of the control unit 90, a motor (not shown) rotates forward, and the pickup roller 81 and the feed roller 82 rotate forward. The forward rotation direction of the pickup roller 81 and the feed roller 82 is the direction in which the paper S is fed in the forward direction Q through the delivery path P1.

[0091] When the pickup roller 81 rotates forward, the topmost sheet S pressed against the pickup roller 81 receives the torque of the forward rotation of the pickup roller 81 and is sent in the forward direction Q. When the topmost sheet S is sent in the forward direction Q, the leading edge of the sheet S hits the rear end of the inclined plate 27, but because the leading edge of the sheet S is inclined upward, the sheet S bends so that the leading edge of the sheet S escapes to the upper side of the inclined plate 27. Then, the leading edge of the sheet S comes into contact with the retard roller 84, which is rotating forward in response to the feed roller 82, and is then sandwiched between the feed roller 82 and the retard roller 84.

[0092] Here, if the second sheet S is fed overlapping the top sheet S, the leading edge of the top sheet S will hit the rear end of the inclined plate 27 and bend upward to escape, but since the second sheet S is unlikely to bend at the same time as the top sheet S, this has the effect of making it difficult for the second sheet S to reach the retard roller 84.

[0093] When the top sheet S is sandwiched between the feed roller 82 and the retard roller 84, the top sheet S is sent to the delivery path P1 at a delivery angle θ1, which is the direction of the common tangent M of the feed roller 82 and the retard roller 84 relative to the horizontal direction. Then, when the top sheet S has been sent a certain distance to the delivery path P1, the hopper 21a is lowered to its original position under the control of the control unit 90. As a result, the pick roller 81 moves away from the top sheet S.

[0094] Here, as described above, the roller member 84b of the retard roller 84 generates an initial torque in the direction opposite to the rotation direction so as to brake the rotation whether it rotates in the forward direction N or the reverse direction −N. Therefore, it operates as follows with respect to the paper S sandwiched between it and the feed roller 82.

[0095] First, when only one regular sheet S is fed by the pickup roller 81, that is, when only the topmost sheet S is fed, only the topmost sheet S is sandwiched between the feed roller 82 and the retard roller 84. Because the feed roller 82 is rotating forward, a driving force is applied to the top surface of the topmost sheet S in the forward direction Q due to friction with the feed roller 82.

[0096] On the other hand, the underside of the top sheet S is in contact with the retard roller 84, and when the top sheet S moves in the forward direction Q, it attempts to rotate the retard roller 84 in the forward direction N. However, since the retard roller 84 is subjected to an initial torque in the opposite direction to the direction of rotation (forward direction N) as described above, a braking force in the opposite direction to the propulsion force in the forward direction Q acts on the underside of the top sheet S.

[0097] Here, the initial torque of the retard roller 84 in the direction opposite to the forward rotation direction N is set to be smaller than the forward rotation torque of the feed roller 82, so the top sheet S is sent in the forward direction Q along the payout path P1 by the propulsion force of the feed roller 82 regardless of the braking force received from the retard roller 84.

[0098] Next, we will explain what happens when the sheets S fed by the pickup roller 81 are double-fed, that is, when a second sheet S in contact with the top sheet S is attracted to the top sheet S by static electricity or the like and is fed out together with the top sheet S.

[0099] When double feeding occurs, the top sheet S and the second sheet S are sandwiched in an overlapping state between the feed roller 82 and the retard roller 84. The top surface of the top sheet S in contact with the feed roller 82 is subjected to a propulsive force that sends the top sheet S in the forward direction Q due to friction with the feed roller 82 caused by being sandwiched between the retard roller 84 and the feed roller 82.

[0100] When the top sheet S moves in the forward direction Q, the second sheet S tries to move in the forward direction Q using the frictional force with the top sheet S as a driving force, but since the bottom surface of the second sheet S is in contact with the retard roller 84 and an initial torque in the opposite direction to the direction of rotation is applied to the retard roller 84, a braking force in the opposite direction to the driving force in the forward direction Q by the retard roller 84 acts on the bottom surface of the second sheet S.

[0101] Here, the propulsive force acting on the second sheet S in the forward direction Q is a frictional force with the top sheet S, and this frictional force is considerably smaller than the propulsive force acting on the top sheet S due to the torque of the feed roller 82, and does not exceed the braking force received from the retard roller 84. As a result, the top sheet S is sent in the forward direction Q along the delivery path P1, but the second sheet S is held between the feed roller 82 and the retard roller 84 and remains stopped.

[0102] This allows the top sheet S to be separated from the second sheet S and fed to the feeding path P1.

[0103] (Action by swing arm member) In the printer 100 of this embodiment, the roller member 84b of the retard roller 84 swings around the axis C1 at the lower end of the swing arm member 84a as a rotation fulcrum due to the swing arm member 84a extending in the height direction H. Therefore, compared to a printer in which the roller member 84b of the retard roller 84 swings up and down around the axis at the front end of the swing arm member extending in the front-to-back direction L from forward of the roller member 84b, the printer can reduce fluctuations in the payout direction of the paper S in response to a shift in the front-to-back direction L in the installation position of the paper tray 20.

[0104] That is, the paper tray 20 is inserted into the main body of the printer 100 in the front-to-back direction L and attached to a reference position, but the printer 100 is configured to operate normally even if the insertion depth of the paper tray 20 into the main body of the printer 100 varies slightly due to manufacturing errors in the printer 100 or convenience in handling the printer 100.

[0105] In order for printer 100 to feed paper S normally and to prevent double feeding, it is necessary for the pressure at which feed roller 82 and retard roller 84 contact each other to be within a predetermined range. Therefore, regardless of the insertion depth of paper tray 20 into the main body of printer 100, when roller member 84b of retard roller 84 contacts feed roller 82, swing arm member 84a swings to change the position of roller member 84b, thereby absorbing the fluctuation in contact pressure between feed roller 82 and roller member 84b of retard roller 84.

[0106] Here, when the paper tray 20 is positioned (see Figure 4B) in a position in front of the reference position (Figure 4A) of the main body of the printer 100 in the front-to-back direction L (a position forward of the reference position in the front-to-back direction L), the part of the roller member 84b that contacts the feed roller 82 is located above and forward of the reference position.

[0107] Therefore, the amount of displacement by which the swing arm member 84a swings forward becomes smaller than that in the reference position, and the payout angle θ2 of the common tangent M between the feed roller 82 and the roller member 84b of the retard roller 84 becomes larger than the payout angle θ1 of the common tangent M in the reference position. The common tangent M is the direction (payout direction) of the paper S sandwiched between the feed roller 82 and the roller member 84b of the retard roller 84 and paid out to the payout path P1.

[0108] According to an experiment, the feed angle θ1 was, for example, 49.49 degrees, and the feed angle θ2 was, for example, 50.12 degrees. In other words, the variation Δθ in the feed direction of the paper S according to the shift in the mounting position of the paper tray 20 in the front-to-rear direction L is, for example, 0.63 (= 50.12 - 49.49) degrees.

[0109] 8A and 8B are diagrams illustrating the structure and operation of a comparative example in which a roller member 84b of a retard roller 84 is swung up and down by a swing arm member 84a' that extends rearward in the front-to-rear direction L from in front of the roller member 84b, with axis C4 at the front end of the swing arm member 84a' as a rotation fulcrum. Fig. 8A shows a state corresponding to Fig. 4A in which the paper tray 20 is placed in the normal position (reference position) of the main body of the printer 100, while Fig. 8B shows a state corresponding to Fig. 4B in which the paper tray 20 is placed in a position forward of the reference position (a position forward in the front-to-rear direction L from the reference position).

[0110] As shown in Figures 8A and 8B, the roller member 84b of the retard roller 84 is supported on the rear end of a swing arm member 84a' that extends in the front-to-back direction L from in front of the roller member 84b, and the swing arm member 84a' swings up and down around the axis C4 at the front end as a rotation fulcrum. This explains the movement of the roller member 84b in the comparative example.

[0111] 8A, in the comparative example, when the paper tray 20 is inserted into the reference position in the main body of the printer 100, when the upper rear portion of the retard roller 84 abuts against the feed roller 82, the swing arm member 84a' of the retard roller 84 assumes a position displaced downward within the swing range around the axis C4. In this state, the payout angle of the common tangent M between the feed roller 82 and the retard roller 84 is θ1'.

[0112] On the other hand, in the comparative example, when the paper tray 20 is positioned in a position in front of the reference position (FIG. 8A) of the main body of the printer 100 in the front-to-rear direction L (a position forward of the reference position in the front-to-rear direction L), as shown in Fig. 8B, the portion of the retard roller 84 that contacts the feed roller 82 is located forward and above the reference position. Note that the state in which the paper tray 20 in the comparative example is positioned in a position in front of the reference position of the main body of the printer 100 in the front-to-rear direction L is set to the same conditions as the state in the printer 100 of this embodiment shown in Fig. 4B.

[0113] In this case, the payout angle θ2' of the common tangent M between the feed roller 82 and the retard roller 84 becomes larger than the payout angle θ1' of the common tangent M between the feed roller 82 and the retard roller 84 when they are in the reference position. Experiments have shown that the payout angle θ1' is, for example, 51.83 degrees, and the payout angle θ2' is, for example, 59.87 degrees. In other words, the variation Δθ' in the payout direction of the paper S due to the misalignment of the installation position of the paper tray 20 in the front-to-rear direction L is, for example, 8.04 (= 59.87 - 51.83) degrees.

[0114] In this way, the printer 100 of this embodiment has a structure in which the retard roller 84 swings the roller member 84b back and forth using a swing arm member 84a extending along the height direction H, and therefore can reduce the variation Δθ in the payout direction of the paper S that corresponds to a shift in the mounting position of the paper tray 20 in the front-to-back direction L, compared to the comparative example in which the retard roller 84 swings the roller member 84b up and down using a swing arm member 84a' extending along the front-to-back direction L.

[0115] As a result, in the printer 100 of this embodiment, regardless of the shift in the mounting position of the paper tray 20 in the front-to-back direction L, the fluctuation Δθ in the paper S's payout direction is small, so that the paper S paid out to the payout path P1 is prevented from getting caught on the surrounding walls (especially the inner walls) that separate the payout path P1, thereby reducing the risk of the paper S getting stuck in the payout path P1.

[0116] The fact that the swing arm member 84a of the printer 100 of this embodiment is longer than the swing arm member 84a' of the comparative example is one factor that causes the printer 100 of this embodiment to have a smaller fluctuation Δθ in the payout direction of the paper S than the comparative example, but the main factor that causes the fluctuation Δθ in the payout direction to be smaller is the structure that causes the swing arm member 84a to swing back and forth.

[0117] In addition, the printer 100 of this embodiment reduces the fluctuation Δθ in the payout direction of the paper S that corresponds to a shift in the front-to-back direction L of the mounting position of the paper tray 20 by orienting the swing arm member 84a in a position along the height direction H, but the effect of reducing the fluctuation Δθ in the payout direction of the paper S is not limited to the roller member 84b supported by the swing arm member 84a functioning as a retard roller 84.

[0118] That is, in a printer in which the orientation of the swing arm member 84a is oriented along the height direction H, even if the roller member 84b supported by the swing arm member 84a is a simple driven roller that does not apply initial torque (braking) in the direction opposite to the rotation direction, it is possible to reduce the variation Δθ in the payout direction of the paper S that occurs due to a shift in the installation position of the paper tray 20 in the front-to-rear direction L. Therefore, in a printer in which the orientation of the swing arm member 84a is oriented along the height direction H, the roller member 84b supported by the swing arm member 84a may be a simple driven roller.

[0119] (Detailed Structure of Retard Roller and Action During Reverse Rotation) The basic action of the retard roller 84 to eliminate double feeding is as described above, but if the feed roller 82 continues to rotate forward even after the trailing end of the top sheet S in the forward direction Q has left the feed roller 82, the torque of the feed roller 82 acts on the second sheet S that is stopped in contact with the retard roller 84, and the second sheet S is fed out to the feed path P1. In this case, continuous feeding occurs, in which the second sheet S is fed out with almost no gap between it and the top sheet S fed out to the feed path P1.

[0120] In order to avoid such continuous feeding, after the leading edge of the top sheet S is fed into the feed path P2 following the feed path P1, the control unit 90 drives another drive roller (one of the conveying means 70: not shown) provided in the feed path P2 to feed the top sheet S in the forward direction Q while stopping the feed roller 82, thereby preventing the second sheet S from being fed continuously.

[0121] However, if the printer 100 is configured to drive the separate drive roller provided in the paper feed path P2 and the feed roller 82 with a single motor, it is not possible to drive only the separate drive roller provided in the paper feed path P2 and stop the feed roller 82.

[0122] Therefore, in this printer 100, the control unit 90 reverses the feed rollers 82 before the trailing edge of the top sheet S in the forward direction Q separates from the feed rollers 82. In other words, at this time, the leading edges of the top sheet S and the second sheet S in the forward direction Q are misaligned.

[0123] Therefore, by rotating the feed roller 82 in the reverse direction, the top sheet S and the second sheet S overlapping it are retreated together toward the paper tray 20. As a result, the second sheet S, whose leading edge in the forward direction Q is positioned at the rear, leaves the position sandwiched between the feed roller 82 and the retard roller 84 before the top sheet S, and only the second sheet S can be returned to the paper tray 20.

[0124] However, if the retard roller 84 is configured to simply generate a torque (reverse torque) in the opposite direction to the direction of rotation, the retard roller 84 will act in the same way as when it rotates in the forward direction described above, causing it to send only the top sheet S in the reverse direction -Q, leaving the second sheet S stopped, and it will not be possible to return only the second sheet S to the paper tray 20 as expected.

[0125] Therefore, in the printer 100 of this embodiment, the retard roller 84 generates different counter torques when rotating in the forward direction and when rotating in the reverse direction. The detailed structure of the retard roller 84 that generates these different counter torques will be described below.

[0126] 6, 7A, and 7B, the roller member 84b includes a rubber roller 84e, a housing 84f, an inner ring 84g, a first torque spring 84h, and a torque spring 84i. The first torque spring 84h and the torque spring 84i are wound in the same direction around the inner ring 84g.

[0127] The rubber roller 84e is provided in close contact with the outer peripheral surface of the housing 84f, and the rubber roller 84e and the housing 84f rotate together. The inner ring 84g has a portion 84g1 (hereinafter referred to as the first portion 84g1) on one axial end side that is disposed inside the housing 84f, and a portion 84g2 (hereinafter referred to as the second portion 84g2) on the other axial end side that protrudes outward from the end of the housing 84f in the width direction W and is disposed inside the swing arm member 84a. The inner ring 84g is rotatable relative to both the housing 84f and the swing arm member 84a.

[0128] The first torque spring 84h is arranged so as to be wound around the outer peripheral surface of the first portion 84g1 of the inner ring 84g, with one end rising outward in the radial direction and fixed to the inner peripheral surface of the housing 84f. The second torque spring 84i is arranged so as to be wound around the outer peripheral surface of the second portion 84g2 of the inner ring 84g, with one end rising outward in the radial direction and fixed to the inner peripheral surface of the swing arm member 84a.

[0129] The first torque spring 84h and the second torque spring 84i have coils wound in the same direction, and the wire diameter of the spring forming the first torque spring 84h is thicker than the wire diameter of the spring forming the second torque spring 84i.

[0130] The operation when the roller member 84b rotates about the axis C2 relative to the swing arm member 84a will be described below. When the housing 84f and the rubber roller 84e attempt to rotate in the forward direction N about the axis C2 relative to the swing arm member 84a, one end 84h1 of the first torque spring 84h, which is fitted into the groove 84f1 of the housing 84f, attempts to rotate in the forward direction N together with the housing 84f.

[0131] Here, because the first torque spring 84h is wound around the first portion 84g1 of the inner ring 84g, in order for one end 84h1 of the first torque spring 84h to rotate in the forward rotation direction N, the first torque spring 84h must rotate integrally with the inner ring 84g in the forward rotation direction N, or only the one end 84h1 of the first torque spring 84h must rotate in the forward rotation direction N. If only the one end 84h1 of the first torque spring 84h rotates in the forward rotation direction N without rotating the inner ring, the first torque spring 84h will elastically deform in a direction increasing its winding diameter. Therefore, even if the inner ring 84g does not rotate in the forward rotation direction N, the rotation of the housing 84f and the rubber roller 84e in the forward rotation direction N is not hindered.

[0132] If the inner ring 84g were to rotate integrally with the first torque spring 84h in the forward direction N, the second portion 84g2, which is part of the inner ring 84g, would also rotate in the forward direction N. Because the second torque spring 84i is wound around the second portion 84g2, the second torque spring 84i would also attempt to rotate in the forward direction N. However, because one end 84i1 of the second torque spring 84i is fitted into and fixed in a groove 84a1 formed in the inner circumferential surface of the swing arm member 84a, the one end 84i1 of the second torque spring 84i does not rotate. In this case, the second torque spring 84i needs to elastically deform in a direction that reduces the winding diameter.

[0133] However, if the winding diameter of the second torque spring 84i is reduced, the second torque spring 84i is wound tightly around the outer circumferential surface of the second portion 84g2, and the second portion 84g2 no longer slips relative to the second torque spring 84i. Therefore, the inner ring 84g does not rotate in the forward rotation direction N and remains stopped.

[0134] Due to the above-described operation, one end of the first torque spring 84h attempts to rotate integrally with the housing 84f in the forward rotation direction N, but the first portion 84g1 around which the first torque spring 84h is wound does not rotate. In order for the housing 84f to rotate in the forward rotation direction N, a torque is required that elastically deforms the first torque spring 84h so as to increase the winding diameter of the first torque spring 84h.

[0135] In other words, in order for the retard roller 84 to rotate in the forward direction N, a torque in the forward direction N must be applied to the rubber roller 84e and the housing 84f, which elastically deforms the first torque spring 84h so as to increase the winding diameter, and initially, a torque in the reverse direction -N, which is opposite to the forward direction N, is generated in the retard roller 84 as a braking force.

[0136] On the other hand, when the housing 84f and the rubber roller 84e attempt to rotate in the opposite direction -N around the axis C2 relative to the swing arm member 84a, one end of the first torque spring 84h attempts to rotate in the opposite direction -N together with the housing 84f.

[0137] Here, if the inner ring 84g does not rotate, one end of the first torque spring 84h will rotate in the opposite direction -N together with the housing 84f, and the first torque spring 84h wound around the first part 84g1 will not rotate, so it is necessary to elastically deform the first torque spring 84h so as to reduce the winding diameter of the first torque spring 84h.

[0138] When the winding diameter of the first torque spring 84h is reduced, the first torque spring 84h is wound tighter around the outer peripheral surface of the first portion 84g1, and the first portion 84g1 becomes one with the first torque spring 84h. Because one end of the first torque spring 84h is fixed to the housing 84f, it rotates together with the housing 84f, and therefore the inner ring 84g also rotates in the reverse direction −N together with the first torque spring 84h.

[0139] When the inner ring 84g rotates, the second torque spring 84i wound around the second portion 84g2 rotates integrally with the second portion 84g2 in the reverse direction -N. However, since one end of the second torque spring 84i is fixed to the swing arm member 84a, in order for the inner ring 84g to rotate in the reverse direction -N, a torque is required to elastically deform the second torque spring 84i so as to increase the winding diameter of the second torque spring 84i.

[0140] In other words, in order for the retard roller 84 to rotate in the reverse direction -N, a torque in the forward direction N must be applied to the rubber roller 84e and the housing 84f, which elastically deforms the second torque spring 84i so as to increase the winding diameter, and initially, a torque in the forward direction N, which is opposite to the reverse direction -N, is generated in the retard roller 84 as a braking force.

[0141] Here, since the wire diameter of the first torque spring 84h is thicker than the wire diameter of the second torque spring 84i, the retard roller 84 is set so that the torque required to increase the winding diameter of the first torque spring 84h, which has a thick wire diameter (initial torque for the forward direction N), is greater than the torque required to increase the winding diameter of the second torque spring 84i, which has a thin wire diameter (initial torque for the reverse direction -N), and the initial torque for the reverse direction -N is set smaller than the initial torque for the forward direction N.

[0142] (Effect of Reverse Rotation) In printer 100 equipped with retard roller 84 configured in this manner, due to the effect of retard roller 84 in eliminating double feeding in the forward direction Q, the feed roller 82 is rotated in reverse before the trailing edge of the top sheet S sent to delivery path P1 in the forward direction Q separates from the feed roller 82. At this time, the leading edges of the top sheet S and the second sheet S in the forward direction Q are misaligned. Then, due to friction with the feed roller 82, a propulsive force acts on the top surface of the top sheet S in contact with the feed roller 82, sending it in the reverse direction -Q.

[0143] When the top sheet S moves in the reverse direction -Q, the frictional force with the top sheet S acts as a driving force, causing the second sheet S to also try to move in the reverse direction -Q. However, since the bottom surface of the second sheet S is in contact with the retard roller 84 and an initial torque in the opposite direction to the rotational direction is applied to the retard roller 84, a braking force in the opposite direction to the driving force in the reverse direction -Q acts on the bottom surface of the second sheet S.

[0144] Here, the initial torque of the retard roller 84 in the reverse direction -N is set smaller than the initial torque in the forward direction N, and this initial torque in the reverse direction -N is set smaller than the frictional force received from the uppermost sheet S fed in the reverse direction -Q. As a result, when the second sheet S attempts to move in the reverse direction -Q due to the frictional force with the uppermost sheet S, the retard roller 84 rotates in the reverse direction -N following the movement of the second sheet S.

[0145] In this way, the top sheet S and the second sheet S sandwiched between the feed roller 82 and the retard roller 84 move in the reverse direction −Q.

[0146] Since the leading edge positions of the top sheet S and the second sheet S are misaligned in the forward direction Q, the second sheet S moves in the reverse direction −Q, and separates from the feed roller 82 and the retard roller 84 before the top sheet S, and the second sheet S falls into the paper tray 20 due to gravity, separating from the top sheet S.

[0147] Then, after the second sheet S falls into the sheet tray 20 and the top sheet S is sandwiched between the feed roller 82 and the retard roller 84, the control section 90 rotates the feed roller 82 in the forward direction again, and sends the top sheet S to the feed path P1 in the forward direction Q with the double feeding resolved.

[0148] In this way, the printer 100 of this embodiment is set so that the magnitude of the counter torque that suppresses rotation when the retard roller 84 rotates in the forward direction N to feed the paper S in the forward direction Q is different from the magnitude of the counter torque that suppresses rotation when the retard roller 84 rotates in the reverse direction −N to feed the paper S in the reverse direction −Q. Specifically, the counter torque that suppresses rotation when the retard roller 84 rotates in the reverse direction −N to feed the paper S in the reverse direction −Q is set to be smaller than the counter torque that suppresses rotation when the retard roller 84 rotates in the forward direction N to feed the paper S in the forward direction Q.

[0149] As a result, when the retard roller 84 rotates in the forward direction N, it stops feeding the second sheet S of the overlapping paper, and allows the second sheet S of the overlapping paper to be fed in the opposite direction -N, thereby reliably eliminating the overlapping of the sheets S.

[0150] Therefore, the printer 100 of this embodiment can reliably prevent continuous paper feeding and double feeding.

[0151] (Paper Tray Incline Plate) Here, the detailed configuration of the inclined plate 27 of the paper tray 20 is as follows: As described above, the printer 100 rotates the feed roller 82 in the reverse direction −N, thereby causing the topmost sheet S and the second sheet S sandwiched between the feed roller 82 and the retard roller 84 to move backward in a direction returning them to the paper tray 20.

[0152] Then, when the second sheet S leaves the feed roller 82 and the retard roller 84, it falls into the paper tray 20 due to its own weight, but the second sheet S is no longer supplied with a backward propulsive force the moment it leaves the feed roller 82 and the retard roller 84. Therefore, the second sheet S loses its backward propulsive force the moment it leaves the feed roller 82 and the retard roller 84.

[0153] Here, as shown in Figures 2 and 4A, the retard roller 84 is positioned so that a portion of it protrudes from the opening 27d formed in the inclined plate 27 of the paper tray 20, so that immediately after the rear end of the retreating second sheet of paper S leaves the retard roller 84, the rear end of the second sheet of paper S rests on the inclined plate 27 shown in Figure 4B.

[0154] The inclined plate 27 is formed with a slope that is higher at the front than at the rear in the front-to-rear direction L and slopes downward at the rear. Therefore, even when the second sheet S loses its backward propulsive force, its rear end rests on the inclined plate 27, which has a lower rear end than its front end, and the second sheet S moves along the inclined surface of the inclined plate 27 due to its own weight. This allows the printer 100 to move the second sheet S backward and drop it into the paper tray 20 even when the feed roller 82 and the retard roller 84 are not applying backward propulsive force to the second sheet S.

[0155] If the second sheet S stops at a position immediately after it leaves the feed roller 82 and the retard roller 84 and does not fall into the paper tray 20, the trailing edge of the second sheet S will be in close proximity to the feed roller 82 and the retard roller 84. When the feed roller 82 is rotated again in the forward direction N to re-send the top sheet S in the forward direction Q, the trailing edge of the second sheet S, which has remained in close proximity to the feed roller 82 and the retard roller 84, may come into slight contact with the top sheet S that has started to move in the forward direction Q and be pulled in the forward direction Q, which may again result in double feeding or continuous paper feeding, but the printer 100 of this embodiment can avoid such a situation.

[0156] The degree of inclination (slope) of the inclined plate 27 with respect to the horizontal direction may be set to such an extent that when the rear end of the second sheet S is placed on the portion immediately after it has separated from the feed roller 82 and the retard roller 84, the second sheet S slides down from the inclined plate 27 under its own weight. As an example, the degree of such inclination is preferably 25 degrees or more, and more preferably 35 degrees or more.

[0157] In the printer 100 of this embodiment, the control unit 90 may control the hopper 21a to repeatedly move up and down in order to reliably prevent the paper S from getting caught on the inclined plate 27. In this case, even if the paper S gets caught on the inclined plate 27, the control unit 90 moves the hopper 21a up and down, and the vibration of the hopper 21a caused by the up and down movement is transmitted to the paper S, thereby releasing the paper S from being caught on the inclined plate 27 and allowing the paper S to be reliably returned to the paper tray 20.

[0158] (Paper guide) Figure 9 is an oblique view showing the positional relationship between the paper tray 20 and the paper guide 89, Figure 10 is a plan view showing the positional relationship between the paper tray 20 and the paper guide 89, Figure 11A is a cross-sectional view showing a vertical cross-section along line A-A in Figure 10, Figure 11B is a cross-sectional view showing a vertical cross-section along line B-B in Figure 10, Figure 11C is a cross-sectional view showing a vertical cross-section along line C-C in Figure 10, and Figure 11D is a cross-sectional view showing a vertical cross-section along line D-D in Figure 10.

[0159] As shown in FIG. 1, the printer 100 of this embodiment includes a paper guide 89 that separates the outer sides of the delivery path P1 and the paper feed path P2, respectively, at a portion of the arc-shaped cross section of each of the delivery path P1 and the paper feed path P2.

[0160] 9, the paper guide 89 is provided in the main body of the printer 100 and is located above and in front of the paper tray 20 when the paper tray 20 is attached to the main body of the printer 100. The paper S that is sandwiched between the feed roller 82 and the retard roller 84 and sent to the delivery path P1 is sent to the delivery path P1 in the forward direction Q from the portion sandwiched between the feed roller 82 and the retard roller 84, with its lower surface in contact with the inclined plate 27.

[0161] 9, the lower edge 89b of the paper guide 89 is located forward and above the upper edge 27f of the inclined plate 27. Therefore, a gap is formed between the upper edge 27f of the inclined plate 27 and the lower edge 89b of the paper guide 89, as shown in FIGS.

[0162] Here, if the paper S is stiff, the front end of the paper S in the forward direction Q, which has been sandwiched between the feed roller 82 and the retard roller 84 from the paper tray 20 and has passed through the upper edge 27f while in contact with the inclined plate 27, is likely to get caught in the gap between the upper edge 27f of the inclined plate 27 and the lower edge 89b of the paper guide 89.

[0163] 2 and 9, in the printer 100 of this embodiment, a portion of the inclined plate 27 of the paper tray 20 in the width direction W is recessed downward and forward from the surface of the inclined plate 27 to form a recess 27c. The recess 27c is formed on both sides in the width direction W, immediately adjacent to the retard roller 84 provided in the center of the width direction W.

[0164] On the other hand, in the printer 100 of this embodiment, the lower edge 89b of the paper guide 89 is not linear along the width direction W, but rather, the portions of the lower end of the paper guide 89 that correspond to the two recesses 27c formed in the inclined plate 27 of the paper tray 20 are formed as protruding pieces 89a that protrude downward from the lower edge 89b, as shown in Figures 9 and 11B. These two protruding pieces 89a are each inserted into the recesses 27c.

[0165] When the protruding piece 89a is inserted into the recess 27c, the surface of the protruding piece 89a is positioned lower than the portions 27a of the inclined plate 27 arranged on both sides of the retard roller 84 as shown in Fig. 11B, and the portions 27b outside the recess 27c in the width direction W as shown in Fig. 11C. The lower edge of the protruding piece 89a extends to the extension range of the inclined plate 27 in the front-rear direction L.

[0166] As a result, in the printer 100 of this embodiment, the front end of the paper S, which is sandwiched between the feed roller 82 and the retard roller 84 from the paper tray 20 and sent in the forward direction Q, begins to pass above the protruding piece 89a of the paper guide 89 while contacting the inclined plate 27.

[0167] Then, when the front end of the paper S has passed the upper edge 27f of the inclined plate 27, a portion of the front end of the paper S has already been guided by the surface of the protruding piece 89a to the paper guide 89, so when the front end of the paper S passes above the gap between the upper edge 27f of the inclined plate 27 and the lower edge 89b of the paper guide 89, the paper S does not get into the gap between the upper edge 27f and the lower edge 89b.

[0168] Therefore, the printer 100 of this embodiment can prevent the paper S from getting into the gap between the upper edge 27f of the paper tray 20 and the lower edge 89b of the paper guide 89, regardless of the stiffness of the paper S.

[0169] Furthermore, since the recess 27c of the paper tray 20 and the protruding piece 89a of the paper guide 89 described above are formed at a position close to the center of the width direction W, which is immediately adjacent to the retard roller 84 that contacts the paper S and feeds the paper S, the effect of preventing the paper S from entering the above-mentioned gap can be enhanced compared to when the recess 27c and the protruding piece 89a are formed at a position close to both sides of the width direction W.

[0170] In addition, the inclined plate 27 of the paper tray 20 is formed with recessed surfaces 27e in the areas near both sides in the width direction W, which become continuously deeper toward the front and downward relative to the surface of portion 27b of the inclined plate 27 as it approaches both side edges, as shown in Figures 2, 9, and 11D.

[0171] In addition, similar to the recessed surfaces 27e of the inclined plate 27 of the paper tray 20, the rear end of the paper guide 89 is formed with recessed surfaces 89c in the areas near both sides in the width direction W, which become continuously deeper toward the front and downward as they approach both side edges, as shown in Figures 9 and 11D.

[0172] Here, the center of the width direction W of the sheet S sandwiched between the feed roller 82 and the retard roller 84 and sent in the forward direction Q is supported by the feed roller 82 and the retard roller 84, so both sides of the unsupported leading end of the sheet S in the width direction W tend to warp in the thickness direction, and these sides in the width direction W tend to droop lower than the center. Therefore, when the leading end of the sheet S passes the upper edge 27f of the inclined plate 27, the support of the inclined plate 27 is lost, and the sides of the leading end of the sheet S droop, making it more likely than the center to get into the gap between the upper edge 27f of the inclined plate 27 and the lower edge 89b of the sheet guide 89.

[0173] However, in the printer 100 of this embodiment, as shown in Figures 9 and 11D, recessed surfaces 27e and 89c are formed in the portion of the inclined plate 27 through which the hanging both sides of the paper S pass and in the portion of the paper guide 89, respectively, so that the hanging side portions of the front end of the paper S are less likely to get caught in the gap between the upper edge 27f of the inclined plate 27 and the lower edge 89b of the paper guide 89 compared to the central portion.

[0174] The printer 100 of this embodiment is an example of a dye-sublimation thermal printer, but the printer according to the present invention is not limited to dye-sublimation thermal printers, and other types of printers, such as inkjet printers and thermal printers, can also be used.

[0175] A first aspect of the present invention is a printer comprising: a feed roller fixed to the main body of a printer; and a paper tray containing a large number of sheets of paper that is detachably attached to the main body of the printer; and a retard rotor that contacts the feed roller when the paper tray is attached to the main body of the printer and transports the paper contained in the paper tray by sandwiching it between the feed roller and the retard roller; the retard roller having a base member fixed to the lower front part of the paper tray, a roller member that contacts the feed roller, and a swing arm member that rotatably supports the roller member at its upper end and has a lower end that is rotatable back and forth relative to the base member, is arranged in a vertically extending position, and the roller member is pressed by the feed roller to swing forward.

[0176] A second aspect of the present invention is a printer comprising: a feed roller fixed to the main body of the printer; and a paper tray containing a large number of sheets of paper that is detachably attached to the main body of the printer; a retard rotor that contacts the feed roller when the paper tray is attached to the main body of the printer and sandwiches and transports the paper contained in the paper tray between the feed roller and the retard roller; and a roller member of the retard roller that contacts the feed roller is set so that the reverse torque in the reverse direction when feeding the paper in the reverse direction is smaller than the reverse torque in the forward direction when feeding the paper in the forward direction.

[0177] A third aspect of the present invention is a printer comprising: a feed roller fixed to the printer body; and a paper tray containing a large number of sheets of paper that is detachably attached to the printer body; and a retard rotor that contacts the feed roller when the paper tray is attached to the printer body and sandwiches and transports the paper contained in the paper tray between the feed roller and the retard roller, and the retard roller contacts the feed roller through an opening formed in an inclined plate at the front of the paper tray that is inclined downward toward the rear.

[0178] A fourth aspect of the present invention is a printer comprising: a feed roller fixed to a printer body; and a paper tray that is detachably attached to the printer body and that contains a large number of sheets of paper; a retard rotor that contacts the feed roller when the paper tray is attached to the printer body and sandwiches the paper stored in the paper tray between the feed roller and the retard rotor to transport it; a paper guide that is provided to the printer body and is positioned above and in front of the paper tray when the paper tray is attached to the printer body; a portion of the width direction of an inclined plate of the paper tray is carved out further forward and downward than the surface of the inclined plate to form a recess; and a portion of the lower end of the paper guide that corresponds to the recess formed in the inclined plate is formed as a protruding piece that protrudes downward from the lower edge of the paper guide, and the protruding piece is in a state where it protrudes into the recess. CROSS-REFERENCE TO RELATED APPLICATIONS

[0179] This application claims priority based on Japanese Patent Application No. 2023-105686, filed with the Japan Patent Office on June 28, 2023, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A printer comprising: a feed roller fixed to the main body of a printer; and a paper tray containing a large number of sheets of paper that is removably attached to the main body of the printer, and a retard roller that contacts the feed roller when the paper tray is attached to the main body of the printer and transports the paper contained in the paper tray by pinching it between the feed roller and the feed roller, and the retard roller has a base member fixed to the lower front part of the paper tray, a roller member that contacts the feed roller, and a swinging arm member that rotatably supports the roller member at its upper end and has a lower end that is rotatable back and forth relative to the base member, is arranged in a vertically extending position, and swings forward when the roller member comes into contact with the feed roller.

2. A printer as described in claim 1, further comprising a coil spring which presses the swing arm member rearward within the rotatable range, and which allows the roller member to be pressed forward by the feed roller, thereby allowing the roller member to swing forward within the rotatable range.

3. A printer according to claim 1 or 2, wherein the roller member is set so that the torque in the reverse direction when feeding the paper in the reverse direction is smaller than the torque in the reverse direction when feeding the paper in the forward direction.

4. The printer according to claim 1 or 2, wherein the retard roller contacts the feed roller through an opening formed in an inclined plate having a downward inclination at the front of the paper tray.

5. A printer as claimed in claim 1 or 2, further comprising a paper guide provided on the main body of the printer and positioned above and in front of the paper tray when the paper tray is attached to the main body of the printer, a portion of the width direction of the inclined plate of the paper tray is hollowed out further forward and downward than the surface of the inclined plate to form a recess, and a portion of the lower end of the paper guide which corresponds to the recess formed in the inclined plate is formed as a protruding piece that protrudes downward beyond the lower edge of the paper guide, and the protruding piece is in a state where it protrudes into the recess.

6. A printer as described in claim 5, wherein the inclined plate of the paper tray is formed with a recessed surface that becomes continuously deeper in a forward and downward direction relative to the surface of the inclined plate in areas near both sides in the width direction W as it approaches both side edges, and the rear end of the paper guide is also formed with a recessed surface that becomes continuously deeper in a forward and downward direction relative to the surface of the inclined plate in areas near both sides in the width direction W as it approaches both side edges, similar to the recessed surface of the inclined plate.

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