Paper feeding device

Abstract

To provide a paper feeding device that more reliably prevents paper feed problems caused by height differences on the top surface of a topmost print medium.SOLUTION: The paper feeding device includes: a paper feed tray 10 on which a plurality of printing media are stacked; a paper feed unit 11 which sequentially pays out the topmost printing medium among the plurality of printing media stacked on the paper feed tray 10 and transports it in the paper feed direction to feed it; a lifting unit 14 which lifts upwardly the upstream end of the plurality of printing media stacked on the paper feed tray 10 in the paper feed direction while supporting it on a flat surface; and a control unit 50 which controls the lifting unit 14 so that the top surface of the topmost printing medium is always maintained horizontal during feeding by the paper feed unit 11.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a paper feeder that sequentially pays out and feeds a plurality of print media stacked on a paper feed tray. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been proposed a paper feeder that sequentially pays out the topmost print medium from among a plurality of print media stacked on a paper feed tray one by one and feeds the medium to a printing device or the like.

[0003] Furthermore, in recent years, printing devices that directly print on envelopes formed in a pouch shape have also been proposed, and paper feed devices that feed envelopes to such printing devices have also been proposed.

[0004] In the case of envelopes formed in a bag shape, the bottom is glued, so when a large number of envelopes are stacked on the paper feed tray, a difference in height occurs on the top of the envelope. Specifically, for example, when an envelope is stacked on the paper feed tray with its flap facing the upstream side in the paper feed direction and its bottom facing the downstream side in the paper feed direction, the top of the top envelope will be higher on the downstream side in the paper feed direction than on the upstream side in the paper feed direction.

[0005] When there is a difference in height between the top surface of the uppermost envelope, the stacked envelopes may be displaced upstream in the paper feed direction due to their own weight.

[0006] Even if the envelopes are stacked in a number that does not cause the envelopes to shift, the position of the top surface of the uppermost envelope cannot be detected properly due to the difference in height of the top surface of the envelope, resulting in problems such as double feeding, empty feeding, and paper feed jams. Also, if the envelopes are stacked in a number that does not cause such problems, only a small number of envelopes can be stacked on the paper feed tray.

[0007] Patent document 1 proposes a device to solve the problem that, when envelopes are stacked, the glued parts of the envelopes are higher than the unglued parts, causing the top surface of the top envelope to be uneven. This problem is solved by deforming a pair of triangular plates into a mountain or valley shape, which lifts the centre of the envelope when there are glued parts on both sides, or lifts both sides of the envelope when there is glued part in the centre, thereby keeping the top surface of the envelope level.

[0008] Furthermore, Patent Document 2 proposes a method in which a lifting member is disposed under an envelope storage section and the end of the envelope on the upstream side in the conveyance direction is lifted vertically upward. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2013-155003 A [Patent Document 2] JP 2016-130164 A Summary of the Invention [Problem to be solved by the invention]

[0010] However, while the pair of triangular plates described in Patent Document 1 can lift the unglued portion of the envelope, they do so at one side of each triangular plate or at the line where the pair of triangular plates meet, making it difficult to keep the top surface of the top envelope horizontal, and there is a risk of problems such as the above-mentioned double feeding occurring.

[0011] Furthermore, in Patent Document 2, the lifting members are provided on a loading platform that is narrower than the width of the envelopes, i.e., the lifting members are provided within a narrow range relative to the width of the envelopes. As a result, it is difficult to keep the top surface of the top envelope horizontal, and there is a risk of problems such as the above-mentioned double feeding occurring.

[0012] In Patent Document 2, the lifting member is made of an elastic member, and the envelopes are lifted by the elastic force. In Patent Document 2, the weight of the envelopes decreases as the number of envelopes stacked decreases, and the amount of lifting by the elastic force increases; however, the change in the amount of lifting by the elastic force alone is not enough to follow the change in the inclination angle of the top envelope with respect to the horizontal plane, and it is difficult to keep the top surface of the top envelope horizontal.

[0013] SUMMARY OF THE PRESENT DISCLOSURE In view of the above circumstances, an object of the present invention is to provide a paper feeder that can more reliably prevent paper feed problems caused by differences in height between the top surfaces of the uppermost print medium. [Means for solving the problem]

[0014] The paper feeding device of the present invention comprises a paper feed table on which multiple printing media are stacked, a paper feed section that sequentially pays out the topmost printing medium among the multiple printing media stacked on the paper feed table and transports it in the paper feed direction to feed it, a lifting section that lifts upwardly while supporting on a flat surface the upstream end of the multiple printing media stacked on the paper feed table in the paper feed direction, and a control section that controls the lifting section so that the top surface of the topmost printing medium is always maintained horizontal while the paper feed section is feeding. Effect of the Invention

[0015] According to the paper feeding device of the present invention, there is provided a lifting section that supports the upstream end of multiple printing media stacked on the paper feeding tray on a flat surface while lifting it upward, and the lifting section is controlled so that the top surface of the topmost printing medium is always maintained horizontal during paper feeding, thereby more reliably preventing paper feeding problems caused by differences in height of the top surface of the topmost printing medium. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an embodiment of a paper feeder according to the present invention; [Diagram 2] FIG. 1 is a top view of a bottom plate member provided on a paper feed table; [Diagram 3]FIG. 2 is a perspective view of the paper feed tray, the separation plate, the bottom plate member, and the side fence; [Figure 4] FIG. 3C is a semi-transparent view of the bottom plate member in FIG. 3B. [Diagram 5] FIG. 2 is a block diagram showing a control system of an embodiment of a paper feeder according to the present invention. [Figure 6] FIG. 1 is a diagram for explaining the operation of the paper feeder at the start of paper feed; [Figure 7] The figure shows the state in which the top surface of the uppermost envelope on the downstream side in the feed direction becomes lower than the top surface on the upstream side in the feed direction during feeding. [Figure 8] FIG. 13 is a diagram showing a state in which the lifting member is operated in advance before the sheet feed tray is raised. [Figure 9] A diagram showing the configuration of the scraper detection unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] An embodiment of a paper feeder of the present invention will be described in detail below with reference to the drawings. The paper feeder of this embodiment is a device that is connected to a printing device such as an inkjet printing device, and feeds a plurality of print media loaded on a paper feed tray one by one in sequence to the printing device, etc., but in particular, the paper feeder of this embodiment is a device that feeds envelopes as print media. The envelopes fed by the paper feeder of this embodiment are formed into a bag shape with the bottom glued, and the flaps are not yet closed.

[0018] Fig. 1 is a schematic diagram of a sheet feeding device 1 of this embodiment. The top, bottom, front and back shown in Fig. 1 are the top, bottom, front and back of the sheet feeding device 1 of this embodiment, the front side of the paper in Fig. 1 is the right direction, and the back side of the paper in Fig. 1 is the left direction. Fig. 1 is a side view of the sheet feeding device 1 of this embodiment as seen from the right side. In the sheet feeding device 1 of this embodiment, an envelope P is fed from the back to the front as shown in Fig. 1, with the back side being referred to as the upstream side in the sheet feeding direction and the front side being referred to as the downstream side in the sheet feeding direction.

[0019] As shown in FIG. 1, a paper feeder 1 of this embodiment includes a paper feed tray 10, a paper feed section 11, a downstream upper surface detection section 12, an upstream upper surface detection section 13, and a lifting section .

[0020] The paper feed tray 10 is a tray on which a plurality of envelopes P are stacked. A lifting section 14 is provided on the paper feed tray 10, and a plurality of envelopes P are stacked on a bottom plate member 14a of the lifting section 14, which will be described later.

[0021] The sheet feed tray 10 is raised and lowered in the vertical direction by a lifting section 30 (see FIG. 5) which will be described later.

[0022] The paper feed unit 11 sequentially feeds the topmost envelope P among the multiple envelopes P stacked on the paper feed tray 10 by conveying it in the paper feed direction. Specifically, the paper feed unit 11 includes a scraper roller 11a, a pickup roller 11b, and a separation plate 11d.

[0023] The scraper roller 11a rotates in the direction of the arrow A to pick up the topmost envelope P among the multiple envelopes P stacked on the paper feed tray 10. The topmost envelope P is the envelope P located at the top.

[0024] Pickup roller 11b and separation plate 11d separate and send out the envelopes P picked up by scraper roller 11a one by one. The separation plate 11d is attached to a part of guide plate 11c provided in front of paper feed tray 10. Specifically, the upper surface of separation plate 11d is made of rubber, and separation plate 11d is attached to guide plate 11c so as to be urged against the surface of pickup roller 11b by urging means such as a spring (not shown).

[0025] The leading edge of the envelope P picked up by the scraper roller 11a is inserted between the pickup roller 11b and the separation plate 11d. Then, the pickup roller 11b rotates in the direction of the arrow B, so that the envelope P is transported in the paper feed direction and is fed to a printing device connected downstream of the paper feeder 1.

[0026] The downstream top surface detector 12 includes a top surface detection roller 12a, a support member 12b, and a positioning sensor 12c. The support member 12b is rotatably attached to the rotation shaft of the pickup roller 11b. The support member 12b may be rotatably attached to a rotation shaft other than the rotation shaft of the pickup roller 11b, which is provided at a position that substantially overlaps with the rotation shaft of the pickup roller 11b when viewed from the left-right direction. The top surface detection roller 12a is rotatably provided at one end below the support member 12b.

[0027] After a plurality of envelopes P are stacked on the paper feed tray 10, the paper feed tray 10 is raised by the lifting section 30, so that the upper surface of the end portion on the downstream side in the paper feed direction of the uppermost envelope P comes into contact with the upper surface detection roller 12a. Then, with the upper surface of the end portion on the downstream side in the paper feed direction of the uppermost envelope P in contact with the upper surface detection roller 12a, the paper feed tray 10 is further raised, so that the support member 12b rotates in the direction of the arrow C, and the end portion 12d of the support member 12b reaches the positioning sensor 12c. When the end portion 12d of the support member 12b is detected by the positioning sensor 12c, the position of the upper surface of the end portion on the downstream side in the paper feed direction of the uppermost envelope P is determined, and the raising of the paper feed tray 10 is stopped.

[0028] The upstream upper surface detector 13 includes an upper surface detection roller 13a, a support member 13b, and a positioning sensor 13c. The support member 13b is rotatably attached to a rotation shaft (not shown). The upper surface detection roller 13a is rotatably provided at one end below the support member 13b.

[0029] After a plurality of envelopes P are stacked on the paper feed tray 10, the upstream ends of the envelopes P in the paper feed direction are lifted by the lifting unit 14, so that the top surface of the upstream end of the top envelope P in the paper feed direction comes into contact with the top surface detection roller 13a. Then, with the top surface of the upstream end of the top envelope P in the paper feed direction in contact with the top surface detection roller 13a, the top envelope P is further lifted by the lifting unit 14, so that the support member 13b rotates in the direction of arrow D, and the end 13d of the support member 13b reaches the positioning sensor 13c. When the end 13d of the support member 13b is detected by the positioning sensor 13c, the position of the top surface of the upstream end of the top envelope P in the paper feed direction is determined, and the lifting operation by the lifting unit 14 is stopped.

[0030] The lifting operation of sheet feed tray 10 and lifting operation of lifting section 14 based on downstream upper surface detection by downstream upper surface detection section 12 and upstream upper surface detection by upstream upper surface detection section 13 will be described in detail later.

[0031] The lifting unit 14 lifts upwardly while supporting with a flat surface the lower surfaces of the ends of the envelopes P stacked on the paper feed tray 10 on the upstream side in the paper feed direction. Specifically, the lifting unit 14 includes a bottom plate member 14a and a lifting member 14c.

[0032] Bottom plate member 14a is a plate-shaped member on which multiple envelopes P are stacked, and has a flat surface that supports the bottom surfaces of the multiple envelopes P. One end of bottom plate member 14a is connected to a rotation shaft 14b provided at the downstream end of paper feed tray 10. Rotation shaft 14b extends in a direction perpendicular to the paper feed direction, and bottom plate member 14a is configured to be rotatable in the direction of arrow E around rotation shaft 14b.

[0033] The lifting member 14c is provided on the upstream side of the paper feed tray 10 in the paper feed direction, between the paper feed tray 10 and the bottom plate member 14a. One end of the lifting member 14c is connected to a rotating shaft 14d provided on the upstream side of the paper feed tray 10 in the paper feed direction, and the other end is provided so as to contact the lower surface of the end portion of the bottom plate member 14a on the upstream side in the paper feed direction. The rotating shaft 14d is provided to extend in a direction perpendicular to the paper feed direction, and the lifting member 14c is configured to be rotatable around the rotating shaft 14d in the direction of an arrow F. The lifting member 14c is rotated by the rotating shaft 14d being rotated by a lifting drive unit 18 (see FIG. 5) described later, whereby the bottom plate member 14a is rotated around the rotating shaft 14b. The bottom plate member 14a is rotated in the direction of the arrow E or in the opposite direction, whereby the lower surfaces of the ends on the upstream side in the paper feed direction of the multiple envelopes P are lifted or lowered. The control of the lifting operation of the lifting unit 14 will be described in detail later.

[0034] Next, the configuration of the lifting unit 14 will be described in more detail. Fig. 2A is a top view of the bottom plate member 14a provided on the paper feed tray 10, and Fig. 2B is a view in which the bottom plate member 14a shown in Fig. 2A is shown semi-transparently so that the lifting member 14c provided below the bottom plate member 14a can be seen. In Figs. 2A and 2B, the paper feed tray 10 is shown with diagonal lines.

[0035] As shown in Fig. 2A, the bottom plate member 14a has a flat surface 14e that supports the bottom surfaces of a plurality of envelopes P loaded on the paper feed tray 10. The bottom plate member 14a is formed in a generally H-shape in plan view with the flat surface 14e, a narrow surface 14g that extends from the flat surface 14e to the front side (downstream side in the paper feed direction), and a wide surface 14h that is continuous with the narrow surface 14g. Cutouts 14f are formed on both sides of the narrow surface 14g of the bottom plate member 14a in a direction perpendicular to the paper feed direction. The wide surface 14h has the function of preventing both ends of the wide envelope P from drooping downward and causing a jam when the wide envelope P is fed.

[0036] As shown in FIG. 2A, side fences 20 and 21 are provided on the upper surface of the paper feed tray 10. The side fences 20 and 21 align both sides of the envelopes P stacked on the paper feed tray 10 in a direction perpendicular to the paper feed direction. The side fences 20 and 21 are configured to be movable in the left-right direction according to the left-right width of the envelopes P stacked on the paper feed tray 10. In addition, in this embodiment, when the left-right width of the envelope P is smaller than the left-right width of the plane 14e of the bottom plate member 14a, the side fences 20 and 21 are configured to be movable into the notch 14f according to the left-right width of the envelope P. That is, in this embodiment, by forming the bottom plate member 14a in a T-shape, the side fences 20 and 21 can move into the notch 14f according to the left-right width of the envelope P even if the left-right width of the envelope P is narrow, so that the alignment process of the envelope P can be appropriately performed.

[0037] 2B, the lifting member 14c is formed of a rectangular plate-like member. The width of the lifting member 14c in the left-right direction is narrower than the width of the flat surface 14e of the bottom plate member 14a in the left-right direction. A rotating shaft 14d is connected to the end of the lifting member 14c on the downstream side in the paper feed direction, and a lifting drive unit 18 is provided at the tip of the rotating shaft 14d.

[0038] The lifting drive unit 18 has a drive motor, gears, and the like for rotating the rotation shaft 14d, and is driven based on a control signal output from the control unit 50, which will be described later.

[0039] Fig. 3A is a perspective view of the paper feed tray 10, the separation plate 11d, the bottom plate member 14a, and the side fences 20 and 21. Fig. 3A shows a state in which the bottom plate member 14a is not lifted. Fig. 3B shows a state in which the end of the bottom plate member 14a on the upstream side in the paper feed direction is lifted by the lifting member 14c. Fig. 4 is a semi-transparent view of the bottom plate member 14a in Fig. 3B, making the state of the lifting member 14c easier to see.

[0040] 5 is a block diagram showing a control system of the sheet feeding device 1 of this embodiment. As shown in FIG. 5, the sheet feeding device 1 of this embodiment includes a lifting unit 30, a lifting drive unit 18, a roller drive unit 40, and a control unit 50.

[0041] The lifting section 30 lifts and lowers the sheet feed tray 10 as described above, and includes a predetermined actuator.

[0042] As described above, the lifting drive unit 18 includes a drive motor that rotates the rotation shaft 14d of the lifting unit 14, a gear that transmits the rotation of the drive motor to the rotation shaft 14d, and the like.

[0043] The control unit 50 controls the lifting / lowering unit 30 and the lifting drive unit 18 based on the top surface detection results of the downstream top surface detection unit 12 and the upstream top surface detection unit 13. The control unit 50 includes a CPU (Central Processing Unit), a semiconductor memory, a hard disk, etc. The control unit 50 controls the operation of the lifting / lowering unit 30 and the lifting drive unit 18 by executing a program stored in advance in a storage medium such as the semiconductor memory or the hard disk, and by operating an electric circuit.

[0044] Next, the operation of the sheet feeding device 1 of this embodiment will be described in more detail.

[0045] First, as shown in Fig. 6A, a plurality of envelopes P are stacked on bottom plate member 14a of paper feed tray 10. At this time, lifting member 14c is not driven, and the upper surface of bottom plate member 14a is in a horizontal state. Therefore, when a large number of envelopes P are stacked as described above, the thickness of the bottom (glued portion) of envelope P is thicker than the thickness of the flap side, so that the upper surface of the uppermost envelope P is higher on the downstream side in the paper feed direction than on the upstream side in the paper feed direction.

[0046] Next, after a plurality of envelopes P are stacked, the control unit 50 controls the lifting unit 30 to raise the paper feed table 10 until the upper surface of the uppermost envelope P on the downstream side in the paper feed direction is detected by the downstream upper surface detection unit 12. Then, when the upper surface of the uppermost envelope P on the downstream side in the paper feed direction is detected by the downstream upper surface detection unit 12, the control unit 50 stops raising the paper feed table 10 and determines the position of the upper surface of the uppermost envelope P on the downstream side in the paper feed direction.

[0047] Then, after determining the position of the top surface of the topmost envelope P on the downstream side in the paper feed direction, the control unit 50 controls the lifting drive unit 18 to rotate the lifting member 14c until the top surface of the topmost envelope P on the upstream side in the paper feed direction is detected, thereby lifting the ends of the multiple envelopes P on the upstream side in the paper feed direction.

[0048] Then, when the upstream top surface detection unit 13 detects the upstream top surface of the top envelope P in the paper feed direction, the control unit 50 stops the rotation of the lifting member 14c and determines the position of the upstream top surface of the top envelope P in the paper feed direction.

[0049] 6B is a diagram showing a state in which the positions of the upper surface of the uppermost envelope P on the downstream side in the paper feed direction and the upper surface on the upstream side in the paper feed direction have been determined as described above, and the upper surface of the uppermost envelope P is in a horizontal state. From this state, the control unit 50 starts rotating the scraper roller 11a and the pickup roller 11b, thereby performing the paper feeding operation.

[0050] Next, the operation of the sheet feeding device 1 while feeding the envelope P will be described in more detail.

[0051] As described above, since the thickness of the envelope P is greater on the downstream side in the paper feed direction than on the upstream side in the paper feed direction, during paper feed, a state occurs in which the top surface of the end portion on the downstream side in the paper feed direction of the uppermost envelope P is lower than the top surface of the end portion on the upstream side in the paper feed direction, as shown in Fig. 7. In this case, if paper feed table 10 is raised until downstream top surface detection unit 12 detects the top surface of envelope P on the downstream side in the paper feed direction, the top surface of the uppermost envelope P on the upstream side in the paper feed direction will be detected earlier than the top surface on the downstream side in the paper feed direction.

[0052] In this case, the control unit 50 controls the lifting drive unit 18 to rotate the lifting member 14c, thereby lowering the upper surface of the uppermost envelope P on the upstream side in the paper feed direction. At this time, the control unit 50 does not lower the bottom plate member 14a until it is horizontal, but lowers it a predetermined distance after the upper surface of the uppermost envelope P on the upstream side in the paper feed direction is no longer detected by the upstream upper surface detection unit 13. If this predetermined distance is small, when the paper feed tray 10 is raised, the upstream upper surface detection unit 13 will again detect the upper surface of the envelope P earlier than the downstream upper surface detection unit 12, so the predetermined distance is set so that the upstream upper surface of the envelope P is at the same height or lower than the downstream upper surface and is higher than the height at which the bottom plate member 14a is horizontal. This makes it possible to shorten the adjustment time required to make the upper surface of the uppermost envelope P horizontal.

[0053] Then, the control unit 50 lowers the top surface of the uppermost envelope P on the upstream side in the paper feed direction, and then raises the paper feed table 10.When the downstream top surface detection unit 12 detects the top surface of the uppermost envelope P on the downstream side in the paper feed direction, the control unit 50 stops raising the paper feed table 10 and determines the position of the top surface of the uppermost envelope P on the downstream side in the paper feed direction.

[0054] Thereafter, the control unit 50 controls the lifting drive unit 18 in the same manner as when paper feeding begins to rotate the lifting member 14c until the top surface of the uppermost envelope P on the upstream side in the paper feeding direction is detected, thereby lifting the top surface of the uppermost envelope P on the upstream side in the paper feeding direction.

[0055] Then, when the upstream top surface detection unit 13 detects the upstream top surface of the top envelope P in the paper feed direction, the control unit 50 stops the rotation of the lifting member 14c and determines the position of the upstream top surface of the top envelope P in the paper feed direction.

[0056] Thereafter, the control unit 50 repeats the above-mentioned operations during paper feeding, and controls the operations of the paper feed tray 10 and the lifting member 14c so that the top surface of the envelope P is always kept horizontal even during paper feeding.

[0057] According to the paper feeding device 1 of the above embodiment, there is provided a lifting section 14 that supports the upstream end of multiple envelopes P in the paper feeding direction stacked on the paper feeding tray 10 on a flat surface while lifting them upward, and the lifting section 14 is controlled so that the top surface of the topmost envelope P is always maintained horizontal during paper feeding, thereby more reliably preventing paper feeding problems due to differences in height of the top surface of the topmost envelope P.

[0058] Furthermore, in the paper feeding device 1 of the above embodiment, the end of the envelope P on the upstream side in the paper feed direction is lifted by rotating the bottom plate member 14a, so that with a simple configuration, the end of the envelope P on the upstream side in the paper feed direction can be lifted evenly, and the top surface of the top envelope P can be more reliably made horizontal.

[0059] Furthermore, in the paper feeding device 1 of the above embodiment, a cutout portion 14f is formed in the bottom plate member 14a, and the side fences 20, 21 are configured to be movable within the cutout portion 14f, so that the side fences 20, 21 can perform alignment processing for envelopes P of various sizes, and can also lift up the end of the envelope P upstream in the paper feeding direction.

[0060] Furthermore, in the paper feeder 1 of the above embodiment, the bottom plate member 14a is formed in a T-shape, so that the manufacture thereof is easy and costs can be reduced.

[0061] In addition, in the paper feeding device 1 of the above embodiment, the lifting section 14 is controlled based on the upstream top surface detected by the upstream top surface detection section 13 and the downstream top surface detected by the downstream top surface detection section 12, so that the top surface of the top envelope P can be more reliably made horizontal.

[0062] Furthermore, in the paper feeder 1 of the above embodiment, when paper feed starts, paper feed table 10 is raised until the top surface of the uppermost envelope P on the downstream side in the paper feed direction is detected, and then the upstream end of envelope P in the paper feed direction is raised until the top surface of the uppermost envelope P on the upstream side in the paper feed direction is detected, so that the top surface of the uppermost envelope P can be more efficiently made horizontal. Note that, conversely, if the top surface of the uppermost envelope P on the upstream side in the paper feed direction was detected first and then the top surface of the envelope P on the downstream side in the paper feed direction was detected, the top surface of the envelope P on the upstream side in the paper feed direction would be raised too high, requiring a lowering operation, which would be inefficient.

[0063] Furthermore, in the paper feeding device 1 of the above embodiment, if the number of envelopes P decreases during feeding of envelopes P and the paper feeding table 10 is raised, if the top surface of the upstream side of the top envelope P in the paper feed direction is detected before the top surface of the downstream side of the paper feed direction, the upstream end of the envelope P in the paper feed direction is lowered a predetermined distance, and then the paper feeding table 10 is raised until the top surface of the downstream side of the paper feed direction of the top envelope P is detected, and then the upstream end of the envelope P in the paper feed direction is lifted until the top surface of the upstream side of the paper feed direction of the top envelope P is detected, so that the adjustment time required to level the top surface of the top envelope P can be shortened as described above.

[0064] In addition, in the description of the above embodiment, when paper feeding begins, the paper feed table 10 is raised to detect the upper surface of the downstream side of the paper feed direction of the topmost envelope P, and then the lifting member 14c is rotated to lift the upper surface of the upstream side of the paper feed direction of the topmost envelope P. However, this is not limited to the above, and as shown in Figure 8, the upper surface of the upstream side of the paper feed direction of the topmost envelope P may be lifted a predetermined distance by rotating the lifting member 14c before the paper feed table 10 is raised or between the time when the paper feed table 10 starts to be raised and the time when the upper surface of the downstream side of the paper feed direction of the topmost envelope P is detected.

[0065] Then, the operation of lifting the paper feed tray 10, detecting the upper surface of the uppermost envelope P on the downstream side in the paper feed direction or the upper surface of the uppermost envelope P on the upstream side in the paper feed direction, and determining its position may be performed in the same manner as described in the above embodiment. This can shorten the time required for the lifting member 14c to determine the position of the upper surface of the uppermost envelope P on the upstream side in the paper feed direction, and shorten the adjustment time for making the upper surface of the uppermost envelope P horizontal. Note that at this time, the lifting of the paper feed tray 10 and the lifting operation by the lifting member 14c may be performed simultaneously.

[0066] Furthermore, as described above, it is preferable that the distance by which the upper surface of the uppermost envelope P upstream in the paper feed direction is pre-lifted is the distance between the upper surface of the uppermost envelope P at the downstream end in the paper feed direction and the upper surface of the uppermost envelope P at the upstream end in the paper feed direction, i.e., the height difference between the highest and lowest positions of the upper surface of the uppermost envelope P.

[0067] The height difference of the top surface of the uppermost envelope P may be set manually by the user or may be calculated by the control unit 50. As a method for the control unit 50 to calculate the height difference of the top surface of the uppermost envelope P, for example, the control unit 50 may receive the basis weight of the envelope P as information on the thickness of the envelope P, and also receive the number of envelopes P loaded on the paper feed tray 10, and calculate the height difference using a pre-set function or table based on this information. This allows the height difference of the top surface of the uppermost envelope P to be calculated by simple processing. The basis weight and number of envelopes P may be set and input by the user, for example.

[0068] Furthermore, when calculating the height difference of the top surface of the uppermost envelope P, the height difference may be calculated and changed by further including information on the size of the envelope P. The size information of the envelope P may be set and input by the user, or may be detected by an optical sensor or the like provided on the paper feed tray 10. This allows the height difference of the top surface of the uppermost envelope P to be calculated with higher accuracy.

[0069] In the above description, the number of envelopes P stacked on the paper feed tray 10 is set and input by the user, but the present invention is not limited to this and the control unit 50 may automatically determine the number of envelopes stacked.

[0070] Specifically, for example, an optical sensor, an upper surface detector configured like the above-mentioned downstream upper surface detector 12 or upstream upper surface detector 13, a laser displacement meter, or the like may be provided to detect information on the height of all envelopes P loaded on paper feed tray 10, and control unit 50 may calculate the number of loaded envelopes based on the height information and information on the thickness of envelopes P. As information on the thickness of envelopes P, for example, the above-mentioned basis weight of envelopes P may be used. This can save the user the trouble of counting the number of loaded envelopes and inputting the setting.

[0071] In addition, in the above embodiment, the upper surface of the uppermost envelope P on the upstream side in the paper feed direction is detected by the upstream upper surface detection unit 13 shown in Figure 1. However, instead of the upstream upper surface detection unit 13, a scraper detection unit 19 as shown in Figure 9 may be used as a means for detecting the upper surface of the uppermost envelope P.

[0072] The scraper detection unit 19 includes a housing 19a, an end 19b, and a positioning sensor 19c. The scraper roller 11a, the housing 19a, and the end 19b are integrally provided, and the scraper roller 11a, the housing 19a, and the end 19b are configured to be able to swing up and down within a predetermined range around the rotation axis of the pickup roller 11b. The positioning sensor 19c is provided above the housing 19a.

[0073] After the downstream top surface detector 12 detects the top surface of the uppermost envelope P on the downstream side in the paper feed direction, the lifting member 14c lifts the upstream ends of the envelopes P in the paper feed direction, so that the top surface of the uppermost envelope P comes into contact with the scraper roller 11a. The scraper roller 11a, the housing 19a, and the end 19b rotate upward about the rotation axis of the pickup roller 11b. Then, the end 19b that has moved upward reaches the positioning sensor 19c. At the point when the end 19b is detected by the positioning sensor 19c, the position of the top surface of the uppermost envelope P is determined, and the lifting operation by the lifting member 14c is stopped.

[0074] In the above embodiment, the configuration has been described for the case where the envelopes P are stacked on the paper feed tray 10 with the flap side of the envelope P facing the upstream side in the paper feed direction and the bottom side of the envelope P facing the downstream side in the paper feed direction, but conversely, it is also possible to consider a case where the envelopes P are stacked on the paper feed tray 10 with the flap side of the envelope P facing the downstream side in the paper feed direction and the bottom side of the envelope P facing the upstream side in the paper feed direction. In this case, the top surface of the uppermost envelope P will be higher on the upstream side in the paper feed direction and lower on the downstream side in the paper feed direction, so the configuration of the bottom plate member 14a and the lifting member 14c of the lifting section 14 may be reversed in the paper feed direction (front-to-back direction) (for example, the configuration is inverted in the front-to-back direction in FIG. 2).

[0075] Also, with regard to the control of the lifting unit 14 by the control unit 50, the upstream side in the paper feed direction and the downstream side in the paper feed direction may be reversed.

[0076] Specifically, the control unit 50 raises the paper feed tray 10 until the top surface of the uppermost envelope P on the upstream side in the paper feed direction is detected, and then lifts the downstream ends of the multiple envelopes P in the paper feed direction until the top surface of the uppermost envelope P on the downstream side in the paper feed direction is detected.

[0077] In addition, when the control unit 50 raises the paper feed table 10 while feeding envelopes P, if the top surface of the uppermost envelope P on the downstream side in the paper feed direction is detected before the top surface on the upstream side in the paper feed direction, the control unit 50 can lower the downstream ends of the multiple envelopes P in the paper feed direction a predetermined distance, then raise the paper feed table 10 until the top surface of the uppermost envelope P on the upstream side in the paper feed direction is detected, and then lift the downstream ends of the multiple envelopes P in the paper feed direction until the top surface of the uppermost envelope P on the downstream side in the paper feed direction is detected.

[0078] In addition, the control unit 50 may control the lifting unit to lift the downstream ends of multiple envelopes P in the paper feed direction by a predetermined distance before the top surface of the uppermost envelope P on the upstream side in the paper feed direction is detected.

[0079] The present invention is not limited to the above-described embodiment, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, all the components shown in the embodiment can be appropriately combined. Of course, various modifications and applications are possible without departing from the spirit of the invention.

[0080] The present invention further discloses the following supplementary notes. (Appendix 1)

[0081] The paper feeding device of the present invention comprises a paper feed table on which multiple printing media are stacked, a paper feed section that sequentially pays out the topmost printing medium among the multiple printing media stacked on the paper feed table and transports it in the paper feed direction to feed it, a lifting section that lifts upwardly while supporting on a flat surface the upstream end of the multiple printing media stacked on the paper feed table in the paper feed direction, and a control section that controls the lifting section so that the top surface of the topmost printing medium is always maintained horizontal while the paper feed section is feeding.

[0082] (Appendix 2) In the paper feeding device described in Appendix 1, the lifting section has a flat surface that supports the upstream ends of the multiple printing media in the paper feed direction, and can be provided with a bottom plate member having one side connected to a rotating shaft extending on the paper feed table in a direction perpendicular to the paper feed direction and rotating around the rotating shaft.

[0083] (Appendix 3) In the paper feeder described in Supplementary Note 2, the bottom plate member may have cutouts on both sides in a direction perpendicular to the paper feed direction and downstream in the paper feed direction.

[0084] (Appendix 4) The paper feeder described in Supplementary Note 3 may include side fences that align both sides of the multiple print media in a direction perpendicular to the paper feed direction, and the side fences may be configured to be movable into the notches.

[0085] (Appendix 5) In the paper feeding device described in any of Supplementary Notes 1 to 4, an upstream top surface detection unit may be provided that detects the top surface of the upstream end of the topmost printing medium in the paper feed direction, and a downstream top surface detection unit that detects the top surface of the downstream end of the topmost printing medium in the paper feed direction, and the control unit may control the lifting unit based on the upstream top surface detected by the upstream top surface detection unit and the downstream top surface detected by the downstream top surface detection unit.

[0086] (Appendix 6) The paper feeding device described in Appendix 5 can be provided with a lifting unit that raises and lowers the paper feeding table, and the control unit can control the lifting unit to raise the paper feeding table until the downstream top surface of the topmost printing medium is detected, and then control the lifting unit to lift the upstream ends of the multiple printing media in the paper feeding direction until the upstream top surface of the topmost printing medium is detected.

[0087] (Appendix 7) In the paper feeding device described in Appendix 6, when the control unit raises the paper feeding table by the lifting unit during feeding of printing media, if the upstream top surface of the topmost printing medium is detected before the downstream top surface, the control unit controls the lifting unit to lower the upstream ends of the multiple printing media in the paper feeding direction a predetermined distance, then raise the paper feeding table until the downstream top surface of the topmost printing medium is detected, and then lift the upstream ends of the multiple printing media in the paper feeding direction until the upstream top surface of the topmost printing medium is detected.

[0088] (Appendix 8) In the paper feeding device described in any one of Supplementary Notes 5 to 7, the control unit can control the lifting unit to lift the upstream ends of the multiple printing media in the paper feeding direction by a predetermined distance before the downstream top surface of the topmost printing medium is detected.

[0089] (Appendix 9) In the paper feeding device described in Supplementary Note 8, the control unit can change the distance by which the upstream ends of the multiple printing media in the paper feeding direction are lifted in advance, based on information on the thickness of the printing media and the number of loaded sheets.

[0090] (Appendix 10) The paper feeding device described in Appendix 9 can be provided with a height detection unit that detects height information of multiple printing media loaded on the paper feeding tray, and the control unit can calculate the number of loaded sheets based on the height information of the multiple printing media and information on the thickness of the printing media.

[0091] (Appendix 11) The paper feeding device of the present invention comprises a paper feed table on which multiple printing media are stacked, a paper feed section that sequentially pays out the topmost printing medium among the multiple printing media stacked on the paper feed table and transports it in the paper feed direction to feed it, a lifting section that lifts upwardly while supporting on a flat surface the downstream end of the multiple printing media stacked on the paper feed table in the paper feed direction, and a control section that controls the lifting section so that the top surface of the topmost printing medium is always maintained horizontal while the paper feed section is feeding.

[0092] (Appendix 12) In the paper feeding device described in Appendix 11, the lifting section can have a flat surface that supports the downstream ends of the multiple printing media in the paper feed direction, and can be provided with a bottom plate member having one side connected to a rotating shaft extending on the paper feed table in a direction perpendicular to the paper feed direction and rotating around the rotating shaft.

[0093] (Appendix 13) In the paper feeder described in Supplementary Note 12, the bottom plate member may have cutouts on both sides in a direction perpendicular to the paper feed direction and upstream in the paper feed direction.

[0094] (Appendix 14) The paper feeder described in Supplementary Note 13 may include side fences that align both sides of the multiple print media in a direction perpendicular to the paper feed direction, and the side fences may be configured to be movable into the notches.

[0095] (Appendix 15) In the paper feeding device described in any of Appendices 11 to 14, an upstream top surface detection unit may be provided that detects the top surface of the upstream end of the topmost printing medium in the paper feed direction, and a downstream top surface detection unit that detects the top surface of the downstream end of the topmost printing medium in the paper feed direction, and the control unit may control the lifting unit based on the upstream top surface detected by the upstream top surface detection unit and the downstream top surface detected by the downstream top surface detection unit.

[0096] (Appendix 16) The paper feeding device described in Appendix 15 can be provided with a lifting unit that raises and lowers the paper feeding table, and the control unit can control the lifting unit to raise the paper feeding table until the upstream top surface of the topmost printing medium is detected, and then control the lifting unit to lift the downstream ends of the multiple printing media in the paper feeding direction until the downstream top surface of the topmost printing medium is detected.

[0097] (Appendix 17) In the paper feeding device described in Appendix 16, when the control unit raises the paper feeding table by the lifting unit during feeding of printing media, if the downstream top surface of the topmost printing medium is detected before the upstream top surface, the control unit controls the lifting unit to lower the downstream ends of the multiple printing media in the paper feeding direction a predetermined distance, then raise the paper feeding table until the upstream top surface of the topmost printing medium is detected, and then lift the downstream ends of the multiple printing media in the paper feeding direction until the downstream top surface of the topmost printing medium is detected.

[0098] (Appendix 18) In the paper feeding device described in any one of Supplementary Notes 15 to 17, the control unit can control the lifting unit to lift the downstream ends of the multiple printing media in the paper feeding direction by a predetermined distance before the upstream top surface of the topmost printing medium is detected.

[0099] (Appendix 19) In the paper feeding device described in Supplementary Note 18, the control unit can change the distance by which the downstream ends of the multiple printing media in the paper feeding direction are lifted in advance, based on information on the thickness of the printing media and the number of loaded sheets.

[0100] (Appendix 20) The paper feeding device described in Appendix 19 can be provided with a height detection unit that detects height information of multiple printing media loaded on the paper feeding tray, and the control unit can calculate the number of loaded sheets based on the height information of the multiple printing media and information on the thickness of the printing media. [Explanation of symbols]

[0101] 1 Paper feeder 10 Paper feed tray 11 Paper feed section 11a Scraper roller 11b Pickup roller 11c Guide plate 11d Cutting board 12 Downstream upper surface detector 12a Upper surface detection roller 12b Support member 12c Position Sensor 12d end 13 Upstream top surface detector 13a Upper surface detection roller 13b Support member 13c Positioning Sensor 13d end 14 Lifting section 14a Bottom plate member 14b Rotation axis 14c Lifting members 14d Rotation axis 14e plane 14f Cutout 14g narrow side 14th floor wide surface 18 Lifting drive 19 Scraper detector 19a Case 19b End 19c Positioning Sensor 20,21 Side fence 30 Lifting section 40 Roller drive unit 50 Control section P Envelope

Claims

1. a paper feed tray on which a plurality of print media are loaded; a paper feed section that sequentially pays out the topmost print medium among the plurality of print media stacked on the paper feed tray and transports the topmost print medium in a paper feed direction to feed the print medium; a lifting section that lifts upwardly an upstream end of the plurality of print media loaded on the paper feed tray while supporting the upstream end of the print media in the paper feed direction on a flat surface; a control unit that controls the lifting unit so that an upper surface of the uppermost print medium is always kept horizontal during feeding by the paper feeding unit.

2. 2. The paper feeding device according to claim 1, wherein the lifting portion has a flat surface that supports the upstream end of the plurality of printing media in the paper feed direction, one side of which is connected to a rotation shaft extending on the paper feed table in a direction perpendicular to the paper feed direction, and a bottom plate member that rotates around the rotation shaft.

3. 3. The paper feeder according to claim 2, wherein the bottom plate member has notches on both sides in a direction perpendicular to the paper feed direction and downstream in the paper feed direction.

4. a side fence for aligning both sides of the plurality of print media in a direction perpendicular to the paper feed direction; 4. The paper feeder according to claim 3, wherein the side fence is movable into the notch.

5. an upstream top surface detection unit that detects a top surface of the end of the uppermost print medium on the upstream side in the paper feed direction; a downstream upper surface detection unit that detects an upper surface of an end portion of the uppermost print medium on a downstream side in the paper feed direction, 2. The paper feeding device according to claim 1, wherein the control unit controls the lifting unit based on the upstream upper surface detected by the upstream upper surface detection unit and the downstream upper surface detected by the downstream upper surface detection unit.

6. A lifting unit that lifts and lowers the paper feed tray, A paper feeding device as described in claim 5, wherein the control unit controls the lifting unit to raise the paper feeding table until the downstream upper surface of the topmost printing medium is detected, and then controls the lifting unit to lift the upstream ends of the multiple printing media in the paper feeding direction until the upstream upper surface of the topmost printing medium is detected.

7. 7. A paper feeding device as described in claim 6, wherein when the control unit causes the lifting unit to raise the paper feed table while the printing media are being fed, if the upstream top surface of the topmost printing medium is detected before the downstream top surface, the control unit controls the lifting unit to lower the upstream ends of the multiple printing media in the paper feed direction a predetermined distance, then raise the paper feed table until the downstream top surface of the topmost printing medium is detected, and then lift the upstream ends of the multiple printing media in the paper feed direction until the upstream top surface of the topmost printing medium is detected.

8. The paper feeding device according to claim 6, wherein the control unit controls the lifting unit to lift the upstream end of the plurality of printing media in the paper feed direction by a predetermined distance before the downstream upper surface of the topmost printing medium is detected.

9. 9. The paper feeder according to claim 8, wherein the control unit changes the lifting distance in advance based on the information on the thickness of the print media and the number of loaded sheets.

10. a height detection unit that detects height information of a plurality of print media loaded on the paper feed tray; 10. The paper feeder according to claim 9, wherein the control unit calculates the number of sheets to be loaded based on information on heights of the plurality of print media and information on thicknesses of the print media.

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