Paper Post Handling Device

Abstract

A paper post handling device includes a stapler to receive a paper image-formed by an image forming apparatus and perform a stapling process. The stapler is controlled so as to move in parallel with a front end of the paper outside a paper width at a predetermined distance from a neighborhood of a center of a paper width, then rotate in a less than 45.degree. arc, moreover move outside the paper width, and perform the stapling process at a desired position.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2005-276594 filed on Sep. 22, 2005, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a paper post handling device for post-handling papers ejected from an image forming apparatus such as a copier, a printer, or a composite device.

[0004] 2. Description of the Related Art

[0005] In recent years, the image forming apparatus performs post handling of papers such as classifying and stapling papers after image forming, so that a paper post handling device may be installed in the neighborhood of a paper ejection section of the main body of the image forming apparatus. Such a paper post handling device, as disclosed in U.S. Pat. No. 6,142,461, to bundle image-formed papers, by setting of a user, is formed so at to perform the stapling process.

[0006] However, various sizes of papers are used to form images, so that when performing the stapling process, due to the relation to the movable area of the stapler, the stapling angle is not fixed. Therefore, in order to properly arrange paper batches after the stapling process, it is not convenient.

SUMMARY OF THE INVENTION

[0007] An object of the present invention is to provide a paper post handling device capable of stapling papers of any size at the same angle.

[0008] According to an embodiment of the present invention, there is provided a paper post handling device comprising a stapler to receive a paper image-formed by an image forming apparatus and perform a stapling process, wherein the stapler is controlled so as to move in parallel with a front end of the paper outside a paper width at a predetermined distance from a neighborhood of a center of a paper width, then rotate in a less than 45.degree. arc, moreover move outside the paper width, and perform the stapling process at a desired position.

[0009] Furthermore, according to another embodiment of the present invention, there is provided a method for receiving and stapling a paper image-formed by an image forming apparatus, comprising moving the stapler in parallel with a front end of the paper outside a paper width at a predetermined distance from a neighborhood of a center of the paper width; rotating the stapler in a less than 45.degree. arc; moving the stapler outside the paper width; and stapling the paper image-formed at a desired position by the stapler.

[0010] Further, according to still another embodiment of the present invention, there is provided a stapler for performing a stapling process, comprising a frame; a rail attached to the frame; a mobile body moving back and forth freely along the rail; a stapler attached to the mobile body; and a slit board composed of a horizontal portion and a slant portion with at least one slit formed, wherein the stapler is joined to the slit, and the stapler moved by the mobile body, when moving at a predetermined distance across the horizontal portion of the slit, is positioned so that staples for bundling papers are positioned in parallel with paper edges, and when moving across the slant portion of the slit, the staples for bundling papers are rotated in a less than 45.degree. arc.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a perspective view showing the essential section of the paper post handling device relating to an embodiment of the present invention;

[0012] FIG. 2 is a schematic block diagram showing the paper post handling device relating to an embodiment of the present invention;

[0013] FIG. 3 is a perspective view showing the stapler of the paper post handling device relating to an embodiment of the present invention;

[0014] FIG. 4 is a schematic view for explaining control of the stapler of the paper post handling device relating to an embodiment of the present invention;

[0015] FIG. 5 is a perspective view showing the longitudinal aligning roller relating to an embodiment of the present invention;

[0016] FIG. 6 is a schematic front view showing the paddle relating to an embodiment of the present invention;

[0017] FIG. 7 is a schematic perspective view showing the transversal aligning plate and conveying belt relating to an embodiment of the present invention;

[0018] FIG. 8 is a schematic front view showing the condition that a paper on the standby tray or receiving tray relating to an embodiment of the present invention is pressed out;

[0019] FIG. 9 is a perspective view showing the frame to which the stapler relating to an embodiment of the present invention is attached; and

[0020] FIG. 10 is a perspective view of the stapler moving mechanism showing the condition that the stapler relating to an embodiment of the present invention is attached to the frame shown in FIG. 9.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Hereinafter, the embodiments of the present invention will be explained with reference to the accompanying drawings. Further, to the same parts as those shown in the respective drawings, the same numerals are assigned and the duplicated explanation will be omitted. FIG. 1 is a perspective view showing the essential section of paper post handling device 7 in which the stapler relating to an embodiment of the present invention is incorporated and FIG. 2 is a schematic block diagram showing paper post handling device 7 arranged in the neighborhood of image forming apparatus 5 such as a copier shown in FIG. 2.

[0022] Paper post handling device 7 is basically composed of standby tray 10, handling tray 12, stapler 14, first receiving tray 16, and second receiving tray 18. Standby tray 10 has a pair of paper supporting surfaces capable of opening and closing left and right. When the pair of paper supporting surfaces are opened, loaded papers drop from standby tray 10 onto handling tray 12.

[0023] Paper P image-formed by image forming apparatus 5 such as a copier and ejected by a pair of paper ejection rollers 6 is received by a pair of entrance rollers 22, is supplied to a pair of paper supply rollers 24, and is sent from paper supply rollers 24 to standby tray 10. Entrance rollers 22 are driven by entrance roller motor 26. Between entrance rollers 22 and standby tray 10, paper conveying guide 36 for leading paper P to paper supply rollers 24 is installed. Entrance rollers 22 are composed of upper entrance roller 22a and lower entrance roller 22b. Paper supply rollers 24 are composed of upper paper supply roller and lower paper supply lower.

[0024] Under standby tray 10, handling tray 12 for loading paper P dropped from standby tray 10 is arranged.

[0025] Handling tray 12, during stapling paper P by stapler 14 which is a processing mechanism for performing post handling, aligns and supports loaded paper P.

[0026] As shown in FIG. 3, stapler 14 receives a control signal from a controller (not drawn) arranged in the paper post handling device and is positioned by stapler driver 49 so as to control the stapling process.

[0027] From the image forming apparatus, information on a paper to be image-formed is sent to the controller of the paper post handling device. Stapler 14 changes first the position from the home position so as to be parallel with the front end of paper P (the paper conveying direction) (the tip thereof) and moves to the neighborhood of the center of the paper width. Then, stapler 14 moves in parallel with the front end of paper P outside the paper width at a predetermined distance from the neighborhood of the center of the paper width. The reason is that the processing time is shortened by parallel movement. Therefore, the predetermined distance, for example, is preferably set between 1/4 and 1/3 of the width of paper P.

[0028] Stapler 14 moved from the neighborhood of the center of the paper width to the predetermined position, as shown in FIG. 4, rotates in a less than 45.degree. arc, for example, in a 30.degree. arc at the predetermined position and furthermore moves outside the paper width. After moving at the movement distance according to the paper width, the stapler staples papers P at desired position A1 or A2. Therefore, even if the paper size is different, staples are processed at the same angle. Here, the desired position, for example, is the position set by an operator using the operation section arranged in the image forming apparatus. Further, when there is no setting of the designated position of the operator, the appropriate position information for each paper size which is prepared beforehand may be set to the desired position.

[0029] Handling tray 12 has a pair of upper longitudinal aligning roller 38a and lower longitudinal aligning roller 38b shown in FIG. 6 for aligning a plurality of papers P dropped from standby tray 19 in the longitudinal direction which is a conveying direction. Upper and lower longitudinal aligning rollers 38a and 38b serve as paper batch conveying rollers for holding and taking out paper batch T after end of the stapling process from stapler 14. Upper longitudinal aligning roller 38b is driven by longitudinal upper aligning roller motor 40 and lower longitudinal aligning roller 38b is driven by longitudinal lower aligning roller motor 42.

[0030] Further, at the position where the rear end of paper P is dropped when paper P is dropped on handling tray 12, rotatable paddle 44 for aligning uppermost paper P loaded on handling tray 12 in the longitudinal direction is arranged. Paddle 44, as shown in FIG. 6, includes receiver 44a of papers P dropped on handling tray 12, slapping portion 44b for slapping down papers P on handling tray 12, and sending away portion 44c for aligning papers P on handling tray 12 and is driven by paddle motor 46. Paddle 44 is made of a rubber material which is elastic.

[0031] At the end of handling tray 12 on the side of stapler 14, stopper 45 for making contact with the rear end of paper P and controlling the position of the rear end is installed. Almost at the center of handling tray 12, conveying belt 50 for conveying paper batch T, which is stapled and taken out from stapler 14 by upper and lower longitudinal aligning rollers 38a and 38b, to first receiving tray 16 or second receiving tray 18 is installed. On conveying belt 50, sending away pawl 50a for catching the rear end of paper batch T is installed.

[0032] As shown in FIG. 2, the paper supporting surfaces of standby tray 10 are opened, and papers P can be dropped on handling tray 12, while papers P can be conveyed toward first receiving tray 16 or second receiving tray 18. Conveyance of papers P toward receiving tray 16 or 18 is executed when standby tray roller 28 for aligning papers P makes contact with papers P on standby tray 12. Standby tray roller 28 is controlled vertical movement by standby tray roller driver 30.

[0033] Standby tray 10, to support paper P in the state that the front end of paper P is higher than the rear end thereof, is arranged so that an inclination angle of .theta.1 is obtained. First receiving tray 16 or second receiving tray 18 is moved up and down by receiving tray driver 52 and either of them is selected. First receiving tray 16 or second receiving tray 18, when loading papers P, is moved up and down almost at the same height as that of standby tray 10 or handling tray 12, thus the aligning capacity of papers P to be ejected is improved. Further, first receiving tray 16 or second receiving tray 18, to support paper P in the state that the front end of paper P is higher than the rear end thereof, is arranged so that an inclination angle of .theta.2 is obtained.

[0034] Between standby tray 10 and handling tray 12, transversal aligning plates 47a and 47b shown in FIG. 7 are installed. Transversal aligning plates 47a and 47b, when opening the pair of paper supporting surfaces of standby tray 10 and dropping papers P on standby tray 10 onto handling tray 12, transversely align papers P so as to prevent them from disordering in the transverse direction perpendicular to the conveying direction. Transversal aligning plates 47a and 47b are installed so as to slide in accordance with the width of papers P by transversal aligning plate motor 48.

[0035] Next, the operation of the invention will be explained. When an image is formed by image forming apparatus 5 and paper P is ejected from paper ejection rollers 6, paper post handling device 7 performs a different operation depending on whether or not to perform post handling for paper P or whether preceding paper P is during execution of the post handling or finishes the post handling.

[0036] When executing no post handling, for example, first receiving tray 16 slides and moves to the position indicated by the dotted line in FIG. 2 and papers P ejected from standby tray 10 can be loaded in good consistency. When executing no post handling, papers P conveyed from entrance rollers 22 to paper supply rollers 24 via paper conveying guide 36 are conveyed onto standby tray 10 by paper supply rollers 24. Next, papers P are dropped onto standby tray 10, are conveyed by standby tray roller 28 rotating in the direction of arrow f, and are ejected onto receiving tray 16.

[0037] In this way, on first receiving tray 16, papers P are loaded sequentially. First receiving tray 16 is arranged so as to set the inclination angle to .theta.2 and the front end of each paper is higher than the rear end thereof. Therefore, for example, even if papers P are ejected onto first receiving tray 16 in the state that they are curved conically as shown by the dotted line in FIG. 8, preceding paper P loaded on first receiving tray 16 is not pressed out by contact with the front end of succeeding paper P. Namely, ejected papers P are sequentially loaded on first receiving tray 16 unless the order is disturbed. Further, even if preceding paper P is pressed by succeeding paper P and is shifted slightly, since the inclination angle .theta.2 is provided, paper P drops by its own weight, thus papers P are loaded on first receiving tray 16 with the rear ends aligned with each other, and the ejection process of papers P is completed.

[0038] Next, a case that the stapling process which is post handling is performed and there is no preceding paper P during the execution of the stapling process on handling tray 12 will be described.

[0039] In this case, standby tray 10 opens the pair of paper supporting surfaces thereof and drops papers P onto handling tray 12. Further, as shown in FIG. 7, transversal aligning plates 47a and 47b, to align dropped papers P in the transverse direction, are arranged so as to make the interval between transversal aligning plates 47a and 47b almost equal to the width of papers P. By doing this, papers P conveyed by paper supply rollers 24 are dropped onto handling tray 12 via standby tray 10.

[0040] When papers P are dropped, upper longitudinal aligning roller 38a is shifted upward and receiver 44a of paddle 44 receives the rear ends of papers P. Papers P are dropped with both sides thereof kept in contact with transversal aligning plates 47a and 47b and are aligned in the transverse direction. Next, paddle 44 rotates in the direction of arrow o, drops the rear ends of papers P from receiver 44a, and slaps down them onto handling tray 12 by slapping portion 44b. Furthermore, paddle 44 sends papers P by sending away portion 44c in the direction of arrow q, allows the rear ends of papers P to make contact with stopper 45, and completes the longitudinal alignment of papers P. Further, the longitudinal alignment of papers P on handling tray 12 may be executed by upper longitudinal aligning roller 38a by moving up and down upper longitudinal aligning roller 38a each time.

[0041] In this way, image-formed papers P are sequentially aligned in the transverse direction and longitudinal direction and are loaded on handling tray 12 via standby tray 19 from paper supply rollers 24. When papers P reach a predetermined number, stapler 14 firstly changes its position from the home position so as to become parallel with the front ends of papers P (paper ends in the conveying direction) and moves to the neighborhood of the center of the paper width. Then, stapler 14 moves in parallel with the front ends of papers P outside the paper width at a distance of 1/4 to 1/3 of the width of papers P from the neighborhood of the center of the paper width. Stapler 14 moved from the neighborhood of the center of the paper width to the predetermined position, as shown in FIG. 4, rotates in a less than 45.degree. arc, for example, in a 30.degree. arc at the predetermined position and furthermore moves outside the paper width. After moving at the movement distance according to the paper width, the stapler staples papers P on handling tray 12 at the desired position and bundles them to form paper batch T.

[0042] Hereafter, upper longitudinal aligning roller 38a moves down on paper batch T and upper longitudinal aligning roller 38a rotating in the direction of arrow r and lower longitudinal aligning roller 38b rotating in the direction of arrow s clamp paper batch T and convey it toward first receiving tray 16.

[0043] The rear end of paper batch T, when passing through upper and lower longitudinal aligning rollers 38a and 38b, is caught by sending away pawl 50a of conveying belt 50 moving in the direction of arrow t and is conveyed onto first receiving tray 16.

[0044] At this time, first receiving tray 16 slides and moves from the position indicated by the dotted line in FIG. 2 to the position indicated by the solid line. First receiving tray 16 is arranged so as to set the inclination angle to .theta.2 and the front end of each paper is higher than the rear end thereof, so that preceding paper P loaded on first receiving tray 16 is not pressed out by contact with the front end of succeeding paper batch T. Further, even if preceding paper batch T is shifted slightly by succeeding paper P, since the inclination angle .theta.2 is provided, paper batch T drops by its own weight, thus papers P are loaded on first receiving tray 16 with the rear ends aligned with each other, and the stapling process of papers P is completed.

[0045] Next, a case that the stapling process which is post handling is performed and there remain preceding papers P during the execution of the stapling process on handling tray 20 will be described.

[0046] In this case, standby tray 10 can support papers P. Further, standby tray roller 28 is shifted upward so as not to disturb papers P. Papers P ejected from image forming apparatus 5 and supplied by paper supply rollers 24, to wait for handling tray 12 to be free, is loaded once on standby tray 10.

[0047] Papers P loaded on standby tray 10 are aligned longitudinally by standby tray roller 28 rotating in the opposite direction of the direction of arrow f. Furthermore, standby tray 10 is arranged so as to set the inclination angle to .theta.1 and the front end of each paper is higher than the rear end thereof, so that papers P align longitudinally by the own weight.

[0048] Further, standby tray 10 is arranged so as to set the inclination angle to .theta.1, so that for example, even if papers P are supplied from paper supply rollers 24 onto standby tray 10 in the state that they are curved conically, preceding paper P loaded on standby tray 10 is not pressed out by contact with the front end of succeeding paper P. Namely, supplied papers P are sequentially loaded on standby tray 10 unless the order is disturbed. Further, even if preceding paper P is pressed by succeeding paper P and is shifted slightly, since the inclination angle .theta.1 is provided, paper P drops by its own weight, thus papers P are aligned and loaded on standby tray 10 with the rear ends aligned with each other.

[0049] During this period, when preceding paper P on handling tray 12 is ejected on the side of first receiving tray 16 and handling tray 12 becomes free, standby tray 10 drops paper P onto handling tray 12. At this time, transversal aligning plates 47a and 47b are arranged so as to set the interval between them to an almost same width as that of papers P. Therefore, papers P dropped from standby tray 10 are controlled both sides by transversal aligning plates 47a and 47b and are aligned in the transverse direction.

[0050] Paper P on the lower side of two papers P dropped on handling tray 12 is sent in the direction of arrow q by lower longitudinal aligning roller 38b rotating in the opposite direction of the direction of arrow s, and the rear end of paper P makes contact with stopper 45, and the longitudinal alignment of the papers P is completed. Paper P on the upper side of two papers P dropped on handling tray 12 is sent in the direction of arrow q by upper longitudinal aligning roller 38a rotating in the opposite direction of the direction of arrow r, and the rear end of paper P makes contact with stopper 45, and the longitudinal alignment of the papers P is completed, and hereafter, upper longitudinal aligning roller 38a is shifted upward.

[0051] Third and subsequent papers P ejected from image forming apparatus 5 are dropped directly onto handling tray 12 without waiting on standby tray 10. Hereafter, third and subsequent papers P are sequentially aligned on papers P loaded previously on handling tray 12 by paddle 44.

[0052] When papers P loaded on handling tray 12 reach a predetermined number, stapler 14 firstly changes its position from the home position so as to become parallel with the front ends of papers P (paper ends in the conveying direction) and moves to the neighborhood of the center of the paper width. Then, stapler 14 moves in parallel with the front ends of papers P outside the paper width at a distance of 1/4 to 1/3 of the width of papers P from the neighborhood of the center of the paper width. Stapler 14 moved from the neighborhood of the center of the paper width to the predetermined position, as shown in FIG. 4, rotates in a less than 45.degree. arc, for example, in a 30.degree. arc at the predetermined position and furthermore moves outside the paper width. After moving at the movement distance according to the paper width, the stapler staples papers P on handling tray 12 at the desired position and bundles them to form paper batch T.

[0053] Hereafter, paper batch T is conveyed toward first receiving tray 16 by upper and lower longitudinal aligning rollers 38a and 38b, and furthermore, the rear end thereof is caught by sending away pawl 50a of the conveying belt 50 and is conveyed onto first receiving tray 16, and the stapling process of papers P is completed.

[0054] Next, the moving mechanism for moving stapler 14 will be explained in detail by referring to FIGS. 9 and 10.

[0055] As shown in FIG. 9, frame 60 to which stapler 14 is attached has a long and narrow box shape. Extending across one side brim 61 of frame 60 and the other side brim 62, round cylindrical rail 63 is arranged. Furthermore, almost at the central part of frame 60, first pulley 64 is installed in the neighborhood of side brim 61 and second pulley 65 is installed in the neighborhood of side brim 62. First pulley 64 is connected to a motor not drawn so as to be driven forward and backward. Between first pulley 64 and second pulley 65, endless belt 66 is stretched. On the opposite side of rail 63 across endless belt 66, slit board 67 is installed. On slit board 67, slit 68 for controlling the movement of stapler 14 is formed.

[0056] Slit 68, as shown in FIG. 9, is composed of one slit in which from the left of the drawing, first end 68a, first slant portion 68b, first horizontal portion 68c, second slant portion 68d, second horizontal portion 68e, third slant portion 68f, third horizontal portion 68g, and second end 68h are continued. First slant portion 68b, second slant portion 68d, and third slant portion 68f are inclined at an angle of 30.degree. (less than 45.degree.) with first horizontal portion 68c, second horizontal portion 68e, and third horizontal portion 68g.

[0057] Stapler 14 moves through the length of slit 68. Namely, stapler 14 is swingably attached to movable plate 69. To one end of stapler 14, a pin not drawn is fixed and the pin is inserted into slit 68. Therefore, stapler 14 swings along the shape of slit 68 so as to be inclined at a predetermined angle. Movable plate 69 on which stapler 14 is loaded is attached movably to rail 63 via support pipe 70 fixed to the bottom of movable plate 69.

[0058] Movable plate 69 is attached to endless belt 66. Namely, by the forward and backward rotations of first pulley 64 on which endless belt 66 is stretched, endless belt 66 rotates in the first and second directions, thus movable plate 69 moves in the first direction and second direction which is an opposite direction.

[0059] When stapler 14 starts from first end 68a of slit 68 by the rotation of endless belt 66, it rotates in a 30.degree. arc at the part where it changes from first slant portion 68b to first horizontal portion 68c. The condition of rotation in 30.degree. arc indicates the condition of stapler 14 at the position shown by A1 in FIG. 4 and at the corner of wide papers P, stapler 14 can staple. When stapler 14 changes from first horizontal portion 68c to second slant portion 68d to staple at the corner of wide papers P, it rotates again in a 30.degree. arc. The condition of rotation in 30.degree. arc indicates the condition of stapler 14 at the position shown by A2 in FIG. 4 and at the corner of wide papers P, stapler 14 can staple.

[0060] Further, on second horizontal portion 68e, stapler 14 is positioned in parallel with the edges of papers P and operates so as to shoot a pair of staples on papers P. Further, the moving speed of stapler 14 between the pair of staples is about 310 mm/s. The first moving speed of stapler 14 to the one-spot stapling position or the two-spot stapling positions is about 110 mm/s. The moving speed of stapler 14 up to the sensor which is set initially and at the home position is about 90 mm/s.

[0061] According to the moving mechanism of the stapler aforementioned, it is possible to move stapler 14 to a predetermined position along the shape of slit 68 only by one driver and rotate it at a predetermined angle, so that the structure is simple. Namely, there is no need to install another driver for rotating stapler 14 at the predetermined angle.

[0062] In this embodiment structured like this, papers of any size can be stapled at the same angle, so that the throughput of the paper post handling can be increased.

[0063] The present invention is not limited to the embodiments aforementioned and can be modified variously within the scope of the invention stated in the claims and it goes without saying that they come within the scope of the present invention.

Claims

1. A paper post handling device comprising: a stapler to receive a paper image-formed by an image forming apparatus and perform a stapling process, wherein the stapler is controlled so as to move in parallel with a front end of the paper outside a paper width at a predetermined distance from a neighborhood of a center of a paper width, then rotate in a less than 45.degree. arc, moreover move outside the paper width, and perform the stapling process at a desired position.

2. The device according to claim 1, wherein the predetermined distance of horizontal movement is 1/4 to 1/3 of the paper width.

3. The device according to claim 1, wherein the angle of less than 45.degree. is 30.degree..

4. The device according to claim 1, wherein the desired position to be stapled can be set by an operator.

5. The device according to claim 1, wherein on the desired position to be stapled, appropriate position information is held beforehand for each paper size.

6. A method for receiving and stapling a paper image-formed by an image forming apparatus, comprising: moving the stapler in parallel with a front end of the paper outside a paper width at a predetermined distance from a neighborhood of a center of the paper width; rotating the stapler in a less than 45.degree. arc; moving the stapler outside the paper width; and stapling the paper image-formed at a desired position by the stapler.

7. The method according to claim 6, wherein the predetermined distance of horizontal movement is 1/4 to 1/3 of the paper width.

8. The method according to claim 6, wherein the angle of less than 45.degree. is 30.degree..

9. The method according to claim 6, wherein the desired position to be stapled can be set by an operator.

10. The method according to claim 6, wherein on the desired position to be stapled, appropriate position information is held beforehand for each paper size.

11. A stapler for performing a stapling process, comprising: a frame; a rail attached to the frame; a mobile body moving back and forth freely along the rail; a stapler attached to the mobile body; and a slit board composed of a horizontal portion and a slant portion with at least one slit formed, wherein the stapler is joined to the slit, and the stapler moved by the mobile body, when moving at a predetermined distance across the horizontal portion of the slit, is positioned so that staples for bundling papers are positioned in parallel with paper edges, and when moving across the slant portion of the slit, the staples for bundling papers are rotated in a less than 45.degree. arc.

12. The stapler according to claim 11, wherein the predetermined distance moving across the horizontal portion is 1/4to 1/3 of the paper width.

13. The stapler according to claim 11, wherein the angle of less than 45.degree. is 30.degree..

14. The stapler according to claim 11, wherein the mobile body includes a first pulley and a second pulley driven forward and backward and an endless belt stretched between the first and second pulleys.