Abstract:
An apparatus for selecting the feed path of sheets of paper capable of being driven by the constant rotation of the existing drive system of a photocopier, or the like. A gate is used for selectively directing paper to one of two feed path directions. The apparatus utilizes a frictional drive torque transfer mechanism that transmits a limited torque to the gate. When the gate is in the proper position, it is stopped by a stopper whose force exceeds the torque limit of the torque transfer mechanism allowing the gate to maintain the proper position while the drive system continues to rotate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a feed path selection mechanism for sheets of paper or the like equipped with a selecting gate which selects the feed path of the sheets of paper or the like, and to an image forming apparatus using this mechanism. 
     2. Description of the Related Art 
     A conventional feed path selection mechanism for sheets of paper or the like in an image forming apparatus comprises a gate plate, a solenoid having a plunger which is operatively connected to the gate plate, and a solenoid driving circuit for actuating the solenoid. When the solenoid is excited, the plunger is retracted to rotate the gate plate in a first direction whereby the gate plate is stopped at the first position. This produces the gate open condition, allowing a sheet of paper that has been copied on to one side to be again fed to a loading unit for copying on both sides. On the other hand, when the excitation of the solenoid is removed, no attractive force is applied to the plunger. As a result, the gate plate is rotated in a second direction opposite to the first direction and stopped at the second position. This produces the gate closed condition, so that a sheet of paper, after having been copied on, is discharged to the outside of the apparatus. 
     In the conventional feed path selection mechanism as described above, the solenoid that is electrically actuated is used as the drive source of the gate plate. This therefore necessitated a solenoid, its mounting bracket, a connecting link, and a solenoid driving circuit etc, causing the problem of high cost. Also, extra space is required to mount the solenoid, resulting in the problem of increased size of the device as a whole. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a feed path selection mechanism wherein the selecting gate can be rotated utilizing the existing drive mechanism, and an image forming device employing this feed path selection mechanism. 
     According to the present invention, there is provided an apparatus for selecting the feed path of sheets of paper, comprising means for conveying the sheet of paper, the conveying means including a first feed path and a second feed path; gate means for selectively leading the sheets of paper to one of the first feed path and the second feed path; means for moving the gate means between a first position corresponding to the first feed path and a second position corresponding to the second feed path, the moving means including first transmitting means for transmitting a rotation torque in a first direction and a second direction opposite to the first direction to the gate means, the first transmitting means no rotation torque transmits to the gate means due to the first transmitting means idles after the gate means moves to the first position by the rotation of the first transmitting means in one direction of the first and second direction; second transmitting means, operatively coupled to the first transmitting means, for transmitting a rotation torque to the first transmitting means, the second transmitting means no rotation torque transmits to the first transmitting means due to the second transmitting means idles after the gate means moves to the second position through the first transmitting means by the rotation of the second transmitting means in the other direction of the first and second direction; and means, operatively coupled to the second transmitting means, for selectively rotating the second transmitting means in the first direction and the second direction; wherein the sheets of paper being led to the first path when the moving means moves the gate means to the first position, and being led to the second path when the moving means moves the gate means to the second position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 to 8 show an embodiment of a feed path selection mechanism according to the present invention in which: 
     FIG. 1 is a diagram showing the gate closed condition of the feed path selection mechanism provided in the image forming apparatus; 
     FIG. 2 is a diagram showing the gate open condition of the feed path selection mechanism provided in the image forming apparatus shown in FIG. 1; 
     FIG. 3 is a perspective view showing the feed path selection mechanism; 
     FIG. 4 is a perspective view showing the pulley drive mechanism portion of the feed path selection mechanism; 
     FIG. 5 is a plan view showing the vicinity of the selecting gate and rotatable shaft; 
     FIG. 6 is a flont view showing the relationship among the stopper, connecting body and gear body; 
     FIG. 7 is a perspective view showing the vicinity of the selecting gate; and 
     FIG. 8 is a front view showing part A of FIG. 7 to a lager scale. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the present invention will now be described in more detail with reference to the accompanying drawings. 
     FIG. 1 is a diagram showing the gate closed condition of a feed path selection mechanism provided in an electronic copier 1 as an image forming apparatus. While, FIG. 2 is a diagram showing the gate open condition of the feed path selection mechanism. Electronic copier 1 is equipped with an upper unit 2 that accomodates the main body part of the copier, and a lower unit 3 provided below this upper unit 2. A paper feed cassette 5 is removably mounted in part of this lower unit 3. Within upper unit 2 and lower unit 3 there are provided: a photosensitive drum 6; feed rollers 8 that feed paper P held in paper feed cassette 5 in synchronization with the rotation of this photosensitive drum 6; a conveyor belt 12 that conveys copy paper P through aligning rollers 11 to photosensitive drum 6, this paper P then being separated from photosensitive drum 6 by a separation charger 10 after a toner image has been transferred to it by a transfer charger 9; a fixing roll pair 13 whereby the toner image is fixed to paper P, this fixing roll pair 13 provided at the end of this conveyor belt 12; and exit rollers 15 provided adjacent this fixing roll pair 13. Thus, copy paper P is discharged to the outside by passing through this exit rollers 15 and a sheet feed path selection mechanism 16. 
     Within lower unit 3 there is provided a feed loop 18 that communicates with the paper discharge end of the interior of upper unit 2. This loop 18 comprises an inverting paper feed guide 19 and a plurality of conveyor roll pairs 20 that face each other on either side of this inverting paper feed guide 19. A paper stack unit 21 is arranged in the middle of lower unit 3. Paper P that is drawn into conveyor loop 18 is temporarily stored in a stacked condition in paper stack unit 21, and is then again fed to photosensitive drum 6 by means of a pick up roll 22. At the discharge end of paper stack unit 21, there is provided a paper feed guide 23 that communicates with the paper feed end in upper unit 2. 
     FIG. 3 is a perspective view showing the feed path selection mechanism. FIG. 4 is a perspective view showing the pulley drive mechanism portion of the feed path selection mechanism. FIG. 5 is a plan view showing the visinity of the selecting gate and rotatable shaft. FIG. 6 is a front view showing the relationship among the stopper, connecting body and gear body. FIG. 7 is a perspective view showing the vicinity of the selecting gate. FIG. 8 is a front view showing part A of FIG. 7 to a lager scale. 
     Paper feed path selection mechanism 16 is arranged between exit rollers 15 and the start of coveyor loop 18, and is equipped with a torque limiter S comprising a gate plate 25, a stopper 26, a cylindrical connector 28, a gear 29, a first coil spring 30, and a second coil spring 31. 
     Gate plate 25 is arranged in the direction normal to the plane of FIG. 1, and has a rotatable shaft 32 integrally fixed at its center of rotation. This rotatable shaft 32 is inserted in a slot 33a formed in the side of a frame 33 (see FIG. 8), so that it is rotatably supported in frame 33, movement in the axial direction being prevented by means of a clip 36 through a washer 35 on a ring shaped groove formed in a portion projecting from this slot 33a. Stopper 26, cylindrical connector 28, and gear 29 are successively mounted on the end of rotatable shaft 32 that projects from slot 33a. Movement of these components in the axis direction is prevented by means of a clip 38 that is pressed into a ring shaped groove formed at one end of rotatable shaft 32. 
     Stopper 26 comprises a cylindrical boss 39, which is 14 mm in outside diameter, and an arm 40 that projects from the outer circumference of this cylindrical boss 39. Rotatable shaft 32 is inserted into a shaft hole 39a formed in the middle of cylindrical boss 39, and pins 41 mounted on rotatable shaft 32 are inserted in grooves 39b formed at an interval of 180° over the entire length of shaft hole 39a. Thus stopper 26 rotates integrally with rotatable shaft 32. At the tip of arm 40, there is integrally formed a stop pin 40a that is parallel with the axis of cylindrical boss 39 and that projects on the opposite side to cylindrical boss 39. This stop pin 40a is inserted in a fan-shaped slot 33b formed in frame 33 and consisting of an arc centered on the axis of rotatable shaft 32. 
     Cylindrical connector 28 is divided, by a flange 28a formed at its center, into a left cylindrical boss 28b and a right cylindrical boss 28d. The outside diameter of left cylindrical boss 28b and right cylindrical boss 28d are 14 mm, respectively. The end face of left cylindrical boss 28b abuts the end face of cylindrical boss 39 of stopper 26 and is mounted on supported shaft 32. Gear 29 comprises a cylindrical boss 42, which is 14 mm in outside diameter, and a gear portion 43. The end face of cylindrical boss 42 abuts the end face of right cylindrical boss 28d of cylindrical connector 28 and is mounted on rotatable shaft 32. A first coil spring 30, which is 13.7 mm in inside diameter, is firstwardly, e.g., leftwardly wound, so that the first coil spring 30 clamps cylindrical boss 39 of stopper 26 and left cylindrical boss 28b of cylindrical connector 28 respectively. A second coil spring 31, which is 13.7 mm in inside diameter, is secondwardly opposite to the firstward, e.g., rightwardly wound, so that the second coil spring 31 clamps right cylindrical boss 28d of cylindrical connector 28 and cylindrical boss 42 of gear 29 respectively. Gear portion 43 of gear 29 is linked to an exit roller drive mechanism 45, which thus constitutes the gear drive mechanism. This exit roller drive mechanism 45 is equipped with a rotary shaft 46, a pulley 48 provided with a gear portion, and a pulley drive mechanism 49. Pulley 48 is fixed to the end of rotary shaft 46 and is rotatably supported on frame 33. Pulley 48 comprises a gear portion 48a and pulley portion 48b. Exit roller 15 is fixed to rotary shaft 46. Gear portion 48a meshes with gear portion 43 of gear 29. Pulley drive mechanism 49 is equipped with a motor 50, a driven pulley 51 and an intermediate pulley 52. Respective belts 53A, 53B and 53C are provided between motor 50 and driven pulley 51, driven pulley 51 and intermediate pulley 52 and intermediate pulley 52 and pulley portion 48b of pulley 48. 
     The operation of the embodiment will be described. When motor 50 rotates in the forward direction, pulley 48 rotates in the direction of arrow F through belt 53A, driven pulley 51, belt 53B, intermediate pulley 52 and belt 53C. When this happens, gear 29, which meshes with gear portion 48a of pulley 48, of torque limiter S rotates in the direction of arrow G. In accordance with the rotation of gear 29, cylindrical connector 28 is rotated in the direction of arrow G integrally with second coil spring 31 since second coil spring 31, which is rightwardly wound, clamps the circumferential surface of right cylindrical boss 28d. By rotation of cylindrical connerctor 28, stopper 26 is rotated integrally with first coil spring 30 in the direction of arrow H until stop pin 40a abuts one end of slot 33b since first coil spring 30, which is leftwardly wound, clamps the circumferential surface of cylindrical boss 39 of stopper 26. Due to this rotation, gate plate 25 rotates in the direction of arrow J, assuming the gate open condition as shown in FIG. 2, and allowing paper P whereof one side has been copied on to be fed into conveyor loop 18 so that copying is performed on to both faces of paper P. 
     In this case, even if pulley 48 rotates further in the direction of arrow F, the open condition will be maintained since all that happens is that second coil spring 31 performs idle rotation over the circumference of right cylindrical boss 28d. 
     On the other hand, when motor 50 is rotated in the opposite direction, pulley 48 rotates in the direction of arrow K through belt 53A, driven pulley 51, belt 53B, intermediate pulley 52 and belt 53C. When this happens, gear 29 rotates in the direction of arrow L, causing stopper 28 is rotated in the direction of arrow L since second coil spring 31 clamps the circumferential surface of right cylindrical boss 28d of cylindrical connector 28. By this rotation of cylindrical connector 28, stopper 26 is rotated integrally with first coil spring 30 in the direction of arrow M until stop pin 40a abuts the other end of slot 33b since first coil spring 30 clamps the circumferential surface of cylindrical boss 39 of stopper 26. This rotation causes gate plate 25 to be rotated in the direction of arrow N, producing the gate closed condition as shown in FIG. 2, so that after paper P has been copied to on one side, it can be discharged to the outside through exit rollers 15. 
     In this case, even if pulley 48 rotates further in the direction of arrow K, cylindrical connector 28 rotates idly over the inner surface of first coil spring 30, so the gate closed condition is maintained. 
     As described above, in selecting the paper feed path, the selecting gate is operated in the forwards or reverse direction by forward or reverse rotation of the torque limiter utilizing the existing drive mechanism, e.g., an exit roller drive mechanism 45. 
     Consequently, the construction can be greatly simplified, enabling a considerable cost reduction, and the entire device can be made smaller.