BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an article pressing device and a sorter with the article pressing device. The article pressing device presses articles to be treated against a receptacle, such as a tray, not to move from a position during transportation of the receptacle to a predetermined operation position, for example, a stapling position. The articles may include sheets, for example. 
     2. Description of the Prior Art 
     There is an article pressing device of this type in which articles to be treated are pressed against each receptacle with a pressing member from a time slightly before the receptacle reaches a predetermined operation position. Then, the receptacle with the articles depressed is moved to and positioned at the operation position. The article pressing device is capable of positively preventing the articles on the receptacle from moving from the latter by such a two step operation. 
     This article pressing device requires a mechanism for pressing the articles to be treated with the pressing member and a mechanism for moving the pressing member to the operation position together with each receptable. These mechanisms are composed of many actuators such as a hydraulic cylinder and an electric motor. 
     On the other hand, in conventional sorters there is a sheet sorter in which sheets which are discharged from a photocopier or a printer are stacked on trays while sorted, and are then bounded by stapling or bonding into books. In a sorter with a stapler among this type of sorters, it is required that each of the trays on which sheets are stacked in a sorted state is moved to a stapling position and then a stapler is positioned at one corner of the sheets stacked on the tray for fastening. 
     Heretofore, such a sorter with a stapler performs positioning of the stapler to sheets on each tray by merely moving the stapler to the tray. Also in sorters with operation devices for applying various operations, such as bonding, to sheets on trays, the operation devices are moved toward the trays and then positioned. 
     As already described, the conventional article pressing device requires a combination of actuators such as a hydraulic cylinder and an electric motor, and is disadvantageous in that the construction thereof becomes complicated and large sized. For this reason, the article pressing device cannot be incorporated into small apparatuses such as a sorter in which each of the trays with sheets is transported to an operation position, for example, a stapling position for stapling. 
     Moreover, the conventional sorter is liable to cause sheets on trays to be slipped or lifted by contacting the sheet operation device such as a stapler when the operation device is moved toward the tray and positioned. Thus, the stapler performs the operation on the sheets out of the stacked alignment. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an article pressing device which overcomes such problems. 
     It is another object of the present invention to provide an article pressing device which enables reduction in size with a less complicated structure. 
     Still another object of the present invention is to provide a sorter which is capable of achieving operations, such as a stapling, with sheets correctly stacked on a tray. 
     In view of this and other objects, an aspect of the present invention is directed to an article pressing device which comprises: 
     a base arranged in the vicinity of an operation position to which receptacle carrying articles to be treated are transported in an receptacle transporting direction; 
     a first moving member arranged on the base for reciprocal movement in the receptacle transporting direction; 
     a second moving member arranged on the first moving member for reciprocal movement in the receptacle transporting direction, the second moving member being adapted to contact the receptacle transported to the oepration position; 
     first biasing means for biasing the first moving member in a direction opposite to the receptacle transporting direction; 
     second biasing means for biasing the second moving member in a direction opposite to the receptacle transporting direction by a biasing force smaller than a biasing force of the first biasing means; 
     pressing arm rotatably mounted on the first moving member for movement toward and away from the articles to be treated on each receptacle at the operation position; and 
     link means, arranged between the pressing arm and the second moving member, for moving the pressing arm when the first and second moving members are relatively moved. 
     Here, the link means may comprise a first link and a second link, each of the first and second links being pivotally supported on the first moving member through a supporting pin; the pressing arm may have a proximal end and a distal end; the first link may be connected at one end thereof to the proximal end of the pressing arm and at the other end to one end of the second link; and the second link may be connected at the other end to the second moving member. 
     The second biasing means may comprise a spring extended between the first link and the first moving member. 
     The pressing arm may comprise a pressing roller rotatably mounted on the distal end of the pressing arm. 
     According to another aspect of the present invention, there is provided a sorter which comprises: 
     a plurality of trays for receiving and stacking sheets thereon, the sheets being discharged from a predetermined sheet discharge position; 
     means for treating the sheets on the trays at an operation position; 
     means for sequentially moving the trays between the sheet discharge position and the operation position and 
     sheet pressing means for downwardly pressing the sheets against the corresponding trays in a manner linked with the movement of the trays toward the operation position. 
     Here, the sheet pressing means may comprise: 
     a base arranged in the vicinity of an operation position to which the tray carrying sheet are sequentially transported in an tray transporting direction; 
     a first moving member arranged on the base for reciprocal movement in the tray transporting direction; 
     a second moving member arranged on the first moving member for reciprocal movement in the tray transporting direction, the second moving member being adapted to contact each tray transported to the operation position; 
     first biasing means for biasing the first moving member in a direction opposite to the tray transporting direction; 
     second biasing means for biasing the second moving member in a direction opposite to the tray transporting direction by a biasing force smaller than a biasing force of the first biasing means; 
     pressing arm rotatably mounted on the first moving member for movement toward and away from the sheets in each tray at the operation position; and 
     link means arranged between the pressing arm and the second moving member for moving the pressing arm when the first and second moving members are relatively moved. 
     The link means may comprise a first link and a second link, each of the first and second links being pivotally supported on the first moving member through a supporting pin; the pressing arm may have a proximal end and a distal end; the first link may be connected at one end to the proximal end of the pressing arm and at the other end to one end of the second link; and the second link may be connected at the other end to the second moving member. 
     The second biasing means may comprise a spring extended between the first link and the first moving member. 
     The pressing arm may comprise a pressing roller rotatably mounted on the distal end of the pressing arm. 
     Each of the trays may comprise means for defining a cutout; and the treating means may comprise a stapler for stapling the sheets at the cutout of each tray. 
     A sorter may further comprise sensing means, located in the vicinity of the operation position, for detecting a sheet placed at the cutout to produce a detection signal, whereby the stapler is controlled in response to the detection signal. 
     A sorter may further comprise sensing means, located in the vicinity of the operation position, for detecting a sheet placed on the tray to produce a detection signal, whereby the treating means is controlled in response to the detection signal. 
     Each of the trays may comprise means for defining a cutout; and the treating means may comprise a stapler for stapling the sheets at the cutout of each tray. 
     A sorter may further comprise sensing means, located in the vicinity of the operation position, for detecting a sheet placed at the cutout to produce a detection signal, whereby the stapler is controlled in response to the detection signal. 
     A sorter may further comprise sensing means, located in the vicinity of the operation position, for detecting a sheet placed on the tray to produce a detection signal, whereby the treating means is controlled in response to the detection signal. 
     The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a diagrammatic side view of a sorter of the present invention; 
     FIG. 2 is a diagrammatic front view of the sorter of FIG. 1; 
     FIG. 3 is a diagrammatic plan view of the sorter of FIG. 1; 
     FIG. 4 is an enlarged perspective view, partly cut away, of the sorter of FIG. 1; 
     FIG. 5 is a perspective view, partly further cut away, of the sorter of FIG. 4; 
     FIG. 6 is a view as viewed in the direction of arrow VI in FIG. 4; 
     FIG. 7 is a sectional view taken along line VII--VII in FIG. 6; 
     FIG. 8 is a perspective view of one of the trays and the tray carrier of FIG. 4 on a reduced scale; 
     FIG. 9 is a side view of the tray carrier of FIG. 4; 
     FIG. 10 is a fragmentary view as viewed in the direction of arrow X in FIG. 9; 
     FIG. 11 is an enlarged exploded view of the sheet putting aside mechanism shown in FIG. 4; 
     FIG. 12 is an enlarged diagrammatic plan view of the sheet putting aside mechanism shown in FIG. 4; 
     FIG. 13 is an enlarged plan view of the feed roller drive unit of the sheet putting aside mechanism shown in FIG. 4; 
     FIG. 14 is a view partly cut away and viewed in the direction of arrow XIV in FIG. 13; 
     FIG. 15 is a sectional view taken along line XV--XV in FIG. 13; 
     FIG. 16 is a view viewed in the direction of arrow XVI in FIG. 13; 
     FIG. 17 is an enlarged perspective view of the sheet putting aside mechanism of FIG. 4; 
     FIGS. 18 to 20 are enlarged side views illustrating the operation of the sheet putting aside mechanism of FIG. 4; 
     FIGS. 21a-21e are enlarged side views of an essential portion of the tray holding mechanism of FIG. 4, illustrating the operation thereof; 
     FIG. 22 is an enlarged side view of an essential portion of the tray holding mechanism of FIG. 4, illustrating how trays are moved by the tray holding mechanism; 
     FIG. 23 is a flow chart illustrating the operation routine of the sheet putting aside mechanism in FIG. 4; 
     FIG. 24 is a flow chart illustrating the operation routine of the stapler in FIG. 4; 
     FIG. 25 is a block diagram showing the stapler control system of FIG. 4; 
     FIG. 26 is a front view, partly in section, illustrating a modified form of the sorter of FIG. 1; and 
     FIG. 27 is a sectional view taken along line XXVII--XXVII of FIG. 26. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A sorter of the present invention will be described with reference to FIGS. 1 to 25. The sorter deals with sheets as articles to be treated and is provided with a stapler. Before describing the construction of the sorter in detail, it will be generally described with reference to FIGS. 1 to 3. 
     In FIGS. 1 to 3, the reference character A designates casing body, and B a tray unit including a plurality of trays projecting from the casing body A. Each tray of the tray section B is arranged to be vertically movable. Reference character C and D each indicates a Geneva wheel mechanism which includes a pair of Geneva wheels. The Geneva wheel mechanisms sequentially shift the plurality of trays and hold the trays in an open state in which the tray is capable of receiving a sheet. The reference character E designates a stapler provided within the casing body A. 
     A detailed construction of the sorter will be described with reference to FIG. 4, in which forward, rearward, rightward, and leftward directions are indicated by arrows FR, RR, RH and LH for facilitating understanding of the invention. 
     BODY CASING A 
     In FIG. 4, reference numeral 10 designates a main frame accommodated in the casing body A. The main frame 10 includes a right side frame 10A and a left side frame 10B which are vertically erected in parallel with the opposite sides of the casing body A. Each of the side frames 10A and 10B is provided with first slots 10C and 10D for guiding trays, respectively. The side frames 10A and 10B are further provided with second slots 10E and 10F for guiding tray carriers, respectively. The tray carriers will be described hereinafter. The first slots 10C and 10D have vertical opposite end portions and arcuate portions 10C 1 , 10C 2  and 10D 1 , 10D 2  formed to be continuous to the vertical opposite end portions, respectively (FIG. 4 and FIGS. 21(a) to 21(E)). The arcuate portions 10C 1 , 10C 2  and 10D 1 , 10D 2  are formed to correspond to radius of Geneva wheels which will be described hereinafter. On the other hand, the second slots 10E and 10F extend vertically. 
     TRAY SECTION B 
     The tray section B includes a plurality of trays 12 l  to 12 n  vertically arranged in a tray carrier 15. As shown in FIG. 8, each of the trays 12 l  to 12 n  is integrally provided with a right side wall 12B extending upwardly at the right angle with a bottom wall 12A on the right side, a rear side wall 12D extending upwardly at the right angle with the bottom wall 12A on the rear side and a left side wall 12C extending downwardly at the right angle with the bottom wall 12A on the left side, the left side wall 12C having a height larger than the right side wall 12B. 
     By providing the upward side wall 12B and the downward side wall 12C to each of the trays 12 l  -12 n , the tray is increased in vertical section modulus, thereby being enhanced in strength. The trays 12 l  -12 n  may be thus reduced in thickness. 
     Each of the trays 12 l  -12 n  is provided at the rear right corner thereof with a cutout 12E for stapling operation for sheets which will be described hereinafter. Each tray is further provided at a front portion thereof with a cutout 12F for facilitating taking out sheets. 
     Imaginary extension lines of the right side wall 12B and the rear side wall 12D perpendicularly intersect at the cutout 12E. 
     In each tray, on the rear right side of the bottom wall 12A and the rear side of the left side wall 12C are respectively provided with horizontal rear tray pins 12G and 12H, which are vertically movably fitted into corresponding through slots 10C and 10D. Front tray pins 12J and 12K are provided on the front right side of the bottom wall 12A and the front side of a horizontal wall 12I which extends from the lower edge of the left side wall 12C of each tray, respectively, to horizontally project. The front tray pins 12J and 12K are slidably engaged with corresponding front guide members 14, which will be described later. Reference characters 12L and 12M designate safety plates which respectively extend from the right side wall 12B and left side wall 12C horizontally outwardly so that an operator may not put his fingers or hand between stacked trays 12 l  -12 n  carelessly. 
     HOLDING MECHANISM OF THE TRAY SECTION B 
     The trays 12 l  -12 n  are held within a tray carrier 15, shown in FIG. 8, in a stacked fashion. The tray carrier 15 has a pair of substantially L-shaped carrier side frames 16 and 18 interconnected with stays 19 so that the carrier side frames 16 and 18 are horizontally spaced. The carrier side frames 16 and 18 are respectively provided at rear portions thereof with a pair of vertically arranged guide pins 16A, 16B and guide pins 18A, 18B, which are vertically slidably guided in respective second slots 10E and 10F of the casing body A. 
     The carrier side frames 16 and 18 are respectively provided at the front end thereof with front guide members 14 and 14 so that the front guide members 14 and 14 are symmetrical about the center line of the tray carrier 15. The front guide members 14 and 14 have substantially V-shaped guide grooves 14A l  -14A n  formed in oppositing surfaces thereof in a number corresponding to the number of the trays 12 l  -12 n  although the guide grooves 14A l  -14A n  of the right side guide member 14 are not shown in FIG. 8. The front tray pin 12J and 12K of each of the trays 12 l  -12 n  are slidably fitted into corresponding guide grooves 14A l  -14A n . 
     The carrier side frames 16 and 18 have vertical poles 16Z and 18Z integrally formed with rear ends thereof, respectively. The vertical poles 16Z and 18Z are provided at respective upper end portions thereof with pivotal first links 16C and 18C, to which pivotably connected are second links 16E and 18E having dummy pins 16D and 18D, respectively. The dummy pins 16D and 18D are vertically slidably fitted into respective first slots 10C and 10D of the main frame 10 as well as the rear tray pins 12G and 12H so that the dummy pins 16D and 18D are located above the rear tray pins 12G and 12H. An upper safety cover 15A is extended between the first links 16C and 18C whilst a lower safety cover 15B between the second links 16E and 18E. The upper safety cover 15A and the lower safety cover 15B prevent a hand of an operator from being placed in the devices. 
     Resist pins 16F and 18F are provided to upper ends of the vertical poles 16Z and 18Z to be adjustable in vertical position, respectively. The resist pins 16F and 18F are mounted to the vertical poles 16Z and 18Z so that they are vertically movably fitted into the first slots 10C and 10D of the main frame 10 and may be urged against the dummy pins 16D and 18D, respectively. In this manner, the rear tray pins 12G and 12H of the trays 12 l  -12 n  and the dummy pins 16D and 18D are inserted into respective first slots 10C and 10D in such a fashion as to be strongly tightly held between the rear ends 16G and 18G and the resist pins 16F and 18F of the side frames 16 and 18, respectively. 
     SHEET TRANSPORTING MECHANISM IN THE CASING BODY A 
     In the casing body A, there is provided a sheet transporting mechanism which transports a sheet, discharged from a copying machine or the like, onto the trays 12 l  -12 n . 
     In FIG. 5, 20 indicates a transporting guide which is composed of a pair of guide plates 20A and 20B mounted to a main frame 10 to arrange the guide plate 20A above the guide plate 20B. The transporting guide 20 is arranged so that an entrance portion thereof is positioned at a sheet discharge opening of a copying machine not shown. The transporting guide 20 is provided at an outlet portion thereof with a sheet putting aside mechanism shown in FIG. 11. 
     The sheet putting aside mechanism has an upper guide plate 80A having a plurality of pinch rollers 82 mounted on it. The sheet putting aside mechanism is further provided with a lower guide plate 80B. The mechanism brings a sheet S (S 1  or S 2 ) downward in FIG. 12 while transporting the sheets S between the pinch rollers 82 and feed rollers 84 located on the side of the lower guide plate 80B. In FIG. 12, the sheet S 1  is a A 4  size sheet arranged along the transporting direction shown by the arrows while the sheet S 2  a A 4  size sheet arranged crosswise. 
     The pinch rollers 82 are rotatably mounted to the upper guide plate 80A through corresponding leaf springs 86. Each of the feed rollers 84 is mounted to a corresponding one of two roller shafts 90 through a pivot roller 88. The roller shafts 90 are rotatably supported on a right side plate 92A and a left side plate 92B of a case 92. The pivot roller 88 is a spherical joint constituting a constant velocity joint which enables to transmit the rotation of the roller shaft 90 to the corresponding feed roller 84, and which makes the axial direction of each feed roller 84 variable. 
     The case 92 includes an upper plate 92C, which has first links 96A and 96B angularly movably supported at opposite ends thereof by means of vertical pins 94A and 94B, respectively. The first links 96A and 96B are spring biased at intermediate portions thereof by springs 98A and 98B not to move upwardly, respectively. The opposite free ends of each of the first links 96A, 96B are connected to corresponding second links 100A and 100B. 
     As shown in FIGS. 11 and 13-15, the second links 100A and 100B engage with corresponding resilient arms 102A which are mounted on roller guides 102 provided to correspond in number to the feed rollers 84. Each roller guide 102 is rotatably supported at a supporting shaft 102B thereof on the upper plate 92C of the case 92, and is angularly moved in accordance with lateral movement of the corresponding second link 100A, 100B which movement is transmitted through the corresponding arm 102A. Each roller guide 102 is provided with a roller restrainer 102C substantially in the shape of U as viewed in FIG. 14. The roller restrainers 102C surround the opposite surfaces of corresponding feed rollers 84 so as not to prevent rotation thereof. Each roller guide 102 changes the direction of the corresponding feed roller 84 according to the rotational angle thereof. Each roller guide 102 has a guide arm 102D horizontally projecting therefrom. Each guide arm 102D is provided at a distal end thereof with a guide pin 102E, which is guided in a corresponding guide groove 92D formed through the upper plate 92C of the case 92. With this guide mechanism, the corresponding roller guide 102 is restricted in rotational angle range. In this embodiment, each of the roller guides 102 are limited in rotational angle range so that the corresponding feed roller 84 is allowed to angularly move 15° between the position, indicated by the solid line, and the position by the dot-and-dash line in FIG. 12. 
     As shown in FIGS. 13 and 14, the second link 100A is connected to an solenoid 104 through a slide arm 100C, which downwardly passes through the upper plate 92C of the case 92. The second link 100A is also connected to a return spring 106. The second link 100A is moved by the actuation of the solenoid 104 in one lateral direction shown by arrow L in FIG. 13 and by the restoring force of a spring 106 in the direction opposite to arrow L. Each of the roller shafts 90 has a driven pulley 107 mounted on a right hand end thereof. A timing belt 112 is extended around the driven pulleys 107 and a drive pulley 110 of a transporting motor 108 which is mounted on the side plate 92A of the case 92. The two roller shafts 90 are thus rotated in a direction to transport sheets in the sheet transporting direction shown by arrows in FIG. 12. 
     In a struck out portion 92E formed in the center of the upper plate 92C of the case 92, there is provided a first passage sensor 114 which detects a central portion of each sheet S 1  or S 2 . In this embodiment, the first passage sensor 114 is a limit switch of which lever 114A is depressed by a sheet S 1  or S 2  for actuation, the lever 114A being located between the upper guide plate 80A and the lower guide plate 80B as shown in FIG. 15. In FIG. 13, the first passage sensor 114 is omitted for illustration purpose. As shown in FIG. 11, a second passage sensor 116 is provided at the right edge of the lower guide plate 80B so as to detect passage of a right hand edge of each sheet S 1  or S 2 . In this embodiment, the second passage sensor 116 is a photosensor. 
     SHIFT MECHANISM OF THE TRAY SECTION B 
     Geneva wheel assemblies 40 and 42 are provided on the outside portions of the side frames 10A and 10B, respectively. The Geneva wheel assemblies 40 and 42 are identical to each other but are mirror symmetrically arranged, and only the right side Geneva wheel assembly 40 will be described. The Geneva wheel assembly 40 includes a pair of Geneva wheels 40 1  and 40 2  as shown in FIG. 4. The Geneva wheel 40 1  is equal in diameter to the Geneva wheel 40 2  and is arranged above the Geneva wheel 40 2 . The Geneva wheels 40 1  and 40 2  are provided with grooves 40C 1  and 40C 2  to engage with a rear tray pin 12G, respectively. The Geneva wheels 40 1  and 40 2  are secured to shafts 40A 1  and 40A 2  rotatably supported on the right side frame 10A, respectively. Gears 40B 1  and 40B 2  which are equal in diameter to each other are also mounted on the shafts 40A 1  and 40A 2  and rotate together with the Geneva wheels 40 1  and 40 2 , respectively. The Gears 40B 1  and 40B 2  engage a gear 40B 3 . As shown in FIG. 21, the shafts 40A 1  and 40A 2  are aligned in parallel with vertical portions 10C 4  and 10C 5  of the first slot 10C. 
     The Geneva wheels 40 1  and 40 2  are arranged so that the grooves 40C 1  and 40C 2  are rotated with a predetermined difference in phase from each other. 
     A timing belt 47 extends between a driven pulley 41 and a transmission pulley 46. The driven pulley 41 is mounted on the lower shaft 40A 2 , and the transmission pulley 46 is secured to a shaft 44 which is rotatably supported on the side frames 10A and 10B. As shown in FIG. 6, a transmission pulley 48 is mounted on the shaft 44, and meshes with a drive gear 52 which is secured to the output shaft of an electric motor 50 mounted on the left side frame 10B. The shaft 44 has another transmission pulley 46 secured at the other end thereof, and this transmission pulley 46 is connected to another driven pulley 41 through another timing belt 47. This driven pulley 41 is mounted on a shaft on which the Geneva wheel 42 2  is mounted. 
     The Geneva wheels 40 1 , 40 2  and 42 1 , 42 2  are, as described hereinafter, arranged so that grooves 40C 1 , 40C 2  and 42C 1 , 42C 2  are engageable with rear tray pins 12G and 12H, respectively. In this embodiment, the Geneva wheels 40 1  and 42 1  are equal in height of the mounted positions thereof, and Geneva wheels 40 2  and 42 2  equal in height of the mounted position thereof. The rear tray pin 12G of each tray 12 l  -12 n  is provided at the same height as the bottom wall 12A thereof whereas the rear tray pin 12H thereof at the height of the lower edge of the left side wall 12C. Consequently, each tray 12 l  -12 n  is held in such a fashion that the bottom wall 12A thereof is inclined rearwardly as well as rightwardly; the tray is thus held with the cutout 12E placed lowermost. 
     With such a construction, the right and left transmission pulleys 46 are rotated in the same direction by energizing the motor 50, so that two pairs of Geneva wheels 40 1  and 42 1  ; 40 2  and 42 2  are rotated. As shown in FIGS. 21 (A) to 21 (E), this causes the rear tray pins 12G and 12H of one tray to engage with grooves 40C and 42C of Geneva wheel assemblies 40 and 42, respectively. The rear tray pins 12G and 12H of the tray are thus elevated along the arcuate portions 10C 1 , 10C 2  of the first slot 10C and arcuate portions 10D 1 , 10D 2  of the first slot 10D, respectively. This rearwardly enlarges the gap between the tray and an adjacent lower tray thereof. As the rear tray pins 12G and 12H move along respective first slots 10C and 10D, the dummy pins 16D and 18D and the resist pins 16F and 18F of the tray carrier 15 move. By the displacement of the resist pins 16F and 18F the tray carrier 15 is moved along the second slots 10E and 10F. 
     A cam 54 is mounted on the upper right shaft 40A 1  at a position determined in connection with the groove 40C 1 , and a position detection switch 56 is provided to the right side frame 10A at a position corresponding to the position of cam 54 for detecting the stop position of the upper Geneva wheel 40 1 . The position detection switch 56 is switched when the cam 54 is brought into contact with an activating lever 56A thereof. 
     A lower limit detection switch 58 is mounted to the right side frame 10A adjacent to the lower end of the first slot 10C. The lower limit detection switch 58 is switched by bringing a lowermost rear tray pin 12G into contact with the actuating lever 58A when the dummy pins 16D and 18D are respectively placed within the grooves 40C 1  and 42C 1  of the upper Geneva wheels 40 1  and 42 1 , and when the position detection switch 56 detects the stop position of the cam 54. 
     DRAWING-OUT MECHANISM OF THE TRAYS 
     Description will be given about a tray drawing out mechanism which draws out trays 12 l  -12 n  for performing stapling operation of sheets stacked on the trays. 
     The tray drawing out mechanism is constituted by combining the first slots 10C and 10D and the pair of the Geneva wheel assemblies 40 and 42 which are mirror symmetrically arranged to the side frames 10A and 10B. Only the right side portion of the tray drawing out mechanism will be hence described. 
     As shown in FIGS. 21(A) to 21(E), the first slot 10C is continuously formed in the right side frame 10A so that it has opposite vertical portions 10C 4  and 10C 5  and symmetrical arcuate portions 10C 1  and 10C 2  communicated to the vertical portions 10C 4  and 10C 5 , respectively. The arcuate portions 10C 1  and 10C 2  are formed to overlap quarters of the circular loci of the groove 40C 1  of the Geneva wheel 40 1  and the groove 40C 2  of the Geneva wheel 42 1 , respectively. The arcuate portions 10C 1  and 10C 2  communicate to each other at an extended portion 10C 3  which extends in a direction of a common tangent of the Geneva wheels 40 1  and 40 2 . While being shifted, each tray is, as shown in FIG. 21(E), pulled out rearwardly by about 3/4 of the diameter of the Geneva wheels 40 1  and 40 2  by the guiding of the first slot 10C. 
     A return spring 10G is provided to the right side frame 10A so that an upper end portion thereof is located at the inner end portion of the extended portion 10C 3 . The upper end portion of the return spring 10G biases a rear tray pin 12G, which comes out of the groove 40C 1  or 40C 2 , against the outer circumferential surfaces of the Geneva wheels 40 1  and 40 2 , and then temporarily holds it. 
     STAPLER E 
     The stapler E is secured to the casing body A at a position to opposed to the cutout 12E of a tray which has been pulled out rearwardly by the tray drawing out mechanism described above. The stapler E performs a stapling operation on sheets S located on the tray. 
     As the stapler E, electric staplers 5000 series sold by Swingline, U.S.A., for example, may be used. 
     SHEET HOLDING MECHANISM 
     In the vicinity of the stapler E, there is provided a sheet pressing mechanism, shown in FIG. 17, for pressing sheets to be stapled. The sheet pressing mechanism includes base plate 60 which is fastened to the main frame 10. The base plate 60 has a plurality of (three in this embodiment) guide pins 60A fixed to it. A slide plate 62 is arranged to be slidable forward and backward by fitting the guide pins 60A into respective slots 62A formed through it. A spring 64 is extended between the forward end of the base plate 60 and the rear end of the slide plate 62 to spring bias the slide plate 62 forward. The slide plate 62 has a pair of guide pins 62B fixed to it, and a slider 66 is provided to be slidable forward and backward by inserting the guide pins 62B into respective slots 66A formed through the slider 66. A touch plate 66B is mounted to a forward end of the slider 66, and is designed to be pushed backward by coming into abutment against the rear side wall 12D of a tray 12 l  -12 n  which is being pulled backward by the tray drawing out mechanism. 
     A sheet pressing lever 68 is rotatably supported at an intermediate portion thereof on a supporting pin 62C which is fixed to a forward portion of the slide plate 62. A forward portion of the sheet pressing lever 68 is curved forwardly, and has a pressing roller 68A rotatably supported on the forward end thereof. The rear end of the sheet pressing lever 68 is related to the slider 66 through a first link 70 and a second link 72. More specifically, the links 70 and 72 are rotatably supported on a supporting pins 62D and 62E mounted on the slide plate 62, respectively. The links 70 and 72 are connected at one ends thereof through a connection pin 74. A connection pin 68B, mounted on the rear end of the sheet pressing lever 68 is fitted into a slot 70A formed through the other end of the first link 70 whilst a connection pin 66C fixed to an intermediate portion of the slider 66 passes through a slot 72A formed through the other end of the second link 72. 
     A spring 76 is provided between the one end of the first link 70 and the rear end of the slide plate 62. The slider 66 is hence biased forwardly while the sheet holding lever 68 is urged in a direction to raise the holding roller 68A. 
     Each tray 12 is pulled rearward by the tray drawing out mechanism, and the rear side wall 12D of the tray thereby moves from an aligned position P 0  in FIG. 18 to a maximum drawn out position P 2  through an intermediate drawn out position P 1 . During this operation, the slider 66 is firstly pushed and moved backward relative to the slide plate 62, and the sheet pressing lever 68 is then swung in the counter-clockwise direction in FIG. 19 to depress the sheets on the tray. Thereafter, as shown in FIG. 20, the slide plate 62 and the slider 66 in unison move backwardly relative to the base plate 60 together with the tray 12 with the sheets on it pressed by the sheet pressing lever 68. In this operation, the spring 64 which biases the slide plate 62 is expanded after the spring 76 which urges the slider 66 is expanded. For this reason, the biasing force of the spring 76 is designed to be smaller than that of the spring 64. 
     When the tray 12 is drawn out to the maximum position, the portion of the stack of sheets placed above the cutout 12E of the rear right corner thereof is guided between upper and lower sheets guides 77A and 77B and then stapled. The sheet guides 77A and 77B are secured at predetermined positions of the main frame 10 in casing body A. As shown in FIG. 5, photosensor 78 is provided to the sheet guides 77A and 77B for detecting whether or not sheets are present at the stapling position. 
     OPERATION OF THE EMBODIMENT 
     The operation of the sorter will be described. Electric signals of information, such as the number of pages and the number of copies of a document to be copied are sent from a host machine, not shown, to a sorter control unit provided to the casing body A. The host machine is a photocopier, for example and the sorter control unit is constituted by a microcomputer not shown. According to the signals, the motor 50 is energized, and the Geneva wheel assemblies 40 and 42 are thereby rotated in the same direction. This causes the rear tray pins 12G and 12H of each trays 12 l  -12 n  to engage with respective grooves 40C and 42C, and the trays are sequentially shifted downwardly. As a result, the uppermost tray 12 l  is, as shown in FIG. 7, positioned just below the outlet of the guide plates 80A and 80B of the sheet putting aside mechanism, and thus the sorter is placed in a tray initial state. 
     In the tray initial state, the rear pins 12G 1  and 12H 1  of the uppermost tray 12 1 , as shown in FIG. 7, come into contact with the circumferential surfaces of the lower Geneva wheels 40 2  and 42 2  in the first slots 10C and 10D, respectively. On the other hand, the dummy pins 16D and 18D of the tray carrier 15 are, as shown by the dots-and-dash line in FIG. 9, engaged with the grooves 40C 1  and 42C 1  of the upper Geneva wheels 40 1  and 42 1 , are thereby guided rearwardly, and are then disengaged. In this event, the dummy pins 16D and 18D are urged against the outer circumferential surfaces of the Geneva wheels 42 1  and 42 2  ; 40 1  and 40 2  by the springs 10G, respectively. In this state, the links 16C and 16E; 18C and 18E which support the dummy pins 16D and 18D are placed in open conditions opening at a maximum angle as shown by the dots-and-dash line in FIG. 9. This tray initial state is detected by activating the lower limit detection switch 58 with the lowermost rear pin 12G, and a shifted tray counter, not shown, is thereby reset. 
     A copied sheet is introduced into the transporting guide 20, through which it is discharged on the uppermost tray 12 1  by the pinch rollers 82 and feed rollers 84 of the sheet putting aside mechanism driven by the motor 32. 
     In this event, the sheet putting aside mechanism changes the direction of the feed rollers 84 according to the control sequence shown by a flow chart of FIG. 23. 
     In step S1 of the control sequence, the sheet putting aside mechanism is initialized, thereby directing the feed rollers 84 forward (leftward in FIG. 12) and starting to drive them. After the detection of a sheet by the first passage sensor 114 is confirmed in step S2, the direction of the feed rollers 84 is changed to turn 15° counterclockwise in FIG. 12 (as shown by broken lines) in step S3. Then, in step S4 it is judged whether or not the second passage sensor 116 detects the edge of the sheet. When an affirmative result is given, in step S5 the feed rollers 84 is returned to the original direction. Thereafter, the routine is returned to step S2. 
     With this operation of the sheet putting aside mechanism, a sheet is moved forwardly and rightwardly (downwardly in FIG. 12), and is discharged on a tray 12 in this fashion. The sheet dropped on the tray slides down the inclined surface of the bottom wall by gravity and is aligned by the right side wall 12B and the rear side wall 12D of the tray. 
     Every time the first passage sensor 114 detects passage of a sheet, the control unit sends a signal to energize the motor 50, and the Geneva wheel assemblies 40 and 42 are thereby rotated to shift trays 12 upwardly. 
     The shift operation and the rearward drawing out operation of the trays 12 will be described in detail with reference to FIGS. 21(A) to (E) and 22. 
     FIG. 21(A) illustrates a state in which a sheet is dischargeable to the fourth tray 12 4  from the top. In this state, the rear tray pin 12G 4  of the tray 12 4  is in contact with the circumferential surface of the lower Geneva wheel 40 2 . The third rear tray pin 12G 3  is positioned at the extended portion 10C 3 , and is out of engagement with the groove 40C 1  of the Geneva wheel 40 1  and the groove 40C 2  of the Geneva wheel 40 2 . The rear tray pin 12G 3  is held against the circumferential surfaces of the Geneva wheels 40 1  and 40 2  by the return spring 10G. Thus, the tray section B is opened between the third tray 12 3  and the fourth tray 12 4 . In this state, the groove 40C 1  of the Geneva wheel 40 1  and the groove 40C 2  of the Geneva wheel 40 2  are, as shown in FIG. 21(A), positioned with a predetermined difference in phase. 
     From this state of FIG. 21(A), the Geneva wheels 40 1  and 40 2  (42 1  and 42 2 ) are turned in respective directions shown by arrows. The rear tray pin 12G 3  is then pushed into the groove 40C 1  during rotation of the Geneva wheel 40 1 , and when the Geneva wheels 40 1  and 40 2  reach positions shown in FIG. 21(B), the Geneva wheel 40 1  transports the rear tray pin 12G 3  to the inlet of the vertical portion 10C 4  of the first slot 10C. On the other hand, the groove 40C 2  of the lower Geneva wheel 40 2  is located at a lower position. 
     The Geneva wheels 40 1  and 40 2  are further rotated from the state of FIG. 21(B), and in a state shown in FIG. 21(C) the third rear tray pin 12G 3  is disengaged from the groove 40C 1  of the Geneva wheel 40 1 . At the same time, the fourth rear tray pin 12G 4  fits in the groove 40C 2  of the lower Geneva wheel 40 2 . 
     In a state shown in FIG. 21(D) in which the Geneva wheels 40 1  and 40 2  are turned further from the state of FIG. 21(C), the fourth rear tray pin 12G 4  is guided in the arcuate groove 10C 2  while it is engaged with the groove 40C 2  of the lower Geneva wheel 40 2 . 
     The Geneva wheels 40 1  and 40 2  are further turned from the state of FIG. 21(D) to the state of FIG. 21(E), during which the fourth rear tray pin 12G 4  is guided by the extended portion 10C 3  of the first slot 10C, and is then disengaged from the groove 40C 2  of the lower Geneva wheel 40 2 . In FIG. 21(E), the fourth rear tray pin 12G 4  is held between the circumferential surfaces of the Geneva wheels 40 1  and 40 2  and the return spring 10G. 
     During the operations of the Geneva wheels 40 1  and 40 2  from the state of FIG. 21(A) to the state of FIG. 21(E), each of the Geneva wheels 40 1  and 40 2  makes one revolution, so that the shift operation of the tray is completed as well as the drawing out operation of the next tray. 
     By this shift of each tray, the dummy pins 16D and 18D and the resist pins 16F and 18F are shifted together with the rear tray pins 12G and 12H, so that the tray carrier 15 is synchronously shifted. 
     In this embodiment, the guiding of the rear tray pins 12G and 12H in the tray drawing out operation is carried out by the extended portion 10C 3  which extends in the common tangent direction of the Geneva wheels 40 1  and 40 2 , and the rearward displacement of the rear portion of each tray is achieved without considerable vertical movement. 
     The shifting operation of trays is carried out according to the number of the copies of the document. 
     In the shifting operation of trays 12, the rear tray pins 12G and 12H of each of the trays are moved upwardly rearwardly while guided in the respective first slots 10C and 10D. On the other hand, the front tray pins 12I and 12J of each of the trays are raised obliquely upwardly while they are guided by respective inclined guide grooves 14A, 14A of the front guide members 14, 14. The guide grooves 14A are formed in a V-shape as shown in FIG. 22, each having a downwardly inclined front portion and an upwardly inclined rear portion. This enables the space between a tray, on which a sheet discharged is received, and an upper tray positioned just above the tray to be enlarged to thereby increase the receiving space of sheets in the tray. The discharging operation of the sheet is thus facilitated. 
     When copying of a predetermined number of sheets is completed for a page of the document, the trays 12 l  -12 n  are returned to the tray initial state by reversing the motor 50. Then, the sorting operation is performed for the next page. 
     When copying of all the pages is finished, the stapling operation will be conducted. The stapling operation is carried out on sheets stacked on the tray which has been pulled rearwardly. The pulling out operation of trays is performed simultaneously with the sequential shifting operation of trays 12 l  -12 n  from the tray initial state. 
     In the tray initial state, the shifts number counter is reset by activating the lower limit detection switch 58. The position detection switch 56 is actuated by the cam 54 at every revolution of the Geneva wheels 40 1  and 42 1 , so that which tray from the top is placed at the drawn out position may be detected. 
     When it is judged that a predetermined tray 12 l  -12 n  is placed at the drawn out position, the stapling operation is performed by the stapler E after confirmation of sheets on the tray with the sensor 78. For this purpose, the sorter control unit has a construction shown by the functional blocks of FIG. 25. 
     FIG. 24 illustrates a flow chart for carrying out the stapling operation by shifting the trays 12 l  -12 n  stepwisely. In the flow chart, a tray is drawn rearwardly (step S11), and then the sensor 78 detects whether or not sheets are placed on the tray (step S12). Subsequently, the stapling operation is performed if sheets are placed on the tray (step S13). These operations (steps S11-S13) are repeated by a predetermined number, and when it is judged that a predetermined number of the stapling operations are conducted (step S14), the routine is ended. 
     During displacement of trays 12 l  -12 n  to the predetermined stapling position for the stapler E, the sheet pressing mechanism is actuated, so that sheets on trays are depressed not to separate. The sheets are thus certainly stapled in an aligned stacked condition. 
     In the embodiment, a tray is stationarily held in the drawn out position, and the stapling operation is surely carried out. Moreover, it is not necessary to stop the Geneva wheel assemblies 40 and 42 at every stapling operation, so that load on the motor 50 is reduced. It is, however, possible to stop the motor 50 and the Geneva wheels 40 1  and 40 2  : 42 1  and 42 2  at every stapling operation, and even if there is somewhat a scattering in the stop position of the Geneva wheels 40 1  and 40 2  : 42 1  and 42 2 , the tray is held in the stationary position so that the positioning accuracy of the tray is secured. 
     The control of the direction of the feed rollers 84 of the sheet putting aside mechanism may be performed by a control unit of a host machine other than a sorter control unit, the host machine including, for example, a photocopier which discharges sheets. 
     MODIFIED FORM 
     A modified embodiment of this invention is shown in FIGS. 26 and 27, in which the sensor 78 is changed in position. A pair of members 78A and 78B which include light emitting and receiving elements respectively are disposed on an upper arm 79A and lower arm 79B, respectively. The upper and lower arms 79B and 79A are away from the sheet guides 77A and 77B. In this modified form, the arms 79A and 79B are integrally formed with the right side frame 10A by molding. 
     The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit of the invention.
A first moving member is arranged on a base for reciprocal movement in an article transporting direction. A second moving member is arranged on the first moving member for reciprocal movement in the article transporting direction. The second moving member is adapted to contact each receptacle which is being transported to an operation position to which receptacles carrying articles to be treated are sequentially transported. A first biasing mechanism biases the first moving member in a direction opposite to the receptacle transporting direction. A second biasing mechanism biases the second moving member in a direction opposite to the receptacle transporting direction by a biasing force smaller than a biasing force of the first biasing mechanism. Pressing arm is mounted on the first moving member for movement toward and away from the articles to be treated on each receptacle at the operation position. A link mechanism links between the pressing arm and the second moving member for moving the pressing arm to press articles on the receptacle when the first and second moving members are relatively moved.