Abstract:
The invention concerns an automatic selective sorting device ( 10 ), for simultaneously loading, transporting and placing objects having very different characteristics in receiving containers, comprising a frame ( 11 ) bearing two toothed wheels ( 12, 13 ) arranged at each end of the frame ( 11 ), and whereon is stretched an endless conveyor ( 15 ). The loading mechanism consist of a line of conveyor belts ( 32 ) made up of a belt for manual insertion ( 32   a ) two accelerating belts ( 32   b ) and a belt for automatic insertion ( 32   c ). The acceleration belts ( 32   b ) are arranged respectively beneath two columns of a buffer storage and untiering system ( 33 ) which bring the objects to be sorted ( 8 ) and set them onto the acceleration belts which then place them on the automatic insertion belt ( 32   c ) to bring them onto the transporting mechanism. The mechanism transporting and loading the objects to be sorted comprise swing trays ( 18 ) including a catching support fixed to the conveyor, a suspension arm fixed to the catching support, a pivoting tray for receiving an object to be sorted articulated to the other end of the arm and an actuating member associated with the pivoting tray. The swing trays are maintained laterally by a guide rail ( 8 ) linked to the frame ( 11 ). The actuating member is designed to cause the tray to pivot by gravity into correspondence with a receiving container ( 30 ) selected in accordance with the object transported by the tray.

Description:
TECHNICAL DOMAIN  
         [0001]    The present invention concerns an automatic selective device for sorting objects which differ in physical characteristics such as shape, type, consistency, weight, dimension, and/or volume and for placing these objects in suitable receiving containers, comprising a means for loading the objects, a means for transporting the objects to said receiving containers, and an unloading means for selectively depositing the objects into the receiving containers, wherein said transporting means and said unloading means are combined and comprise a unit of individual supports, each affixed to at least one endless conveyor ( 15 ), each support comprising a pivoting tray which receives the object to be sorted and having a front rim and a rear rim defined relative to the direction in which the support is displaced, as well as a device ( 22 ) which activates said pivoting tray, said activating device being controlled by an individual control device which, at a predetermined instant, pivots the tray in combination with gravitational force in correspondence with one of said receiving containers ( 30 ) selected as a function of the physical characteristics and/or the destination of the object transported by said tray.  
         PRIOR ART  
         [0002]    Devices of this type operating on the basis of various principles are already known in the art. According to one such principle, the objects are transported on trays displaced along the receiving containers in the form of bags or bins and the objects pivot to the side when they reach their destination, then slide off. This method of operation requires the transported object to fall for quite some distance in relation to its size.  
           [0003]    According to another operating principle, the tray remains horizontal and when the object reaches its predetermined destination, an electrically driven transverse belt ejects the object laterally. Here again, a considerable distance is required for the object to fall and more importantly, the trajectory of the object is uncertain, as it depends upon the relationship between the weight of the object and its volume.  
           [0004]    In other systems, objects fall due to simple gravitational force, and in some cases they are ejected from containers with a movable base that opens automatically when the container passes over the container for which the object is destined.  
           [0005]    Yet other systems use gripping devices which grasp the object, hold it while it is being transported, and open at the appropriate time as the object passes over the container for which it is destined.  
           [0006]    U.S. Pat. No. 4,318,807 describes another type of device designed to sort beams transported by a moving belt and to deposit the beams in different compartments. To perform these operations, the transporting elements are formed of strong, U-shaped hooks articulated to the end of a rod integral with a guide rail. Due to the design of these elements, this device can only be used for moving large, heavy, compact objects.  
           [0007]    The sorting device which is the subject of Japanese Patent Application No. 59 036020 is designed to sort fruit by weight. It has small cups for this purpose which are pivotably attached to an upright metal piece so they can rotate. The cups are locked in horizontal position by a locking system consisting of a lever cooperating with a stop located on the cup. When the device tips, the lever disconnects from the stop and releases the cup.  
           [0008]    Prior art devices, in particular those described above, have various disadvantages. The controls that open the gripping devices or containers in certain cases, or which engage the pivoting motion in other cases, are computer driven and executed by activators, electromagnets, pneumatic cylinders, motors, etc. This results in complex, costly devices which do not fully respond to speed and efficiency requirements of sorting objects which vary considerably from one another in size, shape, type, and consistency, such as, for example, heavy packages weighing several kilograms, large but lightweight packages, very lightweight, flexible envelopes weighing several tens of grams, or cylindrical products such as beverage cans that are placed in an unstable manner inside a flexible pouch. Obviously, other types of situations may arise as well.  
         DESCRIPTION OF THE INVENTION  
         [0009]    The object of the present invention is to overcome these disadvantages with an automatic selective sorting device for simultaneously transporting objects which differ in shape, type, consistency, weight, dimension, and/or volume and placing these objects in receiving containers which may have been preselected by means of a rapid, effective, simple and economical device.  
           [0010]    This goal is achieved by a device such as the one described in the preamble, characterized in that said loading means comprises at least one storage and unloading buffer system, each equipped with at least one window designed to set an object on an acceleration belt, and one automatic insertion belt located downstream from the acceleration belt to deposit the objects on the pivoting trays of the individual supports that are located near at the rear edges of these trays, in that each individual support for said combined transporting and unloading means comprises a pivoting means to allow the tray to pivot from front to back relative to directions in which the individual supports are displaced, and in that the pivoting tray for each support overlaps the conveyor.  
           [0011]    According to a preferred embodiment, the device comprises at least one guide rail for the individual supports and one guide element associated with each individual support which prevents said individual support from falling off the trajectory defined by the endless belt.  
           [0012]    According to an interesting embodiment, the activating device comprises a coil spring designed to release enough energy to cause the pivoting plate to pivot, said coil spring being attached to an axle, having one end connected to said pivoting tray and one end connected to a fixed element on the individual support.  
           [0013]    This activating device may comprise a disc-shaped cam with a peripheral notch which cooperates with a release to make the cam pivot and release the energy in the coil spring.  
           [0014]    Said release preferably comprises an angled lever pivoting on an axle and holding two wheels located at each of its extremities, respectively, said wheels respectively cooperating with a device that controls the pivoting of the pivoting trays and with the cam.  
           [0015]    Said angled lever is advantageously pushed into the stopped position by a spring.  
           [0016]    According to one variation, the activating device may comprise a locking/unlocking mechanism that slides longitudinally and which is integral with the individual support, and which also may cooperate with a stop, integral with the pivoting tray, said locking/unlocking element being activated by an activating finger that pivots on an axis and is activated by a movable block integral with the frame of the device.  
           [0017]    According to a first embodiment, each of said individual supports consists of a swing tray comprising a hook support attached to the conveyor and a suspension arm attached at one end to the hook support, and comprising at the other end, the pivoting tray which is attached in such a way that it remains inclined toward the front while objects are being transported.  
           [0018]    In a particularly advantageous manner, the suspension arm of each swing tray is inclined from the vertical and it is angled in such a way that the center of gravity of the pivoting tray is located essentially on the vertical from the suspension point of the arm of the hook support.  
           [0019]    According to a second embodiment, each of said individual supports consists of a pivoting tray attached directly to the conveyor.  
           [0020]    In general, the pivoting tray comprises a surface for receiving objects defined in the front by a rectangular vertical rim and on each of its lateral sides by a triangular vertical rim, with the rear edge of the tray being open.  
           [0021]    Advantageously, the receiving surface of the pivoting trays may be perforated.  
           [0022]    According to another embodiment, the pivoting tray may comprise a moving belt located on the surface which receives the objects, said belt operating in a loop driven by two parallel rollers located near the front edge and near the rear edge of the tray, respectively.  
           [0023]    Advantageously, the roller located at the front of the tray comprises a means which causes it to rotate when said tray pivots in order to active movement of the belt.  
           [0024]    Advantageously, the means for driving the front roller comprises a friction drive wheel attached to the rotational axis of said roller and cooperating with a rail parallel to the guide rail for the individual supports when the pivoting tray pivots.  
           [0025]    Since the trays pivots from front to back, the belt moves in the opposite direction to the direction in which the pivoting tray pivots.  
           [0026]    The acceleration belt for the loading means moves faster than the displacement speed of the individual supports on the transporting means.  
           [0027]    In the preferred embodiment of the device, when objects are transferred from the loading means to the transporting means, the automatic insertion belt is located in the extension of the pivoting tray while the objects are being deposited and it overlaps the rear edge of said tray while the objects are being transferred.  
           [0028]    Said means for locating the objects onto the pivoting trays may advantageously comprise a manual insertion belt located upstream of the acceleration belt.  
           [0029]    Advantageously, the at least one window in the storage and unloading buffer system comprises two movable armatures holding, at one free extremity, the free end of a retractable lateral curtain, said armatures being connected to two activators, while the other end of the retractable lateral curtain is connected to a spring roller and the activators preferably are pneumatic cylinders. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0030]    The features of the present invention will be more apparent from the following description of different modes of embodiment, with reference to the attached drawings, wherein:  
         [0031]    [0031]FIG. 1 is an elevation of the device according to the invention illustrating in particular a preferred embodiment of the transporting and unloading means;  
         [0032]    [0032]FIGS. 2A, 2B, and  2 C are overhead views of the embodiment of FIG. 1 illustrating three different principles for positioning the loading means;  
         [0033]    [0033]FIG. 3 is an elevation showing the device of the invention equipped with a first embodiment of the loading means and the receiving containers;  
         [0034]    [0034]FIGS. 4A, 4B,  4 C,  4 D,  4 E and  4 F show the operational mode of the first embodiment of the loading means illustrated in FIG. 3;  
         [0035]    [0035]FIG. 5 is an elevation representing the device according to the invention equipped with a second embodiment of the loading means and receiving containers;  
         [0036]    [0036]FIGS. 6A, 6B and  6 C are detailed views of the individual supports for the objects to be sorted;  
         [0037]    [0037]FIG. 7 is an overhead view of the device of the invention illustrating another embodiment of the transporting and unloading means;  
         [0038]    [0038]FIGS. 8A and 8B illustrate front and lateral elevations of the means for activating a pivoting tray;  
         [0039]    [0039]FIG. 9 is a detailed view showing how a swing tray is loaded with objects consisting of packages;  
         [0040]    [0040]FIGS. 10A and 10B are a lateral view and an overhead view, respectively, of a variation of the means for activating a pivoting tray; and  
         [0041]    [0041]FIG. 11 is a partial lateral view of a pivoting tray equipped with a belt for unloading. 
     
    
     HOW THE INVENTION IS ACHIEVED  
       [0042]    Device  10  for automatically selecting objects according to the invention, as shown in the drawings and in particularly in FIGS. 1 through 3, comprises a frame  11  which supports, in the example shown, two wheels  12  and  13 , for example, toothed wheels driven by a motor  14  and which support an endless belt  15 , for example, a chain loop defining a continuous transport circuit. The chain may consist of conventional links joined by articulating axles that are parallel to each other. It may also consist of double articulated links, which provide additional range of motion and allow it to be displaced on several planes. Any other flexible reinforced band type conveyor can be used. Each of the two wheels is located at an extremity of frame  11 . Two adjusting elements  16  (not shown in detail) are attached to the frame for regulating the tension of conveyor  15 .  
         [0043]    The means  17  for transporting and unloading objects, adapted on conveyor  15 , are composed in the example shown of individual supports consisting of swing trays  18  comprising a hook support  19  attached to conveyor  15 , a suspension arm  20  attached at one end to hook support  19 , a pivoting tray  21  articulated to the other end of suspension arm  20  and an activation device  22  associated with pivoting tray  21 . Swing trays  18  are maintained in position laterally by at least one guide rail  8 . This rail is parallel to the endless conveyor  15  and integral with frame  11 . It may be affixed to this frame either at hook support  19 , at suspension arm  20  near pivoting tray  21 , or at some intermediate level between these two positions. Only one guide rail is necessary to prevent the swing trays from falling off the trajectory defined by conveyor  15 . However, it would also be possible to provide two rails, thereby eliminating any risk of lateral imbalance, particularly on the curves formed by endless conveyor  15 . The connection between the swing tray and rail  8  may be established by a guide element such as a guide wheel, a slide or some other suitable means known in the art.  
         [0044]    Beneath swing tray  18  suspended on conveyor  15  are the receptacles, in this case receiving containers  30 , each surmounted by a guide chute  31  which guides the objects initially carried by pivoting trays  21  of swing trays  18  toward the openings in receiving containers  30 , said trays having first pivoted and then discharged the objects they were transporting.  
         [0045]    As shown more specifically in FIG. 2A, loading may take place in a central zone of a rectilinear portion of conveyor  15  according to the first principle of placing the objects on the transporting and unloading means  17 . In this case, the loading operation is performed tangentially in relation to the rectilinear portions of conveyor  15 . Note that in this embodiment the loading means  23 , which is illustrated schematically, necessarily forms a curve that could be considered a disadvantage because it complicates construction or requires that the operation slow down to prevent objects from being ejected when they are transported around the curve. On the contrary, this loading principle offers the advantage of “multi-loading,” that is, it allows several identical or similar loading posts (not shown) to be distributed along the rectilinear portions of the conveyor, improving the output of the device by increasing the number of full trays in each cycle and actually optimizing its capacity.  
         [0046]    As shown more specifically in FIG. 2B, loading can also take place in a central area of the rectilinear section of conveyor  15  according to a second principle of positioning objects on the transporting and unloading means. In this case, loading takes place perpendicular to the rectilinear portions of conveyor  15 . This type of loading is not the most rapid, but loading means  24  may comprise several loading stations (not shown) distributed along the rectilinear portions of the conveyor, thus ensuring that the individual supports holding the objects to be sorted are optimally loaded.  
         [0047]    A third principle for placing the objects on the transporting and unloading means is illustrated in FIG. 2C. In this case, the loading operation is performed tangentially from a toothed wheel at one extremity of each of the two rectilinear portions of conveyor  15 . The loading means comprises two loading stations  25   a  and  25   b.  This arrangement eliminates any curve and consequently, it simplifies installation and performs at a higher speed.  
         [0048]    [0048]FIG. 3 is an elevation of the entire device  10  of the invention; it is a more specific illustration of the principal stages of operation, particularly with respect to the means for loading the swing trays located at the entry to frame  11 , on the left of the drawing. This loading means comprises a line of conveyor belts  32  composed, in the example shown, of a manual insertion belt  32   a,  two acceleration belts  32   b,  and an automatic insertion belt  32   c.  Manual insertion belt  32   a  is used for depositing objects such as, for example, large envelopes to be placed on a swing tray for eventual sorting. Acceleration belts  32   b  are respectively located on two columns of a storage and a unloading buffer system  33  that moves the objects to be sorted and deposits them on the acceleration belt, which in turn places them on automatic insertion belt  32   c.  This automatic insertion belt is located in the extension of pivoting tray  21  when the objects are deposited and it overlaps the rear edge of said tray while the objects are being transferred, said rear edge being defined relative to the direction in which the individual supports are displaced. Each column in the storage and unloading buffer system  33 , shown in more detail in FIG. 4, comprises a transverse conveyor (not shown) which cooperates with three windows  34 ,  35 ,  36  with retractable lateral curtains  37  for depositing objects  9  on acceleration belt  32   b.  Each window comprises two movable armatures  38  which support, at one free end, the free end of a retractable lateral curtain  37 , said armatures being connected to two activators, for example, two pneumatic cylinders  39  or the like, and the other extremity of the retractable lateral curtain being connected to a spring roller  40 .  
         [0049]    A computerized central control unit regulates the opening of retractable lateral curtains  37  on each window to ensure that the objects for sorting  9  are first deposited on acceleration belt  32   b,  then on automatic insertion belt  32   c,  and finally on pivoting trays  21  of swing trays  18 . Note that there is a larger number of swing trays than of receiving containers  30 , which optimizes the output of the automatic sorting device  10  of the invention.  
         [0050]    [0050]FIGS. 4A through 4F illustrate in greater detail the operating mode of the loading means shown in FIG. 3. FIG. 4A illustrates a first phase, during the course of which an object  9 , for example an envelope, has been deposited by the conveyor on the corresponding upper window  34 . The three superimposed windows  34 ,  35  and  36  are closed. FIG. 4B shows a second phase during the course of which upper window  34  is open, allowing object  9  to be deposited on intermediate window  35  which, along with lower window  36 , is still closed. FIG. 4C illustrates a third phase in the course of which upper window  34  is reclosed, intermediate window  35  is open, and lower window  36 , which has received object  9 , is still closed. Closed upper window  34  has simultaneously received a new object  9  that will follow the same course as the preceding object. FIG. 4D shows a fourth phase in which upper window  34  is open to allow the second object  9  to be deposited on intermediate window  35 , previously closed. Lower window  36  opens and has deposited the first object  9  onto acceleration belt  32   b.  FIG. 4E illustrates a fifth phase during which upper window  34 , as well as intermediate window  35 , are closed, with lower window  36  now holding the second object  9 . The first object  9  is simultaneously evacuated by acceleration belt  32   b  toward automatic insertion belt  32   c.  FIG. 4F illustrates a sixth phase during which upper window  34  as well as intermediate window  35  are again closed. Lower window  36  is open and the second object  9  has been deposited on acceleration belt  32   b.  Simultaneously, the first object  9  is deposited on pivoting tray  21  of swing tray  18 .  
         [0051]    The loading system for the device of the invention is not limited to the embodiment described herein. The number of superimposed windows used as buffers could be increased to boost sorting speed. In addition, the number of loading stations located long the conveyor could be increased.  
         [0052]    [0052]FIG. 5 is a view similar to FIG. 3, but in this instance, automatic sorting device  10  of the invention is equipped with a second embodiment of the loading means. The latter comprises a line of transporting belts  50  comprising, for example, a manual insertion belt  50   a,  at least one acceleration belt  50   b,  and an automatic insertion belt  50   c.  Acceleration belt  50   b  is located beneath three columns of a three-level buffer storage and unloading system  51 , said three columns corresponding to three pivoting belts  52 , respectively. The function of pivoting belts  52  is to effect the transition between the columns of the storage/unloading buffer system and acceleration belt  50   b  which transfers the objects to automatic insertion belt  50   c  before they are deposited on pivoting trays  21  of swing trays  18 .  
         [0053]    [0053]FIGS. 6A, 6B and  6 C represent a swing tray  18  for transporting the objects for sorting. Note that suspension arm  20  of this swing tray is inclined and forms an acute angle from the vertical. This angle is regulated so that the center of gravity of loaded pivoting tray  21 , i.e., the tray and its load together, is located approximately on the vertical from the point at which arm  20  is connected to hook support  19 . In addition, pivoting tray  21  is also inclined and it forms an acute angle from the horizontal that can be regulated as a function of the loaded objects it transports, while the front edge of the tray, defined relative to the direction in which the hook support is displaced, is lower than the rear edge. This inclination allows the objects to remain on the pivoting tray while they are being transported, particularly on the turns along the trajectory of the swing trays.  
         [0054]    As shown more specifically in FIG. 6A, pivoting tray  21  comprises a surface for receiving objects that is defined in the front by a rectangular vertical rim  21   a  and by two triangular lateral rims  21   b,  while rear rim  21   c  of the tray remains open. The two raised lateral rims  21   b  extend from the rear rim of pivoting tray  21  to the raised front rim  21   a  so as to form a barrier preventing objects from sliding off the tray when it is displaced. Suspension arm  20 , laterally attached to hook support  19  connected to the conveyor, is angled and pivoting tray  21  thus overlaps said conveyor.  
         [0055]    [0055]FIG. 6B essentially illustrates pivoting tray  21  which has perforations  56 . By way of example, these perforations may be circular, oblong, or another shape and they may be distributed regularly along the tray surface. The purpose of the perforations is to facilitate evacuation of the objects when tray  21  pivots, particularly light objects such as envelopes or the like. The dimension of the perforations may be adapted to the physical characteristics of the objects for sorting.  
         [0056]    [0056]FIG. 7 illustrates a second embodiment of the transporting and unloading means. Automatic selective sorting device  10  comprises a frame  11  which, in the example shown, supports two pairs of motor driven toothed pinions  12   a,    12   b  and  13   a,    13   b  with a chain loop extending between them to define an endless conveyor  15 .  
         [0057]    The means for transporting and unloading objects to be sorted attached to conveyor  15  is composed, in the example shown, of individual supports consisting of pivoting trays  60  attached directly to conveyor  15  instead of being suspended from arms as in the case of the swing trays. The advantage of this arrangement is that the trays can be spaced together tightly. When using swing trays, it is actually imperative to provide a safety buffer between two adjacent swing trays, since there is a risk of collision due to balancing on turns. Consequently, this embodiment may prove more useful than the one which uses swing trays. Additionally, pivoting trays  60  are inclined, allowing them to overlap, thereby increasing the output of the sorting line further. However, this arrangement requires that the conveyor belt be of very sturdy design, since the pivoting trays are cantilevered. If the conveyor belt is a chain, it should preferably be a double chain. If the conveyor belt is a flexible band, the band must be reinforced in order to support the weight of the pivoting trays and the objects transported.  
         [0058]    [0058]FIGS. 8A and 8B are detailed. views of the activation deice  22  for pivoting trays  21  on swing trays  18 , or pivoting trays  60  laterally attached to the conveyor. As shown in the drawings, activation device  22  essentially consists of a cam  61  in the form of a circular disc, partially truncated and attached to an axle  62 . This cam has a peripheral notch  63  that cooperates with a release  64  in the form of an angled lever pivoting on a fixed axle  65  and supporting two wheels  66  and  67 , respectively, attached to each end of the lever. Axle  62  holds a coil spring  68 , one end of which is attached to said axle which is connected to cam  61 . An end branch  60  of coil spring  68  is connected to swing tray arm  20  or directly to pivoting tray  60  when the latter pivots on axle  62 , as is the case in the embodiment illustrated in FIG. 7. Release  64  is pushed into the stopped position shown in FIG. 8B by spring  70 . When the release is pivoted by some element such as, for example, a rigid rod (not shown) that is controlled automatically by a device such as, for example, an electromagnet, a cam, a motor, or the like, it releases the cam that locks the pivoting tray in stopped position, thus allowing the tray to pivot under the dual effects of its own weight and the coil spring armed in this position. Thereafter, the object carried by the pivoting tray is discharged and it falls in the appropriate receiving container. Next, the spring is re-armed and the tray is simultaneously returned to the upright position. The coil spring is designed to make the pivoting tray pivot forcefully to drive the objects, particularly lightweight objects, and accelerate their fall into the appropriate receiving containers.  
         [0059]    [0059]FIG. 9 illustrates the operation of loading the swing trays with objects consisting of packages  100 . These packages pass from acceleration belt  32   b  onto automatic insertion belt  32   c,  then onto pivoting tray  21  of swing tray  18 . Because this tray is inclined, loading takes place from the rear of the tray and the package slides against raised front rim  21  a of the tray, which may also comprise raised lateral rims  21   b  for retaining the objects, particularly when swing trays turn as they move along the trajectory.  
         [0060]    [0060]FIGS. 10A and 10B illustrate a variation of the device that activates the pivoting of pivoting trays  21 . In this arrangement, activation device  22  is composed of a longitudinally slidable locking/unlocking element  80 , located in a housing  81  joined to suspension arm  20 , and a stop  82  joined to lateral rim  21   b  of pivoting tray  21 . This stop  82  is designed to remain in contact with one extremity of locking/unlocking element  80  while the objects are being transported, and to be released at the instant the tray pivots to unload an object it is carrying. Locking/unlocking element  80  is activated by a finger  83  consisting of an angled cylindrical rod, forming an obtuse angle in a horizontal plane, and pivoting on a vertical axis  84 . One extremity of this finger  83  is located inside housing  81  and contacts a longitudinal spring joined to locking/unlocking element  80 . When the tray pivots, the angled portion of other extremity forms a contact with a retractable movable stop  85  integral with frame  11  of device  10 . The displacement of tray  21  and, consequently, of the curved extremity of finger  83  below stop  85  causes finger  83  to pivot and compress the spring connected to locking/unlocking means  80 , which retracts and releases stop  82 , thereby causing the tray to pivot.  
         [0061]    [0061]FIG. 11 is a partial representation of an embodiment of tray  21  equipped with a moving belt that improves the discharge of objects.  
         [0062]    To achieve this, tray  21  has on its receiving surface a belt  90  moving in a loop extending between two rollers  91  and  92 , respectively located near front rim  21   a  and rear rim  21   c  of the pivoting tray. Roller  91 , which is the belt drive roller, is joined to a friction drive wheel  93  attached to the rotational axis of said roller  91  on the exterior of the lateral rim  21   b  of pivoting tray  21 . When the tray pivots from front to back, this drive wheel  93  comes into contact with a rail (not shown) that is parallel to guide rail  8 . This rail is located above the swing trays at a distance calculated to prevent guide wheel  93  from contacting the rail when tray  21  is displaced inside device  10 , such that the belt only operates when tray  21  is activated to pivot. Engaging the pivoting of the tray for unloading brings the wheel into contact with the rail provided for this purpose, and the pivoting motion, which takes place from front to back, activates moving belt  90  which then proceeds in the opposite direction to the direction in which the tray is moving, thus accelerating the unloading process. There is a notch  22   d  formed in either end of rims  21   b  for positioning roller  92  and displacing it in order to regulate the tension of belt  90 .  
         [0063]    In the various embodiments of the device of the invention, it is also possible to equip the guide rail with a means for adjusting the chain that forms the endless conveyor in order to maintain the trajectory of the swing trays.