Tilting tray package sorting apparatus

Abstract: An automatic system (10) for sorting items, such as small parcels, into groups bound for different geographical locations is described. The system (10) includes a carriage (14) for travelling along a track (12), the carriage having an adjustment feature such that it may continuously be held against the track. The carriage also provides a tilt tray (60) in which packages are presented on a convex surface. The convex surface causes the package to be destabilized, so they may be quickly discharged from the tilt tray.

Description: Technical Field The present invention relates to automatic sorting of items such as small packages into groups bound for different geographical locations, and more particularly relates to an automatic sorting apparatus using tilting trays which receive items from input conveyors and deposit them into designated output chutes or bins under programmed control. Background Art Tilt tray sorters have been available for many years. Such systems are useful in sorting small packages for delivery to different regions, such as zip code areas. Under control of a computer or programmed logic controller, packages may be identified or coded as they enter the system, and then tracked for output at a chute or bill corresponding to the coded destination. It is known to form a loop of linked carriages running along a loop of track. A human operator or automatic equipment loads items onto trays mounted on the carriages at one point around the loop, and the system automatically tilts the trays at various output locations adjacent to the track to discharge the packages. Many such systems drive the linked carriages by means of a chain or belt drive, which tends to be expensive and noisy. Such systems also occupy a large amount of space, and include complex mechanisms that are relatively difficult to repair. At a package delivery company, the amount of time a sorter is shut down for repairs has a significant negative effect on the company's ability to meet delivery deadlines. Thus, reliability is a major goal in designing sorting systems. By simplifying mechanical assemblies and providing for easy substitution of failed parts, reliability can be increased and down time reduced. Furthermore, such companies must take steps to reduce noise levels in their facilities as governmental regulations concerning noise become more strict; thus, lowering noise levels in sorting systems is also a major goal. The sorting system disclosed in U.S. Pat. No. 4,712,965 drives linked carriages around a dual rail track by means of one or more drive carriages. The drive carriages contain motors which derive power for operation from sliding contacts. The motors drive rollers which are pressed against a third rail by the weight of the motor. The carriages are separated by bumpers, and unloading is accomplished by driven conveyor belts mounted on the carriages, rather than by tilting trays. Another system of looped carriages, but including a tilting tray mechanism, is disclosed in U.S. Pat. No. 5,054,601, which is incorporated herein by reference. The carriages are driven by induction motors positioned beneath the path of the carriages. A conveyor and overhead loader mechanism automatically load the carriages and shaft encoders monitor the speed of the carriages along the looped track. Rollers mounted on the carriages interact with cams provided along the track to unload the trays at their predetermined destination. The loading and unloading functions are under computer control. A latch mechanism holds the trays in a tilted position until they are straightened by a return mechanism. In those prior art systems which drive a series of carriages by means of a chain or belt positively connected to the carriages, there is no need to link the carriages. In fact they may be spaced apart along the chain to avoid interaction. However, in some prior systems in which the train of carriages has been pulled by a locomotive carriage or by induction, the carriages must be linked. The linkage between carriages is a source of wear and noise. Therefore, a mechanical joint consisting of multiple interacting metal or plastic parts must be designed to reduce friction and possibly lubricated. Even then, the wear and noise problems associated with each linkage can only be alleviated, not eliminated. Tilting tray sorting systems are also shown in U.S. Pat. Nos. 4,089,404; 5,018,928: and 4,982,828. The latter patent discloses a mechanism which tilts the trays by moving rollers mounted along the track into the path of cam surfaces on the edges of the trays. A problem with the tilt tray sorters is that the speed of the tilt trays has been the limiting factor on the operation of the lines. The time it takes to tilt the trays and allow the packages to slide off does not permit the system to operate fast enough to run the lines at the higher rates made available by automation and electronic controls. One of the reasons for the slow speed of the tilt trays is the high degree of tilt (20-40 degrees) of the tray required to discharge the items it carries. Because the mechanical tilt mechanisms used in contemporary tilt trays have not been able to sustain high speed travel, some manufacturers have offered powered discharge of the items with a belt or powered rollers. However, such systems are often expensive and can be unreliable due to power and signal transmission through a rail. There is a need for a more reliable, inexpensive way to provide quick discharge from a sorting system. Another problem which arises in the field of automatic sorting is how to handle and sort large, irregularly shaped items. The prior systems noted above generally are unable to handle such irregular items. As may be seen from the foregoing, prior sorting systems are complex both mechanically and electrically, require a relatively large amount of floor space for the volume of items that can be sorted, require significant maintenance, and by their nature are slow and noisy. There has been a need in the art for a sorting system that is simple in construction, is easy to maintain and keep on line, provides a high throughput of sorted items per occupied floor space, and operates at high speed with low noise levels. Summary of the Invention The present invention provides an apparatus for transporting objects, the apparatus including a track and a plurality of carriages mounted for movement along the track. Each of the carriages includes a tiltable object-holding platform and a frame for engaging the track. The object-holding platform defines a convex carrying surface for the objects, allowing the objects to be destabilized. A selectively-positionable retainer is located at a first end of the convex carrying surface, the retainer operable to two different positions: a first position in which the retainer is set forth in the path of an object at the first end of the carrying surface such that the retainer discourages discharge of the object off the first end of the carrying surface; and a second position in which the retainer is removed from the path of the object moving toward the first end of the carrying surface. In the second position, the object is free to discharge off the first end of the carrying surface. The object-holding platform may be pivotably mounted to the frame and operatively associated with a cam surface. A transfer mechanism may be provided which is operative to unload an object from the carriage and includes a cam follower selectively positionable in the path of the cam surface. A second selectively positionable retainer may be located at a second end of the convex carrying surface, the second retainer is also operable to two different positions: a first position in which the second retainer is set forth in the path of an object at the second end of the carrying surface such that the second retainer discourages discharge of the object off the second end of the carrying surface; and a second position in which the second retainer is removed from the path of the object moving toward the second end of the carrying surface such that the object is free to discharge off the second end of the carrying surface. The first and second retainers may be provided on a retaining tray. The retaining tray may extend along the carrying surface and be attached to the first retainer, the retaining tray being biased away from the second end of the carrying surface and defining the cam surface, such that positioning the cam follower in the path of the cam surface lifts the retaining tray to engage and lift the second end of the carrying surface while lowering the retainer out of the path of the object. Thus, positioning the cam follower in the path of the cam surface operates to discharge the object from the carriage. The present invention further provides an apparatus for sorting objects, the apparatus including a track and a plurality of carriages mounted for movement along the track. Each of the carriages defines an object-holding platform defining a carrying surface and mounted along a first axis. A retaining tray is pivotably mounted on the carriage along a second axis, the second axis being substantially parallel to the first axis and the retaining tray defining first and second retainers. The retaining tray is selectively positionable to two positions relative to the carrying surface. In the first position, the first retainer is set forth in the path of an object moving toward a first end of the carrying surface and the second retainer is set forth in the path of an object moving toward a second end of the carrying surface such that the first retainer discourages discharge of the object off the first end of the carrying surface and the second retainer discourages discharge of the object off the second end of the carrying surface. In the second position, the first retainer is moved from the path of the object moving toward the first end of the carrying surface such that the object is free to discharge off the first end of the carrying surface. Thus, it is an object of the present invention to provide an improved automated sorting system. It is a further object of the present invention to provide a sorting system for small items or packages which sorts such items at a high rate per floor area occupied by the system. Another object of the present invention is to provide a tilt tray which is capable of quickly discharging items on the tray. Still another object of the present invention is to provide a tilt tray which requires very little tilt to discharge a package. Other objects, features, and advantages of the present invention will become apparent upon review of the following description of preferred embodiments and the appended drawing and claims. Brief Description of the Drawing Fig. 1 is a diagrammatic top plan view of a sorting system; Fig. 2 is an end view of a carriage according to the present invention, with a permanent retainer removed for detail; Fig. 3 is a side view of the carriage of Fib. 2. with part of the frame removed for detail; Fig. 4 is an end view of the carriage of Fig. 2, with the carriage in the discharge position; Fig. 5 is a perspective view of the lower carrying wheel cartridge of the carriage of Fig. 2; Fig. 6 is a side view of the trip mechanism for use with the carriage of Fig. 2, with the crank positioned such that the lever arm extends its minimum height; and Fig. 7 is a side view of the trip mechanism of Fig. 6 with the crank positioned such that the lever arm extends its maximum height. Detailed Description Referring now in more detail to the drawing. in which like numerals refer to like parts throughout the several views, Fig.1 shows an automatic sorting system 10 The sorting system 10 includes a monorail 12 and a line or train of carriages 14 mounted for travel along the monorail 12. In the preferred form shown, the monorail forms a closed loop, and the carriages fill the monorail. Thus, the carriages 14 may be driven along the monorail in one direction by a drive mechanism 16. to be described in detail below. The carriages 14 travel through an input section 18 at which they are loaded with items, such as parcels to be delivered to addressee destinations, and then through output sections 20. At the output sections 20, the items are removed from the carriages by tilting mechanisms 22 which remove the items at an output chute corresponding to the item's destination. in a manner described below. Other subassemblies of the sorting system 10 shown in Fig. 1 include a return mechanism 24, which prepares the carriages to receive new items as they return to the input section 18, and a carriage tracking station 26 which positively locates a carriage carrying a particular item so that a controller (not shown) including a digital processor may cause the item to be sorted to the correct destination. An embodiment of the present invention is shown in Figs. 2-7, which portray a tilt tray carriage 200. The carriage 200 provides a high speed parcel discharge features, as well as an automatic adjustment and gripping feature for a rail. The carriage 200 is designed to travel along a monorail 12. shown in the drawing as supported on a post 30 by a bracket 32. The carriage 200 has a frame 202 in the shape of an elongate "C", with the open side of the "C" facing the post 30 and receiving the monorail 12 and support brackets 32. As shown in Figs. 2 and 3, the carriage 200 includes bearing assemblies for contacting the monorail 12 in the form of an upper carrying wheel cartridge 204 and a lower carrying wheel cartridge 206 within the frame 202, above and below the monorail 12, respectively. The right angles 212, 214 point toward the monorail. The wheel cartridges 204, 206 include feet 208, 210 extending from right angles 212, 214, respectively. The feet 208 on the upper carrying wheel cartridge 204 are fixed to the upper surface of the frame 202 by welding, bolts, or other suitable attachments. The lower carrying wheel cartridge 206 includes a unique height adjustment feature, described below, and extends between retaining tabs 216, two each of which are located on the back and front of the frame 202. A plurality of wheels 218 are mounted for rotation on adjacent sides of the right angles 212, 214. The wheels 218 are preferably urethane. As can best be seen in Fig. 2, these wheels 218 are arranged to engage the flat surfaces of the square monorail 12. As will be described in detail below, the ability to adjust the height of the lower carrying wheel cartridge 206 provides an automatic gap adjustment feature such that the wheels 218 engage the monorail 12 with pressure. The gap adjustment feature biases the wheels 218 against the monorail 12, and allows the carriage 200 to be used on a variety of different sized and shaped monorails. The main advantage of the automatic adjustment feature is that urethane rollers used in the past have worn over time and created clearance between the rail and the wheels. This clearance can cause a corresponding rattling, noise or vibration. By providing the adjustment feature, the wheels 218 remain against the surface of the rail despite changes in the diameter of the wheels. Turning now to Fig. 5, details of the lower carrying wheel cartridge 204 and the unique automatic gap adjustment feature are shown. The lower carrying wheel cartridge 206 is suspended on two cylinders 220, 222. The cylinders 220, 222 preferably extend transversely under the back and front ends of the lower carrying wheel cartridge 206, so that the cartridge may remain stable. Pins 224, 226 extend eccentrically out of both ends of the cylinders 220, 222, respectively, and are fixed to the cylinders such that rotation of the pins causes a corresponding rotation of the cylinders. The pins 224, 226 are mounted for free rotation within holes on opposite sides of the frame 202. Lever arms 230, 232 are fixed to the pins 224, 226 at ends which extend out of the side of the frame 202 opposite the post 30. A slack control device in the form of a compression spring 234 extends between the two lever arms 230, 232 and biases the two arms away from one another. In the embodiment shown, the spring 234 may be any mechanical or electromechanical device that can offer a compression force, including but not limited to hydraulic cylinders, electrostatic cylinders, magnetic devices, and steel recoil springs. The cylinders 220, 222 serve as cams and present camming surfaces on their outer diameters for engaging the feet 210 on the lower carrying wheel cartridge 206. The eccentric mounting of the pins 224, 226 relative to the cylinders 220, 222 causes the distance between the camming surface for each of the cylinders and the corresponding pin to increase or decrease, depending upon which portion of the surface is presented to the feet 210. Thus, as the point of contact between the camming surface for each of the cylinders 220, 222 approaches the point A on the outer diameter of the cylinders, the feet 210, and therefore the wheel cartridge 206, moves upward, or away from the respective pin 224, 226. Correspondingly, as the point of contact on the surface of each of the cylinders 220, 222 approaches the point B on the outer diameter of the cylinders, the lower carrying wheel cartridge 206 moves downward, or closer to the pins 224, 226. It can be appreciated that rotating the pins 224, 226 varies the height of the lower carrying wheel cartridge 206, or either end of the cartridge so that the cartridge may snugly engage the monorail regardless of small changes in the dimensions of the wheels 218. Preferably, the camming surfaces of the two cylinders 220, 222 are set such that for a normal or average size of the monorail 12, the camming surfaces of the cylinders engage the feet 210 at some point between A and B on the camming surfaces, so that adjustments both up and down in the height of the lower carrying wheel cartridge 206 are within the range of movement of the spring. As can be seen in the example of Fig. 5, the normal point of contact for the cylinder 220 is the point C and the normal point of contact for the cylinder 222 is the point D. As such. counterclockwise rotation of the pin 224 (and the lever arm 230) and clockwise rotation of the pin 226 (and the lever arm 232) causes the lower carrying wheel cartridge 206 to rise, until the point of contact for each of the cylinders reaches a location between point C and point A at which the wheels 218 firmly contact the monorail 218 and preclude further rising. Contact with the point A represents the maximum "camming action" for the cylinders 220, 222. Likewise, clockwise rotation of the pin 224 (and the lever arm 230) and counterclockwise rotation of the pin 226 (and the lever arm 232) causes the lower carrying wheel cartridge 206 to lower under pressure from an enlargement of the monorail. Contact with the point B represents the minimum "camming action" for the cylinder. Preferably, the variance in size of the monorail 12 will not exceed the distance determined by the camming surfaces of the cylinders 220, 222 reaching the points A and B. It can be appreciated that the cartridge 200 with the adjustment feature may fit without modification any rail having right-angle contact surfaces along the top and bottom sides and not exceeding this distance. From the foregoing discussion, it can be understood that the compression spring 234, by forcing the two lever arms 230. 232 apart, biases the point of contact of the camming surfaces on the cylinders 220, 222 with the feet 210 toward the point A on each of the cylinders. Thus, the compression spring 234 biases the lower carrying wheel cartridge 206 toward the upper carrying wheel cartridge 204, having the effect of closing any gaps that exist between the monorail 12 and the wheels 218. and biasing the lower wheels 218 against the bottom of the monorail, allowing for smooth and constant contact of the wheels 218 with the monorail 12. It is also to be understood that because each of the pins 224, 226 is free to rotate independently, each end of the lower carrying wheel cartridge 206 adapts independently to fit against the monorail 12. For best results, a relatively constant force spring is used between the two lever arms 230, 232. It is to be understood that the camming surfaces on the two cylinders 220, 222 can be reversed and a tension spring may be used. In addition, the automatic gap adjustment feature of the present embodiment can be incorporated into a suspended monorail system. preferably by turning the frame 202 over so that the gap adjustment is along the top of the rail. Furthermore, the gap adjustment feature could be added to each side of the rail. The carriage system 200 also provides a unique tilt tray 250. The tilt tray 250 includes a plurality of elongate idler rollers 252 mounted longitudinally on a carrying idler tray 254. The elongate idler rollers 252 are free to spin on their central axes and, unlike other carrying idler trays, are mounted such that a line extending along the central axes of the rollers would be slightly curved, creating an upwardly convex carrying "surface" indicated by a dashed line 255 in Fig. 2. When viewing the tray 254 from the direction of Fig. 2, the idler rollers 252 in the center of the carrying idler tray 254 are slightly higher than the rollers at each of the ends of the tray, and each idler roller is progressively lower. Preferably, the difference in height between the center rollers 252 and the outer rollers is approximately 1/4 inch. A hub 256 extends from the bottom of the carrying idler tray 254 and is received between two flanges 258 extending upward from the frame 202. A pivot rod 260 extends through the two flanges 256 and the hub 258. Centering springs 262, 264 are provided on opposite sides of the hub 256 and extend from the carrying idler tray 254 to the frame 202 to bias the carrying idler tray to a substantially horizontal orientation. A sheet metal retaining tray 266 having the shape of an elongate "W" is provided around and beneath the carrying idler tray 254. The retaining tray 266 includes openings (not shown) through which the hub 258 and centering springs 262, 264 freely pass. The retaining tray 266 is attached at a horizontal pivot 268 extending through the hub 256 along the bottom center of the carrying idler tray 254. Because of the slight upward curvature in the central portion of the elongate "W" of the retaining tray 266, the retaining tray hangs freely from the ends of the carrying idler tray 254, with a gap formed between the ends of the carrying idler tray and the ends of the retaining tray. Leaf springs 270, 272 positioned in this gap bias the retaining tray 266 away from the ends of the carrying idler tray 254 and keep the gaps on each end substantially the same when no other force is exerted on the tray 266. The leaf springs are attached at one end to either the tray 254 or the tray 266. and the other end presses against the other tray without being fixed thereto. The ends of the retaining tray 266 extend up and define retainers 274, 276, which, in a normal position, extend above the surface of the top of the idler rollers 252. Permanent retainers 277 are provided at the front and rear of the carrying idler tray 254 and are attached to the carrying idler tray or to the hub 256. The retainers 277 extend upwardly to prevent a package 114 from sliding longitudinally off the rollers 252. As with the tilting trays of earlier embodiments, a series of discharge chutes 140, 141 are positioned to receive parcels 114 sliding off the carrying idler tray 254. A trip mechanism 280 is provided underneath at least one side of the retaining tray 266. The trip mechanism 280 includes a roller 282 mounted on an axis 283 which is attached to a pair of lever arms 284. A fulcrum rod 285 extends between the two lever arms 284. The end of the lever arms 284 are pivotally mounted on a fixed pivot rod 286. As can be seen in Figs. 6 and 7, a push rod 287 extends downward from a pivotal connection to the fulcrum rod 285 and is eccentrically attached at its other end to a crank 288. The crank 288 is mounted for rotation about an axel 289 and includes a plurality of holes 290 which vary in radial distance from the axel 289. The axel 289 is driven by a motor 292 through a gear reducer 290. The crank 288 may be inserted into any one of the holes 290 to adjust the travel of the roller 282 toward the tray 250. A train of the carriages 200 may alternate upper and lower level carriages as has been described above, or may be spaced such that all of the carriages are approximately the same height. Furthermore, it should be understood that many advantages of the present embodiment can be incorporated in a monorail system having several different configurations. However, when describing the operation of the carriages 200, it will be assumed that the carriages extend above the monorail 12 (such as shown in Fig. 2). As with the previous embodiments, the present embodiment includes a drive mechanism having a drive roller 296 which is operated by a motor 298. The weight of the motor 298 urges the drive roller 296 against the carriage frame 202. As the drive roller 296 rotates, it engages one carriage after another and propels the entire carriage train forward at an appropriate speed. During operation of a monorail system including the carriages 200 with tilt trays 250, packages 114 are input at an appropriate input section onto the carrying surface 255 of the plurality of idler rollers 252. Preferably, the packages 114 are input over one of the retainers 274, 276. Because of the slight curvature of the rollers 252, the package 114 is destabilized and easily rolls back and forth between the retainers 274, 276, but is prevented from falling off the carrying idler tray 254 by the retainers. In addition. the permanent retainers 277 at the transverse edges prevent the package from slipping off the carrying idler tray 254 along the front and back of the carrying idler tray 254. As the package 114 moves back and forth across the carrying idler tray 254. the tray is held steady by the springs 262, 264. The carriage tracking station, such as is described above, is located immediately downstream of the input section for the packages 114. Other appropriate tracking devices as described above are used to designate the proper output chute for the package as it is input on the tilt tray 250. When the tilt tray 250 and carriage 200 approach the proper discharge chute 278, the motor 292 is engaged such that the reducer 290 turns the crank 288 a one-half turn, advancing the push rod 287 from the bottom dead center position of Fig. 6 to the top dead center position of Fig. 7. This advancement of the push rod 287 correspondingly pivots the lever arms 284 about the pivot rod 286, and thereby raises the trip roller 282 which presses the bottom of the retaining tray 266 upward. Thus, as the carriage 200 moves along the monorail 12, the roller 282 acts as a cam follower, getting in the path of and pressing against the bottom of the retaining tray 266, which acts as a cam surface. As one side of the retaining tray 266 moves upward, the leaf spring 272 on that side is compressed and the gap between the inside right portion of the retaining tray 266, as shown in Fig. 4, and the lower right edge of the carrying idler tray 254 is substantially closed. Closing this gap causes a corresponding widening of the gap between the inside edge of the left side of the retaining tray 266 and the lower, left edge of the carrying idler tray 254. As can be seen in Fig. 4, the separation of the left side of the retaining tray 266 and the carrying idler tray 254 allows the leaf spring 270 to relax, or be in a less compressed state. The movement of the left side of the retaining tray 266 downward also moves the retainer 274 below the carrying surface 255. Further pressure of the roller 282 upon the bottom right edge of the retaining tray 266 causes the carrying idler tray 254 to tilt about the pivot rod 260, compressing the centering spring 262 and tensioning the centering spring 264. This tilting of the carrying idler tray 254 causes the destabilized package 114 to slide to the left along the idler rollers 252 off of the tilt tray 250 and into the discharge chute 278 as shown in Fig. 4. Continued rotation of the crank 288 moves the push rod 287 back into the position of Fig. 6, or bottom dead center, and allows the tray to return to the position of Fig. 2. The tilt tray 250 is then ready to receive another package. The destabilized orientation of the package 114 on the idler rollers 252 allows a quick discharge of the package. The slight convex shape puts the package 114 in a position where it has few contact points (preferably only one or two) with the idler rollers 252, and therefore a minimum amount of friction for quick movement of the package 114. Thus, by slightly tilting the carrying idler tray 254, gravity overcomes the small friction and the package is easily discharged from the tray 254. It has been found that the destabilized condition of the rollers 252 allows a quick discharge of a package with as little as 5-7 degrees of tilt of the tray 254. compared to a necessary tray tilt of approximately 20-40 degrees for non-powered tilt trays in the prior art. By allowing less tilt for the tilt tray 250, the entire system may run at a much higher speed than normally achievable with prior art tilt trays and, as a result, improves productivity. While the present invention in its various aspects has been described in detail with regard to preferred embodiments thereof, it should be understood that variations, modifications and enhancements can be made to the disclosed apparatus and procedures without departing from the scope of the present invention as defined in the appended claims.

Claims: An apparatus for transporting objects, including a track (12) and a plurality of carriages (200) mounted for movement along the track, each of the carriages including an object-holding platform (250) and a frame (202) for engaging the track, characterised by: the object-holding platform (250) defining an upwardly convex carrying surface (255) for the objects, shaped such that position of an object (114) thereon is destabilized; a selectively positionable retainer (274) located at a first end of the carrying surface, the retainer operable to two different positions: a first position in which the retainer (274) is set forth in the path of an object at the first end of the carrying surface (255) such that the retainer discourages discharge of the object off the first end of the carrying surface; and a second position in which the retainer (274) is removed from the path of the object moving toward the first end of the carrying surface (255) such that the object is free to discharge off the first end of the carrying surface. The apparatus of Claim 1, wherein the object holding platform is (255) pivotally mounted to the frame (202) and is operatively associated with a cam surface (266); and further comprising a transfer mechanism (280), operative to unload an object from the carriage and including a cam follower (282) selectively positionable in the path of the cam surface. The apparatus of Claim 2, further comprising a second selectively positionable retainer (276) located at a second end of the carrying surface (255), the second retainer operable to two different positions: a first position in which the second retainer is set forth in the path of an object urged toward the second end of the carrying surface such that the second retainer discourages discharge of the object off the second end of the carrying surface; and a second position in which the second retainer is removed from the path of the object urged toward the second end of the carrying surface such that the object is free to discharge off the second end of the carrying surface. The apparatus of Claim 2, wherein the object-holding platform further comprises a retaining tray (266) extending along the carrying surface and attached to the retainer (274), the retaining tray biased away from the second end of the carrying surface and defining the cam surface, such that positioning the cam follower (282) in the path of the cam surface (266) (a) operates the retaining tray toward the second end of the carrying surface and urges the retainer out of the path of the object and (b) operates to discharge the object from the carriage by tilting the object-holding platform (250). The apparatus of Claim 1, wherein the carrying surface (255) comprises an upwardly convex bed of idler rollers (252). The apparatus of Claim 1, further comprising: a first bearing assembly (204) linked to the frame (202) and for engaging a first side of the track; a second movable bearing assembly (206) positioned between the frame and a second side of the track; and a slack control device (220, 230, 234) positioned to bias the second bearing assembly against the track. The apparatus for transporting objects of Claim 1, wherein said object-holding platform (250) defines a carrying surface (255) and is pivotally mounted along a first axis (260), and wherein said retainer is characterised by: a retaining tray (266) pivotally mounted on the carriage along a second axis (268), the second axis being substantially parallel to the first axis, and the retaining tray defining first and second retainer members (274, 276); the retaining tray being selectively positionable to two positions relative to the carrying surface: a first position in which the first retainer member (274) is set forth in the path of an object (114) at a first end of the carrying surface and the second retainer member (276) is set forth in the path of an object at a second end of the carrying surface such that the first retainer discourages discharge of the object off the first end of the carrying surface and the second retainer discourages discharge of the object off the second end of the carrying surface; and a second position in which the first retainer is removed from the path of the object moving toward the first end of the carrying surface such that the object is free to discharge off the first end of the carrying surface. The apparatus of Claim 7, wherein the retaining tray (266) is operatively associated with the object-holding platform (250) such that tilting the first end of the carrying surface (255) downward a specified amount urges the retaining tray into the second position. The apparatus of Claim 8, wherein the retaining tray (266) defines a cam surface; and further comprising a transfer mechanism (280), operative to unload an object from the carrying surface and including a cam follower (282) selectively positionable in the path of the cam surface such that the cam follower in the path of the cam surface (a) operates the retaining tray (266) toward the second end of the carrying surface and urges the first retainer (274) out of the path of the object and (b) operates to discharge the object from the carrying surface. The apparatus of Claim 7, wherein the retainer tray (266) is biased upwardly to the first position in which the first retainer (274) extends above the carrying surface (255); and means (280) for tilting the retraining tray about the second axis until the first retainer moves against the bias to the second position below the carrying surface and for then tilting the tray (266) and the object-holding platform (250) together about the first axis into a discharge orientation.

Inventors: BONNET HENRI, BONNET, HENRI
Applicants: UNITED PARCEL SERVICE INC, UNITED PARCEL SERVICE OF AMERICA, INC.
Application year: 1995
Main classification: B65G47
IPC codes: B65G47