BACKGROUND

The invention relates generally to power-driven conveyors and in particular to overhead tray conveyors.

Current methods of processing meat, fish, or poultry require cutting bulk product by hand. For example, the bulk meat is conveyed to an operator who loads the meat onto a tray. The operator then cuts the meat into defined portions on the tray's cutting surface. The tools used to cut the meat can score and scratch the cutting surface. Trays marred by scratched surfaces are difficult to sanitize— especially if the trays are sanitized manually. Biofilms, which are especially difficult to remove, can form on and contaminate the trays.

SUMMARY

One version of a tray conveyor system embodying features of the invention comprises a conveyor having an endless overhead track and a plurality of tray movers. Each tray mover includes a trolley operable to be advanced by the conveyor on the endless overhead track around a circuit and a tray holder suspended from the trolley and operable to releasably hold a tray. A workstation area is disposed along a portion of the circuit at which products on the trays are processed. The tray conveyor system also comprises a wash system that includes an entry, an exit, a tray washer, and a conveyor operable to convey trays through the washer from the entry to the exit. A wash system entry junction is positioned along the circuit downstream of the workstation area at which the trays transfer from the tray holders advancing around the circuit to the entry of the wash system. A wash system exit junction is positioned along the circuit downstream of the wash system entry junction at which the trays transfer back onto the tray holders advancing around the circuit.

One version of a tray conveyor embodying features of the invention comprises a conveyor having an endless overhead track and a plurality of tray movers. Each tray mover includes a trolley operable to be advanced by the conveyor on the endless overhead track around a circuit and a tray holder suspended from the trolley. Each tray mover also includes a connecting member that extends downward from the trolley to a yoke having first and second arms extending downwardly to distal ends. The tray holder has a first tray support rotatably retained in the distal end of the first arm and a second tray support rotatably retained in the distal end of the second arm. A bistable latch latches the first and second tray supports in a stable closed configuration to hold a tray and in a stable open configuration to release or accept a tray.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and IB are isometric and top plan views of a tray conveyor system embodying features of the invention including a wash system.

FIG. 2 is an isometric view of an electromagnetically driven trolley for a tray mover usable in a tray conveyor as in FIG. 1A.

FIG. 3 is an exploded view of a tray holder for a tray mover as in FIG. 2.

FIGS. 4A-4C are bottom plan views of a wash system entry junction showing the transfer of soiled trays from the tray movers to the wash system of FIG. 1A with the bottom removed for clarity.

FIGS. 5A-5C are isometric views of a wash system exit junction showing the transfer of washed trays back onto the tray movers of FIG. 3.

FIGS. 6A and 6B are isometric views of polymagnet pairs used in a bistable latch in the tray holders of FIG. 3.

FIG. 7 is an isometric view of a transfer device used to transfer trays 90° in the wash system of FIG. 1A.

DETAIFED DESCRIPTION

A hygienic tray conveyor system embodying features of the invention is shown in FIGS. 1A and IB. The tray conveyor system 10 comprises an infeed conveyor 12, an overhead tray conveyor 14 and a wash system 16. In this example the infeed conveyor 12 is shown as a belt conveyor 17 conveying products P, such as meat, fish, and poultry parts, to a chute 18. The products slide down the chute 18 and onto trays 20. Infeed conveyors other than belt conveyors with chutes can be used to feed products P onto the trays 20.

The trays 20 are held by tray movers 22 suspended from and driven in a circuit around an endless overhead track 24 in a conveying direction 26 (counterclockwise in this example). Products P loaded onto the trays 20 are conveyed to a workstation area 28 at which operators butcher or otherwise process the products P and manually remove the processed products from the trays. The workstation area 28 may include a table 30 or other support surface to support the trays 20 during butchering or other processing. Blood and other residual debris (D) soil the trays 20 leaving the workstation area.

The soiled trays 20' are transferred off the tray movers 22 and into the wash system 16 at a wash system entry junction 32. The soiled trays 20' are conveyed through the wash system in a conveyor such as a belt conveyor or a powered roller conveyor. The wash system 16 may include a scraper segment 34 to scrape solid and gelatinous debris from the soiled trays 20 a wash segment 36, a sanitizing and drying segment 38, and a tray accumulation segment 40. The soiled trays 20' are rinsed in the scraper and wash segments 34, 36. Once washed, the trays 20 are sanitized and dried with heat in the sanitizing and drying segment 38. The trays 20 are accumulated in the accumulator segment 40 for re-entry onto the tray movers 22 at a wash system exit junction 42. From the exit junction 42, the clean trays 20 are conveyed to the infeed conveyor 12 to receive new products P.

The tray movers 22 in this example are driven by an electromagnetic drive 44 in the overhead track 24 as shown in FIG. 2. The tray mover 22 has a trolley 46 that rides around the track 24 on rollers 48. The electromagnetic drive comprises a series of coils 50 that extend along the track 24. The coils 50 are conventionally driven by coil drivers (not shown) under the control of a programmed controller (not shown). The coils 50 produce electromagnetic fields that intersect the trolley 46. C>ne or more permanent magnets 52 in the trolley 46 produce a magnetic field that interacts with the electromagnetic fields of the coils 50 to apply a force to move the trolley along the track 24. In this example the coils form a drive stator of a linear synchronous motor in which the permanent magnet resides in the moving part of the motor. Position sensors 54, such as Hall-effect devices, positioned along the track 24 are used by the controller to determine the positions of the trolley 46. Sensors, wireless communications, and a programmed processor may also be housed in each trolley 46.

A connecting member 56 extends downward from the trolley 46 of each tray mover 22 to a yoke 58 as shown in FIGS. 1A, 2, and 3. The yoke 58 has two arms 60, 61 that terminate in distal ends 62, 63. A pair of tray supports 64, 65 forming a tray holder are rotatably retained in the distal ends 62, 63, of the two arms 60, 61. The tray supports 64, 65 are L-shaped with two legs 66, 68 meeting at a corner 70. The L-shaped tray supports 64, 65 are mirror images of each other. A pivot pin 72 extends from the corner 70 perpendicular to the plane of the L-shaped tray supports 64, 65. A groove 74 sized to receive an edge of the trays 20 is formed along the interior of the L-shaped tray supports 64, 65. Each of the tray supports 64, 65 supports a corner of the trays 20 in the groove 74.

A pair of confronting polymagnets 76, 77 at each distal end 62, 63 of the yoke 58 in the tray mover 22 form a bistable latch for the tray holder. The bistable latch affords the tray holder two stable configurations: (1) a stable closed configuration (as in FIG. 3) for holding a tray 20; and (2) a stable open configuration in releasing or receiving a tray.

The polymagnets 76, 77 are each in the form of annular disks with a central axial bore 78 as also shown in FIGS. 6A and 6B. Each polymagnet 76, 77 has two opposite faces 80, 81 and a reference flat 79 on its periphery for properly aligning polymagnet pairs to form the latch. In this example the polymagnet has three pairs of diagonally opposite magnetic domains of the same polarity angularly spaced apart by a latch angle L. The magnetic domains form north poles (N) on one of the faces and south poles (S) on the other. The rest of the polymagnet 76, 77 has a magnetic domain of the opposite polarity. All the magnetic domains have magnetic axes 82 parallel to the axis of the bore 78. One of the polymagnets 76 in each pair is affixed to the yoke 58 at the distal end 62, 63 of the arm 60, 61. The other polymagnet 77 is affixed to the corresponding tray support 64, 65. The bottom face 81 of the yoke polymagnet 76 is closely spaced from the top face 80 of the support polymagnet 77 to form the bistable latch with the similarly arranged pair of polymagnets on the other arm of the yoke.

The arrangement of the polymagnet pair 76, 77 in FIG. 6A represents the relative orientations of the magnets at the distal end 62 (FIG. 3) of the tray mover when latched in a stable open configuration. In the stable open configuration, two of the three pairs of poles are aligned. The arrangement of the polymagnet pair 76, 77 in FIG. 6B represents the relative orientations of the magnets at the other distal end 63 (FIG. 3) of the tray mover when latched in the stable open configuration. The relative orientations are opposite each other because the two F-shaped tray supports 64, 65 (FIG. 3) rotate open in opposite directions. The polymagnet pairs 76, 77 are in stable attracting positions only when poles are axially aligned. When the poles are out of alignment while the tray supports are opening or closing, the attractive force is small, or the force is repelling. The polymagnet pairs 76, 77 are shown in a stable configuration shifted by an angle +L in FIG. 6A and -L in FIG. 6B from a stable reference configuration of 0° when the tray supports are closed and the reference flats 79 of both pairs and all three of the pairs of poles are aligned. Mechanical stops (not shown) in the tray movers can be used as a redundant limit to the angular position of each of the tray supports to rotational angles in one quadrant: (a) from 0° to +L as in FIG. 6A; and (b) from 0° to -A as in FIG. 6B. The tray supports therefore each have an angular rotation range of A between stable positions. The polymagnets 76, 77 have three pairs of equipolar magnetic domains so that the same polymagnets can be used for both tray supports. But polymagnets with a different magnetic-domain pattern could be used for each tray support since they counter-rotate open in opposite directions.

The transfer of a soiled tray 20' to the wash system 16 at the wash system entry junction is shown in sequence in FIGS. 4A-4C. In FIG. 4 A the soiled tray 20' entering the junction is held firmly by the two L-shaped tray supports 64, 65 latched by the bistable latch in the closed configuration. When the tray 20' is aligned with a conveyor 84 in the wash system 16, an ejector 86 is pushed by the piston 88 of an actuator 90 against the shorter rear legs 68 of the L-shaped tray supports 64, 65. The force of the advancing ejector 86 against rear legs 68 of the tray supports 64, 65 causes the supports to counter-rotate in opposite directions over an angular range from the latched stable closed configuration of FIG. 4A (0°) to the latched stable open configuration of FIG. 4C (+A for the trailing tray support 64 and -A for the leading tray support 65). (In this version the angular rotation range A for each tray support 64, 65 is about 30°, but could be up to about 90° or less than 30° as set by the magnetic-domain pattern of the polymagnets.) In the transition shown in FIG. 4B, the bistable latch is in an unstable configuration. The ends of the rear legs 68 push the tray 20' into the opening of the wash system 16 where it is grabbed between two pairs of pinch rollers 92 (top pinch roller not shown) and pushed onto the powered rollers 94 of the roller conveyor 84 as shown in FIG. 4C. The emptied tray mover 22 with its tray holder latched in the stable open configuration resumes advancing around the track circuit. The ejector 86 is retracted to a ready position to eject the next soiled tray 20'.

Once a tray 20 is conveyed through the wash system 16 by the conveyor 84 from the wash system entry junction to the wash system exit junction, it is returned to a tray mover 22 as shown in FIGS. 5A-5C. In FIG. 5A the tray holder of a tray mover 22 moving into position at the wash system exit junction is shown in a stable open configuration. As the cleaned tray 20 is pushed far enough out of the wash system 16 by pinch rollers (not shown), its leading corners 96, 97 engage the grooves 74 in the tray supports 64, 65 as shown in FIG. 5B. Eventually the cleaned tray 20 is pushed far enough out of the wash system 16 that its corners 96, 97 push against the rear legs 68 of the tray supports 64, 65 to cause the supports to rotate from the stable open configuration to the stable closed configuration to firmly hold the tray 20, as shown in FIG. 5C. The cleaned tray 20 is then ready to receive another product from the infeed conveyor.

The wash system shown in FIG. IB has three 90° turns to return the trays to the overhead tray conveyor track 24. The 90° turns can be accomplished with a conventional transfer device 100 as shown in FIG. 7. The transfer device has powered rollers 94 alternating with belt bands 102 trained around pop-up drive and idle pulleys 104, 105. When no tray is completely on the transfer device 100, the belt bands 102 are lowered below the tops of the powered rollers 94. When a tray is completely on the transfer device 100, the pop up pulleys 104, 105 move to a raised position (shown in FIG. 7) in which the belt bands 102 are above the tops of the rollers 94. The tray then rides on the belt bands 102 and exits the transfer device 100 at a right angle to its entry. That is one way of achieving 90° turns in the wash system. Another way is with conventional powered frustoconical rollers arranged to form a turn.

Although the features of the invention have been described in illustrative examples, other versions are possible. For example the overhead tray conveyor does not have to be an electromagnetic conveyor. It could be an overhead chain conveyor advancing the tray movers around the circuit. And bistable latches can be realized without using polymagnets. So, as these few examples suggest, the claims are not meant to be limited to the illustrative features.