PALLET TRANSPORT

Abstract

Pallet transport device, including: a mobile pallet transport rack; a pallet support arrangement which is carried on the pallet transport frame for a back-and-forth movement relative to the frame and comprises pallet supports which are spaced and shaped to accommodate and support pallets; a lifting frame fixed to the frame and containing guides shaped to support and guide the pallet carrier assembly by a reciprocating lifting and lowering motion, so that the pallet carrier assembly raises and lowers all pallets arranged to be supported by the pallet carriers; a drive machine which is supported by the frame and operatively connected to the pallet carrier assembly and configured to move the pallet carrier assembly by its reciprocating lifting and lowering motion; and a motion control system that is connected to the drive machine and configured to plan the reciprocating lifting and lowering motion of the pallet carrier assembly, wherein the motion control system comprises a mechanical linkage that operatively connects the drive machine to the arrangement, wherein the linkage comprises a cam that is driven by the drive machine and is shaped to plan the reciprocating motion of the arrangement via a movement of a cam tappet that is operatively connected to the arrangement.

Description

BACKGROUND

[0001] The present application relates generally to pallet transport devices. DESCRIPTION OF THE RELATED STATE OF THE TECHNOLOGY

[0002] Typically, various devices are used for transporting and storing pallets of materials, workpieces, or products between workstations and storage areas in factories. These transport devices generally pick up and set down the pallets by alternately lifting them for transport and lowering them onto support surfaces at the desired locations for storage or use. This alternating lifting and lowering is usually accomplished via a hydraulic cylinder or a screw jack / ball screw drive. Depending on the application, a pallet transport device may be necessary to handle large fluctuations in the number of pallets to be transported and to accommodate the weight / fragility of the payload of each pallet.

[0003] Document US 2014 / 0305741A1 discloses a method for handling a load comprising a plurality of objects. The method includes providing a lifting device comprising a plurality of stacked support structures. The support structures are movable between a near and a separated state, with adjacent support structures being spaced further apart in the separated state than in the near state.

[0004] Document US 2019 / 0023297A1 describes a motorized stacking lift for stacked containers, such as bread bins. The stacking lift comprises an essentially U-shaped base and a vertical frame. A movable frame assembly is slidably mounted on the vertical frame. The movable frame assembly comprises a horizontal frame section and a pair of engaging pivot arms. A motor selectively raises and lowers the movable frame assembly.

[0005] Document US 2020 / 0385253A1 discloses a lifting device for a lifting carriage, such as for a storage and retrieval machine, with a drive mechanism comprising a motor drive, a winding drum driven by the motor drive, and a belt unwound from and wound onto the winding drum, which serves to raise and lower the lifting carriage along a mast, wherein the belt may advantageously be designed as a flat belt. SUMMARY

[0006] A pallet transport device rests on a mobile pallet transport frame. A crawler motor is configured to move the frame across a surface. A pallet support assembly supports the pallet transport frame for reciprocating motion relative to the frame and includes pallet supports spaced and shaped to receive and carry pallets. A lifting mast is attached to the frame and includes guides shaped to support and guide the pallet support assembly through a reciprocating lifting and lowering motion, so that the pallet support assembly raises and lowers all pallets arranged to be supported by the pallet supports. A drive motor is supported by the frame and operatively connected to the pallet support assembly. The drive motor is configured to move the pallet support assembly through its reciprocating lifting and lowering motion.A motion control system is connected to the drive motor and configured to control the reciprocating lifting and lowering motion of the pallet carrier assembly. The motion control system includes a mechanical linkage that operatively connects the drive motor to the assembly, the linkage including a cam driven by the drive motor and shaped to control the reciprocating motion of the assembly via the movement of a cam plunger operatively connected to the assembly. DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective side view of a pallet transport device comprising a rotary cam motion control system; Fig. 2 is a side view of the pallet transport device of the Fig. 1 in a direction opposite to the perspective side view; Fig. Figure 3 is a perspective view of a lower part of a lifting frame of the pallet transport device. Fig. 1; Fig. Figure 4 is a close-up side view of a rotary cam motion control system for the device of Fig. 1, whereby some support struts of the lifting frame were removed for the sake of clarity; Fig. Figure 5 is a simplified side view of a motor of the rotary cam motion control system of the Fig. 1, which is shown away from the device for clarity; Fig. Figure 6 is a diagram showing a torque curve of the rotary cam of the Fig. 1 over time when it is turned by a motor; and Fig. Figure 7 is a simplified side view of an alternative motion control system for the device of Fig. 1. DETAILED DESCRIPTION

[0007] A pallet transport device is in the Fig. 1 and Fig. 2 generally shown with 10. To ensure mobility, the device 10 comprises a mobile pallet transport frame 12, and the frame can support a drive train 14 and a crawler motor 16 operatively connected to the drive train 14. The crawler motor 16 and the drive train 14 can be configured to move the frame 12 across a surface.

[0008] To move and store pallets, the device 10 further comprises a pallet support arrangement 18, which is mounted on the pallet transport frame 12 for reciprocating movement relative to the frame 12 and comprises pallet supports 20 that are spaced apart and shaped to receive and support pallets. A lifting frame 22 is attached to the frame 12 and includes guides 24 shaped to carry and guide the pallet support arrangement 18 through a range of reciprocating movement, so that the pallet support arrangement 18 raises and lowers all pallets arranged to be supported by the pallet supports 20.

[0009] The pallet carriers 20 of the pallet carrier assembly 18 can be positioned and connected for synchronized vertical movement, allowing multiple pallets to be raised and lowered simultaneously. The pallet carriers 20 of the pallet carrier assembly 18 can also be arranged in vertically stacked pairs, so that each pair can support a separate pallet. This arrangement allows multiple pallets to be lifted simultaneously from multiple racks without the pallets needing to rest on top of each other.

[0010] As in the Fig. As best illustrated in Figures 3-5, a drive unit 26 (which in a preferred embodiment may include a lifting motor) is supported by the frame 12 and is operatively connected to the pallet carrier assembly 18. The drive unit 26 is configured to move the pallet carrier assembly 18 by its reciprocating lifting and lowering motion. A motion control system 28 is connected to the drive unit 26 and configured to control the direction, speed, and accelerations of the reciprocating lifting and lowering motion of the pallet carrier assembly 18 such that the speeds and accelerations of the pallet carrier assembly 18 and all supported pallets correspond to the distance by which the supported pallets are to be raised and / or lowered.

[0011] If the drive unit 26 includes a lifting motor, it can be any type of motor, including an electric motor, configured to drive the reciprocating motion of the pallet carrier assembly 18 by applying a torque to a mechanical linkage 30 that operatively connects the lifting motor to the assembly 18. Alternatively, the drive unit 26' can be operatively connected to the pallet carrier assembly 18' and configured to drive the reciprocating motion of the pallet carrier assembly 18' by applying a linear force to the assembly 18' (e.g., via a hydraulic circuit or a worm drive 32') through the intermediate linkage 30', as shown in Fig. Figure 7 is shown. (Components of this embodiment are identified with the same number as analogous components of the preferred embodiment, although followed by a dash symbol. For example, bearing 42 is the one shown in the Fig. The embodiment shown in 1-5 is analogous to the bearing 42' of the one in Fig. 7 embodiment shown).

[0012] In the preferred embodiment, the motion control system 28 can comprise a mechanical linkage that operatively connects the driven machine 26 to the arrangement 18, the linkage comprising a cam 34 which is driven by the driven machine 26 and is shaped to control the reciprocating motion of the arrangement 18 via the movement of a cam plunger 36 which is operatively connected to the arrangement 18. The cam 34 can be a rotating cam, although other embodiments may use a sliding cam.

[0013] As in Fig. As best illustrated in Figure 5, the rotatable embodiment of the cam 34 can be coupled to the drive machine 26 via a chain drive 38, and the rotating cam 34 can have a generally circular profile 35 mounted for rotation about an off-center cam rotation axis 33 such that the offset of the circular profile 35 corresponds to a desired profile for the reciprocating motion of the arrangement 18. Alternatively, both the rotary and sliding cam types can have irregular profiles that correspond to a desired profile for the reciprocating motion of the arrangement 18. These cam profiles can be individually adapted and selected to generate the desired motion profiles for pallets by changing and optimizing the range of motion or the speed of movement of the carrier arrangement 18 during its motion.In this way, the system can be optimized for the type of pallet payload and the distance over which the supported pallets are to be raised and / or lowered, so that the pallets do not experience sudden starts and stops near the times when the reciprocating lifting and lowering action causes the pallets to be picked up from or placed down by the pallet carrier assembly 18. Suitable cam profiles can be tailored to the mass or fragility of a particular payload type to achieve a desired balance between rapid operation, leverage, and careful handling, while simultaneously protecting the device 10, the payloads, and nearby equipment from damage.In some embodiments of the motion control system 28, the cam plunger 36 can be supported by a lever arm 40 and attached to the lever arm 40 at a distance from a lever arm bearing 42, which supports the lever arm 40 for rotation on the pallet transport frame 12. The cam plunger 36 can be arranged such that the movement of the cam 34 will push the cam plunger 36 and cause the lever arm 40 to rotate about the lever arm bearing 42. The lever arm 40 can further comprise a support assembly engagement surface 44, which is attached to the lever arm 40 and arranged to engage with the pallet support assembly 18 and force the pallet support assembly 18 to raise or lower itself in accordance with the rotation of the lever arm 40 about the lever arm bearing 42.

[0014] In the Fig. In the embodiment shown in Figures 1-5, the lever arm 40 can form a generally triangular profile. In this triangular shape, the lever arm bearing 42, the support arrangement engagement surface 44, and the cam tappet 36 can be arranged next to the tips of the triangular lever arm, and the angular distance between the engagement surface 44, the bearing 42, and the cam tappet 36 can vary in the same way as in the embodiment shown in Figures 1-5. Fig. 7.

[0015] In the Fig. In the alternative embodiment shown in Figure 7, the lever arm 40' can generally have the shape of an L. The drive unit 26' can be connected to the lever arm 40' at a first end of the L, the engagement surface 44 of the support assembly can be located at a second end of the L, and the lever arm bearing 42 can be located at the corner of the L. In this embodiment of the lever arm 40', the engagement surface 44' includes a roller that carries a lifting plate 19' as part of the support assembly 18. The lever arm 40' can preferably have an L-shape of approximately 90 degrees; however, any angle of the lever arm can be used to accommodate different mounting points for the drive unit 26' and / or the cam 34.

[0016] The shape of the lever arms can also be chosen to meet the requirements for optimal leverage in each embodiment; for example, the angle of the L-shape can be increased or decreased to change the torque required to move the support arrangement 18 at different points along its range of motion, or to change the acceleration of the arrangement 18 relative to the speed of the lifting motor at different points along the range of motion of the arrangement.

[0017] The motion control system 28 can also include a drive motor controller 46 configured to modulate the power of the drive motor 26 (e.g., if the drive motor 26 is a servo motor) to vary the vertical speed of the pallets according to the distance by which the pallet has been raised and / or lowered. Alternatively, the controller can also modulate the power of the drive motor 26 to maintain the rotational speed or motor speed despite varying resistances caused by the payload weight, cam shape, and / or lever arm geometry. This controller 46 can operate in combination with the lever arm 40 and / or the cam 34 to generate a reciprocating motion profile optimized for different payload types.

[0018] For example, and as in Fig.As shown in Figure 5, the cam 34 and the cam plunger 36 can be indexed (by adjusting the mounting points and the shape of the lever arm 40) such that the cam plunger 36 rests at a point on the cam profile 35 where the radial distance between the cam profile 35 and the cam axis of rotation 33 is smallest when the pallet carrier assembly engagement surface 44 of the lever arm is generally horizontal to the lever arm bearing 42. This indexing arrangement allows the movement of the pallet carrier assembly 18 to be slowed down near the upper and lower limits of its travel when the lifting motor 26 is operated at a constant speed, thereby preventing sudden stops, starts, and changes of direction when lifting or setting down pallets by the device 10.

[0019] A pallet transport device equipped with these features can be configured to load and unload pallets by reciprocating movements with desired accelerations, leverage, and motion profiles that correspond to the mass, fragility, or other aspects of a particular type of payload.

[0020] This description does not describe any limitations of the invention, but merely illustrates embodiments of the invention described in the claims. The language of this description is therefore purely descriptive and non-limiting. Of course, it is possible to modify the invention compared to the teachings of this description. Within the scope of protection of the claims, the invention can also be implemented differently than described above.

Claims

[1] Pallet transport device comprising: a mobile pallet transport rack; a pallet support arrangement which is carried on the pallet transport frame for a back-and-forth movement relative to the frame and comprises pallet supports which are spaced and shaped to accommodate and support pallets; a lifting frame fixed to the frame and containing guides shaped to support and guide the pallet carrier assembly by a reciprocating lifting and lowering motion, so that the pallet carrier assembly raises and lowers all pallets arranged to be supported by the pallet carriers; a drive machine which is supported by the frame and operatively connected to the pallet carrier assembly and configured to move the pallet carrier assembly by its reciprocating lifting and lowering motion; and a motion control system that is connected to the drive machine and configured to plan the reciprocating lifting and lowering motion of the pallet carrier assembly, wherein the motion control system comprises a mechanical linkage that operatively connects the drive machine to the arrangement, wherein the linkage comprises a cam that is driven by the drive machine and is shaped to plan the reciprocating motion of the arrangement via a movement of a cam tappet that is operatively connected to the arrangement. [2] Pallet transport device according to claim 1, wherein the pallet carriers of the pallet carrier arrangement are positioned and connected for a synchronized vertical movement, so that several pallets can be lifted and lowered simultaneously. [3] Pallet transport device according to claim 2, wherein the pallet carriers of the pallet carrier arrangement are arranged in vertically stacked pairs, so that each pair can carry a separate pallet. [4] Pallet transport device according to claim 1, wherein the drive machine comprises an electric motor. [5] Pallet transport device according to claim 1, wherein the drive machine comprises a hydraulic pump which is operatively connected to the pallet carrier arrangement via a hydraulic hose. [6] Pallet transport device according to claim 1, wherein the drive machine is configured to drive the reciprocating movement of the pallet carrier arrangement by applying a linear force to a mechanical linkage that effectively connects the drive machine to the arrangement. [7] Pallet transport device according to claim 1, wherein the drive machine is configured to drive the reciprocating movement of the pallet carrier arrangement by applying a torque to a mechanical linkage that effectively connects the drive machine to the arrangement. [8] Pallet transport device according to claim 1, wherein the cam is a rotating cam. [9] Pallet transport device according to claim 8, wherein the rotating cam is coupled to the drive machine via a chain drive. [10] Pallet transport device according to claim 8, wherein the rotating cam comprises a generally circular profile which is mounted to rotate about an off-center cam rotation axis, such that an offset of the circular profile corresponds to a desired profile for the reciprocating movement of the arrangement. [11] Pallet transport device according to claim 8, wherein the rotating cam comprises a generally elongated profile with deviations from a circular profile that correspond to a desired profile for the reciprocating movement of the arrangement. [12] Pallet transport device according to claim 1, wherein the cam tappet is supported by a lever arm which is mounted on the pallet transport frame to rotate around a lever arm axis; the cam tappet is attached to the lever arm at a distance from the lever arm bearing and is arranged such that the movement of the cam will push the cam tappet and cause a rotation of the lever arm about the lever arm axis; and a carrier assembly engagement surface is attached to the lever arm and arranged so that it engages with the pallet carrier assembly and causes the pallet carrier assembly to rise or fall according to the rotation of the lever arm about the lever arm axis. [13] Pallet transport device according to claim 12, wherein the lever arm generally has a triangular shape; the cam tappet is arranged adjacent to a first corner of the triangular shape; the support arrangement engagement surface is arranged adjacent to a second corner of the triangular shape and The lever arm bearing is arranged adjacent to a third corner of the triangular shape. [14] Pallet transport device according to claim 12, wherein the cam and the cam plunger are indexed such that the cam plunger touches a point along a profile of the cam where the distance between the cam profile and the cam axis of rotation is smallest when the pallet carrier assembly engagement surface of the lever arm is generally arranged horizontally to the lever arm bearing. [15] Pallet transport device according to claim 6, wherein the motion control system comprises a mechanical linkage that operatively connects the drive machine to the arrangement, the linkage comprising: a lever arm which is supported on the pallet transport frame for rotation around a lever arm axis; and a carrier assembly engagement surface which is attached to the lever arm and arranged so that it engages with the pallet carrier assembly and causes the pallet carrier assembly to rise or fall according to the rotation of the lever arm about the lever arm axis. [16] Pallet transport device according to claim 15, wherein the lever arm has an L-shape; the drive machine is connected to the lever arm adjacent to a first end of the L; the support arrangement engagement surface includes a roller that is arranged adjacent to a second end of the L; and the lever arm bearing is located adjacent to the corner of the L. [17] Pallet transport device according to claim 1, wherein the motion control system comprises a drive machine control configured to modulate the power of the drive machine to change the vertical speed of the pallets according to the distance by which the pallet has been raised and / or lowered. [18] Pallet transport device according to claim 1, wherein the motion control system is configured to plan the direction, speed and accelerations of the reciprocating lifting and lowering motion of the pallet carrier arrangement in such a way that the speeds and accelerations of the pallet carrier arrangement and of all supported pallets are optimized for the type of payload of the pallets and the distance over which supported pallets are to be lifted and / or lowered. [19] Pallet transport device according to claim 1, further comprising: a caterpillar engine that is supported by the frame; and a drive train which is supported by the frame and which is operatively connected to the crawler motor, wherein the crawler motor and the drive train are configured to move the frame over a surface.

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