JP2024079904A - Cargo receiving stand lifting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cargo receiving stand lifting device configured so that an oil tank can be suppressed from being broken and oil can be suppressed from leaking out from the oil tank when a lifting unit inverts.

SOLUTION: A cargo receiving stand lifting device 10 comprises a lifting unit 11 which has a cargo receiving stand 16, a hydraulic cylinder 22 and an oil tank 25, and an inverting mechanism 30 that inverts the lifting unit 11. The oil tank 25 has a first connection port 25b and a second connection port 25c. A supply oil path 71 for supplying oil to a main oil chamber 22d of the hydraulic cylinder 22 is connected to the first connection port 25b of the oil tank 25. A return oil path 72 for returning oil from the main oil chamber 22d of the hydraulic cylinder 22 to the oil tank 25 is connected to the second connection port 25c of the oil tank 25. The second connection port 25c of the oil tank 25 is communicated with a sub oil chamber 22e of the hydraulic cylinder 22, through the return oil path 72, by a communication oil path 73.

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a loading platform lifting device.

For example, Patent Document 1 describes a loading platform lifting device that is attached to trucks and the like and used for loading and unloading luggage. The loading platform lifting device in Patent Document 1 is a vertical lifting type, and includes a pair of left and right lifting pillars fixed to the rear end of the truck bed, a loading platform that is arranged to be raised and lowered relative to these lifting pillars, a hydraulic cylinder that drives the loading platform to be raised and lowered, and an oil tank that stores oil to be supplied to the hydraulic cylinder. By extending and retracting the hydraulic cylinder, the loading platform can be raised and lowered between a lowered position where it touches the ground and an elevated position where it is flush with the floor of the bed when deployed horizontally. When the loading platform is not in use, it can be rotated upward from the elevated position so that it is stored upright along the rear surfaces of the lifting pillars.

Patent No. 5932933

In the vertical lifting type loading platform lifting device, when the loading platform is not in use, the pair of lifting pillars and the upright stored loading platform are in a state where they protrude below the loading platform. If a truck is driven in this state, there is a risk of damage to the lifting pillars and loading platform. Therefore, in order to prevent damage to the lifting pillars and other components, it is being considered to invert the lifting unit, which includes the lifting pillars, loading platform, hydraulic cylinder, and oil tank, around a horizontal axis relative to the loading platform and position it above the floor level of the loading platform.

However, when the lifting unit is inverted, the oil tank is also inverted, which can cause oil to leak from the breather port in the oil tank. To prevent such oil leakage, it is possible to use an oil tank without a breather port. However, in that case, when the loading platform is raised or lowered, a pressure difference occurs inside the oil tank due to the extension and contraction of the hydraulic cylinder, which can cause the oil tank to deform and become damaged.

The present invention was made in consideration of these circumstances, and aims to provide a loading platform lifting device that can prevent damage to the oil tank and prevent oil from leaking from the oil tank to the outside when the lifting unit is inverted.

(1) The present invention relates to a loading platform lifting device for loading and unloading luggage onto a vehicle loading platform, the device comprising: a loading platform; a lifting unit having a hydraulic cylinder for lifting and lowering the loading platform between the floor surface of the loading platform and the ground; an oil tank for storing oil to be supplied to the hydraulic cylinder; and an inversion mechanism for inverting the lifting unit about a horizontal axis relative to the loading platform and positioning it on the loading platform, the hydraulic cylinder comprising a cylinder body, a piston provided within the cylinder body so as to be freely slidable in the axial direction, and a mesh formed within the cylinder body on one axial side of the piston. The loading platform lifting device has an in oil chamber and a sub-oil chamber formed in the cylinder body on the other axial side of the piston, and the oil tank has a first connection port and a second connection port, and is equipped with a supply oil passage connected to the first connection port of the oil tank for supplying oil from the oil tank to the main oil chamber of the hydraulic cylinder, a return oil passage connected to the second connection port of the oil tank for returning oil from the main oil chamber of the hydraulic cylinder to the oil tank, and a communication oil passage connecting the sub-oil chamber of the hydraulic cylinder and the return oil passage.

According to the present invention, when the lifting unit is reversed by the reversing mechanism, the oil in the oil tank flows back from the second connection port into the return oil passage, but this reversed oil flows from the return oil passage through the connecting oil passage into the sub-oil chamber of the hydraulic cylinder. This makes it possible to prevent oil in the oil tank from leaking out from the second connection port, even if the lifting unit is reversed by the reversing mechanism.

In addition, if a pressure difference occurs in the oil tank while the loading platform is being raised or lowered, the oil in the oil tank flows from the second connection port through the return oil passage and the connecting oil passage into the sub-oil chamber of the hydraulic cylinder, and the oil in the sub-oil chamber returns to the oil tank from the second connection port through the connecting oil passage and the return oil passage. This makes it possible to prevent the oil tank from being deformed and damaged due to the pressure difference.

(2) It is preferable that the loading platform lifting device of (1) above further includes an accumulator connected to at least one of the communication oil passage and the return oil passage for temporarily storing the oil flowing through the oil passage.
In this case, the oil flowing through the oil passage is temporarily stored in the accumulator, which further prevents the oil tank from being deformed and damaged.

The loading platform lifting device of the present invention can prevent damage to the oil tank and prevent oil from leaking from the oil tank to the outside when the lifting unit is inverted.

1 is a perspective view showing a rear part of a vehicle provided with a loading platform lifting device according to an embodiment of the present invention; FIG. FIG. 4 is an electrical and hydraulic circuit diagram of the lifting mechanism. 11A and 11B are side views showing states before and after inversion of the lifting unit. FIG. 5 is a view taken along the arrow I in FIG. 4 . FIG. 6 is a view taken along the arrow II in FIG. 5 . FIG. 6 is a plan view of the left portion of the lifting unit of FIG. 5 as viewed from above. FIG. 8 is a view taken along the line III in FIG. 7 .

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Fig. 1 is a perspective view showing the rear of a vehicle 1 equipped with a platform lifting device 10 according to an embodiment of the present invention. Fig. 2 is a side view of the platform lifting device 10. In the following description of this embodiment, directions such as "up", "down", "right", "left", "front", and "rear" refer to the directions shown in Fig. 1.

In Figures 1 and 2, the vehicle 1 of this embodiment is, for example, a truck, and includes a loading platform 2, a pair of side walls 3 provided on both the left and right sides of the loading platform 2, and a gate 4 provided at the rear end of the loading platform 2. The loading platform 2 has a floor surface 2a on which luggage is loaded. The space above the floor surface 2a of the loading platform 2 is used as a loading space for luggage.

The gate 4 is provided so as to be able to rotate up and down around an axis member 5 that extends in the left-right direction (vehicle width direction) at the rear end of the loading platform 2. The gate 4 can rotate up and down between an open position (position shown in FIG. 2) where it hangs down from the floor surface 2a of the loading platform 2, and a closed position (not shown) where it rises up from the floor surface 2a of the loading platform 2.

[Lifting unit]
The loading platform lifting device 10 is used when loading and unloading luggage from the rear of the loading platform 2 onto the floor surface 2a of the loading platform 2. The loading platform lifting device 10 is equipped with a vertical lifting unit 11. In the state shown in FIG. 1 , the lifting unit 11 in this embodiment is positioned offset to the left side at the rear of the loading platform 2. The lifting unit 11 has a pair of lifting pillars 12, a pair of inner columns 13, a pair of sliders 14, a loading platform 16, a cross member 19, a fastening mechanism 20, and a lifting mechanism 21.

The pair of lifting columns 12 are positioned at the rear of the platform 2 at a distance from each other in the left-right direction, and extend parallel to each other in the vertical direction. Each lifting column 12 is made of a hollow rectangular cylinder. A top plate 12a is fixed to the upper end of each lifting column 12, covering the upper end opening. A slit 12b extending in the vertical direction is formed in the rear wall of each lifting column 12.

An inner column 13 is provided inside each lifting support 12 so that it can rise and fall freely. Each inner column 13 is also made of a hollow rectangular cylinder that is long in the vertical direction. A slit 13b that extends in the vertical direction is formed in the rear wall of each inner column 13. A slider 14 is provided inside each inner column 13 so that it can rise and fall freely.

The rear of each slider 14 passes through each slit 13b, 12b of the inner column 13 and the lifting column 12, and protrudes behind the lifting column 12. Each slider 14 is guided by each slit 13b, 12b and can rise and fall relative to the lifting column 12 and the inner column 13. Each slider 14 is provided with a rotatable roller (not shown) that rolls along the inner surface of the inner column 13, allowing each slider 14 to rise and fall smoothly.

A bracket 15 is fixed to the rear lower end of each slider 14. A load receiving platform 16 is rotatably supported on each bracket 15. The load receiving platform 16 has a main plate 16a and a sub-plate 16b. The base end of the main plate 16a is supported on each bracket 15 so as to be rotatable up and down around a pin 17 that serves as a horizontal axis extending in the left-right direction. The base end of the sub-plate 16b is supported on the tip of the main plate 16a so as to be rotatable up and down via a hinge 18.

In the raised position described below, the load-receiving platform 16 can rotate up and down between an expanded position in which it is expanded horizontally relative to each lifting support 12 (position shown by the dashed line in FIG. 2) and an upright position in which it stands up along the rear wall of each lifting support 12 (position shown by the dashed line in FIG. 2). When the load-receiving platform 16 is in the expanded position, the main plate 16a and the sub-plate 16b extend horizontally behind each lifting support 12, and the surfaces (upper surfaces) of the main plate 16a and the sub-plate 16b form the load-receiving surface 16c on which the load is placed.

When the load-receiving platform 16 is in an upright position, the main plate 16a rotates upward and stands along the rear walls of the lifting columns 12, and the sub-plate 16b rotates downward toward the rear surface (lower surface) of the upright main plate 16a and is folded along said rear surface. This allows the load-receiving platform 16 to be compact in the upright position in the vertical direction.

The fastening mechanism 20 is a mechanism for fastening the load-receiving platform 16 to each lifting support 12 in an upright position. The fastening mechanism 20 has a pair of lock handles 20a provided on both the left and right sides of the main plate 16a, and a pair of hooks 20b fixed to the outer walls of each lifting support 12. Each lock handle 20a is provided rotatably and slidably in the left-right direction relative to the main plate 16a. A corresponding lock handle 20a is releasably engaged with each hook 20b. As shown in FIG. 2, when the load-receiving platform 16 is in an upright position, the load-receiving platform 16 is fastened in an upright position by rotating and sliding the lock handle 20a to engage with the hook 20b.

The cross member 19 is disposed between a pair of lifting columns 12, and almost the entire lower half of both lifting columns 12 is connected by the cross member 19. The cross member 19 is formed in a hollow rectangular box shape, and the internal space of the cross member 19 is connected to the internal space of each lifting column 12. In the state shown in FIG. 1, the upper surface 19a of the cross member 19 is disposed at approximately the same height as the floor surface 2a of the loading platform 2.

[Lifting mechanism]
The lifting mechanism 21 is a mechanism for raising and lowering the load receiving platform 16 in an unfolded position between the floor surface 2a of the platform 2 and the ground with respect to the pair of lifting columns 12. The lifting mechanism 21 includes a hydraulic cylinder 22, a power unit PU, and a fixed sheave, a movable sheave, and a wire (not shown). The fixed sheave, the movable sheave, and the wire are typical components of a vertical lifting mechanism, and therefore detailed description thereof will be omitted.

Figure 3 is an electrical and hydraulic circuit diagram of the lifting mechanism 21. In Figures 1 and 3, the hydraulic cylinder 22 is disposed on the upper side within the cross member 19 in the state shown in Figure 1. The hydraulic cylinder 22 has a cylinder body 22a, a piston 22b, and a rod 22c. The cylinder body 22a is disposed with its axial direction facing the left-right direction. The piston 22b is provided within the cylinder body 22a so as to be able to slide freely in the axial direction. One end of the rod 22c is fixed to the piston 22b within the cylinder body 22a. The other end of the rod 22c protrudes outside the cylinder body 22a and is connected to the movable sheave.

A main oil chamber 22d is defined on one axial side (right side in FIG. 3) of the piston 22b in the cylinder body 22a. A sub oil chamber 22e is defined on the other axial side (left side in FIG. 3) of the piston 22b in the cylinder body 22a. The hydraulic cylinder 22 extends when oil is supplied to the main oil chamber 22d, and contracts when oil is discharged from the main oil chamber 22d.

The power unit PU is disposed below the hydraulic cylinder 22 within the cross member 19. The power unit PU drives the hydraulic cylinder 22 to extend and retract. The power unit PU includes an electric motor 23, a hydraulic pump 24, an oil tank 25, and a valve block 26. These components 23 to 26 are unitized and arranged in a line from left to right in this order.

The electric motor 23 is a drive source that drives the hydraulic pump 24. The electric motor 23 is supplied with power from the battery 7 of the vehicle 1. The main switch S1, the control switch S2, and the contactor 8 are connected in this order from the battery 7 side to the electrical circuit that connects the electric motor 23 and the battery 7.

The main switch S1 is a switch that turns on and off the power supply to the power unit PU, and is provided in the driver's cab of the vehicle 1. The control switch S2 is a switch that controls the raising and lowering of the load receiving platform 16, and is provided, for example, on the right lifting support column 12 (see Figure 1). The control switch S2 has a first contact P1 that is electrically connected to the battery 7 when the load receiving platform 16 is raised, and a second contact P2 that is electrically connected to the battery 7 when the load receiving platform 16 is lowered.

The hydraulic pump 24 draws in and discharges oil from the oil tank 25. The oil tank 25 stores the oil to be supplied from the hydraulic pump 24 to the hydraulic cylinder 22. The oil tank 25 has a tank body 25a, a first connection port 25b formed on the side of the tank body 25a, and a second connection port 25c formed on the top surface of the tank body 25a.

The valve block 26 has a check valve 26a, a solenoid valve 26b, a flow control valve 26c, and a relief valve 26d. These valves 26a to 26d are integrated into a single block. Details of each of the valves 26a to 26d will be described later.

In FIG. 3, the hydraulic circuit between the hydraulic cylinder 22 and the oil tank 25 includes a supply oil passage 71, a return oil passage 72, a connecting oil passage 73, and a bypass oil passage 74, and these oil passages 71 to 74 form a closed circuit. One end of the supply oil passage 71 is connected to the first connection port 25b of the oil tank 25. The other end of the supply oil passage 71 is connected to the main oil chamber 22d of the hydraulic cylinder 22.

The hydraulic pump 24 and the check valve 26a are provided in the supply oil passage 71 as shown in the figure. The check valve 26a allows the flow of oil from the hydraulic pump 24 to the hydraulic cylinder 22 in the supply oil passage 71, and regulates the flow of oil from the hydraulic cylinder 22 to the hydraulic pump 24.

One end of a return oil passage 72 is connected to the intermediate portion 71a between the check valve 26a and the main oil chamber 22d in the supply oil passage 71. The other end of the return oil passage 72 is connected to the second connection port 25c of the oil tank 25. A solenoid valve 26b and a flow control valve 26c are provided in the return oil passage 72 as shown in the figure.

Solenoid valve 26b switches between a de-energized state (the state shown in FIG. 3) and an energized state. In the de-energized state, solenoid valve 26b blocks the flow of oil from supply oil passage 71 to the flow control valve 26c side of return oil passage 72, and allows oil to flow from the flow control valve 26c side to supply oil passage 71. In the energized state, solenoid valve 26b allows oil to flow from supply oil passage 71 to the flow control valve 26c side. Flow control valve 26c is configured to throttle the amount of oil returning from supply oil passage 71 through return oil passage 72 to oil tank 25.

One end of a communication oil passage 73 is connected to the intermediate portion 72a between the flow control valve 26c and the oil tank 25 in the return oil passage 72. The other end of the communication oil passage 73 is connected to the sub-oil chamber 22e of the hydraulic cylinder 22. As a result, the communication oil passage 73 communicates between the sub-oil chamber 22e of the hydraulic cylinder 22 and the return oil passage 72.

When the lifting unit 11 is inverted to the unused position (position shown by the solid line in FIG. 4) by the inversion mechanism 30 described later, the oil tank 25 is also inverted. As a result, the second connection port 25c of the oil tank 25 faces downward, and the oil in the oil tank 25 flows back from the second connection port 25c to the return oil passage 72. However, the oil that flows back into the return oil passage 72 flows from the midpoint 72a of the return oil passage 72 through the connecting oil passage 73 into the sub-oil chamber 22e of the hydraulic cylinder 22, so it does not leak to the outside.

When oil flows into the sub-oil chamber 22e of the hydraulic cylinder 22, the oil in the main oil chamber 22d of the hydraulic cylinder 22 flows out into the supply oil passage 71, causing the hydraulic cylinder 22 to contract. However, the check valve 26a and the de-energized solenoid valve 26b prevent the oil that has flowed out into the supply oil passage 71 from returning to the oil tank 25, so the hydraulic cylinder 22 does not contract.

An accumulator 28 is connected to the communicating oil passage 73. The accumulator 28 temporarily stores the oil flowing through the communicating oil passage 73, and is disposed inside the cross member 19 (see FIG. 1). Note that the accumulator 28 is not shown in FIG. 1. The accumulator 28 has a gas chamber 28a in which gas is sealed, and an oil chamber 28b into which the oil in the communicating oil passage 73 flows. The gas chamber 28a and the oil chamber 28b are configured so that when the volume of one of the chambers increases, the volume of the other chamber decreases.

When the oil pressure in oil chamber 28b becomes higher than the gas pressure in gas chamber 28a, the volume of gas chamber 28a decreases and the volume of oil chamber 28b increases. As a result, oil is sucked into oil chamber 28b from communicating oil passage 73 and temporarily stored in oil chamber 28b. Conversely, when the oil pressure in oil chamber 28b becomes lower than the gas pressure in gas chamber 28a, the volume of gas chamber 28a increases and the volume of oil chamber 28b decreases. As a result, the oil in oil chamber 28b is released into communicating oil passage 73.

One end of a bypass oil passage 74 is connected to an intermediate portion 71b in the supply oil passage 71 between the hydraulic pump 24 and the check valve 26a. The other end of the bypass oil passage 74 is connected to another intermediate portion 72b in the return oil passage 72 between the intermediate portion 72a and the oil tank 25. A relief valve 26d is provided in the bypass oil passage 74.

The relief valve 26d opens when the hydraulic pressure of the oil discharged from the hydraulic pump 24 reaches a set pressure, allowing oil to flow from the intermediate portion 71b of the supply oil passage 71 to the second connection port 25c of the oil tank 25. The set pressure of the relief valve 26d is set to a pressure equal to or higher than the hydraulic pressure required for the extension operation of the hydraulic cylinder 22.

When raising the load receiving platform 16 in the deployed position, the operator turns on the main switch S1 and then raises the control switch S2. This electrically connects the first contact P1 to the battery 7 and turns the contact of the contactor 8 ON, causing the electric motor 23 to rotate. When the electric motor 23 rotates, the hydraulic pump 24 is driven, and the oil in the oil tank 25 is sucked up from the first connection port 25b to the supply oil passage 71 and supplied to the main oil chamber 22d of the hydraulic cylinder 22 via the check valve 26a.

This causes the hydraulic cylinder 22 to extend, and the slider 14 rises along the inner column 13 and the lifting column 12 via the wires wound around the fixed sheave and the movable sheave, and the loading platform 16 rises. At that time, if the oil pressure of the oil discharged from the hydraulic pump 24 exceeds the set pressure, the relief valve 26d opens, and the oil discharged from the hydraulic pump 24 passes through the bypass oil passage 74 and is returned to the oil tank 25 from the second connection port 25c.

When the load-receiving platform 16 in the deployed position is lowered, the operator operates the control switch S2 to lower, electrically connecting the second contact P2 to the battery 7. This switches the solenoid valve 26b to an excited state, allowing oil to flow from the supply oil passage 71 to the return oil passage 72. At that time, the contact of the contactor 8 is OFF, so the electric motor 23 does not rotate and the hydraulic pump 24 does not operate.

When this state is reached, the oil in the main oil chamber 22d of the hydraulic cylinder 22 passes through a portion of the supply oil passage 71 (between the main oil chamber 22d and the intermediate portion 71a) and the return oil passage 72, and is returned to the oil tank 25 from the second connection port 25c. This causes the hydraulic cylinder 22 to contract, and the loading platform 16 descends under its own weight. At that time, the flow control valve 26c throttles the amount of oil returned to the oil tank 25, allowing the loading platform 16 to descend slowly.

As described above, the lifting mechanism 21 can raise and lower the load receiving platform 16 in the deployed posture between the raised position (position shown by the dashed line in FIG. 2) and the lowered position (position shown by the solid line in FIG. 2). When the load receiving platform 16 is in the raised position, the load receiving surface 16c of the load receiving platform 16 is at the same height as the upper surface 19a of the cross member 19. When the load receiving platform 16 is in the lowered position, the load receiving platform 16 is in contact with the ground.

[Reversal mechanism]
Fig. 4 is a side view showing the state of the lifting unit 11 before and after reversal. Fig. 5 is a view seen from the arrow I in Fig. 4. Fig. 6 is a view seen from the arrow II in Fig. 5. In Figs. 4 to 6, the loading platform lifting device 10 further includes a reversing mechanism 30 that reverses the lifting unit 11 in which the loading platform 16 is in an upright position. Note that the reversing mechanism 30 and a swivel mechanism 50 (described later) are not shown in Fig. 1. The reversing mechanism 30 includes a pair of reversing support parts 31, a pair of reversing arms 33, and a reversing drive part 34.

The pair of reversing support parts 31 support each of the pair of lifting columns 12 of the lifting unit 11 so that they can be reversed relative to the loading platform 2. The pair of reversing support parts 31 are arranged at the rear end of the floor surface 2a of the loading platform 2, spaced apart from each other in the left-right direction and positioned corresponding to the pair of lifting columns 12. Each reversing support part 31 has a bottom plate 311, a reinforcing plate 312, a pair of support plates 313, and a pair of reversing shafts 314. The lower surface of the bottom plate 311 is placed on the floor surface 2a of the loading platform 2.

The reinforcing plate 312 is made of an L-shaped plate member in a side view, and has a horizontal plate portion 312a extending horizontally and a vertical plate portion 312b extending vertically. The horizontal plate portion 312a is fixed to the upper surface of the bottom plate 311 by welding or the like. The vertical plate portion 312b extends upward from the rear end of the horizontal plate portion 312a. The pair of support plates 313 are each made of a plate member formed into an approximately triangular shape. The pair of support plates 313 are fixed to the upper surface of the horizontal plate portion 312a and the front surface of the vertical plate portion 312b of the reinforcing plate 312 by welding or the like, with a gap between them in the left-right direction. The horizontal plate portions 312a of each inverted support portion 31 are connected to each other by a connecting plate 32 (see FIG. 5). The upper surface 32a of the connecting plate 32 is located at the same height as the upper surface 19a of the cross member 19.

The pair of support plates 313 of each inversion support section 31 supports an inversion shaft 314 so that the inversion shaft 314 can rotate around a horizontal axis C extending in the left-right direction. In addition, an inversion arm 33 is disposed between the pair of support plates 313 of each inversion support section 31. The inversion arm 33 is made of, for example, a channel material, and one end of the inversion arm 33 is fixed to the inversion shaft 314. As a result, the inversion arm 33 is supported so as to be rotatable relative to the inversion support section 31, and rotates together with the inversion shaft 314.

The other end of the inversion arm 33 is fixed to each lifting column 12 of the lifting unit 11. In this embodiment, when each lifting column 12 is in the position shown by the dashed line in FIG. 4, the other end of the inversion arm 33 is fixed to the upper and front part of each lifting column 12.

With the above configuration, the pair of lifting columns 12 can be rotated up and down by rotating each inversion arm 33 around the horizontal axis C relative to the pair of inversion support parts 31. As a result, the upper part of each lifting column 12, which is in the position shown by the dashed line in FIG. 4, is supported by the inversion support parts 31 so that it can be inverted relative to the loading platform 2. Therefore, the lifting unit 11, with the loading platform 16 in an upright position, can be inverted by the inversion mechanism 30 between a use position (position shown by the dashed line in FIG. 4) and a non-use position (position shown by the solid line in FIG. 4) relative to the loading platform 2.

When the lifting unit 11 is inverted by the reversing mechanism 30, the pair of lifting columns 12 of the lifting unit 11 are inverted while being supported by the inversion support parts 31 installed on the loading platform 2 via the inversion arms 33. Therefore, the inversion mechanism 30 of this embodiment can invert the lifting unit 11 between the use position and the non-use position while supporting each lifting column 12 with respect to the loading platform 2.

In the use position, the lifting unit 11 is in a state where it protrudes rearward (in one direction) outside the loading platform 2 and below the loading platform 2. In this state, by putting the loading platform 16 into an unfolded position, the loading platform 16 can be raised and lowered between the raised and lowered positions. In the non-use position, the lifting unit 11 is positioned on the loading platform 2 above the height of the floor surface 2a of the loading platform 2, and the pair of lifting columns 12 are positioned along the left-right direction (a direction perpendicular to the horizontal direction in the one direction). In this state, the loading platform 16 is positioned on the loading platform 2, so it cannot be raised and lowered between the raised and lowered positions.

When the lifting unit 11 is in the use position, both ends of an abutment plate 29 extending in the left-right direction are fixed to the front walls of the pair of lifting columns 12. When the lifting unit 11 is flipped from the non-use position to the use position, the abutment plate 29 abuts against the gate 4 in the open position, thereby preventing the lifting unit 11 from flipping beyond the use position.

In Figures 5 and 6, the inversion drive unit 34 is arranged on the right side of the lifting unit 11 and performs an inversion operation with less effort. The inversion drive unit 34 includes a driven sprocket 35, a driving sprocket 36, a chain 37, a reducer 38, and an operation unit 39.

The driven sprocket 35 is disposed close to the right side of the reversing support 31. The center of the driven sprocket 35 is connected to the right end of the reversing shaft 314 so as to rotate together with it. The driving sprocket 36 is disposed further forward of the driven sprocket 35 on the vehicle 1. The outer diameter of the driving sprocket 36 is smaller than the outer diameter of the driven sprocket 35. The center of the driving sprocket 36 is connected to the output shaft 38b of the reducer 38 so as to rotate together with it. The chain 37 is formed endlessly and is stretched between the driven sprocket 35 and the driving sprocket 36.

The reducer 38 is installed on the upper surface of a base plate 315 fixed to the outer surface of the support plate 313 of the inversion support part 31. The reducer 38 is, for example, a worm reducer equipped with a worm gear (not shown). The input shaft 38a of the reducer 38 extends forward. The input shaft 38a of the reducer 38 is connected to an operating part 39. The operating part 39 has a lever 39a connected at one end to the input shaft 38a of the reducer 38, and a handle 39b provided at the other end of the lever 39a.

When an operator grips the handle 39b and rotates the operating part 39 so that the lever 39a rotates around the input shaft 38a of the reducer 38, the rotational torque is increased by the reducer 38, and the driving sprocket 36 rotates via the output shaft 38b of the reducer 38. When the driving sprocket 36 rotates, the reversing shaft 314 rotates together with the driven sprocket 35 via the chain 37. This allows the operator to perform the reversing operation of the lifting unit 11 with little effort using the reversing drive part 34.

[Rotation mechanism]
Fig. 7 is a plan view of the left side portion of the lifting unit 11 of Fig. 5 as seen from above. Fig. 8 is a view as seen from the arrow III of Fig. 7. In Figs. 5, 7 and 8, the loading platform lifting device 10 further includes a turning mechanism 50 for turning the lifting unit 11, with the loading platform 16 in the upright position, on the loading platform 2.

The swivel mechanism 50 of this embodiment swivels the lifting unit 11, with the load receiving platform 16 in an upright position, relative to the loading platform 2, within a range of 90° between the unused position (position shown by the solid line in FIG. 7) and the stored position (position shown by the dashed line in FIG. 7). The swivel mechanism 50 includes a swivel support part 51 and a swivel arm part 52.

The swivel support 51 supports the lifting unit 11 so that it can rotate horizontally, and is provided on the floor surface 2a of the loading platform 2 on one side (left side) of the pair of lifting columns 12. The swivel support 51 has a fixed plate 511, a fixed shaft 512, and a rotating cylinder 513. The fixed plate 511 is disposed between the left side wall 3 and the left inversion support part 31 on the floor surface 2a of the loading platform 2, close to the bottom plate 311 of the inversion support part 31. The fixed plate 511 is fixed to the floor surface 2a by a bolt 514 with its lower surface placed on the floor surface 2a. The fixed shaft 512 is fixed so as to protrude upward from the upper surface of the fixed plate 511. The rotating cylinder 513 is made of a cylindrical member. The rotating cylinder 513 is fitted on the outer periphery of the fixed shaft 512 and is supported rotatably around its vertical axis X with respect to the fixed shaft 512.

The swivel arm section 52 connects the swivel support section 51 and the lifting unit 11. The swivel arm section 52 has a tube arm 521 and an axis arm 522. The tube arm 521 is made of a cylindrical member. One axial end of the tube arm 521 (the left end in FIG. 5) is fixed to the outer circumferential surface of the rotating tube 513 of the swivel support section 51.

The shaft arm 522 is made of a cylindrical member. One axial end (right end in FIG. 5) of the shaft arm 522 is fixed to the outer surface of the left support plate 313 of the inverted support part 31. The other axial end (left end in FIG. 5) of the shaft arm 522 is inserted into the cylindrical arm 521 and fixed to the cylindrical arm 521 by a bolt 523. Therefore, the swivel arm part 52, together with the left inverted support part 31, can rotate horizontally around the vertical axis X relative to the swivel support part 51.

With the above configuration, when the swivel arm 52 rotates horizontally relative to the swivel support 51, the lifting unit 11 and the inversion support parts 31 on both the left and right sides rotate horizontally around the vertical axis X. As a result, the lifting unit 11, with the load-receiving platform 16 in an upright position, can be rotated horizontally on the load platform 2 between an unused position and a stored position by the swivel mechanism 50.

In the unused position, as described above, the lifting unit 11 is disposed on the loading platform 2, and the pair of lifting columns 12 are disposed along the left-right direction. In the stored position, the lifting unit 11 is disposed on the loading platform 2, and the pair of lifting columns 12 are disposed along the front-rear direction (one direction). In this embodiment, in the stored position, the pair of lifting columns 12 are disposed near the left side wall 3 and along said side wall 3. The vehicle 1 travels with the lifting unit 11 in the stored position.

Although not shown, the load-receiving platform lifting device 10 further includes a rotation restriction structure and a rotation fixing structure. The rotation restriction structure restricts the lifting unit 11, which rotates horizontally from the storage position to the unused position by the rotation mechanism 50, from rotating horizontally beyond the unused position. The rotation fixing structure disables the horizontal rotation of the lifting unit 11 by the rotation mechanism 50 when the lifting unit 11 is in the unused position or the storage position.

[Effects of this embodiment]
According to the load receiving platform lifting device 10 of this embodiment, when the load receiving platform 16 of the lifting unit 11 is not in use, the lifting unit 11 can be reversed by the reversing mechanism 30 from the use position to the unused position on the load receiving platform 2 with the load receiving platform 16 in an upright position along the pair of lifting columns 12. As a result, the lifting columns 12 and the load receiving platform 16 of the lifting unit 11 are disposed above the height of the floor surface 2a of the load receiving platform 2, so that damage to the lifting columns 12 and the load receiving platform 16 can be suppressed when the load receiving platform 16 is not in use.

In addition, the lifting unit 11, which is in the unused position, can be rotated to the storage position by the rotation mechanism 50. When the lifting unit 11 is in the storage position, the pair of lifting columns 12 are arranged in the front-rear direction along the side wall 3. As a result, when loading and unloading luggage manually from the rear of the loading platform 2, the loading platform 16 in an upright position is not positioned so as to cover the luggage loading space on the loading platform 2 from the rear. As a result, loading and unloading can be performed manually without horizontally expanding the loading platform 16, so that the loading and unloading can be performed efficiently.

The reversing mechanism 30 and the turning mechanism 50 are configured to move the lifting unit 11 while supporting each lifting support 12 with respect to the loading platform 2 by a pair of reversing supports 31. As a result, when the lifting unit 11 is turned over and turned by the reversing mechanism 30 and the turning mechanism 50, each lifting support 12 is supported with respect to the loading platform 2, so that the lifting unit 11 can be moved in a stable state.

In addition, when the lifting unit 11 is reversed to the unused position by the reversing mechanism 30, the oil in the oil tank 25 flows back from the second connection port 25c to the return oil passage 72. However, the oil that flows back into the return oil passage 72 flows into the sub-oil chamber 22e of the hydraulic cylinder 22 via the communicating oil passage 73. This makes it possible to prevent the oil in the oil tank 25 from leaking to the outside from the second connection port 25c even if the lifting unit 11 is reversed by the reversing mechanism 30.

In addition, when the loading platform 16 is rising or falling, a pressure difference occurs in the oil tank 25 due to the expansion and contraction of the hydraulic cylinder 22. At that time, when the pressure in the oil tank 25 increases, the oil in the oil tank 25 flows from the second connection port 25c through the return oil passage 72 and the communicating oil passage 73 into the sub-oil chamber 22e of the hydraulic cylinder 22. In addition, when the pressure in the oil tank 25 decreases, the oil in the sub-oil chamber 22e of the hydraulic cylinder 22 returns to the oil tank 25 from the second connection port 25c through the communicating oil passage 73 and the return oil passage 72. This makes it possible to prevent the oil tank 25 from being deformed and damaged due to the pressure difference.

In addition, the oil flowing through the communicating oil passage 73 is temporarily stored in the accumulator 28, which further prevents the oil tank 25 from deforming and becoming damaged.

[others]
The loading platform lifting device 10 of this embodiment is provided at the rear of the loading platform 2 so that luggage can be loaded and unloaded from the rear of the loading platform 2, but may be provided at the left or right side of the loading platform 2 so that luggage can be loaded and unloaded from the side of the loading platform 2. The loading platform lifting device of the present invention is not limited to a vertical lifting type, but may be an arm type that lifts and lowers the loading platform by a parallel link mechanism.

In this embodiment, the accumulator 28 is provided in the communicating oil passage 73, but in addition to this or instead, it may be provided in the return oil passage 72. For example, the accumulator 28 may be provided between the flow control valve 26c and the second connection port 25c in the return oil passage 72. In addition, although the loading platform lifting device 10 is provided with the accumulator 28, it is not necessary to provide the accumulator 28.

The cargo receiving platform 16 is configured so that the sub-plate 16b folds onto the back side of the main plate 16a, but it may also be configured so that the sub-plate 16b folds onto the front side (the cargo receiving surface 16a) of the main plate 16a.

The lifting unit 11 in the unused position is disposed on the platform 2, but may be disposed behind the platform 2 as long as it is disposed above the height of the floor surface 2a of the platform 2. That is, the reversing mechanism 30 may be configured to move the lifting unit 11 between the used position and the unused position while it is protruding behind the platform 2. In addition, the reversing drive unit 34 of the reversing mechanism 30 is not limited to this embodiment. For example, the reversing drive unit 34 may include an actuator such as an electric motor that rotates the reversing shaft 314.

The inversion mechanism 30 inverts the lifting unit 11 while supporting a pair of lifting columns 12, but the lifting unit 11 may be inverted without supporting one or both of the pair of lifting columns 12. Similarly, the rotation mechanism 50 rotates the lifting unit 11 while supporting a pair of lifting columns 12, but the lifting unit 11 may be rotated without supporting one or both of the pair of lifting columns 12.

The swivel mechanism 50 is not limited to a swivel mechanism that rotates the lifting unit 11 horizontally. For example, the swivel mechanism 50 may slide the lifting unit 11, which is in an unused position, forward on the platform 2, and then rotate the lifting unit 11 90° around a vertical axis provided in the center of the lifting unit 11 in the left-right direction. In addition, the platform lifting device 10 does not need to be equipped with a swivel mechanism 50.

It should be noted that the embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims, not by the meaning described above, and is intended to include all modifications within the scope of the claims and meanings equivalent thereto.

REFERENCE SIGNS LIST 1 vehicle 2 loading platform 2a floor surface 6 fixing hole 10 loading platform lifting device 11 lifting unit 16 loading platform 22 hydraulic cylinder 22a cylinder body 22b piston 22d main oil chamber 22e sub oil chamber 25 oil tank 25b first connection port 25c second connection port 28 accumulator 30 reversing mechanism 71 supply oil passage 72 return oil passage 73 communicating oil passage C horizontal axis

Claims (2)

A loading platform lifting device for loading and unloading luggage on a loading platform of a vehicle,
a lifting unit including a load receiving platform, a hydraulic cylinder for lifting and lowering the load receiving platform between a floor surface of the load receiving platform and the ground, and an oil tank for storing oil to be supplied to the hydraulic cylinder;
an inversion mechanism for inverting the lifting unit about a horizontal axis relative to the platform to position the lifting unit above the floor level of the platform;
The hydraulic cylinder includes a cylinder body, a piston provided within the cylinder body so as to be slidable in the axial direction, a main oil chamber formed within the cylinder body on one axial side of the piston, and a sub-oil chamber formed within the cylinder body on the other axial side of the piston,
The oil tank has a first connection port and a second connection port,
a supply oil passage connected to the first connection port of the oil tank for supplying oil from the oil tank to the main oil chamber of the hydraulic cylinder;
a return oil passage connected to the second connection port of the oil tank for returning oil from the main oil chamber of the hydraulic cylinder to the oil tank;
A loading platform lifting device comprising: a communicating oil passage that connects the sub-oil chamber of the hydraulic cylinder with the return oil passage. The loading platform lifting device according to claim 1, further comprising an accumulator connected to at least one of the communication oil passage and the return oil passage, for temporarily storing the oil flowing through the oil passage.

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