Loading platform lifting device

Abstract

To inhibit a loading platform from being moved up or down when a lifting unit is in a position other than a use position in a loading platform lifting device which enables inversion of the lifting unit.SOLUTION: A loading platform lifting device 10 is used to load / unload cargo to / from a loading space 2 of a vehicle 1 and includes: a lifting unit 11 having a pair of lifting pillars 12, a loading platform 16 which may move up or down relative to the pair of lifting pillars 12, and drive means 22 for moving up or down the loading platform 16; an inversion mechanism 30 which inverts the lifting unit 11 between a use position and a non-use position; detecting means 70 which changes between a detection state and a non-detection state according to a position of the lifting unit 11; and a control unit 80 which controls whether or not the drive means 22 can be driven based on a state change of the detecting means 70.SELECTED DRAWING: Figure 12

Description

Technical Field

[0001] The present invention relates to a load receiving platform lifting device.

Background Art

[0002] As a load receiving platform lifting device that is mounted on a freight vehicle or the like and used for loading and unloading cargo, there is one described in Patent Document 1, for example. The load receiving platform lifting device of Patent Document 1 is of a vertical lifting type, and includes a pair of left and right lifting columns (outer columns) fixed to the rear end of the cargo bed of a freight vehicle, a load receiving platform provided to be liftable relative to these lifting columns, and a hydraulic cylinder that drives the load receiving platform to lift and lower. By expanding and contracting the hydraulic cylinder, the load receiving platform, in a horizontally deployed state, can be lifted and lowered between a lowered position where it contacts the ground and a raised position where it is at the same height as the floor surface of the cargo bed. When the load receiving platform is not in use, by rotating the load receiving platform upward from the raised position, the load receiving platform is stood and stored along the rear surface of each lifting column.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the above vertical lifting type load receiving platform lifting device, when the load receiving platform is not in use, the pair of lifting columns and the stood and stored load receiving platform are in a state of protruding downward from the cargo bed. If the freight vehicle travels in this state, there is a risk that the lifting columns and the load receiving platform may be damaged. Therefore, in order to suppress damage to the lifting columns and the like, it has been studied to support a lifting unit including the lifting columns, the load receiving platform, and the hydraulic cylinder so as to be reversible around a horizontal axis relative to the cargo bed between a use position and a non-use position.

[0005] In its operational position, the lifting unit extends below the cargo bed, allowing the loading platform to be raised and lowered. When the lifting unit is reversed from its operational position to its non-operational position, it is positioned above the height of the cargo bed floor. Driving the truck in this position helps prevent damage to the lifting support columns and loading platform. However, if the hydraulic cylinder is activated due to misoperation or other reasons while the lifting unit is in a position other than its operational position, the loading platform may be raised or lowered.

[0006] This invention has been made in view of these circumstances, and aims to provide a loading platform lifting device in which the lifting unit is reversible, which can prevent the loading platform from moving up or down when the lifting unit is in a position other than the position of use. [Means for solving the problem]

[0007] (1) The present invention relates to a lifting and lowering device for loading and unloading cargo onto the cargo bed of a vehicle, comprising: a lifting unit having a pair of lifting support columns; a cargo bed that is movable up and down in a horizontally extended state relative to the pair of lifting support columns and is also movable upright along the pair of lifting support columns; and a driving means for moving the horizontally extended cargo bed up and down between the floor surface of the cargo bed and the ground; a reversing mechanism for reversing the lifting unit, with the cargo bed in an upright state, around a horizontal axis relative to the cargo bed and positioning it on the cargo bed between a use position in which the lifting unit extends below the cargo bed and the cargo bed is movable up and down, and a non-use position in which the lifting unit is positioned above the height of the floor surface of the cargo bed; a detection means that changes between a detected state and a non-detected state depending on the position of the lifting unit; and a control unit that controls whether or not the driving means can be driven based on the state change of the detection means.

[0008] According to the present invention, for example, when the lifting unit reverses from the usage position to the non-usage position, the detection means is changed to a detected state or a non-detected state, and the control unit can control the driving of the drive means to restrict the driving based on this state change. By controlling in this way, the load receiving platform can be prevented from moving up or down when the lifting unit is in a position other than the usage position.

[0009] (2) In the loading platform lifting device described in (1) above, the detection means has a first detection unit which changes to one of a detection state and a non-detection state when the lifting unit is reversed to the unused position, and the control unit preferably restricts the driving of the driving means when the first detection unit changes to the first state. In this case, when the lifting unit reverses to the unused position and the first detection unit changes to the first state, the control unit restricts the driving of the drive means. This effectively prevents the load receiving platform from moving up or down when the lifting unit is in the unused position.

[0010] (3) In the loading platform lifting device described in (2) above, the detection means has a second detection unit which changes to one of a detection state and a non-detection state when the lifting unit is reversed to the usage position, and the control unit preferably allows the driving means to be driven when the second detection unit changes to the second state. In this case, when the lifting unit is reversed to the usage position and the second detection unit changes to the second state, the control unit allows the drive means to be driven. As a result, when the lifting unit is reversed from the unused position to the usage position, the loading platform automatically becomes ready for lifting and lowering, allowing for quick loading and unloading of goods.

[0011] (4) In the loading platform lifting device described in (3) above, the first detection unit and the second detection unit are composed of a single sensor, and the sensor changes to one of the detection state and non-detection state (the first state) when the lifting unit is reversed to the unused position, and changes to the other of the detection state and non-detection state (the second state) when the lifting unit is reversed to the usage position, and it is preferable that the control unit restricts the driving of the driving means when the sensor changes to one of the states, and allows the driving of the driving means when the sensor changes to the other state. In this case, since the first detection unit and the second detection unit are composed of a single sensor, the configuration of the loading platform lifting device can be simplified.

[0012] (5) The loading platform lifting device described in (4) above is provided so as to be able to swing by its own weight between a first swing position and a second swing position with respect to the lifting support column, and further comprises a swinging part which swings to the first swing position when the lifting unit is reversed to the unused position, and swings to the second swing position when the lifting unit is reversed to the used position, and preferably the sensor is provided on the lifting support column, and changes to one state when the swinging part swings to the first swing position, and changes to the other state when the swinging part swings to the second swing position. In this case, when the lifting unit reverses between the unused position and the used position, the swinging part swings between the first swinging position and the second swinging position due to its own weight relative to the lifting column, thereby changing the sensor mounted on the lifting column between a detected state and a non-detected state. As a result, both the sensor and the swinging part can be mounted on the same member (lifting column), making it easy to align the sensor and the swinging part. Consequently, the detection accuracy of the sensor can be improved.

[0013] (6) In the loading platform lifting device described in (5) above, the swinging part has a dog for changing the sensor between a detected state and a non-detection state, and a safety bar provided integrally with the dog, which can contact a portion of the load on the loading platform when the loading platform is rising with the lifting unit in the operating position and the portion of the load on the loading platform protrudes toward the loading platform side, and it is preferable that the dog swings toward the first swinging position together with the safety bar by the portion of the dog contacting the safety bar. In this case, if a portion of the load on the loading platform that protrudes towards the platform comes into contact with the safety bar while the loading platform is rising, the dog swings to the first swinging position, and the sensor changes to one of the aforementioned states. As a result, the control unit restricts the driving of the drive means, and the raising of the loading platform stops. Consequently, damage to the load due to being caught between the loading platform and the platform can be prevented. Furthermore, since the sensor that changes between a detected state and a non-detected state depending on the position of the lifting unit also serves as the sensor that detects when a portion of the load comes into contact with the safety bar, the configuration of the loading platform lifting device can be further simplified.

[0014] (7) In the loading platform lifting device described in (4) above, it is preferable that the sensor changes to one of the states immediately after the lifting unit is reversed from the usage position toward the non-use position. In this case, immediately after the lifting unit reverses from the usage position to the non-usage position, the sensor changes to one of the aforementioned states, causing the control unit to restrict the driving of the drive means. This effectively prevents the loading platform from moving up or down when the lifting unit is in a position other than the usage position (including the position during the reversal). [Effects of the Invention]

[0015] According to the present invention, in a load-receiving platform lifting device in which the lifting unit is reversible, it is possible to suppress the lifting of the load-receiving platform when the lifting unit is in a position other than the operating position. [Brief explanation of the drawing]

[0016] [Figure 1] It is a perspective view showing a rear part of a vehicle provided with a cargo receiving platform lifting device according to an embodiment of the present invention. [Figure 2] It is a side view of the cargo receiving platform lifting device. [Figure 3] It is a side view showing states of a lifting unit before and after reversal. [Figure 4] It is a view seen from arrow I in FIG. 3. [Figure 5] It is a view seen from arrow II in FIG. 4. [Figure 6] It is a top plan view of a left side portion of the lifting unit in FIG. 4 viewed from above. [Figure 7] It is a view seen from arrow III in FIG. 6. [Figure 8] It is a front view of section IV in FIG. 1 viewed from the rear side. [Figure 9] It is a sectional view taken along arrow V-V in FIG. 8. [Figure 10] It is a sectional view showing a state where the sensor changes to a non-detection state when the cargo receiving platform is lifted while the lifting unit is in a use position. [Figure 11] It is a sectional view showing a state where the sensor changes to the non-detection state when the lifting unit is reversed to a non-use position. [Figure 12] It is a block diagram showing a control configuration of the cargo receiving platform lifting device. [Figure 13] It is a side view of a cargo receiving platform lifting device according to a second embodiment. [Figure 14] It is a block diagram showing a control configuration of the cargo receiving platform lifting device according to the second embodiment. [Figure 15] It is a view corresponding to FIG. 5 of a cargo receiving platform lifting device according to a third embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] Figure 1 is a perspective view showing the rear of a vehicle 1 equipped with a loading platform lifting device 10 according to the first embodiment. Figure 2 is a side view of the loading 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 Figure 1.

[0018] In Figures 1 and 2, the vehicle 1 of this embodiment is, for example, a cargo truck, and comprises a cargo bed 2, a pair of side walls 3 provided on both the left and right sides of the cargo bed 2, and a tailgate 4 provided at the rear end of the cargo bed 2. The cargo bed 2 has a floor surface 2a on which cargo is loaded. The area above the floor surface 2a of the cargo bed 2 is designated as a cargo loading space.

[0019] The tailgate 4 is provided at the rear end of the cargo bed 2 so as to be able to rotate up and down around a shaft member 5 that extends in the left-right direction (vehicle width direction). The tailgate 4 is able to rotate up and down between an open position (position shown in Figure 2) in which it hangs down from the floor surface 2a of the cargo bed 2, and a closed position (not shown) in which it rises up from the floor surface 2a of the cargo bed 2.

[0020] <Lifting Unit> The loading platform lifting device 10 is used when loading and unloading cargo from the rear of the loading platform 2 to 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 Figure 1, the lifting unit 11 of this embodiment is positioned off-center to the left at the rear of the loading platform 2. The lifting unit 11 includes a pair of lifting support columns 12, a pair of inner columns 13, a pair of sliders 14, a loading platform 16, a cross member 19, a securing mechanism 20, and a lifting mechanism 21.

[0021] A pair of lifting support columns 12 are positioned at the rear of the cargo bed 2, spaced apart from each other in the left-right direction, and extending parallel to each other in the vertical direction. Each lifting support column 12 is made of a hollow rectangular tube. A top plate 12a is fixed to the upper end of each lifting support column 12, covering its upper end opening. A slit 12b extending in the vertical direction is formed in the rear wall of each lifting support column 12.

[0022] An inner column 13 is provided inside each lifting support column 12 so as to be able to move up and down. Each inner column 13 is also made of a hollow rectangular tube that is long in the vertical direction. A slit 13b extending 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 as to be able to move up and down.

[0023] The rear of each slider 14 passes through the slits 13b and 12b of the inner column 13 and the lifting support column 12, respectively, and protrudes to the rear of the lifting support column 12. Each slider 14 is guided by the slits 13b and 12b and can move up and down relative to the lifting support column 12 and the inner column 13, respectively. Each slider 14 is rotatably provided with a roller (not shown) that rolls along the inner surface of the inner column 13, and this roller allows each slider 14 to move up and down smoothly.

[0024] A bracket 15 is fixed to the lower rear end of each slider 14. A loading platform 16 is rotatably supported on each bracket 15. The loading platform 16 has a main plate 16a and a sub-plate 16b. The base end of the main plate 16a is supported so as to be able to rotate up and down around a pin 17 that serves as a horizontal axis extending in the left-right direction relative to each bracket 15. The base end of the sub-plate 16b is supported so as to be able to rotate up and down relative to the front end of the main plate 16a via a hinge 18.

[0025] The loading platform 16 is vertically rotatable between a deployed position (shown by the dashed line in Figure 2) where it is horizontally deployed relative to each lifting support 12 in the raised position described later, and an upright position (shown by the double dashed line in Figure 2) where it is erected along the rear wall of each lifting support 12. When the loading platform 16 is in the deployed position, the main plate 16a and the sub-plate 16b extend horizontally behind each lifting support 12, and the respective surfaces (top surfaces) of the main plate 16a and the sub-plate 16b serve as loading surfaces 16c on which cargo is placed.

[0026] When the loading platform 16 is in an upright position, the main plate 16a rotates upward and stands upright along the rear wall of each lifting support column 12, and the sub-plate 16b rotates downward to the back (bottom) side of the upright main plate 16a and folds up along that back side. As a result, the loading platform 16 becomes compact in the vertical direction when in an upright position.

[0027] The securing mechanism 20 is a mechanism for securing the loading platform 16 to each of the lifting support columns 12 in an upright position. The securing 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 wall of each of the lifting support columns 12. Each lock handle 20a is provided so as to be rotatable and slidable in the left and right directions relative to the main plate 16a. A corresponding lock handle 20a is engaged with each hook 20b in a detachable manner. As shown in Figure 2, when the loading platform 16 is in an upright position, the loading platform 16 is secured in an upright position by rotating and sliding the lock handles 20a to engage with the hooks 20b.

[0028] The cross member 19 is positioned between a pair of lifting columns 12, and the cross member 19 connects almost the entire lower half of both lifting columns 12. The cross member 19 is formed in the shape of a hollow rectangular box, and the internal space of the cross member 19 is in communication with the internal space of each lifting column 12. In the state shown in Figure 1, the upper surface 19a of the cross member 19 is positioned at approximately the same height as the floor surface 2a of the loading platform 2.

[0029] The lifting mechanism 21 is a mechanism that raises and lowers the unfolded loading platform 16 between the floor surface 2a of the loading platform 2 and the ground using a pair of lifting support columns 12. The lifting mechanism 21 comprises a drive means 22 located within the cross member 19, a control switch 27 provided on the lifting support columns 12, and fixed sheaves, movable sheaves, and wires (not shown in the figure). The control switch 27 is a switch that operates the raising and lowering of the loading platform 16. The fixed sheaves, movable sheaves, and wires are a common configuration in vertical lifting mechanisms, so a detailed explanation is omitted.

[0030] The drive mechanism 22 includes an electric motor 23, a hydraulic pump 24, an oil tank 25, and a hydraulic cylinder 26. The electric motor 23 is powered by the battery (not shown) of the vehicle 1, which operates the hydraulic pump 24. The hydraulic pump 24 draws in and discharges oil from the oil tank 25. The oil tank 25 stores the oil that is supplied from the hydraulic pump 24 to the hydraulic cylinder 26. The hydraulic cylinder 26 extends and retracts as oil is supplied and discharged.

[0031] When the operator operates the control switch 27, the drive mechanism 22 is driven. In other words, the electric motor 23 activates the hydraulic pump 24, causing the hydraulic cylinder 26 to extend and retract. When the hydraulic cylinder 26 extends and retracts, the slider 14 moves up and down along the lifting support column 12 and the inner column 13 via wires wrapped around the fixed sheave and the movable sheave.

[0032] As a result, the lifting mechanism 21 can raise and lower the unfolded loading platform 16 between a raised position (indicated by a dashed line in Figure 2) and a lowered position (indicated by a solid line in Figure 2). When the loading platform 16 is in the raised position, the loading surface 16c of the loading platform 16 is at the same height as the upper surface 19a of the cross member 19. When the loading platform 16 is in the lowered position, the loading platform 16 is in contact with the ground.

[0033] <Reversal mechanism> Figure 3 is a side view showing the state of the lifting unit 11 before and after inversion. Figure 4 is a view taken along arrow I in Figure 3. Figure 5 is a view taken along arrow II in Figure 4. In Figures 3 to 5, the loading platform lifting device 10 further includes an inversion mechanism 30 that inverts the lifting unit 11, which has the loading platform 16 in an upright position. Note that the inversion mechanism 30 and the swivel mechanism 50 (described later) are not shown in Figure 1. The inversion mechanism 30 includes a pair of inversion support parts 31, a pair of inversion arms 33, and an inversion drive part 34.

[0034] The pair of reversal support sections 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 reversal support sections 31 are positioned at the rear end of the floor surface 2a of the loading platform 2, spaced apart from each other in the left-right direction, corresponding to the pair of lifting columns 12. Each reversal support section 31 has a base plate 311, a reinforcing plate 312, a pair of support plates 313, and a pair of reversal shafts 314. The lower surface of the base plate 311 rests on the floor surface 2a of the loading platform 2.

[0035] The reinforcing plate 312 is made up of an L-shaped plate member in side view and has a horizontal plate portion 312a extending in the horizontal direction and a vertical plate portion 312b extending in the vertical direction. 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 up of a plate member formed in a substantially 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 inversion support portion 31 are connected by a connecting plate 32 (see Figure 4). The upper surface 32a of the connecting plate 32 is positioned at the same height as the upper surface 19a of the cross member 19.

[0036] Each reversing support section 31 has a pair of support plates 313 that support a reversing shaft 314 so as to be rotatable around a horizontal axis C that extends in the left-right direction. A reversing arm 33 is positioned between the pair of support plates 313 of each reversing support section 31. The reversing arm 33 is made of, for example, a channel material, and one end of it is fixed to the reversing shaft 314. As a result, the reversing arm 33 is rotatably supported relative to the reversing support section 31 and rotates together with the reversing shaft 314.

[0037] The other end of the reversing arm 33 is fixed to each of the lifting support columns 12 of the lifting unit 11. In this embodiment, with each lifting support column 12 in the position shown by the dashed line in Figure 3, the other end of the reversing arm 33 is fixed to the upper and front portion of each lifting support column 12.

[0038] With the above configuration, the pair of lifting support columns 12 can be rotated up and down by rotating each reversing arm 33 around the horizontal axis C relative to the pair of reversing support parts 31. As a result, the upper portion of each lifting support column 12 at the position indicated by the dashed line in Figure 3 is supported by the reversing support part 31 so as to be reversible relative to the loading platform 2. Therefore, the lifting unit 11 with the loading platform 16 in an upright position can be reversed by the reversing mechanism 30 between the usage position (the position indicated by the dashed line in Figure 3) and the non-usage position (the position indicated by the solid line in Figure 3) relative to the loading platform 2.

[0039] When the lifting unit 11 is reversed by the reversing mechanism 30, the pair of lifting support columns 12 of the lifting unit 11 are each supported by the reversing support section 31 installed on the loading platform 2 via the reversing arm 33 while being reversed. Therefore, the reversing mechanism 30 of this embodiment can reverse the lifting unit 11 between the usage position and the non-usage position while supporting each lifting support column 12 with respect to the loading platform 2.

[0040] In the operating position, the lifting unit 11 extends outwards to the rear (one direction) and below the loading platform 2. In this state, by deploying the loading platform 16, the loading platform 16 can be raised and lowered. In the non-operating 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 support columns 12 are positioned along the left-right direction (a direction perpendicular to the horizontal direction relative to one direction). In this state, the loading platform 16 is positioned on the loading platform 2, making it impossible to raise and lower it between the raised and lowered positions.

[0041] When the lifting unit 11 is in the operating position, a contact plate 29 is provided on the front wall of each lifting support column 12 (see also Figure 4). The contact plate 29 is made of an elastic material such as rubber. The contact plate 29 is fixed to the front wall of the lifting support column 12 so as to contact the vertical plate portion 312b of the reversal support portion 31 when the lifting unit 11 is in the operating position. When the lifting unit 11 is reversed from the non-operating position to the operating position, the contact plate 29 contacts the vertical plate portion 312b, thereby preventing the lifting unit 11 from reversing beyond the operating position.

[0042] In Figures 4 and 5, the reversing drive unit 34 is positioned to the right of the lifting unit 11 and is used to reverse the lifting unit 11 with minimal effort. The reversing drive unit 34 comprises a driven sprocket 35, a drive sprocket 36, a chain 37, a reduction gear 38, and an operating unit 39.

[0043] The driven sprocket 35 is positioned close to the right side of the reversing support 31. The center of the driven sprocket 35 is integrally rotatable to the right end of the reversing shaft 314. The drive sprocket 36 is positioned further forward than the driven sprocket 35 on the vehicle 1. The outer diameter of the drive sprocket 36 is smaller than the outer diameter of the driven sprocket 35. The center of the drive sprocket 36 is integrally rotatable to the output shaft 38b of the reduction gear 38. The chain 37 is formed in an endless manner and is stretched between the driven sprocket 35 and the drive sprocket 36.

[0044] The reduction gear 38 is installed on the upper surface of a base plate 315 fixed to the outer surface of the support plate 313 of the reversing support section 31. The reduction gear 38 consists of a worm gear reduction gear, for example, equipped with a worm gear (not shown). The input shaft 38a of the reduction gear 38 extends forward. An operating section 39 is connected to the input shaft 38a of the reduction gear 38. The operating section 39 has a lever 39a, one end of which is connected to the input shaft 38a of the reduction gear 38, and a handle 39b provided at the other end of the lever 39a.

[0045] When the operator grips the handle 39b and rotates the operating unit 39 so that the lever 39a rotates around the input shaft 38a of the reduction gear 38, the rotational torque is increased by the reduction gear 38, and the drive sprocket 36 rotates via the output shaft 38b of the reduction gear 38. When the drive sprocket 36 rotates, the reversing shaft 314 rotates together with the driven sprocket 35 via the chain 37. As a result, the operator can reverse the lifting unit 11 with minimal effort using the reversing drive unit 34.

[0046] <Swivel mechanism> Figure 6 is a top view of the left side portion of the lifting unit 11 in Figure 4. Figure 7 is a view taken along arrow III in Figure 6. In Figures 4, 6, and 7, the loading platform lifting device 10 further includes a swivel mechanism 50 that rotates the lifting unit 11, in which the loading platform 16 is in an upright position, on the loading platform 2.

[0047] The swivel mechanism 50 of this embodiment swivels the lifting unit 11, in which the loading platform 16 is in an upright position, relative to the loading platform 2, within a 90° range between the unused position (the position shown by the solid line in Figure 6) and the stored position (the position shown by the dashed line in Figure 6). The swivel mechanism 50 comprises a swivel support section 51 and a swivel arm section 52.

[0048] The swivel support section 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 support columns 12. The swivel support section 51 has a fixed plate 511, a fixed shaft 512, and a rotating cylinder 513. The fixed plate 511 is positioned between the left side wall 3 and the left reversing support section 31 on the floor surface 2a of the loading platform 2, and is positioned close to the bottom plate 311 of the reversing support section 31. The fixed plate 511 is fixed to the floor surface 2a by bolts 514 with its lower surface resting on the floor surface 2a. The fixed shaft 512 is fixed protruding 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 onto the outer circumference of the fixed shaft 512 and is supported so as to be rotatable around its vertical axis X relative to the fixed shaft 512.

[0049] The swivel arm section 52 connects the swivel support section 51 and the lifting unit 11. The swivel arm section 52 has a cylindrical arm 521 and an axial arm 522. The cylindrical arm 521 is made of a cylindrical member. One axial end of the cylindrical arm 521 (the left end in Figure 4) is fixed to the outer circumferential surface of the rotating cylinder 513 of the swivel support section 51.

[0050] The shaft arm 522 is made of a cylindrical member. One axial end of the shaft arm 522 (the right end in Figure 4) is fixed to the outer surface of the left support plate 313 in the reversal support section 31. The other axial end of the shaft arm 522 (the left end in Figure 4) is inserted into the cylindrical arm 521 and fixed to the cylindrical arm 521 by a bolt 523. Therefore, the swivel arm section 52, together with the left reversal support section 31, can swivel horizontally around the vertical axis X relative to the swivel support section 51.

[0051] With the above configuration, when the swivel arm 52 rotates horizontally relative to the swivel support 51, the lifting unit 11 and the left and right reversal support 31 rotate horizontally around the vertical axis X. As a result, the lifting unit 11, with the loading platform 16 in an upright position, can rotate horizontally on the loading platform 2 between an unused position and a stored position by the swivel mechanism 50.

[0052] In the unused position, as described above, the lifting unit 11 is positioned on the cargo bed 2, and the pair of lifting support columns 12 are positioned along the left-right direction. In the stored position, the lifting unit 11 is positioned on the cargo bed 2, and the pair of lifting support columns 12 are positioned along the front-rear direction (one direction). In this embodiment, in the stored position, the pair of lifting support columns 12 are positioned along the left side wall 3 near the said side wall 3. The vehicle 1 travels with the lifting unit 11 in the stored position.

[0053] Although not shown in the diagram, the loading platform lifting device 10 is further equipped with a swivel restriction structure and a swivel lock structure. The swivel restriction structure prevents the lifting unit 11, which horizontally swivels from the storage position to the unused position by the swivel mechanism 50, from swiveling beyond the unused position. The swivel lock structure prevents the lifting unit 11 from swiveling horizontally by the swivel mechanism 50 when the lifting unit 11 is in the unused position or the storage position.

[0054] <Oscillating part> Figure 8 is a front view of part IV of Figure 1, seen from the rear. Figure 9 is a cross-sectional view taken along the VV line in Figure 8. In Figures 8 and 9 (see also Figure 1), the loading platform lifting device 10 further comprises a swinging part 60 provided between a pair of lifting support columns 12, and a sensor 73 provided inside one of the lifting support columns 12 (the left side in this embodiment).

[0055] The sensor 73 consists of, for example, a limit switch and has a contact 73a. The sensor 73 is installed inside the lifting support column 12 in a position that does not obstruct the lifting and lowering of the inner column 13. The sensor 73 is positioned with the contact 73a facing downwards. The sensor 73 changes from a non-detection state to a detection state when the dog 62 (described later) comes into contact with the contact 73a, and changes from a detection state to a non-detection state when the dog 62 moves away from the contact 73a.

[0056] The oscillating section 60 includes a pair of left and right oscillating plates 61, a dog 62, and a safety bar 63. Each oscillating plate 61 is positioned below the inner wall 12c on the left-right inner side of each lifting support column 12. Each oscillating plate 61 is formed in a substantially L-shape and has a support plate portion 61a extending in the front-rear direction and a hanging plate portion 61b extending downward from the rear end of the support plate portion 61a.

[0057] The support plate portion 61a is positioned above the bottom plate 19b of the cross member 19 and is pivotably supported by a pin 64 that protrudes inward in the left-right direction from the inner wall 12c of the lifting support column 12. The hanging plate portion 61b extends behind the bottom plate 19b and below the bottom plate 19b.

[0058] Dog 62 is a component for changing the sensor 73 between a detection state and a non-detection state. Dog 62 is made of, for example, an angle material and is fixed to the upper front corner of the support plate portion 61a on the left side of the oscillating plate 61. Dog 62 passes through a through hole 12d formed in the inner wall 12c of the left side of the lifting support column 12 from the support plate portion 61a and is positioned below the sensor 73 inside the lifting support column 12.

[0059] The safety bar 63 is made of, for example, a cylindrical member and is positioned between a pair of left and right oscillating plates 61. Both axial ends of the safety bar 63 are fixed to the lower ends of the support plate portions 61a of each oscillating plate 61. In this way, the safety bar 63 is integrally provided with the dog 62 via the oscillating plates 61.

[0060] The weight of the safety bar 63 is heavier than the total weight of the pair of dogs 62 fixed to the pair of oscillating plates 61. Therefore, the rear part of the oscillating section 60 (the side with the safety bar 63) is heavier than the front part of the oscillating section 60 (the side with the dogs 62). As a result, as shown in Figure 9, when the lifting unit 11 is in the operating position, the oscillating section 60 swings counterclockwise around the pin 64 due to its own weight and is held in a second swinging position where the rear side of the lower surface of the support plate section 61a abuts against the bottom plate 19b.

[0061] When the oscillating part 60 is in the second oscillating position, the dog 62 contacts the contact 73a of the sensor 73, and the sensor 73 is held in the detection state. When the sensor 73 is in the detection state, the control unit 80 (described later) allows the drive means 22 to be driven, so the operator can raise and lower the loading platform 16 by operating the control switch 27.

[0062] In the state shown in Figure 9, each swing plate 61 and safety bar 63 is positioned in front of the rear surface 12e of the lifting support column 12, so they do not obstruct the raising and lowering of the loading platform 16. Also, in the state shown in Figure 9, the safety bar 63 is positioned in front of the loading platform 16. Therefore, when a load is placed on the loading surface 16c of the loading platform 16 (see Figure 1) in the lowered position and the loading platform 16 is being raised, if a part of the load protrudes in front of the loading platform 16 (towards the loading platform 2), that part of the load will come into contact with the underside of the safety bar 63.

[0063] When a portion of the load comes into contact with the lower side of the safety bar 63, the safety bar 63, together with the swing plate 61 and the dog 62, is forcibly swung clockwise around the pin 64, as shown in Figure 10. As a result, the swinging part 60 reaches a first swinging position where the front side of the lower surface of the support plate part 61a comes into contact with the bottom plate 19b.

[0064] When the oscillating part 60 reaches the first oscillating position, the dog 62 moves downward away from the contact 73a of the sensor 73, and the sensor 73 changes from a detection state to a non-detection state. When the sensor 73 changes to a non-detection state, the control unit 80 (described later) restricts the driving of the driving means 22, and the raising of the loading platform 16 stops. This prevents the load on the loading platform 16 from being pinched and damaged between the loading surface 16c of the loading platform 16 and the bottom plate 19b of the cross member 19 on the loading platform 2 side.

[0065] On the other hand, when the lifting unit 11 is reversed from the usage position to the non-usage position (see Figure 3), the oscillating part 60 and the sensor 73 are inverted, as shown in Figure 11. As a result, the oscillating part 60 swings clockwise around the pin 64 due to its own weight, swinging from the second swinging position to the first swinging position.

[0066] Therefore, as the lifting unit 11 reverses between the unused position and the used position, the oscillating part 60 oscillates between the first oscillating position and the second oscillating position due to its own weight. Accordingly, the sensor 73 changes from a detected state to a non-detected state when the lifting unit 11 reverses to the unused position, and changes from a non-detected state to a detected state when the lifting unit 11 reverses to the used position.

[0067] <Control Configuration> Figure 12 is a block diagram showing the control configuration of the loading platform lifting device 10. In Figure 12, the loading platform lifting device 10 further comprises a detection means 70 and a control unit 80. The detection means 70 changes between a detected state and a non-detected state depending on the position of the lifting unit 11. The detection means 70 has a first detection unit 71 and a second detection unit 72. The first detection unit 71 changes from a detected state to a non-detected state (first state) when the lifting unit 11 is reversed to an unused position. The second detection unit 72 changes from a non-detected state to a detected state (second state) when the lifting unit 11 is reversed to an used position.

[0068] In this embodiment, as described above, the sensor 73 that detects when a part of the luggage comes into contact with the safety bar 63 changes to a non-detection state when the lifting unit 11 is reversed to an unused position, and changes to a detection state when the lifting unit 11 is reversed to an operating position. For this reason, in this embodiment, a single sensor 73 is used as the first detection unit 71 and the second detection unit 72. Thus, the sensor 73 serves as both a sensor that detects when a part of the luggage comes into contact with the safety bar 63 and a detection means 70 that changes between a detection state and a non-detection state depending on the position of the lifting unit 11.

[0069] The control unit 80, although not shown in Figure 1, is located within the cross member 19. The control unit 80 is comprised of a computer with a CPU and the like. Each function of the control unit 80 is performed by the CPU executing a control program stored in the computer's memory. The control unit 80 receives detection signals from the sensor 73 (detection means 70) and operation signals from the control switch 27.

[0070] The control unit 80 controls whether or not the drive means 22 can be driven based on the state change of the detection means 70. Specifically, when the sensor 73 changes to a detection state, that is, when a detection signal is input from the sensor 73, the control unit 80 allows the drive of the drive means 22. When the drive of the drive means 22 is allowed, the operator operates the control switch 27 to drive the drive means 22.

[0071] Furthermore, when the sensor 73 changes to a non-detection state, that is, when no detection signal is input from the sensor 73, the control unit 80 restricts the driving of the drive means 22 regardless of whether or not there is an operation signal input from the control switch 27. As a result, when the lifting and lowering of the loading platform 16 is stopped, the drive means 22 will not be driven even if the worker operates the control switch 27. Also, when the loading platform 16 is being lifted or lowered, the driving of the drive means 22 is forcibly stopped.

[0072] <Effects and Effects> According to the loading platform lifting device 10 of the first embodiment, when the loading platform 16 of the lifting unit 11 is not in use, the lifting unit 11 can be reversed from the usage position to the unused position on the loading platform 2 by the reversing mechanism 30 while the loading platform 16 is in an upright position along the pair of lifting support columns 12. As a result, the lifting support columns 12 and the loading platform 16 of the lifting unit 11 are positioned above the height of the floor surface 2a of the loading platform 2, so that damage to the lifting support columns 12 and the loading platform 16 when the loading platform 16 is not in use can be suppressed.

[0073] Furthermore, the lifting unit 11, which is in an unused position, can be rotated to the storage position by the swivel mechanism 50. When the lifting unit 11 is in the storage position, the pair of lifting support columns 12 are positioned along the side wall 3 in the front-rear direction. As a result, when loading and unloading of cargo is performed manually from the rear of the cargo bed 2, the upright loading platform 16 is not positioned to cover the cargo loading space on the cargo bed 2 from the rear. Consequently, loading and unloading of cargo can be performed manually without horizontally deploying the loading platform 16, thus enabling efficient loading and unloading operations.

[0074] Furthermore, the reversing mechanism 30 and the swivel mechanism 50 are configured to move the lifting unit 11 while supporting each lifting support column 12 with respect to the cargo bed 2 by a pair of reversing support parts 31. As a result, when the lifting unit 11 is reversed and swiveled by the reversing mechanism 30 and the swivel mechanism 50, each lifting support column 12 is supported with respect to the cargo bed 2, so that the lifting unit 11 can be moved in a stable state.

[0075] Furthermore, when the lifting unit 11 is reversed to the unused position and the sensor 73 (first detection unit 71) changes to a non-detection state (first state), the control unit 80 restricts the driving of the drive means 22. This effectively prevents the load receiving platform 16 from moving up or down when the lifting unit 11 is in the unused position.

[0076] Furthermore, when the lifting unit 11 is reversed to the usage position and the sensor 73 (second detection unit 72) changes to a detection state (second state), the control unit 80 allows the drive means 22 to be driven. As a result, when the lifting unit 11 is reversed from the unused position to the usage position, the loading platform 16 automatically becomes capable of being raised and lowered, allowing for quick loading and unloading of goods.

[0077] Furthermore, since the first detection unit 71 and the second detection unit 72 are composed of a single sensor 73, the configuration of the loading platform lifting device 10 can be simplified.

[0078] Furthermore, when the lifting unit 11 reverses between the unused position and the used position, the oscillating part 60 swings between the first oscillating position and the second oscillating position due to its own weight, thereby changing the sensor 73 between a detected state and a non-detected state. As a result, both the sensor 73 and the oscillating part 60 can be mounted on the same member (lifting support column 12), making it easy to align the sensor 73 and the oscillating part 60. Consequently, the detection accuracy of the sensor 73 can be improved.

[0079] Furthermore, if a portion of the cargo on the loading platform 16 that protrudes towards the loading platform 2 comes into contact with the safety bar 63 while the loading platform 16 is rising, the dog 62 swings to the first swinging position, causing the sensor 73 to change to a non-detection state. As a result, the control unit 80 restricts the driving of the drive means 22, stopping the raising of the loading platform 16. Consequently, damage to the cargo caused by being caught between the loading platform 16 and the loading platform 2 can be suppressed. In addition, since the sensor 73 serves as both a sensor that detects when a portion of the cargo comes into contact with the safety bar 63 and a sensor that changes between a detected state and a non-detection state depending on the position of the lifting unit 11, the configuration of the loading platform lifting device 10 can be further simplified.

[0080] [Second Embodiment] Figure 13 is a side view of the loading platform lifting device 10 according to the second embodiment. The loading platform lifting device 10 of this embodiment differs from the first embodiment in that a detection means 70 is provided separately from the sensor 73. In Figure 13, the detection means 70 of this embodiment has a sensor 74 provided on the front wall of one of the lifting support columns 12 (the left side in this embodiment).

[0081] The sensor 74 is, for example, a proximity sensor and has a detection surface 74a. The sensor 74 is positioned directly below the contact plate 29. When the lifting unit 11 is in use, that is, when the contact plate 29 is in contact with the vertical plate portion 312b of the reversing support portion 31, the detection surface 74a of the sensor 74 is positioned at a height close to and facing the vertical plate portion 312b. The sensor 74 changes from a non-detection state to a detection state when the detection surface 74a approaches the vertical plate portion 312b, and changes from a detection state to a non-detection state when the detection surface 74a moves away from the vertical plate portion 312b.

[0082] The sensor 74 functions as a first detection unit 71 that changes from a detection state to a non-detection state (first state) when the lifting unit 11 is reversed to an unused position. In this embodiment, immediately after the lifting unit 11 is reversed from the usage position to the unused position, the detection surface 74a separates from the vertical plate portion 312b, and the sensor 74 changes to a non-detection state.

[0083] Sensor 74 functions as a second detection unit 72 that changes from a non-detection state to a detection state (second state) when the lifting unit 11 is reversed to the operating position. Therefore, in this embodiment, a single sensor 74 is used as both the first detection unit 71 and the second detection unit 72.

[0084] Figure 14 is a block diagram showing the control configuration of the loading platform lifting device 10 of this embodiment. In Figure 14, the control unit 80 allows the driving means 22 to be driven when the sensor 74 changes to a detection state, that is, when a detection signal is input from the sensor 74. When the sensor 74 changes to a non-detection state, that is, when no detection signal is input from the sensor 74, the control unit 80 restricts the driving of the driving means 22, regardless of whether or not an operation signal is input from the control switch 27. Other components of this embodiment are the same as those of the first embodiment, so they are denoted by the same reference numerals and their descriptions are omitted.

[0085] According to the second embodiment of the loading platform lifting device 10, when the lifting unit 11 is reversed to an unused position and the sensor 74 (first detection unit 71) changes to a non-detection state (first state), the control unit 80 restricts the driving of the driving means 22. This effectively prevents the loading platform 16 from moving up or down when the lifting unit 11 is in an unused position.

[0086] Furthermore, when the lifting unit 11 is reversed to the usage position and the sensor 74 (second detection unit 72) changes to a detection state (second state), the control unit 80 allows the drive means 22 to be driven. As a result, when the lifting unit 11 is reversed from the unused position to the usage position, the loading platform 16 automatically becomes capable of being raised and lowered, allowing for quick loading and unloading of goods.

[0087] Furthermore, when the lifting unit 11 is reversed to the operating position and the contact plate 29 on the lifting support column 12 side is in contact with the reversal support part 31 (vertical plate part 312b), the sensor 74 changes to a detection state and the driving means 22 is allowed to be driven. As a result, the lifting support column 12 can raise and lower the loading platform 16 in a stable state, thereby suppressing the lifting support column 12 from swaying around the horizontal axis C while the loading platform 16 is being raised and lowered.

[0088] Furthermore, since the first detection unit 71 and the second detection unit 72 are composed of a single sensor 74, the configuration of the loading platform lifting device 10 can be simplified.

[0089] Furthermore, immediately after the lifting unit 11 reverses from the usage position to the non-usage position, the sensor 74 changes to a non-detection state, causing the control unit 80 to restrict the driving of the drive means 22. This effectively prevents the loading platform 16 from moving up or down when the lifting unit 11 is in a position other than the usage position (including the position during the reversal).

[0090] [Third Embodiment] Figure 15 is a diagram corresponding to Figure 5 of the loading platform lifting device 10 according to the third embodiment. The loading platform lifting device 10 of this embodiment is a modified version of the second embodiment, and the mounting position of the sensor 74 differs from that of the second embodiment. In Figure 15, the sensor 74 of this embodiment is provided directly below the driven sprocket 35 on the left-right outer support plate 313 of the right-side reversal support section 31 (see also Figure 4). The sensor 74 is positioned with its detection surface 74a facing upward.

[0091] A dog 41 is fixed to the outer circumference of the left-right outer side of the driven sprocket 35. The dog 41 is formed, for example, in a block shape and rotates together with the driven sprocket 35 around the horizontal axis C. As shown in Figure 15, when the lifting unit 11 is in an unused position, the dog 41 is positioned at approximately the 12 o'clock rotation position.

[0092] From the state shown in Figure 15, when the driven sprocket 35 rotates around the horizontal axis C and the lifting unit 11 reverses to the operating position (see Figure 3), the dog 41 rotates to approximately the 6 o'clock position and comes into close proximity to the detection surface 74a of the sensor 74. The sensor 74 changes from a non-detection state to a detection state when the dog 41 comes into close proximity to the detection surface 74a, and changes from a detection state to a non-detection state when the dog 41 moves away from the detection surface 74a.

[0093] The sensor 74 functions as a first detection unit 71 that changes from a detection state to a non-detection state (first state) when the lifting unit 11 is reversed to an unused position. In this embodiment, immediately after the lifting unit 11 is reversed from the usage position to the unused position, the dog 41 separates from the detection surface 74a, and the sensor 74 changes to a non-detection state.

[0094] Sensor 74 functions as a second detection unit 72 that changes from a non-detection state to a detection state (second state) when the lifting unit 11 is reversed to the operating position. Therefore, in this embodiment as well, a single sensor 74 is used as both the first detection unit 71 and the second detection unit 72.

[0095] Other components of this embodiment are the same as those of the second embodiment, and therefore are denoted by the same reference numerals, and their descriptions are omitted. The loading platform lifting device 10 of this embodiment also provides the same effects as those of the second embodiment.

[0096] [others] In the above embodiment, the loading platform lifting device 10 is provided at the rear of the loading platform 2 so that cargo can be loaded and unloaded from the rear of the loading platform 2, but it may also be provided on the left or right side of the loading platform 2 so that cargo can be loaded and unloaded from the side of the loading platform 2. The loading platform 16 is configured such that the sub-plate 16b folds to the back side of the main plate 16a, but it may also be configured such that the sub-plate 16b folds to the front side (load receiving surface 16c) of the main plate 16a.

[0097] The lifting unit 11 in the unused position is located on the loading platform 2, but it may be located behind the loading platform 2 as long as it is positioned above the height of the floor surface 2a of the loading platform 2. In other words, the reversing mechanism 30 may be configured to move the lifting unit 11 between the usage position and the unused position while it remains extended behind the loading platform 2. Furthermore, 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.

[0098] The reversing mechanism 30 reverses the lifting unit 11 while supporting a pair of lifting columns 12, but the lifting unit 11 may also be reversed without supporting one or both of the pair of lifting columns 12. Similarly, the swivel mechanism 50 swivels the lifting unit 11 while supporting a pair of lifting columns 12, but the lifting unit 11 may also be swiveled without supporting one or both of the pair of lifting columns 12.

[0099] The swivel mechanism 50 is not limited to a swivel mechanism that horizontally rotates the lifting unit 11. For example, the swivel mechanism 50 may slide the lifting unit 11, which is in an unused position, forward on the loading platform 2, and then rotate the lifting unit 11 by 90° around a vertical axis provided in the center of the lifting unit 11 in the left-right direction. Furthermore, the loading platform lifting device 10 does not necessarily have to be equipped with a swivel mechanism 50.

[0100] The detection means 70 is not limited to the above embodiment. For example, the first detection unit 71 changes to a non-detection state when the lifting unit 11 is reversed to an unused position, but it may change to a detection state. Similarly, the second detection unit 72 changes to a detection state when the lifting unit 11 is reversed to an operating position, but it may change to a non-detection state. Furthermore, the first detection unit 71 and the second detection unit 72 are composed of a single sensor 73 (or 74), but they may be composed of separate sensors.

[0101] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not in the sense described above, and is intended to include all modifications in the sense and scope equivalent to the claims. [Explanation of symbols]

[0102] 1 vehicle 2. Cargo bed 2a Floor surface 10 Loading platform lifting device 11 Lifting Unit 12 Lifting support columns 16 Loading platform 22 Driving means 30 Reversal Mechanism 60 Oscillating part 62 Dog 63 Safety Bar 70 Detection means 71 First detection unit 72 Second detection unit 73 Sensors 74 sensors 80 Control Unit C Horizontal axis

Claims

1. A loading platform lifting device for loading and unloading cargo onto the cargo bed of a vehicle, A lifting unit comprising: a pair of lifting support columns; a loading platform that is horizontally deployed relative to the pair of lifting support columns and can be raised and lowered, and can stand upright along the pair of lifting support columns; and a driving means for raising and lowering the horizontally deployed loading platform between the floor of the loading platform and the ground. A reversal mechanism that inverts the lifting unit, which is in an upright position of the loading platform, around the horizontal axis relative to the loading platform, between a usage position in which the lifting unit extends below the loading platform and the loading platform can be raised and lowered, and a non-use position in which the lifting unit is positioned above the height of the loading platform floor, and positions it on the loading platform. A detection means that changes between a detected state and a non-detected state depending on the position of the lifting unit, A loading platform lifting device comprising: a control unit that controls whether or not the driving means can be driven based on a change in the state of the detection means.

2. The detection means includes a first detection unit which changes to one of a first state, either a detected state or a non-detected state, when the lifting unit is reversed to the unused position. The load-receiving platform lifting device according to claim 1, wherein the control unit restricts the driving of the driving means when the first detection unit changes to the first state.

3. The detection means includes a second detection unit which changes to one of a detection state and a non-detection state when the lifting unit is reversed to the usage position, The load-receiving platform lifting device according to claim 2, wherein the control unit allows the driving means to be driven when the second detection unit changes to the second state.

4. The first detection unit and the second detection unit are each composed of a single sensor. The sensor changes to one of the detection state and non-detection state (the first state) when the lifting unit is reversed to the unused position, and changes to the other of the detection state and non-detection state (the second state) when the lifting unit is reversed to the usage position. The load-receiving platform lifting device according to claim 3, wherein the control unit restricts the driving of the drive means when the sensor changes to one of the states, and allows the driving of the drive means when the sensor changes to the other state.

5. The lifting support column is provided with a pivoting part that can pivot between a first pivoting position and a second pivoting position by its own weight, and the lifting unit pivots to the first pivoting position when it is reversed to the unused position, and pivots to the second pivoting position when it is reversed to the used position. The loading platform lifting device according to claim 4, wherein the sensor is provided on the lifting support column, and changes to one state when the swinging part swings to the first swinging position, and changes to the other state when the swinging part swings to the second swinging position.

6. The aforementioned swinging part is, A dog for changing the sensor between a detection state and a non-detection state, The device includes a safety bar provided integrally with the dog, which can contact a portion of the load on the loading platform when the loading platform is raised with the lifting unit in the operating position, if a portion of the load on the loading platform protrudes toward the loading platform side. The loading platform lifting device according to claim 5, wherein the dog abuts the safety bar with a portion thereof, and swings together with the safety bar to the first swinging position.

7. The loading platform lifting device according to claim 4, wherein the sensor changes to one of the states immediately after the lifting unit reverses from the usage position to the non-use position.

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