Vehicle loading platform lifting device

Abstract

To reduce a cost by dispensing with a change of a control program for a controller when adding a corresponding function to a prescribed loading state to an existing loading platform lifting device.SOLUTION: A loading platform lifting device L comprises: a controller C which operates on the basis of a previously stored control program and performs switching control of communication switching means V1, V2 so as to move a loading platform 1 down when receiving a moving-down command to the loading platform 1; a pressure sensor PS which can detect that the hydraulic pressure of a hydraulic cylinder CL exceeds a prescribed limit pressure px in a prescribed loading state of the loading platform 1; and moving-down regulation means RE2 which can regulate moving-down of the loading platform 1 in the time of operation independently of the controller C. The moving-down regulation means RE2 is connected with the pressure sensor PS via the controller C such that the moving-down regulation means RE2 operates according to the detection of the pressure sensor PS in the moving-down process of the loading platform 1.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a loading platform lifting device for a vehicle, and in particular to a loading platform lifting device that includes a loading platform for transferring luggage between a luggage storage location and the floor of a loading platform on the vehicle body, a lifting guide mechanism arranged between the loading platform and the vehicle body or loading platform and guiding the loading platform up and down between the storage location and the floor, a hydraulic cylinder that is linked to the lifting guide mechanism or loading platform and can drive the loading platform up and down, a hydraulic pump that pressurizes oil from an oil tank to the hydraulic cylinder, and a communication switching means that can selectively switch the hydraulic cylinder to communicate with either the hydraulic pump or the oil tank. [Background technology]

[0002] The vehicle loading platform lifting device described above is known, for example, as disclosed in Patent Document 1. This known device includes an electromagnetic on-off valve as a communication switching means involved in the lifting and lowering of the loading platform, and a controller as a control device that controls the switching operation of the electromagnetic on-off valve. In this case, the controller is a precision electronic device that operates based on a pre-stored control program, and, for example, upon receiving a command to raise the loading platform, outputs a raised position switching signal to the electromagnetic on-off valve to raise the loading platform, and upon receiving a command to lower the loading platform, outputs a lowered position switching signal to the electromagnetic on-off valve to raise the loading platform. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3268527 Summary of the Invention [Problem to be solved by the invention]

[0004] The loading platform lifting device for vehicles in Patent Document 1 has a pressure sensor that detects when the hydraulic pressure in the hydraulic cylinder exceeds a predetermined limit pressure and recognizes that the loading platform is in a predetermined loading state (for example, an overloaded state for the loading platform lifting device).This pressure sensor is connected to a controller, and special control measures are taken, such as the controller automatically stopping the loading platform lifting device when the loading platform is in the predetermined loading state.

[0005] However, when adding such a function to respond to a specified loading condition to an existing loading platform lifting device, not only is a pressure sensor required, but the control program stored in the controller must also be specially modified, which requires time and money to make.

[0006] SUMMARY OF THE INVENTION The present invention has been proposed in view of the above, and has as its object to provide a vehicle loading platform lifting device that can solve the problems of the conventional structure. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a loading platform for transferring loads between a load placement location and the floor of a loading platform on a vehicle body, a lift guide mechanism disposed between the loading platform and the vehicle body or the loading platform and for guiding the loading platform up and down between the loading location and the floor, a hydraulic cylinder interlocked with the lift guide mechanism or the loading platform and capable of driving the loading platform up and down, a hydraulic pump for pumping oil from an oil tank to the hydraulic cylinder, and communication switching means for selectively switching communication between the hydraulic pump and the oil tank, which operates based on a pre-stored control program. The device is equipped with a controller that switches and controls the communication switching means to lower the loading platform when a command to lower the loading platform is received, a pressure sensor that can detect when the oil pressure of the hydraulic cylinder exceeds a predetermined limit pressure when the loading platform is in a predetermined loading state, and a descent control means that can regulate the descent of the loading platform independently of the controller when activated, and its first feature is that the descent control means and the pressure sensor are connected without going through the controller so that the descent control means operates in response to the detection by the pressure sensor during the descent of the loading platform.

[0008] In addition to the first feature, the present invention has a second feature in that the communication switching means has a lowering electromagnetic on-off valve that can open and close the oil passage between the hydraulic cylinder and the oil tank, and the lowering electromagnetic on-off valve is controlled to open by a valve open command signal from the controller that receives the lowering command, and the descent restriction means includes a B-contact relay that is interposed in the current path connecting the controller and the lowering electromagnetic on-off valve and normally closes the current path, and the B-contact relay and the pressure sensor are connected without going through the controller so that the B-contact relay opens in response to the detection by the pressure sensor during the lowering process of the loading platform and controls the lowering electromagnetic on-off valve to be placed in a closed state.

[0009] The present invention also provides a load receiving platform for transferring loads between a load placement location and the floor of a loading platform on a vehicle body, a lift guide mechanism disposed between the load receiving platform and the vehicle body or the loading platform and guiding the load receiving platform up and down between the load placement location and the floor, a hydraulic cylinder interlocked with the lift guide mechanism or the load receiving platform and capable of driving the load receiving platform up and down, a hydraulic pump for pumping oil from an oil tank to the hydraulic cylinder, and communication switching means for selectively switching communication between the hydraulic pump and the oil tank, which operates based on a pre-stored control program and is also provided. The third feature of the device is that it is equipped with a controller that switches and controls the communication switching means so that the loading platform is raised when a command to raise the loading platform is received, a pressure sensor that can detect when the oil pressure of the hydraulic cylinder exceeds a predetermined limit pressure when the loading platform is in a predetermined load state, and a rise control means that can control the rise of the loading platform independently of the controller when activated, and the rise control means and the pressure sensor are connected without going through the controller so that the rise control means operates in response to the detection by the pressure sensor during the raising process of the loading platform.

[0010] In addition to the third feature, the present invention has a fourth feature in that the communication switching means has a lifting electromagnetic on-off valve that can open and close the oil passage between the hydraulic cylinder and the oil tank, and the lifting electromagnetic on-off valve is controlled to open by a valve open command signal from the controller that receives the lift command, the rise restriction means includes a B-contact relay that is interposed in the current path connecting the controller and the lifting electromagnetic on-off valve and normally closes the current path, and the B-contact relay and the pressure sensor are connected without going through the controller so that the B-contact relay opens in response to the detection by the pressure sensor during the lifting process of the loading platform and controls the lifting electromagnetic on-off valve to be placed in a closed state.

[0011] In this invention and this specification, "controlling to place the valve in a closed state" not only includes control of switching the electromagnetic valve to be controlled from an open state to a closed state and maintaining it in the closed state, but also includes control of maintaining the valve in a closed state from the beginning of the descending or ascending process. [Effects of the Invention]

[0012] According to a first aspect of the present invention, a platform lifting device is provided that includes a pressure sensor capable of detecting when the hydraulic pressure of the hydraulic cylinder exceeds a predetermined limit pressure when the platform is in a predetermined load state, and a descent restriction means that, when activated, restricts the descent of the platform independently of a controller. The descent restriction means and the pressure sensor are connected to the descent restriction means without the intervention of a controller so that the descent restriction means is activated in response to the detection by the pressure sensor during the platform's descent. This allows the descent restriction means to be activated in response to the pressure sensor detecting that the hydraulic pressure of the hydraulic cylinder exceeds the predetermined limit pressure (and thus indicating the predetermined load state) during the platform's descent, thereby reliably restricting the platform's descent when the platform is in a predetermined load state. Furthermore, when adding this predetermined load state response function to an existing platform lifting device, it is sufficient to connect and link the pressure sensor to the descent restriction means without the intervention of a controller. Therefore, there is no need to specifically modify the control program of the controller to add the predetermined load state response function. This eliminates the effort of program modification and contributes to cost savings.

[0013] Furthermore, according to the second feature in particular, when the pressure sensor detects that the oil pressure in the hydraulic cylinder exceeds a predetermined limit pressure (and therefore a predetermined load state) during the lowering of the loading platform, the B-contact relay opens and the lowering electromagnetic on-off valve is controlled to be placed in a closed state, thereby reliably restricting the lowering operation of the loading platform when the loading platform is in a predetermined load state. Moreover, when adding this function to accommodate predetermined load states to an existing loading platform lifting device, it is sufficient to connect and link the pressure sensor to the lowering electromagnetic on-off valve via the B-contact relay without going through the controller, and there is no need to make special changes to the control program of the controller to add the function to accommodate predetermined load states, which eliminates the hassle of changing the program and contributes to cost savings.

[0014] According to a third aspect of the present invention, a pressure sensor is provided that can detect when the hydraulic pressure of the hydraulic cylinder exceeds a predetermined limit pressure when the platform is in a predetermined load state, and a lift-up restricting means is provided that, when activated, restricts the lifting of the platform independently of the controller. The lift-up restricting means and the pressure sensor are connected to the lift-up restricting means without the controller so that the lift-up restricting means is activated in response to the detection by the pressure sensor during the platform's lifting process. This allows the lift-up restricting means to be activated in response to the pressure sensor detecting that the hydraulic pressure of the hydraulic cylinder exceeds the predetermined limit pressure (and therefore the platform is in the predetermined load state) during the platform's lifting process, thereby reliably restricting the lifting of the platform at the predetermined load state. Furthermore, when adding this predetermined load state handling function to an existing platform lifting device, it is sufficient to connect and link the pressure sensor to the lift-up restricting means without the controller, and there is no need to specially modify the control program of the controller to add the predetermined load state handling function. This eliminates the hassle of program modification and contributes to cost savings.

[0015] Furthermore, according to the fourth feature in particular, when the pressure sensor detects that the oil pressure in the hydraulic cylinder exceeds a predetermined limit pressure (and therefore a predetermined load state) during the lifting of the loading platform, the B-contact relay opens and the lifting solenoid on-off valve is controlled to be in a closed state, thereby making it possible to reliably regulate the lifting operation of the loading platform when the loading platform is in a predetermined load state. Moreover, when adding this function to accommodate predetermined load states to an existing loading platform lifting device, it is sufficient to connect and link the pressure sensor to the lifting solenoid on-off valve via the B-contact relay without going through a controller, and there is no need to make special changes to the control program of the controller to add the function to accommodate predetermined load states, which eliminates the hassle of changing the program and contributes to cost savings. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a side view of an example of a cargo handling vehicle equipped with a first embodiment of a loading platform lifting device according to the present invention, and a perspective view of a rear portion of a loading box; [Figure 2] 2 is a perspective view of the main part of the loading platform lifting device as seen from the arrow 2X in FIG. [Figure 3] FIG. 3 is a side view of the rear of the cargo handling vehicle, showing the main parts of the loading platform lifting device in a longitudinal cross section taken along line 3X-3X in FIG. 2. [Figure 4] Hydraulic circuit diagram showing an example of a hydraulic control system for a loading platform lifting device [Figure 5] A table showing the relationship between the operating states of the main elements in the hydraulic control system of the loading platform lifting device and the lifting operation of the loading platform. [Figure 6] A timing chart showing the hydraulic pressure change of the lift cylinder during the lifting operation of the loading platform, the relief valve operation state after reaching the lift end, and the lowering operation. [Figure 7] FIG. 5 is a hydraulic circuit diagram corresponding to FIG. 4, showing a second embodiment of the loading platform lifting device. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the accompanying drawings. The embodiment is an example in which a loading platform lifting device of the present invention is applied to a loading vehicle.

[0018] First, a first embodiment will be described. In Figures 1 to 3, a cargo box B with an open top and rear is fixed and supported on a body frame F, which serves as the body of a cargo handling vehicle, and a vertically lifting platform lifting device L is provided at the rear end of the cargo box B. This platform lifting device L lifts and lowers the cargo box 1 while maintaining it in a substantially horizontal position between the ground E, which is the cargo placement location, and the floor of the cargo box B, so that cargo placed on the platform 1 can be loaded and unloaded (i.e., handed over) between the ground E and the floor of the cargo box B.

[0019] Thus, the cargo box B is an example of a cargo platform. Note that a box-shaped cargo box with a closed top may also be used as the cargo box B. The cargo placement location may be the ground E, a platform slightly higher than the ground E, or the floor of a structure such as a warehouse or factory.

[0020] The receiving platform lifting device L comprises a receiving platform 1, left and right lift guide mechanisms G arranged between the cargo box B and the receiving platform 1 to guide the receiving platform 1 up and down between the ground E and the floor of the cargo box B, and left and right lift cylinders CL as hydraulic cylinders that are linked to the left and right lift guide mechanisms G and can lift the receiving platform 1. A cross member 24 extending laterally is fixed to the rear end of the cargo box B at a position roughly aligned with the floor of the box. The lift cylinder CL is arranged laterally within the cross member 24, and the base end of the cylinder body is pivotally connected to the inner wall of the cross member 24.

[0021] The left and right lifting guide mechanisms G each include left and right lifting support columns 2 each consisting of a hollow frame body fixed to the left and right side edges of the rear end of the cargo box B and extending vertically; inner columns 3 each consisting of a hollow frame body inserted into the lifting support columns 2 so that they can be raised and lowered and extending vertically; left and right lifting sliders 14 supported on the left and right lifting support columns 2 via the inner columns 3 so that they can be raised and lowered; hinge brackets 18 fixed to the rear surfaces of the lower parts of the left and right lifting sliders 14 and rotatably support both sides of the base of the cargo receiving platform 1 via pivots 13; and an interlocking mechanism I that interlocks and connects the lift cylinder CL and the lifting slider 14 so that the lifting slider 14 rises and falls in conjunction with the extension and contraction of the lift cylinder CL.

[0022] In addition, Figure 2 only shows the lift guide mechanism G and the lift cylinder CL connected to it, which are arranged corresponding to the left lift support column 2 at the rear of the cargo box B, but the right lift guide mechanism G and the lift cylinder CL connected to it, which are arranged corresponding to the right lift support column 2, are also arranged in the same configuration as the left side (however, the arrangement is symmetrical), although not shown.

[0023] 2, the interlocking mechanism I comprises a wire 30 having one end 30a connected to the inner wall of the cross member 24 and the other end 30b connected to the lift slider 14, and first to third sheaves 31 to 33 wound around the middle of the wire 30. The first sheave 31 is rotatably supported by the piston rod of the lift cylinder CL, the second sheave 32 by the lower part of the lift column 2, and the third sheave 33 by the upper end of the lift column 2. Furthermore, a guide roller 5 that guides the lifting and lowering operation of the inner column 3 is rotatably supported by the lower end of each lift column 2, and a stopper 10 is fixed to the lower end of the lift column 2, which engages with an elastic stopper 12 fixed to the lower end of the inner column 3 to regulate the upper limit position of the inner column 3.

[0024] Another vertical slit 7 is opened in the rear wall of each inner column 3 so as to coincide with the vertical slit 4 in the rear wall of the lifting support column 2. As shown in FIG. 3, a guide roller 8 is rotatably supported via a bracket 9 at the upper end of each inner column 3, and the guide roller 8 rolls on the inner surface of the rear wall of the lifting support column 2 to guide the rising and falling of the inner column 3 when the inner column 3 rises or falls.

[0025] Lift-up and down sliders 14 are inserted into the left and right inner columns 3 so as to be able to move up and down freely. The rear edges of these lift-up and down sliders 14 pass through the vertical slits 4, 7 and extend rearward, and are guided by these vertical slits 4, 7 so as to be able to move up and down relative to the lift-up support columns 2 and inner columns 3. Upper and lower guide rollers 15, 16 are rotatably supported on the top and bottom of the lift-up and down sliders 14, and the upper and lower guide rollers 15, 16 roll on the inner surface of the inner column 3 when the lift-up and down sliders 14 move up and down relative to the inner columns 3.

[0026] A stopper rubber 17 is provided on the upper edge of each lift-up slider 14 , and this stopper rubber 17 engages with the upper end of the inner column 3 to regulate the upper limit position of the lift-up slider 14 relative to the inner column 3 .

[0027] The cargo receiving platform 1 mainly comprises a top plate 1t, which is formed in a horizontally elongated rectangular shape in a plan view and has a basically flat upper surface. The top surface of this top plate 1t functions as a cargo receiving surface on which cargo is placed, and may be roughened (for example, with fine striped patterns) to prevent slipping as needed. Furthermore, a slope is formed at the top edge of the top surface of the top plate 1t to facilitate smooth loading and unloading of cargo. A rectangular back plate 1b is joined to the top plate 1t, overlapping it vertically. A reinforcing frame 1r extending vertically and horizontally is joined to this back plate 1b or is formed integrally with it.

[0028] The base of a hinge plate 19 extending like a strip along the left and right outer surfaces of the left and right side walls of the base of the cargo receiving platform 1 is fastened with screws, and the tip of this hinge plate 19 extends beyond the base end of the side wall of the cargo receiving platform 1 to form a stopper arm portion 19a described below. As is clear from Figure 1, the cargo receiving platform 1 is configured to be manually rotatable about a pivot 13 between a substantially vertical upright storage position 1A and an extended use position 1B expanded substantially horizontally from the upright storage position 1A.

[0029] In addition, a stopper bolt 22 is screwed into the stay 21 fixed to the lower end of each lifting slider 14, which engages with the tip of the hinge plate 19 fixed to the cargo receiving platform 1, i.e., the stopper arm portion 19a, to fix the cargo receiving platform 1 in the extended use position 1B.

[0030] Thus, when the left and right lift cylinders CL are extended and retracted, the left and right lift sliders 14 are raised and lowered via the wires 30, and the load receiving platform 1 connected to and supported by them can be raised and lowered.

[0031] Incidentally, a torsion bar (not shown) is interposed between the receiving platform 1 and the lifting slider 14, which urges the receiving platform 1 in the direction of the upright storage position 1A, thereby assisting in the manual storage operation of the receiving platform 1 (i.e., the rotation operation from the horizontally deployed position 1B to the upright storage position 1A).

[0032] A conventionally known locking mechanism 100 is provided between the receiving platform 1 and the lifting support column 2 for manually locking the receiving platform 1 in the upright storage position 1A at any time when the receiving platform 1 is in that position. The locking mechanism 100 includes, for example, a locking bracket fixed to the lifting support column 2, a locking bar slidably provided within the receiving platform 1 and capable of engaging and disengaging with the locking bracket when the receiving platform 1 is in the upright storage position 1A, and an operating lever interlocked with the locking bar.

[0033] Figure 4 shows a hydraulic circuit diagram illustrating an example of a hydraulic control system for the loading platform lifting device L, and Figure 5 shows a table illustrating the relationship between the operating states of the main elements in the hydraulic control system of the loading platform lifting device L (i.e., the pump drive motor M, the first and second electromagnetic on-off valves V1 and V2, the pressure sensor PS, and the B-contact relay RE2) and the lifting and lowering operation of the loading platform 1. Figure 6 shows a timing chart illustrating the hydraulic pressure changes in the lift cylinder CL during the lifting operation of the loading platform 1, the operating state of the relief valve after reaching the lift end, and the lowering operation.

[0034] The hydraulic equipment present in the area enclosed by the two-dot chain line in the hydraulic circuit diagram of Figure 4 is collectively unitized to form a power unit PU, which is mounted in an appropriate location on the body frame F or cargo box B.

[0035] Next, the hydraulic circuit diagram in Figure 4 will be explained in detail. The suction side of a hydraulic pump P driven by a motor M is connected to an oil tank T via a filter f1. A supply / discharge oil passage 61 extends from the discharge side of the hydraulic pump P, connecting the hydraulic oil of the hydraulic pump P to each oil chamber 60 of the left and right single-acting lift cylinders CL in parallel with each other. A check valve Vc, a filter f2, and a first electromagnetic on-off valve V1 are sequentially installed in this supply / discharge oil passage 61 from the upstream side.

[0036] A discharge oil passage 62 extending to the oil tank T branches off from the oil supply / discharge passage 61 between the check valve Vc and the first solenoid on-off valve V1, and this discharge oil passage 62 is equipped with a filter f3, a second solenoid on-off valve V2, and a flow rate throttle valve V3 in this order from the upstream side. In addition, a relief oil passage 63 extending to the oil tank T branches off from the oil supply / discharge passage 61 between the hydraulic pump P and the check valve Vc, and this relief oil passage 63 is equipped with a relief valve R that opens at a predetermined relief pressure pr to return the hydraulic oil from the hydraulic pump P to the oil tank T. Therefore, as is clear from Figure 6, the relief action of the relief valve R restricts excessive hydraulic pressure rise in the lift cylinder CL.

[0037] The first and second solenoid on-off valves V1 and V2 are normally closed solenoid valves that normally (i.e., when not energized) shut off the oil passages (supply / discharge oil passage 61, discharge oil passage 62) in which they are installed. The excitation sections of the first and second solenoid on-off valves V1 and V2 are separately connected to a controller C in the power unit PU via first and second current passages 71 and 72, which are independent of each other. When the first and second solenoid on-off valves V1 and V2 are energized by receiving output current from the controller C, they switch to an open state, thereby allowing the corresponding oil passages (supply / discharge oil passage 61, discharge oil passage 62) to be electrically connected. A third current passage 73 for energizing the motor M also extends from the controller C.

[0038] Although not shown, the controller C has at least a power switch for starting and stopping, an ascent command operation unit for issuing commands to raise the loading platform 1 at any time, a descent command operation unit for issuing commands to lower the loading platform 1 at any time, and a storage means for storing a control program for controlling the operation of the loading platform lifting device L, and is capable of operating based on the control program to control the loading platform lifting device L. The ascent command operation unit and descent command operation unit may be provided on the outer case of the controller C, or may be provided on a remote control device for remotely operating the controller C wirelessly or via a wire.

[0039] 5, when the lift command operating unit receives a lift command input from the operator, the controller C drives the motor M and sends an output current to the first electromagnetic on-off valve V1 via the first current path 71 to open the first electromagnetic on-off valve V1. As a result, the lift cylinder CL receives the output hydraulic pressure of the hydraulic pump P and extends, and in conjunction with this, the lift slider 14 (and therefore the loading platform 1) is driven to rise.

[0040] 5, when the lowering command operating unit receives a lowering command input from the operator, the controller C keeps the motor M stopped and sends output current to the first and second electromagnetic on-off valves V1, V2 via the first and second current paths 71, 72 to open the first and second electromagnetic on-off valves V1, V2, respectively. As a result, the hydraulic oil in the oil chamber 60 of the lift cylinder CL is pushed out by the load (gravity) of the loading platform 1 and is returned to the oil tank T via part of the supply / discharge oil path 61 and the discharge oil path 62, and at the same time, the lift slider 14 (and therefore the loading platform 1) moves downward, but the speed of this descent is moderately restricted by the throttling action of the flow rate throttle valve V3.

[0041] Furthermore, a pressure sensor PS is connected to the oil supply / discharge line 61 between the check valve Vc and each lift cylinder CL, and is capable of detecting when the oil pressure in the oil line 61 (and therefore the oil pressure in the lift cylinder CL) exceeds a predetermined limit pressure px. The predetermined limit pressure px refers to the oil pressure in the lift cylinder CL when the platform lifting device L is overloaded. In other words, the overloaded state refers to a state in which the oil pressure in the lift cylinder CL exceeds the predetermined limit pressure px. In this context, the "overloaded state" refers to a loading state in which the total weight of the cargo on the platform 1 (including the weight of the carriage, if the cargo is loaded on a carriage) exceeds the maximum load capacity of the platform lifting device L (e.g., 1000 kg). Operating the platform lifting device L below this overloaded state eliminates the risk of deformation or damage to the various components, which is advantageous for enhancing the durability of the device. The overloaded state is an example of the "predetermined loading state" in this specification.

[0042] Furthermore, the relief valve R has its opening pressure (i.e., the predetermined relief pressure pr) set to a hydraulic pressure that is a predetermined pressure (e.g., 1 to 2 MPa) lower than the predetermined limit pressure px, so that when the platform 1 is ascending, the relief valve R performs its relief function before the hydraulic pressure of the lift cylinder CL reaches the predetermined limit pressure px (i.e., when it reaches the predetermined relief pressure pr). Also, when the platform 1 is descending, the check valve Vc prevents oil from the lift cylinder CL from flowing to the relief valve R, so that it is possible to prevent oil from being released from the oil passage of the pressure sensor PS before the high hydraulic pressure caused by overloading is reached in that passage.

[0043] A signal line 75 extends from the pressure sensor PS, which outputs a detection signal current in response to detecting that the pressure exceeds a predetermined limit pressure px, and the tip of the signal line 75 is connected in parallel to a light-emitting diode 70 serving as an alarm means and a relay coil 82 of a B-contact relay RE2, which will be described later. The light-emitting diode 70 emits light in response to the detection signal current from the pressure sensor PS, warning the operator of an overloaded condition.

[0044] The light-emitting diode 70 is disposed in an appropriate location visible to an operator, for example, near a remote control device that is provided inside the vehicle loading box B and operates the loading platform lifting device L, or on the outer case of the power unit PU or controller C, or in the driver's seat. Note that, instead of or in addition to the light-emitting diode 70, a monitor (e.g., a liquid crystal panel) that warns of overloading or an alarm sound generator may be used as the alarm means.

[0045] Therefore, the loading platform lifting device L of the first embodiment is equipped with a control means for controlling the second electromagnetic on-off valve V2 for lowering to a closed state in response to the pressure sensor PS detecting that the hydraulic pressure of the lift cylinder CL when the loading platform 1 is in an overloaded state, i.e., exceeds a predetermined limit pressure px, during the process of lowering the loading platform 1.

[0046] That is, a B-contact relay RE2 that is normally closed (i.e., placed in a conductive state) is provided in the second current path 72, and this B-contact relay RE2 constitutes a descent restriction means, as will be described later. Thus, like conventionally known B-contact relays, the B-contact relay RE2 comprises a normally closed relay contact 81 that is normally held in a closed position by the elasticity of an internal spring, and a relay coil 82 that forcibly drives the relay contact 81 to an open position when it is energized.

[0047] The pressure sensor PS is also connected to the B-contact relay RE2 (and therefore the second electromagnetic on-off valve V2) via the signal line 75 (i.e., not via the controller C), and when it detects that the hydraulic pressure of the lift cylinder CL exceeds the predetermined limit pressure px during the lowering of the loading platform 1, it outputs a detection signal current to the relay coil 82 to operate the B-contact relay RE2. As a result, the relay contact 81 of the B-contact relay RE2 opens and the second current path 72 is cut off, thereby maintaining the second electromagnetic on-off valve V2 for lowering in a closed state.

[0048] Next, the operation of the first embodiment will be described.

[0049] When the cargo handling vehicle is traveling, the cargo receiving platform 1 is locked in the upright storage position 1A by the locking mechanism 100, closing the rear end opening of the cargo box B. At this time, each lift cylinder CL in the cross member 24 is in the most extended position, holding the corresponding inner column 3 and lift slider 14 (and therefore the cargo receiving platform 1) at the upper limit position.

[0050] When the cargo handling vehicle arrives at the cargo loading and unloading location, the locking mechanism 100 is unlocked while the inner column 3 and the lifting slider 14 are held in their upper limit positions, and the cargo receiving platform 1 is then manually rotated from the upright storage position 1A to the overhanging use position 1B. In the overhanging use position 1B, the cargo receiving platform 1 is substantially flush with the floor of the cargo box B, enabling smooth transfer of cargo from the cargo box B onto the cargo receiving platform 1. After that, when the controller C receives a lowering command input based on the operator's operation, the first and second electromagnetic on-off valves V1 and V2 open in response, and the lift cylinders CL contract, sequentially lowering the inner column 3 and the lifting slider 14, thereby lowering the cargo receiving platform 1 in the overhanging use position 1B and allowing it to touch the ground. This enables cargo to be transferred between the cargo receiving platform 1 in the grounded state and the ground E.

[0051] When the transfer work is completed and the controller C receives a lift command input based on the operator's operation, the motor M accordingly drives the hydraulic pump P and the first lifting electromagnetic on-off valve V1 opens, causing the lift cylinder CL to extend and sequentially raise the inner column 3 and the lift slider 14 to their upper limit positions. As a result, the receiving platform 1 in the extended use position 1B is again roughly flush with the floor of the cargo box B, allowing for smooth transfer of the cargo on the receiving platform 1 into the cargo box B.

[0052] Thereafter, the worker rotates the receiving platform 1 from the extended use position 1B to the upright storage position 1A. Thereafter, the receiving platform 1 at the upright storage position 1A is locked to the lifting support column 2 by the locking mechanism 100.

[0053] In the loading platform lifting device L of the first embodiment described above, the relief valve R, which relieves excess oil in the lift cylinder CL to the oil tank T side, opens at a predetermined relief pressure pr that is lower than the oil pressure of the lift cylinder CL when the loading platform 1 is overloaded (i.e., the predetermined limit pressure px) during the process of lifting the loading platform 1.

[0054] As a result, during the lifting of the loading platform 1, not only when the hydraulic pressure of the lift cylinder CL rises due to an overload, but also when the hydraulic pressure of the lift cylinder CL rises due to continued operation of an ascent command to the controller C even after the loading platform 1 reaches the lift end when the loading platform 1 is normally loaded, but also when the hydraulic pressure reaches the predetermined relief pressure pr, the relief valve R opens, returning the oil to the oil tank T, and restricting the lifting of the loading platform 1. Therefore, in either case, there is no need for the controller C to automatically stop the loading platform lifting device L. This eliminates the need to keep a log of an overload in the controller C or to cancel (reset) the automatic stop state of the loading platform lifting device L each time, as in the conventional example. Moreover, since the lifting of the loading platform 1 can be restricted even with a lighter load than in the case of an overload, it not only prevents damage to each part of the loading platform lifting device L but also contributes to improving work safety.

[0055] Furthermore, the loading platform lifting device L of the first embodiment is equipped with a pressure sensor PS that can detect when the oil pressure of the lift cylinder CL exceeds a predetermined limit pressure px that is higher than a predetermined relief pressure pr, and a descent control means (more specifically, a B-contact relay RE2) that controls the second electromagnetic opening / closing valve V2 to a closed state based on the detection of the pressure sensor PS when the oil pressure of the lift cylinder CL exceeds the predetermined limit pressure px during the descent of the loading platform 1.

[0056] As a result, for example, if the loading platform 1 becomes overloaded after reaching the upper end due to loading of cargo, the second electromagnetic on-off valve V2 is controlled to be closed based on the detection of this overload state (i.e., the state in which the hydraulic pressure of the lift cylinder CL has risen above the predetermined limit pressure px), thereby regulating the lowering operation of the loading platform 1, thereby reliably preventing the loading platform 1 from lowering in this overload state.

[0057] Therefore, if the pressure sensor PS detects an overload condition from the beginning of the descending process when the loading platform 1 is at the upper end, the second electromagnetic on-off valve V2 is maintained in a closed state from the beginning of the descending process. On the other hand, if the pressure sensor PS detects an overload condition for some reason while the loading platform 1 is descending (while the second electromagnetic on-off valve V2 is open), the second electromagnetic on-off valve V2 switches from an open state to a closed state in response to the detection, and is maintained in a closed state thereafter.

[0058] Depending on the type of work, the cart carrying the cargo may be loaded onto the receiving platform 1. Even in this case, the alarm means (light-emitting diode 70) is activated in response to the detection by the pressure sensor PS, so that the workers on-site can immediately grasp the overloaded state due to the total weight of the cargo and cart, and can quickly carry out work to resolve the overloaded state.

[0059] Furthermore, since the pressure sensor PS is connected to the B-contact relay RE2 without going through the controller C so that the B-contact relay RE2 opens and the lowering solenoid on-off valve V2 is placed in a closed state in response to detecting an overload state during the lowering process of the loading platform 1, when adding an overload response function during the lowering process to an existing loading platform lifting device L, it is sufficient to connect and link the pressure sensor PS to the lowering solenoid on-off valve V2 via the B-contact relay RE2. Therefore, there is no need to make special changes to the control program of the controller C to add the overload response function, which eliminates the trouble of changing the program, and there is also no need to provide a special connection terminal on the controller C for connecting the pressure sensor PS. As a result of the above, this can greatly contribute to cost reduction.

[0060] Furthermore, in the first embodiment, the pressure sensor PS detects a predetermined limit pressure px that is higher than the predetermined relief pressure pr of the relief valve R, so when the loading platform 1 is lowered without being overloaded after the relief valve R has been activated, the pressure sensor PS will not detect the remaining relief pressure pr in the lift cylinder CL and close the second electromagnetic on-off valve V2. This reliably prevents the loading platform 1 from being unable to be lowered due to the remaining relief pressure pr.

[0061] The first embodiment described above represents an example that embodies the first and second features of the present invention. In the first embodiment, the lifting electromagnetic on-off valve V1 and the lowering electromagnetic on-off valve V2 constitute a communication switching means that selectively switches the communication of the lift cylinder CL as a hydraulic cylinder to the hydraulic pump P and the oil tank T, and the B-contact relay RE2 constitutes a descent restriction means that, when activated, can restrict the descent of the receiving platform 1 independently of the controller C.

[0062] FIG. 7 shows a second embodiment.

[0063] In the first embodiment described above, if the receiving platform 1 is overloaded during the process of descending (including the initial stage of descent immediately after loading a load onto the receiving platform 1 at the end of the ascending direction), the second electromagnetic on-off valve V2 for descending is controlled to be placed in a closed state based on the detection of the pressure sensor PS that detects an overload, thereby restricting the descending operation of the receiving platform 1. In contrast, in the second embodiment, if the receiving platform 1 is overloaded during the process of ascending (including the initial stage of ascending immediately after loading a load onto the receiving platform 1 at the end of the descending direction), the first electromagnetic on-off valve V1 for ascending is controlled to be placed in a closed state based on the detection of the pressure sensor PS that detects an overload, thereby restricting the ascending operation of the receiving platform 1 in an overloaded state.

[0064] That is, in the hydraulic circuit diagram of the second embodiment (Figure 7), a B-contact relay RE1 is interposed in the first current path 71, and in response to the detection signal output by the pressure sensor PS (i.e., when the loading platform 1 is overloaded), the B-contact relay R1 is excited to cut off the first current path 71, and as a result, the first electromagnetic opening / closing valve V1 for lifting is controlled to be placed in a closed state, thereby regulating the lifting operation of the loading platform 1.

[0065] Furthermore, since the restriction on the ascent of the loading platform 1 is controlled based on the detection operation of the pressure sensor PS, there is no need to restrict the ascent of the loading platform 1 by the relief action of the relief valve R as in the first embodiment, and therefore the opening setting pressure (predetermined relief pressure pr) of the relief valve R is set higher than that of the relief valve R in the first embodiment (for example, higher than the predetermined limit pressure px).

[0066] Other configurations of the second embodiment are the same as those of the first embodiment, so the components of the second embodiment are simply given the same reference numerals as the corresponding components of the first embodiment, and further description will be omitted.

[0067] In the second embodiment, the pressure sensor PS is connected to the B-contact relay RE1 without going through the controller C so that the B-contact relay RE1 opens and the lifting solenoid on-off valve V1 is placed in a closed state in response to detecting an overload during the lifting process of the loading platform 1. Therefore, when adding an overload response function during the lifting process to an existing loading platform lifting device L, it is sufficient to connect and link the pressure sensor PS to the lifting solenoid on-off valve V1 via the B-contact relay RE1. Therefore, there is no need to make special changes to the control program of the controller C to add the overload response function, which eliminates the trouble of changing the program and also obviates the need to provide a special connection terminal in the controller C for connecting the pressure sensor PS. As a result, this can greatly contribute to cost reduction.

[0068] The second embodiment described above represents an example that embodies the third and fourth features of the present invention. In the second embodiment, the lifting electromagnetic on-off valve V1 and the lowering electromagnetic on-off valve V2 constitute a communication switching means that selectively switches the communication between the lift cylinder CL as a hydraulic cylinder and the hydraulic pump P or the oil tank T, and the B-contact relay RE1 constitutes a rise restriction means that, when activated, can restrict the rise of the loading platform 1 independently of the controller C.

[0069] Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various embodiments can be implemented within the scope of the present invention.

[0070] For example, in the first and second embodiments, a vertical lifting type loading platform lifting device L is exemplified as the loading platform lifting device L, in which a lifting slider 14 that can be raised and lowered on a lifting pillar 2 fixed to a loading box B (loading platform) is driven to rise and fall via a wire 30 by a lift cylinder CL arranged horizontally within a cross member 24, thereby raising and lowering the loading platform 1 supported on the lifting slider 14.However, in the same vertical lifting type loading platform lifting device, the arrangement of the lift cylinder is not limited to the first and second embodiments, and the lift cylinder may be arranged vertically within the lifting pillar, for example, as disclosed in Utility Model Publication No. 62-22431.

[0071] Furthermore, instead of the structure in which the left and right lifting sliders 14 are individually raised and lowered by a pair of lift cylinders CL as in the first and second embodiments, the left and right lifting sliders 14 may be linked via two wire systems between a single lift cylinder and the left and right lifting sliders so that the left and right lifting sliders 14 can be raised and lowered simultaneously by a single lift cylinder.

[0072] Furthermore, the present invention is not limited to the vertical lifting type loading platform lifting device described above. For example, the present invention may be applied to a loading platform lifting device of an upright storage type in which the lifting guide mechanism for guiding the loading platform up and down has a swing arm whose base is pivotally supported on a cargo box or vehicle frame so as to be able to swing up and down and whose tip supports the loading platform, the swing arm being driven to move up and down by a lift cylinder, and the loading platform being driven to move up and down between an upright storage position and a horizontally extended position by a tilt cylinder when the swing arm is in its uppermost position (see, for example, JP 2020-131780 A). In this case, both the operation of swinging the loading platform upward via the swing arm using the lift cylinder and the operation of swinging the loading platform upward from the horizontally extended position to the upright storage position using the tilt cylinder when the swing arm is in its uppermost position are included in the "load platform lifting operation," and both the lift cylinder and the tilt cylinder are considered to be "hydraulic cylinders capable of driving the loading platform up."

[0073] The present invention can also be applied to an underfloor storage type loading platform lifting device (see, for example, Patent No. 6591867), which is similar to the above-mentioned upright storage type loading platform lifting device in that the lifting guide mechanism that guides the loading platform up and down has the above-mentioned swing arm, but does not have a tilt cylinder and in which the loading platform is folded onto the swing arm and can slide back and forth under the cargo box floor.

[0074] In the first and second embodiments, the lifting support columns 2 of the loading platform lifting device L are fixed to the loading box B as the loading platform. However, the lifting support columns may be fixed to the body frame F.

[0075] Furthermore, in the first and second embodiments, an example of the "predetermined loading state" of the present invention has been described as an "overloaded state," i.e., a loading state in which the total weight on the loading platform 1 exceeds the maximum loading capacity of the loading platform lifting device L (e.g., 1000 kg). However, the "predetermined loading state" is not limited to the embodiments, and for example, the "predetermined loading state" may be a loading state in which the total weight of the cargo and the trolley exceeds a specific weight (e.g., 700 kg) that is set so that the trolley that is to carry the cargo on the loading platform 1 does not deform or break.

[0076] In this case, the specific total weight is a light total weight that takes into consideration the durability of the dolly, and the hydraulic pressure of the lift cylinder CL when a load of this specific total weight is placed on the loading platform 1 becomes the specified limit pressure px. Furthermore, since the specific total weight is lower than the maximum load capacity (e.g., 1000 kg) of the loading platform lifting device L, which is the criterion for determining whether the loading platform is overloaded, if the specified limit pressure px is set lower in accordance with this specific total weight, the safety performance desired by users for the loading platform lifting device L can be further improved, and deformation and damage to the dolly can also be effectively prevented. However, even in this case, the specified limit pressure px is set higher than the specified relief pressure pr described above.

[0077] Furthermore, particularly in the first embodiment, an example of a descent restricting means is shown in which a pressure sensor PS is connected to a B-contact relay RE2 arranged in the second current path 72 via a signal line 75, and the B-contact relay RE2 is opened based on a detection signal from the pressure sensor PS (i.e., without relying on the controller C) to close the second electromagnetic on-off valve V2 for descent, and particularly in the second embodiment, an example of an ascent restricting means is shown in which a pressure sensor PS is connected to a B-contact relay RE1 arranged in the first current path 71 via a signal line 75, and the B-contact relay RE1 is opened based on a detection signal from the pressure sensor PS (i.e., without relying on the controller C) to close the first electromagnetic on-off valve V1 for ascent. That is, although not shown, a receiving platform lifting / lowering device L (first embodiment) having the first and second features of the present invention and a receiving platform lifting / lowering device L (second embodiment) having the third and fourth features are shown separately, but the present invention may also be embodied in a receiving platform lifting / lowering device L having both the first to fourth features (i.e., the structures of the first and second embodiments).

[0078] In particular, in the first embodiment, the B-contact relay RE2 disposed in the second current path 72 was shown as an example of the descent restricting means, but the descent restricting means is not limited to the first embodiment, and various variations (not shown) are possible. For example, the lift guide mechanism G may be provided with a movable stopper (e.g., a tension rod, hook, etc.) that can lock the loading platform 1 at the raised end and restrict the descent of the loading platform 1 when activated, and the movable stopper can be moved between a restricting position and a non-restricting position. The power supply to the electric actuator that can drive the movable stopper between the restricting position and the non-restricting position is controlled by a relay responsive to detection by the pressure sensor PS, so that when the hydraulic pressure of the lift cylinder CL exceeds a predetermined limit pressure px, the movable stopper is driven to the restricting position, restricting the descent of the loading platform 1. In this case, the movable stopper, the electric actuator, and the relay constitute the descent restricting means.

[0079] In particular, in the second embodiment, the B-contact relay RE1 disposed in the first current path 71 is shown as an example of the ascent restriction means, but the ascent restriction means is not limited to the second embodiment, and various variations (not shown) are possible. For example, the lift guide mechanism G may be provided with a movable stopper (e.g., a tension rod, hook, etc.) that can lock the loading platform 1 at the lower end when activated to restrict the ascent of the loading platform 1 and move between a restricting position and a non-restricting position, and the energization of an electric actuator that can drive the movable stopper between the restricting position and the non-restricting position may be controlled by a relay responsive to detection by the pressure sensor PS. When the hydraulic pressure of the lift cylinder CL exceeds a predetermined limit pressure px, the movable stopper is driven to the restricting position to restrict the ascent of the loading platform 1. In this case, the movable stopper, the electric actuator, and the relay constitute the ascent restriction means.

[0080] Alternatively, as another variation of the rise restriction means, although not shown, a B-contact relay that cuts off the third current path 73 in response to detection by the pressure sensor PS may be provided in the third current path 73 connected to the pump drive motor M, and this B-contact relay may stop the motor M (and therefore the hydraulic pump P) in response to detection by the pressure sensor PS. In this variation, the B-contact relay provided in the third current path 73 constitutes the rise restriction means. [Explanation of symbols]

[0081] B. Cargo box as a loading platform C...Controller CL...Lift cylinder as a hydraulic cylinder E. Ground as a place to store luggage F... Body frame as a vehicle body G·····Lift guide mechanism L·····Load receiving platform lifting device P·····Hydraulic pump PS...Pressure Sensor px...Predetermined limit pressure RE1, RE2: B contact relay T·····Oil tank V1: First opening / closing valve for ascent as communication switching means and ascent restriction means V2: Second on-off valve for descent as communication switching means and descent restriction means 1. Loading platform 71, 72...First and second current paths as current paths

Claims

1. The present invention relates to a loading platform (1) for transferring a load between a load placement location (E) and the floor of a loading platform (B) on a vehicle body (F), a lifting guide mechanism (G) disposed between the loading platform (1) and the vehicle body (F) or the loading platform (B) and for guiding the loading platform (1) up and down between the loading location (E) and the floor, a hydraulic cylinder (CL) interlocked with the lifting guide mechanism (G) or the loading platform (1) and capable of driving the loading platform (1) up and down, a hydraulic pump (P) for pumping oil from an oil tank (T) to the hydraulic cylinder (CL), and a hydraulic pump (P) for connecting the hydraulic cylinder (CL) to the hydraulic pump (P) and the oil tank (T). a controller (C) that operates based on a pre-stored control program and controls the communication switching means (V1, V2) to lower the loading platform (1) when a command to lower the loading platform (1) is received; a pressure sensor (PS) that can detect that the oil pressure of the hydraulic cylinder (CL) exceeds a predetermined limit pressure (px) when the loading platform (1) is in a predetermined loading state; and a descent restriction means (RE2) that can restrict the descent of the loading platform (1) independently of the controller (C) when activated. A vehicle loading platform lifting device characterized in that the descent restriction means (RE2) and the pressure sensor (PS) are connected without going through the controller (C) so that the descent restriction means (RE2) operates in response to the detection of the pressure sensor (PS) during the descent of the loading platform (1).

2. the communication switching means has a lowering electromagnetic on-off valve (V2) that can open and close an oil passage between the hydraulic cylinder (CL) and the oil tank (T), and the lowering electromagnetic on-off valve (V2) is controlled to open by a valve open command signal from the controller (C) that has received the lowering command; the descent restriction means includes a B-contact relay (RE2) that is interposed in an electric path (72) connecting the controller (C) and the descent electromagnetic on-off valve (V2) and that normally closes the electric path (72); 2. The vehicle loading platform lifting device according to claim 1, wherein the B-contact relay (RE2) and the pressure sensor (PS) are connected without going through the controller (C) so that the B-contact relay (RE2) opens in response to the detection of the pressure sensor (PS) during the lowering process of the loading platform (1) and controls the lowering electromagnetic on-off valve (V2) to be placed in a closed state.

3. The present invention relates to a loading platform (1) for transferring a load between a load placement location (E) and the floor of a loading platform (B) on a vehicle body (F), a lifting guide mechanism (G) disposed between the loading platform (1) and the vehicle body (F) or the loading platform (B) and for guiding the loading platform (1) up and down between the loading location (E) and the floor, a hydraulic cylinder (CL) interlocked with the lifting guide mechanism (G) or the loading platform (1) and capable of driving the loading platform (1) up and down, a hydraulic pump (P) for pumping oil from an oil tank (T) to the hydraulic cylinder (CL), and a hydraulic pump (P) for connecting the hydraulic cylinder (CL) to the hydraulic pump (P) and the oil tank (T). a controller (C) that operates based on a pre-stored control program and controls the communication switching means (V1, V2) to raise the loading platform (1) when a command to raise the loading platform (1) is received; a pressure sensor (PS) that can detect that the oil pressure of the hydraulic cylinder (CL) exceeds a predetermined limit pressure (px) when the loading platform (1) is in a predetermined loading state; and a lift restriction means (RE2) that can restrict the lift of the loading platform (1) independently of the controller (C) when activated. A loading platform lifting device for a vehicle, characterized in that the lifting restriction means (RE2) and the pressure sensor (PS) are connected without going through the controller (C) so that the lifting restriction means (RE2) operates in response to the detection of the pressure sensor (PS) during the lifting process of the loading platform (1).

4. the communication switching means has an ascending electromagnetic on-off valve (V1) that can open and close the oil passage between the hydraulic cylinder (CL) and the oil tank (T), and the ascending electromagnetic on-off valve (V1) is controlled to open by a valve-open command signal from the controller (C) that has received the ascending command; the rise restriction means includes a B-contact relay (RE1) that is interposed in an electric path (71) connecting the controller (C) and the rise electromagnetic on-off valve (V1) and that normally closes the electric path (71); 4. The vehicle loading platform lifting device according to claim 3, wherein the B-contact relay (RE1) and the pressure sensor (PS) are connected without passing through the controller (C) so that the B-contact relay (RE1) opens in response to the detection of the pressure sensor (PS) during the lifting process of the loading platform (1) and controls the lifting electromagnetic on-off valve (V1) to be placed in a closed state.

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