Loading platform lifting device

Abstract

To provide a loading platform lifting device that can immediately resolve any malfunctions. [Solution] The system includes a loading platform for placing cargo, a lifting mechanism for raising and lowering the loading platform, an operating means 5 for raising or lowering the lifting mechanism, a detection means 63 for detecting an abnormality while the loading platform is being raised by operating the operating means 5 upward, and a forced lowering operation means 64 forcibly lowering the loading platform based on the detection of an abnormality from the detection means 63.

Description

Technical Field

[0001] The present invention relates to a load receiving platform lifting device that raises and lowers a load receiving platform on which loads are placed.

Background Art

[0002] The above load receiving platform lifting device is described in, for example, Patent Document 1, and its configuration includes a pair of posts provided at the rear end of a vehicle carrying a platform, a load receiving platform on which loads are placed, and a lifting mechanism that raises and lowers this load receiving platform with respect to the pair of posts.

[0003] By the way, when the load receiving platform is being raised, for example, if the load protrudes forward from the front end of the load receiving platform, an abnormality such as the load being sandwiched between the lower end and the upper end of the platform may occur. Therefore, when detecting such an abnormality, a safety device is provided to stop the raising of the load receiving platform.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above load receiving platform lifting device, when an abnormality is detected, only the raising of the load receiving platform stops. Therefore, unless an operator operates the load receiving platform to the lower side, the sandwiched state (abnormality) cannot be immediately eliminated, and there is room for improvement.

[0006] Therefore, an object of the present invention is to provide a load receiving platform lifting device that can immediately eliminate an abnormality.

Means for Solving the Problems

[0007] The present invention provides a loading platform lifting device comprising: a loading platform on which loads are placed; a lifting mechanism for raising and lowering the loading platform; an operating means for raising or lowering the lifting mechanism; a detection means for detecting an abnormality while the loading platform is being raised by raising the operating means; and a forced lowering operation means for forcibly lowering the loading platform that is being raised based on the detection of an abnormality from the detection means.

[0008] According to the present invention, if the detection means detects an abnormality while the loading platform is being raised by operating the operating means, the forced lowering operation means forces the loading platform to lower. This allows the abnormality to be resolved immediately.

[0009] Furthermore, the lifting and lowering device of the present invention is configured such that the lifting mechanism raises or lowers the lifting and lowering device by hydraulic pressure generated by supplying or discharging hydraulic fluid, and the forced lowering operation means has a forced switching unit that switches between supplying or discharging hydraulic fluid and discharging or supplying it, and the forced lowering operation may be performed by the switching by the forced switching unit.

[0010] As described above, when the detection means detects an abnormality, the forced switching unit can be used to forcibly lower the load receiving platform while it is being raised.

[0011] Furthermore, the loading platform lifting device of the present invention may also include a stopping means for stopping the forced lowering operation after a predetermined time has elapsed since the forced lowering operation by the forced lowering operation means began.

[0012] As described above, once a predetermined time has elapsed since the forced descent operation began, the forced descent operation can be stopped by the stopping means.

[0013] Furthermore, the loading platform lifting device of the present invention may also include a stopping means that executes a forced lowering operation when the detection means detects an abnormality and the operating means is in an upward position, and stops the forced lowering operation when the upward position of the operating means is released during the forced lowering operation.

[0014] As described above, if the upward operation of the operating means is released during the forced downward operation, the forced downward operation can be stopped by the stopping means. [Effects of the Invention]

[0015] The present invention provides a loading platform lifting device that can immediately resolve an abnormality by forcibly lowering the loading platform when an abnormality detection means detects an abnormality. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic side view showing a loading platform lifting device according to one embodiment of the present invention attached to a cargo vehicle. [Figure 2] This is a rear view showing the inside of the cross member and the safety bar of the loading platform lifting device. [Figure 3] This is an electrical circuit diagram for the lifting and lowering operation. [Figure 4] This is an electrical circuit diagram showing the current flow when the device is in a downward motion. [Figure 5] This is an electrical circuit diagram showing the current flow when the device is in an upward motion. [Figure 6] This is an electrical circuit diagram showing the current flow when the limit switch is turned ON while the device is in an upward movement, forcing it into a downward movement. [Modes for carrying out the invention]

[0017] A loading platform lifting device 1 according to one embodiment of the present invention is installed at the rear of the loading platform 2 of a cargo vehicle V, as shown in Figure 1. In the following description, the direction corresponding to the front and rear of the cargo vehicle V is referred to as the longitudinal direction, the direction corresponding to the width of the cargo vehicle V is referred to as the vehicle width direction (or left-right direction), and the direction perpendicular to the longitudinal direction and the vehicle width direction is referred to as the up-down direction. The left-right direction is the direction when viewing the vehicle from the rear to the front.

[0018] The load receiving platform lifting device 1 is used when loading and unloading goods from the rear of the loading platform 2. As shown in FIG. 1, the load receiving platform lifting device 1 includes a load receiving platform 3 on which goods are placed, a lifting mechanism 4 for lifting and lowering the load receiving platform 3, an operating means 5 (see FIG. 3) for performing an ascending operation or a descending operation on the lifting mechanism 4, and a safety device S (see FIGS. 2 and 3). The load receiving platform 3 moves between a maximum ascending position (see the two-dot chain line in FIG. 1) and a maximum descending position (see the solid line in FIG. 1).

[0019] The lifting mechanism 4 is configured to lift or lower the load receiving platform 3 by hydraulic pressure caused by the supply or discharge of hydraulic oil. Specifically, as shown in FIG. 1, the lifting mechanism 4 includes a pair of left and right outer columns 41, 41 (only the left side is shown), a pair of left and right inner columns 42, 42 (only the left side is shown), a pair of left and right sliders 43, 43 (only the left side is shown), a power unit 44 and a hydraulic cylinder 45 which is a hydraulic drive source shown in FIG. 2, and a fixed sheave 47 and a movable sheave 48 around which a wire for lifting and lowering (not shown) is wound.

[0020] Each outer column 41 is a rectangular tube-shaped member that is arranged at intervals in the left-right direction and extends in the up-down direction. The left and right outer columns 41, 41 are connected by a cross member 7 provided therebetween. The cross member 7 is configured in a box shape for housing equipment for lifting and lowering the load receiving platform 3.

[0021] As shown in FIG. 1, at the lower end of each outer column 41, there is provided a stopper 41B against which the contact portion 42A at the lower end of the inner column 42 abuts to regulate the maximum ascending position of the inner column 42.

[0022] The inner columns 42, 42 are rectangular tube-shaped members having an outer diameter smaller than the inner diameter of the outer columns 41, 41, and are provided inside the outer columns 41, 41 so as to be movable up and down.

[0023] Sliders 43, 43 pass through the vertical slits (not shown) of the outer columns 41, 41 and the inner columns 42, 42, with their rear ends protruding rearward from the outer columns 41, 41 and the inner columns 42, 42. As shown in Figure 1, a bracket 43A is provided at the lower rear end of each slider 43, and the load receiving platform 3 is attached to the bracket 43A so that it can rotate around the left and right axes. In addition, a stopper (not shown) is provided at the upper end of each slider 43 to contact a plate (not shown) provided at the upper end of the inner column 42 and to restrict the upward position of the slider 43 relative to the inner column 42.

[0024] As shown in Figure 2, the power unit 44 constitutes a drive source that generates hydraulic pressure to extend and retract the hydraulic cylinder 45. The power unit 44 is located in the lower part of the cross member 7. The power unit 44 is composed of an electric motor 44A, a hydraulic pump 44P, an oil tank 44B, and a valve block 44C arranged in a single line in the left-right direction.

[0025] The hydraulic cylinder 45 is positioned above the power unit 44 within the cross member 7 and offset to the right in the vehicle width direction (left-right direction). The hydraulic cylinder 45 includes a cylinder tube 45A that is rotatably connected around the front-rear axis while being sandwiched between a pair of front and rear brackets 6, 6 (only the rear bracket is shown in Figure 2), the base end of which is fixed to the inner wall 41a of the right outer column 41, and a piston rod 45B that extends and retracts (contracts and retracts) along the horizontal (left-right direction) axis relative to the cylinder tube 45A by hydraulic pressure supplied from the power unit 44. The piston rod 45B is located on the right side of the cross member 7 when the piston rod 45B is retracted (see the dashed line in Figure 2), and moves to the left side when the piston rod 45B is extended (see the solid line in Figure 2).

[0026] The electric motor 44A is the power source that drives the hydraulic pump 44P. The electric motor 44A is powered and rotated by electricity supplied from the vehicle's battery.

[0027] The hydraulic pump 44P draws in and discharges oil from the oil tank 44B, and through a switching operation of a solenoid valve (corresponding to the forced switching unit in this invention, not shown) described later, hydraulic fluid is supplied to the protruding side hydraulic fluid chamber (not shown) that extends the piston rod 45B of the hydraulic cylinder 45 via the first pipe 8, causing the hydraulic cylinder 45 to extend. In addition, the retraction side hydraulic fluid chamber that retracts the piston rod 45B of the hydraulic cylinder 45 and the oil tank 44B are connected via a second pipe 9 described later, and the hydraulic fluid from the retraction side hydraulic fluid chamber that retracts the piston rod 45B of the hydraulic cylinder 45 is discharged into the oil tank 44B, causing the hydraulic cylinder 45 to shorten. Therefore, when the hydraulic cylinder 45 extends (see solid line in Figure 2), the slider 43 rises and the loading platform 3 rises. Conversely, when the hydraulic cylinder 45 shortens (see dashed line in Figure 2), the slider 43 lowers and the loading platform 3 lowers.

[0028] The oil tank 44B stores the oil supplied from the hydraulic pump 44P to the hydraulic cylinder 45. The oil tank 44B and the hydraulic cylinder 45 are connected by the second pipe 9, and the oil in the hydraulic cylinder 45 is discharged into the oil tank 44B, shortening the hydraulic cylinder 45.

[0029] The valve block 44C is composed of multiple valves, including solenoid valves and relief valves, which are not shown in the illustration, integrated into a single unit.

[0030] As shown in Figure 2, the safety device S is positioned below the cross member 7 and includes a rod-shaped safety bar 61 with its longitudinal direction in the vehicle width direction, a pair of arm portions 62, 62 that support both ends of the safety bar 61 in the vehicle width direction and are capable of vertical rotation around the axis X in the left-right direction, a limit switch 63 as a detection means that operates in conjunction with the upward rotation of the arm portions 62, 62, and a forced lowering operation means 64 (see Figure 4) that forcibly lowers the load receiving platform 3 based on the detection signal from the limit switch 63.

[0031] The forced lowering mechanism 64 is equipped with the solenoid valve. The limit switch 63 also has a b-contact 63A that is biased to close by a spring or the like. As the load-receiving platform 3 rises, the actuating piece 63B of the limit switch 63 is pressed as the arms 62, 62 rotate upward, causing the closed b-contact 63A to open. The opening of the b-contact 63A switches the solenoid valve, and the forced lowering operation is performed.

[0032] Therefore, when the loading platform 3 is raised with the load protruding towards the front of the vehicle, the load comes into contact with the safety bar 61, causing the safety bar 61 to move upward. This movement opens the normally closed contact 63A of the limit switch 63, causing the forced lowering mechanism 64 to forcibly lower the loading platform 3. This immediately resolves the condition (abnormality) where the load is trapped between the lower end of the loading platform 2 and the upper end of the loading platform 3.

[0033] Figure 3 shows the electrical circuit diagram for driving and rotating the electric motor 44A. The electrical circuit diagram consists of a main switch 11, a column switch 12, a relay (electromagnetic relay) 13, a limit switch 63, a solenoid 10, and the electric motor 44A.

[0034] The main switch 11 is an ON-OFF switch for supplying power to the power unit 44. In Figure 3, the main switch 11 is in the OFF state.

[0035] The column switch 12 is a switch that constitutes the operating means 5 for raising or lowering the load receiving platform 3 by operating the lifting mechanism 4 upward or downward.

[0036] Relay 13 is a relay (also called a contactor) installed between the positive side of the DC power supply (in this embodiment, the battery mounted on the freight vehicle V) 14 and the electric motor 44A.

[0037] The limit switch 63 constitutes the detection means for detecting abnormalities while the load receiving platform 3 is being raised. Normally, the contact 63A of the limit switch 63 is closed by a biasing force such as a spring, and the contact 63A is opened when the operating piece 63B of the limit switch 63 pushes against the contact 63A.

[0038] The solenoid 10 is a device for switching the solenoid valve to the side that shortens the hydraulic cylinder 45 (the side that discharges the hydraulic fluid from the retraction side hydraulic fluid chamber that retracts the piston rod 45B of the hydraulic cylinder 45). This switching causes the load receiving platform 3 to descend under its own weight.

[0039] As shown in Figure 3, a relay 15 is connected between the main switch 11 and the column switch 12. Three wires 16, 17, and 18 are connected to the terminals of the relay 15 on the column switch 12 side: the first wire 16, which is the input side of the column switch 12; and the second wire 17 and third wire 18, which are the output sides from the column switch 12. In addition, the terminals of the relay 15 on the main switch 11 side are connected to the fourth wire 19, which is the output side of the main switch 11; the fifth wire 20, which is the input side of the limit switch 63; and the sixth wire 21, which is connected to the third wire 24 and the wire 25 connected to the solenoid 10, which are among the three wires 22, 23, and 24 connected to the output side of the B-contact relay (forced downward operation means 64). Of the three wires 22, 23, and 24, the remaining first wire 22 is connected to the fourth wire 19, and the remaining second wire 23 is connected to the fifth wire 20. The input side of the B-contact relay (forced downward operation means 64) is connected to the other end of an input wire 27, one end of which is connected to a wire 26 that connects the limit switch 63 and the relay 13.

[0040] To lower the loading platform 3, with the main switch 11 turned ON, the column switch 12 is pushed downwards, closing the downward-side A-contact 12A shown in Figure 4, and causing the loading platform 3 to lower. Specifically, when the A-contact 12A closes, current flows from the positive side of the DC power supply 14 (upper side of Figure 4) to the main switch 11 via the input terminal of the relay 13, as indicated by the arrow. Current flows from the downward-side A-contact 12A to the negative side of the DC power supply 14 (shown at the bottom of Figure 4) via the solenoid 10. This energizes the solenoid 10, causing the solenoid valve to switch, as described above, and the hydraulic fluid from the hydraulic cylinder 45 to be discharged into the oil tank 44B. As a result, the loading platform 3 lowers due to its own weight.

[0041] Conversely, to raise the loading platform 3, with the main switch 11 turned ON, the column switch 12 is tilted upward, closing the A-contact 12B on the upward side and raising the loading platform 3. Specifically, as indicated by the arrow, when the A-contact 12B closes, current flows from the positive side of the DC power supply 14 (upper side of Figure 5) to the main switch 11 via the input terminal of the relay 13, and then to the limit switch 63 via the A-contact 12B. The current flowing through the limit switch 63 energizes the coil of the relay 13, causing the contacts of the relay 13 to close. As a result, the positive side of the DC power supply 14 and the negative side of the DC power supply 14 (shown on the lower side of Figure 5) are electrically connected via the relay 13, driving the electric motor 44A to rotate, driving the hydraulic pump 44P, and as described above, extending the hydraulic cylinder 45 and raising the loading platform 3.

[0042] Furthermore, regarding the case where the actuation piece 63B of the limit switch 63 is pressed while the loading platform 3 is being raised, if the actuation piece 63B of the limit switch 63 is pressed in the state shown in Figure 5, that is, while the loading platform 3 is being raised, the contact 63A of the limit switch 63 is switched to the open state, as shown in Figure 6. This interrupts the current to the relay 13, and the contacts of the relay 13 are also opened. As a result, as shown by the arrow in Figure 6, current flows from the positive side of the DC power supply 14 (upper side in Figure 6) to the main switch 11 via the input terminal of the relay 13, current flows to the first line 17 and the fifth line 20 via the A contact 12B, current flows to the second line 23 connected to the fifth line, the third line 24, and the line 25 connected to the third line 24, current energizes the solenoid 10, and the solenoid valve is switched to the side that shortens the hydraulic cylinder 45. Due to this switching, the loading platform 3 descends under its own weight. In other words, even though the column switch 12 is tilted upward to raise the loading platform 3, the loading platform 3 is actually lowered.

[0043] The system may also be implemented with a control unit that includes a stopping mechanism to stop the forced descent of the loading platform 3 when the upward operation of the operating mechanism 5 (column switch 12) is released after the forced descent of the loading platform 3 has started due to the activation piece 63B of the limit switch 63 being pressed. Alternatively, the system may be implemented with a stopping mechanism to stop the forced descent operation after a predetermined time has elapsed since the start of the forced descent operation. In this case, the stopping mechanism is shown only in Figure 6. In Figure 6, a timer circuit 28 that cuts off the current from the second wire 23 to the sixth wire 21 after a predetermined time has elapsed since the start of the forced descent operation may be provided on the second wire 23. The timer circuit 28 may be provided at any position between the positive and negative sides of the DC power supply 14. Furthermore, a detection mechanism (e.g., a proximity sensor) may be provided to detect the height (vertical) position of the inner column 42 and the loading platform 3 during the forced descent operation, and the forced descent operation may be stopped when the detection mechanism detects that the height of the inner column 42 and the loading platform 3 has reached a predetermined height. Alternatively, a stroke sensor may be provided on the hydraulic cylinder 45, and the forced downward movement may be stopped when the stroke sensor detects that the amount of shortening during the forced downward movement has reached a predetermined amount.

[0044] It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, the present invention can also be applied to a type in which the loading platform 3 is stored under the floor.

[0045] In the above embodiment, the forced lowering operation means 64 is composed of a B-contact relay, but it may also be composed of a control unit equipped with a control circuit for forcibly supplying current to the solenoid 10 in response to a detection signal from the limit switch 63, or it may be implemented by providing a hydraulic circuit that forcibly operates the hydraulic cylinder 45, which is in extension mode, to the shortened side in response to a detection signal from the limit switch 63.

[0046] Furthermore, in the above embodiment, the loading platform 3 was raised and lowered by the extension and retraction of the hydraulic cylinder 45, but the loading platform 3 may also be raised and lowered by rotating the electric motor in the forward and reverse directions.

[0047] Furthermore, although a limit switch 63 was used as a detection means for detecting abnormalities in the above embodiment, non-contact sensors such as photoelectric sensors or ultrasonic sensors may also be used. If a non-contact sensor is used, the system can be configured to forcibly lower the loading platform 3 when the non-contact sensor detects that the distance between the load and the loading platform 2 has reached a predetermined distance (that the load has approached), thereby making it easier to avoid the load being caught between the loading platform 2 and the loading platform 3.

[0048] Furthermore, in the above embodiment, an abnormality in which the cargo becomes trapped between the lower end of the loading platform and the upper end of the loading platform may be detected. However, an abnormality in which, for example, the loading platform 3 moves above its highest position may also be detected.

[0049] Furthermore, although a relay (also called an electromagnetic relay or contactor) was used in the above embodiment, an electromagnetic contactor or electromagnetic switch may also be used. These relays, electromagnetic contactors, electromagnetic switches, etc. are referred to as electrical equipment.

[0050] Furthermore, in the above embodiment, the electric motor 44A is controlled by a limit switch 63, but the electric motor 44A may also be controlled by a programmable logic controller (PLC). [Explanation of symbols]

[0051] 1...Loading platform lifting device, 2...Loading platform, 3...Loading platform, 4...Lifting mechanism, 5...Operating means, 6...Bracket, 7...Cross member, 10...Solenoid, 11...Main switch, 12...Column switch, 13...Relay, 14...DC power supply, 15...Relay, 16...Input side first wire, 17...Output side second wire, 18...Output side third wire, 19...Output side fourth wire, 20...Input side fifth wire, 21...Sixth wire, 22...First wire, 23...Second wire, 24...Third wire, 25,26...Lines, 27...Input wire, 28...Timer circuit, 41...Outer column, 41B...Stopper, 4 1a...Inner wall, 42...Inner column, 42A...Contact part, 43...Slider, 43A...Bracket, 44...Power unit, 44A...Electric motor, 44B...Oil tank, 44C...Valve block, 44P...Hydraulic pump, 45...Hydraulic cylinder, 45A...Cylinder tube, 45B...Piston rod, 47...Fixed sheave, 48...Movable sheave, 61...Safety bar, 62...Arm part, 63...Limit switch (detection means), 63A...Contact, 63B...Actuating piece, 64...Forced lowering operation means, S...Safety device, V...Cargo vehicle, X...Axis

Claims

1. A loading platform for placing cargo, a lifting mechanism for raising and lowering the loading platform, an operating means for raising or lowering the lifting mechanism, and a detection means for detecting an abnormality while the loading platform is being raised by raising the operating means. A loading platform lifting device comprising a forced lowering mechanism that forcibly lowers the loading platform while it is rising based on the detection of an abnormality from the detection means.

2. The lifting mechanism is configured to raise or lower the loading platform by hydraulic pressure generated by supplying or discharging hydraulic fluid, and the forced lowering operation means has a forced switching unit that switches between supplying or discharging hydraulic fluid and supplying or discharging it, and the forced lowering operation is performed by the switching by the forced switching unit, as described in claim 1.

3. The loading platform lifting device according to claim 1 or 2, further comprising a stopping means for stopping the forced lowering operation after a predetermined time has elapsed since the forced lowering operation by the forced lowering operation means started.

4. The loading platform lifting device according to claim 1 or 2, wherein the forced lowering operation means executes a forced lowering operation when the detection means detects an abnormality and the operating means is in an upward operation, and the stopped means stops the forced lowering operation when the upward operation of the operating means is released during the forced lowering operation.

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