Loading platform lifting device

Abstract

To provide a loading platform lifting device that can suppress the inertial rotation of an electric motor. [Solution] The system includes a lifting mechanism having an electric motor 44A for raising and lowering a 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, a power supply 14 for supplying power to the electric motor 44A, a first electrical device 64 that connects the power supply 14 and the electric motor 44A when the detection means 63 has not detected an abnormality, and disconnects the connection between the power supply 14 and the electric motor 44A when the detection means detects an abnormality, and a second electrical device 65 that disconnects the connection between the first electrical device 64 and the electric motor 44A and the other line when the detection means 63 has not detected an abnormality, and connects the connection between the first electrical device 64 and the electric motor 44A and the other line when the detection means 63 detects an abnormality.

Description

Technical Field

[0001] The present invention relates to a load receiving platform lifting device for lifting a load receiving platform on which a load is 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 on which a platform is mounted, a load receiving platform on which a load is placed, and a lifting mechanism having an electric motor for lifting and lowering this load receiving platform with respect to the pair of posts.

[0003] By the way, when the load receiving platform is being lifted, 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 load receiving platform may occur. Therefore, when such an abnormality is detected during the lifting of the load receiving platform, a safety device is provided to stop the lifting of the load receiving platform. The safety device is provided on the load platform side and includes an auxiliary member that is pushed upward when a load abuts during the lifting of the load receiving platform, and a detection means for detecting the upward movement of this auxiliary member.

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 the detection means detects the upward movement of the auxiliary member, the rotation of the electric motor is stopped by cutting off the power supply from the power source to the electric motor. However, the electric motor performs coasting rotation. Therefore, until the lifting and lowering of the load receiving platform completely stops after the detection means detects, the electric motor rotates slightly, which does not serve as a safety device.

[0006] Therefore, the present invention aims to provide a loading platform lifting device that can suppress the inertial rotation of an electric motor. [Means for solving the problem]

[0007] The present invention provides a loading platform lifting device comprising: a loading platform on which loads are placed; a lifting mechanism having an electric motor 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; a power supply for supplying power to the electric motor; and a primary line connecting the power supply and the input side of the electric motor, and a secondary line connected to the output side of the electric motor, provided on one of these lines, which connects the power supply and the electric motor when the detection means has not detected an abnormality, and The system includes: a first electrical device that disconnects the connection between the power supply and the electric motor when the detection means detects an abnormality; and a second electrical device provided on one of the lines to connect the first electrical device and the electric motor, and the other of the primary and secondary lines, which disconnects the connection between the first electrical device and the electric motor and the other line when the detection means does not detect an abnormality, and connects the connection between the first electrical device and the electric motor and the other line when the detection means detects an abnormality.

[0008] According to the present invention, as long as the detection means does not detect an abnormality while the loading platform is being raised, the first electrical device connects the power supply and the electric motor. This allows the loading platform to be raised or lowered by operating the operating means in an upward or downward operation. Furthermore, if the detection means detects an abnormality while the loading platform is being raised, the first electrical device disconnects the connection between the power supply and the electric motor, and the second electrical device connects the first electrical device and the electric motor to the other line. This connects the electric motor and the first electrical device to the other line via the second electrical device, forming a closed circuit, and the induced current generated by the inertial rotation of the electric motor flows through the closed circuit. Therefore, the induced current is converted into thermal energy in the coils of the electric motor, and the inertial rotation of the electric motor can be stopped immediately.

[0009] Furthermore, the loading platform lifting device of the present invention may include a timer circuit for connecting the second electrical equipment after a predetermined time has elapsed since the first electrical equipment was shut off.

[0010] As described above, by connecting the second electrical device a predetermined time after the first electrical device is turned off, the first and second electrical devices are connected simultaneously, which prevents a short circuit between the circuit connected by the first electrical device and the circuit connected by the second electrical device. [Effects of the Invention]

[0011] The present invention provides a loading platform lifting device that can suppress the inertial rotation of an electric motor by converting the induced current generated by the inertial rotation of the electric motor into thermal energy using the electric motor's coils, thereby immediately stopping the inertial rotation of the electric motor. [Brief explanation of the drawing]

[0012] [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 the upward movement position. [Modes for carrying out the invention]

[0013] 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.

[0014] The loading platform lifting device 1 is used when loading and unloading cargo from the rear of the loading platform 2. As shown in Figure 1, the loading platform lifting device 1 comprises a loading platform 3 on which cargo is placed, a lifting mechanism 4 for raising and lowering the loading platform 3, an operating means 5 (see Figure 3) for raising or lowering the lifting mechanism 4, and a safety device S (see Figure 2). The loading platform 3 moves between the highest position (see the dashed line in Figure 1) and the lowest position (see the solid line in Figure 1).

[0015] As shown in Figure 1, the lifting mechanism 4 comprises 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 as shown in Figure 2, and a fixed sheave 47 and a movable sheave 48 around which a lifting wire (not shown) is wound.

[0016] 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 to house equipment for raising and lowering the load receiving platform 3.

[0017] 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 uppermost position of the inner column 42.

[0018] 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.

[0019] The sliders 43, 43 penetrate through the respective vertical slits (not shown) of the outer columns 41, 41 and the inner columns 42, 42, and the rear ends protrude rearward from the outer columns​​​​​​​The hydraulic cylinder 45 is disposed above the power unit 44 within the cross member 7 and is offset (shifted in position) toward the right side in the vehicle width direction (left - right direction). The hydraulic cylinder 45 includes a cylinder tube 45A that is sandwiched between a pair of front - rear brackets 6, 6 (only the rear side is shown in FIG. 2) whose base ends are fixed to the inner wall 41a of the outer column 41 on the right side and is connected so as to be rotatable about the front - rear axis, and a piston rod 45B that extends and retracts (moves in and out) along the horizontal direction (left - right direction) axis with respect to the cylinder tube 45A by the 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 shortened (see the two - dotted line in FIG. 2) and moves to the left side when the piston rod 45B extends (see the solid line in FIG. 2).

[0022] The electric motor 44A is a drive source for driving the hydraulic pump 44P. The electric motor 44A is driven to rotate by power supplied from a DC power source provided in the vehicle (in this embodiment, a battery mounted on the freight vehicle V) 10.

[0023] The hydraulic pump 44P sucks and discharges the oil in the oil tank 44B, and the hydraulic oil is supplied to the protruding - side working oil chamber (not shown) that protrudes the piston rod 45B of the hydraulic cylinder 45 via the first pipe 8 by the switching operation of a solenoid valve (not shown) described later, causing the hydraulic cylinder 45 to extend. Also, the retracting - side working oil chamber that retracts the piston rod 45B of the hydraulic cylinder 45 and the oil tank 44B are connected via the second pipe 9 described later, and the hydraulic oil in the retracting - side working oil chamber that retracts the piston rod 45B of the hydraulic cylinder 45 is discharged to the oil tank 44B, causing the hydraulic cylinder 45 to contract. Therefore, when the hydraulic cylinder 45 extends (see the solid line in FIG. 2), the slider 43 rises and the load - receiving platform 3 rises. Also, when the hydraulic cylinder 45 contracts (see the two - dotted line in FIG. 2), the slider 43 descends and the load - receiving platform 3 descends.

[0024] 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, causing the hydraulic cylinder 45 to shorten.

[0025] 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.

[0026] 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 turns ON when the arm portions 62, 62 rotate upward, and a first relay (electromagnetic relay) 64 (see Figure 3) as a first electrical device that operates based on a signal from the limit switch 63.

[0027] As shown in Figure 3, the first relay 64 is positioned between the DC power supply 14 and the electric motor 44A. While a non-detection signal (OFF signal) is output from the detection means (limit switch 63) (while the actuation piece 63B of the limit switch 63 is not pressed), the relay connects the DC power supply 14 and the electric motor 44A. When a detection signal (ON signal) is output from the detection means (limit switch 63) (the actuation piece 63B of the limit switch 63 is pressed), the relay disconnects the connection between the DC power supply 14 and the electric motor 44A. This disconnection cuts off the power supply from the DC power supply 14 to the electric motor 44A, causing the electric motor 44A to stop.

[0028] As described above, the rotation of the electric motor 44A is stopped by interrupting the power supply from the DC power supply 14 to the electric motor 44A, but the electric motor 44A continues to rotate by inertia. Therefore, the electric motor 44A continues to rotate slightly from the time the detection means (limit switch 63) detects until the lifting and lowering of the loading platform 3 comes to a complete stop. For this reason, in the present invention, when the detection means (limit switch 63) detects, a second relay (electromagnetic relay) 11 is provided as a second electrical device to form a closed circuit K for allowing the induced current generated by the inertially rotating electric motor 44A to flow to the electric motor 44A.

[0029] The limit switch 63 is equipped with a c-contact having a common terminal COM, a normally closed terminal NC, and a normally open terminal NO. As the arms 62, 62 rotate upward, the operating piece 63B of the limit switch 63 is pressed, and the c-contact is switched by a biasing force such as a spring from a state in which the common terminal COM and the normally closed terminal NC are connected (see Figures 4 and 5) to a state in which the common terminal COM and the normally open terminal NO are connected (see Figure 6).

[0030] Specifically, the closed circuit K consists of a power supply line (corresponding to the primary line of the present invention) 24 between the input side of the electric motor 44A and the output side of the first relay 64, a wiring 25 with one end connected to the power supply line 24 and the other end connected to one contact of the second relay 65, a secondary line 26 connected to the output side of the electric motor 44A, and a wiring 27 with one end connected to the secondary line 26 and the other end connected to the other contact of the second relay 65.

[0031] Therefore, when the loading platform 3 is raised with the load protruding to the front of the vehicle, the load comes into contact with the safety bar 61, causing the safety bar 61 to move upward. This upward movement presses the actuation piece 63B of the limit switch 63, switching the common terminal COM and the normally closed terminal NC from a connected state (see Figures 4 and 5) to a connected state (see Figure 6). As a result, the coil of the second relay 65 is energized, the second relay 65 closes and turns ON, and the closed circuit K is formed. The first relay 64 and the second relay 65 are composed of B-contact relays that are open when no current flows due to a biasing means such as a spring, and switch to a closed state against the biasing force of the biasing means when current flows.

[0032] 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 first relay 64, a limit switch 63, a solenoid 10, the electric motor 44A, and a second relay 65.

[0033] 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.

[0034] 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.

[0035] The first relay 64 is located between the positive side of the DC power supply 14 and the input side of the electric motor 44A.

[0036] The limit switch 63 constitutes the detection means for detecting abnormalities while the load receiving platform 3 is being raised. The limit switch 63 is equipped with a c-contact, and normally the common terminal COM and the normally closed terminal NC are connected by a biasing force such as a spring (see Figures 3, 4, and 5). When the actuating piece 63B of the limit switch 63 detects an abnormality and is pressed by the safety bar 61, it switches from the state in Figure 5 to a state in which the common terminal COM and the normally open terminal NO are connected against the biasing force such as a spring (see Figure 6).

[0037] 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.

[0038] As shown in Figure 3, a relay 15 is connected between the main switch 11 and the column switch 12. Three wires are connected to the terminal of the relay 15 on the column switch 12 side: the first wire 16 on the input side of the column switch 12, and the second wire 17 and third wire 18 on the output side from the column switch 12. In addition, the terminal of the relay 15 on the main switch 11 side is connected to the fourth wire 19 on the output side of the main switch 11, the fifth wire 20 on the input side of the limit switch 63, and the sixth wire 25 which is connected to the solenoid 10. The input side of the first relay 64 is connected to the normally closed terminal NC of the limit switch 63 by the seventh wire 22. The input side of the second relay 65 is connected to the normally open terminal NO of the limit switch 63 by the eighth wire 23. In Figure 3, the main switch 11 is turned OFF.

[0039] To lower the loading platform 3, with the main switch 11 in the ON position, 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 first relay 64, 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.

[0040] Conversely, when raising the loading platform 3, with the main switch 11 in the ON position, 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 first relay 64, 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 first relay 64, closing the contact of the first relay 64. 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 first relay 64, causing the electric motor 44A to rotate, which drives the hydraulic pump 44P, and as described above, the hydraulic cylinder 45 extends and the loading platform 3 rises.

[0041] Furthermore, regarding the case where the limit switch 63 is turned ON while the loading platform 3 is being raised, as shown in Figure 5, when the limit switch 63 is pressed and turned ON while the loading platform 3 is being raised, the common terminal COM and the normally open terminal NO are switched to a state where they are connected against the biasing force such as the spring, as shown in Figure 6. As a result, the current to the first relay 64 is cut off, the contacts of the first relay 64 are opened, and the rotation of the electric motor 44A stops. Then, as shown by the arrow in Figure 6, current flows from the positive side of the DC power supply 14 (upper side of Figure 6) to the main switch 11 via the input terminal of the first relay 64, current flows from the second wire 17, the fifth wire 20, and the common terminal COM of the limit switch 63 to the normally open terminal NO via the A contact 12B, the coil of the second relay 65 is energized via the eighth wire 23, and the second relay 65 closes and turns ON. As a result, as described above, a closed circuit K is formed, allowing the induced current generated by the inertially rotating electric motor 44A to flow through the electric motor 44A. This allows the rotation of the electric motor 44A to be stopped immediately. In this invention, since it is only necessary to provide a second relay 65 to allow the induced current generated by the inertially rotating electric motor 44A to flow through the electric motor 44A, it is possible to suppress the increase in size and cost of the electric motor 44A compared to, for example, the case in which an electromagnetic brake is provided to forcibly stop the inertially rotating electric motor 44A.

[0042] Alternatively, as shown in Figures 3 to 6, a timer circuit 28 may be provided between the c-contact of the limit switch 63 and the second relay 65. The timer circuit 28 is provided to turn on the second relay 65 a predetermined time after the first relay 64 is turned off. In this way, by turning on the second relay 65 a predetermined time after the first relay 64 is turned off, the first relay 64 and the second relay 65 are turned on simultaneously, which prevents a short circuit between the circuit connected by the first relay 64 and the circuit connected by the second relay 65.

[0043] 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.

[0044] 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.

[0045] 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 electric motor 44A can be stopped when the non-contact sensor detects that the distance to the load has reached a predetermined distance, thereby stopping the electric motor 44A before the load is caught between the loading platform 2 and the loading platform 3.

[0046] 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.

[0047] Furthermore, in the above embodiment, the system was configured to stop the raising of the loading platform 3 when an abnormality was detected while the loading platform was being raised. However, in addition to this configuration, an emergency stop button may be provided near the operating means 5 to stop the raising of the loading platform 3 at any time.

[0048] Furthermore, in the above embodiment, relays (also called electromagnetic relays or contactors) were used as the first and second electrical devices, but electromagnetic contactors or electromagnetic switches may also be used.

[0049] Furthermore, in the above embodiment, a DC power supply 14 was used as the power source for driving the electric motor 44A, but an AC power supply may also be used.

[0050] Furthermore, in the above embodiment, the first relay (electromagnetic relay) 64 as the first electrical device is provided on the power supply line (primary line) 24, but the first relay (electromagnetic relay) 64 may also be provided on the secondary line 26. In this case, the input side of the second relay (electromagnetic relay) 11 as the second electrical device is connected to the power supply line (primary line) 24, and the output side of the second relay (electromagnetic relay) 11 is connected between the output side of the electric motor 44A and the input side of the first relay (electromagnetic relay) 64.

[0051] 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]

[0052] 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, 12A, 12B...A contact, 14...DC power supply (battery), 15...Relay, 16~23...Wire, 24...Power supply side line (primary side line), 25...Wiring, 26...Secondary side line, 27...Wiring, 28...Timer circuit, 41...Outer column, 41B...Stopper, 41a...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 section, 63...Limit switch (detection means), 63B...Actuating piece, COM...Common terminal, K...Closed circuit, NC...Normally closed terminal, NO...Normally open terminal, S...Safety device, V...Cargo vehicle, X around...Axis center

Claims

1. A loading platform for placing cargo, a lifting mechanism having an electric motor 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 power supply for supplying power to the electric motor, A loading platform lifting device comprising: a first electrical device provided on one of the lines of a primary line connecting the power supply and the input side of the electric motor and a secondary line connected to the output side of the electric motor, which connects the power supply and the electric motor when the detection means does not detect an abnormality, and disconnects the connection between the power supply and the electric motor when the detection means detects an abnormality; and a second electrical device provided on the one line to connect the first electrical device and the electric motor and the other line of the primary line and secondary line, which disconnects the connection between the first electrical device and the electric motor and the other line when the detection means detects an abnormality, and connects the connection between the first electrical device and the electric motor and the other line when the detection means detects an abnormality.

2. The loading platform lifting device according to claim 1, further comprising a timer circuit for connecting the second electrical equipment after a predetermined time has elapsed since the first electrical equipment was shut off.

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