JP2013043590A - Under-floor housing type elevating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection mechanism capable of reliably recognizing a folding action of a lifting platform when the lifting platform is housed in a folded manner under a vehicle floor and having a simple configuration.SOLUTION: The detection mechanism includes a body frame 10 slidable with respect to a vehicle, a hydraulic cylinder mechanism 15 for retracting the body frame under the vehicle floor, a lifting platform 60 that is foldable and has a top surface becoming flat-plate-shaped in an expanded state, a linkage mechanism for lifting which is provided on the body frame 10 side, and drives to lift the platform 60, and a detection mechanism that detects a folded state of the platform 60. The detection mechanism has a moving body 110 urged in a direction protruding from a roller 101 toward a folded platform portion, and a sensor 120 that detects a state where the moving body 110 has been pressed down by the folded platform portion.

Description

  The present invention relates to a lifting device that is mounted on the rear part of a vehicle such as a lorry to facilitate the loading and unloading of cargo by lifting and lowering the platform. Relates to the device.

  Conventionally, as an elevating device to be mounted on a truck, it has been common to use a rear gate of a truck as a platform and lift a platform also serving as a rear gate with a link mechanism.

  By the way, in a structure in which the body of a lorry does not have a gate, for example, a structure having a double door, a slide door, an accordion door, a side-open roof, etc., the structure in which the platform also serves as the gate of the body is inconvenient.

  Therefore, in the lifting device disclosed in Patent Document 1 proposed by the present applicant, the platform is configured to be folded, and the platform is folded and stored under the vehicle body floor.

  However, when the platform is folded and stored, it is necessary to recognize the folding operation of the platform, and a detection mechanism for that purpose is necessary.

JP2003-175760

  The present invention has been made in view of such a situation, and an object of the present invention is to provide an underfloor retractable lifting device having a detection mechanism that can reliably recognize the folding operation of the lifting platform when the lifting platform is folded and stored. Is to provide.

  Other objects and novel features of the present invention will be clarified in embodiments described later.

In order to achieve the above object, an underfloor retractable lifting apparatus according to an aspect of the present invention includes a main body frame that is slidable in the front-rear direction with respect to a chassis frame of a vehicle,
A cylinder mechanism for driving the main body frame in the front-rear direction with respect to the chassis frame;
An elevating platform that is foldable and has a flat top surface in the unfolded state;
An elevating drive link mechanism attached to the main body frame for elevating and driving the platform;
A support mechanism having a support member that supports the platform portion to be folded from below when the lifting platform is shifted from the expanded state to the folded state;
A detection mechanism for detecting the folded state of the lifting platform,
The detection mechanism is a moving body biased in a direction protruding from the support member toward the platform portion to be folded,
And a sensor for detecting that the movable body is pushed down by the folded platform portion.

In the above aspect, the support mechanism is an extension member that is fixed to the main body frame and extends to the front end side of the elevating platform;
A support member mounting bracket provided on the extension member;
A pin provided on the bracket;
A roller as the support member that is rotatably attached to the bracket by the pin;
The movable body in the detection mechanism is provided movably with respect to the bracket, and at least a part thereof is a magnetic body,
The sensor may be a proximity sensor that detects the proximity of the magnetic body when the moving body is pushed down by the folded platform portion.

  In this case, it is preferable that the pin is pivotally supported by penetrating one mounting end of a slide driving cylinder included in a cylinder mechanism that drives the main body frame in the front-rear direction.

In the above aspect, the elevating platform is connected to the main body frame side via the elevating drive link mechanism,
A front end side plate that is pivotally connected to the front end side of the main plate and serves as the folded platform portion;
The folding operation of the tip side plate with respect to the main plate may be performed by an opening / closing cylinder.

  In this case, the opening / closing cylinder is a double-acting hydraulic cylinder having two ports, and when the detection mechanism detects the folded state of the lifting platform, the two ports are communicated with each other by an electromagnetic valve. The construction may be such that the working cylinder is in a free state.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods and systems are also effective as aspects of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, when folding and storing an raising / lowering platform, the folding operation | movement of a raising / lowering platform which can recognize the folding operation of an raising / lowering platform reliably, and was equipped with the detection mechanism of a simple structure is realizable.

It is embodiment of the underfloor retractable raising / lowering apparatus which concerns on this invention, Comprising: It is a side view in case a raising / lowering platform performs raising / lowering operation in the state which the main body frame approached the rear end side of the chassis frame. It is a side view which shows the state before storage by the completion of folding of the raising / lowering platform in embodiment. In embodiment, it is a side view which shows the time of completion of storing of a raising / lowering platform in the state by which the main body frame was drawn in the back | inner direction of the chassis frame. It is a side view which mainly shows the raising / lowering platform in embodiment. It is a side view which mainly shows the link mechanism part for raising / lowering in embodiment. It is a side view which shows the support mechanism and detection mechanism in embodiment. It is the same front view. It is a side view which shows the extension member and support member attachment bracket of the support mechanism in embodiment. It is a perspective view of the hydraulic cylinder mechanism for slide drive in an embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, process, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  1 to 3 show an overall configuration of an embodiment of the present invention. In these drawings, for example, a box-shaped vehicle body 2 is mounted and fixed on a chassis frame 1 of a lorry, and a fixed frame 4 of an underfloor retractable lifting device is fixed to a rear portion of the chassis frame 1 of the lorry. ing. A rectangular pipe-shaped slide guide 5 with a slit is fixed to the fixed frame 4 in the front-rear direction on both sides of the chassis frame 1 in the horizontal direction. The slits of the square pipe-shaped slide guide 5 are provided for passing a runner 14 described later.

  The main body frame 10 of the underfloor retractable lifting apparatus has a main square pipe 11 as a connecting portion, brackets 12 and 13 fixed to both sides thereof, and a pair of runners 14 provided inside the brackets on both sides, The lower part of the runner 14 is fixed to the outer periphery of the square pipe 11. Further, a sub-square pipe 19 as a connecting portion parallel to the main square pipe 11 is fixed between the left and right runners 14 (see FIGS. 2 and 3). The sub-square pipe 19 is located behind the main square pipe 11 (when the front and rear of the chassis frame 1 are used as a reference).

  As shown in FIGS. 1 to 3, a runner 14 integrated with the main body frame 10 is provided on the slide guide 5 so as to be slidable in the front-rear direction of the chassis frame 1 of the vehicle. That is, a rectangular plate-like sliding member 14a having a wear resistance and a small friction coefficient such as nylon (registered trademark) resin slidably contacting the upper and lower inner surfaces of the slide guide 5 is fixed to both upper ends of the runner 14. The upper portion of the runner 14 slides smoothly in the slide guide 5 without rattling. The lower portion of the runner 14 extends downward through the slit of the slide guide 5 and is connected to the square pipes 11 and 19 (see FIGS. 2 and 3).

  A slide drive hydraulic cylinder mechanism 15 for moving the runner 14 in the front-rear direction of the chassis frame 1 is attached between the fixed frame 4 side and the main body frame 10 integrally having the runner 14. In addition, a slide drive mechanism that drives the main body frame 10 in the front-rear direction is constituted by the runner 14 that slides in the slide guide 5.

  The hydraulic cylinder mechanism 15 has two hydraulic cylinders arranged in parallel. As shown in FIG. 9, the cylinder body portions 81a and 82a of the two hydraulic cylinders 81 and 82 opposite to each other are mechanically welded or the like. It is an integrated one. The piston rod 81b of the hydraulic cylinder 81 extends from the main body portion 81a to the front of the chassis frame, and the piston rod 82b of the hydraulic cylinder 82 extends from the main body portion 82a to the rear of the chassis frame.

  The tip of one piston rod 81 b in the hydraulic cylinder mechanism 15 is connected to the fixed frame 4 side fixed to the chassis frame 1. Specifically, a rod connection bracket 41 is fixed to an intermediate portion of the lateral connection portion of the fixed frame 4, and the tip end portion of the piston rod 81 b is connected to the bracket 41 with a pin 95. The other piston rod 82b is connected to the main body frame 10 (that is, a frame portion in which the left and right runners 14 are connected and integrated). Specifically, as shown in FIGS. 6, 7, and 9, the tip of the piston rod 82 b is pin 96 on the bracket 18 fixed to the extension member (extension angle pipe 100) fixed to the intermediate portion of the sub-square pipe 19. It is connected with.

  When the piston rods 81b and 82b of the cylinders 81 and 82 are extended, the main body frame 10 (runner 14) approaches the rear end side of the floor portion 3 of the vehicle body 2 as shown in FIG. Then, as shown in FIG. 3, the main body frame 10 moves forward with respect to the chassis frame 1 and is pulled into the back direction below the vehicle body floor.

  As shown in FIGS. 4A and 4B, the elevating platform 60 connected to the main body frame 10 via the elevating drive link mechanism is rotatable to the main plate 61 and the distal end side thereof. It consists of the front end side plate 62 connected, and both plates are connected by a double hinge (double hinge having two rotation fulcrums) 64 so as to be foldable. That is, one of the small connecting links 65 included in the double hinge 64 is connected to the upper portion of the front end of the main plate 61 at a pivot point (rotation fulcrum) 66, and the other is connected to the top end plate 62 at the pivot point (rotation fulcrum) 67. It is connected to the upper part of the base end.

  When the main plate 61 and the tip side plate 62 are flattened, the reinforcing material on the back side of the main plate 61 and the reinforcing material on the back side of the tip side plate 62 (or the end surfaces of both plates 61 and 63) are abutted to each other. Is designed to function as a single flat plate platform. Further, in the folded state, the front end side plate 62 is turned over and overlaid on the main plate 61.

  In order to automatically open and close the lifting platform 60, an opening / closing hydraulic cylinder (double-acting hydraulic cylinder) 70 is disposed on the lower surface side of the main plate 61. That is, the end of the main body of the opening / closing hydraulic cylinder 70 is fixedly attached to the lower surface of the main plate 61 with a fixture (pivotally attached to the lower surface side by the pin 70a), and one end of the opening / closing link 71 is connected to the opening / closing hydraulic cylinder 70. The other end of the opening / closing link 71 is pivotally attached to a bracket 72 integral with the lower portion of the proximal end portion of the distal end side plate 62. Here, the pivot points 71 a and 71 b at both ends of the opening and closing link are on a straight line in the axial direction of the opening and closing hydraulic cylinder 70 in the deployed state of the platform 60 (or in the vicinity of the straight line). Therefore, at the initial stage of the platform folding operation in which the opening / closing hydraulic cylinder 70 starts to extend, the distal end side plate 62 rotates with the pivot point 67 of the small link 65 of the double hinge 64 to the distal end side plate 62 as a rotation fulcrum. To do. Accordingly, the opening / closing link 71 can be prevented from hindering the rotation of the distal end side plate 62. Further, the opening / closing link 71 is curved in an arc shape so as to avoid contact of the main plate 61 and the front side plate 62 with the double hinge 64 on the connection side edge (when the platform is deployed, the opening / closing link 71 is provided). 4B, a roller 75 is pivotally attached to the piston rod tip position of the open / close hydraulic cylinder 70 (the pivot point 71a of the open / close link 71) as shown in FIG. The roller 75 is guided so as to move linearly by a guide rail 76 fixed to the lower surface side of the main plate 61. That is, the piston rod is set to move linearly.

  As shown in FIG. 5, the upper end of the small arm 20 is pivotally attached to the bracket 12 of the main body frame 10 by a pin 21 (rotatably attached), and the lower abutting portion 20a of the small arm 20 faces the square pipe 11 side. The stopper portion 16 is provided in contact with the stopper portion 16. The base end portion of the main arm 25 is pivotally attached to the middle position of the small arm 20 by a pin 26, and the distal end portion is pivotally attached to the base end side upper portion of the main plate 61 by a pin 31. An elevating hydraulic cylinder 27 is pivotally attached by pins 28 and 29 between the lower end of the small arm 20 and a position near the tip of the main arm 25. Further, a sub arm 35 is pivotally connected by pins 36 and 37 between the bracket 13 of the main body frame 10 and the lower part on the base end side of the main plate 61. The main arm 25 and the sub arm 35 constitute a lifting drive link mechanism, and when the lower contact portion 20a of the small arm 20 is in contact with the stopper 16 on the square pipe 11 side, both ends of the main arm 25 are maintained. The pins 26 and 31 and the pins 36 and 37 at both ends of the sub arm 35 are respectively located at the apexes of the parallelogram, and the lift platform 60 in the unfolded state maintains a horizontal state. When the lifting hydraulic cylinder 27 is contracted, the tip of the main arm 25 is lowered (the platform 60 is lowered), and when it is extended, the tip of the main arm 25 is in the raised position (the platform 60 is in the raised position). The rotation of the small arm 20 due to the reaction force when the cylinder 27 is extended is prevented by the lower contact portion 20a contacting the square pipe side stopper 16.

  As shown in FIGS. 6 and 7, a bracket 18 fixed (for example, welded as shown in FIG. 8) to an extension square pipe 100 (connected to an intermediate part of the sub square pipe 19 by welding or the like) as an extension member. In the meantime, the tip 821 of the piston rod 82 b is connected by a pin 96. That is, the pin 96 passes through the bracket 18 and the tip end portion 821 of the piston rod 82b, and the rollers 101 are rotatably attached to both sides of the pin 96. The extension angle pipe 100, the bracket 18, and the roller 101 pivotally supported by the pin 96 serve to fold the platform portion (that is, the tip side plate 62) that is folded when the lifting platform 60 is shifted from the expanded state to the folded state. A support mechanism having a support member (that is, the roller 101) supported from below is configured.

  The detection mechanism for detecting the folded state of the elevating platform 60 is moved by the movable body 110 biased in a direction protruding obliquely upward from the roller 101 toward the front end side plate 62 to be folded, and the front end side plate 62 to be folded. And a sensor 120 that detects that the body 110 has been pushed down.

  Here, the moving body 110 is obtained by integrating a magnetic plate 112 with a screw or the like below a nonmagnetic plate 111 made of plastic or the like (a portion that can face the sensor 120), and protrudes from the roller 101 of the nonmagnetic plate 111. The upper edge has an arc shape, and a pin 96 passes through the central portion of the nonmagnetic plate 111 and a long hole 111 a that allows the nonmagnetic plate 111 to slide is formed. A spring 113 is attached by a mounting bolt 112 fixed to the bracket 18. One end of the spring 113 is locked to the magnetic plate 112, and the other end is locked to the square pipe 100, and the moving body 110 is biased in an obliquely upward projecting direction by the elastic force of the spring 113. The longitudinal direction of the long hole 111a is substantially parallel to a straight line connecting the attachment position of one end of the spring 113 and the pin 96, and the movable body 110 protruding obliquely upward is pushed by the folded front end side plate 62. It can be retracted diagonally downward.

  The sensor 120 is a proximity sensor that can detect the proximity of a magnetic object, and is fixed inside the square pipe 100. As shown in FIG. 8, a window 105 is opened at the position of the square pipe 100 facing the detection portion 120a of the sensor 120.

  Therefore, when the tip end side plate 62 that is turned upside down pushes down the moving body 110, the magnetic plate 112 comes close to and faces the detection portion 120 a of the sensor 120, and the sensor 120 detects the folded state of the lifting platform 60. Output a signal.

  A cover 130 that covers the outside of the bracket 18, the moving body 110, the spring 113, and the like is attached using the mounting bolt 112.

  When the opening / closing hydraulic cylinder 70 is extended from the unfolded state of the platform 60 of FIG. 1, the distal side plate 62 initially starts to rotate around the pivot point 67 as a rotation fulcrum. Rotation about the pivot point 66 on the main plate 61 side is also added, and finally, the distal end side plate 62 is turned over and overlapped with the main plate 61. At this time, the folded front end side plate 62 is received and stopped by the roller 101 as the support member of the support mechanism. At the same time, the moving body 110 is pushed down by the distal end side plate 62 and the sensor 120 outputs a detection signal notifying that the elevating platform 60 is folded. As a result, the supply of hydraulic oil to the open / close hydraulic cylinder 70 is stopped. The open / close hydraulic cylinder 70 is a double-acting hydraulic cylinder having two ports. However, both the ports of the double-acting hydraulic cylinder are brought into communication with electromagnetic valves by the output of the detection signal so that the open / close hydraulic cylinder 70 is free. To do. Accordingly, the distal side plate 62 can take an arbitrary posture with respect to the main plate 61 in the folded state. The reason for this is to allow the posture of the front end side plate 62 to change with respect to the main plate 61 when lifting the lifting platform 60 in a folded state for storage under the floor by the lifting drive link mechanism.

  The operation of the platform 60 from the folded state to the unfolded state can be performed by a reverse operation due to the contraction of the opening / closing hydraulic cylinder 70.

  Next, the operation of the embodiment of the underfloor retractable lifting device will be described.

  The normal cargo handling operation is performed by extending the cylinders 81 and 82 of the slide drive hydraulic cylinder mechanism 15 as shown in FIGS. In a state where the cylinders 81 and 82 are extended, the runner 14 and the main body frame 10 are slid to a state close to the floor end portion of the vehicle body 2, and the main plate 61 and the tip side plate 62 constituting the elevating platform 60 are flat. (The unfolding operation of the lifting platform 60 is performed by contracting the opening / closing hydraulic cylinder 70). Then, by extending or contracting the lifting hydraulic cylinder 27 that drives the main arm 25 included in the lifting drive link mechanism, the main arm 25 and the sub arm 35 in the parallel link state are rotated, and the platform 60 is shown in FIG. While maintaining the horizontal state from the landing state of the imaginary line (A) to the position of the solid line (B) of the height of the floor surface 3A (the upper surface of the floor 3) of the vehicle body 2, the height of the floor surface 3A The platform 60 can be lowered to the landing state, and by using such a lifting and lowering operation of the platform 60, a cargo handling operation from the ground to the vehicle body floor surface or from the vehicle body floor surface to the ground can be performed.

  When the lifting hydraulic cylinder 27 is further contracted in the landing state of the lifting platform 60, the lower contact portion 20a of the small arm 20 is separated from the stopper 16 on the square pipe 11 side (see FIG. 5), and the main arm 25 Since the mounting fulcrum (pin 26) moves to the rear side of the vehicle body 2, the lifting / lowering platform 60 is tilted as shown by the phantom line (c) in FIG. 1 to carry the luggage onto the platform 60 in the landing state. Or it can also be made to carry out efficiently.

  The platform retracting operation after normal cargo handling is completed as follows. In the unfolded state of the lifting platform 60 shown in FIG. 1 (a) or (c), the opening / closing hydraulic cylinder 70 is extended, and the tip side plate 62 is initially rotated around the pivot point 67 as a rotation fulcrum, and then connected. The small link 65 is also pivoted around the pivot point 66 on the main plate 61 side, and finally the tip side plate 62 is turned over so as to be folded on the main plate 61 (the tip side plate 62 is covered with the roller 101). Received from below and stopped.) At the same time, as a result of the sensor 120 outputting the detection signal from the lifting platform 60, the supply of hydraulic oil to the opening / closing hydraulic cylinder 70 is stopped and the opening / closing hydraulic cylinder 70 is made free.

  In this state, the main arm 25 and the sub-arm 35 are made substantially horizontal as shown in FIG. 2, and the cylinders 81 and 82 of the slide drive hydraulic cylinder mechanism 15 are contracted to move the elevator platform 60 folded as shown in FIG. Is pulled under the floor of the vehicle body 2 and stored.

  The operation of unfolding the lifting platform 60 so that cargo handling is possible is the reverse of the storage operation. First, the cylinders 81 and 82 of the slide drive hydraulic cylinder mechanism 15 are extended to runner 14 and main body frame 10. Is moved to the rear end side of the floor portion 3 of the vehicle body 2, and then the opening / closing hydraulic cylinder 70 is contracted to unfold the lifting platform 60 in a folded state to form a single flat platform shape. Thereafter, the lifting hydraulic cylinder 27 is contracted or extended to drive the platform 60 up and down via the main arm 25 and the sub arm 35.

  According to this embodiment, the following effects can be obtained.

(1) A support mechanism having a support member (roller 101) that supports a platform portion (front end side plate 62) to be folded from below when the elevating platform 60 shifts from the expanded state to the folded state, and the folded state of the platform 60. A detecting mechanism for detecting the moving body 110 that is biased in a direction protruding from the roller 101 toward the front end side plate 62 to be folded, and the moving body 110 is pushed down by the front end side plate 62. And a sensor 120 for detecting that. With this configuration, the folded state of the platform 60 can be reliably detected with a simple mechanism.

(2) The moving body 110 in the detection mechanism is provided so as to be movable along the bracket 18 that pivotally supports the roller 101, and at least a part thereof is a magnetic body, and the sensor 120 is a proximity sensor and is folded. When the moving body 110 is pushed down by the distal end side plate 62, the proximity of the magnetic body is detected, and the mechanism along the bracket 18 does not take an installation place and saves space.

(3) The moving body 110 is formed by integrating a magnetic plate 112 with a screw or the like below a non-magnetic plate 111 made of plastic or the like, but the upper edge protruding from the roller 101 of the non-magnetic plate 111 has an arc shape. The angle at which the folded front end side plate 62 hits the non-magnetic plate 111 is almost arbitrary, and it is possible to deal with various types of vehicles having different vehicle heights equipped with lifting devices.

  Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims. For example, the underfloor retractable lifting device has been exemplified in which the lifting platform has a two-plate structure of the main plate and the tip side plate, but the lifting platform may be foldable with a configuration of three or more. Further, the sensor is a proximity sensor that detects the proximity of the magnetic body, but the type of the sensor is arbitrary, and it is sufficient that the change in the position of the moving body can be detected.

DESCRIPTION OF SYMBOLS 1 Chassis 2 Car body 3 Floor part 4 Fixed frame 5 Slide guide 10 Main body frame 11 Main angle pipe 12, 13 Bracket 14 Runner 15 Hydraulic cylinder mechanism for slide drive 16 Stopper part 18 Bracket 19 Sub angle pipe 20 Small arm 25 Main arm 27 Lifting Hydraulic cylinder 35 Sub arm 60 Elevating platform 61 Main plate 62 Front end plate 64 Double hinge 70 Opening / closing hydraulic cylinder 71 Opening / closing link 81, 82 Hydraulic cylinder 81a, 82a Cylinder body 81b, 82b Piston rod 96 Pin 100 Extension angle pipe 101 Roller 110 Moving body 120 Sensor 113 Spring

Claims (5)

A body frame slidable in the front-rear direction with respect to the chassis frame of the vehicle;
A cylinder mechanism for driving the main body frame in the front-rear direction with respect to the chassis frame;
An elevating platform that is foldable and has a flat top surface in the unfolded state;
An elevating drive link mechanism attached to the main body frame for elevating and driving the platform;
A support mechanism having a support member that supports the platform portion to be folded from below when the lifting platform is shifted from the expanded state to the folded state;
A detection mechanism for detecting the folded state of the lifting platform,
The detection mechanism is a moving body biased in a direction protruding from the support member toward the platform portion to be folded,
And a sensor for detecting that the movable body is pushed down by the folded platform portion. The support mechanism is an extension member fixed to the main body frame and extended to the tip side of the lifting platform;
A support member mounting bracket provided on the extension member;
A pin provided on the bracket;
A roller as the support member that is rotatably attached to the bracket by the pin;
The movable body in the detection mechanism is provided movably with respect to the bracket, and at least a part thereof is a magnetic body,
2. The underfloor retractable lifting device according to claim 1, wherein the sensor is a proximity sensor, and detects proximity of the magnetic body when the moving body is pushed down by the folded platform portion.   The underfloor retractable lifting apparatus according to claim 2, wherein the pin is pivotally supported by penetrating one mounting end of a slide driving cylinder included in a cylinder mechanism that drives the main body frame in the front-rear direction. The elevating platform is connected to the main body frame side via the elevating drive link mechanism;
A front end side plate that is pivotally connected to the front end side of the main plate and serves as the folded platform portion;
4. The underfloor retractable lifting device according to claim 1, wherein the folding operation of the tip side plate with respect to the main plate is performed by an opening / closing cylinder.   The open / close cylinder is a double-acting hydraulic cylinder having two ports, and when the detection mechanism detects the folding state of the lifting platform, the open / close cylinder is connected by connecting the two ports with an electromagnetic valve. The underfloor retractable lifting device according to claim 4, which is in a free state.

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