JP6473315B2 - Cargo lift and truck - Google Patents

Description

  The present invention relates to a freight vehicle having a platform lifting device, and in particular, for loading and unloading cargo such as vehicles, the platform is slid rearward and the platform is lowered substantially horizontally to the ground behind the host vehicle. The present invention relates to a hydraulic cylinder for a platform lifting device that can be suitably used for a truck.

As this type of freight vehicle, for example, a technique described in Patent Document 1 is disclosed.
The truck described in the document includes a moving mechanism that uses a plurality of hydraulic cylinders to move the loading platform from a position stored on the chassis frame to a position where the loading platform is lowered to the rear of the host vehicle.
This moving mechanism supplies drive hydraulic oil supplied to a plurality of hydraulic cylinders (front cylinder, rear cylinder) to each hydraulic cylinder sequentially at a predetermined timing when the loading platform is lowered substantially horizontally to the ground behind the host vehicle. By doing so, the driving force to the driving object (moving frame, loading platform) is sequentially switched (hereinafter also referred to as “sequential operation control”).
According to the freight car described in the document, the loading platform can be slid from the position stored on the chassis frame to the position lowered to the rear of the host vehicle by predetermined sequential operation control of the front cylinder and the rear cylinder.

JP 2011-105215 A

  Here, as a measure for performing the sequential operation control, for example, a switching valve having a switch unit is provided in the moving mechanism separately from a plurality of hydraulic cylinders, and the switch unit of the switching valve is set by a moving operation of the driven object itself. It can be configured to push in accordance with the timing of sequential operation. With such a configuration, the plurality of hydraulic cylinders are sequentially driven at a predetermined timing when the object to be driven presses the switch portion of the switching valve at a predetermined position. Therefore, it is possible to sequentially move the driving force to the driving object and move the plurality of driving objects at a predetermined timing.

  However, when a switching valve provided separately from the hydraulic cylinder is used, there is a problem that a hydraulic pipe and a connecting member for connecting the hydraulic cylinder and the switching valve are separately required. In addition, if the switch part of the switching valve is operated by the movement operation of the driving object itself, the switching object of the driving object and the switching valve is configured so that the switching valve is switched at a predetermined timing. There is a problem that it is necessary to adjust the mutual positions of each of them during assembly and maintenance.

  Furthermore, the distance between the switch portion of the switching valve and the drive object may change over time due to backlash of the shaft support part of the drive object or distortion of the drive object itself, and it is stable with high accuracy. There is a problem that it is difficult to perform the operation. Furthermore, foreign matter such as dust may enter the switch portion of the switching valve that detects the operation of the driven object itself. Especially in winter, the switch portion of the switching valve exposed to the outside is covered with snow or frozen. If it is fixed due to, for example, there is a problem that the switching valve may malfunction. Therefore, when a switching valve provided separately from the hydraulic cylinder is used, it is necessary to check the switch portion of the switching valve and to perform a cleaning operation, and there is room for improvement in making the maintenance free.

  In particular, in a lorry as disclosed in the above-mentioned Patent Document 1, a lift and a slide movement operation are performed in which the loading platform is lowered substantially horizontally to the ground behind the host vehicle. For this reason, the loading platform, moving frame, and moving mechanism, which are objects to be driven, are relatively large, and the movement of the loading platform and the moving frame is complicated and long stroke. Therefore, the switch portion of the switching valve is operated by the operation of the driving object itself. If the drive pressure oil is switched and driven at a predetermined timing, it is difficult to stably push the switch portion of the switching valve. In addition, although the switching valve can be controlled by electrical control, electrical control requires a separate control device, control program, electrical wiring, etc., which increases costs. In addition, it is not always a desirable measure for improving maintainability.

The present invention has been made in view of such problems, provides improves the maintainability, stable bed lifting device and cargo vehicles Ru can be carried out the operation with high accuracy This is the issue.

In order to solve the above-described problem, a platform lifting apparatus according to an aspect of the present invention is configured to move two double-acting hydraulic cylinders sequentially to move the platform from the position stored on the chassis frame to the rear of the host vehicle. A loading platform lifting device having a moving mechanism for moving to a lowered position, wherein the two hydraulic cylinders are attached to a tube, a rod slidably provided in the tube, and a bottom side of the tube. Each of which has a switching valve chamber, the switching valve chamber having two ports and a valve body driven by a mechanical force accompanying a pushing force or a pulling force due to the movement of the rod. The supply state of the drive pressure oil supplied to the hydraulic cylinder to which one of the two hydraulic cylinders is attached or the other hydraulic cylinder is switched by switching the communication state between the two ports. Characterized in that switching the state.

According to the platform lifting device according to one aspect of the present invention, the two hydraulic cylinders have the switching valve chamber attached to the bottom side of the tube of the double-acting hydraulic cylinder, and the valve body in the switching valve chamber is Supply / discharge of drive pressure oil supplied to one or the other hydraulic cylinder by switching the communication state between the two ports by driving with the mechanical force accompanying the pushing force or pulling force due to the movement of the rod of the hydraulic cylinder Since the state is switched, there is no need for electrical control for switching the supply / discharge state of the drive pressure oil, and there is no possibility of being affected by the backlash of the shaft support portion of the drive target or the distortion of the drive target itself. Further, foreign matter such as dust can be prevented from entering the switching valve chamber. Furthermore, since the switching valve chamber does not have a movable part exposed to the outside, the switching valve chamber does not adhere due to snow accumulation or freezing. Therefore, it is possible to improve the maintainability of the platform lifting device and to realize a highly accurate and stable operation.
Then, according to the loading platform lifting device according to one embodiment of the present invention, two of each switching valve chambers of the hydraulic cylinder by switching the communication state of two ports each other by driving the valve body, the hydraulic cylinder itself is attached Alternatively, the supply / discharge state of the drive pressure oil supplied to the other hydraulic cylinders can be switched. Therefore, the two hydraulic cylinders are operated in succession, which is suitable for moving the loading platform from the position stored on the chassis frame to the position lowered to the rear of the host vehicle.

  Here, in the loading platform lifting apparatus according to one aspect of the present invention, the loading platform lifting apparatus includes a guide rail provided on the chassis frame, and a moving mechanism that moves the loading platform in the longitudinal direction of the vehicle along the guide rail. A movable frame that can move and tilt in the vertical direction, and as the two hydraulic cylinders, a front cylinder and a rear cylinder having a center trunnion structure in which a middle portion of each tube is rotatably supported. The rod tip is rotatably supported by the front portion of the chassis frame, and the middle portion of the tube is rotatably supported by the middle portion of the moving frame. The tube is supported rotatably at the rear, and the middle part of the tube is rotatably supported at the rear end of the moving frame. It is It is preferable to.

  If such a configuration, as the two hydraulic cylinders (front cylinder and rear cylinder), by adopting a center trunnion structure that rotatably supports the middle part of the tube, while providing a switching valve chamber on the bottom side, It can be used as a rod stroke to the rear end of each tube of the front cylinder and the rear cylinder. For this reason, a switching valve is provided on the bottom side of each hydraulic cylinder tube while ensuring the amount of movement (rod stroke) required to slide the loading platform from the position stored on the chassis frame to the position lowered to the rear of the host vehicle. It is more suitable for providing a chamber.

Further, in the loading platform elevating device according to one aspect of the present invention, the switching valve chamber attached to the bottom side of the tube of the front cylinder has its own valve element pushed by the pressing force due to the movement of the rod of the front cylinder. When in the pushing position, the flow of pressure oil is allowed in either direction of its own two ports, while when its own valve body is in the non-pushing position where it is not pushed by the pushing force due to the movement of the rod, The switching valve chamber attached to the bottom side of the tube of the rear cylinder is a pulling position where its valve body is pulled by the pulling force due to the movement of the rod of the rear cylinder. In the case of, while allowing the flow of pressure oil in either direction of its own two ports, while its own valve body is in the non-pull position where it is not pulled by the pulling force due to the movement of the rod It is preferably adapted to serve as a check valve.
If it is such composition, it will be used for the loading platform raising and lowering device which has a moving mechanism which moves a loading platform from the position stored on the chassis frame to the position where it lowered to the back of the own vehicle. It is suitable as a configuration of a switching valve chamber for performing sequential control.

Moreover, in order to solve the said subject, the lorry concerning one mode of the present invention is a lorry provided with a platform lifting device among the present invention, and relates to one mode of the present invention as said loading platform lifting device. It is characterized by comprising a platform lifting device.
According to the freight vehicle according to one aspect of the present invention, since the load carrier lifting device according to one aspect of the present invention is provided as the loading platform lifting device, the maintainability of the cargo vehicle is improved and high-precision and stable operation is realized. can do.

  As described above, according to the present invention, it is possible to improve maintainability and realize a highly accurate and stable operation.

1 is a left side view of a vehicle transporter that is an embodiment of a truck according to the present invention. The figure shows the storage position of the loading platform in the traveling state. It is the schematic diagram which decomposed | disassembled and showed the movement mechanism part of the loading platform raising / lowering apparatus of FIG. It is explanatory drawing of the hydraulic circuit of the moving mechanism of the loading platform raising / lowering apparatus of FIG. It is sectional drawing of the principal part (switching valve chamber and its vicinity part) of the hydraulic cylinder (front cylinder for inclination) used for the loading platform raising / lowering apparatus of FIG. 1, The figure shows the cross section along the axis line of a hydraulic cylinder. ing. FIG. 2 is a cross-sectional view of a hydraulic cylinder (a rear cylinder for a load bed) used in the load carrier lifting apparatus in FIG. 1, and shows the cross section along the axis of the hydraulic cylinder. It is a figure ((a)-(e)) explaining operation | movement of the platform lifting apparatus of the vehicle transport vehicle of FIG. 1, (a) shows the initial slide movement attitude | position (a platform grounding roller is before grounding) of the platform. , (B) shows a tilted initial posture in which the carrier is further retracted (when the carrier grounding roller is in contact with the ground), (c) shows a state in which the carrier is further retracted (the carrier grounding roller is in a grounded state), and (d) is a carrier (E) further shows the boarding position where the loading platform is lowered to the ground behind the host vehicle. FIG. 4 is a diagram for explaining the operation of the hydraulic circuit of FIG. FIG. 4 is a diagram for explaining the operation of the hydraulic circuit of FIG. It is a figure explaining the operation | movement (the operation | movement 3 at the time of the backward movement of a loading platform) of the hydraulic circuit of FIG. FIG. 4 is a diagram for explaining the operation of the hydraulic circuit of FIG. FIG. 4 is a diagram for explaining the operation of the hydraulic circuit of FIG. It is a figure explaining the modification of the hydraulic circuit used for the moving mechanism in the loading platform raising / lowering apparatus of FIG.

Hereinafter, a vehicle carrier according to an embodiment of a truck according to the present invention will be described with reference to the drawings as appropriate.
As shown in FIG. 1, the vehicle carrier 1 includes a loading platform 3 on a chassis frame 2. A so-called torii gate 5 is integrally provided at the front portion of the loading platform 3, and a rear turn 4 is provided at the rear portion of the loading platform 3. The rear turn 4 is attached so as to be rotatable in the front-rear direction of the host vehicle, and can be positioned in each of a vertical closed position shown in the figure and an open position rotated rearward (see FIG. 6E). ing. When the loading platform 3 is lowered to the ground GL behind the host vehicle in the open position, the rear end 4 serves as a slope when the vehicle is turned back and enters the vehicle.

  A retractable bumper device 60 is provided on the lower rear side of the loading platform 3. A safety part such as a lamp and a bumper main body 100 are attached to the rear end of the bumper device 60. The bumper body 100 is a rush prevention member for preventing rush from the back of another vehicle or the like. The bumper device 60 has a plurality of undulation switching mechanisms (reference numerals 70, 71a, b, 72) composed of links and cams. These undulation switching mechanisms are interlocked with the sliding movement of the loading platform 3 so that when the loading platform 3 is at the storage position K shown in FIG. Position it where required by law.

  Further, the bumper device 60 is substantially parallel to the back surface of the cargo bed 3 by folding the entire bumper device 60 at the boarding position N (see FIG. 6E) where the cargo bed 3 is lowered to the ground GL behind the host vehicle. It becomes a naive lying posture. Further, the bumper device 60 has a support leg roller 63 that supports the loading platform 3, and the undulation switching mechanism is interlocked with the sliding movement of the loading platform 3 when the loading platform 3 is slid rearward of the host vehicle. In the desired posture, the support leg roller 63 is grounded to the ground so that the loading platform 3 can be supported.

The vehicle carrier 1 is equipped with a platform lifting device 10 between the platform 3 and the chassis frame 2. Hereinafter, the platform lifting device 10 will be described. FIG. 2 is an exploded schematic view showing a part of the platform lifting device 10 of FIG.
As shown in FIG. 2, the loading platform 3 has loading platform vertical joists 6 on both sides in the vehicle width direction. The load carrier vertical joist 6 is a long member in the shape of a grooved steel, and is opposed to the grooved steel with the concave groove side facing inward in the width direction along the vehicle longitudinal direction. A load carrier grounding roller 50 is provided at the lower end of the rear end of the cargo bed 3. When the loading platform 3 is lowered to the rear of the host vehicle, the loading platform grounding roller 50 comes into contact with the ground GL and assists the movement in the sliding movement direction (also the front-rear direction of the host vehicle). A loading platform receiving roller 54 is attached to the rear end of the chassis frame 2. The loading platform receiving roller 54 supports the loading platform 3 slidably moved from below.

  The loading platform elevating device 10 includes a moving mechanism that moves the loading platform 3, and by this moving mechanism, the loading platform 3 is stored on the chassis frame 2 (see FIG. 1), and the loading platform K starts from the storing position K. 3 is configured to be slidable to a boarding position N (see FIG. 6 (e)) that is lowered to the rear of the host vehicle and to a position substantially horizontal to the ground GL. As a result, the vehicle transport vehicle 1 can load the vehicle on the loading platform 3 at the boarding position N and can transport the loaded vehicle with the loading platform 3 stored in the storage position K. In addition, if the loading platform grounding roller 50 is in a grounded state, the stacking itself is possible.

  Specifically, as shown in FIG. 2, in the platform lifting device 10, a base frame 8 serving as a base for fixing the platform lifting device 10 is fixed on the chassis frame 2. A guide rail 11 is attached to a position on the base frame 8 at the rear of the vehicle, and the loading platform 3 is placed on the guide rail 11 via a moving frame 20. The guide rail 11 is a long guide member in the form of a grooved steel provided in a pair on both sides in the vehicle width direction, and faces the groove side of the grooved steel serving as the guide groove toward the inside in the width direction. Has been placed. Each guide rail 11 is curved so that the front end portion and the rear end portion thereof are directed downward, so that the side view is formed in a substantially “h” shape. ) In order, the front inclined portion 12, the horizontal portion 14, the rear first inclined portion 16, and the rear second inclined portion 18 are configured.

  The moving frame 20 is formed in a substantially ladder-like frame body in plan view, and includes a pair of front rollers 21 and a rear roller 22 that are spaced apart in the vehicle front-rear direction on both sides of the rear portion thereof. The moving frame 20 is slidably fitted in the guide groove of the guide rail 11 by a pair of front roller 21 and rear roller 22. The front roller 21 and the rear roller 22 project outward from the outer surface of the moving frame 20 in the width direction, and can rotate around the shaft via a support shaft that faces the vehicle width direction.

  The front roller 21 and the rear roller 22 are fitted to the substantially U-shaped guide grooves of the pair of guide rails 11 described above and supported so as to be able to roll, and along the guide rails 11, The sliding movement of the moving frame 20 is smoothly guided. The front roller 21 is provided on the front side of the vehicle in the sliding direction, and is attached to the tip of an arm portion that protrudes downward in the vehicle. The rear roller 22 is provided on the rear side of the vehicle in the sliding direction, and is attached directly to the moving frame 20 portion, unlike the front roller 21, so that the rear roller 22 is located above the front roller 21 in the vertical direction of the vehicle. positioned.

A pair of moving frame rails 24 are fixed to the moving frame 20 on both sides in the vehicle width direction. Each of the moving frame rails 24 is a long guide member made of a channel steel, and supports a front carrier side roller 52 provided on both front sides of the cargo bed 3 so as to be capable of rolling. 3 is smoothly guided.
Here, the loading platform elevating device 10 uses two double-acting hydraulic cylinders as a set as a driving mechanism for sliding the moving frame 20 and the loading platform 3 in the moving mechanism that moves the loading platform 3. In the present embodiment, a front cylinder 30 and a rear cylinder 40 are provided as two double-acting hydraulic cylinders. The front cylinder 30 and the rear cylinder 40 have a center trunnion structure in which a middle portion of the tube is rotatably supported.

  Specifically, the front cylinder 30 is rotatably supported at the front end 8a of the chassis frame 2 by the tip of the rod 32, and the middle portion 36 of the tube 34 is an intermediate portion 20b (downward in this example). Is supported so as to be rotatable in the vicinity of the base end portion of the arm portion of the front roller 21 projecting from the front side. In addition, the rear cylinder 40 is rotatably supported at the rear end 3a of the loading platform 3 by the rear cylinder 40 (in the vicinity of the loading platform grounding roller 50 in this example), and an intermediate portion 46 of the tube 44 is formed on the moving frame 20. The rear portion 20a is rotatably supported. The loading platform 3 or the moving frame 20 is moved along the longitudinal direction of the host vehicle according to the expansion and contraction of the rods of the front cylinder 30 and the rear cylinder 40 (hereinafter also simply referred to as “hydraulic cylinders 30, 40”). By this, it is possible to move from the storage position K where the loading platform 3 is stored on the chassis frame 2 to the boarding position N where the loading platform 3 is lowered behind the host vehicle.

  Here, at the storage position K, the front roller 21 is located on the front inclined portion 12 of the guide rail 11, and the rear roller 22 is located on the horizontal portion 14 of the guide rail 11. Therefore, in the storage position K, the moving frame 20 is substantially horizontal on the chassis frame 2, and the attitude of the loading platform 3 is also supported horizontally. When the loading platform 3 moves, the loading platform front roller 52 moves rearward while being guided by the moving frame rail 24.

  Thereafter, the front roller 21 and the rear roller 22 slide along the shapes of the inclined portions 12, 14, 16 and 18 of the guide rail 11 described above. As a result, the platform lifting device 10 supports the platform 3 while moving and tilting it so that the platform 3 on the moving frame 20 is lowered to the height required for lowering the platform 3 to the rear of the host vehicle, so that the platform 3 is substantially horizontal on the ground. It can be taken down. In the example of the present embodiment, the object to be driven by the hydraulic cylinders 30 and 40 corresponds to the loading platform 3 and the moving frame 20.

Hereinafter, the configuration of a hydraulic circuit and the like for operating the hydraulic cylinders 30 and 40 in conjunction with each other will be described.
As shown in FIG. 3, the hydraulic cylinders 30 and 40 are operated by supplying pressure oil from a hydraulic pump 92 driven by a vehicle engine via a control valve 80. The control valve 80 is a 4-port 3-position electromagnetic valve for controlling the hydraulic cylinders 30 and 40, and includes a main spool (not shown), left and right solenoids, and a spring.

  When the left and right solenoids are demagnetized, the main spool is held in the center position by the left and right springs, and all the ports are closed. The main spool moves in the axial direction in response to the excitation of the left and right solenoids, and the oil path inside the control valve 80 Switch. In this example, the control valve 80 switches the flow direction of the pressure oil to the X state shown on the right side of the load bed 3 when the solenoid is excited in the backward movement operation of the load bed 3. The other solenoid is excited to switch the flow direction of the pressure oil to the parallel state shown on the left side of the figure.

  Here, the supply and discharge states of the pressure oil are controlled by the switching valve chambers 38 and 48 attached to the respective hydraulic cylinders 30 and 40 so as to be interlocked with each other according to the slide position of the loading platform 3. In other words, each switching valve chamber 38, 48 is a sequence valve that switches between a hydraulic oil communication state and a shut-off state so that the two hydraulic cylinders 30, 40 are sequentially operated. The switching valve chambers 38 and 48 are driven in the axial direction in conjunction with the rods of the hydraulic cylinders to which the switching valve chambers 38 and 48 are attached. It has a poppet structure that opens and closes.

Specifically, as shown in FIG. 3, the front cylinder 30 includes a first switching valve chamber 38 attached to the bottom side end surface of the tube 34 of the front cylinder 30. In addition, the rear cylinder 40 includes a second switching valve chamber 48 attached to the bottom side end face of the tube 44 of the rear cylinder 40. Each switching valve chamber 38, 48 has two ports.
In the front cylinder 30, the rod side port B 4 and the second port B 2 of the first switching valve chamber 38 are connected to the service port A of the control valve 80. The tube side port B3 of the front cylinder 30 is connected to the second port A3 of the second switching valve chamber 48.
In the rear cylinder 40, the tube side port A 2 and the first port A 1 of the second switching valve chamber 48 are connected to the service port B of the control valve 80. The rod side port A4 of the rear cylinder 40 is connected to the first port B1 of the first switching valve chamber 38. A flexible resin pipe 82 is used between the service ports A and B of the control valve 80 and the hydraulic cylinders 30 and 40 at a position corresponding to the inclination of the moving frame 20, and the counter balance valve 84. Is intervening.

The first switching valve chamber 38 has a valve body 133 that is driven in the axial direction by a pressing force generated by the movement of the rod 32 of the front cylinder 30, as shown in an enlarged view of the main part in FIG. The first switching valve chamber 38 is configured to switch the supply / discharge state of the driving pressure oil supplied to the front cylinder 30 or the rear cylinder 40 to which the first switching valve chamber 38 is attached by sliding movement of the valve body 133.
Specifically, the first switching valve chamber 38 has a main body block 131 attached to the end surface on the bottom side of the tube 34 of the front cylinder 30 by welding. The main body block 131 is a steel block-like member that is also mounted as a tube bottom cap. The main body block 131 is fitted in the front surface of the main body block 131 (the surface on the left side of the figure) with the end surface on the bottom side of the tube 34. A mating spigot 131h is formed.

  Inside the main body block 131, multistage through holes penetrate along the axial direction at positions eccentric from the axis of the rod 32 of the front cylinder 30 (in this example, positions above the axis of the rod 32). The valve chamber 138 is formed. The valve chamber 138 has a small-diameter hole 131c, a medium-diameter hole 131d, and a large-diameter hole 131e in order from the bottom side of the tube 34. The small-diameter hole 131c includes a first small-diameter portion 131a that penetrates the tube 34 from the bottom side, and a second small-diameter portion 131b that is provided following the first small-diameter portion 131a and has a larger diameter than the first small-diameter portion 131a. Become. An internal thread is formed on the inner peripheral surface of the large-diameter hole 131e.

  A position detection shaft body 137 is slidably fitted into the small diameter hole 131c. A cylindrical valve seat body 136 is fitted in the medium diameter hole 131d. The medium diameter hole 131d is formed along the radial direction so that the two ports B1 and B2 communicate with each other from a direction orthogonal to the axial direction of the medium diameter hole 131d. In this example, the first port B1 is formed in front of the valve seat body 136 so as to communicate with a position closer to the bottom side of the medium diameter hole 131d. The second port B2 is formed behind the valve seat 136 so as to communicate with a position closer to the side opposite to the bottom side from the side opposite to the first port B1 in the radial direction.

A socket 132 having an external thread on the outer peripheral surface is screwed into the large-diameter hole 131e from the rear surface side of the main body block 131. A through hole 132a penetrating in the axial direction is formed inside the socket 132, and a valve body 133 is slidably fitted into the through hole 132a.
The valve body 133 has a truncated cone shape at the bottom side and is a contact surface 133b that contacts the valve seat of the valve seat body 136. A bottomed hole 133c is formed on the side opposite to the bottom side. A cylindrical coil spring 134 is inserted into the bottomed hole 133 c of the valve body 133. A plug 135 is screwed into the through-hole 132a of the socket 132 so as to push the cylindrical coil spring 134 from the rear end face side, and a biasing force is applied to press the valve body 133 toward the bottom end face side of the tube 34. .

  The position detection shaft body 137 slidably fitted into the small diameter hole 131c has a round bar-shaped detection shaft 137a and a protrusion 137b on the front and rear sides in the axial direction. The detection shaft 137a extending to the front side of the position detection shaft body 137 is provided so as to protrude from the first small diameter portion 131a to the position where it is pushed by the piston 33 at the rod base end portion. Further, the protrusion 137 b extending to the rear side of the position detection shaft body 137 is in contact with the front end surface of the valve body 133.

  The first switching valve chamber 38 configured in this way is in a non-pushing position Pf where the position detection shaft body 137 is not pushed by the rod 32 at a position other than the time when the rod 33 of the front cylinder 30 is fully contracted. . At the non-pushing position Pf, the cylindrical coil spring 134 presses the valve body 133 toward the valve seat of the valve seat body 136. At this time, the valve body 133 is in the closed position indicated by the symbol Ps in FIG. Therefore, at the non-pushing position Pf, the valve body 133 is pressed against the valve seat body 136 to close the flow path and serve as a check valve, and the pressure oil from the first port B1 to the second port B2 passes. (However, when the pressure is equal to or higher than a predetermined pressure), the flow of pressure oil from the second port B2 to the first port B1 is prevented.

  On the other hand, when the rod 33 of the front cylinder 30 is at the maximum contracted position, it becomes a push position Pp where the detection shaft 137a of the position detection shaft body 137 is pushed to the rear end face of the piston 33 at the rod base end. At this push position Pp, the position detection shaft 137 slides backward. Thereby, the rod-shaped protrusion 137b on the rear side moves the valve body 133 rearward. At this time, the valve body 133 moves to the open position indicated by the symbol Pk in the drawing. Therefore, the flow path between the valve body 133 and the valve seat body 136 is shifted to an open state, and the flow of pressure oil is allowed in any direction of the first port B1 and the second port B2. It has become.

  Moreover, the 2nd switching valve chamber 48 has the main body block 141 attached to the end surface at the bottom side of the tube 44 of the back cylinder 40, as shown in FIG. The main body block 141 is a steel block-shaped member. Inside the main body block 141, a valve chamber 148 is formed coaxially with the axis of the rod 42 of the rear cylinder 40. The front side of the valve chamber 148 (the right side in the figure) is fitted into an inlay portion 141a formed on the tube bottom cap side of the bottom end surface of the tube 44, and is connected to the tube bottom cap by a bolt (not shown). And is detachably fixed.

  The valve chamber 148 of the main body block 141 is configured by a bottomed hole having a step portion along the axial direction from the spigot portion 141a side, coaxially with the axis of the rod 42 of the rear cylinder 40. The valve chamber 148 has a large diameter portion 148a and a small diameter portion 148b in order from the spigot portion 141a side. Two ports A1 and A3 communicate with the large-diameter portion 148a and the small-diameter portion 148b from the direction orthogonal to the axial direction.

  The first port A1 is formed so as to communicate with the small diameter portion 148b. The second port A3 is formed so as to communicate with the large-diameter portion 148a from a location separated from the first port A1 in the circumferential direction. In this example, the first port A1 is substantially connected to the tube side port A2 by connecting the tube side port A2 of the rear cylinder 40 and the branch path A1 formed in the body block 141 along the axial direction. Thus, the connection port and piping to the first port A1 are unnecessary while forming the first port A1.

  A cylindrical valve body 143 is slidably fitted in the large diameter portion 148a. The second switching valve chamber 48 has a valve seat 136 at the annular surface portion between the large diameter portion 148a and the small diameter portion 148b. The valve body 143 has a frustoconical end at the rear side and serves as a contact surface with the valve seat 136. Further, a stepped through hole 143a is formed in the valve body 143. A cylindrical coil spring 144 interposed between the end surface of the spigot portion 141a is inserted into a step portion of the through hole 143a of the valve body 143, and the cylindrical coil spring 144 allows the valve body 143 to be connected to the main body block from the tube side. The urging | biasing force pressed toward the valve seat 136 of 141 is added.

The rear cylinder 40 uses a hollow cylindrical pipe material for the rod 42, and a through hole is formed in the central portion of the piston 43 coaxially with the axis of the rod 42, from the small diameter portion 148 b to the inside of the tube 44. The position detection shaft 147 is slid and fitted therethrough.
The position detection shaft 147 is a long pipe material having a hollow cylindrical shape, and two cylindrical members 145 and 146 are fitted on outer peripheral surfaces of both ends of the position detection shaft 147, respectively. The cylindrical member 145 at the base end portion of the position detection shaft 147 is located in the small diameter portion 148b, is provided at a position behind the valve body 143 in the axial direction, and faces the valve body 143 in the axial direction. Then touch. The cylindrical member 146 at the distal end portion of the position detection shaft 147 is located in the rod 42 of the tube 44 and faces the front end surface on the inner peripheral side of the piston 43 provided at the proximal end portion of the rod 42 in the axial direction. The cylindrical member 146 at the distal end is an engaging portion for detecting the maximum extension position of the rod 42.

Here, the position detection shaft 147 is a member that is narrower and longer than the inner diameter of the rod 42. Therefore, when the tube 44 is positioned at a required position in the rod 42, the sliding contact state with the rod 42, bending, damage to the sliding contact portion due to generation of rust, and the like become structural problems.
For such a problem, in the rear cylinder 40 of the present embodiment, the position detection shaft 147 has a hollow cylindrical shape, and the pressure oil in the tube side port A2 (first port A1) is discharged from the small diameter portion 148b to the hollow cylindrical shape. The oil is guided to the end opening of the position detection shaft 147 so that the entire space between the inside of the position detection shaft 147 and the outer periphery of the position detection shaft 147 and the inner periphery of the rod 42 is filled. 5 indicates an image in which the pressure oil is filled in the entire space between the inside of the position detection shaft 147 and the outer periphery of the position detection shaft 147 and the inner periphery of the rod 42.
Thus, according to the rear cylinder 40, the sliding contact portion between the position detection shaft 147 and the rod 42 is always lubricated. Therefore, the occurrence of rust is prevented, and the position detection shaft 147 is supported on the entire circumference by the pressure oil filled in the rod 42. Therefore, the coaxiality between the position detection shaft 147 and the rod 42 can be maintained even with a thin and long member.

  In the above configuration, in the second switching valve chamber 48, the cylindrical coil spring 144 presses the valve body 143 toward the valve seat 136 at a position other than when the rod 42 of the rear cylinder 40 is fully extended. Therefore, the flow path of the pressure oil from the first port A1 to the second port A3 is closed. When the rod 42 is extended, the engaging portion (the cylindrical member 146 at the tip) starts to contact the front end surface of the piston 43 at a position slightly before the rod 42 is fully extended, The rod 42 is set so as to move by a predetermined amount in the extending direction from the contact position.

  As a result, the engaging portion is pulled in the extending direction of the rod 42 by the front end surface of the piston 43. Therefore, the entire position detection shaft 147 moves by a predetermined amount in the extending direction of the rod 42. Therefore, the cylindrical member 145 at the base end portion of the position detection shaft 147 slides the valve body 143 in the extending direction of the rod 42 against the urging force of the cylindrical coil spring 144. As a result, the valve body 143 is driven by a predetermined amount in the axial direction with respect to the valve seat 136, and the flow path of the pressure oil from the first port A1 to the second port A3 is opened.

  Thus, the second switching valve chamber 48 of the present embodiment has the first port A1 and the second port A3 when the valve body 143 is pulled by the pulling force due to the movement of the rod 42. The flow of pressure oil is allowed in either direction. On the other hand, when the valve body 143 is in the non-pull position where it is not pulled by the pulling force due to the movement of the rod 42, it acts as a check valve and the flow of pressure oil from the second port A3 to the first port A1 passes through. (However, when the pressure is equal to or higher than the predetermined pressure), the flow of pressure oil from the first port A1 to the second port A3 is prevented.

Next, the movement operation of the loading platform 3 and the moving frame 20 by the hydraulic cylinders 30 and 40 of the loading platform elevating device 10 will be described.
When the vehicle carrier 1 is in the traveling state, the hydraulic cylinders 30 and 40 are both in the minimum contracted state, and the loading platform 3 is in the storage position K stored on the chassis frame 2 as shown in FIG. is there. When the loading platform 3 is in the retracted position K, the main body frame 86 of the bumper device 60 is in an upright posture projecting perpendicularly downward with respect to the loading platform 3 as shown in FIG.
The vehicle carrier 1 drives the loading platform elevating device 10 to lower the loading platform 3 from the storage position K shown in FIG. 1 to the rear of the host vehicle as in the boarding position N shown in FIG. be able to. At this time, the bumper device 60 can be used as a support leg when the loading platform 3 is lowered to the rear of the host vehicle by a plurality of undulation switching mechanisms interlocking with the sliding movement of the loading platform 3.

  When the loading platform 3 moves backward or forward, the hydraulic cylinders 30 and 40 of the loading platform elevating device 10 are sequentially expanded and contracted. In the present embodiment, during the backward operation of lowering the loading platform 3 from the chassis frame 2 to the rear of the host vehicle, the pressure oil is sequentially supplied to the tube side of each hydraulic cylinder 30, 40. And then the rod 32 of the front cylinder 30 extends. Each rod 32, 42 extends sequentially. Further, in the forward movement operation of storing the loading platform 3 on the chassis frame 2, the pressure oil is sequentially supplied to the rod side of each hydraulic cylinder 30, 40, first, the rod 32 of the front cylinder 30 is contracted, and then The rod 42 of the rear cylinder 40 is reduced.

  Specifically, when the vehicle carrier 1 lowers the loading platform 3 to the rear of the host vehicle and loads other vehicles as cargo, for example, as shown in FIG. The rear cylinder 40 of the device 10 is driven to extend the rod 42. Thereby, the loading platform 3 is guided along the moving frame 20, and the sliding movement is started to the rear of the host vehicle. In the bumper device 60, the support leg roller 63 projects downward in conjunction with the sliding movement of the loading platform 3, and the supporting leg roller 63 moves before the loading platform grounding roller 50 at the rear end of the loading platform 3 is brought into the grounded state. Ground. Therefore, when the loading platform 3 is cantilevered behind the host vehicle, the loading platform 3 can be supported by the support leg rollers 63 of the bumper device 60.

  Next, after the rear cylinder 40 is fully extended, the loading platform elevating device 10 starts the extension of the front cylinder 30 by the sequential operation described above. As a result, as shown in FIG. 6B, the front cylinder 30 pushes the moving frame 20 backward, so that the moving frame 20 starts sliding along the guide rail 11. As a result, the entire moving frame 20 is lifted forward by the bent shape of the guide rail 11 and tilted, and accordingly, the loading platform 3 on the moving frame 20 also moves backward while tilting backward. At this time, the bumper device 60 maintains the posture in which the support leg roller 63 is grounded so that the loading platform 3 is not cantilevered. Therefore, the sliding movement of the loading platform 3 can be continued in a stable state. After the predetermined sliding movement, the load carrier grounding roller 50 at the rear end of the cargo bed 3 is brought into a grounded state.

  Further, the extension operation of the front cylinder 30 is continued, whereby the moving frame 20 moves to the horizontal portion of the guide rail 11 and is supported as the loading platform 3 moves rearward. Therefore, as shown in FIG. 6C, the entire moving frame 20 is slid horizontally behind the host vehicle while maintaining the initial inclination posture. At the same time, the loading platform 3 moves further rearward, and the loading platform grounding roller 50 contacts the ground GL, so that the sliding movement is continued in a state where the posture of the loading platform 3 is stabilized. At this time, in the front portion of the loading platform 3, the loading platform front roller 52 is supported by the rear side of the moving frame rail 24 (see FIG. 2), and the loading platform 3 is held in a both-end supported state. Therefore, the support by the support leg roller 63 of the bumper device 60 starts the folding operation by the interlocking operation of the undulation switching mechanism that rotates counterclockwise in accordance with this timing.

  Next, as shown in FIG. 6 (d), the loading platform elevating device 10 further extends the front cylinder 30. As a result, while the moving frame 20 is guided along the guide rail 11, the loading platform 3 further slides backward while grounding the loading platform grounding roller 50 to the ground GL. The bumper device 60 is folded in a direction away from the ground together with the bumper body 100 by the interlocking operation of the undulation switching mechanism.

  Then, as shown in FIG. 6E, the front cylinder 30 is fully extended and pushes the moving frame 20 further rearward, so that the moving frame 20 slides rearward along the guide rail 11. At this time, the front side of the moving frame 20 is supported by the horizontal portion of the guide rail 11, and the rear side is supported by the rear inclined portion. Therefore, the rear side of the moving frame 20 gradually tilts backward as it moves backward.

  As a result, the rear of the moving frame 20 as a whole is further tilted rearward downward, and accordingly, the loading platform 3 on the moving frame 20 is lowered in the direction of the ground GL, and when the front cylinder 30 is fully extended, the ground GL Is located at a boarding position N substantially horizontal. At this time, in the bumper device 60, the folding operation by the interlocking operation of the undulation switching mechanism shifts to the maximum lying state, and the entire bumper device 60 is folded completely and assumes a lying posture substantially parallel to the back surface of the loading platform 3. The forward movement of the loading platform 3 that moves the loading platform 3 from the loading position N to the storage position K is performed by the reverse operation to that described above, and the description thereof is omitted.

Next, the operation of the hydraulic circuit for sequentially controlling the two hydraulic cylinders 30 and 40 of the loading platform elevating device 10 during the movement operation of the loading platform 3 and the moving frame 20 and the effects thereof will be described.
The sequential control of the two hydraulic cylinders 30 and 40 is as follows. In the backward movement of the loading platform 3 at the storage position K, the solenoid on the left side of the control valve 80 shown in FIG. Switch the flow direction of pressure oil to the state. Thereby, pressure oil is supplied from the service port B. At this time, the first switching valve chamber 38 allows the flow of pressure oil because the valve body 133 is in the open position Pk as shown in FIG. On the other hand, the second switching valve chamber 48 prevents the flow of pressure oil from the first port A1 to the second port A3 because the valve body 143 is in the non-pull position as shown in FIG. doing.

  Therefore, as shown in FIG. 7, the pressure oil from the service port B is supplied to the tube side of the rear cylinder 40, and the return oil on the rod side passes through the counter balance valve 84 from the first switching valve chamber 38. Thus, the rod of the rear cylinder 40 extends while being discharged from the T port of the control valve 80 to the tank 90. At this time, the front cylinder 30 is in a state in which the second switching valve chamber 48 is closed, so that the pressure oil from the service port B is blocked by the second switching valve chamber 48 and the front cylinder 30 is pressurized. Since no oil is supplied, the contracted state is maintained. In FIG. 7, an oil path indicated by a thick solid line indicates an image in which driving pressure oil is supplied, and an oil path indicated by a hatched line indicates an image of return oil (hereinafter referred to as other hydraulic pressures). The same applies to the diagrams describing the operation of the circuit.)

  Furthermore, the supply of pressure oil from the service port B is continued, and the rod of the rear cylinder 40 is extended and fully extended. As a result, as shown in FIG. 8, the front end surface of the piston 43 at the base end of the rod moves the cylindrical member 146 at the tip of the position detection shaft 147 of the second switching valve chamber 48 at the fully extended position of the rear cylinder 40. Pull up. Thereby, the valve body 143 moves so that the 2nd switching valve chamber 48 may open the flow path of the pressure oil from 1st port A1 to 2nd port A3 (refer also FIG. 5 also). Therefore, the pressure oil from the service port B is supplied to the tube side of the front cylinder 30, and the return oil on the rod side of the front cylinder 30 passes through the counter balance valve 84 and passes from the T port of the control valve 80 to the tank 90. While being discharged, the rod 32 of the front cylinder 30 starts to extend. When the rod 32 of the front cylinder 30 starts to expand, the pressing force applied to the position detection shaft body 137 by the rear surface of the piston 33 is released. Therefore, the valve body 133 moves to the closed position Ps, and the first switching valve chamber 38 is closed (see also FIG. 4). Thereafter, as shown in FIG. 9, the rod of the front cylinder 30 continues to extend, and the front cylinder 30 fully extends.

  Here, when the rods 42 and 32 are sequentially extended, the return oil on the rod side of the hydraulic cylinders 40 and 30 passes through the counter balance valve 84 and is discharged from the T port of the control valve 80 to the tank 90. . At this time, the counter balance valve 84 prevents unexpected expansion of the hydraulic cylinders 30 and 40.

  On the other hand, in the forward movement of the loading platform 3, the direction in which the pressure oil flows is switched from the state shown in FIG. 9 to the parallel state shown on the left side by exciting the solenoid on the right side of the control valve 80. Thus, as shown in FIG. 10, the pressure oil from the service port A is supplied to the rod side of the front cylinder 30, and the return oil on the tube side of the front cylinder 30 is supplied to the second switching valve in the open position. It passes through the chamber 48 and is discharged from the T port of the control valve 80 to the tank 90 and the rod 32 of the front cylinder 30 is contracted.

  On the other hand, since the first switching valve chamber 38 is closed in the rear cylinder 40, the pressure oil from the service port A is shut off by the first switching valve chamber 38, and the rear cylinder 40 has no pressure oil. Is not supplied, so that the stretched state is maintained. At this time, the pressure of the pressure oil supplied from the service port A is higher than the pressure (force to push the position detection shaft body 137) for opening the first switching valve chamber 38 by the tube side back pressure of the front cylinder 30. Always high. Therefore, the first switching valve chamber 38 is not opened by the back pressure on the tube side of the front cylinder 30.

  Furthermore, the supply of pressure oil from the service port A is continued, and the rod of the front cylinder 30 is contracted and finally fully contracted. As a result, as shown in FIG. 11, the rear end surface of the piston 33 at the base end of the rod pushes the position detection shaft body 137 of the first switching valve chamber 38 at the fully contracted position of the front cylinder 30. Therefore, in the first switching valve chamber 38, the valve body 133 moves to the pushing position Pp and allows the flow of pressure oil in any direction. Therefore, supply of the pressure oil from the service port A to the rod side of the rear cylinder 40 is started, and the return oil on the tube side of the rear cylinder 40 is discharged from the T port of the control valve 80 to the tank 90 to be returned to the rear cylinder. 40 rods begin to shrink. Thereafter, the rod of the rear cylinder 40 continues to contract and fully contracts.

  As described above, according to the platform lifting device 10 provided in the vehicle transport vehicle 1 of the present embodiment, the two hydraulic cylinders 30 and 40 that are sequentially operated are switched to the bottom side end face of the tube of each hydraulic cylinder. The valve chambers 38 and 48 are provided, and the valve bodies in the switching valve chambers 38 and 48 are driven by the pushing force or the pulling force generated by the movement of the rods of the hydraulic cylinders 30 and 40, respectively. Since the supply / discharge state of the drive pressure oil supplied to the cylinder or another hydraulic cylinder is switched, there is a risk of being affected by the backlash of the shaft support portion of the drive object such as the loading platform 3 and the moving frame 20 or the distortion of the drive object itself. There is no. In addition, there is no possibility that foreign matter such as dust enters the switching valve chambers 38 and 48, and each switching valve chamber 38 and 48 does not have a movable part exposed to the outside. The movable structure inside the chambers 38 and 48 is not fixed. Therefore, it is possible to improve maintainability and realize a highly accurate and stable operation.

The loading platform elevating device 10 includes a first switching valve chamber 38 attached to the bottom end surface of the tube 34 of the front cylinder 30 of the two hydraulic cylinders 30 and 40, and the movement of the rod 32 of the front cylinder 30. When the valve body 138 is pushed by the pushing force, the flow of pressure oil is allowed in either direction of the two ports, while the valve body 138 moves the rod 32. The second switching valve chamber 48 attached to the bottom side end face of the tube 44 of the rear cylinder 40 is provided in the rear side when the non-pushing position is not pushed by the pushing force of When the valve body 143 is pulled by the pulling force generated by the movement of the rod 42 of the cylinder 40, the flow of pressure oil is allowed in either direction of its two ports. On the other hand, when the valve body 143 is in the non-pull position where it is not pulled by the pulling force due to the movement of the rod 42, the valve body 143 works as a check valve. This is suitable for sequentially controlling the two hydraulic cylinders 30 and 40 of the loading platform elevating device 10 at the desired timing.
It should be noted that the hydraulic cylinder for the loading platform lifting apparatus, the loading platform lifting apparatus including the same, and the lorry according to the present invention are not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention. Of course.

For example, in the above-described embodiment, the example in which two hydraulic cylinders are sequentially operated has been described. However, the present invention is not limited to this, and the hydraulic cylinder for the platform lifting apparatus according to the present invention operates three or more hydraulic cylinders in sequence. Applicable when
Further, in the case where a plurality of hydraulic cylinders are operated sequentially, it is not limited to adopting the hydraulic cylinders for the platform lifting device according to the present invention for all the hydraulic cylinders, for example, only for one of the hydraulic cylinders. The hydraulic cylinder for a platform lifting apparatus according to the invention can also be employed.

  Further, for example, in the above-described embodiment, the double-acting hydraulic cylinder according to the present invention has been described as an example including the front cylinder 30 and the rear cylinder 40 having a center trunnion structure in which a middle portion of each tube is rotatably supported. However, the present invention is not limited to this, and a support structure other than the center trunnion structure (for example, a foot shape, a clevis shape, a trunnion shape at another support position, etc.) can be used. However, when it is used as a hydraulic cylinder for the platform lifting device, the center trunnion is used to move the cargo platform from the position stored on the chassis frame to the position lowered to the rear of the host vehicle by sequentially operating the two hydraulic cylinders. It is preferably applied to a double-acting hydraulic cylinder having a structure.

  Further, for example, in the above-described embodiment, the switching valve chambers 38 and 48 of the two hydraulic cylinders 30 and 40 flow when the first switching valve chamber 38 is in the pushing position where the valve body 138 is pushed by the pushing force. Open the path, it acts as a check valve when it is in the non-pressed position, and the second switching valve chamber 48 opens the flow path when the valve body 143 is pulled by the pulling force, In the non-pulling position that has not been pulled, the example of acting as a check valve has been described. However, the present invention is not limited thereto, and the two hydraulic cylinders 30 of the platform lifting device 10 during the movement operation of the platform 3 and the moving frame 20 As long as 40 can be sequentially controlled at a predetermined timing, various combinations and connections of hydraulic circuits can be employed.

For example, FIG. 12 shows a modification of the hydraulic circuit.
As shown in the figure, in this modification, the rod side port B 4 of the front cylinder 30 and the rod side port A 4 of the rear cylinder 40 are connected to the service port A of the control valve 80. The tube side port B3 of the front cylinder 30 is connected to the second port A3 of the second switching valve chamber 48, and the first of the second switching valve chamber 48 via the second switching valve chamber 48. The port A1 is connected to the service port B of the control valve 80. The tube side port A2 of the rear cylinder 40 is connected to the second port B2 of the first switching valve chamber 38, and the first switching valve chamber 38 is connected to the first port B2 via the first switching valve chamber 38. The port B1 is connected to the service port B of the control valve 80.

  Even when such a hydraulic circuit connection is employed, the two hydraulic cylinders 30 and 40 of the loading platform elevating device 10 are sequentially controlled at a predetermined timing when the loading platform 3 and the moving frame 20 are moved. be able to. However, with the circuit configuration of this modification, when the back pressure on the tube side is high, the valve body in the switching valve chamber may move due to the back pressure. In order to make the circuit unaffected, it is preferable to employ the hydraulic circuit shown in the above embodiment.

1 Vehicle carrier (lorry)
DESCRIPTION OF SYMBOLS 2 Chassis frame 3 Cargo bed 4 Back roll 5 Torii 6 Car bed vertical joist 8 Base frame 10 Cargo lift device 11 Guide rail 12 Front inclined part 14 Horizontal part 16 Back first inclined part 18 Back second inclined part 20 Moving frame 21 Front roller 22 Rear roller 24 Moving frame rail 30 Front cylinder 32 Rod 34 Tube 36 Tube pivot 38 First switching valve chamber 40 Rear cylinder 42 Rod 44 Tube 46 Tube pivot 48 Second switching valve chamber 50 Loading platform grounding roller 52 Loading platform front roller 54 Loading platform receiving roller 60 Bumper device 70 Elevation switching mechanism 71a, b Elevation switching mechanism 72 Elevation switching mechanism 80 Control valve 82 Resin cable 84 Counter balance valve 90 Tank 92 Hydraulic pump 100 Bumper body K (loading platform) storage position N (Loading platform ) Boarding position

Claims (4)

A loading platform lifting device comprising a moving mechanism for sequentially moving two hydraulic cylinders that are double acting to move the loading platform from a position stored on the chassis frame to a position lowered to the rear of the host vehicle,
Each of the two hydraulic cylinders includes a tube, a rod slidably provided in the tube, and a switching valve chamber attached to the bottom side of the tube.
The switching valve chamber has two ports and a valve body that is driven by a mechanical force associated with a pushing force or a pulling force caused by the movement of the rod. A loading platform lifting apparatus characterized by switching a communication state and switching a supply / discharge state of driving pressure oil supplied to a hydraulic cylinder to which the two hydraulic cylinders are attached or the other hydraulic cylinder . In the loading platform lifting apparatus, the moving mechanism includes a guide rail provided on a chassis frame, a moving frame capable of moving the loading platform in the front-rear direction of the vehicle and tilting the vehicle along the guide rail, As one hydraulic cylinder, a front cylinder and a rear cylinder having a center trunnion structure in which a middle portion of each tube is rotatably supported,
The front cylinder is rotatably supported at the front end of the rod on the front portion of the chassis frame, and the middle portion of the tube is rotatably supported at an intermediate portion of the moving frame,
The rear cylinder, according to claim 1 in which the rod tip is rotatably supported on a rear portion of the loading platform, characterized in that the middle portion of the tube is rotatably supported on the rear end portion of the movable frame Loading platform lifting device described in 1. When the switching valve chamber attached to the bottom side of the tube of the front cylinder is in the pushing position where its own valve element is pushed by the pushing force due to the movement of the rod of the front cylinder, either of its two ports While allowing the flow of pressure oil also in the direction of, while its own valve body is in a non-push position that is not pushed by the pushing force due to the movement of the rod, it works as a check valve,
The switching valve chamber attached to the bottom side of the tube of the rear cylinder has one of its two ports when the valve body is pulled by the pulling force due to the movement of the rod of the rear cylinder. While allowing the flow of pressure oil in the direction of, the valve body works as a check valve when the valve body is in the non-pull position where it is not pulled by the pulling force due to the movement of the rod. The loading platform elevating device according to claim 2 . A truck equipped with a platform lifting device,
A cargo vehicle comprising the carrier lifting device according to any one of claims 1 to 3 as the carrier lifting device.

Images