Dump truck

Abstract

To provide a dump truck that can reduce a work burden for a worker when a guide plate attached to a tail gate is utilized.SOLUTION: A dump truck 1 includes: a cargo box 20 which is provided so as to be tilted and be movable backwardly relative to a vehicular frame 10, and which includes, at a rear portion, a tail gate 21 rotatable in a manner opened upwardly; a guide plate 30 that has a base end portion coupled to the tip portion of the tail gate 21 in a manner freely rotatable; a linkage mechanism 100 coupled to the tail gate 21 and to the guide plate 30; and pushing means 101 for applying pushing force to the linkage mechanism 100 so as to produce assist force that assists the upward rotation of the guide plate 30 when the tail gate 21 is in a standing-upright state and when the guide plate 30 is to be rotated upwardly.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a dump truck that can perform a dumping operation to tilt a cargo box and a sliding operation to slide the cargo box backward to land on the ground, and in particular to a dump truck that has a runway attached to its tailgate that spans between the open tailgate and the ground when the cargo box is landed on the ground. [Background technology]

[0002] There are dump trucks that are not only loaded with soil, crushed stone, and other cargo in a cargo box and discharge the cargo by a dumping motion, but also transport construction machinery and the like in the cargo box and unload the construction machinery and the like by a sliding motion. Some of these dump trucks, as in Patent Document 1, are equipped with a ramp (referred to as a "walking ramp" in Patent Document 1) for loading and unloading construction machinery.

[0003] In the dump truck of Patent Document 1, the ramp is rotatably attached to the tailgate. When loading or unloading construction machinery or the like, the ramp is rotated upward relative to the tailgate, the tailgate is opened, and then the cargo box is slid backward to land on the ground. At this time, the ramp is bridged between the tailgate and the ground. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-230653 Summary of the Invention [Problem to be solved by the invention]

[0005] The ramp has a certain weight because it must be strong enough to withstand the weight of construction machinery and the like that passes over it, and the task of manually rotating the ramp above the tailgate places a great burden on the worker.

[0006] The present invention was devised in consideration of the above-mentioned problems, and aims to provide a dump truck that can reduce the burden on workers when using a ramp attached to the tailgate. [Means for solving the problem]

[0007] A dump truck according to a first aspect of the present invention includes a cargo box provided tiltably and movable rearward relative to a vehicle frame and having a tailgate at its rear that can be rotated upward and open, a runway whose base end is rotatably connected to the front end of the tailgate, and a link mechanism connected to the tailgate and the runway.The dump truck further includes a biasing means that applies a biasing force to the link mechanism so as to generate an assisting force to assist the upward rotation of the runway when the tailgate is in an upright state and the runway is rotated upward.

[0008] A dump truck having such a configuration can assist the worker in manually rotating the ramp upward on the tailgate.

[0009] A dump truck according to a second aspect of the present invention is the dump truck according to the first aspect, wherein the link mechanism includes a first link member having one end rotatably connected to a tip end of the tailgate, and a second link member having one end rotatably connected to the other end of the first link member and the other end rotatably connected to a base end of the runway. When the tailgate is in an upright state and the runway is rotated upward, the biasing means applies a biasing force that biases the middle portion of the first link member upward during at least a part of the rotational movement.

[0010] A dump truck according to a third aspect of the present invention is the dump truck according to the first or second aspect, further comprising an actuator that opens and closes the tailgate.

[0011] A dump truck according to a fourth aspect of the present invention includes a cargo box that is tiltably and rearwardly mounted relative to a vehicle frame and has a tailgate at its rear that can be rotated upward and open, a runway whose base end is rotatably connected to a front end of the tailgate, a link mechanism connected to both the tailgate and the runway, and an actuator that opens and closes the tailgate. The link mechanism is configured to position the runway so that it overlaps with the rear surface of the tailgate when the tailgate is in a closed position, rotate the runway relative to the tailgate so that the front end of the runway moves away from the tailgate when the tailgate rotates from the closed position to an open position, and position the runway on an extension of the tailgate when the tailgate reaches the open position.

[0012] According to a dump truck having such a configuration, when the tailgate is rotated to the open position by the actuator, the ramp can be used without manual effort.

[0013] A dump truck according to a fifth aspect of the present invention is the dump truck according to the fourth aspect, wherein the cargo box has fixed pillars on both sides of the rear part, and the link mechanism has a first link member having one end rotatably connected to the fixed pillar, and a second link member having an intermediate portion rotatably connected to a side portion of the tip part of the tailgate, one end rotatably connected to the other end side of the first link member, and the other end non-rotatably connected to the base end side of the runway.

[0014] A dump truck according to a sixth aspect of the present invention is the dump truck according to the fifth aspect, wherein the first link member includes a fixed-pole-side member having a rod turnably connected to the fixed pole, a second link member turnably connected to the second link member and having a tube member into which the fixed-pole-side member is slidably inserted, and an elastic member interposed between the fixed-pole-side member and the second link member. The fixed-pole-side member is connected to the second link member so as to be slidable in the longitudinal direction of the first link member.

[0015] A dump truck according to a seventh aspect of the present invention is the dump truck according to the fourth aspect, wherein the link mechanism includes a bracket provided on the base end side of the tailgate, a first link member having one end side rotatably connected to the bracket, a support member provided to maintain a fixed position with respect to the floor of the cargo box, a second link member having an intermediate portion rotatably supported by the support member and one end side rotatably connected to the other end side of the first link member, and a third link member having one end side rotatably connected to the other end side of the second link member and the other end side rotatably connected to the runway. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a dump truck that can reduce the burden on workers when using a ramp attached to the tailgate. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a side view of a dump truck according to a first embodiment. [Figure 2] FIG. 2 is a partial perspective view of the rear of the cargo box of the dump truck according to the first embodiment. [Figure 3] FIG. 2 is a partial side view of the rear part of the cargo box of the dump truck according to the first embodiment, showing the state before the ramp is rotated. [Figure 3A] FIG. 2 is a partial side view of the rear part of the cargo box of the dump truck according to the first embodiment, showing the runway before it rotates when a torsion bar is used as the biasing means. [Figure 4] FIG. 2 is a partial side view of the rear part of the cargo box of the dump truck according to the first embodiment, showing the state after the ramp has been rotated. [Figure 5] FIG. 2 is a partial side view of the rear part of the cargo box of the dump truck according to the first embodiment, showing the ramp being rotated. [Figure 6] FIG. 2 is a partial rear view of a cargo box of the dump truck according to the first embodiment. [Figure 7] 7 is a cross-sectional view taken along the line AA in FIG. 6. [Figure 8] FIG. 11 is a partial perspective view of a state in which a cover for a fixed pillar at the rear of a cargo box of a dump truck according to a second embodiment has been removed. [Figure 9] FIG. 10 is a partial side view of the dump truck according to the second embodiment with a cover removed from a fixed pillar at the rear of the cargo box, showing the state before the ramp is rotated. [Figure 10] FIG. 10 is a partial side view of the dump truck according to the second embodiment with the cover removed from the fixed pillar at the rear of the cargo box, showing the state after the ramp has been rotated. [Figure 11] FIG. 10 is a partial side view of the dump truck according to the second embodiment with the cover removed from the fixed pillar at the rear of the cargo box, showing the ramp in the middle of pivoting. [Figure 12] FIG. 10 is a partial side view of the dump truck according to the second embodiment with a cover removed from a fixed pillar at the rear of the cargo box, showing the tailgate in the middle of pivoting. [Figure 13] FIG. 11 is a partial perspective view of the rear of a cargo box of a dump truck according to a third embodiment. [Figure 14] FIG. 11 is a partial perspective view of the rear part of the cargo box of the dump truck according to the third embodiment, showing the ramp in the middle of pivoting. [Figure 15] FIG. 11 is a partial side view of the rear part of the cargo box of the dump truck according to the third embodiment, showing the state before the ramp is rotated. [Figure 16] FIG. 11 is a partial side view of the rear part of the cargo box of the dump truck according to the third embodiment, showing the state after the ramp has been rotated. [Figure 17] FIG. 11 is a partial rear view of a cargo box of the dump truck according to the third embodiment. [Figure 18] FIG. 11 is a partial side view of the rear part of the cargo box of the dump truck according to the third embodiment, showing the tailgate in the middle of pivoting. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a dump truck according to an embodiment of the present invention will be described with reference to the drawings. In this specification, unless otherwise specified, the front-rear, left-right, and up-down directions correspond to the front-rear, left-right, and up-down directions of the dump truck. The rotation described in this specification is rotation about an axis extending in the vehicle width direction.

[0019] First Embodiment 1 to 3, the dump truck 1 according to the first embodiment is made up of a vehicle frame 10, a cargo box 20, a ramp 30, a link mechanism 100, a biasing means 101, an actuator 50, etc. The dump truck 1 according to this embodiment is capable of performing a dumping operation to tilt the cargo box 20, and a sliding operation to move the cargo box rearward and land it on the ground.

[0020] The cargo box 20 is slidably supported by a slide frame. The slide frame is tiltable relative to the vehicle frame 10. When the slide frame is tilted relative to the vehicle frame 10 by a dump cylinder (not shown), the cargo box 20 is also tilted relative to the vehicle frame 10, and a dumping operation is performed. When the cargo box 20 is slid in the front-to-rear direction relative to the slide frame by a slide cylinder (not shown), the cargo box 20 slides in the front-to-rear direction relative to the vehicle frame 10 (sliding operation).

[0021] As shown in FIG. 2, the cargo box 20 includes a tailgate 21, a floor 22, and fixed pillars 23. The fixed pillars 23 are provided on both sides of the rear of the cargo box 20. The tailgate 21 is disposed between the fixed pillars 23. As shown in FIG. 3, the tailgate 21 is connected to the rear of the cargo box 20 via a shaft 27 so as to be pivotable upward and open freely. The shaft 27 extends in the vehicle width direction, and the tailgate 21 pivots around the axis of the shaft 27. As shown in FIG. 2, a bracket 24 is provided on the base end (lower side) of the tailgate 21. The tip end of an actuator 50, the base end of which is supported against the back surface of the cargo box 20, is pivotally connected to the bracket 24 via a shaft 25. The tailgate 21 is opened and closed in response to the extension and retraction of the actuator 50. Note that in this embodiment and other embodiments, a hydraulic cylinder is used as the actuator 50 for opening and closing the tailgate 21, but it is also possible to use a device other than a hydraulic cylinder as the actuator 50 for opening and closing the tailgate 21.

[0022] The runway plates 30 are arranged in a pair on the left and right so as to overlap the rear surface of the tailgate 21. As shown in Fig. 2, the base end of the runway plates 30 is rotatably connected to the front end of the tailgate 21 via a shaft 31. The runway plates 30 are rotatable between a state in which they overlap the rear surface of the tailgate 21 (see Fig. 3) and a state in which they stand up on the front end of the tailgate 21 (see Fig. 4).

[0023] 2 to 5, the link mechanism 100 has a piston member 140, a tube member 150, a first link member 110, and a second link member 120. The link mechanism 100 is connected to the tailgate 21 and the runway plate 30.

[0024] 3, one end of the piston member 140 is rotatably supported relative to the base end of the tailgate 21. A shaft 141 is provided on one end of the piston member 140. The shaft 141 is rotatably supported by a bracket 26 provided on the tailgate 21.

[0025] The tube member 150 has a cylindrical shape. As shown in Fig. 3, one end of the tube member 150 is open, and the other end of the piston member 140 is slidably inserted therein. The other end of the tube member 150 is closed, and a connection portion 152 with the first link member 110 is provided. A pair of opposing openings 151 are provided on the side surface of the tube member 150. The openings 151 extend along the central axis direction of the tube member 150. The shaft 141 of the piston member 140 is inserted into the openings 151. The shaft 141 moves within the openings 151, causing the piston member 140 to slide relative to the tube member 150.

[0026] As shown in Fig. 3, biasing means 101 is housed inside tube member 150. In this embodiment, biasing means 101 is a coil spring. Biasing means 101 is disposed inside tube member 150, between one end side of piston member 140 and the other end side of tube member 150. The biasing means 101 applies force to piston member 140 in a direction in which piston member 140 separates from tube member 150. As shown in Figs. 3 to 5, piston member 140 is slidable within a range in which shaft 141 can move within opening 151.

[0027] As shown in Figures 2 and 3, one end of the first link member 110 is rotatably connected to the tip end of the tailgate 21. An intermediate portion of the first link member 110 is rotatably connected to a connecting portion 152 on the other end side of the tube member 150. One end of the second link member 120 is rotatably connected to the other end side of the first link member 110. As shown in Figure 3, the first link member 110 and the second link member 120 are connected to form a substantially V-shape. The other end of the second link member 120 is rotatably connected to the base end side of the runway board 30.

[0028] As shown in Figures 2 and 6, the tailgate 21 is provided with a locking mechanism 60 for fixing the runway 30 to the tailgate 21. As shown in Figures 6 and 7, the locking mechanism 60 includes a handle 61, a handle guide 62, a spring 63, and a stopper 64. The handle 61 has a rod 61a and a lever 61b connected in a substantially L-shape. The tip of the rod 61a is cut obliquely relative to the longitudinal direction.

[0029] The handle guide 62 is fixed to the side surface of the stiffener 21a of the tailgate 21. The handle guide 62 has a generally cylindrical shape. One end of the handle guide 62 is cut out at an angle of 145° in the circumferential direction relative to the longitudinal direction. As shown in Figure 6, the edge of the handle guide 62 on the cut-out side has an angled portion along the circumferential direction.

[0030] The base of rod 61a is inserted into handle guide 62. The tip of rod 61a is exposed from the runway 30 side of stiffener 21a. Spring 63 applies elastic force to rod 61a in a direction in which the tip of rod 61a exposed from stiffener 21a approaches runway 30. Spring 63 keeps lever 61b in constant contact with the edge of the cutout in handle guide 62.

[0031] The stopper 64 is made of a plate fixed to the back surface of the runway panel 30. As shown in Fig. 7, the stopper 64 is provided with a through-hole 64a into which the tip of the rod 61a is inserted. When the tip of the rod 61a is inserted into the through-hole 64a, the runway panel 30 is fixed to the tailgate 21 so as not to be able to rotate.

[0032] As shown in Figure 6, when the runway board 30 overlaps the rear surface of the tailgate 21 and the lever 61b is facing downward, the tip of the rod 61a is inserted into the through-hole 64a of the stopper 64, and the runway board 30 is fixed so as not to be able to rotate relative to the tailgate 21. When the worker rotates the lever 61b upward, the lever 61b moves in a direction away from the runway board 30 along the diagonal edge of the notch in the handle guide 62. When the tip of the rod 61a is pulled out of the through-hole 64a by the movement of the lever 61b, the runway board 30 is released from its position fixed to the tailgate 21.

[0033] During the dumping operation of the dump truck 1, the runway plate 30 is fixed to the tailgate 21 by the locking mechanism 60 so as not to be able to rotate. In this state, the tailgate 21 is rotated upward by the actuator 50, and the cargo box 20 is tilted by the dump cylinder, thereby performing the dumping operation of the dump truck 1.

[0034] When unloading construction machinery or the like loaded on the loading box 20 of the dump truck 1 from the loading box 20, the worker first rotates the lever 61b upward and pulls the tip of the rod 61a out of the through-hole 64a of the stopper 64, thereby releasing the locking mechanism 60 from fixing the ramp 30 to the tailgate 21. Next, the worker rotates the ramp 30 upward, and at this time, the upward rotation of the ramp 30 is assisted by the biasing force of the biasing means 101, so that the effort required by the worker to rotate the ramp 30 upward is reduced.

[0035] The action of the urging force by the urging means 101 will be explained in more detail using the drawings. In the state before the runway plate 30 rotates relative to the tailgate 21 (see FIG. 3), the urging force of the urging means 101 acts in a direction that pushes the middle part of the first link member 110 upward. However, in the state before the runway plate 30 rotates as shown in FIG. 3, due to the positional relationship between the link mechanism 100 and the urging means 101, the urging force does not act in a direction that rotates the runway plate 30 upward. Specifically, when viewed from the side of the vehicle as shown in Figure 3, a straight line passing through the center of the axis 141 connecting the bracket 26 and the piston member 140 and the center of the axis 153 connecting the connection portion 152 of the tube member 150 and the first link member 110 passes forward of the center of the axis 114 connecting the tailgate 21 and the first link member 110, so when the tailgate 21 is within a range from the fully closed state to a predetermined opening degree, the biasing force of the biasing means 101 acts to rotate the board 30 downward.

[0036] On the other hand, when the worker rotates the runway plate 30 upward and the opening degree of the tailgate 21 exceeds the predetermined opening degree, as shown in FIG. 5, a line passing through the centers of the shafts 141 and 153 passes rearward of the center of the shaft 114, and the biasing force of the biasing means 101 acts in a direction pushing the middle portion of the first link member 110 upward (acting to rotate the runway plate 30 upward). At this time, the biasing means 101 causes the piston member 140 to slide in a direction separating from the tube member 150. As a result, the tube member 150 slides upward while rotating slightly about the shaft 141, and while the middle portion of the first link member 110 moves upward, a force pushing the middle portion of the first link member 110 upward can be continuously applied.

[0037] The biasing force acting on the first link member 110 becomes a force that rotates the runway plate 30 upward via the second link member 120, and serves as an assisting force when the worker rotates the runway plate 30 upward.

[0038] 5, for example, the biasing force acts in a direction that rotates the runway plate 30 upward, and the force of the worker lifting the runway plate 30 upward is reduced by the amount of the biasing force. In this way, the biasing means 101 reduces the effort of the worker to rotate the runway plate 30 upward.

[0039] 4, when the rung plate 30 is rotated until it is positioned on the extension of the tailgate 21, the worker has completed the lifting of the rung plate 30. At this time, the biasing force of the biasing means 101 acts in a direction that rotates the rung plate 30 further in the same direction, so even if the worker releases his or her hands from the rung plate 30, the rung plate 30 does not rotate downward and continues to be held on the extension of the tailgate 21. When the rung plate 30 is rotated upward, the rod 61a is pushed in the direction of the stopper 64 by the biasing force of the spring 63, so the lever 61b rotates downward while moving horizontally along the diagonal edge of the notch in the handle guide 62. Then, due to the horizontal movement of the lever 61b, the tip of the rod 61a returns to the position where it was inserted in the through-hole 64a of the stopper 64.

[0040] After the upward rotation of the runway plate 30 is completed, the actuator 50 is driven to rotate the tailgate 21 from the closed position to the open position, thereby setting it in an upward-open state. At this time, the biasing force of the biasing means 101 acts on the runway plate 30, so that the runway plate 30 can be maintained in a position that is an extension of the tailgate 21. Thereafter, by tilting the cargo box 20 and sliding it rearward, the runway plate 30 comes into contact with the ground, and construction machinery or the like loaded in the cargo box 20 can be driven over the tailgate 21 and runway plate 30 and lowered onto the ground.

[0041] When construction machinery or the like is to be loaded onto the cargo box 20 for transport again, the construction machinery or the like is driven over the cargo box 20 and tailgate 21 with the runway 30 in the grounded state as described above, and moved onto the floor 22 of the cargo box 20. Then, the cargo box 20 is slid forward and tilted downward, and the tailgate 21 is moved from the open position to the closed position, and the runway 30 is rotated downward by the worker to return it to its original position.

[0042] When the runway 30 is returned to its original position, the runway 30 is automatically fixed to the tailgate 21 by the locking mechanism 60 so that it cannot rotate.

[0043] That is, when the runway plate 30 returns to the rear surface of the tailgate 21, the stopper 64 abuts against the tip of the rod 61a. The portion of the stopper 64 that abuts against the tip of the rod 61a is chamfered so that it comes into surface contact with the slanted portion of the tip of the rod 61a, and therefore, when the chamfered portion of the stopper 64 abuts against the slanted portion of the tip of the rod 61a, the rod 61a is pushed back. Then, with the side surface of the stopper 64 in contact with the tip of the rod 61a, the stopper 64 moves until the through-hole 64a of the stopper 64 comes to the position of the tip of the rod 61a, and the tip of the rod 61a is inserted into the through-hole 64a, and the runway plate 30 is fixed so as not to be able to rotate relative to the tailgate 21.

[0044] As is clear from the above explanation, according to the dump truck 1 of this embodiment, by applying a biasing force from the biasing means 101 to the link mechanism 100, the burden on the worker who rotates the ramp 30, which is a heavy object, upward can be reduced, and the ramp 30 can be rotated smoothly.

[0045] Furthermore, since the dump truck 1 has a locking mechanism 60, the locking of the ramp 30 to the tailgate 21 can be released by simply rotating the lever 61b, and the ramp 30 can be fixed to the tailgate 21 by simply rotating the ramp 30 downward without operating the locking mechanism 60.

[0046] The dump truck 1 of this embodiment has been described using a configuration in which the tailgate 21 is rotated downward using the actuator 50, but it is also possible to have a configuration in which the tailgate 21 is opened and closed by an operator without using the actuator 50. When the actuator 50 is not used, it is also possible to adopt a configuration in which the tailgate 21 is not only opened upward, but also switched to being opened downward.

[0047] Furthermore, although the dump truck 1 of this embodiment uses a coil spring as the biasing means 101, other forms of biasing means are also possible. For example, instead of the piston member 140, the tube member 150, and the coil spring, an actuator such as an electric cylinder may be used to apply a biasing force that presses the middle portion of the first link member 110 upward.

[0048] 3A, a torsion bar 101A can also be used as the biasing means. When the torsion bar 101A is used as the biasing means, the link mechanism 100 has a third link member 103 and a fourth link member 104 instead of the piston member 140 and the tube member 150.

[0049] The torsion bar 101A is disposed within the tailgate 21 so as to extend in the vehicle width direction. One end of the torsion bar is fixed within the tailgate 21. At the base end of the tailgate 21, the other end of the torsion bar 101A is fixed to one end of a third link member 103. The third link member 103 is rotatably connected to the base end of the tailgate 21 around the torsion bar 101A as an axis. A force is applied to the third link member 103 by the torsion bar 101A in a direction that rotates the third link member 103 upward (counterclockwise direction indicated by arrow Y in FIG. 3A ).

[0050] The other end of the third link member 103 is rotatably connected to one end of the fourth link member 104. The other end of the fourth link member 104 is rotatably connected to an intermediate portion of the first link member 110. The force acting by the torsion bar 101A in a direction to rotate the third link member 103 upward acts via the fourth link member 104 in a direction to push the intermediate portion of the first link member 110 upward, and becomes a biasing force acting on the first link member 110. In this way, the biasing means that applies a biasing force to the intermediate portion of the first link member 110 can take various forms.

[0051] Second Embodiment Next, a dump truck 1A according to a second embodiment will be described with reference to the drawings. In the following, configurations similar to those described in the first embodiment may be denoted by the same reference numerals in the drawings and descriptions thereof may be omitted.

[0052] The dump truck 1A according to the second embodiment has a configuration in which, when the tailgate 21A is rotated by the actuator 50, the road plate 30A is simultaneously rotated by the link mechanism 100A.

[0053] As shown in Figures 8 and 9, in the dump truck 1A, the cargo box 20A includes a tailgate 21A, a floor 22, and fixed pillars 23A. The fixed pillars 23A are provided on both sides of the rear of the cargo box 20A. A cover (not shown) that covers a first link member 110A, which will be described later, is attached to the fixed pillars 23A. The tailgate 21A is connected to the rear of the cargo box 20A via a shaft 27 so as to be able to pivot upward and open freely. The tailgate 21A is opened and closed by an actuator 50 via a bracket 24 fixed to the tailgate 21A. The tailgate 21A is provided with a stopper 28 for fixing the runway board 30A. A through-hole 28a is formed in the stopper 28.

[0054] The pair of runways 30A are arranged on the left and right so as to overlap the rear surface of the tailgate 21A. As shown in Fig. 8, the base end of the runway 30A is rotatably connected to the front end of the tailgate 21A via a shaft 31A. As the tailgate 21A opens and closes, the runway 30A rotates relative to the tailgate 21A between a state in which it overlaps with the rear surface of the tailgate 21A (see Fig. 9) and a state in which it is positioned on an extension of the tailgate 21A (see Fig. 10) by the link mechanism 100A.

[0055] As shown in FIG. 8, a stopper 32 is provided on the runway plate 30A. Two through holes 32a are formed in the stopper 32. When the runway plate 30A overlaps with the rear surface of the tailgate 21A, the through hole 28a of the stopper 28 and one of the through holes 32a of the stopper 32 overlap. When a pin 70 is inserted into the through hole 28a of the stopper 28 and one of the through holes 32a of the stopper 32, the runway plate 30A is fixed to the tailgate 21A so as not to be able to rotate, as shown in FIG. 8. The pin 70 is detachable, and when the pin 70 is removed from the through hole 28a and the through hole 32a, the runway plate 30A is released from being fixed to the tailgate 21A.

[0056] As shown in FIGS. 8 to 11, the link mechanism 100A has a first link member 110A and a second link member 120A.

[0057] The first link member 110A includes a fixed post side member 111, a second link side member 112, and an elastic member 113. One end of the first link member 110A is rotatably connected to the fixed post 23A.

[0058] As shown in FIG. 9, the fixed-pole-side member 111 has a rod 111a rotatably connected to the fixed pole 23A. The second link-side member 112 has a cylindrical tube member 112a and a connecting member 112b rotatably connected to the second link member 120A. A portion of the fixed-pole-side member 111 is slidably inserted into the tube member 112a. The tube member 112a and the connecting member 112b are connected together. As shown in FIG. 9, the connecting member 112b is connected to the second link member 120A via a shaft 121, and the shaft hole in the connecting member 112b through which the shaft 121 is inserted is an elongated hole 112c. The fixed-pole-side member 111 is connected to the second link member 120A so as to be slidable in the longitudinal direction of the first link member 110A.

[0059] In this embodiment, the elastic member 113 is a coil spring. As shown in Fig. 9, the elastic member 113 is disposed inside the tube member 112a. When a tensile force acts on the elastic member 113 when the runway plate 30A is rotated, the elastic member 113 generates a compressive force.

[0060] 9, the middle portion of the second link member 120A is rotatably connected to a shaft 31A provided at the tip portion of the tailgate 21A. One end of the second link member 120A is rotatably connected to the other end of the first link member 110A. A shaft 121 provided at one end of the second link member 120A is inserted into an elongated hole 112c of the connecting member 112b. Alternatively, an elongated hole may be provided at one end of the second link member 120A, and the shaft may be provided on the connecting member 112b.

[0061] The other end of the second link member 120A is non-rotatably connected to a stopper 32 provided on the base end of the runway plate 30A. A through hole 122 is provided on the other end of the second link member 120A. By inserting a pin 70 into the through hole 122 of the second link member 120A and the other through hole 32a of the stopper 32, the other end of the second link member 120A is connected to the runway plate 30A, as shown in FIG. 9. The pin 70 is detachable, and by removing it from the through hole 122 and the through hole 32a, the connection between the second link member 120A and the runway plate 30A is released.

[0062] In the dump truck 1A of this embodiment, when the tailgate 21A rotates from the closed position to the open position, a first operation in which the runway plate 30A is rotated together with the tailgate 21A while the runway plate 30A is fixed so as not to rotate relative to the tailgate 21A, and a second operation in which the runway plate 30A is released from the tailgate 21A and rotated relative to the tailgate 21A so that the tip side of the runway plate 30A moves away from the tailgate 21A can be switched by inserting and removing the pin 70. The first operation is used during a dumping operation of the dump truck 1A, and the second operation is used during a sliding operation of the dump truck 1A.

[0063] For the first operation, the pin 70 is inserted into the through-hole 28a of the tailgate 21A and one of the through-holes 32a of the runway plate 30A. This fixes the runway plate 30A so that it cannot rotate relative to the tailgate 21A. At this time, the pin 70 is not inserted into the through-hole 122 of the second link member 120A or the other through-hole 32a of the runway plate 30A. In this state, when the tailgate 21A is rotated from the closed position to the open position by the actuator 50, the runway plate 30A rotates together with the tailgate 21A around the shaft 27, as shown in FIG. 12 .

[0064] For the second operation, as shown in Fig. 9, when the pin 70 is inserted into the through hole 122 of the second link member 120A and the other through hole 32a of the runway plate 30A, the second link member 120A is connected to the runway plate 30A. At this time, as shown in Fig. 9, the pin 70 is not inserted into the through hole 28a of the tailgate 21A and the one of the through holes 32a of the runway plate 30A, so the runway plate 30A can rotate relative to the tailgate 21A. In this state, when the tailgate 21A is rotated from the closed position to the open position by the actuator 50, the link mechanism 100A rotates the runway plate 30A relative to the tailgate 21A so that the tip side of the runway plate 30A moves away from the tailgate 21A (see Fig. 11), and finally, the runway plate 30A is positioned on an extension of the tailgate 21A in the fully open state (see Fig. 10).

[0065] When the tip of the runway plate 30A, which is located on the extension of the tailgate 21, touches the ground, the load and unload of construction machinery and the like is possible. At this time, the height of the tip of the runway plate 30A may become lower than the ground due to unevenness of the ground, etc. In this case, an upward force acts on the runway plate 30A, but the elongated hole 112c of the connecting member 112b causes the tip of the runway plate 30A to rotate upward, thereby reducing the load from the ground.

[0066] In some cases, the height of the tip of the runway board 30A becomes high relative to the ground. In this case, a gap is created between the tip of the runway board 30A and the ground, but the first link member 110A expands due to the load of construction machinery or the like placed on the runway board 30A, causing the tip of the runway board 30A to rotate downward, making it easier for the tip of the runway board 30A to come into contact with the ground.

[0067] As is clear from the above description, in the dump truck 1A according to this embodiment, simply by rotating the tailgate 21A from the closed position to the open position with the actuator 50 while sliding the cargo box 20A rearward, the ramp 30A automatically rotates relative to the tailgate 21A and is bridged between the open tailgate 21A and the ground. At this time, there is no need for an operator to lift the ramp 30A, which significantly reduces the burden on the operator when using the ramp.

[0068] Furthermore, according to the dump truck 1A, when the tip of the ramp 30A comes into contact with the ground, the link mechanism 100A allows the tip of the ramp 30A to rotate up and down depending on the height of the ground, thereby making it possible to position the ramp 30A in an appropriate position relative to the ground.

[0069] <Third embodiment> Next, a dump truck 1B according to a third embodiment will be described with reference to the drawings. In the following, configurations similar to those described in the first embodiment may be denoted by the same reference numerals in the drawings and descriptions thereof may be omitted.

[0070] The dump truck 1B according to the third embodiment has a configuration in which, when the tailgate 21B is rotated by the actuator 50, the road plate 30B is simultaneously rotated by the link mechanism 100B.

[0071] As shown in FIG. 13, in the dump truck 1B, a cargo box 20B includes a tailgate 21B, a floor 22, and a fixed pillar 23B. The tailgate 21B is connected to the rear of the cargo box 20B via a shaft 27 so as to be able to pivot upward and open freely. The tailgate 21B is opened and closed by an actuator 50 via a bracket 160 fixed to the tailgate 21B. As shown in FIG. 14, a stiffener 29 is formed on the rear surface of the tailgate 21B. The stiffener 29 is formed with a locking hole 29a that is a hole that penetrates the stiffener 29 in the vehicle width direction. In this embodiment, a sleeve penetrates the stiffener 29, and the locking hole 29a is formed by the inner periphery of the sleeve. The role of the locking hole 29a will be described later.

[0072] The runway plates 30B are arranged in a pair on the left and right so as to overlap the rear surface of the tailgate 21B when the tailgate 21B is in the closed position. As shown in Fig. 15, the base end of the runway plate 30B is rotatably connected to the tip end of the tailgate 21B via a shaft 31B. As the tailgate 21B opens and closes, the runway plate 30B rotates relative to the tailgate 21B between a state in which it overlaps the rear surface of the tailgate 21B (see Fig. 15) and a state in which it is positioned on an extension of the tailgate 21B (see Fig. 16) by the link mechanism 100B.

[0073] As shown in FIGS. 13 to 16, the link mechanism 100B has a bracket 160, a support member 170, a first link member 110B, a second link member 120B, and a third link member .

[0074] As shown in Fig. 14, bracket 160 is provided on the base end side (lower side) of tailgate 21B. As shown in Fig. 15, the tip of actuator 50 is rotatably connected to bracket 160 via shaft 161. As a result, tailgate 21B opens and closes in conjunction with the extension and contraction of actuator 50.

[0075] 14, the support member 170 is provided at the rear of the floor 22 of the packing box 20B and protrudes rearward. The support member 170 is provided so as to maintain a fixed position relative to the floor 22 of the packing box 20B.

[0076] The first link member 110B has a shape that is bent downward when viewed from the side of the vehicle. One end of the first link member 110B is rotatably connected to the bracket 160 and the tip of the actuator 50 via a shaft 161. As a result, the first link member 110B is linked to the tailgate 21B, which opens and closes in accordance with the extension and contraction of the actuator 50.

[0077] 14, one end of the second link member 120B is rotatably connected to the other end of the first link member 110B. An intermediate portion of the second link member 120B is rotatably supported by a support member 170 via a shaft 171.

[0078] As shown in FIG. 14, the third link member 130 has a shape that is bent in a direction away from the tailgate 21B when viewed from the side of the vehicle. The third link member 130 is composed of a left link element 130a disposed on the left side, a middle link element 130b disposed to the right of the left link element 130a, and a right link element 130c disposed to the right of the middle link element 130b. The left link element 130a, the middle link element 130b, and the right link element 130c have contour shapes that overlap each other when viewed from the side of the vehicle. Axle holes 131 that overlap each other when viewed from the side of the vehicle are formed at one end of the left link element 130a, the middle link element 130b, and the right link element 130c, respectively. One end of the left link element 130a, the middle link element 130b, and the right link element 130c is rotatably connected to the other end of the second link member 120B via a slide pin 65 slidably inserted into the shaft hole 131. The other end of the left link element 130a, the middle link element 130b, and the right link element 130c is rotatably connected to the base end of the board 30B.

[0079] The left link element 130a and the middle link element 130b are arranged parallel to each other, with the other end of the second link member 120B interposed between them. The right link element 130c has a stepped portion in its middle. One end side of the right link element 130c from the stepped portion (the second link member 120B side) and the other end side of the right link element 130c from the stepped portion (the runway board 30B side) are arranged parallel to each other at different positions in the vehicle width direction, with the one end side from the stepped portion being farther from the middle link element 130b than the other end side from the stepped portion. A mounting plate 133 (see FIG. 17) is installed between one end side of the middle link element 130b and one end side of the right link element 130c along the longitudinal direction of these link elements 130b and 130c. A first protruding plate 68 and a second protruding plate 69 protruding rearward are provided on the mounting plate 133. The first protruding plate 68 is provided closer to the middle link element 130b than the second protruding plate 69, and the second protruding plate 69 is provided closer to the right link element 130c than the first protruding plate 68.

[0080] The locking mechanism 60B secures and releases the runway plate 30B to and from the tailgate 21B, and connects and releases the third link member 130 and the second link member 120B. The locking mechanism 60B is composed of a slide pin 65, a lever 66, and a lock hole 29a in the tailgate 21B, and functions like a latch. The lever 66 extends radially outward from the side of the slide pin 65, and is formed in part with a protruding plate insertion hole through which a first protruding plate 68 and a second protruding plate 69 can be inserted.

[0081] The slide pin 65 is slidable left and right from a position where the lever 66 abuts against the side surface of the middle link element 130b to a position where the lever 66 abuts against the side surface of the right link element 130c.

[0082] When the slide pin 65 is moved to the left together with the lever 66, the slide pin 65 is inserted through the left link element 130a, the second link member 120B, the middle link element 130b, and the right link element 130c and is pulled out of the lock hole 29a provided in the tailgate 21B. At this time, the second link member 120B and the third link member 130 are rotatably connected to each other, and one end of the third link member 130 is disconnected from the stiffener 29 of the tailgate 21B. In this disconnected state, the runway plate 30B is rotatable relative to the tailgate 21B. This allows the link mechanism 100B of the dump truck 1B to function. The slide pin 65 can be prevented from accidentally sliding from the above position by inserting the first protruding plate 68 into the protruding plate insertion hole of the lever 66 and attaching an auxiliary lock such as a padlock to a hole formed through the first protruding plate 68.

[0083] On the other hand, when the slide pin 65 is moved to the right together with the lever 66, the slide pin 65 is inserted through the middle link element 130b, the right link element 130c, and the lock hole 29a provided in the tailgate 21B, but is not inserted through the left link element 130a and the second link member 120B. At this time, the connection between the second link member 120B and the third link member 130 is released, and one end of the third link member 130 is connected to the stiffener 29 of the tailgate 21B. In this connected state, the runway board 30B is fixed to the tailgate 21B while overlapping with the rear surface of the tailgate 21B. As a result, the link mechanism 100B of the dump truck 1B is not functioning, and the runway board 30B moves integrally with the tailgate 21B. In addition, by inserting the second protruding plate 69 into the protruding plate insertion hole of the lever 66 and attaching an auxiliary lock such as a padlock to the hole formed through the second protruding plate 69, it is possible to prevent the slide pin 65 from accidentally sliding from the above position.

[0084] In this embodiment, when the tailgate 21B rotates from the closed position to the open position, it is possible to switch between a "first operation" in which the runway plate 30B is rotated together with the tailgate 21B while the runway plate 30B is fixed so as not to rotate relative to the tailgate 21B, and a "second operation" in which the runway plate 30B is released from the tailgate 21B and rotated relative to the tailgate 21B so that the tip side of the runway plate 30B moves away from the tailgate 21B, simply by sliding the slide pin 65. The first operation is performed during a dumping operation of the dump truck 1B, and the second operation is performed during a sliding operation of the dump truck 1B.

[0085] When the first operation is performed, the slide pin 65 can be slid to the right, i.e., toward the stiffener 29, by the lever 66 to disable the link mechanism 100B. In this case, as shown in Fig. 18, the runway board 30B always overlaps with the rear surface of the tailgate 21B and rotates integrally with the tailgate 21B.

[0086] When the second operation is performed, the slide pin 65 can be slid to the left, i.e., toward the third link member 130, by the lever 66, to activate the link mechanism 100B. In this case, as shown in FIGS. 14 and 16, the runway board 30B can be rotated relative to the tailgate 21B in conjunction with the opening and closing operation of the tailgate 21B. That is, when the tailgate 21B is in the closed position, the runway board 30B overlaps with the rear surface of the tailgate 21 (see FIG. 15), and when the tailgate 21B opens or closes, the runway board 30B rotates relative to the tailgate 21B (see FIG. 14), and is positioned on an extension of the tailgate 21B when the tailgate 21B reaches the open position (see FIG. 16).

[0087] As is clear from the above description, with the dump truck 1B according to this embodiment, simply by rotating the tailgate 21B from the closed position to the open position with the actuator 50, the link mechanism 100B can rotate the runway 30B relative to the tailgate 21B so that the leading end of the runway 30B moves away from the tailgate 21A. When switching between the first operation and the second operation, the worker needs to operate the lever 66, but operating the lever 66 does not impose a physical burden on the worker. Furthermore, if the runway 30B is always used, the switching operation of the lever 66 is not necessary. Therefore, with the dump truck 1B according to this embodiment, the burden on the worker when using the runway can be significantly reduced. [Industrial Applicability]

[0088] The present invention can be applied to, for example, a dump truck. [Explanation of symbols]

[0089] 1, 1A, 1B Dump Truck 10 car frame 20, 20A, 20B packing box 21, 21A, 21B tailgate 22 Floor 23, 23A, 23B fixed column 30, 30A, 30B road board 50 Actuator 60, 60B locking mechanism 70 pins 100, 100A, 100B link mechanism 101 energizing means 110, 110A, 110B First link member 111 Fixed column side member 112 second link side member 112a Tube member 113 Elastic member 120, 120A, 120B Second link member 130 Third link member 140 Piston member 150 Tube member 160 bracket 170 Support member

Claims

1. a luggage box provided so as to be tiltable and movable rearward relative to the vehicle frame, the luggage box having a tailgate at the rear that can be turned upward and opened; a runway whose base end is rotatably connected to the tip end of the tailgate; a link mechanism connected to the tailgate and the runway; A dump truck comprising: The tailgate further includes a biasing means for applying a biasing force to the link mechanism so as to generate an assisting force for assisting the upward rotation of the runway plate when the tailgate is in an upright state and the runway plate is rotated upward. A dump truck characterized by:

2. The dump truck according to claim 1, The link mechanism includes: a first link member whose one end is rotatably connected to the tip end of the tailgate; a second link member having one end rotatably connected to the other end of the first link member and the other end rotatably connected to the base end of the runway; and When the tailgate is in an upright state and the runway is rotated upward, the biasing means applies a biasing force to the intermediate portion of the first link member in an upward direction during at least a part of the rotational movement. A dump truck characterized by:

3. The dump truck according to claim 1 or 2, A dump truck comprising an actuator that opens and closes the tailgate.

4. a luggage box provided so as to be tiltable and movable rearward relative to the vehicle frame, the luggage box having a tailgate at the rear that can be turned upward and opened; a runway whose base end is rotatably connected to the tip end of the tailgate; a link mechanism connected to both the tailgate and the runway; an actuator for opening and closing the tailgate; A dump truck comprising: The link mechanism includes: When the tailgate is in a closed position, the runway is positioned to overlap the rear surface of the tailgate; When the tailgate is rotated from the closed position to the open position, the runway is rotated relative to the tailgate so that a tip end side of the runway is separated from the tailgate, The tailgate is configured to position the runway in an extension of the tailgate when the tailgate reaches an open position. A dump truck characterized by:

5. The dump truck according to claim 4, The packing box has fixed posts on both sides of the rear part, The link mechanism includes: a first link member whose one end is rotatably connected to the fixed column; a second link member having an intermediate portion rotatably connected to a side portion of the tip end portion of the tailgate, one end side rotatably connected to the other end side of the first link member, and the other end side non-rotatably connected to the base end side of the runway; having A dump truck characterized by:

6. The dump truck according to claim 5, The first link member is a fixed column side member having a rod rotatably connected to the fixed column; a second link side member rotatably connected to the second link member, the second link side member having a tube member into which the fixed column side member is slidably inserted; an elastic member interposed between the fixed pole side member and the second link side member; Including, The fixed pole side member is connected to the second link member so as to be slidable in the longitudinal direction of the first link member. A dump truck characterized by:

7. The dump truck according to claim 4, The link mechanism includes: a bracket provided on a base end side of the tailgate; a first link member whose one end is rotatably connected to the bracket; a support member arranged to hold the box in a fixed position relative to the floor of the box; a second link member whose middle portion is rotatably supported by the support member and whose one end side is rotatably connected to the other end side of the first link member; a third link member having one end rotatably connected to the other end of the second link member and the other end rotatably connected to the runway; having A dump truck characterized by:

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