JPH07228209A - Dash-in preventive device for vehicle - Google Patents

Abstract

PURPOSE:To provide a movable dash-in preventive device for a vehicle having sufficient shock-proof property by a simple and light structure at a low cost. CONSTITUTION:In a dash-in preventive device for a vehicle in which a pair of support arms 1B, etc., extending slantly downward from the rear end of is load stand frame are installed and on whose tip a rear bumper 2 is fixed, the base end part of the support arm 1B, etc., is rotatably connected to the load stand frame by a supporting shaft 3 and can be turned upward and also a stop hole 4 is formed on the support arm part facing to the frame surface of the load stand frame and a pin member 5B, etc., which can be advanced and fitted in the stop hole 4 when the support arm 1B, etc., locate on a downward turn end are installed on the load stand frame. Further, the device in the title is provided with a support arm drive means 6 for turning the support arm 1B, etc., vertically and a pin member drive means 71 for advancing the pin member 5B, etc., in the stop hole 4 at the downward turn end of the support arm 1B, etc., and also retreating the pin member 5B, etc., from the stop hole 4 prior to the upward turn of the support arm 1B, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle plunge prevention device for preventing a passenger car or the like from slipping into a vehicle having a high loading platform such as a dump truck even if it collides with the vehicle.

[0002]

2. Description of the Related Art When a passenger car or the like crashes into a dump truck with large tires and a high cargo bed from behind, it is pointed out that the roof of the passenger car or the like is crushed by rushing (infiltrating) under the cargo bed and the occupant casualty rate increases rapidly. It has been. From these things,
New vehicles such as dump trucks after June 1, 1992 are obliged to install an inrush prevention device (Road Transport Safety Standard, Article 18-2, Paragraph 3). An example thereof is shown in FIGS. This figure shows a vehicle rush prevention device attached to the side surface and the rear surface of the loading platform of the dump truck. Support arm 1 diagonally downward from the left and right positions of the rear end of the frame F
A and 1B extend, and a rear bumper 2 extending in the vehicle width direction is fixed to the tip end thereof which is relatively close to the road surface (the height from the road surface is 550 mm or less). The rear bumper 2 is regulated to a position within 400 mm from the tail end of the vehicle. With such a plunge prevention device, when the rear vehicle collides with the rear vehicle, the front part of the rear vehicle collides with the rear bumper 2 so that problems such as crushing of the roof are eliminated.

[0003]

However, although the above-mentioned plunge-in prevention device effectively prevents the "recession" of the rear vehicle, it may overhang near the tail end and be low near the road surface depending on the work such as a dump truck. This rear bumper, which is projected and supported at the position, became an obstacle to the work. Therefore, in order to overcome such a problem, there has been proposed a device capable of pulling up and storing the rear bumper at the time of work or the like.

For example, a support arm 1 for supporting a rear bumper 2 provided at a rear portion of a vehicle is rotatably coupled at its base end to a rear end of a luggage carrier frame F, and a hydraulic cylinder 10 is used to move the support arm 1 forward and upward. This is a method of swiveling and storing in (FIGS. 8 to 10). A hydraulic cylinder 10 in which the tip end of the support arm 1 and the luggage carrier frame F are coupled by two upper and lower link arms 76 and 77, and the base end is rotatably coupled to the luggage carrier frame F at an intermediate position of the link arm 76. The tip of the piston rod 101 is connected. And the piston rod 101
When it is contracted from the extended state, the two link arms 76 and 77 are broken as shown by the chain line in FIG. 9, the supporting arm 1 is swung forward and upward of the vehicle, and the rear bumper 2 is stored immediately below the frame F. . By adopting such a configuration, the rear bumper 2 is swivel-stored, and one end of the asphalt finisher V can be sufficiently pulled down below the luggage carrier frame F in the road paving work, and the asphalt mixture carried by inclining the luggage carrier. Can be satisfactorily supplied (FIG. 10).

However, in such a movable plunge prevention device, when a rear vehicle collides with the rear bumper 2, the load is directly received by the link arm 76.77 and the hydraulic cylinder 10, so that the hydraulic cylinder 1, the link arm 76, 77
In order to secure the strength such as the above, it is inevitable to increase the size and increase the weight. In particular, in order to withstand a large load, the air cylinder mechanism was not useful and a hydraulic cylinder had to be used. However, the hydraulic power source is limited to some vehicles equipped with a crane or the like, and if this hydraulic power source is installed in a general vehicle, the cost is greatly increased.

The present invention solves the above problems, and an object of the present invention is to provide a movable vehicle plunge prevention device having a sufficient impact resistance with a simple, lightweight and inexpensive structure.

[0007]

A vehicle rush prevention device according to the first aspect of the present invention is provided with a pair of left and right support arms extending obliquely downward from a rear end portion of a carrier frame of the vehicle, and a rear bumper extending in the vehicle width direction at the tip thereof. In a vehicle rush prevention device with a fixed arm, the base end of the support arm is rotatably connected to the carrier frame by a support shaft so as to be pivotable upward, and the support arm that faces the frame surface of the carrier frame. A stopper member is formed in the portion, and a pin member capable of advancing and fitting into the stopper hole when the supporting arm is at the lower turning end is provided on the luggage carrier frame, and the supporting arm is further swung upward and downward. Arm drive means,
Pin member drive means for causing the pin member to enter the stop hole at the downward swing end of the support arm and for retracting the pin member from the stop hole prior to the upward swing of the support arm. And Here, the "support arm driving means" is a means that includes either an electric actuator such as an electromagnetic solenoid or a pneumatic actuator such as an air cylinder and that can swivel the support arm upward and downward around a support shaft.
The "pin member driving means" is a device that includes either an electric actuator such as an electromagnetic solenoid or a pneumatic actuator such as an air cylinder, and can move the pin member back and forth into the stop hole.

The vehicle rush prevention device according to the second aspect of the present invention is the vehicle rush prevention device according to the first aspect of the invention, wherein the actuators for the support arm drive means and the pin member drive means are constituted by air cylinders. Is characterized by. A vehicle rush prevention device according to a third aspect of the present invention is the vehicle rush prevention device according to the second aspect of the invention, wherein the pin member driving means is operated to rotate about a single air cylinder and an intermediate position by the air cylinder. And a first link arm that is connected to both ends of the first link arm and extends in the left and right directions, and linearly moves with the rotation of the first link arm to move the pin members provided on the left and right forward and backward. And a second link arm that allows the second link arm to move.

[0009]

According to the vehicle plunge prevention device of the first aspect of the present invention, during normal traveling, the support arm drive means pivots the support arm to the lower pivot end, and the pin member drive means causes the pin member to stop in the support arm. Enter and fit inside. Then, the rear bumper fixed to the tip of the support arm comes to be located at a predetermined height near the rear end of the vehicle and near the road surface. In such a state, even if the rear vehicle collides with the rear bumper, the pin member blocks the turning of the support arm, so that the rear bumper does not displace and the vehicle plunges (infiltrate) under the luggage carrier frame effectively. To be prevented. At this time, a large collision load is applied to the support arm, but this load is easily received by the rigidity of the pin member. If the material and diameter of the pin member are set appropriately,
It is simple, lightweight, inexpensive, and has sufficient strength as compared with the conventional case where an impact load is received by a hydraulic cylinder and a link arm. This is because the support arm drive means has only to perform an operation of turning the support arm, and does not directly play a role of receiving a collision load. On the other hand, when the vehicle is stopped and the work is performed, the support member is pivoted upward after the pin member is retracted from the inside of the stop hole. Then, the rear bumper is pulled up to the vicinity of the luggage carrier frame, which does not hinder the work.

When the actuators for the supporting arm driving means and the pin member driving means are constituted by air cylinders as in the vehicle rush prevention device according to the second aspect of the present invention, a compressor for a brake booster permanently installed in a dump truck or the like is used. Since compressed air can be supplied, no new compressed air equipment is required, and weight and cost can be significantly reduced. Further, when the pin members for fixing the left and right support arms are driven by the link arms by a single air cylinder as in the vehicle rush prevention device according to the third aspect of the present invention, the structure is further simplified.

[0011]

EXAMPLES The present invention will be described in detail below based on examples. (1) Example 1 An example of the present invention will be described. It is applied to a dump truck. FIG. 1 is a side view of a rush prevention device provided at the rear part of the loading platform of a dump truck, FIG. 2 is a front view of FIG. 1, FIG. 3 is a piping system diagram for supporting arm driving means and pin member driving means, and FIG. 4 is a control circuit. FIG. 5 is a schematic side view showing dimensional specifications of each part of the support arm.

FIG. 1 shows a mounting state of the inrush prevention device,
Support arms 1A and 1B extending rearward (to the right in the drawing) inclining downward are provided at the rear end of the luggage frame F, and the rear bumper 2 is fixedly supported at the tip that is gradually narrowed from the base end. As shown in FIG. 2, the rear bumper 2 extends in the vehicle width direction below the rear end of the luggage carrier, and is positioned at a predetermined height close to the road surface in the illustrated state. The support arms 1A and 1B project from the outer surfaces of the left and right luggage carrier frames F and support the middle position between the left and right rear bumpers 2.

Each of the left and right support arms 1A and 1B is rotatably supported by fitting a support shaft 3 projecting at a substantially central position into a bearing member 31 provided on each carrier frame F. Air cylinders 6 as actuators of the support arm driving means are provided at the inner positions of the left and right cargo frame F (only one is shown in FIG. 1).
Has a base end rotatably supported by the frame F, and a distal end of a piston rod 61 protruding therefrom is closer to the distal end than the support shaft 3 and is a connecting rod 11 (FIG. 2) connecting the left and right support arms 1A and 1B. It is rotatably attached to the left and right positions. In FIG. 2, the air cylinders 6 and 6 are omitted because the drawing becomes complicated. Under such a configuration, when the piston rod 6 is contracted from the extended state (FIG. 1), the support arms 1A and 1B pivot counterclockwise around the support shaft 3 and, as shown by the chain line, the carrier frame F. To the position along. That is, the rear bumper 2 can be pulled upward from the lower advance position.

Each of the support arms 1A, 1B is provided with a through hole at the base end portion on the side opposite to the tip end with respect to the support shaft 3. Cylindrical bosses having a predetermined inner diameter are joined to match the through holes to form the stop holes 4 and 4 (FIG. 2). On the other hand, pin members 5A and 5B which are guided by guide bosses and which can project to the outside of the frame F are provided on the left and right cargo frame frames F facing the stop holes 4 and 4. These pin members 5A, 5
The outer diameter of B is slightly smaller than the inner diameter of each of the stop holes 4. The link arm 7 is attached to each of the pin members 5A and 5B.
3,74 are connected and extend inward in the vehicle width direction,
The link arms 73 and 74 are connected to the upper and lower ends of the central link arm 72 (FIG. 2). An intermediate position of the link arm 72 is a cross member F1 connecting the left and right frames F.
It is rotatably connected to a support shaft 75 provided above. An air cylinder 71 as an actuator of a pin member driving means is arranged between the left and right cargo frame F in the vehicle width direction, and a tip of a piston rod 711 extending from the air cylinder 71 is coupled to an upper end of the link arm 72. To be done. Thus, when the support arms 1A and 1B are positioned at the lower turning ends and the piston rod 711 is moved from the contracted state to the extended state shown in FIG. 2 (FIG. 2), the link arm 72 rotates counterclockwise and the left and right links are moved. The arms 73 and 74 move outward, push out the pin members 5A and 5B at the tips thereof to the outside of the frame F, and enter and fit into the stop holes 4 of the support arms 1A and 1B. When such a fitted state is obtained, the pin member 5
A and 5B fix each support arm 1A and 1B (FIG. 1).
When the piston rod 711 of the pin member driving means contracts, the tip ends of the pin members 5A and 5B are in a retracted state from the inside of the stop hole 4.

Next, an air piping system leading to each of the air cylinders 6 and 71 is shown (FIG. 3). Support arm 1
One of the air cylinders 6 for turning A and 1B is shown. Compressed air to the air cylinders 6, 71 uses a compressor 81 provided for a brake booster, and pipes extending from the compressor 81 are supplied to the air cylinders 6, 71 via electromagnetic valves 82, 83, respectively. That is, the A port of the solenoid valve 82 is the working chamber 6 of each air cylinder 6, 71.
a and 7a, and the B port is connected to the working chambers 6b and 7b, respectively. The coil 8 of each solenoid valve 82, 83
In the state shown in the figure in which the currents 21, 21 are not energized, compressed air is supplied from the P port to the A port,
The piston rods 61 and 711 of 71 are both in the extended state. And the coils 821, 8 of the solenoid valves 82, 83
When electricity is applied to 31, the supply of compressed air is switched from the A port to the B port, and the piston rods 61 and 711 contract. The coils 821 and 831 of the solenoid valves 82 and 83 are connected to the control device 84, and the outputs thereof are energized and excited. Also, the piston rod 6 of each air cylinder 6,71
Limit switches LS1, LS2, LS3, LS4 are provided which are activated when 1, 711 are expanded or contracted, and these output signals are input to the control device 84. The control device 84 includes an “entrance” provided on an instrument panel (hereinafter referred to as an instrument panel) in a driver's seat,
The operation switches PB1 and PB2 for “advance” and the red and green indicator lights L1 and L2 are connected.

FIG. 4 shows a relay circuit within the controller 84. In the figure, each operation switch PB1, PB2 is a push button switch having a normally open and normally closed interlocking contact, and the normally open contact of the operation switch PB1 is connected to the relay coil 91 through the normally closed contact of the operation switch PB2. The normally-open relay contact 911 constitutes a self-holding circuit of the operation switch PB1. A relay coil 92 is connected in parallel with the relay coil 91 via a normally open contact of the limit switch LS4. In addition, the operation switch PB
The normally open contact 2 is connected to the relay coil 93 via the normally closed contact of the operation switch PB1.
Reference numeral 1 constitutes a self-holding circuit of the operation switch PB2. Limit switch L in parallel with the relay coil 93
The relay coil 94 is connected through the normally open contact of S1.

Normally open contact 9 of relay 91 connected in series
The solenoid valve coil 831 is connected between the power supply lines via the 12 and the normally closed contact 941 of the relay 94, and the power is supplied through the normally open contact 921 of the relay 92 and the normally closed contact 932 of the relay 93 which are connected in series. Solenoid valve coil 8 between lines
21 is connected. Further, the red indicator light L1 and the green indicator light L2 are the limit switches LS2 and LS, respectively.
It is connected between the power supply lines via the 3 normally open contacts.

Next, the operation of the rush prevention device having the above structure will be described. When the "retract" operation switch PB1 of the instrument panel is pressed, the relay coil 91 is energized and excited, and the normally open relay contact 912 is closed to energize the solenoid valve coil 831. As a result, the P port and the B port of the solenoid valve 83 communicate with each other, compressed air is supplied to the working chamber 7b of the air cylinder 71, and the piston rod 711 contracts. When the piston rod 711 contracts, the left and right pin members 5A and 5B are moved by the support arm 1 via the link arm 72, as described above.
The support arms 1A and 1B can be swung around the support shaft 3 by retreating from the inside of the stop holes 4 of A and 1B. When the contraction of the piston rod 711 is completed and the pin members 5A and 5B completely move out of the stop hole 4, the normally open contact of the limit switch LS4 is closed and the relay coil 92 is excited, and the normally open contact 921 is formed.
Closes. As a result, the solenoid valve coil 821 is energized and excited, the piston rod 61 of the air cylinder 6 contracts, the support arms 1A and 1B pivot upward, and the rear bumper 2 fixed to the tip of the support arm 1A, 1B is loaded onto the carrier frame as shown by the chain line in FIG. Reach the position along F. When the contraction of the piston rod 61 is completed and the support arms 1A and 1B reach the upper turning end, the normally open contact of the limit switch LS2 is closed, and the red indicator lamp L1 of the instrument panel is closed.
Lights up. By turning on the indicator light L1, the passenger can easily confirm that the rear bumper 2 is pulled up,
After the work is completed, problems such as starting the vehicle with the rear bumper 2 pulled up can be avoided.

On the other hand, when the "advance" operation switch PB2 of the instrument panel is pressed, the excitation of the relay coils 91 and 92 is canceled and the relay coil 93 is energized and excited, and the normally closed relay contact 932 is opened to open the solenoid valve. The power supply to the coil 821 is canceled. As a result, the P port and A port of the solenoid valve 82 communicate with each other, compressed air is supplied to the working chamber 6a of the air cylinder 6, and the piston rod 61 extends. When the piston rod 61 extends, the supporting arms 1A and 1B pivot downward, and the rear bumper 2 fixed to the tip of the supporting arm 1A and 1B advances to a predetermined position near the road surface below the rear of the luggage frame F as shown by the solid line in FIG. When the extension of the piston rod 61 is completed and the support arms 1A and 1B reach the downward turning end, the normally open contact of the limit switch LS1 is closed, the relay coil 94 is energized and excited, and the normally closed contact 941 is opened, and the electromagnetic contact is opened. The energization excitation of the valve coil 831 is canceled. Then, the piston rod 711 of the air cylinder 71 extends, and the left and right pin members 5A, 5 are connected via the link arms 72 to 74 (FIG. 2).
B enters into the stop hole 4 of the support arms 1A and 1B and fits into it. Thus, the turning of the support arms 1A and 1B around the support shaft 3 is restricted. When the extension of the piston rod 711 is completed and the pin members 5A and 5B are fitted into the stop hole 4, the normally open contact of the limit switch LS3 is closed and the green indicator light L2 of the instrument panel is turned on. By illuminating this indicator light L2, the occupant can confirm that the rear bumper 2 has been advanced and fixed at a predetermined position.

When the pin members 5A and 5B are made of, for example, S45C and have a pin diameter of 26 mm, the yield point thereof is 35 kg / mm ² . The collision load P applied to the rear bumper 2 is set to 10 t, and the support arm 1 shown in FIG.
Assuming that the relative dimensions of the rear bumper 2, the support shaft 3 and the stop hole 4 in A and 1B are as follows, the pin members 5A,
The rigidity stress generated in 5B is 25.5 kg / mm ² ,
A large safety factor of 1.3 or more can be obtained. Where l1 =
213.8 (mm), l2 = 210 (mm), l3 = 4
0 (mm), L = 250 (mm), and θ = 10.78 °.

(2) Second Embodiment This embodiment is a push button type operation switch P of the first embodiment.
An ON-OFF changeover switch is provided instead of B1 and PB2. The red indicator light L1 is turned on in the driver's seat during the ON operation, and the green indicator light L2 is not attached. In addition, the limit switch comes into contact when the piston rod 711 of the air cylinder 71 contracts and the solenoid valve 82 is contacted.
The limit switch LS4 sends a switching electric signal to and the limit switch LS1 contacts the solenoid rod 83 when the piston rod 61 of the air cylinder 6 extends and sends a switching electric signal to the solenoid valve 83. Other configurations are the same as those in the first embodiment.

Next, the operation of the rush prevention device having such a structure will be described. When the changeover switch is OFF, the solenoid valve 8
The P ports and A ports of Nos. 2, 83 communicate with each other, and the piston rods 61, 711 are in an extended state. When the changeover switch is turned on, first, the P port and the B port of the solenoid valve 83 communicate with each other, and the piston rod 711 contracts. When this contraction progresses and the pin members 5A and 5B retract from the stop hole 4, the piston rod 711 contacts the limit switch LS4. The limit switch LS4 is connected to the piston rod 71.
1 is transmitted to the solenoid valve 82, and the piston rod 61 of the air cylinder 6 is switched by switching the solenoid valve 82.
Contracts and the rear bumper 2 is stored immediately below the frame F. Here, when the changeover switch is turned on, the red indicator light L1 is turned on. In this way, the obstacle of the plunge prevention device is removed, and at the same time, the indicator light L1 warns that the vehicle will not be accidentally operated. On the other hand, when finishing the work and returning the rush prevention device to the original state, the changeover switch is turned off. Then, the P port and the A port of the solenoid valve 82 communicate with each other, and the piston rod 61 extends. And the piston rod 61
Contacts the limit switch LS1 when is fully extended. This limit switch LS1 transmits a switching signal to the solenoid valve 83, and subsequently the piston rod 711 extends. By the extension of the piston rod, the pin member 5
A and 5B are fitted in the stop hole 4, and the rear bumper 2 is advanced and fixed in a predetermined position. Thus, by turning off the changeover switch, it is confirmed that the indicator light also goes off, the warning is released, and the vehicle is ready for operation.

(3) Effects of the Embodiment The vehicle rush prevention device according to this embodiment has support arms 1A and 1A.
Since the pin members 5A and 5B that enter and fit into the stop hole 4 of B are provided, the rear impact load of the rear vehicle during normal traveling can be received with a simple and lightweight structure with sufficient durability. . Then, the pin members 5A, 5B are driven forward and backward by the pin member driving means, and the pin members 5A, 5B are retracted from the inside of the stop hole 4 at the time of work,
Since the support arms 1A and 1B can be turned upward,
The work obstacle caused by the rear bumper 2 has been resolved. The weight increase due to the modification was lighter than the conventional product, and the impact on fuel consumption was small. In addition, the pin members 5A and 5B for fixing the left and right support arms 1A and 1B are attached to the link arms 72 to 74.
Since it is driven by a single air cylinder 71, the structure becomes simpler. Furthermore, since it is not necessary for the supporting arm driving means to directly oppose the collision load as in the conventional case, the air cylinder 6 can be used instead of the hydraulic cylinder, and compressed air can be supplied from the compressor for the brake booster equipped in the dump truck or the like. It became possible to receive supply. In this way, compared to the conventional example using a hydraulic cylinder, a significant reduction in weight and cost could be achieved.

The present invention is not limited to those shown in the above embodiments, but can be variously modified within the scope of the present invention depending on the purpose and application. For example, instead of the air cylinders 6 and 71 of the support arm driving means and the pin member driving means, an electromagnetic solenoid or the like can be used. The position of the stop hole 4 does not necessarily have to be provided at the base end portion on the side opposite to the tip end as long as it is eccentric to the support shaft 3 by a predetermined amount. The support shaft 3 may be vertically fixed to the carrier frame F, and the support arms 1A and 1B may be rotatably supported by the support shaft. Further, proximity switches or the like may be used instead of the limit switches LS1 to LS4.

[0025]

As described above, the rush prevention device of the present invention allows the rear bumper to be retracted at the time of work or the like to secure a sufficient working area, while at the time of traveling, the rear bumper is advanced to a predetermined position near the road surface. Since the structure is simple, lightweight, and inexpensive and has sufficient impact durability to prevent a rear vehicle from entering, it is extremely useful for a dump truck or the like that is inconvenient when the rear bumper is fixed.

[Brief description of drawings]

FIG. 1 is a side view of a rush prevention device provided at a rear end portion of a luggage carrier frame according to a first embodiment.

FIG. 2 is a front view of the rush prevention device of FIG.

FIG. 3 is a piping system diagram for supporting arm driving means and pin member driving means.

FIG. 4 is a relay circuit diagram of the control circuit of the first embodiment.

FIG. 5 is a schematic side view showing dimensional specifications of each part of the support arm of the first embodiment.

FIG. 6 is a rear side view of the rear part of the vehicle to which the rush prevention device of the conventional example is attached.

FIG. 7 is a front view of FIG.

FIG. 8 is a rear side view of the luggage carrier to which another conventional rush prevention device is attached.

9 is an enlarged side view of FIG.

FIG. 10 is a side view of the rear portion of the loading platform of the vehicle provided with the rush prevention device during work.

[Explanation of symbols]

 1A, 1B Support arm 2 Rear bumper 3 Support shaft 4 Stop hole 5A, 5B Pin member 6 Support arm drive means (air cylinder) 71 Pin member drive means (air cylinder) 72 First link arm 73, 74 Second link arm

Claims (3)

[Claims] 1. A vehicle intrusion prevention device in which a pair of left and right support arms extending obliquely downward from a rear end portion of a luggage carrier frame of a vehicle are provided, and a rear bumper extending in the vehicle width direction is fixed to the tip ends thereof, the base end of the support arms. Part is rotatably connected to the carrier frame by a support shaft so as to be pivotable upward, and a stop hole is formed in a support arm portion facing the frame surface of the carrier frame, and the support arm is provided at a lower pivot end. A pin member that can be fitted into the stop hole at a certain time is provided on the carrier frame,
Further, a support arm drive means for pivotally moving the support arm upward and downward, and a pin member inserted into the stop hole at a downward pivot end of the support arm, and the pin member prior to pivoting upward of the support arm. A rush prevention device for a vehicle, comprising: a pin member driving means for retracting from the inside of the stop hole. 2. The vehicle rush prevention device according to claim 1, wherein the actuators related to the support arm driving means and the pin member driving means are constituted by air cylinders. 3. The pin member driving means is connected to a single air cylinder, a first link arm that is pivotally operated about the intermediate position by the air cylinder, and both ends of the first link arm. 3. The vehicle according to claim 2, further comprising a second link arm that extends in the left-right direction and linearly moves with the rotation of the first link arm to move the pin members provided on the left and right forward and backward. Rush prevention device.