JP2001220095A - Hydraulic equipment protective device of reach-type forklift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic equipment protective device of a reach-type forklift which prevents the breakage of hydraulic equipment or the like even when the forklift is collided with a wall, etc., in the traveling mode and during the reach-out operation. SOLUTION: A bypass pipe 62 having a relief valve 61 is connected to a cap side working fluid feed pipe 70 arranged on the cap 32 side of a reach cylinder 31. A fluid feed pipe 65 with one end thereof connected to the bypass pipe 62 side is connected to a head side working fluid feed pipe 71 via a check valve 64. When the pressure generated by the shock exceeds a set value of the relief valve 61, the relief valve 61 is opened, the working fluid flows in the bypass pipe 62, and the pressure in the reach cylinder 31 is reduced. In addition, the pressure in a head 33 becomes negative, the check valve 64 is opened, and the working fluid in the fluid feed pipe 65 is fed into the head 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for protecting a hydraulic device of a reach type forklift in which a cargo handling device can be moved in the front-rear direction.

[0002]

2. Description of the Related Art In this type of reach-type forklift in which a cargo handling device can be moved in the front-rear direction, it is usual to operate the cargo handling device by pulling it toward a vehicle body during traveling in order to reduce a turning radius.

[0003]

However, when traveling, when it is troublesome to perform the reach-in operation for pulling the fork constituting the cargo handling device toward the vehicle body, or when forgetting to reach the fork, the fork is moved forward. In some cases, the vehicle may travel with the reach-out state that has been issued. If the fork collides with a stopper or a wall, which is an unloading part of the work place, during a reach-out operation in which the fork is extended forward during such traveling, an impact force at the time of collision is applied to the reach cylinder. Moreover, the cap side of the reach cylinder is at a high pressure due to the reach-out state, and a pressure higher than the withstand pressure is generated in the hydraulic circuit in a shocking manner. Therefore, there has been a problem that the hydraulic equipment and the hydraulic hose are damaged by the shock wave.

The present invention has been made in view of the above points, and has been provided in order to prevent a hydraulic device or the like from being damaged even if it collides with a wall or the like during traveling and during a reach-out operation. The present invention provides a hydraulic device protection device.

[0005]

Therefore, in the hydraulic device protection device for a reach type forklift according to the first aspect of the present invention, the reciprocating motion of the piston rod due to the inflow and outflow of hydraulic oil to the head side and the cap side of the cylinder. Thus, in a reach type forklift capable of moving a cargo handling device having a fork connected to the piston rod in the front-rear direction,
In a state where there is no supply of hydraulic oil to the head side of the cylinder, when the piston rod moves to the cap side, a hydraulic device protection device that allows the hydraulic oil pressed by the piston rod to flow out of the cap side, It is characterized in that it is provided by being branched from a cap-side hydraulic oil supply pipe provided on the cap side of the cylinder.

With this configuration, when a fork connected to the piston rod collides with a wall or the like and an impact is applied to the reach cylinder, even if the hydraulic pressure rises, the cap-side hydraulic oil supply piped to the cylinder cap side is provided. The hydraulic device protection device branched from the pipe works to allow the hydraulic oil pressed by the piston rod to flow out of the cap side, reducing the pressure in the hydraulic circuit and preventing damage to the hydraulic devices and hydraulic hoses. Can be prevented.

According to a second aspect of the present invention, in the hydraulic device protection device for a reach-type forklift, the hydraulic device protection device is disposed in a bypass pipe branching from the cap-side hydraulic oil supply pipe, and is provided in the middle of the bypass pipe. And a relief valve for releasing the hydraulic oil flowing out from the cap side.

[0008] As described above, since the hydraulic device protection device is constituted by the relief valve and the bypass pipe, the hydraulic device protection device can be configured with a simple hydraulic circuit configuration and at low cost, but it can be surely constructed. Damage to hydraulic equipment and hydraulic hoses can be prevented.

According to a third aspect of the present invention, there is provided a hydraulic device protection device for a reach type forklift, wherein one end of an oil supply pipe filled with hydraulic oil is piped to a head side hydraulic oil supply pipe piped to a head side of the cylinder. It is characterized by.

[0010] Thus, it is possible to prevent the hydraulic oil from being supplied from the oil feed pipe into the head of the cylinder to which the impact has been applied, thereby preventing the inside of the head from being in a vacuum state. Therefore, since the head is not evacuated, corrosion and malfunction due to vacuum can be prevented.

According to a fourth aspect of the present invention, the other end of the oil supply pipe is connected to the bypass pipe downstream of the relief valve.

Thus, hydraulic oil is supplied from the oil feed pipe through the relief valve and the bypass pipe into the head of the cylinder to which the impact has been applied, and the inside of the head can be prevented from being in a vacuum state. Therefore, since the head does not become vacuum,
Corrosion and malfunction due to vacuum can be prevented.

According to a fifth aspect of the present invention, there is provided a hydraulic device protection device for a reach-type forklift, wherein a flow control valve is provided in the middle of the bypass pipe downstream of the relief valve, and one end is provided with the flow control valve and the relief valve. An oil feed pipe branched from the bypass pipe between the above and a hydraulic pipe supplied to the head side hydraulic oil supply pipe. It is characterized by returning to the head side of the cylinder.

With this arrangement, the hydraulic oil that has escaped from the relief valve and that has not flowed to the flow control valve side is returned to the cylinder head side, so that the flow control valve is adjusted and the head side is adjusted. Adjustments can be made to return the right amount of hydraulic fluid to the
The required amount of hydraulic oil that does not cause a vacuum on the head side can be returned, no extra pressure is applied to the oil feed pipe, and the durability and safety of the circuit can be maintained well.

According to a sixth aspect of the present invention, a pilot check valve is provided in the middle of the cap side hydraulic oil supply pipe, and a pilot port of the pilot check valve is connected to the head side. It is connected to the head side hydraulic oil supply pipe.

Thus, since the pilot check valve is provided in the middle of the cap side hydraulic oil supply pipe and the pilot port of the pilot check valve is connected to the head side hydraulic oil supply pipe, the pilot check valve matches the pilot pressure. Hydraulic oil flows from the cap side only by that amount, so that the hydraulic equipment downstream of the pilot check valve can be protected.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, the overall schematic structure of a forklift provided with a reach mechanism will be described with reference to FIG. The forklift 1 includes a vehicle body 2, a pair of left and right straddle legs 3 integrally projecting forward of the vehicle body 2, a cargo handling device 4 that moves in the front-rear direction along the straddle legs 3, and the like.

A driver's seat 5 is provided at the rear of the forklift 1 for an operator to operate while standing. A handle 6 is provided on the left side of the driver's seat 5, and various hydraulic cylinders to be described later are provided in front. , A reach lever 7, a tilt lever 8, a lift lever 9, and the like are provided. A head guard 10 is provided above the driver's seat 5 to protect the vehicle body and the operator from falling objects such as commodities. The cargo handling device 4 mainly includes a pair of left and right masts 11, a lift bracket 12 that moves up and down along the mast 11, a pair of left and right forks 13 provided on the front surface of the lift bracket 12, and the like.

FIG. 1 shows a hydraulic circuit of the forklift 1 according to the present invention. The hydraulic oil stored in an oil tank 20 is hydraulically piped (hydraulic hose) by a pump 22 driven by a hydraulic motor 21. Are sent to a reach direction control valve 23, a tilt direction control valve 24, and a lift direction control valve 25, respectively. The main relief valve 26 in the hydraulic circuit determines the maximum pressure of the hydraulic circuit by this valve, and when the pressure exceeds that pressure, opens the valve to protect the entire hydraulic circuit.

A cap-side hydraulic oil supply pipe 70 connected to one of the output sides of the reach direction control valve 23 is connected to the cap 32 side of the reach cylinder 31 via the pilot check valve 30. 23 is a head side hydraulic oil supply pipe 71
Is connected to the head 33 on the rod 34 side of the reach cylinder 31. In addition, the pilot check valve 3
The zero pilot port 36 is connected to the head-side hydraulic oil supply pipe 71. One of the output sides of the tilt direction control valve 24 is connected to a pair of tilt cylinders 41.
And the other output side is connected to the head 43 side of the tilt cylinder 41. Further, the output side of the lift direction control valve 25 is connected to the cap 52 side of the pair of lift cylinders 51.

Next, the control valves 23 to 25 are controlled by levers 7 to 9, respectively. In the reach direction control valve 23, the reach lever 7 shown in FIG. F) When it is tilted down, the oil flows to the head 33 side of the reach cylinder 31, and the mast 11 is drawn toward the front and reaches in. When the reach lever 7 is tilted forward in FIG. 2 (to the right in FIG. 1), oil flows toward the cap 32, and the mast 11 moves forward to reach out. The reach lever 7 and the reach cylinder 31 are attached only to the reach type forklift.

Next, in the tilt direction control valve 24, the tilt lever 8 shown in FIG. 2 is moved forward (to the left in FIG. 1).
When tilted, the oil flows toward the cap 42 side of the tilt cylinder 41, and the fork 13 tilts up and tilts up.
When the tilt lever 8 is tilted forward (to the right in FIG. 1), the oil flows toward the head 43, and the fork 13 tilts down to tilt down.

In the lift direction control valve 25, FIG.
When the lift lever 9 is tilted forward (to the left in FIG. 1), oil flows toward the cap 52 of the lift cylinder 51,
The lift bracket 12 is raised. When the lift lever 9 is tilted forward (to the right in FIG. 1), the lift cylinder 51
The oil on the cap 52 side returns to the oil tank 20, and the lift bracket 12 descends. The lift bracket 12 drives the hydraulic motor 21 and the pump 22 to send oil to the lift cylinder 51 when the lift bracket 12 is raised, but is naturally lowered by the weight of the lift bracket 12 and the fork 13 when the lift bracket 12 is lowered. .

In the present invention, as shown in FIG. 1, the cap 32 side of the reach cylinder 31 and each of the control valves 23-2
5 and a return pipe 60 for returning oil to the oil tank 20.
2 are connected. This relief valve 61 is set to the same pressure as the main relief valve 26 (or a pressure slightly smaller than the main relief valve 26). A return pipe 6 to which the head-side hydraulic oil supply pipe 71 on the head 33 side of the reach cylinder 31 and the bypass pipe 62 are connected.
0, an oil feed pipe 65 provided with a check valve 64 on the way is connected. The oil supply pipe 65 contains hydraulic oil.

When the pressure on the side of the cap 32 of the reach cylinder 31 increases and the pressure becomes higher than the pressure set by the relief valve 61, the relief valve 61 is opened through the bypass pipe 62. Return pipe 6 for oil
It is designed to flow to the 0 side. The check valve 64 is connected to the reach cylinder 31 from the return pipe 60 side.
Is a check valve in which oil flows only to the head 33 side and does not flow in the opposite direction.

When the fork 13 collides with a wall or the like while the fork 13 is running in the reach-out state in which the fork 13 is extended forward, an impact force is applied to the rod 34 of the reach cylinder 31, and the impact causes the cap of the reach cylinder 31 to cap. 3
The two sides are pressed to increase the pressure, and a pressure higher than the withstand voltage of the circuit is generated. When the pressure generated by the impact exceeds the pressure set by the relief valve 61, the relief valve 61
Is opened, and the operating oil is caused to flow through the bypass pipe 62 to reduce the pressure in the reach cylinder 31 so that the reach cylinder 3
It is possible to prevent hydraulic equipment such as 1 and damage to piping.

The rod 34 tends to contract due to the impact, but when the oil supply pipe 65 is not connected, there is no supply of hydraulic oil into the head 33 of the reach cylinder 31 and a vacuum state is established. There is a possibility that corrosion or malfunction of the inside of the reach cylinder 31 may occur. However, in the present invention, since the oil supply pipe 65 provided with the check valve 64 is connected to the head 33 side of the reach cylinder 31, the negative pressure in the head 33 opens the check valve 64 and opens the oil supply pipe 65. Hydraulic oil is supplied to the head 33 of the reach cylinder 31 via the oil supply pipe 65 and the check valve 64 to prevent the inside of the head 33 from being in a vacuum state. Thereby, corrosion and malfunction in the reach cylinder 31 can be eliminated.

By the way, in the reach type forklift,
It is naturally conceivable that the vehicle travels while reaching. When the fork 13 collides with a wall or the like at that time, the pilot check valve 30 is not normally provided (conventionally). There is a risk that the generated shock wave may damage the valves (the directional control valves 23 to 25) and the pump 22. However,
By providing the pilot check valve 30 as in the present invention, the pilot pressure at the pilot check valve 30 (because the pilot port 36 in FIG. 1 is connected to the head side hydraulic oil supply pipe 71, the head side hydraulic oil supply at the time of reach-in) Hydraulic oil flows from the cap 32 side only in an amount corresponding to the hydraulic oil pressure in the pipe 71 to the pilot pressure. Therefore, hydraulic equipment downstream of the pilot check valve 30 (the respective directional control valves 23 to 25). And pump 2
2) can be protected.

(Second Embodiment) FIG. 2 shows a second embodiment. Since the piping configuration of the entire hydraulic circuit is the same as that of FIG. 1, different parts will be described in detail. In this embodiment, a flow control valve 68 is provided downstream of the relief valve 61 and in the middle of the bypass pipe 62, and an oil feed pipe branched from the bypass pipe 62 between the relief valve 61 and the flow control valve 68. 72 is the reach cylinder 31
Is connected via a check valve 64 to a head-side hydraulic oil supply pipe 71 connected to the head 33 side.

As a result, a part of the hydraulic oil from the relief valve 61 that has passed through the flow control valve 68 returns to the oil tank 20, and the remaining hydraulic oil that has not passed through the flow control valve 68 passes through the oil supply pipe 72. As a result, it returns to the head 33 side of the reach cylinder 31. This is the reach cylinder 31
Since the cap 34 and the head 33 of the reach cylinder 31 have different capacities due to the presence of the rod 34 on the head 33 side, all the hydraulic oil from the cap 32 side> head 33 side capacity is returned to the head 33 side. That is, the larger amount flows downstream of the flow control valve 68 to return the remaining appropriate amount of hydraulic oil to the head 33 side. Therefore, by adjusting the flow control valve 68, an adjustment suitable for returning an appropriate amount of hydraulic oil to the head 33 side can be performed.

Thus, when returning the hydraulic oil from the cap 32 to the head 33 side, it is possible to return not only the required amount but also the necessary amount of hydraulic oil that does not cause the head 33 side to be in a vacuum state. No extra pressure is applied, and the durability and safety of the circuit can be maintained well. In this case, unless excess hydraulic oil is returned to the oil tank 20 by the flow control valve 68, the amount of hydraulic oil that can flow into the head 33 is smaller than the amount of hydraulic oil that has flowed out of the cap 32. Although the pressure rises in the oil supply pipe 72, the excess hydraulic oil is returned to the oil tank 20 by the flow control valve 68 as described above, so that the pressure in the oil supply pipe 72 is prevented from increasing. I have.

[0032]

According to the hydraulic device protection device for a reach-type forklift according to the first aspect of the present invention, when the piston rod moves to the cap side in a state where hydraulic oil is not supplied to the head side of the cylinder, Since the hydraulic device protection device that allows the hydraulic oil pressed by the piston rod to flow out from the cap side is provided by branching off from the cap-side hydraulic oil supply pipe provided on the cap side of the cylinder, the piston rod Hydraulic equipment protection device that branches from the cap-side hydraulic oil supply pipe that is connected to the cylinder cap even if the hydraulic pressure rises when a fork connected to the cylinder collides with a wall and impacts the reach cylinder. Works, and the hydraulic oil pushed by the piston rod flows out from the cap side, and the pressure in the hydraulic circuit decreases, and hydraulic equipment and hydraulic hoses It is possible to prevent the loss.

[0033] According to the hydraulic equipment protection device for a reach type forklift according to the second aspect, the hydraulic equipment protection device includes:
A simple hydraulic circuit configuration includes a bypass pipe branched from the cap-side hydraulic oil supply pipe, and a relief valve disposed in the middle of the bypass pipe to release hydraulic oil flowing out from the cap side. Although the hydraulic device protection device can be configured at low cost, it is possible to reliably prevent damage to the hydraulic device and the hydraulic hose.

According to the third aspect of the present invention, one end of an oil supply pipe filled with hydraulic oil is connected to a head-side hydraulic oil supply pipe connected to a head side of the cylinder. Therefore, hydraulic oil is supplied from the oil feed pipe into the head of the cylinder to which the impact has been applied, and the inside of the head can be prevented from being in a vacuum state. Therefore, since the head is not evacuated, corrosion and malfunction due to vacuum can be prevented.

According to the device for protecting a reach-type forklift hydraulic device according to the fourth aspect, the other end of the oil supply pipe is connected to the bypass pipe downstream of the relief valve, so that the cylinder to which an impact is applied is provided. Hydraulic oil is supplied from the oil feed pipe to the head through the relief valve and the bypass pipe, and the inside of the head can be prevented from being in a vacuum state. Therefore, since the head is not evacuated, corrosion and malfunction due to vacuum can be prevented.

According to the hydraulic equipment protection device for a reach-type forklift, a flow control valve provided in the middle of the bypass pipe downstream of the relief valve, and one end of the flow control valve and the relief are provided. An oil feed pipe branched from a bypass pipe between the valve and the head side hydraulic oil supply pipe, and the hydraulic oil that has escaped by the relief valve and that has not flowed to the flow control valve side. By returning to the head side, the flow control valve can be adjusted, and adjustment suitable for returning an appropriate amount of hydraulic oil to the head side can be performed. As much oil as possible, no extra pressure on the oil line,
Good durability and safety of the circuit can be maintained.

According to the hydraulic device protection device for a reach type forklift, a pilot check valve is provided in the middle of the cap side hydraulic oil supply pipe, and the pilot port of the pilot check valve is connected to the head side hydraulic oil supply pipe. Since the connection is established, the operating oil flows from the cap side only in an amount corresponding to the pilot pressure in the pilot check valve, so that the hydraulic equipment downstream of the pilot check valve can be protected.

[Brief description of the drawings]

FIG. 1 is a main part hydraulic circuit diagram of a forklift according to an embodiment of the present invention.

FIG. 2 is a main part hydraulic circuit diagram of a forklift according to a second embodiment of the present invention.

FIG. 3 is a perspective view of the forklift according to the embodiment of the present invention as viewed from the rear.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Forklift 4 Cargo handling device 13 Fork 23 Direction control valve for reach 30 Pilot check valve 31 Reach cylinder 32 Cap 33 Head 34 Rod 36 Pilot port 60 Return pipe 61 Relief valve 62 Bypass pipe 64 Check valve 65 Oil feed pipe 68 Flow control valve 70 Cap Side hydraulic oil supply pipe 71 Head side hydraulic oil supply pipe 72 Oil feed pipe

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3F333 AA02 AB13 AE02 BA02 BA08 BB02 BD02 BE02 CA21 FB10 FH08

Claims (6)

[Claims] A reciprocating motion of a piston rod caused by the flow of hydraulic oil into and out of a head side and a cap side of a cylinder makes it possible to move a cargo handling device having a fork connected to the piston rod in a front-rear direction. In the reach-type forklift, when the piston rod moves to the cap side in a state where the hydraulic oil is not supplied to the head side of the cylinder, a hydraulic pressure that allows the hydraulic oil pressed by the piston rod to flow out of the cap side. A hydraulic device protection device for a reach-type forklift, wherein the device protection device is provided by being branched from a cap-side hydraulic oil supply pipe provided on a cap side of the cylinder. 2. The hydraulic device protection device according to claim 1, further comprising: a bypass pipe branched from the cap-side hydraulic oil supply pipe; a relief valve disposed in the middle of the bypass pipe, for releasing hydraulic oil flowing out from the cap side; The hydraulic device protection device for a reach type forklift according to claim 1, further comprising: 3. The reach according to claim 1, wherein one end of an oil feed pipe filled with hydraulic oil is piped to a head side hydraulic oil supply pipe piped to a head side of the cylinder. Type forklift hydraulic equipment protection device. 4. The device for protecting a hydraulic device of a reach type forklift according to claim 3, wherein the other end of the oil feed pipe is connected to the bypass pipe downstream of the relief valve. 5. A flow control valve provided in the middle of the bypass pipe downstream of the relief valve, and one end is branched from a bypass pipe between the flow control valve and the relief valve, and the head-side operation is performed. An oil feed pipe connected to an oil supply pipe, and of the hydraulic oil that escaped through the relief valve, the hydraulic oil that did not flow to the flow control valve side was returned to the head side of the cylinder. The hydraulic device protection device for a reach type forklift according to claim 2. 6. A pilot check valve is provided in the middle of the cap side hydraulic oil supply pipe, and a pilot port of the pilot check valve is connected to a head side hydraulic oil supply pipe provided on the head side. The hydraulic device protection device for a reach-type forklift according to claim 1 or 2.