JPS6030315Y2 - Hydraulic circuit of tail cylinder in forklift truck - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic circuit for a tilt cylinder in a forklift truck.

Generally, in a forklift truck, when the engine stops and the hydraulic pump driven by the engine stops operating, the tilt cylinder will be locked and activated even if the tilt lever for tilting the mast is inadvertently operated. It is equipped with a tilt-lock hydraulic circuit.

Therefore, in a front tilt cab forklift truck equipped with a cabin that can rotate forward, if the engine stops due to trouble when the mast is not fully tilted forward, the front of the mast Since the tilting action is no longer performed, the mast becomes an obstacle and the cabin cannot be completely opened, making it impossible to inspect or repair parts in the engine room.

Therefore, conventionally, in the above case, the joint pin between the tilt cylinder and the mast was removed, or the piping connected to the piston rod side of the tilt cylinder was removed to drain the oil inside the cylinder on the rod side to the outside. I had to either eject it or tilt the mast forward.

However, all of the above-mentioned methods have disadvantages in that the work is troublesome for the driver, takes a long time, and is inefficient.

The present invention aims to eliminate the above-mentioned drawbacks and provide a hydraulic circuit for a tilt cylinder that allows a mast to be tilted forward with a simple operation even when the engine is stopped.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 1, the lower end of a mast 2 erected at the front of a vehicle body 1 of a forklift truck is pivotally supported by a front axle housing 3 via a mast support 4, and the rear surface of an intermediate portion of the mast 2 A beam 7 is horizontally fixed to the vehicle body 1 at its rear end and is pivotally connected to the end of a piston rod 5a of a tilt cylinder 5 via a joint pin 8.

The cabin 10 disposed at the rear of the mast 2 is pivotally supported via a pin 12 to a holder 11 fixed to the front upper surface of the vehicle body 1, and opens the upper part of the engine room 13 when tilted forward.

The tilt cylinder 5 is operated by operating a tilt lever 16 attached to the front protector 15 to operate an oil control valve 17 disposed at the front of the engine room 13.

The oil control valve 17 is pilot-operated by pressure oil from the pump PF, and is a 6-point/3-position switching valve incorporating a tilt lock valve 18 that enables forward tilting of the mast 2. controls the forward, neutral, and backward tilting movements of the mast 2. As shown in Figure 2, a pipe 20 that communicates with the pump PF driven by the engine E in the neutral position, and a check valve 21 between the pipe 20 and the check valve 21 are connected to each other. The ports on the inlet side are connected to the piping 22 that communicates with the oil tank T1 and the piping 23 that communicates with the oil tank T, and the ports on the outlet side corresponding to the ports are connected to the oil tank T1 and the cylinder head side of the tilt cylinder 5. and are connected to piping 24, 25, 26 communicating with the piston rod side, respectively.

In the conventional hydraulic circuit configured as described above, the present invention provides an opening/closing cock 28 attached to the front protector 15 on the piston rod side of the tilt cylinder 5.
The oil control valve 17 is characterized in that one end of the oil control valve 17 is connected to the tank T via a pipe 29, and the other end thereof is connected to the tank T via a pipe 30, thereby forming a bypass line for the pipe line 26 to the oil control valve 17.

Next, the operation of the above configuration will be explained.

As shown in FIG. 1, the cabin 1
When fully opened, the upper front part of the mast 2 collides with the mast 2, so after the mast 2 is rotated to the fully forward tilted position C where it does not interfere with the cabin 10, the cabin 10 is opened.

However, when the mast 2 is within the range described above, if the engine E is stopped due to trouble, the oil control valve 17 is moved from the neutral position shown in FIG. Even if the pump PF is switched to the left position for controlling Oil drainage from the cylinder on the rod side is blocked,
Remain stopped.

Therefore, even if the oil control valve 17 is operated by the tilt lever 16, the mast 2 cannot be tilted forward, and the cabin 10 cannot be completely opened.

In such a case, when the cock 28 is switched from the normally used closed circuit to the open circuit, the oil on the piston rod side of the tilt cylinder 5 will be transferred to the mast 2.
When is tilted forward or ' is in a neutral state, the load pressure of the mast 2 device is used, and when the mast 2 is tilted backward, the load pressure from the manual push causes the piping 29 - opening/closing pot 28 - piping to be closed. 30 and into the tank T, at the same time said mast 2 is pivoted forward and moved into a fully tilted position C.

After this, the cabin 10 can be completely opened to a predetermined position, thereby completely opening the upper part of the engine room 13.

In another embodiment shown in FIG. 3, the discharge side of the opening/closing cock 28 is communicated with the cylinder head side of the tilt cylinder 5. By switching the cock 28 from a closed circuit to an open circuit, the tilt cylinder 5 The oil on the piston rod side of
0 and is discharged toward the cylinder head, so that the mast 2 is simultaneously rotated forward.

As is clear from the above, the present invention provides a system in which a pipe connecting the piston rod side of a tilt cylinder and an oil control valve that controls the tilting operation of the tilt cylinder is branched and connected to a tank or the cylinder head side of the tilt cylinder. It features a communicating bypass pipe and an opening/closing cock interposed in the bypass pipeline, so even if the engine stops due to trouble, the mast can be tilted forward by operating the opening/closing cock. This eliminates the hassle of separating the tilt cylinder from the mast or removing the piping connected to the tilt cylinder in order to tilt the mast forward, which was the case in the past. The mast can be tilted forward efficiently, which has many excellent effects such as allowing the cabin to be fully opened.

[Brief explanation of drawings]

The figures show one embodiment of the present invention. Fig. 1 is a side view of a forklift truck implementing the present invention, and Fig. 2 is a hydraulic circuit diagram thereof. FIG. 3 is a partial hydraulic circuit diagram showing the main parts of another embodiment. 1... Vehicle body, 2... Mast, 5...
...Tilt cylinder, 10...Cabin,
16...Tilt lever, 17...Oil control valve, 1B...Tilt lock valve, 28...Open/close cock, E...
...Engine, PF...Pump, T...
·tank.

Claims (1)

[Scope of utility model registration request] A piston rod side part is pivoted to the middle part of the mast, whose lower end is pivoted to the front wheel housing, and a tilt cylinder whose cylinder head is pivoted to the vehicle body, and a hydraulic oil tank by an engine-driven pump. an oil control valve that enables the tilting operation of the tilt cylinder to be controlled only when oil is supplied from the tilt cylinder; and a pipe line that communicates the valve with a piston rod side and a cylinder head side of the tilt cylinder, respectively. In the forklift truck equipped with the forklift truck, a bypass pipe is formed by branching a pipe line communicating between the piston rod side of the tilt cylinder and the oil control valve to communicate with the tank or the cylinder head side of the tilt cylinder, and A hydraulic circuit for a tilt cylinder in a forklift truck, characterized by having an opening/closing cock interposed in a bypass conduit.