JPS63717Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a forklift truck, and particularly relates to improvements in cargo handling vehicles.

Conventional technology Conventionally, in a full-free type forklift truck equipped with a multi-stage mast device and a plurality of lift cylinders, communication between the front lift cylinder and the rear lift cylinder was limited to the rear lift to eliminate slack in the piping. Piping is connected through the piston rod of the cylinder so that the tip of the piston rod communicates with the bottom side chamber of the front lift cylinder, and the lift cylinders are formed to have different effective diameters. In the examples shown in FIGS. 4 to 6, the effective diameter of the front lift cylinder 2 for directly raising and lowering the fork device 1 is the same as that of the rear lift cylinder for raising and lowering the inner mast 3 to which the front lift cylinder 2 is attached. Since the effective diameter of the cylinder 4 is set to be larger than that of the cylinder 4, when the fork device 1 is raised, pressure is first applied to the cylinder chambers of the front lift cylinder 2 and the rear lift cylinder 4 in the state shown in FIG. When oil is supplied,
The piston of the front lift cylinder 2, which has a large effective diameter, rises, and thereby the fork device 1 rises while being guided by the inner mast 3. When the front lift cylinder 2 reaches the rising end (see Fig. 5), the piston of the rear lift cylinder 4 starts to rise, and the inner mast 3 rises while being guided by the outer mast 5, so that the fork device 1 is a continuous upward movement. In addition, fork device 1
During the lowering of the fork device 1, the fork device 1 is continuously lowered by an operation opposite to that described above.

Problems to be Solved by the Invention However, in the conventional device, the hydraulic circuits for communicating the cylinder chambers of the front lift cylinder and the rear lift cylinder are always in communication state, and the piston rod of the rear lift cylinder is connected at all times. Because the pressure oil pipeline is formed, the diameter of the rear lift cylinder increases with the diameter of the piston rod, so the volume of the cylinder chamber is large, so the change in volume of the entire cylinder chamber is large.
When the rear lift cylinder 4 starts to rise after the front lift cylinder 2 reaches the rising end, or when the lifting/lowering operation of the lift device 1 is stopped midway, fluctuations in oil pressure and each moving part may occur. Due to the interaction with the inertial force of However, this can cause the load to collapse, the load to fall, and even the vehicle to fall.In addition, the load on the oil pump fluctuates due to changes in oil pressure caused by vertical vibration, so in the case of a battery-type forklift, In this case, the motor for driving the oil pump generates a hum, which is unpleasant for cargo handling workers and is one of the causes of increased fatigue.

The present invention provides a forklift truck that enables safe cargo handling work and reduces the burden on cargo handling workers by appropriately closing the hydraulic circuit that communicates the cylinder chambers of the plurality of lift cylinders with each other. The purpose is to provide

Means for solving the problems The present invention provides a fork lift truck of a full free mast type, which is equipped with a multi-stage mast having an inner mast and an outer mast, and a plurality of lift cylinders consisting of a front lift cylinder and a rear lift cylinder, the bottom side chamber of the front lift cylinder and the bottom side chamber of the rear lift cylinder being connected through the piston rod of the rear lift cylinder, wherein a shutoff valve disposed in a hydraulic circuit connecting the cylinder chambers of the plurality of lift cylinders is installed on the inner mast, and a cam surface is installed on the outer mast, and the hydraulic circuit is closed when the inner mast is raised and connected when it is retracted by contacting the shutoff valve in accordance with the cam surface.

Function: Therefore, after the front lift cylinder reaches the rising end, as the piston of the rear lift cylinder rises, the shutoff valve provided between the rear lift cylinder and the front lift cylinder is closed by the cam surface of the outer mast. The cylinder chambers of the rear lift cylinder and the front lift cylinder are no longer in communication with each other.

Embodiments Hereinafter, a forklift truck showing a concrete embodiment of the present invention will be described in detail based on the drawings.

In FIG. 1, a mast device 10 is attached to the front of a vehicle body 100 of a forklift truck, and a fork device 1 consisting of a fork 11 and a lift bracket 12 is moored to the mast device 10 so as to be movable up and down. In FIG. 2, the mast device 10 is directly attached to the vehicle body 100, and the outer mast device 10 is an inner mast moored to the outer mast 5, which is directly attached to the vehicle body 100, via rollers or the like so that it can be raised and lowered. It consists of 3 and
The inner mast 3 is connected to the piston rod 41 of the rear lift cylinder 4 attached to the outer mast 5, and the piston rod 21 of the front lift cylinder 2 attached to the inner mast 3 is connected through a chain wheel 22 and a chain 23. and is moored with the fork device 1. Here, the effective diameter of the front lift cylinder 2 is set to be larger than the effective diameter of the rear lift cylinder 4. 60 is a hydraulic conduit for supplying pressure oil from an oil pump (not shown) to the cylinder chamber 42 of the rear lift cylinder 4 via a control valve (not shown), and 61 is a hydraulic line for supplying pressure oil from an oil pump (not shown) to the cylinder chamber 42 of the rear lift cylinder 4; A hydraulic conduit for communicating the cylinder chamber 42 and the cylinder chamber 24 of the front lift cylinder 2 through an oil hole 44 bored through the piston 43 of (hydraulic circuit). Reference numeral 70 denotes a shutoff valve disposed in the middle of the hydraulic pipe line 61, and the shutoff valve 70 is fixed to the inner mast 3. Reference numeral 8 denotes a cam attached to the outer mast 5 at a position corresponding to the operating portion of the shutoff valve 70 when the mast device 10 is retracted (when the inner mast 3 is at the lower end). The shutoff valve 70 is a third
As shown in the figure, a spool 72 biased in the closing direction by a spring 71 is built in, and a roller 74 attached to an operating arm 73 at the tip of the spool 72 can come into contact with the cam 8.

To explain the operation of the device configured as described above, first, the piston 25 of the front lift cylinder 2 and the piston 43 of the rear lift cylinder 4
When both are at the lowering end and the fork device 1 is at the lowering end, the mast device 10 is in a contracted state, and at this time, the roller 74 is moved toward the cam 8.
, the spool 72 is pushed to the left in FIG. 3 against the biasing force of the spring 71, and the hydraulic line 61 is communicated with the cylinder chamber 42 of the rear lift cylinder 4 and the front lift cylinder. The two cylinder chambers 24 are brought into communication. When pressure oil is supplied from the hydraulic line 60 into the cylinder chamber 42 in order to raise the fork device from this state, the pressure oil passes through the oil hole 44 and the hydraulic line 61 into the cylinder chamber 42.
It is also brought within 4. At this time, the effective diameter of the front lift cylinder 2 is set to be larger than the effective diameter of the rear lift cylinder 4. The piston 25 begins to rise while the piston 43 remains stationary. As the piston 25 and thus the chain wheel 22 rise, the fork device 1 moored to the chain 23 moves upward. When the fork device 1 continues to rise and the piston 25 reaches the rising end, the fork device 1 stops momentarily, but if pressure oil is continuously supplied from the hydraulic pipe 60, the cylinder Inside chamber 24, cylinder chamber 4
2 and the hydraulic pressure line 61 rise rapidly, and the piston 43 of the rear lift cylinder 4 starts to rise. When the piston 43 starts to rise, the inner mast 3 starts to rise, and the fork device 1 continues its upward movement. At this time, at the same time that the inner mast 3 starts to rise, the contact state of the roller 74 of the shutoff valve 70 with respect to the cam 8 is released (see FIG. 3), and the spool 72 moves to the right in the figure, causing the hydraulic circuit 61 is closed, and communication between the cylinder chamber 24 and the cylinder chamber 42 is cut off. As a result, the pressure oil in the cylinder chamber 24 remains confined, making it impossible to flow alternately with the pressure oil in the cylinder chamber 42, which is affected by pressure fluctuations and inertia of each moving part. Nevertheless, harmful vertical vibrations of the fork device 1 do not occur. Thereafter, the fork device 1 can continue to move upward until the piston 43 reaches the rising end. When descending, the operation opposite to that described above is performed. In addition, even if the inner mast 3 is raised to a certain degree and suddenly stopped while rising or falling, the pressure oil in the cylinder chamber 24 and the pressure oil in the cylinder chamber 42 are in a state of isolation from each other. ,
No harmful vertical vibrations occur.

Furthermore, in the above-described embodiment, a configuration including a two-stage mast device and two lift cylinders was shown, but a configuration including a three-stage or more mast device and three or more lift cylinders is also applicable. Of course, it is also applicable.

Effects of the Invention As described above, the present invention is equipped with a plurality of lift cylinders consisting of a multi-stage mast having an inner mast and an outer mast, a front lift cylinder and a rear lift cylinder, and a bottom side chamber of the front lift cylinder and a rear lift cylinder. In a full free mast type forklift truck in which the bottom side chambers of the lift cylinders are communicated through the piston rod of the rear lift cylinder, the hydraulic circuit is arranged in a hydraulic circuit that communicates the cylinder chambers of the plurality of lift cylinders with each other. A shutoff valve is installed on the inner mast, and a cam surface is installed on the outer mast, and when the inner mast is raised, it closes and contracts when the inner mast comes into contact with the shutoff valve according to the cam surface. Sometimes in communication, the movement of the mast device itself is configured to actuate the shutoff valve, thereby preventing harmful up-and-down of the fork device when the mast starts to rise from a fully free condition. Vibration can be prevented. Furthermore, since the shutoff valve opens and closes according to the cam surface, it prevents the fork device from vibrating due to sudden disconnection, thereby enabling safer cargo handling operations. With,
The operator is not required to be careful when suddenly stopping the ascending/descending motion, and there is no need for any special work on the cylinder itself.
It does not cause oil leakage, etc., and can be easily performed with a simple structure. Even in the case of a battery type forklift truck, it has various remarkable effects such as being able to improve work efficiency without being bothered by the harsh noise of the oil pump motor caused by oil pressure fluctuations.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Fig. 1 is a front view showing the whole, Fig. 2 is an explanatory drawing showing the main parts,
Figure 3 is a partially sectional front view showing the shutoff valve, Figures 4-
FIG. 6 is an explanatory diagram showing the operating state. 1...Fork device, 2...Front lift cylinder, 3...Inner mast, 4...Rear lift cylinder,
5... Outer mast, 24... Cylinder chamber, 42...
Cylinder chamber, 61...hydraulic pipe line, 70...closing valve.

Claims (1)

[Scope of utility model registration request] It is equipped with a multi-stage mast having an inner mast and an outer mast, and a plurality of lift cylinders consisting of a front lift cylinder and a rear lift cylinder, and the bottom side chamber of the front lift cylinder and the bottom side chamber of the rear lift cylinder are connected to the piston rod of the rear lift cylinder. In a full free mast type forklift truck that communicates through the inner mast, a shutoff valve disposed in a hydraulic circuit that communicates the cylinder chambers of the plurality of lift cylinders with each other is installed in the inner mast, and A cam surface is installed on the outer mast, and the hydraulic circuit is closed when the inner mast is raised and communicated when the inner mast is retracted by contacting the shutoff valve according to the cam surface. forklift truck.