JPH038700A - Hydraulic circuit of clamp device - Google Patents

Abstract

PURPOSE:To increase the moving speed of a clamp arm by providing a selector on a parallel circuit for connecting two clamp cylinders to an oil pump, and switching the selector to short-circuit the parallel circuit at the time of no load. CONSTITUTION:A clamp arm 3 is swung by two clamp cylinders 4, 5. The clamp cylinders 4, 5, are connected to a hydraulic pump 6 in parallel, and expanded and contracted by the switching of a 4-port 3-positional type oil control valve 7. The rod side pipeline 9 of the second clamp cylinder 5 is connected to a bottom side pipeline 8 by a short-circuit pipeline 11 containing a 3-port 2-positional type pilot operating selector valve 10. The selector valve 10 is communicated to the short-circuit circuit 11 until the arm 3 is brought into contact with a load as the bottom side oil pressure of the cylinder 5 is low, and the operating oil is passed through the pipeline 8 to extend the cylinder 4. According to this extension, the cylinder 5 is also extended, so that the operating oil is collected into the cylinder 4, and the moving speed is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a clamp device which is an attachment for a forklift, particularly a clamp lit type in which one clamp arm is actuated by two clamp cylinders, such as a roll clamp. Regarding hydraulic circuits.

(Prior Art) Generally, a roll clamp used for clamping roll-shaped articles such as newspaper or craft paper is fixed to a clamp base 1 as shown in FIG. (also available) short arm 2 and clamp arm (long arm) 3 that is swingably attached.
The clamp arm 3 is moved to the clamp side or open side by two left and right clamp cylinders 4.5.
(swing). The left and right clamp cylinders 4.5 are generally connected in parallel to a hydraulic pump 6 as shown in FIG. 5, and are operated to expand and contract by switching the oil control pulp 7. .

(Problems to be Solved by the Invention) In recent years, there has been a demand for this type of roll clamp to have a clamp arm that moves at a high speed. However, in the case of the conventional parallel circuit described above, the two clamp cylinders 4.5 are operated to extend,
To move the clamp arm 3, the cross-sectional area of the bottom side oil chamber of both clamp cylinders 4.5 is A10, the cross-sectional area of the bottom side oil chamber is (3/4)A, and the stroke until clamping is S. Then, what you need to do when clamping! The Il flow rate Qa is Qa = 2 (Axe>), and the working flow IQb required when opening is Qb
-2X (3/4)AXS. Therefore, in order to increase the moving speed of the clamp arm 3 and meet the above-mentioned demand, a hydraulic pump with a large capacity had to be used.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a hydraulic circuit for a clamp device that can increase the moving speed of a clamp arm without using a large-capacity hydraulic pump.

<Means for solving problem n) The present invention is configured as follows in order to solve the above problems.

In a clamp device of a type in which one clamp arm is actuated by two clamp cylinders connected in parallel to a hydraulic pump, a switching valve is provided in a parallel circuit connecting the two clamp cylinders and the hydraulic pump. and this switching valve is switched to a position that short-circuits the parallel circuit so that one clamp cylinder follows the other clamp cylinder via the clamp arm when the clamp arm is under no load, and when the clamp arm is under load. The parallel circuit is switched to the initial state so that both clamp cylinders operate in the same manner.

Note that a pilot operated type or an electromagnetic operated type is used as the switching valve.

(Function) According to the present invention configured as described above, when the clamp arm is moved to the clamp side, when there is no load until the clamp arm contacts the cargo, the switching valve is switched to the short circuit position, and the hydraulic Hydraulic oil sent from the pump is sent to the bottom side oil chamber of one clamp cylinder, and the other clamp cylinder simply operates in a driven manner. In other words, the hydraulic oil discharged from the rod side oil chamber due to the driven operation or the hydraulic oil discharged from the drive side clamp cylinder is fed into the bottom side oil chamber of the clamp cylinder on the driven side, and the oil of the clamp cylinder is It only circulates between rooms. Therefore, the amount of hydraulic fluid from the hydraulic pump required to move the clamp arm is approximately equal to the operating valve of one hydraulic cylinder.

When the clamp arm comes into contact with a load and a load is applied, the switching valve is switched to the position that constitutes a normal parallel circuit, and the hydraulic oil from the hydraulic pump is equally distributed to the bottom oil chambers of both clamp cylinders. act. Therefore, the load can be clamped with the clamping pressure determined by the two clamp cylinders.

(Example) Hereinafter, an example of the present invention embodied in an O-le-clambe will be described based on the drawings. Example 1 First, Example 1 will be described based on FIG. 1.

As shown in the figure, two left and right first and second clamp cylinders 4° 5 for swinging the clamp arm (long arm in a roll clamp) are connected to a hydraulic pump 6.
The oil control pulp 7 is connected in parallel to the oil control pulp 7, and is expanded and contracted by switching the oil control pulp 7, which is a 4-bot, 3-position type. That is, two pipe lines 8. connected to the cylinder ports of the oil control valve 7.
One of the cylinders 9 is branched in the middle and connected to the bottom side oil chambers of the first clamp cylinder 4 and the second clamp cylinder 5, respectively, and the other one is branched in the middle and It is connected to each rod side oil chamber of the first clamp cylinder 4 and the second clamp cylinder 5, respectively.

In the parallel circuit of the clamp cylinders 4.5 configured as described above, the pipe line 9 on the Rondo side of the second clamp cylinder 5 is connected to the 3-bot, 2-position pilot-operated switching valve 1.
It is connected to the bottom side pipe line 8 by a short-circuit pipe line 11 including 0. When the pressure in the bottom side oil chamber of the second clamp cylinder 5 is lower than the set pressure, the pilot operated switching valve 10 is held at the position shown in the figure and communicates the bottom side oil chamber with the rod side oil chamber. When the pressure is exceeded, the valve is switched to the left side position in the figure to cut off communication between both oil chambers. Further, the conduit 8 on the bottom side of the second clamp cylinder 5 is provided with a throttle 12 with a check valve.

The hydraulic circuit of this embodiment is constructed as described above, and its operation will be explained below.

When the oil control pulp 7 is switched to the clamp position [a, until the clamp arm 3 comes into contact with the cargo,
Since the pressure in the bottom side oil chamber of the second clamp cylinder 5 is low, the pilot-operated switching valve 10 is held at a position where it communicates with the short-circuit pipe 11, that is, where it communicates between both oils. Therefore, the hydraulic oil flow is as shown by the solid arrow. That is, the hydraulic oil from the hydraulic pump 6 is sent to the bottom side oil chamber of the first clamp cylinder 4 through the bottom side pipe line 8, the cylinder 4 is extended, and the clamp arm 3 is moved toward the clamp side. As the clamp arm 3 moves, the second clamp cylinder 5 expands, and the discharged oil from the bottom oil chamber flows into the bottom oil chamber via the short-circuit pipe 11.

At this time, there is a shortage of hydraulic oil in the bottom oil chamber corresponding to the diameter of the rod, but this is replenished with hydraulic oil from the hydraulic pump 6 via the check pulp.

That is, until the clamp arm 3 comes into contact with the cargo,
The clamp arm 3 is moved by the first clamp cylinder 4, and the second clamp cylinder 5 simply follows the movement, and the hydraulic oil circulates from the rod side oil chamber to the bottom side oil chamber. Therefore, if the cross-sectional area of the bottom side oil chamber of the first clamp cylinder 4 is A10, the cross-sectional area of the bottom side oil chamber is (3/4)A, and the stroke until the clamp arm 3 contacts the cargo is S, then The amount of hydraulic oil Qa required for arm movement is Qa -AxS+ (A-(3/4)xA)xs. Note that A-(3/4)A is the second clamp cylinder 5
This is the replenishment amount for the bottom side oil chamber. In other words, according to this embodiment, the hydraulic oil IQa sent from the hydraulic pump 6 for arm movement is compared to the conventional case where hydraulic oil is sent from the hydraulic pump 6 to the bottom side oil chambers of both clamp cylinders 4.5. If the cylinder diameter is the same, this will be reduced to nearly half, and as a result, the moving speed of the clamp arm 3 will be increased.

However, when the clamp arm 3 comes into contact with the cargo, the second
The pressure in the bottom side oil chamber of the clamp cylinder 5 rises and exceeds the set pressure of the pilot-operated switching valve 10, so the switching valve 10 is switched to the left position in the figure and the short-circuit pipe 11
At the same time, the pipe line 9 on the Rondo side is communicated with the tank. In other words, since the two clamp cylinders 4.5 are returned to the normal parallel circuit, both clamp cylinders 4.5
The load is clamped by the clamping pressure determined by .

When the oil control pulp 7 is switched to the open position 2tb, the hydraulic oil flow is as shown by the dashed arrow.In other words, the hydraulic oil from the hydraulic pump 6 flows to the rod side of the first clamp cylinder 4. The pressure in the bottom side oil chamber of the second clamp cylinder 5 is lower than the set pressure of the pilot-operated switching valve 10, so the switching valve 10 is switched to the illustrated position and communicates with the short-circuit pipe 11. In other words, the bottom side oil chamber and the rod side oil chamber communicate with each other, so the discharged oil on the bottom side passes through the pilot-operated switching valve 10 and flows into the zero side oil chamber. Therefore, in the second clamp cylinder 5, hydraulic oil is circulated between the two chambers, and the contraction operation follows the movement of the clamp arm 3.For this reason, when the clamp arm 3 is opened, Hydraulic oil 11Q required at times
b is the product of the cross-sectional area (3/4) A of the rod-side oil chamber of the first clamp cylinder 4 and the stroke S, and it is the product of the stroke S, which is fed into each rod-side oil chamber of both clamp cylinders 4.5. This is half compared to the conventional method, and therefore the opening speed is increased to twice that of the conventional method.

Regarding the second clamp cylinder 5 mentioned above, when the hydraulic oil discharged from the bottom side oil chamber flows into the rod side oil chamber, it will be subjected to flow path resistance of the pilot operated switching valve 10. A joint 12 provided in the side pipe line 8
By restricting the outflow of discharged oil to the tank by the action of , the flow into the rod-side oil chamber is performed without any problem.

<Example 2> Next, Example 2 shown in FIG. 2 will be described. In this second embodiment, in the parallel four-path system of both clamp cylinders 4.5, a pipe line 8 leading to the bottom side oil chamber of the first clamp cylinder 4 and a pipe line leading to the rod side oil chamber of the second clamp cylinder 5 are arranged. 9 can be short-circuited by a pilot-operated switching valve 10.

Therefore, the oil control valve 7 is at the clamp position 1i.
1a, when there is no load until the clamp arm 3 contacts the cargo, the pilot-operated switching valve 10 is in the position shown, and the bottom side oil chamber of the first clamp cylinder 4 and the The rod-side oil chamber of the second clamp cylinder 5 is short-circuited. Therefore, the hydraulic oil flow is as shown by the solid arrow. That is, the hydraulic oil from the hydraulic pump 6 is sent to the bottom side oil chamber of the second clamp cylinder 5 to cause the clamp cylinder 5 to extend, and the first clamp cylinder 4 follows this. Therefore, the discharged oil from the zero-side oil chamber of the second clamp cylinder 5 is sent to the bottom-side oil chamber of the first clamp cylinder 4.
At this time, the shortage corresponding to the rod diameter is replenished with a portion of the return oil in the rod-side oil chamber of the first clamp cylinder 4.

At this time, the hydraulic oil I sent from the hydraulic pump 6
If the bottom side oil chamber of the second clamp cylinder 5 is 8, and the stroke until the clamp arm 3 contacts the load is S, then Qa is Qa-AXS, which is half of the conventional one, and therefore The arm movement speed will be doubled.

Thereafter, when the clamp arm 3 comes into contact with the cargo and the pressure in the bottom oil chamber of the second clamp cylinder 5 exceeds the set pressure of the pilot-operated switching valve 10, the switching valve 10 is switched to the right position in the figure. The bottom side oil chamber of the first clamp cylinder 4 communicates with the discharge side of the hydraulic pump 6, and the rod side oil chamber of the second clamp cylinder 4 communicates with the tank.

The load is therefore clamped with the clamping pressure determined by the two clamping cylinders 4.5.

On the other hand, open the oil control pulp 7 fib
When switched to , the bottom side oil chamber of the second clamp cylinder 5 communicates with the tank, and therefore the pilot-operated switching valve 10 is held in the position shown. Therefore, the hydraulic pump 6 communicates with both the oil chambers on the bottom side and the rod side of the first clamp cylinder 4, and also communicates with the rod side oil chamber of the second clamp cylinder 5. Here, if the cross-sectional area of the bottom side oil chamber of the clamp cylinder 4 is A10, the cross-sectional area of the bottom side oil chamber is (3/4)A, and the oil pressure is P, then in the first clamp cylinder 4, the pressure received by both oil chambers is The thrust of the area difference, that is, the thrust of (1/4)AxP is generated in the direction of Rondo protrusion,
On the other hand, in the second clamp cylinder 5, (3/4)
AxP thrust is generated in the rod retraction direction. Therefore,
The clamp arm 3 is moved in the opening direction by the difference in the thrust forces mentioned above.

The flow of hydraulic oil at this time is as shown by the broken line arrow, and if the stroke is S, the hydraulic oil of Qa-AXS is pushed out from the bottom side oil chamber of the first clamp cylinder 4, and this hydraulic oil is 0 for both clamp cylinders 4.5
They will each be sent to the oil chamber on the side. At this time,
If the hydraulic oil layer required in both O-side oil chambers is Qb, then Qb - ((3/4) Axe) x2 - (6/4) AXS, and therefore the amount of hydraulic oil sent out from the hydraulic pump 6 is Qb - Qa = (2/4)AxS. In other words, in the conventional oven, (3/4
) AXSX2 - (6/4)AxS is required, but in the case of this embodiment, it is 1/3 of the conventional one, so the arm movement speed during oven operation is three times that of the conventional one.

In addition, what is shown in FIG. 3 replaces the throttle 12 with a check valve in the first embodiment with a relief valve 13 with a check valve.
The same effect as in the first embodiment can be obtained. In addition, the pilot-operated switching valve 10 explained in the embodiment is changed to an electric lamination operated switching valve, and the switching is controlled based on the detection signal of the baggage contact detection sensor provided on the pad of the clamp arm 3. It is possible to configure Further, although the illustrated example has been described as a case of a roll clamp, other clamp devices can be applied as long as they are of a type in which one clamp arm is driven by two clamp cylinders.

(Effects of the Invention) As detailed above, according to the present invention, the moving speed of one clamp arm can be increased compared to the conventional method, without using a large hydraulic pump, both during clamping and during oven. 6, which can increase the speed, is of great help in improving work efficiency, and is also effective in saving energy.

Furthermore, when clamping the load, it is possible to obtain the same clamping pressure as in the past, and the load can be stably held without causing an accident of falling due to insufficient clamping pressure. Moreover, since the amount of hydraulic oil required when moving the clamp arm is reduced,
Hydraulic oil f! ! This is effective in suppressing the deterioration of hydraulic oil and rubber parts caused by increases in oil temperature.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram showing Embodiment 1 of the present invention, Fig. 2 is a hydraulic circuit diagram showing Embodiment 2, Fig. 3 is a hydraulic circuit diagram showing a modification of Embodiment 1, and Fig. 4 is a hydraulic circuit diagram showing a modification of Embodiment 1. A schematic side view of the clamp, FIG. 5, is a conventional hydraulic circuit diagram. 3... Clamp arm 4... First clamp cylinder 5... Second clamp cylinder 6... Hydraulic pump 7... Oil control valve 10... Pilot operated switching valve

Claims (1)

[Claims] In a clamp device in which one clamp arm is actuated by two clamp cylinders connected in parallel to a hydraulic pump, a parallel circuit connecting the two clamp cylinders and the hydraulic pump is connected to an unloaded clamp arm. In this state, the parallel circuit is short-circuited so that one clamp cylinder follows the other clamp cylinder via the clamp arm, and when the clamp arm is under load, the parallel circuit is returned to its initial state so that both clamp cylinders operate in the same manner. A hydraulic circuit for a clamp device equipped with a switching valve that allows