JPH11247806A - Hydraulic cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a suitable hydraulic cylinder for a power tool in hand or the like. SOLUTION: A helical compression spring 26 is inserted in the rod side oil chamber of a hydraulic cylinder 3, and a hydraulic piston 21 is held at a head side initial position. A passage 21a for a communication of the rod side with the head side is formed in the hydraulic piston 21, and a helical compression spring 23 and a poppet type check valve 24 are inserted in the passage 21a. The check valve 24 is constantly in an opening position, and closed while compressing the helical compression spring 23 when a hydraulic pressure is applied on the head side of the hydraulic piston 21. When the hydraulic pressure is applied the check valve 24 is closed, the hydraulic piston 21 is driven to advance, and the oil of the rod side is discharged into a pipe passage 22. When the hydraulic pressure of the head side is released, the check valve 24 is opened, the oil of the head side flows the rod side, and the hydraulic piston 21 is pushed by the helical compression spring 26 to return at the initial position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cylinder, and more particularly, to a hydraulic cylinder capable of simplifying a drive circuit.

[0002]

Conventionally, a hand-held power tool such as a nailing machine generally uses pneumatic power as a power source. However, in a power tool (for example, a hand-held wire cutting machine) that requires a higher output than a nailing machine or the like that directly drives a driver with a pneumatic cylinder, the output is insufficient with the conventional pneumatic driving method, and another type of driving is required. A mechanism is required.

There is a hydraulic mechanism using a hydraulic cylinder as a drive mechanism that can obtain a high output. However, it is difficult to miniaturize a hydraulic circuit including a four-way valve for controlling reciprocating motion of the hydraulic cylinder. It is hard to say that it is suitable for a hand-held power tool or the like that requires light weight.

[0004] Therefore, there is a technical problem to be solved in order to provide a hydraulic cylinder suitable for a hand-held power tool or the like that can simplify the configuration of the hydraulic circuit, and the present invention solves the above-mentioned problem. With the goal.

[0005]

SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above-mentioned object. A double-acting hydraulic cylinder has a built-in spring for urging a piston toward a head, and the piston has a head-side end. And a passage communicating with the rod-side oil chamber, a check valve for preventing oil flow from the head side to the rod side is provided in the passage, and a spring is interposed in the check valve to open the check valve. It is an object of the present invention to provide a hydraulic cylinder configured such that the check valve closes when a hydraulic pressure is applied to the head side and the check valve opens when the hydraulic pressure is released.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a hydraulic-pneumatic wire cutting machine 1 for cutting bolts and wires as an example of use of the hydraulic cylinder of the present invention. A hydraulic oil tank 4 for supplying hydraulic oil to the pneumatic cylinder part 2 is built in a grip part 5 that projects laterally from the front part of the pneumatic cylinder part 2.

A screw hole 6 for attaching an air hose connector is formed at an end of the grip portion 5, and compressed air supplied from an air compressor through an air hose (not shown) passes through an air pressure main pipe 7 in the grip portion 5. The air is supplied to the air chamber 10 between the cylinder tube 8 of the pneumatic cylinder unit 2 and the outer cylinder 9 covering the cylinder tube 8. In FIG. 1, a pneumatic line 11 is formed in the lower part on the back side of the grip portion 5 and communicates from the pneumatic main line 7 to the bottom port of the hydraulic oil tank 4.
Is provided with a pilot-operated switching valve for fast-forwarding (not shown).

A free piston 12 is provided in the hydraulic oil tank 4.
Is supplied, and when pressurized air is supplied to the lower air chamber 4a of the free piston 12, the free piston 12 rises and the hydraulic oil filled in the upper oil chamber 4b of the free piston 12 is discharged to the hydraulic main pipeline 13 Is discharged to

A main hydraulic line 13 for connecting the hydraulic oil tank 4 and the hydraulic cylinder 3 is formed at the front of the pneumatic cylinder 2 through the rear sides of the upper and lower two trigger valves 14 and 15 provided on the grip 5. It intersects with the small-diameter booster cylinder section 16. A ram 18 connected to a pneumatic piston 17 is inserted into the pressure-intensifying cylinder 16 communicating with the hydraulic main line 13, and hydraulic oil flows through the pressure-increasing cylinder 16. Non-return valves 19 and 20 for preventing flow to the hydraulic oil tank 4 are inserted into the hydraulic main pipeline 13 at upstream and downstream of the pressure-intensifying cylinder 16 as viewed from the hydraulic oil tank 4 side.

As shown in FIG. 2, the inner diameter of the hydraulic cylinder 3 is the rear half 3a from the head end to the middle.
Is a dimension that matches the hydraulic piston 21, and the diameter of the front half 3b from the intermediate portion to the rod-side tip is larger than the piston diameter. The main hydraulic line 13 is connected to the head-side port, A hydraulic line 22 branched from the tank side upstream of the valve 19 is connected to the first half 3b to form a differential hydraulic circuit.

The hydraulic piston 21 is formed with a passage 21a penetrating from the outer peripheral surface of the rod portion to the rear surface through the axis. Then, a compression coil spring 23 and a poppet-type check valve 24 are inserted from the rear into a large diameter portion in the latter half of the passage 21a, and a cap 25 is screwed into a rear end of the passage 21a to form the passage 21a.
The check valve 24 is held in a.

As with the hydraulic piston 21, the check valve 24 is formed with a passage 24a penetrating from the outer peripheral surface of the small diameter portion to the rear surface through the axis, and the cap 25 is also formed with a passage 25a penetrating back and forth. Have been. In FIG. 2, the check valve 24 moves forward and is in the closed position. Normally, the check valve 24 is pressed against the rear cap 25 by the bias of the compression coil spring 23 to open the passage 21 a of the hydraulic piston 21. The front and rear oil chambers are in communication. The hydraulic piston 21 is urged toward the head by a compression coil spring 26 built in the front of the hydraulic cylinder 3.

A concave fixed cutter blade 28 is attached to a nose portion 27 provided at the front end of the hydraulic cylinder 3, and a cutter blade 29 attached to the tip of the rod portion of the hydraulic piston 21 is driven forward to fix the fixed cutter blade. Across the 28 recesses,
Bolts, wires, etc. inserted into the recesses are sheared.

As shown in the hydraulic-pneumatic circuit diagram of FIG.
The trigger valve 14 for increasing pressure on the upper side of the grip section 5 controls the main switching valve 30 of the pneumatic cylinder section 2, and the trigger valve 15 for lower traverse operates the switching valve 31 for rapid traverse below the grip section 5. It is configured to control.

The basic configuration of the pneumatic cylinder section 2 is that, as shown in FIG. 1, a reciprocating control mechanism 32 for reciprocating the pneumatic piston 17 is disposed behind the cylinder tube 8 in which the pneumatic piston 17 is housed. On the outer periphery of the reciprocating control mechanism 32, a main switching valve 30 which is in contact with and separates from the rear end face of the cylinder tube 8 is provided.

The reciprocating control mechanism 32 includes a pneumatic piston 17
A piston valve 33 integrally formed on the rear end face, and a switching valve 34 that switches between a first position and a second position by air pressure switched by the piston valve 33 that moves back and forth together with the pneumatic piston 17. By supplying air into the cylinder tube 8 or exhausting air from the cylinder tube 8 to the atmosphere, the pneumatic piston 17 is reciprocated at high speed.

In FIG. 1, the position of the main switching valve 30 below the center of the pneumatic piston 17 indicates the closed position, and the position of the main switching valve 30 above the open position indicates the open position.
Individual ring-shaped parts that slide together into a closed or open position. Then, in the closed position, it comes into pressure contact with the front seat 35, and the cylinder tube 8 and the air chamber 10
And shut off the air passage between them.

When the pressure-increasing trigger valve 14 is operated, the pressurized air acting on the back of the main switching valve 30 is exhausted to the atmosphere through the pressure-increasing trigger valve 14, and the main switching valve 30 is retracted to the open position, and the air chamber is retracted. 10 high-pressure air flows into the cylinder tube 8, and the pneumatic piston 17 is driven forward.

When the pneumatic piston 17 reaches the front end of the movable range, the pressurized air acting on the back of the switching valve 34 of the reciprocating control mechanism 32 is exhausted to the atmosphere, and the switching valve 34 retreats. Is released to the atmosphere through the switching valve 34, and the pneumatic piston 17 is retracted by the elastic force of the compression coil spring 36.

When the pneumatic piston 17 returns to the initial position, the switching valve 34 passes through the passage of the cylinder tube 8.
, The switching valve 34 advances, and the compressed air is supplied from the air chamber 10 to the cylinder tube 8 again, and the pneumatic piston 17 starts to advance. Thus, the pneumatic piston 17 reciprocates at a high speed until the operation of the pressure-increasing trigger valve 14 is released.

Next, the overall operation of the wire cutting machine 1 will be described. Fast-forward trigger lever 37 shown in FIGS.
Is operated, the fast-forward trigger valve 15 is opened, the fast-forward switching valve 31 shown in FIG. 3 is switched to the open position, high-pressure air is introduced into the air chamber 4a of the hydraulic oil tank 4, and hydraulic oil is introduced from the upper oil chamber 4b. Is discharged to the hydraulic main line 13. Then, the hydraulic piston 21 of the hydraulic cylinder 3 advances due to the difference between the front and rear pressure receiving areas, and the discharge oil from the hydraulic oil tank 4 and the oil in the rod-side oil chamber of the hydraulic cylinder 3 become non-return valves 19,
20 to the head side of the hydraulic piston 21,
The hydraulic piston 21 moves forward at high speed.

Subsequently, the pressure-increasing trigger lever 3 shown in FIG.
8, the pressure-increasing trigger valve 14 is opened, the main switching valve 30 of the pneumatic cylinder 2 is switched to the open position, high-pressure air is supplied to the cylinder tube 8, the ram 18 advances, and the pressure-increasing cylinder 16 Compress hydraulic fluid inside. Hydraulic oil in the booster cylinder 16 is supplied to the hydraulic cylinder 3 by the action of a check valve 19 disposed upstream of the booster cylinder 16.
The check valve 24 compresses the compression coil spring 23 and moves forward, closing the passage 21 a of the hydraulic piston 21.

In the subsequent retraction stroke of the ram 18, the pressure on the head side is held by the check valve 20, and the working oil is sucked from the working oil tank 4 into the pressure-intensifying cylinder 16 through the check valve 19, and is fed and sucked. repeat. When the ram 18 moves forward, the air pressure of the air pressure source is converted into a high-pressure oil pressure according to the ratio of the cross-sectional area of the ram 18 to the pressure receiving area of the hydraulic piston 21, and the head-side oil pressure becomes high and the hydraulic piston 2
1 is advanced with high thrust.

Since the hydraulic oil is pressurized by the free piston 12 of the hydraulic oil tank 4 during the reciprocating stroke of the ram 18, cavitation may occur in the hydraulic oil during the hydraulic oil suction stroke in which the ram 18 moves backward. Absent.

When the hydraulic piston 21 reaches the first half 3b of the hydraulic cylinder 3, the first half 3b has a larger diameter than the hydraulic piston 21, so that the head-side oil chamber and the rod-side oil chamber of the hydraulic piston 21 communicate with each other. As a result, the hydraulic pressure on both the front and rear surfaces is balanced and the hydraulic piston 21 stops, and at the same time, the check valve 24 retreats due to the spring force of the compression coil spring 23, and
a is opened.

In the above embodiment, the inner diameter of the front half 3b of the hydraulic cylinder 3 is formed larger than that of the hydraulic piston 21, and when the hydraulic piston 21 advances to the larger front half 3b, the hydraulic piston 21 Although the configuration is such that the front and rear sides are in communication with each other to allow the hydraulic oil to flow, as another embodiment, the inner diameter of the hydraulic cylinder 3 is set to a size matching the hydraulic piston 21 over the entire length, and the first half of the inner wall surface of the cylinder is formed. A configuration may be adopted in which a spline-type groove is formed in the portion to allow both sides of the hydraulic piston 21 to communicate with each other.

When the operation of the pressure-increasing trigger lever 38 is released, the main switching valve 30 of the pneumatic cylinder 2 is switched to the closed position, and the pneumatic piston 17 is retracted to the initial position and stopped. When the operation of the fast-forward trigger lever 37 is released, the fast-forward switching valve 31 is switched to the closed position, and the compressed air supplied to the air chamber 4a of the hydraulic oil tank 4 is discharged to the atmosphere. 21 is pushed to the head side, and the oil on the head side is checked by a check valve 24.
Through to the rod side, the hydraulic piston 21 retreats,
Stop at the initial position.

When actually using the wire cutting machine 1, a wire or the like is inserted into the concave portion of the fixed cutter blade 28 of the nose portion 27 and the trigger lever 37 for fast-forward is operated, so that the movable cylinder mounted on the hydraulic cylinder 3 is operated. The cutter blade 29 moves forward at a high speed, hits a wire or the like, and stops. Subsequently, when the pressure-increasing trigger lever 38 is operated, the movable cutter blade 29 advances at a low speed and high thrust to cut a wire or the like.

The present invention is not limited to the above-described embodiment, and various modifications are possible within the technical scope of the present invention, and it goes without saying that the present invention extends to those modifications. is there.

[0030]

As described above, in the hydraulic cylinder according to the present invention, when the hydraulic pressure is supplied, the piston is driven forward, and when the hydraulic pressure is released, the piston retreats to the initial position by the action of the spring and the check valve. Reciprocating operation is possible with one switching valve, and a directional control valve such as a four-way valve is not required, so that the hydraulic circuit can be reduced in size, and is suitable for a hand-held power tool or the like that needs to be reduced in size and weight. It is.

[Brief description of the drawings]

FIG. 1 is a side cross-sectional view of a wire cutting machine according to an embodiment of the present invention.

FIG. 2 is a sectional view of a hydraulic cylinder portion shown in FIG.

FIG. 3 is a hydraulic-pneumatic circuit diagram of the wire cutting machine of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wire cutting machine 2 Pneumatic cylinder part 3 Hydraulic cylinder 4 Hydraulic oil tank 4a Air chamber 4b Oil chamber 5 Grip part 7 Pneumatic main line 12 Free piston 13 Hydraulic main line 14 Trigger valve for pressure increase 15 Trigger valve for rapid feed 16 Compressor cylinder portion 18 Ram 19, 20 Check valve 21 Hydraulic piston 21a Passage 22 Hydraulic line 23 Compression coil spring 24 Check valve 25 Cap 26 Compression coil spring 31 Fast-forward switching valve 32 Reciprocating control mechanism 36 Compression coil spring 37 Fast-forward trigger lever 38 Pressure-increasing trigger lever

Claims (1)

[Claims] A double-acting hydraulic cylinder has a built-in spring for urging a piston toward a head side, a passage communicating between a head side and a rod side oil chamber is formed in the piston, and a rod is provided in the passage from the head side. A check valve for preventing oil flow to the side is provided, a spring is interposed in the check valve to urge it to the open position, and when hydraulic pressure is applied to the head side, the check valve closes and the hydraulic pressure is released. A hydraulic cylinder configured so that the check valve sometimes opens.