US3921399A

US3921399A - Fluid pressure-operated device

Info

Publication number: US3921399A
Application number: US532386A
Authority: US
Inventors: Masamitsu Ishihara
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-12-14
Filing date: 1974-12-13
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25
Also published as: GB1487407A

Abstract

A fluid pressure-operated device comprises a piston slidably disposed in a cylinder, pump means for feeding a pressure fluid to the cylinder thereby axially moving the piston against the biasing force of a spring, and return valve means for allowing, when the piston has been moved by prescribed stroke, the pressure fluid within the cylinder to escape therethrough so as to return the piston to the original position.

Description

United States Patent Ishihara Nov. 25, 1975 1 FLUID PRESSURE-OPERATED DEVICE 2,618,929 11/1952 Bidin .1 60/478 9,4 [76'] Inventor: Masamitsu Ishihara, 628 Hirai, 53 ,1 32??? D I Kannami-cho, Tagata, Shiluoka, 3,873,844 3/1975 Willis 60/477 Japan [22] Filed: Dec. 13, 1974 App]. No.: 532,386

UNITED STATES PATENTS Riach v.91/401 X Primary ExaminerEdgar W. Georghegan [57] ABSTRACT A fluid pressure-operated device comprises a piston slidably disposed in a cylinder, pump means for feeding a pressure fluid to the cylinder thereby axially moving the piston against the biasing force of a spring. and return valve means for allowing, when the piston has been moved by prescribedstroke. the pressure fluid within the cylinder to escape therethrough so as to return the piston to the original position.

11 Claims, 6 Drawing Figures US. Patent Nov. 25, 1975 Sheet10f2 3,921,399

US. Patent Nov. 25, 1975 Sheet20f2 3,921,399

FLUID PRESSURE-OPERATED DEVICE This invention relates to a fluid pressure-operated device, and more particularly to a fluid pressure-operated device for use with a machine tool, though not limited thereto, by which the reinforcing steel piece shearing or metal plate puncturing as in the case of, for example, the building operations is performed.

conventionally, the reinforcing steel piece shearing or metal plate puncturing was conducted utilizing an extremely large-sized machine or manually operable machine tool. This type of machine or machine tool, however, had the drawback of reducing the operation efficiency or requiring much labour.

Accordingly, the object of the invention is to provide a compact fluid pressure-operated device whose operation is capable of being stabilized and which is capable of achieving a high operation efficiency.

A fluid pressure-operated device according to the invention comprises a piston slidably disposed in a cylinder and partitioning the cylinder into two parts, i.e., a low pressure chamber and a high pressure chamber, pump means for feeding a pressure fluid to the high pressure chamber thereby moving the piston toward the low pressure chamber against the biasing force of a first spring, and return valve means for allowing, when the piston has been moved toward the low pressure chamber by a prescribed stroke, the pressure fluid within the high pressure chamber to escape therethrough into the low pressure chamber so as to return the piston to the original position. Said valve means comprises a first passageway formed through the piston for allowing the low pressure chamber to communicate with the high pressure chamber, a rod slidably extending through the piston and protruded at one end into the low pressure chamber, and a closing member provided within the high pressure chamber on the other end of the rod in a manner integral therewith to close said passageway due to the action of the fluid pressure of the high pressure chamber. When the piston is moved toward the low pressure chamber by the pump means, the valve means is moved together with the piston in a state closing said passageway. When the piston has been moved by a prescribed stroke, said one end is allowed to abut against first stop means to release the closing member to open the passageway, thereby causing the pressure fluid within the high pressure chamber to flow into the low pressure chamber. For this reason, the piston is returned to the original position by said first spring to cause the closing member to abut against second stop means, thereby closing again said passageway. Thereafter, the piston commences to be again moved toward the low pressure chamber.

Said one end of the rod may preferably hold a floating compression spring. When the piston has been moved by a prescribed stroke, the compression spring is sufficiently compressed by the first stop means and subsequently, when the passageway has been opened, acts to rapidly push the rod toward the high pressure chamber.

The piston may be provided with a piston rod extending through the low pressure chamber to be protruded to the exterior and a machine tool on the tip end of the rod. The machine tool is forwardly advanced in accordance with the movement of the piston to machine the object workpiece. In this case, the low pressure chamber can preferably be provided with compensation 2 means for compensating an increase or decrease in the chamber volume produced due to the reciprocating movement of the piston in the low pressure chamber.

In a preferred embodiment of the invention, there is provided safety valve means for allowing, when an accident has occurred, a pressure fluid within the high pressure chamber to escape therethrough into a low pressure chamber. Said valve means consist of a normally closed valve provided in a second passageway for con necting the high pressure chamber with the low pressure chamber.

This invention will now be described in more detail by reference to the appended drawings in which:

FIG. 1 is a longitudinal sectional view illustrating a fluid pressure-operated device according to the inven' tion;

FIG. 2 is an enlarged view illustrating part of the fluid pressure-operated device, wherein the piston is in a position moved by a maximum stroke;

FIG. 3 is a perspective view illustrating another embodiment of the return valve means;

FIG. 4 is an enlarged plan view, partly in section, of the device section on which a machine tool is mounted; and

FIGS. 5 and 6 respectively are enlarged views illustrating a modification of the compensation means.

In FIG. 1, a fluid pressure-operated device of the invention applied to a shearing machine 10 for reinforcing steel is illustrated. The shearing machine 10 comprises a housing 11 for receiving therein a fluid pressure-operated mechanism and a known internal combustion engine 13 fixed to the housing. The internal combustion engine acts as a power source for driving the fluid pressure-operated mechanism and comprises a starter 14, ignition plug 15 and fuel tank 16. The engine 13 may be replaced by an appropriate power source such as, for example, an electric motor. Reference numerals and 81 respectively denote a handle for holding the shearing machine in place.

A reservoir 17 fluid-tightly shut off from the exterior and filled with an operating fluid is defined by the inner wall of the housing 11. A port 82 provided in the bottom portion of the reservoir is used to permit the fluid to be introduced therethrough or exhausted therethrough into or from the reservoir, and is normally closed by a plug 83. The reservoir is divided by a partition wall 18 into two parts, i.e., reservoir sections and 17b, which communicate with each other through a passageway 19. The partition wall 18 defines a cylinder with the cylindrical inner wall portion 20 of the housing 11. Within the cylinder a later described diskshaped piston 21 is slidably and fluid-tightly disposed via a seal ring 22 to form a high pressure chamber 23.

On the right end portion of the housing 11 is rotatably mounted via ball bearings 24 and 25 a shaft 26, the right end of which is connected via a known centrifugal clutch 27 to the engine 13. The clutch consists of a clutch drum 28 fixed to the right end of the shaft and a clutch expander 29 mounted on the drive shaft (not shown) of the engine. When the rotation speed of the engine has increased up to a value larger than prescribed, the expander is frictionally engaged with the drum 28 to transmit a driving force to the shaft 26.

The left end of the shaft 26 is fluid-tightly inserted into the reservoir 17 via a seal ring 30, and is provided with a pump 31 of radial plunger type. The pump comprises a cam rod 32 eccentrically fixed to the shaft 26, a needle roller bearing 33 provided on the cam rod, and

a plurality of radial plungers 34 (only one of which is illustrated) equi-angularly arranged on the circumference of the bearing 33. Each plunger is slidably disposed in each of a plurality of radially extending cylindrical bores 35 formed in the inner wall of the housing 11, and is urged against the outer ring of the bearing 33 by the biasing force of a spring 36. The cylindrical bore 35 communicates with the reservoir 17 via a passageway 37 and with the high pressure chamber 23 via a one-way valve 38 and a passageway 39. When the plunger 34 makes a reciprocating movement in accordance with the eccentrical rotation of the cam rod 32, a fluid within the reservoir 17 is fed under pressure to the high pressure chamber 23 via the passageway 37, bore 35, valve 38 and passageway 39.

The above-mentioned piston 21 is always urged toward the right side of FIG. 1 by the biasing force of a compression spring 40, and, when the force of pressure fluid from the pump 31 has become superior to the biasing force of said spring, is moved toward the left side of FIG. 1.

Referring to FIGS. 1 and 2, the piston 21 is provided with return valve means 41 for allowing, when the piston has been moved toward the high pressure chamber by a prescribed stroke, the pressure fluid within the high pressure chamber23 to escape therethrough into a low pressure chamber, i.e., reservoir section 17b. The return valve means comprises a valve rod 43 fluidtightly and slidably inserted into a hole 42 extending through the piston. The piston wall on the high pressure chamber side is formed with a circular recess 44 concentrical to the valve rod 43, said recess communicating with the reservoir section 17b through a pressure fluid escapement passageway 45 formed through the piston. The valve rod has a disk-shaped closing head 46 at its end portion on the high pressure chamber side, and the edge portion 47 of said head is designed to shut off, when engaging the wall of the piston 21, communication of the chamber 23 with the recess 44. The left end of the valve rod 43 is allowed to projectively extend into the reservoir section 17b and holds a com pression spring or kick spring 48. The spring 48 is fixed at one end to the left end of the rod 43 and projectively extends from the left end of the rod with the other end thereof rendered free. The inner wall portion 49 of the housing facing the left end of the rod 43 constitutes a stop for the rod 43 and the spring 48, and the maximum interval between the portion 49 and the left end of the rod 43 corresponds to the maximum stroke of the piston 21.

When a pressure fluid is fed from the pump 31 to the high pressure chamber 23 with the passageway 45 closed by the closing head 46, the piston 21 commences to be moved leftward against the compression spring. At this time, the closing head 46 is moved jointly with the piston 21 in a state closing the passageway 45 by the high fluid pressure in the high pressure chamber 23. When the piston has been moved by a prescribed stroke, the kick spring 48 first abuts against the stop 49 and then is gradually compressed. When the piston has been further moved, the left end of the valve rod 43 abuts against the stop 49, thereby causing the edge portion 47 of the closing head 46 to be released from the wall of the piston 21. For this reason, the high pressure fluid within the high pressure chamber 23 is enabled to escape into the reservoir section 17b, i.e., low pressure chamber through the interspace between the edge portion 47 and the wall 'of the piston 21,

thereby reducing the internal pressure of the chamber 23 and simultaneously causing the kick spring 48 to forcibly push the valve rod 43 toward the right by its accumulated force. When, at this time, the rotation speed of the engine is decreased and the clutch 27 is released, the pressure fluid within the chamber 23 quickly escapes through the pressure fluid escapement passageway 45 into the reservoir section 17b. Therefore, the piston 21 is returned to the position of FIG. 1 by the biasing force of the compression spring 40. The closing head 46 abuts against the partition wall 18 to close the passageway 45 again, and when a pressure fluid is sent from the pump 31, the same process begins again. A compression spring 50 disposed between the bottom portion of the recess 44 and the head 46 so acts as to apply to the head 46 a weaker force than the high pressure within the high pressure chamber, and serves as means for maintaining the head spaced from the piston wall during the return stroke of the piston 21.

In an embodiment illustrated in FIG. 3, a piston 21a is provided with two return valve means 410 positioned radially of the piston 21a in a manner mutually opposite each other with the piston center intervening therebetween. The respective valve means 41a have a construction substantially the same as the return valve means 41 illustrated in FIGS. 1 and 2 except that their head 46a has a shock absorber 75. In this case, when one valve means 41a is opened, the other valve means is also opened at once due to reduction in the internal pressure of the high pressure chamber. For this reason, the valve means can be constructed to relatively small size measurements. Further, since the pressure fluid within the high pressure chamber is flowed through both said valve means, the piston 21a can be returned to the original position in a well-balanced state.

From the piston 21 there coaxially extends a rod 51, which is fluid-tightly and slidably inserted via a seal ring 53 into a cylindrical bore 52 formed in the housing 11. The outer wall of the rod 51 is formed with a key way 54 extending in the longitudinal direction. To the inner wall of the bore 52, as shown in FIG. 4, is fixed via a bolt 56 a key 55, which engages thekey way. To the tip end of the rod 51 is secured a cutter 57, which is so designed as to cooperate with a cutter 58 secured to the housing 11. An unsheared workpiece such as, for example, a reinforcing steel piece is placed between the

cutters

57 and 58, and subsequently when the cutter rod 51 is moved jointly with the piston 21 to the left of FIG. 1, said reinforcing steel piece is cut off by the

cutters

57 and 58.

In this type of shearing machine, where the unsheared workpiece is too hard to permit the rod 51 to be forwardly advanced, the piston 21 should be backwardly returned halfway. To this end, the housing 11 is formed with another passageway 59 for allowing the high pressure chamber 23 to communicate with the reservoir section 17b. Within the passageway 59 is dis posed a ball valve 60, which is normally pressed by a threaded stem 61 screwed into the housing 11 to shut the passageway 59 off. In the case of accident occurrence, when the operator slows down the rotation speed of the engine and swings the lever 62 secured to the outer end of the stem 61, the passageway 59 is opened to allow the pressure fluid within the high pressure chamber 23 to escape into the reservoir section 17a. For this reason, the piston 21 is returned to permit piece.

The shearing machine according to this embodiment is provided with means for compensating an increase or decrease in the reservoir volume due to fluid leakage or reciprocating movement of the piston. In the embodiment illustrated in FIG. 1, the compensation means comprises a flexible bag 63 made of a material such as rubber or plastic and disposed within the reservoir section 17b. The bag is fixed to a bolt 66 having a through hole 65. The bolt 66 is fitted by screw engagement into a threaded hole 67 formed in the housing and fixed by a nut 68. The head 66a of the bolt fluid-tightly presses the edge of the bag 63 against the inner wall of the reservoir. The bag 63 is expanded or shrunk in accordance with fluid leakage or reciprocating movement of the rod 51, thereby preventing entry of air into the reser- VOlr.

In an embodiment illustrated in FIG. 5 the reservoir section 17b includes a cylindrical hole 69 which communicates with the exterior through an air hole 70. Said compensation means comprises a piston member 72 fluid-tightly and slidably disposed in the cylindrical hole 69 via an O-ring 71. The piston member is always lightly urged toward the right of the illustration by the biasing force of a compression spring 73 and makes a sliding movement in accordance with the volume variation of the reservoir, or with the fluid leakage.

Compensation means illustrated in FIG. 6 comprises a piston member 75 having a flexible bag 74. This piston member is slidably disposed in a cylindrical hole 690. The interior of said bag 74 communicates with the open air through a hole 76 formed through the piston member and an air hole 700. In the case of this embodiment, the volume variation of the reservoir is compensated principally by expansion or shrinkage of the bag 74, while the fluid leakage is compensated principally by the sliding movement of the piston member 75.

In the compensation means illustrated in FIGS. 5 and 6, a filtering member may be provided in the air hole 70 or 70a for the purpose of preventing entry of dust into the cylindrical hole.

The foregoing description referred to the case with the shearing machine, but the fluid pressure-operated device of the invention can also be applied to a puncturing machine, calker, or the like. In such cases a puncturing machine tool or calking machine tool in replacement of said cutters may be mounted on the piston rod.

What is claimed is:

1. A fluid pressure-operated device comprising a cylinder, a piston slidably disposed in said cylinder and partitioning said cylinder into two parts one of which is a low pressure chamber and the other of which is a high pressure chamber, a first spring for urging said piston toward the high pressure chamber, pump means for feeding a pressure fluid to the high pressure chamber, thereby moving the piston toward the low pressure chamber against the biasing force of said first spring, and at least one return valve means for allowing, when the piston has been moved toward the low pressure chamber by a prescribed stroke, the pressure fluid within the high pressure chamber to escape therethrough into the low pressure chamber so as to return the piston to the high pressure chamber, said return valve means including a rod element axially and movably extending through the piston and having one end protruded into the high pressure chamber and the other end protruded into the low pressure chamber, a first passageway formed through the piston and allowing the high pressure chamber to communicate with the low pressure chamber, a closing element integrally provided on said one end of the rod element to close the first passageway due to the action of the fluid pressure in the high pressure chamber, and a stop against which; when the piston has been moved by a prescribed stroke, said other end abuts to permit the closing ele' ment to open the first passageway.

2. A fluid pressure-operated device according to claim 1 wherein said return valve means includes a second compression spring held by said other end of the rod element and projectively extending therefrom.

3. A fluid pressure-operated device according to claim 2 wherein said return valve means includes a third compression spring for maintaining the closing element in a state spaced from the first paassageway during the return stroke of the piston.

4. A fluid pressure-operated device according to claim 1 further comprising a second passageway allowing the high pressure chamber to communicate with the low pressure chamber and a safety valve for normally closing said second passageway.

5. A fluid pressure-operated device according to claim 4 wherein said safety valve includes a manually operable lever for opening the same.

6. A fluid pressure-operated device according to claim 1 wherein said piston includes a piston rod extending through the low pressure chamber to be protruded exteriorly thereof and a machine tool mounted on the outer end of said piston rod.

7. A fluid pressure-operated device according to claim 6 further comprising a reservoir communicating with the low pressure chamber, for holding therein the fluid for the pump, said reservoir having compensation means for compensating the volume variation of the reservoir resulting from the reciprocating movement of said piston rod.

8. A fluid pressure-operated device according to claim 7 wherein said compensation means consists of a flexible bag provided within the reservoir, the interior of said bag communicating with the open air.

9. A fluid pressure-operated device according to claim 7 wherein said reservoir includes a cylindrical section communicating at one end with the open air, and said compensation means includes a second piston slidably and fluid-tightly disposed in said cylindrical section.

10. A fluid pressure-operated device according to claim 7 wherein said reservoir includes a cylindrical section communicating at one end with the open air, and said compensation means includes a second piston slidably and fluid-tightly disposed in said cylindrical section and having a through hole formed therethrough and a flexible bag fixed to said second piston at the res ervoir side and communicating interiorly with the open air via said through hole.

11. A fluid pressure-operated device according to claim 1 wherein said pump means is a radial plunger type.

Claims

1. A fluid pressure-operated device comprising a cylinder, a piston slidably disposed in said cylinder and partitioning said cylinder into two parts one of which is a low pressure chamber and the other of which is a high pressure chamber, a first spring for urging said piston toward the high pressure chamber, pump means for feeding a pressure fluid to the high pressure chamber, thereby moving the piston toward the low pressure chamber against the biasing force of said first spring, and at least one return valve means for allowing, when the piston has been moved toward the low pressure chamber by a prescribed stroke, the pressure fluid within the high pressure chamber to escape therethrough into the low pressure chamber so as to return the piston to the high pressure chamber, said return valve means including a rod element axially and movably extending through the piston and having one end protruded into the high pressure chamber and the other end protruded into the low pressure chamber, a first passageway formed through the piston and allowing the high pressure chamber to communicate with the low pressure chamber, a closing element integrally provided on said one end of the rod element to close the first passageway due to the action of the fluid pressure in the high pressure chamber, and a stop against which, when the piston has been moved by a prescribed stroke, said other end abuts to permit the closing element to open the first passageway.

10. A fluid pressure-operated device according to claim 7 wherein said reservoir includes a cylindrical section communicating at one end with the open air, and said compensation means includes a second piston slidably and fluid-tightly disposed in said cylindrical section and having a through hole formed therethrough and a flexible bag fixed to said second piston at the reservoir side and communicating interiorly with the open air via said through hole.