US3830086A

US3830086A - Impact hydraulic pressure generator

Info

Publication number: US3830086A
Application number: US00400762A
Authority: US
Inventors: H Tominaga
Original assignee: Tokyo Sharyo Seizo KK
Current assignee: Tokyo Sharyo Seizo KK
Priority date: 1972-09-28
Filing date: 1973-09-26
Publication date: 1974-08-20
Anticipated expiration: 1991-08-20
Also published as: DE2347921B2; JPS4952372A; JPS5430152B2; DE2347921A1; DE2347921C3

Abstract

In an impact hydraulic pressure generator wherein high-pressure surges are generated virtually instantaneously by accelerating a hammer in a cylinder using high-pressure gas, where the hammer carries a plunger which is driven into a chamber containing liquid, shock and vibration are minimized by mounting the casing containing the hammer, plunger and chamber in a support in such fashion that said casing can move in the direction opposite to that in which said plunger and hammer move during the generation of a pressure surge. The momentum given the casing is equal to that given the hammer and plunger, but the kinetic energy given the casing is much smaller. This kinetic energy is absorbed at the end of a pressure surge by a compressible material located between an end face of the support and a shoulder on the outer surface of the casing. Means are provided for restoring the casing to a holding position, in which condition the generator is in condition for producing another pressure surge.

Description

United States Patent [191 Tominaga IMPACT HYDRAULIC PRESSURE GENERATOR [75] Inventor: Hiroshi Tominaga, Yokohama,

Japan 22 Filed: Sept. 26, 1973 211 Appl. No.: 400,762

[ 1 Aug. 20, 1974 Primary Examiner-Richard J. Herbst Attorney, Agent, or FirmBlum Moscovitz Friedman & Kaplan ABSTRACT In an impact hydraulic pressure generator wherein high-pressure surges are generated virtually instantaneously by accelerating a hammer in a cylinder using high-pressure gas, where the hammer carries a plunger which is driven into a chamber containing liquid,

shock and vibration are minimized by mounting the I casing containing the hammer, plunger and chamber in a support in such fashion that said casing can move in the direction opposite to that in which said plunger and hammer move during the generation of a pressure surge. The momentum given the casing is equal to that given the hammer and plunger, but the kinetic energy given the casing is much smaller. This kinetic energy is absorbed at the end of a pressure surge by a compressible material located between an end face of the support and a shoulder on the outer surface of the casing. Means are provided for restoring the casing to a holding position, in which condition the generator is in condition for producing another pressure surge.

9 Claims, 4 Drawing Figures ATENTEB M113 2 0 I974 SNEH 10? 3 FIG- $HEU20F3 FIG 2 TENTEflAusamsm 1 IMPACT HYDRAULIC PRESSURE GENERATOR BACKGROUND OF THE INVENTION Equipment for generating a high pressure instantaneously and impulsively is disclosed in U.S. Pat. No.

3,681,959 and West German Patent 1,452,929. The

impact hydraulic pressure generator disclosed operates by the acceleration of a hammer in a cylindrical cavity using gas at high pressure to force a plunger into the en trance of a hydraulic pressure chamber containing a liquid. As is well known, liquids are virtually incom pressible, as a result of which a high-pressure surge is generated virtually instantaneously. The diameters of the hydraulic pressure chamber and the plunger are such that they engage with a sliding fit. As a result, virtually no liquid escapes around the plunger as the surge is produced. As indicated, liquids are virtually but not completely incompressible. As a result of these two factors, the pressure surge is not actually instantaneous, but for all practical purposes connected with the use of such devices, the pressure rise is sufficiently rapid so that it may be regarded as instantaneous and will be so referred to throughout the present disclosure. In the prototype impact hydraulic pressure generators described in the aforenoted patents, serious vibration and shock are tranmitted to the support and to other components of the system mounted either on the support or on the generator itself. As an example of the way in which shock and vibration are generated and transmitted, an impact hydraulic pressure generator of the vertical type may be considered. The main body of the generator is mounted on a foundation or support. The body of the generator consists of an outer casing in the top portion of which is a cylindrical cavity and in the bottom portion of which is a hydraulic pressure chamber filled with liquid. Prior to generation of a pressure surge, a cylindrical hammer supporting a coaxially mounted cylindrical plunger thereon is held at the top of the cylindrical cavity, as by a vacuum.

To deliver a pressure surge, gas at high pressure is introduced into the cylindrical cavity on the face of the hammer farther away from the hydraulic pressure chamber. The hammer and plunger are immediately displaced in a downward direction, and the casing is immediately subjected to an upward force. The upward force of the gas against the inner face of the top end of the chamber causes an immediate shock to the support of said casing and whatever equipment is mounted on said casing or on said support. After an extremely short interval, the hammer enters the upper end of the hydraulic pressure chamber, instantaneously compressing the liquid therein and transmitting a second shock, but in the opposite direction from the first, to the casing, the support and the associated equipment. In short, one upward and one downward impact are given to the foundation in a single cycle of operation. This vibration is detrimental to various relatively sensitive devices such as electromagnetic valves mounted on the equipment, and the shock is severe enough to be transmitted through the floor of the plant to other machinery, generating noise at an uncomfortable level and causing vibration severe enough to be heard and felt not only within the building containing the equipment but outside as well.

To eliminate these drawbacks, a counter-blow type of equipment has been invented (U.S. Pat. No.

3,494,160 and West German 1,602,581) wherein a pair of cylinder, hammer and plunger devices are disposed below the hydraulic pressure chamber so as to strike same simultaneously from above and below, thereby balancing momenta with the objective of eliminating shock and vibration which can be transmitted exterior of the device. The arrangement of this device is advantageous for application to forming processes because the hydraulic pressure chamber is at rest when hydraulic pressure is generated. However, the use of two pairs of cylinders, hammers and plungers disposed above and below opposite to each other makes construction difficult and necessitates an undesired increase in the size of the equipment. Furthermore, all of the auxiliary equipment must be doubled, making the equipment complex, more costly and more subject to failure, so that more time must be allocated for handling and repairing such a device.

SUMMARY OF THE INVENTION A casing has a cylindrical cavity proximate one end thereof and a hydraulic pressure chamber proximate the other end thereof. A cylindrical hammer is contained in the cylindrical chamber, said hammer having coaxially affixed thereto a cylindrical plunger, said plunger being on the face of said hammer nearer to said hydraulic pressure chamber. The diameters of said plunger and said hydraulic pressure chamber are such that said plunger fits within the nearer end of said hydraulic pressure chamber with minimal clearance.

A portion of the end of said casing has a cylindrical periphery which is slidably and sealingly connected with a stationary duct which in turn is connectable to a source of high-pressure gas or, alternatively, to a source of vacuum.

A second portion of the casing has a cylindrical outer surface and is mounted slidably in a support. Biasing means are provided to maintain the casing with respect to its support in a holding position prior to the start of a pressure-surge cycle. To initiate a pressure surge, a valve is opened connecting said duct with said source of high-pressure gas. The high-pressure gas drives the hammer and the plunger affixed thereto toward said hydraulic pressure chamber and simultaneously moves said casing in the opposite direction. Movement of said casing in the opposite direction is possible due to the fact that it is mounted slidably in said support as well as slidably with respect to said duct. For minimizing friction, the opening in said support through which said casing slides is cylindrical and is lined with bearing metal.

To absorb the energy in the outer casing in the sup port, the casing has a shoulder protruding from the outer periphery thereof and the support has an end face around the cylindrical passage therethrough so located that they interfere. An annulus of a soft material such as polyurethane rubber is provided between the protruding shoulder on the casing and the end face on the support to absorb the shock as said shoulder is brought into interference with said end surface after generation of an impulse.

A duct in the casing is provided for filling the hydraulic pressure chamber with liquid, preferably water. An overflow duct is also provided. The hydraulic pressure chamber has an outlet through which a pressure surge can be delivered to processing equipment requiring such surges.

An embodiment in which the axes of the cylindrical cavity, the hydraulic pressure chamber and the casing are horizontal is described. The hydraulic pressure chamber is kept filled by directing a stream of liquid against the inner end thereof to maintain a liquid layer across the inner end of said chamber.

Accordingly, an object of the present invention is an improved impact hydraulic pressure generator wherein shock and vibration are mitigated.

Another object of the present invention is an improved impact hydraulic pressure' generator in which shock and vibration are mitigated by providing for motion in opposite directions of a casing and a hammer contained therein.

A further object of the present invention is an improved impact hydraulic pressure generator in which the shock of a casing is absorbed by means of an annular sheet of shock-absorbing material such as polyurethane rubber.

An important object of the present invention is an improved impact hydraulic pressure generator which can be embodimented for operation with either a vertical axis or a horizontal axis.

Still other objects and advantage of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the inven tion will be indicated-in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a vertical cross-section of an embodiment of the present invention showing the device prior to start of operation;

FIG. 2 is a vertical section of the same embodiment at the instant of production of a pressure surge;

FIG. 3 is a vertical section of another embodiment of the present invention in which the axis of the device is horizontal; and

FIG. 4 is a vertical section in enlarged scale of a portion of the embodiment of FIG. 3 showing how the hydraulic pressure chamber is maintained in filled condition.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the embodiment shown in FIGS. 1 and 2, an outer casing represented generally by the reference numeral 50 has proximate one end a cylindrical cavity 5 and proximate the other end a hydraulic pressure chamber 10. The interior wall 11 of hydraulic pressure chamber is also cylindrical.

Within cylindrical cavity 5 is a hammer 6 engaging the interior wall of cavity 5 in a sliding fit. Affixed to the lower end of hammer 6 is a plunger 7 which also is cylindrical and which is coaxial with hammer 6.

Outer casing 50 has a first cylindrical portion 4 at the upper end thereof and a second cylindrical outer periphery 14 at the lower end thereof. Cylindrical periphery 14 is so dimensioned that it slides freely in

metal bearings

23 and 24.

Metal bearings

23 and 24 are mounted in a cylindrical passage within support body 19, which in turn is mounted on foundation l8.

Casing has a shoulder 21- protruding outward therefrom and support 19 has an upper surface 22 opposed to shoulder 21. Between upper surface 22 and shoulder 21 is located a soft material 17 which may be in the form of a sheet or an annulus of a material such as polyurethane rubber.

Cylinder 5 is connectable through inlet l and valve V, to a source A of compressed gas, and preferably compressed air, or to a vacuum pump or vacuum tank B. Compressed-air inlet 1 is formed of cylindrical pipe 2 and is fitted out at the lower portion thereof on the interior wall with an O-ring 3. As aforenoted, the exterior of portion 4 is cylindrical. Portion 4 engages inlet 1 both slidingly and sealingly by means of O-ring 3. Consequently, portion 4 can move upwardly and subsequently downwardly with respect to fixed inlet 1.

The necessity for air inlet 1 and cylindrical portion 4 of casing 50 can be eliminated if connection from casing 50 to valve V is made by flexible piping.

Casing 50 has therein intermediate cylindrical cavity 5 and hydraulic pressure chamber 10 a liquid inlet 8 connected through valve V to a liquid supply tank which may be a water source. The piping between tank C and inlet 8 is flexible so that it does not interfere with the vertical reciprocation of casing 50.

Casing 50 also has therein a liquid overflow outlet 9 which establishes the level of liquid in hydraulic pressure chamber 10.

Inner wall 11 of hydraulic pressure chamber 10 is cylindrical and coaxial with plunger 7. Moreover, the diameters of plunger 7 and chamber wall 11 are such that they engage each other slidingly.

Liquid in hydraulic pressure chamber 10 is indicated by the reference numeral 12, and the free surface of the liquid 12 is indicated by the reference numeral 13. It is desirable that outlet 9 be so located with respect to hydraulic pressure chamber 10 that free surface 13 of liquid I2 is several centimeters above the upper end of cylindrical wall 11.

Hydraulic pressure chamber 10 has an outlet 15 proximate the bottom end thereof which is connectable with equipment indicated by the reference letter D. Pressure surges generated in the device in accordance with the present invention are transmitted through outlet 15 for purposes such as the plastic deformation of metallic materials, forging, powder molding and spray processing.

Liquid 12 will not flow outward through outlet 15, since equipment D acts as a dead end. Other arrangements are also possible. For instance, if the liquid line leading outward from outlet 15 is brought to a height equal to the free liquid surface 13 and a nozzle (not shown) is provided at the outer end, spray processing becomes possible.

The bottom of hydraulic pressure chamber 10 is indi cated by reference numeral 16 and must be strong enough to withstand the impulse generated by the device. Support body 19 is fixed by flange portion 20 to the upper face of foundation 18.

Metal bearings

23 and 24 are made of metals having low frictional characteristics. Suitable materials are copper alloys such as brass and phosphor bronze.

The preferred shape for outer periphery 14 of casing 50 is cylindrical,but other shapes are, of course, possible, provided that the cross section of the casing remains constant over the portion which must slide in metal bearings, and the

metal bearings

23 and 24 and the interior of support 19 must be correspondingly shaped.

Before start of operations, all movable parts are at rest at the lowest possible position due to gravitational force. To start a cycle of operation, air inlet 1 is connected to vacuum pump B through valve V, and hammer 6 is drawn up through cylindrical cavity 5 to'the upper end of said cavity. A liquid which will be referred to as water henceforth is supplied to hydraulic pressure chamber through water inlet 8 until chamber 10 is full and excess water flows out through opening 9. The equipment at this stage of operation corresponds to FIG. 1.

Supply water inlet 8 is closed, and valve V is operated to connect air inlet 1 with compressed-gas source A. Compressed air is injected into cylinder 5 and accelerates hammer 6 downward, carrying plunger 7 therewith. Plunger 7 makes contact with free surface 13 of water 12 and then enters the upper end of the cylindrical portion of hydraulic pressure chamber 10. The water 12 is compressed to high pressure virtually instantaneously, and the high pressure is transmitted as a pressure surge through outlet to processing equipment D.

At the same time as the compressed air accelerates hammer 6 downward, casing 50 is accelerated upward by reason of gas pressure exerted on horizontal wall 5' ofcasing 50. The cylindrical outer periphery portion 14 of casing 15 is guided by the inside faces of

metal bearings

23 and 24 within the support body 19. Consequently, the compressed air acts on both the hammer and the casing 50 for an equal period of time between the instant of introducing air into the chamber and the instant when plunger 7 causes the increase in hydraulic pressure, so that the product of force multiplied by time is essentially the same for the casing on the one hand and the hammer and plunger on the other. Thus, in accordance with the well-known principle, the momentum of casing 50 is equal to that of hammer 6 and plunger 7 up to the point when the high hydraulic pressure is established. Since the momenta of the two portions of the system are equal in magnitude, the momenta are balanced, but since the casing is much heavier than the combined weight of the hammer and plunger, the velocity of the casing is much lower and consequently the bulk of the kinetic energy generated is carried by the hammer and plunger and not by the casing. It is the kinetic energy of the casing on the return of the casing to the holding position after an impulse which must be absorbed by the soft material body 17, and since this kinetic energy is not great, no substantial vibration is transmitted to foundation 18 by way of flange 20. I

Even more important, when plunger 7 enters hydraulic pressure chamber 10, casing 50 is separated from support 19. Consequently, since the ensuing shock and vibration within the casing are exclusively along a vertical axis, and since there is no vertical constraint between casing 50 and support 19, no shock and vibration are transmitted exteriorly of casing 50 when the instantaneous pressure rise is generated.

After the pressure surge has been generated, the air in the cylinder 5 is removed by connecting vacuum tank or pump B through valve V, to duct 1. This step brings the hammer 6 and the associated plunger 7 to the top of the cylindrical cavity 5. Simultaneously, the casing 50 descends of its own weight until it rests once more upon the pad 17 in contact with upper surface 22 of support 19. The velocity of the casing as it descends is small and the consequent shock is also small. As a result, buffer pad 17 absorbs virtually all of the shock, and the vibration generated is completely negligible.

Another embodiment of the present invention is shown in FIGS. 3 and 4, in which the casing instead of being vertical is essentially horizontal. For the horizontal arrangement, the principal structure, function and features of the equipment remain essentially unchanged. The principal differences are that steps must be taken to prevent emptying of the liquid from the hydraulic pressure chamber and a restoring device must be provided to take the place of gravitational force for returning the outer casing to its original position after a pressure surge.

In order to prevent emptying of the hydraulic pressure chamber, a water layer chamber 25 is provided at the open end of the chamber. Wall face 26 is perpendicular to the axis of the hydraulic pressure chamber 10. Chamber 25 has an inlet 27 which makes a small angle with wall face 26. A water stream is supplied from outside the casing and is jetted at high velocity against the opening of the hydraulic pressure chamber as shown in FIG. 4 in enlarged scale. A relatively thin water layer 28 is formed which rebounds from the water within the hydraulic pressure chamber, thereby applying a force to same to keep the hydraulic pressure chamber full. The water layer jet 28 leaves chamber 25 through outlet 29. Further, water is injected from source C through valve V and inlet 30 at the far end of hydraulic pressure chamber 10. Valve V is a oneway valve, so that when the instantaneous pressure surge is generated, the impulse is transmitted out through outlet 31 to process equipment D. The relative movements of casing 50 and the hammer 6 and plunger 7 are the same as for the system of FIGS. 1 and 2 where the axis is vertical. In the embodiment illustrated in FIGS. 3 and 4, gravity cannot be used directly to return the casing 50 to its original position. Consequently, restoring springs 32 are positioned so as to move casing 50 toward the left after a pressure surge has been generated.

In more detail, hydraulic pressure chamber 10 is filled with water flowing from supply water inlet 30 through valve V to water source C. The water naturally tends to flow out of the inner end of the hydraulic pressure chamber, which opens through wall face 26 of water layer chamber 25. However, simultaneously with supply of water through inlet 30, water is supplied at high pressure independently to inlet 27 to form a highvelocity water layer 28 as shown in FIG. 4. Water layer 28 collides with water 12 within the pressure chamber, and after changing its direction slightly, flows out through outlet 29 to the exterior of casing 50. In this manner, pressure chamber 11 is kept filled with water 12, and the effect of water layer 28 is such that pressure chamber 11 is kept filled with water even if valve V is closed.

Introduction of compressed air from compressed-air source A into cylinder 5 drives hammer 6 and plunger 7 from the right-hand end of easing 6 toward the left. Plunger 7 and hammer 6 reach a high velocity and plunger 7 enters slidingly into wall 11 of pressure chamber 10 through water layer 28. The water 12 is instantaneously compressed to high pressure and the high-pressure impulse is transmitted to processing equipment D.

Outer casing 50 moves toward the right as shown in FIG. 3 during the travel of the plunger and hammer toward the left; after the pressure surge, the casing 50 is returned to its original position by means of spring 32, and the plunger 6 and hammer 7 are retracted toward the right by connection of inlet 1 to vacuum tank B through valve V As is evident, if the present invention can be designed to operate either vertically or horizontally, it can also operate at any angle in between. The vertical type of equipment is preferred when only a small floor area is available. However, it requires either great ceiling height or a deep hole. The horizontal type of equipment requires a long, narrow floor area, but it avoids the necessity for an elevated ceiling or a deep hole in the floor. Selection of the type to be used is made on the basis of the available space.

It is to be noted that the present invention develops the same instantaneous pressure impulse at the same high pressure as produced by the previous equipment but completely avoids generation of excessive shock and vibration by the simple device of making it possible for the casing to move away from its support, so that there is no axial connection between the casing and the support at the instant when the impulse is generated. The system operates by balancing of momenta and requires no complex mechanism such as pressureharmonizing mechanism for balancing. The system is well adapted for continuous operation and is free of the hazards of excessive noise and vibration and shock as are encountered with previous high-pressure impulse systems.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

1. In an impact hydraulic pressure generator for supplying sudden pressure surges to processing equipment, said pressure surges being generated by using a gas at high pressure to accelerate a hammer in a cylindrical cavity to a high velocity until a plunger at the end of said hammer strikes the surface of an essentially incompressible liquid filling a hydraulic pressure chamber, said plunger and the wall of said chamber being dimensioned and positioned to engage each other in a sliding fit, said pressure chamber having an outlet connectable to processing equipment, the improvement which comprises an outer casing having a cylindrical cavity at one end and a hydraulic chamber at the other end, said outer casing having outer-surface first and second portions which are cylindrical, said cavity, said chamber and said portions being coaxial; a hammer having a plunger portion within said cavity, said plunger being oriented toward said chamber; a duct slidingly and sealingly engaged with said first portion, said duct being connectable to a source of high-pressure gas for driving said hammer and plunger toward said chamber and to a vacuum source for retracting said hammer and plunger away from said chamber; and support means slidably engaging said second portion of said casing, said support means having an end face and said outer casing having a shoulder protruding therefrom and so positioned with respect to said end face as to limit the travel of said outer casing through said support means after said generator has supplied a pressure surge.

2. An impact hydraulic pressure generator as recited in claim 1, in which said second portion is cylindrical and said support means has a cylindrical passage therethrough for receiving said second portion.

3. An impact hydraulic pressure generator as recited in claim 2, in which bearing metal is provided in said passage of said support means and said second portion of said outer casing slidably engages and is borne on said bearing metal.

4. An impact hydraulic pressure generator as recited in claim 1, in which a buffer material is disposed between the shoulder portion protruding from said outer casing and said end face of said support body.

5. An impact hydraulic pressure generator as recited in claim 1, in which a restoring means is provided for biasing said outer casing to a position in which said protruding shoulder is separated from said end face.

6. An impact hydraulic pressure generator as recited in claim 5, wherein the axes of said cylindrical portions of said generator are non-vertical, a liquid layer chamber is provided at the end of said chamber closer to said cavity, and liquid inlet and outlet conduits are provided in said liquid layer chamber, said liquid inlet being located appropriately for directing and forming a liquid layer across said end of said chamber and retaining sufficient liquid in said chamber to keep said chamber full.

7. An impact hydraulic pressure generator as recited in claim 5, wherein the axis of said outer casing is vertical and said restoring means is gravity.

8. An impact hydraulic pressure generator as recited in claim 5, wherein the axis of said outer casing is essentially horizontal and said restoring means is a spring means.

9. ln an impact hydraulic pressure generator for supplying sudden pressure surges to processing equipment, said pressure surges being generated by using a gas at high pressure to accelerate a hammer in a cylindrical cavity to a high velocity until a plunger at the end of said hammer strikes the surface of an essentially incompressible liquid filling a hydraulic pressure chamber, said plunger and the wall of said chamber being dimensioned and positioned to engage each other in a sliding fit, said pressure chamber having an outlet connectable to processing equipment, the improvement which comprises an outer casing having a cylindrical cavity at one end and a hydraulic chamber at the other end, said outer casing having an outer-surface portion which is cylindrical, said cavity, said chamber and said portion being coaxial; a hammer having a plunger portion within said cavity, said plunger being oriented toward said chambers; said cylindrical cavity being connectable to a source of high pressure gas for driving said hammer and plunger toward said chamber and to a vacuum source for retracting. said hammer and plunger tioned with respect to said end face as to limit the travel of said outer casing through said support means after said generator has supplied a pressure surge.

Claims

1. In an impact hydraulic pressure generator for supplying sudden pressure surges to processing equipment, said pressure surges being generated by using a gas at high pressure to accelerate a hammer in a cylindrical cavity to a high velocity until a plunger at the end of said hammer strikes the surface of an essentially incompressible liquid filling a hydraulic pressure chamber, said plunger and the wall of said chamber being dimensioned and positioned to engage each other in a sliding fit, said pressure chamber having an outlet connectable to processing equipment, the improvement which comprises an outer casing having a cylindrical cavity at one end and a hydraulic chamber at the other end, said outer casing having outer-surface first and second portions which are cylindrical, said cavity, said chamber and said portions being coaxial; a hammer having a plunger portion within said cavity, said plunger being oriented toward said chamber; a duct slidingly and sealingly engaged with said first portion, said duct being connectable to a source of highpressure gas for driving said hammer and plunger toward said chamber and to a vacuum source for retracting said hammer and plunger away from said chamber; and support means slidably engaging said second portion of said casing, said support means having an end face and said outer casing having a shoulder protruding therefrom and so positioned with respect to said end face as to limit the travel of said outer casing through said support means after said generator has supplied a pressure surge.

9. In an impact hydraulic pressure generator for supplying sudden pressure surges to processing equipment, said pressure surges being generated by using a gas at high pressure to accelerate a hammer in a cylindrical cavity to a high velocity until a plunger at the end of said hammer strikes the surface of an essentially incompressible liquid filling a hydraulic pressure chamber, said plunger and the wall of said chamber being dimensioned and positioned to engage eaCh other in a sliding fit, said pressure chamber having an outlet connectable to processing equipment, the improvement which comprises an outer casing having a cylindrical cavity at one end and a hydraulic chamber at the other end, said outer casing having an outer-surface portion which is cylindrical, said cavity, said chamber and said portion being coaxial; a hammer having a plunger portion within said cavity, said plunger being oriented toward said chambers; said cylindrical cavity being connectable to a source of high pressure gas for driving said hammer and plunger toward said chamber and to a vacuum source for retracting said hammer and plunger away from said chamber; and support means slidably engaging said cylindrical portion of said casing, said support means having an end face and said outer casing having a shoulder protruding therefrom and so positioned with respect to said end face as to limit the travel of said outer casing through said support means after said generator has supplied a pressure surge.