US3740169A

US3740169A - High pressure generating device

Info

Publication number: US3740169A
Application number: US00078738A
Authority: US
Inventors: E Papen
Original assignee: National Forge Co
Current assignee: National Forge Co
Priority date: 1970-10-07
Filing date: 1970-10-07
Publication date: 1973-06-19
Anticipated expiration: 1990-06-19
Also published as: GB1370643A; FR2110263A1; FR2110263B1; SE375264B; BE773148A; DE2150176A1

Abstract

A high pressure generating device comprising two or more double acting hydraulic cylinders mounted along a single longitudinal axis and having pistons within each cylinder which are moved toward a select end of the device by a fluid at low pressure from an external source. The piston closest to the select end of the device drives a plunger slidably mounted in a fluid filled cavity in a high pressure end body. A fluid output passage communicates between the cavity and the exterior of the device. Push rods between each pair of adjacent pistons cumulatively transmit the forces exerted on the pistons by the external fluid source to the plunger. The cross-sectional areas of the pistons exceed the cross-sectional areas of each plunger and each push rod thereby giving a hydraulic advantage and intensifying the pressure from the external source. The ratio of intensification is increased in additive fashion with an increase in the number of pistoncylinder stages utilized. The respective cylinders, pistons, push rods, and plungers of each stage are substantially identical for ease of construction and operation.

Description

United States Patent 1 Papen HIGH PRESSURE GENERATING DEVICE [75] Inventor: Eduard L. J. Papen, Sint-Niklaas,

Belgium [73] Assignee: National Forge Company, Irvine, Pa.

[22] Filed: Oct. 7, 1970 [21] Appl. No.: 78,738

[52] US. Cl. 417/397 [51] Int. Cl.- F041! 35/00 [58] Field of Search 92/151; 417/397,

417/901; 60/545 HA, 54.5 P

[56] References Cited UNITED STATES PATENTS 1,714,425 5/1929 Knab 417/397 3,622,250 11/1971 Conlce.. 417/397 341,099 5/1886 Dow 417/397 2,486,495 11/1949 Rider 417/404 3,385,172 5/1968 Kaminga... 92/151 3,282,167 11/1966 McKenzie. 417/397 3,070,023 12/1962 Glasgow.... 417/397 3,056,353 10/1962 Peters... 92/151 2,399,719 5/1946 Bergh.... 92/151 3,191,383 6/1965 Basset 60/545 HA FOREIGN PATENTS 0R APPLICATIONS 135,869 4/1880 France 417/397 54,530 3/1890 Germany 1,046,641 12/1958 Germany 417/901 June 19, 1973 Primary Examiner-Allan D. Herrmann Assistant Examiner-11. H. Lazarus Attorney-Ronald F. Ball [5 7 ABSTRACT A high pressure generating device comprising two or more double acting hydraulic cylinders mounted along a single longitudinal axis and having pistons within each cylinder which are moved toward a select end of the device by a fluid at low pressure from an external source. The piston closest to the select end of the device drives a plunger slidably mounted in a fluid filled cavity in a high pressure end body. A fluid output passage communicates between the cavity and the exterior of the device. Push rods between each pair of adjacent pistons cumulatively transmit the forces exerted on the pistons by the external fluid source to the plunger. The cross-sectional areas of the pistons exceed the crosssectional areas of each plunger and each push rod thereby giving a hydraulic advantage and intensifying the pressure from the external source. The ratio of intensification is increased in additive fashion with an increase in the number of piston-cylinder stages utilized. The respective cylinders, pistons, push rods, and plungers of each stage are substantially identical for ease of construction and operation.

9 Claims, 2 Drawing Figures 2 Shanta-61mm. 1

ml m

wNN

Patented June 19, 1973 2 Sheets-5huot :2

HIGH PRESSURE GENERATING DEVICE BACKGROUND OF THE INVENTION The present invention relates to pressure generating I devices and more particularly to such devices which are intended to produce high fluid pressure on the order of 10,000 to 200,000 pounds per square inch.

High fluid pressures are required for a variety of industrial and other processes, for example isostatic presses and hydrostatic extrusion presses. There are a number of problems, however, with prior pressure generating devices. Many such prior devices are large in diameter, are heavy, are slow in acting, have a number of non-similar parts, or are not readily adaptable to changes in requirements of pressure intensification.

A common feature of some prior pressure generating devices is a series of pistons of decreasing diameter, each being pushed by and pushing against an adjacent piston. In this way the forces exerted on the pistons are transmitted hydraulicly and a series of chambers of increasing capability to withstand high pressures are necessary.

Still another problem of some prior pressure intensi fication devices is that they are not double acting and thus are relatively inefficient. A general problem common to almost all prior pressure intensification devices is their complexity of construction.

The present invention overcomes these and other disadvantages as will be apparent from the following summary and description of the invention.

SUMMARY OF THE INVENTION A high pressure generating device in accordance with the invention comprises at least a first and a second piston, a push rod linking the pistons, and a plunger operated by the first piston. A stationary high pressure body at one end of the device has a cavity within which one end of the plunger is slidably mounted in a fluid tight manner. Means are provided, including fluid input and exhaust passages, for simultaneously applying fluid from an external source under a low pressure (relative to the output pressures obtained from the device) to both of the piston heads to move them in a predetermined axial direction and thereby exert a force on the plunger.

The end of the plunger within the cavity exerts a force on fluid within the cavity to develop a pressure which is high relative to the fluid pressure from the external source and which is generally on the order of 100,000 psi. An exhaust passage communicates from the exterior of the device to the cavity to conduct the high pressure fluid within the cavity to whatever use is desired, e.g., the pressure vessel of an isostatic press.

The cross-sectional areas of the pistons exceed the cross-sectional areas of the plunger and push rod. This provides a hydraulic advantage to effectively intensify the pressure from the external source. The ratio of pressure intensification, i.e., the ratio of the pressure developed in the high pressure body cavity to the pressure from the external source, is determined by the ratios of the cross-sectional areas of the pistons to the cross-sectional areas of the plunger and push rod as will be explained below. I

In a preferred embodiment the first and second pistons are double acting. Fluid from the external source is first applied to one side of each of the pistons to ultimately exert a force on a first plunger. The low pressure fluid is next exerted against the opposite sides of the pistons to slide them in the opposite direction and ultimately exert a force on a second plunger seated within a fluid filled cavity in a second high pressure end body.

In such a double acting embodiment the plungers are fitted to the pistons by means of slotted spring pins. This is necessary in order that a piston withdrawing from the position of driving its corresponding plunger will pull the plunger along with it and will not act as a hammer upon the plunger when it. returns to its driving position. Calculation of the ratio of pressure intensification in double acting embodiments must take into account the back force exerted upon the end of the plunger not being driven.

Because the additional force from the second piston is transmitted through the push rod to the first piston, the forces exerted on the pistons by the low pressure fluid are additive when applied to the first plunger.

As discussed in greater detail further in the description for an embodiment of the invention having two double acting piston-cylinder assemblies the ratio of pressure intensification is and the addition of still another piston-cylinder assembly increases the ratio of pressure intensification by the term where A, is the cross-sectional area of each of the pistons and A is the cross-sectional area of each of the plungers and push rods.

Thus the ratio of pressure intensification may be altered by the addition or subtraction of piston-cylinder assemblies. This is easily accomplished because the assemblies are held together along a single axis by a systern of tension rods, nuts, and washers. Mounting supports are fitted at each end of one of the tension rods. The embodiments have interchangeable and duplicate parts for each assembly which gives them the advantage of being simple in construction and operation as well as being economical.

Another advantage over many prior pressure generating devices is that the cylinder walls do not have to be excessively thick because the only area where a high pressure is developed in the fluid is in the end body cavities. The push rod allows the forces exerted on the pistons to be cumulated mechanically rather than hydraulicly. Furthermore, since the strain developed in the cylinder walls due to the low pressure fluid is directly proportional to the internal diameter of the cylinder, the walls of a series of relatively small diameter cylinders may be thinner than the walls ofa single relatively large diameter cylinder.

For both of these reasons a device built according to the invention may be assembled using relatively lightweight stages which are easy to transport and handle.

Still another advantage in having a series of pistoncylinder assemblies each having its own fluid input passage is that the device is quicker acting than a pressure generating device with only one fluid input passage. The strain developed in the walls of the input fittings is directly proportional to the diameter of the input passage and .thus there exists a practical limit to the crosssectional size of a single passage. With the series ar rangement of the invention, however, the cumulative cross-sectional areas of the individual input passages can easily exceed such a practical limit. Thus in many embodiments the same volume of fluid may be injected and extracted from the series of cylinders of the invention quicker than from a single larger cylinder of some prior devices.

The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed summary and description of certain preferred embodiments of the invention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2, when joined along the line 22 form a central, longitudinal sectional view of a preferred embodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Referring now more particularly to FIGS. 1 and 2, there is shown a high pressure generating device in accordance with the invention comprising a pair of piston-cylinder assemblies or modules and 12 mounted along the same longitudinal axis 14 and held together by a system of tension rods 16. Each assembly contains a

double acting piston

18 and 20, respectively, which drive separate plungers 22 and 24, respectively. The pistons 18 and are interconnected with a push rod 26.

The assembly 10 is comprised of a cylindrical body 28 having a coaxial bore 30 within which the piston 18 is slidably fitted. By the term coaxial bore as used in this application is meant a bore having its central axis along the axis 14. At opposite ends of the piston 18 are a series of cylindrical shoulders of decreasing diameter. The first set of shoulders 32 each have fitted upon them an annular seal 34 which contacts the side of the bore 30. The next set of decreasing shoulders 36 have fitted upon each of them retaining rings 38 which compress the seals 34 against the ends of the piston 18 so as to make a firm contact with the bore 30.

The shoulder 36 closest to the push rod 26 has an outer portion which is threaded to receive a nut 40. The nut 40 has an axial bore 42, a portion of which is threaded to engage the shoulder 36. The unengaged portion of the bore 42 receives one end 44 of the push rod 26.

A portion of the opposite shoulder 36 is threaded to receive a nut 46. The nut 46 has an axial bore 48 through it which is partially threaded to engage the shoulder 36. The unengaged portion of the bore 48 receives one end 50 of the plunger 22. The nut 46 and the plunger end 50 have aligned diametric bores 52 and 54, respectively, through which a slotted spring pin 56 is fitted. As shown in FIG. 1, the bore 48 of nut 46 is larger than the diameter of plunger 22. Asalso shown in the drawing, the diametric bore 52 in the nut 46 is larger than the diameter of the spring pin 56.

A reduction 58 in the diameter of the bore 30 at its end closest to the plunger 22 together with the nut 46 form a dashpot to prevent mechanical hammering at the end of the piston stroke. I

Starting from the plunger end 50, the plunger extends out of the cylinder 28 and passes in series through a snug fitting coaxial bore 60 in the cylinder 28, and an annular seal 62 retained in place by a ring 64. Both the seal and the retaining ring are fitted in an enlargement 66 of the coaxial bore 60. The plunger continues on to extend through a coaxial bore 68 in a guide cylinder 70. A portion of the guide cylinder is fitted within a coaxial bore 72 in the outer end of the cylinder 28. The bore 72 communicates with the enlargement 66 of the bore One or more diametric orifices 74 in the guide cylin der communicate between the inner bore 68, an annular recess 76 in the portion of the outer surface of the guide cylinder 70 fitted within the bore 72, and the exterior of the cylinder 28. Any fluid leakage through the bore 60 is exhausted through the orifices 74 to prevent the guide cylinder 70 from being forced out of the bore 72 in the end of the cylinder.

Substantially the remaining portion of the guide cylinder 70 is fitted within a coaxial bore 78 in a high pressure end body 80. An annular recess 79 in the bore 78 near the seat for the guide cylinder 70 is in communication with the exterior of the end body 80 through an exhaust passage 81. Together the recess and exhaust passage prevent leakage fluid from building up pressure within the bore 78.

The plunger 22 extends out of the end of the guide cylinder 70 and into a coaxial bore 82 in a liner 84. The liner 84 is fitted within a coaxial cavity 86 in the high pressure end body 80.

The guide cylinder 70 abuts one end of the cavity liner 84. At the point of their contact, within an annular recess 88, are seated a pair of retaining rings 90 each of which has a triangular cross-section. When assembled together the rings have a rectangular crosssection. An O-ring 92 is compressed within the recess 88 by the retaining rings 90 so as to make a seal with the bore 86. In addition, when the cylinder guide 70 is pressed against the retaining rings 90 they shift outwardly against the bore 86 so that the rings also make a tight seal.

A series of diametric orifices 94 in the liner 84 communicate with an annular recess 96 in the exterior surface of the liner 84. The purpose of the annular recess 96 and the orifices 94 is to equalize the pressure within and without the liner such that it will fit in a fluid tight manner about the plunger 22.

The end 98 of the plunger terminates within the liner bore 82 at a point near the closed end of the cavity 86. Opposite the end 98 of the plunger 22 a high pressure fluid output passage 100 communicates between the cavity 86 and the exterior of the high pressure body 80. Fluid put under high pressure by the plunger 22 in the cavity 86 is conducted through the passage 100 to whatever place the pressure is desired, e.g., the pressure vessel of an isostatic press. Suitable valve means (not shown) normally are provided to close off the passage 100.

The end of the cylinder 28 closest to module 12 is fitted within a coaxial bore 102 in a connecting body 104 which is between the

modules

10 and 12. An O-ring 106 within an annular groove in the outer end of the cylinder 28 is compressed between the connecting body 104 and the cylinder 28 to make a seal. A crosssectional reduction 108 in the diameter of the coaxial bore 102 together with the nut 40 provides a dashpot to prevent mechanical hammering at the end stroke of the piston 18.

A fluid input passage 1 l0 communicates between the reduced bore 58 and the exterior of the cylinder 28.

Likewise a fluid input passage 112 communicates between the reduced bore 108 and the exterior of the connecting body 104. By introducing fluid at a low pressure from an external source (not shown) first through one input passage and then the other, the piston 18 may be driven back and forth in the cylinder 28.

During this driving operation one of the input passages, for example input passage 112, has fluid passing through it into the bore 108 on one side of the piston while the passage 110 acts as an exhaust passage for fluid within the cavity 58 on the other side of the piston. After the piston 18 has reached the end of its stroke, the process is reversed and fluid is exhausted through the passage 112 and injected through the passage 110.

The push rod 26 extends outwardly from the cylinder 28 and starting from its end 44 it passes in series through a snug fitting, coaxial bore 114 in the connecting body 104, an annular seal 116 and a retaining ring 118 which holds the seal 116 in an enlargement 120 of the bore 114. The push rod 26 continues on through a coaxial bore 122 in a guide cylinder 124. A first portion of the guide cylinder 124 is fitted within a larger coaxial bore 126 in the connecting body 104.

The construction of the assembly 12 is substantially identical to the construction of the assembly and the respective parts of each are interchangeable. The piston 20 is slidably fitted within a coaxial bore 128 in a hydraulic cylinder 130. The open end of the bore 128 faces the plunger 24.

A second portion of the guide cylinder 124 is fitted within a coaxial bore 132 in the end of the hydraulic cylinder 130 closest to the assembly 10. A pair of .diametric, fluid leakage exhaust orifices 134 communicate between the interior bore 122 of the guide cylinder and an annular recess 136 in the portion of the guide cylinders external surface which is fitted within the bore 132. One of the orifices 134 also communicates to the exterior of the cylinder 130.

After exiting from the guide cylinder 124 the push rod 26 passes through an annular retaining ring 138 and an annular seal 140 held in place by the retaining ring within a coaxial bore 142 in the hydraulic cylinder 130. The push rod passes through a still smaller, snug coaxial bore 144 in the cylinder 130 which communicates with the bore 142. The push rod terminates at an end 146 within a cross-sectional reduction 148 in the coaxial bore 128.

The piston 20 has a series of cylindrical shoulders of decreasing diameter upon which seals, retaining rings and nuts are mounted. The first set of shoulders 150 have fitted upon them annular sealing rings 152. The next set of shoulders 154 each have an unthreaded portion upon which are fitted retaining rings 156 which compress the seals 152 and force them to make contact withthe'walls of the coaxial bore 128. A nut 158 is threaded upon the shoulder 154 closest to the push rod end 146. The nut 158 extends beyond the end of the shoulder 156 to define a space for receiving the end 146 of the push rod 26. The cavity 148 together with the nut 158 create a dashpot to prevent a mechanical hammering at this end of the piston stroke.

A nut 160 is threaded upon the opposite shoulder 154 and extends beyond it to create a receiving space for an end 162 of the plunger. 24. As shown in FIG. 2, the bore of nut 160 is larger than the diameter of plunger 24. The plunger end is attached to the nut by the end of the bore 198 closest to the liner 204 is in a slotted spring pin 164 which passes through aligned diametric bores 166 and 168 in the plunger end and the nut. As also shown in the drawing, the diametric bore 168 in the nut 160 is larger than the diameter of the spring pin 164.

It is unnecessary to attach the push rod 26 to the piston nutsand 158 by spring pins since the pistons move in unison during operation of the device. For ease of manufacture the piston nuts 40,, 46, 158 and are substantially identical and thus the nuts 40 and 158 are shown as having diametric bores.

The end of the cylinder 130 closest to the plunger 24 is slidably fitted within a coaxial bore 170 in a connecting body 172. An O-ring 171 in the end of the cylinder 130 seals against a seat in the connecting body 172. A reduction 174 in the coaxial bore 170 in the connecting body 172 slidably receives the piston nut 160 at the end of the piston stroke. The reduced bore 174 and the nut 160 together constitute a dashpot to prevent mechanical hammering of the piston.

' A fluid input passage 176 communicates between the exterior of the body 172 and the reduced bore 174. Another fluid input passage 178 at the opposite end of the cylinder 130 communicates between its exterior and the coaxial bore 148. During operation of the device, fluid from the external source is injected through the passage 176 and exhausted through the passage 178 to force the piston 20 in the desired direction. This is done simultaneously with the injection of fluid through the passage 112 and extraction of fluid through the passage 110. The piston is moved in the opposite direction by reversing the passages for input and output of the fluid.

The plunger extends from its end 162 through the reduced coaxial bore 174 to be slidably received within a still smaller, snug fitting coaxial bore 180 in the body 172. The plunger 24 further extends through an annular seal 182 held in acoaxial bore 184 of the connecting body 172 by a retaining ring 186.

A coaxial bore 188 in a guide cylinder 190 slidably receives the plunger 24 and is in communication with the bore 184. A portion of the guide cylinder 190 is fit ted within a coaxial bore 192 in the connecting body 172. A pair of diametric orifices 194 in the guide cylinder 190 communicate between the bore 188 and an exterior annular recess 196 in the guide cylinder. One of the orifices also communicates with the exterior of the connecting body 172. The purpose of these orifices 194 is to provide an exhaust passage for any fluid leakage in the bore 188. Substantially the remaining portion of the guide cylinder 190 is fitted within a coaxial bore 198 in a high pressure end body 200.

The plunger 24 extends out of the end of the guide cylinder 190 and into a coaxial bore 202 in a liner 204. The liner 204 is fitted within a coaxial cavity 206 in the high pressure end body 200. An annular recess 199 in communication with a passage 201 which leads to the exterior of the end body 200. The recess and passage serve to exhaust fluid leakage from the bore 198.

The guide cylinder 190 abuts one end of the cavity liner 204. At the point of their contact, within an annular recess 208, are seated a pair of retaining rings 210 each having a triangular cross-section. When assembled together the rings have a rectangular crosssection. An O-ring 212 is compressed within the recess 208 by the retaining rings 210 to makea seal with the I bore 206. In addition, when the cylinder guide 190 is pressed against the retaining rings 210 they shift outwardly against the bore 206 so that they also make a tight seal.

A series of diametric orifices 214 in the liner 204 communicate between the bore 202 and an annular recess 216 in the exterior surface of the liner. The purpose of the orifices and the annular recess is to equalize the pressure within and without the liner such that it will fit fluid tightly with the plunger.

The plunger 24 terminates at an end 218 within the bore 202 and near its mouth. The ends 98 and 218 of the plungers 22 and 24 are shown in FIGS. 1 and 2 as they appear near the end of one piston stroke. The ends as they would appear near the end of the opposite piston stroke are shown in hidden line fashion as the reverse of their positions shown in full line fashion.

Opposite the end 218 of the plunger 24 is an output passage 220 in the end body 200 which communicates between its exterior and the fluid cavity 206. It is through this output passage that fluid is pumped under high pressure by the plunger 24 to whatever place the high pressure is desired. Suitable valve means (not shown) normally will be provided to close off the passage 220.

A pair of parallel tension rods 222 pass through bores, in series, in the end body 80, the connecting body 104, the connecting body 172, and the end body 200. An assembly of suitable nuts and washers 224 on the ends of each tension rod compress the end bodies, cylinders, and connecting bodies together along the common longitudinal axis 14 and put the rods 222 in tension. Mounted at both ends of one of the rods are L-shaped supporting brackets 226.

While the embodiment discussed in reference to FIGS. 1 and 2 has only two piston-cylinder assemblies, other embodiments have a plurality of piston-cylinder assemblies. The additional piston-cylinder assemblies of these other embodiments are constructed in a substantially identical manner as the piston-cylinder assemblies l and 12.

The ratio of the high pressure available at the outputs of the device to the pressure of the operating fluid from the external source is defined as the ratio of pressure intensification. This ratio is determined by the ratios of the cross-sectional areas of the pistons to the crosssectional areas of the plungers and the push rod. The pressure, denoted P available at the output from the cavity in the high pressure end body into which a plunger is driven, such as cavity 86, may be calculated as follows:

Where P low pressure of fluid from the external source applied against the piston heads;

P the high pressure of the fluid obtained at the exhaust port 100 of the high pressure end body 80;

A cross-sectional area of each of the pistons;

A cross-sectional area of the push rod 26 and the plungers 22 and 24;

The equation for the forces due to the fluid pressure P, A,= P, A,+ P, A, (end body) (assembly) (assembly) 80 12 P, A, P XA (push (plunger end rod end 162) 44) P /P [2 (A,l )]/A ratio of pressure intensification The addition of another piston-cylinder assembly increases the right hand side of the above force equation by the term P X A P X A This increases the ratio of pressure intensification to In general the ratio of pressure intensification for N double acting piston-cylinder assemblies is Thus where the number of double acting pistoncylinder assemblies is two and the ratio of the crosssectional area of the ends of the pistons to the crosssectional area of the plungers and the push rod is four, the ratio of the pressure intensification will be six. For the same ratio of cross-sectional areas of pistons to plunger and push rods, if the number of assemblies is three the ratio of pressure intensification will be nine.

By way of example only, if in the latter case the pressure of the fluid from the external source is 12,000 psi the output pressure from the device is approximately 108,000 psi. Naturally much larger ratios of pressure intensification are obtained in embodiments where the diameters of the pistons greatly exceed the diameters of the plungers and push rods.

The high pressure thus developed in the end body cavity 86 is also developed in the end body cavity 206 in the next half cycle of the operation of the device when the plunger 24 is driven into the bore 202. Through the use of suitable valve means (not shown) the fluid under high pressure is normally conveyed from the output passages and 220 to the desired use. Suitable valve means (not shown) also normally allow fluid at low pressure to enter an end body cavity as the plunger is withdrawn.

Although the

passages

100, 110, 112, 176, 178 and 220 are shown in FIGS. 1 and 2 as having threaded enlargements to receive pipe ends, other suitable low and high pressure fluid fittings may be used.

The terms and expressions which have been employed here are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described, or portions thereof, it being recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

v l. A pressure generating device comprising at least a first and a second piston, a push rod slidably interposed between the pistons, such that forces exerted on the second piston in the direction of the first piston will be transmitted to the first piston, said push rod being free to move relative to each of said pistons, a plunger oper- .ated by the first piston, resilient loosely fitting means interconnecting said plunger with said first piston, an end body having a cavity within it, a select end of the plunger being slidably mounted within the end body cavity in a fluid tight manner, and fluid input passages for simultaneously applying fluid under pressure to corresponding sides of the first and second pistons to move them in an axial direction and exert a force on the plunger.

2. A high pressure generating device as recited in claim 1 wherein the first and second pistons are double acting.

3. A high pressure generating device as recited in claim 1 wherein the cross-sectional area of each of the first and second pistons exceeds the cross-sectional area of the select plunger end slidably fitted within the end body cavity.

4. A pressure generating device for use with an external source of fluid comprising at least a first and a second hydraulic piston and cylinder assemblies arranged along a single longitudinal axis, the first assembly having a first cylinder with a first piston slidably mounted within it in a first coaxial bore, a first plunger axially driven by the first piston, resilient loosely fitting means interconnecting said first plunger with said first piston, a first end body having a coaxial cavity, a select end of the first plunger being slidably fitted within the first end body cavity in a substantially fluid tight manner, a first fluid output passage communicating between the first end body cavity and the exterior of the first end body, the second assembly having a second cylinder with a second piston slidably mounted within it in a second coaxial bore, and a push rod slidably interposed between the first and second pistons, said push rod being free to move relative to each of said pistons, the first and second assemblies having a first set of fluid input passages so that fluid from the external source may be applied to the first and second pistons to force them in the direction of the first end body.

5. A pressure generating device as recited in claim 4 wherein the first and second assemblies have corre and second assemblies together while putting the rods in tension.

7. A pressure generating device as recited in claim 4 wherein the first and second pistons are double acting and further comprising a second plunger axially driven by the second piston, resilient loosely fitting means interconnecting said second plunger with said second pis ton, a second end body having a coaxial cavity, a select end of the second plunger being slidably fitted in the second end body cavity in a fluid tight manner, a second fluid output passage communicating between the second end body cavity and the exterior of the second end body, the first and second assemblies having a second set of fluid input passages for applying fluid from the external source to the first and second pistons to force them in the direction of the second end body.

8. A pressure generating device as recited in claim 4 wherein the cross-sectional areas of each of the first and second pistons exceed the cross-sectional area of the end of the first plunger within the first end body cavity.

9. A pressure generating device comprising at least a first and a second piston, a push rod slidably interposed between the pistons, such that forces exerted on the second piston in the direction of the first piston will be transmitted to the first piston, said push rod being free to move relative to each of said pistons, a cylindrical plunger operated by said first piston, said plunger having first and second ends, a nut attached to theend of said first piston, said nut having a bore adapted to receive said first end of said plunger, said bore having a diameter larger than the diameter of said plunger, said nut and said plunger having aligned diametric bores, a slotted spring pin within said diametric bores interconnecting said plunger with said first piston, the diametric bore of said nut having a diameter larger than the diameter of said spring pin, an end body having a cavity within it, the said second end of the plunger being slidably mounted within the end body cavity in a fluid tight manner, and fluid input passages for simultaneously applying fluid under pressure to corresponding sides of the first and second pistons to move them in an axial direction and exert a force on the plunger.

1 Col.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTiON PATENT NO. 3,740,169 DATE?) June 19, 1973 Eduard L. J. Papen H is cerfifted that error appears in the above-identified patent and that said Latte-'5 Patent are hereby corrected as shown beiow:

Col. 2, line 25,

should read Col. 2, line 30,

should read should read Col. line 1,

should read Col. 8, line following line 8,

should read Col. 8, line following line 11,

should read- [SEAL] line 63,

"A third occurrence,

Signed and gcaled this A nest.

RUTH C. MASON Arresting ()fj'izer C. MRRSHALL DANN ('mnml'ssimu'r of Pale/1m and Trademarks

Claims

1. A pressure generating device comprising at least a first and a second piston, a push rod slidably interposed between the pistons, such that forces exerted on the second piston in the direction of the first piston will be transmitted to the first piston, said push rod being free to move relative to each of said pistons, a plunger operated by the first piston, resilient loosely fitting means interconnecting said plunger with said first piston, an end body having a cavity within it, a select end of the plunger being slidably mounted within the end body cavity in a fluid tight manner, and fluid input passages for simultaneously applying fluid under pressure to corresponding sides of the first and second pistons to move them in an axial direction and exert a force on the plunger.

5. A pressure generating device as recited in claim 4 wherein the first and second assemblies have corresponding parts which are substantially identical and interchangeable.

6. A pressure generating device as recited in claim 4 further comprising a pair of substantially parallel, spaced apart tension rods, the tension rods passing in series through the first end body and the first and second assemblies, and means mounted on the ends of the tension rods to compress the first end body and the first and second assemblies together while putting the rods in tension.

7. A pressure generating device as recited in claim 4 wherein the first and second pistons are double acting and further comprising a second plunger axially driven by the second piston, resilient loosely fitting means interconnecting said second plunger with said second piston, a second end body having a coaxial cavity, a select end of the second plunger being slidably fitted in the second end body cavity in a fluid tight manner, a second fluid output passage communicating between the second end body cavity and the exterior of the second end body, the first and second assemblies having a second set of fluid input passages for applying fluid from the external source to the first and second pistons to force them in the direction of the second end body.

9. A pressure generating device comprising aT least a first and a second piston, a push rod slidably interposed between the pistons, such that forces exerted on the second piston in the direction of the first piston will be transmitted to the first piston, said push rod being free to move relative to each of said pistons, a cylindrical plunger operated by said first piston, said plunger having first and second ends, a nut attached to the end of said first piston, said nut having a bore adapted to receive said first end of said plunger, said bore having a diameter larger than the diameter of said plunger, said nut and said plunger having aligned diametric bores, a slotted spring pin within said diametric bores interconnecting said plunger with said first piston, the diametric bore of said nut having a diameter larger than the diameter of said spring pin, an end body having a cavity within it, the said second end of the plunger being slidably mounted within the end body cavity in a fluid tight manner, and fluid input passages for simultaneously applying fluid under pressure to corresponding sides of the first and second pistons to move them in an axial direction and exert a force on the plunger.