US3659967A

US3659967A - Hydraulic intensifier

Info

Publication number: US3659967A
Application number: US40860A
Authority: US
Inventors: Ralph F Mcarthur; Max T Kardoes; Melle F Geurts
Original assignee: Kobe Inc
Current assignee: Kobe Inc
Priority date: 1970-05-27
Filing date: 1970-05-27
Publication date: 1972-05-02
Anticipated expiration: 1989-05-02

Abstract

A hydraulic intensifier operable by a fluid, such as oil, at relatively low pressures to deliver a fluid, such as water, at very high pressures for any desired purpose. The intensifier includes a fluid operated, double acting, reciprocating engine and two single acting, reciprocating pumps respectively located at opposite ends of and in alignment with the engine and connected to the engine for actuation thereby, the displacement of the pumps being small as compared to that of the engine so as to produce a discharge pressure many times the operating fluid pressure. The intensifier is capable of producing discharge pressures of the order of 30,000 to 70,000 psi, or higher, with operating fluid pressures of the order of 2,000 to 5,000 psi. Further, the intensifier is capable of transmitting power of the order of 50 horsepower, or more, in a relatively lightweight unit which is portable and relatively maneuverable.

Description

O United States Patent us] 3,659,967 McArthur et a]. 1 May 2, 1972 [541 HYDRAULIC INTENSIFIER 3,106,169 10/1963 Prosser et al. ..4l7/567 inventors: Ralph E McAnhur, Huntington Park; 37,195 12/1862 Fitzgerald ..92/l69 X Max T. Kardoes, Glendora; Melle F. Prima ry Examiner-Robert M. Walker Gems Angelesv Attorney-Harris, Kiech, Russell & Kern [73] Assignee: Kobe, lnc., Huntington Park, Calif.

ABSTRACT 22 Filed: May 27, 1970 A hydraulic intensifier operable by a fluid, such as oil, at rela- PP Nod 40,360 tiveiy low pressures to deliver a fluid, such as water, at very high pressures for any desired purpose. The intensifier ing y- -g 135;;7313313 51, iif iwi iifgli iitii"$311123?33235123553521; n Fo4b 39/10 Folb 11/02 located at opposite ends of and in alignment with the engine Fi Id Se h 417 397 404 A 542 567 and connected to the engine for actuation thereby, the dis- [58] e o are I placement of the pumps being small as compared to that of the 417/225 91/282 92/169 engine so as to produce a discharge pressure many times the operating fluid pressure. [56] Reierences Cited The intensifier is capable of producing discharge pressures of UNITED STATES PATENTS the order of 30,000 to 70,000 psi, or higher, with operating fluid pressures of the order of 2,000 to 5,000 psi. Further, the 31 5/1863 et "417/397 X intensifier is capable of transmitting power of the order of 50 161,441 3/1875 "417/397 horsepower, or more, in a relatively lightweight unit which is 305,972 884 SJOgl'fli p b and relatively maneuverable 2,642,045 6/1953 Potts ..4l7/397 X 2,548,472 4/1951 Gibson ..4I7/542 13 Claims, 7 Drawing Figures PATENTEDHAY 2 m2 3, 659 867 MELLEF- @Eu/enr fi 7569/? Offer/m m- HYDRAULIC INTENSIFIER BACKGROUND OF INVENTION The present invention relates in general to an apparatus for delivering a fluid, such as water, at a very high pressure.

More particularly, the invention relates to an apparatus which is operable by a fluid, such as oil, at a relatively low pressure to deliver a fluid, such as water, at a much higher pressure. Consequently, the apparatus is referred to herein as a hydraulic intensifier.

The invention uu'lizes a fluid operated, double acting, reciprocating engine similar to those disclosed in US. Pat. Nos. 2,134,174, 2,204,120 and 2,31 1,157, respectively issued Oct. 25, 1938, June ll, 1940 and Feb. 16, 1943, to Clarence J. Coberly. Consequently, the disclosures of these patents are incorporated herein by reference.

SUMMARY AND OBJECTS OF INVENTION General objects of the invention are: to provide a hydraulic intensifier which is operable by oil, or other fluid, at a relatively low pressure, e. g., 2,000 to 5,000 psi, to deliver water, or other fluid, at a very high pressure, e. g., 30,000 to 70,000 psi, or higher; to provide a hydraulic intensifier having such characteristics which is capable of transmitting substantial power, e.g., 50 horsepower, or more, in a relatively lightweight unit which is portable and relatively maneuverable; and to provide a hydraulic intensifier which is capable of long, continuous service with minimum repair and minimum down time for repair.

The invention contemplates achieving the foregoing general objects by providing, and a primary object of the invention is to provide, a hydraulic intensifier which includes a fluid operated, double acting, reciprocating engine and two single acting, reciprocating pumps respectively located at opposite ends of and in alignment with the engine and connected to the engine for actuation thereby, the ratio of the net areas of the engine to pump pistons being such as to provide discharge pressures many times that of the engine input pressures.

More particularly, the invention may be summarized as including, and an important object of the invention is to provide, a hydraulic intensifier which includes: a fluid operated, double acting, reciprocating engine; the engine including an engine cylinder containing an engine piston having engine piston rods extending therefrom in opposite directions; the engine including engine valve means for supplying operating fluid under pressure to opposite ends of the engine cylinder alternately; the engine valve means including an engine valve body connected to one end of the engine cylinder in axial alignment therewith; the engine valve means including a tubular engine valve movable in the engine valve body on one of the engine piston rods between operating positions wherein it supplies operating fluid under pressure to opposite ends of the engine cylinder, respectively; the engine valve means including means on the engine valve and the one engine piston rod for moving the engine valve between its operating positions in response to arrival of the engine piston at the ends of its stroke; two oppositely facing, single acting, reciprocating pumps respectively located at opposite ends of and in alignment with the engine; the pumps respectively including pump cylinders connected to the engine cylinder and the engine valve body; the pumps respectively including pump plungers reciprocable in the pump cylinders and connected to the engine piston rods; each of the pumps including inlet and outlet check valves controlling the admission and discharge of the fluid being pumped; and the cross-sectional area of the pump plungers being small as compared to the net cross-sectional area of the engine piston.

Another object is to provide a hydraulic intensifier of the foregoing character wherein each of the pumps includes an inlet and an outlet communicating with the outer end of the corresponding pump cylinder and respectively controlled by the corresponding inlet and outlet check valves. With this construction, the engine piston rods and the pump plungers are loaded in compression only, thereby avoiding fatigue failures due to tension loading. Still another object is to provide a hydraulic intensifier where the inlet and outlet check valves of each pump are arranged in tandem, i.e., are axially aligned, to avoid discontinuities in highly stressed pulsing sections of the pump, and to reduce the clearance volume to a minimum, thereby minimizing re-expansion losses which result in poor volumetric efficiency.

Yet another object is to provide a hydraulic intensifier including an elongated pulsation reducing chamber extending substantially the full length of the intensifier alongside the engine and pumps, and interconnecting the outlets of the pumps. This elongated chamber contains sufficient water, or other fluid, to smooth out pressure pulsations utilizing the compressibility of the fluid.

An additional object is to provide a hydraulic intensifier wherein each pump cylinder has a concentrically layered construction comprising prestressed layers. With such a construction, the pump cylinders are capable of withstanding the high discharge pressures involved without excessive wall thicknesses. This prestressed construction also resists failure by fatigue far better than does a single-walled configuration.

Another object is to provide a hydraulic intensifier wherein each pump cylinder incorporates means for balancing the internal and external axial pressure gradients to which the innermost layer or liner is exposed. With this construction, the liner may be made of a good bearing type material, e. g., bronze, to achieve a good fluid seal between the plunger and the liner without any danger of failure of the liner in hoop compression.

Still another object is to provide pasage means in each of the pump cylinders adjacent the axially inner ends thereof for bleeding 05 any leakage of pumped fluid between the pump cylinders and the pump plungers therein, and to provide similar passage means in the engine adjacent the respective ends thereof for bleeding ofi any leakage of operating fluid along the engine piston rods.

An additional object is to provide metal-to-metal fits for controlling leakage in both the engine and the pumps, no dynamic seals utilizing elastomers being employed. A related object is to provide static high pressure fluid seals in both the engine and the pump comprising lapped metal surfaces in preloaded sealing engagement by axially thermally shrinking outer tubes enclosing the members involved.

A further object is to provide a hydraulic intensifier wherein all valving members of the engine and the pumps are internal, no external valving members being required.

Yet another object is to provide radial external fluid connections which are orientable circumferentially to facilitate making field connections.

A still further object of the invention is to provide a structure wherein either pump can be removed readily for repair, or, preferably, for replacement by a factory rebuilt or reconditioned pump.

The foregoing objects, advantages, features and results of the present invention, together with various other objects, advantages, features and results thereof which will be evident to those skilled in the art of achieving very high fluid pressures, may be attained with the exemplary embodiment of the invention described in detail hereinafter and illustrated in the accompanying drawings.

DESCRIPTION OF DRAWINGS In the drawings:

FIG. 1 is an elevational view of a hydraulic intensifier which embodies the invention;

FIGS. 2, 3, 4 and 5 are enlarged, fragmentary, longitudinal sectional views respectively taken as indicated by the arrowed lines 2-2, 3-3, 4-4 and 5-5 of FIG. 1; and

FIGS. 6 and 7 are further enlarged, fragmentary, longitudinal sectional views respectively taken as indicated by the arrowed lines 6-6 and 7-7 of FIG. 2 of the drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT OF INVENTION Referring initially to FIG. 1 of the drawings, illustrated therein is a hydraulic intensifier of the invention which includes as its major components a fluid operated, double acting, reciprocating engine 12 and two single acting, reciprocating pumps 14 respectively located at opposite ends of and in alignment with the engine and connected to the engine for actuation thereby, coaxial spacer means 16 being interposed between the engine 12 and the pumps 14. As will be explained in more detail hereinafter, the engine 12 is operable by oil, or other fluid, at a relatively low pressure, e.g., 2,000 to 5,000 psi, to cause the pumps 14 to deliver water, or other fluid, at a much higher pressure, e.g., 30,000 to 70,000 psi, or more. The net piston area of the engine 12 is many times that of the pumps 14 to achieve pressure magnifications of the order indicated.

The fluid operated, double acting, reciprocating engine 12 is fundamentally the same as those disclosed in the aforementioned patents, and particularly U.S. Pat. No. 2,31 1,157. Consequently, the engine 12 will be described only generally herein.

Referring to FIGS. 3 and 4 of the drawings, the engine 12 comprises generally an engine cylinder 22 containing an engine piston 24 having engine piston rods 26 extending therefrom in opposite directions. The engine 12 includes engine valve means 28 for supplying operating fluid under pressure from a supply port 30 to opposite ends of the engine cylinder 22 alternately, spent operating fluid being discharged through a return port 32. The operating fluid, which may be oil, or any other suitable fluid, may be delivered to the supply port 30 by a triplex pump, not shown, such as that disclosed in US Pat. No. 3,077,836, issued Feb. l9, 1963 to Clarence .I. Coberly et al. The return port 32 may be connected to a reservoir, not shown, which furnishes fluid to the triplex pump.

More particularly, the engine valve means 28, which is located at one end of the engine cylinder 22 in axial alignment therewith, includes an engine valve body 34 connected to one end of the engine cylinder. One of operating piston rods 24 extends axially through the engine valve means 28 and slidable thereon within the engine valve body 34 is a tubular, differential area engine valve 36 of the type disclosed in US. Pat. Nos. 2,134,174, 2,204,120 and 2,3ll,l57, and particularly the latter.

The engine valve 36 is hydraulically movable between two axially spaced operating positions wherein it supplies operating fluid under pressure to opposite ends of the engine cylinder 22, respectively. When the engine valve 36 is in the operating position shown in FIG. 3, it supplies operating fluid under pressure from the port 30 to the adjacent end of the engine cylinder 22 through passages one of which is shown in FIG. 3 and designated by the numeral 38. When the engine valve 36 is in its otheroperating position, not shown, it connects the passage 38 leading to the adjacent end of the engine cylinder 22 to the return port 32.

When the engine valve 36 is in the operating position shown in FIG. 3, it connects the opposite end of the engine cylinder 22 to the return port 32 through passages 40, a transfer port 42, an external transfer passage 44 alongside the engine valve body 34 and the engine cylinder 22, and through a transfer port 46 and passages 48, FIG. 4, at the opposite end of the engine cylinder. Conversely, when the engine valve 36 is in its other operating position, not shown, it connects the opposite end of the engine cylinder 22 to the supply port 30 through the passages 40, the transfer port 42, the transfer passage 44, the transfer port 46 and the passages 48.

The engine valve means 28 also includes means of moving the engine valve 36 between its operating positions in response to arrival of the engine piston 24 at the ends of its stroke, such means including control port means 50 in one of the engine piston rods 26 which extends through the engine valve means. Thus, as the engine piston 24 approaches each end of its stroke, the control port means 50 causes the engine valve 36 to move to its other operating position to reverse the direction of movement of the engine piston.

As previously indicated, the foregoing structure and opera tion of the engine 12 are fully disclosed in the patents identified earlier in connection with the engine, and particularly US. Pat. No. 2,311,157. Reference is made to these patents for a more detailed disclosure if one is desired.

The end of the engine valve body 34 remote from the engine cylinder 22 terminates in a fitting 52, FIG. 3, and the end of the engine cylinder opposite the engine valve body terminates in a similar fitting 54, the two spacer means 16 respectively comprising windowed tubes 16 connected to such fittings. The two engine piston rods 26 extend into the respective spacer means or tubes 16 through seals 56 respectively carried by the

fittings

52 and 54. Any leakage of operating fluid between the piston rods 26 and the seals 56 is bled off through passages or passage means 58 in the fitting 52 and 54 and through drain lines 60 connected thereto. Such operating fluid leakage may be returned to the operating fluid reservoir, or otherwise disposed of. The engine valve body 34 includes inner and outer

tubular members

62 and 64, the latter being a fluid collecting sleeve which has a slip fit on the inner member.

Turning now to a consideration of the pumps 14, each includes a pump cylinder designated generally by the numeral 70 and threadedly connected to the corresponding spacer tube 16 at 72, FIGS. 2 and 5. Reciprocable in each pump cylinder 70 is a pump plunger 74 the cross-sectional area of which is small as compared to the net cross-sectional area of the engine piston 24, i.e., as compared to the difference between the over-all cross-sectional area of the engine piston and the cross-sectional area of the piston rods 26. Each pump plunger 74 projects from its cylinder 70 through a fitting 76 into the corresponding windowed spacer tube 16. The pump plungers 74 are detachably connected to the respective engine piston rods 26 within the spacer tubes 16 by connectors 78 which permit relative lateral movement of the pump plungers and the engine piston rods to compensate for any minor misalignments. The connectors 78 are accessible through the windows in the spacer tubes 16 to permit disconnection of the pump plungers 74 from the engine piston rods 26. Thus, whenever it is necessary to repair or replace one of the pumps 14, it may be detached readily by disconnecting the corresponding connector 78 and then disconnecting the corresponding pump cylinder 70 from the spacer tube 16 with which it is associated. As hereinbefore indicated, any pump 14 requiring service or repair is preferably replaced by a factory reconditioned pump.

Each pump cylinder 70 is provided at its axially outer end with an inlet comprising inlet passages 80 extending longitudinally from an inlet chamber 82 having an inlet nipple 84 connected thereto. The two inlet nipples 84 are interconnected by an inlet line 86 disposed alongside of and extending substantially the entire length of the hydraulic intensifier 10. The inlet line 86 is connected to a suitable source of water, or other fluid to be delivered at high pressure.

The inlet passages 80 of each pump 14 terminate into the corresponding pump cylinder 70 and are closed during the discharge stroke of the corresponding pump plunger 74 by an inlet check valve 88 in the form of a disc seatable against a core or valve seat member 140. As shown in FlG. 6, a compression spring 90 biases each inlet check valve 88 toward its seat.

Continuing to refer to FIG. 6 in particular, each pump 14 is provided at its axially outer end with an outlet in the fonn of an axial outlet passage 92 which communicates with the interior of the corresponding pump cylinder 70 through a central port 94 in the corresponding inlet check valve 88. Disposed in the line of the outlet passage 92 is an outlet check valve 96 biased axially inwardly against an outlet valve seat 98 by a compression spring 100. As will be apparent, the outlet check valve 96 is seated during the intake stroke of the corresponding pump plunger 74.

As shown in FIGS. 1, 2 and 5, the axially outer ends of the outlet passages 92 of the two pumps 14 are connected to elbow fittings 102 which, in turn, are connectedto tee fittings 104. The latter are interconnected by a ripple filter 106 located alongside of the engine 12 and the pumps 14 and extending substantially the entire length of the hydraulic intensifier 10. The ripple filter 106 is provided therein with a longitudinal bore 108 of relatively large diameter to provide a pulsation reducing chamber of substantial volume. With this construction, the chamber 108 contains sufficient water, or other fluid, to smooth out pressure pulsations, utilizing the compressibility of the fluid.

Discharge or delivery lines 110 for the high pressure fluid are shown as connected to the respective tee fittings 104 to discharge such fluid at both ends of the hydraulic intensifier 10. However, if delivery at one end only is desired, one of the delivery lines 110 may be omitted and the corresponding tee fitting 104 plugged.

Any leakage of the pumped fluid along the pump plungers 74 is bled off at the axially inner ends of the cylinders through passages or passage means 112 having drain lines 114 connected thereto. The drain lines 114 may return leakage to the source, or to waste.

Each pump cylinder 70 has a concentrically layered construction and comprises, as best shown in FIGS. 6 and 7, an outer layer 116, an outer intermediate layer 118, an inner intermediate layer 120 and an inner layer 122. The outer layer 116 includes a tube 124 threaded at its axially inner end on the layer 118 and at its axially outer end on a fitting 126, FIG. 6. Threaded lock collars 128 engage the ends of the tube 124 and another lock collar 130, FIG. 7, threaded on the layer 118 engages the axially outer end of the corresponding spacer tube 16.

The outer intermediate layer 118 is thermally shrunk onto the inner intermediate layer 120, thereby placing the layer 118 in tension and the layer 120 in compression. Prestressing the layer 120 in compression reinforces it by offsetting the tensile stresses produced by the high pressures in the corresponding pump cylinder 70, and reduces its range of cyclic tensile stress.

Preferably, the inner layer or liner 122 is made of a good bearing type metal, such as bronze. To prevent failure of the liner 122 in hoop compression at the high pressures generated within the pump cylinder 70, the liner is provided, as best shown in FIG. 7, with a plurality of axially spaced groups of circumferentially spaced ports 132, the axially spaced groups of ports being separated from each other by external annular seals, such as O-rings 134, carried by the liner and engaging the layer 120. With this construction, substantially the same axial pressure gradient which exists between the liner 122 and the corresponding pump plunger 74 is applied between the liner and the layer 120 outwardly thereof. Thus, the liner 122 is subjected to pressure gradient balancing to minimize the hoop compression stresses developed therein, and thus permitting the use of a compressively weak but good bearing type metal of the nature indicated, which is an important feature.

The inlet and

outlet passages

80 and 92 of each pump 14 are formed at least partially in the

core members

140 and 142, FIG. 6, which are placed in compression by thermally shrinking a sleeve member 144 and the member 126, respectively, thereon. This reinforces the

core members

140 and 142 against the high pressures in the outlet passage 92. More particularly, prestressing the

core members

140 and 142 in compression offsets the tensile stresses produced by the high internal pressures, and reduces their range of cyclic tensile stress.

Another important feature in connection with the valving region of each pump 14 is that the inlet and

outlet check valves

88 and 96 are arranged in tandem, i.e., in axial alignment. With this construction, discontinuities in highly stressed pulsating-pressure a sections of the pumps 14 are avoided, and clearance volumes are minimized, which are important features.

Another important feature of the invention is that, with the disclosed arrangement of the engine 12 and pumps 14, the engine piston rods 26 and the pump plungers 74 are loaded in compression, thereby avoiding any possibility of tension fatigue failures.

It is important to note that metal-to-metal fits are used throughout the engine 12 and the pumps 14 for all relatively movable parts. No elastomeric or other nonmetallic parts are used for dynamic sealing.

Discussing more general features of the hydraulic intensifier 10, it is sufliciently compact and light in weight that it can be movably mounted for relatively easy maneuvering. At the same time, it is capable of transmitting power in efi'ective quantities. For example, a hydraulic intensifier 10 of the nature disclosed has been constructed which is capable of generating a discharge pressure of 70,000 psi with an operating fluid pressure of 5,000 psi, while transmitting in excess of 50 horsepower, with a total weight for the unit of a little over 500 pounds and a total length of about 11 feet. As will be apparent, such a unit is capable of being maneuvered quite readily.

Although an exemplary embodiment of the invention has been disclosed for purposes of illustration, it will be understood that various changes, modifications and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as defined by the claims which follow.

We claim as our invention:

1. In a hydraulic intensifier operable by a fluid at a relatively low pressure to deliver a fluid at a very high pressure, the combination of:

a. a fluid operated, double acting, reciprocating engine;

b. said engine including an engine cylinder containing an engine piston having engine piston rods extending therefrom in opposite directions;

c. said engine including engine valve means for supplying operating fluid under pressure to opposite ends of said engine cylinder alternately;

. said engine valve means including an engine valve body connected to one end of said engine cylinder in axial alignment therewith;

e. said engine valve means including a tubular engine valve movable in said engine valve body on one of said engine piston rods between operating positions wherein it supplies operating fluid under pressure to opposite ends of said engine cylinder, respectively;

f. said engine valve means including control means on said one engine piston rod for causing said engine valve to move between its operating positions in response to arrival of said engine piston at the ends of its stroke;

g. two oppositely facing, single acting, reciprocating pumps respectively located at opposite ends of and in alignment with said engine;

h. said pumps respecn'vely including pump cylinders connected to said engine cylinder and said engine valve body;

i. said pumps respectively including pump plungers reciprocable in said pump cylinders and connected to said engine piston rods;

j. each of the said pumps including inlet and outlet check valves conn'olling the admission and discharge of the fluid being pumped; and

k. the. cross-sectional area of said pump plungers being small as compared to the net cross-sectional area of said engine piston.

2. A hydraulic intensifier as set forth in claim 1 wherein each of said pumps includes an inlet and an outlet communicating with the outer end of the corresponding pump cylinder and respectively controlled by the corresponding inlet and outlet check valves.

3. A hydraulic intensifier according to claim 2 wherein the inlet and outlet check valves of each of said pumps are axially aligned.

4. A hydraulic intensifier as defined in claim 2 including a pulsation reducing chamber interconnecting the outlets of said pumps.

5. A hydraulic intensifier according to claim 4 wherein said chamber is elongated and extends substantially the full length of said intensifier alongside said engine and pumps.

6. A hydraulic intensifier as set forth in claim 1 wherein each of said pump cylinders has a concentrically layered construction.

7. A hydraulic intensifier as defined in claim 6 wherein each of said pump cylinders comprises prestressed layers.

8. A hydraulic intensifier as set forth in claim 6 wherein each of said pump cylinders incorporates means for minimizing hoop compression in a radially innermost layer thereof.

9. A hydraulic intensifier according to claim 2 including passage means in each of said pump cylinders adjacent its axially inner end for bleeding off any leakage of pumped fluid between such cylinder and the pump plunger therein.

10. A hydraulic intensifier as defined in claim 9 including passage means in said engine adjacent the respective ends thereof for bleeding off any leakage of operating fluid along said engine piston rods.

11. A hydraulic intensifier as set forth in claim 1 including an external passage alongside said engine cylinder and said engine valve body for transferring operating fluid between said engine valve means and the end of said engine cylinder opposite said engine valve means.

12. In a hydraulic intensifier operable by a fluid at a relatively low pressure to deliver a fluid at a very high pressure, the combination of:

a. a fluid operated, double acting, reciprocating engine;

b. two single acting, reciprocating pumps respectively located at opposite ends of and in alignment with said engine and connected to said engine for actuation thereby;

c. the displacement of said pumps being small as compared to that of said engine;

d. each of said pumps including a pump cyiinder having a concentrically layered construction and including prestressed layers; and

e. each of said pump cylinders having in a radially innermost layer thereof axially spaced fluid passage means for substantially balancing the internal and external fluid pressures applied to said radially innermost layer at any point along the length thereof to minimize hoop compression in said radially innermost layer.

13. A high pressure pump cylinder as defined in claim 12 ineluding annular seals disposed between each radially innermost layer and the layer radially outwardly thereof and separating said passage means from each other.

i i i t i

Claims

1. In a hydraulic intensifier operable by a fluid at a relatively low pressure to deliver a fluid at a very high pRessure, the combination of: a. a fluid operated, double acting, reciprocating engine; b. said engine including an engine cylinder containing an engine piston having engine piston rods extending therefrom in opposite directions; c. said engine including engine valve means for supplying operating fluid under pressure to opposite ends of said engine cylinder alternately; d. said engine valve means including an engine valve body connected to one end of said engine cylinder in axial alignment therewith; e. said engine valve means including a tubular engine valve movable in said engine valve body on one of said engine piston rods between operating positions wherein it supplies operating fluid under pressure to opposite ends of said engine cylinder, respectively; f. said engine valve means including control means on said one engine piston rod for causing said engine valve to move between its operating positions in response to arrival of said engine piston at the ends of its stroke; g. two oppositely facing, single acting, reciprocating pumps respectively located at opposite ends of and in alignment with said engine; h. said pumps respectively including pump cylinders connected to said engine cylinder and said engine valve body; i. said pumps respectively including pump plungers reciprocable in said pump cylinders and connected to said engine piston rods; j. each of the said pumps including inlet and outlet check valves controlling the admission and discharge of the fluid being pumped; and k. the cross-sectional area of said pump plungers being small as compared to the net cross-sectional area of said engine piston.

12. In a hydraulic intensifier operable by a fluid at a relatively low pressure to deliver a fluid at a very high pressure, the combination of: a. a fluid operated, double acting, reciprocating engine; b. two single acting, reciprocating pumps respectively located at opposite ends of and in alignment with said engine and connected to said engine for actuation thereby; c. the displacement of said pumps being small as compared to that of said engine; d. each of said pumPs including a pump cylinder having a concentrically layered construction and including prestressed layers; and e. each of said pump cylinders having in a radially innermost layer thereof axially spaced fluid passage means for substantially balancing the internal and external fluid pressures applied to said radially innermost layer at any point along the length thereof to minimize hoop compression in said radially innermost layer.

13. A high pressure pump cylinder as defined in claim 12 including annular seals disposed between each radially innermost layer and the layer radially outwardly thereof and separating said passage means from each other.