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Publication numberUS2979903 A
Publication typeGrant
Publication dateApr 18, 1961
Filing dateJun 21, 1957
Priority dateJun 21, 1957
Publication numberUS 2979903 A, US 2979903A, US-A-2979903, US2979903 A, US2979903A
InventorsLeonard R Beck
Original AssigneeStudebaker Hydraulic Products
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Air-hydraulic apparatus
US 2979903 A
Abstract  available in
Images(3)
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Claims  available in
Description  (OCR text may contain errors)

April 18, 1951 Filed June 21, 1957 1.. R. BECK 2,979,903

AIR-HYDRAULIC APPARATUS 3 Sheets-Sheet 1 f g' 4 j". Z 20 HI I I I n 36 5 0 41A /7 o INVENTOR. LEONARD/g5 f ,7 W, ATO/VEY- April 18, 1951 L. R. BECK 2,979,903

AIR-HYDRAULIC APPARATUS Filed June 21, 1957 3 Sheets-Sheet 2 2 Z 7 N fim MM 7 0 W F e w n L x x 0 w M M a w w W w m w ii 5 8 W X fifl U a J 2 w w 9 wfl w April 18, 1961 R. BECK AIR-HYDRAULIC APPARATUS Filed June 21, 1957 3 Sheets-Sheet I5 nited States Patent'O" 2,979,903 AIR-HYDRAULIC APPARATUS Leonard R. Beck, Villa Park, Ill.,, assignor to Studebaker Hydraulic Products Company, Melrose Park, Ill., a corporation of Illinois Filed June 21, 1957, Ser. No. 667,212

8 Claims. (Cl. 60-545) The principal object of the present invention is the provision of an air-hydraulic system for sequentially and automatically applying low and high hydraulic pressure to a utilization line to operate a desired hydraulic instrumentality such as a press, ram,.vise, or other hydraulically actuated device. v

Another important object is the provision of pneumatic means for rapidly actuating and restoring the hydraulically operating parts of said system.

A further important object is the provision of a compact, rugged, and economically manufactured and operated air-hydraulic device utilizing multiple air-hydraulic pistons working in a simple unitary cylinder assembly having multiple chambers for the several pistons and novel valve means efliciently situated therein relative to certain chambers for cooperation with pistons sequentially controlled thereby.

Still another object relates to the provision of a novel sequence valve operated by the main working air pres- 2,979,903 Patented Apr. 18, 196i 2 As viewed in Fig. 3, the air-hydraulic unit 14 consists of a pair of sleeve cylinders 15 and 16 clamped together between a top or head block casting 17 and a bottom blockcasting 18, there being an intermediate block 19 clamped between the two sleeves by means of tie rods 20 (Fig. 1) which secure the assembly firmly together. -Working in the upper cylinder is a floating piston 25,

7 having loosely attached thereto by plate 26 secured by bolts 27, the annular head 28 of a piston rod 30. A comparable construction is shown to larger scale in Fig. 5, which exemplifies the lower piston, to be later described.

The upper or primary piston 25 is normally lowered by a large compression spring 31 working against the upper block 17, the upper end portion of the piston rod passing througha bore in block 17 guarded by a seal in seat 32, with the upper extremity of the rod projecting into a transparent plastic dome member 35 to which is exposed the open upper end of a longitudinal escape bore '34 leading down into, said rod. A small crosswise bleeder port 33 leads into the escape bore 34 and serves, underconditions to be described, to pass oil and any entrained air into the dome 35 when piston 25 is lowered past theseal level32.

Seated in a, bore 17A (Fig. 4) is a small insert piston 38 (Fig. 3) bored to receive a ball check 40 seated against the reduced passagebore 173 (Fig. 4) by a spring 39 sure automatically responsive to certain. attained backpressure conditions, to eifectuate low and high pressure piston operations.

Yet another object is the provision of pilot valve means as part of said unitary air-hydraulic cylinder means. A still further object is the provision of a control circuit and cooperative instrumentalities for starting and stopping cyclic operation of said air-hydraulic system which begin with a low-pressure operation and conclude following automatic shifting to a high-pressure operation when a desired low-pressure operation is achieved.

. Additional aspects of novelty and utility characterizingthe invention relate to details of the construction and operation of the embodiment described hereinafter in view of theaccompanying drawings, in which:

Fig. 1 is a perspective view to enlarged scale of the novel air-hydraulic unit;

Fig. 2 is a perspective view of the air-hydraulic press in which the unit of Fig. 1 may be utilized;

Fig. 3 is a vertical sectionthrough an air-hydraulic I unit of the type depicted in Fig. 1; Y I

Fig. 4 is a horizontal plan detail of the head block, to enlarged scale, and taken along lines 44 of Fig. 3; Fig. 5 is an enlarged sectional detail through one of the floating-piston structures; p

Fig. 6 is a schematic of an air-hydraulic system,'utilizing the unit of Figs. 1 or 3.

, The novel air-hydraulic unit depicted in Fig. 1, while adaptable to general application, is intended for use in a press such as. illustrated in Fig. 2, which consists of a cast arbor frame 10 having flanges 11 adapted to seat a bench plate or jig (not shown) for holding the work beneath a ram 12 'thereabove.

' The rearwardframe portions 13 .are open and of a dimension to receive therein the air-hydraulic unit 14' (Fig. 3). This ball check constitutes a part of what is termed a pilot check valve means, the purpose of which will appear more fully hereinafter; and the appertaining entrance end of the bore thereof is closed by a connection plug 41 or a nipple 41A, such as shown in Fig; 1. I At.the opposite side of the head block 17 from the ball check (Fig. 3) is a small pilot piston 44, working in a bore 17D (Fig. 4, also) and having a noseportionAS which moves inwardly to engage and unseat the ball of the pilot valve.

A short feed bore 46 (Figs. 4 and 6) leads down: wardly through the bottom of the head block 17 from the pilot piston bore -17D and opens into the cylinder 15 to pass pilot oil to .and from line=100.

Oil also passes at certain times into the dome 35 7 through bores 33, 34, the. dome being sealed ontothe head block by a clamp block 36 secured by the tie rods, there being ascrew-type air-relief valve 37 atthe top of the dome for escape of entrained air rising with the reserve overflow oil.

' The intermediate block 19 houses what is termed the sequence valve, which consists of a small piston 50 (Fig.

3) working in a bore 51 closed at the outside by a plug 52 (or a nipple plate' 52A, as in Fig. 1) with a spring 53 normally retracting the piston to disengage its reduced nose portion 54 from engagement with a sequence piston 55 working in an aligned bore 56 communicating with bore 51. The outer end of the bore 56 is closed by a connection plug 57 or by a coupling nipple.

The front ofthe piston 55 is provided with a seat 58 for a suitable seal, such as an O-ring.

, Vertical, horizontally-offset duct bores 59 and 60 lead from the upper face of the intermediate block (beneath upper piston 25) past the sealing end 58 of the sequence piston (when latter is open or shifted to the left, Fig. 3)

' to the lower face of the intermediate block and therefore into. the lower cylinder 16. w

Working in the lower cylinder 16 is another floating pis ton 70, part of a' booster piston means, which is basically identicalto theupper piston 25. The piston rod 77 of theiboosterpiston passes through a bore and sealing' means 79 in the lower block 18. p I

When the lower booster piston is driven downwardly, its

piston rod 77 passes down into a small booster cylinder 80 attached to theblock 1 8,and adapted to contain hydraulic liquid such as oil, which will be passed into and out of this cylinder through a coupling port 81, so that the rod 77 becomes a piston as respects the cylinder 80.

In Fig. 5 there is shown an enlarged detail of the booster piston (which also is illustrative of the floating piston construction generally) and in which the piston rod :77 is contrived to be shiftable a slight amount laterally of its pis: ton member 70 owing to the provision in the latter O f'aH enlarged cavity 74 to receive a head plate 73 on the. rod, together with a similarly enlarged bolt-head cavity 76 in the piston itself to receive the head of a retaining bolt 75 engaging in the rod; and the further provision of a retaining plate 71 held tightly against the underside .of the piston by bolts 72, this plate having a bore 78 which is slightly oversize to permit a limited wobble to the piston rod and a correspondingly limited shiftability of the head plate 73 in its seat 7 4 owing to a sufiicient thinning of said head plate to permit this movement, notwithstanding that the retaining plate 71 is pulled up in tight fit again'st'the bot tom of the piston.

As a result of the foregoing floating piston construction, a good yet free-working fit is possible for both the piston Elndfiits rod without close-tolerance machining or plating or t. 7

A further feature of the invention is the air-hydraulic booster system utilizing the novel air-hydraulic unit of Figs. 1 and 3 and a press ram, such as shown in Fig. 2, said system being illustrated in Fig. 6 wherein the-air-hydraulic unit 14, the press or ram unit 10, and'certain control appendages are shown schematically and connected in an air-hydraulic circuit operable cyclically in two phases, namely: a low-pressure phase and a high-pressure phase.

In the system of Fig. 6 the'upper or pilot cylinder 15 and a part of the dome 35 are filled with working oil, as also is the lower booster cylinder 80. i

Housed within the upper forward cavity portion of the press arbor 10 is a ram cylinder 90 in which Works a ram piston 91 having above it a quantity of working oil. The ram piston rod 92 projects downwardly into. space above the bench portion 11 and there becomes the exposed working ram 12. The underside of the ram piston 91 is an air chamber which will receive compressed air for the return of the ram, as will appear hereinafter.

The upper working oil chamber 90of the ram connects via oil duct 100 to the bottom of the booster cylinder 80 from which high-pressure booster oil will be passed to the ram cylinder 90 and vice versa. Communicating into oil spring 53 and flow regulating valve 113, the sequence piston or valve 55, will be firmly seated (i.e. inwardly in Fig. 6) and air cannot pass to port 60 but will be passed via port 59 only to the upper pilot or primary cylinder 15 to drive piston 25 upwardly and displace oil past the pilot valve into line 100 via connection 101.

During the foregoing operation the booster piston 7% stands still since the port 60 is now closed by sequence valve 55.

Low-pressure oil now enters cylinder 90 from line 1539 and drives the ram piston 91 and ram 12 downwardly until the ram encounters the work assumed to be in place on bench 11.

When the ram bears on the work and therefore encounters resistance, the back pressure in line 100 builds up instantly, with the result that the upper primary or pilot piston 25 can no longer move and the pilot check valve 40 closes, because the fluid pressures on both sides of the ball check 40 now become equal and the closing efiort of check spring 39 then prevails.

Under the foregoing conditions, owing to the aforesaid closure of pilot check valve 40 resulting from the aforesaid back pressure encountered by piston 25, the sequence valve means comes automatically'into play and the sequence plunger 50 now overcomes the effort of spring 53 and forces the sequence plunger 50 inwardly to back 011 the sequence valve piston 55 and open port 60 to the lower or secondary piston 70, which now drives its piston rod 77 into the booster cylinder and forces oil at much higher pressure (by reason of the working-area ratios of part 70 to part 77) into the ram cylinder, with a resultantly great increase in the force applied by ram 12 to the work.

The aforesaid booster pressure is applied until the limit switch 99 (pro-adjusted to a desired pressure response) closes to actuate the control valve by energizing solenoid 132 via conductor 129, the now (and normally) closed B contacts 130, and conductor 131, thus closing ports 127 and opening ports 128 and the exhaust port 134 so that the pressure may be relieved from the upper and lower cylinders via lines 114, 112.

The series B contacts 130 temporarily break the limit switch circuit to the return or reset solenoid 132 as a safety line 100 is an adjustable type pressure-sensitive limit switch 99 to be described.

The pilot valve piston 44 receives compressed air via duct 102 leading from a solenoid control valve 110 connecting with a supply of compressed air 109, said valve being shown closed to entry of air into line .102 in the condition of Fig. 6.

Another air line 112 branches from said control valve around through a regulating valve 113 in behind the sequence plunger 50, while another connection 114 from line 112 connects behind the sequence-valve piston 55. v

The normal and starting condition of the system is depicted in Fig. 6, and if it is assumed that an object of work isto be placed on the press anvil or bench 11 to be en gaged by the ram 12, the operator will start the cycle by simultaneously depressing two control-switch buttons A and B which may be located conveniently to the press unit, or on it, as desired.

The result of the foregoing switch operation will be to close a starting circuit across the A contacts 120, which are in series with B contacts 121 to the common return conductor or ground G, thereby energizing via conductors 123, 124, the solenoid 125 from power supply,126, which in turn will open the control valve ports,127 and close ports 128, thus admitting compressed air into line 112 and applying same as shown by solid-line arrows to the sequence valvev piston 55 and also to the sequencezplufnger 50, but because of the pressure dilie'rential caused by measure, the control valve being of a known construction such that the valve slides controlled by the two solenoids and 132 will remain in whatever position the solenoid last to be energized leaves them.

Closure of the limit switch 99, as aforesaid, and consequent admittance ofreturn air (as denoted by dotted arrows) into lines 102, 103, 104, results in returning pistons 70 and 91 tostarting position, and in action of the pilot piston 44 in forcing open the pilot ball check 40 to admit part of the returning oil back into cylinder 15 and, residually, into' the sight glass or dome 35 where it may be observed for condition as to level, presence of air bubbles denoting infiltration, and the cleanliness of the oil generally. Exhaust valve means 134, 135 releases air from ports 59, 6t), on resetting.

The returning oil passes into and out of the upper primary cylinder 15, via the offset port 46 (Fig. 4 also), which opens into the meeting portions of pilot bores 17A, 17B, 17B; and while the primary piston 25 (Fig; 3) is in a lowered position to dispose the transverse bleeder port 33 below seal 32, it will be apparent that the escape bore 34 in the piston rod is thereby temporarily rendered di-. rectlyopen into the dome 35 through thepilot duct 46 (Fig. 4) so that an over-flow portion of the returning oil can enter the dome 35, as previously noted, whereby the dome 35 constitutes a surplus reservoir for cylinder 15 as well as a sight glass, so that oillosses will be automatically made up from the reserve in dome 35. Spring 31 assists in positively and quickly returning (lowering) the primary piston to starting position.

Upon the restoration of pistons 25 and 70 to starting position, the limit switch 99 normally will open, and the operating cycle may be considered at an end. Should switch 99 fail to open owing to a pressure lock in line 100, the circuit via conductor 131 to reset solenoid 132 would nevertheless be broken at control switch B, which must be operated along with switch A to start the cycle.

It will now be apparent that the highly compact device of Figs. 1 and 3 affords an automatically acting airhydraulic mechanism embodying only a few rugged and simple components efficiently arranged in a small unitary assemblage capable of utilization in a variety of cooperative devices of which one example is portrayed and described in view of Figs. 2 and 6. v

The fast action of air operation for the primary working stroke of the pilot piston in bringing the ram into quick contact with the work, and thereafter automatically applying high pressure from-the booster means 70, 77, 80, together with quick return of action by air operation, renders the device, and the system of Fig. 6 which utilizes it, a highly useful tool.

If desired, the hydraulic circuit of Fig. 6 may be operated without the flow valve 113, it being understood that the automatic sequencing principle is not altered by so-doing for the reason that the purpose of the flow valve is to compensate for friction in line 100 and (sticking or starting resistance in the Work piston 91 which, owing to ambient temperature changes, periods of idleness, etc., may sometimes cause just enough spurious back pressure to exist in line 100 and the ram to throw the sequence valve. The valve 113 is adjustable to meet such variable working conditions and render the sequence'valve sensitive only to the intended magnitude of back pressure in the working line 100 as distinguished from such spurious back pressures.

I claim:

1. Air-hydraulic pressure booster apparatus for use with an hydraulic utilization line to be pressurized comprising: piston means'including at least a low-pressure piston and a high-pressure piston and cylinder means in which the same work under air pressure acting in corresponding air chambers on one side of each piston, lowpressure working liquid being displaced into said line from the opposite side of said low-pressure piston, the chamber on the opposite side of the high-pressure piston being a return-air chamber; force-multiplying piston means situated on the opposite side of the high-pressure piston and actuated thereby for displacing working liquid into said line at substantially higher pressure than said low-pressure liquid; normally closed pilot valve means interposed in the working liquid-displacement path between said low-pressure piston and said line and acting responsive to displacement of the low-pressure piston means to admit said liquid into said line until a predetermined working back pressure is reached therein and thereupon to close against said back pressure; and se quence valve means connected with said air pressure and having two operating conditions in the first of which said air pressure is connected thereby with the air chamberof the low-pressure piston, and in the second of which said air pressure is connected thereby to the air chamberof the high-pressure piston, said sequence valve means in cluding means responsive to back pressure of a predetermined degree and sensed thereby in said air pressure reflected by-said low-pressure piston for actuating the valve from the first to the second condition automatically to admit said air pressure to said high-pressure piston to pressurize said line further when said degree or back pressure is reached, together with selective control valve means connected for operation to start and stop application of air pressure to the sequence valve means, or to selectively admit said air pressure to said return chamber and said pilot valve means to restore the piston means and working liquid to a predetermined, substantially zeropressure starting condition.

2. Apparatus according to claim 1 wherein said cylinder means is a multi-chambered device constructed as a unit with said lowand high-pressure pistons each working in contiguous ones of said cylinders with their respective.

air chambers juxtaposed, and said sequence valve means is interposed at the contiguum between said chambers to separate one from the other and includes ports communicating respectively with said chambers for admission of air pressure thereto, as set forth.

3. Apparatus according to claim 2 in which said sequence valve means includes a sequence piston working in a cylinder communicating with said air pressure and at all times through one of said ports into said lowpressure air chamber and having a port into the highpressure air chamber closed thereby in a certain position corresponding to said first operating condition of the valve, said sequence piston being moved normally by said air pressure to said certain position to close only the highpressure port; together with a spring-loaded plunger having pressure-regulated connection with said air pressure so as to be movable by the latter responsive to appearance of said predetermined degree of back pressure at said low-pressure port whereby to move said sequence piston to a position corresponding to the second condition to open said high-pressure port for displacement of the high pressure piston.

4. In an air-hydraulic booster device, a unitary casing structure providing a plurality of coaxially aligned piston cylinders with piston means respectively working therein, two of said cylinders being contiguous and the respective first and second piston means thereof dividing each of the same into corresponding'head and bottom chambers; sequence valve means situated in said structure between said two cylinders so as to be subjacent to the respective head chambers thereof and having a compressed air inlet and first and second outlet ports respectively communicating into the head chambers for the first and second pistons for admission of pressure air to displace at certain times the respective pistons therein, a first one of said pistons constituting a low-presusre air piston and the other a high-pressure air piston, the latter having a return air chamber on the bottom side thereof, and the low-pressure piston having low-pressure working liquid in the bottom chamber thereof to be displaced into a working line; a third cylinder constituting a booster-liquid cylinder having a booster piston coaxially displaced with the high-pressure air piston but of substantially lesser diameter than the latter to displace booster working liquid into said line at a multiplied pressure higher than that of the low-pressure working liquid; said sequence valve means including a valve plunger and a spring-loaded plunger piston and at all times admitting said pressure air to the head chamber for the low-pressure air piston to efiect displacement of the same and the appertaining low-pressure working liquid as aforesaid; said valve plunger being moved by said pressure air to normally close the second port and being movable by said plunger piston when the back pressure on said pressure air is of a certain magnitude to open the port to the second head chamber for the high-pressure air piston, said structure including outlets for passing the lowand high-pressure liquid into a working line, and also for admitting return air pressure to said return air chamber.

. 5'. In air-hydraulic booster apparatus improvements comprising: a unitary compound-piston assembly providing aligned cylinder cavities for a plurality of coaxially movable pistons each working in one of the same, and two of which are air-driven and have adjacent air-driving chambers, and constitute first and second contiguous pistons having a predetermined starting position; a sequence valve situated as part of said assembly between said chambers and having ports communicating respectively therewith, said valve being adapted to have pressure air applied thereto from a source and including valve means having two difierential operating conditions, the

' 7 first of which corresponds to the existence of less than a predetermined back pressure on said pressure air and the second of which corresponds to the existence of at least said predetermined back pressure on said pressure air causing operation to admit pressure air to the second of said air chambers; means providing for connection to an hydraulic Working line for a working fluid in which said back pressure conditions will occur; means providing a low-pressure working fluid chamber on the side of said first contiguous piston opposite the air-chamber side thereof, means providing a high-pressure Working fluid piston means and chamber on the side of the second contiguous piston opposite from the appertaining air cham ber; means connecting said lowand high-pressure fluid chambers into said working line; and means for regulating the air pressure applied to said sequence valve for adjusting the magnitude of back pressure required to actuate the sequence valve from the first to the second condition.

6. In an air-hydraulic booster system of the type having separate lowand high-pressure liquid-displacing pistons adapted to be air-driven in succession from a common pressurized air line for pressurizing a utilization line, improvements comprising: sequence-control means for effecting sequential operation of said pistons responsive to sensing of a predetermined back-pressure in the air side of the system, said valve means including an airactuated sequence valve adapted for connection to said air line and having outlet ports respectively communicating with the air drive sides of the lowand high-pressure pistons, together with air-driven valve member exposed constantly to said air pressure and moved normally thereby to close the outlet port to the high-pressure piston, said valve having a second air-moved member also exposed to said air pressure for urgency thereby in opposition to said first member to move the latter to open said outlet to the high-pressure piston; and means yieldingly resisting the opposition movement of the second member, whereby diiferential action of the latter is achieved wherein said opposition movement occurs when the back pressure on the first member is greater than a certain value; and air pilot valve means including a check valve interposed in the flow of low pressure liquid to said utilization line to prevent back flow of the liquid when said high-pressure displacement occurs, together with an air pilot plunger adaptedto be displaced by air pressure for opening said check valve to permit return of working liquid from said line to the low-pressure piston, at least.

7. Air-hydraulic booster apparatus comprising a multiple-cylinder casing constructed as a unitary assembly and including at least three linearly-aligned cylinder cavities each with a piston working therein, a first piston having on one side thereof a low-pressure working liquid displaced thereby and on the other side thereof an air chamber; a second piston having on each side thereof an air chamber, one of which is subjacent the air chamber of the first piston and the other of which is a return air chamber; a third piston driven by the second piston and displacing high-pressure liquid; means providing outlet connections for the lowand high-pressure liquids into a work line; a spring-loaded pilot check valve, part of said assembly, yieldingly closing off the outflow of low-pressure liquid into said line, and including an air-driven pilot piston movable to open said check valve; a sequence valve situated within said assembly between the subjacent chambers and having first and second outlet ports, one leading into each of said subjacent chambers, and a third inlet port adapted for connection with a source of pressure air, the first port to the chamber of the first or low-pressure piston being at all times open, said sequence valve including a first air-driven sequence member normally displaced by said pressure air to close the second port; a differential member in the sequence valve yieldingly urged away from, but movable by pressure air to displace, the sequence member to open the second port but normally of insufficient force to do so; means directing said pressure air against the differential member to augment said force when a certain back pressure exists on the first piston and said first sequence member, whereby the pressure air is ported to the second piston; and means for admitting control air to said return air chamber of the second piston and said air pilot piston to restore the first, second, and third pistons to a normal condition, and open the pilot check valve for return of displaced low-pressure liquid from said work line.

8. In an air-hydraulic system having two air-driven liquid-displacing pistons connecting into a pressure line to be operated in sequence automatically from a starting position under control of back-pressure conditions arising when the first or low-pressure piston encounters a certain resistance and a second or high-pressure piston augments the liquid pressure in said line, improvements in sequence control means comprising: a sequence valve adapted to be connected in an air pressure line between a pressure source and the air-driven side of said pistons and passing said pressure continually to the first or low-pressure piston, said valve having an air-displaceable valve member exposed to said pressure and moved to normally close off said pressure from the air-driven side of the second or high-pressure piston, together with an air-displaced differential member cooperable with the valve member and also exposed to said pressure for movement tending to displace the valve member oppositely to pass said pressure to the first piston, spring means being provided to yieldingly oppose said tending movement of the diiterential member so long as the back pressure on the valve member does not exceed a certain value, said opposition being overcome by action of said air pressure when said value is exceeded to admit the air pressure to the second piston; and air-released, normally closed pilot check valve in the path of outfiowing low-pressure liquid into said line; and piston means cooperable with said check valve and operated by air pressure for opening said check valve to permit return of low-pressure liquid from said line on movement of the first piston back to starting position.

References Cited in the file of this patent UNETED STATES PATENTS 791,075 Carpenter May 30, 1905 825,301 Coddington July 10, 1906 881,376 Carpenter Mar. 10, 1908 2,351,872 Parker June 20, 1944 2,403,912 Doll July 16, 1946 2,526,956 Kugler Oct. 24, 1950 2,603,067 Nissim July 15, 1952 2,744,802 Strayer May 8, 1956 2,793,089 Anderson May 21, 1957 2,827,766 Hufford Mar. 25, 1958

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3867871 *Apr 26, 1973Feb 25, 1975Int Harvester CoPiston-to-rod detachable connection
US4024802 *Nov 6, 1975May 24, 1977International Harvester CompanyHydraulic piston and rod assembly
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US4719844 *Nov 15, 1984Jan 19, 1988Adolph Coors CompanyFor pumping abrasive material such as mud during a drilling operation
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US5169295 *Sep 17, 1991Dec 8, 1992Tren.Fuels, Inc.Method and apparatus for compressing gases with a liquid system
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US5387089 *Dec 4, 1992Feb 7, 1995Tren Fuels, Inc.Method and apparatus for compressing gases with a liquid system
Classifications
U.S. Classification60/541, 92/255, 92/116, 60/593, 92/151, 91/516, 91/4.00R
International ClassificationB30B15/16, F15B11/072, F15B11/032, F15B11/00
Cooperative ClassificationF15B2211/6313, F15B2211/216, F15B2211/327, F15B2211/7053, F15B11/0325, F15B2211/212, F15B11/0725, F15B2211/30525, B30B15/165
European ClassificationF15B11/072B, B30B15/16D, F15B11/032B