US2850981A

US2850981A - Hydraulic pump

Info

Publication number: US2850981A
Application number: US570363A
Authority: US
Inventors: Ewald A Arp
Original assignee: Tobin Arp Manufacturing Co
Current assignee: Sunnen Products Co
Priority date: 1956-03-08
Filing date: 1956-03-08
Publication date: 1958-09-09
Anticipated expiration: 1975-09-09

Description

Sept. 9, 1958 E. A. ARP 2,850,981

HYDRAULC PUMP Filed March 8,. 1956 4 Sheets-Sheet 1 F1511 FIEE` E Sept. 9, 1958 E. A. ARP 2,850,981

HYDRAULIC PUMP 4 Sheets-Sheet 2 Filed March 8, 1956 CZ'E. E

`I\-\\I\ \4\ INVENTOR. 26 67 26 E14/44D ,4. RP

A Tram/srs Sept. 9, 1958 E. A. ARP 2,850,981

' HYDRAULIC PUMP Filed March 8, 1956 4 Sheets-Sheet 3 EF1-ZTL?. 4 46 INVENTOR. Zuma 4 ARP rroRA/Eys Sept. 9, 1958 E. A. ARP l 2,850,981

HYDRAULIC PUMP Filed March 8, 1956 4 Sheets-Sheet 4 IN VEN TOR. .EA/up ,4. ARP

Irren/vers United States Patent HYDRAULIC PUMP Ewaid A. Arp, Minneapolis, Minn., assignor to "Echin- Arp Manufacturing Company, Minneapolis, Mann., a corporation of Minnesota Application March, 1956, Serial No. 576,353

s anims. (ci. rc3/m49) ycylinder of lan hydraulic press.

In a device made according to the present invention, a pair of air driven pistons are connected integrallypto each other each in operational relationship to one of a pair of air cylinders in such a way that air pressurel exerted in either of the cylinders will tend to force the opposite piston toward the head .end of its cylinder. Each of these air driven pistons has an oil displacement plunger integrally attached thereto and mountedto extend inside of one of a pair of oil displacement chambers. Movement of each air driven piston away from the head end of its air cylinder causes the displacement plunger associated therewith to move farther into its displacement chamber. Movement of each displacement plunger into its displacement chamber causes a valve opening to a source of hydraulic iluid to be closedY and a valve opening to the main cylinder to be open. Oil in said chamber will be forced through said open valve into said cylinder. Switching means responsive to the positioning of each of said air driven pistons with respectv to said air cylinders causes each of said air cylinders to become closed toa source of air under pressure and opened to exhaust when said air driven piston reaches a position adjacent the head end of said air cylinder and to become closed to exhaust and opened to air under pressure when said air driven piston reaches a position spaced from thehead end of said cylinder. Such a hydraulic pump will lind .usefulness wherever it is desirable to obtain a high ratio between the hydraulic working pressure and the driving air pressure and where, for example, at the same time, the length of the travel of the air driven piston is short with respect to' the length of travel of the hydraulically drivenl ram. The press shown and described herein willrbe particularly useful in forcing wrist pins into place in connecting rods having no wrist pin bushingsl therein to pivotally mount automotive cylinders on said connecting rods;7 and to remove said wrist pins from said rods to free said cylinders therefrom.

In the drawings,

Fig. 1 is a front elevational viewof a hydraulic press made according to the present invention;

Fig. 2 is a side elevational view of the hydraulic press ot Fig. 1;

Fig. 3 is an enlarged sectional view taken substantially on the line 3 3 in Fig. 2;

Fig. 4 isan enlarged horizontal sectional view taken.

on theline 4 4 in Fig: l;

Fig. 5 is an enlarged fragmentary view of a portion ofthe hydraulic .press as seen inthe lowerright hand corner of Fig. 4; f

Fig. 6 is an enlarged sectional view taken on theline 6`-6in Fig. 3;

, 2,850,981 Patented Sept. 9, 1-958 ice ber 11, a main drive cylinder 12 supported on said base',A

a pair of

upright support columns

13, 13, ,a lheard 14 supported on said columns, and an adjustable head rod 15 mounted in said head and extending downwardly therefrom. A ram assembly 16 includes a rarn table 17 integrally connected to a main driven piston 18 which is operably situated in the main drive cylinder 12; Introduction yof hydraulic uid under pressure into the main drive cylinder 12 between the bottom end thereof and the main piston 18 will tend to cause the main piston to rise in the cylinder to force the ram table 17 in direction towards the adjustable head (rod 1S. The head 14 can be supported on the

upright support column

13, 13 at any convenient height depending upon the size of the article uponwhich the press is to operate. For this pur'- pose a plurality of horizontal openings 19 are provided in each of the support columns 13 and corresponding horizontal openings 20 are provided in the head 14. A pair of

support pins

21, 21 are adapted to extend through openings 20 and into openings 19 to position the head at any desired vertical location. The adjustable head rod 15 is threadably mounted in the head 1,4,so that the vertical position of the head rod can be readily adjusted with respect to the location of the ram table 17.

A pair of oppositely disposed airV cylinders 22 and-23 form a part of said base' member 11. An air driven piston Z4 is operably mounted in said air cylinder 22'and an air driven piston 25 is operably mounted in said air cylinder 23. Said air driven pistons are connected to each other by means of air driven piston connecting rods 26 which extend out of the open ends of the

cylindersr

22 and 23 land through the base member 11. A pair of' oil displacement chambers 274 and 28 are provided withinthe base member 11 and

oil displacement plungers

29 and 30 are integral with air driven pistons 24 and 25l respectively, and are in position to exetnd inside of said

oil displacement chambers

27 and 28 respectively. Y

The

upright support columns

13, 13 are each mounted on the base member 11 as at 31 and an oil sump tank 32 extends downwardly from said support column to completelyY enclosesaid base' member 11.v -Oil filter neck33 on top of said tank 32 is provided with an oilcap 34 which can be removed from the `filter neck to allow introduction of replacement oil into the tank. Thetop levelof the oil in saidy tank 32 isv indicated atV 3S in Fig.V 3.

Air control cylinders

36 and 37 are integralfwith the base member 11. Air control piston 38 -is operably mounted in air control cylinder 36' and air control piston 39 is operably mounted in air control cylinder 3,7. Control pipe 40 extends from the head end of air control cylinder 36`^to an air control ring 42 which is situated.

openings 44'in`th'e air cylinder 22 open from the'int'eriorV oflsaid cylinderV into the control ring 42. A' pluralityl of Vop`enings"45 inthe air cylinder 23 open from thel interiori of said air cylinder into the control 1'ir1`g43'. Said openings 44 are Aso,V positioned that: the head'end ofthe? air cylinderi22 will be" open to said air control ring 42l through said openings when the air driven piston 24 is positioned y'so that oildisplacement plunger 29 iscausing maximum displacement of oil in oil displacement chamber 27. When the air driven piston 24 is in any other position, it serves to seal off connection between said head end of said air cylinder 22 and the interior of the air control ring 42. Said openings are so positioned that the head end of4 air cylinder 23 will be open to said air control ring 43 when air driven piston 25 is positioned so that oil displacement plunger 30 is causing maximum displacement of oil in the oil displacement chamber 28. When the air driven piston 25 is in any other position, it serves to seal off connection between the head end of said air cylinder 23 and the interior of said air control ring 43.

High pressure air enters the oil sump tank 32 through the air supply pipe 46 from a compressor or other source (not shown). Air supply pipe 46 opens to a main air valve 47 which is mounted on the front wall of the oil sump tank 32 as best seen in Figs. 4 and 5. Details of the internal construction of this main air valve 47 are best seen in Fig. 5 and will Vbe set out in detail later in the specification. The valve is operated by depressing a main air valve control lever 48. This permits the high pressure air in pipe 46 to pass into an air pipe 49 which leads outwardly from the main air valve 47. The air pipe 49 is bifurcated and is connected to the base member 11 at a position between the air cylinder 22 and the air control cylinder 36 on one end of said casting and to a position between air cylinder 23 and air control cylinder 37 on the other end thereof. A high pressure air supply passageway 50 is open through base member 11 from inside of the head end of the air cylinder' 22 to one end of the air pipe 49 and a high pressure air supply passageway 51 is open through said base member 11 from inside of the head end of the air cylinder 23 to another end of the air pipe 49. An exhaust passageway 52 extends from inside said head end of said air cylinder 22 to outside of the base member 11 and an exhaust passageway 53 extends from inside of the head end of air cylinder 23 to a position outside of said base member 11. A slideable, stem type valve 54 is integrally connected to air control piston 38 and air control piston 39. It extends through the base members 11 in such a manner as to intersect high pressure air supply passageways 50 and 51 and exhaust passageways 52 and S3. Said slideable valve 54 is provided with four ports designated 55, 56, 57 and 58. When air control piston 39 is at its maximum position away from the head end of air control cylinder 37, port 55 is alined with high pressure air supply passageway 50 to allow passage of air therealong and port S7 is in alinement with exhaust passageway 53 to allow passage of air along said passageway. Passageways 51 and 52 will be blocked by said valve at this time. When air control piston 38 is at its maximum position away from the head end of the air control cylinder 36, passageways 50 and 53l will be blocked but port 56 will be alined way 52 to provide for air way and port 58 supply passageway passageway.

The oil displacement chambers Y27 and 28 are generally cylindrical and extend horizontally through the center of the base casting 11 and are concentric with the air driven

pistons

24 and 25 and the oil displacement passage through saidV passagewill be alined with high pressure air 51 to allow passage of air along this

plungers

29 and 30. These

chambers

27 and 28 are` separated from each other by a plug 59 which has a cylindrical passageway-60 extending therethrough. An oil intake valve member 61 extends through the passageway 60 in the plug 59 and includes a' disc valve 62 positioned to be capable of resting against an outer face of the plug 59 to close ofI the passageway `60 fromthe oil displacement chamber 27 and a disc valve63 capable of resting against an outer face of the plug 59 to close off the passageway 60 from 28. The

disc valves

62 and 63 are permanently positioned with respect to each other by means of a disc with exhaust passagei the oil displacement chamber 4 valve connecting rod 64 which is constituted as a length of pinion stock having a plurality of outwardly extending teeth resting in contact with the cylindrical inner surface of the opening 60. These teeth are cut away as at 66 so that oil passing through the opening 60 can llow between each of said teeth.

An oil supply intake opening 67 extends from the bottom surface of the base member 11 up into the cylindrical passageway 60. An oil displacement chamber discharge conduit 68 extends from the oil displacement chamber 27 into the main drive cylinder 12 and an oil displacement chamber discharge conduit 69 extends from the oil displacement chamber 28 into said drive cylinder 12. A reed valve 70 includes an end portion 71 which is positioned to normally close the opening between the discharge conduit 68 and the main drive cylinder 12 and an end portion 72 which is situated to normally close the opening between the discharge conduit 69 and said cylinder.

As best seen in Figs. 7 and 8, a regulator valve 73 for preventing the build up of destructive pressure inside of the main drive cylinder 12 and for manually relieving the pressure therein to allow the main piston 18 and the ram table 17 to move away from head rod 15 is mounted on said main drive cylinder at position adjacent the closed bottom end thereof. The regulator valve casing 74 is provided with an oil pipe 75 which opens from the interior of the main drive cylinder 12 to the interior of said casing 74. A plurality of release passageways 76 extend through the casing 74 to intersect said oil pipe 75. A ball valve 77 is pressed by the piston 78 under the action of spring 79 to have normal sealing relationship to a valve seat 80 to seal oil pipe 75 from said relief passageways 76. Piston rod 81 extends outwardly of the valve casing 73 and is pivotally connected in an eccentric manner to a regulator valve control rod 82 as best seen in Fig. 7. A regulator valve cover 83 is threadably situated on the regulator valve casing 74 and provides a flat end surface 84 adjacent to or against which the regulator valve control rod can rest. `This control rod 82 extends outwardly through the side wall of the oil sump tank 32 as best seen in Fig. 4 and the regulator valve control rod handle 85 is attached to it outside of the tank.

Referring now particularly to Fig. 5, the main air valve 47 includes a main air valve casting 86, a conical main air valve member 87 normally held in sealing relationship to close the opening of the air pipe 49 to the interior of said valve casting. The spring 88 serves to urge said conical valve member toward this closed position and a valve stem 89 extends outwardly through said casting 86 to be fastened in pivotal relationship to an eccentrically placed inner end of a main air control lever rod 90. The other end of said rod 90 is mounted in an outer wall of the oil sump tank 32 to be concentric with said mounting. Main air control lever 48 is integrally attached to said concentric end of said control rod 90.

Operation When it is desired to use the hydraulic press, the work to be acted upon by the press is placed on the ram table 17 which will, of course, be in its lowest position. The head 14 will be supported on the

upright support column

13, 13 as close as practicable to the work on the ram table and the adjustable head rod 15 will be rotated to lower'it to position immediately adjacent or in contact with the work.

To cause the ram table 17 to move in direction toward the head rod 15, the main air valve control lever 48 is depressed by applying a downward force on a chain 91 which is attached to an outer end thereof. This may be done by the foot of the operator so as to leave both hands free to keep the work properly alined with the head rod 15 as the ram table rises. Downward movement of 'the main air control lever 48 will cause the main air control lever rod 96 to rotate to moveV the, valvestern 89 and the conical valve member S7 in direction away from air pipe 49 against the action of spring 88. This allows the air under pressure in the air supply pipe 46 to pass into air pipe 49 which carries the air into the high pressure air supply passageway 5l) and the high pressure air supply passageway 51. In the event that the parts are initially positioned as disclosed in Fig. 6, port 55 in the slideable stem type valve 54 is in alinement with air sup` ply passageway 5d and the air from the air supply pipe 46 and air pipe 49 will pass along the length of this pas sageway 5@ and into air cylinder 22. This air under pressure will cause the air driven piston 24 to be moved in direction to the right as seen in Fig. 6 to cause oil displacement plunger 2% to enter the oil displacement chamber 27. Build up of pressure in the oil displacement chamber 27 due to the entry of displacement plunger 29 will cause oil intake valve member 61 to move to the right as seen in Fig. 6 to close the vertical passageway 60 with respect to displacement chamber 27. This build up of pressure in chamber 27 will also cause the contents of that chamber to be forced up into oil displacement chamber discharge conduit 68 and to lift the end portion 7i of the valve 70 from the opening of said discharge conduit 68 to allow the contents of said i cause the main piston 18 to move upward to carry the ram table 17 closer to head rod 15.

Since the air driven piston 24 is connected to; the air v driven piston 25 through the instrumentality ofV air driven piston connecting rods 26, movement of piston 24 to the right as seen in Fig. 6 will cause a similar movement of piston 25 to the right as seen in thatfigure. When, port 55 in the slideable stem type vvalve 54 is in alinement with the air supply passageway 50, the port 57` in said valve 54 is in alinement with the exhaust passageway 53. This means that when the air driven piston 25'moves to the right, the air in the air cylinder 23 is free to move through exhaust passageway 53, and port 57` to the atmosphere. As the air driven piston 25 moves to the right, the oil displacement plunger is also moved tothe right to vacate the oil displacement chamber 28. This will cause a reduction of pressure in the oil displacement chamber 23 and consequently the end portion 72 of the reed valve '76 will be held firmly iny place to close the oil displacement chamber discharge conduit 69` with respect to the main cylinder 12 because of the actionof the oil under pressure in that cylinder 12. Since the disc,v

valve 62 is held in position against an o uter surface of the plug 59, the disc valve 53 will be held in position spaced from an oppositeV outer surface of said plug 59 through the instrumentality of the disc valve connecting rod 64. Since the oil level in the sump tank 32 is well above the opening of the oil supply intake conduit 67 into said tank, reduction of pressure in the oil displacement chamber 25 caused by movement of the oil displacement plunger 30 out of the chamber will induce a llow of oil from said sump tank through the oil supply intake conduit 67, into the cutvawayportion ofthe disc valve connecting rod 64, past the teeth 65 on said rod and the disc valve 63 into the chamber 28. This ow is induced by the pressure of the atmosphere on thev oil in the sump tank and the low pressure caused .by the withdrawal of plunger 30.

As the air driven piston 24 moves to the right, it willy finally reach a position when the

openings

4,4 in the ai'r cylinder 22 are between the piston 24 and the closed end of said air cylinder. When this happens, there. willbe a flow of air under pressure throughthe openings v 44', into the air control ring 42, through the air-control pipe and into the air control cylinder 36. Introduction'of high pressure air into the air controlcylinder 36" will seen in Fig. 6. This movement will cause a similar movement to the right of slideable stem type valve 54 and air control piston 39. Movement of the valve 54 will cause the port 56 therein to become alined with exhaust passageway 52 and the port 58 to become alined with high pressure. air supply passageway 51. The port 55 will move out of alinement with high pressure air supply passageway 50 causing the valve 54 to block that passageway and the port 57 will move out of alinement with exhaust passageway 53 causing said valve 54 to block that passageway. Since at this positioning of the parts air driven piston 25 is to the right of the openings 4S in the air cylinder 23 as seen in Fig. 6, the air discharged from the air control cylinder 37 due to the movement of air control piston 39 will pass along air control pipe 41, through air control ring 43 and the openings 45 and out of the open end of the air cylinder 23 to the atmosphere.

With the opening of air cylinder 22 to exhaust through the exhaust passageway 52 `and port 56 in valve 54, and with the opening of air cylinder 23 to the high pressure air supply through the supply passageway 51 and port dit, air driven piston 25 will be caused to move to the left as seen in Fig. 6 and will carry with it, as previously explained, air driven piston 24. Disc valve 63 will move against plug 59 to prevent ilow of oil out of the oil displacement chamber 23 back into the sump tank and the high pressure of the oil in said displacement chamber 28 will cause the end portion 72 of the reed valve 7h to be lifted as oil from said displacement chamber 2S and the discharge conduit 69 Hows into the main cylinder l2. This will further increase the pressure of oil in the main cylinder and will tend to cause the main piston if? and consequently the ram table 17 to be moved in upward direction. This reciprocating action of the air cylinders, the oil intake valve member, the air control pistons and the slideable stem type valve 54 will continue to build up.

thel pressure in main drive cylinder 12 and to force main piston 18 and ram table 17 in direction toward head valve 15 until the operation being performed on ti c wor is accomplished or until the maximum safe Working pres sure is obtained in the main `cylinder 12.

As will be best seen in Fig. 7, this pressure in the main cylinder 12 and exerted in `oil pipe 75 tends to cause ball valve 77' to move from the valve seat 86 against the action of spring 79. When the maximum desirable or sate working pressure is reached in the main cylinder and consequently in the pipe '75, the construction and arrangement of the parts will be such that the pressure against the ball valve 77 will just overcome the force of the spring 79 and the ball valve will move out of contact with the, valve seat E@ to allow Ithe pressure in the main cylinder 12 to be relieved as oil flows along pipe and out through relief passageway '76. Oil passing out of these relief passageways 76 will, of course, fall back into the sump tank 32 in which the regulator valve 73 is situated.

Whenever the main air valve control lever 48 is relleased to allow spring S8 to forcel conical main air valve member S7 back to position to close the air pipe 49 from the air supply pipe 46, the reciprocating action of the air driven pistons, the oil intake valve member and the air control pistons will cease. The reed valve 70, however, will prevent any back flow of oil into either of the oil displacement

chamber discharge conduits

65 and 69. 1n order to relieve the pressure and release the oil from the main cylinder 12 so that the main piston 13 can return to position adjacent the closed end of that cylinder to allow the ram table 17 and the work thereon to move away from and out of contact with adjustable head rod'l, regulator valve control rod handle is operated in an upward direction as seen in Fig. 2 to cause regulator valve control rod 82 to be rotated kin a counter-clockwise direction asseen in Fig. 7; resting againstflat end surface of regulator valve cover i825; this rotation will cause the point of eccentric pivotal cause the air control piston 38 to move to the right as `75 connection of piston rod to said regulator valve cun- Since this control rod 82 is.

7 trol rod 82 to move in direction away from said flat end surface 84 and consequently will move the piston 78 against the action of spring 79 in direction away from ball valve 77. The pressure in the main cylinder l2 and consequently in oil pipe 75 will cause the ball valve 77 to be moved away from valve seat 80 to relieve the pressure in said main cylinder and to allow passage of oil from said cylinder out through relief passageways 76 and back into the sump tank 32. This relieving of the pressure will allow the main piston 18 and the ram table 17 to move away from head rod so that the work can be removed from the press.

It is to be noted that while the regulator valve 73 and the main air valve 47 employ certain springs to accomplish seating of the valve members against the valve seats, the rest of the mechanism is entirely positive in its action and does not involve the use of springs which are apt to fatigue and fail.

As a comparison of the cross sectional areas of the

air cylinders

22 and 23 with respect to the cross sectional areas of the

oil displacement plungers

29 and 30; and of the cross sectional areas of the displacement plungcrs 29 and 30 with respect to the cross sectional area of the main cylinder l2 will indicate, a high ratio of pressure exerted by ram table 17 to the pressure of the incoming air can be obtained. For example, the machine will work very well at a ratio of l0() to l.

The length of stroke of the main piston 18 is limited only by the amount of oil in the sump tank 32 and the length of the main cylinder 12. No limitation of length of travel is imposed by any physical limitations of the air and oil pumping mechanism.

What is claimed is:

l. A hydraulic pump including first and second air cylinders, first and second air driven pistons operably mounted in said cylinders, means for iixedly positioning each of said pistons with respect to the other, an oil displacement chamber, a discharge conduit open from said displacement chamber to a location for use of hydraulic fluid under pressure, a one way valve for permitting ow of oil from said displacement chamber through said discharge conduit to said location for use, an oil supply tank, an oil intake conduit open from said supply tank to said displacement chamber, a one Way valve for permitting tiow of oil from said supply tank through said oil intake conduit to said displacement chamber, an oil displacement plunger supported on one of said first and `second air driven pistons to move therewith from a position substantially entirely within said displacement chamber to a position substantially entirely without said displacement chamber, first and second air supply passageways for delivering air under pressure from a source thereof to said first and second air cylinders respectively, first and second exhaust passageways each extending from inside of the corresponding air cylinder to the outside thereof, first and second air control cylinders, rst and second air control pistons operably mounted in said first and second air control cylinders respectively, means for preventing relative movement of said first and second air control piston with respect to each other, said air control pistons being moveable with respect to said air control cylinders between a `first position having said iirst air control piston adjacent a head end of said first air control cylinder and said second air control piston spaced from a head end of said `second air control cylinder and a second position having said first piston spaced from said head end of said first lair control cylinder and said second piston `adjacent said head end of said second air control cylinder, first and second air control passageways each open from the interior of the corresponding air cylinder to the interior of the corresponding air control cylinder, each of `said air control passageways being positioned to be open to said air cylinder at a side of the air driven piston adjacent its air supply passageway when said air driven piston is positioned adjacent a head end of said lair cylinder and to be sealed off from said air supply passageway by said air driven piston when said piston is in a position spaced from said head end of the airpcylinder; and valve means operative when said first and second air control pistons are in said first position to allow passage through said first air supply passageway and said second exhaust passageway and to block passage through said rst exhaust passageway and said second air supply passageway and when said first and second air control pistons are in said second position to block passage through said first air supply passageway and said second exhaust passsneway and to allow passage through said first exhaust assagewsy and said second air supply passageway.

2, A hydraulic pump including an oil displacement chamber, a discharge conduit open from said displacment chamber to a location for use of hydraulic fluid under pressure, a one way valve for permitting llow of oil from said displacement chamber through said conduit to said location for use, an oil supply tank, an oil intake conduit open from said supply tank to said displacement chamber, a one way valve for permitting flow ot oil from said supply tank through said oil intake conduit to said displacement chamber, an air cylinder', an air driven piston operably mounted in said cylinder, an oil displacement plunger supported on said air driven piston to move therewith from a position substantially entirely within said displacement chamber to a position substantially entirely Without said displacement chamber, an air supply passageway for delivering air under pressure from a source thereof `to said air cylinder, an exhaust passageway open from inside said cylinder to outside thereof, an air control cylinder, an air control piston operably mounted in said-cylinder to move between a rst position adjacent the head end of said air control cylinder and a second position spaced therefrom, an air control passageway open from the interior of said air cylinder to the interior of said air control cylinder, valve means operative to allow passage of air from said air supply passageway through said air cylinder and said air control passageway into said air control cylinder when said oil displacement plunger is at a position substantially entirely within said displacement chamber and operative to block passage of air through said air control passageway into said air control chamber when said oil displacement plunger is at any other position, air control valve means operative in response `to movement of said air control piston to permit passage of air through said air supply passageway and to block passage of air through said exhaust passageway when air control piston is in said iirst position and to block said air supply passageway and to permit passageway of air through said exhaust passageway when said air control piston is in said second position, iirst means operable upon movement of said oil displacement plunger to a position substantially entirely within said displacement chamber for moving said air piston and said plunger to position said plunger substantially entirely without said displacement chamber, and second means operable upon movement of said displacement plunger to a position substantially entirely without said displacement chamber for moving said air control piston from said second to said first position.

3. A hydraulic pump including an oil displacement chamber, a discharge conduit open from said displacement chamber to a location for use of hydraulic liuid under pressure, a one way valve for permitting flow of oil from said displacement chamber through said conduit to said location for use, an oil supply tank, an oil intake conduit open from said supply tank to said displacement chamber, a one way valve for permitting flow of oil from said supply tank through said oil intake conduit to said displacementrchamber, `an air cylinder, an air driven piston operably mounted in said cylinder, an oil displacement plunger supported on said air driven piston toA move therewith from a position substantially entirely within Asaid displacement chamber to a position substantially entirely without said displacement chamber, an air supply passageway for delivering air yunder pressure from a source thereof to said air cylinder, an exhaust passageway from inside .said cylinder to outside thereof, an air control cylinder, an -air control piston operably mounted in said cylinder to move between a iirst position adjacent a head end of lsaid air control cylinder and a second position spaced therefrom, an air control ring situated in surrounding relationship to said air cylinder, an air control passageway open from the interior of said air cylinder to the interior of said air control ring, said air control pas- .sageway being positioned to beopen to said air cylinder at la side lof said air driven piston adjacent saidk air supply passageway when said oil displacement plunger is at a position substantially entirely within said displacement chamber and to vbe sealed off from said air supply passageway by said air driven piston when said oi-l displacement plunger is in any other position, an air control pipe open from the interior of said air control ring to the interior of said air control cylinder, an air control valve supported on said air control piston to move therewith, said air control valve being situated to block both said air supply passageway and said exhaust passageway, a rst air control valve port through said air control valve located to have a position in alinement with said air supply passageway to permit passage of air therethrough when said air control piston is in said first position to have a position out of alinement with said air supply passageway to block said passageway when said air control piston is in said second position, second air control valve port through said air con- `trol valve located to have a position in alinement with said exhaust passageway to permit passage of air through said passageway when said air control piston is in its seclond position and to have a position out of alinement with said exhaust passageway to block said passageway when said air control piston is in its first position, means operable upon movement of said oil displacement plunger to a position substantially entirely within said displacement chamber for moving said plunger to a position substantially without said chamber, and means operably upon movement of said displacement plunger to a position substantially without said displacement chamber for moving said air control piston from said second to said first position.

4. A hydraulic pump including first and second oil displacement chambers, rst and second discharge conduits each open from the correspondingly numbered displacement chambers to a location for use of hydraulic fluid under pressure, first and second one way valves each for permitting flow of oil from the corresponding displacement chamber through the corresponding discharge conduit to said location for use, an oil supply tank, a single, bifurcated oil intake conduit open fro-m said oil supply tank to each of said displacement charnbers, valve means operative in response to pressure differential between said displacement chambers for alternately permitting flow of oil from said oil supply tank through said oil intake conduit into said first displacement chamber while blocking flow between said second displacement chamber and said oil tank through said intake conduit and for permitting flow from said oil supply tank through said oil intake conduit into said second chamber while blocking flow between said iirst chamber and said oil tank through said conduit, first and second air cylinders, first and second air driven pistons each operably mounted in one of said air cylinders, first and second oil displacement plungers each supported to vmove with the corresponding air driven piston from a position substantially entirely within the corresponding displacement chamber to a position substantially entirely without said displacement chamber, air driven piston connecting rods attached to each of said air driven pistons to provide opposed simultaneous movement of each ofV said pistons with respect to its corresponding cylinder and of each of displacement plungers with respect 10 to its corresponding displacement chamber, first and second air supply passageways for delivering air under pressure from a source thereof to said first` and second air cylinders respectively, first and second exhaust passageways each extending from inside of the corresponding air cylinder to the outside thereof, first and second air control cylinders, rst andVv secondy air control pistons operably mounted in said first andsecond air control cylfrom a head end of said secondair control cylinder and' a second position having said lirst piston spaced from said head end of said first airy control cylinder and said f second piston adjacent said head end of said second air control cylinder, first and second air c ontrol passageways each open from-the interior of the corresponding air cylinder to the interior of the corresponding air control cylinder, each of said air control passageways beingv positioned to be open to said air cylinder ata side of its air driven piston adjacent its air supply passageway when its corresponding oil displacementplunger isin a position substantially entirely Within said displacement chamber and to be sealed olf from said air supply passageway by said air driven piston when said oil displacement plunger is in any other position, and an air control valve operative in response to movement of said first and second air control pistons to allow passage through said first air supply passageway and said second exhaust passageway and to block passage through said first exhaust passageway and said second air supply passageway when said air control pistons are in said first position and to block passage through said first air supply passageway and said second exhaust passageway and to allow passage through said first exhaust passageway and said second air supply passageway when said air control pistons are in said second position. i

5. A hydraulic pump including first and second air cylinders located in concentric relationship to each other, first and second air driven pist-ons each operably mounted in a correspondingly numbered one of said air cylinders, iirst and second oil displacement chambers concentric with each other and with said air driven pistons, first and second oil displacement plungers each supported to `move with the corresponding air driven piston from a position substantially entirely within the corresponding displacement chamber to a position substantially entirely without said displacement chamber, first and second discharge conduits each open from the correspondingly numbered displacement chamber to a location for use of hydraulic iiuid under pressure, first and second one way valves each for permitting flow of oil from. the corresponding displacement chamber through the corresponding discharge conduit to said location for use, an oil tank, an oil supply intake conduit open to said oil supply tank, a displacement chamber communicating passagewayV open between said first and second oil displacement chambers and open to said oil supply intake conduit, an intake valve member slideably supported in said chamber communieating passageway, and having a first disc Valve supported thereon in said first displacement chamber and a second disc valve supported thereon in said second displacement chamber, said intake valve member being moveable to a position to cause said `first disc valve to seal said first displacement chamber irom said intake conduit and to bring said second disc valve into spaced relationship to said chamber commu ii ating passageway when the pressure in said first displacement chamber is higher than the pres-- sure in said second displacement chamber and movable to and to bring said first disc valve into spaced relationship 11 to said chamber communicating passageway when the pressure in said second displacement chamber is higher than the pressure in said rst displacement chamber, an air driven piston connecting rod fixedly attaching said first and second air driven pistons to each other, first and second air supply passageways for delivering air under pressure from a source thereof to said first and second air cylinders respectively, first and second exhaust passageways each open from inside of the corresponding air cylinder to the outside thereof, first and second air control cylinders, tirst and second air control pistons opernuly mounted in said first and second air control cylinders respectively, an air control piston rod connecting said air control pistons to each other, said air control pistons being moveable with respect to said air control cylinders between a first position having said first air control piston adjacent a head end of said first air control cylinder and said second air control piston spaced from a head end of said second air cylinder and a second position having said tirst piston spaced from said head end of said first air contro-l cylinder and said second piston adjacent said head end of said second air control cylinder, first and second air control passageways each open from the interior of the corresponding air cylinder to the interior of the corresponding air control cylinder, each of said air control passageways being positioned to be open to the corresponding air cylinder at a side of its air driven piston adjacent its air supply passageway when its corresponding oil displacement plunger is in a position substantially entirely within said displacement chamber and to be sealed off from said air supply passageway by said air driven piston when said oil displacement plunger is in any other position, and an air control valve constituted as portions of said air control piston rod extending through said rst and second air supply passageways and first and second exhaust passageways, said air control pis ton rod having a plurality of ports therein positioned to allow passage through said first air supply passageway and said second exhaust passageway and to block passage through said rst exhaust passageway and said second air supply passageway when said air control pistons are in said inst position and to block passage through said rst air supply passageway and said second exhaust passageway and to allow passage through saidl first exhaust passageway and said second air supply passageway when said air control pistons are in said second position.

References Cited in the le of this patent UNITED STATES PATENTS