US3384029A - Hydraulic pumping apparatus - Google Patents

Description

y 21, 1968 R. E. RAYMOND 3,384,029

HYDRAULIC PUMPING APPARATUS Filed Oct. 12, 1965 4 SheetsSheet 1 INVENTOR. ROBERT ERAYMOND ATTORNEYS May 21, 1968 R. E. RAYMOND 3,384,029

HYDRAULIC PUMPING APPARATUS Filed Oct. 12, 1965 4 Sheets-Sheet l.

INVENTOR. ROBERT E. RAYMOND ATTORNEYS y 21, 1968 R. E. RAYMOND 3,384,029

HYDRAULIC PUMPING APPARATUS Filed Oct. 12, 1965 4 Sheets-Sheet 5 INVENTOR. ROBERT E.RAYMOND BY J ATTORN y 21, 1968 R. E. RAYMOND 3,384,029

HYDRAULIC PUMPING APPARATUS Filed Oct. 12, 1965 4 Sheets-Sheet 4 FIG. 8

INVENTOR. ROBERT E. RAYMOND ATTORNEYS United States Patent 3,384,629 HYDRAULIQ PUMPING APPARATUS Robert E. Raymond, Zanesville, Ohio, assignor to Hydro-Kinetics, Zanesville, (Ehio Filed Oct. 12, 1965, Ser. No. 495,168 12 Claims. (Cl. 103-173) ABSTRACT OF THE DISCLOSURE A hydraulic pumping mechanism that includes a housing with two separate outlet ports, an inlet port, and a control inlet port. Within the housing, a pressurized outlet chamber is isolated from an inlet chamber which communicates with the housing inlet port. A cylinder barrel assembly is slideably mounted within the housing and is provided with a plurality of circumferentially spaced cylinders having a cam driven piston disposed in each cylinder. Each cylinder includes two separate cylinder outlets. The first outlet communicates with an outlet manifold formed in the barrel which in turn communicates with one of the housing outlet ports and the second outlet communicates with the outlet chamber that surrounds the barrel which in turn communicates with the other housing outlet port. Each piston includes an intake port which communicates with a passage or cavity formed in the piston which in turn communicates with the interior of the cylnder. A ball-check valve and valve seat assembly is disposed within the piston to permit only the ingress of fluid through the intake port. An annular piston and cylinder are disposed in the housing in force transmitting relationship with the barrel to control the relative displacement of the pistons in the cylinders. During variable displacement operation, the flow through the second outlet varies with the required flow to the load and performs a cooling function as it passes through the outlet chamber in heat transmitting relationship with the barrel. When the barrel position remains stationary, two fixed displacement outlet flows are delivered through each of the separate housing outlets in any proportion desired as determined by the relative axial spacing of the cylinder outlets with respect to the piston stroke.

The present invention relates generally to hydraulic machines and in particular to a novel piston type pumping apparatus.

In general, the pumping apparatus of the present invention comprises a suitable housing, cylinder means provided with two separate outlets and piston means disposed in the cylinder means and including inlet port means communicating with the cylinder means. Fluid is taken into the cylinder means through the piston inlet means on the suction stroke and then is discharged through the separate cylinder outlets during different portions of the compression stroke thereby providing in essence two pumps in one.

In accordance with the present invention, the novel pumping apparatus permits two separate outlet flows in which flow from one cylinder outlet may be delivered to a load while the other outlet feeds a second circuit to circulate a cooling flow to cool the pump. This is particularly advantageous in variable displacement operation during high pressure holding periods when the pump is deadheading. The flow in the second circuit provides very efiicient cooling of the first circuit.

As another aspect of the present invention, the novel pumping apparatus of the present invention permits two separate outlet flows from one set of pistons which can function as two distinct fixed displacement pumps. The flow from the separate outlets can be divided in any manner by simple adjustment of the piston stroke relative to the position of the cylinder outlets in the cylinder.

.As another aspect of the present invention, the novel pumping apparatus permits one pumping apparatus to function as a low pressure, high volume pump in a conventional high-low pump system. Low pressure is unloaded to one circuit as the high pressure circuit builds up and then the lower pressure circuit circulates to cool the high pressure circuit in the pump.

As another aspect of the present invention, the novel pumping apparatus may incorporate a cylinder barrel cartridge assembly wherein the cylinders, pistons, and valve means are an integral assembly and may be manufactured in a convenient pumping package for use in a variety of housing envelopes for many different applications. A standard size cartridge may be employed to reduce inventory and provide easy access to reduce maintenance costs.

As still another aspect of the present invention, the novel pumping apparatus permits in variable displacement operation, one outlet circuit to be controlled for variable flow with the excess flow being delivered to another outlet circuit depending upon the position of the other cylinder outlet relative to the piston stroke at any instant.

As a further aspect of the present invention, the novel pumping apparatus may be manufactured and fabricated at relatively low cost due to the simplicity of construction and the lack of relatively close tolerance requirements.

It is, therefore, an object of the present invention to provide an apparatus of the type described which provides two separate cylinder outlets in conjunction with one set of piston means to permit the one set of pistons to function as two separate pumps.

It is another object of the present invention to provide an apparatus of the type described which provides a bypass cooling circuit in addition to the main load circuit to permit efiicient cooling of the pump With no loss of efiiciency in maintaining load pressures.

It is another object of the present invention to provide an apparatus of the type described which may be incorporated in a cylinder barrel cartridge assembly to permit manufacture of a convenient pumping package for use in a variety of housing envelopes to meet the requirements of a wide selection of applications.

It is still another object of the present invention to provide an apparatus of the type described which incorporates an outlet valve construction for use with the previously mentioned separate cylinder outlets to permit a convenient, compact construction, easily manufactured and fabricated at low cost using standard procedures.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of embodiment of the invention is clearly shown.

In the drawings:

FIG. 1 is a side sectional View of a pumping apparatus constructed in accordance with the present invention, the section being taken along a vertical plane through the centerline of the apparatus;

FIG. 2 is a side view of a pumping cartridge assembly constructed in accordance with the present invention, the remainder of the apparatus being shown in section as seen in FIG. 1;

FIG. 3 is a side sectional view of a portion of the apparatus shown in MG. 1 illustrating a check valve for the cooling outlet port in the housing, the section being taken along a vertical plane through the centerline of the apparatus;

FIG. 4 is a side view of a portion of the valve assembly shown in FIG. 3;

FIG. 5 is an end view of that portion of the valve assembly shown in FIG. 4;

FIG. 6 is a side sectional view of a portion of the apparatus of the present invention illustrating the novel piston and piston inlet construction, the section being taken along a vertical plane through the centerline of the piston;

FIG. 7 is a diagrammatic view of a typical closed circuit cooling system wherein the fluid may be forced through an oil filter to clean the fluid before returning to the pump inlet port; and

FIG. 8 is an end sectional view of the pump of FIG. 1, the section being taken along the line 8-8 of FIG. 1.

Referring in detail to the drawings, a variable displacement pump constructed in accordance with the present invention is illustrated in FIGS. 1 and 2 and comprises a housing indicated generally at that includes a front housing portion indicated generally at 22 and a rear housing portion indicated generally at 24. The housing portions are joined together at the central portion of the pump and held by a plurality of studs 26.

A drive shaft 28 is mounted in the forward end of the housing by tapered roller bearing assemblies 30 and 32 which are pressed into recesses 34 and 36.

An oil seal 38 is pressed into a recess 40 in housing 20 and includes an annular resilient element 42 that wipes the periphery of drive shaft 28.

As seen in FIG, 1, the inner end of drive shaft 28 carries a cam means indicated generally at 44 which includes a central bore 46 provided with a keyway 48 that receives a key 50 for preventing rotation of cam means 44 relative to shaft 28. The cam means is retained on shaft 28 by a nut 52 which is tightened into locked relationship on a threaded inner end of shaft 28.

With continued reference to FIG. 1, cam means 44 includes an inclined surface 54 which engages a plurality of nylon shoes 56, the latter including sockets 58 which form pivotal ball joints with ball-shaped ends 68 formed on a plurality of pumping pistons 62.

Each of the nylon shoes 56 is surrounded by a metal casing 64 that is crimped around the ball-shaped end 60 of its respective piston 62. Each metal casing 64 also includes an inwardly extended annular protrusion 66 that snaps into an annular recess 68 formed in the base of the nylon shoe portion.

With continued reference to FIGS. 1 and 2, a cylinder barrel cartridge assembly indicated generally at 70 is axially slideably mounted within housing 20 and guided by a plurality of guide grooves 72 which receive longitudinally extending bearing members 76.

Members 76 may best be described as side rail bearings and function not only to absorb piston side thrust reaction imposed on barrel 70 but, in addition, bearing members 76 function as keys against cylinder barrel reaction and thereby serve to absorb torque.

Pistons 62 are disposed in respective barrel cylinders 78 which receive low pressure oil or hydraulic fluid in a novel manner via housing inlet port 80, passage 84 in front housing portion 22, an inlet chamber indicated generally at 86 within housing 20 and barrel inlet passages 88 formed in each piston 62.

Now referring to FIGS. 1 and 6, inlet ports 88 in pistons 62 communicate with a cavity 71 formed in each piston 62 which in turn communicates with a respective cylinder 78 through an orifice 73 in the rearward end of piston 62.

Each of the pistons 62 is provided with an intake valve means formed by a ball-check valve 75 is freely carried in the opening to cavity 71 between a valve seat portion 77 and a stop portion 79 formed in each piston 62.

On the suction stroke of the pistons 62, fluid is drawn into a respective cylinder 78 via the passage and inlet means described above as the low pressure fluid forces ball-check valve 75 away from seat portion 77 to allow fluid to flow into cavity 71 and then through orifice 73 into cylinders 78.

Now referring to FIGS. 1 and 2 each cylinder 78 includes a unique outlet port construction whereby a first cylinder outlet port 81 is disposed in a side wall of each cylinder 78 and a second cylinder outlet passage 83 is axially spaced from outlet port 81 and formed in the rearward end of cylinders 78.

It is important to point out that the axially spaced cylinder outlets 81 and 83 may both be disposed in a side wall of cylinder 78 without departing from the spirit of the invention although the structure shown is preferred. Further, the inlet port may also be formed in the cylinder instead in the pistons as shown in the preferred embodiment without departing from the spirit of the present invention.

As seen in FIGS. 1 and 2 each of the cylinders 78 includes a respective reaction plug, indicated generally at in free self-aligning engagement with the inner end surface 92 of rear housing portion 24.

Each reaction plug 99 is provided with a central bore 94 that carries a pressure responsive outlet valve means formed by a ball check valve 96 which is freely retained in bore 94 by a threaded plug 98.

Each threaded plug 98 includes a seat portion 100, a second barrel outlet passage 102, and a radial passage 103, the latter communicating with an annular passage 104 formed in the outer wall of reaction plug 98.

With continued reference to FIG. 1, bore 94 in each reaction plug 98 includes a valve stop 106 and a compression spring 108 which serve to limit the stroke of the ball and bias its toward a closed position.

A plurality of pressure responsive valves 87, attached to the outer surface of barrel 70 by screws 89, covers each of the first cylinder outlets 81 and is in the form of a substantially flat, flexible reed-type valve. Pressure responsive valves 87 is normally biased in a closed position and the degree of valve opening is limited by a stiff back-up plate 91 attached by screws 89 to pressure responsive valves 87.

It is important to point out that the reed-type valves 87 are preferred because they provide eflicient valve means and yet conveniently take up little space. Further, valves 87 are easily incorporated into the cylinder barrel cartridge assembly 70 to provide an integral package to offer the attractive commercial advantages previously mentioned.

It should be pointed out that the cylinder wall openings for the first barrel outlet passages 81 are each valved by their respective pistons 62 and will be referred to herein as piston position responsive valves for said first barrel outlet passages.

Pressurized fluid from cylinders 78 is first discharged on the compression stroke of the pistons 62 through first cylinder outlet 81, the fluid forcing pressure responsive valves 87 open, and flows into an outlet chamber or cooling chamber 93 formed in rear housing portion 24. Outlet chamber 93 is isolated from the inlet fluid in inlet chamber 86 by an annular seal engaging barrel 70 and an annular cylinder barrel driving piston, indicated generally at 146 which will be described in detail later herein.

Outlet chamber 93 completely surrounds cylinder barrel assembly 70 and forms a passage means for the outlet flow of fluid through a check valve 220 disposed in a housing outlet port 222 formed in the rear housing portion 24.

As best seen in FIG. 1, as a piston 62 advances during the compression stroke, outlet passage 81 is closed by the outer wall of cylinder 78 and flexible reed valve 87 will close.

It is important to point out that the flow through outlet passage 81 depends upon the position of barrel 70, hence passage 81, relative to the stroke of piston 62. Further, since the fluid from outlet passage 81 flows completely around barrel 70, a very effective cooling flow is developed.

When piston 62 advances to the position where outlet passage 81 is closed, the pressurized fluid is then discharged through the second cylinder outlet port 83 through second barrel outlet passages 102 in reaction plugs 90, a plurality of small radially extending passages 103, annular recesses 104, annular manifold 134, barrel outlet port 122, radial passages 112, an outlet member 110, passage 114 and a second housing outlet port 116 to the load.

Hollow outlet member 110 includes the central passage 112 that communicates with high pressure discharge passage 114 that in turn leads to housing outlet port 116.

As seen in FIG. 1, outlet member 110 also includes a foot portion provided with a surface 118 that is in slideable sealed engagement with a longitudinally extending surface 120 formed in the outer wall of cylinder barrel 70.

It will be noted from FIG. 1 that when cylinder barrel 70 is axially shifted relative to the housing means 20 an outlet port 122 formed in the cylinder barrel always remains in communication with central passage 112 in outlet member 110 notwithstanding axial movement of cylinder barrel 7 0.

With continued reference to FIGS. 1 and 2, pressure biased outlet member 110 includes a piston surface 124 that causes the pressurized hydraulic fluid in passage 112 to bias the surface 118 on outlet member 110 downwardly into sealed engagement with longitudinally extending surface 120 on barrel 70. If desired, outlet member 110 can be structurally modified so as to be hydraulically balanced in accordance with the teachings in my co-pending application Serial No. 594,350.

A spring 126 augments the biasing force of the high pressure oil on piston surface 124 and also serves to retain surface 118 in sealed engagement with surface 120 at low pressures and at the outset of operation.

The outer peripheral surface of outlet member 110 is provided with an annular seal 128 and a threaded plug 129 is screwed into the hole forming passage 112 and includes an inner protrusion that forms a retainer for the end of spring 126.

Pressurized oil is also released to a variable displacement hydraulic control unit indicated generally at 135 by a second pressure biased outlet member 110A, FIGS. 1 and 2, which is substantially identical to outlet member 110 previously described. It will be noted that outlet member 110A includes a base surface 136 that is hydraulically biased int-o sealed engagement with a longitudinally extending surface 138 formed in the outer wall of cylinder barrel 70. Outlet member 110A is biased downwardly against longitudinally extending surface 138 by a force exerted by a piston surface 124, pressurized oil in a passage 140.

Referring to FIG. 1, cylinder barrel 70 is constantly biased towards the front of the housing means by a control spring 142 which is interposed between a spider 143 and an annular shoulder 145 formed on cylinder barrel 7 0.

Cylinder barrel 70 is hydraulically shifted axially against the biasing force of control spring 142 by an annular cylinder barrel driving piston indicated generally at 146 in FIG. 1. Piston 146 is mounted in a cylindrical surface 148 and forms therewith control cylinder 150 for receiving pressurized oil in a manner later to be described. A small annular piston surface 152 of large diameter provides suflicient axial force with low control pressures to shift cylinder barrel 70 against the force of control spring 142.

With continued reference to FIG. 1, piston 146 includes a rear end 155 in force transmitting engagement with annular seal which in turn is in force transmitting engagement with an annular base portion 157 on cylinder barrel cartridge 70.

Referring particularly to FIGS. 1 and 8 pressurized oil is delivered through control apparatus to control cylinder via outlet port 122-A, passage 140, passage 144, orifice 147, radial passages 130 in spool housing 151, lateral passage 154 in control block 156, longitudinal passage 158 in control block 156, vertical passage 160 in control black 156 and passage 162 in housing 20 which connects to control cylinder 150.

Referring particularly to FIGS. 1 and 2 spool housing 151 carries a longitudinally shiftable spool member 164 that is normally biased towards a closed position by a spring 166, the latter being contained in a spring housing 168 that is threaded into control block 156 at a threaded hole 170. Compression spring 166 is selectively compressed or compressed by manipulating a control knob 172 that includes a shank 174 in threaded engagement with spring housing 168 at a threaded hole 176. As seen in FIG. 1, a radial passage 178 communicating with passage 162 in housing 20 provides a direct drain back to tank for any fluid that may flow back from control cylinder 150 during shock conditions.

As best seen in FIG. 8, control block 156 is mounted on housing 20 by a plurality of studs 192. It will be understood that other types of control apparatus responsive to various load conditions can be readily adapted to replace control apparatus 135.

The pumping pistons 62 are returned and biased against cam means 44 by a single centrally disposed piston return rod 194, FIG. 1, which includes an arcuate socket 196. A ball 198 fits into socket 196 of rod 194 and also into a socket 200 formed in a piston return yoke 202. Yoke 202 includes a plurality of radially extending slots 204 that fit around neck portions 206. Piston return y-oke 202 applies force to the rear sides of the ball-shaped piston ends 60 and in turn receives force from piston return rod 194 via the pivot joint formed by ball 198 and sockets 196 and 200. A compression spring 210 is disposed between a shoulder 214 on the rear end of piston return rod 194, a shoulder 214 on a spring retainer plug 216 which in turn bears against the front side of spider 143. Spider 143 is restrained from rearward movement by the shoulders 224 formed on the ends of reaction plugs 90. It should be pointed out the reaction plugs 90 are fitted loosely into respective holes 91 in spider 143 and are in free engagement with the inner surface 92 of the housing whereby the plugs are self-aligning with respect to pump cylinders 78.

In operation, when the pumping apparatus is driven by a prime mover, cam 44 reciprocates pistons 62 which, on the suction stroke draw fluid into cylinders 78 via inlet port 80, inlet passage 84, inlet chamber 86, barrel inlet passages 88, cavity or passage 71, and orifice 73.

It is important to point out the inlet port means may be disposed in the cylinders 78 themselves instead of in pistons 62 without departing from the spirit of the invention.

The intake fluid forces ball-check valve 75 away from seat portion 77 as it enters passages 88 and fiows through cavity 71 and out of orifice 73 into cylinders 78.

On the suction stroke, valves 87 are normally biased in a closed position.

On the compression stroke, fluid is delivered first through first cylinder outlet passages 81 as the flexible valves 87 are forced open with the degree of opening being limited by back-up plate 91. The amount of flow through passages 81 depends upon the position of passages 81 relative to the stroke of pistons 62 which in the variable displacement pump illustrated, varies according to the position of barrel 70. Fluid then flows into and through outlet chamber 93 to housing outlet port 222 and out one way check valve assembly 220, best seen in FIGS. 3, 4, and 5.

Referring to FIGS. 3, 4, and 5, check valve 220 is biased against a valve seat portion 226 by a spring 228 and prevents fluid from flowing back into outlet chamber 93.

ressurized fluid from cylinder outlets passages 81 flows through chamber 93 and forces valve 220 open to permit fluid to flow out of housing outlet port 222.

Many types of conventional valves or surge control orifices may be used in place of outlet check valve 220 to prevent flow back through port 222 on the suction stroke of pistons 62.

The fluid from port 222 may then be delivered to a load or recirculated for cooling purposes. A typical closed circuit cooling system is illustrated diagrammatically in FIG. 7.

The fluid from port 222 leads to a heat exchanger 260 and then is forced through a very fine filter 262 before returning to reservoir 250. The fluid from reservoir 250 is pulled through a conventional wire screen filter 252 to inlet port 80. Therefore, the oil circulated through the pump housing 29 is cooled and cleansed before returning to the interior of the housing. It is important to point out that a substantial flow through cylinder outlet passages 81 occurs which is delivered out of outlet port 222 to provide very eflicient cooling of the hydraulic system.

After the wall of piston 62 passes outlet passage 81, the remainder of the pressurized fluid flows through second cylinder outlet port 83 to the other housing outlet port 116 via passages 102 in plugs 90, check valves 96, radial passages 103, annular grooves 104, manifold 134, passage 112 in hollow outlet member 110 and outlet passage 114 which leads to outlet port 116.

The fluid in inlet chamber 86 is isolated from the fluid in outlet chamber 93 by annular seal 95.

Some of the pressurized oil in manifold 134 is delivered to variable control apparatus 135 for shifting annular piston 146 and cylinder barrel 70 as previously mentioned.

A constant pressure at the load is obtained by arranging spool 164 to open only when a predetermined selected load pressure is exceeded. Control knob 172 is adjusted to compress spool control spring 166 so as to bias spool 164 with the proper force to permit its opening when the predetermined selected operating pressure is exceeded. When the pressure at the load rises above the operating pressure oil from the manifold passes through passage 144 and orifice 147 to spool cylinder 149. The increased pressure in the spool chamber overcomes the preset control force exerted by spool control spring 166 whereby the spool is shifted to the left, as viewed in FIG. 1, and oil is released through radial passages 130 in spool housing 151 and thence through the previously described passages to the control cylinder 150. This shifts annular piston 146 and cylinder barrel 70 to the left as viewed in FIG. 1, whereby cylinder outlet passages 81 are moved to the right relative to the pistons 62. This movement increases the flow of fluid through passages 81 because said passages are closed later in the compression stroke whereby more oil is free to fiow out of said ports. Accordingly, this decreases the flow of oil per piston compression stroke out of second cylinder outlets 83 to automatically cut back the pressure in that circuit.

When the pressure drops to the preselected control pressure the biasing force exerted by spool control spring 166 shifts spool 164 to the right, as viewed in FIG. 1, whereby the spool closes radial ports 130 and the flow of oil to control cylinder 150 is terminated.

It is important to point out that the present invention has been described only by Way of illustration, with respect to variable displacement operation and a cooling circuit but is not limited to such an application.

The pumping apparatus may be readily adapted to perform as two fixed displacement pumps with both housing outlet ports 116 and 222 connected to a load. The cylinder barrel 70 may be fixedly positioned to divide the flow between outlets 81 and 83 in any manner desired or a variable flow control may be used to control one circuit with the excess delivered to the second circuit.

It is also important to point out that other valve means than the type shown may be employed such as, for example, an orifice which permits substantial flow in only one direction may be used to replace valves 87 and outlet passage 81, particularly for recirculating cooling fluid, without departing from the spirit of the present invention.

I claim:

1. In a variable displacement axial type pump, the combination of a housing including a housing inlet port and first and second housing outlet ports; an axially shiftable cylinder barrel disposed in said housing and including a cylinder provided with axially spaced first and second barrel outlet passages, a piston mounted for reciprocation in said cylinder, and a barrel inlet passage; intake valve means carried by said barrel for said inlet passage whereby fluid enters said cylinder on the suction stroke and fluid is discharged first from said first barrel outlet passage and one of said housing outlet ports during a portion of the compression stroke of said piston and then through said second barrel outlet passage and the other of said housing outlet ports during a subsequent portion of said compression stroke, said first barrel outlet passage including a piston position responsive valve and a pressure responsive valve; and a pressure responsive outlet valve means for said second barrel outlet passage whereby fluid is diverted through said first barrel outlet passage to cool said pump during operating conditions of reduced flow through said second barrel outlet passage.

2. The apparatus defined in claim 1 wherein said barrel inlet passage and intake valve means are in said piston.

3. The apparatus defined in claim 1 wherein said pressure responsive valve for said first barrel outlet passage consists of a reed-type valve.

4. The apparatus defined in claim 1 wherein one of said barrel outlet passages is disposed in a side wall of said cylinder barrel and the other of said barrel outlet passages is disposed in the pressurized end of said cylinder.

5. In a variable displacement axial type pump, the combination of a housing including a housing inlet port and first and second housing outlet ports; an axially shiftable cylinder barrel disposed in said housing and including a plurality of cylinders, each of said cylinders including a first barrel outlet passage in a side wall of said barrel and a second barrel outlet passage, pistons mounted for reciprocation in said cylinders, an annular manifold communicating with said second barrel outlet passages, and barrel inlet passages communicating with said cylinders; intake valve means carried by said barrel for said inlet passages whereby fluid enters said cylinders on the suction strokes and fluid is discharged first from said first barrel outlet passages and one of said housing outlet ports during portions of compression strokes of said pistons and through said second barrel outlet passages, said annular manifold, and the other of said housing outlet ports during subsequent portions of said compression strokes, each of said first barrel outlet passages including a piston position responsive valve and a pressure responsive valve; and a pressure responsive outlet valve for each of said second barrel outlet passages whereby fluid is diverted through said first barrel outlet passages to cool said pump during operating conditions of reduced flow through said second barrel outlet passages.

6. The apparatus defined in claim 5 wherein said barrell inlet passages and intake valve means are in said pistons.

7. The apparatus defined in claim 5 wherein said pressure responsive valves for said first barrel outlet passages consist of reed-type valves.

8. The apparatus defined in claim 5 that includes a hollow outlet member radially shiftably mounted in said housing and provided with an inner surface slidably engaging the outer surface of said cylinder barrel for the passage of pressurized fluid from said annular manifold to said other of said housing outlet ports.

9. The apparatus defined in claim 5 that includes an annular cylinder barrel driving piston for axially shifting said cylinder barrel, and an annular seal between said barrel driving piston and said barrel, said seal serving to separate an inlet chamber in said housing from an annular cooling chamber in said housing.

10. The apparatus defined in claim 5 that includes a hydraulically actuated control cylinder in said housing; an annular cylinder barrel driving piston disposed in said control cylinder for varying the location of said first barrel outlet passages relative to said pistons.

11. The apparatus defined in claim 5 wherein said barrel includes a plurality of axially extending guides; and a plurality of bearing members disposed between said guides and said housing.

12. The apparatus defined in claim 5 that includes a plurality of reaction plugs carried by said barrel and having inner ends disposed in said cylinders and outer ends freely engaging said housing, said second barrel outlet passages and pressure responsive outlet valves being disposed in said reaction plugs.

References Cited UNITED STATES PATENTS 2,620,733 12/1952 Overbeke 103161 2,990,781 7/1961 Tuck et a1. 10337 3,024,731 3/1962 Heintz 10337 3,050,014 8/1962 Sullivan 103--162 3,067,694 12/1962 Fancher 103173 3,145,660 8/1964 Bush 103202 X 3,183,847 5/1965 Raymond 103-173 3,249,052 5/1966 Karlak 103-173 DONLEY J. STOCKING, Primary Examiner.

WILLIAM L. FREEH, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION- Patent No. 3,384,029 Dated May 21, 1968 Robert E. Raymond Inventor(s) It is certified that error appears in thQabove-identified patent and that said Letters Patent are hereby corrected as shown below:

In Fig. 1, reference numeral 130 has been added with a lead line to the dottedpassage communicating passages 130 and 162. In Fig. 8, reference numeral 124 has been deleted and 110-A inserted therefor. In Fig. 2', reference numeral 92 has been added with a lead line to the barrel surface represented by reference numeral 92 in Fig. 1. Column 6, cancel lines 13 31 and substitute der 150 via cylinder block outlet passage 1221A, passage 140 in outlet member llO-A, passage 144, orifice 147 and a radial passage v130 that connects with a housing passage 162 which in turn connects with control cylinderlSO as seen in Fig. l.

With continued reference to Fig. l, a control spool 149 is axially slideably mounted in a spool housing 151 and is biased toward a left position by compression spring 166 in which position spool 149 normally isolates radial passage 130 from control orifice 147.

When the fluid pressure through control orifice 147 exceeds a predetermined pressure value, established by the selected setting of a control knob 172 that includes a shank 174 in threaded engagement with a spring housing 168 at a threaded hole 176, then spool 149 shifts to the right thereby overcoming spring 166 via self-aligning spool end 164. Radial passage 130 is thereby opened and pressurized fluid is released to control cylinder 150 as explained above. This serves to shift cylinder block 70 to the left, Fig. l, to a new position of equilibrium wherein the force exerted on the cylinder block by compression spring 142 equals the force exerted on said block by annular control piston 146.

Referring again to Fig. 1, a radial passage 178 in the pump housing provides a drain from the control apparatus 135 back to the relatively low pressure outlet chamber 93. When pressure of oil through orifice 147 acting on the end of spool FORM M050 uscoMM-oc wan-Poo i U S. GOVEIHHNI 'IIHYING OT'ICI I... 0-3..3!

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. ,384,029 Dated May 21, 1968 PAGE Z Inventor-(s) Robert Raymond It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

149 drops belowthe preset value established by control spring 166, then spool 149 shifts to the left closing passage 130 to pressurized flow and subsequently opening passage 130 to drain passage 178 in the pump housing via passages 154, 158 and 160. This permits annular control piston 146 to move to the right discharging fluid from annular chamber 150 back to low pressure outlet chamber 93. This permits the cylinder block to shift to the right to a new position of equilibrium.

Signed and sealed this 30th day of May 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. I ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents

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