US2518618A - Means for cooling and lubricating pumps - Google Patents

Description

Aug. 15, 1950 w. HUBER 2,518,

ms FOR COOLING AND LUBRICATING PUMPS.

Filed Jan. 25, 1948 Ma ihw W. Huber INVENTOR ATTORNEYS Patented Aug. 15, 1950 2,518,618 l MEANS ron. coonmc AND LUBRICATING PUMPS Matthew W. Huber, Watertown, N. Y., asslgnor to The New York Air Brake Company, a corporation of New Jersey Application January 23, 1948, Serial No. 3,957

4 Claims.

This invention relates to pumps of the type in which the pump cylinders are arranged in circular series around a drive shaft, the axes of the 03!!- inders being parallel with each other and with the axis of the drive shaft. In such pumps the plungers are commonly actuated by a cam or swash plate fixed on the shaft.

The pump forming the subject of this application includes an improvement upon the pump shown in Patent 2,433,222 issued to the present applicant on December 23, 1947.

In certain types of installation it is desired to operate pumps of this type with a positive intake pressure. This pressure is commonly of the order of 80 pounds per square inch; In a pump arranged as shown in the patent above identified, this intake pressure reacts against the ends of the plungers and tends to neutralize the retracting force of the plunger return springs. The plungers become sluggish on their suction strokes, and difficulties result. For various reasons it is not practicable to increase the strength of the plunger return springs, and the purpose of the present invention is to protect the plungers from the effects of the supply pressure. Since one of the major uses of this type of pump is in aircraft hydraulic systems where weight is a factor of great importance, it is desirable to accomplish the stated purpose with as small an addition to the pumps weight w as possible. Also it is necessary to maintain a flow of oil in the cam chamber even when the pump is operating at zero delivery for the purposes of lubricating and cooling the cam surfaces and the shaft bearings.

These results are accomplished according to my invention by permitting a restricted flow from the intake and spill-back chambers to the cam chamher, the size of the flow restrictor being such that suflicient fluid flow occurs to cool and lubricatethe moving parts in the cam chamber. Free outflow from thecam chamber is permitted to occur, so that no additional pressure can be developed by the restricted inflow.

A preferred embodiment of the invention will now be described by reference to the accompanying drawing in which the single view is an axial section through a nine cylinder pump embodying the invention.

All statements of direction in the description relate tothe pump in the position shown in the accompanying drawing.

The housing of the pump includes a body portion I and a. cap 2 secured thereto. The cap has an inlet connection 3 and a discharge connection 4.

Enclosed in the body I and confined between a shoulder I in the body and a shoulder 6 in the cap are a cylinder block 1 and a guide block 8. Said blocks are annular in form and enclosed between them is a spill-back chamber 9. This chamber communicates with the inlet connection 3 by way of the drilled passage I0 which extends through the cylinder block I. The outer peripheral margin of the cylinder block is an annular channel which receives a ring gasket l2. A second annular channel receives another ring gasket I3. The annular discharge passage it formed in cap 2 is thus isolated. The discharge passage l4 communicates with the discharge connectionl through the drilled passage I5.

A dowel it properly positions the cylinder .block and the guide block and screws I! hold them in assembled relation. Maintained alinement between the bores in the guide block and the cylinder block is thus assured. The bores in the two blocks are nine in number and those in the cylinder block form the cylinders l8. Each cylinder has a. discharge valve I 9 associated therewith, and is maintained in proper alinement with its cylinder by stem 20 which is reciprocable in a drilled guideway 2| in the cap 2. The discharge valves l9 are urged in a closing direction by coil compression springs 23, one confined between each valve and the cap 2.

Each of the cylinders l 8 is encircled by a groove 24 which constitutes the inlet port and is controlled by the corresponding plunger. Each groove 24 communicates wit-h the inlet connection 3 by way of a drilled passage 25.

A plunger 26 is reciprocably mounted in each cylinder l8. Each plunger 26 passes from the cam chamber 35 through the guide block 8, across the spill-back chamber 9 and into the cylinder block 1; Each plunger 26 is retracted by a coil compression spring 21 surrounding its plunger and reacting between the guide block 8 and a flange on the left end of each'plunger. On the end of each plunger is a universally tiltable thru .head 28.

A counterbored drive shaft 29 is rotatably mounted in end bearing 30 which is fixedly mounted in the guide block 8. A metering orifice 3| in the bearing 30 affords a restricted communication from the spill-back chamber 9 to the counterbore of the shaft 29. Keyed to the'shaft 29 is a. cam or swash plate 32. Radial drilled ports 34 lead from the shaft bore to the cam chamber 35. An overflow connection 36 communicates with the cam chamber 35 and is connected to the low pressure sump S. Drilled ports 3'! supply hydraulic fluid to the creep plates 38 and 38, and bushing 40 and to thrust ring 4 I. A conventional oil seal indicated generally at 42 prevents leakage from the interior of the pump along the shaft 29. The part 43 is a conventional spllned driving connection to accommodate possible misalinement of the shaft 29 with reference to the driving shaft (not shown).

Fixed in the central aperture of the annular cylinder block is an annular bushing 45 which is the cylinder of the regulatory motor. A rod 43 passes through the cylinder bushing 45 and is axially slidable therein. This rod 48 carries a cup-shaped spring seat 44. The coil compression springs 49 and50, sustained in tandem between the seat 44 and an adjustable spring-seat 55 in the cap, urge the rod 48 to the left. Fluid at discharge pressure flows through the choke 46, the passage 41 and through a radial port (not shown) in the cylinder bushing 45. This fluid acts on a piston of ordinary form working in cylinder bushing 45 and attached to the rod 48, and urges the piston to the right against the resistance of the springs 49 and 50. The choke 46 is interposed in the passage 41 to prevent surging in the pressure fluid acting on the piston of the regulatory mot-or.

A ported spider is attached to the left end of the rod 48. The spider engages the nine sleeve-like spill-back valves 52. Each of the spillback valves 52 encircles a corresponding one of the nine plungers 26.

The axial position of the spill-back valves determines the effective stroke of all the pump plungers 26. Each plunger has a counterbore leading from its right hand end to radial ports 53 controlled by the spill-back valves 52. The pump is shown with the spill-back valves in the full stroke position. It will be realized that as increased discharge pressure acts to move rod 48 to the right the spider 51 also moves to the right, carrying with it the spill-back valves 52. This has the effect of shortening the effective stroke of the plungers since back-flow through the ports 53 continues until plunger 28 has moved a greater distance to the right than would have been the case had the parts remained in the position shown in the drawing.

In operation the inlet connection 3 is supplied with hydraulic fluid under pressure from some pressure developing means typified by the pump P. This might for example be an impeller type of pump.

Fluid under inlet pressure flows through the passages 25 into the grooves 24 and into those cylinders 18 which are not blanked by their plungers 26. Fluid, at this pressure, fills the counterbore in the plunger and the radial ports which lead therefrom. Fluid at inlet pressure also flows through the passage l0 into the spill-back chamber 9. Fluid passes through the restricted passage 3! into the counterbore of the shaft 29, and outwardly through the radial impeller passages 34 in the cam 32 into the cam chamber 35. The outflow connection 36 from the top of the cam chamber 35 is of substantially larger cross-sectional area than is the restricted passage 3|. As a consequence the fluid in the cam chamber and surrounding the plungers will be under the pressure corresponding to the height of the overflow, which is negligible. Consequently, the retraction of the plungers will not be impeded by hydraulic pressure in the cam chamber, and the operation of the pump will not be adversely affected by supplying fluid under pressure to the inlet connection 3. While the fluid flowing into the cam chamber is actually subjected to a moderate centrifugal pumping effect as it flows through the radial ports 34 in the cam 32, this action is not essential to the proper functioning of the invention. Since the fluid is entering the counterbore 01' the shaft 29 and flowing to the cam chamber 35 under pressure, circulation of fluid is assured at all times. This is so whether the pump is delivering at full capacity or idling at zero delivery.

What is claimed is:

1. In a pump the combination of a housing structure enclosing at least one cylinder, an inlet passage with inlet ports communicating with each cylinder, and a cam chamber having a free overflow and a restricted communication with said inlet passage; a plunger reciprocable in each cylinder, each such plunger having one end exposed in the cam chamber; spring means serving to bias each plunger toward the cam chamber; a rotary cam in the cam chamber engaging the exposed end of 'each plunger to reciprocate the same; discharge valve means for each cylinder; and means for supplying liquid to be pumped to the inlet chamber under a substantial positive pressure, the restricted communication and overflow being so dimensioned and located that the inlet ports are fed at said positive pressure and liquid fills and circulates through said cam chamber without developing material pressure therein.

2. The combination defined in claim 1 in which the cam includes an impeller and the restricted communication leads to the entrance of said impeller whereby rotation of the cam tends to stimulate circulation of liquid through the cam chamher.

3. In a pump, the combination of a housing structure enclosin a plurality of cylinders, a cam chamber and a combined inlet and spillback valve chamber interposed between each cylinder and said cam chamber, there being an inlet port to each cylinder, a restricted flow connection from said combined chamber to the cam chamber and a substantially free overflow from the cam chamber; plungers one reciprocable in each cylinder, each plunger extending from the cylinder, across the combined inlet and spill-back chamber and thence into the cam chamber so as to be exposed at its end in the cam chamber, each plunger having a spill-back port leading from a point within its cylinder to a point in the plunger within said combined chamber; spring means serving to bias each plunger toward the cam chamber; a rotary cam in the cam chamber engaging the exposed ends of the plungers to reciprocate the same; discharge valve means for the cylinders; spill-back valves slidable on the plungers within the combined chamber and controlling the spill-back ports; means for adjusting the positions of the spill-back valves in unison; and means for supplying liquid to be pumped to said combined inlet and spill-back chamber under a substantial positive pressure, said restricted communication and said overflow being so dimensioned and located that the inlet ports are fed at said positive pressure, and liquid fills and circulates through said cam chamber without developing material pressure therein.

4. In a pump of the type in which a, plurality of cylinders are arranged in a circular series with their cylinder axes parallel with the axis of the drive shaft, the combination of a cylinder block having a circular series of cylinder bores, a guideblock having a similar series of guideways, each guideway being alined with a corresponding cylinder bore, said blocks being so formed that the two when assembled enclose an intervening chamber to which an intake passage leads through one of the blocks; a divided housing formed to enclose and confine said blocks and to afford a cam chamber distinct from said intervening chamber and adjacent said guide block, one portion of said housing having a discharge passage communicating with said cylinder bores; a shaft bearing fixed coaxiaily in said guide-block; thrust and radial shaft bearings supported in the housing and axially alined with the bearing in the guideblock; a rotary drive shaft mounted to turn in said bearings and having an axial bore; a cam carried by said shaft within said cam chamber and having an impeller port leading from said axial bore; a plurality of plungers, each extending from said cam chamber through said guideways across said intervening chamber and into corresponding cylinder bores, said plungers being ar- 6 ranged to be reciprocated by said cam; means associated with that bearing which is fixed in said guide block and serving to afford restricted communication from said intervening chamber to the axial bore of said shaft; an overflow connection leading from said cam chamber, said outflow connection having a-substantially greater cross-sectional area than said restricted communication; andmeans for supplying liquid under substantial positive pressure to said intake pas- MA'ITHEW W. HUBER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Ernst Sept. 13, 1938 Ifleld Aug. 4, 1942 Huber Dec. 25, 1947 sage.

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