US3744378A

US3744378A - Pintle pump

Info

Publication number: US3744378A
Application number: US00258121A
Authority: US
Inventors: J Douglas
Original assignee: Oilgear Co
Current assignee: Oilgear Co
Priority date: 1972-05-30
Filing date: 1972-05-30
Publication date: 1973-07-10
Anticipated expiration: 1990-07-10

Abstract

The invention comprises a radial piston hydraulic pump or motor having a control to position the cylinder barrel on a tapered pintle to maintain the necessary flow of leakage fluid in each direction outwardly between their bearing surfaces for different or varying operating conditions. The control includes a servomotor to urge the cylinder barrel on the taper of the pintle in accordance with the flow of the leakage fluid discharged at one end of the pintle with such flow regulated so as to equal or exceed the flow of leakage fluid discharged at the other end of the pintle.

Description

United States Patent [191 Douglas July 10, 1973 PINTLE PUMP 2, 53,153; 3/132; gishgipngl. ..39l/485 [75] Inventor: James K g Shorewood, wis- 3, us et 08/122 [73] Assignee: The Oilgear Company, Milwaukee, Primary Examiner-William L. Freeh Wis. AttorneyT. Lloyd LaFave {22] Filed: May 30, 1972 [57] ABSTRACT PP 258,121 The invention comprises a radial piston hydraulic pump or motor having a control to position the cylinder 52 [1.8. CI. 91/484, 91/492 barrel on a tapered pintle maintain the necessary 51 1111. c1. F0lb 13/06 flow of leakage fluid in direction outwardly [58] Field 01 Search 91/484, 492, 485, tween their bearingsurfacesfor different Orvarying P- 91/489 erating conditions. The control includes a servomotor to urge the cylinder barrel on the taper of the pintle in [56] References Cited accordance with the flow of the leakage fluid dis- UNn-ED STATES PATENTS charged at one end of the pintle with such flow regulated so as to equal or exceed the flow of leakage fluid 5322; discharged at the other end of the pintle. 2:449:29; 9/1948 Hoffer 308/9 5 Claims, 1 Drawing Figure 24 33 I /0 57 2 3 62 /6 I l I 3? 5a PINTLE PUMP BACKGROUND OF THE INVENTION The invention pertains to a radial piston hydrostatic machine operable as a pump or as a motor and having a tapered pintle for valving motive fluid to the cylinders of a cylinder barrel journalled on the pintle. And more particularly it pertains to such a machine having a control to move the cylinder barrel on or off the taper of the pintle to adjust the running clearance between their mating tapered bearing surfaces in accordance with operating pressure and the flow of leakage fluid escaping at each end of the pintle.

This type of tapered pintle hydraulic pump or motor is shown and described in US. Pat. No. 2,231,361 issued Feb. 11, 1941. It shows an end cylinder arranged on the end of the cylinder barrel, a piston fitted in the end cylinder and secured to the driveshaft for coupling the cylinder barrel and drive shaft for rotation with each other. Leakage fluid escaping from between the tapered bearing surfaces of the cylinder barrel and pintle at thpe small end of the pintle enters the end cylinder and is discharged therefrom through a flow restricting passage. The pressure of the leakage fluid in the end cylinder urges the cylinder barrel toward the large end of the pintle. The machine is also provided with built in stops to limit the movement of the cylinder barrel in either direction and a prressure relief valve connected to a discharge passage for the leakage fluid to limit the pressure of leakage fluid in the end cylinder to a preset maximum value.

The prior art control of the running clearance between a cylinder barrel and a tapered pintle is responsive to the flow of leakage fluid at one end of the pintle independent of the flow of leakage at the other end of the pintle.

Although the tapered surfaces are machined to provide mating surfaces, machining tolerances leave some error which may be compensated in part by select fitting of pintle and cylinder barrel parts in order to provide at least as much leakage flow under normal operating condtions at the large end of the pintle as at the small end of the pintle. However this does not give positive protection against operating conditions that may cause the leakage flow along the bearing surfaces at the large end of the pintle to decrease below a minimum value necessary to lubricate and cool such bearing surfaces and prevent seizure therebetween.

The leakage flow at the large end of the pintle may decrease relative to the leakage flow at the small end of the pintle, for example, when'there is a change in oil temperature causing uneven expansion of pintle and or cylinder barrel.

SUMMARY OF THE INVENTION The invention provides a radial piston hydraulic pump or motor having a cylinder journalled on a tapered pintle and axially adjustably positioned on the pintle to vary the running clearance between their bearing surfaces to maintain a prescribed minimum flow of leakage fluid therebetween and escaping at each end of the bearing surfaces sufficient to cool and lubricate the bearing surfaces.

The cylinder barrel is urged in a direction off of the taper of the pintle by bias forces consisting of a spring and the pressure of the leakage fluid flowing between the tapered bearing surfaces. The cylinder barrel is urged in a direction on the taper of the pintle by the pressure of leakage fluid received in a cylinder arranged at one end of the cylinder barrel and pintle and discharged therefrom through a variable orifice or through a fixed orifice in parallel with a variable openmg.

Leakage fluid flows outwardly in both directions from a port located intermediate the ends of the pintle and the end cylinder receives such flow from the small end of the pintle. Flow of leakage fluid along the bearing surface-of the large end of the pintle is conducted to discharge through a fixed orifice. The rate of flow of leakage fluid from each end of the bearing surfaces and discharging through their respective orifices each develop a pressure which are substantially equal when the leakage flows from each end of the pintle bearing surface are equal. The pressures at these orifices are applied in opposition on a valve member of a servovalve controlling the opening of the variable orifice, an opening in parallel with the fixed orifice. When a difference in the pressures at the orifices exists due to the pressure of leakage fluid from the large end of the pintle being less than that from the small end of the pintle, the valve member is displaced by the resulting difference in pressures to increase the opening for the discharge of leakage fluid from the small end of the pintle and thus reduce its pressure until the opposing pressures of leakage fluids are equal. This reduces the pressure in the end cylinder so that the cylinder barrel moves off of the taper to increase the running clearance and increase the leakage flows until the servovalve can equalize its opposing pressures.

Thus, the present invention provides a control for positioning the cylinder barrel on thee tapered pintle in accordance with the lesser effective running clearance occurring at either end portions of their bearing surfaces and as may exist or occur during varying operating conditions. Such positive protection assures not less than a prescribed minimum effective running clearance for each end portion of the bearing surfaces and permits the selection of a lower minimum running clearance that will nevertheless permit sufficient flow of leakage fluid for lubricating and cooling of the bearing surfaces at the most severe operating conditions.

A pump, for example, embodying the present invention and having an output capacity equivalent to 500 horsepower, is designed at rated output to provide a flow of leakage fluid between the bearing surfaces of the pintle and cylinder barrel on the order of 2 percent of pump output. The pump is also designed to have a maximum running clearance of 0.007 inch, as at startup, and a minimum running clearance of 0.001 inch, as at maximum pressure and temperature.

It is therefore an object of the invention to control the position of a cylinder barrel on a tapered pintle to maintain a necessary minimum flow of leakage fluid betweeen both end portions of their bearing surfaces.

Another object of the invention is to control the position of a cylinder barrel on a tapered pintle to maintain an effective minimum running clearance between both end portions of the bearing surfaces of the pintle and cylinder barrel.

Another object of the invention is to urge a cylinder barrel on a tapered pintle by a control cylinder responsive to the pressure of leakage fluid escaping from the small end of their bearing surfaces to effectively override such control in response to a relative decrease in pressure of leakage fluid escaping from the large end of the bearing surfaces.

Another object of the invention is to make cylinder barrel and pintle parts for pumps interchangeable without the necessity for select fitting by providing a control that maintains an effective minimum running clearance between both end portions of said parts to compensate for machining tolerances for all operating conditions of the pumps.

Other objects and advantages of the invention will be apparent from the following description and accompanying drawing, in which:

FIG. 1 is a longitudinal view, with part broken away and part in cross-section of a pump illustrating an embodiment of the present invention.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION A variable displacement hydraulic machine, FIG. 1, is operable as a pump or as a motor, and for convenience is herein referred to as a pump. The pump comprises a closed casing 1, having a removable head 2 attached to its front end and a hub 3 formed integral with the casing at its rear end. A slideblock 4 is supported in a known manner for transverse horizontal movement in the casing. A hollow thrust member 6 is rotatably supported in the slideblock by thrust bearings 7, 8. The eccentricity of the axis of the thrust member 6 with respect to the axis of the cylinder barrel 20 is determined by the position of the slideblock 4. Such eccentricity determines the displacement of the pump.

A stationary valve shaft or pintle 9 has a rear part rigidly secured in the hub 3 of the casing, and the front part 10 of the pintle is arranged within the thrust member. The pintle 9 is provided wiith an upper segmental port 11 and a lower segmental port 12, which communicate respectively with upper and lower passages 13, 14 respectively formed longitudinally in the pintle. The rear end of these passages extend radially outward .through the rear part of the pintle to inlet and outlet ports 16, 17 for connection to an external circuit. Th forward part 10 of the pintle, within the thrust member, is tapered to a reduced diameter and supports the cylinder barrel 20, which has a bushing 21 press fitted therein and accurately fitted upon the forward tapered part 10 of the pintle so that the cylinder barrel is freely rotatable about the pintle.

The cylinder barrel 20 is provided with a plurality of radial cylinders 22 which are arranged in circumferential rows, and in longitudinal rows. The cylinder barrel 20 is provided with a plurality of passages 23 each of which communicates with at least one cylinder in each of the circumferential rows. Each such passage communicates with a cylinder port 24 formed in the bushing which, in turn, communicates with the pintle ports ll, 12, alternately, as the cylinder barrel rotates.

A piston 25 is fitted in each cylinder 22 and prrovided with a contact face upon its outer end. The contact face of each piston engages with the reaction surface formed on a thrust ring 26, fixed within thrust member 6.

Cylinder barrel 20 is connected to a driveshaft 27 so that it may rotate therewith. The driveshat't is rotatably supported by thrust bearings arranged in the end head 2 and by a thrust bearing 29 arranged in a recess formed in the forward end of the pintle.

As shown, the cylinder barrel 20 has its body or main portion extended beyond the small end of the pintle to form and end cylinder 32. This end cylinder has arranged therein a piston 33 which is splined upon the shaft and a shoulder formed thereon limits outward movement of the cylinder barrel. The piston 33 closes the end cylinder and also serves as a driver coupling the cylinder barrel to the shaft 27 for rotation together. A piston ring is fitted in the radially outer part of the piston 33 to prevent liquid from escaping through the outer end of the cylinder. A radially outer or driver part of the piston 33 is reduced in diameter to receive a driving ring 35 suitably pinned to the wall of the cylinder and to the piston to permit axial movement between the cylinder barrel and the piston and to rotatably drive the cylinder barrel 20 along with the piston ring.

Two sets of leaf springs 36, each of which consist of a plurality of leaves, extend across the bore of the end cylinder 32 from opposite sides of the shaft and have their end portions arranged into slots which are formed diametrically opposite each other in the siidewall of the bore. The intermediate ends of the leaf springs 36 are slidable against an abutment reaction membpr secured to the shaft. The springs, by acting upon the abutments and reaction abutment member, urge the cylinder barrel in a direction off the taper of the pintle, and as shown in FIG. 1 th cylinder barrel is in the center of its travel.

Since the bearing surfaces of the pintle part 10 and of the bushing 21 in the cylinder barrel are tapered, the running clearance therebetween is increased by moving the cylinder barrel 20 toward the right and decreased by moving it toward the left. At the limit of its movement toward the right, the running clearance between the pintle and cylinder barrel is just sufficient to permit a relatively low pressure to cause motive liqfuid to form a lubricating film between the cylinder barrel and the pintle.

The high pressure one of the ports l1, 12 in the pintle supplies fluid to the running clearance between the bearing surfaces of the pintle and the cylinder barrel, and this leakage fluid escapes from both ends of the cylinder barrel. The pressure of the leakage fluid in the running clearance between the cylinder barrel and pintle acts to urge the cylinder barrel in direction off the taper of the pintle. Leakage fluid escaping past the front end of the pintle and entering the end cylinder 32 creates a pressure therein which acts upon the end face of the cylinder barrel to urge the cylinder barrel in a direction toward the left in FIG. 1, and on the taper of the pintle. I

Leakage fluid is conducted from end cylinder 32 through a

small passages

37, 38, the latter extends axially through the pintle from one end to the other end thereof and in turn is connected to a passage 43 in a schematically illustrated valve block 39 mounted on the rear end of the pintle and the hub 3 of the casing. The associated passage 43 in the valve block is in turn connected, as hereinafter described, to a passage 48 through the casing 1 so thaat the fluid escaping therethrough may return through a drain passage from the casing to reservoir, not shown. The flow .of liquid through the passage 43 in the valve block is limited by a suitable choke, such as an orifice 44, inserted in that passage downstream of valve 50, so that pressure which may be created in the end cylinderr 32 is sufficient to move the cylinder barrel to a position on the pintle. Thee escape of liquid from the end cylinder is resisted by the choke 44, and therefore results in an increase of pressure in the end cylinder. The pressure of liquid in the end cylinder continues to rise until it is high enough to overcome the resistance of the bias forces provided by hydraulic pressure acting between the pintle and cylinder, and by the force of the springs 36, then the pressure in the end cylinder 32 will move the cylinder barrel toward the large end of the pintle to reduce the running clearance between the cylinder barrel and the pintle, and reduce the flow of leakage through it to the end cylinder at a point where the pressure in the end cylinder can be maintained by the rate of flow through the orifice 44.

According to the present invention however, leakage fluid supplied by the high pressure pintle port and flowing between the bearing surfaces of the pintle and cylinder barrel outwardly toward the large end of the pintle is collected in an annular groove 40 formed in the periphery of the pintle adjacent to the large end of its bearing surface. The collection groove 40 is connected by a radially drilled passage 41 to interconnect with an axially drilled passage 42 extending to the end of the pintle for connection to a passage 45 in the valve block at the large end of the pintle. This passage is also, in turn, connected to drain passage 47 and end drain passage 48 to the interior of the casing through a flow restriction orifice 46 inserted in this passage 45 downstream of valve 50 and it has substantially the same choke or flow restricting properties as provided by the orifice 44 for leakage fluid escaping from the other end of the pintle.

The valve block 39 contains a servovalve 50, comprising a valve chambper 51 one end of which is connected to the passage 43 receiving fluid escaping from the end cylinder at the small end of the pintle and the other end is connected to the passage 45 receiving fuid escaping through the collection groove 40 at the large end of the pintle bearing surface. A drain opening 53 serving as an additional drain opening from said chamber is located intermediate said end passages and is normally blocked by a movable valve member 52 in said valve chamber. The valve member 52 may be moved entirely by hydraulic forces or also may be biased by a light spring 54 in a direction to normally block the drain opening 53 and to prevent hunting of the valve. One end of the servovalve is onnected to the passages 43, 38, conducing leakage fluid from the end cylinder 32 at the small end of the pintle an the other end of the servovalve is connected to the passages 45, 42 conducting leakage fluid from the collection groove 40 at the large end of the pintle. The servovalve 50 is connected ahead or upstream of the

orifices

44, 46 so that the pressure developed at the orifices appears in the servovalve to-react on opposite ends of the valve member.

The servovalve 50 is constructed and arranged so that the movable valve member 52 is normally in the position shown, when the opposing pressures acting on the valve member are equal or when the pressure of the leakage fluid from the large end of the pintle is greater. in that event, the servovalve is inoperative and the servomotor comprising end cylinder 32 is the controlling factor as regulated by the rate of flow of fluid discharging through its associated orifice 44. When, for any reason, however, the leakage flow from the large end of the pintle develops less pressure at its dicharge orifice 46 than is developed at the discharge orifice 44 by the leakage fluid from the small end of the pintle then the differential pressure acting on the servovalve displaces its movable valve membper 52 to open the orifice port 53 and drain additional fluid from the end cylinder 32 through passage 55 until such pressures at the discharge orifices at opposite ends of the cylinder equalize. The drain opening 53 in the valve member being gradually uncovered by the movable valve member provides a variable opening and responds to a differential pressure to operatively connect the drain opening in parallel with the fixed orifice 44 draining fluid from the end cylinder 32. When the effective running clearance between the large end of the pintle and the cylinder barrel is in fact less than the effective running clearance from the smaller end of the pintle and the cylinder barrel, the flow of leakage fluid from the large end of the pintle will be less than the flow from the smaller end of the pintle and will generate less pressure at the orifice 46 discharging leakage fluid from the large end of the pintle. This will cause the servovalve to variably open the drain opening 53 to passage 55 to drain fluid from the end cylinder 32 and cause the cylinder barrel 20 to move off the taper to establish a greater overall running clearance until the differential pressure on the servovalve is minimized. Variable opening 53 is shown connected through a fixed orifice 49 to drain passages 47, 48.

The pressure in end cylinder 32 is positively limited 7 by a relief valve 56 located in the valve block 39 and relief valve 56 operatively connects passage 43 to drain passages 47, 48.

Although it is preferred to use a fixed orifice 44 operatively connected in parallel with a variable opening 53, it is understood that a single variable opening is equivalent thereto when arranged for a predetermined minimum opening serving both as a fixed orifice and a variable orifice.

I claim:

1. A hydraulic pump or motor having a cylinder barrel journalled on a tapered pintle with the axial position of the cylinder barrel varied to maintain a necessary running clearance between the bearing surfaces defined by their mating tapered surfaces, leakage fluid supplied from operating ports in the cylinder barrel and pintle escaping from between their running clearance to opposite ends thereof, a servo-motor responsive to the pressure of leakage fluid escaping at one end of said pintle urges said cylinder barrel in a direction to reduce the running clearance, and a servovalve responsive to thee differences in the pressures of the leakage fluid escaping at both ends of said pintle is operative to bleed fluid from said servomotor when the pressure of leakage fluid therein from said one end is greater than the pressure of leakage fluid escaping from the other end of said pintle.

2. A hydraulic pump or motor having a cylinder barrel with a tapered bore journalled on a tapered pintle and the mating surfaces thereof defining tappered bearing surfaces, inlet and outlet ports in said pintle to con duct fluid between cylinders and said cylinder barrel and passages in said pintle and also to supply leakage fluid along the running clearance between the tapered bearing surfaces, a servomotor to receive leakage fluid discharging from said bearing surfaces at one end of said pintle and position said cylinder barrel on said servomotor for effecting a predetermined minimum flow of leakage fluid between said bearing surfaces at one end of said pintle, said pump or motor characterized by means for effecting a predetermined minimum flow of leakage fluid between said bearing surfaces at the other end of said pintle, said means comprising a servovalve having a discharge opening and a valve member interrupting said opening, opposite ends of said servovalve connected respectively to receive leakage fluid from opposite ends of said pintle valve and operable to conduct leakage fluid from said one end of said pintle to said discharge opening when the pressure thereof on said valve member exceeds its opposing pressure.

3. In a hydraulic pump or motor having a cylinder barrel journalled for rotation on a tapered pintle, inlet and outlet ports in the pintle intermediate the ends of the bearing surface of the pintle, leakage fluid supplied from said ports to flow between the bearing surfaces and escape at both ends thereof, a servomotor comprising a cylinder arranged at one end of the cylinder barrel to receive leakage fluid escaping from said one end and connected to a first orifice for discharging said leakage fluid at a limited rate, passage means collecting leakage fluid flowing between the bearing surfaces and escaping at the other end and a second orifice discharging such leakage fluid at a limited rate, and a valve having ports connected ahead of said first and second orifices to receive leakage fluid from both ends of said bearing surfaces, said valve having a movable valve member between the ports thereof and a discharge opening closed by said valve member when the pressure at said second orifice is equal to or greater than the pressure at said first orifice, and said discharge opening being variably opened to leakage fluid at said first orifice when the pressure thereof is greater than the pressure of leakage fluid at said second orifice, whereby the pressure of the leakage fluid in said cylinder of said servomotor positions said cylinder barrel on said pintle to maintain at least a predetermined minimum flow of leakage fluid to both ends of said bearing surfaces.

4. In a pump or motor as described in claim 3 in which said one end of said bearing surfaces is at the small end of the pintle and the other end is at the large end of the pintle, and the servomotor is arranged at the small end of the pintle.

S. In a pump or motor as described in claim 3 in which said servomotor is arranged at the small end of the pintle to receive leakage fluid escaping from between the bearing surfaces at that end, a valve block mounted on the other end of said pintle and containing said orifices and said valve, a first passage extending axially through said pintle to the cylinder of said servomotor and connected to one port in said valve and said first orifice, a second passage in said pintle connected to a second port in said valve and said second orifice, an annular groove in the periphery of the bearing surface of the pintle adjacent the large end thereof and connected to said second passage in said pintle to conduct leakage fluid escaping from between the bearing surfaces at the large end of the pintle to said second port in said valve and to said second orifice.

Claims

2. A hydraulic pump or motor having a cylinder barrel with a tapered bore journalled on a tapered pintle and the mating surfaces thereof defining tappered bearing surfaces, inlet and outlet ports in said pintle to conduct fluid between cylinders and said cylinder barrel and passages in said pintle and also to supply leakage fluid along the running clearance between the tapered bearing surfaces, a servomotor to receive leakage fluid discharging from said bearing surfaces at one end of said pintle and position said cylinder barrel on said servomotor for effecting a predetermined minimum flow of leakage fluid between said bearing surfaces at one end of said pintle, said pump or motor characterized by means for effecting a predetermined minimum flow of leakage fluid between said bearing surfaces at the other end of said pintle, said means comprising a servovalve having a discharge opening and a valve member interrupting said opening, opposite ends of said servovalve connected respectively to receive leakage fluid from opposite ends of said pintle valve and operable to conduct leakage fluid from said one end of said pintle to said discharge opening when the pressure thereof on said valve member exceeds its opposing pressure.

5. In a pump or motor as described in claim 3 in which said servomotor is arranged at the small end of the pintle to receive leakage fluid escaping from between the bearing surfaces at that end, a valve block mounted on the other end of said pintle and containing said orifices and said valve, a first passage extending axially through said pintle to the cylinder of said servomotor and connected to one port in said valve and said first orifice, a second passage in said pintle connected to a second port in said valve and said second orifice, an annular groove in the periphery of the bearing surface of the pintle adjacent the large end thereof and connected to said second passage in said pintle to conduct leakage fluid escaping from between the bearing surfaces at the large end of the pintle to said second port in said valve and to said second orifice.