US3687012A

US3687012A - Hydraulic motor

Info

Publication number: US3687012A
Application number: US86065A
Authority: US
Inventors: Gary Stein; Allan E Heinrich
Original assignee: Applied Power Industries Inc
Current assignee: Enerpac Tool Group Corp
Priority date: 1970-11-02
Filing date: 1970-11-02
Publication date: 1972-08-29
Anticipated expiration: 1989-08-29

Abstract

A fluid motor of the type having a tiltable cam plate. The cam plate is of a cup-shaped configuration and defines a cavity. Apertures are provided in the walls of the cam plate to permit circulation of hydraulic fluid through the cavity. The cam plate is tilted by hydraulically actuated control pistons on each side of the pivotal axis of the cam plate, with one of the pistons being constantly pressurized to urge the cam plate to a first position. Each of the control pistons, when in the fully extended position, engages a portion of the cam plate in such a manner that the line of contact therebetween is in a plane transverse to the longitudinal axis of the piston.

Description

United States Patent Stein et al.

[ Aug. 29, 1972 [54] HYDRAULIC MOTOR [72] Inventors: Gary Stein, Brookfield; Allan E. Heinrich, Oconomowoc, both of [21] Appl. No.1 86,065

52 us. 01 ..91/507 51 161. c1 ..F0lb 13/04 [58] FieldofSearch ..417/506,507;92/57;91/485 [56] References Cited UNITED STATES PATENTS 2,715,875 8/1955 Towler ..9l/474 2,733,666 2/1966 POUlOS ..91 4s5 2,858,771 .1 1/1958 Cornelius ..92/57 3,067,694 12/1962, Fancher ..9l/486 3,304,885 2/1967 Orth ..91/507 2,525,498 10/1950 Naylor 61 al ..91/4s5 FOREIGN PATENTS OR APPLICATIONS 482,073 6/1953 Italy ..4l7/269 Primary Examiner-William L. Freeh AttorneyJohn J. Byrne 57 ABSTRACT A fluid motorof the type having a tiltable cam plate.

2 The can plate is of a cup-shaped configuration and defines a cavity. Apertures are provided in the walls of the cam plate to permit circulation of hydraulic fluid through the cavity. The cam plate is tilted by hydraulically actuated control pistons on each side of the pivotal axis of the cam plate, with one of the pistons being constantly pressurized tourge the cam plate to a first position. Each of the control pistons, when in the fully extended position, engages a portion of the cam plate in such a manner that the line of contact therebetween is in a plane transverse to' the longitudinal axis of the piston.

3Claims,3Drawingfigures Patented Aug. 29, 1972 3,687,012

2 Sheets-Sheet 1 INVENTORS GARY STE/IV ALLA/V E HEINRICH WV/ LLfL- V ATTORNEY Patented Aug. 29, 1972 2 Sheets-Sheet 2 ble cam plate. to cause the pistons to travel through intake and discharge strokes as the barrel rotates. By varying the angle of the cam plate, the speed and torque of the motor can be varied as is well known in the art.

In many prior art hydraulic motors, attempts have been made to strengthen the'cam plate by employing reinforcing elements made as an integral part of the plate, thereby generally increasing the size of the cam plate. This has in turn resulted in an increase in the size of the motor housing. One particular-reinforcement design has been quite effective, however, in eliminating the requirement of more space while at the same time strengthening the cam plate. This design incorporates a cylindrical wall or skirt on the cam plate extending from the surface of the cam plate toward the barrel to define an open-ended, cup-shaped configuration and defining a cavity.

One of the major drawbacks of the provision of a cylindrical reinforcing wall extending from the bearing surface of the cam plate is that the hydraulic fluid in the housing which serves as a coolant becomes entrapped in the cavity defined by the wall and does not circulate as is necessary to exchange heat and cool the surface of the cam plate, which tends to become very hot due to the frictional engagement between the cam plate and the ends of the pistons.

Therefore, it is an object of this invention to provide an improved cam plate having means to induce the circulation of the hydraulic fluid between the cavity defined by the cup-shaped cam plate and the chamber defined by the housing.

It is an objective of this invention to provide an improved cam plate tilting mechanism of relatively inexpensive and simple construction.

It is a further objective of this invention to provide a cam plate tilting means which will accurately adjust the speed and torque of the motor from a remote point.

More particularly the preferred embodiment of this invention includes a cup-shaped cam plate having a cylindrical wall thereon extending from the plate and toward the piston-containing rotatable berrel and defining an open-ended cavity. The wall is provided with apertures spaced around the periphery of the wall for communicating the cavity with the chamber defined by the motor housing, in which chamber the tiltable cam plate is positioned. The chamber is filled with hydraulic fluid which enter the cam plate cavity and serves as a coolant. As the pistons rotate in abutment with the bearing surface of the cam plate, a centrifugal force is set up which tends to throw the fluid out through the apertures and into the chamber while creating a pressure drop which tends to draw cooler fluid from the chamber into the cavity through the open end thereof. Hence a constant circulation of cooling fluid is provided.

Additionally, the cam plate is tilted between first and second positions by hydraulic means comprising first and second control pistons, the first having a smaller working surface than the other, and engaging the cam plate on opposite sides of the pivotal axis thereof. The small, first control piston is at all times in communication with a suitable pressure source thereby constantly biasing the cam' plate to a first position. Valve means are provided for selectively communicating the pressure source to the second piston when it is desired to pivot the cam plate whereby, due to the larger working area, the second control piston overcomes the biasing force of the smaller first piston to pivot the cam plate to the desired position. The cam plate will be maintained in that position by modulation of the control valve. Ad ditionally, the cam plate,'when in its tilted position, is

constantly urged to the correct or non-tilted position by the great forces applied by the working pistons and vice versa. The control pistons receive the brunt of these forces; therefore, for optimum force absorption, it is desirable for the line of contact between a particular control piston and the cam plate be in a plane normal to the axis of the piston when that piston is in the fully extended position. This arrangement minimizes shear forces experienced when the line of contact is angulated which forces tend to cause the piston to bind against its chamber walls.

These and other objects of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light of the accompanying drawings wherein:

FIG. 1 is a cross sectional view of the motor of this invention taken through the tiltable cam plate and the rotatable barrel; and

FIG. 2 is a cross sectional view of the motor of this invention showing the cam plate tilting mechanism.

Referring now to FIG. 1 wherein like numerals indicate like parts, the motor is generally indicated by the numeral 10 and includes a housing 12 having centrally disposed rotatable shaft 14 therein. Keyed to the shaft 14 for rotation therewith is a barrel 16 having a plurality of axially disposed cylinders 18 reciprocally receiving driving pistons 20. Each piston has a spherical end 22 on'the outward end thereof which pivotally receives a bearing slipper 24 as is well known in the art.

A tiltable cam plate generally indicated by the numeral 26 is mounted on stub axles 28 on opposite sides of the shaft 14 which axles are journalled in the side walls of the housing 12. As is conventional in the art, the cam plate includes an annular bearing surface 30. The piston slippers 24 are held in abutment with the surface 30 by means well known in the art; namely, a keeper ring 32 which, as shown, may be attached to the cam plate by threaded screw 34 and a keeper plate 33 comprising an annular band having circular openings therein for receiving the slippers 24. Annular bearing inserts 37 are positioned between the slippers and the side walls of the openings in the keeper plate. The outer periphery of the keeper plate is in sliding engagement with the keeper ring. Spacer ring 39 positions the keeper ring 32 a distance from the cam plate sufficient to permit substantially free relatively rotation of the keeper plate.

The cam plate 26 comprises basically a solid block having a central opening 27 therethrough for receiving the shaft 14. The opening is flared from the bearing surface 30 rearwardly to permit tilting movement of the cam plate relative to the shaft 14. The cam plate is of rather-heavy construction in order to absorb the great forces exerted by the pistons during the operation of the motor. To give added strength to the cam plate, a cylindrical skirt or wall 36 is provided extending from the surface of the cam plate inwardly toward the barrel 16 to define an open-ended, cup-shaped configuration and a cavity 35. The cylindrical wall is flared outwardly at 38 to permit thecam plate to tilt to a position where a portion of thecylindrical wall 36 overlies the barrel 16.

The use of reinforcing means similar to the abovedescribed wall 36 is known in the prior art. However, a

' particular problem has arisen regarding the cooling of shaft 14, or through one of several openings 47 in spacer ring 39 which communicates chamber 41 with cavity 35 via passageway 43. V

' In normal operation of the motor, the housing chamber 40 is filled with the hydraulic fluid used to drive the motor, which fluid normally serves as a coolant to help cool the aforementioned bearing surfaces. However, in the particular design employing the cylindrical wall, there is a tendency for the fluid to remain in shown in cross-section therein. The view of FIG. 2 is taken from the same side as that of FIG. 1 except that the cross sectional line is closer to the viewed and outside of the walled cam plate. Integrally attached to the cam plate 26 is an extension 46 having

bearing blocks

48 and 50. A stub axle of the cam plate is shown in cross section and is indicated by the numeral 28. The

- arrows adjacent the stub axle 28- indicate the direction chamber 41 and cavity 35 and not to circulate. There- I fore, in accordance with the invention the cylindrical wall 36 is provided with a plurality of

apertures

42 and 47 peripherally spaced around the cylindrical wall and the spacer ring 39 respectively for communicating the cavity 35 and chamber 41 with the chamber 40. As the piston slippers orbit relative to the bearing surface 30, the fluid is subjected to centrifugal forces and is forced outwardly through openings 47 into the annular passageway 43 and apertures 42 and into the chamber 40. At the same time, as the fluid is force through the apertures 42, a pressure drop is created in the chamber 41 and cavity 35 drawing cooler fluid therein from chamber 40 primarily through central opening 27 or the space between the inside diameter of the keeper plate 33 and the shaft 14. In this manner, there is a constant circulation of cooling fluid over the surface and slippers 24.

During operation of the motor shown in FIG. 1, fluid is pumped from a suitable source to the piston chambers l8 sequentially driving the pistons 20 outwardly against the cam plate causing the barrel and shaft to rotate in a manner well known in the prior art. As mentioned, the fluid contained in the chamber 40 is caused to circulate through space 41 and the cavity defined by the side walls 36 and back out into the chamber through the openings 42 by means of the centrifugal forces caused by the orbiting of the pistons and piston slippers around the cam plate 26.

Referring now to FIG. 2, the mechanism for tilting the cam plate between first and second positions is of pivotal movement of the cam plate. The cam plate as shown in FIG. 2 is in the maximum tilted position. When in the extreme position, opposite that shown in FIG. 2, the bearing surface 30 of the cam plate is at right angles to the longitudinal axes of the pistons.

The housing 12 includes cylinders or chamber 52 and 54 which receive first and

second control pistons

56 and 58, the latter having a working surface area greater than tat of the piston 56. The. control pistons move within the cylinders 52 and 54, and at their out-' ward ends engage the bearing blocks 48 and 50. The outer ends of the pistons are spherical and receive piston slipper 49 very similar to those shown on the driving pistons of FIG. 1.

A suitable fluid pressure source'60 for the main system of the motors and for the cam plate tilting means is shown schematically in the lower right hand portion of the drawing. The fluid under pressure is passed through a pressure-regulator 62 via line 64 and to the cylinders of the motor via line 66. A portion of the pressure, however, is taken off via line 68 and is in constant communication with the control piston chamber 54 via line 70 and passageways 72 and 74. Since the chamber 54 is in constant communication with the pressure source as regulated by the pressure regulator 62, the piston 56'is constantly urged outwardly and acts as a constant biasing force against the tiltable cam plate 26 urging it to a first or non-tilted position.

A two-position, two-way valve 76 selectively communicates the chamber 52, with the pressure source, by

any suitable control means either manual or automatic. When the valve is in the position shown in FIG. 2, the chamber 52 is in communication with the pressure source via line 68, valve 76 and passageways 82 and 84, and since the piston 58 has a larger working area than that of piston 56, as mentioned above, the piston 58 will exert a force sufficient to overcome the biasing force of the constantly pressurized piston 56 to thereby move the cam plate toward the fully tilted position. When the valve 76 is in the up position, the cylinder 52 is in communication with reservoir 86 via line 88 and is thereby under tank pressure. The piston 56 then will tilt the cam plate to the upright position.

As mentioned earlier, the control pistons engage the bearing blocks 48 and 50 by means of piston slippers 49. The surface of bearing block 48- lies in a plane which is parallel to the plane of the face of the cam plate 26. The surface of bearing block 50 lies in a plane extending angularly relative to the plane of the face of the cam plate 26. Because of the aforementioned disposition of the bearing blocks 48 and 50, the surfaces thereof when their respective pistons are in their fully extended positions, will lie in a plane substantially at right angles to the longitudinal axes of the pistons. This is clearly shown with reference to FIG. 2 wherein the piston 58 is fully extended and the cam plate is in its fully tilted position. In this position, the surface of the bearing block 50 lies in a plane substantially perpendicular to the longitudinal axis of the piston 58. It can also be easily seen that the surface of the bearing block 48 will also lie in a plane perpendicular to the longitudinal axis of the piston 56 when piston 56 is in the fully extended position, in which position the cam plate is in a non-tilted position. This assures a maximum absorption of the longitudinal forces and eliminates shear forces when either piston is in the fully extended position, the position in which the particular piston is subjected to the greatest force. Also, this arrangement tends to minimize binding of the piston with its chamber walls due to non-straightline forces being exerted against the piston. It can be seen that great forces will be exerted upon the cam plate by the working pistons 20 tending to cause the cam plate to assume the upright or non-tilted position. For positions inbetween the maximum extended position of the control pistons, the line of contact will be somewhat angulated. It is to be understood that while the bearing blocks are angulated in the preferred embodiment, the slippers may be angulated instead while still providing the same result.

In a general manner, while there has been disclosed effective and efficient embodiments of the invention, it should be well understood that the invention is not limited to such embodiments as there might be changes made in the arrangement, disposition, and form of the parts without departing from the principle of the present invention as comprehended within thescope of the accompanying claims.

I claim:

l. A fluid motor of the type having a cam plate, a rotatable barrel having parallel cylinders formed therein in which are carried a plurality of driving pistons having their outer ends in engagement with the cam plate to thereby cause said pistons to travel through intake and discharge strokes as said barrel rotates, a housing enclosing said barrel and cam plate and defining a chamber filled with fluid in which said cam plate is located, the improvement comprising a cylindrical wall extending from the surface of said cam plate toward said barrel and defining a cavity, said wall having radially extending apertures spaced about the periphery thereof communicating the cavity with said fluid chamber.

2. The motor of claim 2 wherein said bearing portions of said cam plate are on an extension affixed to said cam plate, one of'said bearing portions is in a plane parallel to the plane of the surface of said cam plate and the other bearing portion is in a plane angulated relative to the surface of said cam plate.

3. The motor of claim 1, and including piston slippers on the ends of each of said pistons, a keeper plate for receiving and positioning said slippers, a keeper ring circumscribing said keeper plate for positioning said plate, and a spacer ring between said cam plate and said keeper ring for spacing said keeper ring a predetermined distance from said cam plate, said slippers, keeper ring, keeper plate and spacer. ring defining a second chamber and said spacer ring has passageways therein for communicating said second chamber and said cavity.

Claims

1. A fluid motor of the type having a cam plate, a rotatable barrel having parallel cylinders formed therein in which are carried a plurality of driving pistons having their outer ends in engagement with the cam plate to thereby cause said pistons to travel through intake and discharge strokes as said barrel rotates, a housing enclosing said barrel and cam plate and defining a chamber filled with fluid in which said cam plate is located, the improvement comprising a cylindrical wall extending from the surface of said cam plate toward said barrel and defining a cavity, said wall having radially extending apertures spaced about the periphery thereof communicating the cavity with said fluid chamber.

2. The motor of claim 2 wherein said bearing portions of said cam plate are on an extension affixed to said cam plate, one of said bearing portions is in a plane parallel to the plane of the surface of said cam plate and the other bearing portion is in a plane angulated relative to the surface of said cam plate.

3. The motor of claim 1 and including piston slippers on the ends of each of said pistons, a keeper plate for receiving and positioning said slippers, a keeper ring circumscribing said keeper plate for positioning said plate, and a spacer ring between said cam plate and said keeper ring for spacing said keeper ring a predetermined distance from said cam plate, said slippers, keeper ring, keeper plate and spacer ring defining a second chamber and said spacer ring has passageways therein for communicating said second chamber and said cavity.