US 3810419 A
Fixed displacement hydraulic transducer apparatus of axial piston type having a rotatable piston barrel mounted within a body, a rocker cam defining a swash plate mounted in pivotable relation within a cam cradle defined within the body, and a plurality of pistons axially mounted within the piston barrel and abutting the swash plate. The pistons are adapted to reciprocation upon rotation of the barrel relative to the swash plate. The rocker cam may be pivoted to any angle relative to the axis of the pump from a maximum angle in one direction through a zero deviation to a maximum angle in the other direction to provide a constant rate of fluid displacement through the apparatus which is adjustable to a maximum rate from a minimum rate to a maximum rate in either direction. Anchor means are provided in association with the rocker cam and the body to fix the rocker cam at any position within its range of adjustment in a manner permitting the apparatus to be operated at a corresponding rate of fluid displacement.
Claims available in
Description (OCR text may contain errors)
United States Patet ADJUSTABLE FIXED DISPLACEMENT HYDRAULIC TRANSDUCER APPARATUS 7/l965 Great Britain 91/505 Primary Examiner-William L. Freeh Attorney, Agent, or Firm-Thomas S. Baker, Jr.; David A. Greenlee [5 7] ABSTRACT Fixed displacement hydraulic transducer apparatus of axial piston type having a rotatable piston barrel mounted within a body, a rocker cam defining a swash plate mounted in pivotable relation within a cam cradle defined within the body, and a plurality of'pistons axially mounted within the piston barrel and abutting the swash plate. The pistons are adapted to reciprocation upon rotation of the barrel relative to the swash plate. The rocker cam may be pivoted to any angle relative to the axis of the pump from a maximum angle in one direction through a zero deviation to a maximum angle in the other direction to provide a constant rate of fluid displacement through the apparatus which is adjustable to a maximum rate from a minimum rate to a maximum rate in either direction. Anchor means are provided in association with the rocker cam and the body to fix the rocker cam at any position within its range of adjustment in a manner permitting the apparatus to be operated at a corresponding rate of fluid displacement.
2 Claims, 5 Drawing Figures i/jl PATENTEnm 14 19M SHEEI 1 BF 2 m ul Pmmnumw 3.810.419
sum '2 a? 2 FIG. 4
ADJUSTABLE FIXED DISPLACEMENT HYDRAULIC TRANSDUCER APPARATUS BACKGROUND OF THE INVENTION This invention generally relates to fluid flow transducer apparatus such as an axial piston pump or motor and more particularly relates to such a pump or motor of fixed fluid displacement, having its displacement rate adjustably established by a pivotable rocker cam which may be adjustably positioned, then fixed within a rockercradle.
Pumps, when used herein, shall mean both pump and motor hydraulic flow transducer apparatus. Axial piston pumps and motors are well developed as shown in representative U.S. Letters Patents No. 3,405,646 and No. 3,481,277. These patents are herein referenced as additional backgroundand information concerning the following description:
SUMMARY THE INVENTION The invention provides axial piston fluid flow trans ducer apparatus wherein the components are provided as an integral unit of relatively simple construction fo facility of installation and adjustment. 4
This inventionalso provides axial piston fluid flow transducer apparatus wherein the fluid displacement may be adjusted in infinite variety from a maximum displacement in one direction through zero displacement to a maximum displacement in the opposite direction and may be fixed at any rate of displacement in between.
This invention further provides axial piston fluid flow transducer apparatus wherein there is a reduction in the. amplitude of the oscillating moments and resulting structure vibration during operation.
This invention further provides axial piston fluid flow transducer apparatus wherein the fluid displacement may be changed through utilization of a structure requiring no change in components or the requirement to carry an additional inventory of components in order to make such change. I
The foregoing provision and other objects and advantages of the invention are obtained by a fixed displacement hydraulic transducer of .axial piston type having adjustment means to change the fixed displacement rate of the transducer to any fixed fluid displacement rate within the capacity of the transducer, comprising a rotatable piston barrel means mounted within a body;
- fective fluid displacement of the piston means in the piston barrel. Anchor means cooperate with said rocker cam means and said body to releasably fix said rocker cam means at a selected position within the rocker cradle corresponding to a selected fixed fluid displacement rate.
BRIEF DESCRIPTIONOF THE DRAWINGS FIG. 1 is a side elevation of a pump incorporating the DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 through 4, there is shown a hydraulic transducer pump or motor 46 of the axial piston type having a drive shaft 11 rotatably mounted through a port block 12 into a rotatable piston barrel 13, which in turn is rotatably mounted within a pump body 14 by means of a bearing assembly 15. A plurality of pump pistons 16 are mounted within respective cylinders 17 defined within the barrel 13. A piston shoe 18 is pivotably attached to each piston and retained against-a creep plate 19 by means of a shoe retainer assembly 21. Creep pyate l9 is'alsotermed a swash plate herein. Creep plate 19 and retainer assembly 21 are mounted with a rocker cam 22 which is received in pivoted relation within a cradle 23 defined by and within an end cap 24. End cap 24 abuts a spacer ring 25 which supports bearing assembly 15 and barrel 13 into appropriate operating position when end' cap 24 is assembled r with body 14 as shown. End cap 24 is connected with body 14 by means of fasteners (not shown) such as cap screws.
As seen in FIG. 3, shoe retainer unit or assembly 21 is comprised of a shoe retainer plate 26 which retains piston shoes 18 against creep plate 19 during operation ofthe pump 46. Retainer plate 26 is supported from rocker cam 22 through the combination of a thrust bearing 27, a spherical hold-down socket 28 abutting the thrust bearing, and spherical retainer washer 29 received in the socket 28. A cap screw 33 extends through and retains washer 29 in a fixed relation relative to rocker cam 22. Lugs 31 project from socket 28 into slots 32 defined in rocker cam 22 to prevent rotation of shoe retainer assembly 21 relative to rocker cam 22.
Cap screw 33 is resiliently secured in rocker cam 22 by means of a castle nut 36 which retains a springretainer 34. Spring retainer 34 in turn retains spring means 35 (Belleville springs for example) in compression. A retainer key 37 restrains rotation of nut 36 to an adjusted position which establishes the compressive force exerted by spring means 35. It is to be noted that the shoulder of spring retainer 34 slightly clears the counterbore 43 of the rocker cam 22 to enable retainer plate 26 to move very slightly in response to axial force applied along cap screw 33. The purpose of this feature, as shown and described, is to allow only limited lift off of piston shoes 18. Such lift off behavior is well recognized.
Further referring to FIG. 3, the inner end of shaft 11:
is seen to be secured in splined connection within barrel 13 by means of a fastener such as a cap screw 39 drawn down against a spring means 41 (such as Belleville springs) and a support washer 42, the washer 42 being in abuttment with the barrel 13 as shown. The
shaft'll is retained in the opposite direction by thrust means (not shown) provided within port block 12. The counterbore 43 opens into a bore 44, forming a socket which houses the elements 33, 34, 35, 36, and 37 of shoe retainer assembly 21.
FIG. 4, taken in view of FIG. 3, further illustrates the pivotable or rotatable relation of rocker cam 22 within rocker cradle 23. As shown, the rocker cam 22 may be pivoted infinitely from a position of maximum pump displacement in one direction to a position of maximum displacement in the other direction. As shown best in FIG. 4, anchor means, such as anchor screws 45, are provided to anchor or fix rocker cam 22 at any position throughout its movement or adjustment within rocker cradle 23. Anchor screws 45 are provided with screw bevels 38 which are adapted to be rotated into abutt ment with complementary bevels 47 concentrically defined on either side of rocker cam 22 as shown in FIG. 4. Once the rocker cam 22 has been positioned to provide the piston displacement and consequent fluid displacement as desired, the anchor screws 45 are rotated inwardly until screw bevels 38 are in locking contact with cam ring bevels 47. Locking means are providedto prevent inadvertent loosening of anchor screws 45, for example, plugs 48 ofNylon or the like.
laterally disposed in the threads of screws 45, as shown in FIG. 4. As a protective feature, the threaded holes in end cap 24 which receive locking screws 45 are plugged with cover plugs 49 and sealed appropriately as shown. 1
FlG. 5 diagrammatically depicts the structure of rocker cam 22 and rocker cradle 23 whichgives the superior anchoring action for screw bevels 38 and cam bevels 47, as shown in FIG. 4. In FIG. 5, the profiles respectively of rocker cam 22 and rocker cradle 23 are seen to have different respective radii. The radius or radial dimension of rocker cradle 23 is denoted at 51. The radius of rocker cam 22 is denoted at 52. The point of maximum clearance between these respective radii is denoted at 53. The support points of rocker cam 22 and rocker cradle 23 are shown as dots at the intersections of the respective profiles. By providing rocker cradle radius 51 less than rocker cam radius 52, the support points are moved to the extremities of the rocker cam arc, thereby reducing the magnitude of the moments acting upon the cradle within the end cap. In addition, when anchor means such as set screws 45 are provided to preload the rocker and the cradle along or near the point of maximum clearance, a reduction can be obtained of the value of the oscillating load and moments for the nl /2- LhEJLZlI I /Z piston change (with n an odd n cr f PiflZElJliUQ elped that reducing the amplitude of the oscillating moments on the end cap 24 serves to substantially reduce structure vibration.
It is to be noted that, with the structure disclosed and with a simple protractor fixture, the rocker cam can be set at any desired angle to give any desired fluid displacement during assembly of the pump 46 and thereby reduce or eliminate inventory of various fixed displacement cams as would ordinarily be supplied to provide various piston displacements. In the embodiment described, only one rocker cam 22 is needed to give any of the infinite displacements as may be needed.
Example dimensions for the rocker cam radius 52 may be in the order of 3.003 inches to 3.008 inches and dimensions for the rocker cradle radius 51 may be in the order of 2.997 inches to 3.002 inches. The anchor screws 45 do not exhibit sufficient force to stress the maximum clearance 53 into abutting contact but do provide a thorough locking action as needed.
The advantages of the shoe retainer assembly 21 are to provide an even retaining force on each of the piston shoes 18 to retain the shoes appropriately against swash plate 19 while permitting universal movement between the spherical hold-down socket 28 and spherical retainer washer 29 to accommodate for any distortion or misalignment in the system as disclosed. lt is to be noted that the shoe retainer 21 is self-contained with rocker cam 22 and functions completely independentl of the assembly of piston barrel l3.
The foregoing description and drawings will suggest other embodiments and variations to those skilled in the art, all ofwhich are intended to be included in the spirit of the invention as herein set forth.
That being claimed is:
l. A fixed displacement hydraulic transducer of axial piston type having adjustment means to change the fixed displacement rate of the transducer to any fixed fluid displacement rate within the capacity of the transducer, comprising: a rotatable piston barrel means mounted within a body; rocker cam means defining a swash plate on its one side and an arcuate cam face on its opposing side with said arcuate face mounted within an accommodating arcuate cradle face of cradle means defined within said body, a plurality of piston means reciprocatively mounted within said piston barrel and in abutting relation with said swash plate; said swash plate and said rocker cam means being adapted to be pivoted within said rocker cradle means to any angle within a selected range of angles relative to the axis of said piston barrel to change the effective fluid displacement of said piston means in said piston barrel; and anchor means associated with said rocker cam means and said body and operable to releasably fix said rocker cam means at a selected position within said rocker cradle corresponding to a selected fixed fluid displacement rate wherein said arcuate cam face is defined of radius greater than the radius of said arcuate cradle face.
2. The transducer of claim 1 wherein said anchor means comprises arcuate bevel means defined by said rocker cam means and beveled set screw means carried by said body and operable to engage said bevel means to fix said rocker cam meanswithin said rock er cradle means.
, UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,810,419 Dated May 14, 1974 Gary C. Smith, Jr.
Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: a
On the cover sheet  "Gary C. Smith," should read Gary C. Smith, Jr. In line 7 of the Abstract, "to" should read for Signed and sealed this 24th day of September 1974.
C. MARSHALL DANN MCCOY M. GIBSON JR.
Commissioner of Patents Attesting Officer FORM (10'69) uscoMM-Dc scans-Pee I U 5 GOVERNMENT PRNTING OFFICE 1