US3906998A

US3906998A - Pintle for radial piston machines

Info

Publication number: US3906998A
Application number: US401942A
Authority: US
Inventors: Walter Robeller; Roland Steimann; Gerhard Nonnenmacher
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1973-07-07
Filing date: 1973-09-28
Publication date: 1975-09-23
Anticipated expiration: 1992-09-23
Also published as: DE2334592A1; DE2334592C3; DE2334592B2

Abstract

A pintle for radial piston machines has two elongated control chambers separated from each other by lands and flanked by two mirror symmetrical grooves. The distance between the grooves varies periodically and the regions where the grooves are nearest to as well as most distant from each other are spaced apart from the centers of the lands, as considered in the circumferential direction of the pintle. Each groove may have a sinusoidal outline or it may consist of several arcuate sections each forming part of a circle. Alternatively, each groove may consist of straight sections which make an obtuse angle with each other.

Description

United States Patent [191 Robeller et a1.

[ Sept. 23, 1975 PINTLE FOR RADIAL PISTON MACHINES [73] Assignee: Robert Bosch G.m.b.H., Stuttgart,

Germany 22 Filed: Sept. 28, 1973 211 App]. No.: 401,942

[30] Foreign Application Priority Data [58] Field of Search 251/281, 283; 91/486, 491, 91/498, 484; 137/625.24

[56] References Cited UNITED STATES PATENTS 3,280,757 10/1966 Eickmann 91/498 3,430,919 3/1969 Frazier 251/283 3,810,418 5/1974 Bosch 91/498 FOREIGN PATENTS OR APPLICATIONS 1,260,890 6/1960 France 91/498 649,856 2/1951 United Kingdom... 91/491 827,154 1/1952 Germany 91/491 Primary Examiner-Martin P. Schwadron Assistant ExaminerRobert J. Miller Attorney, Agent, or Firm-Michael S. Striker [57] ABSTRACT A pintle for radial piston machines has two elongated control chambers separated from each other by lands and flanked by two rriirror symmetrical grooves. The distance between the grooves varies periodically and the regions where the grooves are nearest to as well as most distant from each other are spaced apart from the centers of the lands, as considered in the circumferential direction of the pintle. Each groove may have a sinusoidal outline or it may consist of several arcuate sections each forming part of a circle. Alternatively, each groove may consist of straight sections which make an obtuse angle with each other.

8 Claims, 3 Drawing Figures MS Pamm Sept. 23,1975 Sheet 1 of 2 3,906,998

US Patent Sept. 23,1975 Sheet 2 M2 3,906,998

PINTLE FOR RADIAL PISTON MACES BACKGROUND OF THE INVENTION The present invention relates to radial piston machines in general, and more particularly to improvements in pintles or valves for radial piston machines of the type wherein a cylinder block rotates about a pintle and is provided with radially extending cylinders for reciprocable pistons, and wherein the peripheral surface of the pintle is provided with at least two control chambers located diametrically opposite each other and communicating alternately with successive cylinders when the cylinder block rotates.

It is already known to provide a pintle with two control chambers one of which constitutes a high-pressure chamber and the other of which constitutes a lowpressure chamber. The control chambers are separated from each other by platforms or lands one of which is adjacent to pistons which assume their inner end positions (i.e., nearest to the peripheral surface of the pintle) and the other of which is adjacent to pistons which assume their outer end positions. It is further known to provide the peripheral surface of the pintle with recesses or grooves which flank the control chambers therewith elongated sealing projections or ribs. When the cylinder block rotates, fluid leaks from the highpressure control chamber and establishes fields between the respective sealing projections and the internal surface of the cylinder block whereby such pressure fields oppose a movement of the adjacent portion of the cylinder block toward the peripheral surface of the pintle. The point of attack of the resultant of forces produced by all pressure fields should coincide with or should be closely adjacent to the point of attack of the force which acts upon the pintle. Such force is produced in part by fluid pressure acting on ring-shaped surfaces in those cylinders of the cylinder block which travel along the high-pressure control chamber of the pintle. The point of attack of the just discussed force travels back and forth about the center of the highpressure control chamber in and counter to the direction of rotation of the cylinder block. The length of the arc along which the point of attack travels back and forth depends on the number of cylinders in the cylinder block.

The pistons exert lateral forces on the walls surrounding the respective cylinders, and the resultant of such forces tends to urge the cylinder block toward the pintle in the region of that land which is adjacent to pistons assuming their inner end positions. The sum of forces generated by fluid pressure and by the pistons produces a resultant force which acts on the pintle in the region between the just mentioned land and the center of the high-pressure control chamber. The point of attack of the resultant force travels back and forth between the land and the center of the high-pressure control chamber. In presently known radial piston machines, the resultant force is not always balanced by an opposing force so that the width of the gap between the pintle and the cylinder block fluctuates with attendant excessive leakage of pressurized fluid.

SUMMARY OF THE INVENTION An object of the invention is to provide a novel and improved pintle which can be used in radial piston pumps or motors and which is constructed and mounted in such a way that it contributes to automatic centering of the cylinder block by enabling the pressure fields between its peripheral surface and the internal surface of the cylinder block to neutralize the aforediscussed forces produced by the piston and pressurized fluid and tending to move the cylinder block nearer to the pintle.

Another object of the invention is to provide the pintle with novel and improved sealing projections which enable the fluid to establish pressure fields capable of opposing excessive radial movements of the cylinder block with respect to the pintle.

A further object of the invention is to provide a pintle which can be used in many existing types of radial piston machines as a superior substitute for conventional pintles.

The invention is embodied in a pintle or valve which can be used in a radial piston pump or motor and has a peripheral surface provided with a plurality of control chambers having a common symmetry plane which is normal to the axis of the pintle. The peripheral surface of the pintle is further provided with a plurality of lands alternating with the control chambers, as considered in the circumferential direction of the pintle, and with two recesses or grooves flanking the control chambers and being mirror symmetrical to each other with reference to the aforementioned plane. The distance between the two recesses varies periodically, as considered in the circumferential direction of the pintle, and the peripheral surface of the pintle includes a section which is disposed between the two recesses and has portions of maximum and minimum width which are spaced apart or offset from the lands, as considered in the circumferential direction of the pintle.

Each of the two recesses can have a sinusoidal outline. Alternatively, each recess may consist of several arcuate sections or portions each of which forms part of a circle and which merge gradually into each other. Still further, each recess may consist of several straight sections or portions whereby the neighboring sections make an obtuse angle with each other.

The novel features which are considered as characteristic of the invention are set forth on particular in the appended claims. The improved pintle itself, however, both as to its construction and. its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of radial piston machine including a pintle which embodies one form of the invention;

FIG. 2 is a fragmentary developed view of the pintle shown in FIG. 1; and

FIG. 3 is a fragmentary developed view of a modified pintle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS stalled in the housing 1. The cylinder block 5 has a shaft 7 which is driven by a suitable prime mover when the machine is operated as a pump and which receives torque from the cylinder block when the machine is operated as a motor.

The cylinder block 5 is formed with radially extending cylinders 8 for pistons 9 each of which is mounted in the respective cylinder with a minimum of play. The pistons 9 are provided with articulately mounted arcuate heads or shoes 10 which engage the cylindrical internal surface of a slide block 11 serving to determine the length of piston strokes. As shown, the slide block 11 is rigid with a spindle nut 14 meshing with a feed screw 15 which is rotatable in a bracket 16 of the housing 1. The means for rotating the feed screw 15 comprises a hand wheel 17. A helical spring 18 reacts against the housing 1 and bears against the slide block 11 diametrically opposite the nut 14.

The hand wheel 17 can be rotated to move the axis of the slide block 11 above or below as well as into a position of coincidence with the axis of the pintle 4. Thus, the operator can change the stroke of each piston 9 at will and can select any one of an infinite number of strokes. The cylinders 8 include conical inner end portions 12 whose diameters decrease in a direction toward the peripheral surface of the pintle 4 and which communicate with radial ports 13 of the cylinder block 5. These ports sweep seriatim past two

elongated control chambers

19, 20 which are machined into the peripheral surface of the pintle 4 diametrically opposite each other. As best shown in FIG. 2, the

control chambers

19, 20 are separated from each other by platforms or

lands

23, 24 and respectively communicate with axially parallel bores 21, 22 (FIG 1) of the pintle 4.

Referring to FIG. 2, it is assumed that the cylinder block 5 rotates in a direction indicated by arrow A. The chamber 19 constitutes a high-pressure control chamber when the axis of the slide block 14 is located above the axis of the pintle 3, as viewed in FIG. 1, and the chamber 20 constitutes a high-pressure control chamber if the axis of the slide block 14 is located at a level below the axis of the pintle. If the chamber 19 constitutes a high-pressure control chamber, the land 24 is adjacent to those pistons 9 which assume their inner end positions at a minimum distance from the peripheral surface of the pintle 4. Those pistons which assume their inner end positions are adjacent to the land 23 if the eccentricity of the slide block 14 is changed in such a way that a control chamber 20 constitutes a highpressure chamber.

The peripheral surface of the pintle 4 is futher provided with two endless recesses or

grooves

25, 26 which are mirror symmetrical to each other with reference to a plane 27. This plane constitutes the central symmetry plane of the

control chambers

19, 20 and

lands

23, 24, and is nornal to the axis of the pintle 4. Each of the

recesses

25, 26 has a sinusoidal outline. The width (as considered in the axial direction of the pintle 4) of that portion or section 4A of the peripheral surface of the pintle which extends between the recesses 25, 26 (this section includes portions of the

lands

23, 24 and is provided with the control chamber 19, 20) varies periodically between several maximum and several minimum values, as considered in the circum ferential direction of the pintle. The portions of minimum width are located between the

portions

28, 28' and 30, of the

recesses

25, 26. The portions of maximum width are located between the

portions

29, 29'

and 31, 31 of the

recesses

25, 26. It will be noted that the portions of maximum and minimum width of the section 4A are spaced apart from the centers of the

lands

23, 24 and from the centers of the

control chambers

19, 20, as considered in the circumferential direction of the pintle 4. The width of the section 4A between 28, 28' equals the width between 30, 30', and the width between 29, 29 equals the width between 31, 31 The periodicity of the

recesses

25, 26 is degrees and, as mentioned above, the nodes of the recesses are shifted in phase with respect to the centers of the

lands

23, 24.

The

recesses

25, 26 define with the cortrol chamber 19 a pair of elongated sealing projections or

ribs

32, 33 whose width (as considered in the axial direction of the pintle 4) varies continuously as considered in the circumferential direction of the pintle. Similar sealing projections or

ribs

34, 35 are provided between the

recesses

25, 26 and the control chamber 20. The sealing

projections

32, 33, 34, 35 have portions of maximum width in the region of

portions

29, 29', 31, 31' of the

respective recesses

25, 26, i.e., in the region of those portions of the recesses which are located at a maximum distance from the symmetry plane 27. The width of the

control chambers

19, 20 is constant. The imaginary centers of the sealing

projections

32, 33 are located between the center of the control chamber 19 and the land 24 (i.e., that land which is located downstream of the control chamber 19, as considered in the direction indicated by arrow A). Analogously, the centers of sealing

projections

34, 35 are shifted from the center of the control chamber 20 toward the land 23.

The

recesses

25, 26 are flanked by two carrying and sealing elements or rings 36, 37 which constitute portions of the peripheral surface of the pintle 4. The sealing element 36 extends all the way to the inner axial end of the pintle.

It is assumed that the chamber 19 constitutes a highpressure chamber and that the cylinder block 5 rotates in the direction indicated by arrow A while the radial piston machine operates as a pump, i.e., the shaft 7 is assumed to be driven by an electric motor or the like. Some pressurized fluid leaks from the control chamber 19, through the gap between the sealing

projections

32, 33 and the internal surface of the cylinder block 5, and into the adjacent portions of

recesses

25, 26. Such fluid establishes pronounced pressure fields between the sealing

projections

32, 33 and the cylinder block. Pressurized fluid also leaks from the

recesses

25, 25, between the sealing

elements

36, 37 and the internal surface of the cylinder block 5, and into the interior of the housing 1. Moreover, and if the fluid pressure in the control chamber 20 is less than in the

recesses

25, 26, the fluid also flows from the recesses, between the sealing

projections

34, 35 and the internal surface of the cylinder block 5, and into the control chamber 20. This results in a reduction of fluid pressure in the

recesses

25, 26 so that such pressure equals the pressure in the control chamber 20. The pressure fields which develop between the sealing elements and

projections

36, 37, 34, 35 on the one hand and the internal surface of the cylinder block 5 on the other hand are less pronounced that the pressure fields in the region of sealing

projections

32, 33. The less pronounced pressure fields compensate each other, either completely or substantially, i.e., the point of attack of a force produced by all pressure fields is close to or coincides with the point of at-- tack of the force produced by pressure fields-in the region of sealing

projections

32, 33. Thus, the force which is produced by pressure fields in the region of projections 32, 33: contributestalmost exclusively to equalization of forces which act upon the pintle-4.

The sinusoidal outlineof the recesses 25, 26'insures that the, centers ofpressure-fields in the region of the sealing

projections

32, 33, 34, 35- areshifted in a-direc phase and the amplitudes ojfthe recesses 25, 26areselected in such a way thatthe point pf'attack of the resultant of .all forces acting on the pintle 4 coincides with the point of attack of the resultant of forces produced by all pressure fields whereby the'two forces neutralize each other. The amplitude of the

recesses

25, 26 determines the maximum and minimum width of the section 4A of the peripheral surface of the pintle 4, and the shift in phase of the

recesses

25, 26 determines the distance between the portions 2831 and 28'-3l' of the

recesses

25, 26 with respect to the centers of the control chambers 19, and the centers of

lands

23, 24.

An advantage of the improved pintle is that the sealing projections establish the relatively large pressure fields which produce substantial forces in regions where the pintle is stressed by forces generated by fluid pressure and pistons in the cylinders of block 5. The forces generated by pressure fields render it possible to enhance the neutralization of forces acting on the pintle so that the cylinder block is centered during each stage of operation of the radial piston machine.

The pintle 4 of FIG. 2 can be modified by replacing the

sinusoidal recess

25, 26 with recesses each of which consists of several arcuate sections which merge gradually into each other and each of which constitutes a portion of a circle. For example, the recess can be replaced by a recess having two arcuate portions (in the region of 28, whose convex sides face the sym metry plane 27, and two arcuate portions (in the region of 29, 31) whose convex sides face the plane 27. The other recess is mirror symmetrical to the just discussed recess the radii of curvature of arcuate portions of such recesses can be readily selected in such a way that the resultant of all forces produced by the pressure fields between the pintle and the cylinder block equals and balances the resultant of all forces acting upon the pintle per unit of time.

FIG. 3 illustrates a portion of a modified pintle 40 wherein all such parts which are identical with or clearly analogous to the corresponding parts shown in FIG. 2 are denoted by similar reference characters. The

recesses or

grooves

41, 42 respectively replace the reof each recess makean beta and each section makes withthe, symmetryplane 27 an acute angle alpha. Each of the

recesses

41, 42 is a circumferentially complete groove and these recessesrespectively define with the

control charnbers

19,20 pairs of sealing projections or ribs. '47,,48 and149, 50. The centers of the sealing projections 47-50 arejshifted in a direction from the

respective control chambers

19, 20 toward the lands 24,- 23, i.e., in the direction of rotation of the cylinderblo'ck (arrow A). The width of the section 40A of the. peripheral surface of the pintle 40 varies periodically between two maximum and two minimum values substantially in the same way as described in connection with the section 4A. The portions of maximum width are locatedbetween 44, 44' and 46, 46', and the portions of minimum width are located'betwe'en 43, 43

and 45, l

The

reference characters

51 and 52 denote two sealing or carrying elements whichare respectively adjacent'to the recesses 41', 42 and correspond to the sealing

elements

36, 37 of'FIG. 2,.

The portions of maximum and minimum width of the section 40A of the peripheral surface of the pintle 40 are again shifted with respect to the centers of the

control chambers

19, 20 and lands 23, 24, as considered in the circumferential direction of the pintle. The periodicity of the

recesses

41, 42 equals 11 and each of these recesses is shifted in phase with respect to the centers of

land

23, 24 in a manner as described above for the

recesses

25, 26, i.e., so that the resultant of forces produced by all of the pressure fields balances and opposes the resultant of all forces acting on the pintle 40. This is due to the fact that the centers of sealing projections 47, 48 are located between the center of the control chamber 19 and the center of the land 24, and the centers of sealing projections 49, are located between the center of the control chamber 20 and the center of the land 23. The designer can readily select the amplitude and the phase shift of the

recesses

41, 42 in such a way that the resultant of forces produced by all pressure fields between the pintle 40 and the internal surface of the cylinder block is equal to and opposes the resultant of all forces which act on the pintle 40 per unit of time. This insures a highly satisfactory centering of the cylinder block and reduces the leakage of pressurized fluid from the high-pressure control chamber toward the interior of the housing of the radial piston machine. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of out contribution to the art and,

therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. For use in a radial piston machine, a pintle having a cylindrical peripheral surface provided with a plurality of control chambers having a common symmetry plane normal to the axis of the pintle, said peripheral surface including a plurality of lands alternating with said control chambers, as considered in the circumferential direction of the pintle, and said surface further having two recesses each constituted by a circumferentially complete groove of unobstructed cross section,

flanking said control chambers and being mirror symmetrical to each other with reference to said plane, the distance between said recesses varying periodically, as considered in the circumferential direction of the pintle, and said peripheral surface including a section located between said recesses and having portions of maximum and minimum width which are spaced apart from the centers of said lands, as considered in the circumferential direction of the pintle.

2. A pintle as defined in claim 1, wherein each of said recesses has a sinusoidal outline.

3. A pintle as defined in claim 1, wherein each of said recesses comprises a plurality of successive straight portions and the successive portions of each of said recesses make an obtuse angle with each other.

4. A pintle as defined in claim 1, wherein each of said lands is disposed intermediate a portion of maximum width and a portion of minimum width of said section, as considered in the circumferential direction of the pintle.

5. A pintle as defined in claim 1, wherein said control chambers are elongated, as considered in the circumferential direction of the pintle, each of said control chambers having a central portion disposed intermediate a portion of maximum width and a portion of minimum width of said section, as considered in the circumferential direction of the pintle.

6. A pintle as defined in claim 1, wherein the periodicity of each of said recesses is 7. A pintle as defined in claim 6, wherein said section of said peripheral surface includes two portions of maximum width and two portions of minimum width, said lands including a pair of lands disposed diametrically opposite each other, one of said portions of maximum width being nearer to one of said pair of lands and the other portion of maximum width being nearer to the other of said pair of lands.

8. A pintle as defined in claim 1, wherein said control chambers are elongated, as considered in the circumferential direction of the pintle, and have a constant width, as considered in the axial direction of the pintle.

Claims

1. For use in a radial piston machine, a pintle having a cylindrical peripheral surface provided with a plurality of control chambers having a common symmetry plane normal to the axis of the pintle, said peripheral surface including a plurality of lands alternating with said control chambers, as considered in the circumferential direction of the pintle, and said surface further having two recesses each constituted by a circumferentially complete groove of unobstructed cross section, flanking said control chambers and being mirror symmetrical to each other with reference to said plane, the distance between said recesses varying periodically, as considered in the circumferential direction of the pintle, and said peripheral surface including a section located between said recesses and having portions of maximum and minimum width which are spaced apart from the centers of said lands, as considered in the circumferential direction of the pintle.

6. A pintle as defined in claim 1, wherein the periodicity of each of said recesses is 180*.

7. A pintle as defined in claim 6, wherein said section of said peripheral surface includes two portions of maximum width and two portions of minimum width, said Lands including a pair of lands disposed diametrically opposite each other, one of said portions of maximum width being nearer to one of said pair of lands and the other portion of maximum width being nearer to the other of said pair of lands.