US3918855A

US3918855A - Adjustable vane pump

Info

Publication number: US3918855A
Application number: US493969A
Authority: US
Inventors: Siegfried Bornholdt
Original assignee: GL Rexroth GmbH
Current assignee: Bosch Rexroth AG
Priority date: 1973-11-16
Filing date: 1974-08-01
Publication date: 1975-11-11
Anticipated expiration: 1992-11-11
Also published as: DE2357182A1; DE2357182C2; JPS58108288U; JPS5080509A

Abstract

A vane pump wherein an annular slide block which surrounds the vanes of the rotor is movable radially of the rotor axis by two plungers which are mounted in the housing diametrically opposite each other. An arresting plug abuts against the slide block midway between the plungers at the higher-pressure side of the rotor and has a flat or spherical contact surface engaging the external surface of the slide block. The outer end of the plug has a socket for the major portion of a ball which bears against the concave surface of an abutment mounted in a recess of a screw which meshes with the housing and is movable radially of the rotor. The radius of curvature of the concave surface exceeds the radius of the ball and the radius of curvature of the contact surface, as considered in the direction of adjustment of the slide block by the plungers, exceeds the distance from the locus of contact between the ball and abutment to the locus of contact between the plug and slide block. This insures that the external surface of the slide block rolls along the contact surface and does not slide with respect to the plungers when the slide block is shifted by the plungers whereby the amount of fluid which is displaced by the vanes can be changed without vibrations and/or hysteresis. Adjustments of the screw relative to the housing serve to change the noise level of the pump.

Description

United States Patent [191 Bornholdt [111 3,918,855 [451 Nov. 11, 1975 1 1 ADJUSTABLE VANE PUMP [75] Inventor: Siegfried Bornholdt, Lohr (Main),

Germany [73] Assignee: Rexroth GmbI-l, Lohr (Main),

Germany [22] Filed: Aug. 1, 1974 [21] Appl. No.: 493,969

[30] Foreign Application Priority Data Primary Examiner-John J. Vrablik Attorney, Agent, or FirmMichae1 S. Striker 5 7 ABSTRACT A vane pump wherein an annular slide block which surrounds the vanes of the rotor is movable radially of the rotor axis by two plungers which are mounted in the housing diametrically opposite each other. An arresting plug abuts against the slide block midway between the plungers at the higher-pressure side of the rotor and has a flat or spherical contact surface engaging the external surface of the slide block. The outer end of the plug has a socket for the major portion of a ball which bears against the concave surface of. an abutment mounted in a recess of a screw which meshes with the housing and is movable radially of the rotor. The radius of curvature of the concave surface exceeds the radius of the ball and the radius of curvature of the contact surface, as considered in the direction of adjustment of the slide block by the plungers, exceeds the distance from the locus of contact between the ball and abutment to the locus of contact between the plug and slide block. This insures that the external surface of the slide block rolls along the contact surface and does not slide with respect to the plungers when the slide block is shifted by the plungers whereby the amount of fluid which is displaced by the vanes can be changed without vibrations and/or hysteresis. Adjustments of the screw relative to the housing serve to change the noise level of the pump.

7 Claims, 2 Drawing Figures I FIG. 1

US. atent Nov. 11, 1975 PEG. 2

ADJUSTABLE VANE PUMP BACKGROUND OF THE INVENTION The present invention relates to hydraulic machines in general, and more particularly to improvements in hydraulic pumps or motors with radially or substantially radially movable liquid displacing elements, such as pistons or vanes. Still more particularly, the invention relates to improvements in hydraulic machines wherein the strokes of radially movable liquid displacing elements are variable to thereby change the amounts of displaced liquid. The invention will be described with reference to vane pumps but with the understanding that it can also be embodied in radial piston machines.

It is already known to install in the housing of a vane pump a cylindrical or ring-shaped slide block which is adjustable radially of the rotor and the internal surface of which serves as a track and/or abutment for the outer edge faces of the vanes which are reciprocable in radially or substantially radially extending slots provided in the periphery of the rotor. The adjustments mechanism for the slide block includes a pair of coaxial plungers which are movable radially of the rotor and engage the external surface of the slide block so that the latter can be moved radially of the rotor to change the distance between its axis and the rotor axis. The adjustment mechanism further normally comprises a plate-like stop which engages the external surface of the slide block at the higher-pressure side of the rotor and is held at a given distance from the rotor axis by an abutment which is fixedly mounted in the housing. A roller bearing is interposed between the abutment and the plate-like stop. Such adjustment mechanisms exhibit the advantage that they allow for substantially hysteresis-free adjustment of the throughput of a vane pump. Such a vane pump is described for example in U.S. Pat. No.

3,107,628 granted Oct. 22, 1963 to R. D. Rynders et al. and in U.S. Pat. No. 3.l37.235 granted June I6. 1964 to F. B. Brown.

Problems arise when the stop is to be mounted for radial movement with respect to the rotor axis. This is normally desirable because the amount of noise which is produced by a vane pump depends, to a certain extent, on the distance from the stop to the rotor axis, i.e., by changing such distance, the operator can select for the slide block a position corresponding to the lowest or to a greatly reduced noise level. In accordance with a presently known proposal, the aforementioned stop, abutment and roller bearing are replaced by a simple screw which meshes with the housing and the inner end of which abuts against the external surface of the slide block. It has been found that the force with which the slide block bears against the screw is extremely high, especially at elevated fluid pressures, so that thev pump tends to vibrate and the hysteresis of its parts is very pronounced whenever the slide block is shifted to change the througput. Thus, though the screw constitutes a simple and effective means for regulating the noise level, the omission of aforementioned stop, bearing and abutment produces undesirable effects (hysteresis and vibration) when the slide block is shifted for the purpose of changing its eccentricity with respect to the rotor and hence the amount of displaced fluid. Such a vane pump is described for example in U.S. Pat. No. 3,45l,344 granted June 24. 1969 to R. E. Trick.

SUMMARY OF THE INVENTION An object of the invention is to provide a novel and improved adjustment mechanism for the annular slide block of a hydraulic machine, especially a vane pump.

Another object of the invention is to provide an adjustment mechanism which allows for displacement of the slide block in order to change the noise level of the machine as well as for hysteresisand vibration-free shifting of the slide block for the purpose of changing the throughput of the machine.

A further object of the invention is to provide a vane pump which embodies the improved adjustment mechanism and wherein the adjustment mechanism occupies a negligible amount of space and consists of a relatively small number of simple, compact and long-lasting components.

An additional object of the invention is to provide an adjustment mechanism for the slide block of a vane pump or the like wherein the means for changing the noise level undergoes a minimum of wear and insures that the slide block can be displaced with respect to the rotor without any or with minimal slippage relative to those parts of the adjustment mechanism which directly engage the external surface of the slide block.

The invention is embodied in a hydraulic machine, particularly in a vane pump, which comprises a housing for a rotor, an annular slide block which spacedly surrounds the rotor in the housing, liquid displacing elements mounted in the rotor for movement substantially radially of the rotor axis and abutting against the internal surface of the slide block, at least while the rotor is driven, and an adjustment mechanism for the slide block. The adjustment mechanism includes at least one plunger or an analogous adjusting member which abuts against the external surface of the slide block and is movable in the housing substantially radially of the rotor in a predetermined direction to thereby change the distance between the axes of the slide block and rotor and hence the amount of liquid which is displaced by the liquid displacing elements, an arresting member which is angularly offset from the adjusting member by less than 180 (preferably by as considered in the circumferential direction of the rotor and has a flat or convex contact surface abutting against the external surface of the slide block at the higher-pressure side of the rotor, an adjustable abutment located in the housing radially outwardly of the arresting member, and a spherical insert interposed between the arresting member and abutment and preferably extending with minimal clearance into a socket provided therefor in a second surface of the arresting member opposite the contact surface. The abutment is preferably formed with a concave surface which is engaged by the insert and has a radius of curvature greater than the radius of the insert.

In accordance with a feature of the invention, the radius of curvature of the contact surface, as considered in the direction of movement of the slide block under the action of the adjusting member or members, exceeds the distance from the locus of contact between the insert and abutment to the locus of contact between the arresting member and slide block. This insures that the throughput of the machine can be changed without hysteresis and/or vibration because, when the slide block is shifted radially of the rotor by the adjusting member or members, the external surface of the slide block rolls along the contact surface and such external 3 surface does not slide with respect to the adjusting member or members.

The abutment is preferably rigid with or forms part of a screw which meshes with and is rotatable relative to the housing to move the abutment radially of the rotor. This screw is preferably provided with a recess for the abutment and insert as well as for the major portion of the arresting member. Radial adjustments of the abutment through the medium of the screw are effected to change the noise level of the machine.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved hydraulic machine 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 DRAWING FIG. 1 of the drawing is a transverse sectional view of a vane pump which embodies the improved adjustment mechanism for the slide block, and

FIG. 2 illustrates a modification of an element shown in FIG. 1.

DESCRIPTION OF THE PREFERREE! EMBODIMENTS The drawing shows a vane pump having a housing 1 for a rotor 2 which is secured to or made integral with a drive shaft 3. The periphery of the rotor 2 has radially extending slots 4 for liquid displacing vanes 5 having outer end portions 5a which abut against the endless internal surface 6a of an annular slide block 6. When the shaft 3 is driven by a motor (not shown) and the pump is to convey fluid from the inlet means to the outlet means of the housing 1, the axis of the slide block 6 is parallel to but spaced apart from the common axis A of the rotor 2 and drive shaft 3. The direction in which the shaft 3 rotates is indicated by an arrow 14. The configuration of inlet means, outlet means and the customary valve plate in the housing 1 may be similar to or identical with that disclosed in the commonly owned copending application Ser. No. 463,781 of Bornholdt et al. filed Apr. 24, 1974 for Hydraulic Machine With Air Vent Valve".

The adjustment mechanism for changing the eccentricity of the slide block 6 includes parts which engage the endless external surface 6b of the slide block. Such parts include two hydraulically operated adjusting

plungers

7 and 8 which are located diametrically opposite each other with respect to the axis A. These plungers are respectively reciprocable in radially extending cylinders 7a, 8b of the housing 1 and the outermost position of the plunger 7 (at a maximum distance from the axis A) is determined by an adjustable stop 9 having external threads in mesh with the internal threads of a cover 12 forming part of or secured to the housing 1. The stop 9 can be fixed in a selected axial position by a lock nut 11. A sealing ring in a circumferential groove of the stop 9 prevents leakage of fluid from the cylinder 7a toward the lock nut 11, and a gasket 13 prevents leakage of fluid between the cover 12 and the main body portion of the housing 1.

The means for shifting the slide block 6 (in directions indicated by a double-headed arrow 22) by admitting pressurized fluid into the chamber 7a or 8b forms no part of the invention; such means may include a manually actuatable or automatic follow-up control system serving to change the eccentricity of the slide block 6 with respect to the rotor 2 and hence the amount of fluid which is conveyed by vanes 5 from the inlet means to the outlet means of the housing 1. The vanes 5 define with the slide block 6 chambers or cells 15 whose volume increases during travel of vanes from the adjusting plunger 8 toward the adjusting plunger 7 (the chambers 15 then draw fluid from the inlet means) and whose volume decreases during travel of vanes 5 from the plunger 7 toward the plunger 8 (the chambers 15 then discharge pressurized fluid through the outlet means which is connected with one or more consumers, not shown). The crescent-shaped space between the internal surface 6a of the slide block 6 and the periphery of the rotor 2 is shown at 16.

Since the upper chambers 15 of the pump shown in the drawing contain pressurized fluid, such fluid tends to move the slide block 6 upwardly, as viewed in the drawing, i.e., at right angles to the common axis of the adjusting

plungers

7, 8. The rotor 2 cannot be moved sideways because both ends of its shaft 3 are journalled in the housing 1. Such shifting of the slide block 6 is prevented by an adjustable arresting member 17 which is mounted in the housing 1 substantially midway between the

plungers

7, 8, as considered in the circumferential direction of the slide block.

That surface 17a of the arresting member 17 (hereinafter called plug for short) which faces away from the external surface 612 of the slide block 6 has a socket or recess 17b bounded in part by a cylindrical surface and in part by a conical surface and receiving with relatively small clearance the major portion of a spherical insert 18. The insert 18 abuts against the conical surface 17c and its exposed portion abuts against a concave surface 19a at the inner side of a pressure transmitting abutment member 19. The latter resembles a post which is secured to (e.g., partly recessed into) an adjusting screw 20. The screw 20 has threads 20b meshing with a portion of the housing 1 and has an axially extending recess 20a receiving the major portion of the plug 17 so that the

parts

17, 18, 19, 20 occupy a minimum amount of space. The outwardly extending shank of the screw 20 carries a lock nut 21 which prevents accidental axial displacement of the plug 17. A cap 21a conceals the lock nut 21 and can be held in the illustrated position owing to frictional engagement with the facets of the nut 21 or by being separably connected to the housing 1.

The radius of curvature of the concave surface 19a exceeds somewhat the radius of the spherical insert 18. This insures that the insert 18 produces a restoring moment in a direction toward the illustrated end position of the slide block 6 and plug 17. The inner or contact surface 17d of the plug 17 abuts against the external surface 61) and has a radius of curvature R (as considered in the direction of arrow 22) which is greater than the distance from the locus (line) 23 of contact between the surfaces 6b, 17d to the locus (point) 24 of contact between the spherical insert 18 and the concave surface 190.

If the slide block 6 is moved by one of the adjusting plungers 7, 8 (to the left or to the right, as viewed in the drawing), the external surface 6b rolls along the contact surface 17d whereby the plug 17 causes the sperical insert 18 to roll along the concave surface 190.

, This entails a minute movement of the plug 17 radially of the rotor 2 which compensates for radial movement of the locus 23 due to rolling of the slide block 6 along the contact surface 17d. Consequently, the axis of the slide block 6 continues to intersect the common axis of the

plungers

7 and 8. This, in turn, prevents any sliding of the surface 6b with respect to the abutting inner end faces 7b, 8a of the adjusting plungers, i.e., the adjustment of the output of the vane pump is practically free of hysteresis and/or vibration.

If the contact surface 17d is flat as shown in FIG. 2, its radius of curvature is infinitely large. If the surface 17d is curved, as considered in the direction of arrow 22, the radius of curvature R is still greater than the distance between the loci 23, 24.

The screw 20 is adjusted (upon loosening of the lock nut 21) in order to move the abutment member 19 radially of the rotor 2 and to thus change the level of noise which is produced by the pump. When the slide block 6 is shifted by the adjusting plunger 7 or 8 (arrow 22) and its external surface 6b rolls along the contact surface 17d, the inclination of the axis of the plug 17 changes, i.e., the plug 17 can swivel about the locus 24 of contact between the periphery of the spherical insert 18 and the concave surface 19a. The aforedescribed selection of the radius R and the distance between the loci 23, 24 insures that the axis of the slide block 6 moves in the general direction of the arrow 22 when the adjusting

plunger

7 or 8 is moved axially to change the throughput of the pump. This, in turn, insures that the surface 6b does not slide with respect to the

end face

7b or 8a when the cylinder 7a or 8b receives pressurized fluid to change the extent of radial movement of the vanes 5.

The improved hydraulic machine can be modified in a number of ways without departing from the spirit of the invention. For example, the abutment member 19 may constitute an integral part of the screw 20. Also, the housing 1 can be provided with a scale and the screw 20 can carry a pointer to facilitate the positioning of plug 17 at a selected distance from the axis A of the rotor 2. If the operator wishes to change the position of the slide block 6 through the medium of the plug 17, the lock nut 21 is loosened and the screw 20 is rotated. The fluid in the upper chambers of the space 16, as viewed in the drawing, urges the surface 6b against the contact surface 17d so that the axial position of the screw is always indicative of the setting of slide block 6.

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 my 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. In a hydraulic machine, particularly in a vane pump, a combination comprising a housing; a rotor mounted in said housing; an annular slide block located in said housing and spacedly surrounding said rotor, said slide block having endless internal and external surfaces; liquid displacing elements mounted in said rotor for movement substantially radially of the rotor axis and abutting against said internal surface, at least while said rotor is driven; and an adjustment mechanism for said slide block, including at least one adjusting member abutting against said external surface and movable in said housing in a predetermined direction substantially radially of said rotor to thereby change the distance between the axes of said slide block and said rotor, an arresting member angularly offset from said adjusting member by less than 180, as considered in the circumferential direction of said rotor, and having a contact surface abutting against said external surface, said contact surface being flat or convex, as considered in said predetermined direction, an adjustable abutment member located in said housing radially outwardly of said arresting member, and a spherical insert interposed between said abutment member and said arresting member, said abutment member having a concave surface which is engaged by said spherical insert and having a radius of curvature greater than the radius of saidinse'rt, the distance from the locus of contact between said abutment member and said insert to the locus of contact between said contact surface and said external surface being less than the radius of curvature of said contact surface.

2. A combination as defined in claim 1, wherein said arresting member is angularly offset from said adjusting member by substantially 3. A combination as defined in claim 1, further comprising means for moving said abutment member radially of said rotor, said means for moving having a recess for said insert and a portion of said arresting member.

4. A combination as defined in claim 1, wherein said displacing elements are vanes defining with said slide block a plurality of variable-volume liquid-containing chambers including a first group of chambers wherein the fluid pressure is lower and a second group of chambers wherein the fluid pressure is higher, said arresting member being located radially outwardly of said second group of chambers.

5. A combination as defined in claim 1, wherein said arresting member has a second surface located opposite said contact surface and having a socket receiving a portion of said insert with minimal clearance.

6. A combination as defined in claim 5, further comprising means for moving said abutment member radially of said rotor.

7. A combination as defined in claim 6, wherein said means for moving said abutment member comprises an externally threaded member meshing with said housing and being rotatable to thereby effect a movement of said abutment member radially of said rotor.

Claims

1. In a hydraulic machine, particularly in a vane pump, a combination comprising a housing; a rotor mounted in said housing; an annular slide block located in said housing and spacedly surrounding said rotor, said slide block having endless internal and external surfaces; liquid displacing elements mounted in said rotor for movement substantially radially of the rotor axis and abutting against said internal surface, at least while said rotor is driven; and an adjustment mechanism for said slide block, including at least one adjusting member abutting against said external surface and movable in said housing in a predetermined direction substantially radially of said rotor to thereby change the distance between the aXes of said slide block and said rotor, an arresting member angularly offset from said adjusting member by less than 180*, as considered in the circumferential direction of said rotor, and having a contact surface abutting against said external surface, said contact surface being flat or convex, as considered in said predetermined direction, an adjustable abutment member located in said housing radially outwardly of said arresting member, and a spherical insert interposed between said abutment member and said arresting member, said abutment member having a concave surface which is engaged by said spherical insert and having a radius of curvature greater than the radius of said insert, the distance from the locus of contact between said abutment member and said insert to the locus of contact between said contact surface and said external surface being less than the radius of curvature of said contact surface.

2. A combination as defined in claim 1, wherein said arresting member is angularly offset from said adjusting member by substantially 90*.

3. A combination as defined in claim 1, further comprising means for moving said abutment member radially of said rotor, said means for moving having a recess for said insert and a portion of said arresting member.