U.S. patent number 3,918,855 [Application Number 05/493,969] was granted by the patent office on 1975-11-11 for adjustable vane pump.
This patent grant is currently assigned to Rexroth GmbH. Invention is credited to Siegfried Bornholdt.
United States Patent |
3,918,855 |
Bornholdt |
November 11, 1975 |
Adjustable vane pump
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.
Inventors: |
Bornholdt; Siegfried (Lohr
(Main), DT) |
Assignee: |
Rexroth GmbH (Lohr (Main),
DT)
|
Family
ID: |
5898236 |
Appl.
No.: |
05/493,969 |
Filed: |
August 1, 1974 |
Foreign Application Priority Data
|
|
|
|
|
Nov 16, 1973 [DT] |
|
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2357182 |
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Current U.S.
Class: |
418/24; 417/220;
418/30; 418/31 |
Current CPC
Class: |
F04C
14/223 (20130101) |
Current International
Class: |
F01C
21/00 (20060101); F04C 15/00 (20060101); F04C
2/344 (20060101); F04C 2/00 (20060101); F04B
49/00 (20060101); F01C 021/16 (); F03C 003/00 ();
F04C 015/04 (); F04B 049/00 () |
Field of
Search: |
;418/24-27,30,31 ;91/497
;417/219,220,221 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Vrablik; John J.
Attorney, Agent or Firm: Striker; Michael S.
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.degree., 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.degree..
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.
Description
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..sup.+
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.
.sup.+.sup.+ 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 the 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.
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 hysteresis-
and 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.degree. (preferably by 90.degree.) 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 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 PREFERRED 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 10 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 6b 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 17c 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 6b 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 19a.
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 19a. 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 15 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 20 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.
* * * * *