U.S. patent number RE29,985 [Application Number 05/862,764] was granted by the patent office on 1979-05-08 for sprag clutches.
This patent grant is currently assigned to Renold Limited. Invention is credited to Ralph Booth, Edward J. Brownhill, Roy Heaton.
United States Patent |
RE29,985 |
Brownhill , et al. |
May 8, 1979 |
Sprag clutches
Abstract
A sprag clutch utilizing the principles of U.S. Pat. No.
3,651,908 has an improved energizing spring arrangement in which
the individual sprag energizing springs are mounted on intermediate
portions of bars forming part of the sprag retainer assemblage.
.Iadd.The retainer is made in two identical annular parts which
clip together. .Iaddend.The bars define with end rings parts of the
retainer, separate compartments, one for the outer end of each
sprag, end portions of the bars acting to position the sprags
circumferentially, and the energizing springs extend inwardly from
the bars. The arrangement .Iadd.facilitates the manufacture and
assembling of the assemblage and .Iaddend.allows more sprags to be
accommodated in a given diameter. .[.and, conveniently, the
retainer is made in two identical annular parts which clip
together..].
Inventors: |
Brownhill; Edward J. (Cheadle,
GB2), Heaton; Roy (Timperley, GB2), Booth;
Ralph (Cheadle, GB2) |
Assignee: |
Renold Limited (Manchester,
GB2)
|
Family
ID: |
26256572 |
Appl.
No.: |
05/862,764 |
Filed: |
December 20, 1977 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
576654 |
May 12, 1975 |
03952849 |
Apr 27, 1976 |
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Foreign Application Priority Data
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May 28, 1974 [GB] |
|
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23531/74 |
|
Current U.S.
Class: |
192/41A;
192/45.1 |
Current CPC
Class: |
F16D
41/07 (20130101) |
Current International
Class: |
F16D
41/00 (20060101); F16D 41/07 (20060101); F16D
041/07 () |
Field of
Search: |
;192/41A,45.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Herrmann; Allan D.
Attorney, Agent or Firm: Flynn & Frishauf
Claims
We claim:
1. In a sprag retainer assemblage for use in an annular gap defined
between confronting cylindrical surfaces of inner and outer races
of a sprag clutch to transmit uni-directional drive between the
clutch driving and driven race, the assemblage comprising an
annular sprag retainer, a ring of sprags in the retainer, and for
each sprag, an energising spring individual to the sprag and
comprising a spring arm for biasing the sprag into substantially
line contact with the inner race of the clutch, by tilting the
sprag about substantially a line of contact with the outer race of
the clutch, an improved sprag retainer comprising axially extending
bars having first lengthwise portions presenting sprag positioning
faces acting to position the sprags circumferentially with respect
to one another, and wherein each energising spring has a mounting
portion at least in part enwrapping a further lengthwise portion of
one of the bars, the mounting portion thereby mounting the
energising spring fixedly on the bar .Iadd., and the retainer is
formed in two identical annular parts which are joined together,
the springs of each pair of adjacent energising springs being
mounted one on one of the annular parts of the retainer and the
other on the other of the annular parts of the
retainer.Iaddend..
2. A sprag retainer assemblage as claimed in claim 1 wherein the
radially outer ends of the sprags are confined each in a separate
compartment of the retainer defined between axially spaced annular
end walls on end ring parts of .[.the retainer.]. .Iadd.said two
retainer parts respectively .Iaddend.and sprag positioning faces on
an adjacent pair of said bars, said bars extending axially between,
and being connected with, said end ring parts, and the spring arms
extend inwardly from said bars.
3. A sprag retainer assemblage as claimed in claim 2 wherein the
bars of each adjacent pair of said bars have first lengthwise
portions, one towards each end, presenting, towards the radial
outer periphery of the adjacent one of said end walls, parallel,
confronting, flat, sprag positioning faces which co-operate with
oppositely facing curved surface portions of one of the sprags, at
the radially outer end of the sprag, to position the sprag
circumferentially with respect to all the other sprags and to
maintain the sprag with its tilt axis parallel with the axis of the
sprag retainer assemblage.
4. A sprag retainer assemblage as claimed in claim 3 wherein the
first lengthwise portions of the bars of each adjacent pair of said
bars have, radially inwardly of said sprag positioning faces,
further flat, opposed radially equally inwardly directed tilt
limiting faces which act to limit tilting of the sprag positioned
by the sprag positioning faces of the bars.
5. A sprag retainer assemblage as claimed in claim 4 wherein the
tilt limiting faces on opposite sides of each of said bars
intersect one another and also the sprag positioning faces on the
bar, all the bars being of uniform cross-sectional shape and
dimensions throughout the first lengthwise portions thereof which
portions are symmetrical about radial planes through the lines of
intersection of their tilt limiting faces.
6. A sprag retainer assemblage as claimed in claim 1 wherein each
energising spring has an ear carried by its mounting portion and
engaging the curved surface portion of the sprag energised by the
spring on the side of the sprag adjacent the spring to restrain the
sprag against radial inward movement in the sprag retainer when the
assemblage is free of any races, the spring then holding the sprag
in engagement with its tilt limiting faces on the bar on the side
of the sprag remote from the spring to restrain the sprag against
radial outward movement in the sprag retainer. .[.7. A sprag
retainer assemblage as claimed in claim 1 wherein the retainer is
formed in two identical annular parts which are joined together,
the springs of each pair of adjacent energising springs being
mounted one on one of the annular parts of the retainer and the
other on
the other of the annular parts of the retainer..]. 8. A sprag
retainer assemblage as claimed in claim .[.7.]. .Iadd.1
.Iaddend.wherein each bar has two endwise abutting parts one of
which is longer than the other, the parts of the bar being formed
in one piece respectively with the two annular parts of the
retainer .Iadd., said further lengthwise portion of each bar is
formed as a lengthwise portion at the free end of said longer part
of the bar, and said further lengthwise portion of each bar is
generally of the same cross-sectional shape as said first
lengthwise portions thereof but has its faces inset with respect to
the corresponding faces of the first lengthwise portions by an
amount which is a little greater than the thickness of the mounting
portion of the energising spring enwrapping said further lengthwise
portion.Iaddend.. .[.9. A sprag retainer assemblage as claimed in
claim 8 wherein said further lengthwise portion of each bar is
formed as a lengthwise portion at the free end of said longer part
of the bar..]. .[.10. A sprag retainer assemblage as claimed in
claim 9 wherein said further lengthwise portion of each bar is
generally of the same cross-sectional shape as said first
lengthwise portions thereof but has its faces inset with respect to
the corresponding faces of the first lengthwise portions by an
amount which is a little greater than the thickness of the mounting
portion of the energising
spring enwrapping said further lengthwise portion..]. 11. A sprag
retainer assemblage as claimed in claim .[.10.]. .Iadd.8
.Iaddend.wherein the
energising springs are disposed in staggered relation. 12. A sprag
retainer assemblage as claimed in claim 8, wherein the two endwise
abutting parts of each bar have a spigot-and-socket connection with
one
another. 13. A sprag retainer assemblage as claimed in claim
.[.7.]. .Iadd.1 .Iaddend.wherein the two identical annular parts of
the retainer
are held together by spring clips. 14. A sprag retainer assemblage
as claimed in claim 13 wherein the spring clips are of U-shaped
configuration and each embraces the outer circumferential edge of
the retainer between an adjacent pair of said sprags, the clip
being circumferentially located
in a pair of recesses one in each of the two retainer parts. 15. A
sprag clutch comprising inner and outer races and at least one
sprag retainer assemblage disposed in an annular gap between the
races and arranged to transmit a uni-directional drive between the
clutch driving and driven race, the assemblage comprising an
annular sprag retainer, a ring of sprags in the retainer, and for
each sprag, an energising spring individual to the sprag and
comprising a spring arm for biasing the sprag into substantially
line contact with the inner race of the clutch, by tilting the
sprag about substantially a line of contact with the outer race of
the clutch, the sprag retainer comprising axially extending bars
having first lengthwise portions presenting sprag positioning faces
acting to position the sprags circumferentially with respect to one
another, and wherein each energising spring has a mounting portion
at least in part enwrapping a further lengthwise portion of one of
the bars, the mounting portion thereby mounting the energising
spring fixedly on the bar .Iadd., and the retainer is formed in two
identical annular parts which are joined together, the springs of
each pair of adjacent energising springs being mounted one on one
of the annular parts of the retainer and the other on the other of
the annular parts of the retainer.Iaddend..
Description
This invention relates to sprag clutches and concerns sprag
retainer assemblies therefor.
In our U.S. Pat. No. 3,651,908, we describe a sprag retainer
assemblage for use in an annular gap defined between confronting
cylindrical surfaces of inner and outer races of a sprag clutch to
transmit uni-directional drive between the clutch driving and
driven race. The assemblage comprises an annular sprag retainer, a
ring of sprags in the retainer, and, for each sprag, an energising
spring individual to the sprag and comprising a spring arm for
biasing the sprag into substantially line contact with the inner
race of the clutch, by tilting the sprag about substantially a line
of contact with the outer race of the clutch.
The spring arm biases the sprag with a component of spring force
directed radially inwardly of the assemblage the centre of gravity
of each sprag being disposed close to or in the radial axial plane
of the assemblage containing said line of contact between said
sprag and the outer race.
The centrifugal force acting on the spring arm during overrunning
of the outer race of the clutch, in use of the assemblage, relieves
the spring force on the sprag, and the centrifugal force acting on
the sprag during overrunning of the outer race of the clutch acts
in conjunction with the spring force on the sprag so as to maintain
a small load between the sprag and the inner race on overrun of the
outer race, at least within a predetermined limit of outer race
overrunning speed.
This construction gives rise to an improved clutch outer race
overrunning speed compared with its inner race overrunning speed
for which a clutch may be designed.
An object of this invention is to provide a sprag retainer
assemblage for a sprag clutch which can retain this advantage
whilst exhibiting an improved manner of mounting the energising
springs so as to take up less circumferential space in the
assemblage whereby more sprags can be accommodated at a given
diameter and the torque capacity of a clutch thereby improved.
SUMMARY OF THE INVENTION
.[.Thus, the.]. .Iadd.The .Iaddend.present invention is directed to
a sprag retainer assemblage as defined in the second paragraph of
this specification in which the sprag retainer comprises axially
extending bars having first lengthwise portions presenting sprag
positioning faces acting to position the sprags circumferentially
with respect to one another, and wherein each energising spring has
a mounting portion at least in part enwrapping a further lengthwise
portion of one of the bars, the mounting portion thereby mounting
the energising spring fixedly on the bar .[...]. .Iadd.,
.Iaddend.
.[.Conveniently,.]. the retainer .[.is.]. .Iadd.being
.Iaddend.formed in two identical annular parts which are joined
together,
the springs of each pair of adjacent energising springs being
mounted one on one of the annular parts of the retainer and the
other on the other of the annular parts of the retainer.
This invention also comprehends a sprag clutch comprising inner and
outer races and at least one sprag retainer assemblage according to
this invention, as hereinbefore defined, disposed in an annular gap
between the races and arranged to transmit a uni-directional drive
between the clutch driving and driven race.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and still further features of this invention will
become clear from a consideration of the following description of
specific embodiments of sprag retainer assemblage according to this
invention and a sprag clutch which embodies the assemblage, which
will now be described, by way of example, and not by way of
limitation, with reference to the accompanying drawings in
which:
FIG. 1 is a front elevation of a sprag retainer assemblage
according to the invention,
FIG. 2 is a view in the direction of arrow 2 in FIG. 1,
FIG. 3 is a view corresponding with FIG. 1 and showing one half of
the sprag retainer of the assemblage,
FIG. 4 is a view in the direction of arrow 4 in FIG. 3,
FIG. 5 is a partial cross-sectional view of one half of the sprag
retainer of the assemblage showing a detail of its
construction,
FIG. 6 shows one of the spring clips used to hold the two halves of
the sprag retainer together in assembled relation,
FIG. 7 is an enlarged view of part of a sprag clutch of this
invention in the outer race overrunning condition and showing the
sprag retainer with one sprag and energising spring in position,
between the confronting cylindrical surfaces of the inner and outer
races of the clutch,
FIG. 8 is a view corresponding with FIG. 7 but showing the clutch
in its fully loaded condition,
FIG. 9 is an enlarged view of part of a further sprag retainer
assemblage according to the invention, and
FIGS. 10 and 11 are details of the assemblage shown in FIG. 9.
DETAILED DESCRIPTION
Referring to the accompanying drawings, the assemblage of FIG. 1
comprises an annular sprag retainer generally indicated at 10 in
FIGS. 1 and 2, and a ring of identical sprags 11 each having its
radially outer end confined in a separate compartment 12 of the
retainer defined between axially spaced annular end walls 14 on end
ring parts 14' of the retainer and axially directed retainer bars
18 extending axially between, and connected with, the end ring
parts.
Adjacent bars 18 have lengthwise portions 18' and 18", one towards
each end, presenting towards the radial outer periphery of the end
walls 14, parallel, confronting flat faces 15, 16 which co-operate
with oppositely facing curved surface portions 11a, 11b (see FIGS.
7 and 8) of the sprag at the radially outer end of the sprag to
position the sprag circumferentially with respect to all the other
sprags and to maintain the sprag with its tilt axis parallel with
the axis of the assemblage, and, radially inwardly of the faces 15,
16 further flat, opposed, radially equally inwardly directed faces
20 and 21 which act to prevent "turnover" and "pop out" of the
sprag in use of the assemblage. Thus, the faces 20 and 21 limit
tilting of the sprag in one direction or the other, beyond a
position in which it can move out of engagement with the clutch
inner and outer races.
The faces 20 or 21 on opposite sides of each bar 18 intersect one
another and also the face 15 or 16 on the same side of the bar, all
the bars being of uniform cross-sectional shape and dimensions
throughout their lengthwise portions 18' and 18" which portions are
symmetrical about radial planes through the lines of intersection
of their faces 20 or 21. This configuration of the bars 18 enables
the retainer to be formed in two identical annular parts 14a one of
which is shown in FIGS. 3 and 4. Thus, each bar 18 has two endwise
abutting parts 18a and 18b respectively one on each of the parts
14a. Each longer part 18a has a lengthwise portion 18a' at its free
end, generally of the same cross-sectional shape as the lengthwise
portions 18' and 18" but the faces of which are inset with respect
to the corresponding faces of the portions 18' and 18" by an amount
which is a little greater than the thickness of a spring metal
strip mounted on the portion 18a' and forming a sprag energising
spring 24 (see also FIGS. 7 and 8). The axial length of each porton
18a' is equal to the width of the strip forming the spring.
In FIGS. 7 and 8 outer and inner races are indicated at 31 and 32
respectively with an annular gap 33 defined between their
confronting cylindrical surfaces 31' and 32'.
The sprag retainer assemblage is positioned in the gap 33 with the
sprags 11 positioned circumferentially and correspondingly tilted
with respect to the radial directions initially, with the races
stationary, generally in the attitude depicted for the single sprag
11 which is shown in FIG. 7.
The radially inner and outer end faces 11c and 11d of the sprags
are shaped by radii or compound radii, and the initial tilt of the
sprags is such that the radially inner end face of each sprag has
one lower corner 11c'. (See FIG. 7). The overall shape of the
sprags is such that as the sprags tend to assume a more exactly
radial disposition between the races, the overall height of the
sprags increases and tends to become greater than the width of the
gap 33 so that the sprags lock solidly between the races to
transmit drive from the driving race to the driven race.
The springs 24, one for each sprag, energise or bias the sprags
lightly into contact with the inner and outer races when the races
are stationary so that such drive may be taken up.
Each spring 24 has a mounting portion 24' having a straight sided
shape conforming in shape to, and closely enwrapping the portion
18a' of one of the bars 18, the mounting portion in this way
holding a straight blade spring portion 24" of the spring in a
predetermined inwardly projecting position, with its inner free end
engaging and energising one of the sprags 11.
Whilst the mounting portion 24' is shown completely enwrapping the
portion 18a' in this example, this is not essential. A partial
enwrapping, sufficient to support the portion 24" in a fixed
angular orientation in its undeflected state is all that is
necessary.
In its deflected state, each blade spring portion 24" extends
inwardly at an angle to the radial direction so that it exerts an
energising force on its sprag, in the gap 33, with a component
directed radially inwardly of the races.
The energising force biases the radially inner end face 11c of the
sprag into substantially line contact with the inner race, the
energising force tending to tilt the sprag about substantially a
line of contact between the radially outer end face 11d of the
sprag and the outer race 31 in the same way as is described in the
specification of our U.S. Pat. No. 3,651,908.
On overrun of the outer race, in the direction of arrow X (see FIG.
7), the action of centrifugal force on the blade spring portion 24"
relieves the spring force on the sprag, thus reducing the rubbing
load between the sprag and the inner race.
The centre of gravity of the sprag may be positioned such that the
action of the centrifugal force on the sprag increases this rubbing
load between the sprag and the inner race to an extent in whole or
in part compensated for by the reduction of rubbing load due to the
action of the centrifugal force on the blade spring portion so that
the action of the centrifugal force on the sprag has no effect on
or acts to reduce the rubbing load between the sprag and the inner
race, the criterion being however that the sprag remains spring
biased into contact with the inner race under all outer race
overrunning conditions for which a clutch may be designed.
In order to locate the retainer parts 14a correctly with respect to
one another, the endwise abutting bar parts 18a and 18b have
spiggot and socket connections 40, 41. The parts 14a are held
together by four spring clips 44 of generally U-shaped
configuration, one of which is shown in FIG. 6, the clips embracing
the outer circumferential edge of the retainer. The annular end
rings of the retainer parts are circumferentially recessed as at 46
(see FIG. 5) at the outer peripheral edge of their outside faces to
receive these clips, the clips being circumferentially located each
in a pair of axially directed recesses 47 one in each of the end
walls 14 and being received flush against the outer surface of one
of the bars 18, which has a lesser radial thickness in order to
accommodate the clip.
The retainer parts are conveniently formed as plastics mouldings
from nylon loaded with glass fibre and graphite to provide strength
and thermal stability. Other suitable materials may however be
used.
The sprags are of uniform cross-section throughout and have plane
end faces one adjacent each of the walls 14 of the sprag
retainer.
The energising spring arrangement described, with the spring
mounting portions enwrapping lengthwise portions of the retainer
bars 18, takes up .[.less.]. .Iadd.very little
.Iaddend.circumferential space.Iadd.. .Iaddend..[.than the spring
mounting arrangements described in our U.S. Pat. No. 3,651,908.
More.]. .Iadd.A maximum number of .Iaddend.sprags can therefore be
accomodated at a given diameter whereby the torque capacity of a
clutch can be increased.
The springs 24 are assembled simply by pushing their mounting
portions onto the free ends of the bar portions 18a' of the two
retainer parts, the springs on one part being laterally inverted in
relation to the springs on the other part. Alternate sprags are
then inserted in position in the retainer parts one in engagement
with each spring blade. The two retainer parts are then assembled
to form the sprag retainer assemblage, the retainer parts being
secured together by means of the clips.
As assembled the springs 24 are located axially of the retainer
bars by the shoulders formed at the junction of the portions 18'
and 18a' and 18a' and 18b respectively.
The staggered arrangement taken up by the energising springs in the
final assemblage permits the retention of confronting cage faces
15, 16 on lengthwise portions of adjacent retainer bars 18 at each
end of each sprag whilst allowing the retainer to be manufactured
in two identical parts. This represents a further significant
manufacturing advantage.
The spring mounting portions 24' enwrapping the bars 18 lie below
the level of the face 15, 16 where they confront the surface
portions 11a and 11b of the sprags, and these spring mounting
portions are, therefore, protected from wear by the sprags, the
wear being taken at the faces 15 and 16.
Each blade spring portion 24" extends inwardly at an angle .alpha.
to the radial direction in the outer race overrunning condition.
The angular deflection of the blade spring portion is then greater
than .alpha.+.beta. where .beta. is the angle which the spring arm
makes with the radial direction in the fully loaded condition of
the clutch. (See FIG. 8). In the outer race overrunning position,
as shown in FIG. 7, the blade spring portion exerts an energising
force on the sprag, in the gap 33 between the races 31 and 32, with
a component directed radially inwardly of the races as already
stated. In the fully loaded condition, the blade spring portion
exerts an energising force on the sprag, in the gap between the
races, with a component directed radially outwardly of the races.
In a predetermined, intermediate load condition, the blade spring
portion extends radially inwardly and exerts an energising force on
the sprag in a tangential direction in the gap between the races.
At this predetermined, intermediate load condition the spring
energising force has a zero radially inwardly directed component.
Above the predetermined, intermediate load condition the spring
energising force has a radially outwardly directed component which
increases with load.
It is to be understood that when the inner race overruns, it
rotates in the direction of arrow Y (see FIG. 7) and the sprags and
the outer race remain stationary. When the outer race overruns, in
the direction of arrow X, it takes with it the sprags and the sprag
retainer, only the inner race remaining stationary.
As may be seen from FIG. 8 in the fully loaded position of the
clutch in which the blade spring portion extends at an angle .beta.
to the radial direction such as to exert its energising force on
the sprag with a component directed radially outwardly of the
races, the action of the centrifugal force on the blade arm
reinforces the spring energising force acting on the sprag, and
this condition applies in the whole of the upper part of the load
range in which the angle .beta. is greater than zero.
FIGS. 9, 10 and 11 show a modification of the sprag retainer
assemblage in which each energising spring 24a has ears P one at
each side of its blade spring portion 24a" corresponding with the
blade spring portion 24" previously described and carried by the
mounting portion 24' corresponding with the mounting portion 24'
previously described. The ears P engage with the curved surface
portions 11a of the sprags to restrain the sprags against radial
inward movement in the sprag retainer when the assemblage is free
of any races. In this condition, each sprag is held by its
energising spring against the next adjacent bar 18 the face 20 or
21 of which restrains the sprag against radial outward movement
relative to the sprag retainer. Because of these restraints, the
sprag retainer assemblage may be freely handled prior to fitting it
between a pair of races, or directly onto a shaft for example.
The ears P are preferably curved in conformity with the surface
portions 11a of the sprags.
FIGS. 10 and 11 show one of the energising springs 24a in a
non-deflected condition. Although the ears P exert some spring
force on the sprags in the assembled condition of the springs, the
dimensions of the ears are such that this spring force is of no
practical significance.
Parts in FIG. 9 corresponding with parts already described with
reference to earlier figures, are indicated by the same reference
numerals as used previously.
By staggering the springs 24, wider springs may be incorporated,
using the mounting arrangement described, with adjacent springs
being carried on identical annular parts 14a respectively. Far
narrower springs 24 could however be employed since the stiffness
of the springs is their sole criterion. Using narrower springs, all
the springs 24 could be arranged centrally of the bars 18 if
desired, the retainer still being formed in two identical annular
parts having the construction of the parts 14a. For example, the
width of the springs could be limited to a dimension equal to the
overlap of the springs 24 shown in FIG. 2, the axial length of the
portions 8a' being correspondingly reduced and the axial length of
the lengthwise bar portions 18" being correspondingly
increased.
* * * * *