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. The retainer is made in two identical annular parts which clip together. 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 facilitates the manufacture and assembling of the assemblage and allows more sprags to be accommodated in a given diameter. and, conveniently, the retainer is made in two identical annular parts which clip together.
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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 , 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.
2. A sprag retainer assemblage as claimed in
3. A sprag retainer assemblage as claimed in
4. A sprag retainer assemblage as claimed in
5. A sprag retainer assemblage as claimed in
6. A sprag retainer assemblage as claimed in
7. A sprag retainer assemblage as claimed in
the other of the annular parts of the retainer. 8. A sprag retainer assemblage as claimed in claim 7 1 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 , 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. 9. A sprag retainer assemblage as claimed in
10. A sprag retainer assemblage as claimed in
spring enwrapping said further lengthwise portion. 11. A sprag retainer assemblage as claimed in claim 10 8 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 1 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 , 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. |
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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.
very little circumferential space. than the spring mounting arrangements described in our U.S. Pat. No. 3,651,908. More A maximum number of 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 α to the radial direction in the outer race overrunning condition. The angular deflection of the blade spring portion is then greater than α+β where β 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 β 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 β 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.
Brownhill, Edward J., Heaton, Roy, Booth, Ralph
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| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Dec 20 1977 | Renold Limited | (assignment on the face of the patent) | / |
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