GB2142992A - Overrunning clutch - Google Patents

Abstract

An overrunning clutch comprising a drive-half (1) with axially-spaced eccentric discs (1a) 180 DEG out of phase and two longitudinal portions (1b) extending from each disc to the other on opposite sides of the plane (G) containing the eccentricities (e) of the discs; a driven half having a race (2a) whose inner surface (H) is concentric with the axis of the drive half; wedging members made as eccentric sleeves (3) with longitudinal portions (3b) embracing the discs and their longitudinal portions (1b); elements (3d) for local interaction of the eccentric sleeves (3) with the race (2a), and means limiting displacement of the eccentric sleeves (3). The latter means comprised circumferential end faces (3c) of the longitudinal portions (3b) of the eccentric sleeves (3). To this end, circumferential lengths of these longitudinal portions (3b) are made such as to enable their end faces (3c) to come into contact when the outer surface of the eccentric sleeves (3) is concentric with the inner surface (H) of the race (2a). In another embodiment, the sleeves have teeth for engaging teeth on the race. <IMAGE>

Description

SPECIFICATION Overrunning clutch The present invention relates to clutches for coupling two coaxial rotating members, and more particularly to overrunning clutches which provide transmission of rotation from a drive member to a driven one in one of two possible directions of rotation and independent freewheeling of the driven member in the same direction when its rotational speed exceeds that of the drive member.

There is provided an overrunning clutch comprising a drive half-clutch with two similar eccentrics spaced apart along the axis thereof, rotated relative to each other with their eccentricities through 1800 of an arc, and having longitudinal portions extending from each of them to the other one on opposite sides from the plane of arrangement of the eccentricities of the eccentrics, a driven half-clutch having a race concentric with the axis of the drive half-clutch, wedging members made as two similar eccentric sleeves arranged around the eccentrics and having longitudinal portions embracing corresponding longitudinal portions extending from the eccentrics, limiters of the direction of displacement of the eccentric sleeves from a position in which their outer surfaces are concentric with the inner surface of the race, and elements of local interaction of the eccentric sleeves with the race of the driven half-clutch, wherein according to the invention the function af the limiters of the direction of displacement of the eccentric sleeves from a positioned in which their outer surfaces are concentric with the inner surface of the race is performed by circumferential end faces of the longitudinal portions of the eccentric sleeves, circumferential lengths of the longitudinal portions being such as to enable their circumferential end faces to come into contact when the outer surfaces of the eccentric sleeves are concentric with the inner surface of the race.

Due to such a design, when the drive half-clutch and the driven half-clutch are disengaged,the eccentric sleeves move towards each other until the circumferential end faces of their longitudinal portions come into contact with each other. In so doing, the eccentric sleeves are located with their outer surfaces concentric relative to the inner surface of the race, their further displacement is stopped, and they are reliably locked as the cylindric surfaces of the eccentrics bear up against the inner surfaces of the eccentric sleeves. Such a design also eliminates any stress concentrators in the eccentric sleeves and thus provides their high strength. This makes it possible to decrease radial dimensions of the eccentric sleeves and of the race of the drive half-clutch and thus to reduce dynamic loads.

The overrunning clutch according to the present invention may utilize a variety of elements of local interaction of the eccentric sleeves with the race of the driven half-clutch. The function of such elements may be performed by a pair of projections on the outer surface of each concentric sleeve, equidistant from the circumferential end faces of the longitudinal portions of these sleeves and capable of wedging interaction with the smooth inner surface of the race of the driven half-clutch.In this case, to obtain reduced radial dimensions of the eccentric sleeves, according to the invention, the sections of the eccentrics and longitudinal portions extending therefrom, located in a sector between each pair of the projections of the eccentric sleeves as the circumferential end faces of their longitudinal portions come into contact, should be made along a line shorter than the circumferential length of the eccentrics in the same sector. In such a construction of a radial force is transmitted from the eccentrics and their longitudinal portions to the eccentric sleeves, as the latter are being wedged, in the direction of the projections on the eccentric sleeves.This makes it possible to prevent a bending momentfrom being created between these projections on the eccentric sleeves, which would occurr if the surfaces of the eccentrics and their longitudinal portions were made along the full length thereof around the circumference of the same radius when a radial force is transmitted from the eccentrics to the eccentric sleeves, as the latter are being wedged, in the direction of a middle section between the projections of each eccentric sleeve.The function of the elements of local interaction of the eccentric sleeves with the race of the driven half-clutch may be also performed, according to the invention, by toothed sectors made in the middle sections between the circumferential end faces of the longitudinal portions of the eccentric sleeves and capable of meshing with a toothed inner surface of the race of the driven half-clutch. In-this case, reduced radial dimensions of the elements of the clutch, according to the invention, may be obtained when the surfaces of the eccentrics and longitudinal portions extending therefrom are made around the circumferences of the same radius.

The nature and advantages of the present invention will become more apparent upon consideration of the following detailed description of its embodiments illustrated by the accompanying drawings.

Figure 1 shows an overrunning clutch according to the invention, a general view with a longitudinal section taken along the eccentric sleeves and driven half-clutch; Figure 2 shows the overrunning clutch of Figure 1, a cross-sectional view on the line ll-ll taken across the longitudinal portions extending from the eccentrics, the circumferences of the eccentrics shown in dotted lines being aligned; and Figure 3 shows another embodiment of an overrunning clutch according to the invention, across- sectional view similar to Figure 2.

An overrunning clutch shown in Figure 1 is made according to the present invention and comprises a drive half-clutch la a driven half-clutch 2 and similar wedging members disposed therebetween and made as eccentric sleeves 3.

The drive half-clutch 1 is made as an integral member including two similar elements made as disc-shaped eccentrics 1a arranged with an eccentricity e from the axis of the half-clutch 1. The eccentrics 1 a are spaced from each other and have longitudinal portions 1 b extending from each eccen tric to the other. As shown in Figure 2, the eccentrics 1 a whose cylindrical surfaces are denoted by F are rotated with their eccentricities e relative to each other through 1800 of an arc, and the longitudinal portions 1b are a continuation of the portions of the eccentrics 1 a, lying on one of the sides from a plane G of arrangement of the eccentricites e of the eccentrics 1a,these longitudinal portions 1b running relative to each other on the opposite sides from the plane G.

The driven half-clutch 2 comprises a race 2a which is concentric with the drive half-clutch 1 and has a smooth cylindricsurface H (Figure 1).

Each eccentric sleeve 3 has an annular portion 3a arranged around one of the eccentrics 1a and a longitudinal portion 3b extending therefrom and embracing the longitudinal portion 1b of the corresponding eccentric 1 a. As shown in Figure 2, the axes of an outer surface K and inner surface L of eacheccentric sleeve 3 are spaced at a distance equal to the eccentricity e of the eccentrics 1a, which enables the eccentric sleeves 3 to be located with their outer surfaces K concentric with the inner surface H of the race 2a.The longitudinal portions 3b of the eccentric sleeves 3 are provided with flat circumferential end faces 3c, the circumferential length of each longitudinal portion 3b being such as to enable their flat circumferential end faces 3c to come into contact as the eccentric sleeves 3 are arranged with their outer surface K concentric with the inner surface H of the race 2a. This is accomplished in the embodiment considered herein by making the circumferential length of each longitudinal portion 3b equal to half the annular portion 3a disposed on any of the sides from a longitudinal diametral plane of symmetry of the eccentric sleeves. In a position shown in Figure 2 this plane coincides with the plane G of arrangement of the eccentricities of the eccentrics la.

The outer surface K of each eccentric sleeve 3 is provided with a pair of projections 3d equidistant from the circumferential end faces 3c. These projections have cylindric peripheral surfaces M capable of wedging interaction with the inner surface H of the race 2a. To this end, using known design formulas, it is necessary to calculate an angle by which the projections 3d of each pair are circumferentially separated from each other, a circumferential length of the projections 3d, and a diameter of their cylindric peripheral surface M. Such calculations are presented, for example, in our published Application PCT/SU 80/00219.To prevent a bending moment of forces from being formed in the eccentric sleeves 3, as radial forces are transmitted through the projections 3d, sections P of the surfaces of the eccentrics 1 a and their longitudinal portions I b within a sector R between each pair of the projections 3d of the eccentric sleeves 3 when their outer surfaces K are concentric with the inner surface H of the race 2a should have a length shorter than that of the main cylindricsurface Fofthe eccentrics 1a. For example, said section of the surface of the eccentrics 1a may be cut to a radius longer than that of the main cylindric surface F of the eccentrics 1 a.

The overrunning clutch described hereinabove operates in a known way. When the drive half-clutch 1 rotates clockwise as shown in Figure 2, the driven half-clutch being stationary, the eccentrics 1 a with the longitudinal portions 1b rotate inside the eccentric sleeves 3 and cause their radial displacement towards the inner surface H of the race 2a of the driven half-clutch 2. When the surfaces M of the projections 3d come into contact with the inner surface H of the race 2a, the eccentric sleeves 3 are wedged between the drive half-clutch 1 and the driven half-clutch 2, and thus rotation is transmitted to the latter.When the rotational speed of the driven half-clutch 2 exceeds the rotational speed of the drive half-clutch 1 in said direction, such as when the driven half-clutch 2 is accelerated by some other drive or when the drive half-clutch 1 is stopped, the eccentric sleeves 3 are brought out of engagement with the race 2a and shift to the center. As soon as their outer surfaces K become concentric with the inner surface H of the race 2a, the circumferential end faces 3c of the longitudinal portion 3b of one of the eccentric sleeves 3 come into contact with the circumferential end faces 3c of the longitudinal portion 3b of another eccentric sleeve 3 (as shown in Figure 2), and thus the eccentric sleeves 3 are prevented from further displacement in said direction and their wedging in this direction becomes impossible.In so doing, reliable locking of the eccentric sleeves 3 in said position is additionally provided due to contact action of the eccentrics la and their longitudinal portions 1 b on the inner surface L of the eccentric sleeves 3.

From the above it follows that the overrunning clutch according to the invention comprises elements which are not subjected to bending moments of forces, and its eccentric sleeves 3 are free from stress concentrators, which ensures a high mechanical strength of such a clutch, the clutch being able to transmit substantial rotational forces by means of the projections 3d made on the outer surface K of the eccentric sleeves 3. Taken together, these factors make it possible to reduce radial dimensions of the clutch, simultaneously providing its high loadcarrying capacity, and thus to decrease dynamic forces acting in the clutch itself as well as in the mechanisms coupled therewith.

Figure 3 shows another embodiment of the overrunning clutch made in accordance with the invention. This embodiment differs from the aforementioned one in that it utilizes different elements of local interaction of the eccentric sleeves 3 with the race 2a of the driven half-clutch 2. The function of such elements is performed by a toothed sector 3e made on the outer surface K of each eccentric sleeve 3 and disposed in the middle section between the circumferential end faces 3c of the longitudinal portions 3b of the eccentric sleeves 3 and teeth 4 made on the inner surface H of the race 2a of the driven half-clutch 2, said toothed portions 3e and 4 having the same radius of a pitch circle and the same pitch, preferably of a small value.

In such a construction, as the toothed sector 3e of the eccentric sleeves 3 comes into engagement with the teeth of the race 2a, a radial force exerted by the drive half-clutch 1 is transmitted through the toothed sector 3e. Hence, the surfaces P of the eccentrics 1 a and their longitudinal portions 1 in this construction should have a regular cylindric shape around the entire circumference thereof such as to provide transmission of the radial force therefrom directly through the central section of the eccentric sleeves 3 between the circumferential end faces 3c of their longitudinal portions 3b.

The overrunning clutch made according to said another embodiment of the invention offers the same advantages as the clutch of the first mentioned embodiment of the invention, its construction and fabrication being complicated only slightly since the toothed portions 3e and 4 can be made using high-efficiency techniques, such as by cold tooth generating.

While particular embodiments of the present invention have been shown and described, various modifications thereof will be apparent to those skilled in the art and therefore it is not intended that the invention be limited to the description of the proposed overrunning clutch considered hereinabove or to the details thereof and the departures may be made therefrom within the spirit and scope of the invention as deined in the claims below.

Claims (4)

1. An overrunning clutch comprising a drive half-clutch with two similar eccentrics spaced apart along the axis thereof, rotated with their eccentricities relative to each other through 180 of an arc, and each having one longitudinal portion extending from each eccentric on one of the sides from a plane of arrangement of the eccentricities of the eccentrics to the other eccentric, a driven half-clutch having a race concentric with the axis of the drive half-clutch, wedging members made as two similar eccentric sleeves arranged around the eccentrics and having longitudinal portions embracing corresponding longitudinal portions of the eccentrics, limiters of the direction of displacement of the eccentric sleeves from a position in which their outer surfaces are concentric with an inner surface of the race, and elements of local interaction of the eccentric sleeves with the race, wherein the function of said limiters of the direction of displacement of the eccentric sleeves from a position in which their outer surfaces are concentric with the inner surface of the race is performed by circumferential end faces of the longitudinal portions of the eccentric sleeves, circumferential lengths of the longitudinal portions of the eccentric sleeves being such as to enable their end faces to come into contact when the outer surfaces of the eccentric sleeves are concentric with the inner surface of the race.

2. An overrunning clutch according to Claim 1, wherein the elements of local interaction of the eccentric sleeves with the race are made as a pair of projections on the outer surface of each eccentric sleeve, equidistant from the circumferential end faces of the longitudinal portions of the eccentric sleeves and capable of wedging interaction with the smooth inner surface of the race, and a section of the surface of each eccentric and its longitudinal portion, located in a sector between a pair of the projections on the outer surface of the eccentric sleeve when the outer surface of the eccentric sleeve is concentric with the inner surface of the race, is made along a line shorter than the circumferential length of the main cylindric surface of the eccentric in the same sector.

3. An overrunning clutch according to Claim 1, wherein the elements of local interaction of the eccentric sleeves with the race are made as a toothed sector disposed in the middle section of the outer surface of each eccentric sleeve between the circumferential end faces of its longitudinal portion and capable of meshing with a toothed inner surface of the race

4. An overrunning clutch according to any of the preceding Claims substantially as described and shown in the accompanying drawings.