Constant velocity joint

Details Constant velocity joint Constant velocity joint

1998-04-27

2001-03-20

Browne, Lynne H. (Department: 3629)

Rotary shafts, gudgeons, housings, and flexible couplings for ro

Coupling accommodates drive between members having...

Coupling transmits torque via radially directed pin

C464S905000

Reexamination Certificate

active

06203438

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to constant velocity, universal joints in general.
BACKGROUND OF THE INVENTION
A universal joint, in general, is a mechanical coupling between two rotating shafts, used to transmit power, motion, or both. The axes of the shafts are always intersecting and the bending angle between them is permitted to change during operation. The “Cardan joint” (also called “Hooke's joint”) is a well known example of a universal joint. It is noted that the Cardan joint transmits rotary motion but does not ensure that the angular velocities of the shafts are equal at all times.
A constant velocity universal joint, on the other hand, is a universal joint that transmits a rotary motion while keeping the angular velocities of the shafts equal at all times.
True constancy of angular velocity transmission is achieved by a widely used arrangement of two Cardan joints in series, the output member of the first joint comprising the input member to the second joint. It is noted, however, that the constancy is kept only under strict geometrical requirements: both input and output shafts must lie in one plane and both bending angles of the two Cardan joints must be kept equal at all times. This principle is used in the so called Double Cardan Universal Joint, as described for example in U.S. Pat. Nos. 4,257,243 and 5,419,740, where two Cardan joints are connected by a relatively short intermediate member designed to meet said geometrical requirements.
Another known constant velocity universal joint, which is commonly used in motor vehicle front-wheel drives, is the Rzeppa joint. It operates on the basic principle that constancy of transmission is ensured when the contact point or points between the two shafts lie in the so called “homokinetic plane” of the joint. This plane is normal to the plane defined by the two shaft axes and lies along the bisector of the angle between the two shaft axes. The Rzeppa joint consists of a cage that keeps six balls in the homokinetic plane at all times. A further development of the Rzeppa joint, that allows not only angular but also axial relative movement of the shafts, is described in U.S. Pat. No. 4,573,947.
Examples of other types of universal joints, or constant velocity universal joints, are described in U.S. Pat. Nos. 4,786,270, 5,474,500, and 5,256,107, as well as European Patent Publication 668 452 A1.
SUMMARY OF THE PRESENT INVENTION
It is an object of the present invention to provide a novel constant velocity, universal joint and a novel, fixed angle constant velocity joint.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a constant velocity joint which includes first and second shafts, inner and outer members and a constraining unit. The first shaft has a first yoke attached thereto and the second shaft has a second yoke, smaller than the first yoke, attached thereto. Each shaft has a socket at one end thereof where the socket is concentric about its respective shaft axis. The outer member is pivotally connected to the first yoke about a first rotation axis which is perpendicular to the axis of the first shaft. The inner member is pivotally connected to the second yoke about a second rotation axis which is perpendicular to the axis of the second shaft. The outer member is pivotally connected to the inner member about a third rotation axis which is perpendicular to both the first and second rotation axes. All of the five axes intersect at a joint center point. The constraining unit constrains the third rotation axis to continuously lie generally within the instantaneous homokinetic plane of the joint and includes two balls which slide in the sockets of the shafts.
Additionally, in accordance with a preferred embodiment of the present invention, the constraining unit includes a cylindrical stud unit, a cylindrical jacket and first and second rods. The cylindrical stud unit includes a stud axis, the two balls, the first rod and a third ball. The centers of the two balls are connected by a center line which is at least one of parallel and coincident with the sleeve axis. The cylindrical jacket has a jacket axis and a slot. The second rod is connected to the cylindrical jacket, extends away from the jacket axis and ends in a fourth ball. The first rod extends away from the stud axis and the cylindrical stud sits rotatably about the stud axis within the cylindrical jacket. The first rod extends through the slot and the center points of the third and fourth balls lie in a plane that perpendicularly bisects the center line and the inner member has two socket portions concentric about the third rotation axis for slidably receiving the third and fourth balls.
Further, in accordance with a preferred embodiment of the present invention, the constraining unit includes a disk and an annular housing. The disk has the two balls connected thereto, a disk axis connecting the center points of the two balls and two parallel planar surfaces which are perpendicular to the disk axis. The annular housing has parallel inner walls and opposing bores. The parallel inner walls form an inner annular groove within which the disk may slide and rotate. The annular groove is of a width to permit a sliding contact between the parallel planar surfaces of the disk and the parallel inner walls and the opposing bores lie along a pivot axis which is in a plane that perpendicularly bisects the disk axis. The annular housing is pivotally connected to the inner member about the pivot axis such that the pivot axis coincides with the third rotation axis.
Moreover, in accordance with a preferred embodiment of the present invention, the disk can be either concentric about or eccentric with the socket axis.
The above embodiments provide a universal, constant velocity joint. The present invention is also operative to provide a non-universal constant velocity joint.
In accordance with one embodiment, the constraining unit includes a pair of rollers of the same radii and a fixed planar ring. The pair of rollers are connected externally to the outer member along the third rotation axis and rotate about the third rotation axis. The rollers are located on opposite sides of the joint center point along the third rotation axis. The planar ring is fixed along a plane parallel to the fixed homokinetic plane and distant therefrom by the radius of the rollers wherein the pair of rollers are capable of rolling along a surface of the fixed planar ring.
Finally, in a further embodiment, the constraining unit includes a fixed housing, an outer ring and a rod. The outer ring is connected to the fixed housing by bearings whose axis of rotation is normal to the fixed homokinetic plane. The rod is connected externally to the outer member and ends with a ball whose center point lies along the third rotation axis. The ball sits slidably in a radial bore of the outer ring that is concentric with an axis perpendicular to the axis of rotation and lies within the fixed homokinetic plane.


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