GB2588854A

GB2588854A - Near constant velocity joint

Info

Publication number: GB2588854A
Application number: GB2015977.8A
Authority: GB
Inventors: Parker Simon
Original assignee: Punk Couplings Ltd
Current assignee: Punk Couplings Ltd
Priority date: 2019-10-09
Filing date: 2019-10-09
Publication date: 2021-05-12
Also published as: GB201915769D0; GB202015977D0

Abstract

A near constant velocity joint comprising a central axle 40 supported in a first spherical bearing 10, a second spherical bearing 20, and a third spherical bearing 30 allowing change of the alignment of a central axis, the second spherical bearing 20 being between the first 10 and the third spherical bearing 30, the spherical bearings 10, 20, 30 being each mounted in a separate housing 16, 26 and 36. To minimise wear between the bearings and housings, roller bearings 14, 24, and 34 may be provided. The constant velocity joint comprises first and second concentric couplings 1 and 2, the first coupling having an inner first member 211, an intermediate annular member 221 and an outer annular member 231 which is a common annular member and forms an inner for the second coupling 2 that also comprises an intermediate annular member 241 and outer annular member 251. The members 211, 221, 231, 241, 251 have convex and concave inner/outer peripheries so that they nest one within the other and there is a gap between each inner and outer periphery.

Description

NEAR CONSTANT VELOCITY JOINT

Technical Field

[0001] The present invention relates to a constant velocity joint or coupling. Background Art [0002] Constant velocity joints are used typically, but not exclusively, in transmission and steering systems.

[0003] A double cardan joint consists of two universal joints mounted back to back with a centre yoke. Provided that the angle between the input shaft and centre yoke is equal to the angle between the centre yoke and the output shaft, the second cardan joint will cancel the angular velocity errors introduced by the first cardan joint and the aligned double cardan joint will act as a constant velocity. A slightly smoother joint in operation is a Thompson joint, but it is very much more complex. In sea going vessels couplings having double Cardan Joint arrangement with self-centring mechanism are used to link off-set drive shafts. This arrangement ensures both Cardan joints experience the same angle of misalignment as each other thus forcing a Constant Velocity output. However, such joints are very heavy, and have high inertia forces, and considerable losses through friction. Furthermore, such joints have been known to fail in an uncontrolled manner, which under the high inertial forces experienced by such joints can lead to extensive damage and danger to life.

[0004] More recently introduced is a Thompson Joint, which is smoother in operation but has proven to be unreliable. Wear and centrifugal loadings which eventually cause the joint to break apart in an uncontrolled manner.

[0005] The present invention seeks to provide a near constant velocity joint which can be used in heavy duty applications such as marine propulsion systems and bulldozers and dredgers, is as smooth as the Thompson Joint, but which avoids the lack of reliability associated with that design.

Summary of the Invention

[0006] According to the present invention a near constant velocity joint comprises a central axle supported in a first spherical bearing, a second spherical bearing, and a third spherical bearing allowing change of the alignment of the central axis, the second spherical bearing being between the first and the third spherical bearing, the spherical bearings being each mounted in a separate housing.

Brief description of drawings

[0007] Some examples of the invention are described below with reference to the accompanying drawings, in which: [0008] Figure 1 is a section of a first example of the present invention; and [0009] Figure 2 is a section of a second example of the present invention. Description of examples [0010] In figures 1 and 2, connecting between an input I and an output 0 comprises concentric a couplings 1 and 2, with coupling 2 disposed around coupling 1, a first support means allowing change of the alignment of the central axis in the form of a first spherical bearing 10, a second intermediate support means allowing change of the alignment of the central axis in the form of a second intermediate spherical bearing 20, and a third support means allowing change of the alignment of the central axis in the form of a third spherical bearing 30 supporting a shaft 40; the second intermediate bearing 20 is between the first and third bearings. The first and second couplings 1, 2 and the first, second and third bearings 10, 20, 30, when aligned, are disposed around a central axis H-X. The couplings 1 and 2 having a first central axis H, and the bearings 10, 20 and 30 having a central axis X. The bearings 10, 20, and 30 are supported in housings 16,26 and 36 respectively. Cylindrical bosses 13, 23 and 33 are formed on the shaft 40 for support in the spherical bearings 10, 20, 30.

[0011] The inner coupling 1 comprises an inner first annular member 211 and intermediate annular member 221 and an outer annular member 231. The annular member 231 is also the inner member of the second outer coupling 2 and is described below as the common annular member 231.

[0012] Coupling 2 thus comprises the common annular member 231, an intermediate member 241 and an outer member 251.

[0013] The inner member 211 of coupling 1 has a central bore 200 with splines 201 around the bore to receive a splined input output shaft (not shown).

[0014] The inner member 211, the intermediate annular members 221 and 241, and the common annular member 231 each comprise spherical segments. Each of the annular members (211, 221, 231, 241, 251) is disposed around common first axis H and have a common centre CC on said first axis H. The common annular member 231 serves as the outer annular member of first coupling 1 which is effectively rigidly attached to the inner member of second coupling 2.

[0015] The inner first annular member 211 has an outer convex spherical periphery 212 and the second intermediate annular member has an inner spherical concave periphery 223 in which the outer convex periphery 212 of the inner first annular member 211 is received.

[0016] The intermediate annular member 221 of first coupling 1 has an outer convex spherical periphery 222 and the common annular member 231 has an inner spherical concave periphery 233 into which the outer convex periphery 222 of the intermediate annular member is received.

[0017] The common annular member 231 has an outer convex spherical periphery 232 and the intermediate annular member 241 of the second coupling 2 has an inner spherical concave periphery 243 in which the outer convex periphery 232 of the common annular member 231 is received.

[0018] The intermediate annular member 241 of the second coupling has an outer convex spherical periphery 242 and the outer annular member 251 of the second coupling 2 has an inner spherical concave periphery 253 in which the outer convex periphery 242 of intermediate annular member 241 is received.

[0019] Gaps 203 are provided between the annular members of couplings 1 and 2. The appropriate width of the gaps 203 varies according to the intended use of the coupling, the speed of rotation, load profiles, and the materials used in the annular members. However, as a rule, the gaps 203 would be 0.5% of the overall diameter of the coupling concerned where the overall diameter is less than 100mm, and 1% of when the overall diameter of the coupling concerned is 100mm in diameter or more.

[0020] A splined input shaft (not shown) would engage with the splines 201 in central aperture 200 of the inner member 211 of coupling 1 to provide input I. Through the common member 231, torque from the input I is transmitted to outer annular member 251 of second coupling 2.

[0021] The inner member 211 of coupling 1 is connected to the cylindrical housing 16 of the first bearing 10.

[0022] The common annular member 231 is connected by a cylindrical member 27 to the housing 26 of the second spherical bearing 20.

[0023] The outer annular member 251 is connected by a cylindrical member 37 to the housing 36 of the third spherical bearing 30. The housing 36 extends laterally as a boss 38 which can be connected to an output shaft (not shown).

[0024] An axle 40 having a central axis X is supported in the central apertures 12, 22,32 of the spherical bearings 10, 20, 30, but is not connected to them so is free to rotate about its axis X independently in those bearings so no torque is transmitted though the axle 40. The effect of the axle 40 is to ensure that the axes of the spherical bearing are always aligned with the axis X of the axle 40, with the centres of the bearings CB(1), CB(2), and CB(3) on the axis X. [0025] The joint described in figures 1 and 2 retains the outer annular member 251 of the second coupling 2 and the bearing 30 in a fixed relationship with one another, with rotation of the input I transmitted to the output 0.

[0026] To minimise wear between the bearings 10, 20 and 30 and housings 16, 26 and 36, roller bearings 14, 24, and 34 can be provided around spherical bearings 10, 20, 30 respectively, between the relevant spherical bearing and its housing as shown in figure 2. The roller bearings 14, 24, 34 can be omitted as shown in figure 1, but it has been found that doing so reduces the life-expectancy of the joint.

Claims

Claims 1. A near constant velocity joint comprising a central axle supported in a first spherical bearing, a second spherical bearing, and a third spherical bearing allowing change of the alignment of the central axis, the second spherical bearing being between the first and the third spherical bearing, the spherical bearings being each mounted in a separate housing.
2. A near constant velocity joint according to claim 1 having roller bearings between each spherical bearing and its housing.