GB2215434A - Universal joints for torque transmission - Google Patents

Abstract

A Hookes universal joint comprising two yokes (11, 12) whose limbs (15, 16; 115, 116) have radially outwardly extending journals (17) pivoted in an annular member (18) disposed radially outwardly of the yokes, the annular member having flexible portions able to accommodate relative axial movement between its journal-receiving portions so as to give some axial resilience in a drive line. The annular member may be of metal with journal-receiving bosses (19) connected by relatively thin flexible portions (25), or may be of an elastomeric material. Centering means may be provided to ensure the two yokes of the joint remain centered relative to one another. <IMAGE>

Description

UNIVERSAL JOINTS FOR TORQUE TRANSMISSION This invention relates to universal joints for torque transmission between two shafts or other rotary elements.

The universal joint according to the invention is generally of the Hookes type, i.e. it comprises two yokes for connection to the rotary elements which the joint is to connect, the yokes being joined to one another by a member which is pivoted to both yokes by journals supported in bearings. A first pair of journals provide a pivotal connection to one yoke, and a second pair of journals disposed perpendicularly to the first pair provide the pivotal connection to the other yoke. The best known form of Hookes joint has a cross member with radially outwardly extending journals, which are received in bearing cups held in spaced limbs of the yokes.

Such best known form of Hookes joint has the characteristic that because the cross member is a solid component, usually a steel forging, the two yokes are unable to move axially of the universal joint relative to one another. When we refer to orientations such as "axially" and "radially", it is to be understood that the joint is to be envisaged in the aligned, i.e. not articulated, condition, wherein the joint yokes and cross member have a common rotational axis. However, for some applications of Hookes joint it is desirable if the joint could be made to incorporate some ability to yield axially and accommodate a small amount of relative axial movement between the two yokes of the joint.This may be desirable in certain automotive applications, e.g. in the shaft extending longitudinally of a vehicle (usually termed the propeller shaft) between a forwardly mounted engine and a driven rear axle. Under certain conditions an axial impulse force may be introduced into the propeller shaft which could be absorbed if the shaft were to have some axial resilience, this requirement being independent of large scale length changes in the shaft caused by vehicle suspension movement and accommodated by a sliding splined or other coupling in the shaft.

It is the object of the present invention to provide a Hookes universal joint with the ability to yield axially and meet the requirement above described.

According to the present invention, a Hookes universal joint has its two yokes each provided with a pair of radially outwardly extending diametrically opposed journals, and a member of annular form disposed radially outwardly of the yokes and having circumferentially spaced portions wherein the journals are received, the annular member being provided with portions able to accommodate relative axial movement between the journal-receiving portions.

Preferably the journals are pivotally supported in bearing cups held in the annular member.

The annular member may be a metal component, having circumferentially spaced bosses in which the bearing cups are received, and relatively thin web portions therebetween which provide the necessary resilience for the relative axial movement between adjacent bosses.

Alternatively, the annular member may be of a material which is inherently resilient, e.g. an elastomer possibly with fibre, fabric or cord reinforcement so that it has the necessary torque transmitting ability. When an annular member of this type is used, the joint preferably incorporates centering means to ensure that the two yokes of the joint remain centered relative to one another and the joint retains stability when operating at high rotational speeds.

However, centering means may be provided in a joint with a metal annular member.

Such centering means may comprise a ball held in a central position between the yokes of the joint and engaged by ends of the journals opposite to those which are received in the bearing cups in the annular member.

The invention will now be described by way of example with reference to the accompanying drawings, of which:- Figure 1 shows a joint according tb the invention in an axial view partly in section on the line B-B of Figure 2; Figure 2 is a side view of the joint, partly in section on the line A-A of Figure 1; Figures 3 and 4 are views as Figures 1 and 2, of a further embodiment of the invention; Figure 5 is an axial view as Figures 1 and 3, partly in section on the line B-B of Figure 6, of yet a further embodiment of the invention; Figure 6 is a side view, partly in section, of the joint of Figure 5.

Referring firstly to Figures 1 and 2 of the drawings, the universal joint there shown comprises a first yoke 10 and a second yoke 11. The yoke 10 has a flange 12 with bores 13 for receiving locating dowels, the flange also having holes 113 to receive bolts for it to be bolted to a shaft part. Yoke 11 has a spigot 14 to fit within a tubular shaft part, the yoke being secured to such shaft part by welding. Each yoke has two spaced parallel axially extending limbs, those of yoke 10 being indicated at 15, 16 and those of the yoke 11 being shown in section at 115, 116.

Each limb of each yoke 10, 11 is provided with a radially outwardly extending journal, that of the limb 15 being clearly seen-at 17 in Figure 2. Around the yokes there is disposed an annular member 18 which is most clearly seen in Figure 1, having four circumferentially spaced bosses 19. Each boss 19 has a bore 20 in which is received a bearing cup 21 receiving the outermost end of the respective journal, the bearing cup being retained by a circlip 22. These parts are most clearly seen in the section of Figure 2, including needle roller bearings 23 and a seal 24.

Between the bosses 19, the annular member 18 is provided with portions 25 of reduced thickness. Such portions give the member 18 the ability resiliently to deform slightly so that one pair of opposed bosses 19 undergoes a slight axial displacement relative to the other pair of bosses 19.

The joint thus transmits torque in the manner of a Hookes universal joint, but with the ability for the two yokes to undergo slight axial displacement relative to one another, by virtue of the resilience of the portions 25 in the annular member 18.

Referring now to Figures 3 and 4 of the drawings, these show a universal joint whose basic structure is the same as that of the embodiment of Figures 1 and 2. The same reference numerals are applied to parts corresponding to those of the Figures 1 and 2 embodiment, and the above description likewise applies. In this case, however, each journal as the journal 17 has a portion 27 which extends radially inwardly of the respective yoke limb. The innermost end of each journal engages a ball 28 at the centre of the joint. Ball 28 is held in a component 29 of elastomeric material, which is in the form of a hollow sleeve with a closed end, aadjacent which the ball 28 is disposed, and four apertures in its wall through which the portions 27 of the journals 17 engage the ball. To enable the ball 28 to be seen, together with the adjacent parts 27 of journals 17, part of the elastomeric sleeve component 29 has been omitted from Figure 3. The open end of the component 29 receives a closure plug 30, to retain lubricant in the component 29 to lubricate the engagement between the ends of the journals 17 and the ball 28, and exclude dirt.

The use of the ball 28 at the centre of the joint, and engagement therewith by the inner ends of the journals 17 ensures that the two yokes of the joint remain in alignment with one another when the joint is not articulated, and that when the joint is articulated the articulation takes place about the centre of the ball 28 rather than about any point which is less well defined. With an annular member 18 of metal, and configuration above described, such centering may not be necessary.

To enable the two yokes of the joint to move axially relative to one another while being kept properly centered, the ends of one pair of portions 27 of opposed journals 17 engaging the ball 28 may be part-spherical to hold the ball between them, while the ball-engaging ends of the other opposed pair of journal portions 27 have grooves extending axially of the joint as a whole, along which the ball can slide or roll.

Referring now to Figures 5 and 6, these show diagrammatically part of a further embodiment of joint wherein the yokes, journals, and centering arrangement are the same as the corresponding parts of the joint of Figures 3 and 4. In this case, however, there is an annular member 31 which is of rubber or other elastomeric material to give it the necessary flexibility, without requiring portions of reduced thickness. Such material may be reinforced by cords or fibres. As shown in Figure 6, bearing cups for receiving the outermost ends of the journals of the joint are received in respective elements 32 which are positioned in the annular member 31 in a moulding process by which the member is manufactured.

Because such an elastomeric element 31 is flexible radially of the joint as well as axially thereof, the arrangement of a centering ball is necessary to ensure alignment in the joint.

The annular member may be braced by a first element extending diagonally between one pair of bearing cup-receiving elements, and a second element extending diagonally between the other pair of bearing cup-receiving elements, the two diagonal elements being spaced axially of one another and arranged to clear the yokes in the assembled joint.

Claims (7)

1. A universal joint comprising two yokes each provided with a pair of radially outwardly extending diametrically opposed journals, and a member of annular form disposed radially outwardly of the yokes and having circumferentially spaced portions wherein the journals are received, the annular member being provided with portions able to accommodate relative axial movement between the journal-receiving portions.

2. A joint according to Claim 1 wherein the journals are pivotally supported in bearing cups held in the annular member.

3. A joint according to Claim 2 wherein the annular member is a metal component, having circumferentially spaced bosses in which the bearing cups are received and relatively thin web portions therebetween to permit relative axial movement between adjacent bosses.

4. A joint according to Claim 2 wherein the annular member is of an elastomeric material.

5. A joint according to any one of the preceding claims further comprising centering means for centering the two yokes relative to one another.

6. A joint according to Claim 5 wherein the centering means comprises a ball held between the yokes of the joint, engaged by radially innermost ends of the journals.

7. A joint substantially as hereinbefore described with reference to Figures 1 and 2, Figures 3 and 4, or Figures 5 and 6 of the accompanying drawings.