THIS INVENTION relates to a universal joint or cardan joint, more specifically of the Hooke type.

A Hooke type universal joint is commonly used in, eg, drive shafts of motor vehicles, especially central drive shafts of front engined rear wheel drive motor vehicles. The invention is not limited to universal joints for motor vehicles, a fortiori, it is not limited to universal joints for front engined rear wheel drive motor vehicles.

A conventional Hooke type universal joint has two yokes pivoted on a central cross-piece or spider in the form of two pins (integral with each other) intersecting at right angles. The pins provide journals at their ends, and bearing caps with internal needle bearings are rotatable over the journals. The bearing caps are press-fitted within round cylindrical seats in the yokes. Typically, they are located by means of circlips received in circular grooves in the round cylindrical seat in the yokes. The yokes are fast with shafts. Hooke type universal joints are conventionally used in pairs drivingly to connect parallel shafts which are off-set.

In accordance with a first aspect of the invention, there is provided a universal joint including

a pair of opposing yokes, each yoke having aligned, transverse apertures through respective limbs of the yokes; annular rotation-support members in the respective apertures through the yokes; two pairs of opposing pins, each pin having a journal and at least a first pin of each pair of pins being insertable into the respective annular rotation-support members from externally of the respective yokes; a central support supportingly locating inner ends of the respective pins; and axial retainers for checking the respective first pins against axially outward displacement.

All of the pins may be insertable into the respective annular rotation-support members from externally of the respective yokes, and axial retainers may be provided for all of the pins to check the pins against axially outward displacement.

The annular rotation-support members may be in the form of bushes, bearings, roller bearings, or the like. In one kind of embodiment, the annular rotation-support members may be in the form of bushes of a self lubricating synthetic polymeric material.

The central support may be in the form of a block having orthogonally arranged connection formations to receive the inner ends of the respective pins. Said connection means and inner ends of the pins may be in the form of male-female screw threaded spigot-socket connectors. The pins may then have the male screw threaded spigots and the block may have the female screw threaded sockets or vice versa.

The pins may be identical so as to be interchangeable. The journals of the pins may be complemental to passages of the bushes.

Outer ends of the pins may include a-circular formations, to facilitate turning the pins for screwing and unscrewing, eg hexagonal formations, such as sockets for Allen keys.

The retainers may be in the form of circlips received outwardly of the pins in the apertures through the limbs. Axially outer ends of the pins may be embedded in the apertures of the yokes, and may be covered by means of thrust plates located by the circlips.

In accordance with a second aspect of the invention, there is provided a repair kit or a replacement kit for a universal joint, including, annular rotation-support members; two pairs of pins, each pin having a journal and the pins being insertable into the annular rotation-support members; a central support having connection formations to receive inner ends of the pins; and retainers for retaining the pins axially in use.

The annular rotation-support members may be in the form of bushes.

The central support may be in the form of a block, and the connection formations may be orthogonally arranged to receive the inner ends of the respective pins.

The inner ends of the pins and the connection formations, respectively, may be in the form of male and female screw threaded spigot and socket connectors.

Outer ends of the pins may include a-circular formations, to facilitate turning the pins for screwing and unscrewing, eg hexagonal formations, such as sockets for Allen keys.

The retainers may be in the form of circlips.

The repair kit or replacement kit may further include round cylindrical thrust plates.

The invention is now described by way of example with reference to the accompanying diagrammatic drawings. In the drawings Figure 1 shows an exploded view of a universal joint in accordance with this invention; and Figure 2 shows, at an enlarged scale, in section, a portion of the universal joint of Figure 1 in assembled form.

With reference to the drawings, a universal joint in accordance with this invention is generally indicated by reference numeral 10. The universal joint 10 includes two halves 12 which, to all intents and purposes, are identical and of which only one is described in more detail.

Each half 12 comprises a yoke 14 connected to a shaft 15.

The yoke 14 has opposing limbs 16 which are mirror images.

Components cooperating with the respective limbs are identical, so as to be interchangeable, and are orientated in mirror image fashion. Thus, the components interacting with only one of the limbs 16 are described in more detail.

Each limb 16 includes a bore 18 which is aligned with a bore in the opposing limb along a centre line 40 which is at right angles to an axis of the shaft 15. The yokes 14 of the respective halves 12 of the universal joint are oriented at right angles to each other such that their centre lines 40 are at right angles to each other. However, it is to be appreciated that generally, the shafts 15 will not be in alignment although the axes will be in the same plane.

The bore 18 has, toward an outer end thereof, an outwardly stepped portion 18. 1 of larger diameter which can best be perceived from Figure 2. The stepped portion 18.1 provides a peripheral groove 18.2.

The universal joint 10 includes four bushes, generally indicated by reference numerals 20. A bore of each bush 20 is round cylindrical. The bush 20 fits tightly in the bore 18. However, it will not necessarily be an interference fit or a press fit.

In a preferred embodiment of the invention, the bush 20 is of a self-lubricating synthetic polymeric material. Generally, such material will not be brittle and will be relatively elastic compared to the material of the yoke 14 which will generally be of metal, eg steel. In such an embodiment, the bush 20 may well be an interference fit into the bore 18

as its elasticity will allow it readily to be tapped into the bore 18 and to be removed from the bore 18 by gentle tapping.

The universal joint 10 includes also four pins generally indicated by reference numerals 30. Also the pins are identical so as to be interchangeable. Each pin 30 includes a journal 32 adapted to be snugly received within the bore of the bush 20 such as to be rotatably supported therein. At one end of the pin 30, it has a screw threaded portion 34 which is of slightly smaller diameter than the journal 32 such as to be readily received through the bore of the bush 20. At an opposed end, which will be an outer end in use, the pin 30 has an axial socket, indicated by reference numeral 36, for an Allen key.

The universal joint 10 further includes four disk-shaped thrust plates 38 and axial retainers in the form of four circlips 39. The thrust plate 38 is sized to be received within the stepped portion 18.1 at an outer end of the pin 30. The circlip 39 is received, at an outer end of the thrust plate 38, in the peripheral groove 18.2, thereby to check the thrust plate 38 and hence the pin 30 against axially outward displacement.

The universal joint 10 includes a single central block 50 having four orthogonal sides 52 and a screw threaded blind socket 54 within each side 52.

With reference more specifically also to Figure 2, the universal joint 10 is readily assembled by means of hand tools. The bushes 20 are gently tapped into the respective bores 18. The block 50

is positioned on one of the centre lines 40 with one opposing pair of screw threaded sockets 54 along the centre line 40. The pins 30 are then, from opposed sides, from outwardly of the yoke 14, passed into the bushes 20 and screwed into the sockets 54 by means of an Allen key via the socket 36. The thrust plates 38 are inserted into the stepped portion 18.1, thus covering outer ends of the pins 30. The circlips 39 are clipped into the grooves 18.2, and checks via the thrust plates 38, the pins against axially outward displacement.

The other yoke 14 is assembled in identical fashion at 90° angular displacement to the block 50.

The Applicant has found it a disadvantage of conventional universal joints that they require special tools, for example an accurate press, to assemble a universal joint. Thus, in the event of breakdown of a universal joint, for example when a roller bearing has ceased, the universal joint cannot readily be repaired and the machine, for example a motor vehicle, is left stranded. Generally, repairs can be effected only in a well equipped workshop and provided that appropriate spare parts are available.

In contrast, a universal joint in accordance with the invention, can easily be dismantled and reassembled using hand tools as described above. Furthermore, spare parts, such as the bushes 20, are inexpensive and can easily be kept in reserve. The Applicant envisages that a universal joint which is broken down can easily be repaired by an operator or driver of a vehicle-even at the road side. Furthermore, it is feasible to have a repair kit in accordance with the invention available to

replace or repair a broken down universal joint. It is even envisaged that a repair kit in accordance with the invention can be used to repair a conventional universal joint provided that the repair kit's components are of appropriate size.

It is further an advantage that, in the embodiment illustrated, the bushes 20 are of a self lubricating material thus obviating the need for lubrication.