SHAFT COUPLING

Abstract: A shaft coupling includes a shaft (1) with a circumferential groove (2) near one end, a shaft receiving member (3) and a resiliently loaded shaft retention member (4) in the shaft receiving member (3). The shaft retention member (4) can be reciprocated in an elongate slot with or against the resilient bias so that upon insertion of the shaft in the shaft receiving member the shaft retention member (4) snaps into engagement with the groove (2) in the shaft (1). Any tendency to draw the shaft out of the shaft receiving member causes the shaft retention member to bed more firmly in the groove (2). In an alternative arrangement, the shaft retention member can be a torsion spring (9) fitted about a clamping bold (4), with one end (9A) of the spring engaging in the groove (2) of the shaft. The shaft (1) can be a vehicle steering column shaft and the shaft receiving member (3) can be a yoke of a universal joint.

Description: SHAFT COUPLING This invention relates to a shaft coupling. More particularly, the invention relates to a snap retention coupling between a vehicle steering column and a universal joint. In the past, various methods have been applied to coupling steering column shafts with universal joint yokes and most of these provide a permanent connection. A typical shaft coupling is shown and described in GB-A-2 124 739. With detachable connections, it has been the practice to insert the shaft into the yoke and then to fit a bolt to clamp the yoke around the shaft. However, where the coupling is one where the shaft end is splined and is inserted into a splined bore in the yoke, if the shaft has not been inserted in the yoke sufficiently far, then tightening of the bolt will cause the clamping effort to be applied on the splines. There is then the risk that the splines in use can become worn or fretted so that, in perhaps one or two years' time, there is a risk of the shaft being able to rotate and therefore not to transmit steering motion. According to one aspect of the present invention, there is provided a shaft coupling comprising a shaft receiving member having a transversely extending aperture therethrough and a shaft receiving bore therein; a shaft having a groove in its circumference, the shaft being insertable into the shaft receiving bore; and a retention means for biasingly engaging the shaft groove to retain the shaft in the shaft receiving member; characterised in that the retention means includes a transversely extending pin member within the shaft receiving member aperture. According to another aspect of the present invention, there is provided a shaft coupling comprising a shaft, a shaft receiving member and a resiliently-loaded shaft retention means in the shaft receiving member, the shaft having a groove in its circumference into which the shaft retention means is resiliently urged upon insertion of the shaft in the shaft receiving member and the shaft retention means being so arranged in the shaft receiving member that movement apart of the shaft and shaft receiving member is prevented by the shaft retention member, characterised in that the shaft retention means is arranged to act in a one-way sense to prevent said movement. Preferably, the end of the shaft in the region of the groove is splined, the splines of the shaft engaging in corresponding splines of a shaft receiving bore of the shaft receiving member. It will be appreciated that other shapes of cross-section can be utilised, e.g. triangular, to permit transmission of rotary force. Preferably, the pin member being guided in an elongate slot in the shaft receiving member, the slot allowing movement of the pin member in a direction to enter the groove and in an opposite direction when urged against the resilient bias acting on the pin member. Preferably, the pin member is a bolt which can be tightened when it is in engagement with the shaft in the shaft receiving member. Instead of the pin member itself acting as a shaft retention means, a separate shaft retention means can be provided. This can be in the form of a wire spring with one end intended to engage in the groove and the other end being restrained from rotation in at least one direction. This wire spring can be a torsion spring fitted around the pin member. The invention has particular applicability where the shaft is a vehicle steering column shaft and where the shaft receiving member is a yoke of a universal joint. For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, in which: - Figure 1 is a diagrammatic side view of one embodiment of a shaft coupling showing a vehicle steering column shaft prior to retention in a universal joint yoke, Figure 2 is an end view showing the rear face of the yoke shown in Figure 1, Figure 3 is a view similar to Figure 2 and illustrating a yoke of a second embodiment of shaft coupling, Figure 4 is a diagrammatic side view of the yoke and shaft, the yoke including a bore to receive a clamping bolt. Figure 5 is a plan view of the yoke shown in Figure 3, Figure 6 is a side view of the yoke of Figures 3 and 5 and showing the vehicle steering column shaft prior to retention by a torsion spring in the yoke, Figure' 6A shows an alternative construction to hold the torsion spring in place, and Figure 7 is a diagrammatic view of the torsion spring itself. The drawing shows one end of a vehicle steering column shaft 1, which has splines 1A. A circumferential groove 2 is provided in the shaft 1 near the end IB of the shaft 1 and interrupting the splines 1A. The groove 2 could be in the form of a flat. A shaft receiving member is in the form of a slotted yoke 3 of a universal joint for the steering column, the yoke 3 being provided with a splined through-bore 3A to receive the splined end of the shaft 1. Interaction of the splines on the shaft and in the bore facilitate mutual rotation of shaft and yoke. To facilitate retention of the shaft 1 in the bore 3A, a resiliently-loaded shaft retention means is provided. This takes the form in the embodiment illustrated in Figures 1 and 2 of a pin member in the forms of a clamp bolt 4 which is located in an elongate slot 5 in the yoke 3. The arrangement of the bolt 4 and slot 5 is such that the bolt extends transversely of the longitudinal axis 10 of the shaft 1 and in one end bolt position 6 in the elongate slot 5 the bolt 4 will sit snugly in the groove 2 in the shaft. A coil compression spring 8 is located in another bore in the yoke 3 , one end of the spring 8 always bearing on a length of the bolt 4 to urge it into the first bolt end position 6. Prior to assembly of the steering column shaft 1 in the yoke 3, the situation is as shown in. Figure 1, with the bolt 4 being urged by the spring 8 into the bolt end position 6. The shaft 1 is moved in the direction of the arrow A and the splines 1A of the shaft enter the splined bore 3A of the yoke 3. The head end IB strikes the bolt 4 and moves it against, the resilient bias of the spring 8 in the slot 5 towards a position 7 of the bolt. Further movement of the shaft 1 in the direction of the arrow A allows the bolt 4 to snap into the groove 2, thereby returning to its position 6. It will be noted that the angular relationship between the elongate slot 5 and the direction of entry of the shaft 1 and therefore of the longitudinal axis of the shaft 1 and bore 3A is such as to prevent the shaft from being pulled out of the bore 3A because any tendency for movement in this pulling apart direction (opposite to the arrow A) will force the bolt 4 to bed into the groove 2. Should it be necessary to remove the shaft 1 from the yoke 3, the bolt 4 must be moved manually outwards in the slot 5 towards the position 7 against the bias of the spring 8. Once the shaft and yoke have been coupled together, the bolt 4 can be tightened to cause the yoke to clamp on the shaft. It will be appreciated that the present coupling allows swift snap recention whilst subsequently resisting pulling apart without requiring additional action to release the bolt 4 from the groove 2. Referring now to Figures 3 to 7 , an alternative embodiment of shaft retention means is illustrated in which the resiliently loaded bolt 4 is replaced by a torsion spring 9. The torsion spring 9, as best seen in Figure 7, includes a barbed end 9A for engaging the groove or flat 2, a central coiled portion 9B for location about the bolt 4 and a bent other end portion 9C for engagement under its own resilient pressure against an outer surface of the yoke 3 (Figure 6) in order to prevent the torsion spring 9 from rotating. In an alternative arrangement illustrated in Figure 6A, the end 9C of the torsion spring 9 is held in a retention groove 3B in the yoke 3. In use, as the shaft 1 enters the bore 3A of the yoke 3, the barbed end 9A of the torsion spring 9 is flexed upwards as viewed in Figure 6 until the shaft 1 is pushed sufficiently far in for the end 9A to snap into the groove 2. The barbed end 9A of the torsion spring 9 locks into the groove 2 upon any tendency for the shaft and yoke to be pulled apart. As can be seen in Figure 4, the yoke 3 is provided with a bore 3C to receive the bolt 4 and Figure 5 shows that the torsion spring 9 is housed in the slotted part 3D of the yoke 3. In the embodiments illustrated, it will be appreciated that the constructions provide a shaft to yoke connection that will fit together easily but will not pull apart and so will ensure that correct spline/shaft penetration is made before the bolt is tightened. When correct penetration has been reached, the operator cannot pull the shaft out and so the operator then knows there is correct positioning for the yoke to be clamped about the sh^.ft by tightening the bolt 4. Instead of the form of springs illustrated, it will be appreciated that the springs could be in other forms such as a leaf spring or a rubber or plastics spring.

Claims: CLAIMS ; 1. A shaft coupling comprising a shaft receiving member (3) having a transversely extending aperture therethrough and a shaft receiving bore (3A) therein; a shaft (1) having a groove (2) in its circumference, the shaft being insertable into the shaft receiving bore (3A) ; and a retention means for biasingly engaging the shaft groove to retain the shaft in the shaft ' receiving member; characterised in that the retention means includes a transversely extending pin member (4) within the shaft receiving member aperture. 2. A shaft coupling according to claim 1, wherein the retention means includes a spring (8, 9) engaging the pin member. 3. A shaft coupling according to claim 1 or 2, wherein the end of said shaft (1) in the region (1A) of said groove (2) is splined, the splines of the shaft engaging when coupled in corresponding splines of the shaft receiving bore (3A) of said shaft receiving member (3) . 4. A shaft coupling according to claim 1, 2 or 3, wherein said pin member (4) is guided in an elongate slot (5) in said shaft receiving member, said slot allowing movement of said pin member in a direction to enter said groove (2) and in an opposite direction when urged against a resilient bias acting on said pin member. 5. A shaft coupling according to any one of the preceding claims, wherein said pin member is a bolt (4) which can be tightened when it is in engagement with said shaft (1) in said shaft receiving member (3) . 6. A shaft coupling according to claim 4 or 5, wherein the angular relationship between said elongate slot (5) and the direction of entry of said shaft (1) into said shaft receiving member (3) is such as to prevent the shaft from being pulled out of said shaft receiving member by causing said pin member (4) to be urged into said groove (5) upon application of force to draw said shaft out of said shaft receiving member. 7. A shaft coupling according to claim 1, 2 or 3, wherein said retention means comprises a spring (9) having a part for engagement in said groove (2) . 8. A shaft coupling according to claim 7, wherein said spring is a torsion spring (9) . 9. A shaft coupling according to claim 7 or 8, wherein said spring (9) is located in said shaft receiving member (3) and is prevented from rotation in one direction. 10. A shaft coupling according to claims 8 and 9, wherein said torsion spring (9) is wound around the pin member, which is a clamping bolt (4) provided to clamp said shaft receiving member onto said shaft when said spring is urged into said groove (2) of said shaft (1) . 11. A shaft coupling comprising a shaft (1), a shaft receiving member (3) and a resiliently-loaded shaft retention means (4, 9) in the shaft receiving member, the shaft having a groove (2) in its circumference into which the shaft retention means is resiliently urged upon insertion of the shaft in the shaft receiving member and the shaft retention means being so arranged in the shaft receiving member that movement apart of the shaft and shaft receiving member is prevented by the shaft retention member, characterised in that the shaft retention means (4, 9) is arranged to act in a one-way sense to prevent said movement. 12. A shaft coupling according to any one of the preceding claims, wherein said shaft is a vehicle steering column shaft. 13. A coupling according to any one of the preceding claims, wherein said shaft receiving member is a yoke (3) of a universal joint. 14. A vehicle incorporating a shaft coupling according to any one of the preceding claims.

Inventors: HANCOCK MICHAEL THOMAS, WORMALL DAVID THOMAS, HANCOCK, MICHAEL, THOMAS, WORMALL, DAVID, THOMAS
Applicants: NASTECH EUROP LTD, NASTECH EUROPE LIMITED
Application year: 1996
Main classification: B62D1
IPC codes: B62D1, F16B21, F16D1, F16D3