Shaft coupling

A shaft coupling includes a shaft with a circumferential groove near one end, a shaft receiving member and a resiliently loaded shaft retention member in the shaft receiving member. The shaft retention member is fitted about a clamping bolt with one end of the spring engaging in the groove of the shaft. The shaft can be a vehicle steering column shaft and the shaft receiving member can be a yoke of a universal joint.

BACKGROUND OF THE INVENTION 
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. 
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. 
The foregoing illustrates limitations known to exist in present shaft 
couplings. Thus, it is apparent that it would be advantageous to provide 
an alternative directed to overcoming one or more of the limitations set 
forth above. Accordingly, a suitable alternative is provided including 
features more fully disclosed hereinafter. 
SUMMARY OF THE INVENTION 
In one aspect of the present invention, this is accomplished by providing a 
shaft coupling comprising: a shaft receiving member, the shaft receiving 
member having a transversely extending aperture therethrough, a shaft 
receiving bore therein and a longitudinally extending slot substantially 
coextensive with said shaft receiving bore; a shaft having a groove in its 
circumference, the shaft being inserted into the shaft receiving bore; and 
a retention means within said longitudinal slot for engaging a 
transversely extending pin member and for biasingly engaging the shaft 
groove. 
The foregoing and other aspects will become apparent from the following 
detailed description of the invention when considered in conjunction with 
the accompanying drawing figures.

DETAILED DESCRIPTION 
According to the present invention, there is provided a shaft coupling 
comprising a shaft, a shaft receiving member and a resiliently-loaded 
shaft retention member in said shaft receiving member, the shaft having a 
groove in its circumference into which said retention member is 
resiliently urged upon insertion of the shaft in said shaft receiving 
member, the shaft retention member being so arranged in said shaft 
receiving member that movement apart of said shaft and shaft receiving 
member is normally prevented by said shaft retention member being urged 
into said groove. 
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 utilized, e.g. triangular, to permit 
transmission of rotary force. Preferably, the shaft retention member is a 
rod-like member extending transversely of the axis of the shaft, the rod 
like member being guided in an elongate slot in the shaft receiving 
member, the slot allowing movement of the rod-like member in a direction 
to enter the groove and in an opposite direction when urged against the 
resilient bias acting on the rod-like member. Preferably, the rod-like 
member is a bolt which can be tightened when it is in engagement with the 
shaft in the shaft receiving member. 
Instead of the bolt itself acting as a shaft retention member, a separate 
shaft retention member 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 bolt. 
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. 
FIG. 1 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 1B 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 member is provided. This takes the form in the embodiment 
illustrated in FIGS. 1 and 2 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. In one end of the elongate slot 5 (bolt position 6), the bolt 4 
will sit snugly in the groove 2 in the shaft. In a second, opposite end of 
the slot 5 (bolt position 7), the bolt 4 is clear of the groove 2. 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 FIG. 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 1B strikes the bolt 4 and moves it against the 
resilient bias of the spring 8 in the slot 5 towards the position 7. 
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 1 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 1 and yoke 3 have been coupled together, the bolt 4 can be 
tightened to cause the yoke 3 to clamp on the shaft 1. 
It will be appreciated that the present coupling allows swift snap 
retention while subsequently resisting pulling apart without requiring 
additional action to release the bolt 4 from the groove 2. 
Referring now to FIGS. 3 to 7, an alternative embodiment is illustrated in 
which the resiliently loaded bolt 4 is replaced by a torsion spring 9 to 
act as the shaft retention member. The torsion spring 9, as best seen in 
FIG. 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 (FIGS. 3 and 6) in order to prevent the 
torsion spring 9 from rotating. 
In an alternative arrangement illustrated in FIG. 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 FIG. 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 1 and yoke 3 to be pulled apart. 
As can be seen in FIG. 4, the yoke 3 is provided with an aperture 3C to 
receive the bolt 4 and FIG. 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 1 to yoke 3 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 4 is tightened. When 
correct penetration has been reached, the operator cannot pull the shaft 1 
out and so the operator then knows there is correct positioning for the 
yoke 3 to be clamped about the shaft 1 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.