The Present invention relates to a clutch cable adjuster.

Originally clutch cables were adjusted by a simple screw threaded mechanism which altered the position of one end of the clutch cable sleeve relative to, for example, the bulkhead to which it was attached. Initial setting up of the cable and subsequent adjustment had to be carried out by a skilled mechanic and was therefore expensive.

More recently automatic adjusters have been used which adjust the clutch cable each time the clutch is operated. Initial setting up of the clutch cable is also achieved automatically on the first operation of the clutch after installation. Automatic adjusters also have the advantage that they provide a pre-load on the clutch release bearing which reduces lost travel in the clutch pedal.

However automatic adjusters comprise a large number of parts and are expensive to manufacture and difficult to maintain.

The present invention aims to provide a clutch adjuster which is relatively cheap and simple to produce and which does not require skilled servicing.

The present invention provides an adjustable cable actuation system for a clutch, the system comprising clutch release means movable between an engaged position and a disengaged position and biased towards the engaged position, actuating means connected to the clutch release means by a cable and movable between an engaged position and a disengaged position, a conduit surrounding the cable and including first and second guide means movable axially in first and second directions relative to one another respectively to increase and decrease the effective length of the conduit, stop means movable between a plurality of positions for limiting relative movement of the guide members in the second direction when the actuation means is moved towards the disengaged position, and biasing means for urguing the guide means in the first direction relative to one another thereby applying a pre-load to the clutch release means when the actuating means is in the engaged position.

Preferably when the actuation means is in the engaged position the stop means allows at least some relative movement of the two guide means in either direction.

For this to occur the biasing means must be supporting all the compression applied to the conduit by the tension in the cable.

Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:-

Figure 1 is a schematic view of a clutch cable and adjuster assembly according to a first embodiment of the invention;

Figure 2 is part-sectional view of the adjuster of Figure

1;

Figure 3 is a view, similar to Figure 2, of a second embodiment of the invention; and

Figure 4 is an enlargement of part of Figure 3.

Referring to Figures 1 and 2, the first embodiment of the invention comprises a flexible conduit 10 having its ends fixedly mounted, one on a vehicle bulkhead 12 and the other on a support bracket 14. A cable 16 extends through the conduit 10 and has one end attached to actuation means in the form of a clutch pedal 18 and the other end attached to a clutch release lever 20 which operates a push type clutch 22 which includes a diaphragm spring 23 and release bearing 25.

The conduit 10 comprises first and second flexible sleeve portions 24, 26 joined respectively to first guide means comprising a guide member in the form of an outer rigid

tubular member 28, and second guide means comprising a guide member in the form of an inner rigid tubular member 30 and a collar 29. The collar is crimped onto the second sleeve portion 26 in a position spaced from the inner tubular member. The inner tubular member 28, is slidably received inside the outer tubular member 30 such that relative movement of the two tubular members alters the length of the conduit 10.

The outer tubular member 28 comprises a tubular main body portion 32 with a tubular connector 34 at one end for connecting to the first sleeve portion 24 and a tubular spring support 36 at the other end. The main body portion 32 is thicker than the spring support 36 and the step between the two forms a first spring abutment 38.

The inner tubular member 30 has a first bore 40 in one end which supports the end of the second sleeve portion 26 and a second bore 42, extending from the other end and meeting the first bore. A series of circumferential grooves 44 are formed on a part of the outer surface 46 of the inner tubular member, in the region of the second bore 42, which can be slid inside the outer tubular member.

A circlip 48 is mounted on the collar 29 and a helical spring 50 is situated around the inner tubular member

having one end abutting against the circlip 48 and the other end against the spring abutment 38 on the outer tubular member 28. The spring 50 is under compression and

% urges the two tubular members 28, 30 apart to increase the length of the conduit 10. A circlip 52 is mounted in one of the grooves 44 and forms a stop for the end of the spring support 36, preventing the two tubular members 28, 30 from moving together beyond a set point, and thereby locating the guide members relative to one another.

In use, when the clutch cable is first installed, the clutch 22 is engaged, and the clutch pedal 18 is not depressed and is at the end of its travel in the engaged position. The cable 16 is held under tension by the effect of the helical spring tending to increase the length of the conduit 10 until all slack in the cable is taken up. The tension in the cable 16 provides a pre-load on the diaphragm spring 23.

The circlip 52 is then inserted in the first slot 44 beyond the end of the spring support 36. This limits movement together of the tubular members 28, 30 when the clutch pedal is depressed pulling on the cable 16 to disengage the clutch. The tubular members can only move together until the spring support 36 abuts the circlip 52, this movement appearing as lost travel of the clutch pedal 18. Further movement of the clutch pedal 18 moves the clutch release lever 20 to release the clutch.

As the clutch wears the diaphragm spring can move further away from its released position when the clutch is engaged. Initial wear is taken up by the tubular members moving together so that the spring support 36 on the outer tubular member 28 approaches the circlip 52. After the spring support 36 reaches the circlip 52, as shown in Fig 2, further wear is compensated for by the cable 16 stretching slightly, the sleeve portions 24, 26 compressing slightly and connections between the cable 16 and the clutch release lever 20 and clutch pedal 18 giving slightly. The tension in the cable when the clutch is engaged is therefore increased as a result of clutch wear as is the pre-load on the disphragm spring 23.

To adjust the cable the circlip 52 is removed. The tension in the cable 16 causes the tubular members 28, 30 to move together until the helical spring 50 again reaches equilibrium. The circlip 52 'is then replaced in one of the grooves 44 which is the nearest exposed groove to the end of the spring support 36.

Referring to Figures 3 and 4 the second embodiment of the invention is similar to the first embodiment having an outer tubular member 128 and an inner tubular member 130 urged apart by a helical spring 150. The inner tubular member 130 has circumferential grooves 144 in its outer surface.

The second embodiment differs from the first in that the outer tubular member has a slot 160 in its main body portion 132 exposing a part of the grooved outer surface of the inner tubular member 130. The slot 160 is of such width that only one of the grooves 144 is exposed over its whole width as can be seen in Figure 4. A circlip 152 is fitted into the one exposed groove through the slot 160. This embodiment has the advantage that, when adjustment is made, there is only one possible position for insertion of the circlip 152 and so no judgement is needed to carry out adjustment.