Importance

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Abstract

An indicator device for signalling that the wear limit has been reached for servo-operated clutches, particularly for motor vehicles. A servo housing comprises a servo piston, which can be moved forward and backward therein for disengaging and engaging the clutch respectively, and the servo piston's rest position, i.e. the position in which it is located when the clutch is engaged, in the event of an increase in clutch wear is gradually moved towards the rear end wall of the housing. The servo housing further comprises a control valve which controls the supply of pressurized fluid to a cylinder space which is located between the servo piston and the rear end wall. An indicator comprises a through-going bore provided in the end wall, which bore extends in the piston's direction of movement, and a slide valve positioned in the bore which can be moved between a first position, wherein the front end of the slide valve projects into the cylinder space, and a second position wherein the slide valve is shifted rearward of the servo piston in relation to the first position. The bore has a front section and a rear section whose diameter is greater than the diameter of the front section, and the slide valve has a rear section and a front section whose diameter is adapted to the diameter of the front bore section. The front slide valve section at its rear has a packing which sealingly abuts against the front bore wall when the slide valve is located in the first position, and a return channel extends from the rear bore section near the front bore section to a return reservoir for the pressurized fluid.

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First Claim