192 clutches and power-stop control – Clutches
Patent
1995-06-07
1997-07-01
Pitts, Andrea L.
192 clutches and power-stop control
Clutches
192 85R, 92 5R, 116277, 188 111, F16D 6602
Patent
active
056427930
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an indicator of the said type warns the user when the clutch has become worn to such an extent that there is a risk that the servo piston will come into contact with the rear end wall of the servo housing, thus avoiding that the clutch is not completely engaged. An indicator of this type is known, e.g., from U.S. Pat. No. 4,084,671. The indicator described therein provides a connection between the cylinder space and the atmosphere when it is actuated. The pressure in the cylinder space is Thereby lowered, the servo effect thus being reduced and the clutch pedal becoming correspondingly heavy to operate. This indicator, however, causes a major leakage of air, which is undesirable, since such a leakage also affects other user systems.
Furthermore it is known that a separate choke valve can be provided the air supply line to the servo unit, but the installation of such choke valve is expensive.
The object of the device according to the invention is to provide an indicator device of the known type, which is not encumbered by the above-mentioned disadvantages.
The characteristics of the device according to the invention are characterized by the features in the claims presented.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail with reference to the drawing which illustrates an embodiment of a device according to the invention.
FIG. 1 is a vertical section through a servo unit with an indicator according to the invention.
FIG. 2 shows a section along the line II--II in FIG. 1.
The terms "forward" and "backward" will hereinafter refer to the directions to the left and right of the figures respectively. Correspondingly the terms "front" and "rear" will refer to relative positions in this respect.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As illustrated in the figures there is provided in the servo housing 1 a servo piston 2 which can be moved towards and away from a rear end wall 3 of the housing.
In a boring 4 which is provided in the end wall 3, and which extends parallel to the direction of movement of the servo piston 2, there is slidably provided a slide valve 10. The boring 4 has a front section 5 and a rear section 6 whose diameter is greater than the diameter of the front section 5, and the slide valve 10 has a front section 1 whose diameter is adapted to the diameter of the boring's front section 5, and a rear section 12 whose diameter over a large part of the length of the section 12 is adapted to the diameter of the boring's rear section 6.
The rear slide valve section 12 has a front area 13 and a rear area 14 whose diameter is reduced in relation to the diameter of the front area 13, in such a manner that between these areas there is formed a radially extending, annular shoulder or surface section 15 of the slide valve. The area of this annular surface section 15 is greater than the area of the transverse end surface of the slide valve's front end section 11.
Behind the rear section 6 of the boring 4 there is a portion having a greater diameter than the rear section 6 and being adapted to receive a rear packing 20 which sealingly abuts against the rear area 14 of the slide valve 10, and which at the rear is supported by a securing ring 21, which is inserted in a groove in the servo housing 1 thus preventing the packing 20 from being moved backward.
The slide valve can thus be moved between a first position where the step 16 which is formed between the front and the rear slide valve sections 11 and 12, respectively, abut%against the step 7 which is formed between the front and the rear sections 5 and 6 respectively of the boring 4, and a second position where the surface 15 abuts against the rear packing 20.
Near the rear slide valve area 14 there is provided on the front slide valve section 11 a front packing 24 which is arranged to abut sealingly against the front boring section 5. In front of this packing there is located between the front slide valve section and the front boring section a clearance
REFERENCES:
patent: 3406800 (1968-10-01), Buchanan et al.
patent: 4084671 (1978-04-01), Ternehall
Kongsberg Automotive AS
Pitts Andrea L.
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