Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1999-03-16
2000-09-19
Lopez, F. Daniel
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
92 78, F15B 910, F15B 2104
Patent
active
061195782
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a pneumatic brake booster of the type comprising: a rigid casing; a moving partition delimiting, in leaktight fashion, a front chamber and a rear chamber inside the casing, the front chamber in operation being connected to a first pressure source delivering a first pressure; a pneumatic piston moving with the moving partition and ending in a hub mounted to slide in an opening in the casing; a three-way valve housed in the hub and capable selectively of adopting a state of rest and an actuating state, in which states the rear chamber is respectively connected to the first pressure source and to a second pressure source which delivers a second pressure higher than the first pressure; an operating rod mounted to slide in the hub in a first axial direction between first and second extreme positions for which the valve is respectively in its state of rest and in its actuating state, this operating rod being subjected to an elastic force acting in a second axial direction the opposite of the first; and an annular purification filter inserted between the second pressure source and the rear chamber and housed in the hub around the operating rod.
BACKGROUND OF THE INVENTION
Devices of this type are well known in the prior art, and described, for example, in FIG. 1 of Patent document FR-2,706,403.
Research in recent years, illustrated, for example, in Patent documents EP 0,796,188 and FR-2,731,668, has, in particular, made it possible to reduce the operating noise and response time of boosters.
The search for further progress in this field has, however, led to the question of the filtering of the air and of the noise at the inlet of boosters to be re-examined, the objective still being to make the filtering all the more selective, the more crucial the reduction in booster response time.
SUMMARY OF THE INVENTION
The invention falls within this context, and its object is to provide a booster in which the filter adapts automatically to the stress transmitted to this booster.
To this end, the booster of the invention which in other respects conforms to the above preamble, is essentially characterized in that the filter is made of a compressible material, in that a first face of the filter is kept stationary with respect to the hub, in that a second face of the filter is kinematically connected to the operating rod so that it can be displaced with respect to the hub, and in that the filter has a volume that varies with the displacement of the second face of the filter, the filter having a minimum volume for which it is compressed, when the operating rod is in its first extreme position, and a maximum volume, for which it is relaxed, when the operating rod is in its second extreme position.
By virtue of these features, the filter is all the more selective, the greater the amplitude of displacement of the operating rod with respect to the hub, this parameter precisely constituting an appropriate measure of the intensity of the stress transmitted to the booster.
The booster of the invention may comprise an annular support secured to the hub, to which the first face of the filter is attached, the second face of the filter being attached to an outer edge of a flange, an inner edge of which is secured to the operating rod.
In one possible embodiment of the invention, the flange follows on from the annular support in the first axial direction, and the second face of the filter follows on from its first face in the first axial direction.
In another possible embodiment of the invention, at least part of the second face of the filter is kinematically linked with an active region of a tilting member resting both on the hub and on the operating rod, a displacement of a first amplitude of the operating rod with respect to the hub producing a displacement of a second amplitude, greater than the first, of the active region with respect to the hub.
Finally, the filter may be made of a porous polymer, the first and second faces of which are bonded to the annular support, to the flange, or to the til
REFERENCES:
patent: 3499288 (1970-03-01), Randol
patent: 3897716 (1975-08-01), Ramage et al.
patent: 3972263 (1976-08-01), Welsh
Bosch Systemes de Freinage
Comstock Warren
Lopez F. Daniel
McCormick, Jr. Leo H
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