Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1996-04-10
1998-12-01
Nguyen, Hoang
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
F15B 910
Patent
active
058424032
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a pneumatic brake booster using first and second sources of air pressure delivering first and second respective and different pressures, this booster comprising a rigid casing divided by at least one leaktight moving partition into at least two chambers, the first of which is connected to the first source, and the second of which can be connected selectively, by means of a valve, to either one of the two sources, it being possible for the moving partition to be urged by the difference in the pressures prevailing in the chambers in order to drive along an essentially cylindrical pneumatic piston sliding in leaktight fashion with respect to the casing and bearing the valve, the inside of this piston being separated from the second source by a purification filter, and the valve being actuated by an operating rod capable of sliding with respect to the piston along an axis from a position of rest to a forward actuating position.
Devices of this type are well known in the prior art, and for instance disclosed in the U.S. Pat. No. 3,972,263.
Despite the traditional nature of the techniques involved, boosters continue to form the subject of substantial, research, aiming to optimize their operating characteristics.
Among this research feature especially attempts to reduce both the noise level of boosters in operation and their response time following actuation, the simultaneous reduction in these two parameters being made very difficult by the fact that a booster is all the quieter if the air it lets into the rear chamber is filtered to a greater extent, while it has a response time which is all the shorter if the air it lets in is filtered to a lesser extent.
This problem is already disclosed in the previously mentioned U.S. Pat. No. 3,972,263, and solved in this prior patent by the use of a compressible filter, which is compressed in response to an input force of high value, so as to increase the air flow and to reduce the response time of the booster.
However, such an arrangement implies the use of a push rod having several sections, and leads to a specific choice of the material used for the filter.
The invention falls within this context, and its object is to provide a booster which meets the expectations of the public as regards reduction in noise level in operation, while at the same time offering a response time which is at least as satisfactory as those of boosters of the prior art, in all cases where the need for a short response time is felt.
To this end, the booster of the invention is essentially characterized in that the operating rod slides in a sleeve which passes axially through the purification filter, in that the sleeve and the operating rod have first and second respective sections facing one another, at least the second of which extends along the said axis, these sections adopting different relative positions depending on whether the operating rod is in its position of rest or in its forward actuating position, and in that the respective sections of the operating rod and of the sleeve cause there to appear between them, when the operating rod is in its forward actuating position, an air passage which is set up between the second source and the inside of the piston, and which is, in contrast, closed off by the respective sections of the operating rod and of the sleeve when the operating rod is in its position of rest.
The sleeve preferably includes internal guide pegs allowing the operating rod to be centered with respect to the sleeve.
Other features and advantages of the invention will emerge clearly from the description thereof which is given hereafter by way of non-limiting indication with reference to the appended drawings in which:
FIG. 1 is a diagrammatic sectional view of a pneumatically boosted braking system using a conventional booster;
FIG. 2 is a part sectional view of a booster in accordance with a first possible embodiment of the invention, the lower part of which represents the operating rod in the position of rest, and the upper part of which rep
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patent: 5233908 (1993-08-01), Gautier et al.
patent: 5249504 (1993-10-01), Gautier et al.
patent: 5350224 (1994-09-01), Nell et al.
Bosch Systems de Freinage
McCormick Jr. Leo H.
Nguyen Hoang
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