Booster with a porous bellows forming a filter

Details Booster with a porous bellows forming a filter Booster with a porous bellows forming a filter

1994-05-20

1996-06-25

Nguyen, Hoang

Motors: expansible chamber type

Working member position feedback to motive fluid control

Follower type

92 96, F15B 910

Patent

active

055289754

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a pneumatic brake booster using first and second sources of pressure delivering first and second respective and different pressures. The booster comprising a rigid casing separated by at least one sealed movable partition into at least two chambers the first of which is connected to the first source and the second of which is capable of being connected selectively by means of a valve to either one of the two sources. The movable partition is capable of being forced by the difference in the pressures prevailing in the chambers to move an essentially cylindrical pneumatic piston sliding in a sealed fashion in the casing. The piston has a cylindrical projection which is housed outside the casing in a tubular protective bellows. One first end of the bellows is connected to the casing and the other end is connected to a control rod.
Devices of this type, which are well known in the prior art, are used today on a great number of motor vehicles.
Despite the conventional nature of the techniques in question, boosters continue to form the subject of significant research aiming in particular to reduce the cost, response time to a stimulation, and operational noise level thereof.
The invention as disclosed in this application contributes to the reduction of at least one of these three parameters.
To this end, the booster of the invention is essentially characterized in that the bellows protecting the piston is at least partially produced from a porous and deformable material which constitutes a purifying filter to remove any contamination in the air prior to being presented to the valve.
By virtue of this arrangement, a conventional filter may in effect be eliminated, which leads to a reduction in cost.
Moreover, the surface area of the bellows which is in contact with the second pressure source (generally the atmosphere) is easily much greater, due to its shape and arrangement, than the surface area offered by a conventional filter, such that in the communication of the second chamber is much faster and quieter as noise is substantially reduced.
According to a preferred embodiment, the bellows is at least partially produced of a porous elastomeric material and its second end surrounds the control rod which serves to control the operation of the valve.
Other features and advantages of the invention will emerge clearly from the detailed description thereof given hereafter:


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic sectional view of a pneumatically boosted braking system using a conventional booster; and
FIG. 2 is a view in partial section of a booster in accordance with the invention.


DETAILED DESCRIPTION OF THE INVENTION

Insofar as the invention relates only to an improvement made to pneumatically boosted braking systems, and the general constitution and operation of the latter are well known to the person skilled in the art, these systems will be recalled briefly here solely to allow a complete understanding of the improvement which the invention represents.
The pneumatically boosted brake system illustrated in FIG. 1 comprises a booster 1 and a master cylinder 2.
The booster includes a rigid casing 3 which is separated into front and rear chambers 3a and 3b in a sealed fashion by a movable partition 4. The movable partition forms a pneumatic piston 5 which can move inside the casing 3.
The front chamber 3a, the front face of which is closed in a sealed fashion by the master cylinder 2, is permanently connected to a source of low pressure D via a non-return valve 6.
The back chamber 3b is, in contrast, capable of selectively being connected either to the source of low pressure D, or to a source of high pressure, for example the atmosphere A.
Communication or access to the back or rear chamber 3b is controlled by movement of a valve 7 and a plunger 8. The plunger 8 is connected to a brake pedal 9 by means of a control rod 10.
When the control rod 10 is in the rest position, in this case pulled to the right, the valve 7 normally establishes a communication betwee

REFERENCES:
patent: 2800770 (1957-07-01), Edge et al.
patent: 4716814 (1988-01-01), Yamakoshi
patent: 4718324 (1988-01-01), Gautier et al.
patent: 5161454 (1992-11-01), Frasier

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