Expansible chamber devices – Collapsible chamber wall portion – Wall portion formed of flexible material
Patent
1992-08-28
1994-03-29
Denion, Thomas E.
Expansible chamber devices
Collapsible chamber wall portion
Wall portion formed of flexible material
921691, 913691, 29510, 29513, F01B 1900
Patent
active
052974715
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is related to a housing for a pneumatic power booster of a type comprised of a first and a second bowl shaped housing half which are coated with a protective surface finish. The housing halves are assembled with their open sides facing each other and telescoped one into the other and permanently fixed to each other. The first housing half has a rim which is bent out and back reversely and the second housing half is formed with an edge of a preferably cylindrical configuration. An elastic diaphragm is compressed between the housing halves to create a seal. The diaphragm comprises a movable wall dividing the inner space of the housing into two pneumatic chambers. The edge of the second housing half is formed with a plurality of uniformly distributed circumferential slots having portions which are parallel to the cylindrical edge and to the bent-over rim of the first housing half, so that localized zones weakened in the radial direction are formed.
This invention is also concerned with a process for manufacture of this type of housing.
A housing of this kind and a process for its manufacture are described in European patent application EP-A-0 300 857. The housing half having the cylindrical edge is formed about its edge with a plurality of circumferential slots which are symmetrically distributed about its circumference and preferably have an oval or rectangular shape, and which, with the outer edge of the cylindrical edge, define web-like zones weakened in the radial direction, which upon the two housing halves being telescoped one into the other are pressed in in such a way that their center portions move away in an axial direction from a plane running parallel to the bent-over rim of the other housing half through the end points of the webs. In this manner, the risk of corrosion is largely eliminated in particular along the connecting seam of the two housing halves.
In the prior-art pneumatic power booster, the extremely high surface tension which occurs due to the pressing-in of the webs in particular in their central portions, on the inside and on the outside, may lead to damaging of the applied protective coating layer. Those portions which are no longer protected against corrosive attack, are subjected to a considerable axial stress especially during operation of the power booster, and thus are particularly subject to corrosive attack and can, upon an extended service period, cause the failure of the power booster.
It is, therefore, the object of the present invention to provide a coupling of the two housing halves of a pneumatic power booster which does not result in areas of high surface tension.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved in that the radially weakened zones are each formed by two tongues which are positioned opposite each other and which in the assembled condition of the housing engage behind the reversely formed rim of the other housing half in an axial direction.
According to the process, axial slots are formed extending into respective circumferential slots such as to create two tongues disposed opposite each other along each circumferential slot, extending in the circumferential direction.
Subsequently, the two housing halves are provided with a protective coating. The radially outer perimeter of the elastic diaphragm is compressed by pressing the two housing halves together in such a way that a slight axial clearance is created between the internal sides of the tongues and the reversely formed rim of the other housing half. The two tongues are simultaneously bent inwardly in the radial direction and afterward the axial force pressing the two housing halves together is relieved, so that the housing assumes its final assembled condition.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of a housing of a pneumatic power booster which is assembled in the manner according to the present invention;
FIG. 2 is a view from the direction "A" in FIG. 1 in an enlarged fragmentary representation;
REFERENCES:
patent: 3732616 (1973-05-01), Masrrodonato et al.
patent: 4604944 (1986-08-01), Tsubouchi
patent: 5074024 (1991-12-01), Gautier
patent: 5195421 (1993-03-01), Shinohara et al.
Boehm Peter
Graichen Kai-Michael
Jakobi Ralf
Mattheis Lothar
Ruffer Manfred
Alfred Teves GmbH
Denion Thomas E.
Lewis J. Gordon
Seitter Robert P.
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