Power plants – Pressure fluid source and motor – Pulsator
Patent
1994-01-07
1995-12-12
Look, Edward K.
Power plants
Pressure fluid source and motor
Pulsator
60591, 91422, F15B 708, B60T 1128
Patent
active
054738962
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention generally relates to a piston for hydraulic vehicle brake systems. Pistons for such brake systems are known, for example, from DE-OS 39 32 248.
It is considered disadvantageous in conventional central valves that special care must be taken when mounting the valve case; the combination of the valve seat and supporting insert. If the valve pin is not particularly reliably coupled to the supporting insert, e.g. by vulcanization or cementing, the valve seat may become detached from the supporting insert due to the lateral friction at the receiving bore in the piston when the entire valve case is fitted. This is because only the forces which result from the frictional engagement or the adherence effect of the adhesive, respectively, can counteract an axial displacement of the two inserts.
Therefore, the present invention provides a piston for hydraulic vehicle brake systems and its object is to further simplify this piston by affording, in particular, greater ease of manufacture and assembly.
SUMMARY OF THE INVENTION
This object is achieved by providing a piston having two end surfaces on an annular collar enclosed by a valve seat within the piston. Hence, in principle, the present invention resides in providing the combination of a valve seat and supporting insert with axially defined undercuts adapted to receive, without difficulties, the axial forces which develop during the assembly and also during the operation so that the valve seat cannot move axially relative to the supporting insert.
In the prior-known valve case according to DE-OS 39 32 248 the supporting insert extends with an annular end into a stepped bore of the piston. Therefore, in order to be able to fit the valve case, spiral-shaped venting grooves are necessary, and a double centering results relative to the valve case which is usually undesirable. Further, the exact manufacturing tolerances necessary for this purpose are difficult to achieve.
Further, special attention must be paid, in the case of automated assembly, that the valve case is not fitted in an axially wrong position. This invention affords further simplifications by providing the combination of a collar having end surfaces enclosed by the valve seat with the valve case symmetrically disposed about a median plane of the collar which extends transversely to an axis through a central duct. In other words, this implies that one manages without the annular projection at the supporting insert and, hence, without a continuous guidance of the valve tappet within this supporting insert. Therefore, the valve case can be mounted in both axial positions. In addition, the sealing effect of the valve case relative to the piston bore is still augmented, because the two-sided sealing surface and the end surface of the valve case contribute to the sealing relative to the piston bore at the bottom of this bore. Further, the valve case is easier to manufacture because of the measure mentioned above, since the position of the supporting insert during the coupling with the valve seat is unimportant.
The valve member in the known central valve according to DE-OS 39 32 248 is provided with an annular projection in order to enhance the sealing effect. It may be disadvantageous in such an arrangement that the sealing seat of the valve seat will possibly be damaged by the rigid edges of the valve member. It is considered another disadvantage that the annular projection must be manufactured very accurately such that finishing usually is necessary. Admittedly, this could be remedied by particularly precise casting processes, such as aluminum die casting, but manufacturing costs are high for such processes. As a remedy, the present invention provides an annular projection on the valve seat disposed toward the valve member. An augmented sealing effect is achieved by casting an annular projection on the valve seat. This measure permits constructing the valve member in a simple fashion as a drop-forged steel element and removes the need for a casting proces
REFERENCES:
patent: 4237770 (1980-12-01), Harrison et al.
patent: 4706459 (1987-11-01), Burckhardt
patent: 4918922 (1990-04-01), Nakano et al.
patent: 5179834 (1993-01-01), Rauschenbach
patent: 5214917 (1993-06-01), Crumb et al.
Bergelin Klaus
Konig Harald
Kramer Thomas
Ludwig Rudolf
Saalbach Kurt
ITT Automotive Europe GmbH
Look Edward K.
Ryznic John
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