Power plants – Pressure fluid source and motor – Pulsator
Patent
1997-06-20
1999-09-07
Nguyen, Hoang
Power plants
Pressure fluid source and motor
Pulsator
60591, 60585, B60T 1120
Patent
active
059469137
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a hydraulic tandem master cylinder comprising: a body pierced with an essentially cylindrical bore closed by an end; a primary piston and a secondary piston which are capable of sliding in leaktight fashion in the bore; a primary pressure chamber defined between the primary and secondary pistons, this chamber containing at least a first spring exerting a first elastic force between the pistons, which force tends to separate these pistons from one another; a secondary pressure chamber defined between the secondary piston and the end, this chamber containing at least a second spring exerting a second elastic force between the secondary piston and the end, which force is in a direction which tends to separate this secondary piston from the end; a first seal and a second seal respectively borne by the primary piston and secondary piston in order to seal the primary pressure chamber; and a ring interposed between the first spring and the second seal slidably mounted on a bearing surface of the secondary piston and capable of pushing the second seal back against a shoulder of the secondary piston in order to transmit to the second seal a compressive force which varies with the first elastic force.
BACKGROUND OF THE INVENTION
Master cylinders of this type are very widely used nowadays.
A problem which commonly arises in tandem master cylinders is of contriving for the pressure in the secondary chamber to be as close as possible to that prevailing in the primary chamber.
One of the difficulties to be overcome in order to solve this problem lies in the conflicting nature of two requirements, namely on the one hand the need to reduce friction between the cylinder and the various seals, especially the second one, in order to reduce the pressure difference between the chambers and, on the other hand, the need to ensure that the seals are leaktight even for the highest pressures that the master cylinder is to be capable of delivering.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a master cylinder making it possible to satisfy these two requirements simultaneously.
To this end, the tandem master cylinder of the invention is essentially characterized in that the bearing surface of the secondary piston has a stop piece limiting the sliding of the ring in the direction of the second seal, so as to limit the compression of the second seal.
Furthermore, according to the preferred embodiment of the invention, the ring bears reliefs pointing toward this second seal and bears on this second seal via these reliefs.
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.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a section through a tandem master cylinder of the prior art, liable to benefit from the teaching and features of the invention;
FIG. 2 is an enlarged section of a detail denoted by the reference II-III in FIG. 1, this detail being produced in accordance with the teaching of the prior art;
FIG. 3 is an enlarged section of the detail denoted by the reference II-III in FIG. 1, this detail being produced in accordance with the invention; and
FIG. 4 is a front-on view of a detail of FIG. 3, viewed on IV--IV of this figure.
DETAILED DESCRIPTION OF THE INVENTION
Since the tandem master cylinder of the invention is noteworthy merely with regard to very precise points which will be detailed later on in a comparative manner with reference to FIGS. 2 to 4, the master cylinder of FIG. 1 on the whole resembles all known tandem master cylinders and the description thereof will therefore not be burdened with details which are well known to the person skilled in the art and are of no relevance with regard to the invention.
This tandem master cylinder essentially comprises a body 1 pierced with a longitudinal and cylindrical bore la closed by an end 1b and by end members 2a, 2b, 2c which provide sealing of the bore 1a on th
REFERENCES:
patent: 3557555 (1971-01-01), Wilson et al.
patent: 4229940 (1980-10-01), Higgerson et al.
patent: 4510752 (1985-04-01), Gaiser
patent: 5542253 (1996-08-01), Ganzel
Manzo Vincenzo
Varrese Francesco
Comstock Warren
McCormick Jr Leo H.
Nguyen Hoang
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