Compact dual master cylinder with offset primary outlet

Details Compact dual master cylinder with offset primary outlet Compact dual master cylinder with offset primary outlet

1998-03-03

1999-12-14

Lopez, F. Daniel

Power plants

Pressure fluid source and motor

Pulsator

B60T 1120

Patent

active

060002204

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a tandem hydraulic master cylinder comprising: cylindrical wall, a first end of which forms an opening, and a second end of which is closed by a bottom, the first and second ends being separated by a distance over which first and second length sections contiguous with one another are defined, and this body exhibiting an upper part in which first and second inlets for a hydraulic fluid at low pressure are pierced; of sliding respectively in the first and second length sections; primary and secondary pistons, this chamber containing at least one first spring exerting between the pistons a first elastic force which tends to separate these pistons from one another; secondary piston and the bottom, this chamber containing at least one second spring exerting between the secondary piston and the bottom a second elastic force in a direction which tends to separate this secondary piston from the bottom; upstream and downstream cups sealing the primary chamber and surrounding the primary piston, and second upstream and downstream cups surrounding the secondary piston and separating the primary and secondary pressure chambers in a leaktight fashion, each downstream cup being closer to the bottom of the body than the upstream cup which surrounds the same piston; intermediate volume situated between the first upstream and downstream cups, a second resupply duct connecting the second fluid inlet to a second intermediate volume situated between the second upstream and downstream cups; and communicating respectively with the primary and secondary pressure chambers and constituting the respective outlets from these chambers, the first orifice being situated in the second length section and between the first downstream cup and the second upstream cup.


BACKGROUND OF THE INVENTION

A master cylinder of this type is known in the prior art, and depicted, for example, in patent document EP-0,387,012.
The master cylinder described in this document, essentially designed to exhibit satisfactory axial compactness, does, however, employ a cylindrical cartridge inside the body, and this necessarily leads to a not insignificant increase in the outside diameter of the master cylinder.
Moreover, insofar as the internal arrangement of this master cylinder is designed in such a way that the cartridge is some distance from the primary piston, the latter is, by construction, deprived of effective guidance which means that any oblique thrust during actuation of the master cylinder carries the risk of causing the primary piston to jam in the bore.


SUMMARY OF THE INVENTION

In this context, the present invention sets out to overcome the aforementioned drawbacks.
Thus the master cylinder according to the invention, which in other respects is in accordance with the definition thereof given in the preamble above, is essentially characterized in that the primary and secondary pistons are guided by the wall of the bore, with which they are in contact, and in that the body is furthermore pierced with a first longitudinal passage connecting the first downstream cup, the second upstream cup and the first orifice and communicating with the primary pressure chamber via at least one first radial passage situated between the first and second length sections.
In an embodiment suited to mass production, the bottom may comprise a blanking piece attached to the body and slidably accommodating the secondary piston, it then being possible for this blanking piece to be pierced with a second longitudinal passage placing the second downstream cup in communication with the second orifice and with a second radial passage placing the second orifice in communication with the secondary pressure chamber.
The resupply to the primary pressure chamber can be accelerated if the master cylinder is provided with a cylindrical resupply connection inserted in the first resupply duct and passing through the first downstream cup to reach the first intermediate volume directly.
Furthermore, it may be advantageous to make provision for a guide pi

REFERENCES:
patent: 4524585 (1985-06-01), Coll et al.
patent: 4685301 (1987-08-01), Bacardit et al.
patent: 5187934 (1993-02-01), Mori

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