Title of Invention

"COMPACT TANDEM MASTER CYLINDER WITH OFFSET PRIMARY OUTLET"

Abstract

The invention relates to a tandem hydraulic master cylinder mainly comprising a body (1) pierced with a bore, first and second inlets (2a, 2b) for a hydraulic fluid at low pressure, a primary piston (3) and a secondary piston (4) which slide respectively in first and second length sections (SI, S2) , a primary pressure chamber (5), a secondary pressure chamber (6), first and second upstream and downstream sealing cups Ola, 91b, 92a, 92b) , first and second resupply ducts (21, 22) and first and second outlet orifices (41 and 42) for the pressurized hydraulic fluid. According to the invention, the primary and secondary pistons (3, 4) are guided by the wall (100) of the bore, with which they are in contact, and the body (1) is further pierced with a first longitudinal passage (51) connecting the first downstream cup Olb), the second upstream cup (92a) and the first outlet orifice (41) and communicating with the primary pressure chamber (5) via a first radial passage (61) situated between the first and second length sections (S1, S2) .

Full Text

COMPACT TANDEM MASTER CYLINDER WITH OFFSET PRIMARY OUTLET The present invention relates to a tandem hydraulic master cylinder comprising: a body pierced with a longitudinal bore delimited by an at least partially 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; - a primary piston and a secondary piston, of cylindrical shape, both capable of sliding respectively in the first and second length sections; - a primary pressure chamber defined in the first length section between the 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; - a second pressure chamber defined in the second length section between the 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; - at least four sealing cups which are secured to the body and comprise first 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; - a first resupply duct connecting the first fluid inlet to a first 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 - first and second orifices situated in the upper part of the body, 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. 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. 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 seccnd upstream cup and the first orifice and communicating with the primary pressure chamber via at least one first rad-al 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 siiciabiy 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 piece carrying the first upstream cup to be mounted on the first end of the wall to optimize guidance of the primary piston. 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 piece carrying the first upstream cup to be mounted on the first end of the wall to optimize guidance of the primary section. Accordingly, the present invention relates to compact tandem master cylinder with offset primary outlet comprising a body pierced with a longitudinal bore delimited by an at least partially 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 a primary piston and a secondary piston, of cylindrical shape, both capable of sliding respectively, in the first and second length sections a primary pressure chamber defined at least in part in the first length section between the 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, a second pressure chamber defined in the second length section between the 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, at least four sealing cups which are secured to the body and comprise first 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, a first resupply duct connecting the first fluid inlet to a first 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 first and second orifices situated in the upper part of the body, 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, 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. Other features and advantages of the invention will emerge clearly from the description thereof given hereafter by way of non-limiting indication with reference to the appended drawings in which: Figure 1 is a sectional view through a master cylinder in accordance with a first alternative embodiment of the invention; and Figure 2 is a sectional view through a master cylinder in accordance with a second alternative embodiment of the invention. The invention relates to a tandem hydraulic master cylinder mainly comprising a body 1, first and second inlets 2a, 2b for a hydraulic fluid at low pressure, a primary piston 3 and a secondary piston 4, a primary pressure chamber 5 a secondary pressure chamber 6, four sealing cups 9la, 91b, 92a, 92b, first and second resupply ducts 21, 22 and first and second outlet orifices 41 and 42 for the pressurized hydraulic fluid. The body 1 is pierced with a longitudinal bore delimited by an at least partially cylindrical wall 100, a first end 101 of which forms an opening, and a second end 102 of which is closed by a bottom 103. The first and second ends 101 and 102 are separated by a distance D over which first and second length sections S1, S2 contiguous with one another are defined. The first and second inlets 2a, 2b for the hydraulic fluid at low pressure are pierced in the upper part la of the body 1. The primary piston 3 and secondary piston 4, which are of cylindrical shape, are arranged in the bore in such a way that they can slide respectively in the first and second length sections S1, S2. The primary pressure chamber 5 is defined at least in part in the first length section S1 and is delimited by the primary and secondary pistons 3, 4, this chamber 5 containing at least one first preloaded spring 7 exerting between the pistons a first elastic force which tends to separate these pistons from one another. The secondary pressure chamber 6 is defined in the second length section S2 between the secondary piston 4 and the bottom 103, this chamber 6 containing at least one second preloaded spring 8 exerting between the secondary piston and the bottom 103 a second elastic force in a direction which tends to separate this secondary piston from the bottom. The four ceiling cups 91a, 91b, 92a, 92b are secured to the body 1 and comprise first upstream and downstream cups 91a, 91b sealing the primary chamber 5 and surrounding the primary piston 3, and second upstream and downstream cups 92a, 92b surrounding the secondary piston 4 and separating the primary and secondary pressure chambers 5, 6 in a leaktight manner, each downstream cup 91b, 92b being closer to the bottom 103 of the body than the upstream cup 91a, 92a that surrounds the same piston. The first resupply duct 21 connects the first fluid inlet 2a to a first intermediate volume 31 situated between the first upstream and downstream cups 91a, 91b, while the second resupply duct 22 connects the second fluid inlet 2b to a second intermediate volume 32 situated between the second upstream and downstream cups 92a, 92b. The first and second orifices 41, 42 which constitute the respective outlets from the primary and secondary pressure chambers 5 and 6 for the pressurized hydraulic fluid are situated in the upper part la of the body and communicate respectively with these primary and secondary pressure chambers 5, 6, the first orifice 41 being situated in the second length section 52 and between the first downstream cup 91b and the second upstream cup 92a. According to the invention, as shown in Figure 1, the primary and secondary pistons 3, 4 are guided by the wall 100 of the bore, with which they are in contact, and the body 1 is furthermore pierced with a first longitudinal passage 51 connecting the first downstream cup 91b, the second upstream cup 92a and the first orifice 41 and communicating with the primary pressure chamber 5 via a first radial passage 61 situated between the first and second length sections SI, S2. The bottom 103 may comprise a blanking piece 13 attached to the body and slidably accommodating the secondary piston 4, this blanking piece being pierced with a second longitudinal passage 52 placing the second downstream cup 92b in communication with the second orifice 42 and with a second radial passage 62 placing the second orifice 42 in communication with the secondary pressure chamber 6. Figure 2 illustrates an alternative embodiment of the master cylinder of Figure 1, in which the first resupply duct 21 and the first longitudinal passage 51 are not coplanar, the first longitudinal passage 51 therefore not having been depicted in this figure, for clarity. Furthermore, as shown in Figure 2, a cylindrical resupply connection 210 may be inserted in the first resupply duct 21 to pass through the first downstream cup 91b and reach the first intermediate volume 31 directly. Finally, as shown in Figures 1 and 2, it may be advantageous to improve the guidance of the primary piston by providing a guide piece 14 carrying the first upstream cup 91a and mounted on the first end 101 of the wall 100. We claim: 1. Compact tandem master cylinder with offset primary outlet comprising: - a body (1) pierced with a longitudinal bore delimited by an at least partially cylindrical wall (100), a first end (101) of which forms an opening, and a second end (102) of which is closed by a bottom (103) of the cylinder body, the first and second ends being separated by a distance (D) over which first and second length sections (SI, S2) contiguous with one another are defined, and this body exhibiting an upper part (la) in which first and second inlets (2a, 2b) for a hydraulic fluid at low pressure are pierced; - a primary piston (3) and a secondary piston (4), of cylindrical shape, both capable of sliding respectively, in the first and second length sections (S1, S2); - a primary pressure chamber (5) positioned at least in part in the first length section (S1) between the primary and secondary pistons (3,4) said chamber (5) containing at least one first spring (7) exerting between the pistons a first elastic force which tends to separate these pistons from one another; - a second pressure chamber (6) positioned in the second length section (S2) between the secondary piston (4) and the bottom (103) of the cylinder body wherein said second chamber (6) containing at least one second spring (8) exerting between the secondary piston and the bottom (103) a second elastic force in a direction which tends to separate this secondary piston from the bottom of the cylinder body; - at least four sealing cups (9la, 91b, 92a, 92b) which are secured to the body and comprise first upstream and downstream cups (9la, 91b) sealing the primary chamber (5) and surrounding the primary piston (3), and second upstream and downstream cups (92a, 92b) surrounding the secondary piston (4) and separating the primary and secondary pressure chambers (5, 6) in a leaktight fashion, each downstream cup (91b, 92b) being closer to the bottom (103) of the cylinder body than the upstream cup (9la, 92a) which surrounds the same piston; - a first resupply duct (21) connecting the first fluid inlet (2a) to a first intermediate volume (31) situated between the first upstream and downstream cups (9 la, 91b) a second resupply duct (22) connecting the second fluid inlet (2b) to a second intermediate volume (32) situated between the second upstream and downstream cups (92a, 92b); and - first and second orifices (41, 42) situated in the upper part (la) of the body, communicating respectively with the primary and secondary pressure chambers (5, 6) and constituting the respective outlets from these chambers, the first orifice (41) being situated in the second length section (S2) and between the first downstream cup (91b) and the second upstream cup (92a); characterized in that the primary and secondary pistons (3, 4) are guided by the wall (100) of the bore, with which they are in contact, and in that the body (1) is furthermore pierced with a first longitudinal passage (51) connecting the first downstream cup (91b) the second upstream cup (92a) and the first orifice (41) and communicating with the primary pressure chamber (5) via at least one first radial passage (61) situated between the first and second length sections (SI, S2). 2. Master cylinder as claimed in claim 1, wherein the said bottom (103) of the cylinder body comprises a blanking piece (13) attached to the body and slidably accommodating the secondary piston (4) and in that this blanking piece is pierced with a second longitudinal passage (52) placing the second downstream cup (92b) in communication with the second orifice (42) and with a second radial passage (62) placing the second orifice (42) in communication with the secondary pressure chamber (6). 3. Master cylinder as claimed in claim 1 or 2, wherein it has a cylindrical resupply connection (210) inserted in the first resupply duct (21) and passing through the first downstream cup (91b) to reach the first intermediate volume (31) directly. 4. Master cylinder as claimed in any one of the preceding claims, wherein a guide piece (14) carrying the first upstream cup (9 la) is mounted on the first end (101) of the wall (100) to guide the primary position (3). 5. Compact tandem master cylinder substantially as herein described with reference to the accompanying drawings.

Documents:

557-del-1998-abstract.pdf

557-del-1998-claims.pdf

557-del-1998-correspondence-others.pdf

557-del-1998-correspondence-po.pdf

557-del-1998-description (complete).pdf

557-del-1998-drawings.pdf

557-del-1998-form-1.pdf

557-del-1998-form-13.pdf

557-del-1998-form-19.pdf

557-del-1998-form-2.pdf

557-del-1998-form-3.pdf

557-del-1998-form-4.pdf

557-del-1998-form-6.pdf

557-del-1998-gpa.pdf

557-del-1998-pct-210.pdf

557-del-1998-pct-409.pdf

557-del-1998-petition-137.pdf

557-del-1998-petition-138.pdf

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