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Title: Hydraulically operated disc brakes for vehicles
Claims: I claim: 1. An hydraulically operated disc brake comprising a rotatable disc, two pressure plates for applying respective friction pads to opposite faces of the disc and at least one hydraulically-operated actuator for urging the pressure plates towards each other on application of the brake, said actuator comprising a cylinder housing having an open outer end, an end wall of the housing acting on one of the pressure plates and having a bore, a piston movable in the housing and having a stepped bore comprising a first bore portion of smaller diameter located adjacent to said open outer end, a second bore portion of larger diameter located adjacent to said end wall, and a step between said first bore portion and said second bore portion, a draw bar detachably connected to the piston and extending through said bore in said housing and over the peripheral edge of the disc to act on the second pressure plate, said draw-bar having a screw-threaded, reduced diameter end first portion having a free end, a second portion of a diameter larger than and continuous with said first portion, and a shoulder between said first portion and said second portion, at least part of said second portion of said draw bar being firmly accommodated within said second bore portion of said stepped bore over a contact area such that said shoulder engages said step in said bore, a first seal between said second portion of said draw bar and said housing disposed within said contact area, a second seal between said second portion of said draw bar and said second bore portion of said stepped bore in the piston, at least one nut screwed onto said first portion of the draw bar which projects through said piston and which is accessible through said open end of said housing, said nut clamping said shoulder and said step together, and positive locating means on said free end of said draw bar for engagement with a tool to enable said draw bar to be held against rotation at least when said nut is being tightened and untightened. 2. An hydraulically operated disc brake as in claim 1 wherein the pressure plates are chordal with respect to the disc and are urged towards each other in the application of the brake by a pair of said hydraulically operated actuators acting between complementary end portions of the pressure plates which extend outwardly beyond the peripheral edge of the disc, and the draw bar of each actuator projects through openings in a stationary drag-taking member in which the friction pads are guided. 3. An hydraulically operated disc brake as in claim 1 wherein said cylinder housing, said piston and said draw bar comprise a subassembly removably carried on said pressure plates. 4. An hydraulically operated disc brake as in claim 3 further including means cooperating with said housing to preclude rotation thereof with respect to said pressure plates. 5. An hydraulically operated disc brake as in claim 1 wherein said positive locating means comprises a screwdriver slot in the inner end of said draw bar. 6. A disc brake assembly for a vehicle including a first rotatable disc, a second rotatable disc rotatable with and spaced axially from said first disc, each disc having an inner face and an outer face, said inner face of said first disc facing said inner face of said second disc and said outer face of each disc facing outwardly away from the other disc, a first pair of friction pads for engagement with said inner and said outer faces of said first disc, a second pair of friction pads for engagement with said inner and said outer faces of said second disc, first and second fluid-pressure operated actuating means for applying said first and second pairs of friction pads to said inner and outer faces of each respective said first and said second disc, said first and second actuating means being both located adjacent to said outer face of said second disc, a first pair of inner and outer axially movable pressure plates for urging said first pair of friction pads into engagement with said inner and outer faces of said first disc, a second pair of inner and outer axially movable pressure plates for urging said second pair of friction pads into engagement with said inner and outer faces of said second disc, wherein said first actuating means comprises a pair of circumferentially spaced actuators and at least one of said actuators comprises a cylinder housing having an open outer end and a part extending over said second disc, an end wall of the housing acting on said inner pressure plate of said first pair of pressure plates and having a bore, a piston movable in the housing and having a stepped bore comprising a first bore portion of smaller diameter located adjacent to said open outer end, a second bore portion of larger diameter located adjacent to said end wall, and a step between said first bore portion and said second bore portion, a draw-bar detachably connected to the piston and extending through said bore in said housing and over the peripheral edge of said first disc to act on said outer pressure plate of said first pair, said draw-bar having a screw-threaded, reduced diameter end first portion having a free end, a second portion of a diameter larger than and continuous with said first portion, and a shoulder between said first portion and said second portion, at least part of said second portion of said draw-bar being firmly accommodated within said second bore portion of said stepped bore over a contact area such that said shoulder engages said step in said bore, a first seal between said second portion of said draw-bar and said housing disposed within said contact area, a second seal between said second portion of said draw-bar and said second bore portion of said stepped bore in the piston, at least one nut screwed onto said first portion of the draw-bar which projects through said piston and which is accessible through said open end of said housing, said nut clamping said shoulder and said step together, and positive locating means on said free end of said draw-bar for engagement with a tool to enable said draw bar to be held against rotation at least when said nut is being tightened and untightened. Other info: Inventors: Newstead, Charles (Walsall, EN) Application Number: 559591 Filing Date: 1975-03-18 Publication_date: 1976-06-29 Assignee: Girling Limited (Birmingham, EN) Primary Class(es): 188/72.5 92/172 Other Classes: US Patent Ref:
Other Refs:
Primary Examiner: Blix, Trygve M. Assistant Examiner: Kazenske, Edward R. Attorney: Imirie, Smiley & Linn |
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