Hydraulic braking systems for vehicles

Claim 2

A master cylinder for use in an hydraulic braking system comprising a cylinder body having a bore, a positively actuated main piston assembly working in a portion of said bore, a secondary piston located in said bore between said main piston assembly and one end of said cylinder body, a main pressure space in said bore defined between adjacent ends of said main piston assembly and said secondary piston, a first inlet passage in said cylinder body for connection to a source of hydraulic fluid under pressure and in communication with said main pressure space, a second inlet passage in said cylinder body for connection to a reservoir for fluid and in communication with said main pressure space, a normally closed first valve controlling communication between said first inlet passage and said main pressure space and adapted to open when said main piston is advanced in said bore, a normally open second valve controlling communication between said second inlet passage and said main pressure space and adapted to close when said main piston is advanced in said bore before said first valve opens, closure of said second valve and opening of said first valve causing pressurization of said main pressure space which acts to advance said secondary piston, a second pressure space between said secondary piston and said one end of the cylinder body, a third inlet passage in said cylinder body for connection to a reservoir for fluid and in communication with said second pressure space, an outlet port in said cylinder body in communication with said second pressure space and adapted to be connected to a wheel brake, first and second axially spaced stationary annular seals fixed in said bore, the secondary piston working through said seals and the third inlet passage in communication with a chamber defined in said bore between said seals, said secondary piston having a recuperation port normally providing communication between said chamber and said second pressure space, a hollow inner piston working in an axially extending bore in the end of said secondary piston adjacent said main piston assembly, and an axial extension associated with said main piston assembly normally spaced from the adjacent end of said inner piston being adapted to engage and to close said inner piston upon failure of said main pressure space, whereby movement of said main piston assembly is transmitted directly to said piston through said inner piston and a column of hydraulic fluid trapped in the axially extending bore in which said inner piston works.

Claim 3

A master cylinder for use in an hydraulic braking system comprising a cylinder body having a bore, a positively actuated main piston assembly working in a portion of said bore, a secondary piston located in said bore between said main piston assembly and one end of said cylinder body, a main pressure space in said bore defined between adjacent ends of said main piston assembly and said secondary piston, a first inlet passage in said cylinder body for connection to a source of hydraulic fluid under pressure and communicating with said main pressure space, a second inlet passage in said cylinder body for connection to a reservoir for fluid and communicating with said main pressure space, a normally closed first valve controlling communication between said first inlet passage and said main pressure space and adapted to open when said main piston is advanced in said bore, a normally open second valve controlling communication between said second inlet passage and said main pressure space and adapted to close when said main piston is advanced in said bore before said first valve opens, closure of said second valve and opening of said first valve causing pressurization of said main pressure space which acts to advance said secondary piston, first and second annular bearing members secured in said bore at a fixed axial spacing, an annular seal housed in an annular recess in each bearing member, the secondary piston supported in said bearing members and working through said seals, said cylinder body having a third inlet passage communicating with a constant volume chamber defined in said bore between said seals and adapted to be connected to a reservoir for hydraulic fluid, a second pressure space defined by a portion of said bore beyond one end of said secondary piston and the seal in said first bearing member which is located adjacent to the said one end of said secondary piston, said secondary piston having a radial recuperation port normally providing communication between said chamber between said seals and an axially extending recess in said secondary piston opening into said second pressure space, and said cylinder body having an outlet port communicating with said second pressure space and adapted to be connected to a wheel brake, the arrangement being such that when said secondary piston is advanced in said bore into said second pressure space, said recuperation port is closed by the seal in said first bearing member and thereafter further movement of said secondary piston in the same direction pressurizes hydraulic fluid in said second pressure space.

Claim 4

A master cylinder for use in an hydraulic braking system comprising a cylinder body having a bore, a positively actuated main piston assembly working in a portion of said bore, a secondary piston located in said bore between said main piston assembly and one end of said cylinder body, a main pressure space in said bore defined between adjacent ends of said main piston assembly and said secondary piston, a first inlet passage in said cylinder body for connection to a source of hydraulic fluid under pressure and communicating with said main pressure space, a second inlet passage in said cylinder body for connection to a reservoir for fluid and communicating with said main pressure space, a normally closed first valve controlling communication between said first inlet passage and said main pressure space and adapted to open when said main piston is advanced in said bore, a normally open second valve controlling communication between said second inlet passage and said main pressure space and adapted to close when said main piston is advanced in said bore before said first valve opens, closure of said second valve and opening of said first valve causing pressurization of said main pressure space which acts to advance said secondary piston, first and second annular bearing members secured in said bore at a fixed axial spacing, an annular seal housed in an annular recess in each bearing member, the secondary piston supported in said bearing members and working through said seals, said cylinder body having a third inlet passage communicating with a constant volume chamber defined in said bore between said seals and adapted to be connected to a reservoir for hydraulic fluid, a second pressure space defined by a portion of said bore beyond one end of said secondary piston and the seal in said first bearing member which is located adjacent to the said one end of said secondary piston, said secondary piston having a radial recuperation port normally providing communication between said chamber between said seals and an axially extending recess in said secondary piston opening into said second pressure space, and said cylinder body having an outlet port communicating with said second pressure space and adapted to be connected to a wheel brake, the arrangement being such that when said secondary piston is advanced in said bore into said second pressure space, said recuperation port is closed by the seal in said first bearing member and thereafter further movement of said secondary piston in the same direction pressurizes hydraulic fluid in said second pressure space.