Master cylinders for hydraulic braking systems

Claim 1

In an hydraulic master cylinder of the triple type comprising a cylinder body having a longitudinally extending bore which is open at one end and closed at an opposite end, a positively actuated first piston, a floating second piston, and at least one floating third piston all working in said bore, a first pressure space defined in said bore between adjacent ends of said first and second pistons, a second pressure space defined in said bore between adjacent ends of said second and third pistons, and a third pressure space defined in said bore between said third piston and said closed end of said bore, a first normally-open valve means for controlling communication between said first pressure space and first inlet means for connection to fluid reservoir means, a second normally-open valve means for controlling communication between said second pressure spAce and second inlet means for connection to fluid reservoir means, a third normally-open valve means for controlling communication between said third pressure space and third inlet means for connection to fluid reservoir means, and return springs housed in said pressure spaces for urging said pistons into retracted positions in which said valve means are normally open, the arrangement being such that when said pistons are advanced in said bore in a first direction, initial movement thereof causes said pressure spaces to be isolated from said inlet means and, thereafter, additional movement of said pistons in said first direction is adapted to pressurize fluid in said pressure spaces, the improvement wherein said cylinder body comprises at least two separate body parts each provided with longitudinally extending bore portions, at least one piston being adapted to work only in said bore portion of one of said body parts, and at least one piston being adapted to work only in said bore portion of the other of said body parts, and wherein an abutment ring having opposite faces is clamped between mating faces of said body parts and extends radially into said cylinder bore, one of said opposite faces of said abutment ring defining an abutment for one end of one of said return springs of which the opposite end acts on an adjacent end of that piston which is adjacent to said one face.