Vehicular hydraulic brake system

Claim 2

In a vehicular hydraulic brake system comprising a tandem master cylinder having front and rear sections respectively connected through two independent fluid circuits with front and rear brake cylinders for respectively effecting braking in front and rear wheels of a vehicle, a fluid pressure modulator valve provided intermediately of one of said fluid circuits, comprising: a first inlet port communicating with one of the front and rear sections and with one of the brake cylinders for providing constant fluid communication therebetween; a second inlet port communicating with the other of the front and rear sections; an outlet port communicating with the other of said brake cylinders; a chamber for providing fluid communication between said second inlet port and said outlet port to pass an unmodulated fluid pressure from said second inlet port to said outlet port; and means responsive to a force of inertia resulting from a deceleration of the vehicle with a predetermined magnitude for blocking said fluid communication between said second inlet port and said outlet port, and responsive to a failure in said fluid circuit with front brake cylinder for transmitting an unmodulated fluid pressure from said second inlet port to said outlet port.

Claim 3

A fluid pressure modulator valve according to claim 1, wherein said means comprises a ball member accommodated in said chamber and resting on a ramp which is inclined at an angle to a horizontal line, a ball seat secured to an outlet portion of said chamber to said outlet port and positioned relative to said ball member, the weight of said ball member being determined so that the ball member is responsive to a predetermined deceleration of the vehicle to roll up said ramp and seat on said ball seat for blocking the fluid communication between said chamber and said outlet port, a control member having a leading end extending toward said ball member through said outlet portion and an enlarged portion slidably mounted in a bore leading from said first inlet port and having formed on its peripheral wall an annular projection, a compression spring mounted behind said enlarged portion to force the enlarged portion to a position in which said leading end projects into said chamber past said ball seat, the compression of said spring and the relative diameter of said annular projection being determined to cause said spring to yield to a fluid pressure applied to said enlarged portion through said first inlet port for causing the enlarged portion to be moved to a position in which the leading end of said control element in withdrawn from said chamber when the fluid pressure in said first inlet port is higHer than a predetermined level, a second chamber formed in said housing and communicating on one side with the first named chamber and on the other with said outlet port, two individual pistons slidably mounted in said second chamber and held in contact with each other, one piston of which is exposed to the fluid pressure in said second inlet port and the other to the fluid pressure in said outlet port, the former being larger in diameter than the latter, and a compression spring mounted in said second chamber to force the latter piston toward said outlet port.