Anti-theft vehicle brake-supervising device

In an anti-theft vehicle brake-supervising device of the type which selectively prevents reverse flow of fluid from at least one vehicle wheel cylinder back to the vehicle master cylinder to thereby maintain the braking function of said fluid within said wheel cylinder, the improvement comprising means defining a flow chamber having opposite distal and proximal ends, a first and a second fluid connection respectively connected from said flow chamber distal end to said vehicle master cylinder and from said flow chamber proximal end to said wheel cylinder to normally allow opposite direction fluid flow between said master cylinder and wheel cylinder through said flow chamber, means defining a main valve opening including a seat in said flow chamber distal end for selectively interrupted to prevent flow between said first and second fluid connections incident to the closing of said valve opening, a valve support member operatively arranged to be manually urged through movement in said flow chamber between opposing operative positions respectively adjacent said distal and said proximal ends of said flow chamber, said valve support member being of a prescribed smaller diameter than said flow chamber so as to define an encircling annular fluid passage for allowing fluid flow through said flow chamber, a first valve and a cooperating biasing spring operatively disposed in said valve support member so that movement of said member from said flow chamber proximal end to said flow chamber distal end correspondingly urges said first valve through closing movement upon said valve seat and only allows directional flow of fluid from said master cylinder fluid connection to said wheel cylinder fluid connection to the extent of opening movement permitted in said first valve relative to said valve opening by said biasing spring, means in said first valve defining an internal flow passage having a pressure release valve opening, a second valve normally closing said pressure release valve opening, and valve-unseating means on said valve support member effective to unseat said second valve incident to further movement of said member towards said flow chamber distal end so as to release pressure fluid from said flow chamber proximal end through said second valve and into said master cylinder through said first fluid connection thereof, whereby the aforesaid release of pressure fluid facilitates the manual urging of said valve support member through movement back to said flow chamber proximal end and the corresponding opening of said main valve for normal use of said fluid for braking service for said vehicle.