Brake proportioning valve with blend back

Claim 2

In a brake control mechanism for use in a vehicle hydraulic system: a housing having an inlet port, an outlet port and a bore communicating the inlet port with the outlet port; valve means disposed within the bore and dividing the bore into an inlet chamber and an outlet chamber, said inlet and outlet chambers communicating respectively, with the inlet and outlet ports, said valve means including a valve member in the inlet chamber, a valve piston reciprocably positioned in the bore and having a passage therein connecting the inlet and outlet chambers for fluid communication, a valve seat located at that end of the passage which terminates in the inlet chamber for engagement with the valve member, said valve piston having a smaller end of lesser effective area exposed to inlet chamber pressure and a larger end of greater effective area exposed to outlet chamber pressure, said valve piston having an open position wherein fluid communication is established between the chambers until a first fluid pressure level in the outlet chamber is reached whereupon the valve piston responds to the first fluid pressure level to proportionally restrict fluid flow between the chambers to permit the fluid pressure level in the inlet chamber to rise more rapidly than the fluid pressure level in the outlet chamber rises until a second fluid pressure level in the outlet chamber is reached; first resilient means biasing said valve piston in a direction away from said valve member to establish the aforesaid open position; and additional means in the passage of said valve piston responsive to the second pressure level in the outlet chamber for lifting the valve member from the valve seat and maintaining a varying gap between the seat and valve member so that the fluid pressure level in the outlet chamber now rises more rapidly than the fluid pressure level in the inlet chamber up to a pressure level in the outlet chamber substantially the same as that in the inlet chamber whereupon said valve means opens to permit uninterrupted flow of fluid between the chambers.

Claim 3

The invention of claim 1: said valve piston having a fluid passage therein communicating the inlet chamber with the outlet chamber; said valve member being positioned adjacent the smaller end of the valve piston to open and close the passage to effectively regulate fluid flow through the passage.

Claim 4

The invention of claim 1: said additional means including a stepped piston having opposed annular ends and an annular shoulder between the ends, one of the ends having an effective area greater than the effective area of the other end, said opposed ends being acted upon by the pressure level appearing in the outlet chamber, a coil spring in the passage having one end abutting the valve piston and the other end abutting the shoulder on the stepped piston to urge the latter toward a first position so that The pressure in the outlet chamber which acts on the opposed ends of the stepped piston establishes a net force on the piston opposing the force of the coil spring and urges the piston to a second position, and a finger carried by the stepped piston for engagement with the valve member to unseat the same upon movement of the stepped piston to the second position.

Claim 5

The invention of claim 1: said additional means including an internal piston coaxially located in the passage of the valve piston and slidable between a first and a second position; second resilient means in the passage urging the internal piston toward the first position; said internal piston having an axial opening therethrough and opposed annular ends, one of the ends having an effective area greater than the effective area of the other annular end, said opposed ends being acted upon by the pressure level existing in the outlet chamber, the pressure in the outlet chamber acts on the ends of the internal piston to establish a net force on the piston tending to slide the piston against the second resilient means and toward the second position; and an element carried by the internal piston and extending along the passage for engagement with the valve member upon movement of the internal piston to its second position.

Claim 6

The invention of claim 4: said second resilient means being a coil spring having opposite ends engaging respectively, the valve piston and the internal piston; said element being in the form of a pin extending along the passage toward the smaller diameter end of the valve piston and through the coils of the spring.

Claim 7

In a brake control mechanism for a vehicle hydraulic system: a housing having an inlet port, an outlet port and a bore communicating the inlet port with the outlet port; valve means in the bore dividing the bore into an inlet chamber and an outlet chamber, said inlet and outlet chambers communicating respectively, with the inlet port and the outlet port; said valve means including a valve piston slidably arranged in the bore and provided with a passage therethrough communicating the inlet and outlet chambers, a seat in the passage, a valve member slidably located in the bore for seating on the seat, an internal piston slidably positioned in the passage of the valve piston and having a longitudinal opening in registry with the passage, and a pin element mounted in the longitudinal opening of the internal piston and extending through the passage toward the seat for engagement with the valve member to prevent seating; said valve piston having a smaller diameter end of lesser effective area exposed to fluid pressure in the inlet chamber and a larger diameter end of greater effective area exposed to fluid pressure in the outlet chamber, said valve piston being spring biased to a first position unseating the valve piston from the valve member; said internal piston having opposed annular ends, one annular end having an effective area greater than the effective area of the other annular end, said internal piston being spring biased in a direction causing withdrawal of the pin element from engagement with the valve member, said annular ends being exposed to outlet chamber pressure so that the net force developed on the opposed annular ends of the internal piston acts so as to move the internal piston against the spring bias; said valve piston being responsive to a predetermined pressure level in the outlet chamber to seat said piston against the valve member and subsequently regulate the fluid flow between the chambers so that the fluid pressure level in the inlet chamber rises more rapidly than the fluid pressure level in the outlet chamber rises until a second predetermined pressure level in the outlet chamber is reached whereupon the spring biased internal piston is moved in a direction which drives the pin element against the valve member to unseat the latter so that the fluid pressure level in the outlet chamber rises more rapIdly than the fluid pressure level in the inlet chamber until the fluid pressure level in the outlet chamber is almost the same as the fluid pressure level in the inlet chamber, at which time the valve piston and internal piston have moved the valve member to its maximum open position.

Claim 8

In a brake control mechanism for a vehicle hydraulic system: a housing having an inlet port, an outlet port and a bore communicating the inlet port with the outlet port; valve means in the bore dividing the bore into an inlet chamber and an outlet chamber, said inlet and outlet chambers communicating respectively, with the inlet port and the outlet port; said valve means including a valve piston slidably arranged in the bore and provided with a passage therethrough communicating the inlet and outlet chambers, a seat in the passage, a valve member slidably located in the bore for seating on the seat, an internal piston slidably positioned in the passage of the valve piston and having a longitudinal opening in registry with the passage, and a pin element mounted in the longitudinal opening of the internal piston and extending through the passage toward the seat for engagement with the valve member to prevent seating; said valve piston having a smaller diameter end of lesser effective area exposed to fluid pressure in the inlet chamber and a larger diameter end of greater effective area exposed to fluid pressure in the outlet chamber, said valve piston being spring biased to a first position unseating the valve piston from the valve member; said internal piston having opposed annular ends, one annular end having an effective area greater than the effective area of the other annular end, said internal piston being spring biased in a direction causing withdrawal of the pin element from engagement with the valve member, said annular ends being exposed to outlet chamber pressure so that the net force developed on the opposed annular ends of the internal piston acts so as to move the internal piston against the spring bias; said valve piston being responsive to a predetermined pressure level in the outlet chamber to seat said piston against the valve member and subsequently regulate the fluid flow between the chambers so that the fluid pressure level in the inlet chamber rises more rapidly than the fluid pressure level in the outlet chamber rises until a second predetermined pressure level in the outlet chamber is reached whereupon the spring biased internal piston is moved in a direction which drives the pin element against the valve member to unseat the latter so that the fluid pressure level in the outlet chamber rises more rapIdly than the fluid pressure level in the inlet chamber until the fluid pressure level in the outlet chamber is almost the same as the fluid pressure level in the inlet chamber, at which time the valve piston and internal piston have moved the valve member to its maximum open position.