Pedal ratio control for hydraulic booster

Claim 2

A booster brake mechanism operated by a source of hydraulic pressure and capable of being manually operated when said source of hydraulic pressure is insufficient to achieve desired braking, said booster comprising: a housing having a large bore portion and a smaller bore portion contiguous therewith; a power piston movable in said large bore portion and forming at one side thereof and within a portion of said large bore portion a power chamber; an output piston movable in said smaller bore portion and extending into said large bore portion to form between the other side of said power piston, the remaining portion of said large bore portion and said output piston a fluid-containing, sealable ratio control cavity; said output piston having a generally cylindrically-stepped hollow interior configuration, said power piston having a generally cylindrically-stepped exterior configuration received at least in part within said interior configuration of said output piston to define a fluid-containing, sealed piston chamber therebetween; pilot valve means extending within said power piston providing fluid communication between said ratio cavity and said piston chamber in a normal unactuated position of said booster and movable to a second position to provide fluid communication between said ratio control cavity and said power chamber while trapping said fluid within said piston chamber; inlet and outlet valve means between said source and said power chamber operative to pressurize said power chamber for moving said power piston thereby pressurizing at approximately equal pressure said ratio cavity and said piston chamber, such movement of said power piston simultaneously effecting a greater movement of said output piston; and manually actuable valve means associated with said inlet and outlet valve means operable to actuate said pilot valve means to said second position for effecting approximately equal movements of said power piston and sAid output piston.

Claim 3

The booster brake mechanism of claim 1 further including: an axially extending recess in said housing opening to said large bore portion; said power piston aligned in predetermined relationship with said recess when said booster is unactuated; a seal circumscribing said power piston ineffective to prevent fluid communication between said ratio control cavity and said power chamber through said recess when said booster is unactuated and effective upon movement of said power piston to seal said ratio control cavity thereby trapping said fluid therein.

Claim 4

The booster brake mechanism of claim 2 wherein: said output piston has a cylindrical external configuration and said cylindrically-stepped interior configuration further defined by a first cylindrical portion at one end of said output piston, a second, smaller cylindrical portion at the opposite end of said output piston and an annular step at the juncture therebetween; said cylindrically-stepped exterior configuration of said power piston further defined by a first cylindrical portion approximately equal in diameter to said large bore portion, a second, smaller intermediate cylindrical portion and a third cylindrical portion smaller in diameter than said second portion at the opposite power piston end, the juncture of said second and third cylindrical portions defined as an annular step; said second intermediate portion of said power piston sealingly received within said first cylindrical portion of said output piston and said third cylindrical portion of said power piston sealingly received within said second cylindrical portion of said output piston to further define said piston chamber between said annular surfaces of said power and output pistons.

Claim 5

The booster brake mechanism of claim 3 wherein: said second intermediate cylindrical portion of said power piston has a cylindrically-stepped, cup-shaped interior configuration defining a portion of said piston chamber; said second intermediate portion of said power piston further having a cylindrical passage extending therein in fluid communication at a first end with said power chamber, a smaller opening at the opposite second end of said cylindrical passage in fluid communication with said piston chamber and a second opening communicating said ratio cavity and said cylindrical passage in between the ends thereof; said pilot valve means including a cylindrical elastomer valve element disposed within said cylindrical passage and axially retained therein by a circular retainer insert in said first end of said cylindrical passage having a central opening extending therethrough, said valve element having a first cone-shaped end adapted to seat within said smaller opening adjacent said first end of said cylindrical passage, and a second cone-shaped end for seating within said central opening of said retainer insert; said pilot valve element further defined by a plurality of circumferentially disposed flutes maintaining said pilot valve element aligned within said cylindrical passage and biasing means normally maintaining said second end of said valve element seated in said central opening of said retainer insert.

Claim 6

The booster brake mechanism of claim 4 wherein: an actuating rod extends from said pilot valve element through said opening in said retainer insert into said power chamber; said inlet and outlet valve means including an input member extending within said first bore portion of said housing and adapted to be axially moved within said housing by the operator to effect actuation of said booster; and said manually actuable valve means including abutment means extending from said input member operable to engage said actuating rod to seal said smaller opening by said first end of said valve element and contact said cup-shaped portion of said power piston to effect movement of said output piston when said source of hydraulic pressure is insufficient to achieve desired braking.

Claim 7

In a hydraulic booster brake normally operable by a source of pressurized fluid and capable of being manually operated when said source of pressure is insufficient to achieve desired braking, said booster brake including a housing having a small bore portion contiguous with a large bore portion therein, an input member extending within said large bore portion and movable further therein by the operator of said booster, an output member extending from said small bore portion and movable further therefrom in response to inward movement of said input member, power piston means movable within said large bore portion and defining a power chamber within said first bore portion, inlet and outlet valve means associated with said input member operable in response to movement of said input member to pressurize said power chamber and move said piston means; output piston means sealed within said small bore and defining with said power piston means a fluid-containing ratio control cavity in a portion of said large bore portion, said ratio control cavity being isolated upon movement of said power piston means; said power piston means and said output piston means further effective to define a fluid-containing piston chamber therebetween effective with said ratio control cavity to cause said output piston to travel a greater distance than said power piston upon said power chamber being pressurized by said inlet and outlet valves, the improvement comprising: passage means within at least one of said piston means providing fluid communication between said ratio control cavity, piston chamber and power chamber; pilot valve means associated with said passage means having a normal first position providing fluid communication between said ratio control cavity and said piston chamber and a second position providing fluid communication between said ratio control cavity and said power chamber while isolating the fluid within said piston chamber, said pilot valve means being in said first position when said input member moves to actuate said inlet and outlet valve means; and abutment means associated with said input member and operable during said manual operation of said booster to shift said pilot valve means to its second position for pressurizing said piston chamber only to effect a rate of travel of said output piston means different from that when said output piston means is actuated at said first position of said pilot valve means.

Claim 8

In a hydraulic booster brake normally operable by a source of pressurized fluid and capable of being manually operated when said source of pressure is insufficient to achieve desired braking, said booster brake including a housing having a small bore portion contiguous with a large bore portion therein, an input member extending within said large bore portion and movable further therein by the operator of said booster, an output member extending from said small bore portion and movable further therefrom in response to inward movement of said input member, power piston means movable within said large bore portion and defining a power chamber within said first bore portion, inlet and outlet valve means associated with said input member operable in response to movement of said input member to pressurize said power chamber and move said piston means; output piston means sealed within said small bore and defining with said power piston means a fluid-containing ratio control cavity in a portion of said large bore portion, said ratio control cavity being isolated upon movement of said power piston means; said power piston means and said output piston means further effective to define a fluid-containing piston chamber therebetween effective with said ratio control cavity to cause said output piston to travel a greater distance than said power piston upon said power chamber being pressurized by said inlet and outlet valves, the improvement comprising: passage means within at least one of said piston means providing fluid communication between said ratio control cavity, piston chamber and power chamber; pilot valve means associated with said passage means having a normal first position providing fluid communication between said ratio control cavity and said piston chamber and a second position providing fluid communication between said ratio control cavity and said power chamber while isolating the fluid within said piston chamber, said pilot valve means being in said first position when said input member moves to actuate said inlet and outlet valve means; and abutment means associated with said input member and operable during said manual operation of said booster to shift said pilot valve means to its second position for pressurizing said piston chamber only to effect a rate of travel of said output piston means different from that when said output piston means is actuated at said first position of said pilot valve means.

Claim 9

The booster brake mechanism of claim 6 wherein: said output piston means includes an output piston having a generally cylindrically-stepped hollow interior configuration, said power piston means includes a power piston having a generally cylindrically-stepped exterior configuration received at least in part within said interior configuration of said output piston to further define said fluid-containing piston chamber; said power chamber formed in said large bore portion at one side of said power piston and said ratio control cavity formed between the other side of said power piston and said output piston in said large bore portion.

Claim 10

The booster brake mechanism of claim 6 wherein: said output piston has a cylindrical external configuration and said cylindrically-stepped interior configuration further defined by a first cylindrical portion at one end of said output piston, a second, smaller cylindrical portion at the opposite end of said output piston and an annular step at the juncture therebetween; said cylindrically-stepped exterior configuration of said power piston further defined by a first cylindrical portion approximately equal in diameter to said large bore portion, a second, smaller intermediate cylindrical portion and a third cylindrical portion smaller in diameter than said second portion at the opposite power piston end, the juncture of said second and third cylindrical portions defined as an annular step; said second intermediate portion of said power piston sealingly received within said first cyLindrical portion of said output piston and said third cylindrical portion of said power piston sealingly received within said second cylindrical portion of said output piston to further define said piston chamber between said annular surfaces of said power and output pistons.

Claim 11

The booster brake mechanism of claim 8 wherein: said second intermediate cylindrical portion of said power piston has a cylindrically-stepped, cup-shaped interior configuration defining a portion of said piston chamber; said second intermediate portion of said power piston further having a cylindrical passage extending therein in fluid communication at a first end with said power chamber, a smaller opening at the opposite second end of said cylindrical passage in fluid communication with said piston chamber and a second opening communicating said ratio cavity and said cylindrical passage in between the ends thereof; said pilot valve means including a cylindrical elastomer valve element disposed within said cylindrical passage and axially retained therein by a circular retainer insert in said first end of said cylindrical passage having a central opening extending therethrough, said valve element having a first cone-shaped end adapted to seat within said smaller opening adjacent said first end of said cylindrical passage, and a second cone-shaped end for seating within said central opening of said retainer insert; said pilot valve element further defined by a plurality of circumferentially disposed flutes maintaining said pilot valve element aligned within said cylindrical passage and biasing means normally maintaining said second end of said valve element seated in said central opening of said retainer insert.

Claim 12

The booster brake mechanism of claim 9 wherein: an actuating rod extends from said pilot valve element through said opening in said retainer insert into said power chamber; said inlet and outlet valve means including an input member extending within said first bore portion of said housing and adapted to be axially moved within said housing by the operator to effect actuation of said booster; and said manually actuable valve means including abutment means extending from said input member operable to engage said actuating rod to seal said smaller opening by said first end of said valve element and contact said cup-shaped portion of said power piston to effect movement of said output piston when said source of hydraulic pressure is insufficient to achieve desired braking.