Method for control of a power brake and apparatus embodying said method

Claim 2

The combination of a control valve for a power brake with a booster, wherein said control valve includes a housing having a cylindrical bore extending forwardly and rearwardly, a first port in said housing for communicating with a fluid pressure source, a second port in said housing for connection to wheel cylinders, and an exhaust port in said housing, a first piston reciprocatively engaged in the rear portion of said bore and provided with a small piston jutting forwardly from the front portion thereof, the forward end of the small piston being biased rearwardly by a first spring engaged therebetween and the inner surface of the forward wall of said housing, the rear end of the small piston being operatively connected with a push-rod to be urged forwardly by a brake pedal, a second piston snugly and reciprocatively engaged in said bore and having the small piston of said first piston pass through an opening in the central portion thereof, a piston valve reciprocatively engaged in said cylinder and having the forward portion of the small piston of said first piston pass reciprocatively through an opening in the central portion thereof, a second spring interposed between said second piston and said piston valve so as to bias said second piston normally toward the rear portion of said bore and said piston valve normally toward the front portion of said bore, and a passageway in said housing providing constant communication between a first chamber formed in the bore between said second piston and said piston valve and a second chamber formed in the fore in front of said piston valve, said first chamber being connected with said exhaust port, said booster including actuating means operatively connected to said first piston and for engagement by a brake rod whereby said piston valVe, when the first piston is urged forwardly, opens said first port, and when said first piston is in its normal position said piston valve closes said first port, and said booster being operative to urge said first piston further forwardly only when a counter force of predetermined value is generated by fluid pressure in one of said chambers acting rearwardly against said first piston and said booster actuating means.

Claim 3

The combination as set forth in claim 1, wherein said booster comprises a housing attached to the rear end of said control valve housing, said booster housing being divided into two evacuated chambers by a diaphragm, said diaphragm having a rod forming part of said booster actuator means and extending axially of the cylindrical bore of the control valve housing and projecting from the booster housing into contact with said first piston of the valve, the rear end of said booster housing having an air inlet controlled by a valve member, and a spring forming part of said booster actuator means normally urging said valve member to closed position, said spring being overcome by said counter force of predetermined value acting rearwardly against said first piston to open said valve member and permit entry of air into one of said booster chambers, whereby to move said diaphragm and connected rod forwardly to increase the pressure of fluid in said control valve.

Claim 4

The combination set forth in claim 2 wherein said diaphragm is supported by a drive piston connected to said rod, a transmission member slidably engaging said rod at one end and coupling with said brake pedal rod at the other end, said booster actuator spring being disposed to urge the transmission member rearwardly with respect to said drive piston so as to engage said valve member and hold it closed until receipt of said counter force of predetermined value.

Claim 5

The combination set forth in claim 3 wherein said booster actuator spring is preset to greater tension than said first spring of the control valve and less tension than the combined tension of the first and second springs of the control valve.

Claim 6

In a vehicle having a braking fluid pressure source, a pressure fluid reservoir, wheel brake cylinders, a brake pedal and a pressure fluid braking circuit to supply pressure fluid to said wheel cylinders from said source under control of the brake pedal, the combination comprising a power brake control valve means interposed within said pressure fluid braking circuit, said control valve means being operative to initially connect said braking fluid pressure source to said wheel cylinders in response to stepping force applied to the brake pedal, and then to increase the braking fluid pressure supplied to said wheel cylinders with continuing application of force to the brake pedal, said valve means being further operative to shut off communication between said pressure source and said wheel cylinders and to return pressure fluid to the reservoir from said wheel cylinders in response to release of the stepping force on the brake pedal, and a brake booster operatively connected with said control valve means to cause said control valve means to further increase the braking fluid pressure acting on said wheel cylinders in response to increase of force applied to the brake pedal, said booster including actuating means for initiating its pressure boosting operation only upon receipt of a counter force of predetermined amount acting on the brake pedal from said control valve means, said control valve means including a housing having a cylindrical bore extending forwardly and rearwardly, a first port in said housing communicating with said fluid pressure source, a second port in said housing connected with said wheel cylinders, and an exhaust port in said housing, a first piston snugly and reciprocatively engaged in said bore so as to be positioned in the rear portion thereof and provided with a small piston jutting forwardly from the front portion thereof, the forward end of the small piston being biaSed rearwardly by a first spring engaged therebetween and the inner surface of the forward wall of said housing, the rear end of the small piston being operatively connected with a push-rod urged forwardly by the brake pedal, a second piston snugly and reciprocatively engaged in said bore and having the small piston of said first piston pass through an opening in the central portion thereof, a piston valve snugly and reciprocatively engaged in said cylinder and having the forward portion of the small piston of said first piston pass reciprocatively through an opening in the central portion thereof, a second spring interposed between said second piston and said piston valve so as to bias said second piston normally toward the rear portion of said bore and said piston valve normally toward the front portion of said bore, a passageway in said housing providing constant communication between a first chamber formed in the bore between said second piston and said piston valve and a second chamber formed in the bore in front of said piston valve, and said first chamber being connected with said exhaust port, said actuating means in said booster being so connected to said first piston and said brake rod that when the first piston is urged forwardly said piston valve opens said first port to connect said fluid pressure source to the wheel cylinders through said first chamber and said second port, and when said first piston is in its normal position said piston valve closes said first port, and said booster being operative to urge said first piston further forwardly only when a counterforce of predetermined value is generated by fluid pressure in one of said chambers acting rearwardly against said first piston and said booster actuating means.

Claim 7

In a vehicle having a braking fluid pressure source, a pressure fluid reservoir, wheel brake cylinders, a brake pedal and a pressure fluid braking circuit to supply pressure fluid to said wheel cylinders from said source under control of the brake pedal, the combination comprising a power brake control valve means interposed within said pressure fluid braking circuit, said control valve means being operative to initially connect said braking fluid pressure source to said wheel cylinders in response to stepping force applied to the brake pedal, and then to increase the braking fluid pressure supplied to said wheel cylinders with continuing application of force to the brake pedal, said valve means being further operative to shut off communication between said pressure source and said wheel cylinders and to return pressure fluid to the reservoir from said wheel cylinders in response to release of the stepping force on the brake pedal, and a brake booster operatively connected with said control valve means to cause said control valve means to further increase the braking fluid pressure acting on said wheel cylinders in response to increase of force applied to the brake pedal, said booster including actuating means for initiating its pressure boosting operation only upon receipt of a counter force of predetermined amount acting on the brake pedal from said control valve means, said control valve means including a housing having a cylindrical bore extending forwardly and rearwardly, a first port in said housing communicating with said fluid pressure source, a second port in said housing connected with said wheel cylinders, and an exhaust port in said housing, a first piston snugly and reciprocatively engaged in said bore so as to be positioned in the rear portion thereof and provided with a small piston jutting forwardly from the front portion thereof, the forward end of the small piston being biaSed rearwardly by a first spring engaged therebetween and the inner surface of the forward wall of said housing, the rear end of the small piston being operatively connected with a push-rod urged forwardly by the brake pedal, a second piston snugly and reciprocatively engaged in said bore and having the small piston of said first piston pass through an opening in the central portion thereof, a piston valve snugly and reciprocatively engaged in said cylinder and having the forward portion of the small piston of said first piston pass reciprocatively through an opening in the central portion thereof, a second spring interposed between said second piston and said piston valve so as to bias said second piston normally toward the rear portion of said bore and said piston valve normally toward the front portion of said bore, a passageway in said housing providing constant communication between a first chamber formed in the bore between said second piston and said piston valve and a second chamber formed in the bore in front of said piston valve, and said first chamber being connected with said exhaust port, said actuating means in said booster being so connected to said first piston and said brake rod that when the first piston is urged forwardly said piston valve opens said first port to connect said fluid pressure source to the wheel cylinders through said first chamber and said second port, and when said first piston is in its normal position said piston valve closes said first port, and said booster being operative to urge said first piston further forwardly only when a counterforce of predetermined value is generated by fluid pressure in one of said chambers acting rearwardly against said first piston and said booster actuating means.

Claim 8

The combination as set forth in claim 5, wherein said brake booster is preset to initiate its operating to urge said first piston further forwardly when a counter force of predetermined value produced by fluid pressure acting in said first and second chambers acts on said first piston and booster actuating means.

Claim 9

The combination as set forth in claim 5, wherein said brake booster is preset to initiate its operation to urge said first piston further forwardly when a counter force of predetermined value produced by fluid pressure acting in said second chamber acts on said first piston and booster actuating means.

Claim 10

The combination as set forth in claim 5, wherein an accumulator is interposed in said pressure fluid braking circuit between said pressure fluid source and said control valve means.

Claim 11

The combination as set forth in claim 5, wherein said brake booster is a vacuum booster connected to the suction manifold of a combustion engine of the vehicle.

Claim 12

The combination as set forth in claim 9 wherein said brake booster comprises a housing attached to the rear end of said valve control means housing, said booster housing being divided into two evacuated chambers by a diaphragm, said diaphragm having a rod forming part of said booster actuator means and extending axially of the cylindrical bore of the valve control means housing and projecting from the booster housing into contact with said first piston of the valve control means, the rear end of said booster housing having an air inlet controlled by a valve member, and a spring forming part of said booster actuator means normally urging said valve member to closed position, said spring being overcome by said counter force of predetermined value acting rearwardly against said first piston to open said valve member and permit entry of air into one of said booster chambers, whereby to move said diaphragm and connected rod valve to increase the pressure of fluid in said control valve means.

Claim 13

The combination set forth in claim 10 wherein said diaphragm is supported by a drive piston connected to said rod, a transmission member slidably engaging said rod at one end and coupling with said brake pedal rod at the other end, said booster actuator spring being disposed to urge the transmission member rearwardly with respect to said drive piston so as to engage said valve member and hold it closed until receipt of said counter force of predetermined value.

Claim 14

The combination set forth in claim 11 wherein said booster actuator spring is preset to greater tension than said first spring of the control valve means and less tension than the combined tension of the first and second springs of the valve means.