Anti-skid control means for air pressure braking systems

Claim 2

A valve mechanism for insertion in a fluid pressure braking system including a source of air under pressure, brake operating means, a control valve controlling the connection of said brake operating means to said air pressure source, driver operated control means for said control valve, and a skid sensing device, said valve mechanism when inserted in such a systEm between said control valve and the brake operating means being controllable by said skid sensing device and controlling the connection of said brake operating means to said control valve and to exhaust, wherein the improvement comprises said valve mechanism comprising: i. a main passage adapted to provide a connection between the control valve and the brake operating means, and including upstream and downstream portions; ii. a first valve interposed between said upstream and downstream passage portions and having first and second positions in which it respectively connects said upstream passage position to said downstream passage portion and separates said passage portions one from the other whilst connecting the downstream passage portion to an exhaust passage; iii. a second valve interposed in said upstream portion of said main passage; iv. means responsive to pressure in the downstream portion of said main passage to operate said second valve to provide a degree of restriction of flow in said main passage decreasing with increase of the pressure in said downstream portion of said main passage; and v. a pilot valve operated by the skid sensing means to control the action of air pressure from the control valve on operating means for said first valve so that said first valve is held by said air pressure in its first position during normal braking and is urged by said air pressure to its second position when a skid is sensed.

Claim 3

A valve mechanism for insertion in a fluid pressure braking system including a source of air under pressure, brake operating means, a driver''s control valve controlling the connection of said brake operating means to said air pressure source, and a skid sensing device, and valve mechanism when inserted in such a system between the driver''s control valve and the brake operating means being controllable by said skid sensing device and controlling the connection of said brake operating means to said driver''s control valve and to exhaust, wherein the improvement comprises said valve mechanism comprising: i. a main passage adapted to provide a connection between the driver''s control valve and the brake operating means, and including upstream and downstream portions; ii. a first valve interposed between said upstream and downstream passage portions and having first and second positions in which it respectively connects said upstream passage portion to said downstream passage portion and separates said passage portions one from the other whilst connecting the downstream passage portion to an exhaust passage; iii. a second valve interposed in said upstream portion of said main passage comprising a profiled member movable to provide a variable degree of restriction of an orifice, the position of said profiled member relative to said orifice being controlled by the resultant pressure on a diaphragm exposed on one side to the input pressure and on the other side to the braking pressure; iv. means responsive to pressure in the downstream portion of said main passage to operate said second valve to provide a degree of restriction of flow in said main passage decreasing with increase of the pressure in said downstream portion of said main passage; v. a pilot valve operated by the skid sensing means to control the action of air pressure from the driver''s control valve on operating means for said first valve so that said first valve is held by said air pressure in its first position during normal braking and is urged by said air pressure to its second position when a skid is sensed; and vi. a restrictor by which the side of a diaphragm exposed to input pressure communicates with the inlet of the valve mechanism so that movement of the diaphragm with a reduction of braking pressure relative to input pressure is damped.

Claim 4

A valve mechanism for insertion in a fluid pressure braking system including a source of air under pressure, brake operating means, a driver''s control valve controlling the connection of said brake operating means to said air pressure source, and a skid sensing device, and valve mechanism when inserted in such a system between the driver''s control valve and the brake operating means being controllable by said skid sensing device and controlling the connection of said brake operating means to said driver''s control valve and to exhaust, wherein the improvement comprises said valve mechanism comprising: i. a main passage adapted to provide a connection between the driver''s control valve and the brake operating means, and including upstream and downstream portions; ii. a first valve interposed between said upstream and downstream passage portions and having first and second positions in which it respectively connects said upstream passage portion to said downstream passage portion and separates said passage portions one from the other whilst connecting the downstream passage portion to an exhaust passage; iii. a second valve interposed in said upstream portion of said main passage comprising a profiled member movable to provide a variable degree of restriction of an orifice, the position of said profiled member relative to said orifice being controlled by the resultant pressure on a diaphragm exposed on one side to the input pressure and on the other side to the braking pressure; iv. means responsive to pressure in the downstream portion of said main passage to operate said second valve to provide a degree of restriction of flow in said main passage decreasing with increase of the pressure in said downstream portion of said main passage; v. a pilot valve operated by the skid sensing means to control the action of air pressure from the driver''s control valve on operating means for said first valve so that said first valve is held by said air pressure in its first position during normal braking and is urged by said air pressure to its second position when a skid is sensed; and vi. a restrictor by which the side of a diaphragm exposed to input pressure communicates with the inlet of the valve mechanism so that movement of the diaphragm with a reduction of braking pressure relative to input pressure is damped.

Claim 5

A valve mechanism according to claim 2, wherein the improvement further comprises said valve mechanism including a fourth valve provided in the exhaust passage from the First valve to control the rate of escape of air from the downstream portion of the main flow passage.

Claim 6

A valve mechanism according to claim 2, wherein the improvement further comprises the bypass being controlled by a second spool valve urged towards a maximum flow restricting position by a spring and in the opposite direction by the braking pressure.

Claim 7

A valve mechanism according to claim 2, wherein the improvement further comprises a second diaphragm provided to assist in controlling the position of the profiled member, the second diaphragm being exposed on one side to the braking pressure and on the other side to atmospheric pressure, the braking pressure acting in the same direction on both diaphragms.

Claim 8

A valve mechanism according to claim 2, wherein the improvement further comprises the fourth valve comprising an outlet chamber connected to the downstream portion of the main flow passage only when the first valve is in its second position, a control chamber constantly connected to the downstream portion of the main flow passage, a flexible diaphragm separating said chambers, and a valve closure member carried by said flexible diaphragm and cooperating with an outlet orifice in said outlet chamber.

Claim 9

A valve mechanism according to claim 6, wherein the improvement further comprises the control chamber being connected to the downstream portion of the main flow passage through a larger orifice controlled by a non-return valve allowing flow of air into the said chamber only, and also through a smaller, constantly open, orifice.

Claim 10

A valve mechanism according to claim 2, wherein the improvement further comprises the first valve comprising a diaphragm assembly consisting of two flexible diaphragms connected at their centres by a rod and each dividing one of two cavities into two chambers, the rod extending through a bore connecting the chambers on the sides of the diaphragms facing each other and valve seats being provided one at each end of the bore which are selectively engaged to close the corresponding ends of the bore by displacement of the diaphragm assembly in one direction or the other, the said bore being connected to the downstream portion of the main flow passage, the chambers connected by the bore being respectively connected to the driver''s control valve through the second valve and to exhaust, the chamber on the outer side of the diaphragm and the chamber on the inner side thereof, which is connected to the driver''s control valve being connected by an opening in that diaphragm and the chamber on the outer side of the other diaphragm being connected to the pilot valve.