Patent GB-611918-A (GB)
Title: Control systems for vehicle brakes
IPC: B60T8/32
Filed: 1945-11-23
Abstract: 611,918. Fluid-pressure brakes. TECALEMIT. Nov. 23, 1945, No. 31715. Convention date, June 30, 1944. [Class 103 (i)] [Also in Group XIX] In a control system for vehicle brakes, each wheel of a pair of running wheels of the vehicle is associated with a shaft in such manner that when the wheels are running at the same speed the shafts rotate at different speeds, the wheels being unequally loaded, and a clutch is provided between the shafts so that they may be coupled together to cause slipping of the more lightlyloaded wheel, the shaft of this wheel being associated with means adapted to produce a control force dependent on the resistance to slipping of the wheel, whereby the degree of braking may be controlled in accordance with the adherence between the wheel and the rail. As shown, a pair of wheels 10, 101 are mounted on axles 1, 2 carrying helical gears 3, 4 meshing with pinions 5, 5<SP>1</SP> keyed to shafts 7, 7<SP>1</SP> which may be coupled together by a dog clutch 9, 91. The loading of the wheels and the ratio of the gearing are such that the wheel 10 is driven at increased speed by the wheel 10<SP>1</SP> and slips on the rail when the clutch is engaged, The pinion 5 is slidable on the shaft 7 and carries a stop 12 adapted to engage a plate 13 connected to a spring-loaded piston 14 in a cylinder 15. The shaft 7<SP>1</SP> is slidable in the pinion 51 and is connected to a piston 29 in a cylinder 28 which is urged to the left by a spring 30. The apparatus is used in conjunction with means for regulating the degree of braking in accordance with variations of the coefficient of friction with speed in an automatic compressed air brake comprising a main reservoir R, driver's valve 52 and triple valves 501, 50<SP>2</SP>, 50<SP>3</SP> operated by reduction in pressure in a pipe 40. A governor 45, driven by a vehicle axle, controls the position of the slidable pivot 53 of a sector 42 having a cam surface 42<SP>1</SP>, designed to correct for variation of the coefficient of friction with speed, on which rocks a beam 41 coupled to pistons 35-38 in cylinders 31-34 and to a slide valve 48 arranged to open and close an exhaust port 49 and a connection between the pipe 40 and a pipe 39 connected to the reservoir R and the right-hand end of the cylinder 15. Cylinder 34 is connected to the pipe 40, cylinders 32 and 33 to the pipe 39, and cylinder 31 to a pipe 25 connected to the cylinders 28 and 15. The pressure in the pipe 25 acts on a spring- loaded piston 23 controlling a slide valve 22 arranged to open and close a pipe 21, connecting the cylinder 15 with the driver's valve, and a pipe 20 connecting a port 18 in the cylinder 15 with the reservoir R. The port 18 together with an exhaust port 19 are opened and closed by a slide valve 16 movable with the piston 14. Operation of the driver's valve produces in the first instance a decrease in pressure in the cylinder 15 and a corresponding decrease in pressure in the pipe 25 and cylinders 28 and 31, this pressure decrease being insufficient to allow the spring 30 to engage the clutch 9, 9<SP>1</SP> and the spring of piston 23 to move the valve 22 to the left to close the pipe 21. The beam 41 then rocks on the sector 42, its point of contact being determined by the position of the pivot 53, and the valve 48 is moved downwardly to cause a decrease in pressure in the pipe 40 and an application of the brake. The exhaust port 49 remains open until the pressure decrease in the pipe 40 is equal to the pressure decrease in the cylinder 31 multiplied by the ratio of the right and left lever arms of the beam 41. Further operation of the driver's valve produces a decrease in pressure sufficient to allow the clutch 9, 9<SP>1</SP> to engage and the valve 22 to close the pipe 21 and open the pipe 20. The wheel 10 is now driven by the wheel 101 and slips on the rail, thus producing a reaction force which causes movement of the pinion 5 to the right to move the piston 14 and slide valve 16. The pressure in cylinder 15 and hence in cylinder 31 and pipe 40 is now governed entirely by the movements of the slide valve as determined by variations in the adhesive conditions of the rail. In a modification (see Group XIX), the movement of the pinion 5 actuates a manometric capsule to effect movement of the pointer of a dial gauge in the driver's compartment, the brakes in this case being controlled manually by observation of the gauge.