Patent GB-491849-A (GB)
Title: Improvements in pneumatic braking devices
IPC: B60T8/32
Filed: 1937-03-08
Abstract: 491,849. Fluid-pressure brakes ; locking rods. HOUPLAIN, G. E. March 8, 1937, Nos. 6842 and 6843. Convention dates, March 7, 1936 and July 6, 1936. [Class 103 (i)] [Also in Group XXIV] A pneumatic braking device for rail vehicles &c., e.g. as described in Specification 426,720, comprises a centrifugal governor for regulating the braking force, said governor being adapted to actuate means for controlling an inlet and an outlet valve of a control device in such manner as to close the inlet valve for the entire period of braking from the moment the wheel speed drops, characterized in that the means for allowing the inlet valve to close and for controlling the outlet valve comprises a rod carrying a piston on one face of which the compressed air in the braking cylinder is arranged to act so as to tend to move the rod in a direction opposite to that in which it is tended to be moved by the centrifugal governor. The control device, adapted to be mounted on the auxiliary cylinder of a two-cylinder braking device, comprises a valve body 1 having a connection 2 to the compressed-air supply, and passages 3, 31 to the auxiliary braking cylinder. A valve 4 loaded by a spring 6 is adapted to be held open by a rod 7 actuated by a rod 8 on the brake cylinder piston. Transverse to the rod 7 and passing through a slot therein is a rod 9 connected at 10 to a centrifugal governor and loaded by a spring 11, the rod carrying a part 14 connected with lost motion to a release valve 16. The rod 9 carries also a piston 18 which is always subject to the pressure of the air in the brake cylinder. When the vehicle is in motion and the brakes are off, the valve 4 is held open by rod 7 and. locked by rod 9. When the brakes are applied air is sent to the brake cylinder and the wheel speed falls, the rod 9 moves to the right and unlocks the valve 4 which closes. If the wheels tend to lock, rod 9 moves further to the right and opens the release valve 16. When the wheel speed rises, the rod 9 moves to the left and allows valve 16 to close. The governor action is modified by the air pressure on the piston 18, the provision of which ensures a progressive braking to be obtained without locking of the wheels owing to the fact that as soon as the wheels slow up, due to braking, the centrifugal force decreases and the air pressure acting on piston 18 moves the rod 9 towards the right and allows valve 4 to close, any further decrease of speed causing the valve 16 to open. In a modification, Fig. 4, a single control device for a number of brake cylinders is shown. A casing 21 is divided by a partition 22 into chambers 23, 24 the chamber 23 communicating at 25 with the compressed-air supply and the chamber 24 at 26 with the pipe leading to the brake cylinders, the chambers being separated by a valve 27 loaded by a spring 28 and adapted to be held open by a rod 29 actuated by a flexible diaphragm 30 on the other face of which acts a rod 31 loaded by an adjustable spring 32 to produce a force equal to that of the air pressure at the slippage limit. The rod 29 is adapted to be locked by a part 35 engaging a shoulder 34. The part 35 is connected to a control rod 36 carrying a piston 37 and a sleeve 39 adapted to be actuated by the governor weights 41. The part 35 also actuates a release valve 46 loaded by a spring 47. With the vehicle at rest and brakes off, the valve 27 is open and the rod 36 in its right-hand position. As the vehicle starts, the rod 36 is moved to the left and locks the valve 27. If the brakes are applied, the air pressure moves rod 36 to the right and unlocks the rod 29, but if the braking is moderate the valve 27 remains open. If, however, the braking is violent, the excessive air pressure raises diaphragm 30 and rod 29 and the valve 27 closes. A tendency of the wheels to look will displace the rod 36 to the right to open the release valve 46. To render the device for releasing the rod 29 more sensitive and quicker acting, the part 35 is coupled to the rod 36 by a wedging device comprising a conical part 48 with balls 49 in contact with the rod 36 and with a conical bore 50 on the end of the part 35. On movement of rod 36 to the left the balls are released, and when the rod reaches its extreme right-hand position, the balls are also released by a projection 51 striking a stop 52.