Patent GB-319611-A (GB)
Title: Improvements relating to track braking apparatus for railways and the like
IPC: B61K7/08
Filed: 1929-08-09
Abstract: 319,611. Westinghouse Brake & Saxby Signal Co., Ltd., (Assignees of Bone, H. L.). Sept. 24, 1928, [Convention date]. Arresting-grips or frictional apparatus on permanent way; force-transmitting mechanism; fluid-pressure.-The brake bars of track braking- apparatus are moved into operative position by a fluid-pressure motor the stroke of which is manually controlled. The stroke of the brakeoperating piston 19 is determined by a second piston 20 forming an adjustable stop, both pistons being operated by electrically-controlled fluid pressure. The operating piston is connected to the brake-bars by a toggle mechanism which occupies a dead-centre position when the piston has made a full stroke. Before this the brake reaction is cushioned against the pressure in the cylinder. The brake-bars may tilt upwards when applied to the wheels. Fluid-pressure supply to the brake cylinder 18 is controlled by magnet valves P<1> - - K<5>, Fig. 11, connected to a main supply pipe 80 and operated by current from a battery 103, and controlled by a lever 95 and circuit controllers P<1>, P<2>, P<3> operated by the pressure in the cylinder and circuit controllers S<1>, S<2>, S<3> operated by movement of the brake piston. The valve K<3> maintains pressure fluid by pipe 82 in the right-hand end of the cylinder in order to hold the piston 30 to the left so as to limit the stroke of the piston 19 until the manual control lever 95 is in the full brake power position, when a circuit is closed, by means of a contact 102 through the battery 103 and this valve so as to open the pipe 82 to atmosphere. Pressure fluid is maintained between pistons 19, 20 to hold the piston 19 to the left, when the brakes are off. This pressure is maintained through a pipe 81 and flutes in the: piston 20 by the valve K<2> which if the pressure falls is opened due to a circuit completed through the valve by contacts 93, 93a and a Bourdon tube P<1> connected to this part of the cylinder. To apply the brakes lightly the lever 95 is moved to engage a contact 98 which closes circuits through contacts 87, 88 of the controller S<2> and valves K<1>, K<5>. The valve K<1> releases fluid on the right of the piston 19 and the valve K<5> admits pressure to the left of the piston until the circuit controller S<2> bv its connection with the piston-rod is moved to open the contacts 87, 88, and thus break these circuits. But contacts 87, 89 are simultaneously closed to complete these circuits through the contacts 93, 93<a> of a Bourdon tube P<2> unless the pressure exceeds 10 lbs. per square inch, when the Bourdon tube, which is connected to the left end of the cylinder, opens the contacts, and if the pressure exceeds 20 lbs. per square inch closes contacts 93, 93b to complete a circuit through the valve K<4> so as to exhaust the brake cylinder and reduce the pressure the required amount. To apply the brakes powerfully, the lever 95 is moved to contact 99 which brings circuit controllers S<3>, P<3> into operation. By moving the lever 95 to a contact 100 a circuit is completed through the valve K<5> which maintains it open to supply the full fluid pressure. By moving the lever to contact 102 the piston 20 is allowed to move back and the piston 19 moves the toggle mechanism to dead-centre position. Movement of the lever 95 back to engage contacts 96, 97 restores the brake to its ineffective position. Should the valve K<5> leak and the brake piston be moved to "on" position, the resulting engagement of contacts 85, 86 of the controller S<1> closes a circuit for the exhaust valve K<4>, thus releasing the brake. The toggle mechanism comprises a lever 23, Fig. 1, pivoted on a fulcrum arm 25 pivoted at 25a and connected by adjustable links 26, 32 with cranks 27, 33 which operate the brake-bars outside and inside the rails respectively. The cranks are connected by links 28, 30, cranks 29, 31 and links 38 with the driving-bars 4. The brake-bars B, C, B<a>, C<a> rest directly on the driving-bars and are made of a number of sections 6 engaging by tongue and grooves 15, 16 and are flared horizontally and vertically for ease of engagement with the vehicle wheels. The movement parallel to the rails and to the left transmitted by the driving-bars to the brake-bars causes the latter to move towards the rail in view of the mounting of the brake-bars on resilient links G. The driving-bars 4, Fig. 4, engage the brake-bars 6 by driving-lugs 41 engaging in sockets 45 in the brake-bars. Each lug 41 has a projection 43 adapted to engage a lip 49 in the socket 45 and limit vertical movement and also the tilting movement when the brake-bar engages the vehicle wheels. When the brake is operated shoulders 42 on the lugs 41 engage under projections 14 on yokes 12 on which the apparatus is mounted in order to prevent vertical movement. Extensions 17 on the brake-bars and a cover-plate 63 having guide-strips 64, protects the mechanism underneath. Two pairs of stringers 8, 9 are located on either side of each rail and are cross-connected by the yokes 12 extending beneath the rails and having the ends interposed between the stringers to form a cradle to support the apparatus. The links G comprise a bolt 54, Fig. 5, passing through a trunion D pivoted between the stringers 8, 9 and having a coil spring 57 encircling it and compressed between an adjusting sleeve 53 screwed into the trunnion and a head 55 engaging a brake-bar by means of a stud 56. The pressure of the spring is adjusted by a nut 61 screwed on the end of the bolt and the position of the head 55 of the bolt is adjusted by the sleeve 53 which is locked in position by a collar 58 adapted to engage a groove in the sleeve by a rib 59 and held from movement with respect to the bolt by ribs 60 engaging the flattened sides of the bolt. An equalizing unit E, Figs. 1 and 7, which tends to hold the arm 25 in its central position comprises a spring arrangement adjusted to overcome friction in the apparatus and thus prevent unequal movements of the parts of the apparatus. The spring 74 is contained in a casing 64 between members 72, 73 bearing on the end plates of the casing and through holes in which passes a rod 67 connected to the arm 25, Fig. 1. The head 68 of the bolt engages the member 73 and an adjusting sleeve 71 passing through a hole in the end plate and screwed on the rod engages the member 72 so that one or other end is moved to compress the spring according to the direction of movement of the arm 25. The end plate 66 is screwed in the casing so that the spring pressure may be adjusted. The links and cranks of the toggle and transmission mechanism are arranged to give a constant mechanical advantage, in spite of adjustments for wear in the mechanism. All the apparatus is isolated from the rail so that signalling track circuits may be run through it.