GB1135401A - Improvements in and relating to braking systems - Google Patents

Abstract

1,135,401. Endless conveyers. G. A. BLACK and E. H. HANDS. 14 Jan., 1966 [14 Oct., 1964], No. 41992/66. Heading B8A. [Also in Division F2] The common anchorage pin 3 for a pair of brake shoes 1, 2, which are applied to an external drum surface by a spring unit 7 carried by the shoe 2 and acting on both shoes via lever 8 and link 9, and which are released by hydraulic pressure acting in a cylinder 13, is movable circumferentially by the braking torque, the pin being carried by a bell crank lever 4 pivoted on a support 5 and the consequent pivotal movement of the lever, limited by a stop plate 6, being arranged to operate a valve 16 to bypass fluid to a tank, thereby causing the brake to be applied by the spring unit, when the torque is in one direction, and to retain pressure in the cylinder 13 (provided other valves are also closed), whereby the brake is released, when the torque is in the other direction. As shown applied to a brake for a conveyer belt which is driven by an electric motor via a controllable fluid coupling of the rotary vaned impeller type controllable by a scoop, hydraulic pumps 10 deliver both to the cylinder 13, via a valve 11 arranged to retain pressure at the pump outlet when the cylinder 13 is by-passed, and to a cylinder 14, by way of an electromagnetic reversing valve 28, restrictor 29 and reducing valve 12, the cylinder 14 containing a piston which acts via a lever 21 on the scoop adjusting mechanism of the fluid coupling and on a rod 20 carrying cams 19, 24. The latter control normally open by-pass valve 18 and normally closed by-pass valve 22, respectively, the valve 22 being in series with a further normally open, valve 25 operated together with a still further by-pass valve 23, which is normally closed, by a centrifugal device 26 responsive to the speed of the conveyer. The arrangement is such that, on starting up the conveyer drive by switching on the driving motor, valve 28 is actuated electromagnetically to cause a gradual insertion of the scoop of the drive coupling to take up the drive and, as the torque transmitted to the conveyer increases, the valves 18 and 22 are operated successively, the former closing to allow build up of pressure in cylinder 13 while the latter acts as a safety device, since it normally opens only after valve 25 has been closed by the device 26, whereby if for some reason, e.g. loss of fluid from the couplings, the conveyer has not attained sufficient speed cylinder 13 is again by-passed and the brake re-applied. Valve 23 is opened as a result of overspeeding of the conveyer, together with a switch 27 in the motor circuit, to stop the conveyer in this event. Manual operation of the brake is also provided for by a valve 15. In the modification of Fig. 2 (not shown) cam-operated valves 18 and 22 are omitted and replaced by a modified arrangement in which all the valves, viz. bypass valve (36), speed - dependent valve (37) and overspeed valve (45) with associated switch (46) in the motor circuit, are controlled by a centrifugal device (33), valve (34) being manually operated in conjunction with a switch (35) to start up the conveyer.