Patent GB-1272590-A (GB)
Title: Brake control systems
Inventor: MORRIS EDWARD HOLLINGWORTH
IPC: F16D65/28
Filed: 1968-09-07
Abstract: 1,272,590. Fluid pressure control of disc brakes and band brakes; positive detents; stopping at definite positions. DOWTY ROTOL Ltd. 28 Aug., 1969 [7 Sept., 1968 (2)], Nos. 42687/68 and 42688/68. Headings F2E and F2F. [Also in Divisions F1 and G3] A brake control system, Fig. 1, for a rotor, e.g. shaft 14, Figs. 1 and 2, comprises adjustable speed governor means 24, 25, 27-29, 31, Fig. 1, a friction brake 41 to 43 operative on the rotor and under the control of the speed governor means, and cam or like means 32 driven by the rotor 14 and operable, when it is required to stop the rotor 14, to adjust the speed governor means from a high speed setting to a low speed setting within a short period of time, during which the governor means effects application of the friction brake, to cause rapid deceleration of the rotor. As described, a jack, drivable by shaft 14 through gears 50, and whose screw-threaded member is shown at S, Fig. 2, is in the retracted position; the jack is connected to a controlled member 46, Fig. 1, shown correspondingly retracted. To extend the jack, hand lever 21, Fig. 1, is pivoted counterclockwise. This sets a circuit to open valve 8 admitting compressed air through passage 6 to inlet volute 4 of radially-inward-flow bleed-air turbine 1 having exhaust passage 5. Impeller shaft 9 is thereby rotated, and is available to drive power output shaft 14 through an epicyclic reduction gear 11. Lever 21 has shifted a selector valve 19, whereby air now supplied from passage 6 through 52 and unit 49 passes along pipe 17 to the cylinder 15 of a spring-operated brake band to disengage the brake band from cage gear 13. The driving of shaft 14 thereby permitted is in the direction to effect extension of the jack. Unit 49 has raised bolt 48 from recess 47 on member 46, permitting member 46 to move to the right and close switch 57. Shaft 14 is associated with a disc brake comprising a disc 42 secured to it, pads 43, and cylinders 41 to which liquid may be supplied through one or both of pipes 38, 73. Impeller shaft 9 drives, through bevel gears 23, a governor shaft 24 connected to a governor valve sleeve 25 in a fixed casing having ports 36, 37; gears 23 also drive a gear pump 26 connected at certain places to the casing and to an hydraulic reservoir. Output shaft 14 drives, through bevel gears 33 and worm gear 34, a cam 32 which acts on a cam follower 31 to vary the compression applied by springs 28 and 29 to a flyweight assembly 27 connected to sleeve 25. Gear 34 provides for rotation of cam 32 through 270 degrees during rotation of shaft 14 through the predetermined number of revolutions necessary to extend the jack fully. The flyweight assembly and springs 28, 29, together determine the position of a piston valve 35 vertically in sleeve 25, the valve in turn controlling hydraulic pressure in pipe 44 connecting port 37 with the control mechanism of a butterfly valve 7 in passage 6 and also hydraulic pressure in pipe 38 connecting port 36 with disc brake 41-43. Cam 32 is shaped to provide the following sequence of phases. In the first phase, pressure in pipe 44 (initially high and thereby closing butterfly valve 7) is progressively reduced to permit shaft 9 to accelerate. No pressure is present in pipe 38, so brake 41-43 is off. In the second phase the cam follower is in contact with large-constant-radius portion 93 of cam 32, so the speed of shaft 9 is at a maximum and remains so for nearly 180 degrees rotation of the cam. In the third phase the turbine 1 is decelerating; high pressure is present at ports 37 and 36, to close butterfly valve 7 and apply the brake, respectively. A nut 64, Fig. 2, prevented from rotating but travelling along a screw-threaded rod 58 driven by shaft 14, is approaching an abutment 61 rotating with rod 58. Just before the end of its travel, the nut 64 touches and turns clockwise a lever 71 which acts on a piston - and-cylinder unit 67 to supply additional hydraulic pressure through pipe 73 to the disc brake 41-43. When nut 64 reaches abutment 61 it positively stops rotation of shaft 14 by engaging projection 63, and opens limit switch 76, causing closure of valve 8. Bolt 48, Fig. 1, is in raised position, now resting on member 46, and switch 57 is closed.  To retract the jack, hand lever 21 is restored to the Fig. 1 position, whereupon a circuit is completed to open valve 8, and compressed air passes via 52 and 49 and pipe 18 to the cylinder 16 of another spring-operated brake band to disengage the band from its cage gear 12. Though impeller shaft 9 begins to rotate in the same sense as before, shaft 14 is this time rotated in the sense opposite to that appropriate to the previous sequence, so the jack (and member 46) is progressively retracted; cam 32 is rotated in the opposite direction. When the jack, and member 46, are in fully retracted position, recess 47 has reached bolt 48, so switch 57 opens, cutting off supply to valve 8, which thereupon closes. At any time during one sequence (jack retraction or extension), lever 21 may be moved over, whereupon the direction of movement of the jack is immediately reversed. The control system enables a device such as a jet engine thrust reverser to be operative very quickly and as repetitively as necessary.