Patent GB-648307-A (GB)
Title: Improvements in and relating to brake-applying devices for vehicles
IPC: B60T8/26
Filed: 1947-03-13
Abstract: 648,307. Aircraft wheel brakes. HELLER, B. March 13, 1947, No. 7058. Convention date, March 13, 1946. [Class 4] [Also in Groups XXIX and XXXIV] Means for varying the rates of the pressures applied to two brakes or sets of brakes of a vehicle, comprising a distribution member adjustable to vary the length of the arms of two levers by which it transmits the pressure to the two sets of brakes is shown as automatically acting to vary the distribution of the pressure applied to front and rear brakes to correspond with the load displacement due to the retardation, by means of a longitudinally movable pendulum or inertia device. The invention may be used with aeroplanes and with brakes on the same axle in which case an inertia device arranged to swing transversely of the vehicle may effect the control. As shown, levers 24, 26 pivoted at 28 and each having a cranked arm 27 connected respectively to the pistons 32, 34 of master cylinders which operate the front and rear brakes of a motor vehicle are engaged by a lever 23 pivoted at its middle point by a pin 22 in the forked end of a member 21 to which is fixed a rod 16 connected by a ball-and-socket joint 15 to the pedal lever 9. The member 16, 21 is rotatable about its vertical axis in a bearing 46 connected by a link 49 to a pedal lever 50 which is normally locked in position. The lever 23 may thus be turned about the axis of the member 16, 21 to vary the length of one arm of each of the levers 24, 26 and thus the ratio of the pressures applied by the pedal to the pistons 32, 34 and thus to the front and rear brakes. This adjustment of the lever 23 is effected by a mass 97 suspended from a bracket 98 and which may act directly on the lever or through a servomotor. As shown, the piston 63 of a vacuum servomotor S is connected by rod 62, cranked lever 57, 59 and link 56 to an arm 19 on the member 21. The control valve comprises a tubular member 68 slidable in a fixed casing and forming therewith chambers 70, 72 connected respectively by pipe 87 to the engine suction pipe and by a port 85, a pipe 86 and port 84 to the interior of the cylinder 65. A member 75 is slidable in the member 68 and a rod 82 slidable in member 75 is connected by a link 96 to the mass 97. Normally, the cylinder 65 is open to atmosphere through ports 84, 85, chamber 72, radial passages 74, 80, passage 79 in member 75 and an air filter 91. Retardation of the vehicle upon an application of the brakes causes forward movement of the mass 97 and thus of the rod 82 first to close the passage 79 and then to move the member 75 to connect radial passages 71, 73 through an annular chamber 76 whereby the cylinder 65 is connected to the vacuum source through the chambers 72, 70 and pipe 87. The piston 63 is thus moved to the right to turn the lever 23 to a position such as shown in broken lines, whereby the ratio of the pressure applied to the front brakes to that applied to the rear brakes is increased. Movement of the piston 63 effects movement of the valve member 68 through racks 62a, 69 and pinion 90, so that when the relative movement of the mass 97 ceases the passages 73 are again blanked to cut off the cylinder 65 from the vacuum source. When the pressure applied to the pedal lever 9 is reduced, the mass 97 moves back causing the rod 82 to re-open the passage 79 to admit air to the cylinder 65 and movement of the piston 63 to retain the lever 23 towards the normal position.. Movement of the piston 63 also moves back the valve member 68 and with it the member 75 so that the passage 79 is re-closed upon cessation of the relative movement of the mass 97. A spring may be disposed between the adjacent ends of the members 68, 75 to ensure the return movement of the member 75. When the vehicle is travelling on a down gradient, the mass 97 is moved forward by gravity action and thus alters the brake pressure ratio to correspond substantially to the displacement of the load due to the gradient. Adjustment of the angular position of the lever 23 to correspond with the change in the ratio of the load on the front and rear wheels which takes place when the loading of the vehicle is varied, may bo effected by so forming the lever 57, 59 that the angle between the arms thereof can be varied by a manual setting device. The effective length of the link 56 may also be adjustable to vary the position of the lever 23. The effective length of the lever arms 24, 26 may be simultaneously reduced or increased by operating the lever 50 by the pedal 53 which is pivoted to the lever at 52 and carries a locking pawl for engagement with a fixed rack 5. The ratio of the pressure applied to the brakes at the two sides of a vehicle may similarly be adjusted to correspond with the displacement of the load caused by travelling in a curved path by a mass arranged to swing in a direction transverse to the direction of travel.