Patent GB-520127-A (GB)
Title: Improvements in or relating to servo-braking for motor vehicles
IPC: B60T11/10
Filed: 1938-08-02
Abstract: 520,127. Controlling motor vehicles. VAU, J. B. P. Aug. 2, 1938, No. 22783. [Class 79 (v)] [Also in Group XXXIV] In a combined power and brake control for motor vehicles in which a spring-urged pedal when released first cuts-off the engine supply and then applies a power-operated brake a part 13 must be engaged by the driver's heel to permit operation of the brake. The brake may also be applied directly and by the power by the usual pedal 40. Upon removal of the heel it is necessary to depress the pedal to unlock it for brake operation. The brake is of the kind in which a pedal 7 controls the motor vehicle throttle 9 in one part of its range II-III and when released by the foot a spring 1 forces it through the range II-I wherein the brake is applied by a cylinder 2 and valve 4. The heelpiece 13 is connected to a bell-crank 15 having an extension 21 which on release of the heelpiece is forced by a spring 20 to engage with a projection 22 on the pedal 7 which it retains out of the braking range. When the heel-piece is released a spring latch 25 is moved by the crank 15 and also engages the projection 22 which it holds if the heel-piece is again depressed by the foot and until the pedal 7 is again depressed. The latch comprises a pawl 29 pivoted on a member 25 pivoted at 24 on a fixed bracket and limited in movement by a pin and slot 27. The latch may be put out of action by a control on the dashboard. There is interposed in the transmission between the brake cylinder 2 and the brake 1 a member 45 carrying a lever 46 connected to the brake control valve 4 and to a spring 47 and the brake pedal 40 carries a stud 44 adapted to engage the lever 46 and thus apply the brake directly and by'power when the pedal 40 is depressed, the force applied directly being proportional to that applied by power. The heel-piece may be connected with crank 15 by a pin and slot and the pin be adapted to slide down an inclined member and engage a notch in order to relieve the driver's foot of most of the pressure of the return spring. In a modification Fig. 5 (not shown), the pedal 7 is pivoted and not sliding and 'the lever 46 instead of operating the valve 4 directly moves a carrier 'carrying the latch 25, 29 which it moves with the extension 21 away from the projection 22 a distance corresponding to the depression of the pedal 40 so that the brake is applied by the spring-urged pedal 7 and to an extent dependent upon the pressure on the pedal 40. The transmission between the pedal 7 and the devices 4, 9, in this case is of the type described in Specification 502,726. The plate 13 may instead actuate a valve to inhibit brake operation by the pedal 7. In a further modification, Figs. 9, 11, the arm 75 of the pedal 7b is pivoted at 78, is urged upwardly by spring 81 and is connected to the throttle bv a link and crank arm 91 and spindle 93 and to the brake valve 4 by similar connections. In the position of the parts shown in Fig. 9, the pedal 7b is free to move to apply the brake. Removal of the heel from the plate 13b closes the switch 133 and a switch 106 and the ignition switch 143 being also closed, magnet 121 is energized to operate valve 122 thereby closing the chamber of piston 111 to atmosphere and connecting it to suction by pipe 119. The piston thus rises moving the pawl 97 by projection 113 into the path of a projection 89 on the pedal arm 87 which is thus locked against movement in a direction to apply the brake. In this position of the pawl 97 it opens the switch 106 by the plunger 108, so that magnet 121 is again de-energized and the piston 111 returned by the spring 115. Subsequent depression of the pedal and plate effects the unlocking of the pedal as in Fig. 9 the pawl being operated by the plunger 103. The switch 106 is closed but if the plate 13b has been previously depressed, the circuit of magnet 121 is not closed. A press-button 150 on the change-gear lever 151 may also be used to close the circuit and the piston rod 110 may alternatively be operated from the dashboard through a shaft 153 and fork 152. In a further construction, Fig. 15 (not shown), the rod 110 is directly operated by an electromagnet.