GB1023861A - Improvements in and relating to brakes for vehicles - Google Patents

Abstract

1,023,861. Compressed air brakes. OERLIKON-BUHRLE HOLDING A.G. Jan. 14, 1963 [Jan. 22, 1962], No. 1603/63. Heading F2F. A speed-responsive change-over device for rail vehicle brakes, the device comprising a tachometric generator 48, the voltage from which actuates, through an adjustable attenuator, an electromagnetioally controlled brake booster valve 35, two outputs from the attenuator being variable independently of each other. The valve circuit is subjected to one or other of the attenuator outputs by a switching member which is operated simultaneously with the actuation of the valve 35. In the construction shown, a triple valve 8 functions under the influence of the pressures in the brake pipe 6 and reservoir 9, the triple valve controlling the pressure in a chamber 11 of a relay valve 12. A chamber 23 of the relay valve is connected through a spring-loaded brake valve 22 to an auxiliary reservoir 14, to the brake cylinder 25, to a switch 28, through valve stem 21 to atmosphere at 29 and through valve 35 to a third relay valve chamber 32. The attenuator comprises either two resistors each variably tapped (Fig. 2, not shown) on one resistor variably tapped at two points (Fig. 3, not shown), the outputs being calibrated, as on scale 59, to correspond with the speeds at which the valve 35 is to be energized and de-energized respectively. The output of the tachometer may be alternating or direct, in the former case the output being rectified before the attenuating part of the circuit. When the brake is applied through the pressurization of chamber 11 and the subsequent closing and opening of valve stem 21 and valve 22, switch 28 is closed. With the speed below that required for booster braking relay, valve 12 moves into the selflapping position. If, however, the speed is above that predetermined, a relay 64 (Fig. 2, not shown) is triggered from one output of the attenuator to actuate the valve 35 which cuts off the brake cylinder from chamber 32 and a flexible diaphragm 19, these latter being vented to air through the valve at 41. Thus the pressure in chamber 11, that is against diaphragm 18, becomes dominent again as the brake cylinder pressure is acting on a small area diaphragm 20, the brake valve 22 being opened again. The speed at which the boosting is discontinued is governed by the second output of the attenuator which is switched into circuit also by relay 64.