GB1249315A - Improvements in or relating to couplings for brake systems - Google Patents

Abstract

1,249,315. Fluid-pressure trailer-brake operation; safety device. GIRLING Ltd. 29 Jan., 1969 [1 Feb., 1968; 18 July, 1968], Nos. 61262/68 and 34184/68. Divided out of 1,249,312. Heading F2F. An hydraulic brake system includes a twinline coupling between a tractor vehicle and a trailer vehicle; at least the trailer-mounted coupling heads are each provided with a closure member adapted to seal the head when it becomes detached from its mating tractormounted coupling head; the trailer vehicle is fitted with hydraulic brake actuators and with an accumulator adapted to store hydraulic fluid under pressure; and a safety device, associated with the twin-line coupling, cpmprises a valve closure member with which a member on the tractor vehicle co-operates for interconnecting the accumulator and brake lines on the trailer vehicle in the event of trailer breakaway. As shown in Fig. 1, the trailer braking system includes a twin-line quick-release self-sealing breakaway coupling 25 comprising coupling heads 27, 29 fitted to the housing 11 of the safety valve arrangement 10 on the trailer and coupling heads 46 and 65 fitted in a block 21 secured to the tractor vehicle. Assuming a pin 43 to be absent, on trailer breakaway, coupling heads 27 and 29 separate from coupling heads 46 and 65, respectively, whereupon a valve in each of the four heads automatically closes to shut off the relative pipeline. At the same time, block 21 and the upper end 42 of a valve closure member 22 separate, enabling a spring 36 to withdraw the valve closure member, thereby providing communication between a passage 19 leading from the accumulator line 26 and a passage 19a leading to the brake line 28. The trailer brakes are thereby automatically applied. For normal unhitching of the trailer the pin 43 is inserted, so that when the trailer is unhitched the valves in the coupling heads close automatically as before, but the valve closure member 22 is prevented by the pin 43 from unseating, so the trailer brakes are not applied. Preferably pin 43 is secured by a chain to housing 11. In a second embodiment (Fig. 4, not shown), the upper end of the valve closure member 22 is in two parts including a coaxial cushioning spring, and the pin for preventing automatic brake-application during normal unhitching is here provided in a transverse bore through an extension of valve member 22 beyond the other end of housing 11, and co-operates with a washer and a stronger spring than spring 36 to hold the valve closed when it is inserted. In Fig. 7, the safety valve arrangement 58, 59, is held closed by a spring-loaded ball (not shown), which co-operates with a detent groove 85 in valve stem 82. A shear pin 91 attached to tractor vehicle block 121 co-operates with a further groove 92 and is normally left in. In the event of trailer breakaway, the coupling heads become detached while shear pin 91 pulls on stem 82, the spring-loaded ball thereby being forced out of groove 85, and the valve 58, 59, opening in consequence. On detachment of trailer from tractor vehicle the pin 91 shears. For normal unhitching, pin 91 is withdrawn, so the spring-loaded ball keeps the valve closed. The trailer brakes may be applied by pulling on stem 82 to unseat the ball. Fig. 10 differs from Fig. 7 mainly in the safety valve arrangement, which here includes spring- loaded balls 111 co-operating with a conical surface 114 on valve stem 106 for valve opening.