GB523917A - Improvements in or relating to brakes for use with tractors and trailers - Google Patents

Abstract

523,917. Vehicle brakes. KNORR-BREMSE AKT.-GES. Jan. 17, 1939, No. 1622. Convention date, Jan. 19, 1938. [Class 103 (i)] Relates to fluid-pressure systems for the simultaneous application of the brakes on tractor and trailer vehicles, of the kind in which the braking effort on the trailer is automatically controlled by the tendency of the latter to overrun or lag behind the tractor so that the decelerations of the two vehicles are equalized. According to the invention, the controlling device or slide for the trailer brake is coupled to the brake pedal lever of the tractor so that when the latter lever is but slightly depressed only the trailer is braked, whilst a larger depression results in both vehicles being braked, and also, when the brake pedal lever is not operated at all, over-running by the trailer has no effect upon the brake system. As shown, the application of the tractor brakes is effected by means of a foot pedal 21 or hand-lever 19, while the trailer brakes are normally held in a released condition, Fig. 1, by admitting compressed air from a reservoir 34 on the tractor to the trailer brake line 35 via passages 30, 31 in a valve housing 1. The valve housing 1 also has an additional port 32 opening. to atmosphere which may be placed in communication with the passage 31 for applying the trailer brakes, or may communicate with a further passage 33 controlled by a valve 38 which closes at a definite reduction in the pressure in the brake line 35 so as to effect a partial application of the trailer brakes. The connections between the passages 30 ... 33 are controlled by a lower slide 17 having passages 23 ... 27, and an upper slide 10, which has an elongated passage 12, and the position of which depends on the position of the trailer relative to the tractor. Springs 22, 13 tend to maintain the slides 17, 10 in the normal or rearward position, Fig. 1. If the brake pedal 21 is operated, the tractor brakes are applied, while the trailer brakes after a partial application, are .released (Fig. 3, not shown), but, as the trailer in this condition tends to overrun the tractor, the brake line 35 is vented to atmosphere via passages 26, 12, 24 as shown in Fig. 4, to a degree determined by the overrun, whereby the trailer is braked to an extent corresponding with the deceleration of the tractor. Movement of the upper slide 10 can produce no application of the brakes, while the slide 17 is in its normal position, Fig. 1, i.e., when the tractor brakes are released. When the hand-lever 19 is operated, both slides 17, 10 are moved to the braking position, Fig. 4, with the springs 22, 13 compressed, and, owing to the provision of a loose connection between the parts 9, 5 of the drawbar, lag of the trailer produces no relief of the braking effort thereon.