GB1265078A - - Google Patents

Abstract

1,265,078. Trailer over-run brakes; internal shoe drum brakes; one-way acting; hand-lever and linkage. S. H. V. FORSBERG. 2 July, 1969 [4 July, 1968], No. 33396/69. Heading F2E. The trailer is provided with internal shoe drum brakes which are automatically applied when the trailer tends to over-run, but not appreciably when it is being reversed. Preferably the brakes may also be applied by hand when the trailer is moving in either direction for parking. As shown, the eccentric 8, lever arm 9 and steel wire 10 are common to all Figures. During normal running (Fig. 3, not shown), the draft vehicle coupling member 22 pulling on thrust rod 20 forces stop 24 against trailer part 26, eccentric 8 is horizontal, and the brakes are off. On over-running, the thrust rod 20 moves backwards relative to trailer part 26 to the position shown in Fig. 4 and applies the brake via lever 19; Fig. 1 shows the same angular orientations of eccentric 8 and lever arm 9. In Fig. 1, each brake member 5 has pins 14 engaged in slots 15, 16, in a supporting member 4 pivoted at the end remote from the eccentric 8. The supporting members 4 may be hinged to each other instead of pivoting on the backing plate. The brake member 5 is normally retained in its outermost and rightward position by a tension spring 17, and it also occupies this position during braking in the forward direction, as shown in Figs. 1 and 4. A pivoted hand lever 23, Fig. 4, may be provided, quite separate from the thrust rod 20, to act on lever 19 and keep it in the Fig. 4 position after forward braking, irrespective of the position of the thrust rod 20 (Fig. 5, not shown); the same brake of Fig. 1 thus also serves as a parking brake. When the draft vehicle and trailer are being reversed, thrust rod 20 is moved so far rearwardly that front stop 25 engages part 26 and eccentric 8 is thereby rotated through a greater angle than that shown in Fig. 4: this is the position of Fig. 2 (and Fig. 6, not shown). When the brake lining 13 of brake member 5 has first engaged the drum, the friction thereby engendered moves member 5 slightly relative to supporting member 4 in the direction of rotation (backward) of the drum (against the action of spring 17), and inwards. At least slot 16 further from the pivot 6 (and preferably slot 15 as well) is inclined at an angle to the diameter passing through it, so eccentric 8 can move the supporting member 4 towards the periphery of the drum without actuating brake member 5 with great force. The angle of turn of eccentric 8 is limited because of the engagement of stop 25 with part 26, so the left-hand ends of slots 15, 16 do not make contact with pins 14, and in all these circumstances, no significant braking occurs, so reversing may proceed unimpeded. When reversing is complete, hand lever 23 may be used to turn eccentric 8 even more than as shown in Fig. 2 (Fig. 7, not shown), whereupon the left-hand ends of slots 15, 16 make contact with pins 14, and thereafter the degree of braking depends upon the force applied to lever 23. As soon as the brake mechanism is disengaged after reversing, spring 17 returns brake member 5 to its front position relative to supporting member 4, Fig. 1. When only slot 16 is inclined to the diameter, movement inwards of brake member 5 in the Fig. 2 situation occurs at the end nearer eccentric 8.