Patent GB-1208448-A (GB)
Title: Improvements in and relating to a tow truck for use in conveyor systems
IPC: B61B10/04
Filed: 1967-11-09
Abstract: 1,208,448. Conveyer systems. MECHANICAL HANDLING SYSTEMS Inc. 9 Nov., 1967 [10 Nov., 1966], No. 50961/67. Heading B7L.  In a tow truck conveyer system wherein a plurality of trucks are moved over a floor by tow pins on the trucks extending downwardly through a main slot in the floor and detachably engaging a main conveyer driving chain and wherein the trucks may be accumulated at a station or pushed by succeeding trucks into spur or transfer slots, each truck 20, Figs. 1 and 3 comprises a body 26 having a substantially vertically movable tow pin 21 movable into and out of engagement with the drive chain 24 in the floor slot 22 and operatively associated with a front accumulation bumper 36 slidable in the body 20, and a rear accumulation bumper 56 slidable in the body 26 and having a lost-motion connection 70, 71, 72, 74 with the front bumper 36, the arrangement being such that when the front bumper 36 engages an obstacle (at an accumulation point) the bumper 36 moves relative to the body 26 to lift the pin 21 from the chain 24 and at the same time moves and/or holds the rear bumper 56 to or in its rearmost position where it can cause the operation of the front bumper of a succeeding truck and thus lift the tow pm of that truck. As shown in Fig. 3, the front accumulation bumper 36 has longitudinal tubes 37 guided by rollers 41, Fig. 1, on the body 26 and is pivotally connected to a two-pin operating cam 45 engageable with rollers 50 on the body 26 and a collar 51 on the pin. The bumper 36 is urged forwardly by a spring 36a. The rear accumulation bumper 56 has longitudinal tubes 57 guided by rollers 60 on the body 26 and pivoted to levers 62 fixed on a cross-tube 63 rotatable in the body 26. The bumper 56 is urged rearwardly by a spring 75 which is weaker than the spring 36a. When the bumper 36 meets an obstruction it is moved rearwardly to lift the pin 21 and apply brakes 92 on rear truck wheels 91 by cams 73 on the tubes 37 engaging rollers 102 on brake mechanism. At the same time rollers 74 at the ends of the cams 73 engage cams 70 on the tube 63 to thereafter prevent rotation of the tube 63 and retain the rear accumulation bumper in its rearmost position. If by any chance a truck front bumper 36 engages a preceding truck which has not engaged an obstacle then the rear bumper 56 of that preceding truck is not locked and can be moved inwardly without moving the front bumper 36 of the succeeding truck inwardly. Thus the succeeding truck is not disconnected from the drive chain 24 and can thereafter push the preceding truck along the main slot or a transfer slot. For this purpose the truck has a shock-absorbing bumper 80 at its front end for engaging a fixed rear bumper 53 on a preceeding truck. By the nature of the lost-motion between the front and rear accumulation bumpers, the front accumulation bumper can according to truck inertia move rearwardly relative to the rear bumper after the latter has been moved to its rearmost position. The front accumulation bumper is lockable in its rearward position by latch means described with reference to Figs. 6 or 12 (not shown). The lost-motion connection between the front and rear accumulation bumpers may be modified as described with reference to Fig. 15 (not shown).