938,791. Fork lift trucks. YALE & TOWNE MANUFACTURING CO. Feb. 14, 1962 [March 2, 1961], No. 5618/62. Class 78 (3). The gripping arms 16, 17, Fig. 1, of a lifting truck are movable in unison transversely of the truck as well as in the normal load-engaging manner and to prevent the truck overturning, due to a load being lifted towards the extreme lateral positions of the arms, sensing means are provided which detect lateral movement of the centre point between the arms 16, 17 and operate control and indicating means when a limiting position is reached. The arms 16, 17 are moved by hydraulic rams 26, 27 controlled by the circuit shown in Fig. 10. The sensing means include a cam 33, Figs. 1, 10, which is moved laterally by the arms 16, 17 so that at extreme positions either one or other of ball and check valves 29, 30 are allowed to close by either a rod 36 and pivoted arm 34 or rod 37 and arm 35 as either wheel 68 or 69 runs off the end of the cam 33. When either of valves 29 or 30 are closed further movement of the arms 16, 17 in the same direction is prevented. Movement of the arms 16, 17 is controlled by valves 39, 59, as described in U.S.A. Specification 2,795,346. In one embodiment the cam 33 is moved by rods 86, 93, Figs. 1, 6, which connect the gripping arms with the upper and lower runs of a chain 81, respectively. The chain 81 is supported on sprockets 82, 83 pivoted to a laterally slidable member 78 on which is mounted the cam 33. When the gripping arms move in opposite directions at the same speed the chain 81 merely runs round the sprockets and the cam is not moved. If the arms move in the same direction, or in opposite directions at different speeds, the slidable member 78 and the cam 33 are moved laterally. In a second embodiment, Fig. 11, the chain 81 is replaced by pinions 97 which are interconnected by pinions 98 and the rods 86, 93 are replaced by toothed racks 99, 100 which engage the pinions 97 to move a slider 74 and the cam 33 laterally. Fig. 12 shows a third embodiment in which a lazy-tongs linkage 101 provides the connection between the gripping arms and a slider 74 and the cam 33. In Fig. 13, a lever 106 is supported by cables 112, 114 attached to the gripping arms and to a plate 64. The lever 106 carries mercury switches 109, 110 and is urged downwards by a spring 111. Movement of the arms in opposite directions at the same speed moves the lever 106 up and down. Movement in the same direction tilts the lever, closes one of the mercury switches, and energizes one of solenoids 116, 117 to close one of the ball check valves. In addition one of horns 119, 121 is sounded and one of warning lights 118, 120 is lit. The other embodiments may also incorporate audible and visible signals by using limit switches.