Patent GB-570746-A (GB)
Title: Improvements in and relating to motorised lift trucks
IPC: B62B3/06
Filed: 1943-03-11
Abstract: 570,746. Motor trucks. YALE & TOWNE MANUFACTURING CO. March 11, 1943, No. 3997. Convention date, Feb. 18, 1942. [Classes 79 (iii) and 79 (v)] [Also in Groups XXXIV and XXXVII] Comprises a motor truck of the kind having a lifting platform 11 and a steering lever or handle 85 swinging from side-to-side to steer the truck and in a vertical plane to control the drive, characterised in that the truck is driven when the steering lever is in a zone intermediate its upper and lower limits of movement and the drive is stopped or disconnected when the lever is in either of its upper or lower limit positions. In the construction shown the truck is mounted on trailing wheels and a steerable motor forecarriage 71 having an electric motor 44 driving a road wheel 62 through a double train of reducing gear 54, 55 and 59, 60. The forecarriage comprises a main casting 41 and a cover 42 and supports an arm 38 on the truck frame through a radial and thrust bearing 39, 73. Lateral thrusts are absorbed by means of circular surfaces 70 on a part of the forecarriage, these surfaces bearing against the inner surface of a ring 40 secured to a standard 35 of the main frame. The steering lever 85 is fixed to a shaft 87 rotatable on the main frame and is normally kept in a vertical position by means of a compression spring 111 housed in the lever and bearing through a link 101 against a fixed pin 100. The lever shaft 87 carries a cam 89 which, when the lever is either vertical or horizontal is clear of rollers 90 carried by brake levers 91 normally applied by springs 94 to a brake drum 51 on the motor shaft, so that when the lever is released or is held in a horizontal position the brake is applied ; as the lever is moved from either of the limit positions the cam 89 acts on the rollers 90 and releases the brake. The rollers are adjustably carried by screw plugs 96 which can be rotated to adjust the brake. The steering lever controls two sets of switches in series for controlling the speed and direction of the motor drive. One switch comprises contact strips 115, 116, 117 on the lever shaft 87, these strips being adapted to be contacted by fingers 115a, 116a, 117a. The other switch is mounted on the lever handle 125 and comprises three contacts 140c, 141c, 142c adapted to be closed by the depression of pins 140, 141, 142 actuated by cams 140a, 141a, 141c on a shaft 131 rotated by a twist grip 126 carried by the handle 125. A spring 132 normally returns the grip 126 and shaft 131 to the neutral position whichever way it has been rotated. Normally, when the lever 85 is released all six contacts are separated. When the lever is raised or lowered from the neutral position the contacts 115a, 117a are closed. If now the grip 126 is rotated in one direction the contact 140c (say) is closed by its cam 140a and pin 140, coils 151, 155 are energised and the forward motor circuit is completed through contacts 158, 159 and resistance R, so that the motor drives at its first speed. For second speed, the resistance R is cut out and this is effected by (1) moving the lever 85 still further to its central position between the two limit positions and so closing the contact 116a, and (2) rotating the grip 126 until contact 142c is closed by cam 142a and pin 142. The second speed does not come into operation until both sets of switches are in the second speed position. To reverse the motor the grip 126 is rotated in the opposite direction. The load platform 11 of the truck is carried by levers 15, 19 linked together by rods 23 and is raised by an hydraulic cylinder 25 operated by a pedal 26.