Patent GB-1158621-A (GB)
Title: Improvements relating to Steering Means for Lift Trucks
Inventor: DRAKE RONALD
IPC: B62D7/02
Filed: 1965-07-30
Abstract: 1,158,621. Steering vehicles. JOSHUA SHAW & SONS Ltd. 18 July, 1966 [30 July, 1965], No. 32733/65 Heading B7H. A fork lift truck comprises a front section 20 having wheels 3, 4, connected by a member 22 to a rear section 21 having wheels 1, 2. A steering mechanism including a chain and sprocket drive may be brought into a position wherein the rear wheels 1 and 2 are locked and the front wheels are steerable for movement in a generally longitudinal position, and into another position wherein the wheels 1 and 3 are locked in a position at right angles to the longitudinal direction of the truck, and the wheels 2 and 4 are steerable for movement in a generally transverse direction. A steering shaft 61 is connected to a mechanism comprising a pair of sprockets 35, 38. Sprockets 1A and 3A may be clutched to the pivot shafts (25) of the wheels 1 and 3 and sprockets 2A and 4A are connected to the pivot shafts of the wheels 2 and 4. A chain 34 passes around the sprockets 3A, 4A and 35 and a chain 37 passes around sprockets 1A, 2A and 38. Suitably placed idler sprockets 36 and 39 guide the two chains. Discs 44 and 46 are secured to the pivot shafts (25) of wheels 3 and 1 respectively, disc 44 being slotted at 45 to receive a detent rod 49 and disc 46 being slotted at 48 and 46 to receive the other end of the detent rod 49 which may be slid backwards and forwards. A crank 40 connected to disc 46 can be moved by an hydraulic ram 42 from a position in which slot 48 registers with detent 49 to a position at 90 degrees thereto where slot 48 registers with detent 49. The clutches (31) through which sprockets 3A and 1A may be connected to their pivot shafts (25) are operated through a rod 52 and bell cranks 53, when rod 52 is in a forward position, both clutches (31) being engaged, and when rod 52 is in a rearward position, both clutches (31) are disengaged. The steering transmission includes an input shaft 62 from the steering shaft connected through gears 65 and 66 to a shaft 67 to which is splined for axial displacement a gearset 69, 68 which may be moved from a lower position in which the gearset engages a pair of gears 63, 64 respectively fast with the sprockets 35, 38, to an upper position in which the steering drive is transmitted to only the sprocket 35. A control lever 72 is pivoted at 77 to a member 78 fast with a shaft 74 so that the lever 72 may be moved in a gate 79 to provide longitudinal movements of the lever and rocking movements of the shaft 74. Microswitches 81 and 82 control the operation of a valve by which the ram 42 is operated and in the left hand (as seen in Fig. 3) position of the lever 72, switch 81 is operated to bring slot 48 into register with detent 49, and by rocking the lever, and shaft 74, detent 49 is engaged in the slot 47 by means of an arm 84, which in the left hand position of lever 72, engages only a slot in rod 49. In this position of lever 72, the rod 52 is in a forward position in which both clutches 31 are engaged and the gearset 68, 69 is in the raised position so that the steering transmission is effective only on the wheels 3 and 4 and all four wheels are generally longitudinally disposed, the rear wheels 1 and 2 being locked in this disposition. By rocking the control lever and then moving it to the right, to the full line position shown, detent 49 is disengaged from slot 47, switches 81 and 82 are operated to move disc 46 to a position where slot 48 registers with detent 49 and wheels 1 and 2 are both disposed transversely of the vehicle and the member 84 engages slots in both rods 49 and 52. The lever 72 is now rocked to a position wherein the gearset 68, 69 is lowered, both discs 46 and 44 are locked (the locking movement of both being possible by slot 48 being smaller than slots 47 and 45 and the front wheels first having been steered to a position transversely of the vehicle in which the detent 49 may be first entered into the slot 45) and the rod 52 is in a rearward position wherein both clutches 31 are disengaged. In this position, the'steering transmission is effective through the chains 34 and 37 upon the wheels 2 and 4 only for steering the vehicle generally at right angles to its longitudinal direction. The hydraulic ram 42 may be replaced by a rack and pinion mechanism or by an electric motor and quadrant.