Patent GB-812236-A (GB)
Title: Electric truck control
IPC: B66F9/075
Filed: 1957-05-07
Abstract: 812,236. Controlling vehicles. CLARK, EQUIPMENT CO. May 7,1957 [May 16, 1956], No. 14477/57. Class 79(5) [Also in Group XXXVII] An electric motor driving a fork lift truck has an armature 34 and field windings 32 supplied from battery 42. The direction of drive of the motor is selected by means of actuator 64, the vehicle being driven in the forward direction if contacts 40, 46 are respectively engaged with contacts 52, 60. The speed of the motor is controlled by a carbon pile regulator 68 associated with contacts 74, 76 which short-circuit the regulator and a portion of the field windings when the pile has been compressed to a predetermined extent. Pivoting of a manually operable selector lever causes limited rotary movement of a rod 106 which is mechanically linked with a shaft 86 for effecting rectilinear movement of the shaft and pivotal movement of the actuator 64. The driver's seat, Fig. 5 (not shown) is secured to a shaft 136 carrying a crank arm 140 connected to a clevis 142 which is mounted on a rod 144. When the seat is not occupied, bolts at the upper ends of crank arms 166, 168, engage and centre a plate 170 whereby the switch actuator shaft 86 is held in a neutral position for preventing energization of the drive motor. When a foot-operated brake lever, Fig. 6 (not shown), is depressed, a shaft 188 is actuated to move shafts 194, 196, to the right so that actuating rods 202, 214, are moved toward each other. Thus, the application of the vehicle brakes causes the switch actuator 64 to be centred in a neutral position for de-energizing the drive motor. During pivoting of the actuator 64 back to a neutral position, the particular spring-biased plunger 100, 102, toward which the actuator is pivoted, moves into its associated cylinder for permitting movement of the actuator while the shaft 86 remains in its preselected position. This allows the actuator to be returned immediately to its selected position for energizing the motor upon release of the brakes, and affords efficient inching operation of the vehicle. When an accelerator pedal 221 is depressed, levers 230, 242, are pivoted and regulator rod 250 is actuated for compressing the carbon elements of the regulator 68. A spring 248 ensures that a minimum compressive force is always applied to the carbon pile. Time delay mechanism comprising a dashpot 270 is provided so that depression of the pedal exerts a downward force on piston rod 266 which is resisted by oil within the cylinder of the dash-pot. The accelerator pedal is interlocked with the shaft 86, whereby the actuator 64 can be moved only when the pedal is completely released. The shaft 86 has bosses 272 co-operating with plate 276 having notch 274, the plate being secured to shaft 262. If the shaft 86 is in one of its selected positions and the accelerator pedal is depressed, the plate 276 is disposed in the path of movement of the bosses 272 so preventing further movement of the shaft 86. A coil 280 is energized by the backelectromotive force of the motor when the switch actuator 64 is returned from an operative position to the neutral position prior to being disposed in the opposite driving position. Attraction of armature 282 moves rod 284 to prevent pivotal movement of the plate 276, and, after the actuator has been disposed in the opposite drive position, pressure cannot be applied to the carbon pile. The coil 280 remains energized until the speed of the motor has decreased to a predetermined value. The contact 74 is supported by bracket 286 secured to plate 82, the contact 76 being carried on bar 288 which is guided for floating movement in channel member 294. As pressure is applied to the regulator 68, levers 308 and member 306 are pivoted to extend spring 304 until the carbon elements are completely compressed and the member 306 snaps over to its alternative position. Arm 292 and bar 288 are thus pivoted for snapping contact 76 into engagement with contact 74. A coil spring 298 effects yieldable engagement between the contacts. In a modified control system the reversing switches are operated electromagnetically under the control of a manual selector lever. Depression of the brake pedal separates interlock contacts for opening a line contactor, other contacts being opened by releasing pressure on the accelerator pedal to stop the motor. Other interlocks comprise key-operated contacts and seat-operated contacts. The short-circuiting of the carbon pile regular tor may also be effected by means of an electromagnetic switch, Fig. 14 (not shown) .