Patent GB-923856-A (GB)
Title: Drive system for lift truck
Inventor: JR CECIL JACK ROSS
IPC: B60K17/10
Filed: 1959-08-31
Abstract: 923,856. Regulating. HYSTER CO. Aug. 31, 1959, No. 29690/59. Class 7(6). [Also in Groups XXIV and XXXI] A speed control pedal for a motor vehicle is provided with means whereby the direction of drive is selected. As shown in Fig. 1, the vehicle has a conventional transmission 9 having fluid operated clutches F and R, the engagement of which provides for forward and reverse motion respectively, and a torque converter 11. A fluid pump 33 supplies liquid to an inching valve 37 and to the torque converter and from the valve 37 the pressure fluid passes through a line 39, and selector valve 13 to one or other of the clutches F and R. The position of selector valve 13 is controlled by a valve 15 associated with the vehicle speed control pedal 17, which, as shown in Fig. 2, comprises an arm 23 pivoted at 25 and connected through a link 27 to the throttle and is urged against a stop 31 by a spring 29. A foot bar 21 is pivoted to the pedal shaft 23 at right angles to the pivot 25 and has a pad 46 on one side or is provided with a central ridge 46a, Fig. 3, or other means whereby the location of the foot to the left or right of the pedal is readily determined. An arm 49 is secured to the pedal shaft 23 and supports the control valve 15 which comprises a movable spool member 51 having a shoulder and a member 57 co-operating with valve seats 53 and 59 respectively. A spring 47 urges the foot bar 21 so as to press the shoulder of spool 51 against the seat 53. In this position fluid from the pump 33 enters valve 15 through line 61 and passes to line 63, whereby the spool 75 of valve 13 is moved against spring pressure to a position whereby the forward clutch F is supplied with pressure fluid from the line 39 and is engaged, the reverse clutch R being at the same time connected to reservoir. By depressing the right hand side of bar 21 against the pressure of spring 47, the spool 51 is allowed to rise under the action of the fluid pressure and the part 57 co-operates with the seat 59 to cut off the supply of pressure fluid to the right hand end of valve 13, and open this end, through lines 63 and 83, to the reservoir, whereby the spring 71 will move the valve spool 75 to the position whereby the reverse clutch is supplied with pressure fluid from the line 39, the other clutch being opened to the reservoir. Lines 81 and 89 connect the clutches F and R to valve 13 and lines 77 and 87 are connected to the reservoir. The pressure required to move the bar 21 to the left or right to engage forward or reverse drives is less than that required to turn the pedal about its pivot 25 whereby the vehicle speed is increased in the selected direction. When the pump 33 is operating, the bar 21 will stay in whichever position it is put so that the driver's foot may be removed from the pedal. This permits engine retardation on hills. When the pump stops, the spring 47 causes the bar to move in the direction whereby the forward drive is engaged. A stop 50 upon arm 49 limits the movement, e.g. to 2 degrees of. bar 21. The spool of inching valve 37 is urged to the right against a stop 101 by a spring 103, in which position fluid from line 35 passes through the space 113 and line 107 around the transmission 9, where it acts as a cooling fluid, and through line 109 to the sump. When the spool of valve 37 is moved to the left, line 107 is blocked but line 35 remains open and is now connected through line 39 and the clutch selector valve 13 to one or other of clutches F and R. At its right hand end, the spool of valve 37 has an enlarged portion 118 sliding within an auxiliary member 117 which is a sliding fit in the valve casing and is normally pressed to the left against stop 101 by a spring loaded pedal 119, 121. When the fluid enters valve 37 from a line 111 (from line 35 through a solenoid operated valve 155) liquid also passes through a bore 113 into space 115 within member 117, but the fluid pressure in that space is not sufficient to overcome the force of the spring upon pedal 119, 121 but is sufficient to move the valve spool to the left against spring 103 whereby liquid can pass from line 35 to line 39. If pedal 119, 121 is now depressed, the spool moves to the right as a unit under the influence of spring 103. A point may be reached whereby the line 39 is throttled causing slip of the clutch being engaged whereby the vehicle may " inch " in the desired direction of motion at slow speed. When the pedal is fully depressed, the position shown is reached whereby supply to line 39 is cut off and, the pedal 119, 121 also being connected to the vehicle brakes, causes the brakes to be applied. Fluid passing through the torque converter 11 and out through line 171 passes through a non-return valve 173, filter 175, heat exchanger 177 and is also used as a transmission coolant passing through line 179. Pressure responsive valves 41, 43 and 45 are provided, valve 41 maintaining pressure in line 35 so that the brake or valve spool extension 117 may be operated, valve 43 maintaining sufficient pressure to operate the clutches, and valve 45, being a pressure-relief valve exhausts back pressure from the torque converter to reservoir. The vehicle starting system comprises a switch 141 having " off " " run " and " start " positions, " park " and " drive " switches 147 and 151 mounted on a common lever 157 and a seat cushion switch 153 in series with a solenoid valve 155 controlling the fluid line 111. To start the vehicle the " park " switch 147 is depressed thereby opening switch 151 and de-energizing solenoid 155 thereby causing valve 37 to cut off liquid supply line 39, and the switch 141 is moved to the start position energizing the starter motor through line 145. In both " start " and " run " positions line 149 is energized. When drive switch 151 is depressed, and with the operator sitting on the seat so depressing switch 153, the coil 155 is energized thereby admitting pressure fluid into line 111 and causing spool of valve 37 to move to the left. A brake device 163 normally setting the brakes through a cable by the action of a spring 165 against a piston 162 is simultaneously acted upon by fluid pressure through line 162 to release the brakes. The valve 15 may be mounted on the vehicle frame and operated through a linkage. In a modification, the pedal comprises an arm 23a  upon a wing piece 49a of which is pivoted a pad 21a having foot engaging members 213 and 215. Stops 50a and 50x are provided to limit the pivotal movement of the pad and a spring 217 urges the pad against stop 50a, corresponding to the engagement of forward drive. The pedal is urged upwardly by a spring 29a. A bell crank arm 231 is pivoted at 233 to the arm 23a and has an adjustable screw bearing against pad 21a. At its lower end the bell crank engages a rod 237 which is slidable in a bore in the arm 23a and bears against a plunger 239, Fig. 5, which projects into a valve chamber 241. When the foot pad 21a is moved in the direction towards stop 50x it presses against screw 216 and through bell crank 231 moves plunger 239 into a tubular member 255 in valve chamber 241 so acting as a valve to check the flow of fluid to a connection 83a, the valve chamber 241 having connections 63a, 61a and 83a corresponding to the lines 63, 61 and 83 of Fig. 1. In the other position of the member 239 induced by fluid pressure, a member 257 shuts off the line 61a, the fluid pressure being sufficient to hold the member 257 against its seat against the action of spring 217 so that the operator may remove his foot from the pedal if desired. The members 215 and 213 are of different heights to facilitate location of the foot. In another modification, Fig. 8, a pad member 21b is pivoted at 24b to a pedal 23b and has a spring loaded detent member 301 locating the pad in its two positions corresponding to forward and reverse drive engagements. Movement of the pad 21b to the right causes an actuator 305 to close a switch 307 in a circuit completed by an ignition switch 141b, battery 143b and coil 309, so moving an armature 311 to the right. When the switch 307 is opened a spring 313 moves the armature to the left. The armature is connected to the spool of valve 13. In another modification, Fig. 9, microswitches 405 and 409 actuated by buttons 407 and 411 respectively, are mounted on a fixed transverse member 403 of pedal 401 and, when operated energize coils 421 and 423 respectively, associated with a common armature connected to the spool 75c of the selector valve 13. A spring loaded detent 431 co-operates with recesses 433 to locate the armature in its two positions.