Patent GB-1167018-A (GB)
Title: Improved Transmission Control System
IPC: B66F9/075
Filed: 1966-11-22
Abstract: 1,167,018. Change-speed control. HYSTER CO. 22 Nov., 1966 [29 Nov., 1965], No. 52275/66. Headings F2D, F2E and F2F. In an hydraulic control for forward and reverse ratio establishing brakes F, R of a lifttruck wherein an engine-driven pump 40 supplies pressure liquid through a flow divider 104 and line 44 to a hoist and through lines 46, 56, 58, 60, 64, 68, a forward-reverse distributer valve 30 and line 74 to brake engaging servomotors 54, 54<SP>1</SP>, a modulator valve 32 between the pump 40 and distributer 30 permits initial rapid servo-pressure build-up until a predetermined pressure sufficient for light brake engagement is obtained and thereafter restricts the flow to the servos to provide gradual and smooth full brake engagement. The modulator valve spool 92 is moved down by a spring 94 to connect lines 64, 68 for initial rapid pressure buildup. When the pressure exceeds a predetermined value it acts through a line 98 on the lower end of the spool 92 and moves the spool up against the bias of the spring 94 whereafter pressure liquid is supplied to the selected servo through a restrictor 102 (or 102<SP>1</SP>). The distributer valve 30 is biased upwardly to a reverse ratio position by a spring 78 and is moved down to the forward ratio position, shown, by pressure liquid supplied through a valve 83 to the upper end of the distributer valve. The valve 83 is opened for forward ratio by depressing the left side of an accelerator pedal 82 and is closed for reverse ratio by depressing the right side of the accelerator pedal. Three pressure regulating valves 34, 36, 38 respectively control the pressure supplied to the valve 83, the brake servo-pressure and the pressure supplied to a torque converter 20. An inching valve 110 normally connects the ratio establishing brake supply lines 60, 64. The servo-pressure acts on differential lands 112, 114 of the valve spool 110 which is biased right by a force which is balanced by a spring 118 that reacts on a piston 120. Pressure liquid supplied through a solenoid-operated valve 42 normally holds the piston 120 in a position spaced from the end of the inching valve chamber 28 so that the spool 110 provides free communication between lines 60, 64. When a hand brake 174 is applied it operates a micro-switch 168a to de-energize the solenoid of the valve 42 and vent the right-hand end of the inching chamber 28 whereupon the valve spool 110 moves right to vent the line 64 at 168 and disengage the brakes F, R. A second micro-switch 168b completes the circuit to a starter motor 194 when the hand brake 174 is applied. On initial depression of a service brake pedal 140 pressure liquid is supplied from a master cylinder 138 to the left end of the inching chamber 28 and moves right the valve spool 110 to throttle flow between the lines 60, 64 for inching the truck. Further depression of the brake pedal 140 moves the valve 110 further right to vent the brakes F, R and to apply the service brakes. When the brakes F, R are disengaged and the service brakes are applied a pressure-sensitive switch 178 completes the circuit to the starter motor 194. The brakes F, R are shown as spring released multi-plate disc brakes.