GB672850A - Improvements in or relating to hydraulic power transmission systems - Google Patents

Abstract

672,850. Fluid-pressure servomotor-control systems. INTERNATIONAL HARVESTER CO. June 27, 1950, No. 16023/50. Class 135. In a manually - operable hydraulic servomotor-control system having a differential lever mechanism operable to move a control valve from its neutral closed position to operate a ram and hydraulic power means responsive to liquid flow between the valve and the ram to restore the valve to its neutral position, selective adjusting means associated with the hydraulic power means are provided to vary the rate of restoration of the valve, so that the volume of pressure liquid passing through the valve may be varied in order that rams of different sizes may be operated. As shown, a control valve, 14, Fig. 1, having a landed plunger 19 controlling a supply port 48, exhaust ports 46, 77 leading to a common return line 13, ports 38, 39, communicating through a common line 35 with the space 33 behind the piston 41 of a piston-actuated, by-pass valve 34, and motor ports 49, 74, is connected by a rod 19a to a differential lever 17. The port 49 is connected by a line 51, a piston-actuated check valve 52 and a line 101 to the left side of a ram 24 and by a line 57 to the space above the piston 55 of a piston-actuated check valve 53, whilst the port 74 is connected by a line 71, the check valve 53, a hydraulic gear motor 21 and a line 102 to the right side of the ram and by a line 79 to the space above the piston 81 of the check valve 52. The ram and its cylinder B may be mounted on a tractor or its trailer and operatively connected to an agricultural implement. The lever 17 is connected by a link 16 to a control lever 15 and by a link 23 to a member 22 which is slidable on a rod 115 and pivotally connected to the upper end of a lever 112 having a slot 119 and connected at its bottom end to a nut 109 coacting with a screw 106 rotatable by the motor 21. The slot 119 engages a pin 118 carried by a nut member 121 mounted upon a screwed shaft 122 held against endwise movement and rotatable through bevel gearing 128 by a handwheel 126 mounted on a screwed spindle 125. A nut 129 mounted on the spindle 125 has a projection engaging a helical groove in a member 133 carrying a pointer 136 to indicate the position of the pin 118 in the slot 119. With the valve 14 in its inoperative neutral position, pressure liquid from a pump 29 flows through lines 31, 32 and a restriction 47 to the space 33 to move the piston 41 to unseat the ball 42 of the by-pass valve 34. On moving the control lever 15, e.g. towards the position X, the plunger 19 is moved to the left where the ports 38, 46, 49, and 74 are uncovered, permitting liquid behind the piston 41 to escape to the line 13 to close the valve 34, pressure liquid from the line 31 to pass through the ports 48, 49 and the line 51 to unseat the check valve 52 and thence pass to the left side of the ram 24, and pass through the line 57 to act on the piston 55 to unseat the check valve 53 to permit exhaust liquid from the right side of the ram to pass through the motor 21, line 71, port 74, a plunger bore 75 and port 46 to the line 13. The motor 21 is then rotated to position the nut 109 and, through the lever 112, member 22, link 23, lever 17 and rod 19a, return the plunger 19 to its neutral position. The pin 118 is shown in the mid position of the slot corresponding to a ram 24 of medium size. Should the ram being operated be smaller than the ram 24, the amount of liquid passing to and from its cylinder will be less whence the motor 21 will operate for a shorter time, the nut 109 not moving a sufficient distance to preserve the correlation between the movement of the control lever 15 to its terminal position and the full stroke of the ram. To compensate for this, the nut 118 is moved downwards by rotation of the handwheel 126. Should the ram being operated be larger than the ram 24, conversely the nut 118 is moved upwards. Valves V having projecting pins arranged to engage the cylinder ends to open the valves are fitted to phase the ram with the control lever 15 which may become necessary when changing from one ram to another.