Patent GB-1070754-A (GB)
Title: Improvements in or relating to hydromechanical transmissions
IPC: F16H47/02
Filed: 1964-08-07
Abstract: 1,070,754. Hydromechanical variable-ratio gear. INTERNATIONAL HARVESTER CO. Aug. 7, 1964 [Aug. 8, 1963], No. 32184/64. Headings F2C and F2D. A hydromechanical transmission for an agricultural tractor comprises a swash-plate pump having a cylinder barrel 71 fast with an input shaft 11 and a swash-plate 79 fast in rotation with an intermediate shaft 76, the pump supplying motors 19, 20 in parallel, the motors having non-rotatable swash-plates and cylinder barrels 21, 21<SP>1</SP> fast with countershafts 22, 221 which have gears 102-104 and 102<SP>1</SP>-104<SP>1 </SP>of corresponding sizes meshing gears 102a-104a clutchable to an output shaft 12, the shafts 22, 22<SP>1</SP> also having gears 105, 105<SP>1</SP> meshing reverse idler gears 111, 1111 which mesh a gear 105a clutchable to the output shaft. The gears are clutched to the output shaft by double-dog clutch members 115 rotationally fast on the output shaft and axially slidable to engage external teeth (such as 116), thereon with internal teeth (such as 102b) formed on the gears 102a-105a. The intermediate shaft 76 is geared to the countershafts by gears 101a, 101, 101<SP>1</SP>. The pump and motor swash-plates are all adjustable from a negative maximum to a positive maximum position to vary the pump and motor displacements. With the pump swash-plate set to a stroke producing position and the motor swashplates set for zero stroke the pump is locked and the intermediate shaft 76 rotates at the same speed as the input shaft 11, the intermediate shaft driving the countershafts 22, 22<SP>1</SP> through the gears 101a, 101, 101<SP>1</SP>, and the countershafts driving the output shaft 12 at a speed determined by the spur train which is engaged. In operation the operator is supposed to choose the mechanical gear ratio which brings the hydraulic transmission nearest to its locked condition. Both motors are identical, and comprise a swash-plate 32 pivotally mounted at 33 on a stationary housing and adjusted by servo rams 40, 41 in cylinders selectively connectible to the pressure side of the hydraulic transmission by a follow-up servo control valve 44 having a spool 59 shiftable under the control of the operator, and a followup sleeve 46 which is connected to the swashplate. The spools of the motor servo control valves are rigidly interconnected so that the motor swash-plates are adjusted simultaneously to identical positions. The control for the pump swash-plate is similar but is independently operated. In operation and on starting, an input driven pump 45 draws liquid from a sump 13c through a strainer 120 and filter 121 and supplies liquid through a filter 126 and heat exchanger 127 to a conduit 128, whence it passes through check valves 129, 131 to transmission lines 135, 136, and thence through check valves 130, 132 to a line 133 supplying the servo control valves 44, 44<SP>1</SP> and 90 for the motors and the pump. Fluid pressure is now available for engaging the swash-plate control rams 40, 41, 401, 41<SP>1</SP>, 91, 92 so that the pump can now supply liquid to the motors and raise the pressure in the servo line 133. Pressure is now also available for hydraulically operated accessories such as an hydraulic motor 122 and an hydraulic ram 123 which are controlled by a valve 124. Make-up fluid to replace losses due to leakage or to, the operation of the accessories is supplied by the pump 45 to the low pressure line 135 or 136. When the motor swash-plates are set to a stroke producing position and the pump displacement is zero hydraulic braking is achieved, a braking valve 138 between the transmission lines 135, 136 determining the braking effect.