GB1019593A - Hydraulic transmission - Google Patents

Abstract

1,019,593. Motor vehicle hydraulic transmissions. DOWTY HYDRAULIC UNITS Ltd. Oct. 19, 1962 [Oct.30, 1961], No. 38760/61. Heading B7H. [Also in Division F2] In a motor vehicle transmission comprising a reversible positive displacement pump 1 driven by the vehicle engine and supplying positive displacement motors 2, 3 driving the front and rear wheels of the vehicle, a valve 4 is manually operable to restrict the supply to either the motor 2 or the motor 3 if wheel spin at the front or rear wheels occurs or to cut off the supply to the rear motor 3 entirely to increase the driving ratio. Reversible feed and return lines from the pump 1 are connected to ports 16, 17 each communicating with two ports 21, 22 and 23, 24 connected to reversible feed and return lines 26, 27 and 28, 29 to the motors 2, 3. Axial displacement of a valve spool 7 by means of a lever 32 restricts the ports connected to both the feed and return lines to one motor but non- return valves 34, 35, 36, 37 ensure that only the feed line is restricted. When the supply to the rear motor 3 is cut off entirely a port 25 connected to a branch 31 from the line 28 communicates with the port 24 to ensure that fluid may circulate freely through the motor 3. A pump 38 supplies make-up fluid to the return line 16 or 17 through a non-return valve 39 or 41 and also supplies cooling fluid to the casings of the motors 2, 3 through a restrictor 44. A non-return valve 48 supplies make-up fluid to the rear motor 3 when it is isolated.