Patent GB-895162-A (GB)
Title: Improvements relating to variable speed gears
IPC: F16D67/00
Filed: 1957-05-13
Abstract: 895,162. Variable-speed gear. HERRIOTT, J. A. Aug. 13, 1958 [May 13, 1957], No. 15128/57. Class 80 (2). [Also in Groups XXVI and XXIX] An automatic variable-speed gear between driving and driven shafts 1, 2, Fig. 2, of a vehicle transmission system comprises an hydraulic coupling having a slidable obstructor member 21 which controls the resistance to fluid flow in the coupling, the position of the member being controlled by means sensitive to the difference in speeds of the shafts. The shaft 1, which is driven by an internal combustion or compression ignition engine, is connected to a casing 11 secured to a vaned wheel 3 of the coupling co-operating with a second vaned wheel 4 connected by epicyclic gear 13 and planet-wheels 15, which are carried on a member 16 attached to the shaft 1, to a sun-wheel 14 on the driven shaft 2, the wheel 4 thus rotating faster than the wheel 3 when the shaft 2 is held stationary. The obstructor member consists of vanes 21 connected either directly or by rack- and-pinion gearing to a collar 22 which is moved according to the speed of the driven shaft 2 under the control of a governor 46 and a transmitter. The governor may be mounted on an output shaft 34 which is connected to the driven shaft 2 by a gear-box M having an epicyclic gear train controlled by braking means or, as shown, a sliding synchromesh gear 41 engaging either of gears 39, 40 to provide for forward or reverse rotation of the shaft 34. A pump 42, driven from the casing 11, and shaft 1, and a pump 43 driven by the shaft 2, supply pressure fluid through a passage 53 to a chamber 119, Fig. 7, in a collar fixed to the shaft 34 and connected to the governor by a port 118 controlled by a piston 112 attached by a rod 114 to a weight 111. A further piston 113 on the rod controls an exhaust port 122. In the neutral position, the pistons close both ports. Upon increase in speed of the shaft 34, the weight 111 moves outwardly against the hydraulic pressure in the space between the pistons to open the port 118 to permit the fluid pressure from the pumps to enter the space between the pistons and pass through a channel 103 connected by a pipe 47 to the outer surface of the piston 55, Fig. 3, of the transmitter. The inward movement of the piston displaces a cam 59 which abuts an anvil 61 to permit a spring 62 to move a valve spool 58 to the right and fluid from the pumps to pass to the right hand end of a cylinder 66, the piston 65 of which is connected by a rod 71 to the collar 22 and moves to the left to withdraw the vanes 21 from the coupling and increase the output torque and the slip within the coupling. The rod 71 is also connected by a link 72 to the anvil 61 which is thus moved to reposition the spool 58 to its control position and close both ports to the cylinder 66 to lock the piston 65 in position until further adjustment is effected by the governor. A decrease in speed of the shaft 34 connects the space between the pistons 112, 113 to the exhaust port 122 to move the vanes in the opposite direction. An over-riding cam 75 also operates the valve spool 58 to provide a " down " gear change if desired when the governor has selected a higher gear ratio, the cam being connected by a link 77 to the accelerator pedal 79, Fig. 6, of the vehicle. The pedal has a first portion of movement AB controlling the throttle of the engine, and a second portion BC controlling the cam 75. The pressure from the pumps 42, 43 is also supplied to a lever-operated valve 80, which controls the fluid supply to a cylinder 83 operating a brake on the casing 11, the coupling then acting as a brake, and a pressure switch 87 which may control the ignition or fuel supply circuit to the engine. In alternative constructions, the vane 22 may be arranged to restrict the fluid flow within the wheel 4 connected to the driven shaft 2, the vanes being mounted on a disc connected to the collar 22 by a ball-bearing, and the pumps may be driven directly from the input shaft 1 to which they are connected by bevel gearing, one of the pumps being connected by a hollow passage in the driven shaft to the input to the coupling.