Patent GB-564846-A (GB)
Title: Improvements in the operation and control of change speed mechanism
IPC: F16H61/02
Filed: 1943-03-04
Abstract: 564,846. Variable-speed gearing. CORNELIUS, J. R. March 4, 1943, No. 3552. [Class 80 (ii)] [Also in Group XXIX] Variable-speed gearing is controlled automatically in accordance with the speed of the engine and the torque on the driven shaft. The range of speed ratios may be varied manually, or alternatively the gearing may be wholly manually controlled. The output shaft 9, Fig. 2, of the gear-box drives a shaft 12 through bevel planets 10 mounted in a casing 11 on the shaft 12. The planets 10 have spur teeth 10a meshing with racks 14 slidable in the casing 11 and carried by a plate 15 connected to a piston 18 through a thrust bearing 16. Piston 18 is slidable in a fixed cylinder 19 to which pressure fluid from an engine-driven pump is admitted by a pipe 20. 'Movement of the piston 18 is communicated to a rotary valve 23, Figs. 3 and 8, by a flexible cable 22 and rack and pinion 27, 28. A similar valve 24 is connected to a hand lever 29 by a cable 30 and rack-and-pinion 31, 32, Each valve has a helical rib 23a, 24a, with a channel 23b, 24b thereon, which is connected to the valve interior by a port 46. The interior of the two valves are connected by a duct 85, Fig. 8, and a pipe 64a on the valve 23 leads fluid pressure thereto. The space 86 round the valves is connected to exhaust. Passages 47 lead from the valves 23, 24 to a, sliding valve 37 having aseries.of ports 48, 48a arranged so that in one position of the valve 37 the valve 23 is connected to ports 53 and in the other position valve 24 is connected to the ports 53. The valve 37 is moved by a hand lever 33 connected thereto by a cable 34 and rack-and-pinion 35, 36. The valves 24, 23 have wide and narrow meshing gears 40, 41 respectively, the latter having a dog 43 for co-operation with a dog 42 on the valve 23. When the lever 34 is moved to the non-automatic position, the dogs are disengaged ; in the automatic position of the lever 34, the dog 43 limits the extent of movement of the valve 23 and hence the range of automatic gear ratios is determined by the position of the lever 29. A piston 25 in a cylinder 50 is provided for each gear setting. Each piston is open to a port 53 and has ducts 52, 54 leading to an annular groove 55. The top of each piston is acted upon by a plunger 61 subjected to fluid pressure from a pipe 64. The cylinders 50 have interconnecting ducts 56 leading by a pipe 58 to a clutch operating cylinder 60, Fig. 11. Interconnected ducts 65 lead by a pipe 66 to the underside of a piston 67 having a groove 67a. When a gear change is required, whether manually or automatically, the appropriate valve 23 or 24 leads pressure fluid to a port 53 to lift the corresponding piston 25. As the latter rises its groove 55 registers with the ducts 56 and fluid pressure passes to the clutch cylinder 60 and disconnects the clutch through linkwork 74, 75, 76. Upon final movement of the clutch piston 73, a pipe 71, Figs. 5, 11, leads fluid pressure to neutralizing pistons 72 of the gear-box, thus bringing the gearing to neutral. Further movement of the-piston 25 connects the groove 55 with a duct 84 connected by a pipe 83 to the piston 81 of a gear shifter fork 80 and a gear change is thus made. Finally, the bottom of the piston 25 uncovers the ports 65 and pressure fluid flows by pipe 66 to the underside of the piston 67 which lifts so that its groove 67a registers .with the ducts 56 and a pipe 57 leading to a drain. The pressure in the clutch cylinder 60 is thus reduced and the clutch re-engages under its usual spring pressure.. When the valve 23 or 24 is again rotated to select another gear ratio; the piston 25 previously actuated immediately descends. To enable the fluid in the pipe 66 to escape and the piston 67 to descend, the latter has a small central bore 93 through which the fluid. leaks past a ball valve 68 to the top of the piston and to exhaust.