Patent GB-1456717-A (GB)
Title: Combined superimposed steering gears for track-laying vehicles
IPC: F16H47/04
Filed: 1974-09-18
Abstract: 1456717 Change-speed gear ZAHNRADFABRIK FRIEDRICHSHAFEN AG 18 Sept 1974 40650/74 Heading F2D In an hydrostatic-mechanical split-torque steering drive, superimposed on the main drive to opposite sides of a track-laying vehicle, the hydrostatic component is directly driven by the engine 1, whilst the mechanical component is driven by the turbine 3 of an hydrodynamic torque converter through which the engine drives the vehicle. This reduces the loss of steering differential due to negative slip in the torque converter when the vehicle overruns the engine. The turbine shaft 57 drives, through bevel reverse gear 56 with forward-reverse clutches 61, 62, a hollow shaft 71 and a main change speed gear 92, an inner shaft 70, driving track sprockets 98, 100 on opposite sides of the vehicle through differentiating gears 94, 96, which latter also receive oppositely superimposed steering components through gear trains 111, 112, and 113, 114, 115, and a cross shaft 110. The drive to the steering cross shaft 110 is taken through meshed wheels 51, 52 from the planet carrier 50 of a torque-combining sunring train 45, the ring 46 of which receives a mechanical drive component from the converter turbine shaft 57 through the main reverse gear 56, forward-reverse clutches 63, 64, used for obtaining small radius turns and arranged inside the main forward-reverse clutches 61, 62, shaft 72, and meshed wheels 81 ... 89. The sun 47 of the torque-combining train 45 receives an hydrostatic component from the engine 1 through the torque converted impeller 3, and meshed wheels 9 ... 19, driving variable-capacity hydrostatic pumps 16, 20, which deliver to motors 25, 30, driving through meshed wheels 27a, 27b, 27c and 32, 33 respectively, a sun 44 and ring 38 of a sun-ring train 36, the planet carrier 40 of which drives the sun 47 of the combining train 45 under control of a clutch 32 providing the following different conditions of operation. (1) Normal.-The clutch 42 connects the sun 44 of the train 36 to the output wheel 27c of the hydrostatic motor 25, the ring 38 being directly driven by the motor 30. The carrier 40 thus supplies the engine-driven hydrostatic component to the sun 47 of the combining train 45, whilst the turbine-driven mechanical component, as above described, drives its ring 46, steering being effected by varying pump capacities, and, for tight turns, using the forwardreverse clutches 63, 64 in the mechanical component path. (2) All hydrostatic steering drive.-Application of a brake 86 to an intermediate shaft 83 of the mechanical component drive holds the ring 46 of the torque combining train 45, whereby its sun 47, hydrostatically driven, provides the sole drive to the steering shaft 110. (3) Emergency dead-engine main drive.-Provided there is an auxiliary motor-pump unit to supply the first hydrostatic motor 25, the vehicle can be driven and steered without the main engine 1 operating, as follows. The clutch 42 disconnects the sun 44 of the first planet gear 36 from the drive gear 27c of the first hydrostatic motor 25, which thereafter becomes inoperative for steering control and is connected by sliding a wheel 67, rotating with the wheel 27b, axially into mesh with a wheel 66, secured to one, 60, of the main bevels, so that the main bevel reverse gear 56, and hence the vehicle, can be driven by the hydrostatic motor 25. At the same time the clutch 42 is further moved to connect the sun 47 of the torque-combining train 45 through the inner shaft 43 to the fixed casing to provide a reaction for the ring 46, which continues to be driven by the mechanical component path 72, 81 ... 89 which supplies the sole steering component under control of the tight-turn forward-reverse clutches 63, 64 driving the shaft 72. The second hydrostatic motor 30 remains inoperative.