Rolls-royce Corporation

Gm Global Technolgoy Operations, Inc.

Allison Engine Company, Inc.

John M Hawkins

Douglas A Wagner

John B Dunsil

A twin turbine engine helicopter has a two-stage main reduction gearbox, the input stage having a speed reduction ratio exceeding 5.5:1, into an epicyclic gear train second stage ratio about 6:1 for approximately 30:1 or higher overall ratio output to the main rotor. In various embodiments, the first stage uses face gears, or bevel gears, with a reduction greater than 5.5:1 and a second stage epicyclic gear train using single or double row helical or spur gears. The first stage gears are straddle mounted in the housing.

Helicopter two stage main reduction gearbox

An aircraft (,) having turboprop propulsion has a plurality of gas turbine engines (,), each with a two stage reduction gearbox (,) with the engine output shaft (,A) inline with the propeller drive output shaft (,) to drive a propeller (,) in front of the engine in a tractor mode of propulsion. The input gear reduction stage (,) and output gear reduction stage (,) share a plurality layshafts (,) mounted in fixed circularly-spaced relation to each other about the axis of the output shafts in the mechanical housing in the aircraft. Each layshaft of said plurality of layshafts has a layshaft first end toward the rear, input end of the gearbox, and a layshaft second end toward the output, front end of the gearbox. The layshaft gears are arranged to avoid any net thrust loading of the layshafts. Spur (,) and double helical (,) are used in FIG.,while spur gears,and,are used in FIG.,with suitable helix settings to neutralize end thrust on layshaft,Cantilever layshaft input gear (,) mounting in rear bearings (,) enables it to share some layshaft output gear,load sharing with the front bearing (,). A torquemeter (,) is conveniently situated at the gearbox input end. The engine output gear (,) and gearbox output gear (,), and propeller (,) all have colinear rotational axes.

Propeller gearbox

A gear reduction gearbox connected to a gas turbine engine to reduce the shaft speed and increase the output torque. In one form of the present invention an input shaft and an output shaft are rotatable within a mechanical housing. A face gear set connects between the shafts for changing the speed of the output shaft relative to the input shaft. The present invention, in one embodiment includes load sharing wherein a plurality of pinion gear assemblies distribute the load transmitted through the gearbox.

Epicyclic face gear reduction gearbox particularly for a gas turbine engine

A load sharing right angle bevel gear drive comprises a housing having a power bevel gear that meshes with two bevel gears that are mounted in the housing for rotation about a second axis that is perpendicular to the axis of rotation of the power bevel gear. The power bever gear is mounted in a sleeve that automatically translates to equalize the power transmitted from the power bevel gear to the two bevel gears. The power bevel gear is axially retained in the sleeve by spaced rolling bearings and the sleeve translates on slides that retain the sleeve axially to counteract the axial components of the forces that automatically translate the sleeve. In one embodiment, One bevel gear is a power output gear and the other bevel gear is an idler gear that also drives the power output gear through a fourth bevel gear. In another embodiment both bevel gears are power output gears. The sleeves of both embodiments preferably translate on slide pins via recirculating bearing balls to reduce friction. Both embodiments may employ hydraulic damping for the slide pins.

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Greenwood, IN, United States of America

John M Hawkins