CONCENTRIC SHAFTS DRIVING ADJACENT FANS FOR AIRCRAFT PROPULSION
A propulsion system for an aircraft has at least two fans, each fan having a fan drive shaft. A turboshaft gas turbine engine drives each of the at least two fans, and drive an output shaft which drives a gear to, in turn, engage for driving a gear on a first intermediate shaft extending from the turboshaft gas turbine engine in a rearward direction toward an intermediate fan drive shaft. The intermediate fan drive shaft drives ng the fan drive shaft, and the first intermediate shafts extending over a distance that is greater in an axial dimension defined between the turboshaft gas turbine engine and the fan than in a width dimension defined between the at least two fans. The first intermediate shafts are concentric.
1 . A propulsion system for an aircraft comprising:
at least two fans, each said fan having a fan drive shaft;
a turboshaft gas turbine engine for driving each of said at least two fans, said turboshaft engines driving an output shaft which drives a gear to, in turn, engage for driving a gear on a first intermediate shaft extending from said turboshaft gas turbine engine in a rearward direction toward an intermediate fan drive shaft, said intermediate fan drive shaft driving said fan drive shaft, and said first intermediate shafts extending over a distance that is greater in an axial dimension defined between said turboshaft gas turbine engine and said fan than in a width dimension defined between said at least two fans; and
said first intermediate shafts being concentric.
2 . The propulsion system as set forth in claim 1 , wherein said intermediate fan drive shaft extends for a greater distance in the width dimension than in said axial direction and said fan drive shaft extending for a greater distance in said axial direction than in said width direction.
3 . The propulsion system as set forth in claim 2 , wherein said first intermediate shafts and said fan drive shafts extend parallel to an axis of rotation of said at least two fans.
4 . The propulsion system as set forth in claim 3 , wherein said intermediate fan drive shaft extends perpendicularly to said axis of rotation of said at least two fans.
5 . The propulsion system as set forth in claim 4 , wherein a central axis of each said turboshaft gas turbine engine is parallel to said axis of rotation of said at least two fans.
6 . The propulsion system as set forth in claim 5 , wherein said first intermediate shafts each extend to an output gear which engages a gear on said intermediate fan drive shaft, with said output gear on one of said first intermediate drive shafts extending to a position spaced rearwardly relative to one of said output gears on a second of said first intermediate shafts.
7 . The propulsion system as set forth in claim 4 , wherein a central axis of each said turboshaft gas turbine engines is non-parallel to said axis of rotation of said at least two fans.
8 . The propulsion system as set forth in claim 7 , wherein bevel gears drive said first intermediate shafts from said turboshaft gas turbine engines.
9 . The propulsion system as set forth in claim 8 , wherein said first intermediate shafts each extend to an output gear which engages a gear on said intermediate fan drive shaft, with said output gear on one of said first intermediate drive shafts extending to a position spaced rearwardly relative to one of said output gears on a second of said first intermediate shafts.
10 . The propulsion system as set forth in claim 1 , wherein said first intermediate shafts and said fan drive shafts extend parallel to an axis of rotation of said at least two fans.
11 . The propulsion system as set forth in claim 10 , wherein said intermediate fan drive shaft extends perpendicularly to said axis of rotation of said at least two fans.
12 . The propulsion system as set forth in claim 11 , wherein a central axis of each said turboshaft gas turbine engine is parallel to said axis of rotation of said at least two fans.
13 . The propulsion system as set forth in claim 12 , wherein said first intermediate shafts each extend to an output gear which engages a gear on said intermediate fan drive shaft, with said output gear on one of said first intermediate drive shafts extending to a position spaced rearwardly relative to one of said output gears on a second of said first intermediate shafts.
14 . The propulsion system as set forth in claim 11 , wherein a central axis of each said turboshaft gas turbine engines is non-parallel to said axis of rotation of said at least two fans.
15 . The propulsion system as set forth in claim 14 , wherein bevel gears drive said first intermediate shafts from said turboshaft gas turbine engines.
16 . The propulsion system as set forth in claim 15 , wherein said first intermediate shafts each extend to an output gear which engages a gear on said intermediate fan drive shaft, with said output gear on one of said first intermediate drive shafts extending to a position spaced rearwardly relative to one of said output gears on a second of said first intermediate shafts.
17 . The propulsion system as set forth in claim 1 , wherein a central axis of each said turboshaft gas turbine engine is parallel to said axis of rotation of said at least two fans.
18 . The propulsion system as set forth in claim 1 , wherein a central axis of each said turboshaft gas turbine engines is non-parallel to said axis of rotation of said at least two fans.
19 . The propulsion system as set forth in claim 18 , wherein bevel gears drive said first intermediate shafts from said turboshaft gas turbine engines.
20 . The propulsion system as set forth in claim 1 , wherein said first intermediate shafts each extend to an output gear which engages a gear on said intermediate fan drive shaft, with said output gear on one of said first intermediate drive shafts extending to a position spaced rearwardly relative to one of said output gears on a second of said first intermediate shafts.