Machine element or mechanism – Gearing – Pressure distributing
Reexamination Certificate
1999-10-15
2001-07-17
Herrmann, Allan D. (Department: 3682)
Machine element or mechanism
Gearing
Pressure distributing
C074S416000, C074S420000, C074S66500G
Reexamination Certificate
active
06260430
ABSTRACT:
The present invention relates to a face gear transmission, in particular for aircraft application.
BACKGROUND OF THE INVENTION
In aircraft applications, motion is known to be transmitted from an input shaft to an output shaft using a face gear transmission, which comprises two coaxial, counter-rotating face gears positioned facing each other, and at least one floating pinion meshing with both face gears.
In most applications, the face gears are the same size, and the pinion rotates about a respective axis perpendicular to the axes of rotation of the face gears.
Inclined-axis solutions are also known, in which the face gears are again the same size, but the angle between the axis of rotation of the pinion and those of the face gears is other than 90°.
Whereas perpendicular-axis solutions pose substantially no problems, inclined-axis solutions, though used, are functionally inefficient and unreliable.
In actual use, in fact, the face gears transmit to the pinion respective actions which, since both face gears are the same size, generate on the pinion a tilting torque acting in the pinion axis plane and which moves the pinion unpredictably with respect to the face gears, thus resulting in an equally unpredictable variation in theoretical torque flow to the two face gears and, consequently, in a variation in stress on the teeth. In particular, a tilting torque on the pinion causes an unpredictable and uncontrollable variation in the specific pressure pattern along the teeth of both the face gears and the pinion, with the generation of localized pressure peaks. Since both the face gears and the pinion must obviously be sized on the basis of maximum possible stress values, the teeth of both the face gears and the pinion are considerably larger than they would be in the absence of said tilting torque, i.e. in a perpendicular-axis arrangement, thus resulting in a considerable increase in weight, size and, hence, cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a face gear transmission, in particular for aircraft application, designed to eliminate the aforementioned drawbacks.
According to the present invention, there is provided a face gear transmission, in particular for aircraft application, comprising at least one floating pinion rotating about a first axis; and two face gears rotating about a common second axis, positioned facing each other, and both meshing with said floating pinion; said first and second axis forming an angle of other than 90°; characterized in that said two face gears have different diameters; and in that the resultants of the forces exchanged between the face gears and the floating pinion are applied at respective points, the projections of which on said first axis are substantially coincident with each other.
REFERENCES:
patent: 5802918 (1998-09-01), Chen et al.
patent: 5807202 (1998-09-01), Sammataro
patent: WO 98/16762 (1998-04-01), None
Fiatavio S.p.A.
Herrmann Allan D.
Kinney & Lange , P.A.
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