Over the years, a number of proposals for generators with constant speed drives have evolved. In general, the proposals have been for use in aircraft but those skilled in the art will readily recognize that the same may have applicability in any instance where a prime mover, whose speed is varied from time to time in the course of its operation, is coupled to the generator which in turn is intended to provide a constant frequency output.
Generally speaking, there are two general categories of generator and constant speed drive constructions. One category is exemplified, for example, in U.S. Pat. No. 4,315,442 issued Feb. 16, 1982 to Cordner. In this category, the generator and the constant speed drive are placed side by side, that is, their respective rotational axes are non-coaxial and generally parallel. Such a construction provides a unit of short axial length which in turn is an advantage where the unit is mounted on only one of its ends and hangs from the mounting in a cantilevered fashion. Specifically, the relatively short axial length minimizes the bending moment placed on the mounting by the weight of the unit.
However, this type of unit necessarily has a large frontal area, that is, the area of a cross section of the unit projected on a plane extending transversely to the rotational axes of the components. As a consequence, some difficulty may be present when it is attempted to place the unit in an engine compartment in an aircraft where the frontal areas of cowlings and the like are generally kept to a minimum for aerodynamic purposes.
To solve this difficulty, the art has evolved the second general category of constant speed drive and generator units. It is the so-called in-line unit and is exemplified, for example, by U.S. Pat. No. 3,576,143 issued Apr. 27, 1971 to Baits. In an in-line unit, the rotational axes of the input to the constant speed drive and the generator are coaxial. This arrangement minimizes frontal area thus lending itself to utilization in aircraft engine compartments where small frontal area is required. At the same time, however, this arrangement increases the axial length of the unit so that, when cantilever mounted, there is an increase in the bending moment placed on the mounting. This in turn may require the use of a stronger mounting which, in the case of aircraft, will usually result in an undesirable increase in weight.
Thus, there exists a need for an in-line constant speed and generator unit to satisfy the needs of applications requiring minimal frontal area and which has a minimal axial length to minimize the bending moment produced on mountings to thereby avoid the creation of a weight penalty.