A conventional face-gear drive is formed by an involute spur pinion and a conjugated face-gear (Fig. 18.1.1). Such a gear drive may be applied for transformation of rotation between intersected and crossed axes. An important example of application of a face-gear drive with intersected axes is in the helicopter transmission (Fig. 18.1.2).
The manufacturing of face-gears by a shaper was invented by the Fellow Corporation. The basic idea of generation is based on simulation of meshing of the generating shaper with the face-gear being generated as the meshing of the pinion of the drive with the face-gear. In the process of generation, the surfaces of the teeth of the shaper and the face-gear are in line contact at every instant. However, when the shaper is exactly identical to the pinion of the face-gear drive, the generated face-gear drive becomes sensitive to misalignment. This causes an undesirable shift of the bearing contact and even separation of the surfaces. Therefore, it is necessary to provide an instantaneous point contact between the tooth surfaces of the pinion and the face-gear instead of a line contact. Then, the bearing contact will be localized and the face-gear drive will be less sensitive to misalignment. Point contact between the pinion and face-gear tooth surfaces is provided by application of a shaper of number of teeth Ns > Np where Np is the number of teeth of the pinion of the drive (see Section 18.4).
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