Plane spiroid gears currently applied in feed motion rotary drives are roughly described in this paper. The theoretical possible methods of backlash adjustment in this kind of gear are mentioned. Referring to industry experience the only applied method, which uses the eccentric, is described. Its advantages as well as disadvantages related to operation and wearing process are pointed. The disadvantages are mainly connected with changing the gear axis distance while rotating eccentric in order to adjust backlash. A graph depicting the movements of the worm in the direction of backlash reducing and in the perpendicular one, which changes the axis distance, is given. In order to provide some information about the influence of changing axis distance on the mating of face toothing with the worm, mathematical model was created. Some effects of numerical calculations based on that model and showing the bearing contact of the face gear drive supplied with eccentric backlash adjustment are depicted. It can be noticed, how changing the axis distance influences the bearing contact. It can be also estimate if within the chosen range of eccentric rotation the theoretical bearing contact is still acceptable to operate correct. A simplified model presenting the wearing process is also provided. It reveals that after some operating time an edge contact appears while reducing backlash. It significantly decreases the operating time till the next adjustment. There are two methods of backlash reducing described: the first is typical whilst the second is improved and proposed by the author. The advantage of the proposed method is lengthening the operating time between two backlash adjustments. In the end a new type of spiroid gear mating with double-lead worm and deprived of aforesaid disadvantages is mentioned.

This content is only available via PDF.
You do not currently have access to this content.