The backlash must be able for adjustment where necessary. You find here several methods to do this.
1. STATIC METHOD
1.1 Fixed center distance and fixed gear
Along with the design there is chosen for a fixed center distance with a tooth thickness such selected that the backlash is minimal. This method requires a precise fabrication method.
1.2 Fixed center distance and axial customizable tooth thickness
- Two identical gears with straight teeth are mounted in such a way that by making a small rotation relative to each other, the tooth thickness and thus the backlash are adaptable to your wish. See left picture above.
- Two identical helical gears are mounted in such a way that reduces the backlash by an axial displacement. See above the middle picture.
- Two dentical conic milled straight gears, mounted opposite and brought together axially in order to reduce the backlash. See right picture above.
1.3 Adjustable center distance
At an adjustable center distance there are two possible center distance options by:
- A linear displacement of one of the centers to desired backlash such as the left picture indicates.
- A circular displacement where one of the gears can rotate around a center outside the gear center to achieve the desired backlash as the right pictures indicates.
2. DYNAMIC METHOD
2.1 Backlash reduction by forced tooth contact
This method is derived from the static method but instead of clamping both wheels with a bolt connection this is held under constant spring pressure.
2.2 Backlash reduction by force
This method is derived from the static method as describe above but here also the bolt connection is replaced by a constant spring pressure.
In a duplex worm the pitch is specially designed so that the backlash can be reduced by an axial displacement of the worm, left in case of the picture. The pitch of both tooth flanks is not equal, for example, in the picture the stitch of the left tooth flank is smaller than the pitch of the right tooth flank. (pr>pl). The production of such gear pairs requires special tools.
This gear pairs find their application in milling tables and precision turntables.