Panetary gears with an outer diameter of only 32 mm
By definition gears are jointed connections between pieces that serve to transmit and convert forces or for guiding parts on a track. In the vernacular this term is usually used only for mechanical devices for transmitting and converting rotary movements, rotational directions and torques. For this purpose gears are used in a wide variety of devices. Small motors generate the required high outputs by means of high rpm. With the aid of gears these are reduced to the right speed. Depending on the applications, the requirements of the gear used are completely varied: for example, high torques in the smallest possible installation space, thermal stability, break resistance, optimised efficiency and low noise are required. Hence it is advantageous to have modular gear families that can be adapted flexibly to the respective requirement.

Today there is a trend towards increasingly small devices; the gears used must keep pace with this development. This means that for many applications very compact planetary gears are ideal. The Performax gear family from Zeitlauf, the gear specialists, provides the solution to match almost any gear problem (Figure 1). To date the lowest limit for the gear diameter was 42 mm; but many applications require even smaller diameters. From mid-September the product family has gained a new member: The Performax 32 will then be added to the lower end of the range.

Compared to worm and spur gears, high performance planetary gears reach a high gear reduction performance but with compact dimensions, good efficiency and very low wear. Owing to the interlocking toothed wheels a high degree of packing density is reached, which is capable of transmitting maximum torque in a minimal installed space; the distribution of output over many stages is favourable for this. In order to minimise noise, the toothed wheels of the first stage have helical teeth and they are therefore able to engage fluidly and with little noise. Even engagement throughout the effective involute is achieved owing to an optimised modification of the teeth. Furthermore, this ensures that the forces that arise are better distributed over the toothed wheel flanks. Damaging local power surges are thus excluded.

The gears of the Performax family provide a very high power density while running extremely smoothly. In the first stage reductions of up to 17:1 are possible. Hence single-stage gears can be used where other gear concepts already require a two-stage design. In the case of two-stage versions reductions of up to i = 204:1 can be achieved, with three stages even up to i = 3468:1. Since planetary gears are very compact, several reduction stages can be built adjoining each other in a very small space. At the output on the motor side the rpm are high and the torques low. With each stage the speed is lower. Depending on the desired speed on the output side it is possible to use up to three stages (Figure 2). However with each stage the load on the tooth flanks increases because when the speed is reduced the torque also increases. The heavily loaded final stage is therefore equipped with planetary wheels on needle bearings for big reduction and the corresponding torque load.