A toothed belt drive transfers power between two parallel shafts. Each shaft has a toothed belt pulley attached, and the belt then connects the pulleys. This design is also sometimes referred to as synchronous drive because it has a fixed transmission ratio and, unlike with a V-belt drive, no slippage can occur. The tension cords integrated into the toothed belt are one of the factors that determine belt strength. They can be made of fibreglass, steel, carbon or aramid.
There are many different types of standard and customer-specific toothed belts, each of which has a specific field of application. For example, toothed belts made from the synthetic rubber polychloroprene (PCP): These are available in classic imperial toothing (MXL, XL, L, H and XH) as well as with Powergrip HTD or Powergrip GT toothing. In addition, polyurethane toothed belts are available in metric dimensions with T and AT profiles, and these are often used for transport purposes in addition to the usual power transmission. These belts can be welded to size on request, and if necessary also given an additional covering layer to provide a higher friction coefficient or equipped with cleats.
Rubber belts with small divisions are generally used when (positioning) accuracy plays an important role but adequate power still needs to be transferred. On the other hand, rubber belts with large divisions are more suitable for drives that need to transfer high levels of power.
For drives with extremely high torque at low speed, the PolyChain range of toothed belts provides a suitable solution. The PolyChain Carbon Volt, for example, is the strongest belt currently available. This belt is not only ideal for transferring high torque at low speed, but is at the same time the only polyurethane toothed belt on the market to meet the ATEX directives and therefore be suitable for use in a potentially explosive environment.
Open-ended toothed belts are available in PU as well as rubber variants, and in this form they are ideal for Omega drives. The outer ends of these belt versions are fastened with clamping plates to enable both back-and-forth and up-and-down motion.
Several factors determine which toothed belt type is best suited to a particular drive, for example the application (what is being driven?), the power to be transferred, the desired speed (acceleration or deceleration) and the centre-to-centre distance between the pulleys. It is also important to know what ambient conditions are present and whether there are any space limitations (what is the maximum permissible diameter and width of the pulleys?).
It is very important that the toothed belt is pre-tensioned correctly for optimal drive function. Tension can be measured with a testing device such as the Sonic Tension Meter. This uses the sound waves transmitted by the belt to determine its vibration frequency, which is in turn used to calculate the tension value. As well as ensuring correct tensioning, it is also important that the pulleys are aligned correctly. This is done using a laser-guided alignment system.
Common standards for toothed belt drives are DIN 7721 and ISO 5294. Finally, it is important to consider whether the toothed belts need to be static-conductive to meet ISO 9563 (ATEX environments).