Maintenance free couplings from Renold Hi-Tec

Gear couplings and grid spring couplings, for instance, require lubricating every three months and on very arduous applications they may require lubricating weekly, or even daily. This can be even more problematic where access is difficult. For example, on large ladle cranes, for transporting molten metal in foundries, an engineer has to climb up to where the couplings are located and then remove the guards before they can be lubricated.

Renold Hi-Tec's PM and RB ranges of rubber-in-compression couplings provide the solution. They are not only maintenance free they also help to reduce maintenance and extend the working life of the machinery on which they are installed. Additionally, because of their design, they are intrinsically fail-safe eliminating the problems that can occur as a result of coupling failure.

Rubber-in-compression couplings are comprised of two round metal sections fitting one inside the other with what looks like the paddles of a paddle steamer projecting inwards from the outer section and outwards from the inner. The rubber blocks are placed in the spaces in-between the paddles, and, as the outer section is turned by the motor, it drives the inner section through the rubber blocks. As this happens the rubber is compressed and hence the term rubber-in-compression.

As the rubber blocks are totally encased in metal they can only change shape during operation, thus ensuring that the drive is always maintained. This is particularly important on applications where coupling failure would be catastrophic resulting in complete loss of power, or load being dropped by cranes or hoists.

The rubber blocks, that are carefully selected for each application, absorb vibration within machinery that if left unchecked would cause premature wear and early fatigue failure. They also eliminate backlash, a cause of torque amplification, and ensure that the natural frequency of the system does not coincide with its running speed.

Rubber-in-compression couplings provide the lowest lifetime costs and are a truly fit and forget option as they require zero maintenance and will operate quietly without requiring any attention for many years. Renold Hi-Tec's PM range of couplings are designed for heavy-duty applications up to 6,000kNm of torque and where severe shock loads and vibration could cause problems.

For smaller, less arduous applications the RB range of couplings is a cost-effective maintenance free option suitable for up to 41kNm of torque. Typical applications include, main mill stands for rolling mills, cranes and hoists, table roller drives, picking lines, coilers, fan drives, mine winders, grinding mills, crushers and conveyors.