ZERO BACKLASH

Backlash is defined as the free movement or "play" occurring between two connected elements when subjected to a reversing movement. Backlash is different from the angular displacement that occurs with change of load i.e. elastic deformation. A Gates EuroGrip® flexible coupling is classed as a zero backlash coupling, this is to say that though it will deform elastically whilst turning, on reversing it will return to the starting point. This feature is particularly required for positioning drives, actuators etc where the final position is critical. The effect of zero backlash can be clearly seen in the hysteresis curve (see left). As the displacement moves through the zero condition, there is a positive distance between the two boundary lines (points A & B). In a backlash situation, the two boundary lines would coincide becoming a single line along the displacement axis, the length of this line indicating the amount of backlash in the connection.

APPLICATION

Kisters ZVT, a market leading German packaging machinery company, produces machines for a world wide base of food and beverage producers. Their packaging machines are both flexible and economical in operation as various conveyor belts are accurately positioned next to each other. Thanks to the use of Gates’ EuroGrip® flexible couplings, which allow radial misalignment up to 1 mm, Kisters have increased the performance of their packaging machines further. Other convincing reasons for Kisters to install EuroGrip® couplings were ease of assembly, compact design and long service life.

HIGH VIBRATION DAMPING

The chart at the right compares the damping coefficient of Gates EuroGrip® flexible couplings against other popular flexible couplings.

SURE-flex® is a registered trademark of T.B. Wood's Company, Chambersburg, PA, USA. All figures taken from the relevant manufacturer's catalogues.

For some time Gates has been working closely together with VW in supplying EuroGrip® couplings on a number of car engines. Two couplings per engine are used. One EuroGrip® coupling drives the alternator, the other drives the AC compressor. The nominal static load is approximately70 Nm due to the power absorbed by the alternator or the air conditioning compressor. The couplings compensate for angular and axial displacement of the shafts connecting the engine’s components. Torsional vibration caused by the crankshaft is damped by the EuroGrip® couplings. Damping increases with the load thus counteracting resonance.

The EuroGrip® couplings are used on two engine types. The 2.5 litre TDI 5 cylinder in line engine with a 128 kW power output and a maximum torque of 400 Nm and the 5 litre TDI V10 engine with a 230 kW power output and maximum torque of 750 Nm. The superior durability of Gates EuroGrip® couplings versus competition was the decisive factor for installing the Gates coupling on the 5 cylinder engine. For the V10 engine type VW opted for EuroGrip® because of its outstanding NVH characteristics (Noise, Vibration, Harshness) properties.