Flexible shaft couplings

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The Reli-a-Flex flexible shaft coupling is suitable for high integrity, high reliability, accurate positioning applications.

Reliance modified its own in-house gear testing equipment to provide an accurate trace of the kinematic error across various coupling prototypes. With accuracies of arc seconds and a data input rate of 200 kHz, dynamic performance graphs were easily produced. A combination of this equipment and finite element analysis enabled Reliance engineers to experiment with different slit configurations in order to determine the criteria that best suited their requirements.

Their design goal was to produce a one-piece flexible shaft coupling which features high torsional stiffness low kinematic error low bearing load and long life.

High torsional stiffness was achieved by putting the beams radially around the coupling. In this way the loads are supported by beams in compression - a definite advantage over other types of coupling where the beams are in spiral pattern and rely on the twisting of the beam to support the drive loads. In addition, with radial rather than spiral beams, the centrepiece is much better supported, therefore higher speeds are attainable than with other types of one-piece coupling.

Based on the double Hooke''s joint principle, using two sets of slits and a solid centrepiece, the Reli-a-Flex coupling achieves low theoretical kinematic error. The second set of slits introduces an equal and opposite angle which allows it to cater for parallel as well as angular offsets.

The Reli-a-Flex coupling is suitable for accurate measuring and responsive precision motion control, both for servos and steppers, and allows feedback devices to operate to higher standards.

The Reli-a-Flex coupling standard range includes: a minute, yet high performance, 6 mm outside diameter micro coupling a range of insulated couplings designed to isolate delicate measurement equipment from the electrically-powered drive with negligible loss of performance and the optional Reli-a-Grip clamp allows the Reli-a-Flex flexible shaft couplings to transmit greater torques by achieving a high clamping force without the need to use set screws.