The primary purpose of a coupling, either bellow or helix, is to join two pieces of rotating equipment, while permitting some degree of misalignment or end movement, or both.
Shaft coupling is used in machinery for several reasons, the most common of which are:
- to provide a means of connecting two separately manufactured devices such as a motor and encoder
- to provide compensation for misalignment
- to enable easy disconnection for repairs or alterations
- to provide a reduction of shock loads form one shaft to another.
Multiple factors should be taken into account when looking to use flexible shaft couplings. These are torsional stiffness, backlash, torque, and attachment style.
Bellows couplings generally have high torsional stiffness and may be used in any drive system where high levels of motion integrity are essential. This is because bellow couplings are backlash free and capable of speeds of up to 10000rpm. This coupling also offers vibration damping, radial offsets, axial offsets & angular offsets.
Bellow couplings are manufactured from either stainless steel or wrought copper with nickel plating, and either material option is available with flanged ends and attachment style options include set screw or clamp.
Helix, or beam, couplings are manufactured as one piece therefore achieving flexibility in all three modes; angular, radial and axial, by means of a slot or slots machined through the wall of the material. The slots are machined helically around the circumference of the coupling and can have one, two or three starts to increase the torsional stiffness while providing backlash free operation.
These helix couplings are capable of speeds of up to 8000rpm and are manufactured from aluminium, stainless steel or nylon. Attachment styles options also include set screw or clamp.
A typical application for both bellows and helix couplings include encoder drives in closed-loop servo systems.