RULAND Manufacturing Co. has expanded its line of zero-backlash jaw couplings to include more compliant spider elements for applications where greater shock absorption is desired.
Zero-backlash jaw couplings are three-piece couplings comprised of two hubs with curved jaws and an elastic element.
The spider, made of an advanced polyurethane material, provides dampening of impulse type loads, minimising shock to the motor and other sensitive equipment.
As a result of this addition, spider elements of three different hardness levels are offered with each represented by a different colour.
The new blue spiders have a durometer of 85 shore, yellow spiders are 92 shore and red spiders 98 shore.
The availability of spiders with three hardness levels allows the end user to customise the jaw couplings performance.
Selecting the new soft spider element will give the jaw coupling the greatest dampening characteristic, while a harder spider element will provide the greatest in torsional rigidity.
All spiders are press fit onto a curved jaw profile - generous chamfers on the spiders and jawed hubs make this assembly easy. Because of this press fit, Ruland jaw couplings operate with zero backlash. This would not be possible without the special design of the curved jaw profile.
In standard jaw couplings, the jaws have a straight profile and a pressed fit would result in distortion of the elastic element as forces push the spider's "limb" out.
With a curved jaw profile, forces on the spider's "limb" are concentrated to the centre, improving the effectiveness of the elastomer material.
Standoffs, located on the spider "limbs", assist in angular misalignment capabilities, as well as electrical isolation.
Ruland jaw couplings are ideal for many servo applications with reversing torque since the spiders absorb shock and dampen vibration, yet the couplings are zero backlash.
The three piece design of jaw couplings eases blind assemblies and allows for an easy mixing of inch and metric bore sizes.
Jaw couplings are considered fail safe should the spider element ever fail, the jaws on the hubs provide a direct power transmission, allowing the application to safely shut down, after which the spider can easily be replaced.
The couplings are available from stock in a choice of seven outside diameters from 15mm to 57.2mm in both set screw style and clamp style.
A large variety of metric and inch bore sizes from 3mm to 30mm are available.
Naismith Engineering & Manufacturing represents Ruland in Australia and New Zealand.