Curved jaw shaft couplings from Techdrives are now available with four larger sizes. These couplings consist of two hubs and a central flexing element. The hubs have jaws with curved surfaces that mesh with the moulded curved surfaces of the polyurethane elements so that torque transmission is made with the polyurethane in compression.
With steel, aluminium and cast iron hub options together with elements of varying stiffness, curved jaw couplings give machine designers freedom of choice. The Techdrives range of GR couplings has been expanded from shafts of 5 to 90mm up to 145mm with the addition of 4 new sizes, making 13 sizes in all. The simplicity of the design leads to highly economic selections.
A choice of three polyurethane grades for the central element allows a play-off between torque and coupling stiffness. Increasing the element stiffness also increases the torque but reduces the misalignment capacity. Standard yellow elements with rated torques from 10-6650Nm and moderate torsional softness are suitable for the majority of customer applications. Harder red elements increase rated torque and stiffness by about 50 per cent. Green elements are a step up again with 25 per cent more torque and about 50 per cent high stiffness. Engineers can opt for low cost un-machined hub jaws which give a small amount of backlash, or for reversing drives they can choose machined jaws which give a backlash-free coupling.
The lowest-cost hub options use a keyway connection to the hubs. Some designers prefer to avoid keyways because they are stress raisers, expensive to machine and they do not allow adjustment of timing. Here the GR curved jaw couplings have an answer with aluminium clamp hubs available for shafts 5 to 45mm. A single side-mounted bolt compresses the split hubs onto the shaft and torque is transmitted by friction. This makes precise setting of radial and axial position possible, and also the assembly is backlash free. Other variants of these curved jaw couplings include double couplings with a customised central spacer and couplings to connect from diesel engine flywheels to shafts.
Curved jaw shaft couplings from Techdrives are similar and largely interchangeable with the European models, but offer good availability, high quality and a long service life. More details are given on the Techdrives website www.techdrives.co.uk.