Mechanical coupling targets gen-sets, pumps, compressors

Diesel Progress North American Edition, Nov, 1997

The couplings are manufactured by Centa in Germany, and distributed to the North American industrial markets by Lovejoy, Downers Grove, Ill.

The Centamax series B coupling is designed primarily for main and auxiliary diesel drives powering nonflanged, remote-mounted equipment such as generator sets, pumps and compressors. This includes flywheel-to-shaft and shaft-to-shaft applications, and both flexible- and rigidly-mounted driven units.

"The biggest advantage is that this design is essentially free of any backlash," said Dick Deible, Centamax product manager at Lovejoy. "On the original SB series, the element is affixed into the ring with gear teeth. It works very well, but eventually, you have some degree of backlash.

"With this coupling, the element is pinned in place and there is no backlash at all."

Available in 10 standard sizes, series B couplings can be tailored to specific torsional stiffness ranges by choice of elastomer shore hardness ratings of 50, 60 and 70. This provides nominal torque capacities from 515 ft.lb. to 11,000 ft.lb. (700 to 15,000 Nm), with maximum torque ratings of two times nominal.

The patented design features a steel-plate input flange ringed with 24 single-bolted steel bushings, which mate with the teeth of the output hub's rubber elastomeric disk. Locked in precompression during assembly - with bushings pressed into place and bolts tightened - the elastomer suffers almost no distortion while absorbing axial tensions and misalignment forces in operation. This minimizes internal heat build-up that could otherwise lead to hardening of the elastomer and eventual destruction under load.

"The precompression takes place when the element is pinned in place," said Deible. "Rubber precompressed provides better life and better operating characteristics."

The Centamax B couplings are engineered to provide extended service while protecting the entire drivetrain from vibratory torques and misalignment stresses throughout the system's power range. An optional fail-safe design employs an alternate bolt arrangement that directly links the hubs to ensure uninterrupted power transmission should the elastomer fail. In critical situations, this prevents system downtime until the elastomer can be more conveniently replaced, the company said.

The couplings can be used with SAE (J620) flywheel sizes from 11.5 to 24 in. and the temperature-resistant rubber Centamax element can be blind-assembled. It can also be maintained and exchanged without displacing either driving or driven equipment.

The Centamax series B couplings can also be equipped with Lovejoy's Centaloc spline shaft clamping hub, which prevents spline chatter and distortion and the resulting spline fretting and/or driven shaft, seal and bearing damage. The hub secures with a set screw which, when torqued, forces clamping pressure to be applied evenly around the entire spline shaft profile. This unifies hub and shaft into a single assembly absolutely free of play, and avoids set-screw damage to the shaft.

Like all of Lovejoy's products, which include elastomeric, metal and specialty couplings, universal joints, chain/belt tensioners, motor bases and pulleys, the new series B couplings are available through a worldwide network of distributors, supported by 20 sales offices and eight regional warehouses in North America and Europe.