Residential Elevators designs, manufactures and installs elevators for home use. So the company is always on the lookout for design enhancements that will keep its elevators moving with the least amount of maintenance.
One such change has been the adoption of Ringfeder Locking Assemblies to attach heavy-duty cable sheaves onto the motor-driven shafts that raise and lower the elevators. These sheaves undergo constant clockwise and counterclockwise changes in rotational direction as the elevator rises and falls.
The locking assemblies have taken the place of a keyed connection, which is the traditional way of connecting shaft to sheaves.
Keyed connections work just fine in many applications, but not this one. That’s because the constantly reversing torque creates high, concentrated stresses in the keys. Over time, the keys in these reversing applications tend to wear and fatigue—adding an ongoing maintenance cost to the operation of the elevator.
Locking Assemblies Distribute Forces Uniformly
Locking assemblies take a very different approach to torque transmission. They feature a pair of double-tapered thrust rings that, when tightened, expand radially to create a compression fit between a shaft and its mating component, locking them together.
Unlike keyways, which concentrate stresses along a single line of contact, locking assemblies distribute torque-transmission stresses evenly over 360 degrees of contact. This uniform stress distribution eliminates the wear and maintenance costs associated with keyways in reversing applications.Locking assemblies are available for shafts ranging from 16 to 1,000-mm in diameter as well as standard inch sizes from 5/8- to 8-inches. Depending on the size, they can transmit torques from 300 to more than 2 million Nm. In addition to elevator applications, they’re commonly to connect shafts to chain wheels, gear mechanisms, pulleys, and belt drums.