When called on to investigate wear problems with a customer’s rotary lathe, the engineers from The Rowland Co., Philadelphia, were faced with several issues.
The lathe’s electric clutch used a pinstyle connection to transmit torque. Unfortunately, the high inertia of the bull gear resulted in a shock load, which wallowed out the pin drive holes in the clutch over a short period of time. This process then accelerated, until a component failed. There were also problems from an operational standpoint. As the clutch was an on/off device, the operator could not control the engagement to cushion the shock.
Switching to an air-actuated friction clutch seemed to be the logical choice, but the original design positioned the clutch between two bearings with no room on either end. The clutch also connected directly to a large chain sprocket. But Rowland wasn’t fazed. According to Bob Gartrell, sales engineer, “The clutch was buried in a very small space in the gear train, so it required some design modifications to be a ‘drop in’ for the original electric clutch. We decided to completely eliminate the pin connection, replacing it with a spline engagement, which gives us increased surface area to absorb the shock.”
The air clutch turned out to be the right solution, maximizing torque in the confined area. With the new design, lathe operators are able to control the air pressure, providing smooth startups. And Rowland reports that the customer has reported several years of maintenance- free operation with the setup.