Overrunning Clutch Selection Guide
OVERRUNNING: NORMAL ENGAGEMENT — REVERSE OVERRUNNING
Disconnecting driver and driven elements Cam Clutch units are often used to protect critical pump/drive equipment from being reversed upon start-up, or when overloaded. Pumps can be overloaded with stacked material on the discharge side, resulting in reverse rotation. To prevent these damaging conditions from occurring, a Cam Clutch is installed between the pump and the motor. In this application, the Cam Clutch will engage to allow normal pump operation, and overrun to prevent reverse rotation. Please reference Figure 31 for a depiction. Disconnection of driven side Figure 32 depicts an application in which the hose drum of a pipe flusher is being driven. When the hydraulic motor is rotated in reverse in the counter- clockwise direction, the Cam Clutch inner race rotates in reverse, and the Cam Clutch overruns. The flushing pump is driven in this state. The flushing water passes through the hose and gushes out of the nozzle toward the back. The force of this water jet starts the nozzle running and pulls and unwinds the hose. At the same time, the hose drum starts reverse rotation in the same counter-clockwise direction, and increases its speed of rotation until it reaches the overrunning speed of the inner race. At this point, the Cam Clutch engages, and the hydraulic motor works as a brake to stop the acceleration of the drum. Therefore, the running speed of the water jet nozzle is kept constant. When the hydraulic motor is rotated normally in the clockwise direction, the Cam Clutch engages to wind the unwound hose onto the drum.
Cam Clutch
Water surface
Figure 31: Inclined pump – Medium Overrunning Application
Application in pipe flusher
Cam Clutch
Figure 32: Pipe Flusher – Medium Overrunning Application
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