Overrunning clutches

Overrrunning clutches

These devices prevents transmission of inertial loads from implement to the tractor during deceleration or stopping of the PTO.

An overrunning clutch transmits rotary motion only in one direction. It is used to eliminate torque peaks generated by the inertia of implements with heavy rotating masses, such as rotors or flywheels during deceleration or stopping.

A standard overrunning clutch is designed to operate with counter-clockwise rotation of ther driveline on which it is installed. This is the typical rotation of an overrunning clutch installed on the implement side of a driveline connecting a tractor's rearmounted PTO (Clockwise rotation viewed into the shaft) to the implement (counter-clockwise rotation rotation viewd into the shaft).

Two versions of overruning clutches

The RA overrunning clutches are equipped with grease fittings and requires lubrication every 50 hours of use with NLGI grade 2 grease.
The RL overruning clutches are lubricated during assembly and does not require any further lubrication. The RL overruning clutches and are not equipped with any grease fittings.

Function

During normal operation when the tractor is driving the implement, the pawls transmit motion from the housing to the hub. During sudden deceleration og stopping, the driveline is driven by the inertia of the implement, which is connected to the hub of the overrunning clutch.
The Pawls are depressed into grooves machined into the hub, and consequently motion is not transmitted into the housing or other driveline components.
The pawls, under pressure will form the underlying springs, automatically reengage the grooves in the housing when transmission of motion is restored in the normal direction. The torque transmitted creates compressive stress in the pawls of the clutch for a smoother and more reliable operation.
The pressure applied to the pawls is a function of the power transmitted.