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The TorqueSentry

The TorqueSentry Device is a torque limiting coupling. Its main purpose is to avoid catastrophic failure or destruction in the case of overload of the driveline, which can result in injuries or unexpected and expensive downtime of the entire system.

The TorqueSentry design offers several design features:

• Immediate and precise point of release
• Adjustable release torque possible
• Selected release torque remains constant and is not susceptible to fatigue
• Back-lash free power transmission
• Minimal maintenance requirements

Function and Design

The principle of the TorqueSentry is very simple, but highly effective. A pair of tapered pressure rings are forced over a tapered sleeve by oil under pressure. The pressure ring is then locked in place by mechanical fuse pins. This produces a friction connection between a sleeve and a shaft. At overload, the coupling instantaneously releases the fuse pins and interrupts the drive.

Design:
The TorqueSentry consists of a pair of tapered pressure rings and an inner tapered sleeve. The volume between the pressure rings can be pressured up to 15,000 psi (1000 bar) using oil. A series of pins are then positioned under the teeth of a feedback ring. The feedback ring is fixed to the shaft. If any overload occurs, this feedback ring rotates forcing the fuse pins out from between the pressure rings. The pressure rings release their clamp force and the shaft and sleeve are free to rotate. The area around the pressure surface and bearing is filled with oil, which supports a constant friction coefficient and, in turn, gives a precise release torque. In contrast to shear element couplings the release torque of the TorqueSentry is not influenced by material fatigue. The release torque always remains constant.

Function:
To start operation of the coupling, oil is pumped between the pressure rings. The required oil pressure can be selected from a calibration diagram. The selected hydraulic pressure generates a defined friction load between the sleeve and shaft. If the operating torque exceeds the selected slip torque, the shaft rotates within the sleeve. The feedback ring is fixed to the shaft, which makes it rotate along with the shaft and forces the fuse pins out from between the pressure rings. This causes an instantaneous drop in clamp force and releases the friction connection.