A manufacturer of geophysical surveying trucks, facing a need to provide a winch drive for lowering a sensitive scanner into Arctic-region boreholes up to 3,000 m deep, launched a search for a suitably robust, reliable and accurate clutch and found the solution in the model E320 VAR-04 tooth clutch from Warner Electric division of Altra Industrial Motion.
Warner Electric’s model E320 tooth clutch.
Tooth clutches have two contacting plates—one driving, the other driven—with intermeshing teeth. When the clutch is engaged the plates are brought into contact, with the teeth alternating and providing a positive drive; when disengaged, the plates are separated by a distance sufficient for the teeth of the driving plate to rotate without touching those of the driven plate. They can be set up to be normally engaged or normally disengaged, and the actuation can be mechanical, electromechanical, electromagnetic or pneumatic.
According to Warner Electric, tooth clutches are recognized as providing great torque in a small envelope size. In operation, they have zero backlash and thus can attain and hold a set position with precision accuracy, ideal for the borehole survey work to be undertaken.
In the final winch solution, the tooth clutch is positioned between a slow-moving gear motor and the winch drive. This arrangement enables slow, controlled movement up and down the borehole and also allows positioning of the scanner at set points, so that accurate measurements can be taken.
The geosurvey winch clutches are electromagnetic and activated by power-on. They are designed for engagement at very low speeds, while serving as a positive coupling drive without slipping. The E320 VAR-04 clutches require no wear adjustment and feature sealed bearings for dry operation and a fixed inductor mounted on the ball bearings. Their 3,200-Nm static torque capacity makes them ideal for the winch drive. Other versions of the E320 clutches are also available, such as models with unsealed bearings for use with external lubrication systems.
In use, the clutch is used to control the slow, careful descent of a scanner down the borehole, so that it does not swing against the sides and cause damage to the instruments. It allows the scanner to be stopped at precise points in order to take readings. Its simple robust design is suitable for use in the ultra-harsh Arctic environment, according to the vendor, where more delicate mechanisms would be likely to fail.