What is a casing?
A Casing is a tube or conduit the flexible shaft rotates within. It is part of the overall flexible shaft assembly and has its own end fittings, called ferrules, which attach the casing to the stationary mounting points at either end of the drive system.
A Casing serves several purposes depending on the application:
- Protection from moisture, dust, dirt and other environmental factors
- Retaining lubricant
- Limiting the phenomenon of helixing or “corkscrewing” a shaft may experience in high torque applications
- Controls the bending of the enclosed shaft by guiding it through natural and gradual bends while limiting how tight of a bend radius it can achieve
- Prevent injury to the operator by contact with unprotected rotating shaft at high speed
What types of ferrules are typically used?
Ferrules are used to attach the casing to its mounting points. They are typically made of metal or plastic and have mounting features allowing them to be securely attached to a mating surface.
Ferrules give axial and torsional support to the casing. Without the ferrule the casing would just float on top of the rotating shaft, being free to rotate somewhat with the shaft due to the friction between the shaft and casing. The ferrule prevents this from happening. Also, the ferrules can be used to create and environmental seal, keeping moisture, dirt, and dust out of the inside of the casing and away from the flexible shaft. Ferrules can be simple slip fits or more involved machined parts that screw into their mating points.
Here are some of the most popular configurations:
- Threaded Nut
- Flange (two & three holes)
- Panel Mount
- Quick Disconnect