The relevant health and safety at work provisions state that handwheels must be attached to spindles such that they are not turned along together with the machine drive assembly. Safety handwheels meet this requirement:
- If not in operation, the wheel is disengaged. Shifting it in axial direction (pushing or pulling) will intermesh two serrated bushings, formlocking the wheel with the shaft.
- After releasing, the wheel will disengage again automatically.
A number of user notices are listed below. These notices are non-binding and given without liability. They do not constitute a warranty of proper function. The user must in any case determine whether the safety handwheels are suitable for the intended purpose and use.
All coupling elements are housed in an enclosed component known as coupling attachment. It is designed such that it can be installed in all current types of handwheels and also in other machine elements.
Optionally, the same coupling attachment can be mounted in the handwheel such that the axial movement for dis-engagement is either “pulling” or “pushing” for disengaging. The “pushing” version is safer in terms of health and safety at work because the risk of inadvertent engagement is lower.
Type A (without handle)
As there is no unbalance (handle), this handwheel will also turn along with the drive, but it can be stopped by hand.
With the wheel moving along, the bearing is not put under excessive strain, with the effect that this type is particularly suitable for continuous operation. At higher speeds, the unbalanced handwheel may cause vibrations, however. Also, the friction heat which develops when braking the wheel must be kept in mind.
Type D (with handle)
The handle (unbalance) causes the disengaged handwheel to stop while the shaft is turning. Owing to the type of construction and bearing design of these couplings, the use of these handwheels is usually limited to relatively slow-turning spindle speeds or spindle speeds running at higher speed for short periods. A high risk of dirt deposits (grinding dust) and dry-running can limit the user options even further.
If the handwheel and its handle are deliberately or inadvertently set in (concurrent) motion while the shaft is turning, bearing friction may cause the wheel to turn permanently. At higher speeds, this may cause vibrations and, considering the rotating mass of the handle, can result in injuries also if disengaged. This risk / operating status must therefore be avoided at all cost.