Vacuum-powered cup cluster hoist for milking parlour - has piston with permanent magnet which contacts hall effect switch to operate vacuum release valve when load is removed from hook

摘要

This pneumatic hoist is intended for use in a milking parlour. A piston rises inside the cylinder, due to the partial vacuum above it, pulling up a cable with the milking cup cluster clipped onto a hook. When the load on the hoist is removed, a central portion in the piston rises, bringing a permanent magnet into contact with a Hall-effect switch. The switch opens a vacuum valve allowing the piston to drop, and the hook to be re-loaded. The advantage of the Hall effect switch over conventional mechanism microswitches is that it is unaffected by dirt, vibration or mechanical shock.