Cone valves are leak elimination valves that are used in conjunction with medium sized (30 – 50 mm) flat vacuum cups.
Cone valves seal off cups that are not in contact with a workpiece to limit the amount of leakage that is caused by cups not in sealing contact.
Like mechanical valves, if workpiece edges vary in position, a cone valve could be opened by the workpiece while the vacuum cup is not in sealing contact. This would defeat the purpose of using a cone valve.
Cone valves are closed until the stem contacts a workpiece; This opens the valve and admits vacuum to the vacuum cup.
Since cone valves need contact with the workpiece to operate, it’s good practice to limit relative movement to reduce the risk of leaving a mark on the workpiece.