Pneumatically actuated swing clamps that incorporate a mechanical locking action and ensure that the full holding force (200-600N) is maintained in the case of air pressure reduction or loss, has been introduced by Hitchin-based Roemheld UK Ltd (www.roemheld.co.uk).

The clamp, which operates at a pressure of between two and six bar, is a pull-type cylinder with a piston that is automatically locked when the workpiece has been clamped, after which the air line can be depressurised or uncoupled (such as during pallet change).

For unclamping, which is monitored, only the minimum pneumatic pressure is needed. A feature of the clamps is a pair of flow control valves (easily adjusted from above) that allow the speed of the swing mechanism to be reduced if the flow rate is too high or when heavy clamping arms are being used. The valves also allow synchronisation or sequencing of the closure of several connected clamps.

Swing angle is normally 90deg (clockwise or counter-clockwise), although 60deg, 45deg — or even zero deg — can be specified. If machining dry or with minimum quantity lubrication, the ingress of small particles can be prevented by the use of an additional wiper ring.