Abstract: A holding mechanism for holding a workpiece in position during an operation being performed by an operating device (7) passing along the workpiece includes a toggle linkage (1, 2, 3), a projecting member (9) attached to the device, and a cam track (2) connected to one part of the toggle linkage, the arrangement being such that, towards the end of the pass of the device, after it has completed its operation on the workpiece, the projecting member (9) engages the cam track (2), further movement of the device causes the projecting member (9) to move the middle pivot (3) of toggle linkage to release it and, hence, release the workpiece as the device completes its pass. Preferably the toggle linkage is arranged as an over-center toggle linkage with its other component formed by a telescopic arm (1).

Abstract: A control unit for a gas-fired appliance comprises a service tap that acts also as a flame failure device. The flame failure device controls gas flow to a gas governor which is an integral part of the unit and associated with the gas governor is a low gas pressure cut-off. The unit also incorporates a modulating gas flow control valve operatively coupled to a thermostat which, in the case of a gas-fired water heater, is responsive to water temperature in the heater. When used with a water heater, the unit also includes a further thermostat set to terminate gas flow in the event that a predetermined maximum water temperature is exceeded.