A torsion spring assembly for a throttle

A throttle 10 biased closed in a fail safe position comprises a helical spring 32 mounted on a shaft and assembled to an insert 30 and sector gear 38 to oppose opening. Insert 30 has a bore 50 and a collar for mounting and centralising spring 32, an aperture for receiving a portion of one end of the spring 32 and prevents spring 32 rotating, slots 54 which accommodate fingers of a winding tool for turning the insert 30 and subsequently tensioning spring 32 and also provide clearance for snap fit features of a cap, and a wide tab 52 and narrow tab 56 which correspond and secure with slots in a pocket of a motor cover 16 when the insert is rotated. Gear 38 has an aperture 40 for receiving a portion of the other end of spring 32 and is connected to a drive train including a motor 18 having a gear 34 and cog 36 for turning the shaft mounted on a bore 39 in gear 38. The assembly may also be used for any valve such as butterfly, ball, gate and globe valves and plug cocks. The motor maybe replaced by other actuators such as pneumatic or hydraulic cylinders and the gear maybe replaced by levers, screws, pulleys or other suitable mechanical means.