Abstract: A controller opens or closes a valve in response to the ambient temperature crossing a threshold value, for example to prevent the continued supply of water to pipes that might have frozen and burst. An output shaft (4) acts on a stem of the valve to rotate it between the open and closed positions. A clock spring (8) biases the output shaft towards one of those positions but is restrained by a latch (28) until a thermal actuator (30) operates mechanically to release the latch in response to a change in temperature. The latch may be a pawl (28) acting on a ratchet gear (22) that allows the output shaft (4) to rotate in one direction but not the other. The ratchet gear (22) may be mounted on an input shaft (14), which is connected to the output shaft (4) through a gear train (16-19) to give a mechanical advantage when turning the output shaft (4) against the force of the spring (8).

Abstract: A controller opens or closes a valve in response to the ambient temperature crossing a threshold value, for example to prevent the continued supply of water to pipes that might have frozen and burst. An output shaft (4) acts on a stem of the valve to rotate it between the open and closed positions. A clock spring (8) biases the output shaft towards one of those positions but is restrained by a latch (28) until a thermal actuator (30) operates mechanically to release the latch in response to a change in temperature. The latch may be a pawl (28) acting on a ratchet gear (22) that allows the output shaft (4) to rotate in one direction but not the other. The ratchet gear (22) may be mounted on an input shaft (14), which is connected to the output shaft (4) through a gear train (16-19) to give a mechanical advantage when turning the output shaft (4) against the force of the spring (8).