| 摘要 |
An actuator suitable for valves in refrigeration systems comprises a chamber 15 containing an expansible medium 25, electrical means 27 for heating or cooling the medium, means 29, 31 for producing an electric signal representative of the temperature of the medium, and actuating means 11, 9 movable in response to the pressure exerted by the expansible medium. To protect the chamber from draughts etc. it is arranged within a hollow protective screen 33 which ensures that heat transfer between the chamber and its surroundings is predominantly due to convection currents passing between the screen and chamber. <IMAGE> |
