Thermo-actuator

A thermo-actuator having an actuating rod, a guide member slidably mounted on the actuating rod, a resilient seal bag provided around a first end portion of the actuating rod and hermetically sealed to the guide member, a heat conductive cylinder housing the seal bag and the actuating rod and secured to the guide member, wax provided in the heat conductive cylinder to enclose the seal bag, and a tubular sealing member made of rubber slidably mounted on a second end portion of the rod, the improvement comprising:

• the seal bag having a base portion secured to the guide member, and a bag portion around the actuating rod with a gap which is filled with lubricating oil;
• a seal device comprising an O-ring and a retainer and provided in the guide member around the actuating rod so as to prevent the lubricating oil in the gap from entering the sealing member;
• the sealing member having a tubular body having a straight tubular form in a free condition, skirt portion, a head portion, and a plurality of thinner portions and thicker portions which are alternatively disposed so as to be shrunken into a bellows, the skirt portion being secured to the guide member and engaged with the retainer so as to hold the seal device, the head portion being secured to the rod at an end of the second end portion of the rod.