PURPOSE: To improve the heating efficiency of water stored in a tank by arranging an electric heater in a case protruded to the inside from the outside of the bottom part of the tank, and pressing and holding its lower face by a pressing plate of a metal whose thermal conduction is good.
CONSTITUTION: A heater case 24 obtained by working a stainless steel plate is formed by protruding the center part in a circular shape, and attached in a watertight structure to the bottom face of a tank 2 made of plastics with a screw, etc., through packing 27 whose outside peripheral part is annular. A mica heater 23 is arranged in the protruding part of the heater case 24, and pressed against the heater case 24 and fixed by bring the pressing plate 25 formed by a metal whose thermal conduction is good such as stainless steel to press fitting from its lower part and engages its outside peripheral part 25a with a projecting shape 24a. The fitting plate 29 of a temperature sensor for detecting the abnormal rise of a temperature uses a metal and brought to thermal coupling to the heater case 24, extended to the lower part and the temperature sensor 30 is disposed at some distance from the mica heater 23.
SUGITA MAKOTO
TAKEI HAJIME
SHIMIZU NORIYASU
