| 摘要 |
An electric resistance heater engageable with work to be heated including a work-engaging heater structure of minor thermal mass per unit area and including an elongate primary heating element arranged to establish high watt density throughout said heater structure, a power supply, a temperature control means between and connected with the primary heating element and the power supply; said temperature control means including a work engaging body of greater thermal mass per unit area than the heater structure and carried by said heater structure in spaced relationship with the primary heating element, a normally closed thermal responsive switching device within the body and operable to open when the temperature of the body is heated by heat conducted from the work to a predetermined operating temperature, an elongate secondary heating element arranged in the body to delivery sufficient heat into the body to normally maintain the temperature thereof at a temperature slightly below said operating temperature whereby little heat need be conducted from the work into the body to raise its temperature to said operating temperature, said elements and device being series connected with the power supply. The device further includes a heat pipe extending between the heater structure adjacent the primary heating element and the body to rapidly and directly conduct heat and to raise the temperature of the body to said operating temperature when the temperature differential between the heater structure and body becomes excessive and before the temperature of the heater exceeds a predetermined maximum operating temperature. |
