1. Field of the Invention
The present invention relates to an apparatus for local forced heating of a joint on the steel plate of an auto body when the joint is reinforced with a buildup of plastic solder. More specifically, it relates to a heating apparatus for hardening to be used in the process of building up the joint on the steel plate of an auto body with plastic solder. The process comprises the four steps of pretreatment of the steel plate, building up by plastic solder spraying, hardening by heating, and grinding to a smooth finish.
2. Description of the Prior Art
In the conventional practice of heating plastic solder built up on a joint of steel plate, an ultrared heater has been used for local heating. This process has drawbacks, such as the temperature rise characteristic being easily affected by environmental conditions like atmospheric temperature or wind, the feedback control of temperature being difficult for an auto body being carried on a conveyor, or a wide variance occurring in the rate of temperature rise along the joint even when the heater arrangement is adjusted to change the watt density along the joint.
Also, in the conventional practice, even if a hot air blast is adopted for heating a joint, the hot air escapes and the efficiency of temperature rise is poor. Further, heating extends to unnecessary parts thereby burning the anti-rust oil applied to the auto body, and a wide variance occurs in the rate of the temperature rise.
Japanese Utility Model Applications Sho 51-158035 and Sho 51-122612 are typical examples of the conventional method and apparatus.