| 摘要 |
PURPOSE:To ground a motor shaft without causing a growth of corrosion by forming multiple triangular protrusions with their sides facing outwardly at the root of the threaded stem so that the bearing surface may tightly contact with the bottom wall of the heating chamber as the screw is screwed-in. CONSTITUTION:Equally spaced three (multiple) triangular protrusions 10 are formed at the root of the steam 6a of a screw 6. When the screwing-in of the screw 6 is about to be over, the end surface of a hole 7 is scraped by the protrusion 10... which remove the coating film on the surface, and when the screwing-in is completed, the bearing surface of the screw 6 tightly contacts with the bottom wall of the heating chamber 1. A motor shaft 3 can be grounded to the main unit body through the screw 6, motor mounting plate 2a and heating chamber 1 without forming a gap between the bearing surface of the screw 6 and bottom wall of the heating chamber 1. Corrosion due to the intrusion of water and foreign substances into the hole 7 can thus be prevented, and, as the electrical connection is done by scraping the end surface of the hole 7, the grounding is ensured.
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