| 摘要 |
PROBLEM TO BE SOLVED: To secure the indoor-side heat insulating property of a steel door frame which is installed on the assumption that it may be renovated in the future. SOLUTION: The steel door frame A is formed of a base frame 1 which is to be fixed to a concrete skeleton 8, and an annexed frame 3 which is screwed to and integrated with the base frame 1. The steel door frame A serves as a double frame in which the newly annexed frame is installed by removing a screw 6 of the annexed frame 3. A position to fix the annexed frame 3 to the base frame 1 corresponds to a portion in which an indoor-side L-shaped portion 15 of the base frame 1 and an airtight-material bottom plate portion 33 of the annexed frame 3 overlap each other in the airtight-material receiving groove 14 of the door frame. A spot facing-contact portion 4 with a small area of the order of 1-4 cm<SP>2</SP>, in which a screw through-hole 41 is provided in a penetrating manner in a plane, is formed by applying press-forming to the bottom plate portion 33. The screw 6 is fixed by screwing the screw 6 into the internal thread of the L-shaped portion 15 from the screw through-hole 41. Since the base frame 1 and the annexed frame 3 are fixed together by the point contact of the facing-contact portion 4, they are thermally insulated, so that cold air can be prevented from reaching an indoor-side casing 16 of the base frame 1. COPYRIGHT: (C)2008,JPO&INPIT
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