ELECTROMAGNETIC SHIELD-TYPE DOORWAY FOR BUILDINGS AND ELECTROMAGNETIC SHIELDING SYSTEM THEREFOR

Abstract: An electromagnetic shield-type doorway or entrance for a building is provided with two doors (2, 3) having an effectively curved passageway between them. By lengthening the passageway to such an extent that the two doors (2,3) cannot be opened simultaneously, electric waves can be blocked at either of the doors (2,3). The electromagnetic shielding effect can be enhanced by installing a revolving door (10) in the passageway and attaching electrically conductive brushes (13) to at least the lower edge and one side edge of the revolving door to fill the gaps (12) at these edges. In a system for electromagnetically shielding a building, a doorway passage of the building is partitioned by three or more doorways (A, B, C) each having an electromagnetic shielding function. When persons leaving and exiting a building simultaneously approach entrance and exit doors (A, C) at the ends of the doorway passageway so that these doors (A,C) open at the same time, the central doorway (B) remains closed to maintain the integrity of the electromagnetic shield. If a large number persons are entering and exiting, the doors (A,B,C) are opened and closed in an interlocked manner so that one of the three doorways (A,B,C) will always be closed, thereby maintaining the intergrity of the shield in reliable fashion without hampering entry and exit.

Description: This invention relates to an electromagnetic shielding doorway and revolving door for an electromagnetically shielded building. In many modern office buildings, information generally is communicated between the interior and the outside of the building by making joint use of information communicating equipment such as multiple electronic exchanges and computers. With the increasing value of information, diversification of user needs with regard to information and the increasingly individual nature thereof, the accurate and rapid transmission of information into large-scale buildings has become of prime importance. For this purpose, data highway-type information networks utilizing optical fiber cables or coaxial cables have been proposed. However, such cables must be stretched throughout all parts of the building, and this work takes time and expense. If electromagnetic waves are used to transmit information within the building, laying cables is unnecessary, but radio law may limit the usable frequency to no more than 3 T(tera) Hz owing to the emission of electrical noise waves from such a building. Another problem is that the communication system may malfunction due to radiation from outside the building, television intermediate frequencies from inside the building, electric radiation from wireless microphones, and the like. Accordingly, in a building of the above type, the overall building is electromagnetically shielded, even at window openings and doorways, by using glass containing a conductive mesh or glass to which an electrically conductive film has been affixed. DE-3434676 describes a cabin having metal walls containing screening insulation. Merely providing the door at a doorway with an electromagnetic shielding structure does not make it possible to maintain a perfect electromagnetic shielding effect at all time since the door is opened whenever someone enters or leaves the building. At such times electromagnetic radiation leaks in from the doorway and impairs electromagnetic communications within the building. Therefore, in a building the overall structure of which is electromagnetically shielded, it is essential that the shielding effect be maintained constantly even when a door is opened and closed. In a case where a doorway employs a revolving door, to provide the revolving door with an electromagnetic shielding property is an effective way to maintain a constant shield since the interior and exterior of the building are never electromagnetically opened to each other, regardless of the angular position of the revolving door. However, in order to obtain smooth rotation in a conventional revolving door, a gap is provided along one longitudinal side edge and the lower edge of the door. As a result, electric radiation leaks through the gap whenever the revolving door is used, and a satisfactory electromagnetic shield cannot always be maintained. DE-U-7112241 shows a revolving door for a nuclear radiation shelter which has metallic strips at its side edges; there is no suggestion that such door be used in a building as described above and because it is not intended to provide an electromagnetic shield, there is no suggestion or need for the metallic strips to be grounded to the rotary shaft. Moreover if such strips were used on a door in a building, the door would not revolve smoothly. Though it has been contemplated to provide double automatic doors in order to solve the above problems, there are instances where both doors open simultaneously, as when one individual is entering while another is leaving at the same time. In such instances the integrity of the electromagnetic shield is not maintained. An object of the present invention is to maintain a satisfactory electromagnetic shielding effect at all times by preventing the leakage of electric waves around a revolving door in a shielded building without impairing the smooth rotation of the door. According to the present invention we provide an electromagnetic shielding doorway and revolving door, for a building in which electromagnetic shielding members are used to construct a body of a building and window and doorway openings to provide the overall building with an electromagnetic shielding structure, in which door and doorway electrically conductive brushes are attached to at least a lower edge and side edge of a revolving door arranged in said doorway, thereby filling gaps at said edges, and material which absorbs electromagnetic radiation is positioned around the periphery of said revolving door; characterised in that said electrically conductive brushes are electrically interconnected and grounded at the rotary shaft of said revolving door. The electrically conductive brushes attached to at least the lower edge and side edge of the revolving door fill the gaps at these edges. This improves the effectiveness of the electromagnetic shield and at the same time leaves the gaps present around a conventional revolving door, so that the door will revolve smoothly without impediment. In addition, a revolving door having the same size as that of the conventional revolving door can be used. By installing an electromagnetic wave absorber in the walls, ceiling and floor surrounding the revolving door, electromagnetic radiation blocked at the revolving door can be absorbed there, whereby the electromagnetic shielding performance is improved. In the accompanying drawings: Fig. 1 is a sectional view illustrating an embodiment of an electromagnetic shielding doorway and revolving door for a building in accordance with the present invention; and Fig. 2 is a plan view of the doorway and revolving door shown in Fig. 1, and of an adjacent window. Fig. 1 illustrates the invention, in which the doorway is constituted by a revolving door 10. In order for the revolving door 10 to be revolved about a rotary shaft 11 its lower edge and one side edge are provided with a gap 12. Accordingly, even if the revolving door 10 proper is furnished with an electromagnetic shielding property by using mesh-containing glass or glass having an affixed electrically conductive film, electric waves can leak from the gap 12. As a result, the electromagnetic shielding effect is not satisfactory. Therefore, in accordance with the present invention, electrically conductive (e.g. metallic) brushes 13 are attached to the lower edge and one side edge of the revolving door 10 to fill the gap 12 thereby enhancing the electromagnetic shielding performance of the doorway. The electromagnetic shielding performance is improved even further by electrically interconnecting the brushes 13 and grounding them at the rotary shaft 11. If an absorber 14 of electromagnetic radiation is arranged in the walls, ceiling and floor at the periphery of the revolving door 10, radiation is absorbed at the door periphery without reflection. This makes it possible to reduce the amount of radiation blocked at the revolving door 10. Since the upper edge of the revolving door 10 generally has but a small gap, an electrically conductive brush is not necessarily required; however, if it is feared that the door may become deformed after long use, the upper edge should be furnished with the electrically conductive brushes just as the lower and side edges. Fig. 2 is a plan view of a doorway 17 using the revolving door shown in Fig. 1. The revolving door 10 and a window 15 are electromagnetically shielded by using glass containing a conductive mesh or glass having an affixed electrically conductive film, electrically conductive (metallic) brushes are attached to the lower and side edges of the revolving door 10, and a body 16 of the building is constructed of steel mesh- or ferrite-containing concrete. With a building structure of this type, electromagnetic waves are blocked at the doorway 17, window 15 and body 16, so that the building is provided with an overall electromagnetic shield. We have previously proposed structures for electromagnetically shielding the outer wall surface of a building body and having openings for windows, entrances, exits and the like. These will now be described in brief. In one type, the body of the building is constructed of concrete incorporating an electromagnetic shielding member. For example, this can be concrete containing a steel mesh or concrete mixed with ferrite. In another type, the outer wall of a building is constructed of precast (PC) panels having an embedded mesh, the mesh in the PC panels is electrically connected to building body fastening members, and the PC panels of upper and lower floors are electrically interconnected and grounded. In still another configuration, curtain walls fabricated using electromagnetic shielding members are fixed by anchor bolts to the building body via metal fasteners, electrically conductive cushions are affixed to the side faces of the curtain walls, and mutually adjacent curtain walls are electrically integrated to form an electromagnetically shielded space.

Claims: An electromagnetic shielding doorway and revolving door, for a building in which electromagnetic shielding members are used to construct a body (16) of the building and window and doorway openings to provide the overall building with an electromagnetic shielding structure, in which door and doorway electrically conductive brushes (13) are attached to at least a lower edge and side edge of a revolving door (10) arranged in said doorway, thereby filling gaps (12) at said edges, and material (14) which absorbs electromagnetic radiation is positioned around the periphery of said revolving door; characterised in that said electrically conductive brushes (13) are electrically interconnected and grounded at the rotary shaft (11) of said revolving door (10). A shielding doorway and revolving door as claimed in Claim 1, wherein said conductive brushes (13) are metallic.

Inventors: ISHIKAWA, TOSHIYUKI, NAGATA, KOJI, NAKAMURA, MASATAKE, TAKAHASHI, TAKESHI, YABANA, YOSHIJI
Applicants: SHIMIZU CONSTRUCTION CO. LTD.
Application year: 1987
Main classification: E06B5
IPC codes: E06B5, H05K9