Communications: directive radio wave systems and devices (e.g. – Radio wave absorber
Reexamination Certificate
1999-09-03
2001-07-10
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Radio wave absorber
C342S003000, C342S004000
Reexamination Certificate
active
06259394
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electric wave absorber used in an electric wave dark room, an electric wave absorbing wall, etc.
In recent years, use of electric waves has been spread rapidly in the field of mobile communication the like to realize a high-grade information oriented society. On the other hand, various electronic appliances have been popularized with the reformative advance of today's microelectronics technology. With the advance of such information communication technology, however, the influence of unnecessary electromagnetic noise on apparatuses relevant to precision machinery has become a subject of discussion.
An electric wave dark room (electric wave anechoic room) having no electromagnetic wave reflection is used for measurement of electromagnetic noise. An electric wave absorber is disposed in an inner wall of such an electric wave dark room. Examples of the background-art electric wave absorber used in the electric wave dark room include electric wave absorbers made from organic materials such as foamed styrol, foamed styrene, foamed urethane, etc., mixed with carbon black, or the like, to obtain electrical conductivity.
With the increase of electric wave interference, however, a large electric power test such as an immunity test, or the like, has been intended as a matter of duty. In the electric wave dark room used in a closed state, a nonflammable material needs to be used in terms of improvement of safety.
An example of the nonflammable electric wave absorber include a molded material containing inorganic grains, comparatively low in raw material cost and having a large number of closed cells, such as SHIRASU balloons, glass beads, perlite, etc., and carbon black which are integrally bonded by a heat-resistant inorganic adhesive agent such as water-glass (Japanese Patent No. 2743227).
The aforementioned electric wave absorber is, however, low in mechanical strength. There is a problem that the occurrence of breaking, the generation of dust upon collision, etc. cannot be avoided when, for example, the electric wave absorber is provided as a quadrangular pyramid- or wedge-shaped large-size structure which is about 100 cm high.
SUMMARY OF THE INVENTION
The present invention is designed upon the aforementioned actual circumstances. The object of the present invention is to provide an electric wave absorber which is light in weight and which is excellent in mechanical strength, nonflammable characteristic and electric wave absorbing power.
In order to achieve the above object, according to an aspect of the present invention, there is provided an electric wave absorber which is formed by bonding a powdered or granulated material of an inorganic hollow body and inorganic reinforcing fiber to at least one member of the group consisting of carbon black, graphite and carbon fiber as an electrically conductive member by an inorganic adhesive agent.
Preferably, the amount of the electrically conductive member is in a range of from 0.5 to 80 g/l. Preferably, the amount of carbon black and/or graphite as the electrically conductive member is in a range of from 30 to 50 g/l. Preferably, the amount of carbon fiber as the electrically conductive member is in a range of from 0.5 to 15 g/l.
Preferably, the inorganic hollow body is constituted by at least one member of the group consisting of SHIRASU balloons, silica balloons, glass beads, and alumina-silica balloons. Preferably, the mean grain size of the inorganic hollow body is in a range of from 5 to 1000 &mgr;m.
Preferably, the inorganic reinforcing fiber is constituted by at least one member of the group consisting of glass fiber, rock wool fiber, stainless steel fiber, silica-alumina fiber, and potassium titanate fiber. Preferably, the amount of the inorganic reinforcing fiber is in a range of from 1 to 20 g/l.
Preferably, the electric wave absorber is provided with a nonflammable layer which is integrally bonded to at least one portion thereof and which is constituted by at least one member of the group consisting of a nonflammable sheet made from a slurry containing sepiolite as a main component, and an inorganic coating agent layer.
Preferably, the electric wave absorber is provided as a quadrangular pyramid- or wedge-shaped structure which is hollow in its inside. Preferably, the nonflammable layer is integrally bonded to at least one exposed portion of the electric wave absorber.
In the present invention, the electrically conductive member and the powdered or granulated material of the inorganic hollow body give excellent electric wave absorbing power to the electric wave absorber whereas the inorganic reinforcing fiber gives mechanical strength to the electric wave absorber. Furthermore, the powdered or granulated material of the inorganic hollow body and the inorganic reinforcing fiber have a function of giving excellent nonflammable characteristic to the electric wave absorber. In addition, since the nonflammable layer is integrally bonded, the mechanical strength of the electric wave absorber is enhanced more greatly.
In order to achieve the above object, according to another aspect of the present invention, there is provided an electric wave absorber comprising an electric wave absorbing molded body, and a nonflammable layer integrally bonded to at least one portion of the electric wave absorbing molded body, wherein the electric wave absorbing molded body contains at least one member of the group consisting of carbon black, graphite, and carbon fiber as an electrically conductive member, and a powdered or granulated material of an inorganic hollow body bonded to the electrically conductive member by an inorganic adhesive agent whereas the nonflammable layer is made from at least one member of the group consisting of a nonflammable sheet made from a slurry containing sepiolite as a main component, and an inorganic coating agent layer.
Preferably, the inorganic hollow body is made from at least one member of the group consisting of SHIRASU balloons, silica balloons, glass beads, and alumina-silica balloons.
Preferably, the amount of the electrically conductive member contained in the electric wave absorbing molded body is in a range of from 0.5 to 80 g/l. Preferably, the amount of carbon black and/or graphite contained as the electrically conductive member is in a range of from 30 to 50 g/l. Preferably, the amount of carbon fiber contained as the electrically conductive member is in a range of from 0.5 to 15 g/l.
Preferably, the mean grain size of the inorganic hollow body is in a range of from 5 to 1000 &mgr;m.
Preferably, the electric wave absorbing molded body contains inorganic reinforcing fiber in addition to the powdered or granulated material of the inorganic hollow body. Preferably, the inorganic reinforcing fiber is constituted by at least one member of the group consisting of glass fiber, rock wool fiber, stainless steel fiber, silica-alumina fiber, and potassium titanate fiber. Preferably, the amount of the inorganic reinforcing fiber contained in the electric wave absorbing molded body is in a range of from 1 to 20 g/l.
Preferably, the electric wave absorber is provided as a quadrangular pyramid- or wedge-shaped structure which is hollow in its inside. Preferably, the nonflammable layer is integrally bonded to at least one face of the electric wave absorber exposed to the outside.
In the present invention, the electric wave absorbing molded body containing an electrically conductive member, a powdered or granulated material of an inorganic hollow body and inorganic reinforcing fiber if necessary, which are bonded to one another by an inorganic adhesive agent gives excellent electric wave absorbing power to the electric wave absorber. The electric wave absorbing molded body is given mechanical strength by the nonflammable layer. The nonflammable layer has a function of giving excellent nonflammable characteristic to the electric wave absorber. Further, by provision of an inorganic coating agent layer as the nonflammable layer, both surface void filling ef
Fujimoto Kyoichi
Hayashi Kozo
Kurihara Hiroshi
Murase Taku
Saitoh Toshifumi
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sotomayor John B.
TDK Corporation
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