JPH01248699A - Electromagnetic wave shielding body - Google Patents

Abstract

PURPOSE:To shield, from an electromagnetic wave effectively an opening section for a cable to pass by superposing beltlike conductive rubbers so that each side face of the conductive rubbers is brought into contact with each other and the directions of array of each pair of the conductive rubbers are made to differ respectively. CONSTITUTION:Sheets A, B in which beltlike conductive rubbers 1 are arrayed so that each side face is brought into contact mutually without clearances have a function as an electromagnetic-wave shielding material because separate conductive rubber is brought into contact with mutually adjacent conductive rubbers and equipotential is kept as a whole. When cables 5 are penetrated through the contacting sections 2 of the conductive rubbers, clearances are generated along contacting sides. Since superposing structure in which the directions of arrangement of the conductive rubbers 1 of pairs A, B of plural pairs of sheets are made to differ mutually is formed, however, the clearances generated by the penetration of the cables is limited to the extremely slight sections of the peripheries of the cables. Accordingly, the deterioration of an electromagnetic-wave shielding effect is inhibited minimally.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electromagnetic wave shielding body used in a cable penetration opening of a metal casing of an electrical or electronic device.

[Conventional technology]

Various electromagnetic wave shielding materials have been developed in the past, but most of them are made by mixing conductive flakes or powder 7 with a plastic material 6 in order to minimize the transmission of electromagnetic waves, as shown in Figure 5. Gasket materials have been used to reduce leakage at the contact surfaces of molded or electronic equipment housings (for example, Kogyo Materials Vol. 32, No. 2).

However, when configuring a system by connecting two devices, it may be necessary to provide an opening in the housing of the device to allow a coaxial cable, bus cable, etc. to pass through. This type of opening is flexible, as the number and type of cables will vary depending on the system configuration, and should be at least larger than the connectors connected at both ends of the cable. Since the diameter is required to be large, the diameter is relatively large.

[Problem to be solved by the invention]

However, this is not preferable for the purpose of shielding electromagnetic waves. Moreover, since these openings cannot be covered with shielding material, no measures were taken to shield electromagnetic waves. The use of equipment without countermeasures can easily cause electromagnetic interference with other equipment, which can interfere with normal operation. Therefore, some kind of electromagnetic wave shielding measure for the essential opening of the housing has been desired.

An object of the present invention is to provide an electromagnetic wave shield for use in an opening for passing cables such as signal cables and bus cables.

[Means and steps for solving problems]

In order to achieve the above object, the electromagnetic wave shielding body of the present invention includes two or more sets of strip-shaped conductive rubber containing metal powder, conductive filler, etc., arranged in parallel so that their sides are in contact with each other. The device has a set of sheets, and the conductive rubbers of each set are stacked one on top of the other so that the arrangement direction of each set is different, and a cable can be inserted between the conductive rubbers of each set of sheets that intersect with each other.

[Effect]

A sheet in which strip-shaped conductive rubber is arranged so that each side is in contact with each other without any gaps is in contact with the conductive rubber next to each other, and the equipotential is maintained as a whole, so electromagnetic waves are prevented. It functions as a fast-sealing material. When a cable is passed through this contact portion, a gap is created along the contact edge. However, by creating a structure in which multiple sets of sheets are stacked so that the conductive rubber is arranged in different directions, the gap created by the cable penetration is limited to a very small area around the cable, and the electromagnetic wave shielding effect is reduced. The decrease in is kept to a minimum.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an electromagnetic wave shield according to the present invention.

The embodiment includes a first sheet set A in which a plurality of strip-shaped conductive rubbers 1 are arranged so that their side edges 2 are in contact with each other without any gaps;
The second sheet set B is stacked on top of the other so that the conductive rubber 1 arrangement direction is perpendicular to each other. The cable consists of two sets of overlapping sheets, A and B, of conductive rubber 1.1
In order to pass through the intersection at , the number of conductive rubbers used in both sets A and B is adjusted according to the maximum number of cables to be passed through the opening where the electromagnetic wave shield is attached. The peripheral edges of both sheet sets A and B are fixed to a conductive frame 3 made of metal or the like, as shown in FIG. These are fixed by means such as sandwiching or conductive adhesive so as to always maintain an equal potential, so they function as electromagnetic wave shields.

FIG. 3 shows an example in which the electromagnetic wave shield according to the present invention is attached to a cable penetration opening of a metal housing 4 of an electronic device. The metal casing 4 and the conductive frame 3 are screwed together.

It is fixed by crimping or the like while maintaining conductivity, and suppresses electromagnetic waves leaking through the opening. A cable 5 for connection to an external device is provided through the intersection of the conductive rubber sheets 1.1 of the two sets A and H.

When inserting the cable 5, due to the viscoelasticity of rubber,
It can easily pass through cables with relatively large connectors, bus cables with elongated connectors, etc.

A gap is created between adjacent conductive rubber sheets 1.1 due to the penetration of the cable 5, but since the two sets of sheets are stacked so that the conductive rubber sheets are arranged perpendicularly to each other, the gap is shortened due to the slight gap near the cable. The shielding effect remains small, and the reduction in shielding effect is kept small.

By using sets of three or more sheets and stacking them so that the arrangement directions of the conductive rubber in each set are different from each other, the gap is further reduced and the electromagnetic wave shielding effect is enhanced.

However, in order to simplify the structure, it is also possible to remove the conductive frame 3 and fix each set of conductive rubber 1 directly around the opening of the metal casing 4, as shown in FIG. At this time, as in FIG. 2, it is necessary that the electrically conductive rubber 1 and the metal casing 4 are always in a state of equal potential by using means such as screwing or conductive adhesive.

〔Effect of the invention〕

As described above, the present invention has the effect of realizing effective electromagnetic wave velocity shielding for the opening through which the cable is passed.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the electromagnetic wave shield according to the present invention, Fig. 2 is a diagram showing an example in which a conductive frame is used to fix the electromagnetic wave shield, and Fig. 3 is the present electromagnetic wave shield. Figure 4 shows the state in which the cable is installed in the cable penetration opening of the metal casing.
The figure shows an electromagnetic shielding body with a simplified structure, and FIG. 5 is a perspective view of the electromagnetic shielding body according to the prior art. DESCRIPTION OF SYMBOLS 1... Band-shaped conductive rubber 2... Contact side part of conductive rubber 3... Conductive frame 4... Metal casing 5 of the device
...Cable patent applicant NEC Corporation

Claims (1)

[Claims] 1. Two strips of conductive rubber containing metal powder, conductive filler, etc. are arranged in parallel so that their sides are in contact with each other.
It is characterized by having more than one set of sheets, stacked so that the conductive rubber of each set is arranged in a different direction, and allowing a cable to be inserted between the conductive rubber of each set of sheets that intersect with each other. Electromagnetic wave shielding body.