Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1986-10-22
1988-06-14
Dawson, Robert A.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
1562724, 1562753, 1563044, 174 35MS, 428 61, B32B 3112, B32B 708
Patent
active
047509570
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of making a shield that is substantially opaque to electromagnetic radiation, which method comprises joining together pieces of flexible metallic or metallized shielding material of sheet form.
The need to protect certain types of electronic equipment, such as telecommunications and computer equipment, against perturbations induced by electromagnetic radiation, or to prevent radiation emitted by such equipment from diffusing in an undesirable manner, has become increasingly apparent because of the increasing knowledge of the damage that such radiation can induce.
Protection can be provided by a shield which completely encloses the space to be protected and which is substantially opaque to radiation in the frequency range of interest or, in other words, sufficiently difficult for the radiation to penetrate. Such shields can be made of materials which are either essentially absorptive towards the radiation or essentially reflective (in which case the shield forms a so-called Faraday cage) or of combinations of the two.
An essentially reflective shield can be made of metal foils or sheets which are welded or soldered together to form a cage or other enclosure. The cage may have openings for the passage of electricity, fluids, etc. which must be provided with closing systems that prevent radiation from passing through them.
A shield constructed in this manner using conventional techniques is, as can be easily seen, very expensive if it has to be provided around an already existing space. It can therefore be justified only in particular cases where high costs can be tolerated.
Another way of making a shield is to paint the surfaces defining the space to be shielded with an electrically conductive paint. Paint having sufficiently high electrical conductivity exists but is very expensive and thus cannot be used where high costs are unacceptable. Another drawback is that cracks in the painted surface easily lead to cracks in the applied layer of paint so that the shielding effect is reduced or entirely disappears.
It has also been proposed to use metallized textiles as shielding material.
Commercially available metallized textile materials are of woven, knitted or nonwoven construction and based on synthetic or natural polymers, inorganic fibres, carbon fibres, etc. subsequently covered with a metallic coating. Typically, they have a surface resistance substantially less than say 30 ohms and possess suitable mechanical properties (the term "surface resistance" here denotes the electrical resistance of a square piece of the material as measured between opposed edges of the square).
A practical problem in using metallized textile materials for shielding purposes is to achieve a shield where in terms of electrical properties the joints between adjacent pieces of the material are sufficiently similar to the bulk of the material. Incidentally, this problem is not satisfactorily solved for other shielding materials either, since welded or soldered joints between sheet metal pieces as well as conductive paint layers can have, or develop, hidden cracks or other discontinuities which reduce the shielding effect.
An object of this invention is to provide a method of making a shield using a metallic or metallized flexible shielding material of sheet form which method solves the above-explained problems while meeting electromagnetic, constructional and economic requirements.
This object is achieved by making the shield according to the method set forth in the claims.
Briefly, the invention comprises joining adjacent shielding material pieces together through an overlap joint, at least one of the overlapping portions being formed of a fluid-permeable shielding material and joined with the other overlapping portion through an electrically conductive glue applied in fluid state, whereby the joint provides an electrical path of a resistance approximately equal to or less than that of the bulk of the shielding material.
The method of the invention can take many forms according to the particular s
REFERENCES:
patent: 4067765 (1978-01-01), Heller et al.
patent: 4126287 (1978-11-01), Mendelsohn et al.
patent: 4410575 (1983-10-01), Obayashi et al.
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