Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-03-29
2001-04-24
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C174S034000, C277S653000, C277S920000
Reexamination Certificate
active
06219906
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to EMI/RFI shielding devices, and more specifically, to a self-terminating EMI/RFI shielding gasket and a method of making the same.
Various types of EMI/RFI gaskets are known for reducing the transmission of electromagnetic interference (EMI) and radio frequency interference (RFI). Among the known devices are gaskets having a resilient core surrounded by a deformable wire-mesh gasket material. Suitable known wire-mesh materials are tin-plated phosphor bronze, tin-coated copper-clad steel, silver-plated brass, monel, beryllium copper and aluminum. Different core cross sections and materials are used depending upon the particular application. Wire-mesh gaskets are generally used to shield conventional computer or other electronic equipment by compressing the gasket around an openable access panel, door, or the like.
Known wire-mesh gaskets are manufactured in various lengths and then cut to size for particular installations. In so doing, however, the wire-mesh tends to fray at the terminal ends of the gasket and thus produces an unacceptable appearance. A secondary treatment such as the in situ application of an adhesive has previously been utilized to overcome the poor appearance of the fraying ends. That treatment is a labor intensive process, however, and is not well suited for quick and cost-productive installations.
Other prior art gaskets have attempted to overcome this problem by knitting a conductive layer over a foam core before the foam has completely cured. In such cases, the uncured foam adheres to the knitted layer to prevent the terminal ends from fraying; however, utilizing an uncured core presents problems of dimensional stability and thus limits the shapes and sizes that can be successfully manufactured. U.S. Pat. No. 5,045,635, assigned to Schlegel Corporation, for example, describes a process whereby a urethane foam core expands and cures in a traveling mold that is surrounded by a sheath with a conductive surface having embedded metal fibers or the like.
In addition to aesthetic considerations, EMI/RFI leakage may also occur due to the reduced shielding coverage that occurs as a result of the fraying terminal ends of the gaskets. Further, cutting the wire-mesh gasket during installation may produce particles of metallic debris within the shielded housing.
A further design consideration for EMI/RFI gaskets is galvanic compatibility in the ultimate application. More particularly, when a conductive gasket for excluding electromagnetic interference is placed between two metal flange plates or metalized plastic components, dissimilar metals having dissimilar electrochemical potentials are quite likely to be placed in contact with one another. The use of dissimilar metals or metal coating/plating in metalized plastics is expected because desirable attributes in flange plates, such as strength and rigidity, are not the same as those for gaskets, such as flexibility and maximum electrical conductivity. The difference in the electrochemical potential of the two dissimilar metals is the force that drives the movement of ions therebetween and thus causes galvanic corrosion. Heretofore, knitted gaskets have conventionally used silver plating as the conductive metal therein. While these gaskets function adequately in shielding against electromagnetic and radio frequency interference, the range of materials on which they can be utilized is limited due to the limited galvanic compatibility of the silver plating.
SUMMARY OF THE INVENTION
The present invention is directed to a gasket structure for shielding against electromagnetic and radio frequency interference and which overcomes the prior art problems associated with terminal end fraying without sacrificing dimensional stability of a core.
The gasket structure includes a first tubular layer formed from a hot melt yarn, a second tubular structure formed from a conductive yarn and disposed over at least a portion of the first tubular layer, and a core disposed within the first tubular layer. The hot melt yarn forming the first tubular layer adheres the second tubular structure to the core such that fraying of the gasket structure is substantially prevented. The first tubular layer is preferably knit around the core and the second tubular structure is then knit therearound. A preferred core material is a neoprene sponge and a preferred conductive yarn is a nylon yarn plated with silver, although tin, aluminum and nickel plating is also possible.
A further aspect of the present invention is directed to a method of forming a knitted metalized yarn gasket. The method includes selecting a core, selecting an adhesive yarn, selecting a conductive yarn, forming the adhesive yarn into a tubular layer around the selected core, constructing a composite tubular structure by forming the conductive yarn into a tubular structure surrounding at least a portion of the adhesive yarn tubular layer, and heating the composite tubular structure to melt the adhesive yarn such that the conductive yarn will adhere to the core. The method further includes, after the heating step, shaping the composite tubular structure by drawing it through a die. Finally, after the shaping step, the composite tubular structure is cooled and then cut to the desired length.
REFERENCES:
patent: 5045635 (1991-09-01), Kaplo et al.
patent: 5142101 (1992-08-01), Matsuzaki et al.
patent: 5294270 (1994-03-01), Fenical
patent: 5386345 (1995-01-01), Matsuzaki et al.
patent: 5603514 (1997-02-01), Jencks et al.
patent: 5804762 (1998-09-01), Jones et al.
patent: 5902956 (1999-05-01), Spies et al.
Burns Doane Swecker & Mathis L.L.P.
Chang Rick Kiltae
Instrument Specialties Co., Inc.
Young Lee
LandOfFree
Method of forming a self-terminating, knitted, metalized... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of forming a self-terminating, knitted, metalized..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of forming a self-terminating, knitted, metalized... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2515716