United States Patent: 3562402

[US Patent & Trademark Office, Patent Full Text and Image Database]

( 9158 of 9158 )

United States Patent	3,562,402
Dwyer	February 9, 1971

ELECTRICALLY AND MAGNETICALLY SHIELDED LAY-IN WIREWAY APPARATUS

Abstract

A shielded duct assembly comprised of a plurality of individual elements, each having completely removable cover portions to allow wires and the like to be placed or laid directly therein after the elements have been assembled to form a continuous duct. Complete magnetic and electrostatic shielding is accomplished through the establishment of a continuous current conducting path through means disposed in the sealing gaskets for the removable cover portions and intermediate adjacent individual members of the duct assembly and the further establishment of a parallel, continuous magnetic flux conductive path through the use of suitably configured joint forming members intermediate the ends of individual conduit sections whereby magnetic flux energy is shunted toward the interior of the duct in areas of flux concentration occurring at laterally outwardly opening joints, or discontinuities in the duct assembly.

Inventors:	Dwyer; John Michael (Elk River, MN)
Assignee:	Federal Cartridge Corporation (Minneapolis, MN)
Appl. No.:	04/742,377
Filed:	July 3, 1968

Current U.S. Class: 174/373 ; 138/164; 174/101; 174/371; 174/68.3

Current International Class: H02G 3/06 (20060101); H02G 3/04 (20060101); H02G 3/02 (20060101); H05k 009/00 ()

Field of Search: 174/35.2,35.4,68C,101 138/155,158,164 277/235,236,227

References Cited [Referenced By]

U.S. Patent Documents


2917083	December 1959	Duvall et al.
3331916	July 1967	George et al.
3351699	November 1967	Merckle
3370121	February 1968	Merckle

Primary Examiner: Clay; Darrell L.

Claims

I claim:

1. A shielded duct comprising in combination;

a. a plurality of magnetically and electrically conductive body members, each of said body members being open along one side thereof and having at least one open end, including flange means, engaging a like adjacent open end, including flange means, on said another body members forming a joint therebetween, said plurality of body members joined together in abutting relation forming a continuous duct that is accessible through the open side therein;

b. a magnetically and electrically conductive joint sleeve member disposed interiorly of and extending longitudinally of each of the adjacent open ends and bridging said joint between said body members for a distance of at least one-half of the largest of the cross-sectional dimensions thereof, said joint sleeve having a removable top portion comprised of current conductive and magnetic energy conductive material; and

c. cover means removably disposed on the side openings in each of said body members and extending intermediate the removable top portions on each of said joint sleeve members, said cover means including a first current conductive means and a second magnetic energy conductive means disposed in energy transferring relationship with the current conductive and magnetic energy conductive means on the removable top portions on said joint sleeve members and said body members.

2. The apparatus of claim 1 in which the portions of the body members adjacent the open sides thereof includes opposed flange portions.

3. The apparatus of claim 2 in which the second magnetic energy conductive means extends inwardly of the body members.

4. The apparatus of claim 1 in which the second magnetic energy conductive means in the cover means extends inwardly of the body members.

5. The apparatus of claim 4 in which the inwardly extending portions of the second magnetic energy conductive means in the cover means extends inwardly of the open side in the body members.

Description

This invention is related generally to ducts or raceways for removably receiving one or more electrical current conducting cables, or the like. It is more particularly directed to ducts which may be formed of a plurality of individual members, or fittings to form a rigid continuous duct that is open at one side prior to the insertion of cables therein and which is provided with a removable continuous cover which, when assembled over the side opening in the duct, is operative to completely shield the cables or wires contained therein from the effect of high and low frequency electrostatic and electromagnetic energy whereby extraneous signals will not be emitted from the ducts or will any such extraneous signals be transmitted into the duct.

As examples of applications of the principles of my invention, the integrity of the security surrounding communications over wires or cables disposed within a duct constructed according to the principles of my invention is substantially enhanced over known prior art constructions. Further security may readily be seen from the requirements in the controlling of the operation of defense type missiles in which the presence of an inadvertently generated signal from equipment in proximity to a duct containing control cables could result in undesired launching of such a device with catastrophic results.

Briefly, my invention provides for a plurality of duct members, each being open at one side and open at one or more ends. Means are provided for joining the members into a continuous duct and each joint contains a sleevelike member which extends for a considerable distance on either side of a joint to provide for a continuous magnetic flux conducting path and a gasket member adapted to provide a fluid tight and current conductive seal is likewise disposed intermediate the individual members on either side of a joint. Continuous removable cover means are provided for the sleeve member disposed in each joint and for each of the other individual members and these, too, provide for complete continuity with respect to current conduction and magnetic flux conduction while also providing a substantially fluid tight seal so that when the covers are disposed on the continuous duct, any cables contained therein are secure from the effects of electrostatic, electromagnetic and atmospheric or other interference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a portion of a completely assembled duct.

FIG. 2 is a partially disassembled exploded perspective view of the apparatus shown in FIG. 1.

FIG. 3 is a sectional view of the apparatus shown in FIG. 1 taken along section line 3-3.

FIG. 4 is a sectional view of the apparatus shown in FIG. 1 taken along section line 4-4.

FIG. 5 is a top perspective view of still other elements of an assembled duct, shown in an assembled position; and

FIG. 6 is an exploded partly disassembled view of the apparatus shown in FIG. 5.

Referring now to the drawings wherein like elements have been identified by like reference characters with a view toward simplifying the explanation and understanding of the principles of my invention, there is shown in FIG. 1 an assembled duct comprised of a straight section of a duct member indicated generally by reference character 10 which is connected to a duct member shown in the form of a 45.degree. elbow and indicated generally by reference character 40.

In FIGS. 5 and 6 a duct member in the form of a 90.degree. T-member is indicated generally by reference character 60 and is shown connected to a female-to-box connector 61 and a male opening cover 62.

Straight duct member 10 is shown having laterally outwardly extending end flanges 11 and 12 at opposite ends thereof, and a continuous side opening 13 having edge flanges 14 and 15 disposed at the outer edges thereof respectively to form cover receiving portions, the surfaces of which lie in a common plane. A cover member is indicated generally by reference character 16 and is provided with a neoprene gasket sealing member 17 which is shown surrounding a meshlike current conducting means shown in the form of a compressible conductive gasket. Cover 16 is further provided with a central inwardly extending insert member 19 having a pair of inwardly extending side flange portions 20 and a like pair of inwardly extending end flange portions 21 in proximity to the ends thereof.

A C-shaped joining sleeve 25 having an open top portion 26 defined by a pair of inwardly extending parallel side flange portions 27 is shown disposed at the left end of duct section member 10 and at other suitable locations in the joints intermediate individual duct members in the other views of the drawings. A U-shaped gasket 22 comprised of neoprene portion 28 and compressible conductive mesh portion 29 is disposed intermediate the end flanges on adjacent individual duct members.

The open top 26 on joining flange 25 is shown covered with a sealing plate assembly 30 which is comprised of a laterally extending top plate 31, a filler plate 32 disposed in open top 26 of joining sleeve 25, a spacer member 33 and a bottom member 34 which extends under the inwardly extending parallel side flanges 27 on joining sleeve 25. A neoprene gasket 35 and compressible mesh gasket 36 are shown disposed in suitable locations to provide the sealing conductive relationship.

The 45.degree. elbow duct member indicated generally by reference character 40 is shown attached to the right-hand end of straight duct member 10. Elbow duct member 40 includes a continuous side opening 41 having a pair of flanges 42 and 43 at the sides thereof, the flanges having edges lying in a common plane; and a pair of end flange portions 44 and 45 that are adapted to be releasably connected to corresponding end flange members on other duct member elements. Elbow 40 is also shown provided with a cover member 46 which includes a neoprene gasket 47 and a compressible mesh gasket 48 and further includes an insert portion 49 having a side flange 50 and a pair of end flanges 51 and 52, all of which extend inwardly of cover member 46 when disposed in position over the side opening 41 on elbow 40.

FIGS. 5 and 6 show a 90.degree. T-duct member element indicated generally by reference character 60, to which a female-to-box connector 61 and a male opening cover 62 are shown attached in FIG. 5 and in exploded, partly disassembled relationship on FIG. 6. It may be noted that some of the details have been omitted for the sake of clarity and that the principles of my invention may be readily applied to other duct member elements such as telescoping straight sections, 221/2 and 90.degree. elbows, reducers, increasers and the like and that my invention is by no means limited to apparatus wherein a side opening and its removable cover elements is limited to any particular side or the side shown in the several views of the drawings illustrating a preferred embodiment of my invention.

In applying the principles of my invention to a typical installation, the necessary individual duct members are provided with a conductive plating that is compatible with the environment in which the duct is to be installed and all of the parts are preferably constructed out of low carbon steel or other conductive metal exhibiting a high degree of permeability to the flow of magnetic flux therethrough. One suitable material is wrought iron. In any event, as may become clear in the description of operation to be set forth below, it is desirable that the magnetic flux conductive path existing longitudinally of the assembled duct be comprised of material exhibiting a high degree of permeability and that the current conducting path be comprised of material exhibiting a high degree of electrical conductivity commensurate with the additional joint sealing compressibility necessary with any joint, or discontinuity, in a continuous structure that is comprised of a number of smaller units.

It may also be noted at this point that joint sleeve members 25 may be removably disposed in the end openings in a duct section member or may be suitably welded in place or fastened by any other suitable means, the primary requirement being that one or the other end of joint sleeve member 25 is rigidly connected to a duct member at one of its ends. In one preferred embodiment of my invention, the joint sleeve members 25 extended for approximately 2 inches on either side of a joint effected intermediate adjacent duct section members having a 4.times.4 cross-sectional size.

As stated above, a continuous duct of any length and shape desired may be provided by assembling suitably configured, open sided individual duct segment members through the use of the joint sleeve members 25 and gasket members 22 disposed intermediate adjacent flanged end portions, which are then suitably joined by fastening means, such as nuts and bolts (not shown). This provides a continuous troughlike opening into which wires, cables or the like may be laid. The assembly continues with the positioning and installation of sealing plate assemblies 30 in the open portion of the C-shaped joint sleeves in the manner shown in the several views of the drawings. Further installation of the respective cover members, such as 16 and 46, complete the installation of a duct and its associated internally disposed wiring. Once the assembly has been completed, there is at least one continuous current conductive path provided through the conductive engagement of contiguous portions of the compressible conductive mesh, or gasket, present in the several cover members and sealing plate assemblies disposed intermediate the cover members on adjacent duct section members. Likewise, at least one parallel magnetic flux conductive path is provided by the filler plate 32 and bottom plate 34 in sealing plate assemblies 30 and the inwardly flanged insert portions 19 and 49 on cover members 16 and 46 of straight duct section 10 and elbow 40 respectively. While these paths are essentially contiguous to one another, it has been noted that there is a substantial separation between a current and magnetic flux and this is believed to contribute materially to the improved performance of apparatus constructed in accordance with the principles of my invention. It may further be noted that while the current conductive path provided by the conductive compressible gasket, shown in the form of a mesh may be operative in the absence of other environmental sealing means shown in the form of a neoprene gasket, the combination of the two gasket materials is complementary in the sense that improved sealing over and above what has been observed to be present when the conductive gasket is used by itself, is obtained. Further, the downwardly depending flanges on the individual cover members also serve to enhance and improve the performance of the conductive portion of the gasket.

* * * * *

Current U.S. Class:	174/373 ; 138/164; 174/101; 174/371; 174/68.3
Current International Class:	H02G 3/06 (20060101); H02G 3/04 (20060101); H02G 3/02 (20060101); H05k 009/00 ()
Field of Search:	174/35.2,35.4,68C,101 138/155,158,164 277/235,236,227