US 3089915 A
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Description (OCR text may contain errors)
May 14, 1963 w. A. PLuMMl-:R 3,089,915
ELECTRIGALLY SHIELDED TUBULAR JACKET Filed June 2v, 195o Fl G. 4. I
INVENTOR. F G. 5. WALTER A. PLUMMER United States Patent C M 3,089,915 ELECTRECALLY SHIELDED TUBULAR JACKET ti/alter A. illuminer, 3546 Crown Ridge Drive, Sherman Oaks, Calif. Filed lune 27, 1960, Ser. No. 38,997 9 Claims. (Cl. 174-36) This invention 'elates to tubular jacketing and more particularly to an improved laminated tube of flexible material featuring an inner layer of electrically conductive material adapted to form a continuous tubular enclosure having its opposite lateral edges in electrical Contact throughout the length thereof and including a conductive extension from one end by Iwhich the conductive layer can be grounded.
The present application is a continuation-in-part of a related invention disclosed in my co-pending application for United States Letters Patent Serial No. 687,476 filed October l, 19-57, now Patent No. 2,960,561, entitled Shielded Wire Harness.
There are many electrical environments in which it is mandatory that electrical flux fields be confined to or excluded from a designated zone. it has been common practice heretofore to achieve these ends by erecting an electrically conductive shield about .the zone in such manner as to confine the iiux fields in the particular manner required for each application. The present invention is directed to an improved jacket for these purposes formed from lightweight, compact, laminated material specially constructed for assembly into a tubular enclosure of the particular size required to protect the zone involved. The present product is particularly suitable for enclosing cabling, instrumentation and the like equipment and comprises an elongated strip of laminated material having at least one layer of non-conductive electrically insulating material and a second layer of very flexible high eiiiciency conductive material. To effect the expeditious assembly and disassembly of this jacketing about the items to be protected the opposite lateral edges are provided with non-metallic slide fastener tapes having interlocking tongues and grooves .to form `an easily opened and closed seam.
rflic construction incorporates certain new and irnproved features of the general nature just discussed and others specially designed with a view to increasing the utility, effectiveness and convenience of use of the closely related shielding jacket disclosed and claimed in `the above identified co-pending application. For example, in the identified prior `disclosure a preferred conductive layer consists of metal foil bonded to the main body layer of thin flexible plastic material. To assure a continuous conductive path circumferentially of the foil layer the free edge of the guard iap of that construction was overturned upon itself :and suitably so secured. Since this guard flap was arranged to underlie the jacket seam with its overturned metallic edge positioned in direct contact with the juxtaposed lateral edge of the conductive layer, assurance was provided of the desired continuous conductive path between the two longitudinal edges of the metallic layer. However, in practice in environments wherein the jacketing was subjected to rough handling and to repeated severe flexing it was found that the metallic layer tended to rupture and 'to separate from the non-conductive layer particularly at the overturned reverse bend portion along the free edge of the guard flap. Such failure of the metal foil interfered `seriously with tlie electrical shielding effectiveness of the construction. An additional disadvantage of the prior construction resides in the fact that lacking was a convenient and satisfactory means for grounding the conductive layer. Additionally, it was found that the metal foil layer was not as effective an electric shield at certain frequencies as was desired.
3,089,915A Patented May 14, 1963 The foregoing and other shortcomings are avoided by the present invention wherein the conductive layer is provided by a very soft highly flexible fabric material of high strength. Preferably this fabric comprises a nonconductive filament core of nylon or the like high strength filament having a continuous metallic film exterior coating. Threads of such material are utilized to provide a very closely woven fabric exhibiting unusual strength while being so soft and liexible `as to belie the presence of a metallic lrn. This fabric has the feel, softness and flexibility of a soft cotton fabric yet has high conductivity and an unusual-ly high efliciency as an electrical shield for high frequency flux fields. This conductive layer is easily laminated to a plastic main body layer in a variety of ways but most readily and easily by stitching along its opposite lateral edges. Owing to its softness and flexibility this conductive layer is readily overturned about the free edge of the guard flap one or more times and stitched or otherwise secured in place.
Anotherimportant feature of the construction is the inclusion of a continuous flexible electrical conductor lengthwise of the jacket and preferably along the free edge of the guard flap and secured to the latter along with the fabric layer as by stitching. Fine wire braiding makes an excellent conductor and its opposite ends may extend beyond Athe jacketing `and be encased with an `insulating cover up to its terminal fitting.
Accordingly, it is a primary object of the present invention to provide an improved electrically shielded tubular jacket having novel features not heretofore available.
Another object of .the invention is the provision of an elongated flexible vwalled jacket adapted to be readily assembled into tubular form and featuring a flexible electrical conductor intimately associated with the conductive layer of the jacket and extending from one end thereof.
Another object of the invention is the provision of an electrically shielded jacket having an outer layer of iiexible plastic material formed with interlocking tongue and groove seam means along its edges and featuring an interior conductive layer of soft fabric material having one edge thereof folded over to embrace the edge of the jacket guard Iflap and adapted to lie in intimate Contact with the juxtaposed other edge of the conductive layer to form a continuous tubular electrical shield.
These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawing to 'which they relate.
Referring now to the drawing in which a preferred embodiment of the invention is illustrated.
FGURE 1 is a fragmentary View in perspective of a short length of a shielding jacket incorporating the features of the present invention;
FIGURE 2 is a perspective view of a length of the jacketing assembled into =a tube;
FIGURE 3 is a fragmentary enlarged cross-sectional view `taken along line 3 3 on FIGURE 2;
FIGURE 4 is a fragmentary view on enlarged scale taken along line 44 on FGURE l; and
FGURE 5 is a cross-sectional view similar to FIG- URE 3 but showing a Variant in the mode of securing the flexible grounding wire to the iiexible shielding layer.
Referring first to FIGURES l to 4 there is shown a preferred embodiment of `an electrically shielded jacket according `to the present invention and designated generally it). Although various non-conductive flexible ma terials may be used to form the main body strip 11, thin sheet thermo-plastic material offers many advantages. Polyethylenes and vinyls are particularly suitable as are numerous other thermo-plastics. Such materials are inexpensive, easily processed, readily available, very liexible, have excellent electrical insulating properties, resist abrasion and attack by many materials and are impervious to liuids.
Secured along the opposite lateral edges of the main body strip 11 are suitable seam forming means, as for example, the extruded slide fastener tapes 12 and 13. Each is provided along its free edge with suitable complementally shaped interlocking tongue and groove means with the grooves of each facing in opposite directions in the manner illustrated in FIGURE 1, wherein they are adapted to form a seam 14 extending longitudinally of the jacket. The details of these slide fastener tapes are well known and Iare disclosed more fully in the above mentioned co-pending application. As is made clear by the drawing, tape 13 is preferably spaced appreciably inwardly from one edge of body strip 411 to provide a guard flap 15 suiciently wide to bridge the seam when closed for purposes to be explained more fully presently.
Co-extensive with the main body strip 11 of the jacket is van interior layer 17 of conductive material, the material here shown comprising very closely woven fabric, the individual threads of which have a non-conductive filament core 13 (FIGURE 4) of nylon or the like Ihigh strength lament. The exterior of this core is coated with a continuous film of metal 19 such as annealed aluminum. This provides a very flexible continuous conductive layer having superior shielding characteristics particularly for high frequency iiux fields. Layer 17 may be suitably laminated against the interior surface of body layer 11 as by bonding or by stitching Ztl'. As here shown, stitching Ztl* extends along spaced apart junction areas, as for example, along the juxtaposed lateral edges of layers 11 and 17. To be noted from FIGURES l and 3 is the fact that the left-hand edge of the conductive fabric is overturned to embrace the free edge of guard flap 15. Thereafter, a flexible conductor 22 of fine wire braid Iis pressed fiat against the exterior fold 23 of the fabric and is then stitched securely to the edge of the guard ap by stitching 20.
The ends of braid 22 preferably project a suitable distance beyond the end of the jacket proper and are encased in insulation 24 after the tip end of the wire braid is provided with a convenient terminal tab 25 by which the same may be attached to a ground connection. Supplemental reinforcing may be employed to anchor the braid to the end edge of the guard flap. Such anchorage may comprise a pair of grommets 26 extending through the conductor and the underlying portion of the guard flap and serving to reinforce the assembly and to prevent stitching 20 `from being pulled loose.
It is pointed out that braid 22 preferably extends the full length of the guard liap and therebeyond `for an aph propriate length. In certain applications it will be desirable to cut the jacketing to length and to make provision for an additional length of braid 22. This can be accomplished by cutting a length of jacketing longer than is needed. Thereafter, several inches of the excess tubing is cut away leaving a corresponding length of the braid exposed beyond the jacket end. Grommets 26 are then inserted to anchor the parts together and the exposed end of the braid is covered with insulation 24 and secured to a terminal tab 25. In this manner it will be understood that the jacketing may be manufactured in a continuous length and shipped coiled flat to the place of use. There the jacketing is cut to length in the manner just described with at least one end of the grounding bra-id 22 extending beyond one end of each cut length of the jacketing.
It is further pointed out that in certain applications of the jacketing `it is desirable to provide for venting the interior space to the atmosphere. For this purpose it will be understood that the outer non-conducting layer 11 is provided at intervals with vent holes 28, these preferably being of small diameter and spaced as necessary lengthwise of the jacketing. Desirably, however, vent holes 28 extend through only the non-conducting layer and not through conductive layer 17. The interstices between the closely Woven threads of this fabric suffice to pass air for venting purposes without, however, breaking the continuity of the continuous shielding provided thereby.
A second preferred embodiment of the invention shown in FIGURE 5 comprises the same constituents and is constructed in the same manner discussed above in connection with FIGURES 1 to 4. For this reason it will be understood that the same reference characters have been employed as in the first embodiment and are distinguished therefrom by the application of a prime. The principal feature of difference in the two embodiments resides in the fact that flexible conductor cable 22' is wrapped within the fabric layer of conductive material so as to be enclosed by the fabric before being secured by stitching 20' to the free edge of guard ap 15. This expedient prevents the harsher and stiffer material constituting conductor 22 from abrading and cutting through the much softer material of conductive layer 17'. In all other respects it Will be understood that the second embodiment conforms with the described details of the lirst embodiment.
In use, it will be understood that the jacket is wrapped about conductors or equipment to be enclosed and shielded. Usually the jacket is tailored or manufactured to size fitting the parts to be enclosed rather snugly. The interlocking tongues and grooves constituting seam 14, 14 are then pressed together in the usual manner to complete the assembly, care being exercised that guard fiap 15 underlies and bridges the seam with the free conductive edge thereof overlapping and in intimate contact with the juxtaposed lateral edge of the conductive layer.
If desired, the interitting tongue and groove portions of the seam are provided with a suitable sealant prior to being closed and serving to ybond the same permanently closed. In other applications, however, there will be need for gaining access to the interior of the jacketing in which event the sealant is not employed. After the jacket has been installed the free end of the ground lead braid 22 is connected to a suitable ground in known manner to the end that charges tending to accumulate on conductive layer 17 may be quickly bled away.
While the particular electrically shielded tubular jacket herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.
1. An elongated tubular jacket for electrical conductors and the like to be shielded with respect to electrical ux fields, said jacket comprising a long narrow thinwalled main body of liexible pliant .electrically non-conductive material having secured along its opposite lateral edges interlocking tongue and groove seam means for holding said jacket assembled about electrical conductors, one lateral edge of said main body projecting throughout its length laterally beyond said seam means to provide a guard flap adapted to underlie and bridge said seam in the closed assembled position of the seam, an interior layer of compactly woven soft-textured fabric of electrically conductive material substantially coextensive in area with said non-conductive main body and having one lateral edge thereof embracing the edge and both opposed surface areas of the free edge portion of said guard ap, and means securing said conductive fabric loosely assembled against one surface of said non-conductive main body and about the free edge portion of said guard flap to provide a continuous tubular shield of conductive material in the assembled condition of said jacket seam.
:2. An electrically shielded tubular jacket as defined in claim 1 characterized in that said electrically conductive 5 fabric is secured to said non-Conductive main body by stitching.
3. An electrically shielded tubular jacket as defined in claim 1 characterized in that said conductive and nonconductive layers thereof are held laminated loosely together by stitching extending along the lateral longitudinal edges of said main body.
4. An electrically shielded tubular jacket as defined in claim 1 characterized in that the individual threads of said soft-textured conductive fabric have a high strength textile core coated with a tenacious lm of metal.
5. An electrically shielded tubular jacket as dened in claim 1 characterized in the provision of a thin flexible high strength electrical conductor secured to the free edge of said guard flap and in intimate contact with said conductive fabric and by which said fabric is adapted to -be grounded.
6. An electrically shielded jacket as dened in claim 5 wherein said fabric and said high strength conductor are held assembled to the free edge of said guard flap by a common row of stitching.
7. An electrically shielded jacket as defined in claim 1 characterized in the provision of small perforations forming vent openings at intervals along said non-conductive main body which vent openings are covered on the interior side of the jacket by said layer of conductive fabric.
8. An elongated tubular jacket for electrical conductors and the like to be protected with respect to the ingress or egress of electrical -ux fields, said jacket having a laminated main body strip including an exterior layer of thin flexible non-conductive plastic material secured along spaced apart junction areas to an interior layer of substantially equally ilexible conductive fabric material, plastic slide fastener seam means secured to said main body strip in a. manner providing a guard flap along one edge adapted to underlie and bridge the interior side of said seam in the closed condition of the seam, and electrically conductive material embracing the free edge of said guard flap and including a long Wide but thin exible electrical conductor separate from said fabric layer extending beyond the end of said jacket, said last-named means being electrically joined to the conductive layer of said laminated main body and being positioned to lie in direct contact with the opposite lateral edge of said conductive layer in the assembled condition of said seam to provide a continuous tubular shield throughout the length of said jacket and including a grounding terminal portion extending beyond one end of the jacket for convenience in forming a ground connection for said jacke 9. A tubular jacket as dened in claim 8 wherein said ilexible grounding electrical conductor comprises a strip of fine ilexible wire having an insulating covering enclosing only the end portion thereof extending beyond said jacket.
References Cited in the tile of this patent UNITED STATES PATENTS 2,536,003 Du Pre Dec. 26, 1950 2,585,054 Stachura Feb. l2, 1952 2,848,390 Whitehurst et al. Aug. 19, 1958 2,960,561 Plummer Nov. 15, 1960