The invention relates generally to ground adapters for electrical cables, especially those used aboard marine vessels and platforms. In particular, the invention relates to embodiments for low-impedance designs of a cable shield ground adapter (CSGA).
The United States Navy currently employs two technologies to provide electromagnetic (EM) protection from coupling to topside (i.e., above-deck) cables; conduit which provides an overall EM shield to cables placed within the conduit, and shielded cables with CSGAs used as termination connectors. Both technologies are viable but components used are expensive and difficult to maintain. The proposed CSGA embodiments deal almost exclusively with shielded cables and conduits. These are not explicitly described herein with respect to further applications, although the technology could be applied to the conduit shell whether flexible or rigid.
Conventional CSGA designs have been proven to be effective at grounding cable shielding when properly installed, achieving grounding effectiveness measures that exceed 80 decibels (dB), but are not easily repaired. The conventional designs are designed for use with swage tubes, also known as stuffing tubes. Specification requirements for the swage tube are provided in MIL-S-21239. Commonly utilized CSGA designs include Glenair® CSGA from Glenair Inc. of Glendale, Calif. and SkinTop® available from LAPP Group Inc. of Florham Park, N.J. The background section of parent application publication 2013/0090004 includes further details about the conventional configurations.
Conventional electrical ground adapters yield disadvantages addressed by various exemplary embodiments of the present invention. In particular, various exemplary embodiments provide an electrical grounding adapter within a conduit sealing assembly for electrically and environmentally shielding an electric cable. Various exemplary embodiments provide an adapter for electrically connecting an interior surface of a conduit and an external surface of a cable. The adapter includes a flat strip extending longitudinally from first to second ends with first and second transverse edges and composed of an electrically conductive and mechanically flexible material.
In exemplary embodiments, the strip includes a longitudinal ribbon that forms a ring for wrapping around the cable by curling the first and second ends together in a direction transverse to the sheet, and a plurality of first and second incisions from the transverse edges towards the ribbon, the incisions being disposed at respective intervals that correspond to a longitudinally regular pattern. The first incisions form tapering tabs for bending in the direction transverse to the sheet to produce petals that extend radially inward from the ring to engage the cable. The second incisions form peripheral tabs for bending in an opposite direction transverse to the sheet to produce flanges that extend radially outward from the ring to engage the conduit.
The assembly includes a conduit having a receiving end through which the cable passes axially; a lower seal that inserts into the receiving end; a gland boss that inserts into the receiving end; an external seal that inserts into the boss and extends axially outward from the receiving end; and the grounding adapter disposed between the internal and external seals.
These and various other features and aspects of various exemplary embodiments will be readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which like or similar numbers are used throughout, and in which:
In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.
Various exemplary embodiments related to the invention were developed for the purposes of providing a Cable Shield Ground Adapter (CSGA) with the following characteristics important for use in marine environments and in particular shipboard environments:
Patent Application Publication 2013/0090004 describes three designs for CSGAs for maritime utility, notionally referred to as “snowflake”, “roll-o-dex” and “lantern” for purposes of description. An activity report: “Cable Shield Ground Adaptor Resistance to Indirect Lighting Effects Test” of June 2013 describes performance of the roll-o-dex and snowflake CSGA configurations of copper and stainless steel, both in D and K sizes, with the snowflake design demonstrating generally better grounding performance. The lantern configuration exhibited structural weakness and was hence not included. The terms “adapter” and “adaptor” are considered synonymous as spelling variants.
Swage stuffing tubes, as military part M24235/17, have several standard sizes as listed at http://www.shipboardelectrical.com/swagetubes.html including a tube body, gland nut and gland ring. The tube body can be stainless steel or aluminum. For purposes of disclosure, sizes B, C, D and K are described herein, although the principles described herein can be extended to additional cable sizes. Respective cable bore diameters for sizes B, C, D and K are Ø0.515 inch (″), Ø0.640″, Ø0.750″ and Ø1.171 inches (″).
The particular dimensions identified herein represent explanatory examples and are not limiting. Thus, other stuffing tube and conduit sizes can be contemplated within the spirit of the claims. MIL-S-24235/2C provides the military standard dimensions for electrical cable packaging, available at http://dornequipment.com/milspecs/pdf/24235-2C.pdf.
For purposes of grounding, an improved design for the CSGA is disclosed herein, combining advantages from the snowflake and roll-o-dex configurations in terms of performance and ease of manufacture. The roll-o-dex and lantern configurations can be produced as a metal ribbon or strip with a repeating pattern, cut to length, the tabs bent inward or outward, and the ends joined together for wrapping around an electrical cable to be grounded.
The snowflake configuration can be produced by cookie-cutter stamping of a circular coupon having an angularly regular pattern. The improved “stetson” or “boater” or “porkpie” configuration maintains the metal strip with repeating pattern of the roll-o-dex design combined with the denser penetrating contact capability of the snowflake design. The name stetson evokes a short broad-brim hat common at American political conventions, which the disclosed configuration resembles.
Additionally, the disclosure provides for lower and upper annular gaskets to provide environmental seals for the CSGA in the swage tube. The B-size lower gasket has an outer diameter (OD) of Ø0.970″ and a bore inner diameter (ID) of Ø0.190″ and a height of 0.563″. The B-size upper gasket has a base rim of Ø0.996″, a stem OD of Ø0.500″, a stem ID of Ø0.190″ and a height above the rim of 1.000″. The C-size lower gasket has an OD of Ø1.090″ and bore IDs of alternatively Ø0.397″ and Ø0.230″, and a height of 0.563″. The C-size upper gasket has a base rim of Ø1.040″, a stem OD of Ø0.608″, stem IDs of alternatively Ø0.397″ and Ø0.230″, and a height above the rim of 1.000″.
The D-size lower gasket has an OD of Ø1.210″ and bore IDs of alternatively Ø0.635″ and Ø0.474″, and a height of 0.583″. The D-size upper gasket has a base rim of Ø1.280″, a stem OD of Ø0.750″, stem IDs of alternatively Ø0.636″ and Ø0.474″, and a height above the rim of 1.000″. The K-size lower gasket has an OD of Ø1.655″ and bore IDs of alternatively Ø1.000″, Ø0.750″ (D insert), Ø0.635″ (C insert) and Ø0.500″ (B insert), and a height of 1.020″. The K-size upper gasket has a base rim of Ø1.040″, a stem OD of Ø1.160″ (expanding to Ø1.222″ at the base), stem IDs of alternatively Ø1.000″, Ø0.750″, Ø0.635″ and Ø0.500″ (for accepting smaller size inserts), and a height above the rim of 1.500″. While these dimensions are derived for use with commonly available swage tube and cable sizes, artisans of ordinary skill will understood that these dimensions could be adjusted to account for future variants without departing from the scope of the invention.
An upper pair of slip rings 140 and 145 provides axial restraint between a CSGA diaphragm 150, shown herein as the stetson configuration, and the gland ring 130. A lower pair of slip rings 160 and 165 provides axial restraint between the CSGA diaphragm 150 and a lower gasket 170. Another optional insert upper gasket 125, together with the lower gasket 170, provide an environmental seal for the stuffing tube interior of a swage tube 180 (also called a stuffing tube), into which the components can be inserted. The insert upper gaskets 125 enable a large size swage tube 180 to accept a thinner cable and maintain environmental integrity, thereby expanding installation flexibility.
The upper gaskets 120 and 125 have a geometric configuration reminiscent of a top-hat or stove-hat. The lower gasket 170 has a geometric configuration approximating a frustum (e.g., truncated cone). The gaskets 120, 125 and 170 are composed of rubber. The swage tube 180 narrows at a choke neck 190 before extending to shield an internal cable. The upper gaskets 125 enable a thin cable to be protected in a larger diameter swage tube 180, thereby enabling additional flexibility in cable shielding. An alternative configuration, features a pair of CSGA diaphragms 150 disposed over the upper shim 240, with the lower shim 230 and the gland ring 130 disposed over the CSGA 150. The CSGA diaphragm 150 functions equally well in either orientation.
The CSGA diaphragm 150 can be disposed over the lower shim 230. An upper shim 240 and the gland ring 130 are disposed over the CSGA diaphragm 150 (downstream of the lower gasket 170). Prior to screwing the gland nut 110 into the swage tube 180, the upper gasket 120 or 220 inserts into the gland nut 110 from its threaded end. The gland nut 110 then screws into, and its hexagonal head 250 extends axially outward from the swage tube 190.
To form this pattern arrangement for the peripheral tabs 1430, the template 1410 has lower lateral incisions 1460 that repeatedly extend from the bottom peripheral edge upward towards the ribbon 1420. The peripheral tabs 1430 can be rounded or chamfered at the corners. To form the tapered tabs 1440, the template 1410 also has upper lateral incisions 1460 that repeatedly extend from the top peripheral edge downward towards the ribbon 1420. The peripheral tabs 1430 can be folded transversely outward from view 1400 to form the outer petals 1330, and the tapered tabs 1440 can be folded transversely inward from view 1400 to form the inner petals 1340 when configured to the CSGA diaphragm 150. The outer petals 1330 can be disposed adjacent to the lower gasket 170 or the gland ring 130.
The ribbon 1420 forms the walls 1310 when the template 1410 is curled so as to join the opposite axial ends 1470 and 1480 together, thereby forming a ring in which the direction of lateral incisions substantially corresponds to the cable axis. This can be accomplished, for example, by raising these ends 1470 and 1480 transversely outward from the view 1400. Thus, the template 1410 can be wrapped around a cable after folding the tapered tabs 1440 outward, folding the rounded tabs 1430 inward, and then bending and joining the ends 1470 and 1480 together, thereby forming the ring of walls 1310.
The ribbon 1420 can further be folded parallel to the incisions 1450 and 1460 to form the joints 1320 separating the walls 1310. The lower tabs 1430 become the flanges 1330 to engage the inner annular surface of the swage tube 180. The upper tabs 1440 become the petals 1340 to engage the cable. If desired, the template 1410 can be wrapped multiple times around a cable after folding the tapered tabs 1440 outward, folding the rounded tabs 1430 inward, thereby forming overlapping layers that can provide enhanced conductivity between a cable shield and the inner wall of a swage tube 180.
The commercial potential for the ground shield adapter described within broad and global in nature. The designs can be used for commercial as well as naval ship construction. Due to the inherent design tolerance for either SAE or metric dimensions for swage tubes 180, the design can be utilized for both domestic and foreign ship construction. Although designed with maritime applications in mind, the designs can also be utilized for general construction practices where swage tubes or breach type fittings might be required for facility cable penetrations that require grounding, stabilization, or weather sealing.
The United States Navy utilizes hundreds of topside components that require electrical power or signal connections to systems internal to the ship via cable. Because of the complex and system hostile EM environment the connecting cables must be protected from unwanted EM coupling to the signal or power cable. The cables therefore are protected from the EM environment by a conductive cable shield grounded via a CSGA to the ship's bulkhead.
Current CSGA technologies utilized by the Navy are difficult to manufacture due to machining, difficult to install, repair and replace due to design characteristics, have relatively short service life due to poor environmental design, and are very expensive (approximately $300.00 per unit in quantity). The Navy also currently purchases CSGAs in multiple sizes due to the conventional CSGAs inability to adapt to multiple swage tube sizes or cable diameters. This significantly increases acquisition, logistics and design costs. The strategic goal of the proposed design is to provide the Navy a cost efficient technology that can significantly reduce total ownership costs via acquisition maintenance and logistics across the fleet.
The exemplary embodiments utilize relatively few parts. Common components include environmental seals that also perform as stabilizing structural components for cable centering and conductive spacers that perform diaphragm deformation control functions. The grounding diaphragm or CSGA diaphragm 150 itself is a cut stamped component made out of conductive sheeting.
The sheeting can be any useable conductive material depending on application such as brass, copper, stainless steel, aluminum or carbon impregnated sheeting. The required thickness of the sheeting depends on the design. The exemplary designs also utilize all components of the stuffing tube assembly. This includes the brass gland nut used as an integrating component and currently unused for shielded cable applications due to design characteristics of conventionally available CSGA designs. For conventional replacement operations of the CSGA assembly, the gland nut 110 may be discarded, resulting in waste higher incurred costs to the Navy.
While certain features of the embodiments of the invention have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.
The invention is a Continuation-in-Part, claims priority to and incorporates by reference in its entirety U.S. patent application Ser. No. 13/385,470 filed Jan. 26, 2012, published as U.S. Patent Application Publication 2013/0090004 and assigned Navy Case 101421, which claims the benefit of priority, pursuant to 35 U.S.C. §119, the benefit of priority from provisional application 61/628,298, with a filing date of Oct. 11, 2011.
The invention described was made in the performance of official duties by one or more employees of the Department of the Navy, and thus, the invention herein may be manufactured, used or licensed by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
Number | Name | Date | Kind |
---|---|---|---|
4022966 | Gajajiva | May 1977 | A |
4273405 | Law | Jun 1981 | A |
4515991 | Hutchison | May 1985 | A |
4687263 | Cosmos et al. | Aug 1987 | A |
4772212 | Sotolongo | Sep 1988 | A |
4904826 | Dixon | Feb 1990 | A |
5308250 | Walz | May 1994 | A |
5477159 | Hamling | Dec 1995 | A |
5691506 | Miyazaki et al. | Nov 1997 | A |
6027349 | Chang | Feb 2000 | A |
6062910 | Braquet et al. | May 2000 | A |
6406330 | Bruce | Jun 2002 | B2 |
6468100 | Meyer et al. | Oct 2002 | B1 |
6683773 | Montena | Jan 2004 | B2 |
7942679 | Gretz | May 2011 | B1 |
8299362 | Vaughan | Oct 2012 | B2 |
8337229 | Montena | Dec 2012 | B2 |
8506325 | Malloy et al. | Aug 2013 | B2 |
8506326 | Purdy | Aug 2013 | B2 |
8529279 | Montena | Sep 2013 | B2 |
8550835 | Montena | Oct 2013 | B2 |
8562361 | Corbett et al. | Oct 2013 | B2 |
Entry |
---|
Glenair Installation Instructions—Threaded-Stem Stuffing Tube. http://www.airmartechnology.com/uploads/installguide/17-423-01.pdf. |
MIL-S-24235/2C(SH), Military Specification Sheet—Stuffing Tube, Dec. 28, 1992. http://domequipment.com/milspecs/pdf/24235-2C.pdf. |
Research Tool & Die Catalog Numbering System Stuffing Tubes. http://www.rtnd.com/catalog/4-8.pdf. |
Activity Report Cable Shield Ground Adaptor Resistance to Indirect Lightning Effects Test, Jun. 2013. |
MIL-S-24235/2C(SH) Military Specification Sheet—Stuffing Tube, 1992. http://domequipment.com/milspecs/pdf/24235-2C.pdf. |
Swage Type, Stuffing Tubes, Shipboard Electric Supply. http://www.shipboardelectrical.com/swagetubes.html. |
Number | Date | Country | |
---|---|---|---|
20140041938 A1 | Feb 2014 | US |
Number | Date | Country | |
---|---|---|---|
61628298 | Oct 2011 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 13385470 | Jan 2012 | US |
Child | 14051385 | US |