Patent Application
20170352451
The present disclosure relates generally to a Metal-Clad cable type. More particularly, the present disclosure relates to a Metal-Clad cable assembly including parallel laid conductors.
Armored cable (“AC”) and Metal-Clad (“MC”) cable provide electrical wiring in various types of construction applications. The type, use and composition of these cables should satisfy certain standards as set forth, for example, in the National Electric Code® (NEC®). (National Electrical Code and NEC are registered trademarks of National Fire Protection Association, Inc.) These cables house electrical conductors within a metal armor. The metal armor may be flexible to enable the cable to bend while still protecting the conductors against external damage during and after installation. The armor housing the electrical conductors may be made from steel or aluminum, copper-alloys, bronze-alloys and/or aluminum alloys. Typically, the metal armor sheath is formed from strip steel, for example, which is helically wrapped to form a series of interlocked sections along a longitudinal length of the cable. Alternatively, the sheaths may be made from smooth or corrugated metal.
Generally, AC and MC cables have different internal constructions and performance characteristics and are governed by different standards. For example, AC cable is manufactured to UL Standard 4 and can contain up to four (4) insulated conductors individually wrapped in a fibrous material which are cabled together in a left hand lay. Each electrical conductor is covered with a thermoplastic insulation and a jacket layer. The conductors are disposed within a metal armor or sheath. If a grounding conductor is employed, the grounding conductor is either (i) separately covered or wrapped with the fibrous material before being cabled with the thermoplastic insulated conductors; or (ii) enclosed in the fibrous material together with the insulated conductors for thermoplastic insulated conductors. Additionally, in AC type cable, a bonding strip or wire may be laid lengthwise longitudinally along the cabled conductors, and the assembly is fed into an armoring machine process. The bonding strip is in intimate contact with the metal armor or sheath providing a low-impedance fault return path to safely conduct fault current. The bonding wire is unique to AC cable and allows the outer metal armor in conjunction with the bonding strip to provide a low impedance equipment grounding path.
In contrast, MC cable is manufactured according to UL standard 1569 and includes a conductor assembly with almost no limit on the number of electrical conductors. The conductor assembly may contain a grounding conductor. The electrical conductors and the ground conductor are cabled together in a left or right hand lay and encased collectively in an overall covering. Similar to AC cable, the assembly may then be fed into an armoring machine where metal tape is helically applied around the assembly to form a metal sheath. The metallic sheath of continuous or corrugated type MC cable may be used as an equipment grounding conductor if the ohmic resistance satisfies the requirements of UL 1569. A grounding conductor may be included which, in combination with the metallic sheath, would satisfy the UL ohmic resistance requirement. In this case, the metallic sheath and the grounding/bonding conductor would comprise what is referred to as a metallic sheath assembly.
One embodiment of the disclosure may include a metal clad (MC) cable assembly, including a core including a plurality of conductors laid parallel to one another, each of the plurality of conductors including an electrical conductor, insulation with or without a jacket layer, and a metal sheath disposed over the core.
Another embodiment of the disclosure may include a method of making a metal clad cable assembly, the method including providing a core including a plurality of parallel laid conductors, each of the plurality of conductors including an electrical conductor and insulation, with or without a jacket layer. The method further includes disposing a metal sheath over the core.
Yet another embodiment of the disclosure may include a metal clad (MC) cable assembly including a plurality of conductors laid substantially parallel to one another, each of the plurality of conductors including an electrical conductor, an insulation layer provided directly atop the electrical conductor, and a jacket layer provided directly atop the insulation layer. The MC cable assembly may further include a metal sheath disposed over the plurality of conductors, a subassembly including a set of conductors, and an assembly jacket layer disposed over the subassembly.
The accompanying drawings illustrate approaches of the disclosed metal clad cable assembly so far devised for the practical application of the principles thereof, and in which:
The drawings are not necessarily to scale. The drawings are merely representations, not intended to portray specific parameters of the disclosure. Furthermore, the drawings are intended to depict example embodiments of the disclosure, and therefore is not considered as limiting in scope.
Furthermore, certain elements in some of the figures may be omitted, or illustrated not-to-scale, for illustrative clarity. The cross-sectional views may be in the form of “slices”, or “near-sighted” cross-sectional views, omitting certain background lines otherwise visible in a “true” cross-sectional view, for illustrative clarity. Furthermore, for clarity, some reference numbers may be omitted in certain drawings.
The present disclosure will now proceed with reference to the accompanying drawings, in which various approaches are shown. It will be appreciated, however, that the disclosed MC cable assembly may be embodied in many different forms and should not be construed as limited to the approaches set forth herein. Rather, these approaches are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. In the drawings, like numbers refer to like elements throughout.
As used herein, an element or operation recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or operations, unless such exclusion is explicitly recited. Furthermore, references to “one approach” or “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional approaches or embodiments that also incorporate the recited features.
For the sake of convenience and clarity, terms such as “top,” “bottom,” “upper,” “lower,” “vertical,” “horizontal,” “lateral,” and “longitudinal” will be used herein to describe the relative placement and orientation of these components and their constituent parts with respect to the geometry and orientation of a component of a device as appearing in the figures. The terminology will include the words specifically mentioned, derivatives thereof, and words of similar meaning and/or significance.
As stated above, approaches provided herein are directed to a Metal-Clad (MC) cable assembly. In one approach, the MC cable assembly includes a core having a plurality of conductors laid parallel to one another, each of the plurality of conductors including an electrical conductor, insulation and an optional jacket layer. The MC cable assembly further includes a metal sheath disposed over the core and the bonding/grounding conductor. In some approaches, the MC cable assembly further includes an assembly tape disposed around the plurality of conductors. In some approaches, the MC cable assembly further includes a subassembly having a set of conductors, and an assembly jacket layer disposed over the subassembly. In some approaches, a polymeric protective layer is provided over the insulation layer of one or more of the plurality of conductors and the subassembly. In some approaches, a bonding/grounding conductor may also be cabled with the plurality of conductors or laid straight.
Referring now to
It will be appreciated that the plurality of conductors 2A-C may be laid parallel, or substantially parallel, with one another along a length of the cable assembly 1. In some embodiments, to be considered parallel or substantially parallel, the plurality of conductors 2A-C can include a small number of twists along the length of the cable assembly 1. In one example, the plurality of parallel laid conductors 2A-C may have less than three (3) twists along the length of the cable assembly 1. In another example, the plurality of parallel laid conductors 2A-C may have one (1) twist along the length of the cable assembly 1. Stated another way, in some examples, the plurality of parallel laid conductors 2A-C may have between 0.1-0.25 twists/ft.
As shown in the side view of
In various approaches, the plurality of conductors 2A-C of the cable assembly 1 may each be, for example, solid conductors having a size between 28 American Wire Gauge (AWG) and 6 AWG, or may each be, for example, solid and/or stranded electrical conductors having a size between 18 AWG and 6 AWG. In some approaches, the plurality of conductors 2A-C include first, second and third power conductors (e.g., 120V or 277V), wherein each of the conductors 2A-C can have a size between 18 AWG and 2000 KCM.
In example embodiments, the metal sheath 4 may be formed as a seamless or welded continuous sheath, and has a generally circular cross section with a thickness of about 0.005 to about 0.060 inches. Alternatively, metal sheath 4 may be formed from flat or shaped metal strip, the edges of which are helically wrapped and interlock to form a series of convolutions along the length of the MC cable assembly 1. In this manner, metal sheath 4 allows the resulting MC cable assembly 1 to have a desired bend radius sufficient for installation within a building or structure. The sheath 4 may also be formed into shapes other than generally circular such as, for example, rectangles, polygons, ovals and the like. Metal sheath 4 provides a protective metal covering around the plurality of conductors 2A-C.
Although not shown, it will be appreciated that MC cable assembly 1 and MC cable assembly 6 of
Referring now to the side views of
The electrical conductor 12, insulation layer 14 and jacket layer 16 may define an NEC® Type thermoplastic fixture wire nylon (TFN), thermoplastic flexible fixture wire nylon (TFFN), thermoplastic high heat resistant nylon (THHN), thermoplastic heat and water resistant nylon (THWN) or THWN-2 insulated conductor. In other approaches, the conductors 2A-C may define an NEC® Type thermoplastic heat and water resistant (THW), thermoplastic high heat and water resistant (THHW), cross-linked polyethylene high heat-resistant water-resistant (XHHW) or XHHW-2 insulated conductor. In one example approach, the insulation layer 14 is polyvinylchloride (PVC) and has a thickness of approximately 15-125 mil. In one approach, jacket layer 16 is nylon and has a thickness of approximately 4-9 mil.
In some embodiments, one or more conductors of the MC cable assembly 1 may include a fibrous covering (e.g., a paper layer). For example, as shown in
Referring now to the cross-sectional view of
Referring now to the cross-sectional view of
The protective covering 24 may be a polymeric protective layer such as polypropylene. Furthermore, the protective covering 24 may have a thickness between 2-15 mils and may be disposed over the plurality of conductors 22A-C and, more particularly, may be extruded over the plurality of conductors 22A-C. Although the protective covering 24 has been disclosed as being polypropylene, in some approaches it can be made from other materials such as, but not limited to, polyethylene, polyester, etc. The protective covering 24 can provide mechanical strength to resist buckling, crushing and scuffing of the conductors 22A-C.
Referring now to the cross-sectional view of
The first and second conductors 36A-B of subassembly 32 may each be, for example, 16 American Wire Gauge (AWG) solid conductors, while the plurality of conductors 22A-C may each be, for example, 12 AWG solid and/or stranded electrical conductors. In some embodiments, the plurality of conductors 22A-C includes first, second, and third power conductors (e.g., 120V or 277V). In an example approach, each of the conductors 36A-B can have a size between 28 AWG and 6 AWG such that conductors 36A-B are configured to conduct a voltage between zero (0) and approximately 300 Volts. In some approaches, each of the plurality of conductors 22A-C can have a size between 18 AWG and 2000 KCM.
As shown, the first and second conductors 36A-B can each include a stranded or solid electrical conductor 12 having a concentric insulation layer(s) 14, and a jacket layer 16 disposed on the insulation layer 14. In some approaches, the concentric insulation layer 14 and the jacket layer 16 are extruded over each of the individual electrical conductors 12 of the first and second conductors 36A-B of the subassembly 32.
Furthermore, the subassembly 32 is disposed within the assembly jacket layer 41, which extends along the length of the subassembly 32 and is located within metal sheath 4 in an area adjacent the plurality of conductors 22A-C. In approaches, the assembly jacket layer 41 is PVC and has a thickness in the range of 5-80 mils. In one non-limiting example approach, assembly jacket layer 41 has a thickness of approximately 15-30 mils. However, it will be appreciated that the thickness of assembly jacket layer 41 can vary depending on the diameter of the conductor(s) it surrounds. For example, larger diameter conductors generally translate to a thicker jacket layer.
As stated above, the subassembly 32 may be cabled, in a right or left handed lay, with the plurality of conductors 22A-C, which are parallel laid with respect to each other, to form the core 35. Alternatively, the subassembly 32 may extend longitudinally along the metal sheath 4 such that the longitudinal axis of each conductor 36A-B of the subassembly 32 runs parallel to a longitudinal axis of metal sheath 4.
Referring now to the cross-sectional view of
Referring now to the cross-sectional view of
Referring now to the cross-sectional view of
Referring now to the cross-sectional view of
As shown, the bonding/grounding conductor 72 may be in direct contact with an inner surface 74 of the metal sheath 4 and may act in combination with the sheath 4 to define a metal sheath assembly having an ohmic resistance value about equal to or lower than the ohmic resistance requirements necessary to qualify as an equipment grounding conductor. Alternatively, the bonding/grounding conductor 72 may itself have sufficient ohmic resistance to qualify as an equipment grounding conductor.
In some embodiments, the bonding/grounding conductor 72 may have undulations (alternating crests and troughs) applied as part of an in-line process of forming an MC cable. Alternatively, the undulations can be imparted to the bonding/grounding conductor 72 in a separate off-line process and then brought “pre-formed” to the cabling/twisting process used to form the MC cable.
The bonding/grounding conductor 72 may be made from any of a variety of materials, including aluminum, copper, copper clad aluminum, tinned copper and the like. In one non-limiting example approach, the bonding/grounding conductor 72 is aluminum. It will be appreciated that a bonding/grounding conductor may be similarly included with any of the MC cable assemblies described herein, including MC cable assembly 1, MC cable assembly 6, MC cable assembly 10, MC cable assembly 20, MC cable assembly 30, MC cable assembly 40, MC cable assembly 50, and MC cable assembly 60.
Referring now to
As will be appreciated, the various approaches described herein for providing parallel laid conductors provide a variety of advantages/improvements including, but not limited to, reducing cable installation time and cost, and reducing materials, while providing mechanical protection for all conductors within the cable.
While the present disclosure has been described with reference to certain approaches, numerous modifications, alterations and changes to the described approaches are possible without departing from the sphere and scope of the present disclosure, as defined in the appended claims. Accordingly, it is intended that the present disclosure not be limited to the described approaches, but that it has the full scope defined by the language of the following claims, and equivalents thereof. While the disclosure has been described with reference to certain approaches, numerous modifications, alterations and changes to the described approaches are possible without departing from the spirit and scope of the disclosure, as defined in the appended claims. Accordingly, it is intended that the present disclosure not be limited to the described approaches, but that it has the full scope defined by the language of the following claims, and equivalents thereof.
This application claims priority to U.S. Provisional Patent Application No. 62/345,027, filed Jun. 3, 2016, entitled “Metal Clad Cable Having Parallel Laid Conductors,” and incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62345027 | Jun 2016 | US |
