Patent Application
20200075196
Statement of the Technical Field
The present disclosure relates generally to electrical cables. More particularly, the present disclosure relates to electrical cables and methods of making the same.
Circuit Integrity (“CI”) cables have traditionally been used to provide electrical power and/or data transmission to equipment and electrical systems that are required to function during a fire. The equipment includes, but is not limited to, fire suppression equipment and/or plenum cables. The electrical systems include, but are not limited to, fire alarm controllers, sprinkler pumps, communication systems, lighting systems, elevator systems, and/or ventilation systems.
Such CI cables are required to continue to operate and provide circuit integrity when they are subjected to fire. To meet certain standards, the CI cables must maintain electrical circuit integrity when heated to a specified temperature in a prescribed way for a specified period of time (e.g., 15 minutes, 30 minutes, 60 minutes, 2 hours). In some cases, the CI cables are subjected to regular mechanical shocks, before being heated, while being heated, and/or after being heated. The CI cables are also often subjected to water jet spraying, either in the latter stages of the heating cycle or after completion of the heating cycle in order to gage the CI cables' performance against other factors likely to be experienced during a fire.
Such CI cables are required to be fire tested for circuit integrity compliance in accordance with a given Compliance Standard. The fire test involves: installing the CI cable(s) in a manufacturer's specified system; and testing the CI cable(s) for functionality in a furnace that models petroleum-fueled fire.
Compliance standards may be developed by U.S. certification companies. For instance, Underwriters Laboratories (“UL”) has developed Compliance Standard UL 2196, 2012 (“UL 2196”). To obtain a UL 2196 certification, the circuit integrity of electrical cables is evaluated during a UL 2196 test. The UL 2196 test involves evaluating the circuit integrity of electrical cables during a period of fire exposure and evaluating the circuit integrity of electrical cables during subsequent exposure to a fire hose stream. In order to meet the requirements of the UL 2196 test, electrical functionality of the electrical cables must be maintained throughout the fire exposure period and the following fire hose stream exposure period. The UL 2196 test is intended to evaluate the fire resistive performance of the electrical cables as measured by functionality during a period of fire exposure, and during a period of following fire hose stream exposure.
In order to maintain the functionality of the electrical cables during a fire exposure, the electrical cables are tested using a fire resistive barrier. The fire resistive barrier may be provided by a cable jacketing that is designed to provide fire resistance. If the cable jacketing is not designed to provide fire resistance, the electrical cables are either placed within a fire resistive barrier or installed within an hourly rated fire resistive assembly. Fire resistive cables intended to be installed with a non-fire resistive barrier (such as a conduit) are tested with the non-fire resistive barrier included as part of the test specimen. Otherwise fire resistive cables incorporating a fire resistive jacket are tested without any barrier. To demonstrate each cable's ability to function during the test, voltage and current are applied to the cable during the fire exposure portion of the UL 2196 test. The electrical and visual performance of the cable is monitored. The cable is not energized during the fire hose spray portion of the UL 2196 test, but it is visually inspected and electrically tested after the fire hose spray portion of the UL 2196 test.
One of the most widely used communication cables in a building is a coaxial cable. Coaxial cables typically include a center conductor surrounded by an outer conductor. The outer conductor is spaced apart from the center conductor via a dielectric (e.g., air or dielectric material). The dielectric is chosen such that it has good electrical conductivity properties. However, such dielectric cannot withstand high temperatures required by CI cables and disintegrates at about 300-400° F.
The present disclosure concerns implementing systems and methods for making an electrical cable. The electrical cable comprises: an inner conductor member formed of a conductive material; a dielectric member disposed as a single non-solid layer on the inner conductor member such that the inner conductor member is only partially covered by the dielectric member; and an outer conductor member that is formed of a conductive material, encompasses the dielectric member and the inner conductor member, and is coaxial with the inner conductor member. The dielectric member is formed of a silica material (a) with a melting point equal to or greater than 1500° F., 1850° F. or 2200° F., (b) that does not experiences a transformation from a flexible material to a rigid material when exposed to temperatures less than 1000° F. or 1850° F., and (c) that comprises 60% or more silica. The diameters of the inner conductor member, dielectric member, and outer conductor member may be selected to produce an impedance value for the electrical cable of 50 ohms or 75 ohms.
In some scenarios, the dielectric member comprises a rope. The rope is helically wrapped around the inner conductor member. A lay length of the rope may be between 1.0 inches and 1.5 inches in those or other scenarios.
In those or other scenarios, the dielectric member comprises a plurality of discs. The plurality of discs are formed of a silica rubber. Adjacent discs have equal spacing therebetween or different spacing therebetween.
In those or other scenarios, the dielectric member is coupled to the inner conductor member. The outer conductor member is corrugated. A protective jacket may be provided that encases the outer conductor member.
In those or other scenarios, the electrical cable is transformed into a circuit integrity cable structure using a conduit wrapped in at least one layer of fire insulating material. The circuit integrity cable structure meets a UL 2196 Compliance Standard.
The methods comprise: forming an inner conductor member from a conductive material; disposing a dielectric member as a single non-solid layer on the inner conductor member such that the inner conductor member is only partially covered by the dielectric member, the dielectric member formed of a material with silica properties and a melting point equal to or greater than 1500° F.; and forming an outer conductor member from a conductive material, the outer conductor member encompassing the dielectric member and the inner conductor member, and is coaxial with the inner conductor member.
The present solution will be described with reference to the following drawing figures, in which like numerals represent like items throughout the figures.
It will be readily understood that the components of the embodiments as generally described herein and illustrated in the appended figures could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the present disclosure, but is merely representative of various embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The present solution may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the present solution is, therefore, indicated by the appended claims rather than by this detailed description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present solution should be or are in any single embodiment of the present solution. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present solution. Thus, discussions of the features and advantages, and similar language, throughout the specification may, but do not necessarily, refer to the same embodiment.
Furthermore, the described features, advantages and characteristics of the present solution may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the present solution can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the present solution.
Reference throughout this specification to “one embodiment”, “an embodiment”, or similar language means that a particular feature, structure, or characteristic described in connection with the indicated embodiment is included in at least one embodiment of the present solution. Thus, the phrases “in one embodiment”, “in an embodiment”, and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
As used in this document, the singular form “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. As used in this document, the term “comprising” means “including, but not limited to”.
When used in this document, terms such as “top” and “bottom,” “upper” and “lower”, or “front” and “rear,” are not intended to have absolute orientations but are instead intended to describe relative positions of various components with respect to each other.
The present document concerns electrical cables and methods of making the same. The electrical cables include, but are not limited to, coaxial cables. The electrical cables of the present solution continue to operate at temperatures up to 1100° F. or 1850° F., while conventional coaxial cables fail at about 300° F. This feature of the present solution allows the electrical cables to be used as stand-alone components or in combination with a conduit or insulation materials to meet high temperature circuit integrity requirements of fire codes easier than existing coaxial cables. The electrical cables of the present solution has been certified to meet the UL 2196 Compliance Standard requirements when used in combination with a conduit encompassed by an insulating fire material (e.g., an insulating fire material Interam™ Endothermic Mat 5-5A-4 available from 3M of Maplewood, Minn.
One prior art cable is described in U.S. Pat. No. 9,773,585 to Rogers (“the '585 patent”). The prior art cable includes a center conductor member and an outer conductor member spaced apart from each other by a multi-layer dielectric member. The multi-layer dielectric member comprises a plurality of solid layers of a dielectric material that is entirely absent of any silica or is 60% or less silica, where the plurality of solid layers are encompassed by a layer of silicon glass separator tape. Although this cable can survive conditions of 1850° F., it is complex and costly to manufacture.
Accordingly, the present solution provides an electronic cable that can survive high temperature conditions, has a less complex design, and is less costly to manufacture. In this regard, it should be understood that the dielectric member of the present solution electronic cable (1) is formed as a single non-solid layer on the inner conductor member such that the inner conductor member is only partially covered by the dielectric member (and not entirely surrounded or covered by the dielectric as is the case in the '585 patent), (2) is formed of a silica material with a melting point equal to or greater than 1500° F., 1850° F. or 2200° F. (and not formed of a component material with a melting point between 350° C. (or 677° F.) and 482° C. (or 899.6° F.) as taught in the '585 patent), (3) is formed of a silica material that never transforms from a flexible material to a ceramic when exposed to temperatures less than 1000° F. or 1850° F. as taught in the '585 patent, and (4) is formed of a material that comprises 60% or more silica (and not 60% or less silica as is suggested by the chemical compositions of the dielectric materials discussed in the '585 patent). In some scenarios, the melting point is equal to or greater than 2200° F. instead of 1500° F. The dielectric member configuration of the present solution eliminates the need for any additional layers of dielectric material and/or silicon glass separator tape, and therefore simplifies the overall cable design and reduces the cost of manufacture.
Referring now to
Coaxial cable 100 is used as a transmission line for Radio Frequency (“RF”) signals. In this regard, the coaxial cable 100 may be used as a feedline connecting a radio transmitter to an antenna, a feedline connection a radio receiver to an antenna, a feedline connecting a radio transceiver to an antenna, a computer network cable, a digital audio cable, a cable television cable, or a power cable.
In some scenarios, the coaxial cable 100 is disposed in a building. A fire may occur in the building, and spread throughout the building by traveling along the length of cables. In order to prevent the spread of fire in buildings, the coaxial cable 100 is designed such that it is resistant to catching fire and/or such that it maintains a desired attenuation coefficient α for losses in conductors of the cable at relatively high temperatures (e.g., >300° F.).
As shown in
The inner conductor member 102 is formed of an electrically conducting material that has a relatively high temperature resistance. Such electrically conducting materials include, but are not limited to, copper, copper alloys, copper plated steel, or aluminum. The inner conductor member 102 is flexible and comprises a solid wire, a hollow wire, a stranded wire, a corrugated wire, a plated wire, or a clad wire.
The inner conductor member 102 has a circular cross-sectional profile, as shown in
The dielectric member 106 comprises a rope that is helically wrapped around the inner conductor member 102. The rope comprises a single rope or multiple ropes braided together. The rope is formed from a dielectric material. The dielectric material includes, but is not limited to, a silica material (a) with a melting point equal to or greater than 1500° F., (b) that does not experiences a transformation from a flexible material to a rigid material when exposed to temperatures less than 1000° F., and (c) that comprises 60% or more silica. Such materials include, but are not limited to, silica, a silica based woven rope, a silica-rubber based polymer (e.g., silicone rubber), and/or zirconia. The dielectric member 106 provides a cable 100 that operates in temperatures up to 1100° F. or 1850° F. (e.g., in a temperature range of 0° F.-1100° F. or 1850° F., or a temperature range of 300° F.-1100° F. or 1850° F.), while maintaining a desired attenuation coefficient α for losses in conductor members 102, 104.
As noted above, conventional coaxial cables fail at about 300° F. This failure is due to the fact that the dielectric member is formed of a polyethelene material that could be solid, foamed, or extruded shape has a softening point around 300° F. In contrast, the dielectric member 106 of the present solution is not a solid layer formed over the inner conductor member 102, but rather has a non-solid arrangement and is formed of a silica material (a) with a melting point equal to or greater than 1500° F., (b) that does not experiences a transformation from a flexible material to a rigid material when exposed to temperatures less than 1000° F., and (c) that comprises 60% or more silica. A cable 100 that is operative at temperatures greater than 300° F. is surprising and an unexpected result from use of such a non-solid layer of silica material.
In some scenarios, a lay length of the helically wrapped dielectric rope may be between 1.0 inch and 1.5 inches. The term “lay length”, as used herein, refers to the distance between a full revolution of the dielectric member 106 around the inner conductor member 102. For example, in some scenarios, the lay length is about 1.00 inch to about 1.50 inches, about 1.10 inches to about 1.40 inches, about 1.20 inches to about 1.30 inches, about 1.20 inches, about 1.25 inches, or about 1.30 inches. The present solution is not limited to the particulars of this example.
The dielectric member 106 has a circular cross-sectional profile, as shown in
An optional bonding agent 200 may be provided as shown in
The outer conductor member 104 is disposed around the inner conductor member 102, optional bonding agent 200, and dielectric member 106. The outer conductor member 104 is coaxial with the inner conductor member 102 meaning that they both have a common elongate center axis 108. The outer conductor member 104 is formed from an electrically conductive material. The electrically conductive material includes, but is not limited to, copper and/or aluminum.
As shown in
The outer conductor member 104 has an outermost diameter 206 between 0.24 inches to 0.80. The diameters 202, 204, 206 are selected to provide a coaxial cable with a required impedance value (e.g., 50 ohms or 75 ohms), attenuation, and/or return loss.
An optional protective jacket 300 may be provided as shown in
The protective jacket 300 has a thickness 302 between 0.01 inches to 0.200 inches. For example, in some scenarios, the protective jacket 300 has a thickness of about 0.01 inches to about 0.05 inches, about 0.02 inches to about 0.04 inches, about 0.02 inches, about 0.03 inches, or about 0.04 inches. The present solution is not limited to the particulars of this example.
A conduit wrapped in a fire insulating material can be used to transform the coaxial cable 100 into a CI cable. As shown in
Although three layers of the fire insulting material is shown in
The present solution is not limited to the coaxial cable architecture discussed above in relation to
As noted above, conventional coaxial cables fail at about 300° F. This failure is due to the fact that the dielectric member is a layer formed of a polyethelene material that could be solid, foamed, or extruded shape that has a softening point around 300° F. In contrast, the discs 606, 706 provide a dielectric member that does not have a solid layer arrangement but rather a non-solid arrangement formed over the inner conductor member 602, 702. The discs are formed of a silica material (a) with a melting point equal to or greater than 1500° F., (b) that does not experiences a transformation from a flexible material to a rigid material when exposed to temperatures less than 1000° F., and (c) that comprises 60% or more silica. Such a material can include, but is not limited to, a silica rubber. A cable 600, 700 that is operative at temperatures greater than 300° F. is surprising and an unexpected result from use of such a non-solid layer of silica material.
Referring now to
Next in 806, a bonding agent (e.g., bonding agent 200 of
One or more dielectric members (e.g., dielectric member 106 of
In 810, a conductive material is disposed over the inner conductor member, the bonding agent and/or the dielectric member. This disposition involves drawing the conductive material over the other members, helically winding the conductive material around the other members, longitudinally pulling the conductive material onto the other members, braiding the conductive material onto the other members, extruding the conductive material onto the other members, and/or plating the other members with the conductive material.
In the extrusion scenarios, the result of 808 is fed through an extruder where a pre-coat of an adhesive bonding agent is applied. The pre-coated structure is then fed through the same or another extruder where the conductive material is applied. In some non-extrusion scenarios, a strip of the conductive material is seam welded into a tube. The tube is then drawn over the helically wrapped inner conductor in a continuous process. The present solution is not limited to the particulars of these scenarios.
The conductive material may be optionally annually corrugated in 812. The corrugation process may involve welding a strip into a tube and corrugating the structure. The present solution is not limited to the particulars of this corrugation process.
As a result of the corrugation process, a series of spaced apart crests are formed along an elongate length of the conductive material. The crests are vertically and horizontally aligned with each other so as to have a generally parallel arrangement. Valleys are provided between adjacent crests. As such, the crests are discontinuous along the elongate length of the coaxial cable. Similarly, the valleys are discontinuous along the length of the coaxial cable. In this regard, it should be understood that each crest and valley extends around the circumference of the conductor material only once, until it meets itself, and does not continue in the longitudinal direction.
Upon completing 812, method 800 continues with 814 where a protective jacket (e.g., protective jacket 300 of
In next 816, one or more layers of a fire insulating material (e.g., fire insulating material 402, 404, 406 of
Although the present solution has been illustrated and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature of the present solution may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Thus, the breadth and scope of the present solution should not be limited by any of the above described embodiments. Rather, the scope of the present solution should be defined in accordance with the following claims and their equivalents.
The present application claims the benefit of U.S. Patent Application Ser. No. 62/681,177 filed on Jun. 6, 2018. The content of which are incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2019/034153 | 5/28/2019 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62681177 | Jun 2018 | US |
