Patent Publication Number: US-2015075838-A1

Title: Cables for a cable bundle

Description:
BACKGROUND OF THE INVENTION 
     The subject matter herein relates generally to cables having differential twisted pairs. 
     Data cables are typically bundled together as a cable bundle and used in many applications, including data communication applications, medical applications, and others. Some known data cables include pairs of insulated conductors that are twisted together, sometimes referred to as “twisted pairs.” As operating frequencies of data cables increase, improved performance of the twisted pairs becomes more important. For example, data cables must meet electrical performance characteristics required for transmission at frequencies above a predetermined threshold. 
     Various cable designs have been used to attempt to improve signal quality and meet industry standards. For example, some known data cables use a shield around the twisted pairs to provide electrical shielding and improve signal quality. Different types of shields are known; however such shields have known problems. For example, some shields use a conductive braid to provide the shielding. The conductive braids are durable and flexible; however such conductive braids do not electrically perform as well as other shield types, particularly in higher frequencies, such as in the GHz range. Some shields use a metal film or tape wrapped around the twisted pair; however such films are fragile and break or tear when mechanically stressed, such as when the cable is bent. Additionally, such shields are susceptible to mechanical degradation, such as from moisture or chemical exposure even within the outer jacket of the cable bundle. 
     Achieving high speed digital signal performance requires consistency in the physical elements of the cable, such as the conductors and shield, throughout the length of the transmission line. When data cables are used in some applications, such as medical applications that require multiple sterilization processes and/or tortuous manipulation of the cable, the properties of the physical elements may be compromised over time. For example, data cables used with camera based medical endoscopes for internal imaging of a patient&#39;s body during surgical procedures require high data speeds to transmit the video images. Such cables are also subjected to chemical sterilization processes after use. A need remains for a cable that supports high data rates and that is capable of undergoing high temperature sterilization processes. 
     BRIEF SUMMARY OF THE INVENTION 
     In one embodiment, a cable bundle is provided including a bundle jacket having a central core and a plurality of cables received in the central core and surrounded by the bundle jacket. Each cable includes a twisted pair of insulated conductors, a dedicated inner shield surrounding the corresponding twisted pair of insulated conductors, a dedicated outer braid surrounding the corresponding inner shield and being electrically coupled to the corresponding inner shield, and a dedicated jacket surrounding the corresponding outer braid. 
     Optionally, the inner shield and outer braid may cooperate to provide a continuous shield along the entire length of the cable. The inner shield may be segmented into a plurality of shield segments. The outer braid may electrically connect the shield segments along the length of the cable. The outer braid may include a plurality of conductive strands each being electrically connected to at least two shield segments of the inner shield. 
     Optionally, the inner shield may be manufactured from a material having better electrical shielding characteristic than the outer braid and the outer braid may be manufactured from a material having better flexibility characteristics than the inner shield. 
     Optionally, the inner shield may be a film having an insulating layer and a metal layer. The metal layer may face the outer braid and the outer braid may be electrically connected to the metal layer. The film may be a polyester (e.g. Mylar) film. The metal layer may be a copper layer. 
     Optionally, the cable jacket may provide a moisture barrier for the corresponding outer braid, inner shield and twisted pair of insulated conductors. The cable jacket may be a fluorocarbon material. The outer braid of each cable within the central core may be separated from other outer braids by the cable jackets of the corresponding cables. 
     In another embodiment, a cable bundle is provided that includes a bundle jacket having a central core and a plurality of cables received in the central core and surrounded by the bundle jacket. Each cable may include a twisted pair of insulated conductors, a dedicated inner shield, a dedicated outer shield, and a dedicated cable jacket. The inner shield includes a film having an insulating layer and a metal layer. The inner shield surrounds the corresponding twisted pair of insulated conductors with the metal layer facing away from the twisted pair of insulated conductors. The outer shield includes a conductive braid surrounding the corresponding inner shield that is electrically coupled to the corresponding inner shield at a plurality of locations along a length of the conductive braid. The cable jacket surrounds the corresponding outer braid. The cable jacket includes a hydrophobic material defining a moisture barrier for the corresponding outer shield, inner shield and twisted pair of insulated conductors. 
     In a further embodiment, a cable bundle is provided that includes a bundle jacket having a central core, a bundle shield in the central core that is metal and defines an electrical shield for the central core, a drain wire in the central core that is electrically connected to the bundle shield, and a plurality of cables received in the central core and surrounded by the bundle jacket and bundle shield. Each cable includes a twisted pair of insulated conductors, a dedicated inner shield surrounding the corresponding twisted pair of insulated conductors, a dedicated outer braid surrounding the corresponding inner shield and being electrically coupled to the corresponding inner shield, and a dedicated jacket surrounding the corresponding outer braid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view of a portion of an exemplary embodiment of a cable bundle. 
         FIG. 2  is a perspective view of the cable bundle. 
         FIG. 3  is a cross sectional view of a cable of the cable bundle. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION 
       FIG. 1  is a cross sectional view of a portion of an exemplary embodiment of a cable bundle  10 .  FIG. 2  is a perspective view of the cable bundle  10 . In the description that follows, the cable bundle  10  will be described and/or illustrated in terms of high-speed cabling, such as, but not limited to, a data communication cable for use in high resolution video imaging. The cable bundle  10  may be used in medical applications, such as camera based medical endoscopes used for internal imaging of the body during minimally invasive surgical procedures. The cable bundle  10  may be particularly adapted for repeated high temperature and/or low temperature chemical sterilization as the cable bundle  10  may be used in surgical applications. However, it is to be understood that the benefits described and/or illustrated herein are also applicable to other types of cables, including, but not limited to, wires, cords, cables, and/or the like of any type. The following description and illustrations are therefore provided for illustrative purposes only and are but one potential application of the subject matter described and/or illustrated herein. 
     The cable bundle  10  includes an insulative bundle jacket  12  and a plurality of cables  14  positioned within the bundle jacket  12 . The bundle jacket  12  surrounds the cables  14 . Specifically, the bundle jacket  12  includes a passageway or central core  16  within which the cables  14  extend. The cables  14  extend within the central core  16  along the length of the cable bundle  10 . The bundle jacket  12  is fabricated from any insulative, non-conductive materials, such as, but not limited to, a polymer such as polyvinyl chloride (PVC), polypropylene, a fluoropolymer, polyethylene, and/or the like. Optionally, the bundle jacket  12  may be fabricated from a hydrophobic material and the bundle jacket  12  may be water resistant or water proof. In the exemplary embodiment, the bundle jacket  12  includes an approximately smooth inner surface  18  and an approximately smooth outer surface  20 . The cable bundle  10  and the bundle jacket  12  extend along a central longitudinal axis  22  that extends along the length of the cable bundle  10 . 
     In an exemplary embodiment, each of the cables  14  includes a plurality of twisted pairs  26  of insulated conductors  28  arranged in the central core  16 . In the illustrated embodiment, four twisted pairs  26  of insulated conductors  28  are provided, however any number of twisted pairs  26  of insulated conductors  28  may be provided. The twisted pairs  26  may each be referred to herein as a “first”, a “second”, a “third”, and/or a “fourth” twisted pair. In an exemplary embodiment, each of the conductors  28  is at least partially surrounded by an insulative layer  30 . The conductors  28  may be fabricated from any conductive materials, such as, but not limited to, copper and/or the like. The insulative layers  30  are fabricated from any insulative, non-conductive materials, such as, but not limited to, a polymer such as PVC, polypropylene, a fluoropolymer, polyethylene, and/or the like. 
     In an exemplary embodiment, the twisted pairs  26  are independently sealed and electrically shielded. The sealing provides protection from the environment in the central core  16 , such as moisture protection. For example, each twisted pair may have a moisture barrier to protect the conductors  28  from water or chemicals in the central core  16 . The sealing may ensure that the cable maintains mechanical and electrical integrity during use in harsh environments, after cleaning or sterilization, and the like. The electrical shielding provides low differential signal attenuation, which enhances the electrical performance of the cable  14 , such as for high speed applications. Optionally, the electrical shielding is flexible and maintains mechanical and electrical integrity with use and manipulation. 
     In an exemplary embodiment, the cable bundle  10  includes a bundle shield  32  in the central core  16 . The bundle shield  32  is arranged along the inner surface  18  of the bundle jacket  12 . The bundle shield  32  provides electrical shielding for the cables  14 . The bundle shield  32  may be fabricated from any conductive materials, such as, but not limited to, a braid of conductive strands, fibers, and/or the like, a laminated metal tape, an aluminum polyimide laminated tape, an aluminum biaxially-oriented polyethylene terephthalate (BoPEt) laminated tape, a tube formed from a continuous (e.g., a sheet) conductive material, and/or the like. The bundle shield  32  is optionally connected to a ground or other source of electrical energy to provide active shielding. The bundle shield  32  extends around the central core  16  and the cables  14 . 
     Optionally, one or more filler elements  34  is positioned within the central core  16  of the bundle jacket  12 , for example to facilitate holding the cables  14  in proper positions within the cable bundle  10  to facilitate providing the cable bundle  10  with a predetermined shape (e.g., cylindrical), and/or the like. Each of the filler elements  34  may be fabricated from one or more dielectric materials such that the filler element  34  is at least partially insulative and non-conductive. Optionally, the cable bundle  10  includes one or more drain wires  36  positioned within the central core  16  of the bundle jacket  12  between and/or along the cables  14 . The drain wires  36  may be electrically commoned with the bundle shield  32 . The drain wires  36  may provide electrical shielding between and/or along the cables  14 . The drain wires  36  may provide a source of ground or other electrical energy for the cables  14 . Optionally, the cable bundle  10  may include one or more low speed wires  38 . The low speed wires  38  may be insulated conductors. The low speed wires may be arranged in pairs and may carry differential signals. The cables  14 , filler elements  34 , drain wires  36  and/or low speed wires  38  may be loaded into the central core  16  of the bundle jacket  12  during a cabling operation. 
       FIG. 3  is a cross sectional view of one of the cables  14 . The cable  14  includes the twisted pair  26  of insulated conductors  28 , which is independently sealed and electrically shielded. The cable  14  includes a dedicated inner shield  50 , a dedicated outer shield  52  and a dedicated cable jacket  54 . 
     The inner shield  50  surrounds the corresponding twisted pair  26  of insulated conductors  28 . In an exemplary embodiment, the inner shield  50  is a film having a metal layer  56  and an insulating layer  58 . The metal layer(s)  56  may be located on a radially outer side of the inner shield  50  (e.g., facing radially toward the outer shield  52 ). The insulating layer  58  may be a biaxially-oriented polyethylene terephthalate (BoPEt) layer; however the insulating layer  58  may be made from other materials in alternative embodiments. The metal layer  56  may be a copper layer applied to the insulating layer  58 , such as by plating, laminating, adhering or other processes. The metal layer  56  may be other metals in alternative embodiments, such as silver, aluminum, and the like, however copper tapes provides high temperature resistance and better flex life than aluminum tapes as copper flexes better than aluminum and can be applied thinner. The inner shield  50  may be other materials in alternative embodiments, such as, but not limited to, a metal laminated polyimide tape, a braid of conductive strands, fibers, and/or the like, a tube formed from a continuous (e.g., a sheet) conductive material, and/or the like. In an exemplary embodiment, the inner shield  50  is highly conductive and has high coverage for good electrical shielding around the twisted pair  26  of insulated conductors  28 . 
     The outer shield  52  surrounds the corresponding inner shield  50  and is electrically coupled to the inner shield  50 . In an exemplary embodiment, the outer shield  52  is a braid of conductive strands or fibers. The outer shield  52  may be referred to hereinafter as an outer braid  52 . The outer braid  52  may be a silver plated copper braid. The outer braid  52  has high flexural endurance and is capable of withstanding tortuous manipulation with use. In an exemplary embodiment, each of the conductive strands engages the inner shield  50  at multiple points of contact along the length of the cable  14  to electrically connect the outer shield  52  to the inner shield  50  at such multiple points of contact. The outer shield  52  provides electrical continuity along the length of the cable  14 . The outer shield  52  may be another type of shield in alternative embodiments, such as, but not limited to, a laminated metal tape, a metal laminated polyimide tape, a metal laminated biaxially-oriented polyethylene terephthalate (BoPEt) tape, a tube formed from a continuous (e.g., a sheet) conductive material, and/or the like. 
     The inner and outer shields  50 ,  52  define a double shield structure for the twisted pair  26  of insulated conductors  28 . The double shield structure maintains electrical integrity of the shield structure during use. In an exemplary embodiment, the inner shield  50  has a different structure than the outer shield  52 . For example, the inner shield  50  is a metal film designed or selected to have high quality electrical shielding characteristics, while the outer shield  52  is a conductive braid designed or selected to have high flexibility and durability characteristics. As is typical of metal films, the metal film may break, crack, tear, or otherwise separate into different pieces or segments  60  over time, such as during manipulation or bending of the cable  14 . The shield segments  60  may be separated by breaks  62  or spaces between the segments  60 . With conventional designs, such segmenting of the shield detrimentally affects the electrical shielding ability of such shield. However, with the cable  14 , the outer shield  52  is electrically coupled to the inner shield  50  along the length of the cable  14 . The outer shield  52  bridges the segments  60 , thus electrically commoning the segments  60 . The outer shield  52  is able to withstand the tortuous manipulation and bending of the cable  14  without damage to the outer shield  52  part of the shield structure. The outer shield  52  electrically connects each of the shield segments  60  of the inner shield  50  (e.g. after the inner shield  50  breaks apart from manipulation) to provide electrical continuity of the shield segments  60  along the length of the cable  14 . Additionally, as is typical of braid shields, the electrical shielding and coverage is less effective than with films or tapes. However, because the cable  14  includes the inner shield  50 , the electrical shielding is greatly improved as compared to conventional cables that only include a braid shield. The double shield structure provides the dual benefit of high quality electrical shielding and cable flexibility. 
     The cable jacket  54  surrounds the outer shield  52 , inner shield  50  and the conductors  28 . The cable jacket  54  seals the conductors  28  and shields  50 ,  52  from the environment within the cable bundle  10  (shown in  FIG. 1 ). The cable jacket  54  is fabricated from any insulative, non-conductive material, such as, but not limited to, a polymer such as PVC, polypropylene, a fluoropolymer, polyethylene, and/or the like. In an exemplary embodiment, the cable jacket  54  is fabricated from a hydrophobic material defining a moisture barrier for the corresponding inner shield  50 , outer shield  52  and twisted pair  26  of insulated conductors  28 . The cable jacket  54  provides durability to support sterilization processes of the cable  14 . For example, the cable jacket  54  prevents moisture from the sterilization process from contacting the inner shield  50 , outer shield  52  and twisted pair  26  of insulated conductors  28 , thus maintaining the mechanical and electrical integrity of the inner shield  50 , outer shield  52  and twisted pair  26  of insulated conductors  28 . Even if moisture permeates the central core  16  of the cable bundle  10  (both shown in  FIG. 1 ), such moisture will be unable to permeate the inner shield  50 , outer shield  52  or insulated conductors  28  because of the moisture barrier defined by the cable jacket  54 . The cable jacket  54  may be fabricated from a material that is resistant to one or more particular chemicals, such as chemicals used in sterilization processes. The cable jacket  54  may provide high temperature resistance, such as for use in high temperature sterilization. The cable jacket  54  provides an extra level of protection for the inner shield  50 , outer shield  52  and twisted pair  26  of insulated conductors  28  in addition to the bundle jacket  12  (shown in  FIG. 1 ). The cable jacket  54  may provide a dielectric material in the vicinity of the twisted pair  26  of insulated conductors  28  to maintain the electrical dielectric constant in the air gap between two cables  14 . 
     With reference back to  FIG. 1 , embodiments described herein provide a high speed cable bundle  10  adapted for use in harsh environments. The cable bundle  10  includes a plurality of cables  14 , each providing dedicated shielding for the conductors of such cable  14  as well as dedicated protection of such shielding to maintain mechanical and electrical performance of such shielding and cable for prolonged use. The cable bundle  10  may be particularly adapted for use in applications that require sterilization compatibility as each of the cables  14  includes a cable jacket  54  that surrounds the corresponding shield structure of the cable  14 . Such cable jacket  54  is independent of and used in addition to the bundle jacket  12  that surrounds the entire cable bundle  10 . 
     One particular application the cable bundle  10  may be suited for is camera based medical endoscopes used for internal imaging of the patient&#39;s body during surgical procedures. Such endoscopes have need for high speed cables  14  capable of sending high speed signals, such as at speeds of 5 gigabits per second or more. The system demands consistency and reliability of the images during use and over repeated uses for patient safety. Such cables  14  are subjected to manipulation and bending during use at a much greater frequency as compared to typical data communication cables that are laid in an office environment and rarely, if ever, moved once laid. The cables  14  are capable of maintaining mechanical and electrical integrity even with the manipulation and bending of the cable bundle  10  with the use of the dedicated double shield structure for the twisted pair  26  of conductors  28 . The double shield structure includes an inner shield  50  (e.g. a metal foil or tape) having good electrical shielding characteristics and an outer shield  52  (e.g. a conductive braid) having good flexibility characteristics that maintains electrical continuity along the length of the cable  14  by electrically connecting all segmented or separated shield portions. 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means—plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.