Abstract:
A cable is provided, configured for tandem communication and power transmission. The cable has a plurality of twisted pair conductors and a jacket surrounding said twisted pair conductors. The jacket includes a plurality of either ridges, valleys or both, disposed substantially perpendicular to the longitudinal axis of the cable, the ridges and/or valleys are dimensioned and spaced apart in a manner sufficient to create an air passage when the cable is arranged adjacent to and abutting other cables.

Description:
BACKGROUND 
     Field of the Invention 
       [0001]    This invention relates to a cable jacket. More particularly, this invention relates to a novel cable jacket design that helps dissipate heat from the cable. 
       Description of Related Art 
       [0002]    A recent development in communications cabling is the tandem delivery of power and data signals through a single cable. Although not always the case, a typical arrangement would utilize a normal LAN (Local Area Network) twisted pair cable, usually having four twisted pairs of insulated copper conductors therein. In normal LAN operations all four pairs are for data communication. However, in tandem power/data applications some of the pairs are dedicated to data communications but one or more of the pairs can be used to deliver power though the same cable. In some cases, a twisted pair carrying data can also carry power at the same time as the data transmits via AC (alternating current) and the power transmits via DC (direct current) so it is possible to split the power and data signals from one another as needed. Such data/power tandem arrangements can be used for example with security cameras or VoIP phones which require a small amount of power as well as data communication. 
         [0003]    Initially, IEEE (Institute for Electrical and Electronics Engineers) adopted the 802.3af standard for Power over Ethernet (Or PoE) which has been widely accepted in the industry setting the relevant parameters, such as wattage, negotiation parameters/routines, DC loop resistance etc . . . , for delivering power in tandem with data. The total amount of power that can be delivered under this standard is 12.95 W which is adequate for such basic applications such as the standard VoIP phones and security cameras noted above. 
         [0004]    However, growing lists of features on devices that are connected and powered with tandem power/data cables as well as new communication equipment that likewise can make use of the tandem power/data through LAN cables, has necessitated even more power throughput allowance. IEEE 802.8at is an updated standard that allows for an increase to 25.5 W power (PoE+) to be delivered through such tandem cables. Another even newer standard is IEEE 802.3bt that sets the parameters for using all four twisted pairs to simultaneously send data and power. In the conditions according to this newer standard cables sending both data and power in some cases will be delivering as much as 100 Watts. These high rates of power transmission can lead to the operating temperatures of the cable exceeding its maximum allowable operating temperature according to the cables own heat tolerance thresholds. This is especially true when large numbers of cables are installed together or bundled adjacent to and abutting one another. 
         [0005]    With this increase in power throughput through one or more of the twisted pairs of a LAN cable, there is a corresponding increase in heat that needs to be dissipated from the cables to the environment. This leads to concerns about fire safety and data transmission performance and ultimately limits the number of such tandem operation cables that can occupy a single pathway or be arranged next to one another in order to stay within the range of safe operating temperatures. For example the NFPA (National Fire Protection Association) 70 standard, setting the National Electrical Code covering these cables, requires that the cables do not exceed their listed maximum operating temperature which is typically 60 C. 
         [0006]    As shown in prior art  FIGS. 1 and 2 , typical LAN cables are constructed having four insulated twisted pairs, an optional cross filler (depending on the data signal requirements), and an outer jacket enclosing the cable. The prior jackets for twisted-pair cables do not take heat dissipation into consideration, and therefore, are not optimized for supporting power provided through one or more of its twisted pairs. Standard cable jackets such as those shown in  FIGS. 1 and 2  possess an outer surface that generally maintains an equal distance from the center of the cable for the entire length of the cable. When multiple LAN cables are placed together they touch along their entire longitudinal axis (longest axis) and entrap the heat generated by the power conductors as conductive heat transfer is less efficient than convective heat transfer. 
       OBJECTS AND SUMMARY 
       [0007]    The present arrangement overcomes the drawback by providing a novel design for the outer surface of a LAN cable jacket, intended to be used for tandem power/data signaling applications, that allows for better air flow around the cables. 
         [0008]    In one embodiment, a series of ridges or valleys are disposed, circumferentially or helically around the outer surface of the cable jacket, such ridges or valleys spaced apart from one another over the length of the cable. Such structures, either ridges or valleys generate an air gap between adjacent cables allowing air to flow between, allowing the heat released from the one or more powered twisted pairs to escape more easily through the outer surface of the jacket and to generate a convection air flow upward around and in between the cables. 
         [0009]    This design allows installers and end-users to install larger numbers of LAN cables, intended for tandem power/data communication, within a single pathway without exceeding the allowable temperature rise and thus the maximum operating temperature. 
         [0010]    To this end a cable is provided, configured for tandem communication and power transmission. The cable has a plurality of twisted pair conductors and a jacket surrounding said twisted pair conductors. The jacket includes a plurality of either ridges, valleys or both, disposed substantially perpendicular to the longitudinal axis of the cable, the ridges and/or valleys are dimensioned and spaced apart in a manner sufficient to create an air passage when the cable is arranged adjacent to and abutting other cables. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS: 
         [0011]    The present invention can be best understood through the following description and accompanying drawings, wherein: 
           [0012]      FIGS. 1 and 2  illustrate prior art LAN cables, capable of supporting tandem power and data communications in the same cable; 
           [0013]      FIGS. 3 and 4  illustrate a LAN cable, capable of supporting tandem power and data communications in the same cable, with a jacket according to one embodiment; 
           [0014]      FIG. 5  illustrates a LAN cable having a plurality of ridges disposed on the outer circumference of the jacket, according to one embodiment; 
           [0015]      FIG. 6  illustrates a LAN cable having a plurality of valleys disposed on the outer circumference of the jacket, according to one embodiment; 
           [0016]      FIG. 7  illustrates a LAN cable having a plurality of ridges and valleys disposed on the outer circumference of the jacket, according to one embodiment; and 
           [0017]      FIG. 8  illustrates a plurality of LAN cables, arranged adjacent to and abutting each other, each having a plurality of ridges disposed on the outer circumference of the jacket, according to one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    In one embodiment of the present arrangement,  FIGS. 3 and 4  illustrate a LAN cable according to one embodiment. Cable  10  has four twisted pairs  12 , each made from two twisted insulated copper conductors, a cross filler  14 , a drain wire  16  and a jacket  18 . It is understood that that this form of tandem power/data communications cable is being shown for illustration purposes only, but is not intended to limit the scope of the application. The applicable heat dissipating features as described below can be applied to any tandem power/data communication cable arrangement. 
         [0019]    As illustrated more clearly in  FIG. 4 , jacket  18  is constructed from any suitable polymer such as PVC (PolyVinylChloride) or PE (PolyEthylene) etc. . . . , but unlike typical jackets with smooth outer surfaces, jacket  18  has a series of circumferentially disposed ridges  20  and/or valleys  22 , angled substantially perpendicular to the longitudinal axis of the cable. 
         [0020]    In the embodiment shown in  FIG. 4  either ridges  20  or valleys  22  are shown as complete rings around the entire outer circumference of jacket  18 .  FIG. 5  shows jacket  18  in another embodiment where ridges  20  are disposed, not completely surrounding cable jacket  18 , but rather as partial arcs, around jacket  18  (i.e. covering about ¼ to ⅓ of circumference of jacket  18 ). The partial arc ridges  20  are disposed randomly about the outer surface of jacket  18 , perpendicular to the longitudinal axis of cable  10 , but at random intervals as shown in  FIG. 5 . The spacing and location of the arc ridges  20  are such so that when jacket  18  is arranged next to a jacket  18  of an adjacent cable  10  they allow for airflow there between as described in more detail below.  FIG. 6  shows an alternative arrangement with valleys  22  disposed around jacket  18  in a similar arrangement as ridges  20  as shown in  FIG. 5  and as described above.  FIG. 7  shows another alternative arrangement with both ridges  20  and valleys  22  disposed around the same jacket  18 , for example in an alternating fashion, in a similar arrangement as shown in  FIGS. 5 and 6 . 
         [0021]    In each arrangement, ridges  20  or valleys  22  are arranged perpendicular to the longitudinal axis of cable  10  and are spaced apart in a manner that is sufficient to generate the desired air passages between cables  10 , when arranged next to other cables, and are otherwise structured and spaced so that either ridges  20  or valleys  22  of jacket  18  do not deform under the weight of the cable itself or allow for the desired air passages to close. 
         [0022]    In one embodiment ridges  20  are ideally constructed to a thickness of approximately 50%-100% of the thickness of jacket  18 . Valleys  22  are ideally approximately 50% of the thickness of jacket  18 . The shape of ridges  20  and/or valleys  22  are not critical (e.g. can be triangular, squared, irregular etc . . . ) as long as they create the desired air pathways between jackets  18  of adjacently arranged and abutting cables. 
         [0023]    In one embodiment, ridges  20  and valleys  22  can be made from a rotating drum that is located closely after jacket  18  is extruded onto cable  10 . Such a drum would have its own ridges or cutters that would imprint/cut such ridges  20 /valleys  22  into jacket  18  while jacket  18  is still warm and malleable (semi-molten). In another embodiment, to forms ridges  20 , a second extruder head can be aligned after the primary jacket  18  extruder so that a “surge” of additional material can be periodically applied onto the still hot jacket  18 . In a third possibility, ridges  20  or valleys  22  can be formed after jacket  18  is cooled, in an additional step where ridges  20  can be applied/deposited, or valleys  22  cut, independent from the primary jacket extrusion process. 
         [0024]    To illustrate the desired effect of the present arrangement,  FIG. 8  shows three adjacently arranged cables  10 , each having ridges  20  (as partial arcs) around jacket  18  as per  FIG. 5 . Such ridges  20  generate air gaps  30  between the outer surfaces of jackets  18  of adjacent cables  10 . This allows air to flow between jackets  18  via gaps  30 , allowing the heat released from the one or more powered twisted pairs to dissipate from adjacent cables  10 . Once such heat is able to pass through jacket  18 , it can more easily escape the cable bundle as the heat can move upward through gaps  30  between cables  10 . The rising heat in turn draws cool air upwards by convection for further cooling. Air gaps  30  formed by ridges  20  essentially create vertical ‘chimneys’ as defined by the non-contacting surfaces of adjacent cables  10 . 
         [0025]    These convection pathways allow for warm aft to exit upwards and draw cool aft into the cable  10  bundle. It is further noted that, generally speaking, shielded cables generally dissipate heat better than UTP (Unshielded twisted pair) cables. However, shields or tapes add weight and cost to the overall cable design. In some cases where the LAN cable is to be used for tandem power/data communications, installers choose shielded cables, not for their electrical shielding benefits but for their heat dissipation advantage. The present arrangement could mitigate or negate the need to use shields for their heat dissipation properties even though such jackets  18  as described herein would be obviously beneficial for shielded cables as well. 
         [0026]    While only certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes or equivalents will now occur to those skilled in the art. It is therefore, to be understood that this application is intended to cover all such modifications and changes that fall within the true spirit of the invention.