Abstract:
A surge protection element for a conventional cable connector includes a printed circuit board preferably shaped as two concentric rings connected by two spokes. The outer ring is electrically connected to the grounded portion of the cable connector body. A printed circuit trace on one of the spokes is separated from a printed circuit trace on the inner ring by a spark gap. If a high voltage surge is carried by the coaxial cable transmission line, a spark is formed in the gap. As a consequence, the high voltage surge is transferred to the surge protection element which in turn conducts the electricity to the grounded body of the connector.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation in part of co-pending application U.S. application Ser. No. 09/726,821 filed Nov. 30, 2000 and entitled HIGH VOLTAGE SURGE PROTECTION ELEMENT FOR USE WITH CATV COAXIAL CABLE CONNECTORS, incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to devices for interconnecting coaxial cable to CATV systems, and more particularly to surge protection devices that protect the integrity of electronic components positioned within interconnect devices from high voltage surges of electricity.  
         BACKGROUND OF THE INVENTION  
         [0003]    In the CATV industry, cable television signals are traditionally transmitted by coaxial cable. As the cable is extended through a distribution network, several types of electrical devices, such as filters, traps, amplifiers, and the like, are used to enhance the signal and ensure signal integrity throughout the transmission. It is therefore necessary to prepare a coaxial cable for interconnection to these devices in such a manner so as to ensure that the signal is not lost or disrupted.  
           [0004]    In a traditional interconnection of the coaxial cable to the electrical device, the coaxial cable is attached in axially aligned relation to a conductive pin extending outwardly from the electrical device. The pin then transmits the signal from the coaxial cable to the electrical device. A conductive lead extending rearward from the electrical device carries the electrically treated signal to the distribution cable in the CATV system.  
           [0005]    It is also necessary to terminate a coaxial cable distribution line at its end point. To terminate the coaxial cable, its central conductor is interconnected to a termination connector, such as a UMTR (Universal Male Terminator). The termination connector includes a first end, a body portion which defines a cavity, electrical components mounted within the cavity such as a capacitor to dissipate the charge, a resistor for impedance matching purposes, and an end cap that concludes the connector. The central conductor of the coaxial cable is electrically attached to a pin extending outwardly from the electrical components. As used herein, “connector” refers to either a termination type connector or any other standard coaxial cable connectors used in a CATV system.  
           [0006]    On occasion, a high voltage surge is transmitted through the coaxial cable, for instance, due to a lightning strike. If this high voltage surge is permitted to be picked up by the input pin and transmitted to the electrical device within the connector, the device becomes inoperable due to the electrical components essentially melting or otherwise deteriorating as a consequence of the surge. A new connector then needs to be installed at the site of the surge.  
           [0007]    A cable connector having a device that provides an alternate path for high voltage surges of electricity in order to protect the integrity of any electrical components positioned within the connector is therefore highly desired.  
         SUMMARY OF THE INVENTION  
         [0008]    Briefly stated, a surge protection element for a conventional cable connector includes a printed circuit board preferably shaped as two concentric rings connected by two spokes. The outer ring is electrically connected to the grounded portion of the cable connector body. A printed circuit trace on one of the spokes is separated from a printed circuit trace on the inner ring by a spark gap. If a high voltage surge is carried by the coaxial cable transmission line, a spark is formed in the gap. As a consequence, the high voltage surge is transferred to the surge protection element which in turn conducts the electricity to the grounded body of the connector.  
           [0009]    According to an embodiment of the invention, a surge protection element for use in a cable connector includes a printed circuit board including an inner ring and a first arm extending outward from the inner ring; a first trace on at least a portion of the inner ring, the first trace being disposed such that the first trace is electrically connected to a signal portion of the cable connector when the surge protection element is installed in the cable connector; and a second trace on at least a portion of the first arm, the second trace being disposed such that the second trace is electrically connected to a ground portion of the cable connector when the surge protection element is installed in the cable connector; wherein the first and second traces are separated by a spark gap.  
           [0010]    According to an embodiment of the invention, in a CATV system that includes a coaxial cable having a central conductor, an outer conductor concentrically positioned in surrounding relation thereto, and a dielectric layer disposed between the central and outer conductors, a high voltage surge protection device adapted for use in the CATV system includes a connection housing having a first end and a body portion that defines an internal cavity; an electronic component positioned within the cavity; and a surge protection element positioned entirely within the cavity and between the body portion and the electronic component, wherein the element includes a printed circuit board which includes an inner ring and a first arm extending outward from the inner ring; a first trace on at least a portion of the inner ring, the first trace being disposed such that the first trace is electrically connected to the electronic component; and a second trace on at least a portion of the first arm, the second trace being disposed such that the second trace is electrically connected to the housing; wherein the first and second traces are separated by a spark gap. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 shows a partial, longitudinal cross-sectional view of a CATV system, including a coaxial cable connector according to an embodiment of the invention.  
         [0012]    [0012]FIG. 2 shows an exploded perspective view of the embodiment of FIG. 1.  
         [0013]    [0013]FIG. 3 shows a perspective view of a first embodiment of a surge protection element used in the embodiments of the present invention.  
         [0014]    [0014]FIG. 3A shows a perspective view of a second embodiment of a surge protection element.  
         [0015]    [0015]FIG. 3B shows a perspective view of a third embodiment of a surge protection element.  
         [0016]    [0016]FIG. 3C shows a perspective view of a fourth embodiment of a surge protection element.  
         [0017]    [0017]FIG. 3D shows a perspective view of a fifth embodiment of a surge protection element.  
         [0018]    [0018]FIG. 4 shows a partially cutaway perspective view of device using a sixth embodiment of the invention.  
         [0019]    [0019]FIG. 5 shows an exploded view of the device of FIG. 4 using the sixth embodiment of the invention.  
         [0020]    [0020]FIG. 6A shows a rear elevation view of the sixth embodiment of the invention.  
         [0021]    [0021]FIG. 6B shows a front elevation view of the sixth embodiment of the invention.  
         [0022]    [0022]FIG. 6C shows a front perspective view of the sixth embodiment of the invention.  
         [0023]    [0023]FIG. 6D shows an enlarged view of a portion of the sixth embodiment of the invention showing a spark gap.  
         [0024]    [0024]FIG. 7 shows a perspective view of a seventh embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]    Referring to FIGS.  1 - 2 , a connector  10 , shown here as a termination connector, extends along a longitudinal axis X-X. Although a termination connector is not connected directly to a cable, a cable connector forms a direct electrical connection with a coaxial cable. Although not expressly illustrated in the drawings, it should be understood that the coaxial cable includes a central conductor immediately surrounded by a layer of dielectric material of predetermined thickness, an outer conductor concentric with the central conductor and surrounding the dielectric material, and an optional outer layer of insulating material surrounding the exterior surface of the outer conductor.  
         [0026]    Connector  10  generally includes a conductive body  14  having a first end  16 , a second end  18 , and a cavity  20  defined therein. Body  14  includes an externally threaded portion  22  positioned at its first end  16 , a shoulder  24  formed interiorly of threaded portion  22  at the interface of first end  16  and cavity  20 , and a rear end  26  formed at second end  18 . It should be understood that although connector  10  is illustrated as being a “male” UMTR (Universal Male Terminator) termination connector, the present invention works equally well with female connectors and other standard type connectors used in a CATV system.  
         [0027]    An electrical component, designated generally by reference numeral  28 , and shown illustrated as being composed of a capacitor  30  and a resistor  32  extending rearward therefrom, is positioned within cavity  20 . It should be understood that electrical component  28  could be any standard type of electrical component that is incorporated into coaxial cable conductors, such as integrated circuits that form filters, amplifiers, traps, and the like. A pin  34  is soldered or otherwise connected to electrical component  28  and extends forward therefrom along longitudinal axis X-X. Pin  34  terminates in a head  36  of a conductive pin  12  at which point it is electrically interconnected to conductive pin  12 . Electrical component  28  further includes a lead  38  which extends rearward from resistor  32  along longitudinal axis X-X that is soldered or otherwise securely connected to rear end  26  of body  14 .  
         [0028]    Connector  10  further includes a standard end cap  40  positioned in covering relation to second end  18  to protect the connection of lead  38  to body  14 , among other things, and an O-ring  41  positioned at the interface of body  14  and threaded portion  22  which prevents moisture, dust, and other contaminants from entering connector  10 .  
         [0029]    Under normal operating conditions, the coaxial cable carries and transmits 90 Volts AC. There may be occasions, however, where high voltage surges impact upon and are carried by the coaxial cable, such as, for example, in the event it is struck by lightening. If this high voltage surge were to be transmitted to pins  12  and  34  and then carried to electrical component  28 , the devices comprising electrical component  28  would in most instances become inoperable as they would not be able to receive such surges without their conductive elements melting or otherwise deteriorating.  
         [0030]    Referring also to FIG. 3, to prevent a damaging amount of such high voltage surges from being transmitted to electrical component  28 , the present invention includes a surge protection element  42 , which is composed of a conductive material, such as bronze, and is of a predetermined width W. Surge protection element  42  generally includes a ring-shaped outer body  44  and at least one prong  46  extending radially inward therefrom. Although surge protection element  42  is illustrated in the drawings as including four, equally spaced apart prongs  46 , it has been found that three prongs  46  work just as well, and they need not be equally spaced apart, and one (or any number) prong would also work. The width W and material composition of surge protection element  42  dictate how much voltage element  42  can withstand, but element  42  has been found to withstand voltages of up to 6,000 Volts at 3,000 Amps for a period of 50 microseconds when composed of brass and of a width W of about 0.020 inches, as is required by IEEE Specification 62.41.  
         [0031]    Surge protection element  42  is positioned with its body portion  44  in electrically conductive contact with shoulder  24 , and prong(s)  46  extending radially inward therefrom. To ensure that body portion  44  remains in electrically conductive contact to shoulder  24  of conductive body  14 , surge protection element  42  is press fit or otherwise securely engaged with connector  10 . When in this position, prong(s)  46  are positioned in close proximity to, but in non-contacting relation to, head  36 , thereby leaving a spark gap  48  therebetween (FIG. 1). As is well known in the art, the dielectric strength of air is 3,000,000 Volts/Meter and thus a voltage of 300 Volts produces a spark in an air gap of 0.1 mm. Thus, the size of spark gap  48  dictates the voltage level at which surge protection element  42  triggers the electric current to pass through body  14  and go to ground instead of through electrical component  28 .  
         [0032]    Thus, in the event of a high voltage surge of electricity passing through connector  10 , if the surge is above a predetermined value as determined by the size of spark gap  48 , a spark arcs across gap  48 , and the majority of current runs through prong(s)  46  and to ground through the conductive connection between body portion  44  and shoulder  24 . A small amount of current may pass into connector  10 , but due to the differences in resistive properties between surge protection element  42  and electrical component  28 , only a non-harmful amount of current will pass into connector  10 . Accordingly, surge protection element  42  protects electrical components  28  from high voltage surges of electricity by providing an alternate path for the current that goes around the components and to ground through body  14 .  
         [0033]    Referring to FIG. 3A, an alternate embodiment of surge protection element  42 ′ is illustrated. Surge protection element  42 ′ includes a ring-like body  44 ′, such as a washer, with at least one prong  46 ′ integrally formed on and extending radially outward from a head  36 ′ of pin  34 ′. Prongs  46 ′ are defined by star shaped protrusions extending radially outwardly from head  36 ′. Again, surge protection element  42 ′ would work if it included only a single, or any other number of protrusions  46 ′.  
         [0034]    Referring to FIG. 3C, surge protection element  42 ′ is optionally composed of only head  36 ′ having at least one prong  46 ′ extending radially outward therefrom, provided the length of each prong  46 ′ is sufficient to leave an appropriate spark gap between their ends and the internal surfaces of a threaded portion  22 ′ of connector body  14 .  
         [0035]    Referring to FIG. 3B, a surge protection element  42 ″ includes a ring-like body  44 ″ such as a washer, with at least one prong  46 ″ integrally formed on and extending radially outward from a head  36 ″ of a pin  34 ″. Prongs  46 ″ are defined by annularly extending, sinusoidal curved shaped protrusions extending radially outward from head  36 ″. Again, surge protection element  42 ″ would work if it included only a single, or any other number of protrusions  46 ″.  
         [0036]    Referring to FIG. 3D, surge protection element  42 ″ is optionally composed of only pin  34 ″ having at least one prong  46 ″ extending radially outward therefrom, provided the length of each prong  46 ″ is sufficient to leave an appropriate spark gap between its end and the internal surfaces of threaded portion  22 ″ of connector body  14 .  
         [0037]    Referring to FIGS.  4 - 5 , another embodiment of the invention is shown. A coaxial cable connector  10  includes a connector body  14  with an end cap  40  at its second end. An O-ring  41  adjacent a threaded portion  22  seals connector  10  when connector  10  is screwed into a female connection. An electrical component  28  is shown here consisting of a capacitor  30  and a resistor  32  which are housed within cavity  20  inside connector body  14 . Capacitor  30  is connected to a lead  38  which in turn is connected, preferably by solder, to connector body  14 . Resistor  32  fits inside and is connected to a cover  31  which in turn connects with conductive pin  12 . A printed circuit board  50  is held in place within connector body  14  by an insulator  52 , which is preferably of plastic. PCB  50  is preferably of standard PCB fiberglass material. A head  36 ′ is preferably integral with conductive pin  12 .  
         [0038]    The resistor-capacitor network of electrical component  28  which is preferably used in the UMTR of connector  10  consists of a 75 Ohm, ¼ watt, carbon film, non-inductive resistor coupled in series to a 20,000 pF ceramic disc capacitor. The manner in which this series coupling is accomplished allows the network to be packaged very small. The manufacturing steps are as follows: (1) A single-lead bare resistor is placed inside a counterbore in an aluminum block. A bare resistor is one without epoxy coating. The resistor lead protrudes through a hole in the bottom of the counter bore. (2) A small amount of solder paste is applied to the leadless end of the resistor which is pointing upward. (3) A single-lead bare capacitor is placed in a larger counterbore which is coaxial with the resistor counterbore, with the lead facing up. The leadless end of the capacitor contacts the end of the resistor with the solder paste. (4) An aluminum plate with a through hole is placed over the capacitor lead and secured to the first aluminum block to keep the assembly secure and prevent any movement of the electronic components. (5) The entire assembly including the aluminum blocks is placed into an oven to cure the solder paste which physically and electrically bonds the capacitor to the resistor. (6) The entire assembly is removed from the oven and allowed to cool. (7) The RC network is removed from the aluminum blocks. (8) The RC network is coated with epoxy and allowed to cure. The epoxy insulates the assembly and provides additional strength.  
         [0039]    Referring also to FIG. 6A, a front view of printed circuit board (PCB)  50  is shown. PCB  50  is wheel-shaped with an outer ring  54  and an inner ring  58  connected by two arms or spokes  56 ,  57 . Inner ring  58  defines a circular hole  60  which fits over and makes contact with a head  36 ′ of conductive pin  12 .  
         [0040]    Referring to FIG. 6B, a printed circuit trace  62  on PCB  50  extends around the surface of a portion of a surface  55  of outer ring  54  so as to make electrical contact with connector body  14  at shoulder  24  (FIG. 4), while a printed circuit trace  66  is on a surface of inner ring  58  so as to make electrical contact with head  36 ′. Insulator  52  (FIGS.  4 - 5 ) ensures good electrical contact of printed circuit trace  62  and printed circuit trace  66  against shoulder  24  and head  36 ′ respectively. An arm  64  of printed circuit trace  62  extends from outer ring  54  to near, but spaced apart from, printed circuit trace  66  on inner ring  58 . The space between an end  65  of arm  64  and printed circuit trace  66  forms a spark gap. Using a PCB with printed circuit traces permits much stricter tolerances in the spark gap than do the solid metal embodiments of FIGS.  1 - 3 , and thus increased reliability. Traces  62 ,  66  are preferably 2 oz copper. In circuit board manufacturing, the copper thickness is specified by a weight in ounces, which is the weight of copper present on a 12″× 12 ″ area of board. In the case of a 2 oz copper trace, the thickness of the trace is 0.0028″.  
         [0041]    [0041]FIG. 6C shows a perspective view of printed circuit traces  62  and  66  on outer ring  54  and inner ring  58 , respectively.  
         [0042]    [0042]FIG. 6D shows the spark gap explained with reference to FIG. 6B in greater detail. Printed circuit  66  preferably includes two triangular pointed members  68  which are joined at a sixty degree angle corresponding to a sixty degree angle of end  65  of arm  64 . The three points shared between the two sides of the spark gap ensure reliability when a spark is jumping the gap. It is well known that electrical charge prefers to build up at points rather than along flat areas. When three points are used, one of the points will always be the first point, i.e., the preferred point, jumped by the spark. Should the printed circuit at that point become pitted or vaporized, one of the remaining points theoretically becomes the preferred point. In practice, a layer of carbon from the sparking is deposited on the PCB between the metal traces. This carbon layer is conductive at the high voltage surge levels caused by lightning and becomes the preferred path for the electricity.  
         [0043]    Referring to FIG. 7, an embodiment of the present invention is shown in which a PCB  50 ′ has a hole  60  therein. A trace  66 ′ around hole  60  corresponds to inner ring  58  in the embodiment of FIGS.  6 A- 6 D in that trace  66 ′ makes electrical contact with head  36 ′ of conductive pin  12 . A trace  62 ′ at an opposite end of PCB  50 ′ from trace  66 ′ corresponds to outer ring  54  of the embodiment of FIGS.  6 A- 6 D in that trace  62 ′ makes electrical contact with shoulder  24  of connector body  14 . An arm  64 ′ of trace  62 ′ includes an end  65 ′ which forms a spark gap with pointed members  68 ′ of trace  66 ′. Because insulator  52  ensures good electrical contact between traces  62 ′,  66 ′ on PCB  50 ′ and shoulder  24  and head  36 ′, respectively, the shape of PCB  50 ′ can be varied as long as the proper electrical contacts are made.  
         [0044]    The relationship between the size of the spark gap and the voltage level which triggers a spark is well known in the art. For instance, a spark gap of 0.005″ air is typical. For CATV systems, the systems typically carry an operating voltage of 90 VAC at 60 Hz to power intermediate amplifiers and other conditioning equipment. This voltage is of course blocked before entering the internal cabling of a house or other end user. The spark gap is preferably set so that a trip voltage of 300 Volts or more is required to bridge the gap. The carbon layer described above lowers the trip voltage for subsequent surges, so after the first major surge, the trip voltage goes down from 300 Volts to around 200 Volts. The trip voltage has to be above the operating voltage of the cable system but below the voltage which would damage the electrical components in the device which are protected by the present invention.  
         [0045]    While the present invention has been described with reference to a particular preferred embodiment and the accompanying drawings, it will be understood by those skilled in the art that the invention is not limited to the preferred embodiment and that various modifications and the like could be made thereto without departing from the scope of the invention as defined in the following claims.