Abstract:
An over-voltage surge protection device includes a circuit board having a signal carrying conductive member with a plurality of nodes positioned therealong, and a conductive member running to ground positioned therealong. The nodes on the signal carrying member and the ground conductive member each extend along a common path with corresponding ones of the signal carrying nodes positioned in adjacent, but spaced relation to the ground member, wherein the conductive member running to ground is formed along the interior of the main body enclosing the circuit board and the signal carrying conductive member. The peripheral edges of the nodes accumulate and discharge transient high voltage surges. The nodes can be shaped in the form of triangles due to this particular geometry&#39;s favorable ability to accumulate and discharge voltage, but may also be formed in a variety of other geometries.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
   This patent application is a continuation in part application of U.S. Ser. No. 11/178,885, filed Jul. 11, 2005, now abandoned; which is a continuation in part application of Ser. No. 10/339,730, filed Jan. 9, 2003, now allowed (U.S. Pat. No. 6,930,872); which is a continuation-in-part of U.S. Ser. No. 09/858,739, filed May 16, 2001, now U.S. Pat. No. 6,510,034, issued Jan. 21, 2003, the entire contents of each being incorporated by reference in their entirety. 

   FIELD OF THE INVENTION  
   This invention relates to electrical surge protection devices, and more particularly to surge protection devices having spark gaps. 
   BACKGROUND OF THE INVENTION  
   Broadband coaxial cable communications networks, such as CATV networks, include various types of electronic equipment mounted to outdoor utility poles. This electronic equipment is subjected to all types of weather conditions including, for example, lightning storms. Due to the importance of these communications networks to society, it is important that they be able to withstand the harsh conditions under which they operate. 
   On occasion, a high voltage surge may be transmitted through the coaxial cable to which the electronic components are interconnected, for instance, due to a lightning strike. If this high voltage surge is permitted to be picked up by the input or output pins of the interconnect device and transmitted to the electrical devices housed therein, the device would become inoperable due to the electrical components essentially melting or otherwise deteriorating as a consequence of the surge. A new electronic device would then need to be installed at the site of the surge. 
   In order to improve the reliability of the electronic components in a communications network, the interconnect units are generally equipped with some type of over-voltage surge protection device. IEEE Standard C62.41-1991 sets forth a recommended practice on surge voltages in low voltage power circuits. The surge protectors incorporated into the interconnect units may include, for instance, a single, conductive element positioned in adjacent, but spaced relation to the incoming signal. In the event of a transient, high voltage surge, the element will accumulate and discharge the over-voltage surge to ground prior to it passing through the electrical components. Incorporation of such surge protectors, however, add significantly to the complexity in manufacturing, and hence, the cost of an interconnect unit. In addition, if a voltage surge above what the protector is designed to handle is experienced by the connector unit, it will need to be replaced in any event. 
   It is therefore a desired object and advantage of the present invention to provide an over-voltage surge protection device that is inexpensive to manufacture relative to the state of the art. 
   It is a further object and advantage of the present invention to provide over-voltage surge protection device that can withstand multiple surges, hence increasing the life of the coaxial cable interconnect device. 
   It is yet a further object and advantage of the present invention to provide surge protection, while at the same time not increasing the overall size or complexity of the cable interconnect device. 
   SUMMARY OF THE INVENTION  
   In accordance with the foregoing objects and advantages, and others, the present invention provides an over-voltage surge protection device comprising a printed circuit board having a signal carrying conductive member having a plurality of nodes positioned therealong, and a conductive member running to ground positioned therealong. The nodes on the signal carrying member and the ground member extend along a common path with corresponding ones of the signal carrying nodes positioned in adjacent, but spaced relation to the conductive area of the ground member. In one version, the nodes of the signal carrying member are shaped in the form of triangles due to this particular geometry&#39;s favorable ability to accumulate and discharge voltage. 
   The over-voltage surge protection device may be entirely fabricated according to one version directly into the board without mounting any additional structure thereto. A circuit board substrate that contains a layer of conductive material coated thereon may be fabricated by removing conductive material (e.g., by laser ablation, chemical or photolithographic etching, or other conventional fabrication process) in all areas on the board other than those assumed by the signal carrying members and the conductive member leading to ground, respectively. The area of non-conductive material, i.e., air, separating the signal carrying members from the ground member, become the spark gaps. 
   According to an alternative construction, the ground conducting member can be formed along the interior of the housing of the device, which can be similarly ablated or etched with a conductive material, such as brass, the ground conducting member being aligned with the nodes of the signal conducting member and separated by non-conductive material e.g., air, providing spark gaps. In this particular design, surge protection can be provided while optimizing space consumption of the circuit board. 
   The spacing between the nodes (and their shape) determine the voltage level at which a spark will generate and shunt the circuit. The number of nodes present in the device will determine the number of over-voltage surges the device will be able to withstand. 
   In operation, and as the relative voltage potential between the node of the signal carrying member and the conductive area of the ground conducting member approaches a predetermined value, a spark will generate across the gap separating the node and the ground member. This spark discharges the voltage from the signal carrying member to the grounded member, thereby shunting the circuit. Any particular spark may cause a deterioration of the particular node, which discharges the surge. However, due to the device having a plurality of corresponding sets of nodes, the device, including the circuit board, will be able to withstand at least an equal number of over-voltage surges. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
     For a further understanding of these and objects of the invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawing, where: 
       FIG. 1  is a plan view of a preferred embodiment of the present invention; 
       FIG. 2  is a plan view of the present invention after it has been exposed to over-voltage surge; 
       FIG. 3  is an exploded perspective of an interconnect device in which the present invention is used; 
       FIG. 4  is a longitudinal cross-sectional view of the interconnect device illustrated in  FIG. 3 ; 
       FIG. 5  is a plan view of a second alternate embodiment of the present invention; 
       FIG. 6  is a plan view of a third alternate embodiment of the present invention; 
       FIG. 7  is a plan view of a fourth alternate embodiment of the present invention; 
       FIG. 8  is a plan view of a fifth alternate embodiment of the present invention; 
       FIG. 9  is a plan view of a sixth alternate embodiment of the present invention; 
       FIG. 10  is a plan view of a seventh alternate embodiment of the present invention; 
       FIG. 11  is a plan view of an eighth alternate embodiment of the present invention; and 
       FIG. 12  is a partial perspective view of the device according to the eighth alternate embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION  
   Referring now to the drawings, wherein like reference numerals refer to like parts throughout, there is seen in  FIG. 1  a printed circuit board, designated generally by reference numeral  10 , for use in a coaxial cable interconnect device, shown generally by reference numeral  12 . Circuit board  10  is composed of a non-conductive substrate (e.g., a ceramic substrate of fiberglass) having a pair of parallel planar surfaces wherein a layer of conductive material, such as copper, that is coated on at least one planar surface  14  thereof. A series of electrical components, shown generally be reference numeral  16 , are mounted in a conventional manner to either planar surface of board  10 . 
   Interconnect device  12  serves, for instance, as a trap with electrical components  16  comprising a filter having a narrow pass band response within a predetermined frequency range (e.g., 5-40 MHz) with a fixed level of attenuation across the return path frequency spectrum. Such devices are commonly used in CATV networks. 
   Referring specifically to  FIGS. 3 and 4 , interconnect device  12  includes an elongated main body  18 ; a rear insulator  20  mounted concentrically within body  18  and positioned adjacent the terminal end thereof; a non-conductive (e.g., rubber) seal  22  positioned adjacent insulator  20 ; a conductive female pin assembly  24  (which receives a conductive output pin  26  therein) concentrically extending though insulator  20  and seal  22 ; the circuit board  10  being electrically connected a one edge to the female pin assembly  24 ; a conductive input pin  28  electrically connected to and extending outwardly from the opposing edge of circuit board  10 ; a front insulator  30  positioned concentrically around the input pin  28 ; and a nut  32  threadingly engaging the main body  18  and housing the front insulator  30 . In operation, conductive input pin  28  receives a signal being transmitted through a coaxial cable (as part of a communications network), and the conductive output pin  26  sends the signal towards its destination after having been conditioned by electrical components  16  mounted on either planar surface of the circuit board  10 . 
   Referring specifically to  FIGS. 1 ,  2  and  5 , the printed circuit board  10  includes the afore mentioned electrical components  16  mounted on at least one planar surface  14 , a signal carrying, input member  34  electrically connected to the input pin  28 , and a signal carrying, output member  36  electrically connected to female pin assembly  24 . Signal carrying members  34  and  36  are preferably mounted on the other side thereof (although these elements could be mounted on the same side as electrical components  16 , it is more space efficient to mount them on opposing sides and electrically interconnect there with vias). Signal carrying input member  34  comprises electrically conductive material extending from the input pin  28  to a terminal node  38 , and includes a plurality of nodes  40  positioned between the input pin  28  and terminal node  38 . Output member  36  comprises an electrically conductive material extending from a terminal node  42  to the female pin assembly  24 , and a plurality of nodes  44  positioned between node  42  and pin assembly  24 . Nodes  40  and  44  are preferably triangular in shape ( FIGS. 1 and 2 ), but may be shaped in other geometries, as well, as noted herein. 
   Terminal node  38  is electrically connected to electrical components  16  which are, in turn, electrically connected to the output terminal node  42 . Thus, when the low voltage signal (e.g., device  12  generally operates on a circuit that passes 100 volts AC, with an RF level typically between +10 and −10 dBm) is received through the input pin  28 , the signal is transmitted through the signal carrying input member  34  to the electrical components  16  on the circuit board  10 . Electrical components  16  then appropriately condition (e.g., filter) the signal and sent it through the signal carrying output member  36 . The signal is then sent towards its final destination via the output pin  26 . 
   According to this embodiment, an electrically conductive ground member  46  is also mounted on the printed circuit board  10 . The conductive ground member  46  includes a first plurality of nodes  48  which correspond in shape and number to the nodes  40 , and a second plurality of nodes  50  which correspond in shape and number to nodes  44 . Nodes  48  are positioned in adjacent, but spaced relation to corresponding ones of nodes  40 , thereby forming a first plurality of arc or spark gaps  52  (each arc or spark gap  52  being defined by corresponding ones of nodes  40  and  48 ). Nodes  50  are positioned in adjacent, but spaced relation to corresponding ones of nodes  44 , thereby forming a second plurality of arc or spark gaps  54  (each arc gap  54  defined by corresponding ones of nodes  44  and  50 ). Nodes  48 ,  40 ,  50 , and  44  are defined by (and the sparks accumulate at and are discharged from) the peripheral edges of the respective conductive members of they form a part. 
   The arc gaps  52  and  54  separating nodes  48  from nodes  40 , and nodes  50  from nodes  44 , respectively, are composed of non-conductive material (such as a gap of air) and are of generally uniform thickness. If a transient surge of high voltage (e.g., as a consequence of a lightning strike) is received by either the input pin  28  or the output pin  26 , the voltage will travel to nodes  40  and  44 , respectively, at which point a spark will generate and arc across arc gaps  52  and  54 , respectively. The high voltage surge will then be grounded by the conductive ground member  46 , thereby shunting the circuit and protecting the mounted electrical components  16  therefrom. If the high voltage surge is not shunted, electrical components  16  would be destroyed through the heat generated by the surge. Consequently, it is essential to the long-term reliability of the interconnect device  12  that the device contain the over-voltage surge protection capabilities embodied by spark gaps  52  and  54 . 
   Spark gaps  52  and  54  according to this embodiment are preferably between 1 and 10 mils in thickness. Obviously, the smaller the spark gap distance, the lower the voltage level that will generate a spark. 
   If a transient high voltage surge does come through pins  28  or  26  and a spark does generate across nodes  40  to  48  or  44  to  50 , it is possible that a portion of the nodes  48 ,  50  will deteriorate and vaporize, as illustrated in  FIG. 2  by reference letters V. However, even if portions of nodes  48 ,  50  do deteriorate, the remainder of the plurality of nodes  48 ,  50  remain intact. Accordingly, spark gaps  52  and  54  provide an over-voltage surge protection device that can withstand numerous over-voltage surges. 
   Nodes  40 ,  48 ,  44  and  50  are preferably triangular in shape (as illustrated in  FIGS. 1 and 2 ), thereby forming a zigzag arc gap pattern, as this geometry appears to most effectively accumulate and discharge voltages. It should be clear that “nodes” is referring to the peripheral edge geometry of the conductive regions, as it is defined in the drawings and this accompanying specification. It should also be noted that these nodes could be shaped in other patterns so long as the spacing between corresponding nodes is small enough to maintain the efficiency of spark gaps  52 ,  54  (e.g., the spacing can be variable, but preferably within the range of 1 to 10 mils.). For instance, corresponding nodes could be shaped sinusoidally (see  FIG. 5 ), rectangularly shaped (see  FIG. 6 ), arbitrarily shaped (see  FIG. 7 ), rectangularly shaped with triangularly shaped corresponding nodes (see  FIG. 8 ), linear and substantially uniformly spaced apart (see  FIG. 9 ), or linear with the spacing being varied along their lengths (see  FIG. 10 ). 
   In forming spark gaps  52 ,  54 , the printed circuit board  10  is provided with a coating of conductive material on one of its planar surfaces as previously noted. Conductive material is then removed through any conventional process (e.g., laser ablation, photolithographic or chemical etching, or the like) from the areas of the circuit board  10  that are to be non-conductive, i.e., all areas other than input member  34 , output member  36 , and ground member  46 . Forming spark gaps  52 ,  54  in this manner causes the gaps to be co-planar with the printed circuit board  10 , thereby using minimal space and not requiring the mounting of any additional structure to board  10 . 
   It should be readily apparent that the spark gaps that have been described herein need not be directly etched solely onto the printed circuit board  10 . Referring to  FIGS. 11 and 12 , an alternative embodiment is herein described in which the ground conducting member is formed in the main body  18  of the interconnect member  12  wherein a defined gap (e.g., an air spacing) is defined between a first conductive area  60 , etched in the same manner as described above in a planar surface of the printed circuit board  10  wherein a plurality of nodes  62  are formed, and a second conductive area  66 , that is formed (e.g., etched, ablated, etc) in like manner on the interior of the main body  18 , the main body already being made from a conducting material, such as brass, such that the formation of nodes are not necessary. Advantageously, the preceding embodiment permits the same cost-savings in terms of surge protection for the interconnect device while at the same time permitting the printed circuit board  10  to have adequate space for electrical componentry. As in the preceding, the spark gaps  64  formed between the first and second conductive area  60 ,  66  should be spaced between about 1 mil and 10 mils and as in the preceding the nodes though shown herein according to this embodiment with triangular shape, can assume other suitable geometries with varied or constant spacing between the nodes  62 , as needed or selected. 
   While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawings, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the following claims.