Geometrical and symmetrical gas tube lightning protectors
United States Patent [191 [111 3,875,467 Riedel 1 Apr. 1, 1975 GEOMETRICAL AND SYMMETRICAL GAS Primary Examiner-J. D. Miller TUBE LIGHTNING PROTECTORS Inventor:  
 Filed:  
 Appl.  
 Laboratories Incorporated, Northlake. 111.  
 Oct. 23, 1973 Charles E. Riedel, Villa Park. 111.  
 Assignee: GTE Automatic Electric References Cited UNITED STATES PATENTS Bigwood Rich I:  
 Assistant E.\&#34;aminerPatrick R. Salce Arrornev, Agent. or F irm-Robert .1. Black [57] ABSTRACT A gas tube lightning protector includes a glass rod about which are disposed a pair of elongated, substantially semi-annular, failsafe electrodes which are also disposed so as to face each other and thereby define therebetween four arcing surfaces comprising two areing slots or areas. The protector further includes a pair of caps disposed upon the ends of the electrodes and the glass rod, and the entire assembly is encased within a glass sleeve which is sealed to the outer peripheral surfaces of the end caps so as to retain a pressurized inert atmosphere therewithin. Lost gas indicating means in the form of a dessicant electrolyte may also be associated with the electrodes for automatically indicating the leakage or loss of the pressurized gaseous atmosphere.  
 8 Claims, 4 Drawing Figures GEOMETRICAL AND SYMMETRICAL GAS TUBE LIGHTNING PROTECTORS BACKGROUND OF THE INVENTION 1. Field of the Invention:  
  The present invention relates generally to gas tube lightning protectors and more particularly to a gas tube lightning protector which, through means of its improved geometrical and symmetrical configuration, is simple and economical to manufacture and yet within which it is possible to incorporate various structural features which improve the protector performance, safety, and reliability.  
 2. Description of the Prior Art;  
  While several different types of lightning protectors, such as for example, the carbon-block type and air-gap type, have been utilized in the past as means of protecting subscriber and office equipment from electrical surges, modern telephonic systems are employing gas tube lightning protectors with ever increasing frequency, the primary reasons being the increased service life, that is, the number of repeated surges of average magnitude which a device can withstand without failure.  
  However, balanced against such increased service life, in addition to reduced maintenance, gas tube protectors are characterized by higher initial manufactur ing costs as compared to conventional protectors. In addition, there is a substantial need for gas tube protectors within which various structural features may be incorporated so as to improve existing protector performance. safety, and reliability.  
 SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved gas tube lightning protector.  
  Another object of the present invention is to provide an improved gas tube lightning protector which is simple and economical to manufacture.  
  Still another object ofthe present invention is to provide an improved gas tube lightning protector which has an increased arc electrode area whereby protector performance is enhanced.  
  Yet another object of the present invention is to provide an improved gas tube lightning protector within which solder failsafe structure may be incorporated so as to improve operational safety and protection of the equipment which is desired to be protected.  
  A further object of the present invention is to provide an improved gas tube lightning protector within which lost gas indicator structure may likewise be incorporated so as to further improve the operational safety and protection of the particular equipment, as well as insure the reliability of the protective system and apparatus.  
  The foregoing objectives are achieved according to the present invention through the provision of a gas tube lightning protector which includes a glass rod about which are disposed a pair of elongated, substantially semi-annular. failsafe electrodes which are also disposed so as to face each other and thereby define therebetween four arcing surfaces comprising two arcing slots or areas. The protector further includes a pair of caps disposed upon the ends of the electrodes and the glass rod, and the entire assembly is encased within a glass sleeve which is sealed to the outer peripheral surfaces of the end caps so as to retain a pressurized inert atmosphere therewithin. Lost gas indicating means in the form of a dessicant electrolyte may also be associated with the electrodes for automatically indicating the leakage or loss of the pressurized gaseous atmosphere.  
 BRIEF DESCRIPTION OF THE DRAWING Various other objects, features, and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the several views, and wherein:  
  FIG. 1 is a longitudinal view partly in section, of a gas tube lightning protector constructed according to the present invention and showing its cooperative parts;  
  FIG. 2 is a cross-sectional view of the gas tube lightning protector as illustrated in FIG. 1, taken along line 2-2 of FIG. 1, some component parts having been removed;  
 FIG. 3 is a view similar to that of FIG. 1, showing however another embodiment of a gas tube lightning protector constructed according to the present invention; and  
  FIG. 4 is a view similar to that of FIG. 1, showing however still another embodiment of a gas tube lightning protector constructed according to the present invention.  
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and more particularly to FIGS. 1 and 2 thereof, there is shown a gas tube lightning protector generally indicated by the reference character 10 which comprises a centrally located glass supporting rod 12 about which are disposed a pair of identical, elongated, substantially semi-annular, failsafe electrodes 14 and 16, the electrodes facing each other so as to define arcing areas therebetween. In manufacturing the gas tube lightning protector of the present invention, a glass rod of approximately 0.125 inches in diameter is initially dipped into a platinum solution and subsequently wiped between two diametrically disposed cards so as to remove the coated platinum from two diametrically disposed areas 17 of the rod. As a result, platinized circuits 18 of approximately /2 mil., corresponding respectively in circumferential extent to that of electrods l4 and 16 are formed upon the glass rod, the circumferential extent of the gapped areas 17 being approximately 0.050 inches which is normal for gas tube protectors.  
  The glass is fired as in mirror manufacture, and subsequent to the platinizing process, is burnished and tin plated so as to present a surface upon which the failsafe solder comprising electrodes 14 and 16 may adhere and be supported. The glass rod is then severed into sections approximately one foot in length, such sections in turn being inserted within a mold wherein the failsafe solder is introduced so as to be deposited upon the platinized circuits 18, the solder coating layer comprising the electrode having a thickness of approximately 0. lOO inches. Upon completion of such solder electrode molding process, the rod sections are removed from the mold and once again severed into sections having a length of approximately 34 inches, such sections comprising the electrode assemblies.  
  Still referring to FIGS. 1 and 2, it will be seen that the electrodes include arcing surfaces 19, the arcuate extent of each of the electrodes 14 and 16 being slightly less than 180 so as to define therebetween longitudinal arcing areas or slots 20 which correspond to the gapped areas 17. Cup-shaped end caps 22 and 24, which may be tinned Kovar, are sweated onto the end portions of rod 12 and electrodes 14 and 16 with the aid of a solder which is tinned upon the inside of the caps and which fuses at a slightly lower temperature that that of the failsafe solder comprising the electrodes, the use of such cap solder preventing any detrimental effect upon the failsafe solder. A glass sleeve 26 is disposed around the entire electrode assembly.  
  The entire assembly may then be placed within a vacuum chamber and upon attaining vacuum conditions, a desired inert, noble gas, such as for example, argon, may be introduced therewithin to a pressure of approximately one-fourth atmosphere. A suitable sealing compound, 28, such as for example, boron nitride,  
 is then applied to the area interposed between the outer periphery of end caps 22 and 24 and the lip portions 30 of sleeve 26 so as to seal such members together and retain the assembly 10 under pressurized conditions, the pressure within the vacuum chamber then being increased so as to force the sealant 28 somewhat interi orly within the annular spaces 32 respectively defined between the end caps 22 and 24 and the end portions of sleeve 26. Subsequently, the assembly 10 is cured at a temperature of, for example, 300C in the instance that boron nitride is utilized as the sealing means, such process of course imparting structural integrity to the sealing means and the entire assembly.  
  In order to insure the fact that the circuits respectively associated with the electrodes 14 and 16 are respectively associated with the end caps 22 and 24, the lower portion 34 of electrode 14 and the upper portion 36 of electrode 16, the depth of such portions corresponding to the depth of the end caps 22 and 24, are respectively insulated from the end caps 22 and 24, whereby the effective portions of the electrodes are symmetrically disposed upon opposite sides of a radi ally disposed median plane 37. Such a result is accomplished during the failsafe solder molding process wherein due to broaching, particularly located voids are developed whereupon the failsafe solder is permitted to flow out of the mold whereby solder is not retained upon those areas of the platinized rods corresponding to the electrode portions 34 and 36.  
  Subsequently, a refractory type, electrically insulative material, such as for example, Sauerizen cement, or alternatively, an insulative, lost gas indicating mate rial, is applied to the voided areas of platinized rod 12, and consequently the resulting electrical circuit encompasses end cap 22, electrode 14, the arc area or gap 20, electrode 16, and end cap 24. When in lieu of the Sauerizen cement, a lost gas indicating material, such as for example, a dessicant electrolyte, is em ployed, in addition to attaining the insulating characteristics, such as a composition supplies an automatic indication of any leakage or loss of the noble gas from the assembly 10. In operation, under normal, nonleakage gaseous conditions, the electrolyte remains inert. however, upon the occurrence of leakage and loss of the inert gas from the assembly 10, atmospheric moisture is able to enter the assembly and react with the dessicant electrolyte rendering the same electrically conductive, such being of course detectable by conventional means as talking noise or excessive loop conductance.  
  It may thus be appreciated that due to the efficient utilization of available geometry, the arcing area of the present protector is twice the slot length and in fact the total arcing area is proposed to be 0.300 square inches which compares favorably with 0.098 0.125 square inches which is attained with conventional one-quarter inch diameter gas tube protectors. Transient surges will apparently strike at random within either of the two electrode slots 20 and the large electrode area should provide longer service life and increased thermal inertia since the locus of the surge strikes are likely to be farther apart than with conventional protectors. In addition, as the electrodes are not in contact with the surrounding sleeve, there being inert gas present therebetween, the entire tube can ionize during a power cross.  
  Still further, under severe heating, the failsafe electrodes will melt and cause a direct short. Such is seen to be the case for occurrence of extreme surges cause melting of the failsafe solder, which due to the elevated temperatures and gas pressure, tends to assume a configuration which will lower the gas pressure. As a result of such aforenoted factors, in addition to the surface tension present, the failsafe solder is wrapped about the&#39; glass rod so as to eventually produce a low resistance path between the electrodes. It should be noted further that while the failsafe solder per se is quite effective as an electrode, the same may be electroplated with other metals whereupon the electrodes are able to withstand a substantial number of additional lightning surges, the service life of the protector being substantially in creased still further.  
  Turning now to FIG. 3, another embodiment of the present invention is disclosed wherein electrodes 14&#39; and 16 are somewhat smaller than electrodes 14 and 16 and are longitudinally offset relative to one another so as to be symmetrically disposed upon opposite sides of the radially disposed median plane 37. The glass rod 12 has been severed so as to have a particular configuration corresponding to the overall array of the electrodes and in this manner, the appropriate circuitry through the end caps and electrodes is established without the requirement of particular molding apparatus and use of the refractory, electrically insulative material being disposed upon rod 12.  
  Reference now being made to FIG. 4, still another embodiment of the present invention is disclosed wherein in lieu of the glass sleeve 26, a split sleeve has been utilized and the same includes upper sleeve portion 38 and lower sleeve portion 40, such sleeves being interconnected by means of a metal grounding sleeve 42 which includes a plurality of receptacles 44 within which the upper lip portions 46 and the lower lip portions 48, of sleeves 40 and 38 respectively, are seated, suitable glass-to-metal sealing means being interposed therebetween. During transient surges, it will of course be apparent that arcing will occur between the electrodes and the grounding sleeve 42 as well as between the electrodes themselves.  
  Thus, it may be seen that the lightning protector of the present invention has important advantages over the known prior art structures in that the subject protector includes a symmetrical and geometrical arrangement of the failsafe electrodes whereby the total arcing area is substantially greater than that of conventional present invention are possible in light of the above teachings. It is to be understood therefore, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.  
 protectors, and in addition, the large electrode area plays an important factor in increased thermal inertia and service life. The electrodes are also appropriately insulated from the circuit end caps, and the assembly is also able to include automatic lost gas indicating 5 means. Still further, the electrodes are particularly adapted to failsafe under severe conditions whereby further protection of the equipment is insured.  
 Obviously, many changes and modifications of the What is claimed as new and desired to be claimed by Letters Patent in the United States is:  
 l. A geometrical and symmetrical gas tube lightning protector comprising:  
 a supporting member;  
 a pair of electrodes, each of which in turn includes a pair of arcing surfaces, supported upon said supporting member in such a manner whereby said electrodes and said arcing surfaces face each other so as to define a pair of arcing areas therebetween;  
 a pair of end caps secured to the end portions of said supporting member and said electrodes;  
 insulation means associated with said electrodes for respectively insulating selected portions of each of said electrodes from one of said end caps;  
 an inert, pressurized gas disposed within said protector; and  
 sleeve means disposed about said electrodes and sealed to said ends for retaining said pressurized gaseous atmosphere within said protector.  
  2. A lightning protector as set forth in claim 1 wherein said supporting member is a glass rod and said electrodes are substantially semi-annular.  
  3. A lightning protector as set forth in claim 2, wherein the non-insulated portions of said electrodes are symmetrically disposed upon opposite sides of a radially disposed median plane of said protector.  
  4. A lightning protector as set forth in claim 2, wherein said insulation means further includes means for indicating the leakage and loss of said pressurized gaseous atmosphere from said protector.  
  5. A lightning protector as set forth in claim 4, wherein said indicating means comprises a dissicant electrolyte which remains inert under normal, nonleakage conditions and which upon the occurrence of leakage conditions, may react with atmospheric moisture so as to become electrically conductive.  
  6. A lightning protector as set forth in claim 1 wherein said electrodes are longitudinally offset relative to one another so as to be symmetrically disposed upon opposite sides of a radially disposed median plane of said protector and be respectively insulated from one of said end caps.  
  7. A lightning protector as set forth in claim 1 wherein said electrodes are formed of a solder which, under severe heating, may melt whereby said electrodes will be joined together so as to produce a failsafe short therebetween.  
  8. A lightning protector as set forth in claim 1, wherein:  
 said sleeve means comprises upper and lower sleeve portions; and a grounding sleeve is interposed between said upper and lower sleeve portions.