Abstract:
A spark electrode assembly has an elongate electrode with an inner insulator arranged for operable attachment to a support structure. The inner insulator surrounds the electrode with one end of the electrode positioned adjacent a ground element across a spark gap and another end of the electrode extending relative to the support structure for attachment to a source of electrical power. An outer insulator is spaced radially outwardly from the inner insulator and surrounds the inner insulator generally adjacent the end of the electrode adjacent the ground element. The inner and outer insulators cooperate to inhibit the formation of a continuous lubrication layer thereon, thereby establishing an area generally free from the lubrication layer between the end of the electrode adjacent the ground element and the support structure.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to forming glassware, and more particularly to lubricating glass forming molds. 
   BACKGROUND OF THE INVENTION 
   It is known to lubricate a glassware forming mold by igniting a carbonaceous gas with a spark electrode to deposit a thin layer of carbon soot in the mold. To ignite the gas, the spark electrode creates a spark across a gap between an electrode and a ground element. In use, the carbon soot builds up along the electrode, and particularly on an insulative coating around the electrode. Over time, an electrical path created by the carbon build up along the insulative coating establishes a path of least resistance through which electrical energy passes preventing the generation of a spark at the spark gap. Ultimately, this results in a failure to ignite the combustible gas and hence, failure to lubricate the glass contacting surface of the glass mold with the carbon soot. 
   SUMMARY OF THE INVENTION 
   A spark electrode assembly is provided for igniting a combustible gas to lubricate a glassware mold surface. The spark electrode assembly has an electrode with an inner insulator surrounding the electrode at least in part to facilitate mounting the electrode to a support structure. One end of the electrode is disposed on one side of the support structure for connection to a source of electrical power, and another end of the electrode is positioned adjacent a ground element across a spark gap. An outer insulator is spaced at least in part from the inner insulator and surrounds the inner insulator generally adjacent the end of the electrode adjacent the ground element. 
   In use, the spark electrode assembly generates a spark across the gap defined between the electrode and the ground element to ignite a combustible gas within a glassware mold. The ignited combustible gas deposits a lubrication layer on the glassware mold surface. The inner and outer insulators cooperate to inhibit the lubrication layer from forming completely and over a continuous path thereon, thereby maintaining an area generally free from the lubrication layer between the end of the electrode adjacent the ground element and the support structure. As a result, electrical leakage from the electrode to the support element is inhibited by causing an interruption in any potential electrical path between the electrode and the support structure. Accordingly, the integrity of the spark between the electrode and the ground element is maintained to increase the useful life of the spark electrode assembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, features, advantages and aspects of the present invention will be apparent from the following detailed description of the preferred embodiments and best mode, appended claims and accompanying drawings in which: 
       FIG. 1  is a partial cross-sectional view of a glass molding assembly showing a spark electrode assembly constructed according to one embodiment of the invention for igniting a combustible gas within the glass molding assembly; 
       FIG. 2  is a similar view as  FIG. 1  showing a layer of deposited material from the combustible gas coating a portion of the spark electrode assembly with an air stream inhibiting the build-up of the layer, and 
       FIG. 3  is a sectional view taken generally along line  3 — 3  of  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring in more detail to the drawings,  FIG. 1  illustrates a spark electrode assembly  10  constructed according to one aspect of the invention received in an opening  12  of a support structure or housing  14  of a glass mold (not shown in detail). To facilitate an airtight seal between the spark electrode assembly  10  and the housing  14 , desirably the housing  14  has an annular recess  16  sized for receipt of a seal  18 , such as an O-ring. The spark electrode assembly  10  produces a spark upon receiving an electrical impulse from an electrical power source (not shown) to ignite a combustible gas within a cavity  20  of the glass mold, preferably a carbon-containing gas such as acetylene, that is preferably delivered via a nozzle  22 . The nozzle  22  is arranged to deliver an oxidant, such as pure oxygen, in addition to the combustible gas, wherein the mixture of the oxidant and the gas provides for the desired amount of carbon deposit on a glassware mold surface within the glass mold. In addition to the glassware mold surface at least a portion of the spark electrode assembly  10  is generally contacted by or covered by a thin layer of carbon deposit or residue  23  ( FIG. 2 ). The spark electrode assembly  10  resists the formation or buildup of a continuous layer of the carbon residue thereon, thereby resisting electrical leakage and the formation of a short circuit between the spark electrode apparatus  10  and the housing  14 . As such, the spark electrode assembly  10  operates over extended periods of time without requiring maintenance, such as cleaning or replacement, operates at an optimal efficiency, and inhibits or prevents misfires. 
   As shown in  FIGS. 1 and 2 , the spark electrode assembly  10  has an inner insulator  24  with opposed ends  26 ,  28  and an inner passage  30  extending between the ends  26 ,  28 . The inner insulator  24  has a generally cylindrical outer surface  32  with an enlarged mid-section  34  extending radially outwardly from the outer surface  32 . The mid-section  34  has an annular groove  36  extending radially inwardly therein defining a pair of axially spaced upper and lower portions  38 ,  40  having outer surfaces  42 ,  44 , respectively, preferably sized for receipt within the opening  12  of the housing  14 . Desirably, to facilitate locating the inner insulator  24  within the opening  12  of the housing  14 , a flange  50  extends radially outwardly from the lower portion  40  to define a shoulder  52  for engagement with the housing  14 . The inner insulator  24  has an air passage  46  communicating with a source of pressurized air (not shown). The air passage  46  is formed in part by the annular groove  36  and by a plurality of ports  48  extending axially through the lower portion  40  of the mid-section  34 , with the ports  48  preferably being spaced circumferentially and equidistant from one another. 
   The spark electrode assembly  10  has an outer insulator  54  generally surrounding the inner insulator  24 . The outer insulator  54  has a generally cylindrical wall  56  with an outer surface  58  extending generally between opposed ends  60 ,  62  and an inner surface  64  spaced radially outwardly at least in part from the outer surface  32  of the inner insulator  24 , wherein the inner surface  64  extends generally from the end  62  axially toward the other end  60  to a radially inwardly extending shoulder  66 . Desirably, the outer insulator  54  has a-flange  68  extending radially outwardly adjacent or at the end  60  for mating engagement with the flange  50  of the inner insulator  24 . Desirably, the flanges  50 ,  68  establish a uniform cylindrical outer surface  70  when engaged with one another for receipt of a generally annular retainer  72  that captures the flanges  50 ,  68  and secures the outer insulator  54  to the inner insulator  24 . By way of examples without limitations, the retainer  72  may be threaded to the outer surface  70  of the shoulders  50 ,  68 , or the retainer  72  may be attached to or carried by the housing  14 . 
   The outer insulator  54  has a plurality of air passages  74  preferably corresponding in number and arrangement to the ports  48  in the inner insulator  24 . As such, when the outer insulator  54  is attached to the inner insulator  24 , the ports  48  and the air passages  74  are in at least partial axial alignment with one another to establish an air flow path there between. The air passages  74  in the outer insulator  54  communicate with a space or gap  76  defined between the inner surface  64  of the outer insulator  54  and the outer surface  32  of the inner insulator  24 . 
   An electrode  78  is sized for receipt in the inner passage  30  of the inner insulator  24  and desirably extends beyond the ends  26 ,  28  of the inner insulator  24  to a pair of opposite ends  80 ,  82 . Desirably, the end  80  is sized for receipt of an electrode terminal  84 , wherein for example, the terminal  84  may be crimped on the end  80  to facilitate attachment of an electrical cable or wire (not shown) to the spark electrode assembly  10 . The end  82  is preferably sized for receipt of an electrode cap  86 , wherein for example, the electrode cap  86  may be crimped on the end  82  to facilitate attachment of an electrode extension  88 . The electrode extension  88  extends generally perpendicularly from the electrode  78  to a generally free end  90 . The free end  90  is spaced a predetermined distance from a free end  92  of a ground element  94  to define a gap  96  therebetween. 
   The ground element  94  has another end  98  preferably attached to an air purge nozzle  100 . The air purge nozzle  100  has an end  102  operably attached to a source of pressurized air (not shown), and may be the same source of pressurized air directing air flow through the air passage  46  in the inner insulator  24  and the air passages  74  in the outer insulator  54 . The air purge nozzle  100  has an air passage  104  extending axially therethrough and terminating adjacent an end  106  of the air purge nozzle  100 . Desirably, the air purge nozzle  100  has a plurality of ports  108  oriented to direct air flow outwardly from the air passage  104  and toward the electrode extension  88  and the ground element  94 . Further, the air purge nozzle  100  preferably has at least one additional port  110  oriented to direct air flow generally upwardly toward the nozzle  22 . Accordingly, pressurized air is directed through the ports  108 ,  110  to facilitate removal of any deposits, such as carbon buildup, that may otherwise accumulate on the nozzle  22 , the electrode extension  88  and the ground element  94 . The removal of the carbon buildup helps to ensure that an adequately sized spark arcs across the gap  96 , as desired. 
   To further ensure that the spark electrode assembly  10  does not misfire, the outer insulator  54  and the inner insulator  24  cooperate to resist carbon build-up between the electrode extension  88  and the housing  14 . By resisting such carbon build-up, an electrical short circuit is inhibited from forming, thereby promoting the flow of electricity from the electrode extension  88  to the ground element  94  across the gap  96 . As shown in  FIG. 2 , the path created between the electrode extension  88  and the housing  14  is generally a serpentine path extending along the outer surface  32  of the inner insulator  24  and along the inner and outer surfaces  64 ,  58  of the outer insulator  54 , with a portion of the path extending across the ports  74  in the lower shoulder  66 . As such, the ability of the carbon to form a continuous path between the electrode extension  88  and the housing  14  is hampered. To further inhibit formation of a deposited carbon layer, pressurized air is emitted outwardly from the ports  74  to facilitate cleansing away any carbon residue from between the inner surface  64  of the outer insulator  54  and the outer surface  32  of the inner insulator  24 . 
   In use an electric current is provided to the spark electrode assembly.  10  and through the electrode  78 . The current seeks ground through the path of least resistance, and thus, arcs across the gap  96  defined between the end  90  of the electrode extension  88  and the end  92  of the ground element  94 . The arcing electricity creates a spark and ignites the combustible gas mixture provided through the nozzle  22  into the cavity  20  of the glass mold, thereby causing a film of carbonaceous material to be deposited on the glassware mold surface within the glass mold. 
   It should be recognized that upon reading the disclosure herein, one originally skilled in the art of glass forming would readily recognize other embodiments than those disclosed herein, with those embodiments being within the scope of the claims that follow. Accordingly, this disclosure herein is intended to be exemplary, and not limiting. The scope of the invention is defined by the claims that follow.