Fluid-working spark discharge electrode assembly

Claim 1

A SPARK DISCHARGE ELECTRODE ASSEMBLY HAVING A WORKING TIP PORTION IMMERSED IN A SUBSTANTIALLY NON-COMPRESSIBLE WORKING FLUID AND A TERMINAL PORTION, WHICH COMPRISES A LONGITUDINALLY EXTENDING METAL ROD, A HOLLOW COAXIAL METAL SHEATH CONCENTRICALLY POSITIONED WITH RESPECT TO AND SUBTANTIALLY COEXTENSIVE WITH SAID ROD TO DEFINE A CONTINUOUS ANNULAR SPACE, SOLID DIELECTRIC MEANS OCCUPYING SAID ANNULAR SPACE FLEXIBLY BONDING SAID SHEATH TO SAID ROD TO FORM A UNITARY SOLID CONSTRUCTION FOR SUBSTANTIALLY THE ENTIRE LENGTH OF THE ELECTRODE ASSEMBLY, AND DIELECTRIC MEANS COMPRISING A PLURALITY OF PARTICLES OF AN INSULATING FIRED CERAMIC MATERIAL FLEXIBLY BONDED TOGETHER BY AN ELASTOMERIC ORGANIC DIELECTRIC MATERIAL HAVING A DUROMETER HARDNESS OF FROM ABOUT 50 TO 150 MEASURED ON THE SHORE "A" SCALE TO FORM A COMPOSITE INSULATING BODY HAVING SUBSTANTIALLY THE SAME EROSION CHARACTERISTICS DURING USE AS THE CONDUCTIVE METAL MEMBERS, SAID TERMINAL PORTION BEING DISPOSED AT THE OPPOSITE END OF SAID ELECTRODE ASSEMBLY FROM SAID WORKING TIP AND COMPRISING AN ELECTRICALLY CONDUCTIVE RING MEMBER AFFIXED DIRECTLY TO THE OUTER SURFACE OF SAID SHEATH MEMBER, AND DIELECTRIC BUSHING MEANS IN CONTACT WITH AND SEPARATING SAID RING MEMBER FROM THE ADJACENT END OF SAID METAL ROD.