Vibration resistant electron tube

Claim 1

AN ELECTRON TUBE COMPRISING A GLASS BULB, A RELATIVELY HEAVY SUBSTANTIALLY FRUSTO-CONICAL END MEMBER SEALED TO ONE END OF THE BULB, A TUBULAR ANODE MOUNTED AT ONE END ADJACENT THE SEAL BETWEEN THE END MEMBER AND BULB, AN INVERSE RELATIVELY HEAVY RUSTO-CONICAL TERMINAL MEMBER SEALED TO THE OPPOSITE END OF THE BULB, A PAIR OF RIGID SUBSTANTIALLY FRUSTO-CONICAL INWARDLY EXTENDING SUPPORTS MOUNTED ON THE INNER SIDE OF THE TERMINAL MEMBER, A CATHODE FIXEDLY MOUNTED ON ONE OF THE SUPPORTS, A FIRST GRID FIXEDLY MOUNTED ON THE OTHER SUPPORT AND ENCIRCLING THE CATHODE, A RELATIVELY HEAVY PARTLY CONICAL SUPPORTING PLATE SPACED OUTWARDLY FROM THE TERMINAL MEMBER, A SECOND GRID LOCATED BETWEEN THE CATHODE AND FIRST GRID, MEANS RIGIDLY AFFIXED TO THE PLATE AND FREELY PENETRATING THE TERMINAL MEMBER AND HAVING THE SECOND GRID FIRMLY MOUNTED THEREON, THE UNSUPPORTED ENDS OF THE CATHODE AND BOTH GRIDS CARRYING APERTURED CAPS, AND A NONCONDUCTIVE CYLINDER OF HEAT EXPANDABLE CERAMIC MATERIAL MOUNTED IN SAID CAPS AND RETAINING THE CATHODE AND GRIDS IMMOVABLY IN ASSEMBLED SPACED RELATION.