Electrical insulation suitable for commutators

Claim 1

A THIN LAMINATED SHEET OF ELECTRICAL INSULATING MATERIAL OF A THICKNESS NOT EXCEEDING 0.050 INCH AND HAVING A HIGH STRENGTH AND RESISTANCE TO CRACKING AND BREAKING, AND PARTICULARLY ADAPTED FOR USE AS A COMMUNTATOR SEGMENT, THE LAMINATED SHEET COMPRISING A CENTER SHEET OF OPEN WAVE GLASS FIBER CLOTH OF FROM 0.003 TO 0.015 INCH THICKNESS, A COEXTENSIVE SURFACE SHEET OF ASBESTOS PAPER OF A THICKNESS OF 0.025 TO 0.035 INCH BONDED TO EACH FACE OF THE CENTER SHEET, A COTAING OF A COLLODIAL DISPERSION OF SILICA ON THE GLASS FIBER CLOTH, THE ASBESTOS PAPER BEING IMPREGNATED TO A RESIN RATIO OF FROM 1.3 TO 1.7 WITH THE THERMOSET REACTION PRODUCT OF FROM 25 TO 65 PARTS BY WEIGHT OF MONOSTYRENE AND 100 PARTS OF THE POLYESTER PRODUCED BY REACTING ONE MOL OF MALEIC ANHYDRIDE AND ONE MOL, WITHIN 2%, OF A GLYCOL, THE GLASS CLOTH AND IMPREGNATED ASBESTOS PAPER HAVING BEEN SUBJECTED TO HEAT AT TEMPERATURES OF 125* C. TO 175* C. AND A PRESSURE OF FROM 1000 TO 2000 POUNDS PER SQUARE INCH TO PRODUCE A HARD CURED SHEET SUITABLE FOR USE AS COMNUTATOR SEGMENT INSULATION.