Insulator Historical Timeline! 1940-Present

Key events are noted by approximate date.  Hyperlinks will provide additional information.  Please feedback additional key dates or note any needed corrections.  Dates considered particularly significant are highlighted in red.

• April 26, 1940:  Frank Brookfield died.  Frank Brookfield was the Vice President and Treasurer for the Brookfield Glass Works in the early 1900's.
• October 15, 1940:  D.H. Smith of the Western Union Telegraph Co. patent for a threaded rubber insulator.  This patent was implemented in the smaller Continental Rubber Works insulators.  (US Patent 2,218,497) -- [Full Patent Text]
• December 16, 1941:  Nevin Y. Sindlinger of Toledo, OH patent for a no-tie insulator style similar to the August 11, 1914 Purkey patent for a slot top locking insulator.  This version uses a V shaped groove to hold the wire by friction.  No known insulator has been attributed to this patent.  (US Patent 2,266,340) -- [Full Patent Text]
• December 16, 1941:  Frederick Foster Reed of Lyndhurst, NJ patent for a cable style insulator for secondary power distribution.  This patent was implemented in glass styles CD 216 & CD 219. (US Patent 2,266,400) -- [Full Patent Text]
• December 14, 1943:  Minot K. Holmes of Muncie, IN patent for an insulator mold.  This patent was assigned to the Owens Illinois Glass company and appears to match the design of the CD 1030 lag bolt insulator attributed to Hemingray (Owens Illinois).  (US Patent 2,336,864) -- [Full Patent Text]
• January 8, 1946:  Alwin G. Steinmayer of Milwaukee, WI patent for a combination insulator and spark gap arrestor.  This patent was assigned to the Line Material Company and was implemented in Hemingray insulator CD 186.1 and CD 186 and CD 186.2 were likely similar experimental pieces.  (US Patent 2,392,342) -- [Full Patent Text]
• November 30, 1948:  Rogers Case patented a mid-span transposition bracket as used with the Owens Illinois CD 1049 insulators.  (US Patent 2,455,229) -- [Full Patent Text]
• November 24, 1953:  Lapp Insulator Corporation trademark is registered as #582,766.  Products listed as "ELECTRIC INSULATORS AND ELECTRIC CONDENSERS".
• February 7, 1956:  E.J. Bonnesen patents an enhanced transposition insulator with the addition of a rubber skirt between the two wires.  This was implemented on Armstrong's CD 203.2 although most known pieces no longer have the rubber piece.  (US Patent 2,734,098) -- [Full Patent Text]
• October 30, 1962:  William F. Markley and James L. Slater patent covering the design of several insulator styles made of rubber.  This patent was assigned to the Western Union Telegraph Co.  Several styles made by the Continental Rubber Works match this patent.  (US Patent 3,061,667) -- [Full Patent Text]

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