Insulator Historical Timeline! 1930-1939

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.

• June 3, 1930:  Chester Gordon and James Lowe with A.T.&T. Co patent for a two piece transposition with a more water-tight joint.  This patent covers the rare Pyrex CD 194.5/195.5. (US Patent 1,760,983) -- [Full Patent Text]
• August 2, 1932:  Charles L. Stroup of Oak Park, IL patent for a helical insulator designed to capture rainwater to ensure that the insulator was cleaned of contamination during rains.  Both Jeffery Dewitt and Lapp made insulators of this style, examples are U-819 and U-820 with Lapp making post style insulators.  (US Patent 1,869,397) -- [Full Patent Text]
• April 17, 1934:  Davidge H. Rowland of Baltimore, MD patent for a two part glaze-welded hollow insulator.  This patent was assigned to the Locke Insulator Corp. also of Baltimore. I do not know if any insulators were made using this patent, no known styles currently exist. (US Patent 1,955,609) -- [Full Patent Text]
• 1935:  Crystallite Products Co. takes over production from McLaughlin and marks their insulators Maydwell.  They made nine styles of insulators until about 1940. 
• January 15, 1935: Harold H. Brown of Appleton, WI patent for a conductive wire groove and pin insert to reduce radio noise.  This was likely the idea that later led to the development of conductive glazes currently used on power insulators to reduce AM radio noise.  This patent was assigned to the Locke Insulator Corp. of Baltimore, MD. (US Patent 1,988,369) -- [Full Patent Text]
• June 22, 1937:  Bentley A. Plimpton of Victor, NY patent for a porcelain high voltage insulator with additional petticoats and flanges.  This patent was implemented in the porcelain "Hi-Top" series of insulators (U-782 through U-805) as well as glass styles CD 220 and CD 221.  (US Patent 2,084,866) -- [Full Patent Text]
• July 27, 1937: Bentley A. Plimpton of Baltimore, MD patent for a fog type insulator that was assigned to the Locke Insulator Corp. of Baltimore, MD.  This patent was implemented in U-816, U-816A, and U-816B styles.  These closely correspond to his third patent drawing.  (US Patent 2,088,433) -- [Full Patent Text]
• November 16, 1937: Donald H. Smith assigned to the Western Union Telegraph Co. patent for a metal insulator shield to go around the base of a CD 154 style insulator.  I have seen these in use on Canadian dominion CD 154's.  (US Patent 2,099,540) -- [Full Patent Text]
• 1938 (Unknown exact date):  The Armstrong Cork Co. purchases the Whitall Tatum Glass Co.   Armstrong continued to mark their insulators Whitall Tatum for some time after the purchase, eventually marking them their logo.
• July 11, 1939:  H.H. Wheeler assigned to Western Union Telegraph Co.  patent for a low loss telegraph insulator.  This patent was implemented in CD 122.4 by Corning and Hemingray.  Of more interest, this patent covers the carnival glass coating used on many of the telegraph styles including the CD 118, 142 and 142.4.  It states that the coating increased the surface resistance of the insulator, thereby improving its performance in damp weather. (US Patent 2,165,773) -- [Full Patent Text]

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