Inventions
name: label: Collection Creator
content: Pratt, Charles Richardson, 1860-1935
setName: label: See more items in
content: Charles Richardson Pratt Papers
unitdate: label: Date
content: 1860 - 1927
dataSource: label: Archival Repository
content: Archives Center, National Museum of American History
identifier: label: Identifier
content: NMAH.AC.0958, Series 5
objectType: label: Type
content: Archival materials
scopecontent: label: Scope and Contents
content: This series consists of materials related to Pratt's inventions.  The materials include correspondence, patents, patent applications, sketches, calculations, blueprints, and some photographs. The materials are arranged chronologically by patent issue date. Researchers should consult Series 3: Correspondence for additional information.

There is substantial documentation about Pratt's cable tension equalizing device which he co-patented with John Heslip on November 30, 1923 (US 1,474,911) and the subsequent patent interference case.  The patent, filed on April 6, 1921, was intended, "to provide an improved apparatus whereby the tension on several load carrying cables may be maintained substantially uniform while operating." The invention would be most valuable to elevators whose load needs to be properly distributed. 

Edward E. Wright of Detroit patented an equalizer (US 1,465,705) on August 21, 1923, three months before Pratt. Wright suggested to Pratt that he abandon his pursuit of filing a patent and that he was the rightful inventor.  According to Pratt's records, namely his sketches, he and Heslip conceived of the idea in Kansas City first, implementing their invention in the Commerce Trust Building. Pratt's November 30, 1920 sketch, made on the back of a menu for the Hotel Baltimore in Kansas City,  details his elevator rope equalizer. Wright began an patent interference with the United States Patent and Trademark Office, Edward E. Wright v. Charles R. Pratt (Interference No. 48, 278) on November 16, 1922. An interference proceeding, also known as a priority contest, is a proceeding before patent judges to determine the priority issues of multiple patent applications. On March 16, 1923, Pratt and Wright resolved their patent interference with the following agreement: Wright paid Pratt $500 in cash; Pratt would no longer pursue the patent interference; and Wright would grant Pratt an exclusive license to manufacture, use, and sell all forms of the equalizer except the form shown in Wright's patent