If you find a patent number or patent date by this manufacturer that is not on this
list, please contact the Site Historian.
Key to Links for Patent Information
USPTO = U.S. Patent Office .
Images of the actual patent can be viewed on the U.S. Patent Office web site but
a special TIFF viewer must be installed with your browser in order properly work.
More information on how to configure your computer to view these patents can be
found at TIFF image Viewers
for Patent Images.
DATAMP = Directory of American Tool And
Machinery Patents . A sister site to VintageMachinery.org with information
on patents related to machinery and tools. A much easier user interface than the
USPTO's for finding information on machinery patents.
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1,323,531
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Dec. 02, 1919
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Means to measure the suction in the manifolds of internal combustion engines
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Edward R. Hewitt |
Midvale, NJ |
This patent was the subject of a Federal Trade Commission investigation; see link. Joseph Weidenhoff, Inc., licensed this patent and then included this patented vacuum gauge as part of various motor analyzers. They then entered into "agreements and understandings between itself and other manufacturers or distributors of such devices to fix and maintain prices to be extracted from purchasers thereof...through threatened infringement suits based on said patented vacuum gauge". |