Chronological Distribution of Milker Patents, 1860-1910
Early attempts at developing a satisfactory pressure type milker did not give way to the likelier prospect of a vacuum milker until well into the 20th century. Instead, both pressure and vacuum type milkers were patented at about the same rate during thirty years of active development.
© 1996, Greybird Publishing
From "American Milking Machines" by Richard Van Vleck