Lewill2, You are quite correct, there was a pipe wrench made. I have one of this same general design but with a much coarser rack. It was patented by C.E. Bonner on August 25, 1903 and is No. 737,199. The first patent was Dec. 23, 1902 and is No. 716,515 by W.S. Bonner. It was apparently never manufactured. It also does not resemble the production version, although that is not unusual.
This works the same as the Wright Wrench in that you push the bottom of the moveable jaw in towards the shank in order to move the jaw up or down as required.
Mike