Ice cream freezerIn 1843, a U.S. patent was issued, antedated to 29 Jul 1843, for a hand-cranked ice-cream freezer invented by Nancy M. Johnson (No. 3,254). In previous designs, the ice-cream mixture was held in an inner container, which vessel was itself was rotated within an outer container of ice and salt. Her invention was to add a vertical shaft with curved, perforated paddles within the inner vessel, and reaching nearly to its inside wall. Stirring in one direction would carry the the liquid or semi-fluid mass from the centre to the circumference. Turning in the opposite direction would scrape frozen material and carry it from the inner walls to the centre of the freezer. Thus fresh matter continuously reached the freezing surface.«[Image: detail from patent diagram showing inner container and its paddle.] |
