The Push Pin: A Glass Handle Sealed Round a Steel Point

Moore's push-pins are "adapted to support one article upon another and being particularly employed for holding photographic films stretched upon a surface, such as a board, for drying and the like." The earlier kind had a wooden body with the pin clamped by a metal collar; with it "the fingers slip and tear or blotch the film", and "the water employed upon the film corrodes the pin and the metallic cap, thus causing stains upon the film." His handle 1 "is constructed of glass, porcelain, or other vitreous substantially non-corrosive substance", preferably "formed from glass tubing", and tapers so it can be "firmly grasped by the fingers". An annular flange or collar 3 at the pin end is "an additional safeguard to prevent slipping of the fingers against the film." The pin 2 is embedded and should have a coefficient of expansion substantially that of the handle, "whereby cracking of the handle due to expansion of the pin is avoided". The projecting pin may be coated against rust, and Fig. 3 adds an enlarged end to pull the pin out by.

Glue a cork sheet to a board. Wet a sheet of paper as a stand-in for film and pin its corners, once with drawing pins and once with push pins, with wet fingers each time. Count slips and note any tears. Push one of each into the cork and hook the spring scale under the head to pull it straight out; compare the holding force. Leave one of each in a damp dish for a week and look for rust marks on the paper under it.

**Edwin Moore** of Newark, New Jersey, filed US 654,319 on 24 July 1899, and it is dated 24 July 1900. He describes the handle, its taper and flange, and the matched pin. **Honest limits.** Moore names no pin metal. The expansion coefficients in the notebook are typical values, and the stress formula is a first estimate that ignores the seal's geometry and annealing.