"电气安全光栅",美国专利申请模型, 约1905年

Patent No. 763890 by Gustav T.E. Henriksen, Milwaukee, 28 June 1904, painted metal case with 2 horizontal crossbars and 21 vertical tubes with sliding inner rods with electric terminals connected to alarm bell system mounted on the top, with door, lock and brass plaque engraved: "Henriksen Electric Safety Grating System, Pat. Jun. 28 1904, Chicago, USA", height 16 in. (41 cm) x width and depth 16 ¼ in. (41,5 cm). In original metal transport case. Henriksen filed his patent application for "improvements in safety-gratings" on 2 December 1903. The object of his invention was to "prevent the severing of grating-bars and togive an alarm in case of an attempt to do so". It features an arrangement of vertical tubes encasing revolvable rods suspended from notched collars at the upper ends and connected to electrical terminal at the lower ends. The rods are held loosely in their collars by cross-pins. Attempting to cut through the outer tube rotates the inner rod, the pin drops into the notch in the collar and the lower end of the rod engages with the electrical terminal, which closes the circuit and activates the alarm. Included with the model are copies of the original patent application, patent, a 1910 patent by Henriksen for "Oiling Devices" and related papers. A fascinating exhibition piece!