British Army uniform and equipment in World War I It contained an inner can of explosive with an outer can of metal fragments or ball bearings. The fuses that were developed for the Jam Tin Grenade were activated by friction or a by lighted taper which was often replaced by a lighted cigarette. This was followed by the highly successful Mills bomb in 1915. It was oval in shape to fit into a clenched fist and time fused. The detonator was activated by a spring driven firing pin which was restrained by a lever that in turn was locked by a safety pin. The Mills bomb was a defensive
Term of patent in the United States patents in the U.S., since the patent term now depends on the priority date, not the issue date. Design patents have a shorter term than utility patents. Design patents filed on or after May 13, 2015 have a term of 15 years from issuance. Design patents filed prior to May 13, 2015 have a term of 14 years from issuance. The original patent term under the 1790 Patent Act was decided individually for each patent, but "not exceeding fourteen years". The 1836 Patent Act (5 Stat. 117, 119, 5) provided (in addition to the fourteen-year term) an extension "for the