The Circle-Cutting Can Opener: A Spur at the Centre and a Blade Set to the Can's Size

"On the opposite end of the bar a, and on the under side, is fixed a sharp spur, a3, curved outward, and designed to be thrust through the top of the can. When it is thrust through, the bar a can be turned down against the top of the can." "The device can be employed on any size of can. The spur a3 is thrust through the top of the can and the block e is drawn outward till the stud e2 will pass down on the outside of the can. The bar is then pressed down against the can. This movement pushes the blade e4 through the top and the stud e2 down on the outside of the can. By pushing the bar sidewise the blade moves in a circle and cuts the top open."

**Bar.** Cut 22 cm of 20 × 5 mm mild steel flat bar. At one end, file a curved spur a3 on the underside, pointed and hardened. Next to it, saw and file a slot a4 8 cm long along the bar, and file its edges to a bevel as the guides a5. **Head block and blade.** File a block of flat bar with V grooves on its edges that slide on the guides. Screw a short stud e2 to its underside, and fix a small two-edged blade e4, filed from spring steel and hardened, just inside the stud. Fit a thumb screw and plate to lock the block anywhere along the slot, in place of Arment's spring f. **Corkscrew and wax blade.** Wind a small steel-wire helix and pivot it in a recess filed in the bar's other end so it folds away; fix a short stub blade d beside it. **Test.** Push the spur through the middle of a small can's lid, slide the block out until the stud is outside the can's rim, press the bar down so the blade pierces the lid, and swing the bar round. Reset the block and open a larger can.

**Isaac N. Arment** of Dayton, Columbia County, Washington Territory, filed US 234,646 on 24 September 1880; it is dated 23 November 1880. His block e had channels e′ fitting the guides a5, a friction roller e3 on the stud e2, and a spring f coupling it to the bar's end to hold the stud against the can's side; the brush b cleaned the can or bottle top. His claims cover the bar, slot, guides and spur with the adjustable block, stud and blade, and the whole opener with its blade d, corkscrew, block and spring. **Honest limits.** Filed flat bar and a thumb-screw lock stand in for his spring-held block, and the brush is left out. The notebook ignores friction; its forces and lengths are examples. Your opened cans are the result.