The Locking Mop Clamp: A Spring and an Over-Centre Lever

"Between the ring E and the T-head B, is a spiral spring, F, the expansive tendency of which holds the clamp firmly closed, as in the position shown in Fig. 1, when the lever D is thrown back." "In the operation the rags, not here shown, are placed in the clamp, and since the ends of the rod C are pivoted between the ends of the lever D, the lever when carried back against the stick exerts a leverage on the rod C and compresses the spring F, thus firmly holding the rags, during which action the pivotal points c are carried a little below the horizontal plane of the pivoted ends s, of the lever D, thus locking the clamp."

Screw a hardwood cross-piece across the end of a broom handle as the T-head, with a groove in each end. Bend steel wire into the clamp rod: straight across the T-head, then back through the grooves to meet at the handle. Slide a loose wooden ring or a short tube onto the handle, with a spring from the assortment between it and the T-head. Make a small lever from hardwood, pivot its forked end to the ring, and pin the rod's ends to it a little forward of that pivot. Lay rags in the clamp and throw the lever back until it snaps past centre. Pull the rags with the force meter to measure the grip, then mop a floor. Compare with the notebook.

**Thomas W. Stewart** of Detroit, Wayne County, Michigan, filed US 499,402 on 26 September 1892; it is dated 13 June 1893. The patent is a clamp for holding the rags; it describes no wringer. **Honest limits.** The notebook treats the linkage as an ideal toggle and the spring force as constant near centre, and ignores friction. Spring rate, compression and sizes are examples. Your force-meter reading is the measurement.