The Gripping Shoe Horn: A Jaw That Locks Over Centre

"My invention relates to certain new and useful improvements in shoe-horns; and the object of my improvements is to provide a device adapted to take hold of or grip a shoe and maintain its temporary position thereon by a setting action and allow of yet further gripping action on the said shoe in putting it on the foot." "As ordinarily formed the shoe-horn has no gripping action on the shoe itself to assist in its adjustment on the foot, and my device is especially adapted for low-cut shoes, or those not provided with a back strap." The clamping-piece has "a rubber lining-surface D, corrugated or otherwise adapted to promote the contact of the clamping device with the leather without marring the same." "This setting action of the handle and clamping-piece occurs as soon as the point e arrives in line with or passes the pivot F of the handle and clamping-piece. The farther this bearing-point e passes said pivot the greater the setting action, since any pressure on the clamping-piece tending to force it outward or open the jaws will only tend to force this point e still farther past the pivot."

Cut a jaw and a handle from stiff card. Pivot the jaw to a base strip with a nail pushed through an awl hole, and hinge the handle to the jaw so that its end presses on the base. Push the handle down slowly and feel the moment it snaps past the line and holds. Press on the jaw: before the snap it opens, after it stays shut. Then put on a snug low shoe ten times without a horn and ten times with one, timing each, and hook the force meter into the heel to feel how hard the shoe has to be held.

**Elmer E. Wolf** of Springfield, Ohio, filed US 466,643 on 17 January 1891; it is dated 5 January 1892. He writes that a salesman can set the horn on the heel and hand it to the buyer, whose own pull then tightens the grip. **Honest limits.** The notebook treats the handle as a rigid lever with a point contact and ignores friction at the cam, which in practice makes the lock hold a little before the line. The huge grips near the line are never reached: the jaw lining, the shoe and the card give first. Lengths and forces are examples. Your times and force readings are the measurement.