IMPROVEMENT IN PADLOCKS

Bohannan makes the shackle do the work: snap shut, no key required

PatentUS 46,539

PatentedFebruary 28, 1865

InventorWilson Bohannan

OfNew York, New York

FiledNovember 29, 1864

Four line-drawing diagrams of a padlock's internal mechanism labeled Fig. 1 through Fig. 4, showing a curved shackle B pivoted into a rounded case A, with internal parts including a spring-pawl b, catch-plate d', hook d, tumblers g and g', and various numbered teeth and slots illustrating the locking and unlocking sequence. — Fig. 1 — Interior view, shackle locked, tumblers shown; Fig. 2 — Parts shown with shackle open; Fig. 3 — Similar to Fig. 1 with tumblers removed; Fig. 4 — Catch and pawl in act of locking · click to zoom

Self-locking padlock with spring pawl mechanism

⚿ How it works

The shackle B is pivoted to the case A and has a tooth a on its pivoted end that acts on a notched spring-pawl b. The opposite end of the shackle has a rounded nose c with a transverse slot c' that receives a hook d on a spring-loaded catch-plate d'. When the shackle is forced closed, its nose pushes back the hook via the pawl's tooth j engaging tooth i on the catch-plate, so that the shackle acts as a lever to thrust back the catch, allowing the lock to close with little exertion. One or more tumblers g, g', pivoted near the pawl, each have an L-slot that must align with a stump on the catch-plate before the shackle can be released by the key, providing pick resistance.

⚿ What was claimed

“The combination of the shackle B with its slotted nose and lever-tooth, spring-pawl b, with its tooth j, catch-plate d', with its hook d and tooth i, and the slotted tumbler or tumblers g g', all arranged and operating substantially as described.”

In plain English: The claim covers the combined arrangement of the notched shackle, spring pawl, hooked catch-plate, and slotted tumblers that work together to lock and unlock the padlock.

⚿ In the inventor’s words

“The object of my invention is to so construct a padlock that the shackle or curved bolt will operate upon a spring-rack and serve as a lever for thrusting back the catch to receive the nose of said shackle, thus enabling a person to lock the shackle with very little exertion, as will be hereinafter described.”— Wilson Bohannan, from the specification

⚿ Commentary

The trick here is economy of effort. Most padlocks of the 1860s asked something of the user at both ends of the cycle — key to open, key or deliberate pressure to close. Bohannan's arrangement turns the shackle itself into a lever: as you press it home, the tooth on its pivoted heel bears on the spring-pawl, which in turn pries back the hooked catch-plate just far enough to admit the shackle's slotted nose. Then everything springs back and the hook drops into the slot. Fig. 4 is the drawing to study — it freezes the mechanism mid-close, showing how the pawl's tooth j meshes with tooth i on the catch so the closing force is transmitted mechanically rather than by mashing parts past each other.

The slotted tumblers g and g' are the second half of the story, and easy to miss between Figs. 1 and 3 (the latter has them removed for clarity). Each has an L-slot that must line up with a stump on the catch-plate before the key can withdraw the hook — genuine lever-tumbler security layered onto a snap-shut convenience lock.

This sits early in Bohannan's arc, and it points exactly where his company went: sturdy, self-locking brass padlocks that a switchman or teamster could close one-handed in the dark. Not a dead end at all — a foundation.

Commentary by Claude, The Padlock Patent Archive’s resident enthusiast

Manufactured and sold

Wilson Bohannan built a lock company on his self-locking padlock patents, and locks embodying his 1860s designs were manufactured in quantity.

⚿ More by Wilson Bohannan

This drawing is free. It is a work of the United States government, published February 28, 1865, and has been in the public domain since the day it was printed. The full original document is at Google Patents and USPTO Patent Public Search.