Priority issues with mousetrap patents

Leaving cage traps and other designs aside, the flat snap trap with a spring loaded bar or striker has a long history. But neither all its historical changes have been patented nor all of its predecessors were made for mice.

1. Using one patent for advertising a different device
An early patent that has later been claimed to be incorporated in a flat rat trap with a spring loaded bar seems to have been Job Johnson's patent on a fish hook  (US patent no. 5,256 by Johnson 1847).

Rat trap marked: "JOB JOHNSON, BROOKLYN NY, PATENTED 1847"
(via BioImplement by courtesy of Rick Cicciarelli)

Though the imprint on the wooden base suggests that this trap incorporates Johnson's patent for a spring loaded fish hook, this was probably a gig for advertising its reliability to farmers, who have already been in the habit of using Johnson's fish hook as a rat trap instead (see here).

If you compare the above rat trap with the below drawings of the fish hook patent, you will see that they are quite different.

Drawings from US patent no. 5,256 (Johnson 1847) rotated for clarity.

As you can see, the fish hook has a spring, d, powering the trap by tension whereas the rat trap above has a spring working by torsion. The set/release mechanism of the fish hook is way more sophisticated than in the rat trap. In the rat trap the wire that serves as bait hook at one end runs through the wooden base. The other end engages directly with the striker, that is, it functions as the set/release mechanism itself. In the fish hook, however, the bait hook, f, is linked to a trigger beam or lever, e. The other end of lever e has a hole at x engaging with a cock-pin, 8, at the movable dart hook, b.

The part of the rat trap resembling a plain fish hook was not patent-worthy, as claimed by Johnson (1847, p. 1) himself: 

"I do not claim to have invented the common fish-hook, as that is well known and in general use; but [...]" 

That what has been patented in the fish hook is not incorporated in the rat trap, again, as Johnson's (1847, p. 1) claim continues: 

"[...]; but I do claim as new and of my own invention and desire to secure by Letters Patent of the United States: l. The original application of the stock or frame piece a, the original application of the helical contractile spring d, together with the original constructive arrangement of these parts for these purposes, conjointly with a crooked and barbed dart, b, acting, through the cock-pin 8, trigger-lever e, and contractile helical spring d to strike the fish or animal by disengaging the dart b from the trigger d [sic, must be e] through the combined action of the change able hook f with and upon the foregoing parts, the whole constructively arranged and combined to strike the fish or animal with the dart b at the instant of the fish or animal biting at or touching the bait on the hook f"

In conclusion, the above rat trap is an early flat trap with a spring-loaded striker, but it is not the first such trap to have been patented. The patent that is advertised on the trap is not incorporated in the trap.

2. Parallel patents granted in different nations

This and the next issue is with William C. Hooker's patent of 1894 (US patent no. 528,671). Though this is clearly a patent given for a flat snap trap with spring loaded bar, priority is often given falsely to James Henry Atkinson or John M. Mast.

James Henry Atkinson was a British inventor, who patented a flat snap trap with spring loaded bar called the Little Nipper in 1899 (GB patent no. 27,488). It is still being produced by Procter Bros. and sold with its initial name. It may therefore hold the record for the longest marketed product name of a brand mousetrap. Formulations meant to explain the provenance of current Little Nippers such as "the flat spring loaded mouse trap has been invented by Atkinson in  ..." may well have lead to the misunderstanding that this was the first such flat snap trap to receive a patent.

Current Little Nipper

Drawings from GB patent no. 27,488 by Atkinson (1899)

As you can see it has a treadle cut out of the whole width of the base and hinged to it. Atkinson (1988) claimed that this assures that the mouse releases the trap even if it only pass over the trap without being attracted to the bait as may be usual in bakeries and other places replete with food.

Another source of confusion is the way in which British and US patents differ in giving dates. On British patents the date of submission is featured prominently at the top, whereas the date of acceptance is given in the third line and in smaller font.

On US patents the date of acceptance is given in the heading line instead.

A third date for the invention of the Little Nipper, 1897, can also be found. For example, the company's website About Procter Machine Guarding says: "In 1897, a Leeds inventor called James Henry Atkinson invented a better mousetrap which he named “The Little Nipper”." Whether Atkinson invented his Little Nipper earlier or not, he received the patent no sooner than 1899.

A confusion of dates may also be the reason why Atkinson's Little Nipper patent (applied 1898, accepted 1899) is sometimes confused with another by Atkinson (GB patent no. 13277 filed in 1899 and accepted in 1900). The latter is a modification of Atkinson's earlier design that transformed the trap that was sprung by pressing a treadle into one that is sprung by pulling on a bait hook. It used to be marketed by Procter Bros. as the Alert, but is no longer produced.

Drawing from GB patent no. 13277 by Atkins (1899/1900)

The wooden base of the Alert did not need to be as thick as in that of the Little Nipper, and its general appearance is more similar with the patent by Hooker 1894.

Out O' Sight build according to Hooker's US patent 528,671 (1894) 

Entangled enterprises
Finally, a great source for confusion is the entanglement of the enterprises of the inventors William C. Hooker and John M. Mast. Both their patents and companies were closely related.

In 1899, John Mast of Lititz, Pennsylvania, filed US patent no. 744379 for an improvement of Hooker's design that can be "readily set or adjusted with absolute safety to the person attending thereto, avoiding the liability of having his fingers caught or injured by the striker when it is prematurely or accidentally freed or released." He obtained the patent at 17 November 1903.

After William Hooker had sold his interest in the Animal Trap Company of Abingdon, Illinois, and founded the new Abingdon Trap Company in 1899, the Animal Trap Company moved to Lititz, Pennsylvania, and fused with the J.M. Mast Manufacturing Company in 1905. The new and bigger company in Lititz, however, retained the name Animal Trap Company (see Drummond, Brandt & Koch (2002) at mousetrapbookscom). Compounding these different but related patents and companies may have contributed to the widespread misattribution of priority to Mast rather than Hooker.

P.S.: A remarkable 'coincidence' is the fact that the trap designs patented by Hooker (1894), Atkinson (1899 and 1900) and Mast (1903) all had the spring and striker formed of one piece of wire (see figures above). Job Johnson's rat trap, and many other traps for that matter, had spring and striker formed by separate parts.