[Geezer]

OK, you asked for it;

How many cans can a cannibal nibble if a cannibal can nibble cans?

[imatfaal]

Why don't can openers last as long as they used to? My parents had the same one for like 15 years, and I can't get more than a year out of one, whether I pay a lot or get it at the dollar store.

They ate less canned food?  Seriously tho... low quality manufacturing, built in obsolescence, and deliberately poor lifespan are just a part of our times

[menageriemanor]

I still use a curved bayonet opener I have to puncture the lid with first, then seesaw around the edge.  Any other wheeled. more refined version seems to not work after a week or 2.  As I get a bit of arthritis, I am muttering more, when I use it, but more and more, things I buy in tins have ring pull systems, ie tinned toms, etc

[Crank]

May I, a naked and as yet unbaptized member of this forum, belatedly offer a modest contribution to this important topic? I have two different can opener designs to report that were doubtless very important in their day.

Menageriemanor's post brought to mind a childhood recollection (from England, once a great seafaring nation). Some of the boys owned a cheap-looking, very well-worn, but sturdy old pocket knife of a type known as a jack-knife. It had a blade and next to it, a forked, blade-like tool of unknown purpose: on the opposite side there was usually a large, full-length, robust spike.

Landlubbers claimed the spike was for removing stones from horses' hooves (no doubt for lack of a better explanation, as we never found a hoof laying around with a stone lodged in it, perhaps because by the 1950's, there were few horses still walking the streets.) Many years later I realized that the spike is a marlin spike, used in ropework. suggesting a nautical origin for the knife design.

A search in Wikipedia finds mention of a jack-knife, but does not discuss its history. It does however, reference an article from the Norwalk Hour (of Connecticut), which appeared on the comics page (24) on May 31st, 1961, in the form of an answer to a puzzle question in The Junior Editor's "Quiz on words: QUESTION: How did the jackknife get its name?" One Gregory F. McIntyre received what then was the princely sum of $10 for submitting it, but it remains unclear if he also provided the answer.

It is there stated that in the 19th century "jack" was a term applied to a device smaller than usual: supposedly the reason a pocket knife, necessarily small, was called a jack-knife. Aboard ship the term "jack" was applied to a flag smaller than the main ensign (giving short shrift to the the British national ensign, the Union Jack, and throwing some doubt on the reliability of this source.)

You may know that sailors (in England, at least) were known as "Jack Tars" for ceaselessly caulking the hip's seams in dock. If so, you will have deduced that the marlin-spiked knife was designed for, and used by sailors, and so I propose, gained its name of jack-kniife (I later found that I am not the first to suggest this).

I actually own such a knife, dated 1945. It never had a marlin spike, and was probably made for civilian use. Like most jack-knives, its stout secondary blade is cleft from the tip about an inch deep towards the hinge, and the lower portion is longer and pointed, the two opposing sides filed into blunt blades: the upper portion is blunt and not sharpened. In the light of the foregoing discussion, it is clearly a can-opener: the tip is perfectly adapted to punch through a tin can, allowing the lower, slightly sharpened prong to be inserted to cut or rip open the can, perhaps a half inch or more at a time, using the top portion for leverage.

A more primitive can opener, merely comprising  a 1 1/4"" fold out, stout, dagger-like blade to punch open a can was found on British jack-knives from 1905 until 1939, when it was replaced with the more effective design I described. Neither design depends on the can having a rim, as did the more modern design that followed.

Marhoofer mentioned that canned food was invented for the navy, another nautical association.

One can Goog "British Jack Knife and immediately see some fine army examples. Dig deeper, and it emerges that Jack-knives had their origin in France in the 18th century, are distinguished from other folding knives of the time by having both blades hinged at the same end. They appeared in the US navy during the civil war (sans can opener). They became widely established, with an added can opener in the British army and navies and her allies' counterparts in WW1, and also in the US military and in civilian use by WWII. Several minor variants were manufactured by many companies. The army and civilians eventually discarded the spike, but similar, updated knives remain military issue.

In the age of the steamship, and certainly after WWII, such knifes became obsolete and so landed in boys' ever open pockets.  (The only other type of knife I recall English boys owning in those days was another obsolete design, the pen-knife).
 
I have one other indirectly related suggestion to offer. Perhaps Peter Durand was not so careless about providing a means of opening the can as he seemed: he did prescribe a chisel. It was mentioned that Napoleon's army used cans of food sufficient for several men. This meant that only the most junior officers would need to carry a chisel, and thus the rate of food consumption could be controlled, a critical factor in military logistics. In later years individual cans evidently became preferable, and so the jack-knife can openers appeared.

[Ernest F]

I would think that most items were put into tins before can openers were made. Like metal flasks were used instead of bottles. most earlier cans were coated on the insides

[CristinaFinn]

Peter Durand of England patented a can made of wrought iron with a tin lining

[AnnaSmith]

That's a great invention and it does solve a big problem.

[DrMortimer]

I read that William Lyman  invented the can opener