07-07-2021, 02:48 AM
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Back in 1909 Herr Georg Friedrich Hofmann, from München, Germany, saw that there was little to improve on when it come to the Gillette-style double edged safety razor. So he did the perhaps not so logical thing and tried to improve on the blade instead. And by improve I mean make them harder to manufacture, more expensive, and quite possible less durable. In hindsight not the best of improvements.
But first, a little recap. King Gillette patented his safety razor and blade – see British patent 1902-28763 and US patent 775135 – he also patented the three hole, two edged blade. While this blade didn’t immediately push other blades out of the marked, it was a clear improvement on most of them in that it could be manufactured and distributed reasonable cheaply.
However, in the eyes of Georg Friedrich Hofmann, it was still room for improvements to the blade. To quote the patent text on the problems with the Gillette blade and his ideas of improvements:
Quote:The production of blades of this kind is attended with very great difficulties in consequence of the important requirements which the blades are required to fulfil when ready for use. The cutting edges must be very hard but at the same time so flexible that when put into the blade holder they can be slightly bent.
In order to meet this requirement it has been usual hitherto to make every blade out of a single piece of steel that could be tempered. This involves the employment of a particularly expensive kind of steel, which on the one hand must be capable of a high degree of hardness, but on the other hand must be tough and flexible. Each blade is provided with holes, which serve to receive pins or projections on the backing plate of the holder, for the purpose of holding the blade in its proper, position when put in the holder. For the sake of simplicity and cheapness the holes are made by being punched out. As, however, it would be difficult to punch the holes out of hardened steel the blades are only hardened after the holes have been punched out.
Consequently a hardening of the whole blade is necessary, although in the operation of shaving the cutting edges .only come into action and therefore the hardening of a small strip near -each cutting edge would suffice. The hardening of the blade occupies a great deal of time, as each blade must be hardened separately and it is difficult to harden a large number of blades uniformly in the manner requisite for making them serviceable. This involves the production of a considerable number of blades which are unsuitable for practical use and are not serviceable for other purposes, thus constituting waste, which substantially increases the total cost.
According to this invention a blade web or strip of non-hardened metallic or non-metallic material has fixed thereto one or more blades which are made independently of the web and are only connected therewith after tempering.
This construction enables the blades proper to be made of the narrowest possible strips of hardened steel, which does not need to be tough and flexible, so that the employment of an expensive kind of steel is not necessary, a cheaper kind of steel being serviceable. The strip of steel serving for the manufacture of the blades may be hardened throughout, so that the troublesome and expensive hardening of the different blades separately is dispensed with and for making the blades it is only necessary to cut the strip of steel into proper blade lengths.
The blade web or strip may consist of very inexpensive material, for example -impregnated paper, celluloid, stiff textile fabric, sheet metal, wood-veneer or the like. As the manufacturing costs of the blades are very small, the blades can be cheaply renewed, even after being used only a few times or only once, whereby considerable advantages in a hygienic sense are ensured.
There is a couple of assumptions made by Georg Friedrich Hofmann that invalidates his logic,* but lets ignore those for now. Focusing instead of his improved blade, it’s obvious that it would be easier to grind and temper strips of steel without having to worry about keeping them flexible… but what you gain on the straights you loose in the curves. Assembly of the blades would present problems.
Attaching the narrow edge-pieces to the central web would be tricky. If you use a sheet metal web, you could spot-weld – but that introduces heat to your carefully tempered steel. One could use rivets, but then you need a machine for drilling tiny holes, inserting rivets, and punching them. Rivets could also work for some of the other materials he suggests. Today an engineer might look into the use of various glues, but sticky stuff has come a very long way in the last century. I know of no glue available to Georg Friedrich Hofmann in 1909 that would have held up to heat, water, and mechanical forces. Even less so when used to secure two different materials.
The concept of having very hard edges while keeping the middle of the blade flexible is sound. But the execution is, well, novel to the point of being impractical. Gillette and others instead worked on their tempering process, so only the outermost parts of the blade got the high heat, while the centre around the holes remained reasonable cool. But at least the patent image provides a very nice view inside a Gillette Old Type razor.
[Image: GB_190909905_A-768x1218.png]
The patent drawing for British patent 1909-9905


Given that no double edged blade I’m aware of have a composite type construction, it is obvious that Georg Friedrich Hofmann failed to get his invention manufactured in any great number. And even if he had, the blades would most likely have been even more expensive than Gillette’s offerings.
The full patent can be found on Espacenet. If you enjoyed this and want to read more, I have plenty other shaving patents and oddities on my blog.



*) For starters, he seems to assume that hole punching, grinding and hardening was done on individual blanks. In reality, Gillette were making blades from rolls of steel, which meant that punching, grinding and tempering were continuous operations. For a little more on how much thought Gillette put into the manufacture of blades, see this old blogpost.

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 07-07-2021, 04:13 AM
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Interesting.  Thanks!

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