A few days ago we looked at a guard bar for safety razors. In that post, I mentioned wanting to take a look at a patent for a double edge injector. Guess what we’re doing today? That’s right – we’re looking at the double edge injector!

The patent was filed by Gerald Stahl and Charles A Johnson Jr in 1961, and granted four years later. And it is delightfully detailed and lavishly illustrated. Even the full title is quite a mouthful; “Injector razor having means for flexing a flexible double edge blade as it moves into position and arrangements for operating the same”.

So what problem did they set out to solve with their patent? Well, to quote from the patent text:

Injector-type safety razors and associated blade magazines for both single and double-edge blades are known to the prior art, with those for single-edge blades having been at least reasonably widely accepted by the shaving public. Difficulties have, however, attended the provision of commercially acceptable injector razors for double edge blades.

From US patent 3,171,198

In short, they set out to solve how to make a commercially acceptable double edged injector. As pointed out further down the text, the problem of an double edge injector is the the fact that you can’t easily inject a double edged blade between the top cap and bottom plate without separating the two. So what Gerald and Charles set out to do is to make a razor where you could do that.

The whole thing was done with wobbler pawls, a wobbler bar, a couple of push rods, and more mechanical widgets. Overall the whole thing looks significantly more complex than a regular single edge injector.

I’m not going to go into too much details. The patent is information dense enough that if I were going to do it justice, this post would be as long as the patent itself. I strongly recommend browsing through it if you’re interested in seeing the how as well as the why of the invention.

What is interesting though, is the fact that it ought to be possible to modify the construction to work with standard double edged blades. And since the patent expired fourty years ago, there may be an opening for a small scale razor manufacturer to bring a double edged injector onto the market. If there is a market, that is.

Either way, the idea is an odd and fun one. And I am happy I decided to have a closer look at the patent.

As usual, the full patent can be read at Google Patents.