The safety razor was the cutting edge of shaving technology a hundred and twenty years ago. You could even say the bleeding edge, if your razor featured a replaceable blade that wasn’t quite secure… something Walter J Smart sought to fix with a trio of razor patents.
In chronological order, the patents are British patent 1905-24,010, US patent 881,033, and US patent 960,424. The all revolves around the same idea though; using a spring loaded top cap to pin the blade down. To quite from the earliest of the three, the idea was to:
…provide a razor of this character where in the blade may be easily inserted in its holder and withdrawn therefrom and which will be held accurately in place.British patent 1905-24,010
As can be seen from the drawings, the basic idea is that a narrow blade is held in place by an arrangement similar in concept to the clothes pins I grew up with. The user would push the rear of the top cap down, insert a blade, and let go of the top cap. To remove the blade, the user would push down the cap and give the razor a shake. All the variations featured blade stops to prevent the blade for sliding too far forward.
I can see this design being easily adapted for most of the narrow single edge blades we use today – the various Feathers, Schick’s Prolines, injector blades… even half a DE-blade would work. And the patents are long expired, so it’s a free for all.
The patents are all available for your reading pleasure at EspaceNet and Google Patents, or alternately over at razors.click: