Patents: Mechanism for various uses

In 1977, Frenchmen Alain Dagonat and Jacques Drailler-Duffert applied for a patent for a mechanism, with which the sheath of a knife could be folded to form the handle – or the handle unfolded to form the sheath. The patent was granted under number 2397 270.
 
The description is as follows (translated from French):
“The mechanism comprises an articulated sheath which can be bent and folded, and an elongated flattened element which can be used as a knife, and this element is pivotally connected by one of its ends to the sheath inside which it is placed, while its opposite end can slide through a retaining and guiding member integral with the sheath when the latter is folded or unfolded, so as to extend the said element outside the sheath or, on the contrary, to retract it inside the latter.
According to a mode of implementation of the mechanism according to the invention, the articulated scabbard comprises a first pair of arms articulated at one of their ends on the aforementioned retaining member, so as to be able to pivot both in the same plane, and on the other hand, at their opposite ends, on a second pair of arms, which are complementarily mounted rotatably on the terminal part of the elongated flattened element, opposite the said retaining and guiding member.
Accordingly, if pulls are exerted in opposite directions on the joints between the said two pairs of arms, the flattened elongate member connected to the second pair of arms is caused to slide in one direction or the other, depending on the direction of the pulls exerted. Thus, when the flattened element is first retracted into the sheath, if the joints between the arms are pulled [outwards], the two pairs of arms pivot relative to each other and the flattened element, for example a cutting blade, slides through the retainer.
Once this slide is complete, the flattened element is completely removed from the sleeve and the sleeve can be closed again. The sheath then forms the handle of a knife, penknife or letter opener.”
 
While this may sound rather complicated, the drawings clearly show how the mechanism works. The arms at both sides of the blade function as joints which can be opened or closed. The arms are fixed to the rear of the blade at one end, and connected to the guiding member (3) at the other end. They operate together. If one arm moves, so does the other.
 

The drawings from French patent 2397 270.