Already a certain number of connecting mechanisms with fast unlocking and with or without ejection are known, whereof the motive power is generally supplied by a pyrotechnic system belonging to the mechanism or located outside the latter. Thus, the embodiment of FIGS. 2A and 2B of FR-A-2 616 857 describes a connecting mechanism with fast unlocking and without ejection controlled by a pyrotechnic system belonging to the mechanism.
This mechanism comprises a rod entirely located within a cylinder belonging to a first of the said subassemblies. One of the ends of the said rod has a thread onto which is normally engaged a segmented nut surrounded by a rigid ring connected to an annular piston arranged coaxially around the rod and able to slide within the cylinder. The segmented nut bears on a bush screwed into a part, which bears on the second subassembly. The opposite end of the rod also has a thread onto which is screwed a nut, which bears on an abutment washer mounted within the cylinder. This nut makes it possible to apply the two subassemblies to one another with a given prestress via the rod and the segmented nut, prior to the closing of the cylinder.
In this mechanism, the unlocking or disengaging of the two subassemblies is obtained by means of a pyrotechnic system placed in a chamber formed between the cylinder and the face of the piston turned towards the second subassembly. The released combustion gases bring about the displacement of the piston and the rigid ring which it supports on moving away from the second subassembly and thus releases the segmented nut from the thread formed at the corresponding end of the rod.
The mechanism illustrated in this document, as also in other documents including FR-A-2 616 856, U.S. Pat. No. 3,597,919 and U.S. Pat. No. 3,196,745, is in particular characterized by a particularly complicated and difficult fitting and by a not very precise checking of the tightening or locking tension.
Thus, in FR-A-2 616 857, the connecting mechanism is fixed to the second subassembly by a nut, which it is very difficult to manipulate when there is reduced accessibility between the two parts. Therefore the reliability of the fixture is also reduced. Moreover, the tightening tension is applied by screwing a nut onto the threaded end of the rod opposite to the second part in such a way that said tension can only be controlled by measuring the torque applied to the said nut. Due to the fact that this torque measurement integrates the different frictions, the tension can only be checked with a very limited accuracy of approximately .+-.30%.