A endless screw is a cylinder comprising a helicoid groove (sometimes several), making it resemble a threaded Tige. Associated with a pinion, it constitutes a left Engrenage (the two axes are not in the same plan), in which it behaves like a wheel with a tooth (or more, according to the number of grooves). One calls also sometimes this system coils and endless screw.

One sometimes wrongly gives the name of endless screw to the Archimedes' screw, but the latter is connected with the Hélice S.

Features

The screw is generally interdependent of the axis which supports it (connection supplements), the groove being sometimes realized on the tree even. But one finds examples of use where the screw has a degree of freedom in translation on its axis (fluted shaft, with flat part.) as of the examples of temporary connection (the screw is “disengageable”).

The formed gears are generally irreversible (the screw can actuate the pinion, but not the opposite).

Contrary in the majority of the other systems of gears where the drive is obtained by bearing of a profile of tooth on the other, here, the drive is obtained by slip , which results in characteristics of output and wear particular to this system.

Case of uses

This system is very much used whenever a very great reduction is sought, or when the irreversibility of the system ensures a correct operation. It is the case of the keys of tension of the cords of unquestionable musical instrument like the Guitare, or of the wiring of the Ascenseur S.

Certain systems use sometimes the irreversibility to produce a translation on the axis of the screw starting from the rotation of the pinion; the screw behaves then like a Crémaillère. Security systems, of self-regulation or similar, use this possibility, supplemented by some springs, of the linkage and/or the electrical contacts.

History

(To be filled)

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