How to technically understand involute gears

dicembre 21, 2022
Straight-toothed and involute gears are certainly the ones that are mostly used in the projects that are entrusted to us every day. The former are used to transmit power between parallel shafts. While the latter are used when the motion between two wheels must be transmitted in a regular manner and without dragging.

What is envelope?

As you know, our goal here is to make mechanics simple by providing useful information to the sales department that is preparing to choose its own partner for the realization of company projects. Well, I would start right from the title of the paragraph because the gears are really all about the envelope. Both technically and practically, gears are created by the intersection of plane curves with a tangent at at least one point. In the case of the involute the realization of the motion is based on two circles defined as primitive. Let's assume that a tangent meets the latter at a point, and with the movement of the circumference and the rolling of the tangent on it, it gives rise to the enveloping process. The active profile of the generated tooth is an involute of a circle which cannot extend inside the base circumference. During the process, a connection is also created at the base of the tooth between the profile and the circumference of the gear, however this has no substantial function for the transmission of motion.

However, the real fortune of involute wheels is the principle according to which two involute profiles of a circle are conjugate profiles even if the relative motion takes place with primitives different from those used during the generation by envelope. This is why the involute has the characteristic of meshing correctly even when the working primitive does not coincide with the cutting one.

To conclude, you will understand that knowing how to apply involute profile wheels correctly can only lead to enormous advantages for your projects. You will have a more solid, economical and quick kinematic system to create.

To realize your project together, write to us at:



GSI Ingranaggi S.r.l.
Via S. Quasimodo, 9 - 42023
Cadelbosco Sopra (RE)

Tel. +39 0522.917750 / 917365

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