Abstract
In automatic machinery the movements of the various bodies are usually obtained from the motion of a follower compelled by a driver. The driver is usually assumed to rotate at a uniform speed and the follower is given some definite motion, ordinarily a definite rotation. When the follower motion is to be a rotation at uniform speed, the driver and follower are usually connected by ordinary circular gears. When the follower motion is to be a rotation of nonuniform speed, elliptical gears are sometimes used. When the follower is to move in a more complicated manner, all kinds of devices, such as cams or planetary levers, are used. Very frequently the designer does not know of any means for producing the desired follower motion. Therefore, he is compelled to use an undesirable motion which he knows how to produce, and abandons what he considers the best.
This article discusses rollcurve gears. It shows that by using such gears, the follower can be given practically any desired motion, thereby enabling the designer to produce the follower motion desired and obtain the best condition in the new machine. The article first illustrates actual rollcurve gears installed and in use on actual machines. It discusses their durability and applicability, and gives a short history of some of them. This is to assure anyone that these gears are reliable and that their production is practical.
The article next shows the production of the “speedgraf,” which is a standard method developed by the author to make the desired method perfectly definite. It is then shown how to convert the speedgraf into rollcurves which may then be drawn and tested on the drawing board. The rollcurves can then be used to obtain patterns for the gear blanks. These gear blanks then have the teeth cut into them, converting them into a pair of gears. When the driver moves at uniform speed, the follower moves in the desired motion. The result is positive and reliable.
Certain features that occur in connection with the rollcurve gears are explained. Also, to show the broad applicability of the gears, a few speedgrafs, for which gears have already been made, are shown and are commented upon.
