OF
A MACHINE
For Engraving the Cylinders of Calico Printers by Power.
The principle of this Machine is as follows: When two equal toothed wheels a b (see [Plate 39], [fig. 1],) geer together, a given tooth of either wheel visits a given tooth of the other, once every revolution: and will continue to do so as long as the wheels continue to revolve. But, when the wheels are unequal, as A B [fig. 2], then different teeth in one wheel, visit the same tooth in the other, until, after a certain number of turns, the revolutions of both wheels have a common divisor. My System of [equable Geering] (see Part 2d. of this Work,) justified me in applying this principle to Engraving; and is the chief foundation of the Machine now to be described: for this System, as we have seen, communicates the very same kind of motion that two touching cylindrical surfaces would impart to each other by mere contact. The punch, therefore, will not scrape the cylinder, when brought into the desired places of contact by the aforesaid process. Let us suppose then, ([fig. 2]) that the wheels A B, are to each other in diameter and teeth, as the numbers 2 to 3; and that a given tooth in the wheel A, (which we have pointed out by a dot) now touches a certain spot on the wheel B, marked by a dot like the former. When, now, this spot on the wheel B has made one revolution, the wheel A will have made 3⁄2, or 11⁄2 revolution: and the tooth first mentioned, will be found diametrically opposite to the place where it touched the spot first adverted to. And if, further, we give the wheel B another turn, the wheel A will again have made 11⁄2 turn; and the tooth first mentioned will again visit the spot with which it coincided at the beginning.
| To recapitulate— | The | 1st. | turn of B gave | 1.5 | turns of A, and |
| The | 2d. | turn of B gave | 1.5 | turns of A: | |
| Sum. | 2 | turns of B & | 3.0 | turns of A:— | |
which numbers are thus in the inverse ratio of the number of teeth in the wheels respectively.
