What a rapid change gear device is. The old pin wheel and lantern pinion . device. The first patent for a rapid change gear device. The inventors' claims. Classification of rapid change gear devices. The inventors of rapid change gear devices. Paulson's originality. "Change gear devices" by the author. Le Blond's quick change gear device. The Springfield rapid change gear attachment. Criticism of the device. The Bradford rapid change gear device. Judd's quick change gear device. Newton's quick change gear device. The Flather quick change gear device.

By the term "rapid change gear" we understand that the mechanism so denominated is one capable of performing all the functions of the former change-gears but without the necessity for exchanging one gear for another or one set of gears for another, that is, without removing a gear.

These gears were formerly called "change-gears" because they were subject to change for each new operation of the lathe in which their use was essential.

In the old-fashioned " chain lathe," having a lead screw driven by "pin wheels" and "lantern pinions," which is illustrated and described in Chapter II (The Development Of The Lathe Since The Introduction Of Screw Threads), it will be seen that the builder had provided for changing the pitch of the thread to be cut by changing only one gear. This was about the year 1830. In 1882, George A. Gray, Jr., obtained a patent, No. 252,760, for a change gear arrangement whose principal feature was that only one gear need be removed and changed to cut any of the usual threads.

The first effort in the direction of devising a rapid change gear mechanism was, so far as the United States Patent Office is concerned, made by Edward Bancroft and William Sellers, who on February 7, 1854, obtained Patent No. 10,491, for a device consisting of two cones of gears intermeshing, one set fast to the shaft and the other set adapted to fix any single gear to the shaft by means of a pin passing through a fixed flange and into a hole in a gear or the hub of a gear; the set being made with telescoping hubs, the ends of all coming against the fixed plate. It is interesting, in the light of present developments in this line, to read the first claim of their patent, so prophetic of the developments to come, as follows: "The method of varying the motions of the mandrel or screw-shaft, or leader, by means of two series of wheels of different diameters, and all of the wheels of one series being connected and turning together, and imparting motion to all the wheels of the second series with different degrees of velocity, substantially as described."

While a number of the later inventors claimed these same features of the mechanism and apparently considered themselves as the original inventors, it will be readily seen that the mechanical ideas involved in this invention anticipated their claims by a goodly number of years.

In considering the question of rapid change gear devices it will be well to adopt some classification based upon their design or structural differences. We may then illustrate and describe these general classes by well-known or readily understood examples, whereby all devices of this kind may be more easily understood and their special features appreciated at their proper value.

Thus we may classify these devices in their general groups as follows:

First, those in which the gears representing the former change-gears are all placed on one shaft;

Second, those in which these gears were placed on several shafts or studs, and arranged in a circle; and Third, those in which neither of these arrangements existed.

Of the first class, using what has become well known as the "cone of gears," the most notable inventors are Bancroft and Sellers, Humphreys, Miles, Riley, Hyde, Joseph Flather, Peter and William Shellenback, Norton, William Shellenback, Herbert L. Flather, Ernest J Flather, Wheeler, Isler, Le Blond, Johnson and Wood.

Of this number it was usual to use one or two cones of gears, but this number did not seem to satisfy the ambition of some of the inventors, since one of them, Isler, used no less than six cones of gears. Usually these cones of gears were located under the head or in front of it, but sometimes within the bed. But Johnson, apparently being determined to have a cone of gears somewhere, places them on a loose sleeve running on the main spindle. It remained for Wheeler to find a new location for his cone of gears by placing them in the apron.

Among all these devices, as in other spheres of mechanical effort, the inventors produced mechanisms ranging all the way from "good and bad, to indifferent."

Of the second class, that is, those who located the gears on short shafts arranged in a circle, the first to devise this arrangement was Edward Flather, who obtained patent No. 536,615, on April 2, 1895, and was later followed by Benj. F. Burdick, William L. Shellenback, Edward A. Muller, and Herman R. Isler, in the order named, the latter's last patent having been granted in 1902.

Of the exceptional examples, included in class third, the most notable one is the invention of Carl J. Paulson, who adopted the very original method of making a series of rings fitting inside each other, cutting gear teeth on a portion of the face of each and arranging the proper mechanism to thrust out from its fellows, the gear having the desired number of teeth that might be needed. This was probably the most original of all the methods employed up to the present time.

While this device was not a commercial success, it had a counterpart and was the prototype of a quite similar arrangement consisting of two sets of sleeves in line with each other and having teeth cut on their outer surfaces precisely as Paulson had done, and arranging them and their connecting gears in a more practical and operative combination.

An interesting review might be written and illustrated of the various patented change gear mechanisms that have been invented since the days of Bancroft and Sellers, but it is hardly within the scope of this work to give the necessary space to this portion of lathe description. If the reader desires to pursue the subject in detail and to have dates, patent numbers, and illustrations from the drawings in the patent office, he is referred to a book by the author entitled "Change Gear Devices," wherein all this data is presented in detail.