According to the specification, Ludlum evidently had the idea that he could stop the adding gear H, while under the high rate of speed it would receive from a quick depression of a key, by jabbing the detent J between the fine spacing of the gear teeth shown in his drawing. But to those familiar with the possibility of such stop devices, its inoperativeness will be obvious; not that the principle properly applied would not work, for its application by Felt prior to that of Ludlum proved the possibilities of this method of gauging additive actuation.
The detent lever J, [as shown in the drawings], is operated by the hinged plate D, through action of the key levers, as any one of them are depressed.
Under depression of a key, the hinged plate D, being carried down with it, engages the arm J³ of the detent and throws the tooth at its upper end into the teeth of the gear H.
The timing of the entry of the tooth of the detent is supposed to be gauged to enter the right tooth, but as the action of these parts is fast, slow or medium at the will of the operator, considerable time must be allowed for variation in the entry of the detent tooth, which requires space, as certain parts will fly ahead under the sudden impact they may receive from a quick stroke, where they would not under a slow stroke, but no allowance was provided for such contingency.
The means provided for the carry of the tens consist of the gears G⁹, meshing with the numeral wheel gears and the single gear tooth g⁹, attached to it, which, at each revolution of the lower wheel, as it passes from 9 to 0, engages the gear of the numeral wheel of higher denomination and was supposed to turn the higher gear one-tenth of a revolution, thus registering one greater.
On account of the Gears G⁹, of one order and the gear tooth g⁹, of another order operating on the same numeral wheel gear, the transfer gears are arranged alternately on separate shafts, one at the side and one below the numeral wheels.
Ludlum machine inoperative
The mechanical scheme disclosed in the Ludlum patent, to the unsophisticated may seem to be operative. But to those familiar with the Art of key-driven adding mechanism it will at once be obvious that even if the typewriter feature was constructed properly the possibility of correctly adding the items as they were printed was absolutely impossible.
Laying aside several other features of inoperativeness, obvious to those who know such mechanism, the reader, although not versed in the Art of key-driven adding mechanism, will observe from the preceding chapter, that the means provided for transferring the tens without any control for the numeral wheels against over-rotation, would make correct addition impossible.
The drawings and specification of the Ludlum patent disclose a mere dream and show that they were not copied from the make-up of an operative machine.