There is one feature about the machine of these two divisional patents which stands out very prominently to those acquainted with the fine points of the physical laws of mechanics. It is a feature that was not printed into the specifications. It may be found only in the time allowed for the mechanical movements to take place, which shows that theoretical reasoning was the foundation for the distribution of the functions in the machine of these patents into increments of time, and that the arrangement of mechanism was especially designed to carry out this primary theoretical reasoning. While it is obvious that such procedure must accompany successful invention of mechanism, it is seldom that we find such fineness displayed as may be found in the timing of the mechanical functions of the later Comptometer.
The force of the above statement may be realized by study of the mechanical motions of the old Comptometer and then trying to improve on them to attain greater speed of operation. Such a possibility would depend on more rapid key-strokes.
According to the physical laws of force and motion, to attain greater speed of action demanded a decrease in resistance. Thus, less key resistance must be attained to increase speed of operation.
Felt probably knew from experience that lighter key action could not be had by juggling with springs or by polished surfaces. He was also aware of the infinitesimal space of time allotted to each function, as the parts of the mechanism flew about in the merry dance they performed in whirling the numeral wheels around while under the manipulation of an expert operator. He couldn’t see the parts work—he could only theorize when there was trouble; thus he alone knew the difficulties to be met in attempting to make a more rapid calculator.
To describe the mechanism of the new machine from drawings of these patents would leave the reader still in the dark. What was really accomplished can best be understood by reference to the mechanical action in the old Comptometer.
In order that the reader may understand the significance of what was accomplished, let him consider this fact; that the key action of the old “Comptometer” measured as high as eighty-six ounces to a key depression, while in the new machine made under the two named later patents the key depression was reduced to but twenty-two ounces maximum, or a little over a fourth of the power required to operate the keys of the old “Comptometer.”
Power consumed by old carrying method
Facts show that a very large part of the resistance met with in the key depression of the old machine was caused by the high tension of the springs which performed the carrying. This high tension was necessary on account of the extremely small fraction of a second allowed for the performance of their function of supplying the power that turned the higher wheel in carrying.
By referring to the description of the inoperative features of the Hill machine ([page 25]) a parallel example of the time for the carry of the tens in the old Comptometer may be found, showing that but a ¹/₁₆₅ of a second was the allowance.
The carrying means employed in the old Comptometer consisted of levers with dogs or pawls hinged on their free ends, which co-acted with the ten pins of the higher numeral wheels to ratchet them forward a step at a time. The power for supplying such ratcheting action, in the delivery of a carry, was produced in a spring attached to the carrying-lever to actuate it.