Part 17

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.”

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.

The means used to produce the power in the carrying-lever actuating springs, or best termed carrying springs, was through the turning of an envolute cam attached to the lower order numeral wheels, which, acting upon an arm of the carrying levers, forced them away from the wheels, and thus tensioned the carrying springs. The cam and lever is best shown in Fig. 7, page 130.

The timing of the delivery of the carry, as the numeral wheel passed from nine to zero, was brought about by the high point of the cam passing from under the arm of the carrying lever, which, when released, allowed the carrying springs to act and ratchet the higher wheel forward a tenth of a revolution.

This form of carrying action had a peculiarity of reaching a certain set tension when three wheels were employed, so that for all the wheels employed in greater numbers no higher tension was required and no lower tension could be attained. Another feature about this type of transfer device was the fact that to get the set tension as low as possible required that at least eight-tenths of the rotation of the lower wheel should be utilized in camming back the carrying lever or storing the power for the carry. A decrease in this timing meant an increase in the resistance offered in turning the lower wheel by the steeper incline of the cam, and when the wheel in turn received a carry, the increase of resistance increased the work of carrying, and so on by a geometric ratio.

In a recent patent suit, a physical test was made as high as three orders with a one-point cam; that is, a cam operating to store power during a one-tenth rotation of the lower wheel (not an uncommon combination as shown in patents that have been issued), and it was found that by the time the third carrying was reached the springs were so large and powerful that to turn the next wheel would require a railway-coach spring, and that under the same ratio a fifty-four ton hydraulic press would be required to depress the keys in the eighth order.

The foregoing illustration of the idiosyncrasies of mechanical construction offer a good example of why perpetual motion is not possible, viz., that no mechanism was ever made that would not consume a certain per cent of the power delivered to it, through friction and inertia. Of course, expert knowledge of the physical laws of mechanics allow of the application of force along the lines of least resistance, and it is with this feature that the new improvements in the Comptometer have to do.

It would seem that the old carrying means could not be improved upon under the circumstances, but Felt conceived a means which gave more time for the storage of power for the carry and all kinds of time for its delivery, which decreased the power required for carrying by a very large per cent. The means he devised was a motor-type of carrying mechanism that could receive and deliver power at the same time without interference. Thus the full revolution of the lower wheel could be utilized in storage and the same amount of time could be consumed in delivery if necessary, but it was never required.

This tremendous reduction in power required to turn the higher wheel in a carrying operation so decreased the resistance of turning the numeral wheels that the former means used to control the wheels during actuation was unsafe; that is, the old method of jabbing the stop detent between the pins of the numeral wheel to stop it was not dependable with the increased speed that the numeral wheels revolved, under the reduced resistance.

Again, the feature of time was at issue. The wheels could be whirled at tremendous speed or at a very slow speed. A sudden jab at a key with the finger sent the numeral wheels kiting ahead of the rest of the mechanism so that the detent could not be depended upon to enter between the right pins, which would result in erroneous calculation.

In the new machine, we find that to overcome this unevenness of action, Felt reversed the ratchet action of the denomination actuators, so that no wheel action occurred on their down-stroke under the action of the keys, but on the upstroke of the actuators the numeral wheels were turned by the power of the actuator springs stored by the key depression, thus giving an even set rotating action that could not be forced and that could be controlled by a stop detent.

As the timing of this stop-action was coincident with the stopping of the actuators on their upstroke, the actuator was used to perform this function in combination with a detent device that could be released from the wheel independent of the actuators to allow a carry to be delivered.

A feature worthy of note connected with this change is displayed in the method in which Felt overcame the timing of the stop action of the actuators in the downward action they received from the keys, which would have been as hard to control as it was to control the wheels under direct key action.

The scheme he devised gave more than double the time to perform the function of intercepting the lightning action with which the actuators moved under a quick key-stroke. The scheme shows a dual alternating stop-action constructed by the use of two stops acting at different levels and co-acting alternately with five equi-spaced stop-shoulders on the front end of the actuators, which were also arranged in different levels.

The two stops were actuated by the keys in a similar manner to the single stop which co-operated with the pins of the wheel in the old “Comptometer,” except that the odd keys operated one stop while the even keys operated the other.

Thus in the new “Comptometer” the (1) key acted to throw the higher level stop into the path of the lowest stop-shoulder on the actuator, and the (2) key acted to throw the lower level stop into the path of the same stop-shoulder on the actuator. In the same manner the (3) and (4) keys caused the odd and even stops to engage the next higher stop-shoulder on the actuator and so on with the rest of the keys.

As the spacing was doubled by the use of but five stop-shoulders, the stops were allowed double the time for entry between the stop-shoulders plus the space that the pin occupied as compared with former method, which was considerably more than double the time allowed for the same function in the old machine.

Besides the redistribution of mechanical functions, another very noteworthy feature is found in these patents which, in the specific means disclosed, constituted another distribution of time for mechanical action. This in the capacity of the machine was what has become commercially known as the “Duplex” feature.

In the old “Comptometer” it was necessary to operate the keys alternately, as a carry from one order to a higher order might be taking place and thus be lost in the action of the higher order wheel while rotating under key-action.

In the machine of the later patents the carry was delayed while the higher-order wheel was under key-action. The construction shown consisted of a latch operated by the actuators, which, when the actuator was depressed, latched up the delivery end of the motor carrying-device so that a carry due to take place at that time would be intercepted until the actuator returned to normal again, at which time the carrying motor device was again free to deliver the carry. This feature allowed the striking of keys in several or all the orders simultaneously, alternately, or any way the operator pleased, which was a great improvement in speedy operativeness.

While the genus of this elastic keyboard invention consisted of control of the carry by the next higher actuator, the specie of the generic feature shown was the delayed control. The first production of this generic feature of control of the carry by the next higher actuator that gave the elastic keyboard-action is shown in the two Felt patents.

It may be argued that this new keyboard feature was simultaneity of key-action and that simultaneity of keyboard-action was old. True it was old, but the flexible simultaneity was new and depended upon individuality of ordinal control for its creation, and Felt created the ordinal control that gave the flexible keyboard.

Simultaneity of key-action was old in key-driven cash registers; such invention as had been disclosed in this line, however, would defeat the usefulness of simultaneity in a key-driven calculator. The useful feature of depressing keys in several orders at once in a key-driven calculating machine lay only in the increased speed of manipulation that it could offer.