Cam and lever carrying mechanism
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.
One-point carrying cam impossible
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.
Felt’s improved method of carrying
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.