An arm or pin P, fixed in and extending from the left side of the carrying lever and through a hole in the detent lever, acted to withdraw the detent lever from its locking engagement with the numeral wheel as the carrying lever reached the extreme point of retraction; thus the wheel to be carried was unlocked.
Pivoted to the side of the detent lever is a catch O. This catch or latch is so arranged as to hook on to a cross-rod q, especially constructed to co-act with the catch and hold the detent lever against immediate relocking of the numeral wheel as the carrying lever and pawl act in a carrying motion. The latch has a tail or arm p, which co-acts with the pin P on the carrying lever in such a way as to release the latch as the carrying lever finishes its carrying function.
Thus the detent lever N is again free to engage one of the control or stop-pins T to stop and lock the carried numeral wheel when the carrying lever and pawl, through the action of the spring stored in the carrying, has moved the wheel the proper distance.
Bill for First Manufacturing Tools of the “Comptometer”
A lot of functions to take place in ¹/₁₆₅ of a second, but it worked. The timing of the stop and locking detents, of course, was one of the finest features.
Early Comptometer
The normal engagement of the carrying detent, it may be understood, would prevent the movement of the wheel by key action or prime actuation, but the patent shows how Felt overcame this.
The carrying stop and locking detent lever N is provided with a cam-arm or pin N, which was arranged to co-act with the cam disc E ([see Fig. 1]), fast to the prime actuating pinion E. The cam surface was short and performed its function during a short lost motion arranged to take place before the ratchet pawl would pick up and move the numeral wheel under key actuation.