[Fig. 28] gives a clear demonstration of the connection of a selecting needle, c, to the key-wire, f by means of the lever, e, movable around the fixed pin, d. Each key (D, [Fig. 27],) consists of a cylindrical plug of metal, which, projecting over a punch, forms an abutment to keep that punch from rising, but if withdrawn, allows the punch to rise without resistance.
Fig. 28.
Fig. 29.
A step arrangement of the punches and keys is adopted; that is, the upper ends of the outer rows of punches are highest and the punches in the several rows decrease in height till the inner row is reached, where the punches are the lowest. Hence, the keys of the upper rows, which correspond to the outer rows of punches, are carried over the inner rows of punches and terminate over the punches in the outer rows.
Normally, all the keys are above the punches, and all would punch when the die ascends, but when a pattern card is carried by the pattern cylinder against the ends of the selecting needles, certain needles are moved and produce a reverse movement of the corresponding key-wires, and draws certain keys out of reach of their punches; no resistance being offered to the upward movement of such punches, they do not perforate the cards.