There are several methods available for
operating the pins. The rising-holder bell may be made to actuate a train
of wheels which terminate in a disc revolving horizontally on a vertical
axis somewhere just below the catches; and this wheel may bear an
eccentric pin which hits each catch as it rotates. Alternatively the
carbide boxes may be made to revolve horizontally on a vertical axis by
the movements of the bell communicated through a clutch; and thus each
box in succession may arrive at a certain position where the catch is
knocked aside by a fixed pin. The boxes, again, may revolve vertically on
a horizontal axis somewhat like a water-wheel, each box having its bottom
opened, or, by a different system of construction, being bodily upset,
when it arrives at the bottom of its circular path. In no case, however,
are the carbide receptacles carried by the bell, which is a totally
distinct part of the apparatus; and therefore in comparison with M, the
pressure given by the bell is much more uniform. Nevertheless, if the
system of carbide boxes moves at all, it becomes easier to move by
decrease in weight and consequent diminution in friction as the total
charge is exhausted; and accordingly the bell has less work to do during
the later stages of its operation.
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