Backing-up the shells with the metal base, i. e., casting, is done
automatically by The Rapid Electrotype Company.
A rotary casting-table with a capacity of ten pans revolves around its
axis on a plane that brings each pan immediately below a spout through
which the required metal is automatically flowed from the bottom of
the metal pot on the tinned shell placed therein. When the required
metal backing has been flowed, the table turns to bring the next pan
with its shell under the metal-spout. The amount of metal flowed is
exactly regulated. As the casting table completes a circuit, the first
shell backed up has cooled so that it can be removed to the scrubbing
machine.
This method, of course, eliminates the hand-ladling of hot metal from
the metal-pot to the casting-table, as is the ordinary practice, and
obviates any possibility of the oxidized metal or dross on the surface
getting into the casts, besides effecting a marked economy in time and
handling. In addition, it casts the plates flat, thereby eliminating
about 75 per cent of the finishing, which, of course, means a better
printing plate. Three of these machines are used.
The Rapid Electrotype Company developed and built these
casting-machines in its own machine shop and owns the patents covering
them.