Page 117 - My FlipBook

Figs. i_'4 and 125 sliow the operation of the magnetic cnt-off switch.
Fig. 124A shows the switch closed and Fig 125C shows it after the cir-
cuit is opened. The terminals of switch are protected with heavy plati-
num contacts and the breaking of the circuit is accomplished through
the magnet E, in an instantaneous manner. D shows the wires leading
from main current to the terminals of the magnetic cut-ofif at A and B.
F shows the steel bar, which, when in contact with A, completes the
circuit.
Fig. 126 shows the Hammond pyrometer furnace and Fig 128 shows
the pyrometer designed by Dr. Marshall Weaver, of Cleveland, and

Fig. 127.

attached to the Pelton furnace. This pyrometer has an advantage that it
may be attached to any furnace. These pyrometers are constructed with
the thermo-couple system. While these instruments record both tem-
perature and resistance on the face of the milli-ammeter. the temperature
scale is of no special value in fusing the porcelain. It must be borne in
mind that porcelain has no definite fusing point, as a piece of metal has,
and the mere fact of heating the furnace up to the degree of heat indi-
cated on the scale for the fusing of a given porcelain will not neces-
sarily cause the porcelain to fuse. Time is a large factor in the fusing
of porcelain, and unless sufficient time is given the porcelain will not
be properly fused. If, on the other hand, too much time is consumed
when the porcelain is heated to the point of high biscuit, it will become
over-fused. It is just as wellto fuse the porcelain at a given point of
resistance on the scale as to fuse it at a given temperature point.

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