coal trade bulletin - Clpdigital.org

FOUR DIFFERENT SIZES,
ranging in weight from 1% to 5 pounds I- 1 , to
2Vi kg.), but it is also made with two storage
battery cells connected in series, resulting for the
entire line in capacities ranging from four to 16
hours of life for one discharge and producing light
from 0.75 to 3 cp.
Besides this, a number of other modifications
have been developed, so that mines can be completely
equipped today with electric safety lamps,
wherever a permanent wiring in connection with
the lighting plant is impossible. Lamps are made
for rescue parties, cages, powder magazines, shaft
lighting, shaft inspection, loading places, blasting,
cars and locomotives (head and tail lamps),
etc.
The standard lamp, being of the "lighthouse"
type, distributes its light uniformly over the entire
surroundings. The modification known as
the "trip" lamp, has the incandescent lamp
mounted on one side combined with a reflector
concentrating the light rays in one direction.
This design is mostly used for inspection trips
and head and tail lamps for cars and locomotives.
It is made in the same capacities as the standard
lamp.
The "shaft" lamp is arranged with an adjustable
ami, on which the incandescent lamp is
mounted, so that the light can be sent in any desired
direction. It is made for from 8 to 24 c.p.
and from 7 to 12 hours of life for one charge.
Another type of "shaft" lamp, without an adjustable
arm, is made for 8 to 12 c.p. and for 15
and 10 hours of life for one charge.
The lamps so far described were designed to
take the place of the Davy safety lamp, which is
in use in gaseous mines all over the world. In
this country, however, the designer of electric
safety lamps is confronted with another problem
besides. In a great many mines the crews have
and still use "naked" lamps fastened to their
caps. On account of the strict enforcement of
the niining regulations in recent years, a great
many of these mines have been and will be compelled
to substitute safety lamps. It is only logical
that the men in these
MINES CLAMOR FOR A TYFE
of electric lamp which is as near identical as possible
with the present form of naked lamp. To
meet this demand, electric cap lamps have been
developed, the batteries of which are carried by
the miner on his belt and are connected to the
lamp by a well protected special flexible cord.
The principles of construction of the cap lamp
are identical with those of the hand lamp, besides
several new features which have been added. One
is that the incandescent lamp is mounted inside
a parabolic reflector, the opening of which is
THE COAL TRADE BULLETIN. 45
closed by a lens, instead of being covered with a
glass dome; another is a ball joint permitting the
miner to direct the light rays wherever they are
needed. The third feature is embodied in the
flexible conductors connecting battery and lamp.
In case of an accident, there is a possibility that
the two conductors may become short-circuited and
therefore red hot, eventually setting the insulation
afire, if they are made of copper or similar
material. To prevent this a special alloy has
been prepared, the melting point of which is considerably
below the temperature which is required
to ignite insulation or mine gas. Consequently,
if a short circuit should take place, the
conductors would melt and interrupt the circuit,
before there could be a possibility of danger.
From the foregoing description, it can be seen
that portable self-contained electric mine lamps
of this type have passed the first state of development,
if one considers that more than 1,000 are in
daily use in Europe, apparently producing excellent
results, there is no reason why the adoption
of electric mine lamps in this country should not
make rapid progress in the immediate future.
The question whether hand lamps or cap lamps,
or both, should be used, is a mere matter of detail,
which will adjust itself. European practice
has adopted the hand lamp exclusively; the sentiment
in this country, however, seems to be in
favor of the cap lamp. Men who continually
change their location in performing their duties
will prefer the cap lamp, leaving both hands free
for action; men who stay at work in the same
place most of the time will favor the hand lamp,
which can be set aside or hung up in the neighborhood,
relieving them from carrying unnecessary
weight.
When the crew leaves the mine, the lamps have
to be delivered to the lamp room for recharging
and cleaning. For this purpose the magneticlock
has to be opened, so that the battery can be
removed from the housing and placed on the
charging rack. The unlocking is accomplished
by pushing the
LAMP LOCK AGAINST THE POLE PIECES
of an electromagnet, which lifts the soft Iron pin
holding the upper and lower parts of the housing
together.
Special charging racks have been designed to
receive the batteries. The rack is intended for
80 cells connected in two series of 40 each. Each
circuit is equipped with a switch, ammeter and
rheostat, so that the operator can determine the
status of the charge at any time. The rheostats
are provided with a surplus of resistance, so that
less than 40 cells in a series can be charged, if
necessary. A portable voltmeter with a capacity
of about three volts is provided to take the volt-