Improvements in Electric Arc Lamps.
Year: 1898

page_text: Date of Application, 16th May, 1898-Accepted, 2nd July, 1898
COMPLETE SPECIFICATION.
Improvements in Electric Arc Lamps.
We, SIEMENS BROTHERS & Co. LIMITED, of 12, Queen Anne's Gate, West-
minster, S.W., Electrical Engineers, do hereby declare the nature of this inven-
tion (which has been communicated to us from abroad by Siemens & Halske
Aktien-Gesellschaft, of Markgrafen Strasse No. 94, Berlin, S.W., Electrical
Engineers) and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement: —
In electric arc lamps, in many constructions at present in use in which the
are has a fixed position the oscillating frame carrying the actuating gear employed
in many constructions has to carry both carbon holders with their carbons, the
arrangement being generally such that the pivots of the frame are situated
between the two parts of the device carrying the carbon holders, such as the chain,
cord or band, so that the upper carbon holder tends to turn the frame in one
direction and the lower carbon holder tends to turn it in the other direction.
Such an arrangement is shewn in the part side view at Figure 1 of the accom-
panying drawing, Figure 2 shewing the complete lamp to a smaller scale.
In this arrangement a cord pulley A Figure 1 is provided, in the groove of
which is laid a copper cord B; the right hand end of this cord passes down to
and carries the upper carbon holder J, while the left hand end carries the lower
carbon holder K Figure 2.
The pulley A is mounted with its axis in a frame C and is engaged with
toothed gearing also carried by the frame, the last wheel D) of which, in the
middle or normal position of the frame, is prevented from rotating by a spring
pawl E.
The frame C rocks upon the pivots F and carries on the right hand end the
armature or core G of an electromagnet or solenoid which is excited in the
known manner either by the main current or by a shunt current or by a com-
bination of both. When, on the increase of the arc, the armature of the electro-
magnet sinks, the frame C will turn in the direction of the hands of a clock,
and the last wheel I will at a definite position of the frame, be liberated from
the pawl E so that the pulley A can turn and allow the carbon holders to
approach each other.
With this arrangement the frame C has to carry the, weight of both carbon
holders, with their carbons, but irrespective of the action of the magnetic forces
and of the preponderance of the side of the frame that carries the armature (if
any) the frame is only subject to a turning action due to the excess of weight of
the upper carbon holder over that of the lower one. A comparatively weak
spring H is therefore sufficient to maintain the frame in equilibrio.
It has been found that this spring power is too weak to insure the accurate
medium position of the frame, in particular as the pivots thereof are loaded with
the weight of the two carbon holders in addition to that of the frame itself.
This load produces considerable frictional resistance, in proportion to which the
spring H is too weak.

page_text: According to the present invention this defect is obviated by making the
said spring stronger and counteracting the excessive strength by means of a
second spring arranged on the opposite side of the pivots and acting on the frame
in the opposite direction to the first spring so as to relieve the pivots of the frame
of pressure and friction. H2 on Figure 1 shews an additional spring arranged
to operate in the above described manner, that is to say, it acts upon the frame C
in the contrary direction to the spring H¹ and is so proportioned as to counter-
balance the excess of strength of the latter beyond that required to maintain
the frame in equilibrio.
The arrangement of both springs is preferably such that they exert a vertical
upward pull upon the frame C. By this opposing action of the two springs it
will be seen that if their strength be duly proportioned to the load on the frame,
the pivots of the latter can be more or less entirely relieved of the frictional con-
tact with their bearings that would otherwise be caused by such load.
Thus by means of the above described improvement, the action of the lamp
will be rendered much more sensitive, and it will be brought very accurately to
the middle position, as the opposing forces required for such adjustment can be
made comparatively great.
Instead of employing only two such springs, a larger number may be employed.
The total action should always be such that the one set of springs tends to pro-
duce a direction of rotation of the frame C contrary to that which the other
set tends to impart, and that the resulting force of all the springs relieves the
bearings of the frame of pressure.
The considerable degree of sensitiveness which is obtained for the regulation of
the lamp by the above described means, causes however, another inconvenience,
which requires to be obviated by a special appliance.
Namely, on putting the lamp into circuit, the separation of the carbons is
effected so rapidly that the extinction of the arc may be caused thereby as soon
as it is formed.
This is due to the fact that with the carbons in a cold condition (at any rate
if these have already been in use) a much greater pressure is required than the
nominal one for permanently maintaining the arc. The separation of the carbons
should therefore take place quite gradually, and for this purpose the usual brake
appliances and air pumps are made use of.
For preventing such rapid separation of the carbons an air pump L the piston
of which is provided with a valve, the piston rod being pressed upon by an
adjustable screw M, arranged on the end of the frame, when the latter rises to
a certain extent beyond its middle position and which piston opposes a strong
resistance to the rising of the frame and upper carbon holder, such as can only
be overcome very gradually. On the other hand the downward motion of the
frame is not hindered in any way, as it is not attached to the piston of the air
pump, which can also readily descend by gravity, as the valve of the piston will
then open.
The downward stroke of the pump piston is limited in such manner that in
its lowest position it is sufficiently removed from the frame C when this is in
the position for the normal working of the lamp, to enable the frame to oscillate
freely to the required extent for the purpose of regulation, without coming in
contact with the pump. This pump therefore enables the lamp to work in a
perfect manner even with a very small working pressure.
It will be obvious that the arrangement of the rocking frame and mechanism
as also the general construction of the lamp can be variously modified for the
purpose of this invention, the arrangement shewn only serving as an example;
it is also immaterial whether the lamp be arranged as a differential lamp, as a
shunt circuit lamp, or as a main current lamp, and whether it be used with con-
tinuous or with alternating current and with electro magnets or solenoids.

page_text: Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed we declare that what we
claim is:-
1. In an electric arc lamp for continuous c: alternating current wherein the
two carbon holders are suspended from cord chain or band from a pulley or wheel
mounted on a rocking frame, suspending such frame by means of two springs or
two sets of springs. so arranged that while the one spring tends to turn the frame
in the opposite direction to the other spring, both springs or sets of springs have
the effect of counteracting the downward pressure exerted by the load on the
frame upon the bearings of its pivots, substantially as and for the purpose
described.
2. In an electric arc lamp such as is referred to in the First Claim, the use of
an air pump with valvular piston so arranged in connection with the rocking
fraine as to leave this perfect freedom of action when in the normal position of
working, but to oppose a considerable and slowly yielding resistance, when the
frame rises to a certain extent beyond the normal position its descent being
entirely unhindered thereby, substantially as described.
1
101
1900
ABEL & IMRAY,
Agents for the Applicants.