Improvements in Electric Arc Lamps and Current Regulators therefor.
Year: 1894

page_text: Date of Application, 4th July, 1894-4ccepted, 17th Nov., 1894.
COMPLETE SPECIFICATION.
Improvements in Electric Arc Lamps and Current Regulators
therefor.
We STEFAN DOUBRAVA, Ph. D., Engineer, and JOSEF DONAT, Engineer,
both of 71 Neugasse, Brünn, in the Province of Moravia, Austria, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
The object of the present invention is to provide a powerful magnetic system for
the direct regulating of electric arc lamps by means of a new co:ubination of
solenoids iron cores and shells or casings. The essential feature of the improvement
is the use of partially open magnetic systems.
As is well known a cylindrical iron core is drawn into the interior of a solenoid,
and, by changing the cross section of said iron core the curve of attraction can be
modified as desired. Both kinds of iron cores are used in the construction of
electric arc lamps and current regulators.
The attractive forces obtained in this way are however so slight that it is only
by operating on a large scale that sufficient sensitiveness can be given to, the
apparatus.
In our invention all these difficulties are removed by using cores, which are
hereinafter termed casing or shell cores.
Referring to Fig. 1 of the drawings, said casing or shell core consists of an iron
core which is inserted in a solenoid S. The iron core carries on one end a thick
iron plate i to which is fastened an iron casing or shell M. By this arrangement
of iron core, a magnetic system is formed, in which the lines of force run in their
longest course a, e, d, c, or a, e, a, f in the iron and in their shorter course ƒ b
ore in the air (see Fig. 2). The result of this is that they encounter the
surface a, b, of the core in a very concentrated condition and, in consequence,
produce a great repulsion which forces the casing or shell core strongly into the
interior of the solenoid. The attractive power exercised by a solenoid on a casing
or shell core is from two to fourfold greater than in the case of an ordinary core of
equal length. Besides this great attractive power, the power curve of a casing or
shell core also shows characteristic differences from the power curves of an ordinary
core. In Fig. 3, is shown the curve of attraction of a cylindrical core the lengths
reaching into the solenoid being the abscissa and the corresponding attractive forces
the ordinates.
The curve cuts the axis of the abscissa at the point a which corresponds to the
moment when the centre of the core coincides with the centre of the solenoid.
When therefore, the length of the core L is equal to the length of the coil, the
Let.l.
The
'
core, to form the point a projects into the solenoid to the extent of 2
curve of attraction may be modified by varying the cross section of the core. If,
for instance, a conical core be used, the point a is moved towards the thick end of
the core, the curve becoming meanwhile flatter (Fig. 4). When the core is formed
in the ordinary way, the attractive power is nil in a certain position; all core
curves have this in common. It is, however, quite different in a casing or shell
core where the curve of force need no longer cut the axis of the abscissa but the
attraction has a positive value up to the end of the casing or shell core as is shown

page_text: in Fig. 5. By partially cutting away the surface of the casing or shell M as
shown in Fig. 6 and thickening its front surface or face this effect can be so
increased that the maximum attractive power is concentrated at the end as shown
in Fig. 7. This phenomenon forms a characteristic feature, whereby the action of
a casing or shell core differs from the action of an ordinary core. The casing or
shell core can also be modified in various ways; the same can be narrowed down
into one, two or more bars m m (Figs. 8 and 9). The course of the lines of force
remains the same and in consequence also the action. As will be seen from Figs. 2
and 8 the lines of force k are concentrated on the end a, inserted in the solenoid,
whilst at the casing or outer core they are distributed over the whole surface.
In order to likewise concentrate these lines of force on the end, and, in this
way, to increase the attractive power of the core, it is merely necessary to place on
the core a second solenoid which has however opposite poles to the former one
(Fig. 10). Several cores and solenoids may also be combined (Figs. 11 and 12)
the action remaining always the same. As already mentioned the curve of
attraction of the casing or shell core and also of the double core formed of same
(and which, seeing they must always be connected by a yoke, we will call a yoke-
core) can be modified in any way required, by altering the size and the cross
section of the casing and core and especially the yokes connecting same. All the
curves have however a common characteristic feature in that they display a
positive attractive force up to the end of the core, which force is much greater
than that of an ordinary core with equal quantity of material.
By means of these two hitherto unknown properties, a core constructed in
accordance with our invention is most suitable for use in the construction of arc
lamp regulators and especially current regulators, since, on the one hand, they take
up infinitely less room, whilst on the other hand, on account of their great attractive
power, they exhibit great sensitiveness for regulating purposes.
Fig. 13 shows an arc lamp regulator with casing or shell cores.
Two casing or
Bhell cores M' M' are suspended on a cord running over a roller or pulley c and
carry the carbon holders hj. The cores extend into the solenoids S', S³, of
which S¹ lies in a shunt circuit and S' in the main circuit. By means of the main
circuit solenoid the carbons are made to recede from each other, whilst, by the
shunt circuit solenoid they are brought together. Seeing the attractive power is
thus considerably increased the regulating is effected in a highly sensitive way.
Fig. 14 shows a lamp with two yoke-cores 1, 12,-the regulating of same being
effected exactly as before. Fig. 15 is a further modification. The cores I, I³ and
the coils S', S are here movable. Each yoke-core carries two coils. Both pairs
of coils S', S are connected by means of a cord running over a roller or pulley c.
The cores are fastened with the yokes on the under plate P. The pair of
coils S lie in the main circuit whilst the pair of coils S₁ lie in the shunt circuit.
Seeing the coils have a constant tendency to move towards the yoke the carbons
are made to recede from each other by the coils S' and brought together by
coils S¹.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is
+
1. A device for regulating are lamps and more particularly electric currents, in
which device the regulating takes place directly without any intermediate mechanism
by means of the attraction of one or more cylindrical, conical or other shaped iron
cores provided with a shell or casing M'M' (Fig. 13), and of one or more
solenoids SS, (as shown in Figs. 1, 2 and 7).
2. A modification of the regulator or regulating device more particularly for arc
lampe, and electric currents, in which the regulating takes place by the attractive
force of one or more double cores (1' 12 Fig. 15 or m Figs. 8, 9) of suitable form
and connected by a yoke, one of these double cores being inserted in a solenoid

page_text: (Figs. 8 and 9) or both of them in solenoids (S'S' Fig. 15 or Figs. 10 to 12) in
the latter case the ends lying on a level with each other having opposite poles
substantially as described.
Dated this 2nd day of July 1804
WM. P. THOMPSON & Co.,
6, Bank Street, Manchester, Patent Agents.