A NEW OR IMPROVED ELECTRIC ARC LAMP
Year: 1882

page_text: COMPLETE SPECIFICATION filed by the said Charles Scott Snell at the
Office of the Commissioners of Patents on the 17th October 1882.
CHARLES SCOTT SNELL, of Culver Park, Saltash, Cornwall, A NEW OR IMPROVED
ELECTRIC ARC LAMP,
Fig 1 is an elevation, part in section, of my improved lamp.
Fig 2 is a cross section of my magnetic brake.
Fig 3 is an elevation, part in section, of a modification of the brake, of which the
lower part is the upper part of the lamp, and is shown in Fig. 4.
Fig. 4 is an elevation of the upper part of the lamp, part in section, showing
another modification of the brake.
Fig. 5 is a top plan view above the brake fig. 4.
Fig. 6 is a plan view of the brake contact fig. 4.
Fig. 7 is a diagram of a device equivalent to, or capable of being substituted for,
the spring acting on the soft iron core
Similar letters of reference indicate corresponding parts in all the figures.
The principle of my improved lamp is as follows: The main electric current enters
the lamp at the terminal on bobbin A, passes through metal of bobbin, thence down
upper carbon B to lower one C, producing the light between the two carbons. From
the lower carbon, the electricity flows into the strap D which forms lower carbon
bolder and out by terminal E thereon.
To keep the carbons the proper distance apart, the following combination is used,
A "shunt circuit" of fine wire connects the two terminals, in its course forming
a Solenoid by being wound around the bobbin to give power enough to compress
the spring of strength stated below.
This solenoid acts upon a "soft iron" core F annular in section, loosely inserted

page_text: within, or partly within, the upper portion of it, its downward progress being resisted
by a brass or steel spring G coiled immediately under it.
The said spring may be replaced by levers with adjustable weights working on
centre above the bobbin as shown in diagram fig. 7.
Through the cylinder or core F (made of soft charcoal iron, and sliding without
excessive play, yet very freely within the tube of the bobbin) passes the brass
rod El forming the holder of the upper carbon at about 2" from the lower end of
which two copper strips B' touch the carbon.
The said tube is continued lower than the coil, and the end closed by brass
block F' perforated to let brass rod or carbon holder pass through, and having a
small piece of pipe F fitted to prevent spring G coming in contact with rod H.
The section of brass block will be similar to that shown in fig. 2, but so that only
three surfaces can touch the enclosed rod H which of course will be entirely clear
of every other part of the apparatus except the top of the iron cylinder Fat the
brake, and the extreme end of bobbin at brass block.
The brass rod H will be accurately turned and polished, of sufficient strength to
allow one end to touch lower carbon holder whilst the other end stands half an
inch above the brake hereinafter mentioned.
The descent of the said brass rod, due to gravity, is regulated by a brake of the
following construction:
At the top of the iron cylinder F, a brass lining is inserted, allowing free play
for the brass rod H. This lining I, and also the iron cylinder F, have an opening
or slot near the top, allowing a brass brake block J to pass through and press upon
the enclosed rod. This block can turn freely upon a pin K passing through its
contre into the arms L on either side. These arms are part of a semi-circular piece
of soft iron M which encloses the side of iron core opposite the brake block, and is
centred near the pin which runs through the block, in such a way that its weight
tends to increase the pressure of the block upon the rod H.
The movement of weight on brake armature will so accurately adjust brake, that
the steady and continuous descend of the carbon rod can be assured at any given
potential between the lamp terminals, that is between the two ends of the shunt
circuit.
When the lamp is out of action, the brake is tightly applied, owing to the semi
circular piece of soft iron mentioned above, witli its screw arm and adjustable
weight N so that the brass rod or carbon holder H will move in accordance with
the movements of the soft iron F. The screw of the weighted arm can be
screwed in to prevent actual contact of armature ever occurring, and for regulating
the play.
The spring G will have pushed the core F well out of the solenoid, and the carbon
points will be well separated, but when a current of Electricity passes through or
father is applied to the lamp, the following action takes place.
The carbons being separated, a strong current of Electricity flows through the
shunt circuit P, the solenoid sucking down the core F, and with it the rod carbon H,
until the magnetism at the end of the core attracts the brake armature (seini
circular iron piece mentioned above), and thus relieves the pressure on the brake
block due to its (the armature's) gravity, and the rod El descends until the carbons
make contact. With this, the current becomes much weakened in the shunt circuit,
the main portion going through the carbons, and the result is the sucking action of
the solenoid cannot compress the spring G to the same extent, and the core Frises
until its magnetism cannot sufficiently counteract the force of gravity of the brake
armature, therefore the brake J is once more applied, and the carbons separated to
an extent such, that the resistance caused by their separation makes enough current
take the alternative or shunt circuit to increase its effect upon the core, and hold
it steady in one position. This position is the one which gives the maximum
intensity of light, and that this distance apart of the carbon points, may be

page_text: maintained constant in spite of the consumption of the carbons, the brake is so set
that the slightest excess in that distance will so increase the effect of the solenoid
and therefore the magnetism in the core, that the extra attraction upon its armature
will so slacken the brake that a steady and continuous downward motion of the
carbon rod results, at the same rate that the carbon is consumed.
Should the feed be accidentally too much, the resulting decrease of current in
the shunt circuit will weaken its hold upon the core, and the spring will slightly
raise it with the rod until the normal distance is again attained.
If accidentally extinguished, the points will be again put in contact, and their
normal distance attained in the same manner as described above with regard to
the first lighting of the lamp.
Fig. 3 In this modification of the brake, the brass block J touches the rod H and
is attached by a pin K which allows of free oscillation to a lever Q having a fork
at its upper end which partly embraces the rod H. This forked end of the lever
is free to swing from two pins R in the same straight line with each other, one in
each fork. The pins are firmly attached to the similar arms of two levers S (one
each side of fork), their centres of oscillation being a line which is a continuatica
of the pin in block mentioned above.
By this means the turning of the outer levers S alters the angle at which the
block J hangs with respect to the vertical line of the rod H without in any way
disturbing the actual position of the block J, and therefore the amount of friction
or retarding influence upon the downward tendency of the rod is lessened or.
increased accordingly.
This brake is fitted to the annular iron core F at its upper end, and the outside
levers S are prolonged by horizontal arms T from their centres of oscillation in
a direction away from the block, and are connected together at or near their
extremities
Upon the top of the bobbin U is fixed a vertical rod V with nut X screwed upon
it, and the outer levers (when the solenoid sucks down the core F with brake)
catch upon this, turn upon their centres, and make the angle of the lever S from
which the brake block J hangs, assume a position tending to become vertical; this
motion continues until the "sliding angle" is obtained, when a slow downward
motion of the rod H, due to gravity, takes place.
When the lamp is out of action, the brake J is firmly applied owing to weight
on end of catch or outside levers causing the angle of the fork lever to be such
that there is an excess of friction between the block J and opposite side of brass
lining of annular iron core F.
With this brake it is so arranged by the position of nut X on vertical rod V,
that the normal distance apart is obtained when the Electricity in the shunt
circuit P counteracts the effect of the spring G upon the core F at a point where
the catch lever is in the position which allows the descent of the rod just at the
rate the carbon is consumed.
Fig. 4. By this modification of the brake, the latter has a spring pressing upon
the brake block J and is pivotted upon a pin K around which it turns when the
horizontal arm T¹ which forms part of it, catches upon a nut X on a vertical rod V.
The working of this is somewhat similar to the last, at least as regards the
projecting lever and adjustable nut on a rod being the means of releasing the
brake.
Having thus described the nature of my Invention and the manner of carrying
it into effect, I would have it clearly understood that I do not confine myself to the
precise details above enumerated as these may obviously be modified without
departing from the principle of my Invention, but what I claim and desire to secure
by the said Letters Patent is, in an Electric Arc Lamp:
1 The regulation of the upper carbon by an attachment of a brake regulated
by the magnetism induced therein, and acting on a soft iron core, and a brass rod
forming the holder of the upper carbon, and

page_text: 2° The elastic feeding of the carbons by the direct combination of the brake, core,
and spring, substantially as above described and represented in the accompanying
drawings.
In witness whereof, I the said. Charles Scott Snoll, have hereunto set my
hand and seal, this sixteenth day of October in the year of our Lord One
thousand eight hundred and eighty two.
C. SCOTT SNELL (L.S.)