AN IMPROVED MODE OF GOVERNING THE FEED OF ELECTRIC ARC LAMPS
Year: 1882

page_text: LETTERS PATENT to James Mathieson of Stratford in the County of Essex,
Electrical Engineer for an invention of "AN IMPROVED MODE OF GOVERNING
THE FEED OF ELECTRIC ARC LAMPS
"
t
PROVISIONAL SPECIFICATION left by the said James Mathieson at the
Office of the Commissioners of Patents on the 10th June 1882.
JAMES MATHIESON of Stratford in the County of Essex Electrical Engineer
"AN IMPROVED MODE OF GOVERNING THE FEED OF ELECTRIC ARC LAMPS."
"
This invention relates to a novel method of regulating electric arc lamps, whether
used as single lamps or in series, the object being to maintain the relative positions
of the carbon electrodes by giving to the moving electrode a progressive motion so
timed as to make its advance almost imperceptible, and thereby to maintain the
steadiness of the light.
This result has been nearly approached in the "Gramme” lamps, but with a
disadvantage which I now propose to avoid.
In the "Gramme" lamp, as in many others the armature lever which locks and
releases the clock work is operated by an electro magnet which is placed in a circuit
derived from the main circuit.
This armature lever, as arranged by Gramme, not only released the train which
fed the carbon, but at the same moment broke the circuit of its own magnet coils.
The armature thus released returned to its normal position and relocked the train.
During this movement only one arm of the escapement wheel passed, but a
repetition of the armature's movement caused a step-by-step advance of the carbon,
until the differential balance between the resistance of the arc and the resistance of
the shunt magnet coils was re-established.
.
This arrangement ensured an almost continuous, but imperceptible approach of
the carbons in exact proportion as they were consumed, and the distance between
the points remained virtually constant. As however a spark is given off at the
points of contact in this arrangement at every motion of the armature, the points
[Price bd21

page_text: Boon become oxidised, and the resistance of the shunt thus constantly varies and,
the contact frequently failing, the feed of the carbon is arrested.
To avoid this disadvantage, instead of breaking the shunt circuit as in the
Gramme lamp, I cause the armature at the moment it is attracted to make also
an electrical contact, which has the effect of bridging over, or cutting out, the
magnet. The magnet. being thus demagnetized, the armature is free under the
action of a slight spring to return to its normal position and relock the feeding
device. As this operation is repeated the carbon is advanced step by step until
the differential balance is re-established between the arc circuit and the derived or
shunt circuit.
In order to attain this object I connect say the positive, pole by a wire with the
pivot of the armature lever, and this pivot with the coils of the electro magnet.
An extended end of these coils I lead to an insulated contact piece, and from this
contact piece I lead a wire to a resistance coil or its equivalent in connection with,
say, the negative pole of the lamp. The armature or locking lever I form with an
extension piece which, as the armature is attracted, will bear upon the contact
piece and thus cut out the magnet from the derived circuit; the current, instead of
passing into the magnet coils as before and thence to the contact piece, now
passing directly by the armature extension piece to the contact piece and so to the
resistance coil.
By thus turning the course of the current all sparking and consequent corroding
of the contact points is avoided, whilst an unvarying length of arc is maintained.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said James Mathieson in the Great Seal Patent Office on the
8th December 1882.
JAMES MATHIESON of Stratford in the County of Essex, Electrical Engineer
AN IMPROVED MODE OF GOVERNING THE FEED OF ELECTRIC ARC LAMPS
"
This Invention relates to a novel method of regulating electric arc lamps, whether
used as single lamps or in series, the object being to maintain the relative positions
of the carbon electrodes by giving to the moving electrode a progressive motion so
timed as to make its advance almost imperceptible, and thereby to maintain the
steadiness of the light.
This result has been nearly approached in the "Gramme" lamps, but with a
disadvantage which I now propose to avoid.
In the Gramme lamp, as in many others, the armature lever which locks and
releases the clock work is operated by an electro magnet which is placed in a circuit
derived from the main circuit.
This armature lever, as arranged by Gramme, not only released the train which
fed the carbon but at the same moment broke the circuit of its own magnet coils.—
The armature thus released returned to its normal position and relocked the train
of wheels. During this movement, only one arm of the escapement wheel passed,
but a repetition of the armature's movement caused a step-by-step advance of the
carbon, until the differential balance between the resistance of the arc and the
resistance of the shunt magnet coils was reestablished.
This arrangement ensured an almost continuous, but imperceptible approach of
the carbons in exact proportion as they were consumed, and the distance between
the points remained virtually constant. As however a spark is given off at the
points of contact, in this arrangement, at every movement of the armature, the
points soon become oxidized, and the resistance of the shunt thus constantly
varies, and the contact frequently failing, the feed of the carbon is arrested.
To avoid this disadvantage, instead of breaking the shunt circuit as in the
Gramme lamp, I cause the armature, at the moment it is attracted, to make also an
electrical contact, which has the effect of bridging over, or cutting out, the magnet.
The magnet being thus demagnetized, the armature is free, under the action of a
light spring, to return to its normal position, and relock the feeding device.-As
this operation is repeated, the carbon is advanced step-by-step until the differential
balance is re-established between the arc circuit and the derived, or shunt circuit.
In the accompanying drawing Fig: 1 shows in front view an arc lamp of the
Gramme" type with my Invention applied thereto, the enclosing box for the
mechanism being removed. Fig: 2 is a back elevation of the same, and Fig: 3
is a side elevation of the lamp, the box enclosing the mechanism for working the
upper carbon holder being in section.
"
A is the upper or positive carbon fitted to the carbon holder A¹ which is
provided with rack teeth for gearing into a clock-work train. B is the lower or
negative carbon carried by a stationary holder B¹ and supported by the ordinary
metallic suspension frame C.
D is a metallic box which contains the clock-work mechanism E, and also the
electro magnet F and its armature f, for releasing the clock-work.
E' is a rock lever for carrying the armature f. and the detent e.
This armature lever rocks on a pivot-pin e' carried by suitable metallic supports
attached to the box D, and it releases or arrests the escapement wheel E³ of the
clock-work.

page_text: 1
A coiled spring es connected with the armature lever serves to raise that end of
the lever with which it is connected, and thereby to depress the detent e. and lock
the clock-work.
The office of the electro magnet F is, as is well known, to release the clock work
by lifting the detent e. out of contact with the escape wheel, and the spring e² besides
pressing the detent serves to counteract the weight of the armature and to balance
the attractive force of the electro magnet. For this purpose the spring is made
adjustable by means of a screw e³.
The arm of the lever E¹ which carries the armature is extended and. bent
downwards to reach a contact post G, when the magnet is caused to act.
This post is insulated, and is provided with an adjustable contact surface for
making contact with the tail of the armature lever, and it is brought within the
shunt circuit which serves to excite the electro magnet F, by the means which I
will now proceed to explain.
The positive carbon A I connect through the brass work of the lamp with the
pivot el. of the armature lever, and this pivot I connect by a wire with the coils of
the electro magnet F. An extended end of these coils I lead to the insulated
contact post G, and from this contact post, I lead a wire to a resistance coil H or its
equivalent in connection (through the frame of the lamp) with the negative pole
of the lamp. When therefore the armature f. is attracted by the magnet F, the
tail of the lever E¹ will bear upon the contact post G and thus cut out the magnet
from the derived circuit without breaking contact, the current, instead of passing
into the magnet coils as before, and thence to the contact post, now passing directly
by the tail of the armature lever to the contact post G and through the resistance
coil H to the negative carbon.
.
By thus turning the course of the current all sparking and consequent
corroding of the contact points is avoided, whilst an unvarying length of arc is
maintained.
Having now set forth the nature of my Invention of "An improved mode of
governing the feed of electric arc lamps," and explained the manner of carrying the
same into effect I wish it to be understood that I claim:
The means above described whereby the electro magnet placed in the derived
circuit for the purpose of releasing the clockwork or equivalent device, is cut out
from the circuit without breaking the same, thus maintaining the steadiness of the
light.
In witness whereof I the said James Mathieson have hereunto set my hand
ԲՐԱ.
Damhou On thousand sight hundred and
J. MATHIESON (L.S.)