Improvements in Electric Arc Lamps.
Year: 1889

page_text: Date of Application, 10th Oct.,
1889
Complete Specification Left, 10th July, 1890-Accepted, 16th Aug. 1890
PROVISIONAL SPECIFICATION.
Improvements in Electric Arc Lamps.
.
I, SIDNEY PRATT BLACKMORE, of the Wolverhampton Electrical Company,
Wolverhampton in the County of Stafford, Electrical Engineer, do hereby declare the
nature of this invention to be as follows:-
-
This invention relates to the automatic feed and regulation of the carbon of an
electric arc lamp, and has for its object more especially a simple and compact
arrangement of solenoid, core, and clutch apparatus, by which the movement of the
carbon holder is provided for and by which it is controlled.
According to this invention the solenoid core is tubular in section and is passed
around and fixed to a tube which surrounds the tube of the carbon holder, and the
lower end of the core or of the tube to which it is fixed is connected with a frame or
bridle the sides of which pass down on each side of the holder tube. The clutch for
sustaining the weight of the holder tube and the parts carried thereby is formed of
two main portions each of which is carried at its outer end by the sides of the frame
and passes at its inner end partially around the holder tube, the inner ends being
pivoted together on each side of the tube and the outer ends being free to move
endways in the frame and being sufficiently easy therein to allow of the inner ends
moving vertically in relation thereto. When the inner or pivoted ends of the clutch
are moved down, in relation to their outer ends, the edges of the parts which pass
around the tube bind tightly there against and thus securely hold the tube.
In its
normal position the clutch holds the tube in the manner described, its inner ends being
moved into such position by their weight, acting alone or assisted by extra weight, or
by a spring which may be conveniently carried around the tube. As the carbons burn
away, and thus increase the length of the electric arc, the slight momentary reduction
of current through the solenoid causes the core and consequently the clutch and holder
tube to fall until the increased current caused by the nearer approach of the.carbons,
causing an increased current through the solenoid, checks the downward movement.
When a certain amount of "feed" has taken place in this manner any further
downward movement of the tube holder brings the inner ends of the clutch upon a
fixed plate (which may be the bottom of the case) and the grip of the clutch¹ is thus
momentarily relaxed allowing the tube to slip therethrough sufficiently to bring the
carbons near enough together to cause a sufficient current through the solenoid
to raise the core and thus again causes the clutch to grip the tube. If at any point
the holder tube falls too far, the current through the solenoid is instantaneously
increased and the tube thereby slightly raised again, and thus the arc is constantly kept
at its proper length.
$6
The tube which carries the core is fitted at its upper end with a dash-pot
apparatus of the usual character employed with the automatic feed apparatus of arc
lamps; but the holder tube has a collar around its upper end which is made a good
sliding fit within the outer tube, and a rod is carried down from the bottom of the
dash-pot (which closes in the top of such tube) down the axis of the holder tube and
carries a piston which is a good sliding fit within such latter tube, and the bottom of
the holder tube is closed when the holder is fixed thereon. By this arrangement an
air check is provided against the too sudden movement of the bolder tube, as any
vertical movement of such tube causes a partial vacuum on one side of the piston and
a partial compression on the other side, and the balance of pressures is restored only
by a rush of air around the collar at the upper end of the tube and around the piston
in such tube.
Dated this 9th day of October 1889.

page_text: COMPLETE SPECIFICATION.
Improvements in Electric Arc Lamps.
I, SIDNEY PRATT BLACKMORE, now of 47 Birchfield Road, Aston, in the County
of Warwick (late of the Wolverhampton Electrical Company, Wolverhampton in the
County of Stafford), Electrical Engineer 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:-
This invention relates to the automatic feed and regulation of the upper carbon of
an electric arc lamp, and has for its object more especially a simple and compact
arrangement of solenoid, core, and clutch, by which the movement of the carbon
holder is provided for and by which such movement is controlled or regulated.
That the invention may be clearly understood I will proceed to describe it with
reference to the accompanying drawings, of which those on sheet 1 illustrate a
modification of the invention applied to a lamp for working in series, and that on
sheet 2 illustrates an improved modification of the invention applied to a lamp for
working either in series or in parallel.
Referring first to the drawings on sheet 1, figure 1 is a vertical section through the
centre of an electric arc lamp to which the invention is applied. Figure 2 is a side
elevation of the clutch hereinafter described; figure 3 is a view looking up at the
underside thereof; and figure 4 is an end view thereof. The lamp shewn in figure 1
is broken off in its length for convenience of illustration.
A
A is a cylindrical casing closed in by a cap B. C is a circular box within which is
contained the clutch mechanism hereinafter described. To the lower side of this box C
is fixed a plate D which carries tubes E to the lower ends of which is fixed the cross
bar which supports the lower carbon. These tubes E are shewn broken off in length,
and the cross bar for the lower carbon is omitted, for convenience of illustration.
vertical tube a fixed at its lower end to the top of the box C passes up, concentrically
with the vertical axis of the lamp, to near the top of the casing A. Around the tube a,
and in the position shewn, is wound a series coil b. A concentric vertical tube d,
capable of endway movement and sufficiently less in diameter than the tube a for the
purpose hereinafter shewn, passes down within such tube a and into the box C, as
shewn. Around such tube d is fixed a soft iron core e, in such position in relation to
the coil that when the tube d is in its normal working position vertically, that is its
normal position when the current is passing through the carbons of the lamp and the lamp
is consequently alight, the force which is exerted by the coil will maintain the upper
carbon (which is carried by the tube d in the manner hereinafter described) constantly
in its normal working position as the carbons burn away, automatically adjusting it
thereto for a short distance, after the arc has been struck, and subsequently operating,
in combination with the clutch bereinafter described, to allow the upper carbon to be
fed downwards, and to be constantly automatically adjusted in position to maintain a
constant length of are. Within the upper end of the tube a is fitted a tube fƒ¹, of
which the portion f stands above the top of the tube a and of which the portion f¹ is
reduced in external diameter to fit within the tube a and is passed down thereinto, as
shewn. Within the top of the tube d is fixed a cap or plug h having a projecting rim
around its top which is an easy fit within the part f¹ of the tube ff, and serves as a
guide for the upper end of the tube d within the tube a. The holder tube or carrier j
passes down within the tube dand out through the bottom thereof and through a hole
in the plate D, and carries at its lower end the usual or any suitable description of
holder for the upper carbon. To the lower end of the tube d is fixed a bridle-piece F,
formed of a horizontal piece or plate k at the top and a downward projection ¹ k¹ at
each end. Each projection is provided with an ear on each side which extends
downwards from the projection, and through each pair of ears is passed a pin min
position somewhat below the bottom of the corresponding projection. A pair of
plates n, one on each side of the holder tube j, are hinged or pivotted together at o on
opposite sides of such tube, as best shewn by figures 2, 3 and 4, and the inner ends of

page_text: these plates are rounded out, as shewn at figure 3, to bear against and grip the tubej
when the plates are in the position shewn by figure 1. The rear ends of the plates
rest on the pins m and are capable of moving endways between the tops of such pins
and the bottoms of the projections. In the normal position of the parts due to the
lamp being alight, the bolder tube jis gripped between the inner rounded ends of the
plates n, and its weight and that of the carbon which it carries is thus supported by
the clutch formed by these plates and the bridle F. The weight of the inner ends of
the plates n tends to maintain then in a position to clutch the holder tube j, and they
are released from such grip only when resting on the plate D, as hereinafter described,
or when the tube is being pushed up for the supply of fresh carbon.¨¨
The positive lead G passes, from the binding screw by which it is connected with
the lamp, to one end of the series coil b, and the other end of such coil is connected
direct with the frame, so that the whole of the current passes direct through the coil b
to the upper carbon. The negative lead G¹ passes up, from its connection with the
lower carbon, through one of the tubes E, box C, and casing A, to the binding screw
by which the exterior lead passes from the lamp.
The action of the lamp is as follows:-
Previously to the turning on of the current the upper carbon rests on the lower.
When the current is turned on the coil b exerts an upward pull upon the core e and
such core,
and consequently the tube d, clutch which it carries, and holder tube j, are
drawn up to their normal working position. As the distance between the carbons
increases the resistance occasioned thereby causes a diminished current through the
coil b, and the forces tending to move the carbon, that is to say the weight of the
moving parts and the force exerted by the coil b upon the core e, by constantly
tending to balance one another tend constantly also to adjust the carbon to its normal
working position. As the carbons burn away the tube d, and clutch which it carries,
and the holder tube j, gradually move downwards by gravity, acting against the force
of the coil b, because as the distance between the carbons tends to increase by their
burning away there is a corresponding diminution in the strength of the coil b, which
increases again however as the carbons approach one another and the downward
movement of the upper carbon is thereby checked or controlled; and the movement
of the upper carbon is thus controlled or regulated in this manner, until the inner ends
of the clutch plates n touch upon the top of the plate D, when the grip of the inner
edges of the plates around the tube j is momentarily relaxed, allowing the tube j to
fall slightly in the tube d. In consequence of the reduced resistance thus occasioned
between the carbons, and the consequently increased current through the coil b, the
clutch is slightly raised again, and again grips and retains the holder tube. The
carbon is then continued to be fed down in this manner by a series of very minute
movements, the rate of repetition and degree of which is automatically controlled.'
A piston rod p, which may be formed with or fixed to the plug h, has a
piston at its top which is a good sliding fit within a close-topped cylinder which
forms a cap to the tube a. The cylinder is greased with glycerine or other suitable
lubricant and, on account of the enclosed space between the top of the piston and
the upper end of the cylinder, acts as a check or dash-pot to any sudden movement
of the tube d and consequently also of the upper carbon. A dash-pot arranged in
this manner, that is having a direct rigid connection with the part which carries the
clutch which supports the moving carbon holder, is a great improvement on the usua!
arrangements which involve the use of pivoted joints, as there is no play or looseness
in the connections. It will be readily understood that the dash-pot piston may be fixed
(by being hung for instance from the cap B) and the cylinder be carried by the moving
parts, in lieu of a fixed cylinder and moving piston.
A rod 8 is carried down from the plug h to nearly the bottom of the holder tube j
and has a collar t fixed around its lower end, of a diameter to allow the holder,
tubej to slide easily along it, the collar thus acting as a guide to the holder tube.
A second collar u is fixed around the rod 8 in position shewn, and the top of the
holder tube is fitted with a plug cap which is an easy fit within the tube d and
around the rod 8.and acts as a guide for the upper end of the holder tube, and also,

page_text: by coming in contact with the collar, as a stop to the downward movement of the
holder tube.
The core e, instead of being connected with the clutch through the medium of the
tube d, may be carried down and connected direct with the clutch.
Figure 5, sheet 2, shews, in vertical section corresponding to figure 1, a lamp to
which an improved modification of this invention is applied, such lamp being
capable of working either in series or in parallel. Except for the features herein-
after specially described this lamp is the same in construction as the one already.
described, and the clutch and the lower portion of the box C are omitted from the
drawing for convenience of illustration. In this modification, both a series coil 6
and a shunt coil c are wound around the tube a. The shunt coil c is wound around
the lower end of the tube a, and a series coil b is wound around such tube imme-
diately above the shunt coil c. The core e, which is fixed around the tube d, is in
such position in relation to the coils 61 and c as to be acted upon by the coil b¹ in a.
direction to raise it and by the coil c in a direction to move it downwards. Within.
the bottom end of the portion f¹ of the tube ff is fixed a collar g, and between this
collar and the collar of the plug h is inserted a spiral spring which supports the
weight of the tube d and of the parts which it carries.
The positive lead G passes from the binding screw by which it is connected with
the lamp to one end of the series coil b¹, and the other end of such coil is connected
direct with the frame, so that the whole of the current passes direct through the
coil b. A greater or less portion of the current, as will hereafter appear, passes from
thence to the upper carbon. The negative end of the shunt coil is connected also
direct with the frame, and the other end of such coil is connected direct with the
negative lead G1, thus forming it a shunt to the arc.
The action of this lamp is as follows:-Previously to the turning on of the current
the carbons are somewhat nearer together (say, by about th of an inch) than their
normal working position. When the current is turned on the shunt coil c exerts a
downward pull upon the core e somewhat in excess of the upward pull of the series
coil b', and such core and consequently the tube d, clutch which it carries, and holder
tubej, are drawn down against the upward pressure of the spring i, and the carbons
are brought together and the electric arc is struck. When the carbons approach
closely to one another, however, the resistance in the circuit is thus lessened and a
greater proportion of the current passes through the carbons and a less proportion
passes consequently through the shunt coil c, and the force exerted by the coil b¹
(owing to the increased flow of current due to the reduced resistance between the
carbons) is increased, and thus the upward pull of the coil b¹ upon the core e is
greater than the downward pull of the shunt coil c upon such core, and the tube d,
and clutch which it carries, and carbon holder tube jare slightly raised and
increase the length of the electric are; and should the carbon be raised too high
the increased resistance to the current thus occasioned reduces the strength of the
series coil 61 and causes an increased flow of current through the shunt coil c
and the core e and consequently the upper carbon also are drawn down.
As the
carbons burn away the tube d, and clutch which it carries, and the holder tube j,
gradually move downwards, by the increase in force exerted by the shunt coil c, and
the diminished force exerted by the series coil 61, which results from an increased.
distance, between the carbons, until the inner end of the clutch plates n touch upon.
the top of the plate D, when the carbon holder tube is fed down through the clutch
by a series of minute movements in the manner described with reference to the first.
modification; but in this case the holder tube is constantly gripped by the clutch
after each downward movement, in consequence of the reduced resistance between the
carbons caused by their nearer approach causing a momentarily greater current. to
flow through the series coil 6¹ and a momentarily reduced current to flow through the:
shunt coil c.
:
The methods above described of providing for and controlling the movement of the.
upper carbon causes an extremely steady are to be maintained, and the parts are of:
the simplest character and are not liable to derangement.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In an electric are lamp, a core capable of vertical movement, connected, simply
through the medium of a part to which it is itself rigidly fixed, or (alternatively)
directly, with a clutch operating substantially in the manner described, in combination
with means by which the electric current is utilized to raise the core on the resistance
between the carbons becoming reduced during working and to lower, or admit of the
lowering of, such core on the resistance between the carbons increasing, substantially
as described.
2. In an electric arc lamp, the combination of a core e carried by a part which is
itself connected direct with a clutch for gripping the holder tube or carrier, and the
series coil b, such core, clutch, and coil being constructed and arranged, and operating,
substantially as described and shewn.
3. In an electric are lamp, the combination of a core e carried by a part which is
itself connected direct with a clutch for gripping the holder tube or carrier, and the
series coil 6 and shunt coil c, such core, clutch and coils being constructed and
arranged, and operating, substantially as described and shewn.
4. In an electric arc lamp, the carbon holder tube or carrier j, the tube d
surrounding such tube or carrier i, the core and clutch both carried by the tube d,
and the coil b (or coils b¹ and c) all combined substantially as shewn by the drawings
herewith, and operating in the manner described.
5. The clutch constructed and operating substantially as described and shewn, for
the purpose set forth.
6. In a clutch for the purpose set forth, the gripping parts hinged or pivoted at
their inner ends and having their outer ends carried by a suitable bridle or frame in
which they are free to move, substantially as described.
7. The means, substantially as described with reference to the drawings herewith,
by which the movement of the upper carbon of an electric arc lamp is effected and
controlled.
8. In an electric arc lamp, a dash-pot piston or cylinder rigidly connected with the
part which directly carries the clutch for supporting the moving carbon holder, sub-
stantially as described and shewn, for the purpose set forth.
9. In an electric arc lamp, the combination of the tube or part d, carrying a clutch
for gripping the carbon holder tube or carrier j, with the dash pot piston q (or,
alternatively, the dash pot cylinder ») rigidly connected with such tube or part d
substantially as described.
10. The general combination and arrangement of parts forming an electric arc
lamp, substantially as described with reference to the drawings on sheet 1 herewith,
and also the modification thereof substantially as described with reference to the
drawings on sheet 2 herewith, for the purpose or purposes set forth.
Dated this Ninth day of July 1800.
Dated this Ninth day of July
STEPHEN WATKINS,
Wolverhampton, Agent for the Applicant.
STEPHEN WATKINS,
Wolverhampton, Agent for the Applicant.