Improvements in Electric Aro Lamps.
Year: 1896

page_text: Date of Application, 29th Dec., 1896-Accepted, 13th Feb., 1897
Improvements in Electric Aro Lamps.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, Electrical
Engineers, of 83, Cannon Street, in the City of London, do hereby declare the
nature of this invention (which has been communicated to us from abroad
by Elihu Thomson, of Swampscott, in the County of Essex, State of
Massachusetts, United States of America), and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
Our present invention, relates to improvements in arc lamp mechanisms whereby
simplicity and ease of construction are secured, as well as certainty of action.
We will fully describe our improvements in reference to the accompanying
drawings in which
Figs. 1 and 2 are side elevations of the mechanism, Fig. 2 being partly in
section;
Fig. 3 is a perspective view of the mechanism particularly concerned in regulating
the feed of the carbon;
Fig. 4 is a detail.
In Fig. 1 P is the top plate and B is the base plate of the lamp mechanism box,
the latter having depending side pieces for supporting the lower carbon, not shown
in the figure. The upper plate P carries the terminal binding posts of the
lamp a, b, Fig. 2, and is insulated from them. The lower frame F of the lamp is
also insulated from the mechanism contained between the plates P and B, it being
understood that a surrounding sheet metal casing, not shown in the figure, is used to
enclose the parts. Joining the two plates P and B, though insulated from them, is
a.frame or casting HH, which sustains the parts of the lamp mechanism proper;
at A, Fig. 2, is a screw which passes through the frame H and sustains the
solenoids CC through which the current of the lamp passes. These magnets' may
be either in series with the arc and conveying the current to it, or they may be
compound-wound or differential magnets. Entering the open ends of the coils CC
are two iron cores II yoked together in the usual manner by a soft iron yoke Y,
as best seen in Fig. 3. These parts form the magnetic element of the mechanism,
which is raised or lowered by the resultant of the attraction of the coils C C and
gravity. A central carbon-holding rod 'R passes between the coils C C, and is
arranged to be clutched and lifted when the magnet cores II rise, through the
intervention of a special clutch which forms a main feature of our invention, while a
dash-pot D, the plunger of which is attached to the yoke Y, Fig. 2, and the casing
or body of which is secured to the fixed framework of the lamp, serves to check
too violent motions.
The special clutching device of our invention is seen in Fig. 3, where the carbon
feeding rod R or the carbon pencil itself is gripped by a pair of jaws J J' bearing
laterally thereon. These jaws are pivoted to levors L L' by a lug or extension
extending from the levers toward the rod R and entering a slot in the jaws J J'.
The levers L L' are fulcrumed or pivoted at their lower ends in a frame K, and at
their upper free ends are pivoted to small links QQ; the links turn on a pivot
carried either directly or indirectly by the cores, being thus free to swing upon a
pivot ou the cores 1 1. This, of course, might be replaced by any other pivotal

page_text: arrangement carried by the magnetic structure, or whose movements were controlled
thereby the position of the pieces QQ is normally at an angle to the horizontal.
Surrounding the rod R is a loose sleeve S having at its lower end a flange which,
when the magnetic mechanism and clutch is lowered engages on inclined surfaces
carried by lugs or projections OO on the levers L L at their upper ends; the
upper end of the sleeve has a flange which provents it dropping too far. This is
effected by the flange catching upon the fixed supports, which may be and are here
shown as the flanges of the magnet spools. The middle flange of the sleeve S also
prevents it from being carried too far up, so that the sleeve has what may be called
a restricted free motion vertically. The levers L L' pass.through openings in the
horizontal magnetic yoke Y through which yoke the rod R also passes. The
frame K is shown separately in Fig. 4, the points of pivoting of the levers LL
being marked. We also provide an adjustment or means for varying the
distance apart of the points ', which may consist of any suitable device. which
lengthens or shortens the frame work K; we have shown a division of the frane
into two parts and the separation of the parts by packings V V, the thickness of
which may be varied. This adjustment is useful in taking up for wear of the
clutch surfaces,, or in setting the parts originally in proper working position.
Assuming now that there is no current in tho magnet coils CC, the cores I [
and yoke will be at their lowest position, in which the inclined surfaces OO of
the levers L L rest on the lower flange of the sleeve S, in such position that the
jaws J J of the clutch are wedged open and the rod is free to move. This is the
feeding condition, when the current in CC has been 30 reduced as to cause release
of the cores II and yoke Y. On an increase or accession of current the first
effect is to relieve the inclined surfaces 00 from the lower flange of the sleeve S;
the weight of the parts pulled upward by the raising of the cores II causes the
clutch.to lock upon the rod R with great firmness and certainty, owing not only to
the leverage obtained in the levers L L' themselves, but also the inclined position
of the connecting pieces QQ, which tend to approach the horizontal and thus get
a toggle grip. The jaws.J Jare situated much nearer the lower pivots than the
points of attachment of the connecting pieces QQ, and thus the leverage magnifies
the force available for clutching three or four times; the angle given to the
pieces QQwith respect to the horizontal will, if it be small, cause an increase in
'the power of the clutch, while yet it is easy to make the angle such that the proper
effect may be obtained. At the same time the release of the clutch for feeding on
the weakening of the current is secured with great delicacy by the engagement of
the inclined surfaces 00 upon the lower flange of the sleeve S. This sleeve
on the upward movement of the parts is itself carried or lifted, though this is, not
essential to the action of the mechanism, but is merely a convenience in preventing
the necessity for allowing the lower flange to pass through the yoke piece Y. The
lamp circuit connections and other parts are not shown, as they are obviously the
same as those employed in arc lamps; the present invention relating chiefly to:
the improvement in the clutch mechanism for controlling the movement of the
carbon rod.
Having now particularly described and ascertained the nature of this inven-
tion (as communicated to us from abroad) and in what manner the same is to be
performed, we declare that what we claim is :-
1. In an electric arc lamp, a pair of solenoids for regulating the lamp, and cores
connected by a yoke co-operating with the solenoids, in combination with a clutch
comprising a pair of levers connected with the cores by toggle levers and having
portions engaging with the carbon rods, the whole arranged to increase the grip of
the clutch as the cores are drawn upward.
2. A clutch for an electric arc lamp, comprising a frame having levers pivoted
therein at one end, toggle levers conuected with the other end of the first levers
and also to the solenoid cores, and a gripping part engaging with the carbon rod
and situated nearer the fixed eud of the levers than the movable end.

page_text: 3. A clutch for an electric aro lamp, comprising a frame to which the lower ende
of a pair of levers are pivoted, toggle connections between the solenoid cores and
the upper ends of the levers, a sleeve sliding upon the carbon rod and having
projecting portions co-operating with the upper ends of the levers, and a portion of
the levers organized to grip the carbon rod.
4. A clutch for an electric are lamp, comprising a frame of adjustable length
having a pair of levers pivoted at their lower ends therein, the upper ends of the
levers connected to the solenoid cores by links or toggles, and a pair of jaws
actuated by the levers for gripping the carbon rod.
Dated this 29th day of December 1896.
For the Applicants,