IMPROVEMENTS IN APPARATUS FOR ELECTRIC LIGHTING com
Year: 1882

page_text: "
"
LETTERS PATENT to John Muirhead of 23 Regency Street Westminster and
Thomas Marshall Collet of 29 Mornington Crescent in the County of Middlesex
for an Invention of IMPROVEMENTS IN APPARATUS FOR ELECTRIC LIGHTING
commmunicated to them from abroad by George Annesley Grindle of
Rampart Row Bombay India.
PROVISIONAL SPECIFICATION left by the said John Muirhead and Thomas'
Marshall Collet at the Office of the Commissioners of Patents on the
13th November, 1882.
"
JOHN MUIRHEAD of 23 Regency Street Westminster and THOMAS MARSHALL
COLLET of 29 Mornington Crescent in the County of Middlesex. "IMPROVEMENTS
IN APPARATUS FOR ELECTRIC LIGHTING [communicated to them from abroad
by George Annesley Grindle of Rampart Row Bombay India]
"
This Invention has for its object improvements in apparatus for electric lighting
and relates to a shunt or switch capable of shunting a heavy current from one
circuit to another without sparking at the points of contact and without any period
of total extinction in both circuits. This is effected by a switch consisting of a
handle turning on a centro and carrying a spring arm which moves through a
segment of a circle and makes a sliding contact with one or other of two blocks on
which the spring slides and rests. These blocks are so arranged as to extend a
short distance past each other at the centre position of the spring so that it makes
contact with the one before it leaves the other and thus the circuit is never wholly
interrupted and no sparking can occur. The surfaces of the two blocks have also a
slight incline towards their point of intersection, so that the spring rests moro
lightly upon them in passing the central position than when it is in a state of rest
at either extremity of its arc of motion.
In order to keep the contacts clean and free from oxidation we cause the centre
of the circle from which the segments are struck to be other than that on which
the spring turns, so that that point of the spring which rests on the blocks or
segments at the centre of motion where in ordinary switches the sparking and

page_text: burning take place is not the same as that which makes contact with the blocks
when it is at rest.
The invention relates also to an automatic switch which gives warning in case
of the conductor of an electric light current becoming heated by excess of current,
and first gives warning. by ringing a bell, and then if the heat continues, cuts off
the circuit entirely. This is effected by a balance metallic bar weighted at ono
end which rests on a block of wax paraffin resin or other similar fusible substance,
which block is supported on a thin strip of copper or other metal the electric
conducting power of which is the same or slightly less than that of the general
circuit this strip of metal forms part of the main conducting circuit, and if heated
by excess of current the wax melts and allows tho weighted end of the lever to
descend-in its descent it first makes contact with a light spring in connection
with an ordinary trembling bell, and some portion of the current passing through
the bell circuit causes it to ring and give warning-if the wax continues to be
melted, the weighted lever descends still further, and in doing so its opposite end
breaks the connection of the circuit altogether and cuts off the current-it is
obvious that by a slight modification of the arrangement, the conducting strip of
metal may bo replaced by a curved wire embedded in paraffin or wax, which when
it becomes heated by the current allows itself to be drawn out of the wax, and thus
makes the necessary contacts.
The invention relates also to a special cap for supporting incandescent electric
lamps-allowing them to be attached or removed at pleasure, the electric circuit
being completed by the act of attachment. This cap is in two pieces, the upper
half is in a form suited for fixing to a bracket or chandelier, and has a central holo-
it is provided with two insulated curved metal segments, with the convex sides of
the segments facing each other. The lower half of the cap is also providod with
-two-insulated-plates_of_metal_which_are_in_connection_with_the_wires_of_the
incandescent lamp, and these plates carry two projections or springs which stand
upright and which when the two halves of the cap are placed together pass within
the central hole and engage with the curved metal segments of the upper half of
the cap, and are thus held in position at the same time making the necessary
electrical contact-in order still further to secure the attachment, these two springs
are bent slightly at the top into a hooked form and these hooks pass above the top
of the curved metal segments; and being slightly turned round they tighton
themselves upon the segments by a kind of bayonet movement.

page_text: SPECIFICATION in pursuance of the conditions of the Lotters Patent filed by
the said John Muirhead and Thomas Marshall Collet in the Great Seal Patent
Office on the 12th May 1883.
JOHN MUIRHEAD of 23, Regency Street, Westminster, and TпоMAS MARSHALL
COLLET of 29, Mornington Crescent, in the County of Middlesex "IMPROVEMENTS
IN APPARATUS FOR ELECTRIC LIGHTING A Communication to us from abroad by
George Annesley Grindle, of Rampart Row, Bombay, India
"
This Invention has for its object improvements in apparatus for electric lighting
and relates to a shunt or switch capable of shunting a heavy current from ono
circuit to another without sparking at the points of contact and without any period
of total extinction in both circuits. This is effected by a switch consisting of a
handle turning on a centro and carrying a spring arm which moves through a
segment of a circle and makes a sliding contact with one or other of two blocks on
which the spring slides and rests. These blocks are so arranged as to extend a
short distance past each other at the centre position of the spring so that it makes
contact with the ono before it leaves the other and thus the circuit is never wholly
interrupted and no sparking can occur. The surfaces of the two blocks have also a
slight incline towards their point of intersection so that the spring rests more
lightly upon thom in passing the central position than when it is in a state of rest
at either extremity of its arc of motion.
In order to keep the contacts clean and free from oxidation we cause the centre
of the circle from which the segments are struck to be other than that on which
the spring turns so that, that point of the spring which rests on the blocks or
segments at the centre of motion where in ordinary switches the sparking and
burning tako place is not the same as that which makes contact with the blocks
when it is at rest.
Figure 1 of the drawings annexed is an elevation partly in section and Figuro 2
is a plan of a shunt or switch constructed according to this invention.
a a is a wooden base block. b is a handle mounted on the baso a to which it is
connected by the centre c and about this centre the handle is able to turn through
a segment of a circle. d is a spring arm fixed to the handle; it consists of a broad
band or bands of copper competent to carry the current to be transmitted and
terminating in the block d' which is of bronze. e¹e are two other blocks of bronze
fixed to the base a they overlap each other at the centre. f is a spring which
presses the block d' down upon the block e' or ea over which it stands.
The surfaces of the blocks e¹ and e³ are slightly inclined the one towards the
other so that when the handle is passing the central position the block & bears
more lightly on the surfaces supporting it than when the handle is in its normal
position at either end of the arc in which it can move.
The flexibility of the band & permits of the block d' bearing fairly on the surface
beneath whether it be upon the block e' or e².
The blocks e e' are also so formed that the parts making contact when the handle
is at the end of the arc are not entirely the same as those which close the circuit in
passing the central part.
9, is a binding scrow for the attachment of the conductor by which the spring
arm d and block d' are placed in electrical connection with the dynamo or source
of current. h and i are other binding screws by which the blocks e¹ e are
connected with the two circuits into one or other of which the current is to
bo led.
The same apparatus may be employed when required simply to put the current

page_text: on to and off a single circuit.
unconnected.
In this case one of the blocks e', e', is left
Or the apparatus may if desired be employed to connect either of two dynamos
with an outside circuit.
The invention relates also to an automatic switch which gives warning in case 5
of the conductor of an electric light current becoming heated by excess of current
and first gives warning by ringing a bell and then if the heat continues cuts off the
circuit entirely. This is effected by a balanced metallic bar weighted at one end
which rests on a block of waxed paraffin, resin or other similar fusible substance which
block is supported on a thin strip of copper or other metal the electric conducting 1
power of which is the same or slightly less than that of the general circuit-this
strip of metal forms part of the main conducting circuit and if heated by excess of
current the wax melts and allows the weighted end of the lever to descend-in its
descont it first makes contact with a light spring in connection with an ordinary
trembling bell and some portion of the current passing through the bell circuit 1
causes it to ring and give warning-if the wax continues to be melted the weighted.
lever descends still further and in doing so its opposite end breaks the connection
of the circuit altogether and cuts off the current.
Figure 3 illustrates the foregoing description.
L is the lever with its fulcrum at L'. W is a weight upon the lover. M is a 2
-curved-contact-spring-bearing-on-the-opposito-end-of the lever Land closing the
main circuit. This circuit may be traced from the conductor C¹ through the lever L
the curved spring M and the thin conducting strip of copper H to the second
conductor C. The main circuit is complete through the dynamo or electric source.
P is a piece of paraffin wax, or a composition which will melt when the conductor H
against which it is pressed by the lever L becomes overheated.
S is a light contact spring which is included in a bell circuit-D.-When-the-block-
P commences to melt the spring S makes contact with the stop T and completes
the bell circuit which may either be a shunt on the main circuit or it may contain
a bell battery. The bell is thus sounded as soon as the block P commences to yield
and so warning is given. If this warning be not attended to the parts assume the
position indicated by dotted lines and the main circuit is opened.
It is obvious that by a slight modification of the arrangement, the conducting
strip of metal may be replaced by a curved wire embedded in paraffin or wax, which
when it becomes licated by the current allows itself to be drawn out of the wax
and thus makes the necessary contacts.
Figures 3 and 3b are sectional views of another form of shunt in which paraffin
wax or like fusible material is employed to automatically open the circuit when
the main conductor becomes heated. a is a wooden box. b b are two metal plates
through which the main circuit passes they are fixed in pieces of ebonite c c. The
current is carried by fragments of metal wire d d fitted between the plates bb
where they are inclined to each other. cis paraffin wax poured in melted between
the platos bb and pressed firmly against the picces d. When these pieces become
heated by excessive current the wax melts and allows the pioces d to fall away
thus opening the circuit.
The invention relates also to a special cap for supporting incandescent electric
lamps allowing them to be attacked or removed at pleasure, the electric circuit
being completed by the act of attachment. This cap is in two pieces, the upper
half is in a form suited for fixing to a bracket or chandelier, and has a central
hole it is provided with two insulated curvod metal segments, with the convex
sides of the segments facing each other. The lower half of the cap is also provided
with two insulated plates of metal which are in connection with the wires of the
incandescent lamp, and these plates carry two projections or springs which stand
upright and which when the two halves of the cap are placed together pass within
the central hole and engage with the curved metal segments of the upper half of
the cap, and are thus held in position, at the same time making the necessary
ólectrical contact. In order still further to secure the attachment, these two

page_text: springs are bent slightly at the top into a hooked form and these hooks pass above
the top of the curved metal segments, and being slightly turned round they tighten
themselves upon the segments by a kind of bayonet movement.
Figure 4 is a vertical section of an incandescent lamp cap or holder constructed
according to this invention.
Figure 5 is also a vertical section, it is taken at right angles to the line of
section in Figure 4.
The lower part consists of a cylindrical wooden block a to which is fixed tho
metal basket holder b to receive the neck of the electric lamp. a' is a stem
forming part of the block a, it projects upwards and is grooved at a*.
cc are two
insulated plates of metal fixed to the block a and the springs or metal
projections c, c are of a piece with the plates c c. Figure 6 is a plan of this lower
part. The wires attached to the lamp are lod up through the holes c³ c² and are
secured to the plates cc by the screws c³ c².
Figure 7 is an underside view of the upper part of the cap or holder. It
consists of a wooden block d adapted to be screwed on to the end of a metal pipo
or support containing the circuit wires.
The hole is carried through the block d and the sides of the block are cut away
so as to leave standing two lumps d¹ d¹. ecaro curved metal strips fixed to the
lumps d' and the circuit wires are connected with them by the same screws which
attach them to the lumps.
In putting the lump into its place the two parts of the holder are brought
together the stem a¹ is entered between the lumps d' and it is then turned about
one quarter round. This movement brings the inclined upper ends of the springs,
over the top of the metal strips and bearing firmly upon them so as both to sustain
the lump and to make the electrical contact. is a retaining screw which is
screwed in until its end enters the groove so that the lamp cannot be removed
until the screw is first withdrawn. The lamp can at any time be put out of
circuit by turning it until the springs no longer bear upon the metal strips
Having thus described the nature of our said invention and the manner of
performing the same we would have it understood that we claim :-
First. Our improved shunt or switch substantially as described.
Second. Our automatic switch sounding an alarm and opening the circuit when
the conductor becomes heated from excess of current substantially as described.
Third. The use in an automatic switch of a fusible or yielding material in
contact with a metallic conductor conveying the current and which when melted or
softened permits movement of mechanical parts by which the circuit is opened
substantially as described.
Fourth. The improved cap or holder for supporting incandescent lamps
substantially as described.
In witness whereof I the said Thomas Marshall Collet have hereunto set my
hand and seal this Twelfth day of May in the year of our Lord Ono
thousand eight hundred and eighty three