Improvements in Resistance Coils.
Year: 1899

page_text: Improvements in Resistance Coils.
We, COWANS LIMITED, of Bridgewater Street, Salford, Manchester, in the
County of Lancaster, and EDWARD WOODROWE COWAN, of the same place, Managing
Director of the said Cowans Limited, and ALFRED STILL, of Bow Green Farm,
Bowdon, in the County of Chester, Civil Engineer, do hereby declare
the nature of this invention to be as follows:
This invention has for its object to provide a resistance coil which is econo-
mically manufactured and is capable of withstanding high temperatures. The
said invention is very useful in cases where the windings of the coils have to be
of fine wire which cannot be conveniently wound in open spirals. Coils made
according to this invention are particularly well suited for use in electric motor
starting switches, as the coils for such switches are often subjected to excep-
tionally heavy currents resulting in rise of temperature liable to destroy an
ordinary coil."
According to this invention, the wire which is to be used for the coil, is covered
with cotton, or other carbonizable material and is wound on a body part, or bobbin,
preferably of metal, (on account of its large capacity for heat, and its heat conduct-
ing and radiating properties) insulated by means of heat resisting material, such
as asbestos, enamel, or mica. The winding is then sealed up by means of insulating
cement which will stand a high temperature, such for instance, as plaster of paris,
or the cement known in the trade as thermic cement. Then, by means of an
electric current or otherwise, the temperature is raised until the cotton, or other
carbonizable material, is carbonized. The coil, can then be covered with another
coat of cement. A small hole, or small holes, should be made in the first covering
of cement, before carbonizing to allow of the escape of smoke. The cement
protects the carbonized material from mechanical injury, and also prevents access
of air, which would cause some combustion of the carbon if the coil be submitted
to high temperatures.
The metal body upon which the wires are wound is preferably made of four
cheek pieces with a boss thereon, so that when the said pieces are placed together,
they form two spaces for the windings the wire at one end being pinched between
the parts of one pair and at the other end between the parts of the other pair.
To one of the cheek pieces of each pair the terminal screws are secured.
The two
pairs are separated from each other by insulating material, such for instance, as a
mica disc, and the parts are secured together by a central screw, insulated so as
to prevent metallic contact between the two pairs of the said pieces. The windings
of each pair are connected by the wire passing through the inner cheeks of each
pair. The said inner checks may be formed so as to present a V groove at their
periphery, the edge of the mica, or other disc between the said cheeks, pre-
ferably projecting as far as the outer edges of the cheek pieces, and the coils
being wound so as to leave a space for insulating cement which is brought up to
the edges of the cheeks or general periphery of the coil. Asbestos paper, enamel,
mica, or other insulating material is placed between the windings and the metal

page_text: cheeks. The coil, as a whole, is wound, non inductively, the current passing, from
the one terminal and the one pair of cheek pieces, to the end of the winding
pinched between them and through the winding in the one space to the outer
circumference thereof, and then across to the outer circumference of the winding in
the other space, and inwards and through the end of the said winding pinched
between the pair of cheek pieces forming the said space and through the said cheek
pieces and out by the other terminal.
Do th: 0011
1 1000
COMPLETE SPECIFICATION.
Improvements in Resistance Coils.
We, COWANS LIMITED, of Bridgewater Street, Salford, Manchester, in the
County of Lancaster, and EDWARD WOODROWE COWAN, of the same place, Managing
Director of the said Cowans Limited, and ALFRED STILL, of Bow Green Farm,
Bowdon, in the County of Chester, Civil 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 has for its object to provide a resistance coil which is econo-
mically manufactured and is capable of withstanding high temperatures. The
said invention is very useful in cases where the windings of the coil have to be
of fine wire which cannot be conveniently wound in open spirals. Coils made
according to this invention are particularly well suited for use in electric motor
starting switches, as the coils for such switches are often subjected to excep-
tionally heavy currents resulting in rise of temperature liable to destroy an
ordinary coil.
We will describe the invention with reference to the accompanying drawing
shewing in Fig. 1 in face view and in transverse section in Fig. 2 a resistance
coil made in accordance with this invention.
According to this invention, the wire a which is to be used for the coil, is
covered with cotton, or other carbonizable material, and is wound on a body
nart, or bobbin, preferably of metal (on account of its large capacity for heat,
and its heat conducting and radiating properties) insulated by means of heat
resisting material, such as asbestos, enamel, or mica. The winding is then sealed
up by means of insulating cement which will stand a high temperature, such for
instance as plaster of paris, or the cement known in the trade as thermic cement.
Then, by means of an electric current, or otherwise, the temperature is raised
until the cotton, or other carbonizable material is carbonized. The coil can then be
covered with another coat of cement. A small hole, or small holes, should be made in
the first covering of cement, before carbonizing, to allow of the escape of smoke.
The cement protects the carbonized material from mechanical injury, and also
prevents access of air, which would cause some combustion of the carbon
if the coil he submitted to high temperatures.
The metal body upon which the wires are wound is preferably made of four
cheek pieces 61 62 63 64 with a boss thereon, or on one of each pair as shewn, so
that, when the said pieces are placed together, they form two spaces for the
windings the wire at one end being pinched between the parts of one pair and at
the other end between the parts of the other pair as shewn at c and d. To one of
the cheek pieces of each pair the terminal screws T T are respectively secured.
The two pairs are separated from each other by insulating material, such, for

page_text: instance, as a mica disc e, and the parts are secured together by a central screw f
the nut and washer on which are insulated by a disc m of mica or the like the body
of the screw being insulated by ferrules of fire clay, cement, or other suitable
material, g, as a precaution against metallic contact between the two pairs of the
said pieces. The windings of each pair are connected by the wire passing through
the inner cheeks of each pair as at h. The said inner cheeks may be formed so as
to present a V groove at their periphery, the edge of the mica, or other, disc,
between the said cheeks, preferably projecting as far as the outer edges of the
cheek pieces, and the coils being wound so as to leave a space for insulating cement i
which is brought up to or beyond the edges of the cheeks, or general periphery of
the coil. Asbestos paper, enamel, mica, or other insulating material, placed
between the windings and the metal cheeks as shewn at j.
In the arrangement shewn in the drawing as the mica or other insulating
material forming the layers outside the inner cheek pieces are continued to
the central screw f rings k are provided to give a bearing for the pinched ends
of the wires but if desired the mica or like layers may not be continued so far
inwards so that the ends of the wires are directly pinched by the cheek pieces and
then the ferrules g may be in one piece. The coil, as a whole, is wound non-induc-
tively, the current passing, from the one terminal and the one pair of cheek pieces,
to the end of the winding pinched between them and through the winding in the
one space to the outer circumference thereof, and then across to the outer circum-
ference of the winding in the other space, and inwards and through the end of the
said winding pinched between the pair of cheek pieces forming the said space, and
through the said cheek pieces and out by the other terminal.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
1. A resistance coil made by covering the wire with carbonizable material
and suitably winding and mounting it and then sealing up the covered wire by
means of an insulating and heat-resisting material, and then applying heat to
carbonize the carbonizable material; substantially as herein before described.
2. A resistance coil constructed substantially as herein before described and
illustrated particularly in Figure 2 of the accompanying drawing.
Dated this 19th day of January 1900.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.