IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
Year: 1882

page_text: LETTERS PATENT to Alfred James Jarman Electrician 10 Glenarm Road
Hackney, London, E for an invention of IMPROVEMENTS IN DYNAMO
ELECTRIC MACHINES.
PROVISIONAL SPECIFICATION left by the said Alfred James Jarman at
the Office of the Commissioners of Patents on the 31st May 1882.
ALFRED JAMES JARMAN Electrician 10 Glenarm Road Hackney London E
IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
My improvements consist in a new form of armature, comprising an outer thin
sheet Iron cylinder-enclosing an inner divided and separate cylinder of thin
sheet iron, an annular air space existing between the inner and outer cylinders.――
The outer cylinder is continuous, the inner one is divided at its centre, or at any
convenient distance from the ends so as to form practically two short cylinders.
By dividing the inner cylinder-it is quite impossible for currents induced by the
wire surrounding the outer and inner cylinders to circulate in the metal, Stays
or ribs of Wrought Iron are rivitted radially to the external face of the outer
cylinder and are made wide enough to allow-several tubes of copper, silver or
other good heat conducting metal to be inserted along their length passing from
the periphery of the ribs through them to the annular space-between the two
cylinders, the object of the tubes being to carry off any heat, which may be
generated by freely ventilating the cylinders, and by their conduction assisting to
that end-I also find that it is advantageous to cover the opposed iron parts of the
armature and also of the field magnets with very thin sheet silver, copper or other
good heat conducting metal, as the conduction assists in keeping the iron cool-
I sometimes prefer to employ two cylinders or armatures-part of the current
derivable from one being used as an exciting current for the field upon the shunt
method the current remaining, and that from the other cylinder being used
externally-The outer cylinder can be made of Cast Iron and solid bars may be
used of silvered copper to conduct heat away. the separating rings at each end
of cylinder may be of a magnetic or non magnetic substance and if a plain irou
cylinder be used-it may be split parallel with its axis.

page_text: The stays or Ribs may be fastened at their ends into brass or other non magnetic
metal discs or plates and the spindle to which the armature is fixed is driven
through them passing through the centre of the inner divided cylinder in the
direction of its length.
Under some circumstances it is not convenient to excite the field magnets by
an independent and separate machine which is a necessity if a number of lamps
are to be maintained with any approach to regularity. In order to obtain the
advantage of a separate exciter I employ two cylinders as before mentioned which
can be used as exciter and distributer or part of the current from one can be used
the remainder and that from the other being available for external work or both
can be coupled up and part of the current from both be used as exciter for the
field or the whole current from both cylinders may be put through it.
The coils composing the armature can be coupled up in several different ways I
obtain a very good effect by coupling the inner wire of one coil to the outer of
the next but it is obvious that the coupling up will depend upon the effect which
it is desired to obtain from the machine.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Alfred James Jarman in the Great Seal Patent Office on
the 2nd November 1882.
ALFRED JAMES JARMAN Electrician of 10 Glenarm Road. Hackney. London E
IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
My Improvements consist, in a new form of armature comprising an outer or
thin sheet iron cylinder, enclosing an inner divided, and seperate cylinder of thin
sheet iron an annular air space existing between the inner and outer cylinders.
The outer cylinder is continuous, the inner one is divided at its centre, or at any
convenient distance from the ends so as to form practically two short cylinders.
My object in dividing the inner cylinder is to prevent the circulation of the current
or currents induced by the wire surrounding the outer, and inner cylinders, in the
metal which would happen were the cylinder solid, and undivided. I am also
enabled by this means to reduce the mass of the metal, gaining by the hollow
divided cylinder of which my armature is made, nearly the same magnetic effect as
if it were solid, and avoiding the heating effect inseperable from the use of iron
of any mass or substance, while the circulation of currents in the metal is prevented,
as no complete ring is formed, the inner cylinder being divided so as to avoid this-
Stays or ribs of wrot iron are rivetted radially to the external face of the outer
cylinder, and project beyond it, they are wide enough to allow several tubes of
copper, silver or other good heat conducting metal to be inserted along their length
passing from their periphery, through the ribs to the annular space between the
two cylinders, the object of the tubes being to carry off any heat that may be
generated, by freely ventilating the cylinders, and by their conduction assisting to
that end I also find that by covering the opposed iron parts of the armature, and
also of the field magnets with thin strips or depositing by electrolysis, some good
heat conducting metal such as silver or copper greatly tends to keep the machine
cool, when running, as the heat is conducted from the mass of the metal, to the
surface, where meeting the current of air engendered by the rotating armature
it is dispelled. The conducting metal referred to can be laid on in thin sheets,
and be sweated or it can be rivetted, or electrolytically deposited. The stays or
ribs may be fastened at their ends to brass or other non magnetic discs, or plates, and
the spindle to which the armature is fixed is driven through them, passing through
the centre of the inner divided cylinder in the direction of its length. I sometimes
employ cast iron for my outer, and inner cylinders, and may coat the same with
good conducting metal strips, fastened as above described, or electrolytically
deposited, or I can use a cast iron outer cylinder, with the bars or ribs cast on it,
and a ring cast on the under or inner side, into which two thin liners of wrought,
cast, or malleable iron may be forced. When the cylinder or cylinders are cast,
or if by being annealed, they are converted into homogeneous, or malleable iron,
which is very well suited to my purpose, the cheeks or disc plates can be made of
cast iron, rivetted to the ribs, or under some circumstances the cheeks can be made
in one casting, with the inner, and outer cylinders, room being left between the
cheeks, and the side of the cylinders to allow the folds of wire to pass freely round
such cylinders and out through holes cored or drilled in such cheeks to the
comutator. The spindle is insulated from the cheek plates, by suitable rings or
liners of some non-conducting substance, such as ebonite hard wood vulcanite
fibre etc. I sometimes ventilate my armature, by useing plain holes drilled through
the ribs or stays, and the outer cylinder, or if the cylinder be cast they may be
cored. I also find that groving, the ribs or by placing them upon the cylinder in

page_text: several peices with air spaces, or gaps between them, helps to keep the cylindrical
armature cool. If the external cylinder be cast, such air spaces may be arranged
for in the casting.
I also employ two cylinders or armatures, the body of the machine with its field
magnets, being arranged in a duplex form, to admit of this. When two cylinders
are used, part of the current derivable from one, being used as an exciting current
for the field or inducing magnets, either the whole current from it being sent
round the field, or part of it (this being regulated by the manner in which the
field or inducing magnets are wound) the remainder with the current derivable
from the other armature being available for external use, or the current derivable
from both armatures can be sent round the field which will then form part of the
direct main circuit, or a part of the current derivable from both armatures can be
sent round the field or inducing magnets, the residual current being used for
external purposes or one armature may be caused to give out, what is known as a
tension current while a low tension or quantity current is given out by the other.
Although I have hitherto spoken of my invention as being applicable to machines
of the cylinder type, it is equally applicable to armatures of machines made upon
the disc or wheel pattern, in which the diameter is much greater than the width.
The field magnets also can be wound in a variety of ways, to suit circumstances,
as for instance they can be wound with wire of smaller sectional area, and much
greater length and consequently much higher resistance, than the armature, and
form a derived circuit from the main or external circuit, beyond the commutator
or they can be wound so as to form a low resistance compared with the armature.
The coils of insulated wire surrounding the armature may be coupled up in a
variety of ways. I obtain a very good effect by coupling the inner wire of one
coil, to the outer of the next, and also by winding my wire over the cylinder, and
by bringing the end through one of the ribs, which is drilled or cored for the
purpose, or the inner or outer end of each coil may be brought through each rib,
such rib being cored or drilled to receive it.
Having now described my invention I will proceed to do so more completely by
means of the drawing
Fig. 1. Represents a sectional view of my invention as applied to a machine of
the ordinary cylinder type, the thin inner and outer cylinder is shewn at A A¹
with the ribs or stays B. B' rivetted to it by the rivets C the ends or cheeks D D
being screwed to such stays which it will be seen project beyond the cylinder a
sufficient distance to allow the folds of wire to cover it as shewn in the lower side
of the drawing at E the plates being drilled or cored out as at F to allow the ends
of the wire to pass out to the commutator G
Fig. 2. Shews an end view of the cylinder and the method of fastening the ends
or cheeks to the stays by the screws at A the openings by which the wire passes
to the commutator are also shewn at F.
Fig 3. Represents a duplex machine in which one armature A. can be wound to
a low tension, the other armature B being wound to a high tension, one method of
placing the field magnets C is also shewn, but they can be arranged in a variety
of forms as circumstances may require, my invention being applicable to nearly
every type of machine in use.
Figs 4 and 5 Shew my invention applied to the armatures of machines of the
disc or wheel type
Figs 6 Shews a cylinder of cast iron with the ribs cast upon it, and two thin
liners forced in to cylinder the sides being screwed to the stays, or ribs or under
certain conditions, they can be cast in one peice with the cylinder the spindle
being insulated from them.
Having now described my invention, and the best means with which I am
acquainted, for carrying the same into effect, I would have it understood that
the shape of the armature may be modified or varied to suit required circum-
stances, and although I have by my description, and drawings shewn how my
invention may be carried out. I do not confine myself to the precise details

page_text: described and shewn as they may be varied in many ways without departing from
the peculiar features of my invention
I claim as under.―
1st An armature constructed of thin sheet iron, cast iron or malleable iron
consisting of an outer cylinder, enclosing an inner divided, and seperate cylinder
an aunular air space existing between such inner and outer cylinders as shewn
and described.
2nd Stays or ribs rivetted, or screwed to the outer cylinder, or forming part of
it, and projecting over both ends, such stays being one seperate peice, or consisting
of several peices with gaps or spaces between them. The stays being wide enough
to allow tubes of copper, silver or other good heat conducting metal to pass through
them to the annular air chamber between the inner and outer cylinders
3rd The covering of closely opposed parts, of armature and field with thin sheet
silver, copper, or other good conducting metal, deposited electrolytically or by
rivetting, screwing, or sweating thin sheets of the conducting metals to such
surfaces
4th The employment of two cylinders so wound as to supply a tension or
quantity current or both together from the same machine
In witness whereof I the said Alfred James Jarman have hereunto set my
hand and seal this 25th day of October in the year of our Lord, 1882
Witness. FRANCIS M ROGER
21 Finsbury Pavt EO
ALFRED, JAMES, JARMAN. (LS.)