IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
Year: 1882

page_text: LETTERS PATENT to Rookes Evelyn Bell Crompton of the Mansion House
Buildings, Queen Victoria Street in the City of London, Engineer for an
invention of "IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES"
PROVISIONAL SPECIFICATION left by the said Rookes Evelyn Bell
Crompton at the Office of the Commissioners of Patents on the 3rd June
1882.
ROOKES EVELYN BELL CROMPTON of the Mansion House Buildings Queen
Victoria Street in the City of London Engineer "IMPROVEMENTS IN DYNAMO
ELECTRIC MACHINES
"
My improvements in dynamo electric machines relate more particularly to those
in which the rotating armature is of disc or flat ring form, although some portions
of the invention may be adapted to dynamo machines of other form.
In the following description, I use the word disc to mean any ring or disc the
radial width of which is considerable, in relation to its width measured parallel to
the axis of revolution
The great difficulty hitherto met with by those using the disc form of armature
is that the total number of coils, that can be wound on to it, is governed by the
measurement of the inner edge of the winding and as from this measurement has
to be deducted, the space taken up by the spokes or other attachments to the
central hub by which, the disc is sustained and driven, if the radial width of the
covered portion of the disc is at all great in proportion to the whole of the radius*
the surface of the outer circumference covered by the winding will be relatively
small in proportion to what is left uncovered In the case of the radial width of
the covered portion being one half of the total radius not more than forty five per
cent of the whole outer circumference will be covered with wire
By my improved method of winding which I hereafter call step winding I avoid
this waste of space.
My step winding may be briefly described as follows:-I divide the disc off into
as many segments as I intend to have separate coils and on to each of these
segments I wind as many equal and parallel turns of wire as its inner circum-

page_text: ferential width will admit of, I then continue the winding through a series of holes.
pierced through the disc or steps cut in the segments in such manner and order
that each successive turn of wire or group of turns of wire is rather shorter than
the one preceding it; in this manner I fill up the otherwise unoccupied triangles
with winding in a series of turns or groups of turns of wire arranged stepwise, so
that the whole of the wedge shaped segments are completely covered.
This plan may be carried out in various ways either with discs built up of
separate segments or made solid with suitable holes pierced in them or otherwise.
The core or disc may consist of soft iron or of nonmagnetisable material as may be
preferred.
I generally mount the disc in the usual manner on a hub, with axis capable of
being revolved between magnetic poles.
In the case of the machines being of such dimensions, that the wire I wind on
to the disc becomes really a bar of copper of great weight and size I prefer to put
each turn of winding on in the form of a staple or stirrup of copper, the connection
being made to the next turn of the winding by means of a copper bolt passing
through the hole in the disc, or instead of using stirrups of copper I can use
straight copper bars, having holes pierced at both ends to enable connection to be
made by copper bolts as before described, the holes in the disc being pierced in
such positions as to enable the step by step arrangement above described to be
carried out
By this arrangement built up disc cores can be employed of very large dimensions
"say to 20 or 30 feet diameter" and each several pair of bars can be removed for
examination or repair without necessitating the removal or disturbance of any
other bar or any other portion of the disc
In certain cases I find it convenient to build up my core of soft iron spokes
separated by wedge shaped pieces of nonmagnetisable material
I sometimes use a continuous ring of soft iron or of nonmagnetisable material
possessing considerable tensile strength this ring being placed external to the
winding, and for the purpose of resisting the strain due to centrifugal force.
In order to give facilities for removing the disc from the machine, I fit the pole
pieces of my magnets with certain liners or extensions of the same, so that by
removal of the liners alone, space can be obtained to allow of the passage inwards
or outwards of the disc
To allow of the use of bearings of great length in which the axis of the machine
can revolve with a minimum of heating and wear I construct the same on what is
known in mechanics as the spherical principle, the exterior surface of the metal
forming the bearings being formed to a spherical contour and resting in pedestals
suitably formed so that these bearings can adjust themselves accurately in line
with one another.
I prefer to mount the mechanism carrying the brushes or contact pieces on the
above mentioned bearings.
I construct the brushes or contact pieces for Dynamo Electric machines as
follows Instead of obtaining the motion to or from the axis of the commutator
by pivoting the outer end of the brush on an axis parallel to that of the com-
mutator I mount my brushes in boxes or slides, and propel them into contact with
the surface of the commutator by suitable springs acting from behind them so as
to move them forward in a longitudinal direction In order to obtain the requisite
elasticity of each part of the brush I build it up of a series of thin plates of copper
or other suitable material, slightly spaced apart by distance pieces, at their back
ends I sometimes make these plates slant over to the right or to the left as may be
found most convenient further I cut the ends of the plates at an angle so that the
direction of the motion of approach of the brush may be at a considerable angle
with the axis of the main spindle.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Rookes Evelyn Bell Crompton in the Great Seal Patent Office
on the 2nd December 1882.
ROOKES EVELYN BELL CROMPTON of the Mansion House Buildings Queen
Victoria Street in the City of London Engineer.
"IMPROVEMENTS IN DYNAMO-
ELECTRIC MACHINES"
My improvements in dynamo electric machines relate more particularly to those
in which the rotating armature is of disc or flat ring form although some portions
of the invention may be adapted to dynamo machines of other form. In the
following description I use the word disc to mean any ring or disc the radial
width of which is considerable in relation to its width measured parallel to the
axis of revolution.
The great difficulty hitherto met with by those using the disc form of armature
is that the total number of coils that can be wound on to it is governed by the
measurement of the inner edge of the winding, and as from this measurement has
to be deducted the space taken up by the spokes or other attachments to the
central hub by which the disc is sustained and driven if the radial width of the
covered portion of the disc is at all great in proportion to the whole of the radius ;
the surface of the outer circumference covered by the winding will be relatively
small in proportion to what is left uncovered.
In the case of the radial width of the covered portion being one half of the
total radius not more than forty five per cent of the whole outer circumference
will be covered with wire.
By my improved method of winding which I hereafter call step winding I avoid
this waste of space.
My step winding may be briefly described as follows:-
I divide the disc off into as many segments as I intend to have separate coils
and on each of these segments I wind as many equal and parallel turns of wire
as its inner circumferential width will admit of; I then continue the winding
through a series of holes pierced through the disc, or steps cut in the segments
in such manner and order that each successive turn of wire or groups of turns of
wire, is rather shorter than the one preceding it-In this manner I fill up the
otherwise unoccupied triangles with winding in a series of turns or groups of
turns of wire arranged stepwise so that the whole of the wedge shaped segments
are completely covered.
Figures 1 to 5 show varied methods of my improved system of winding―
Figure 1 shews the side view and part cross section of a wrought iron disc with
holes a. b. pierced through it in the manner shewn in the Drawing-The interior
surface of these holes is lined with a suitable insulating material-There are other
sets of holes c also lined or bushed with insulating material.
I commence to wind one of the segments shewn, at the oblong hole a and
continue to wind the section as above described until the hole a is filled with
wire- Afterwards I continue the winding through c¹ c² c³ et cetera until I have
reached the hole most remote from the centre-This process has to be repeated for
every individual section until the entire surface of the disc is covered with wire
starting the winding at a hole a or b alternately The ends of the wire of each
section are dealt with in the usual way according to the system on which the

page_text: machine is built either by bringing the finishing end of the wire of one section
together with the starting end of the next section to the commutator or otherwise
as the case may be.
It may be seen that I do not confine myself to only one layer of wire but I can
in the manner described wind on layer after layer until the required length of wire
is wound on to the disc.
In Figure 2 I show another method of winding-In this case the disc core
is built up of several segments made of malleable cast iron or other suitable
magnetizable material one edge of each segment being formed stepwise as shewn
at d. These segments are arranged by preference in pairs, that is to say, two or
more segments are so bolted or secured together or connected in such manner that
they form a rigid and self contained double or compound segment capable of
withstanding the tangential strain caused by the rotation of the disc. The
advantage of this arrangement is, that the respective segments can be wound
separately and, built up into the disc or be subsequently removed and replaced
without disturbing the rest of the segments forming the disc. The winding is
precisely similar to that shewn in Figure 1 but it is evident that it can be effected
much more easily and cheaply, as each segment can be wound before it is bolted
to the next segment and the winding can be effected in the lathe or by other
suitable mechanical contrivance.
Figure 3 shows one of my methods of winding which may advantageously be
adopted for dynamo machines of large dimensions where the armature coils are
of such thickness that they virtually consist of copper bars-m, m, m indicate the
position of the steps of the winding.
The Drawing sufficiently shows the arrangement-each turn of the winding
consisting of a stirrup formed of copper bar by preference of rectangular section
the connections between adjacent turns being made by copper bolts passing
through the holes in the discs. In this the iron core may be either formed of
several thicknesses of plate iron rivetted together or the centre may consist of
a wheel shaped body built up of phosphor bronze manganese bronze or any other
nonmagnetizable metal of sufficient strength and tenacity having spokes and a rim
connecting the spokes as shewn in Figure 5. To the sides of this rim I rivet soft
wrought iron plates as shewn at b Figure 5-these plates to be of such radial
dimensions as are required for the core. The space between these two side plates
I fill by winding into it wrought iron tape of a width corresponding to the
distance between the plates until the whole space is completely filled with wrought
iron tape and the core thus completed.
In Figure 4 I shew another method of constructing the core so as to afford
greater facilities for winding on the wire-The holes a and b corresponding to the
oblong holes a and b in Figure 1 are in this case connected by radial slots extending
to the inner circumference of the plates-This enables the wire I use for winding
to be first coiled on a small bobbin which can be passed through the hole in the
centre of the disc and so the wire can pass through the radial slots into the position
it occupies in the finished winding.
The construction of the core in Figure 4 may be similar to that above described
for Figures 3 and 5 that is to say the core may be constructed of a central casting
of phosphor bronze or other suitable material having the oblong holes a and b
formed in the casting the side plates being subsequently rivetted on at the rim
as in Figures 3 and 5-the space between the side plates being subsequently filled
with wrought iron tape and the external holes c, c being subsequently drilled out
and bushed with insulating material.
Having thus described the nature of my said invention and means adapted
for carrying the same into effect I would have it understood that what I claim is,
First, The system of step by step winding of the wire or rods forming the
armature coils of dynamo electric machines substantially as herein set forth.

page_text: Secondly. The arrangement or combination of parts forming the coils of the
armatures of dynamo electric machines by means of rods of varying lengths as
described in respect of Figure 3.
In witness whereof I the said Rookes Evelyn Bell Crompton have hereunto
set my hand and seal this Second day of December in the year One
thousand eight hundred and eighty two:
Witness
ALFRED G BROOKES
59 Chancery Lane London.
R. E. B. CROMPTON (L.S.)