IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
Year: 1882

page_text: LETTERS PATENT to William Edward Ayrton Professor of Technical Physics,
Fellow of the Royal Society and John Perry Professor of Mechanical
Engineering and Applied Mathematics in the City and Guilds of London
Technical College, Finsbury in the county of Middlesex for an Invention of
IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
PROVISIONAL SPECIFICATION left by the said William Edward Ayrton &
John Perry at the Office of the Commissioners of Patents on the 27th June
1882.
WILLIAM EDWARD AYRTON Professor of Technical Physics Fellow of the Royal
Society, and JOHN PERRY Professor of Mechanical Engineering and Applied
Mathematics in the City and Guilds of London Technical College Finsbury in the
County of Middlesex IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES.
The first part of our Invention consists in the use of a combination of steel and
wrought iron in the field magnets of a Dynamo Electric Machine. The steel and
iron may be combined together as a tube of steel enclosing a wrought iron core or
a tube of wrought iron enclosing a steel core or alternate tubes of wrought iron
and steel enclosed within one another or alternato plates of steel and wrought iron
or any combination of these arrangements. We find that a Dynamo Machine with
field magnets of this kind behaves to somo extent like a combination Magneto and
Dynamo Machine and the result is that with a proper arrangement of winding at
a certain speed it is possible to obtain a constant Electro motive force between the
two ends of the outside circuits whatever be the resistance of the outside circuits
and with other arrangements of winding and with other speeds it is possible to
obtain a constant current through the outside circuit. In fact we are able to obtain
either constancy of electro-motive force or constancy of current; so that whether
we work incandescent Lamps or Motors in parallel circuit or Lamps or Motors in
series we got a very large increase in steadiness that enables one Motor or Lamp
to be independent of all the rest.
The second part of our invention consists in a method of winding any ring
armature with wire. The coils which wo place upon an iron ring are not numerous
enough to cover it completely. The ring is made of two pieces which aro jointed

page_text: together in such a way that the screws or rivets or bolts are flush with the
ordinary surfaces of the ring. The coils are slipped on these halves and between
every two is also slipped a ring of wrought iron out of which a small portion is
cut at one place, so that the ring is incomplete, for the purpose of preventing
induction currents so that it looks somewhat like a horse-shoe. In some cases this
iron piece is nearly like the letter U and does not require to be slipped on when
the armature is in two halves but may be put on after the halves are joined
together. In any case it will be observed that as the coils of wire may be very
expeditiously made and baked after the manner described in our Patent No. 1178
of 1880 the labour of winding the ring armature is very materially reduced; since
after the two halves are fastened together only one or in some cases two coils
require to be wound by hand. Indeed when the pieces of iron are not so shaped
that they require to be strung upon a ring, so that they may be placed on after
the ring is made up, No coils require to be wound by hand and this is also the
case if the oblique coiling is employed which is described in Patent No. 1178 of
1880 Sometimes the attachment of our armature to its spindle is effected by
means of a wooden centre as described in the above mentioned Patent or by means
of a metallic boss and arms which can be screwed at their outer ends to more or
less of the iron separating pieces.
The third part of our invention consists in a method of connecting up when any
even number of pairs of field magnets are used near the armature Thus when we
employ four bar magnets on each side of a rotating armature as figured with the
specification of the above mentioned patent No. 1178 of 1880 so that four equal
portions of the ring are in alternately dissimilar fields of force, we use an odd
number of coils for the ring; thus there may be 9 coils for example whose one set
of similar ends with respect to the ring are a, c, e, g, i, k, m, o, q, the other set
being b, d, f, h, j, l, n, p, r; a is joined to the commutator piece A, a to C, e to E,
g to G, and so on; whereas d is joined to K, e to M, ƒ to O, h to Qj to A, 1 to 0,
and so on. In this way we are able to obtain very intense magnetic fields with
magnetic poles which are near together and which may be of any even number round:
any ring and yet only two brushes are needed on the commutator When more
than four fields are used round the ring it is not merely an odd number of coils
that must be employed, but such a number as will enable us to have them joined
as in a Grammo ring using only two brushes When more than four fields are
used round the ring we can still use two brushes. Thus taking six as an example of
any even number. If 1, 2, 3, 4, 5, 6, are six points of equal division of a circle.
Suppose a coil to be at 1 whose ends are a, b. Suppose the distance between two
coils to be a. Let the distance of a coil past 3 be and of another past 5 be. Then
if a, b a¹, b¹ a", 6", be the similar ends of these three coils a and a¹ and a" are
joined to three commutator pieces; b is joined to a¹, b' to a" and " to o if o
is the first end of the coil beyond the first coil. Thus if there are six fields there
must be a total number of coils on the ring 3 n 1 where n is any integer; thus
there may be 5 or 8 or 11 etc. coils. If there are N fields the number of coils on
the ring may be any number of the form 1 where n is any integer.
Nn
-
The fourth part of our invention consists in the strengthening of such an
arrangement of magnets as is shown in the drawings attached to the specification
of the above mentioned patent No. 1178 of 1880 by joining together similar poles
by pieces of wrought iron which pass outside the rotating ring, and this we do
whether our coils are wound obliquely or not.
The fifth part of our invention consists in the use of a core for our armature of
Phosphor-bronze or Brass or Steel or any other strong material with a great many
rivets of soft iron passing through it. In practice we use just so many rivets as
cause the ring everywhere to be of much the same strength as it is at the joint.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Edward Ayrton & John Perry in the Great Seal Patent
Office on the 27th December 1882.
WILLIAM EDWARD AYRTON Professor of Technical Physics Fellow of the Royal
Society and JOHN PERRY Professor of Mechanical Engineering and Applied
Mathematics in the City and Guilds of London Technical College, Finsbury in the
County of Middlesex IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
The first part of our invention consists in the use of a combination of steel and
wrought iron in the field magnets of a Dynamo-electric machine. The steel and
iron may be combined together as a tube of steel enclosing a wrought iron core or
a tube of wrought iron enclosing a steel core or alternate tubes of wrought iron
and steel enclosed within one another or alternate plates of steel and wrought iron
or any combination of these arrangements. The plate arrangement is shown in
figs 1, 2 and 3 at A and B. We find that a dynamo machine with field magnets
of this kind behaves to some extent like a combination magneto and dynamo
machine and the result is that with a proper arrangement of winding at a certain
speed it is possible to obtain a constant electromotive force between the two ends
of the outside circuits whatever be the resistance of the outside circuits and with
other arrangements of winding and with other speeds it is possible to obtain a
constant current through the outside circuit. In fact we are able to obtain either
constancy of electromotive force or constancy of current so that whether wo work
incandescent lamps or motors in parallel circuit or. lamps or motors in series we
get a very large increase in steadiness that enables one motor or lamp to be inde-
pendent of all the rest. The second part of our invention consists in a method of
winding any ring armature with wire. The coils which wo place on an iron
ring are not numerous enough to cover it completely. The ring is made of two
pieces which are joined together in such a way that the screws or rivets or bolts
are flush with the ordinary surfaces of the ring. The coils are slipped on these
halves and between every two is also slipped a ring of wrought iron out of which
a small portion is cut at one place so that the ring is incomplete as shown at C
fig 2 and D fig 4 for the purpose of preventing induction currents so that it
looks somewhat like a horse shoe. In some cases this iron piece is nearly like the
letter and does not require to be slipped on when the armature is in two halves
but may be put on after the halves are joined together. In any case it will be
observed that as the coils of wire may be very expeditiously made and baked
after the manner described in our patent No. 1178 of 1880 the labour of winding
the ring armature is very materially reduced since after the two halves are
fastened together only one or in some cases two coils require to be wound by hand.
Indeed when the pieces of iron are not so shaped that they require to be strung
upon a ring so that they may be placed on after the ring is made up no coils
require to be wound by hand and this is also the case if the oblique coiling is
employed which is described in Patent Nº. 1178 of 1880. Figs 8, 9 and 10
show other methods of carrying out our invention. The iron ring F has iron
screws standing out in radial rows and our coils are wound by hand as shown.
This method we find very useful when the coils are very oblique. The pins shown
at E prevent the wire bulging out on the exterior portion of the ring. Sometimes
we use iron radial pieces scrowed on instead of a set of radial screws.
In all cases
the heads of screws or surfaces of the pieces of iron stand out beyond the coiled
wire. These iron pieces or screws in all cases serve the double purpose of keeping
the coils in their places and causing the magnetic lines of force passing through
the coils to be those of very intense magnetic fields. Figs 11 and 12 show a

page_text: non-conducting ring into which and partly round which fit a great number of
radial plates of iron. The coils of wire are wound by hand as shown in fig
in this case being usually very oblique. In this case also the dissimilar magnetic
poles of the field magnets which form a field are not oblique to one another as
shown in figs 1, 2, 3 and 4, the whole necessary obliquity of our Patent No. 1178
of 1880 being obtained in the coils of wire themselves. In this case also our pole
pieces are much smaller radially than as shown in figs 1, 2, 3 and 4. Sometimes
the attachment of our armature to its spindle is effected by means of a wooden
centre as described in the above mentioned Patent or by a metallic boss and arms
which can be screwed at their outer ends to more or less of the iron separating
pieces
When the iron partial rings H and K are very thin instead of bolting the metal
centres to them we allow parts of the rings or plates to pass through slots or saw
cuts in the centres and then insulate them and fasten them in various ways.
When the core of the armature is non-conducting, as in figs 11 & 12 we solder
the partial rings or plates into the saw cuts or slots of the metallic centres
The third part of our invention consists in a method of connecting up when any
even number of pairs of field magnets are used near the armature. Thus when
we employ four bar magnets on each side of a rotating armature as shown in
figs 1, 2, 3 & 4 so that four equal portions of the ring are in alternately
dissimilar fields of force we use an odd number of coils for the ring; thus there
may be nine coils, for example, whose one set of similar ends with respect to the
ring are a, c, e, g, i, k, m, o, q, the other set being b, d, f, h, j, l, n, p, r; a is joined
to the commutator piece A, c to C, e to E, g to G and so on; whereas d is joined
to K, to M, f to O, h to Q, j to, to C and so on. In this way we are able to
obtain very intense magnetic fields with magnetic poles which are near together
and which may be of any even number round any ring and yet only two brushes
are needed in the commutator. The joining up of the coils when there are four
fields is illustrated in fig 6. When more than four fields are used round the ring
such a number of coils must be employed on the ring as will enable us to have
them joined as in a Gramme ring using only two brushes. Thus taking six as an
example of any even number. If 1, 2, 3, 4, 5, 6 are six points of equal division
of a circle. Suppose a coil to be at 1 whose ends are a, b. Suppose the distance
between two coils to be . Let the distance of a coil past 3 be and of another
past be. Then if a b, a' b', a¹¹ b¹¹ be the similar ends of these three coils
a and a¹ and a" are joined to three commutator pieces, 6 is joined to a¹, b¹ to a¹¹
and a to c if c is the first end of the coil beyond the first coil. Thus if there are
six fields there must be a total number of coils on the ring 3 n-1 where n is any
integer. Thus there may be 5 or 8 or 11 etc. coils. If there are N fields the
number of coils on the ring may be any number of the form NA - 1 where n is
any integer. The joining up of the coils for the case of six fields is illustrated in
fig 6. The fourth part of our invention consists in the strengthening of such
an arrangement of magnets as is shown in the drawings attached to the specifi-
cation of the above mentioned Patent by joining together similar poles by pieces
of wrought iron which pass outside the rotating ring and this we do whether
our coils are wound obliquely or not. Two of these picces of metal are shown
at G in fig 2. The fifth part of our invention consists in the use of a core for
our armature of phosphor bronze or brass or steel or any other strong material
with a great many rivets of soft iron passing through it. In practice we use just
so many rivets as cause the ring everywhere to be of much the same strength as
it is at the joint but this merely concerns the strength of the armature. If the
armature is strong enough the more rivets or pins or screws and the smaller they
are the better. We prefer in many cases for these pins or screws to pass com-
pletely through the ring standing out on both sides so that the coils of wire may
be kept in their places by them and also that they may maintain a strong magnetic

page_text: field. In this case we prefer to use very oblique coiling the opposite poles of the
field magnets being in a line parallel to the axis of rotation.
Having thus described the nature of our Invention and the means of par-
forming the same we would have it understood that we claim:-First. The use
of a combination of steel and soft iron in the field magnets of dynamo machines
substantially as described. Second. The use of separating pieces of soft or malleable
cast iron which are distinct from the core in coiling the armature of a dynamo
machine substantially as described and shown in figs 2, 4 & 5. Third. The use
of screws or of pieces of iron fastened with iron screws to the surfaces of the core
of the armature of a dynamo machine which come most nearly to the poles of the
field magnet for the purpose of producing an intense magnetic field and also of
holding very oblique coils in their places substantially as described and illustrated
in figs 8, 9 & 10. Fourth. The use of the thin iron separating pieces arranged
as at H and K figs 11, 12 & 13 substantially as described. Fifth. The use of
the method of connecting up the coils of an armature when there are four or
any other even number of magnetic fields produced in it substantially as described
and illustrated by the figs 6 & 7. Sixth. The use of the core for the armature
of a dynamo machine formed of any strong material preferably non-conducting
with a great many rivets or pins or screws of soft iron passing through it from
side to side substantially as described.
In witness whereof, I, the said John Perry have hereunto on my own
behalf and on behalf of William Edward Ayrton set my hand and seal
this
day of December in the year of our Lord One thousand
eight hundred and eighty two
TAME