Improvements in Alternating Current Generators.
Year: 1894

page_text: Date of Application, 21st Mar., 1894
Complete Specification Left, 21st Dec., 1891-Accepted, 26th Jan., 1895
PROVISIONAL SPECIFICATION.
Improvements in Alternating Current Generators.
I, JOHN SMITH RAWORTH, of 49 Queen Victoria Street, in the City of
London, Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention has reference to improvements in the construction of the coils or
bobbins of armatures of the disc or annular types used in alternating current
generators of the kind known as alternators. In such coils or bobbins the core is
usually made of some non-conducting and non-magnetic material such as slate, and
the conductor is of copper ribbon separated and insulated with suitable material
such as silk or cotton tape.
The defect of all such coils or bobbins is that they are deficient in strength, the
copper ribbon being too thin to resist the circumferential strains to which it is
unavoidably subjected.
According to my improved construction I support the conductor of which each
coil or bobbin is composed by tightly wound ligaments of suitable material such as
cord or metal wire, threaded through holes in the core and embracing the several
turus of the conductor on each side of the coil bobbin.
The cord or wire does not bear directly on the conductor but upon an insulating
backing piece which is recessed to receive the bindings. The said conductor may
also be protected by insulating armour introduced between the conductor and the
bindings. To render the binding process effective for the purpose set forth,
each coil or bobbin is or may be held between clamps, or in a clamping frame,
whereby it is subjected to great pressure which is maintained until the binding
thereof is complete.
Improvements in Alternating Current Generators.
I, JOHN SMITH RAWORTH, of 49 Queen Victoria Street, in the City of London,
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 reference to improvements in the construction of the coils or
bobbins of armatures of the disc or annular types used in alternating current
generators. In such coils or bobbins the core is usually made of some non-
conducting and non-magnetic material, such as slate, and the conductor is of
copper wire or ribbon, separated and insulated with suitable material, such as
silk or cotton tape. The principal defect of all such coils or bobbins, as at present
constructed, is that they are deficient in strength, the copper wire or ribbon being
1

page_text: too fine to resist unaided the circumferential strains to which it is unavoidably
subjected.
According to my improved construction the conductor of which each coil or
bobbin is composed is supported by tightly bound ligaments or bands of suitable
material such as hemp or linen cord or metal wire, preferably the former, threaded
through holes in the core and embracing the several turns of the conductor on each
side of the coil or bobbin. The cord or wire does not bear directly on the con-
ductor but upon an insulating backing piece which is recessed at intervals to receive
the bindings. I also further protect, stiffen, and insulate the said turns of the con-
ductor by an insulating armour that is introduced between the conductor and the
above described bindings, and which may be constructed of any suitable insulating
material, such as mica-cloth or varnished paper.
To render the binding process effective for supporting the turns of the conductor
as set forth, each coil or bobbin before and during the process of winding
should be held tight in a clamping frame of sufficient strength to exert a pressure
upon the conductor, in excess of that to which it could be subjected by the
mechanical strains which will be generated in the alternator for which the coil is
intended.
In the accompanying drawings,
Fig. 1 is a front elevation, and Fig. 2 a side view, as seen by making a cross
section of the armature, of one of the improved coils.
Fig. 3 is a front elevation of a portion of an insulating piece hereinafter
referred to.
A is the slate core, and A1 and A2 are the bolt holes therein for attaching the
bobbin to the armature ring. A³, A*, A³, Aº etc. are slotted holes in the slate for
admitting the cord or wire bindings B. C₁ and C³ represent the insulating
stiffening piece which is arranged to surround the conductor D and is provided
with recesses C3, C4, C5, C6, etc. for retaining the bindings B in place at the sides
of the coil. The insulating armour is shewn at E¹ and E; it will be observed that
it projects across the joint line between the conductor and the slate which is shewn
dotted.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is :-
1. Strengthening and protecting the coils or bobbins of an alternating current
generator by binding them with tightly wound ligaments or bands of suitable
material such as fibrous cord or wire substantially as hereinbefore described
whether or not an insulating armour be introduced between the bindings and
conductor.
2. In an alternating current generator, armature coils or bobbins constructed
substantially as described and shown.
Dated this 21st day of December 1894.