Improvements in Dynamo-electric Generators and Motors.
Year: 1891

page_text: COMPLETE SPECIFICATION.
Improvements in Dynamo-electric Generators and Motors.
We, CLAUDE WILLIAM ATKINSON, and LLEWELYN BIRCHALL ATKINSON,
of Woodfield Works, Harrow Road, in the County of London, Civil Engineers,
do hereby declare the nature of this said 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 relates to improvements in dynamo electric-generators and motors
and has for its object in general the provision of means for enclosing the brushes
and commutators of such machines so as to render them suitable for working in the
presence of inflammable or explosive atmospheres and in particular to improve-
ments in the arrangement and construction of the commutator and brushes as
described in Patent No. 16,62387 in which the brushes and commutator are enclosed
within a casing in such a manner as to prevent any ignition of the explosive
atmosphere being effected from the interior by the sparking of the brushes.
In the arrangement of commutator and brushes as described in the aforesaid
Specification No. 16,62387 it has been found that the wearing of the commutator
during continuous working effects a considerable change of volume in the space
within the enclosing chamber so much so that should the gaseous contents of the
enclosed chamber explode the explosion might be communicated to the atmosphere.
In order that our invention may be the better understood we now proceed to
describe the same in relation to the drawings hereunto annexed reference, being
had to the letters and figures marked thereon. Like letters refer to like parts in
the various figures.
Figure 1 is a part sectional view of commutator, brushes, and the casing around
them.
Figure 2 is an end view of the casing showing the position of one brush
dotted in.
Figure 3 is a modified arrangement having a butt brush.
We carry out our invention as follows-
In Figure 1A is the shaft of the dynamo or motor upon which is rigidly
attached a facial commutator B, upon the face of which the contact strips fare
attached, these latter being connected in the usual way to the various coils of the
armature. Upon the bearing carrying the shaft A, or preferably upon the shaft
itself is loosely mounted a casing d having circular rings d¹ between which is
arranged a screwed ring 6 which engages with a further ring a a part of which lies
in close proximity to the periphery of the commutator. The air space e existent
between the rotating commutator and the stationary casing must of necessity be as
small as possible in order that any explosion of gases within the casing shall not be
communicated to the outside.
Upon the casing d we arrange two or more excrecences or boxes C, within which
the brushes g are situated and fixed. The space existing between the shaft or bush
and the casing may be filled up by any material H which can be cut away as
desired. The necessity of the cutting of this material will be hereinafter more fully
described.
The casing may be prevented from rotation by being either detachably attached
to the bush of the bearing or the pedestal. As the space available in such an
arrangement of commutator is very limited with regard to the disposition of the
brushes we prefer to arrange the commutator strips f tangentially so as to enable
the brushes to be disposed within the casing and to make contact with the com-
mutator in the novel manner

page_text: We can however arrange the strips radially where desirable. As the com-
mutator wears it becomes necessary to move the case carrying the brushes nearer
to the commutator.
The object of moving the whole case to the commutator rather than moving the
brushes carried within the case towards the commutator is to keep the volume of
gas contained within the casing d as small as possible. This adjustment we effect
by means of the union nut which by its screw engagement with the casing A
draws the casing d by means of the rings d' nearer or further from the commutator B
in accordance as to whether it is screwed on or off.
The material H which fills the space between the casing and the shaft may be
cut away should the left hand face come in contact with the commutator nuts m
when the casing is screwed up towards the face of the commutator.
Figure 3 shows a modified arrangement of casing adapted to carry a butt brush.
It is quite obvious that this casing may be used in conjunction with the main casing
surrounding the armature as described in Figures 1 & 2 of Specification No. 12,67687
The joint between the armature casing and the commutator casing may be made by
means of a flange or in any other equivalent manner.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1st. In a dynamo electric generator or motor the combination of a commutator
having contact strips on its face at or about right angles to the axis of rotation;
with a casing adjustably attached to the framing of the machine, carrying the
brushes, the said casing being capable of adjustment towards the face of the com-
mutator, to compensate for wear and maintain the smallest volume, the space
between the rotating periphery of the commutator and the casing being as small as
possible, and of such a length as to prevent the passage of flame.
2nd. In such an enclosed commutator casing the combination of the casing
carrying the brushes and a union nut with a casing embracing the periphery of the
commutator and connected to the commutator casing by means of the said union
nut substantially as described.
3rd. The construction and arrangement of a commutator and casing substantially
as described and illustrated in the accompanying drawings and for the purposes
set forth.
Dated 041 1
T
1001
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicants.