Improvements in Electrical Brush-holders.
Year: 1899

page_text: Improvements in Electrical Brush-holders.
WILLIAM JOHN POOLE, 19, Waverley Park, Shawlands, Glasgow, Electrical
Engineer, do hereby declare the nature of this invention to be as follows:-
A loose grip-plate, inserted between one side of the carbon brush & corre-
spondingly placed projections on the brush holder, & inclined at an angle with
the face of the carbon in such a manner that stress, applied in any convenient
way, which tends to set the plate at right angles with the face of the carbon
brush, will hold the brush firmly against the conducting surfaces of the holder.
Also the employment of link-bars fitted so as to restrict the brush to a
straight-line movement.
Dated this 6th day of June 1899
improvements in Electrical Drusд-nolders.
I, WILLIAM JOHN POOLE, Electrical Engineer, residing at 19, Waverley Park,
Shawlands, Glasgow, Scotland, 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:--
sur-
The head of the brush-holder is a metal casting or stamping, consisting of
the plate P having a rib G running up the centre, this rib being carried out
so as to form a projection similar to G. The plate P is to be of the same area
as the surface of the carbon block with which it is desired to make electrical
contact, and the surface of the plate is to be of such a nature that the electrical
contact between the plate and the carbon block shall be a uniformly good one.
The carbon block C being placed in contact with the plate P, a loose grip-
plate L is inserted between a notch in the end of the projecting piece Gand
the surface of the carbon block C. The length of the grip-plate L is greater
than the shortest distance measured from the notch in G to the nearest
face of C, so that when one end of the grip plate is placed in the notch and
the opposite end rests against the carbon block, pressure applied to the grip-
plate L will tend to set L at right angles to the surface of the plate P, and
in so doing will press and hold the carbon block firmly against P, as long as the
pressure is maintained. Pressure is applied to the grip-plate L in the follow-
ing manner. A slot is formed in the upper part of the projection G, the
major axis of the stot running at right angles to the plate P. The width of
the slot is such that it will let the shank of the screw W pass through it, but
not the shoulder at the upper end of the screw, this shoulder or head being
larger in diameter than the width of the slot. The length of the major axis
of the slot is such that it will allow the screw to move in a vertical plane at

page_text: right angles to the plate P as far as may be required. The screw W is inserted
into the slot in such a manner that its head rests on the top of the projection G
and its lower end is screwed into the centre of the grip-plate L. Now when W
is screwed home the grip-plate is drawn upwards, but one end being held in
the notch at the end of the projection G, the other end tending to swing
upwards comes into contact with the front side of the carbon block & forces the
opposite side of C against the surface of the plate P, the pressure increasing
as the grip-plate L approches a horizantal position, that is a position at right
angles to the surface of the plate P. In order to keep a uniform pressure on
the grip-plate L and at the same time to provide for the necessary contraction
or expansion of the brushholder and carbon block due to changes of temperature
or other causes, a spring washer is placed between the head or shoulder of the
screw W, and the top of the projection G where the screw passes through it.
This spring washer R when slightly compressed by turning the screw W
exerts a uniform pressure on the grip-plate L and holds the carbon block
firmly in position against the surface of the plate P, at the same time providing
for the necessary contraction or expansion of the metalic parts and carbon
block, and also preventing movement of the screw grip-plate, or carbon block,
through vibration or shock. In order to hold the carbon block C in its proper position
with regard to the commutator or other conducting surface with which it is
required to make electrical contact and at the same time provide for the
necessary movement in a vertical plane with that surface, the plate P is con-
nected with the fixed casting H by means of the foliated spring S, and the link-
bars B. These bars swinging on pins, one of which passes through the rib G
near its lower end, and the other connects the link-bars to a projection on the
lower side of the fixed casting H. The link-bars run parallel to the spring S
and are placed one on each side of the rib G¹ and the projection on the lower side
of H. The function of these bars is to restrict the motion of the plate P to a
vertical plane in relation to the conducting surface and to prevent lateral and
longitudinal movements of the carbon block C, the joint action of the spring S
and the bars B giving an approximately straight line motion to the carbon
block, so that as the block wears away and the pressure of the spring S feeds
it forward on to the conducting surface, it will always maintain an approximately
straight line movement in a vertical plane with that surface.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
First. The retention of a carbon brush in a predetermined position in its
holder by means of a loose plate one edge of which bears against the surface
of the carbon while the opposite edge bears against a fixed projection on the
brush holder, the plate being inclined at such an angle and being of such
dimensions that slight pressure applied to it in the proper manner, and acting
in the proper direction will hold the carbon brush firmly in the position desired,
even when subjected to vibration or shock, and at the same time allowing
the carbon to expand or contract freely.
Secondly. The use of link-bars in such a manner as to prevent longitudinal
and lateral motion or vibration of the carbon brush, while allowing it a free
but approximately straight line movement in the direction required to take
up wear.
Dated this 5th day of March 1900
WILLIAM JOHN POOLE,
Applicant.