IMPROVEMENTS IN OR CONNECTED WITH THE COMMUTATORS OR COLLECTORS OF ELECTRICAL MACHINES
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson at the Office of
the Commissioners of Patents on the 8th November 1883. Communicated to
him from Zenobe Théophile Gramme a person resident at Paris in the Republic
of France.
JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex,
Gentleman, "IMPROVEMENTS IN OR CONNECTED WITH THE COMMUTATORS OR
COLLECTORS OF ELECTRICAL MACHINES" a communication [to him] from Zenobe
Theophile Gramme a person resident at Paris in the Republic of France
This Invention relates to dynamo electric and electro dynamic machines and
combination of devices hereinafter described for operating the commutator brushes
or rubbers by causing the brush holders or carriers to oscillate simultaneously upon
supports arranged as hereinafter explained. In place of an oscillating motion the
brush holders may bo caused to partake of any other equivalent motion towards or
from the commutator.
When it is desired to operate a number of brushes simultaneously they have
usually been placed upon a single support or carrier which is caused to turn upon
the axis of the commutator but this arrangement renders the adjustment difficult
and an equal pressure of all the brushes impossible in practice.
According to the present invention the support of the brushes is stationary and
all the brush holders are operated simultaneously by the intervention of accessary
appliances arranged as hereinafter described.
In carrying out the said Invention as applied to a dynamo electric machine for
example presenting say six poles the three positive brushes are carried by suitablo
brush holders connected by studs or pivots to a stationary disc or support and the
three negative brushes are similarly carried by three other holders connected in like
manner to another disc or support also fixed or stationary. A star shaped plate
carries a series of pins which engage with corresponding recesses provided in the
extremities of the brush holders. By suitable means such as by a lever the star
shaped plate may be caused to turn on its centre and thereby operate all the
brushes simultaneously which preferably coincides with the axis of the machine
and thereby operate all the brushes so as to place them in or out of contact with
the commutator and adjust their pressure with great precision
In place of pivotting the two sets of brush holders upon the two separate discs
all the said brush holders may be carried by a single disc provided that they are
suitably insulated. If preferred the disc or discs may be dispensed with the brush

page_text: holders being supported directly by the frame of the machine. The star shaped
plate by which the brushes were operated in the arrangement hereinbefore
described may be stationary the discs carrying the brushes being caused to move
upon their axis relatively to the said plate instead of causing this plate to move
relatively to the discs. In place of the pins or the plate herein before described
tappets cogs or other equivalent devices may be employed to impart the requisite
motion to the brushes or collectors.
In the case of a machine having say twelve or other large number of poles the
series of positive brushes is preferably carried by one disc and the negative brushes
are carried by another disc. These two discs are screwed or rigidly connected
together and to a third disc or ring capable of turning on a support arranged
concentrically to the shaft of the machine. This ring and the two discs carrying
the brushes are insulated. Pins which operate the positive brushes are carried by
one annular plate and the pins which operate the negative brushes are carried by
another annular plate. These two plates are screwed or rigidly connected together
and to a ring preferably arranged at the side and on the same support as the ring.
connected to the discs carrying the brushes. This ring and the annular plates
connected thereto are insulated. By means of an endless screw or worm gearing
with a rack or segment of a worm wheel connected to the annular plates carrying
the pins for operating the brushes these plates may be turned to the right or to the
left and thereby take off.or put on and adjust the pressure of the brushes which
collect the current from the commutator.
The position of the brushes relatively to the polar axes is first adjusted by
causing the discs carrying the brushes to turn on the axis of the machine and
securing them in the proper position by means of a bolt working in a slot in a
fixed plate. When this bolt is removed the brushes may be turned completely
round on their support for the purpose of adjusting them accurately to the required
length. This may be done with great precision by bringing each brush in turn
opposite a fixed nick or mark and causing the carrier to describe exactly one
twelfth of a revolution at a time.
I