Year: 1896

page_text: Date of Application, 11th Nov., 1896
Complete Specification Left, 28th July, 1897-Accepted, 4th Sept., 1897
We, SIEMENS BROTHERS & Co., LIMITED, and GEORGE SYLVESTER GRIMSTON, of
12 Queen Anne's Gate, Westminster, in the County of London, Electrical Engineers,
do hereby declare the nature of this invention to be as follows:-
This invention relates to means of automatically retarding and arresting the
rotation of the armature of an electric motor when the electric circuit is opened.
For this purpose, the armature shaft is mounted in bearings allowing certain end
play, and is urged by a spring towards such a position that the magnetic middle line of
the armature is a little to one side of the magnetic middle line of the field. When
the motor is in circuit, the armature is attracted so as to bring the two magnetic
middle lines into coincidence or nearly so, the armature then revolving freely. But
when the circuit is opened and the attraction ceases, the spring moves the armature
shaft lengthwise and thereby presses a surface fixed upon the shaft on a surface
fixed on the framing of the motor, so that the friction of these rubbing surfaces.
retards and finally arrests the rotation of the armature. When the circuit is again
closed the armature is again attracted, separating the rubbing surfaces and thus
allowing the armature to rotate freely.
Dated this 11th dove a
Cavern bon 1900
ABEL & IMRAY,
Agents for the Applicants.
We, SIEMENS BROTHERS & Co. LIMITED, and GEORGE SYLVESTER GRIMSTON, of
12 Queen Anne's Gate, Westminster, in the County of London, Electrical Engineers,
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 relates to means of automatically retarding and arresting the
rotation of the armature of an electric motor when the electric circuit is opened.
For this purpose, as shewn in side view partly sectional in the accompanying
drawings, the armature shaft A is mounted in bearings BB allowing certain end
play, and is urged by a spring S towards such position that the magnetic middle
line M of the armature is a little to one side of the magnetic middle line F of
the field.
When the motor is in circuit, the armature being attracted tends to bring

page_text: the two magnetic middle lines into coincidence, the armature then revolving freely.
But when the circuit is opened and the attraction ceases, the spring S moves the
armature shaft A lengthwise and thereby presses the surface of the druin D which is
fixed upon the shaft on a surface E which is fixed on the bearing B¹ part of the
framing of the motor, so that the friction of the rubbing surfaces D and E retards
and finally arrests the rotation of the armature. When the circuit is again closed
the armature is again attracted, separating the rubbing surfaces D and E as shewn
in the drawing and thus allowing the armature to rotate freely.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, we declare that what we claim is :-
An automatic brake for an electric motor comprising a spring which presses a
friction surface on the armature shaft against a stationary friction surface when the
circuit being opened the field magnet ceases to attract the armature in opposition to
the spring, substantially as described.
Dated this 90th day of T... 1907
ABEL & IMRAY,
Agents for the Applicants.