Improvements in Electro-motors and Apparatus used therewith for Dental and other Purposes.
Year: 1889

page_text: Date of Application, 11th May, 1889
Complete Specification Left, 10th Mar., 1890-Accepted. 19th Apr., 1890
PROVISIONAL SPECIFICATION.
Improvements in Electro-motors and Apparatus used therewith for
Dental and other Purposes.
I, THOMAS (UTTRISS 72 New Briggate Leeds, Electrical Engineer do hereby declare
the nature of this invention to be as follows :-
My Improvements consist of an arrangement for instantly stopping the rotation of
the burr, drill, stone, or other tool actuated by the motor, by making use of an electro-
magnet for actuating a clutch arrangement attached to the motor, the current for
working the electro magnet being preferably obtained from the same source as used
for driving the motor.
The magnet coil or coils are connected electrically, either series or shunt with the
motor.
The motor is started or stopped and the speed regulated by means of a current
interrupting device and a variable resistance or resistances in the main circuit and
worked by either hand or foot.
When in use the motor is suspended or supported in a convenient position near the
operator, the hand piece & tool being connected to the motor by a rigid or flexible
shaft & sheath in the usual manner.
When portability & extremo lightness of motor is required it is made of small
weight & dimensions and is attached direct to the hand piece and tool, so that the
whole apparatus can be held in the hand thus giving more freedom of action or if
proferred the motor can be fixed in some simple manner such as by a strap &c. to
the arm, shoulder or other convenient part of the operator & a short flexible
connection used to connect the motor to the hand piece & tool.
The apparatus as above constructed may be used for many purposes such as are
required by dentists &c. or for engraving polishing drilling &c. &
where a portable electric-motor would be of use.
many other
purposes
COMPLETE SPECIFICATION.
Improvements in Electro-motors and Apparatus used therewith for
Dental and other Purposes.
THOMAS CUTTRISS, 72 New Briggate, Leeds, Electrical 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:-
My improvements consist of an arrangement for instantly stopping the rotation of
the tool driven by an electro-motor and of an improved form of adjustable resistance
or current regulator for varying the speed of the motor. In the accompanying
drawings, A is one of the bearings of the motor supporting the hollow shaft B to
which the armature is attached.
The shaft C is free to revolve in B from which it receives motion when desired by
means of the clutch to be described. One half of the clutch D is rigidly attached to
shaft B the other half of the clutch D 1 is free to move along the shaft C in and out
of gear with D. The end of the shaft C carrying part D 1 of the clutch is squared
so that motion can be communicated from shaft B to shaft C when the clutch is
in gear.
The movement of the portion D1 of the clutch is controlled by the electro magnet E
and armature F by the tongues H H.
The electro-magnet E is in electrical connection with the motor so that the same
current which works the motor energizes the electro magnet & brings the clutch into
DC77

page_text: gear the motion of shaft B thus being communicated to shaft C. On interrupting
the current the clutch flies out of gear by means of the antagonistic spring J.
The motion of shaft C is thereby instantly arrested although the armature of the
motor continues to revolve by virtue of its acquired momentum.
Fig. 4 is a sectional view of the adjustable resistance or current regulator. The
metallic plates K & L are separated by the insulating ring M composed of slate or
other suitable material. The enclosed space P is filled with a mixture of granulated
carbon & asbestos fibre and the loose metal plate N. On pressure being applied to
plate N the mixture of carbon and asbestos is compressed & the electrical resistance
reduced.
The regulator is connected in series with the motor so that any variation in its
resistance, & consequent variation of the strength of the electric current in the motor
affects the speed of the latter as desired.
By mixing asbestos fibre with the granulated carbon a greater variation of
resistance is obtained than when using carbon alone as is the usual method.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed I declare that what I
claim is-
1. An electro-motor with an inner loose shaft & clutch substantially as illustrated
and described.
2. An electric current regulator or resistance composed of a mixture of granulated
carbon and asbestos fibre substantially as described.
AL 1800
THOMAS CUTTRISS.