Improvements relating to Electric Motors.
Year: 1894

page_text: Date of Application, 11th Aug., 1894
Complete Specification Left, 11th May, 1895-Accepted, 29th June, 1895
Improvements relating to Electric Motors.
I, WILLIAM ROUTLEDGE, of 46, Low Friar Street, Newcastle-on-Tyne, in the
County of Northumberland, Engineer, do hereby declare the nature of this
invention to be as follows :-
This invention relates to electric motors and has for object to adapt them for
driving dental engines.
In carrying out my invention 1 provide the motor with a frame having one or
more recesses and clamps whereby the motor is adapted to be secured to the
pedestal of an ordinary dental engine, the opening formed by a recess and its
clamp being of a lozenge shape having flat or curved sides. In the said frame is
formed one of the bearings for the driving shaft of the motor.
In order to instantaneously stop the motor when the current is switched off,
I provide a brake adapted to engage the periphery of a wheel upon the driving
shaft of the motor by the pressure of an adjustable spring, the said brake being
renioved from the wheel when the current is switched on by means of a pivotted
frame actuated by the magnetism of the pole-pieces of the field magnet.
The brake is advantageously provided on portions of its surface with a lining
formed of pieces of leather or other suitable material let into cuts or nicks in the
brake shoe and cemented therein, the free ends projecting so
frictional or rubbing surface.
as to form the
For reversing the motor I provide a switch for reversing the current through
the armature, the said switch being mounted upon the motor and consisting of a
cylinder of insulating material designed to be rotated in a frame by a suitable
thumb-piece or head, one end of the cylinder being provided with a metal disc in
contact with the said frame which is in electrical connection with one end of the
line, while the other end of the cylinder is provided with two curved metal strips
near its edges in contact with spring contact pieces in electrical connection with
the commutator brushes. One of the said curved strips is in electrical connection
with the metal disc on the other end of the cylinder while the other strip is formed
with an extension arranged in the centre between the two strips but slightly higher
than them, the said extension being in contact with a spring contact piece forming
one of the terminals of the wire wound round the field-magnet. The other terminal
of the field-magnet is connected to the other end of the line.
Dated the 11th day of August 1894
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements relating to Electric Motors.
I, WILLIAM Routledge, of 46, Low Friar Street, Newcastle-on-Tyne, in the
County of Northumberland, 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:-
This invention relates to electric motors and has mainly for object to adapt them
for driving dental engines.

page_text: Figures 1 and 2 are respectively elevations of opposite ends of an electric motor
provided with my improvements:
Figures 3 and 4 are respectively a side elevation and a plan of the same:
Figures 5 to 9 are details hereinafter described.
a is the coil of the field magnet, and b, bare the pole-pieces. c is the driving
shaft carrying the armature d and commutatore; f,f are the commutator brushes,
and y is a pulley for transmitting the movement of the shaft c to the dental engine,
all of which parts are of well known construction.
According to my invention I provide a frame constructed of uprights h, h by
which it is secured to the pole-pieces b, b of the motor and cross-pieces 1, 2,
connecting the uprights h, together, the cross-piece / serving as a
bearing for
one end of the shaft e while the cross-pieces 12, 12 are provided with recesses i, i
and clamps j, j whereby the motor is adapted to be secured to the pedestal k of a
dental engine, as shewn clearly in Figures 3 and 4.
As in dental engines the pulley to be driven is arranged in close proximity to
the surface of the pedestal, it is essential that the driving pulley g should maintain
a similar position notwithstanding that different diameters of pedestals may be
employed in different dental engines. To enable this to be effected I make the
openings formed by the recesses i, i and clamps j, j of a lozenge shape, as shewn
clearly in Figure 4, whereby it will be seen that while they are enabled to fit
equally well any size of pedestal within certain limits they can do so without
materially affecting the relative position of the pulley g with the adjacent surface
of the pedestal. Instead of the sides of the opening just described being flat as
shewn they may be curved.
In order to instantaneously stop the motor when the current is switched off,
I provide a brake 1 designed to fit and be pressed against the periphery of a
wheel m (advantageously formed in one with the pulley g) by means of a spring n
located in a socket on a cross-bar o' attached to the vertical members h, h. The
brake is provided on the side portions of its inner surface with a lining formed of
pieces of leather or other suitable material let into cuts or nicks * and cemented
therein, the free ends of such pieces projecting so as to form the frictional or
rubbing surface. The brake is also formed with lugs having adjustable
screws therein and with a cylindrical projection p passing through the spring n
and into a guiding hole in a plug q screwed into the socket o, the said plug serving
to vary the pressure of the spring n upon the brake . The said brake is
removed from and maintained free of the wheel m when the current is switched
on by the magnetism of the pole-pieces b, through the medium of a frame r
of magnetic metal pivoted on screws, to the uprights h, has shewn in
Figures 2 and 3. The frame r is shewn detached at Figures 5 and 6 which are
respectively an elevation and a section on the line 6-6, Figure 5, and is provided
with lugs s, located beneath the screws 12, in the brake whereby when the
said frame is attracted towards the pole-pieces the brake is lifted free of the
wheel m.
For reversing the motor I provide a switch for reversing the current through
the armature d. The said switch is shewn detached in Figures 7 and 8 which are
respectively a sectional elevation and a horizontal section on the line 8-8, Figure 7,
and is secured upon a block t of insulating material attached to the pole-pieces b, b.
It consists of a cylinder u of insulating material designed to be rotated in a
frame by a thumb-piece or head u', the said frame being secured to the block t
and arranged in electrical connection with one end of the line by means of a binding
post w. One end of the cylinder u is provided with a metal disc in contact with
the frame and carrying the pivot pin u of the said cylinder, while the other
end, as shewn in Figure 9 which is an underside view of the cylinder u, is provided
with two curved metal strips a', x² near its edges in contact with spring-contact
pieces y, y' in electrical connection with the brushes f,f. The curved strip
is in electrical connection with the metal disc x through the medium of a

page_text: pin while the strip is formed with an extension arranged in the centre of
the cylinder u but slightly higher than the strips x1, x2 and in contact with a spring
contact piece z forming one of the terminals of the wire on the field-magnet. The
other terminal of the field-magnet is connected to a binding post z¹ to which the
other end of the line is attached. By this construction, assume the parts of
the switch to be in the position shewn and a current to be flowing through the
parts ir, v, x, 23, a, y and, through the armature and parts f¹, y, x³, and z to
the field-magnet. By turning the cylinder a half a revolution the current will
flow through the armature in the reverse direction, that is to say, it will flow into
the armature through the parts w, v, x, x³, x', y' and f¹ and out through the
parts f, y, a, a, and z.
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. The combination with an electric motor of a frame cousisting of uprights for
attachment to the motor and cross-pieces one of which serves as a bearing for one
end of the driving shaft while the other or others are provided with recesses and
clamps for securing the motor to the pedestal of a dental engine, the openings
formed by such recesses or clamps being of a lozenge shape with flat or curved
sides, all substantially as herein before described and illustrated in the accompanying
drawings.
2. The combination with an electric motor of a wheel having a brake designed
when the electric current to the motor is switched off to be applied by means of a
spring, but when the current is on to be taken and maintained off by the attraction
due to the magnetism of the pole-pieces of the field-magnet, substantially as
described.
3. The combination with an electric motor of a wheel having a brake designed
when the electric current to the motor is switched off to be applied by means of a
spring, but when the current is switched on to be taken and maintained off by the
movement of a pivotted frame attracted by the magnetism of the pole-pieces of
the field-magnet, substantially as hereinbefore described and illustrated in the
accompanying drawings.
4. The combination with an electric motor of a switch for reversing the current
through the armature, such switch consisting of a rotating cylinder of insulating
material having on one end a metal disc in electrical connection with one end of
the line and with one of two metal strips on the other end of the said cylinder, the
said strips being in contact with spring-contact pieces in electrical connection with
the commutator brushes and one of them provided with an extension slightly
higher than the metal strips in contact with a spring contact piece in electrical
connection with the wire on the field-magnet, substantially as hereinbefore described
and illustrated in the accompanying drawings.
5. The combination of parts forming the improved electric motor hereinbefore
described and illustrated in the accompanying drawings.
D
11 1
1005
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.