Improvements in Electric Dental Motor Apparatus.
Year: 1894

page_text: Date of Application, 7th June, 1894-Accepted, 21st July, 1894
COMPLETE SPECIFICATION.
Improvements in Electric Dental Motor Apparatus.
I, FRANCIS NAPIER DENISON, of 26, Denison Square, in the City of Toronto,
in the County of York, in the Province of Ontario, Canada, Electrical Expert, 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 invention relates to Improvements in Electric Dental Motor Apparatus and
the object of the invention is to devise a simple, cheap and convenient apparatus,
more particularly adapted for dental work in which the motor, switch and various
parts of the outfit are under easy control of the operator, and it consists essentially
in the construction and arrangement of a swinging table motor, supported within
the case of the same, and communicating motion to the dental engine, switches
and other parts of the apparatus as hereinafter more particularly explained.
Fig. 1, is a perspective view of my electric dental motor apparatus complete as
it will appear when attached to the dental chair.
Fig. 2, is a longitudinal section through the dental table showing the means for
supporting the motor and for journalling the dental engine shaft.
Fig. 2, is a sectional plan view of the electro magnetic brake.
Fig. 2B, is a sectional end view from the line -y looking towards the ends of
the cores of the magnet.
Fig. 3, is a view partially in perspective and partially diagrammatic showing
wiring, brake, motor, hand and foot switches and their connections, the foot switches
being shown in an enlarged perspective view, a portion of the plate or frame of the
switch being broken away.
Fig. 4, is a plan view of the rheostat.
In the drawings like letters of reference indicate corresponding parts in each
figure.
A, is the dental chair, B, the head rest, and, C, the dental table.
The dental table, C, is provided with drawers, c, at all sides and extending
inwardly into a table so as to leave a central chamber, C¹.
D, is an electric motor secured in a suitable casing as indicated in Fig. 2. The
motor, D, is located in the chamber, C¹, and is supported by the casting D', which
is secured at the edge by screws, d, to the bottom of the table, the motor being
secured to the bottom of the downwardly extending portion of the casting by
screws, D. The motor is of course, cushioned upon the bottom of the casting by
the insulating plate, D³, bushing and washers.
E, is a tube leading from the bottom of the case of the motor and secured in
the ends of the bracket, F, by the nut, e. The tube, E, forms a pivot upon which
the casting, D', and consequently the table, C, turns and also forms a guide for the
circuit wires, G.
The circuit wires, G, lead through an opening in the bracket, F, which. is
swivelled on the top of the tubular standard, H, which is adjustably supported in
the usual manner within the bracket, I, attached to the bottom of the chair. The
circuit wires, G, lead through the tubular standard, H, to the bottom end from
which part diverge and pass to the switch board J, and the other portion to the
adjustable foot switch, K. The construction of the switch board and adjustable
foot switch I shall describe hereinafter.
The table, C, has the inner partition, c', and the outer sides, c².
L, is the main shaft of the motor, and, L', the brush-holder, one of which only

page_text: M, are the magnet coils which form part of the brake, the current of which is
derived through the wires, m.
N, is a disc armature which is made of soft iron and forms part of the
pulley, N'.
I shall now describe the construction of the brake, referring particularly to
Figures, 24, and, 2B.
Q, is the yoke of the magnet, which is suitably secured to the bearing standard, D'.
M², are the cores of the magnet, which are secured to the yoke, M', by the screws, m²,
and are provided with end Hanges, m³, of the full diameter of the coils. M, are the
coils of the magnet, which are wound in the usual way and in this case upon the
= spools, M³, having end flanges as shown.
The disc, N, is provided with an inwardly extending hub, N2. n, is a key inserted
through the shaft and extending into longitudinal slots, n', made in the hub, N2,
and normally abuts the inner end of the slots, n'. N', is a spiral spring, which
encircles the hub, N2, and extends between the disc, N, and the key, n, secured to
the shaft.
.
Ordinarily the disc, N, rotates with the shaft and is held away from the
demagnetized cores, M³, by the spiral spring, N. Immediately, however, upon the
current being turned into the magnets, a magnetic pull is exerted through the ends
of the cores, M2, upon the disc, N, which pull or suction draws the disc to the
cores of the magnet and holds the disc against such cores in such a manner
that the rotation of said disc and consequently the shaft is of course, instantly
stopped.
Although I show only one double magnet it will of course, be understood that
there may be a number of magnets arranged around the shaft.
The pulley, N', is longitudinally adjustable upon the motor shaft, L, and when
the current is thrown in as hereinafter described in reference to the diagrammatic
view the disc armature is drawn towards the magnet so as to almost instantaneously
stop the rotation of the motor shaft. The grooved pulley, N', is connected by the
round belt, N³, to the grooved pulley, O, which is suitably keyed to the removable
spindle, P.
The spindle, P, has a longitudinal groove, p, cut into it extending from near the
outer end of the spindle to the inner end thereof. The spindle, P, is held in
self-aligning bearings, P1, P2.
The self-aligning bearing, P', has an arc-shaped periphery so as to permit it to
rock horizontally and is pivoted on the screw, p, so as to permit it to rock vertically,
the bearing being supported in the ring shaped end, Q', of the arm, Q, which is
secured to the casing D₁ of the motor, and forms the yoke of the magnet.
2, is a sleeve which extends through the bearing, P, and upon which the
pulley, O, is primarily secured. 3, is a collar which is secured to the inner end of
the sleeve, p, within the bearing, P.
p, is a set screw which extends through the collar, p³, into the longitudinal
groove or key slot, p made in the spindle, P.
q, is a tubular thimble which extends through the top board of the table, C,
and, g, is a passage way as an extension to the tube, g, through the self aligning
bearing. This passage way is for the purpose of pouring oil in to keep the bearing
lubricated.
The self aligning bearing, P2, is constructed in identically the same manner as
the bearing, P, having an arc-shaped periphery and being pivoted upon the
screw, p. The self aligning bearing is preferably journalled in a rubber ring, P³,
having a metallic centre so that the sound vibrations caused by the rotation
of the shaft will not be carried by the table so as to cause an undue noise.
2, is a sleeve extending through the self aligning bearing provided with a
collar, p, through which a set screw, p, extends. The set screw, 28, projects into
the longitudinal groove or key slot, p, of the spindle, P.
R, is the cleaning brush for the points, which is secured on the outer end of the
sleeve, p. It will be noticed by the construction adopted that the rotating cleaning

page_text: brush, R, and pulley, O, will always remain in position in the selt aligning bearings
and that the central spindle may be withdrawn without disturbing the brush, R, or
pulley, O. When the spindle is withdrawn it may be again readily pushed into
position so as to rigidly connect the brush, R, and pulley, O, to it by passing the
spindle inwardly so that the set screws, p, p, will pass into the longitudinal
groove, p, when the spindle is pushed home.
S, is a flexible shaft, the inner end of which is soldered into the end of the rigid
spindle, P. The flexible shaft, S, has a sleeve, s, attached to it which is screwed
into the sleeve, T', forming part of the bracket, T.
t, are hooks secured to the bottom of the table and designed to support the outer
end or dental hand piece of the flexible shaft, S.
By the construction above described it will be seen that the table so constructed,
with the motor in the centre and the spindle extending out through the end or
side of the table will be much more convenient and effective for dental work than
any form of dental outfit at present in use. Although 1 show the counter
spindle, P, as driven from the main shaft of the motor it will of course, be
understood that with a high speed motor, the shaft of the motor might be continued
through the side of the table and be just as effective as the means described and
shown above.
I shall now describe the system of wiring in relation to the foot switch, switch
board and motor referring particularly to Fig. 3. I shall however, first describe
the construction of the foot switch.
U, is the base plate of the foot switch which is made hollow as shown, and, V, is
the pedal which is stiffly pivoted on the side lugs, v, upon the trunnion, V', forming
part of the hollow pin, V2, which extends through the boss, U₁, forming part of
the base plate, U. The hollow pin, V2, has a shoulder, v, at the top, which
rests upon the base plate, U, and has a threaded bottom end upon which is screwed
the nut, which is sufficiently tight to hold the pin in position and yet permit
the swivelling of the pedal. The trunnion, V, extending through the lugs, v,
permits of the tilting of the pedal.
U2, U³, are hollow stop pins attached to or forming part of the base plate, U.
W, is a bar of insulating material secured to the bottom of the base plate, U.
A great deal of the bar W, is broken away so as to exhibit details of construction.
X, is a bar of insulating material pivoted at the centre by the screw pin, a, to the
bar, W.
,, are pins which are secured on the ends of the bar, X. The pins, ¹, x²,
extend rearwardly into the slots, 23, 4, formed at the bottom of the
plungers X', X. The plungers, X1, X2, are preferably provided with convex
pushing caps, x³, xª.
V4, is a downwardly extending plug of insulating material secured to the forward
end of the pedal. The plug, V, is surrounded at the top by a ring, V³, of
insulating material which is designed to limit the downward movement of
the plug.
v, is a boss formed underneath the heel portion of the pedal, V. The boss, v³,
is provided with a rubber cushion, 10, which is designed to limit the downward
movement of the heel portion of the pedal.
Y, is a contact plate which is secured to the bottom of the base plate, U, and is
insulated from it by the plate, Y¹.
V5, V6, are spring contact plates which are rigidly secured at the bottom of the
insulating plug, V4, by the screw, Vs.
The spring plate, V, is held out of contact with the plate, Y, and the plate, V6,
is held out of contact with one of the plates, Z', of the flat rheostat, Z, which is
situated beneath the base plate, U, except when the foot switch is pressed either at
the toe or heel to throw in the motor or brake as the case may be.
The plates, Z', are separated from each other and are insulated from the rheostat
by the plate, Z³.
'
Z3, are the binding posts of the rheostat which extend through the insulating

page_text: prate into the rheostat. I here is one binding post for each plate and the posts are
connected to the plates by the wires, z.
w, w, are contact blocks secured at one end of the bar, W, and, w³, w³, w, are
bars flush with the inner side of the bar, W.
X3, X, are contact plates secured to the front side of the pivoted bar, X. The
plates, X, X, have at one end, the spring ends, X, X, which are continuously
held in contact with the contact blocks, w, w', secured to the bar, W, and at the
other, spring ends, X, X, which are designed to be respectively brought in contact
with the bars, w², w³, or w³, w³, as shown in Fig. 3, this depending on which of the
plungers X', X2, is pressed down.
The rheostat above mentioned in this instance as indicated in Fig. 4, has the
greatest amount of resistance at the right hand side, and the resistance decreases
from right to left, the left-hand-binding post having no resistance at all.
The left hand binding post, Z3, is connected by the wire, ', to the contact bar, w³.
The bar, w², is connected to the bar, wo, by the wire, 2².
W₁, W, W³, W, W, are binding posts of the motor, switch and switch board
circuits which are secured in the bottom of the bar, W.
2, is a wire connecting the contact plate, Y, with the binding post W1
3, is a wire connecting the wire, 22, and contact plate, wo, with the binding
post, W
4, is a wire connecting the contact block, w, with the binding post, W*.
5, is a wire connecting the contact block, w', with the binding post, W.
6, is a wire connected at one end to the screw, and consequently to the contact
plates, V, V, and extending up through the insulating pin, V4, underneath the
pedal through the opening, 8, down through the hollow pin, V2, as indicated by
dotted lines forward to the central binding post, W³.
7, is a positive wire through which when the switch, 8, is thrown into the position
shown in dotted lines the current passes ordinarily when the foot switch is not
thrown in through the wire, 9, shunt field, 10, wire, 11, and back by the negative
wire, 12.
When the forward end of the pedal of the switch is pressed down the circuit is
completed and passes through the positive wire, 7, in to the binding post, W³,
thence by the wire, 6, to and through the insulating plug, v, contact plate, V, one of
the plates, of the rheostat, through the rheostat, finally on the wire, z, to the
binding post, Z3, at the left hand side of the rheostat, the wire, 2', to the contact
bar w, thence by the contact plate, X³, to the contact block, w, thence by the
wire, 4, to the binding post, W4, thence by the wire, 13, to the motor, through the
motor, and by the wire, 14, back to the binding post, W, from the binding
post, W, by the wire, 5, to the contact block, w', thence by the contact plate, X,
to the contact bar, 0, thence by the wire, 3, to the binding post, W², thence by
the wire, 12, back to and through the switch board, J. The course above described
is that shown when the plunger, X', is pressed down and the bar, X, in the position
shown in Fig. 3.
It will of course, be understood that the nearer the pedal is swung to the left
hand side of the figure so as to bring the contact plate, V6, upon the plates nearer
the left hand side, the less the resistance will be (see Fig. 4.) and consequently the
greater the speed of the motor.
Should the bar, X, be tilted so as to bring the spring ends, X', X³, of the
contact plates, X3, X, against the bars, w², w³, the direction of the current will be
reversed and the circuit will then be through the wire, 7, binding post, W³, wire, 6,
contact plate, V6, rheostat contact plate, 71, wire, Z, binding screw, Z³, to the left
hand side of the figure, wire, , bar, w³, contact plate, X, wire, 5, binding
post, W³, wire, 14, through the motor in the opposite direction, back by the
wire, 13, binding post, W4, wire, 4, to the contact block, W, through the contact
plate, X³, bar, w³, wire, 22, wire, 3, and wire, 12, out through the switch board, J.
By pressing downwardly upon the heel however, the brake will be thrown in as
will be understood from the circuit I shall now describe.

page_text: The contact plate, V, in this instance is brought against the contact plate, Y,
secured at the bottom of the base plate, U. The current will now pass through
the switch board in the same direction along the wire, 7, through the binding
post, W³, wire, 6, contact plate, V³, contact plate, Y, wire, 2, to the binding
post, W, thence by the wire, 15, to and through the brake, M, out through the
switch board.
From this description it will be seen that I provide a very simple and easily
controlled apparatus which is not only noiseless but brings all the implements of
the dentist close at hand and in a position where it is most convenient for his use.
It will also be seen that the pedal may be left by the foot in such a position so
that the toe is down and the motor will consequently be running at a speed
commensurate with the position in which the pedal is placed.
I also wish to finally draw attention to the simplicity of attachment of the motor
within the table as by such connection it will readily be seen that by taking out
the screws, d, from the casting, D' and withdrawing the spindle, P, of the flexible
shaft of the dental engine that the table may be removed so that the motor may be
readily inspected or repaired.
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. In a dental outfit the combination with the dental table pivoted, and swung in
proximity to the chair as specified, of an electric motor in a chamber under the
central portion of the table between the drawers and having the rigid spindle of
the dental engine deriving motion from the motor, journalled in suitable bearings
in the inner partition and side of the table and having the flexible shaft of the
dental engine extending outwardly from the end of the rigid spindle as and for the
purpose specified.
2. In a dental outfit the combination with the dental table pivoted and swung in
proximity to the chair as specified, of an electric motor supported in a chamber
under the central portion of the table between the drawers by a casting, D¹, which
is secured to the bottom of the table and has a downwardly extending portion to
which the bottom of the motor is secured, the downwardly projecting portion
resting on the end of the supporting bracket being secured and pivoted thereon by
the tubular bolt, E, as and for the purpose specified.
3. In a dental outfit the combination with the dental table pivoted and swung
in proximity to the chair as specified, of an electric motor suitably supported in
a chamber under the central portion of the table between the drawers and having
a pulley situated on the main shaft which is connected by a belt to a pulley
secured to the rigid spindle which is journalled in self-aligning bearings and has
the flexible shaft of the dental engine extending from the outside of the table as
and for the purpose specified.
4. In a dental outfit the combination with the dental table pivoted and swung
in proximity to the chair as specified and an electric motor supported in a chamber
under the central portion of the table between the drawers, of a rigid spindle
suitably journalled beneath the table, extending outwardly beyond the side,
deriving motion from the motor and having the flexible shaft attached to the outer
end of the spindle and the cleaning brush secured to the outer end of the rigid
spindle as and for the purpose specified.
5. In a dental outfit the combination with the table pivoted and swung in
proximity to the chair as specified, of the electric motor, D, rigid counter.
spindle, P, flexible shaft, S, pulley, N', on the motor shaft, L, connected by a
belt, N3, to the pulley, O, on the counter spindle, P, the brake consisting of an
adjustable disc, N, forming part of the pulley, N', and magnets, M, all arranged
as and for the purpose specified.
6. The combination with the dental table, C, motor, D, situated in a chamber.
between the central portion of the table in the drawers and having the shaft of the .

page_text: motor connected to the rigid counter spindle, P, as specified, of the self-aligning
bearings, P1, P2, with arc-shaped peripheries and pivoted at the bottom as
specified upon the bracket, Q, and ring, P³, respectively, as and for the purpose
specified.
7. The combination with the dental table, the motor and counter spindle driven
from the motor as specified, of the pulley, O, and brush, R, secured on the
sleeves, p, p, journalled in the self-aligning bearings, P1, P2, respectively, which
collars are secured from rotation by the screws, P4, P8, extending into the
longitudinal groove or keyed slot, p, in the counter spindle, P, as and for the
purpose specified.
8. The combination with the dental table and motor suitably supported within a
chamber below the_centre_of_the_table_and between the drawers by a casting
located on the end of the bracket arm, F, the motor communicating motion to the
rigid counter spindle, P, and flexible shaft, S, of the dental engine as specified, of
the tubular bolt, E, bracket, F, swivelled in the tubular standard, H, which is held
on the bracket, I, attached to the bottom of the chair, the tubular bolt, bracket
and tubular standard forming a conduit for the circuit wires as and for the purpose
specified.
9. The combination with the dental table, C, motor, D, communicating motion
to the flexible shaft S, as specified and supported underneath the central portion of
the table between the drawers and pivoted upon the end of the arm, F, standard, H,
arranged as specified, of the foot switch, K, having a pedal, V, arranged as
specified connected to the circuit wires to the motor and brake and the switch-
board J, connected by the wires G, to the main circuit wires as shown and for the
purpose specified.
10. The combination with the main driving shaft and double magnets secured to
one of the bearing standards of the shaft by means of its yoke through which
the shaft passes, of a disc secured on the shaft opposite the face of the cores of
the magnet and having a hub extending inwardly between the magnets, the discs
being so arranged that when the current is passed through the magnet a magnetic
pull is exerted upon the disc and means being provided that when the current is
thrown out of the magnet the disc is thrown away from the cores of such magnet
a limited distance as and for the purpose specified.
.
11. The combination with the main driving shaft, the yoke, the double magnet,
the cores of which are secured to the yoke through which the shaft passes, of a
disc having a hub extending inwardly between the coils of the magnets, which hub
is provided with a longitudinal slot by which it is secured on the shaft by means
of the key extending through the hub and caused to normally abut the inner end
of the slot by the spiral spring encircling the hub and extending between the key
and the inner side of the disc as and for the purpose specified.
12. The combination with the main driving shaft, the yoke secured to the
bearing standard of the shaft, the double magnet comprised of the two coils, the
cores of which are secured to the yoke by the screws, the flanges made on the end
of the cores, the coils wound upon the flanged spools between the flange of the
cores and the yoke, of a disc provided with an inwardly extending hub, the
longitudinal slot, the key secured in the shaft and extending through the slot and
the spiral spring as and for the purpose specified.
13. In a dental outfit the combination with the dental table and motor as specified,
of the foot switch, K, consisting of the pedal, V, stiffly pivoted on the trunnion
and means whereby upon pressure being applied to the forward end of the pedal,
.contact is made so as to throw the circuit through the rheostat and motor and when
pressure is exerted upon the heel portion of the pedal, contact is made and the
circuit thrown into the brake as and for the purpose specified.
14. In a dental outfit the combination with the dental. table and motor as specified,
of the peddle, V, stiffly pivoted on the trunnion, V', which is swivelled upon the
tubular bolt, V, and means whereby upon the toe of the pedal being depressed
contact is made with one or other of the plates of the rheostat so that the

page_text: resistance is decreased as the pedal is depressed and swung to the left so as to
ncrease the speed of the motor as and for the purpose specified.
15. The combination with the foot pedal pivoted swivelled and making contact
as specified; of the stops, U2, U³, arranged as and for the purpose specified.
16. The combination with the foot pedal pivoted, swivelled and making contact
as specified, of the insulating plug, V4, provided with an insulating ring, V³,
arranged as and for the purpose specified.
17. The combination with the foot pedal pivoted, swivelled and making contact
as specified, of the boss, v³, extending downwardly from the bottom of the heel
portion and provided with a rubber cushion, 10, arranged as and for the purpose
specified.
18. The combination with the pedal stiffly pivoted and swivelled upon the
tubular bolt, V2, as specified, of the insulating plug, V₁, having connected to its
lower end the spring contact plate, V³, which is designed to be brought against the
plate, Y, and means whereby the circuit is completed from the plate, Y, to the
brake as and for the purpose specified.
19. The combination with the foot pedal pivoted, swivelled and making contact
as specified, of the plug, V, having connected to its lower end the spring plate, V6,
which is designed to be brought against one of the plates, Z', of the rheostat and
means whereby the main circuit is completed from the plate through the rheostat
to and through the motor as and for the purpose specified.
20. The combination with the pedal stiffly pivoted and swivelled upon the
tubular bolt, V2, as specified, of the insulating bar, W, provided with metal contact
bars, w², w³, w, and contact blocks, w, w', and the pivoted insulating bar, X,
provided with spring contact plates, X3, X4, the right hand ends, X5, X6, of which
are designed to be held in continuous contact with the blocks, w, w¹, while the
left hand ends are designed to be brought either in contact with the bars, w³, w,
or w², w according to whether the plunger X', connected to the bar X by the
pin a, or the plunger, X, connected to the bar, X, by the pin, a² is depressed
and means whereby upon the toe of the pedal being depressed the circuit is thrown
through either of the two courses so as to change the direction of the rotation of
the motor by the depression of either the plungers, X' or X2, as and for the purpose
specified.
21. The combination with the pedal stiffly pivoted and swivelled upon the tubular
bolt, V, as specified, of the insulating bar, W, provided with the metal contact
bars, w², w³, w, and contact blocks, w, ¹, and the pivoted insulating bar, X,
provided with spring contact plates, X3, X4, the right hand ends, X, X, of which
are designed to be held in continuous contact with the blocks, w, w', while the
left hand ends are designed to be brought either in contact with the bars, w³, w,
or w², w, the plungers, X1, X2, connected to the bar, X, the rheostat arranged
with the separate plates, the contact plate, V6, secured in the end of the insulating
block, V, circuit wire, 7, binding post, W3, wire, 6, contact plate, V6, rheostat
with contact plates, Z', wire, 2, binding post, ³, wire, ¹, spring contact plate, X³,
contact block, w, wire, 4, binding post, W, wire, 13, motor, D, wire, 14, binding
post, W³, wire, 5, contact block, w', spring contact plate, X, contact bar, 10,
wire, 3, binding post, W2, wire, 12, all arranged as and for the purpose specified.
22. The combination with the pedal stiffly pivoted and swivelled upon the tubular
bolt, V2, as specified, of the wire, 7, binding post, W³, wire, 6, extending through
the insulating plug, V₁, contact plate, V³, plate, Y, insulated from the base
plate, U, wire, 2, binding post, W', wire, 15, and brake, M, all arranged as and
for the purpose specified.
L
T
1001
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.