Improvements in Dental Engines.
Year: 1891

page_text: Date of Application, 9th May, 1891
Complete Specification Left, 8th Feb., 1892-Accepted, 12th Mar., 1892
PROVISIONAL SPECIFICATION.
Improvements in Dental Engines.
I, JOHN SMALLEY CAMPBELL of 10 Park Square West, Regents Park in the
County of Middlesex, Dentist, do hereby declare the nature of this invention to
be as follows:-
My improvements relate mainly to dental engines such as are described in the
Specification of a former Patent granted to me No. 4574 of 1888.
In the Specification of my former Patent I described a dental engine in which
the tool carrying standard rose up from a base other than the base which carried
the main driving wheel. According to my present invention I make the standards
not only to be carried by an independent base as described in my former Patent
but also to be capable of swivelling somewhat in a vertical socket which stands
up from the base and also of being folded down over the top of the driving
wheel when out of use.
The driving wheel I make in sections which can readily be taken apart for
convenience of packing or put together when required for use.
This I do by making the hub of the wheel with two arms extending out from
it in opposite directions and each formed at its extremity with two short
segments of the rim of the wheel. The ends of two other segments of the rim
are made to fit to the ends of these short segments and are drawn towards and
against them by spokes with right and left handed screw threads on their ends.
The screw thread on one end being made to screw into a radial hole formed in
the segment of the rim and the screw thread on the other end to screw into a
radial hole formed in the hub.
The crank on the axis of the driving wheel I place below the wheel as
described in my former Patent-the pitman or connecting rod which passes from
the crank to the bell crank lever which is rocked by the action of a pedal I
bend upwards as soon as it is clear of the wheel and then horizontally to the
top of the vertical arm of the bell crank lever. The bar which carries the axis
of the bell crank lever and which swivels around the axis of the driving wheel
is likewise cranked upwards in the same way. In this way the bar and pitman
can pass over the feet of a dental chair so that the feet of the chair do not
interfere with the pedal mechanism being placed in any desired position.
The link which connects the base of the tool carrying standard with the axis
of the driving wheel is likewise arched upwards in a similar manner and to such
an extent that it can pass over the top of the arched pitman. In this way if the
base which carries the driving wheel be placed below the foot board of a dental
chair, the tool carrying standard can be moved freely to either side of the chair
quite independently of the pedal mechanism or the pedal mechanism can be shifted
to either side independently of the tool carrying standard.
The pedal I couple directly to the horizontal arm of the bell crank lever by a
ball and socket joint. The other end of the pedal rests on and is jointed to the top
of a bar which at its other end is jointed by a pin joint to the bar which carries
the axis of the crank lever-the pin of this joint is made to be vertically below
the ball and socket joint-so that the bar and pedal are free to be turned into
any position.
The two arms of the bell crank lever are normally at right angles to one
another and cannot move further apart but are free to turn towards one another
so that if any obstruction got below the pedal no harm would result.
The pedal is for the most part simply a straight cylindrical bar surrounded by
tube of vulcanized india rubber or other suitable material. The tube gives
good foothold and when worn on one side can be partially turned to expose a fresh

page_text: surface to wear. At the end of the pedal is a ball, this is received between two
cup surfaces carried by the extremities of a fork on the end of the horizontal arm
of the bell crank lever above mentioned.
Dated this 8th day of May 1891.
JOHN SMALLEY CAMPBELL.
COMPLETE SPECIFICATION.
Improvements in Dental Engines.
I, JOHN SMALley Campbell of 10 Park Square West, Regents Park, in the
County of Middlesex, Dentist, 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 relate mainly to dental engines such as are described in the
Specification of a former Patent granted to me No. 4574 of 1888.
In the Specification of my former Patent I described a dental engine in which
the tool carrying standard rose up from a base other than the base which carried
the main driving wheel.
According to my present invention I make the standards not only to be carried
by an independent base as described in my former Patent but also to be capable of
swivelling somewhat in a vertical socket which stands up from the base and also of
being folded down over the top of the driving wheel when out of use.
The driving wheel I make in sections which can readily be taken apart for
convenience of packing or put together when required for use.
This I do by making the hub of the wheel with two arms extending out from it
in opposite directions and each formed at its extremity with a short segment of the
rim of the wheel. The ends of two other segments of the rim are made to fit to
the ends of these short segments and are drawn towards and against them by spokes
with right and left handed screw threads on their ends. The screw thread on one
end being made to screw into a radial hole formed in the segment of the rim and
the screw thread on the other end to screw into a radial hole formed in the hub.
The crank on the axis of the driving wheel I place below the wheel as described
in my former Patent-the pitman or connecting rod which passes from the crank
to the bell crank lever which is rocked by the action of a pedal I bend upwards
as soon as it is clear of the wheel and then horizontally to the top of the vertical
arm of the bell crank lever. The bar which carries the axis of the bell crank
lever and which swivels around the axis of the driving wheel is likewise cranked
upwards in the same way. In this way the bar and pitman can pass over the fect
of a dental chair so that the feet of the chair do not interfere with the pedal
mechanism being placed in any desired position.
The link which connects the base of the tool carrying standard with the axis of
the driving wheel is likewise arched upwards in a similar manner and to such an
extent that it can pass over the top of the arched pitman. In this way if the base
which carries the driving wheel be placed below the foot board of a dental chair,
the tool carrying standard can be moved freely to either side of the chair quite
independently of the pedal mechanism or the pedal mechanism can be shifted to
either side independently of the tool carrying standard.
The pedal I couple directly to the horizontal arm of the bell crank lever by a
ball and socket joint. The other end of the pedal rests on and is jointed to the top
of a bar which at its other end is jointed by a pin joint to the bar which carries
the axis of the crank lever-the pin of this joint is made to be vertically below the
ball and socket joint-so that the bar and pedal are free to be turned into
any position.
The two arms of the bell crank lever are normally at right angles to one another
and cannot move further apart but are free to turn towards one another so that if
any
obstruction got below the pedal no harm would result.

page_text: The pedal is for the most part simply a straight cylindrical bar surrounded by a
tube of vulcanized india rubber or other suitable material. The tube gives good
foothold and when worn on one side can be partially turned to expose a fresh
surface to wear.
At the end of the pedal is a ball, this is received between two
cup surfaces carried by the extremities of a fork on the end of the horizontal arm
of the bell crank lever above mentioned.
My improvements are shewn in the drawings hereunto annexed.
Figure 1 is a view in perspective of a dental chair and the dental engine in
position beneath the footboard of the chair with the pedal and the tool carrying
standard unfolded and extended for use. Figure 2 is a plan view and Figure 3 a
side elevation of the dental engine unfolded and ready for use. Figure 4 is a plan
view and Figure 5 a side elevation of the dental engine when folded up. Figure 6
is a side elevation of the base of the tool carrying standard and of the lower part of
the standard. Figure 7 is a vertical section of Figure 6. Figure 8 is a horizontal
section on the line - Figure 6. Figures 9 are plan views of the parts into which
the driving wheel can be divided. Figure 10 is a vertical section of the central
part of the driving wheel. Figure 11 is a side elevation and Figure 12 an end
elevation both partly in section of a portion of the pedal mechanism. Figures 13
and 14 shew portions of the two parts of the crank lever which is rocked by
the pedal.
A is the base carrying the driving wheel B of the dental engine. C is the base
upon which is mounted the tool carrying standard D. E is a bar by which the
base C is linked to the base A. it is secured at one end to a bar E' which is held in
a horizontal socket in the lower part of the base C and at the other end is capable
of turning around the upper part of the vertical axis of the driving wheel B. The
upper part of the base forms a vertical socket in which is received a tube F.
To the upper part of the tube F is jointed the lower end of the tool carrying
standard D. Within the tube is a small piston G pressed upwards by a spiral
spring H to cause it to bear against the square lower end of the standard and tend
to hold the standard either in a vertical position or in a horizontal position lying
over the driving wheel B.
A projection D' on the lower end of the standard prevents the standard being
turned in the opposite direction beyond a vertical position. The tube is prevented
from rising out of the socket by a screw F1 screwing through the side of the socket
and entering a groove cut partly around the exterior of the tube as shown at
Figure 8. The groove being cut partly around the tube allows of the tube
swivelling to some extent in the socket.
The standard D is made telescopic and at its upper end it carries a horizontal
axis I to which is jointed as is usual a flexible shaft which drives the operating
tool. The horizontal axis I is driven by an endless cord which is led over a pulley
on the end of this axis and around guide pulleys J to and then around the rim of
the driving wheel B.
The way in which the driving wheel is constructed will readily be understood
from Figures 9 and 10. B¹ is the hub of the wheel. B2 two arms extending
from it. B³ small segments of the rim at the ends of these arms. B₁ two larger
segments of the rim held to the short segments by the rods B³ which have right
and left handed screw threads cut upon them one screw thread to screw into the
hub and the other screw thread into the centre of one or other of the larger
segments.
K is a bar free to turn around the lower end of the vertical axis of the driving
wheel B. The portion of this bar which is beyond the circumference of the
driving wheel is arched upwards as shown in Figures 3 and 5 so that as shown at
Figure 1 the feet of the dental chair may not interfere with this bar being placed
in any desired position. The outer extremity of the bar K rests on the ground
and has pivotted to it the crank lever L. Mis the arched or bent connecting rod
which passes from the upright arm of this lever to the crank on the axis of the
driving wheel.

page_text: It will also be seen from Figures 3 and 5 that the bar E is arched or bent to
such an extent that the bar K and connecting rod M can readily be made to pass
beneath it. N is the pedal jointed directly by a ball and socket joint N' to the
horizontal arm of the crank lever L-the way in which I prefer to construct
the joint is shown clearly in Figure 11. O is the bar to which the other end of the
pedal is jointed—this bar is jointed at O' to the foot of the bar K the joint being
vertically below the joint N'. The way in which the two arms of the crank
lever L are held normally at right angles and yet allowed to incline towards one
another in case of need is shown at Figures 11, 12, 13 and 14. As shown at
Figure 12 the two arms are placed side by side on a fixed pin on which they are
free to turn and as shown at Figures 13 and 14 the boss of one arm has a projection
standing out from it which enters a recess of greater length in the boss of the other
arm. The projection on the one boss is normally kept at one end of the recess in
the other boss by a coiled spring P-one end of which is attached to one arm and
the other to the other arm.
The form of the pedal is shown best in the plan view Figure 2. At its outer
end there is a flat surface on which the heel of the operator may be made to rest
and from this a cylindrical stem extends surrounded by a tube of vulcanized india
rubber or like material as above explained, and at the end of the stem there is a
rod which passes through the ball of the ball and socket joint which couples the
pedal to the crank and the rod is free to slide to and fro through the ball.
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 engine the combination of a tool carrying standard jointed to a
base which is separate from but linked to a base which carries the driving wheel so
that the standard may be turned down and made to lie horizontally over the top of
the driving wheel substantially as described.
2. A. dental engine with its driving wheel made in sections substantially as
hereinbefore described which can readily be taken apart for convenience of packing.
3. In a dental engine having a horizontal driving wheel driven from a bell crank
rocked by a pedal making the bar which carries the axis of the crank lever and
which swivels around the axis of the driving wheel of an arched form to pass
over the feet of a dental chair substantially as described.
4. A dental engine having a horizontal driving wheel and pedal bar cranked
for the purpose above mentioned and a tool carrying standard on a base separate
from the base which carries the driving wheel but linked to it by a bar so arched
as to allow of the pedal mechanism passing below it substantially as described.
5. In a dental engine having a horizontal driving wheel driven from a bell
crank rocked by a pedal making the two arms of the bell crank separate and free
to incline in one direction towards one another-one arm being connected by a
connecting rod with a crank on the axis of the driving wheel and the other directly
to the pedal.
6. The straight bar pedal surrounded by a tube of vulcanized india rubber or
like material substantially as described.
7. Connecting the pedal to the crank arm by a ball and sliding pin connection
substantially as described.
8. The construction of dental engines substantially as herein before described.
Dated this 18th day of January 1892.
JOHN SMALLEY CAMPBELL.
Witness-
JOHN HIGSON,
125, Corbyn Street, Hornsey Rise, London, N.