Improved Dental Machine.
Year: 1898

page_text: Date of Application, 18th Oct., 1898-Accepted, 23rd Dec., 1898
Improved Dental Machine.
I, ALBERT EDWARD MACDONALD, of 21, Powell Street, in the City and County of
San Francisco, State of California, U.S.A., Dentist, do hereby declare the nature of
this invention and in what manner the same is to be performed, to be par-
ticularly described and ascertained in and by the following statement :-
My invention relates to improvements in dental machines or engines. It consists
essentially of an adjustable bracket, a driving mechanism supported at the outer
end of the bracket, a flexible shaft and a means for connecting it with the driving
mechanism so that the speed may be increased or diminished and the motion of the
shaft and attached instrument reversed, intermediate connections for producing these
results, and details of construction which will be more fully explained by reference
to the accompanying drawings, in which :-
Figure 1 is a side elevation of my invention.
Figure 2 is a vertical section through x-x of Fig. 1.
Figure 3 is a plan of the switch. Figure 4 is a side elevation of the switch-
actuating foot-piece.
A is the bracket arm, of any usual or suitable construction, hinged to the wall or
other support at B so as to be turnable horizontally about the hinge and it may have
an extension arm at the end if desired.
Upon the end of this bracket is mounted a flat disc C, the shaft of which is jour-
nalled in the bracket arm, as will be hereafter described, and has a pulley D fixed
to it.
Around this pulley passes the endless belt d which passes over guide pulleys D¹
essentially in line with the bracket hinge at B, and passing from these pulleys to a
motor of any desired description from which power is transmitted to drive the parts
described.
The disc C is enclosed by a yoke or bracket E through the lower part of which its
shaft passes, and the sides of the yoke extending outward beyond the periphery of
the disc, serve to hold the journals of the shaft F through which power is transmitted
to drive the flexible shaft F1 to which is operatively connected a dental tool carried
by a hand-piece.
Upon this shaft F is mounted a wheel or roller G, the periphery of which contacts
with the surface of the disc C and the wheel and its shaft are rotated by this con-
tact when the disc is in motion.
By sliding the wheel upon a feather on its shaft, it may be moved to the centre
of the disc which may be depressed to prevent contact and where the wheel will not
be revolved in either direction.
By moving the wheel outward toward the periphery of the disc upon one side, it
will be rotated in one direction with a speed increasing as it is moved from the
centre toward the periphery. By moving it toward the opposite side of the disc the
rotation of the shaft and the tool or implement will be reversed, which is necessary
under certain conditions.
In order to steady the movement and insure a regular rate of motion to the shaft
and tool, and prevent irregularity, I have shewn a sleeve F2 which fits the shaft F

page_text: extending entirely across between the sides of the yoke E and which has its ends
journalled in boxes in the yoke as shewn.
The shaft F has a longitudinal key-way or slot ƒ made in it, and a lug, screw, or
feather H passing through the side of the tube F2 enters the slot f of the shaft and
thus ensures the tube and shaft rotating in unison.
Through the hub of the wheel G passes a screw g which enters a slot made longi-
tudinally in the sleeve F2 so that the rotation of the wheel by its contact with the
disc C is transmitted to the sleeve F2 and the shaft F. At the same time, the
wheel G may be moved along the shaft from one end to the other, traversing
the entire diameter of the dise C for the purpose of changing the rate of speed upon
either side of the centre, or reversing its movement as previously described.
In the thickened ends of the yoke are journalled pulleys I I. A sleeve K is
slidable upon a guide rod L which extends across the yoke parallel with the shaft F,
and a clutch lever extends from the sleeve to engage a groove in the hub of
wheel G. The ends of a cord J connect with opposite sides of the sleeve K, passing
thence over the guide pulleys, I I, thence through openings in the yoke, the two
parts are brought together passing over guide pulleys 12 which are journalled in a
yoke M fixed to the bracket arm A so that the pulleys 12 are essentially in line with
the shaft of the disc C.
From the pulleys 12 the cord J leads through the hollow bracket over small
pulleys D2 within it, thence to the pulleys N and into the casing P where they
connect with the foot lever O. This lever is turnable upon a vertical shaft o and
the ends project through the sides of the casing P to form foot pieces as shewn.
The cords J pass through openings and over pulleys P in the casing P and connect
with tension screws Q by which the length of the cords can be adjusted and lost
motion prevented. By pressing the foot against either end of the foot-piece, the
cord J will act to move the wheel G to one side or the other of the disc C and thus
increase, diminish or reverse the speed of the tool driven thereby. A depression R is
made in the casing beneath the foot lever O to receive and hold it when the wheel G
is exactly central with the disc C. I prefer to make the periphery of the wheel G of
leather or other material having a sufficient frictional surface but not essentially
elastic, and the depression in the centre of the disc C frees the wheel from contact
and prevents wear when in this position. As soon as it is moved to either side of the
centre it contacts with the disc and begins to revolve. In order to maintain a perfect
contact and compensate for wear or irregularities of motion the disc shaft c is verti-
cally slidable in its journal sleeve and is normally pressed upward by a spring cl
which will yield to uneven pressure, but will maintain a constant contact between the
wheel and the disc.
The tension of this spring is regulated by a nut c² turnable upon the upper end of
the threaded sleeve S.
The means for adjusting the shaft c are as follows:
The shaft c passes through a sleeve S which forms its journal-box. This sleeve is
screw-threaded on the periphery and itself screws into an exterior sleeve S¹. This
sleeve S¹ is immovably fixed in the bracket arm A. The screw sleeve S has its outer
end made polygonal so that by the use of a wrench, it can be turned and this will
advance it, and with it the shaft c and compensate for any wear.
It is locked at any
point by a set screw.
The central portion of the yoke E is perforated and fits over the exterior
sleeve S¹, the bottom or side adjacent to the bracket armı A resting upon a collar or
washer.
Upon the outer end of the sleeve S¹ is a nut S² which may be screwed down upon
the inner side of the bracket E so as to hold it snugly between the nut and the
washer, at the same time allowing it a sufficient freedom of motion to turn upon
its centre to accommodate the varying positions of the flexible shaft and driven
parts.
This nut may be locked by a set screw, or in any other convenient or suitable
manner.

page_text: 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
1st. In a dental engine, the combination of a hinged swinging bracket arm, a
vertical shaft journalled in the outer end thereof, a disc carried by said shaft,
pulleys and a driving belt by which the disc is rotated, a yoke enclosing the disc, a
horizontal shaft within the yoke and a wheel adjustable thereon and having its
periphery in contact with the face of the disc, a treadle and connections between the
same and the wheel whereby the latter may be moved along its shaft to contact with
any portion of the face of the disc.
2nd. In a dental engine, a hinged swinging bracket arm, a disc, a shaft journalled
in the outer end of the bracket arm and means whereby the disc is rotated, a shaft
extending across exterior to the face of the disc at right angles with the disc shaft, a
wheel slidably mounted upon said shaft having its periphery in contact with the disc,
an arm connecting with the hub of the wheel, a guide parallel with the wheel shaft
upon which the arm is slidable, cords connecting with the end of the arm, extending
in opposite directions, a yoke carrying the wheel and its shaft and having direction
pulleys for the cords, other direction pulleys over which the two parts of the cord
pass, and an oscillating treadle, to the opposite ends of which the cord is connected
whereby the movement of the treadle serves to move the wheel along its shaft to
contact with any portion of the face of the disc.
3rd. In a dental engine of the character described, a hinged swinging bracket
arm, a disc and a shaft upon which it is carried, a yoke partially enclosing said and a
second shaft journalled therein outside of the dise and at right angles with the shaft
of the latter, a wheel adjustably mounted upon said second shaft with its
periphery in contact with the disc, the cords and a connection therefrom to the wheel
whereby the latter is moved along its shaft.
4th. In a dental engine of the character described, a driven disc journalled in the
bracket arm, a wheel having its periphery in contact with the disc surface and
movable across its face to vary its speed or reverse its motion, a spring acting upon
the disc shaft to maintain the disc and wheel in contact, and a turnable foot lever and
cords connecting it with the wheel to move the latter across the face of the
disc.
For the Applicant,
GEDGE & FEENY,
Chartered Patent Agents, 60, Queen Victoria Street, London, E.C.