Year: 1887

page_text: 1, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, (a communi-
cation to me from abroad by August Weber of the City, County and State of New
York, United States of America, Mechanic,) 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 :-
Dental engines have heretofore been made with a fly wheel actuated by a treadle,
and a vertical standard, to the upper end of which a jointed arm is connected, with a
hand piece and drill, or other tool, at the end of the outer section of the arm, and an
endless cord or belt has passed around the driving wheel, or fly wheel, and over
pulleys at the joints between the standard and the arm, and, also, over pulleys between
the sections of the arm and of the hand-piece.
In consequence of the motion given to the hand-piece, in properly placing it for
operation, the belt is liable to become slack or too tightly strained. Efforts have
been made to compensate this difference in the tension of the belt by placing the
joints between the respective parts of the arm at a distance from the axis of the pulleys,
but this is not accurate in its operation, because, in certain positions, the belt will be
wound further upon the pulley than in other positions, and the uniformity of tension
will not be maintained.
My improvement relates to the combination with the standard, and the arm that is
jointed thereto, of pulleys over which the endless cord is passed, the axis of the
pulleys coinciding with the centre of the joint, and the endless cord passing over one
pulley in one direction, and the other pulley in the opposite direction, so that when
the arm is raised or lowered in relation to the standard one part of the endless cord
is wound upon the pulley to exactly the same extent that the other part of the endless
cord is wound or given off the pulley, whereby the absolute uniformity of tension is
maintained. And with the joint in the arm, and with the joint between the arm and
the hand-piece, idler pulleys are made use of, so as to allow for the endless cord or
band passing in the opposite direction for the purposes before mentioned; and I make
use of a standard that is provided with an adjustment for tightening the cord to
whatever extent may be desired.

page_text: Figure 1 is a general elevation of the dental engine.
Figure 2 is an elevation of the top of the standard, and a part of the arm that is
jointed thereto.
Figure 3 is an elevation of the same at right angles to Figure 2, the weight and
cord being removed.
Figure
standard.
is a sectional elevation of the pinion and moveable portion of the
Figure is an elevation of the cap over the pinion upon the standard.
Figure 6 is a side view of the joint between the two sections of the arm.
Figure 7 is an elevation of the same, endwise of the arm.
Figure 8 is a side view of the parts of the junction of the hand-piece with the arm.
Figure 9 is an elevation of the parts endwise of the hand-piece; and,
Figure 10 is a detached view of the slotted standard carrying the fly-wheel, in
larger size than Figure 1.
The base, A, is usually triangular, and from the middle thereof the standard, B,
rises, and it is adapted to receive the fly wheel, C, and its crank shaft, D, as usual,
and the treadle, E, and connecting rod, F, are or may be used to drive the fly wheel.
The tubular standard, G, rises above the standard, B, and the arm is made of two
parts, Hand K, that are jointed together, and the part, H, is united by a joint to the
top end of the standard, G, and the hand piece, 1, is jointed to the end of the
section K. These parts are of the general character heretofore in use, except in
the particulars hereafter named, and I remark that the hand-piece, I, is to be of any
desired character, and the central shaft thereof operates a plugger, a drill, an angle
piece, or any other tool to which the hand-piece is adapted.
The belt, N, is endless, and of any desired material, and it is to bo passed around
the fly wheel, and over the pulleys to the hand-piece, but it is advantageous to be able
to take the belt off or put the same on with facility, without cutting disconnecting or
opening the endless belt, N. To provide for so doing, I make the standard, B, with a
removeable section, 2, at one side of the fly wheel, and at the ends of this section
there are lugs that receive through them the cross-pins, 3, so that when in place, this
section closes the opening that there would otherwise be in one side of the two-part
standard or inclosing frame, and the two sides of the standard are rendered uniform,
or nearly so, in strength, but when the pins, 3, are pulled out, the section, 2, can be
removed, and the endless belt is removed or inserted, so as to pass properly around
the fly wheel the section may be swung open by removing one of the pins.
At the top of the tubular standard, G, there is received an axial rod or tube, 4,
that may be moved endwise to raise or lower the joint, 6, that connects the arm, H,
and I make use of the pinion, 8, that is upon a horizontal shaft, 9, with a thumb
wheel, 10, at the end, by which the pinion is moved to raise or lower the rod, 4.
There is a block upon the side of the standard, G, with a cap, 11, secured by screws,
so that the necessary friction can be obtained, to prevent the pinion turning by the
weight that is supported by it. The teeth of the pinion gear into teeth upon the
rod, 4, and I prefer to make these teeth by a screw-thread cut into the surface of said
rod, 4, so that the rack will not be liable to wear out, and the rod can be revolved as
the arm, H, is swung, without the teeth becoming separated from the teeth of the
pinion. And, in addition to this, the standard can be lengthened or shortened by
rotating the rod, 4, and its screw thread teeth; the pinion, in this case, forming a
nut for the same.
I prefer to make this rod, 4, in two parts, as seen in Figures 2 and 3, one part
being tubular to receive the other part, there being bearing discs, 14 and 15, upon
the respective parts, so that lubricating material can be introduced between these
bearing discs to allow the arm, H, to swing, when in use, with but little friction.
The joint pin, 20, of the joint, 6, is preferably extended to form the shaft or
gudgeon for the pulleys, 21, 22, that are grooved for the endless cord to pass around.
The endless cord passes simply up over the pulley, 21, but in order to pass in the
opposite direction around the pulley, 22, it is wound almost around the same, as seen

page_text: in Figure 2. It will now be evident that if, for illustration, the endless cord was tied
fast to the arm, H, where it passes along at the sides thereof, and the cord properly
tightened by the pinion, S, the arm, H, can he swung up or down without tightening
or loosening the cord or band, because it will be wound upon the pulley, 22, to exactly
the same extent as it is unwound off the pulley, 21, or vice versa, the fly wheel,
however, will be slightly turned as the cord gives down on one side, and is drawn up
on the other side. Of course the same effect takes place when the engine is running,
that is to say, the cord or belt is not tightened, or loosened by the movement of the
arm H up or down.
At the joint 26 between the arm sections, H and K, the joint pin 27, becomes the
shaft for the pulleys 28 and 29 and the cord goes above one pulley, and below the other
pulley, so as to act in the same manner as has been described with reference to the
pulleys 21, 22, but to lessen wear upon the band, that would result from the rubbing
of one part of the band against the other in passing entirely around the pulley 29,
I prefer to lead the band or cord over the idler pulley 30, and thence down over and
beneath the pulley 29, the action of the parts being identically the same, and the
object of the idler 30 being only to prevent or lessen wear upon the band or cord.
It will be evident that an idler pulley might be used in connection with the pulley 22
to prevent the rubbing of one part of the band against the other at the place where
it crosses. This idler is indicated by dotted lines in Figure 2. In each instance the
idler is supported by an armn or branch extending out from the arm H.
At the rear end of the hand-piece is a pulley 32 around which the endless band
passes, and by which motion is given to the drill or other instrument at the end of
the hand piece, as usual, and the pivot pin of the hinge that unites the arm K to the
hand piece, is in line with or extended to form the shaft or gudgeon for, the pulleys 38
and 34 and the cord or band passes at one side of the pulley 33 and at the other side
of the pulley 34 in order that the band may not be slackened or tightened by the
swinging of the hand piece upon the joint by which it is connected to the arm K and
in order to guide the belt in passing around the pulley 32, I make use of the guide
pulleys 35 and 36 that are placed almost in contact with the respective pulleys 33
and 34, and in such positions that the band will be properly guided to the pulley 32:
the distance between the respective pulleys 33 and 35, and 34 and 36, being only
sufficient for slipping in the cord or band. It will now be apparent that when the
hand-piece is moved to an acute angle with the arm K, the cord or band will be wound
further upon the pulley 33, and it will be unwound from the pulley 34 to the same
extent, and if the movement towards the arm K be continued, the cord will leave
the pulley 34 and bear only upon the pulley 33, and, on the other hand, if the hand-
piece assumes an obtuse angle to the arm K, the cord will be wound more upon the
pulley 34, and partially unwound from the pulley 33, and by the further movement
will feave the pulley 33 and be further wound around the pulley 34; in any instance,
the winding and unwinding being in the opposite direction on one side from what it
is on the other side, the cord or band will not be tightened or slackened, but will be
maintained at a uniform tension.
It is usual to connect the hand-piece by a swivel with the arm H so that the hand-
piece may be partially rotated upon the swivel, as said hand piece is turned in the
necessary direction for operating the tool; this, however, does not materially interfere
with the tension of the cord or band, because the angle that the cord or band assumes
in relation to the arm H is but slight.
Below the arm H and connected with the same, is a sector 40, passing through a
mortice in the upper part of the standard and extending sufficiently to the rear for
receiving the counterpoise 41, by which the weight of the arm H and the parts
connected therewith, is balanced, and it is preferable to have the weight sufficiently
heavy to cause the outer end of the arm H to rise when not otherwise acted upon, as
this facilitates the use of the hand-piece.
The clamping screw 43 is employed for holding the sector and the arm H at a fixed
angle to the standard, whenever so desired.
It will be observed that I have shown the driving belt or cord wound about one of

page_text: the coincident pulleys, at the top of the standard, in order to gain the effect of the
third idler or guide pulley shown at the other joints, therefore virtually making of
the one belt pulley the third pulley or guide also for the belt or cord, and they are
equivalent with the belt so wound. The third or idler pulley is simply a guide for the
belt or cord, to keep it in proper relation to the co-incident pulleys.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what I
claim is
1. The forked standard or inclosing frame, fitted with bearings for the pulley thereof,
and having a removable section, and securing device therefor, substantially as described,
whereby the endless cord may be inserted in the groove of said inclosed pulley, and
readily removed, while the pulley is inclosed in operation, as before set forth.
2. The combination with the tubular standard of a dental engine and the extension
rod or section thereof, having teeth or threads thereon, of the pinion wheel mounted
on said standard, and engaging said teeth to raise and lower said extension rod, and
the operating-shafi of said pinion, substantially as described.
3. In a belt-compensating device, the combination of two jointed arms and two
pulleys, the axes of which are coincident with the joints of said arms, and a third
belt pulley or guide, substantially as described.
4. The combination of the engine standard, the jointed arms thereof, the pulleys
coincident with the joints of said arms, and the endless driving belt or cord passing
over one and under the other of the coincident pulleys, substantially as described.
5. The combination with the engine standard and the lateral arm (H) jointed to
said standard, of the segment of said lateral arm, and the counterpoise of said segment,
substantially as described.
Dated this 16th day of December 1887
CARPMAEL & Co.,
Agents for the Applicant.