IMPROVEMENTS IN DENTAL ENGINES
Year: 1879

page_text: LETTERS PATENT to George Pitt, of Sutton, in the County of Surrey, for the
Invention of "IMPROVEMENTS IN DENTAL ENGINES." A communication from
abroad by Samuel Stockton White, of Philadelphia, Pennsylvania, in the United
States of America.
Sealed the 18th November 1879, and dated the 13th August 1879.
PROVISIONAL SPECIFICATION left by the said George Pitt at the Office
of the Commissioners of Patents on the 13th August 1879.
GEORGE PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN DENTAL
ENGINES." [A communication from abroad by Samuel Stockton White, of Phila-
delphia, Pennsylvania, in the United States of America.]
The Invention relates to apparatus for revolving the burring or milling tools used
by dentists for drilling and cleaning cavities in decayed teeth, and belongs more
especially to dental engines of the class comprising in their structure a base or stand
carrying a foot-treadle and driving pulley, an arm or frame rising from the base;
a driven pulley connected with the upper end of the engine arm; a belt connection
between the driving and driven pulleys; and a flexible power conveyor or shaft
receiving motion from the driven pulley, and imparting motion to the operating tool
mounted in a handle or hand-piece, the hand-piece being free to be removed about
in various directions to operate at different points in the patient's mouth.
I have found it desirable to give the engine base or tripod the capacity of being
tilted or inclined so as to throw or bring the head or upper end of the engine arm
in front of or towards the patient, irrespective of the rocking movement of said arm
upon the base, and without bringing the base or treadle inconveniently close to the
patient or operating chair, which capacity affords great freedom to the flexible
driving-shaft and to the flexible sheath or cover when that is employed to envelop
and protect the said shaft. The treadle being mounted upon the base or tripod
is also inclined therewith, thus presenting said treadle to the foot in a proper
manner to enable it to be worked by the operator with ease and comfort, the foot
not being compelled to constantly maintain and operate in an unnatural and strained
position.
To attain these ends I have devised improvements constituting the first branh of
my present Invention, which improvements consist,
First. In providing the base or tripod of a dental engine with an inclining device

page_text: or mechanism whereby the base may be tilted and the arm of the engine thrown
out of the perpendicular; and
Secondly. In providing the base or arms of the tripod of a dental engine with
devices or mechanism capable of being adjusted either to incline the base and tilt
the engine arm carried thereby in different directions (or to either side of the per-
pendicular), or to allow said base or tripod to rest evenly and squarely upon the
floor or supporting surface.
The next branch of my present Invention relates to the method of pivoting or
mounting the engine arm upon the fixed standard or post rising from the base or
tripod so as to allow it to rock or vibrate thereon, and to the method of main-
taining said arm in a normal position relatively to the base, to which position it is
automically returned after the force exerted upon the arm to rock or deflect it has
ceased.
The object of this part of my Invention is so to pivot or mount the rocking arm and
organize the counterbalance or spring which maintains the arm in its normal posi-
tion, that the normal position of the said arm relatively to the base may be varied;
or, in other words, so to organize the rocking arm and its counterbalance that the
said arm may be changed or adjusted at pleasure from the perpendicular or from its
vertical position in line with the fixed standard of the base to any desired angle
relatively to the base, while preserving its rocking capacity.
The next branch of my present Invention relates to an improved engine lead,
whereby great freedom of movement is given to the hand-piece and operating tool
carried thereby, and to the flexible power conveyor relatively to the engine arm,
without interrupting the transmission of the driving power.
In carrying out my Invention I provide the base, tripod, or stand with a fixed
upright, standard, or post forming part of the base, the upper end of which is forked
or divided for the reception of the driving-pulley or fly wheel, the journal or
trunnions of which turn in suitable bearings or boxes in said standard in the usual
manner. A driving-crank is usually attached to one end of the pulley-journal or
axle, and is connected by a plate-spring pitman with a treadle, pedal, or foot board
pivoted or jointed upon one arm of the tripod or upon the base as usual.
The forked or divided end of the standard is also provided outside the pulley with
trunnions or pivots for the reception of the forked lower end of the engine arm,
which is also of well known construction, carrying upon its upper end the engine
head or lateral arm, to which is connected the flexible power conveyor, its sheath or
cover, and the band-picce of the engine, as hereafter fully described.
In order to give the tripod or base the capacity of being tilted or inclined at
pleasure in different directions, so as to throw or bring the head or upper end of the
engine arm in front of or towards the patient, or out of the perpendicular irrespec-
tive and independently of its rocking movement upon the base, and withont at the
same time necessitating bringing the base or treadle inconveniently close to the
patient or operating chair; and furthermore, also, in order to incline the pedal,
treadle, or foot board so that it may be operated when the foot is thrown out with
ease and comfort, I provide the base or tripod with mechanism consisting by pre-
ference of pivot-pieces or toes, which are attached preferably one to each arm of the
tripod opposite the arm or portion upon which the treadle is mounted. These pivot-
pieces are acted upon by retaining plate-springs, said springs acting to maintain the
pivot-pieces in their adjusted position, whether that be a position to tilt the base or
otherwise.
The toes or pieces are pivoted, when the tripod form of base is employed, by pre-
ference in the ends of the arms of the tripod, so that when thrown out or adjusted
in line with said arms the base is permitted to rest squarely and evenly upon the
floor or supporting surface, but when moved, rocked, or adjusted inwardly at right
angles or neary so to said arms, raise that portion of the tripod base to which they
are pivoted, consequently tilting or inclining the base, its standard, and the engine
arm with its appurtenances, together with the treadle.

page_text: It will be obvious that when both the inclining toes or devices are adjusted to
tilt the base, said base will be tilted in the direction of the length of the treadle,
while if one only at a time of the toes be used or adjusted, the base will be tilted
sidewise, whereby I am enabled to incline or tilt the base and its appurtenances
in different directions or to either side of the perpendicular, as may be desirable or
necessary.
The upper end or head of the engine arm may therefore be brought, if the engine
be in proper position, towards or in front of the patient, affording great freedom
of movement to the flexible driving shaft and to its enveloping sheath or cover,
which is a desideratum of much importance in the perfect working of dental
engines.
It will be obvious that various changes in the details of the inclining or tilting
devices or mechanism will readily suggest themselves to skillful mechanicians
without departing from my Invention; for instance, the toes or inclining devices
may be made in sections longitudinally extensible, so as to incline the base and
engine arm to a greater or less degree.
To control the rocking movement of the engine arm upon the base, or to return
it automatically to and maintain it in a normal position, various counterbalances
have been employed, the best form of which I consider to be a spring, the tension
of which, as soon as the force exerted to rock or deflect the arm is removed, returns
said arm to its normal position. The returning or counterbalancing springs (both
spiral and plate springs) have been applied in various ways.
In order however to enable the normal position of the engine arm relatively to
the base to be varied at pleasure, and also in order to permit this variation in
normal position without destroying the rocking capacity of the arm, I employ an
adjustable plate pivoted concentrically with the rocking engine arm, and secure to
said plate one end of the counterbalancing and returning spring, the opposite end of
which is connected with the engine arm.
The upper end of the pivoted plate is bent outward and upward, or is formed
with a shoulder so as to limit the range of rocking movement of the engine arm, the
branch or member of said arm next the pivoted plate being provided with depending
ears or lugs, one of which passes down upon each side of the shoulder.
The pivoted plate at its lower end and next the standard is provided with a series
of teeth or notches, and the corners of the said plate are also provided with lugs or
projections which limit the range of movement of the plate around its pivot by
coming in contact with a pin or stud projecting from a plate-spring, which spring
lies in a recess in the standard with its upper end firmly secured thereto, and is
provided with one or more projections or teeth which engage the teeth or notches
of the pivoted plate to lock it firmly to the standard in any desired position in its
range of movement.
The tension or force of this plate-spring locking device is exerted at all times to
throw its locking tooth or teeth into engagement with the plate, and is operated or
retracted when the said plate is to be adjusted to a different position by pressing it
inwardly, it being preferably provided with an arın or extension to be acted upon
by the foot in order to avoid the necessity of stooping.
The construction of this spring locking device obviously may be varied in well
known ways, and need not of necessity be a plate spring. It will also be obvious
that the adjustable plate may be locked to the standard in various ways other
than by a spring locking device (which however is the preferred form), as for
instance by a set screw.
It will be obvious that by adjusting the plate the normal position of the engine
arm relatively to the base may be varied without destroying the rocking capacity
of the arm, the counterbalancing spring, when the deflecting strain is removed,
returning the arm to a position with one of its lugs abutting against the shoulder
of the adjusting plate, the rocking movement of the arm being then permitted in
the opposite direction against the tension of the spring.

page_text: The counterbalancing or returning spring may be a coiled spring surrounded by
a sectional telescoping tube or cover, so as to protect the spring and present a
handsome appearance, one end of said spring being connected with a threaded
shank of a forked plate or clevis pivoted to one of the lugs of the plate, said pivot
being crosswise of the path in which the engine arm rocks or vibrates, so as to
permit the tubular sectional covering of the spring to rock or yield during the
vibration of the engine arm. The upper end of the counterbalancing spring is
connected with a curved arm or extension of the engine arm by means, preferably,
of a screw-shank which passes through the arm and receives a thumb or set nut,
whereby the tension of the spring may be adjusted or varied at pleasure.
I will now particularly describe the upper works of the engine and the driving
connections..
The upper end of the engine arm may be tubular for the reception of the
pivoted shank, journal, or spindle of the engine head or lateral arm, to that said
head may turn or swivel freely horizontally around or upon the engine arm as
usual. The upper end of said pivotal shank is provided in this instance with a
bent or lateral split portion or extension, the outer or upper end of which receives
the pivotal bolt or pivots of the crosswise pivotal connection which connects the
lateral arm or engine head with the engine arm, with the capacity of rocking or
vibrating freely, relatively to the engine arm and to the shank, hereinafter described.
The engine head or lateral arm may have the form of a tube fitted near its butt
or rear end with a depending ear or flattened lug forming a part of the rocking
pivotal connection with the engine arm, although it will of course be understood
that the members of the pivotal connection, which are connected by the pivot or
pivots need not necessarily be formed as above described, as they may be of yoke
or other suitable form as desired.
This tubular lateral arm or engine head forms a bearing for the journal, shaft, or
spindle on which is mounted a pulley constituting the driven pulley of the engine,
said pulley imparting the required rotary motion to the said spindle when driven
by the belt connection hereafter fully described. The driven spindle is locked
from endwise movement in the bearing by means of the pulley at the butt of the
spindle, and by the adjustable collar which bears or abuts against the annular
shoulder formed by the front end of the tubular bearing.
The outer end of this driven spindle or shaft is preferably socketted for the
reception of the inner end of the flexible power conveyor or shaft, said inner end
of the conveyor being inserted in the socket and secured therein. The driven
spindle and flexible-shaft are secured together by a clamp, the walls of the socket
being split so as to form spring clamping jaws which are compressed upon the
flexible shaft, or an inner stiff section thereof, by means of a screw-nut which
works upon suitable threads formed upon the inclined or tapering circumference of
the walls of said socket.
The flexible power conveyor, which preferably consists of a coiled-wire shaft,
such as are in common use, is connected at its outer or free end with a suitable
chuck, mandril, or tool-holder of any suitable construction so as to turn it, said
tool-holder being mounted in suitable bearings in a hand-piece casing, and being
also adapted for the ready interchange of the operating tools used with this class of
engines in performing dental operations.
The tubular lateral arm at its outer end is provided with screw-threads for the
reception of a correspondingly internally-threaded sleeve, ferrule, or portion secured
or connected by screw-threads preferably to the inner end of a flexible sheath or
cover such as those in common use which envelopes and protects the flexible power
conveyer. At the outer or free end of the flexible sheath is secured the hand-
piece casing, while the enveloped power conveyor is connected with the butt end
of the tool-holder mounted in said hand-piece casing to turn it as before stated.
By means of the threaded sleeve with which the flexible sheath is connected I
am enabled to vary the relation of the said sheath to the flexible driving shaft,

page_text: this result being accomplished by turning said sleeve so as to screw it either
towards or from the butt of the tubular engine head or lateral arm, the movement
of the sleeve towards the butt of the arm drawing the flexible sheath end wise
towards the driven spindle whose clamp-nut may limit the movement in this
direction, while the movement of the sleeve in an outward direction forces said
flexible sheath away from said spindle, the range of movement being limited in this
direction by a suitable annular shoulder on the tool chuck, against which a similar
internal shoulder on the hand-piece casing abuts.
In some instances I contemplate dispensing with the flexible sheath or cover for
the flexible power conveyor in order to give more flexibility or freedom of move-
ment to said conveyor.
The driving belt passes from the driving pulley at the lower end of the engine
arm around the driven pulley, which pulley, it will be observed, is mounted upon
the spindle, journal, or shaft carried by the engine head or lateral arm in such
manner as to swing, vibrate, or rock around the pivots or pivot-bolt as a centre.
Upon a suitable cross-arm or depending portion at the butt of the lateral arm or
engine head are mounted small guide-pulleys for the driving belt when the engine
head is rocked to a position requiring their aid.
In order that the tension of the driving belt may not be materially changed by
the variation of position of the engine head or lateral arm and pulley carried thereby
when that head is rocked or turned, I preferably secure upon the upper end of the
engine arm a collar or annular shoulder fastened by a set screw, and interpose
between said collar and the annular shoulder or portion, near the upper end of the
turning shank, a spiral spring which tends to cause the shank of the engine head
to slide end wise in the engine arm.
This shank spring, it will be obvious, operates upon the engine head and the
driven pulley carried by it with a yielding pressure, and preserves the requisite
tension of the driving belt connection in all the movements of said head.
The driven pulley is arranged to overhang the pivot of the rocking pivotal
connection of the engine head or lateral arm, the said pulley being at the side of
said pivot opposite that at which the arm extends, and the belt connection when in
place practically prevents the said pulley from rising, while the spring, operating
through the pivot, tends to force the lateral arm upward. As this upward pressure
is exerted between the driven pulley and the larger portion of the lateral arm the
shank spring exerting it counterbalances in whole or in part the downward pressure
due to the weight of the lateral arm and its appurtenances, and causes it to stand out
laterally from the engine arm.
The upward movement of the lateral arm is limited by the depending portion
which comes in contact with and rests in the concave seat formed on the turning
shank.
It will be obvious that the collar may be reversed, that is, the said collar may
be secured upon the upper end of the turning sliding shank, and the spring inter-
posed between said collar and the top of the engine arm in which the shank works.
Or the shank may be tubular, and the spring may be inserted within it; or the
spring may be inserted in a tubular cavity in the engine arm, and it may operate
against the end of the shank.
From the foregoing description it will be obvious that the hand-piece is given
great freedom of movement not only by the flexure of the flexible power conveyor
rocking of the engine arm upon the base and tilting of the base and arm, but by
the universal-engine head or lateral arm which possesses the capacity of turning or
swivelling horizontally and of rocking vertically, whilst at the same time the proper
tension of the belt is maintained and the weight of the rocking head is counter-
balanced by the action of the shank spring.
The rocking lateral arm or engine head and its appurtenances when not in use
may also be rocked downward so that the flexible power conveyor will hang
vertically and straight at one side of the engine arm, which position tends to prevent
it from taking a set in a curved direction.
•

page_text: The pivot bolt which passes through the split extension or lateral portion of the
shank, and through the ear or lug of the lateral arm or engine head, inay be in the
form of a thumb or set bolt or screw whereby I am enabled to rock the lateral arm
or engine head to any desired position upon its crosswise pivotal connection, and
lock it firmly in such position against the returning action of the shank spring by
tightening the thumb screw pivot which will compress the members of the split
portion upon the ear of lug and securely clamp the parts together.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said George Pitt in the Great Scal Patent Office on the 12th February
1880.
GEORGE PITT, of Sutton, in the County of Surrey.
"IMPROVEMENTS IN DENTAL
ENGINES." (A communication from abroad by Samuel Stockton White, of Phila-
delphia, Pennsylvania, in the United States of America.)
The Invention relates to apparatus for revolving the burring or milling tools
used by dentists for drilling and cleaning cavities in decayed teeth, and belongs
more especially to dental engines of the class comprising in their structure a base
or stand carrying a foot-treadle and driving-pulley; an arm or frame rising from
the base; a driven pulley connected with the upper end of the engine-arm; a belt
connection between the driving and driven pulleys; and a flexible power conveyor
or shaft receiving motion from the driven pulley and imparting motion to the
operating tool mounted in a handle or hand piece, the hand-piece being free to be
moved about in various directions to operate at different points in the patient's
mouth.
It has been found desirable to give the engine base or tripod the capacity of being
tilted or inclined so as to throw or bring the head or upper end of the engine arm
in front of or towards the patient, irrespective of the rocking movement of said arm
upon the base, and without bringing the base or treadle inconveniently close to the
patient or operating chair, which capacity affords great freedom to the flexible
driving-shaft and to the flexible sheath or cover when that is employed to envelop
and protect the said shaft. The treadle being mounted upon the base or tripod is
also inclined therewith, thus presenting said treadle to the foot in a proper manner
to enable it to be worked by the operator with ease and comfort, the foot not
being compelled to constantly maintain and operate in an unnatural and strained
position.
To attain these ends I have devised improvements constituting the first branch
of the present Invention, which improvements consist,―
First. In providing the base or tripod of a dental engine with an inclining device
or mechanism whereby the base may be tilted and the arm of the engine thrown
out of the perpendicular; and
Secondly. In providing the base or arms of the tripod of a dental engine with
devices or mechanism capable of being (adjusted either to incline the base and tilt

page_text: the engine arm carried thereby in different directions (or to either side of the
perpendicular) or to allow said base or tripod to rest evenly and squarely upon the
floor or supporting surface.
The next brauch of the present Invention relates to the method of pivotting or
mounting the engine arm upon the fixed standard or post rising from the base or
tripod, so as to allow it to rock or vibrate thereon, and to the method of maintain-
ing said arm in a normal position relatively to the base, to which position it is
automatically returned after the force exerted upon the arm to rock or deflect it has
ceased.
The object of this part of the Invention is so to pivot or mount the rocking arm
and organize the counterbalance or spring which maintains the arm in its normal
position that the normal position of the said arm relatively to the base may be
varied, or, in other words, so to organize the rocking arm and its counterbalance
that the said arm may be changed or adjusted at pleasure from the perpendicular or
from its vertical position in line with the fixed standard of the base to any desired
angle relatively to the base while preserving its rocking capacity.
The next branch of the present Invention relates to an improved engine head,
whereby great freedom of movement is given to the hand piece and operating tool
carried thereby, and to the flexible power conveyor, relatively to the engine arm,
without interrupting the transmission of the driving power.
The subject matter claimed by me is hereinafter specifically designated.
In the accompanying Drawings, which show all the improvements as embodied
in the best way now known to me,-
Figure 1 is a side elevation of the improved engine; Figure 2 is a view thereof from
the rear; Figure 3 is a side view partly in section, the upper portion of the engine
arm and the base being broken away; Figure 4 is a longitudinal central section
there-through on the line 4, 4, of Figure 3; Figure 5 is a side elevation of the upper
works of the engine; Figure 6 is a longitudinal central section on the line 6, 6, of
Figures 7 and 9 through the engine head or lateral arm and the hand piece of the
engine; Figure 7 is an inverted sectional plan of a portion of the engine head or
lateral arm on the line 7, 7, of Figure 5; Figure 8 is a side view of the engine head
rocked to a position different from that shown in Figure 5; Figure 9 is a transverse
section through the lateral arm on the line 9, 9, of Figures 5 and 6; Figures 10, 11,
and 12 shew the tilting toe feature of the engine.
The base, tripod, or stand A is provided with a fixed upright standard or post a
forming part of the base, the upper end of which is forked or divided for the recep-
tion of the driving pulley or fly wheel B, the journal or trunnions of which turn in
suitable bearings or boxes in said standard in the usual manner. A driving crank
b is attached to one end of the pulley, journal, or axle in this instance, and is con-
nected by a plate-spring pitman C with the treadle, pedal, or foot board D pivotted
or jointed upon one arm of the tripod or upon the base as usual.
The forked or divided end of the standard is also provided outside the pulley with
trunnions or pivots a', a¹, for the reception of the forked lower end of the engine
arm E, which is also of well known construction, carrying upon its upper end the
engine head or lateral arm, to which is connected the flexible power conveyor, its
sheath or cover, and the hand piece of the engine, as hereafter fully described.
In order to give the tripod or base the capacity of being tilted or inclined at
pleasure in different directions, so as to throw or bring the head or upper end of
the engine arin in front of or towards the patient, or out of the perpendicular
irrespective and independently of its rocking movement upon the base, and without
at the same time necessitating bringing the base or treadle inconveniently close to
the patient or operating chair; and furthermore, also, in order to incline the pedal,
treadle, or foot-board so that it may be operated, when the foot is thrown out, with
ease and comfort, I provide the base or tripod with mechanism consisting by prefer-
ence of pivot pieces or toes A¹, A', which are attached preferably one to each arm of
the tripod opposite the arm or portion upon which the treadle is mounted. These
pivot pieces are acted upon by retaining plate springs a³, a², as clearly shown in

page_text: Figures 11 and 12, said springs acting to maintain the pivot pieces in their adjusted
position, whether that be a position to tilt the base or otherwise.
The toes or pieces are pivotted, when the tripod form of base is employed, by
preference in the ends of the arms of the tripod, so that when thrown out or adjusted
in line with said arms the base is permitted to rest squarely and evenly upon
the floor or supporting surface; but when moved, rocked, or adjusted inwardly at
right angles, or nearly so, to said arms, raise that portion of the tripod base to which
they are pivotted, consequently tilting or inclining the base, its standard, and the
engine arm with its appurtenances, together with the treadle.
It will be obvious that when both the inclining toes or devices are adjusted to
tilt the base said base will be tilted in the direction of the length of the treadle,
while if one only at a time of the toes be used or adjusted the base will be tilted
sidewise, whereby I am enabled to incline or tilt the base and its appurtenances in
different directions, or to either side of the perpendicular, as may be desirable or
necessary.
The upper end or head of the engine arm may therefore be brought, if the engine
be in proper position, towards or in front of the patient, affording great freedom of
movement to the flexible driving shaft and to its enveloping sheath or cover, which
is a desideratum of much importance in the perfect working of dental engines.
It will be obvious that various changes in the details of the inclining or tilting
devices or mechanism will readily suggest themselves to skillful mechanicians
without departing from the Invention. For instance, the toes or inclining devices
shown may be made in sections longitudinally extensible, so as to incline the base
and engine arm to a greater or less degree.
To control the rocking movement of the engine arm upon the base, or to return
it automatically to and maintain it in a normal position, various counterbalances
have been employed, the best form of which I consider to be a spring, the tension
of which, as soon as the force exerted to rock or deflect the arm is removed, returns
said arm to its normal position. The returning or counterbalancing springs (both
spiral and plate springs) have been applied in various ways.
In order however to enable the normal position of the engine arm relatively to
the base to be varied at pleasure, and also in order to permit this variation in
normal position without destroying the rocking capacity of the arm, I employ in
this instance an adjustable plate Q, pivotted at f concentrically with the rocking
engine arm, and secure to said plate one end of the counterbalancing and returning
spring, the opposite end of which is connected with the engine arm.
The upper end of the pivotted plate F is bent outward and upward, or is formed
with a shoulder q so as to limit the range of rocking movement of the engine arm,
the branch or member of said arm next the pivotted plate Q being provided with
depending ears or lugs e, e, one of which passes down upon each side of the
shoulder q, as clearly shown by the dotted lines in Figure 3; said lines also showing
the formation of the shoulder q and the extent of movement allowed the engine
arm by its ears or lugs, which abut against said shoulder when the engine arm is
rocked to its limit.
The pivotted plate Q at its lower end and next the standard a is provided with
a series of teeth or notches s, and the corners of the said plate are also provided
with lugs or projections 81, 8', which limit the range of movement of the plate Q
around its pivot by coming in contact with a pin or stud t, projecting from a plate
spring T in this instance, which spring lies in a recess in the standard a with its
upper end firmly secured thereto, and is provided with one or more projections or
teeth t which engage the teeth or notches of the pivotted plate Q to lock it firmly
to the standard a in any desired position in its range of movement.
The tension or force of this plate spring locking device is exerted at all times to
throw its locking tooth or teeth into engagement with the plate Q, and is operated
or retracted when the said plate Q is to be adjusted to a different position by
pressing it inwardly, it being preferably provided with an arm or extension to be
acted upon by the foot in order to avoid the necessity of stooping.

page_text: The construction of this spring locking device obviously may be varied in well
known ways, and need not of necessity be a plate spring. It will also be obvious
that the adjustable plate may be locked to the standard in various ways other
than by a spring locking device (which however is the preferred form), as, for
instance, by a set screw.
It will be obvious that by adjusting the plate Q the normal position of the
engine arm relatively to the base may be varied without destroying the rocking
capacity of the arm; the counterbalancing spring when the deflecting strain is
removed returning the arm to a position with one of its lugs e abutting against
the shoulder q of the adjusting plate, as shewn in Figure 3, the rocking movement
of the arm being then permitted in the opposite direction against the tension of
the spring.
The counterbalancing or returning spring R in the present instance is a coiled
spring surrounded by a sectional telescoping tube or cover S, so as to protect the
spring and present a handsome appearance, one end of said spring being connected
with a threaded shank u of a forked plate or clevis U pivoted to one of the lugs 8'
of the plate Q, said pivot being crosswise of the path in which the engine arm
rocks or vibrates, so as to permit the tubular sectional covering of the spring to
rock or yield during the vibration of the engine arm. The upper end of the
counterbalancing spring is connected in this instance with a curved arm or
extension E of the engine arm by means preferably of a screw shank V, which
passes through the arm El and receives a thumb or set nut W, as clearly shown
in Figure 3, whereby the tension of the spring may be adjusted or varied at
pleasure.
I will now particularly describe the upper works of the engine and the driving
connections.
The upper end of the engine arm is shewn as tubular for the reception of the
pivotal shank, journal, or spindle F of the engine head or lateral arm, so that said
head may turn or swivel freely horizontally around or upon the engine arm as
usual. The upper end of said pivotal shank F is provided in this instance with a
bent or lateral split portion or extension f, as clearly shewn, the outer or upper end
of which receives the pivotal bolt or pivots g of the crosswise pivotal connection,
which connects the lateral arm or engine head G with the engine arm E, with the
capacity of rocking or vibrating freely relatively to the engine arm and to the
shank hereinafter described.
In the present instance the engine head or lateral arm has the form of a tube G
fitted near its butt or rear end with a depending ear or flattened lug g', forming a
part of the rocking pivotal connection with the engine arm E; although it will of
course be understood that the members of the pivotal connection which are con-
nected by the pivot or pivots g need not necessarily be of the form shewn, as they
may be of yoke or other suitable form, as desired.
This tubular lateral arm or engine head G forms a bearing for the journal, shaft,
or spindle H, on which is mounted a pulley I constituting the driven pulley of the
engine; said pulley imparting the required rotary motion to the said spindle when
driven by the belt connection hereafter fully described. The driven spindle H is
locked from endwise movement in the bearing G, in this instance by means of the
pulley I at the butt of the spindle and by the adjustable collar i, which bears or
abuts against the annular shoulder formed by the front end of the tubular bearing
G, as clearly shown in Figure 6.
The outer end of this driven spindle or shaft H is preferably socketted for the
reception of the inner end of the flexible power conveyor or shaft J, said inner end
of the conveyor being inserted in the socket and secured therein. The driven
spindle and flexible shaft are shown as secured together by a clamp, the walls of the
socket being split so as to form spring clamping jaws, which are compressed upon
the flexible shaft, or an inner stiff section thereof, by means of a screw nut K, which
works upon
suitable threads formed upon the inclined or tapering circumference of
the walls of said socket, as clearly illustrated in the Drawings.

page_text: The flexible power conveyor, which preferably consists of a coiled wire shaft such
as are in common use, is connected at its outer or free end with a suitable chuck,
mandril, or tool holder L of any suitable construction so as to tnrn it, said tool
holder being mounted in suitable bearings in a hand piece casing M, and being also
adapted for the roady interchange of the operating tools used with this class of
engines in performing dental operations.
The tubular lateral arm G at its outer end is provided with screw threads g³ for
the reception of a correspondingly externally threaded sleeve, ferrule, or portion N,
secured or connected by screw-threads, preferably to the inner end of a flexible
sheath or cover N', such as those in common use, which envelopes and protects the
flexible power conveyor. At the outer or free end of the flexible sheath is secured
the hand piece casing M, as clearly shown in Figures 2, 5, and 6, while the enveloped
power conveyor is connected with the butt end of the tool holder mounted in said
hand piece casing to turn it, as before stated.
By means of the threaded sleeve N, with which the flexible sheath is connected,
I am enabled to vary the relation of the said sheath to the flexible driving shaft,
this result being accomplished by turning said sleeve N so as to screw it either
towards or from the butt of the tubular engine head or lateral arm G. The move-
ment of the sleeve N towards the butt of the arın G, drawing the flexible sheath
endwise towards the driven spindle H, whose clamp nut K limits the movement in
this direction, in this instance, as clearly shewn in Figure 6, while the movement of
the sleeve N in an outward direction forces said flexible sheath away from said
spindle, the range of movement being limited in this direction in this instance by
a suitable annular shoulder on the tool chuck, against which a similar internal
shoulder on the hand piece casing abuts.
In some instances I contemplate dispensing with the flexible sheath or cover for
the flexible power conveyor in order to give more flexibility or freedom of movement
to said conveyor.
The driving belt O passes from the driving pulley at the lower end of the engine
arm around the driven pulley I, which pulley it will be observed is mounted upon the
spindle, journal, or shaft H carried by the engine head or lateral arm in such
manner as to swing, vibrate, or rock around the pivots or pivot bolt g as a centre.
Upon a suitable cross arm or depending portion G¹, in this instance at the butt
of the lateral arın or engine head G, is mounted small guide pulleys c, c, for the
driving belt when the engine head is rocked to a position requiring their aid, as in
Figure 8, for instance.
In order that the tension of the driving belt may not be materially changed by
the variation of position of the engine head or lateral arm and pulley carried
thereby when that head is rocked or turned, I preferably secure upon the upper
end of the engine arm E a collar or annular shoulder p fastened by a set-screw p',
and interpose between said collar and the annular shoulder or portion f¹ near the
upper end of the turning shank Fa spiral spring P, which tends to cause the shank
F of the engine head to slide endwise in the engine arm.
This shank spring, it will be obvious, operates upon the engine head and the
driven pulley carried by it with a yielding pressure, and preserves the requisite
tension of the driving belt connection in all the movements of said head.
It will be noticed that the driven pulley I is arranged to overhang the pivot g
of the rocking pivotal connection of the engine head or lateral arm G, the said pulley
being at the side of said pivot opposite that at which the arm extends, and the
belt connection when in place practically prevents the said pulley from rising,
while the spring P operating through the pivot g tends to force the lateral arm
upward. As this upward pressure is exerted between the driven pulley and the
larger portion of the lateral arm, the shank spring exerting it counterbalances in
whole or in part the downward pressure due to the weight of the lateral arm and
its appurtenances, and causes it to stand out laterally from the engine arm.
The upward movement of the lateral arm is limited in this instance by the

page_text: depending portion G', which comes in contact with and rests in the concave seat ƒ³
formed on the turning shank F, as clearly shown in Figures 6 and 8.
It will be obvious that the collar p may be reversed, that is, the said collar may
be secured upon the upper end of the turning sliding shank F, and the spring P
interposed between said collar and the top of the engine arm in which the shank
works; or the shank F may be tubular, and the spring may be inserted within it;
or the spring may be inserted in a tubular cavity in the engine arm, and it may
operate against the end of the shank F.
From the foregoing description it will be obvious that the hand piece is given
great freedom of movement, not only by the flexure of the flexible power conveyor
rocking of the engine arm upon the base and tilting of the base and arm, but by
the universal engine head or lateral arm, which possesses the capacity of turning or
swivelling horizontally and of rocking vertically, whilst at the same time the proper
tension of the belt is maintained, and the weight of the rocking head is counter-
balanced by the action of the shank spring.
The rocking lateral arm or engine head and its appurtenances when not in use
may also be rocked downward, so that the flexible power conveyor will hang
vertically and straight at one side of the engine arm, which position tends to prevent
it from taking a set in a curved direction.
It will be noticed that the pivot bolt g, which passes through the split extension
or lateral portion f of the shank F, and through the ear or lug g¹ of the lateral arm
or engine head G, is in the form of a thumb or set bolt or screw, whereby I
am enabled to rock the lateral arm or engine head to any desired position upon its
crosswise pivotal connection, and lock it firmly in such position against the returning
action of the shank spring by tightening the thumb screw pivot, which will compress
the members of the split portion fupon the ear or lug g¹, and securely clamp the
parts together.
Having thus described the nature of the Invention, and the manner of performing
the same, I would state that I am aware that rocking and turning or universal
dental engine heads are very common, and I do not broadly claim such a device,
but I claim as the improvements in dental engines,―
First. The combination with a dental engine (comprising in its structure a base
or stand carrying a foot treadle and driving pulley, an arm or frame rising from the
base and carrying a driven pulley at its upper end, and a flexible shaft receiving
motion from the driven pulley, and imparting motion to the operating tool) of
mechanism for inclining the base or stand and engine arm of such dental engine,
substantially as herein before set forth.
Second. The combination in a dental engine, substantially as herein before set
forth, of a base or stand and engine arm capable of rocking on said base, and
mechanism to lock said arm in different positions relatively to the base.
Third. The combination in a dental engine, substantially as hereinbefore set
forth, of a base or stand and engine arm capable of rocking on a pivot or hinge
coincident with the axis of the fly or driving wheel which is carried by the base,
and also nechanism for locking the arm in the desired position or angle relatively
to the base.
Fourth. The combination in a dental engine, substantially as herein before set
forth, of a base or stand and engine arm rocking thereon, and mechanism to tilt
the base and arm in a plane at an angle to the plane in which the arm swings or
rocks.
Fifth. The combination in a dental engine, substantially as herein before set forth,
of a base or stand and rocking engine arm, with a locking device for varying the
normal position of the rocking engine arm, while still permitting it to have a certain
amount of free rocking movement.
Sixth. The combination in a dental engine, substantially as herein before set forth,
of a base or stand and rocking arm, with an adjustable plate for varying the normal
position of said arm and spring connected with said plate at one end, and acting

page_text: upon the rocking arm at the other, to maintain it in its normal position while
permitting it to be deflected or rocked upon its pivots.
Seventh. The combination in a dental engine, substantially as herein before set
forth, of the base or stand, the forked engine arm pivoted thereon, and the ears or
lugs upon said arm to limit its range of movement.
Eighth. The combination in a dental engine, substantially as hereinbefore set
forth, of the base or stand, the engine arm, mechanism for varying the normal
position of said arm, lugs or devices for limiting the range of rocking movement of
the arm, and the counterbalancing spring acting upon the arm.
Ninth. The combination, substantially as hereinbefore set forth, with the lateral
arm or engine head of a dental engine, of a pivot crosswise of said arm upon which
said arm rocks, the driven pulley at one end of the arm being on one side of the
pivot, whilst the end of the arm which carries the flexible power conveyor extends
on the opposite side of the pivot.
Tenth. The combination in a dental engine, substantially as hereinbefore set
forth, of the flexible power conveyor, the lateral arm, the rocking pivot thereof,
the pivotting spindle by which said rocking pivot is carried by the engine arm,
and a spring for pressing upwards said spindle and the overhanging driven
pulley.
Eleventh. The combination in a dental engine, substantially as hereinbefore set
forth, of the flexible power conveyor, the lateral arm, the rocking pivot thereof,
and an adjusting device to lock the arm when desired in the position to which it is
rocked.
In witness whereof, I, the said George Pitt, have hereunto set my hand
and seal, this Fifth day of February, in the year of our Lord One thousand
eight hundred and eighty.