IMPROVED PROCESS AND APPARATUS FOR SHARPENING DENTAL BURRS AND OTHER SIMILAR REVOLVING CUTTING TOOLS."
Year: 1879

page_text: LETTERS PATENT to Milo A. Richardson, of Bridgeport, in the County of
Fairfield, and State of Connecticut, one of the United States of America, for
the Invention of "IMPROVED PROCESS AND APPARATUS FOR SHARPENING
DENTAL BURRS AND OTHER SIMILAR REVOLVING CUTTING TOOLS."
PROVISIONAL SPECIFICATION left by the said Milo A. Richardson at the
Office of the Commissioners of Patents on the 8th September 1879.
"
MILO A. RICHARDSON, of Bridgeport, in the County of Fairfield, and State of
Connecticut, one of the United States of America. "IMPROVED PROCESS AND
APPARATUS FOR SHARPENING DENTAL BURRS AND OTHER SIMILAR REVOLVING
CUTTING TOOLS."
My improved process for sharpening dental burrs and other similar tools consists
in revolving the tool backward while it is immersed in sand, corundum, emery, or
other abrasive powder or granulate.
In carrying out my process I place a sufficient quantity of the abrasive material
in a suitable vessel or receptacle. I then mount the dental burr or other tool on
the end of a spindle which is capable of revolving, immerse the cutting portion of
the tool in the abrasive material, and by means of the spindle rotate the tool back-
ward or in a direction the reverse of that given to it in use. As the tool thus
revolves the particles of abrasive material come in contact with the backs only of
its teeth, which they cut or wear away, and thus bring to a new and fine edge.
I prefer to divide the operation into two parts, as follows:-I first rotate the
tool somewhat slowly in the abrasive, and at the same time I force the latter against.
the tool and into close contact therewith by lateral pressure, whereby the tool is
abraded more rapidly than otherwise, and this operation I continue until the tool
is coarsely sharpened. I then finish the sharpening and polish the teeth of the tool
by removing the pressure and revolving the tool at a higher speed in the same or a
finer abrasive.
My improved apparatus for sharpening by the above described process consists of
a suitable spindle provided with a holder or clutch for the tool to be sharpened,

page_text: arranged to be revolved by a crank or clock work, or, as I prefer, by both, and
used in connection with a suitable receptacle for the abrasive material. Between
the tool and the spindle a flexible connection is interposed, so that the tool may be
deflected out of the axial line of the spindle while revolving without being ground
unevenly. This flexible connection may consist of any known form of universal
joint or flexible shaft, or it may be simply a piece of rubber tube fastened to the
end of the spindle and embracing the tool.
The receptacle or one of the receptacles, if more than one are used for the
abrasive material, is made with sides that can be forced toward each other by
lateral pressure, being preferably formed of elastic india rubber. It is hung upon
a pivoted bracket, so that it can be held under the revolving spindle or turned
back out of the way at will, and the bracket is so constructed as to be capable of
moving vertically so that the receptacle may be depressed to bring it under the
revolving tool and raised so as to immerse the latter in its contents.
The spindle which carries the tool may be revolved slowly by the crank and
rapidly by the clock-work, and the crank and clock-work may be capable of being
disconnected from each other.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Milo A. Richardson in the Great Seal Patent Office on the 2nd March
1880.
"
MILO A. RICHARDSON, of Bridgeport, in the County of Fairfield, State of
Connecticut, one of the United States of America. IMPROVED PROCESS AND
APPARATUS FOR SHARPENING DENTAL BURRS AND OTHER SIMILAR REVOLVING
CUTTING TOOLS."
The object of my Invention is to provide dentists and others who use "burrs"
and similar revolving cutting tools having inclined teeth with a handy and
rapid means of sharpening the same. My process consists in revolving the tool
backward while it is immersed in sand, corundum, or other abrasive powder or
granulated substance.
In
The cutting action of moving particles of sand, quartz powder, corundum, and
other abrasive powders and granulates upon hard bodies is well known, being fitly
exemplified in the "sand blast." My process depends for its success upon this
action, and to render it most effective a very sharp and hard abrasive should be
selected, granulated or powdered corundum being well suited to the purpose.
practicing my process the abrasive material is placed in a suitable receptacle, and
the dental burr or other tool to be sharpened is immersed therein, and then revolved
in a backward direction, or the opposite of that which is given to it in use.
particles of abrasive material are thus actively agitated, and at their contact with
the teeth of the tool they cut or abrade it sharply, thus removing the metal from
the back of the tooth, and bringing the latter to a smooth fine edge. The revolution
of the tool in the granulate causes the particles of the latter to move and roll across
its surface, and to shift and change among themselves so as constantly to bring
fresh sharp grains into contact with the metal, and their attrition cuts away the
back of the teeth until a new edge is formed thereon, as described.
The
I prefer to divide the operation into two steps, the first that of grinding the tool
or taking a coarse cut therefrom, and the second that of finely finishing and polishing
the same. To accomplish the first most rapidly and effectively the tool must be
revolved in the abrasive material somewhat slowly, and the material firmly forced
or pressed against its surface, preferably by lateral pressure. The second step is
performed by revolving the tool very rapidly in either the same, or, as I prefer, a
different and finer material without pressure, thus completing the process.
The tool may be revolved by the use of the ordinary dental engine or by other
means, and any convenient vessel may be used as a receptacle for the abrasive
substance, but I prefer for the practice of my process the apparatus shown in the
accompanying Drawings, in which Figure 1 is a front elevation, the enclosing case
being partly in section; Figure 2 is a side elevation; Figure 3 is a plan, the case
being in section; Figure 4 is an enlarged detached detail view; Figure 5 is a plan
of a receptacle and its bracket; and Figure 6 is a vertical section of the tool holder
enlarged.
Let A represent a suitable case or frame for the necessary mechanism; B, a clock
work as a whole; C, the spindle which bears the tool; D, a crank by which to
rotate the spindle, and E and F receptacles for the abrasive powder or granulate. a is
the last wheel of the train forming the clock-work proper, and it meshes with a
pinion b on the spindle c which bears the crank D. The crank spindle c may be
identical with the tool spindle C, but as it is desirable that the latter should rotate
faster than it is convenient to turn the crank I prefer to make them separate, and
to provide the former with a wheel & gearing with a pinion e on the latter spindle,
as shown.
G is a suitable holder for the tool to be sharpened, and may consist of any.
convenient form of clutch, chuck, or socket arranged at the extremity of the

page_text: spindle C, and capable of grasping the tool with sufficient force to prevent its falling
out, and to effect its rotation when immersed in the abrasive powder. The holder G,
if fixed rigidly to the extremity of the spindle C, must be accurately concentric
therewith, as a very slight eccentricity on the part of the tool which is being
operated upon will cause it to grind unevenly, wearing away upon one side more than
upon the other. To obviate this difficulty I provide a flexible connection H between
the tool and the spindle C, whereby the tool can be deflected from the axial line of
the spindle without affecting its rotation, and without causing it to wabble or rotate
eccentrically. This may consist of a universal joint, or of any known form of flexible
shaft, and may be either separate from the tool holder G, or, as I prefer, made in
one piece with the same, as shown. The construction of this part is best illustrated
in Figure 6, a tool being shown in its place in the elastic holder which is formed
of a simple piece of rubber tube fixed to the spindle C and projecting sufficiently
below it to grasp the tool and to permit a sufficient deflection of the latter from the
axial line of the spindle. To accommodate tools of different lengths the spindle
may be made hollow for a short distance that the shank of the tool may be thrust
up into it, as shown, but the inside diameter of the spindle must somewhat exceed
the outside diameter of the tool shank, or the deflection of the tool will be
prevented.
The receptacle E must be so constructed that its opposite sides may be forced
toward each other by pressing between the thumb and finger. I prefer to make
this receptacle of elastic rubber, and to form it with a contracted neck or throat, as
shown, that its contents may not readily escape in use. The receptacle F is a small
cup of rigid material, and is preferably mounted upon a pivoted arm or bracket f so
as to stand back out of the way when not needed, while it can be swung out under
the tool when required. The bracket should be capable of some vertical play, and
be kept pressed upward by a spring g that it may be depressed to bring it under
the tool, and it should be provided with a catch or stop h to keep it from swinging
out of place when operating upon the tool.
The receptacles E and F may both be employed in the process of sharpening, or
either of them may be used alone, the other being omitted from the apparatus.
To sharpen a dental burr or other tool by my machine I insert its shank in the
holder G, fill the receptacle E with the abrasive substance, and holding it in the
left hand apply it to the tool so that the latter is immersed in its contents, and with
the right hand rotate the crank D, thereby turning the tool backward in the abrasive
substance, at the same time compressing the receptacle E so as to force the particles
of abrasive closely against the revolving tool. This is continued for a short time
until the tool has been roughly sharpened or ground down, and it is then finished
by permitting the clock work B to rotate it rapidly, the pressure upon the receptacle.
E being released, or, as I prefer, this receptacle being removed and the cup F
substituted for it, the latter containing by preference an abrasive of finer grain;
or if a lateral compression is not required for the first operation the receptacle E
may be discarded and the cup F alone used.
If the clock work were wound up before beginning the operation the rotation of
the tool by the crank would run down the spring to a considerable extent, and to
avoid this the means shown for disconnecting them is provided. The spindle c is
capable of a slight vertical play, controlled by a slider k operated by a button / and
its swiveled stem. By raising the button the spindle c is lifted until its pinion b
is clear of the wheel a, the pinion e on the spindle C being long enough to retain
the wheel d in engagement therewith. The apparatus from the crank D to the
spindle C is now isolated from the clockwork, but to prevent the latter from
running down when thus disconnected a stop or pawl m must be arranged to engage.
some part of the clockwork, and be operated by or from the button . This
also serves to hold the clock work while it is being wound up. The button
may be held up or down by a stop or pin n, shown in Figure 4, which permits the
button stem to move only when turned so as to coincide with the elongated hole in

page_text: the case A, or any other suitable device may be used to retain the button in
position.
Having thus fully described and ascertained the nature and operation of my said
Invention, I declare that I claim,―
First. The improved process of sharpening a dental burr or similar tool, which
consists in immersing its toothed portion in sand or other powdered or granulated
abrasive, and revolving it backward therein.
Second. The improved process for sharpening dental burrs and similar tools,
which consists, first, in immersing the tool in an abrasive powder or granulate, forcing
the same against the tool by lateral pressure and revolving the tool backward
therein at a comparatively low speed, and, second, in revolving the tool in the
same or a finer abrasive without lateral pressure, and at a comparatively high
speed.
Third. The improved apparatus for sharpening dental burrs and other similar
tools, which consists of a suitable holder for the tool, borne by a revolving spindle
in combination with a receptacle for sand or other abrasive powder or granulate,
whose sides are capable of being forced toward each other by lateral pressure, sub-
stantially as set forth.
Fourth. A receptacle for the abrasive substance borne by a bracket f capable of
vertical play, and pressed upward by a spring g in combination with the spindle C
and a suitable holder G for the tool to be sharpened, substantially as set forth.
Fifth. The combination of the receptacle F carried by the bracket f, which is so
hung as to be capable of vertical play, with a spring g arranged to press the bracket
upward, and with suitable means to prevent the lateral movement of the bracket
when at its highest position, substantially as set forth.
Sixth. The combination with a suitable receptacle for the abrasive substance of
a spindle C provided with a flexible connection H and tool holder G, substantially
as set forth.
Seventh. The combination of a case or frame A, clock work B, crank D, and
spindle C, provided with a tool holder G, constructed and arranged to operate
substantially as set forth.
Eighth. The combination with the case or frame A the clock work B with its
gear a, and the spindle c bearing the pinion b and crank D'of a suitable device for
simultaneously throwing the pinion ỗ out of mesh with the gear a, and forcing a
suitable stop me into contact with some part of the clock work to stop the further
movement of the latter, substantially as set forth.
In witness whereof, I, the said Milo A. Richardson, have hereunto set my hand
and affixed my seal, this Fifteenth day of December, in the year Eighteen
hundred and seventy nine.
MILO A. RICHARDSON. (L.S.)