Improvements in Electric Dental Pluggers.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Electric Dental Pluggers.
I, WILLIAM EDWIN GIBBS of No. 111 Liberty Street in the City, County and
State of New York, United States of America, Electrical Engineer, 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 invention relates to a device intended to be used by dentists as a substitute for
the well known mallet for compressing gold fillings; and it relates particularly to
that class of mallet or plugger in which electric energy is employed for giving the
blows.
The object of my invention is to provide such an instrument similar to those known
in the art except as to certain practical and commercial advantages in detail which
render the device free from difficulties met with in other forms of pluggers.
Referring to the drawings:-
--
Figure 1 is a view of the plugger complete with the dental plugging-point
attached.
Figure 2 is a longitudinal sectional view of the complete instrument.
Figure 3 shows, for the sake of clearness, part of the plugger in section and part in
elevation, and
Figure 4 is a detail view of the tool holder.
In each figure, like letters refer to the same parts.
My electric dental plugger consists of an outer case A of metal, within which, at
one end, is a tubular piece of soft iron B, having screwed or otherwise attached to one
end a hollow conical section C, also of soft iron. The parts B and C, when conjoined,
form a hollow cylinder of uniformi interior diameter except at D, where the diameter
of the bore is enlarged, as shown.
Within the cylinder formed by the parts B and C is a loosely fitting bar of iron E
(shown separately in Figure 4) baving near its centre an enlarged ring F. One end
of the bar E is adapted to hold the dental plugging-point by being bored out
and threaded, or in any convenient way, while in the other end is a hole extending
downward to the ring F. This loosely fitting bar, being placed within the section BC
is pressed upward or toward B by a spiral spring inserted in the enlarged portion D
of the bore of B and bearing on the enlarged ring F of the bar E. When in
position, as described, the ends of the bar E project slightly beyond the terminal
parts of B and C, as shown in Figure 2.
Within the tube A and beyond the iron parts B, C and E slides freely an electro
magnet formed of a soft iron core H, surrounded by a coil of insulated wire and
having at each end non-conducting washers G I. Those washers are surrounded by
short tubes of brass L K, which form within the tube A smooth bearing surfaces.
The wire upon
the core H has one of its ends in electrical connection with said core
and the other end similarly connected with the brass tube L. A coiled spring M
within the bar E presses upon a rod of hard rubber, which bears upon the downward
end of the core H.
The upper end of the case A is closed by a plug of insulating material N, through
which passes the circuit breaker constructed as follows:-
A brass cylinder of the form shown at O has within it a loosely fitting sliding bar
of iron P, the outer end of which is enlarged by a flange. A coiled spring surrounds
this rod P, as shown in Figure 2, and lightly presses it against the adjustment

page_text: screw R. The inner end of the iron har P projects through the cylinder 0 and
rests in contact with the iron core of the electro-magnet, which in turn is
pressed against the rod P by the retracting spring M bearing upon the hard rubber
rod.
-
The action of my plugger is as follows:-
The wires marked + being connected with a source of electricity of sufficient
power, the electric current comes in through the wire marked + to the circuit breaker
at O, passes down the rod P to the core H of the electro-magnet, through the
insulated wire coil, and thence to the brass tube L, thence to the casing A, and back
to the source by the wire, all these parts being in electrical contact. The moment
the current passes, the core H becomes magnetised and is violently drawn toward
the lower end of the instrument by the mutual attraction between the magnetised
core H and the mass of iron forming the parts B, C and E, the spring M yielding us
the parts come together. The core H, by virtue of its magnetic force, draws down the
rod P of the circuit breaker, with it, the spring surrounding the rod yielding as the
rod advances. When the core H, with its surrounding coil of wire, reaches the end
of its downward stroke, it comes in contact with the plugging-point holding bar E,
and the blow is, by this bar, transmitted to the plugger or point, and by it to the
gold or other filling impacted in the tooth; but when the core II comes in contact
with the end of the bar E, the electric current is no longer compelled to pass
through the long coil of wire upon the core H, but takes a more direct road
from the core EL through the parts B and E directly to the outer case A, thus cutting
the coil out of the circuit. As soon as this happons, the core H becomes
demagnetised and no longer draws upon the circuit breaking rod P, which is thrown
back into contact with the adjustment screw R by the spring surrounding it. The
retracting spring M immediately returns the electro magnet to its original position
and the operation is repeated so long as the current is applied. It is of the utinost
importance that this operation should be effected without any adhesion or hesitation
on the part of the different parts of the instrument brought into conjunction and
released by the shifting of the current, as herein before described. To obviate a
defect in this particular, which was found to exist to the impairment of the utility
of my invention, I face the upper end of the core H with a thin plate or washer
of platinum and screw or otherwise fasten into the lower end of the sliding rod P
a button or point of platinum, so that the contact of the core H and sliding bar P
is made upon this metal and instantaneously severed upon the shifting of the
current after the blow is delivered upon the rod E. By means of those points or
washers of platinum, the burning of the ends of the soft iron core H and rod F
by the passing current, and also any tendency to the adhesion of those parts
because of the residual magnetism remaining after the shifting of the current, are
avoided.
In all vibrating electrical instruments hitherto invented, the circuit is broken
just before the blow is given, thereby losing the force of the magnetic attraction,
which is strongest at the moment of contact of the armature and the magnet.
I am aware that electro-magnetic dental pluggers have been invented having many
of the features embraced in my invention, but nearly all of those features were common
to the art and unpatentable as separate inventions, but none of those prior instruments
have been found of sufficient practical use by dentists to warrant their application to
the purposes for which they were intended to be applied and have been, for the most
part, dispensed with. Ono of the defects of such instruments, which rendered them
comparatively useless, was the breaking of the electric current, as herein before
explained, before contact between the armature and the magnet, and, consequently,
before the delivery of the blow which my invention overcomes.
I make no claim upon any portion of the instrument embraced in this Specification
contained in the lower section thereof, or so much as is shown beyond the lower
termination of the core H downward, as such parts consist either singly or in
combination of hitherto well known devices; but

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 :-
1. An electrical dental plugger, consisting of the combination of elements sub-
stantially as hereinbefore described.
2. In an electrical dental plugger, means for maintaining the electrical circuit
through the magnet until the blow or impulse is delivered.
3. The combination of the sliding bar P, maintained in electrical connection with
the core H, by the retracting spring M, the core H, the non-conducting washers GI
at either end of the core H, surrounded by the brass tubes L K, and the wire upon
the core H in electrical connection with the core H and the brass tube L, for the
purpose and substantially in the manner herein described.
4. The combination of the circuit wires + and
-
with the circuit breaker O, the
circuit breaking rod P, the sliding electro-magnet core H and its surrounding coil,
the outer casing A, and the armature B, for the purpose and substantially in the
manner herein described.
T: 04h da T.... 1940
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.