Improvements in Dental Chairs.
Year: 1892

page_text: Date of Application, 4th Oct., 1892-Accepted, 12th Nov., 1892
COMPLETE. SPECIFICATION.
Improvements in Dental Chairs.
We, WILLIAM ARMOUR JOHNSTON of Prince's Bay, in the County of Richmond
and State of New York, United States of America, Manufacturer, and ARTHUR
WILLIAM BROWNE, of corner Amboy & Rossvill Avenues, Prince's Bay, aforesaid,
Mechanical 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 :-
:
Our invention relates to improvements applicable to chairs of the class in which
the chair frames or bodies are so mounted upon suitable supports or plungers as to
be vertically and horizontally adjustable, our improvements being in this instance
shown as applied to the well-known "Wilkerson Chair" for which United States
Letters Patent No. 197,441, were granted Nov. 20th, 1877, and also British
Patent No. 4662 in the same year. Our invention comprises certain improvements,
to be hereinafter designated by the claims, whereby the chair frame or body may
be so attached to its vertically adjustable support or plunger as to bring the lever,
by the actuation of which the chair body is raised, to either the rear or side of the
chair-body to suit the convenience of the operator; the back be adjusted relatively
to the seat and locked in position; and the arms adapted to be readily removed to
leave either side of the seat frame clear of projections, whilst provision is made for
quickly adjusting and securing the arms in position.
In the accompanying drawings
Fig. 1 is a side elevation of the improved chair.
Fig. 2 is a side elevation with parts in section, of the back pad, its carrier, etc.
Figs. 24 and 2 are detail views showing the manner in which the back pad
carrier is rendered vertically adjustable and adapted to be locked to the back
frame, Fig. 2 being a rear elevation with parts broken away, and Fig. 2B a cross
section in different planes as indicated by the line 2° of Fig. 2.
Fig. 3 is a view in perspective of the back pad locking latch.
Fig. 4 is a side elevation, and Fig 5 a front elevation of one of the arm frames.
Fig. 5 is a section on line 5* of Fig. 5.
Fig. 6 is a side elevation of a portion of the seat frame.
Fig. is a top or plan view of the seat frame portion of the chair body and
attachments thereof.
Fig. 8 is a rear view of a portion of the seat frame and attachments thereof.
Figs. 9 and 10 are detail views of the back frame clamping devices.
Fig. 11 is a section on the lines 11 of Figs. 7 and 8.
Figs. 12 and 13 represent portions of the support or plunger and the yoke by
which the chair seat frame is removably and adjustably connected with the
plunger.
Figs. 14, 14, 15 and 16 are views showing modifications of the means employed
for adjustably connecting the frame-carrying cross-bar or yoke with the chair seat
support or plunger.
Fig. 17 is a detail view showing in rear elevation portions of the back pad
carrier and head-rest support; and Fig. 18 is a section on the line 18 of Fig. 17.
A support for the chair frame or body A is shown as consisting of the plunger A¹
having vertically adjustable connection with the base or pedestal A² and actuated
by means of the jointed lever A3 and suitable connections, the lever being jointed
to the cylinder B which is adapted to turn in the pedestal and to be locked therein
by the locking lever B', all as set forth in the above-mentioned Patent, No. 197,441
and English Patent No. 4662 of 1877. As in said Patents the supporting plunger
has no horizontal or turning movement in the cylinder B.to which the elevating

page_text: lever is attached, and as the cylinder and the plunger turn together in the pedestal,.
the only variation in the relative positions of the lever and chair seat are due
merely to alterations in the altitude of the chair frame seat or body by the up and
down movements of its supporting plunger. To provide for a horizontal adjustment
of the chair seat relatively to the elevating lever in order that the lever may be
caused to project either rearwardly.or sidewise relatively to the seat frame, this
frame and its connections-that is to say, the entire chair-body- -are detachably
. connected to the plunger, and provision is made for adjusting the chair body
'horizontally upon the plunger in the following way :-
The frame-carrying cross-bar or yoke C, upon journals or trunnions at the ends
of which the seat frame of the chair body is pivoted to rock as usual, is split at one
side of its socket for embracing the upper end of the plunger or support, and
provided with the clamp screw c by the turning of which the size of the socket
may be slightly reduced or enlarged, as will readily be understood, to enable the
carrying bar or yoke to be properly adjusted and clamped upon the plunger. In
addition to this clamping attachment formed by the split yoke and clamp screw, an
interlocking connection between the carrying yoke and plunger by which to clamp
or lock them together is provided consisting of a threaded inclined pin or lug D
screwed into a hole in the wall of the socket of the carrying frame or yoke,
projecting into said socket and adapted for engagement with the desired one of the
holes d in the plunger end. Two of these holes are shown, but three or more
may be provided as desired according to the required horizontal adjustments of the
chair seat.
'
From the above description it will be seen that the chair body may be raised
from its support, turned and then lowered upon the support and interlocked
therewith, thus locating the elevating lever in the position suited to the convenience
of the operator.
In lieu of the above described clamping and interlocking connection between the
chair body and its support or plunger, modifications thereof, such for example as
next to be described, may be employed.
As shown by Figs. 14 and 14 the upper end of the plunger is reduced, thus
forming a shoulder D' upon which the cross-bar or yoke C rests so that it may be
turned when desired. Two or more vertical holes d are provided at proper intervals
in the edge of the reduced end of the plunger or support A', and a similar hole is
'formed in the wall of the yoke socket. When this hole in the yoke is brought to
register with either of the holes in the plunger end the yoke may be prevented
from turning by the insertion of the locking pin D in the registering holes in the
plunger and yoke. This locking pin may be an ordinary screw, as shown, to render
it readily removable when the yoke is to be turned to adjust the chair body
relatively to the lifting lever, or this pin may be left unthreaded and made of a
length such as to project, when in place, sufficiently above the plunger and yoke to
be taken hold of for ready removal to allow of adjustment of the yoke. Obviously
instead of duplicating the holes in the periphery of the plunger end, but one hole
may be there provided, and duplicate holes made in the wall of the yoke socket
instead of the one hole as shown and above described.
Instead of reducing the plunger end to form the shoulder D₁ this shoulder may
be formed by a collar (see Fig. 15) firmly secured to the plunger, thus leaving the
plunger proper of uniform diameter throughout.
Fig. 16 shows the yoke C as provided with a socket extending only part way
therethrough and fitting upon the plunger so as to be capable of turning thereon.
A removable threaded locking pin D adapted to pass through a threaded hole in
the yoke engages by its unthreaded tapered end with the desired one of a series of
correspondingly tapered holes in the edge of the plunger end. By making the
locking pin tapering at its end for engagement with the holes formed partly in the
yoke socket wall and partly in the plunger and tapered as shown it serves as a
clamp to draw the yoke socket firmly against the side of the plunger opposite to
that engaged by the pin, and thus prevent any movement between the parts.

page_text: The mechanism for inclining the chair-body by rocking it about its pivotal
connection with its support is substantially similar to that shown in the above-
mentioned Wilkerson Patent, consisting of the lever E pivoted to the frame-carrying
yoke, acted upon by the spring e, and adapted to operate in obvious way in
connection with a detent rack El carried by the chair frame.
An adjustable back frame F is pivoted at f to arms or rearward extensions G of
the seat frame of the chair body, and is extended below its pivotal connection,
terminating at its lower end in a curved forwardly projecting arm or tongue a. As
the back frame is pivoted in advance of its centre of gravity the normal tendency
of the frame is to tilt at its upper end rearwardly or away from the chair seat.
The back frame is clamped in any desired position in the following way:-To the
rear portion H of the seat frame, which as shown is made separate from and
bolted to the side portions H'H' thereof, is secured a forked clamp piece I by
means of a screw h. A socket in which the arm g of the back frame may slide and
be clamped in the desired position is provided between the arms or side portions i i
of the clamp, which are adapted to yield or spring slightly to release and lock
the arm g. The arms of the clamp socket project between two lugs JJ on the
rear of the seat frame, and these lugs are perforated and threaded to receive
clamping screws kk provided with actuating handles or levers KK projecting
sufficiently from the chair to be readily reached by the foot, knee or hand of the
operator. It will be seen that by depressing the clamp handles K K, the yielding-
armed clamp will be caused to tightly embrace the arm g, and lock the back frame
in position, and that by raising the handles the back frame will be released from
its clamp. It will be noticed that although preferable it is not necessary to provide
duplicate clamps k, and that the combination of parts is such that when the two
clamps are provided proper actuation of one of them will suffice to grip and release
the back frame.
A back-pad carrier L is carried by the back frame F, being vertically adjustable
by sliding up and down, and suitably guided in its movements, and locked when
adjusted by a clamp screw L'. As will be understood by reference to Figs 2, 24
and 2B, the back frame has vertically extending inwardly projecting ribs V entering
corresponding grooves in the back pad carrier. The clamp screw engages a cross
bar W of the back pad carrier and passes loosely through a clamp plate W¹ which
at its ends projects into sockets w formed in the back pad carrier so that this clamp
plate may be forced against the ribs of the back frame to lock the parts together.
The back-rest or back-pad proper m (see dotted lines Fig. 1) is secured to its
frame M which is hinged at its upper end to the corresponding end of its vertically
adjustable carrier L so that the back pad is adapted to be swung back and forth.
To hold the back pad in the position to which it may be adjusted by swinging it
about its jointed connection with the carrier L, a detent or locking latch N pivoted
to this carrier in a recess thereof so as to rock vertically is provided for engaging
with the back pad frame. This vertically vibrating latch or detent is curved in
advance of its pivot and provided on its upper surface with a series of shoulders or
ratchet-like teeth n, and in rear of its pivot has an operating handle n' by means
of which to rock the latch about its pivot. The teeth of the locking latch are
adapted to engage with a detent stop or shoulder o shown as formed by the protected
upper wall of an opening O in the back pad frame. The lining or protecting
plate O¹ of the opening O may be dispensed with if desired. In adjusting the
back pad this opening provides for the movements of the latch, the forward portion
of the latch as rocked downward projecting into this opening as will readily be
understood. Normally the back pad frame lies close to and parallel with its
carrier, with the locking latch or detent occupying the position in which it is
represented by dotted lines Fig. 2. As the pad frame is inclined the teeth of the
latch engage it nearer to or farther from the latch pivot, according to the inclination
of the pad. The range of movement of the pad is limited by the chain P which
connects it with the carrier.

page_text: Each arm Q of the chair is detachably connected with the seat frame in such
manner that it may be quickly placed in position and locked securely against.
accidental displacement, and be readily removed. The construction of the sides
of the seat frame is such that when the arms are removed the sides of the chair are
left free from any projection liable to interfere with the movements and work of the
operator. Each arm is carried by a standard or frame R the lower portion of
which (projecting slightly inward by preference) is provided with two inwardly
projecting flanges or lugs, the one above the other, which lugs have shallow
longitudinal grooves formed in them, the groove in the upper lug being on the
under side thereof and extending horizontally to fit and slide upon a vertical
horizontally extending flange or rib s upon the top surface of the side of the seat
frame; whilst the groove in the lower lug is formed in the upper surface thereof
and is inclined so as to fit and slide upon a vertical rib s on the under surface of
the side of the chair seat frame, which rib is inclined downward toward the rear
of the seat frame, and like the rib s, extends in the direction of from front to rear of
the chair seat frame. This construction constitutes a wedge-like locking connection
between the arm-frame and seat frame, the grooves of the arm-frame nicely fitting
and freely sliding upon the ribs of the seat frame whilst these are so formed, as will
be apparent upon reference to the drawings, as to leave no lateral projection on the
seat frame to interfere with the movements of the operator by catching in his
clothing or watchguard. To securely lock the arm in place when adjusted, instead
of relying solely upon frictional contact of the parts, a lock consisting of a latch t,
is pivoted at one of its ends-that next the front of the chair-to the seat frame
slightly inside of the line of the rib and in advance thereof. An. inclined
laterally projecting lug u on the arm frame, at the front lower corner thereof, rides
under the lock and lifts it as the arm frame is being slid in place, and when the arm.
frame has completed its sliding movement, its lug having passed beyond and released
the lock, the arm frame is retained in position by the fall of the lock, the rear end
of which abuts against the lug as shown in Fig. 1. In removing the arm frame
the lock is first lifted by means of the downwardly projecting handle or knob
thereof, and the arm frame having been started in its movement of displacement,
the stop lugu passing beneath the latch holds it up out of the way and no impedi-
ment is offered to the outward slide of the arm frame.
Although we have described and shewn the lower rib s¹ of the chair seat frame
as inclined and the upper rib s thereof as horizontal, and prefer this construction,
we do not wish to be understood as limiting ourselves thereto, as obviously the
upper rib may be inclined upwardly from front to rear, and the lower rib be made
to extend horizontally; and in this event the grooves in the lugs would be
correspondingly changed, the upper groove being inclined and the lower one
horizontal, so as to fit and slide upon the ribs of the chair seat frame. It will be
obvious that neither rib need be inclined provided a shoulder or similar stop on the
seat frame be employed to limit the inward sliding movement of the arm frame,
accidental outward movement thereof being prevented by the lock. The employ-
ment of the inclined guide rib is, however, advantageous as it acts not only as a
stop to limit rearward movement of the arm frame but also ensures a snug fit of
the arm in place and produces sufficient frictional contact between the parts to
effectually prevent motion of the arin when in place.
The upholstered seat T is made wider at top than at bottom so that, at its sides
above the level of the sides of the seat frame, the seat is flush with the outer
surfaces of the sides of the seat frame, the outward, curvature or inclination of the
arm-standards above their lugs r, permitting of this construction of the seat.
A head-rest X is carried by its supporting bar Y which has vertically adjustable
connection with the back pad carrier L. As shown by Figs. 17 and 18 the head-
rest support Y has sliding dove-tail connection with an arm or downwardly projecting
portion at the upper end of the back pad carrier, a set screw y serving to lock the
head-rest support in its position of vertical adjustment.

page_text: Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. The combination of the chair frame or body, the support or plunger therefor
the carrying frame or yoke having the split socket for connecting the chair frame
and its support or plunger, and the clamp screw by which the carrying frame is
adjustably secured upon the support or plunger, substantially as set forth.
2. The combination of the chair frame or body, the support or plunger therefor
provided with the holes at its upper end, the socketed carrying frame or yoke
detachably connecting the chair frame and its support or plunger, and having a
hole in the wall of its socket, and the locking pin for engagement with the holes in
the support and yoke, substantially as and for the purpose set forth.
3. The combination, substantially as set forth, of the vertically adjustable and
turning support or plunger, the elevating lever turning with the support, the
carrying frame or yoke connected with and horizontally adjustable by turning about
the support, the chair frame or body, carried by the yoke, and the locking devices
for clamping the yoke to the support in the position of horizontal adjustment to
which the yoke may be brought by turning it about the support, whereby
horizontal turning adjustment of the chair body independently of the support and
relatively to the elevating lever is provided for, the lever is caused to project in
the desired direction relatively to the chair seat, and these relative positions are
maintained throughout vertical and turning movements of the support, as described.
4. The combination of the chair frame or body, the back frame projecting in
rear thereof and pivotally connected therewith and provided beneath its pivot
with the forwardly projecting arm, the yielding-armed clamp piece, and a lever-
actuated clamp acting upon the armed clamp-piece for engaging it with the
projecting arm of the back frame, substantially as and for the purpose set forth.
5. The combination of the back pad carrier, the handled detent or locking
latch pivoted in a recess in the carrier and curved and toothed in advance of
its pivot, and the back pad frame hinged to the carrier, engaged by said locking
latch and provided with the opening in which said latch works and acts against
a detent stop or shoulder, substantially as and for the purpose set forth.
6. The arm frame carrying the arm at top and having on the inside of its
lower portion the two grooved lugs, one above the other, the groove in the one
lug extending horizontally and that in the other being inclined, substantially as
and for the purpose set forth.
7. The combination of the seat frame provided with the horizontally-extending
and inclined top and bottom side ribs, and the arm frame having on the inner side
of its lower portion the two lugs grooved to adapt them to slide upon the ribs of the
seat frame, substantially as and for the purpose set forth.
8. The combination of the chair seat frame provided at its sides below the level
of the upper surface of the upholstered seat with the guide ribs, the detachable
arm frames grooved to slide upon said guide ribs, and the lock to retain each arm
frame in position, substantially as set forth.
9. The combination of the seat frame provided with the horizontally extending
top rib and the inclined bottom rib, the pivoted lock in advance and inside of said
bottom rib, and the arm frame provided with the two inwardly projecting grooved
lugs, one above the other, the upper one extending horizontally and the lower
inclined to correspond with the inclination of the bottom rib of the seat frame, the
said arm frame being also provided at its front lower corner with the inclined
laterally projecting lug, substantially as and for the purpose set forth.
Dated thie Tonth dor of August 1899
WILLIAM ARMOUR JOHNSTON.
ARTHUR WILLIAM BROWNE.