IMPROVEMENTS IN DENTISTS' CHAIRS
Year: 1879

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for the
Invention of "IMPROVEMENTS IN DENTISTS' CHAIRS." A communication from
abroad by Samuel Stockton White, of Philadelphia, Pennsylvania, United'
States of America.
Sealed the 7th October 1879, and dated the 26th July 1879.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 26th July 1879.
«5
SYDNEY PITT, of Sutton, in the County of Surrey. IMPROVEMENTS IN DENTISTS'
CHAIRS." [A communication from abroad by Samuel Stockton White, of Phila-
delphia, Pennsylvania, United States of America.]
This Invention relates to chairs of the class having a wide range of adjustment,
and more especially intended for the use of dentists, commonly called dentists'
chairs, whereby the patient while in the operating chair is completely under the
control of the operator, and may be placed in the different positions necessary for
the easy and skilful performance of dental operations, the chair being adjustable in
its several parts in order to accommodate persons of different sizes, and insure their
ease and comfort.
The objects of the present Invention are to give the chair back a universal and
wide range of adjustment, enabling it to be placed with ease and facility in any
position desired in reference to the seat, and securely locked; to give the head-rest,
carried by the back, an independent, universal, and wide range of adjustment; to
provide a superior and easily adjusted arm-rest for the operator, also carried by the
back; to provide an improved chair baving a tilting or rocking body or seat in
which the pressure of the operator's foot in releasing the devices which secure the
body or seat in its inclined position may be utilized to aid or assist in the adjusting
or reclining operation; to provide an improved foot-rest or limb-support having a
wide range of adjustment to accommodate persons of different size; and, finally,
to provide a dental-chair in which the several parts are capable of rapid and easy
adjustment, and of being securely and firmly clamped in such adjusted positions.
The base of the chair is by preference made similar to the base of the pedal-lever
hydrostatic chair shown in the Specification of a Patent granted to me, No. 109 of

page_text: 1878, that is, with a fluid reservoir, a plunger cylinder communicating therewith by
means of suitable ducts or channels and valves, and with a pivoted elevating foot-
lever which actuates clamping devices or engaging mechanism, taking hold of the
plunger or spindle, which carries the chair-body, upon its side or sides to elevate it,
the fluid in said reservoir, as the plunger is raised, flowing through the communi-
cating channel into the plunger cylinder, so as to follow and cushion or support the
plunger at any height to which it may be raised, the descent of the plunger being
governed by the opening of an outlet-valve, which permits the fluid to escape from
the plunger cylinder back into the reservoir.
The base and the elevating mechanism may however be of any suitable and pre-
ferred construction.
The elevating and supporting plunger carries upon its upper end a fixed cross-bar
or yoke, upon which the chair body or seat, or the frame thereof, is pivoted in a
well known way, so that said chair-body or seat is free to be rocked, tilted, or
inclined relatively to the vertically moving plunger and to the base in which said
plunger is reciprocated in raising and lowering the chair.
The plunger, instead of having a perfectly smooth periphery or circumference, is
provided with a straight longitudinal groove or recess for the reception of a tongue
or the suitably shaped end of a bolt or pin working endwise through the upper end
of the base, and transversely to the bore thereof. The said tongue or bolt, when
the groove or recess in the plunger is in line therewith, is projected into said groove
by means of a suitable spring surrounding the bolt, and compressed between the
enlarged head or end thereof and the wall of the enlarged socket or opening in
which the ball or tongue moves.
This tongue or groove is for the purpose of guiding the plunger in its reciproca-
tions or movements up and down in the fluid cylinder or base, and to prevent it
from rotating or turning, while permitting its free endwise movement. When how-
ever it is desired to change the position of the seat or chair-body horizontally
relatively to the base, which is accomplished by turning or rotating the plunger in
its cylinder, or, in other words, when it is desired to adjust the chair-body hori-
zontally, the tongue or bolt is withdrawn from the guide groove in the plunger by
means of a lug or pin which projects from the bolt outside the base, said lug being
acted upon by a suitable cam-surface carried by or formed on a turning hub or
enlargement of a clamp screw working through the base. The plunger is then free
to be turned around horizontally or swivelled to carry the chair-body or seat, it
being supported as against end wise downward movement by the cushioning and
sustaining fluid column, and may be clamped in any position desired by the clamp
screw, which is provided with a foot lever for opening it, said screw forcing against
the side of the plunger a suitable shoe of well known construction to lock the
plunger and base together.
As soon as the plunger is turned around to its normal position the groove therein
is brought in line with the bolt or tongue, which is immediately automatically pro-
jected into said groove and the plunger locked from turning.
The seat-frame of the chair-body is pivoted so as to rock upon the plunger or
spindle, as stated, and is provided with arm or side frames and also with a pendent
foot-board supporting-frame, preferably forming a continuation of the side or arm-
frames.
Projecting from the front of the yoke or cross-bar on which the chair-body rocks
is a vertical sector or curved rack, in the teeth of which engage a lug or locking-
projection of a pivoted detent frame, which frame preferably consists of a U shaped
central portion, the upper ends of the arms of which are pivoted to the seat frame or
to a suitable extension thereof, while from the lower part of said U shaped portion
upon each side of the chair extend rearwardly foot-levers, the outer ends of which
are provided with foot pieces or suitably shaped rests, whereby the foot of the
operator may be applied to release the locking lug from the rack to enable the chair
body to be tilted or rocked to any desired angle. The detent frame is acted upon
by a spring secured to the extension of the seat-frame, the force of the said spring

page_text: being exerted at all times to throw the locking lug into engagement with the sector-
rack.
The range of the rocking movement of the chair body is limited in a backward
direction by a flange or projection on the upper end of the rack, against the under-
side of which the bend of the U shaped detent frame comes in contact, while the
forward tipping or rocking of the chair-body is limited by suitable lugs or projec-
tions of the seat frame extension, said lugs when the seat reaches a horizontal
position resting upon the upper surface of the flange on the end of the rack.
The prime characteristics of this locking device are that it may be operated from
either side of the chair to disengage it from the rack, and that the pressure of the
foot and weight of the operator aids or assists in the operation of rocking or tilting
the chair upon its pivots, the position assumed in releasing the detent from the
stationary rack enabling the operator to brace himself, and with his hand or hands
upon the chair frame and foot upon the lever to easily and quickly tilt the chair
with the heaviest patient seated therein, the detent being forced into engagement
with the rack by its spring the instant the pressure of the foot is removed.
The foot board or platform is supported as usual by side pieces or brackets, pre-
ferably of metal, projecting forwards from a pendent frame. The outer ends of the
two side brackets are bent upward at an angle or curve to the platform, and have
each a longitudinal slot formed in them. To each bracket below the slots, and upon
the inside of said brackets, are pivotted arms or links, and upon the opposite ends
of said arms or links is pivotted at its ends and near one side a foot-rest board
capable of swinging backwards and forwards on its pivots relatively to the seat.
In order to give this foot-rest a wide range of movement with a capacity of being
firmly locked in its adjusted position, there is pivoted or jointed to the arms or
links, at or about their centre, brace-bars, said bars being slotted at their outer ends
correspondently with the side brackets. These bars project forward of their point
of jointing with the arms or links so as to afford a support to the foot-rest board
when turned over towards the seat, while their opposite slotted ends support said
board when turned over away from the seat to lengthen the rest. Through the
slots in said brackets and in said bars from side to side is passed a clamp rod or
bolt, having at one end a suitable head to abut against the outside of one of the
brackets, and provided at the other end with screw-threads for the reception of a
clamp-nut to abut and be tightened, screwed up, or forced against the outside of
the opposite bracket.
Between the slotted brace-bars and brackets, and surrounding the clamp rod, are
interposed suitable friction washers; and between the inner sides of the said brace-
bars, and surrounding the said clamp-rod or bolt, is interposed a tubular rod or
envelope. This arrangement of washers and tubular rod admits of clamping the
brackets firmly together and the slotted brace-bars between the washers and tubular
rod, as will be obvious.
To free the connection between the foot-rest board and the foot board or platform
proper or its brackets, the clamp nut is loosened or unscrewed, which leaves the
arms and brace-bars free to move about their pivots and said bars to slide upon the
clamp-rod by reason of their slots, and consequently allows the foot rest to be
adjusted backwards and forwards relatively to the seat to and from the platform or
supporting brackets, and in other various desirable positions.
By tightening or screwing up the clamp nut the foot-rest will be firmly retained
in any position to which it is adjusted.
It will thus be seen that the foot-rest or limb-support is supported by a connec-
tion with the platform of a dental chair, which permits of a wide range of adjust-
ment relatively to the seat, which in connection with the pivotting of the rest at its
ends near one edge, so as to allow of its being turned over backwards and forwards
on its pivots, gives all the required adjustments to accommodate persons of different
size to insure their ease and comfort.
The back of the chair is so mounted that it can be moved in any direction
desired.

page_text: To effect this the side frames or arms of the chair at a suitable distance above
and back of the seat may be made to converge, or are extended so as to form sup-
ports or bearings for a cross bar or connecting rod, said rod being fixed or keyed so
as to be incapable of turning. Upon this rod, which is preferably round, is mounted
an universal clamp-joint; this clamp joint receives and carries an endwise moving
and turning rod, supporting at one end the chair back, said joint forming an
universal connection between the back and the body or frame of the chair.
The clamp joint consists of a sectional frame, one section of which is capable of
turning relatively to the other, and both sections having a transverse opening, one
of said openings being for the reception of the cross bar or connecting rod, and the
other for the end wise moving and turning rod, which carries the chair-back, whereby
by means of suitable clamping-" shoes" contained within the frame and acted upon
by a set screw the frame of the joint is clamped to the fixed cross-bar or connecting
rod, while the moving and turning rod is clamped in the frame. The clamp-joint is
maintained at or about the centre of the fixed cross bar or connecting rod by means
of loose sleeves, one on each side of the joint and between it and the frame of the
chair, while its freedom of movement around the rod is unimpeded, except when the
clamp screw is tightened.
It will thus be seen that the back of the chair is given an universal movement,
or in other words it is free to be moved about in various directions, rocked from
side to side relatively to the seat, and given a wide range of movement in a back-
ward and forward direction, all of which is permitted by the rocking of the joint
upon the fixed cross bar or connecting rod by the swivelling or turning of one
section of the clamp-joint upon the other at right angles to its movement on such
cross bar or rod, and by the turning and endwise movement of the moving and
turning rod in said joint, the parts being firmly and quickly locked by the clamp
screw to secure the back in its adjusted position relatively to the seat.
The back is connected to its supporting rod preferably by a joint, which permits
the back to rock upon said rod, and to be locked at any desired angle thereto, this
adjustment being independent of the movements of the rod in the clamp joint.
This rocking joint may consist of a circular toothed plate projecting from a plate
secured to the back, said toothed plate being pivotted in a yoke formed on the end
of the rod, and of a locking bolt sliding freely end wise in a socket in the rod, and
thrust outward by a suitable spring to engage it with the teeth of the plate, and
thus lock the back at any desired angle relatively to its supporting rod, while it
may readily be retracted against the force of its spring by the projecting ends of a
guide pin which works in longitudinal slots in the walls of the socketted rod.
It will be obvious that clamp-joints other than the ones above described may be
used in place thereof.
Or in place of carrying the back of the chair in the above manner, the chair
frame may be provided at each side above and in rear of the seat preferably with
lugs or bearings, to which may be pivotted a supporting frame or carrier, which con-
stitutes in fact the back frame of the chair. This carrier has the capacity of being
rocked or adjusted backwards and forwards or horizontally relatively to the seat, and
is locked and braced in its adjusted position by means of a rod or bar pivotted to
Baid carrying frame, and passing through a clamping or locking device mounted
upon the seat frame, or a lug or projection extending therefrom.
The carrier or support consists preferably of a curved skeleton frame, and is
provided at its upper end with suitable bearings for the reception of a bolt rod or
suitable trunnions to form the pivot or axis, around which a clamp joint or connec-
tion between the carrier and the back or pad may turn, rock, or swivel indepen-
dently of the adjustment of the carrier frame.
This clamp consists of a hollow flat sided frame working between the bearings or
lugs at the upper end of the carrier and around the bolt which forms the pivot or
axis of the clamp, and which is locked or keyed from turning in said lugs. The
hollow flat sided frame carries at its front end a plate, the two being firmly con-
nected together while held a short distance apart by suitable connections or bolts.

page_text: The plate carried at the front end of the hollow flat sided frame fits and works within
a longitudinally slotted plate firmly secured to the back or pad or forming part thereof,
whereby the said pad is supported and allowed to slide up and down, or be adjusted
endwise or vertically upon said rocking clamp. Interposed between the longitu-
dinally slotted plate and the front end of the hollow flat sided frame is a friction
plate or block, which is prevented from displacement by the bolts which connect
the two plates together, and in order to lock or clamp the back or pad in any
position to which it may have been adjusted by sliding upon the clamp joint con-
nection, and inclined or rocked upon its pivot or axis, the hollow frame is provided
with clamping shoes, which are tightened by means of a screw and handle. The
tightening of the screw forces one clamping shoe tightly against the bolt, which
forms the pivot of the clamp, and as the hollow frame is moved outward by the
tightening of said screw also draws the other clamping shoe firmly against the bolt
and the plate carried at the front of the hollow frame against the inside of the
slotted plate, thus clamping said plate firmly, and thereby locking the back firmly
to the carrier or support in the desired position.
Or the lock or pad may have a longitudinally slotted plate projecting backwards
from it, and the bolt which forms the pivot of the clamp may pass through this slot.
The bolt may be a screw bolt, and serve to clamp the lugs which carry it one against
one side of the slotted projection and the other against its other side.
By these arrangements the back or pad will have the capacity of adjustment
independently of the carrier or support, that is, it may be adjusted vertically, and
rocked, tilted, or variably inclined independently of said carrier, and then firmly
locked in its adjusted position.
A wide range of movement is consequently given to the back of the chair, as it
is obvious said back being capable of adjustment by its support or carrier back-
wards and forwards to any desired extent relatively to the seat of the chair, which
together with the capacity for adjustment, independently of said carrier, insures the
ease and comfort of patients of all sizes, and enables the operator to place the patient
in the position most convenient for the easy and skilful performance of the delicate
dental operations.
To provide a head rest, a head rest bar is fixed to the back near its upper end,
so that the said bar or a round portion thereof is vertical or in the longitudinal
line of the back. Mounted upon this bar so as to turn thereon at right angles or
horizontally relatively to the back is an universal clamp-joint substantially similar
to the joint that supports the back hereinbefore referred to. The head rest or pad,
cushion or support, is mounted upon the end of a carrying bar or rod by means of
a joint substantially similar to that before described between the back and the rod
that supports it, which joint permits the head rest to be rocked and secured at any
desired angle relatively to said bar.
This head rest carrying bar is fitted to turn and move endwise backwards and
forwards relatively to the back in one of the turning or swivelling sections of the
universal-joint, whereby, as will be obvious, the bead rest, pad, cushion, or support
may be adjusted backwards and forwards, and turned to any desired position
relatively to the chair back, and securely clamped, all of said movements or adjust-
ments being permitted by the turning of the clamp joint horizontally around the bar
which is fixed to the chair back, or at right angles to the length of the back, by the
rocking of the bar which carries the head rest or pad at right angles to the movement
of the clamp joint around the bar fixed to the chair back owing to the swivelling
sectional joint-frame, by the turning and end wise movement of the bar which carries
the head rest in said clamp joint, and by the independent rocking capacity of the
head rest upon said bar.
Just behind the head rest and intermediate of it and the joint which permits
said head rest to rock or be inclined independently of its carrying bar, is mounted
an arni rest for the operator, said arm rest of course partaking of all the variable
adjustments of the head-rest, whether permitted by the universal clamp joint or
the independent rocking-joint.

page_text: The arm rest is capable of being shifted to either side of the chair or head rest,
it being detachable for that purpose. The arm rest is mounted so that a wide
range of movement may be given to it in order to render it capable of being placed
at any angle or position desired relatively to the head rest, which movement is
permitted by the swivelling or turning of its support upon the arm that carries it,
which will carry the rest towards or from and to the front or back of the head
rest, and by the swivelling or turning of a joint upon the support at right angles
to the swivelling or turning movements of said support, and by the swivelling or
turning of the arm rest board or cushion upon a pivot in the swivelling-joint.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sydney Pitt in the Great Seal Patent Office on the 24th January
1880.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN DENTISTS'
CHAIRS." A communication from abroad by Samuel Stockton White, of Phila-
delphia, Pennsylvania, United States of America.
This Invention relates to chairs of the class having a wide range of adjustment,
and more especially intended for the use of dentists, commonly called dentists'
chairs, whereby the patient while in the operating chair is completely under the
control of the operator, and may be placed in the different positions necessary for
the easy and skilful and expeditious performance of dental operations, the chair
being adjustable in its several parts in order to accommodate persons of different size
and insure their ease and comfort.
Figures 1 to 9 of the Drawings hereunto annexed shew a dental chair in which
some of the improvements are embodied.
The object of the improvements shewn in these Figures is to improve the con-
struction of dental chairs by giving the backs thereof, while connected with and
supported by the chair-frame, a wider range of adjustment relatively to the chair
seat than has heretofore been possible, while rendering the back capable of being
firmly locked at any desired point in its range of movement, thus insuring easy,
reliable, and comfortable support to the patient in whatever position placed.
Figure 1 is a view in elevation of a complete chair, with the improvements
attached.
Figure 2, a view from the rear of so much of the chair on an enlarged scale as is
necessary to exhibit the improvements clearly.
Figure 3, a vertical central section therethrough on the line 3, 3, of Figure 2.
Figure 4, a transverse section on the line 4, 4, of Figure 3.
Figure 5, a section on the line 5, 5, of Figure 3.
Figure 6, a section of the clip which connects the head rest to the chair
back.

page_text: Figure 7, a sectional view on the line 7, 7, of Figure 8 through a mouined form
of device.
Figure 8, a sectional view thereof on the line 8, 8, of Figure 9; and
Figure 9, a section therethrough on the line 9, 9, of Figure 8.
In Figure 1 is shewn a complete chair. It will be unnecessary to give a descrip-
tion in detail of the base A, the plunger or spindle B, the foot board or platform C,
the adjustable foot-rest D, the seat and seat-frame E, or the chair frame proper F,
as they are of well known construction, and especially is such a description
unnecessary, as the improvements are applicable to other forms of base, etc., than
those shown.
The chair-frame F is provided at each side, above, and in rear of the seat, pre-
ferably with lugs or bearings f. f, to which is pivotted in this instance a supporting-
frame or carrier G which carries the back of the chair. This carrier, by reason of
its pivotal connection with the chair frame, has the capacity of being rocked or
adjusted backwards and forwards, or horizontally, relatively to the chair seat E,
and is locked and braced in its adjusted position through the intervention of a rod
or bar H pivotted to said carrying-frame at h, and passing through a clamping or
locking device I mounted upon the chair-frame, or a lug or projection e extending
therefrom in this instance.
The
This clamp consists in the example shown of a bolt i extending through an
opening or bearing in the lug e of the seat or chair-frame, said bolt being surrounded
by suitable sleeves or washers i¹, i, upon each side of the supporting lug e.
bolt has a transverse opening or socket at one end, through which the rod H
passes, as well as through a similar opening in the sleeve or washer ¹ surrounding
that end of the bolt, and said bolt is also provided at its opposite end with screw-
threads is for the reception of a crank handle or clamp-nut a.
By tightening this handle or clamp-nut, the rod is clamped by the bolt and its
sleeve ¹, because said bolt is moved endwise in the sleeve, and draws the rod H
firmly against the edges or walls of the slot or opening in the sleeve. The clamping
of the rod H necessarily clamps the carrier G with which said rod is connected.
By loosening the clamping handle the rod H is left free to move endwise in the
locking device, to permit the carrier or support G to be adjusted.
Any other suitable clamping device however may be employed for the purpose of
locking the carrier in its adjusted position.
The carrier or support Ġ consists preferably of the skeleton frame curved as
shown in the Drawings, and is provided at its upper end with suitable bearings
g. g, for the reception of a bolt, rod, or suitable trunnions ; which forms the pivot
or axis of the joint or conuection J which connects the carrier and the back or pad
K, and permits the back to be turned, rocked, or swivelled independently of the
adjustment of the carrier-frame G.
This joint or connection is fitted with a clamp which has a hollow, flat-sided
frame 1 working between the bearings or lugs g, g, around the bolt j which is
locked or keyed from turning in said lugs. This frame 1 carries at its front end a
plate 2, the two being firmly connected together, while held a short distance apart
by suitable connections or bolts 3, 3. The plate 2 fits within a longitudinally
slotted slide L which is firmly secured to the back or pad K, or forms part thereof,
and which is constructed to slide longitudinally upon the plate 2. By reason of
the connection of the back and carrier by the plate and slide, the said pad is sup-
ported and allowed to slide up and down, or be adjusted endwis or vertically,
relatively to the carrier and to the chair seat. Interposed between e slide Land
the front end of the frame 1, is a friction plate or block 4, which is prevented from
displacement by the bolts 3, 3, and in order that the back may be locked or clamped
in any position to which it may be adjusted by being slid upon the connection
with the carrier, or by being inclined or rocked upon its pivot or axis, the clamp-
frame 1 is provided with clamping shoes 5, 6, as clearly shown in Figure 3, which
are tightened by means of the screw or handle M. The tightening of the screw M
forces the shoe 5 tightly against the bolt j, and as the frame 1 is moved outward

page_text: by the tightening of said screw, also draws the shoe 6 firmly against the bolt j, and
the plate 2 against the inside of the slide L, thus clamping said slide L firmly
between the plate 2 and the friction block 4, and the frame 1 by its shoes to the
bolt j, thereby locking the back firmly to the carrier or support in the desired
position.
In Figures 6, 7, and 8 of the Drawings, I have shown a modified form of slide
connection and clamp for the back which are sufficiently represented in the
Drawing to render unnecessary a specific description, these permitting both the
independent vertical or endwise adjustment of the back, and its rocking or tilting
relatively to the carrier or support G, and also enabling the back to be clamped in
its various positions.
It will thus be seen that the back or pad K has the capacity of adjustment
independently of the carrier or support G, that is, it may be adjusted vertically or
end wise, and rocked, tilted, or variably inclined, independently of said carrier, and
then firmly locked or clamped in its adjusted position.
. A wide range of movement is consequently given to the back of the chair, as is
obvious, said back being capable of adjustment by its support or carrier
1-
and forwards to any desired extent relatively to the seat of the chair, which,
together with the capacity for adjustment independently of said carrier, insures the
ease and comfort of patients of all sizes, and enables the operator to place the
patient in the position most convenient for the easy and skilful performance of the
delicate dental operations.
It will also be noted that if the back carrier be fixed to the chair-frame, the back
may be tilted and moved upwards and downwards relatively to the chair seat, by
reason of the tilting and sliding connection between the chair back and the back
carrier, and that the back when so moved may be clamped or locked in its position.
It will also be noted that the back may be moved backwards and forwards relatively
to the seat, and to be tilted relatively to the back carrier without being slid either
upwards or downwards, and that the back when thus moved may be clamped or
locked in the position to which it is moved.
The back carries a head rest bar N, and a variably adjustable head rest N¹ (or
one having a wide range of adjustment), the said bar, head rest, and its clamping
or adjusting mechanism O, being substantially the same as that shown in the
Specification of former Letters Patent granted to me, No. 109 of 1878, or it may
be of any other suitable construction preferred.
Figures 10 to 21 of the accompanying Drawings represent a chair embodying
other of the improvements in the best way now known to me; obviously, however,
some of the improvements may be used without the others, and in chairs differing
in their details of construction from the one therein shown. The details of con-
struction shown may, obviously, also be modified in various ways within certain
limits, without departing from the spirit of the Invention, some of which variations
would readily suggest themselves to a skilled mechanic on examining this Specifi-
cation and the Drawings aforesaid, in which Drawings,—
Figure 10 is a side elevation of a dental chair with the improvements attached.
Figure 11, a rear elevation thereof.
Figure 12, a vertical central section through a portion of said chair on the line
12, 12, of Figure 11.
Figure 13, a top or plan view of the mechanism which locks the chair body or
seat in its inclined position, and aids in its adjustment, a part of the seat frame
being broken away, and other parts of the chair frame shown in section.
Figure 14, a face view of said mechanism, or a view thereof from the rear of the
chair.
Figure 15, a longitudinal central section through the universal joint that carries
the chair back on the line 15, 15, of Figure 10.
Figure 16, a longitudinal central section through the universal joint that carries
the head rest on the line 16, 16, of Figure 11.

page_text: Figure 17, a view of the head rest pad from the rear, its supporting or carrying
bar being in cross section; and also of the arm rest partly in section.
Figure 18, a section through said head rest pad and arm rest on the line 18, 18,
of Figure 17.
Figure 19, a side view of my improved foot rest as folded, the foot rest board
being shown in dotted lines as thrown outward to lengthen the foot rest.
Figure 20, a bottom plan view thereof, and
Figure 21, a section therethrough on the line 21, 21, of Figure 19.
The base A is shown as of a shape somewhat similar to that of the base of the
pedal-lever hydrostatic chair shown in the Specification of the Patent granted to
me, No. 109 of 1878, and is intended to be constructed substantially in accordance
with the description contained in said Specification, that is, with a fluid reservoir,
a plunger cylinder communicating therewith by means of suitable ducts or channels
and valves, and with a pivotted elevating foot lever which actuates clamping devices
or engaging mechanism taking hold of the plunger or spindle which carries the chair
body upon its side or sides to elevate it, the fluid in said reservoir, as the plunger is
raised, flowing through the communicating channel into the plunger cylinder so as to
follow and cushion or support the plunger at any height to which it may be raised,
the descent of the plunger being governed by the opening of an outlet valve which
permits the fluid to escape from the plunger cylinder back into the reservoir.
The base and the elevating mechanism may however be of any suitable and
preferred construction.
The elevating and supporting plunger B carries upon its upper end a fixed cross
bar or yoke C upon which the chair body, or seat, or the frame thereof is pivotted
in a well known way, so that said chair body or seat is free to be rocked, tilted, or
inclined relatively to the vertically moving plunger, and to the base in which said
plunger is reciprocated in raising and lowering the chair.
The plunger B instead of having a perfectly smooth periphery or circumference
is provided with a straight longitudinal groove or recess 6 for the reception of a
tongue or the suitably shaped end of a bolt or pin D working endwise through the
upper end of the base, and transversely to the bore thereof. The said tongue or
bolt, when the groove or recess in the plunger is in line therewith, is projected into
said groove by means of a suitable spring & surrounding the bolt and compressed
between the enlarged head or end d' thereof and the wall of the enlarged socket or
opening in which the ball or tongue moves.
This tongue or groove is for the purpose of guiding the plunger in its reciprocations
or movements up and down in the fluid cylinder or base, and to prevent it from
rotating or turning, while permitting its free endwise movement. When however
it is desired to change the position of the seat or chair body horizontally relatively
to the base, which is accomplished by turning or rotating the plunger in its cylinder,
or in other words, when it is desired to adjust the chair body horizontally, the tongue
or bolt D is withdrawn from the guide groove in the plunger by means of a lug or
pin d which projects from the bolt outside the base, as clearly shown in Figures 10,
11, and 12, said lug being acted upon by a suitable cam surface e carried by or
formed on the turning hub or enlargement e¹ of a clamp screw E working through
the base. The plunger is then free to be turned around horizontally or swivelled
to carry the chair body or seat, it being supported as against endwise downward
movement by the cushioning and sustaining fluid column, and may be clamped in
any position desired by the screw E which is provided with a foot lever E¹ for
operating it, said screw forcing against the side of the plunger a suitable shoe e* of
well known construction to lock the plunger and base together.
As soon as the plunger is turned around to its normal position the groove therein
is brought in line with the bolt or tongue which is immediately automatically
projected into said groove, and the plunger locked from turning.
The frame of the chair body consists in this instance of a seat frame F which is
pivotted so as to rock upon the plunger or spindle B as stated, arın or side frames F'

page_text: carried by the seat frame, and a pendent foot board supporting frame F² preferably
forming a continuation of the side or arm frames.
Projecting from the front of the yoke or cross bar Con which the chair body
rocks is a vertical sector or curved rack G, in the teeth of which engage a lug or
locking projection h of a pivotted detent frame H, clearly shown in Figures 10, 11,
12, 13, and 14, which frame preferably consists of a U shaped central portion, the
upper ends of the arms of which are pivoted at h¹ to the seat frame or a suitable
extension thereof, while from the lower part of said U shaped portion upon each
side of the chair extend rearwardly foot levers I, I, the outer ends of which are
provided with foot pieces or suitably shaped rests whereby the foot of the operator
may be applied to release the locking lug h from the rack G to enable the chair
body to be tilted or rocked to any desired angle. The detent frame is acted upon
by a spring i secured to the extension of the seat frame, the force of the said
spring being exerted at all times to throw the locking lug h into engagement with
the sector rack.
The range of the rocking movement of the chair body is limited in a backward
direction by a flange or projection g on the upper end of the rack G against the
underside of which the bend of the U shaped detent frame comes in contact, while
the forward tipping or rocking of the chair body is limited by suitable lugs or
projections f¹, f, of the seat frame extension f, said lugs, when the seat reaches a
horizontal position, resting upon the upper surface of the flange g.
One advantage derived from this locking device is that it may be operated from
either side of the chair to disengage it from the rack, and also that the pressure of
the foot and weight of the operator aids or assists in the operation of rocking or
tilting the chair upon its pivots, the position assumed in releasing the detent from
the stationary rack enabling the operator to brace himself, and with his hand or
hands upon the chair frame and foot upon the lever to easily and quickly tilt the
chair with the heaviest patient seated therein, the detent being forced into
engagement with the rack by its spring the instant the pressure of the foot is
removed.
The foot board or platform I' is supported as usual by side pieces or brackets J, J,
preferably of metal, fitted to and supported by the pendent frame F³, the platform
being a stationary or unadjustable one in this instance. The outer ends of the
brackets J are shown as bent upward at an angle or curve to the platform, and
longitudinally slotted at j. To each bracket J, below the slots j and upon the inside
of said brackets, are pivotted at their lower ends arms or links K, K, and upon the
opposite ends of said arms is pivotted at its ends and near one side a foot rest,
board, or limb support L capable of swinging backwards and forwards on its pivots
relatively to the seat.
In order to give this foot rest L a wide range of movement with a capacity of
being firmly locked in its adjusted position there is pivotted or jointed to the arms
or links K at or about their centre brace bars M, M, said bars being slotted at their
outer ends correspondently with the brackets J, J. These bars project forward of
their point of jointing with the arms K so as to afford a support to the foot rest
board when turned over towards the seat, as in Figure 10 for instance, while their
opposite slotted ends support said board when turned over away from the seat to
lengthen the rest, as in Figure 19 for instance. Through the slots in such brackets
and in said bars from side to side is passed a clamp rod or bolt N having at one end
a suitable head n to abut against the outside of one of the brackets J and provided
at the other end with screw threads for the reception of a clamp nut n¹ to abut and
be tightened, screwed up, or forced against the outside of the opposite bracket J.
Between the slotted brace bars M, M, and brackets J, J, and surrounding the
clamp rod N are interposed suitable friction washers k, k, and between the inner
sides of the said brace bars and surrounding the said clamp rod or bolt is interposed
a tubular rod or envelope N¹. This arrangement of washers and tubular rod admits
of clamping the brackets J, J, firmly together, and the slotted brace bars M, M,
between the washers and tubular rod, as will be obvious.

page_text: To free the connection between the foot rest board and the foot board or platform
proper or its brackets, the clamp nut is loosened or unscrewed, which leaves the
arms and brace bars free to move about their pivots, and said bars to slide upon
the clamp rod by reason of their slots, and consequently allows the foot rest to be
adjusted backwards and forwards relatively to the seat to and from the platform or
supporting brackets, and in other various desirable positions, several different
positions or adjustments of the rest being exhibited in the Drawings.
By tightening or screwing up the clamp nut the foot rest will be firmly retained
in any position to which it is adjusted. The slots in the brace bars and brackets
may of course be lengthened to increase the range of adjustment of the foot rest if
desired.
It will thus be seen that the foot rest and limb support is supported by a connec-
tion with the platform of a dental chair which permits of a wide range of adjustment
relatively to the seat which in connection with the pivotting of the rest at its ends
near one edge, so as to allow of its being turned over backwards and forwards on
its pivots, gives all the required adjustments to accomodate persons of different size
to insure their ease and comfort.
At a suitable distance above and back of the seat in this instance the side frames
or arms of the chair converge or are extended so as to form supports or bearings
for a cross bar or connecting rod O, said rod being fixed or keyed so as to be
incapable of turning. Upon this rod, which is preferably round, is mounted an
universal clamp joint P which receives and carries an end wise moving and turning
rod supporting at one end the chair back R, said joint forming a universal con-
nection between the back and the body or frame of the chair. The way in which
it is preferred to form this clamp joint is shown in the Drawings.
It consists of a sectional frame one end or section of which is capable of turning
relatively to the other, as shown at Figure 12, and both sections having a transverse
opening, one of said openings being for the reception of the rod O, and the other
for the endwise moving and turning rod Q which carries the chair back, whereby
by means of suitable clamping "shoes" contained within the frame and acted upon
by a set screw S, the frame of the joint is clamped to the fixed rod O, while the
rod Qis clamped in the frame. The clamp joint is maintained at or about the
centre of the rod O by means of loose sleeves o, one on each side of the joint and
between it and the frame of the chair, while its freedom of movement around the
rod is unimpeded except when the clamp screw is tightened.
It will thus be seen that the back of the chair is given an universal movement,
or in other words, it is free to be moved about in various directions, rocked from
side to side, relatively to the seat, and given a wide range of movement in a
backward and forward direction, all of which is permitted by the rocking of the
joint upon the rod by the swivelling or turning of one section of the clamp
joint upon the other at right angles to its movement on the rod O, and by.
the turning and endwise movement of the rod Q in said joint, the parts being
firmly and quickly locked by the clamp screw to secure the back in its adjusted
position relatively to the seat.
The back R is connected to its supporting rod Q preferably by a joint which
permits the back to rock upon said rod and to be locked at any desired angle
thereto, this adjustment being independent of the movements of the rod in the
clamp joint P. This rocking joint is shown as consisting of a circular toothed
plate projecting from a plate secured to the back, said toothed plate being
pivotted in a yoke q formed on the end of the rod Q. A locking bolt ql slides freely
endwise in a socket in the rod Q being thrust outward by a suitable spring to
engage it with the teeth of the plate r, and thus lock the back at any desired
angle relatively to its supporting rod, while it may readily be retracted against
the force of its spring by the projecting ends of a guide pin q² which works in
longitudinal slots in the walls of the socketed rod.
It will be obvious that clamp joints other than the ones above described may be
used in place thereof.

page_text: A head rest bar T is carried by the back R being fixed thereto in this instance
near its upper end, so that the said bar or a round portion thereof is vertical or in
the longitudinal line of the back. Mounted upon this bar T so as to turn thereon
at right angles or horizontally relatively to the back is an universal clamp joint T",
substantially similar to the joint that supports the back herein before referred to.
The head rest or pad, cushion, or support U is mounted upon the end of a carrying
bar or rod U' by means of a joint U2, substantially to that between the rod Q
and back R before described, which joint permits the head rest to be rocked and
secured at any desired angle relatively to said bar U¹.
This head rest carrying bar is fitted to turn and move endwise backwards and
forwards relatively to the back in one of the turning or swivelling sections of the
universal joint T¹, whereby, as will be obvious, the head rest, pad, cushion, or
support may be adjusted backwards and forwards and turned to any desired
position relatively to the chair back, and securely clamped by the screw V, all of
said movements or adjustments being permitted by the turning of the clamp joint
horizontally around the bar T or at right angles to the length of the back, by the
rocking of the bar U₁ at right angles to the movement of the clamp joint around
the bar T, owing to the swivelling sectional joint frame, by the turning and end-
wise movement of the bar U in said clamp joint, and by the independent rocking
capacity of the head rest upon said bar.
Just behind the head rest and intermediate of it and the joint which permits
said head rest to rock or be inclined independently of its carrying bar is mounted
an arm rest for the operator, said arm rest of course partaking of all the variable
adjustments of the head rest, whether permitted by the universal clamp joint T¹ or
the independent rocking joint 02.
'n
1
This arm rest consists of a bent arm or support W slotted longitudinally at
1, the slot wat the inner end of the arm forming a fork to be slipped over a
redu. part of the head rest carrying bar, while the slot w' is provided with an
enlargement w² at one end for the reception or passage of a headed pin or bearing
point y, one of said points being at each side of the head rest frame, at the back
thereof, as shown in Figures 11, 17, and 18. Upon the outer end of the arın W a
support or upright Y is pivotted or jointed so as to be capable of swivelling freely
relatively to the bar W, it being locked however at any point desired in the range
of its turning or swivelling movement by a clamp or set screw y¹, the opposite bent
end of this bar Y being fitted to receive the end of a shaft or pin x, upon the outer
end of which is fitted, so as to swivel or turn freely, a joint X, said joint having the
capacity of being locked as against endwise or turning movement upon the pin x
by a set screw ¹ which engages the circumferentially grooved end of the said pin,
as clearly shown in Figures 17 and 18. The arm rest proper, consisting of a
suitable board, cushion, or pad Z, is fitted so as to swivel freely relatively to the
joint X, being preferably retained in its bearing or socket therein by a split spring,
jawed stud, or journal z, which may be inserted in its socket, which is shown as
passing entirely through the joint from either side.
The arm rest is capable of being shifted to either side of the chair or head rest,
it being detachable for that purpose. By sliding the bar W in the proper direction,
it will be obvious that the opening w² which permitted the head of the retaining
pointy to pass through the slot w¹ in the bar will be brought opposite said head,
when the bar can be removed or detached from the head rest and reversed, its
slotted end w being passed over the bearing u from the opposite side of the head
rest, and the enlarged slot w² over the head of the retaining point, and then by
moving the bar endwise to carry the head of the retaining pin or point out of line
with said enlarged end of the slot the bar will be firmly supported and locked in
position.
It will be seen that the arm rest is given a wide range of movement in order to
render it capable of being placed at any angle or position desired relatively to the
head rest, which movement is permitted by the swivelling or turning of the bent
support Y upon the arm W, which will carry the rest towards or from and to the

page_text: front or back of the head rest by the swivelling or turning of the joint X upon
the support Y at right angles to the movements of said support upon the arm W,
and by the swivelling or turning of the arm rest board or cushion Z upon its
pivot in the swivelling joint:
Having thus described the nature of the Invention, and the manner of performing
the same, I would have it understood that I claim,-
First. A chair back provided with a slotted supporting plate or slide to permit it
to slide vertically or endwise upon a rocking clamp connecting said chair back with
a support.
Second. The combination, substantially as hereinbefore set forth, of the sliding
and rocking chair back, a single clamp to lock the said back firmly in its adjusted
position both as to sliding and rocking movements, and a head rest carried by the
chair back, and adjustable thereon.
Third. The combination, substantially as hereinbefore set forth, of the chair
frame, the back carrier, the connection between the back carrier and chair frame
which permits the said carrier to be moved backwards and forwards relatively to
the chair seat, the chair back, the pivotal connection between the chair back and
its carrier which permits the back to rock or tilt, and the clamp which locks the
chair back firmly to the carrier as against its rocking movement.
Fourth. The combination, substantially as herein before set forth, of the chair
frame, the back carrier, the connection between the back carrier and chair frame
which permits the said carrier to be moved backwards and forwards relatively to
the chair seat, the chair back, the pivotal and sliding connection between the back
carrier and chair back which permits said back to both tilt or rock and to slide
or be adjusted upwards and downwards relatively to said carrier, and the clamp
which locks the chair back to the back carrier both as against its sliding and
rocking movements.
Fifth. The combination, substantially as herein before set forth, of the base, the
plunger provided with a longitudinal groove or guide, the tongue or bolt engaging
said groove to prevent the plunger from turning while leaving it free to move
endwise under the operation of the elevating mechanism, the lever or mechanism
to retract said tongue or bolt to permit the turning or swivelling of the plunger,
and a clamp to lock the plunger to the base when desired.
Sixth. The combination, substantially as hereinbefore set forth, of the base, the
plunger, the cross bar carried by the plunger, the chair body pivotted so as to tilt or
rock on said cross bar, the sector or curved rack fixed upon the plunger and projecting
towards the front of the chair, the detent frame pivotted at the front of the tilting
chair body to engage the fixed rack and lock the chair body in its inclined position,
and the foot lever for disengaging said detent frame from said rack and for assisting
in tilting the chair, these members being constructed to operate as described.
Seventh. The combination, substantially as herein before set forth, of the plat-
form or foot board proper, the arms or links pivotted thereto carrying the foot rest
board, the brace bars jointed to said arms, and clamping mechanism to maintain
said arms in various positions to vary the relation of said foot rest to the chair
rest.
Eighth. The combination, substantially as herein before set forth, of the foot rest
board pivotted at its ends near one edge to arms or supports, so as to be capable of
swinging over towards or from the chair seat to shorten or lengthen the rest
without necessarily moving the supports upon which it is pivotted, with an adjust-
able bearing, rest, or bar to maintain the foot board in the desired position when
turned over upon its pivots towards or from the seat.
Ninth. The combination, substantially as hereinbefore set forth, in a dental chair
of a tilting chair body, with a chair back carried by the chair body and adjustable
in different directions, sidewise as well as vertically, relatively to the chair seat, by
means of a clamp joint, which forms the connection between the chair body and
its back.

page_text: Tenth. The combination, substantially as hereinbefore set forth, of a dental chair
body, a back carried thereby and adjustable relatively to the seat thereof, a
universal clamp joint carried by said back, and a head rest mounted upon one end
of an endwise moveable rod, fitting said universal clamp joint so that said head rest
may be moved backwards and forwards by its carrying rod and rocked relatively
to said back and to the chair seat, and securely clamped in its adjusted position,
whereby an improved dental chair is obtained, the back and head rest being moved
simultaneously when the back is adjusted, while the head rest is given a wide
range of movement independently of said back.
Eleventh. The combination, substantially as hereinbefore set forth, of a dental
chair body having a back adjustable vertically and backwards and forwards
relatively to the chair seat, a universal clamp joint carried directly by said adjust-
able back, and a rod carrying a head rest at one end moveable endwise in said
clamp joint, whereby the head rest partakes of the movements of the chair back
relatively to the chair seat, while independently adjustable backwards and forwards
relatively to said chair back by the sliding of the head rest rod in its clamp joint,
and is also capable of being rocked to different positions by the turning of said
clamp joint.
Twelfth. The combination, substantially as hereinbefore set forth, of the head
rest, the arm rest support adjustable to carry the arm rest board or cushion to
either side of said head rest at will, and two pivotal connections between said
support or arm and said board or cushion, the axis of which are crosswise of each
other to permit a wide range of adjustment of the arm rest.
Thirteenth. The combination, substantially as hereinbefore set forth, of the head
rest, the retaining pins or bearings on said head rest, and the slotted arm or support
of the arm rest, adjustable to carry said arm rest to either side of the chair, said
arm or support being firmly locked in its adjusted position by said retaining pins.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Twelfth day of January, in the year of our Lord One thousand
eight hundred and eighty.
SYDNEY PITT. (L.S.)