Improvements in Dental Chairs.
Year: 1897

page_text: COMPLETE SPECIFICATION.
Improvements in Dental Chairs.
I, BASIL MANLY WILKERSON, of No. 857 North Eutaw Street Baltimore City,
and State of Maryland, United States of America, Dentist, 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 has relation to means for clevating, lowering and adjusting the
seat of the chair; to the means for adjusting the foot board, the back, and the head
rest; to providing the foot board with a folding step which automatically assumes
its position of use when the foot board occupies an elevated position; and to com-
bining with the body of the chair an arm rest detachable at will therefrom, and
also so jointed thereto that it may be turned forward and down out of the way
whenever desired.
The nature of my improvements and the manner in which they are or may be
carried into practical effect can best be explained and understood by reference to
the accompanying drawings in which--
Figure 1 is a side elevation of a dental chair embodying my improvements in
their preferred form;
Figure 2 is a plan on enlarged scale of the chair base, with the pivot of the eleva-
ting lever in section;
Figure 3 is a section on line 3-3 of Figure 2;
Figure 4 is a section of the chair base on line 4-4 Figure 5;
Figure 5 is a section on line 5-5 Figure 4;
Figure 6 is a section on line 6-6 Figure 3;
Figure 7 is a detail section on line 7-7 Figure 5 intended to illustrate the valve
arrangement for regulating the flow of liquid to and from the plunger cylinder;
Figure 8 is a section illustrative of the device for opening the valve which per-
mits the liquid to pass out from the plunger cylinder, when it is desired to allow
the plunger to descend;
Figure 9 is a side elevation partly in section of the chair base, designed more
particularly to illustrate the plunger locking and releasing devices.
In this Figure, I have shown in section the ball member of the ball and socket
chair supporting joint, attached to the plunger, and provided with a socketed
bracket for carrying a spittoon and other appurtenances;
Figure 10 is a perspective view of the upper part of the base;
Figure 11 is a considerably enlarged perspective view of a portion of the plunger
locking and releasing devices;
Figure 12 is a plan of the chair with the seat and a portion of the back frame
removed;
Figure 13 is a longitudinal vertical central section of the chair, with the head
rest carrier in elevation;
Figure 14, is a section of the two members of the ball and socket joint on
line 14-14 of Figure 12;
Figure 15 is a partial section on line 15-15 Figure 14;

page_text: Figure 16 is a section of the foot board of the chair on line 16-16 Figure 12,
showing the folding step for use in getting into or out of the chair when the latter
is in elevated position;
Figure 17 is a sectional view on enlarged scale of a portion of the foot board,
one of its hinged supporting brackets, and the locking mechanism for holding the
latter in adjusted position;
Figure 17 is an enlarged cross section (on line 17" Figure 17) of the upper end
of the locking pawl and of the rack bar which it engages;
Figure 18 is a horizontal section of part of the rear cross bar of the foot board
frame, and a sectional elevation of a portion of one of the adjusting bars connected
thereto;
Figure 19 is a sectional side elevation of part of one of the arm rests and the por-
tion of the chair frame to which it is attached.
Figure 20 is a rear elevation of the chair back;
Figure 21 is a vertical central section of the same on line 21-21 Figure 20;
Figure 21 is a view of the toggle lever by which the different joints of the head
rest carrier are locked;
Figure 22 is an elevation of the back-pad frame;
Figure 23 is a section on line 23-23 Figure 21;
Figure 24 is a section on line 24-24 Figure 21:
Figure 25 is a section on line 25-25 Figure 20-through the handle which con-
trols the locking devices for the back frame;
Figure 26 is a section on line 26-26 Figure 21;
Figure 27 is an enlarged sectional plan of the device by which the back pad is
adjusted and held at different inclinations relatively to the back frame;
Figure 28 is a top view of the head rest;
Figure 29 is an enlarged section on line 29-29 Figure 21, through one of the
side bars of the back frame showing the spring pressed friction pad for preventing
too rapid drop of that frame when the latter is released;
Figure 30 is an enlarged section of the pivoted bayonet joint between the arm
rest (Figure 19) and its frame;
Figure 31 is a perspective view of the male member of the joint;
Figure 32 is an enlarged perspective view of the cam and finger (shown in
Figures 9, 10 for tripping the releasing valve and plunger clamping mechanism;
Figure 33 is a sectional view of a modification which will be hereinafter more
particularly referred to.
CHAIR ELEVATING MECHANISM.
It is my object to impart immediate and continuous upward movement to the
chair body, while applying the power which produces that movement inter-
mittently and through the medium of a foot-lever operated step-by-step movement.
A further object is to obtain a dental chair having an extensive vertical range of
movement and capable of being rigidly locked at any point in said range. This
portion of my improvements is illustrated in Figures 1-11 inclusive and 32.
The chair is one having a hydraulic lift comprising a plunger which supports the
chair body, a plunger cylinder, a pump and a reservoir from which the pump
draws the liquid which is to be forced into the plunger cylinder for the purpose of
lifting the plunger-the pump being operated by a foot lever as customary.
A is the base which constitutes also the liquid reservoir-the liquid employed
being usually oil. It sets and can rotate in the pedestal B, and contains the
pump C and its connections, as well as the plunger cylinder D in which is con-
tained the chair body supporting plunger. A suitable lock can be provided to
hold, when desired, the base from rotating in the pedestal. The rod of the pump
piston C¹ has (as indicated in Figure 4) a forked upper end c which is entered by
pin c¹ on an arm ca fast on the pivot of, and vibrating with, the foot lever (³
(Figure 1). The depression of the lever, gives the down stroke to the piston-the
stroke which forces the oil from the pump into the plunger cylinder.
a
The up

page_text: stroke is occasioned by the spring surrounding the piston rod and confined
between the head of the pump cylinder and a washer on the rod-which spring
is compressed on the down stroke. The check valve controlling the oil inlet from
the reservoir is shown at c and the outlet check valve for preventing back flow
from the plunger cylinder is shown at e (Figure 4)—this valve being interposed in
the passage c', between the pump and the plunger cylinder, the liquid entering the
latter cylinder at the point cs (Figs. 3, 4, 5) and passing down to the under side of
the plunger through a clearance d (Figure 3) provided for that purpose between
the plunger and the cylinder D.
Under the arrangement thus far described the upward movement of the plunger
would be intermittent and step by step responding only to the down movement of
the foot lever. To make that intermittent movement immediately continuous, I
provide a pressure storage chamber C³, which communicates with the passage c
on the side of the check valve 6 next to the plunger cylinder. This chamber con-
tains a piston, diaphragm or movable head C which by the pressure of the oil
forced in by the pump is forced up in that chamber, and is influenced also by a
strong spring C6 (or its mechanical equivalent such a weight) which tends to force
the head in a direction opposite to that in which it is moved by the hydraulic
pressure. I have thus in effect a pressure storage chamber whose capacity is made
invariably by means of a movable bulkhead or partition influenced in one direc-
tion by the pump
and in the other direction by a spring or its equivalent. It is
to be observed also that the inlet to the plunger cylinder is smaller in cross
sectional area than the passage c".
Under this arrangement, at each stroke of the pump, the oil will not only be
forced into the plunger cylinder to lift the plunger but the pressure storage
piston C will be forced back into its chamber C3 thus compressing the spring.
Then after the stroke of the pump has been delivered, the spring C6 takes up the
work instantly and by its recoil continues to force the oil into the plunger cylinder
while the pump piston and its operating foot lever are on the up stroke. In this
way the upward movement of the plunger from the start is made continuous. I
am aware of course that pumps have been provided with air chambers for the pur-
pose of equalizing the flow. But such a device would be unfitted for the purposes
which I have in view. The chair in such event would not respond immediately to
the movement of the foot lever. Nor when once in movement would that move-
ment be at once continuous. In the passage c at a point near to the inlet to the
plunger cylinder is still another check valve (Figure 7) to prevent the weight
carried by the plunger from affecting the piston . The return passage from the
plunger cylinder back into the oil reservoir is shown at eo Figure 7. It is con-
trolled by a valve which when tripped or lifted permits the liquid from the
The device for this
plunger cylinder to flow back into the oil reservoir A.
purpose consists of a vertically movable rod 12 (Figures 4, 8) having at its lower end
a toe or lateral projection c¹³ that comes under the stem of the valve c¹¹. This rod
at its upper enu passes out through the top of the oil chamber, is supported in a
fixed guide bracket c, and has a spring cl which normally holds it down in
position where the valve cll will not be lifted. The spring 5 for this purpose is
confined between the fixed guide bracket c¹ and a flange or shelf c6 fast to the rod.
It will be remarked that the pump, the pressure storage chamber and all valves
and connections are comprised in one organism, as shown clearly in Figure 4 and 5
-the connection of pipe e to the plunger cylinder inlet being made by means of
a nipple which fits into the inlet opening in that cylinder.
These devices thus are removable in one piece or as a whole from the oil reservoir
for examination and possible repairs or cleaning, which may be necessary. It is
for this purpose that I make the joint e c¹ between the pump piston and its oper-
ating arm of such character that the two can readily be disengaged whenever
desired. And the top or dome of the oil reservoir for the same purpose is made so
that it or so much of it as is over the pressure storage chamber and pump and
connections can be taken off to uncover said parts and permit them to be lifted

page_text: out from the oil reservoir. The nipple end of the passage c7 can readily be dis-
engaged from the inlet opening in which it fits by tilting a little the pump
casting in a direction to withdraw the nipple from the opening.
The pump casting and its connections are held down tight in place when in the
base or oil reservoir in any suitable way, as for example by a cross bar and pressure
screw, which also serve to maintain the fluid tight connection between the nipple
end of the passage C¹ and the inlet opening C.
General reference only has thus far been made to the plunger-the improve-
ments already described as well as others hereinafter described being applicable
to various kinds of plungers or vertically movable chair supporting bars or stems.
But the plunger shown in the drawings, both in itself and in its adjuncts, possesses
peculiar characteristics which gives it extensive range of movement and permit it
to be rigidly locked at any point throughout that range.
The plunger itself is telescopic in structure, consisting in this instance of two
members E F. The outer member E is tubular. Above the clearance, d it fits
the plunger cylinder closely; and the joint between the two is packed at d*. The
inner member F fits and is movable up and down in the outer member E and has
its lower end packed like a piston, as at f; and upon it is placed the chair body.
The oil, when first admitted to the plunger cylinder raises both members as one,
until the outer tubular member reaches its upward limit and stops; then the inner
member (provided of course the pumping action is continued) alone rises moving
up in the now stationary tubular outer member, until it too has reached its upward
limit of motion or until the chair body has been raised within that limit to the
desired height. In this way I obtain a "high-low" chair, in which all parts are
contained in a base which may be wholly above the floor, instead of having the
plunger cylinder extending partly below the floor as heretofore usually has been
the case, owing to the fact that the plunger has been made of a single continuous
piece.
Various means for limiting the upward movement of each number obviously
may be employed. What I prefer for the purpose so far as concerns the outer
member E is to connect it at its upper end to a vertical bar e, which is held
between and can move up and down between guide flanges e in a seat upon the
exterior of the base. From the inner face of the bar projects a stop pin e4 which
enters a groove in the seat; and the bar can move up with the member E until
the pin brings up against the closed upper end of the groove, which arrests
further movement of the bar and consequently of the plunger member E.
The independent upward movement of the inner member F is limited in the
following way: In this member is formed an external vertical groove f which
affords clearance way for a loose vertically movable lifting pin carried by the
outer member E. For convenience sake it is mounted in the present instance in
the locking wedge which locks the two members together at any desired point
as hereinafter described-this wedge fitting the clearance groove f¹ in the inner
member F. Upon the outer face and along one edge of the bar e is mounted
a rod e SO as to be capable of limited independent vertical move-
ment thereon, it being connected for this purpose with the bar at suitable points
by a pin and slot connection as indicated at 8. The rod at its upper end has a
head which overhangs the lifting pin e", and at its lower end it has a stud elo
which is beneath an angular extension 7 of the shelf or flange el on the down-
wardly spring-pressed valve lifting rod 12. The stud el is so positioned that when
the outer plunger member E has reached its upward limit it (the stud) will be a
immediately under the angular extension e as indicated in Figure 11.
If now, with the outer member E at rest, the inner plunger member F continues
its upward course, the movement will continue until the lower closed end of the
groove f¹ meets the lifting pin ef. When this takes place then any further rise
of the member F will raise the lifting pin e which in turn will lift rod e with the
effect of causing the latter through its stud elo to raise the valve lifting rod ”
thus opening the oil discharge valve e" and permitting any further oil supply. from

page_text: the pump to return directly to the oil reservoir without entering the plunger
cylinder. Under these circumstances further upward movement of the inner
plunger member F is of course impossible. The moment there is sufficient escape
of oil to permit the plunger the downward movement (a very slight movement)
requisite to lower the stud eo, then the lifting rod c¹² will be depressed by its spring
and the discharge valve cl will at once close and prevent further escape of oil.
I proceed now to a consideration of the means for locking the plunger in its
adjusted position. Each member of the telescopic plunger should be individually
locked, that is to say, the inner member should be locked to the outer member and
the outer member should be locked to its cylinder; and it is also desirable that
these two locking devices should be so connected as to be operated by one and the
same handle, lever or other instrumentality.
The neck of the plunger cylinder (this cylinder being as shown a casting made
in one with the base) is formed as a split ring, as shown in plan in Figure 2,
having ears D1 D2 and being divided for a portion of its periphery from the body
of the casting by a horizontal slot or slit d', by drawing together the two ends or
ears D D² the ring section formed by this slot or slit can be compressed most
tightly upon the outer plunger member E, which in this way is locked.
The ear D is rigid and has no movement; the ear D2 is upon, and moves with,
the movable ring section.
The drawing together of the cars, or rather the drawing of the ear 12 towards
the ear D', is effected by a cross bar 2 which passes loosely through both ears, and
has pivoted on one end a cam or eccentric which bears against the outer face of
the ear 12. By the action of this cam and in accordance with the direction of its
movement, the ears will be drawn together or allowed to separate as the case may
be. The cam normally is held in position to lock the ring upon the plunger by a
stout stiff spring connected to the tail or stem of the cam by a strap d; the
parts are shown in normal position in Figure 9.
It is desirable as beforesaid, that the locking of the two plunger members shall
be occasioned by the movement of one and the same handle or lever. To this end,
I proceed as follows:
Upon the outer face of the bar e, is mounted a second bar the two being con-
nected by links a¹ (as indicated by dotted links in Figures 9 and 10) after the
fashion of the two members of a parallel rule. Upon top of the bar e is placed
the pivoted lever b having one of its ends jointed to the locking wedge e (as seen
in Figure 3) and its other end overhanging the top of the bar a. Upward move-
ment of the bar a will by lifting the tail of the lever, cause its other end to depress
the wedge and jam it tight between the two members E F of the telescopic
plunger, thus locking the two tightly together. A spring normally holds the
lever bin a position where the wedge is lifted and the member F is unlocked.
The upward movement of the bar for locking purposes is effected by the cross
bar Under this arrangement the ear D' is a mere guide through which one
end of the cross bar passes and in which it can move freely lengthwise. This end
of the bar has on it a lateral offset or shoulder d (Figure 2) which abuts against
the adjoining edge of the bar a.
When therefore the pivoted cam d³ is turned in locking direction, the first effect
is to draw the shoulder of the cross bar against the bar a thus moving it to the
right swinging it up on the links a' until it has (through lever b) depressed the
wedge as far as it can. Then it furnishes a rigid abutment for the shoulder ';
thus holding the end of the cross bar while the unlocking cam by its further
movement draws up the ear 12 and causes the split ring to clamp the outer
member E of the plunger. Thus by one and the same movement of the cam d³,
both members of the plunger are locked, the locking of the inner member taking
place slightly in advance of that of the outer member. It will of course be under-
stood that in its locking movement to the right the bar a does not travel far enough.
o meet or interfere with the rod e.

page_text: If desired gibs
or flat pieces el (shown in dotted lines in Figure 2) can be set
in the inner face of the outer tubular plunger member E at points on a level with
that at which the wedge bears against the inner plunger inember F but on the
side of the latter member opposite to the wedge, the plunger member F will of
course be correspondingly shaped to fit against the flat faces of the gibs e As
the latter incline towards each other forming approximately a V, the effect of fore-
ing the locking wedge home will be to jam the plunger member over into the
V recess formed by the gibs ell thus binding it tightly against rotation.
In order to lower the chair, make use of the pivoted foot lever G (Figures 2,
9, 10, 32). This lever, suitably journaled in the base, has upon its axle an arm g
for acting upon the tail of cam d³, and a projection g¹ which is designed to lift
the valve opening rod 12 and for this purpose extends under the shelf of flange clu
as indicated more plainly in Figure 8-these two parts g g¹ being so arranged that
the arm will operate to unlock the plunger before the projection gl acts to open
the valve. The lowering lever G is depressed by the foot of the operator. And
when that pressure is removed, it is returned to normal position by the spring.
Normally the plunger is locked, but when the chair is to be elevated it is then
desirable that convenient means should be provided for unlocking the plunger
and holding it unlocked during the continuance of the elevating operation. To
this end I connect the plunger locking mechanism to the elevating lever C² in such
manner that the act of adjusting the elevating lever to its position of action shall
cause the unlocking of the plunger and shall hold it unlocked so long as the
elevating lever maintains said position.
The elevating lever in this instance is made in two parts joined together upon a
vertical pivot C as shown clearly in Figure 2, so that when the lever is not in
use, its outer portion can be folded up or swung in towards the chair base, and
thus be out of the way of the operator. It is represented in this folded position in
Figure 9, and by dotted lines in Figure 2.
I avail myself of this construction to conveniently attain the end that I have
in view. The outer section of the elevating lever C is provided with an arm (³,
which by a link C8 is joined to the tail or stem of the cam d³.
The arrangement is such that when the lever is unfolded and in position for use
as shown in Figure 10, and in full lines in Figure 2, the link Cs will thereby be
caused to turn the cam in a direction to release or unlock the plunger. Thus
the plunger is automatically unlocked whenever and so long as the elevating lever
is adjusted to its position of use. It will be noted that whether the lever is either
in folded or unfolded position the joint C7 between the two sections of the elevat-
ing lever is to one side of a straight line between the points at which the link is
attached to the cam tail and the arm C respectively-the arrangement being
such that whenever the outer lever section is swung past the dead center in either
direction, it will be drawn and held in the position towards which it may be mov-
ing at that time by the force of the spring . The lever will thus be held folded
or unfolded as the case may be by the stress of the spring, and must be turned
by the operator past the dead center from either of those positions before it can by
the action of the spring be drawn to and held in the other position.
It is further to be noted that the link C8 is joined to the arm C by an eye C³,
which permits the requisite lost motion to allow the link to move freely on the
arm without disturbing the elevating lever, when he cam ³ is operated by the
lowering foot lever G.
To complete the description of the base it only remains to say that at the point
where the valve tripping or lifting rod c¹ passes out through the top of the oil
chamber, the opening through which it passes (which may be used as the filling
orifice) can readily be closed by means of a cock or stopper c7 (Figure 8) mounted
and movable up and down on the rod. This is a considerable convenience in
packing the chair for transportation. That portion of the base on which the
orifice is located is formed as a pan c¹8 (Figure 6) to catch any drip or leakage.

page_text: CHAIR TILTING MECHANISM.
I proceed now to a description of the manner of and means for mounting the
chair body upon the plunger so that it may be tilted both lengthwise and laterally
to any desired angle and there secured.
The joint between the chair body and the plunger may be described in a general
way as a ball and socket joint-the ball carried by the plunger and the socket
carried by the chair body.
The ball is shown more particularly in Figure 9 at H. It is not a complete
sphere, but merely a segment formed by cutting off the sphere horizontally at top
and bottom so as to leave an intermediate segment. This segment is hollow and
its top is closed or partly closed by a head h (Figure 12). The plunger, or rather
the inner member F of the plunger passes up through this hollow spherical
segment and is secured at its upper end to the top or head h.
This arrangement gives very much greater vertical range of movement to the
chair body than otherwise would be possible. As the ball is open on its under-
side, it will pass over and surround the neck or upper part of the base when the
chair is lowered, thus allowing the latter to descend until the head h brings up or
very nearly brings up against its base.
Moreover the ball on its rear side is cut away as indicated at
Figure 12–
this being to afford room for the movement of the adjoining mechanism for the
chair back to be presently described.
It may here be noted that the plunger is secured to the ball at a point which
laterally is to one side of the vertical axis or centre of the latter as seen in
Figure 12. Thus the weight of the chair body will be more to one side of the
plunger and consequently the tendency will be to tilt the plunger towards that
side with the effect of binding it in its bearings, thus further insuring a rigid
lock for the plunger at all points throughout its vertical range of movement. This
feature is applicable to any plunger whether a telescopic plunger or a single stem
plunger.
The plunger is secured to the head of the ball in any suitable way-in this
instance by a split ring and clamping screw device shown at 4, Figures 12 and 13.
The socket which fits upon the hollow ball segment is a socket divided
horizontally into an upper section I and a lower section 1. The upper section is
carried by and secured to the spider like arms j of the chair seat frame casting J
(Figure 12). This section in depth is less than half the ball, the parting line
between the two sections I-I' being a short distance say one half inch or more
or less above the horizontal axis of the ball.
The lower section I is divided vertically into two parts secured at the rear to
the chair seat frame at 7 (Figure 12) and held to the upper section by bolts or
screws (Figures 12 and 14) passing into and through ears with which both
sections are provided at suitable intervals. This lower section I forms in effect a
sput clamping ring, its two free front ends having ears through which passes
a suitable clamping screw or rod by rotating which the ears will be drawn
together or allowed to spread apart according to the direction of rotation of the
clamping device. The rotation of the clamp in the direction to close the ring
upon the hall is effected by a crank handle (Figures 1, 12, 15) within convenient
reach of the operator. It is, when released, automatically pulled in the other
direction to clamp the socket upon the ball by means of a spring (Figure 15).
A very slight movement of the handle serves to release the hold of the socket
on the ball, to allow the rocking or tilting of the chair on its joint.
in
To prevent horizontal rotation of the socket on the ball the socket is provided
with a stud (Figure 14)-in this instance formed upon the inner face of the
lower section I which enters and permanently engages a vertical groove
the exterior of the ball. This stud is radial and on the prolongation of the
horizontal axis of the ball crosswise of the chair so that the chair body can rock
from front to rear without impediment-the stud occupying virtually the position
of a pivot or journal on which the rocking movement from front to rear takes

page_text: place, which position it always maintains no matter 'what may be the extent to
which the chair body is tilted laterally.
Under the arrangement thus far described, whenever the socket is free to move
on the ball there is nothing to prevent the chair body from rocking laterally as
well as from front to rear. The lateral rocking movement is not so frequently
availed of as that from front to rear, and it is often desirable to hold the chair
against lateral rocking, while permitting it to rock from front to rear.
To this end, I form in the bottom of the groove a vertical series of holes (8,
any one of which is adapted to be entered and engaged by a longitudinally movable
locking pin that passes axially through the stud and is inwardly pressed by a
spring held in a pocket i upon the lower socket section I'. The stem of this
locking pin passes out through the head of the pocket and is to be provided with a
suitable handle or other means for drawing the pin out from engagement with the
hole in which it may happen to be. It is desirable, for convenience sake that the
locking pin should be manipulated by the same instrumentality which operates
the lower clamping socket section I. To this end (as shown in Figure 15) I,
in the present instance, provide the projecting outer end of the locking pin stem
with a projection or shoulder 12 between which and the pocket extends one
limb of an angle lever pivoted at its elbow to a bracket bearing on the socket
section and having its other end connected by a chain or some equivalent
instrumentality to the crank handle . The crank handle it will thus 'operate
and control both locks or clamps for the socket. But, as hereinbefore, stated, it
is often desirable to operate the split ring clamp which controls the rocking of
the chair from front to rear, without operating the lock which controls the lateral
rocking the connection between the crank handle and the angle lever 13
is made sufficiently slack for the handle to move far enough to open the clamping
ring without affecting the angle lever. Further movement of the crank handle
beyond this point will operate the angle lever also, and will leave the socket free
to rock both laterally and from front to rear upon the ball. Suitable stops are
of course to be provided for limiting the tilting range of movement of the chair
body, as will be understood by the skilled mechanic without further explanation.
To complete the description of this portion of the chair it only remains to say
tha the hall can be conveniently provided with a bracket H' (Figure 9) for support
of a spittoon or other attachment or appurtenance.
FOOT BOARD.
The main object I have in view in this portion of my improvements is to provide
a foot board capable of a vertical adjustment independently of the seat frame and.
maintained at all times practically in parallelism with the seat so that when
raised to the level of the seat it will form practically an extension of the latter.
My object in this is that the chair may be converted at will into what is tanta-
mount to a couch. The adjustment is light and ready owing to the fact that the
foot board is counterbalanced, and is automatically locked in its adjusted position.
It is also cushioned for safety against sudden strain as well as to prevent the
movement of the feet of the patient upon the board from shaking the body of
the chair, this shaking being frequently a source of annoyance to the operator in
performing a delicate operation. The foot board arrangement is represented more
particularly in Figures 1, 12, 13, 17, 17 and 18.
The foot board consists of the foot board proper K, and the foot board frame.
The frame consists of two side arms or brackets L, each hinged at to the under
side of the seat frame, and a screen L¹ of any ornamental design extending between
said brackets. The frame can be swung up and down upon its hinge and is
held in its adjusted position by any suitable locking device. The locking device
(shown more clearly in Figures 17 and 17") consists in the present instance of a
dog pivoted at 2 to the foot board frame, and adapted to take into one side of
the notches in the underside of a rack bar fast to the seat frame, the dog being

page_text: normally held in engagement with the bar by a weight or its equivalent. I
prefer to form the rack bar with a horizontal laterally projecting shelf and to
provide the dog with a frame overhanging the shelf, there being enough clear-
ance between the flange and the shelf to allow the dog to be disengaged from the
notch in the rack bar before the flange meets the shelf. The object of this
arrangement is to provide a stop against excessive movement of the dog. The
flange slides freely and easily upon the shelf, when the frame is being adjusted.
There is one of these locking devices on each side of the chair and the two dogs
are rigidly connected by a cross-rod or bar 17 (Figure 17) so that they will move
always in unison. A handle 18 (Figures 1 and 12) within convenient reach of the
operator, is provided for the purpose of manipulating the dogs. The foot board
proper K is hinged to the foot board frame at k. It is provided on each side at
its rear end with a downwardly projecting car or lug, with a cross bar k
extending between and pivoted or journaled at its ends in said ears, the pivotal
point being indicated at + (Figures 1 and 17). To this cross bar, at about its
center is fastened the lower end of the spring for balancing the weight of the
foot board structure. The upper end of this spring is made fast to a rod
line with the axis of movement of the foot board frame.
in
On each side of the chair there is made fast to the cross bar a controlling
10d the upper end of which is pivoted at 8 to a bracket 4 secured to the seat
frame J. It is through this instrumentality that the parallelism of the foot
board K with the chair seat is preserved. When the foot board frame is swung
up on its hinge it will be seen that the rods will pull upon the ears in a
direction to slightly turn the foot board down so as to compensate for the upward
tilt which otherwise would be given to the board.
The foot board can be raised to the level of the chair seat preserving practically
its parallelism therewith. In this position the foot board frame will intervenc
to a slight extent between the chair seat and the foot board proper, but this will
be a matter of no moment. The body of the patient will rest upon and be sup-
ported by the chair seat (and the chair back as well-which! latter can also be
turned back so as to be on a level with the chair seat if desired) and the foot board
will support the legs of the patient without discomfort.
In order to cushion the foot board for the purposes hereinbefore mentioned,
I interpose between the ends of the controlling rods and the points on the cross-
bar to which the same are attached, pads or cushions 10 of elastic material such
as vulcanized rubber (Figure 13) these pads being capable of yielding to any
sudden strain or jar upon the foot-board proper, so as to prevent the movement
due to this cause, from being appreciably transmitted to the chair body.
With a view to permit the foot board to be folded up against the body of the
chair in compact form for transportation, the joint between the cross har ² and
the ears is made by forming the cross bar at its ends with half round bearings,
as in Figures 17 and 18 which rest upon pins or journals projecting inwardly from
the interior opposite faces of the ears . Under this arrangement the foot board
can by hand be moved to disengage the journal pins from the half-round bearings
in the cross bar, and can then be folded up independently of the cross bar. To
prevent the cross bar when thus released, from being pulled up by the spring ki
I form upon the interior opposite faces of the controlling rods and the side
arms or brackets L, stops 15 (Figure 17) which engage each other, and arrest
any upward movement at this time of the rods and the cross bar which they
carry. These stops are so shaped and proportioned that their meeting faces will
slide upon and move by one another as the parts and L vary their positions
relatively to each other during the adjustment of the foot board; and they also
hold the cross-bar always in such position that when the foot board is turned
down again from its folded position the journal pins on the ears will enter their
half round bearings on the under side of the cross bar.
At the front of the foot board is a foot rest K' carried. by a support K2 which is
essentially a crank arm swiveled upon a vertical axis in a socket ¹ in the foot
R

page_text: board. The object of this arrangement is that the foot rest may be brought
nearer to or further from the chair seat as the convenience of the patient may
require. On the front and rear of the socket klare diametrically opposite
notches, one or the other of which will be engaged by the pivoted detent
lever This lever is weighted or spring-pressed so as to automatically engage
the notch opposite which it may be brought. And its handle end is conveniently
placed so that it may be reached and manipulated by the operator at the time he
takes hold of the foot rest for the purpose of reversing its position; or it may
indeed be operated by the patient using merely the foot for that purpose.
26
AUXILIARY STEP.
In high-low" chairs an auxiliary step by means of which when the chair body
is raised, the patient can get up into the chair, is an important adjunct. But any
such step which comes between the foot board and the floor on which the chair
stands, will necessarily limit the extent to which the chair can be lowered, unless
it be so arranged that it can fold up when occasion requires so as to allow the chair
to be lowered even to the point where the foot board is practically in contact with
the floor as at times is necessary. With this in view, I have combined with the
foot board what I term an automatically-adjustable step one which when the
chair is raised will be automatically unfolded or projected into position for use as
well as braced in that position; and which on the other hand, when the chair body
in its descent reaches a position where the step brings up against the floor, will,
when the chair descends further, automatically fold up so as to permit that descent
to be unimpeded.
The manner in which I obtain this result will be understood by reference to
Figures 1, 12 and 16-the Figure last named being a section on line 16-16 of
Figure 12.
The step proper M which is below the foot board K is intended to project laterally
beyond the latter as indicated in Figure 12. It is held between the forked outer
end of a supporting arm m connected to the underside of the foot board by
straps m¹. The arm is hung between and pivoted at about its middle
to the lower ends of these straps, as shown at m² Figures 1 and 16; and
the straps at their upper ends are hinged at m³ to the underside of the foot board
near one of its edges. The arm m back of its pivot is extended to form a brace, the
upper end of which is adapted to take into a notch m in an abutment on the
underside of the foot board. In this position it will be seen that the step is
thoroughly braced to sustain the weight of the person stepping upon it. It is
brought to this position by the action of a spring m³ coiled upon the pivot m³ and
bearing outwardly at its ends against the straps m'. This spring is put under
compression when the step is folded up and by its stress tends to cause the step to
resume its unfolded position shown in Figure 16.
Under the arrangement shown when the chair has descended far enough for the
step to reach and bear against the floor, then further descent of the chair body will
cause the step to fold up towards the straps m¹ the latter swinging inward at the
same time, until, when the chair body has descended far enough, the step as a whole
will be folded up flat against the bottom of the foot board as indicated by dotted
lines in Figure 16. On the step supporting arm m I mount idlers or friction
rollers which will cease the folding movement of the step, and prevent the friction
and drag between the arm m and the floor surface which otherwise would take
place. The moment the chair is raised far enough the step will resume its unfolded
position shown in full lines in Figure 16.
I remark here that the spring may be dispensed with and the frame can be so
weighted or made so heavy as to automatically unfold by gravity, when permitted
to do so, and I desire to be understood as including any such obvious modification
or substitution in my claim.
ARM REST.
My invention in this direction contemplates combining with the chair an
Arm

page_text: rest, which at the lower end of its support is pivoted to the seat frame in such
manner that when desired the arm rest can be turned upon its pivot forward and
down along side of the foot board, a suitable lock being provided for holding it rigid
when in its normal position. The object is to provide an arm rest which when
occasion demands may be brought to a position in which it is entirely out of the
way of the operator. This portion of my invention is illustrated in Figures 1, 12,
19, 30 and 31.
The arm rest is shown at N and its support at N¹. The support at its lower end
is pivoted at n to the seat frame, at or near the forward end of the latter on a
horizontal axis, which will permit it to be swung forward and down as indicated
by dotted lines in Figure 19. In this position it is alongside of the operator and
entirely out of his way. stop on the support is provided to limit the extent
to which the arm can be turned down. This stop when the proper limit is reached
meets a shoulder or abutment n² on the seat frame, and prevents further movement
in that direction.
The arm rest when raised and in normal position can be rigidly locked in that
position by any suitable means--in this instance by a cam lever Figure 12, 19,
pivoted to the seat frame, having a cam end to bear against a proper abutment n'
on the arm rest support N and a handle end by which it is operated. By
depressing the handle end the cam end of the lever will be jammed and wedged
against the abutment n' thus rigidly locking the arm rest in position. By lifting.
the handle end of the lever, the arm rest will be released.
The hinge or pivot point n of the support N is at a point considerably below the
seat and at or near the front end of the seat frame, thus allowing the arm rest to
swing forward and down so as to practically be clear of the side of the chair. When
the arm rest is raised into position its support N₁ rests by gravity upon the rail on
the side of the seat frame where the cam lever n³ is located; and this lever engages
the support at a point above the hinge n, and between the latter and the arm
cushion or rest proper N. Thus the arm rest when raised into position always
stops in the right place, and can be most firmly locked in that position.
The
It may be desirable at times to entirely remove the arm rest from the chair. A
convenient arrangement to permit this is illustrated in Figures 30, 31.
cylindrical pivot stud n attached to the arm seat support N¹ enters a suitable
socket or bearing formed for it in the seat frame J and is peripherally grooved at n³
to receive a cross pin which holds it in its bearing without impeding its frev
rotation therein. The stud on one side is cut away back of this groove as shown
at n so that when it is turned far enough to bring this cut away portion opposite
the pin the latter will no longer engage the stud and the latter can then be
withdrawn from its socket in the seat frame. The parts are shown in Figure 30 in
the nosition which they occupy when the arm rest is raised and in normal position.
When the arm rest is swung forward and down as in dotted lines in Figure 19, the
cutaway part n of the pivot stud n will be brought opposite to the cross pin 76 and
the arm rest is then free to be removed from the chair.
THE BACK.
The back of a dental chair generally consists of a back supporting frame hinged
to the seat frame so as to be inclined from front to rear relatively to the seat, in
combination with a back proper carried by and vertically adjustable upon the back
supporting frame. Usually the back supporting frame is hinged to the seat frame
by pivots held in suitable bracket supports. These pivots and their supports unduly
limit the range of vertical movement of the back proper-preventing the latter from
being lowered as far as it otherwise might be, and are also in the way of the
operator. To obviate these objections unite the back supporting frame to the
seat frame by arc-shaped concentric hinge pieces the one moving in or upon the
other, and a lock being provided to hold the parts in their adjusted position. I
have also improved the construction and arrangement of the parts which compose
the back proper.

page_text: This portion of my improvements is illustrated in Figures 1, 12, 18, 20-27
inclusive and 29.
The arc-shaped hinge member which is carried by the seat frame is shown at
O Figures 1, 12, 13. It has the shape of an inverted trough, and is fastened
concave side uppermost to the rear of the seat frame, below the top of the same,
with its inner end projecting under the seat frame, as seen in Figure 13. On
each of its interior opposite side walls it has a tongue o curved longitudinally in
the arc of a circle to engage a corresponding groove in the back supporting frame.
And it is further provided with a rack or series of teeth o¹ in the under face of
its top to receive and engage a locking dog carried by the back supporting
frame.
The back supporting frame consists of two guide rails P straight for the greater
portion of their length but at their lower ends curved in the arc of a circle
corresponding to that of the arc shaped hinge member O-these curved lower
ends being connected on the side or face next to the seat frame by a web " which
runs under the correspondingly curved top of the hinge member O. In the
exterior opposite faces of the curved ends of the rails l' are curved grooves p, into
which the tongues o are received when the two concentric hinge members are fitted
together. Under this arrangement the hinge is entirely out of the way of the
operator, and as it below the seat, it allows the back to descend until if need be
the lower end of the back pad will come between the seat and the back supporting
frame. As the hinge members are placed concave side uppermost, the tendency
when the back is inclined rearwardly is to close any interval between the back
pad and the seat.
Moreover the extended contact between the two hinge members, produces
friction which tends to prevent sudden drop of the back supporting frame when
the latter is unlocked. To increase this frictional resistance, I provide the back
supporting frame with a friction pad (Figures 20, 21 and 29) which projects
through one of the grooves p in position to bear upon the tongue o of the hinge
member 0, and for this purpose is outwardly spring-pressed by a coil spring 2³
surrounding the stem of the pad and confined between the head of the latter and
an abutment 3 on the web li of the back supporting frame.
The locking together of the hinge members is effected by the toothed dog 24
pivoted to the underside of the web P with its toothed end projecting through
an aperture in the web in position to engage the rack o as seen in Figures 21
and 13. The toothed end of the dog being outwardly pressed for this purpose by a
spring. For the purpose of unlocking the dog I provide a handle 76 mounted
upon the upper part of the chair supporting frame--my object in thus locating the
handle being to permit the operator to use the same handle by which he unlocks
the back supporting frame, to uphold that frame also. The handle 26 thus
located can be connected to the locking dog by various devices which will suggest
themselves to the skilled mechanic. The mechanism which I now prefer for this
purpose, and which is shown in Figures 20, 21 and 25, consists of an arm 7
fixed to the axle 78 to which the dog also is fixed, and a connecting rod 7 jointed
at its lowest end to the arm and at its upper end to a crank on the stem
or arbor of handle 7. The connecting rod is housed in one of the rails P which
is suitably formed for this purpose.
I am aware that a hinge consisting of two concentric arc-shaped members fitted
together and adapted to slide the one on or in the other, is not new and has been
used for various purposes. But I am not aware that such a hinge has ever before
been applied and used in the manner hereinbefore described to connect a seat frame
and a back supporting frame whether provided or not with a back vertically
adjustable thereon. The location of the unlocking handle in a position on the
back supporting frame to permit the operator to use the same handle at once for
unlocking the frame and supporting it at the same time, I also believe to be new
with me.
I proceed now to a description of the vertically adjustable back,

page_text: The back consists of a back pad Q, and a carrier R therefor.
11
The carrier R is a skeleton frame which fits between the rails P on the back
supporting frame, and is held in ways therein in which it can move up and down.
I prefer to form on the interior opposite faces of the rails longitudinal tongues ll
(Figures 12 and 24) which enter and engage corresponding grooves in the exterior
opposite edges of the carrier R. I prefer that these tongues and grooves should
have a dove-tail formation as indicated in the Figures referred to, so that the
carrier may serve to hold together the upper unconnected ends of the rails P and
prevent any tendency on their part to spread apart, the undercut forming the
dovetail being preferably on one side only of the tongue and that side the front
side or the side next to the back pad. The back pad carrier R can move freely up
and down between the rails 1', the extent of its downward movement being limited
by stops p (Figure 20) against which brings up the cross bar r on the carrier R.
This cross bar I utilize as a clamp to fasten the carrier R in its adjusted position.
The cross bar (as shown in Figure 23) is a loose bar and at the point where it is
located the carrier is cut away so as to expose the sides of the tongues 2 adjoin-
ing the bar. Thus the tongues 2 at this point are embraced between the carrier
on one side and the clamp bar r on the other. The clamp bar is controlled by a
knob or handler which screws upon a screw ² passing loosely through the clamp r
and is fixed rigidly to the carrier as shown in Figure 23. By screwing the handle
down upon the cross bar the latter will be forced up against the tongues p" and
the latter will thus be tightly bound and clamped between the cross bar clamp on
one side and the body of the carrier R on the other. With a view to still exert
upon the carrier R even when the latter is released, a frictional contact of the
clamp r which will prevent sudden drop of the carrier, I provide a spring held
in a socket in the clamp and confined between the latter and the inner end of the
handler. This spring which is strongly compressed when the handle is screwed
home, tends when the handle is turned in a direction to release the carrier, to cause
the clamp to still exert pressure sufficient to prevent too free movement of the
carrier R.
The back pad Q is hinged at its upper end upon a horizontal axis to its carrier R,
so that it may be tilted or inclined from front to rear upon that hinge as an axle.
The hinging of the two together is effected in this instance by blocks q having
pivot pins q mounted in bearings or bosses in the back pad frame Q₁ as
illustrated more particularly in Figures 22 and 26-the blocks q being fastened to
the carrier R, by screws 4 (Figures 20 and 26). Thus while all parts of the
hinge-joint are covered by the upholstery of the back-pad, yet 'the pad can at any
time be readily removed simply by taking out the screws r
The frame Q is a suitable skeleton frame of some appropriate material upon
which as a foundation the pad is upholstered. The pad Q is held in its adjusted
position relatively to the carrier by a pivoted latch or detent 5 on the carrier
(Figures 21 and 27) which engages a rack or notched bar q³ the inner end of which
is made fast to and contained in a pocket in the back or rear face of the pad—
this pocket being for reception of the dog when the pads are folded up against
the carrier. To prevent the back pad from being swung out far enough to
disengage its rack 73 from the detent, the rack has on its outer end a laterally
projecting stop which is in the path of a finger r6 on the detent (Figures 13, 21, 27).
When the back pad has been swung out away from its carrier a certain distance
the finger will bring up against the stop 5 thus preventing further movement
of the back pad in that direction. The detent drops by gravity into engagement
with the rack, but a spring may be used to insure the engaging action if desired.
By a handle 7 (Figure 27) with which the detent is provided, the latter can be
lifted by hand so as to be disengaged from the rack, q³.

page_text: head, and all of its various joints are simultaneously locked or unlocked as the
case may be by the operation of a single handle. It is illustrated more particularly
in Figures 1, 13, 20, 21, 21, 24, 26 and 28.
The head rest carrier is a jointed stem composed of three sections S S¹ S2, united
together by universal joints. The lowermost section $ which is tubular or
hollow is mounted and adapted to slide up and down on a dove-tailed way 8
(Figures 20, 21, 24, 26) provided for it on the back pad carrier R-the section S
(as indicated in Figure 24) being formed with a base grooved to fit upon and
embrace the dove-tailed way 8. It will be noted that this way is inclined from
front to rear with respect to the back supporting frame P in which the carrier R
moves, its inclination being to the front at its upper end. The inclination is
such in fact as to cause the upper portion of the way to be received as it were,
within the compass of the back pad Q-the upper portion of the rear face of which
except at the point where it is indented to accommodate the way being in rear
of the way when the back pad is folded up against the carrier R, and its hinge
being to the rear of the way 8. The object of this formation is to give a greater
range of forward movement to the head rest stem, in order to bring the head
rest pad further to the front than otherwise would be practicable.
To the uppermost section Sa is attached the head rest proper T.
The intermediate section S¹ is connected to its two fellow sections by ball and
socket joints.
The uppermost section S2 is solid and has a balls on its lower end.
The middle section S has a ball s2 on its lower end, and at its upper end has a
socket to receive the ball of section S2. This socket is formed by the concave
upper end of section S¹, in conjunction with a sleeve which screws upon the
section and has a concave interior shaped to fit upon the ball s. In both the ball
and socket ends of the intermediate section ST are formed, pockets to receive
pressers 3 and the section between these pockets is longitudinally bored to receive
à spindle s which extends between and contacts at its ends with e presser si¹³.
These pressers project a little beyond their pockets into the sockets to which they
respectively pertain.
The balls on the lower end of the middle section S¹ is held in a socket formed
by the sleeves screwing upon the upper end of the lowermost section S in con-
junction with the concave upper end of the push piece s mounted and longi-
tudinally movable in section S. Under this arrangement when the push piece 56
is forced up, it will jam the balls of the midlle section S¹ tight in its socket, and
at the same time, will, through the lower presser and spindle s cause the upper
presser in a similar manner to jam the balls of the top section $2 tight in its
socket. Thus by upward movement of the push piece s, both joints of the head
rest stem will be locked rigidly. And correspondingly when the push piece s is
allowed to drop, both joints will simultaneously be unlocked. Manifestly various
means can be employed to thus actuate the push piece. The device which I now
prefer for the purpose consists of the toggle-levers provided with a spring 8 by
which the toggle is kept normally bent. This toggle lever is placed in the
section S in the position shown in Figure 21, with its ends bearing at the top 4
against the push piece and at the bottom against an abutment
on the interior of the section. A pressure screw $10 provided with
an external operating handle or knobs" enters the section through a
suitable screw threaded socket in a position where its inner end will bear
against the toggle lever. By screwing in the pressure screw it will straighten the 5
lever with the effect of forcing up the push pieces and thus locking both joints.
When the toggle lever is relieved from the pressure of the screw, it will resume
its normal bent condition and the joints will unlock by gravity.
$9
While other means may be employed to lock the head rest stem against vertical
movement upon the way, yet it is very much to be preferred that this locking 5
action should be effected by the same instrumentality which locks the joints
between the sections of the stem. This result is attained by the mechanism just

page_text: described. The toggle lever at its lower end is seated in the angle at the junction
or meeting point of the abutments and the face of the way 8, and bears against
both. When therefore the toggle lever is straightened by the action of the
pressure screw, its lower end will be jammed not only against the abutment but
also with equal force upon the face of the way, and the section S in this way
will be rigidly clamped or locked to the way by the same movement of the same
instrumentality which locks the joints between the sections of the head rest stem.
This feature, I believe to be new with me beyond its particular embodiment repre-
sented in the drawings and just described.
Manifestly other means besides the toggle lever can be employed. I might use,
for example, the arrangement illustrated in Figure 33, in which the instrumen-
tality which operates upon the push piece is a lever 12 pivoted in the section S,
and provided with an off-set or projection which comes under and is adapted to
lift the push piece. The free end of the lever has a screw threaded boss, engaged
by a pressure screw $13 which passing loosely through the section. S, screws into
and through the boss with its inner end contiguous to the face of the way 8. A
stiff spring s encircling the stem of the screw is interposed between the lever s¹²
and the shell or case of section S. By turning the screw in the proper direction
the free end of the lever will be caused to travel upon it in a direction to lift the
push piece and consequently to lock the joints between the sections of the stem.
The inward movement of the lower end of the lever s¹ is limited by coming in
contact with a stop S5 on the section S, against which the lever is pressed by the
spring when the screw 13 is turned in a direction to unlock the joints between
the sections of the stem. The main object of the spring s" is to prevent the acci-
dental locking of the ball joints by the pulling out of the screw $13 when this
screw is being turned to unlock the ball joints for the purpose of adjusting the
head rest, as will readily be understood.
The head rest proper (Figures 20, 21 and 28) consists of a pair of pads T
adjustably mounted upon a bracket to the upper stem section S2. One pad is held
to its bracket arm by a clamping screw t¹ which passes through a longitudinal
slot in the arm. The other pad is held to the other bracket by means of a
split ring to which the pad is fastened, this ring encircling and being adapted
to rotate upon a hub carried by the bracket arm; a clamp screw serves to hold
the split ring in its adjusted position. In this way I can regulate with ease the
distance between the adjoining ends of the two pads as well as the angle at which
the pads are to stand relatively to one another.
I have herein described the best way known to me of carrying my improvements
into effect, and I state in conclusion that I do not restrict myself to the particular
mechanical details hereinbefore set forth and illustrated in the accompanying
drawings, for manifestly the same, in many respects can be widely varied without
departure from the spirit of my invention.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is―
1. The combination with the plunger cylinder and plunger, the pump and the
duct leading from the pump to the cylinder, of a pressure storage chamber inter-
posed between the pump and cylinder, and communicating with said duct, a
movable head or diaphragm in said chamber, and a spring which presses said
diaphragm in a direction opposite to that in which it is forced by the liquid on its
way from the pump to the cylinder, substantially as and for the purposes
hereinbefore set forth.
2. The combination with the base and the plunger cylinder, of the pump and
pipe connections between it and the cylinder, together with the controlling valves
therein formed as one structure, detachably connected to the plunger cylinder
and independently removable from the base, substantially as and for the purposes
herein before set forth.
3. The combination with the chair supporting plunger, and elevating mechanism

page_text: therefor, of an operating foot lever for said mechanism adapted to be turned into
or out of operative position at pleasure, automatic plunger locking mechanism
and connections between said locking mechanism and foot lever, whereby the
locking mechanism is brought and held out of engagement with the plunger
whenever and so long as the foot lever is in operative position, substantially as and
for the purposes hereinbefore set forth.
4. The combination of the chair supporting plunger, elevating mechanism
therefor;
automatic plunger locking mechanism; a foot lever for operating said
elevating mechanism having a jointed outer or free end; and connections between
the locking mechanism and the jointed outer end of the lever whereby the locking
mechanism is brought and held out of engagement with the plunger whenever and
so long as the said jointed lever is in position for use, substantially as hereinbefore
set forth.
5. The combination of the chair supporting plunger, step by step elevating
mechanism therefor; a jointed foot lever for actuating said mechanism;
automatic plunger locking mechanism; connections between the jointed outer
end of the foot lever and said locking mechanism whereby the latter is held out
of engagement with the plunger whenever and so long as the jointed outer end
of the lever is extended in position for use; and spring controlled retaining
devices whereby the jointed outer end of the lever is held in either its folded or its
extended position, substantially as and for the purposes hereinbefore set forth.
6. The combination of a chair supporting plunger: sustaining and locking
mechanism therefor; plunger elevating mechanism; and an operating foot lever
for said mechanism adapted to be turned into or out of operative position at
pleasure connections between said foot lever and locking mechanism, whereby
the plunger is released from control of the locking mechanism whenever and so
long as the foot lever is in operative position; a lowering lever independent of the
and connections
said operating lever for the plunger elevating mechanism;
between said lowering lever and the plunger sustaining and locking mechanism
respectively, whereby the lever by one movement unlocks the plunger and trips
its sustaining mechanism, substantially as and for the purposes set forth.
7. The combination of a chair supporting plunger and elevating mechanism
therefor plunger locking mechanism; a foot lever for said elevating mechanism
adapted to be turned into and out of operative position at pleasure; a lowering
lever and connections between the plunger locking mechanism and the elevating
and lowering levers, whereby either one of said levers may operate the locking
mechanism, independently of the other to effect the release of the plunger,
substantially as herein before set forth.
8. A telescopic chair supporting plunger, elevating mechanism therefor, a
separate locking mechanism for each member of the telescopic plunger, and
connections whereby said locking mechanisms are operated simultaneously to
lock or release their respective plunger members, substantially as and for the
purposes hereinbefore set forth.
9. The combination with a plunger cylinder, a liquid reservoir and a force pump
by which the cylinder is supplied with liquid for lifting and sustaining the
chair supporting plunger therein, of a telescopic chair supporting plunger, a stop
for arresting the upward movement of the lower plunger member, a normally
closed relief or discharge valve, and connections between said valve and the upper
plunger member whereby when the latter is raised to a predetermined height,
said relief valve will open to permit any further liquid supplied to the pump to
return to the reservoir, substantially as and for the purposes hereinbefore set
forth.
10. The combination of a plunger cylinder, a force pump by which the cylinder
is supplied with liquid for lifting and sustaining the chair supporting plunger
therein a telescopic chair supporting plunger; means for limiting the upward
movement of each member of said plungen; individual locking mechanisms
for each plunger member: and a lever and connections whereby the individual

page_text: locking mechanisms of all the plunger members are actuated to release their
respective members, by one and the same movement of the lever.
11. The combination of the plunger cylinder, the telescopic plunger therein,
mechanism for locking together the members of said plunger, a separate
mechanism for locking the outer or lower member to the plunger cylinder a single
operating lever, and connections whereby said lever is caused to operate both sets of
locking mechanisms to release the several plunger members from one another and
from the plunger cylinder, substantially as and for the purposes set forth.
12. In a chair, a pedestal, a plunger or chair body support composed of a
plurality of sections vertically extensible relatively to the pedestal and to each other
other, means for locking and unlocking said sections at any point within their
vertical range of movement, and a single lever or operating device for controlling
said locking and unlocking means, substantially as and for the purposes set forth.
13. In a chair, a pedestal, a plunger or chair body support composed of a
plurality of sections vertically extensible relatively to the pedestal and to each other,
and elevating mechanism common to all of said plungers sections, connections
whereby said elevating mechanism is caused to lift each plunger section, and
for locking each section in its vertically adjusted position, substantially
as herein before set forth.
mens
14. The combination with the base, the chair body, and a plunger for supporting
the chair body, of a ball and socket joint connecting the chair body and plunger
consisting of a socket attached to the chair body, and a hollow spherical or ball
segment open at the bottom and attached by it on its head or top to the plunger,
substantially as and for the purposes set forth.
15. The combination with the chair body and the supporting plunger therefor,
a hall and socket joint connecting the two, of which the ball member is attached to
the plunger and the socket member is attached to the chair body, the socket mem-
ber being divided horizontally and in the axial plane of the ball, into two parts, the
upper part being attached to the chair body and the lower part formed as a split
ring attached to the upper part, and provided with means for clamping it upon the
ball, substantially as hereinbefore set forth.
16. The combination with the chair body and its supporting plunger of a
connecting ball and socket joint, the two members of that joint being united by
a groove and pin connection located and arranged substantially as described, to
permit the chair body to rock both laterally and forward and back, but to prevent
its rotation horizontally or in the plane of the seat, substantially as and for the
purposes set forth.
17. The combination with the chair body and its supporting plunger of a ball
and socket joint connecting said parts, the two members of the joint having a
groove and pin connection with each other, permitting the chair to rock both
laterally and forward and back, a clamp or lock for holding the members rigidly
together and a separate locking dog for preventing lateral tilting of the chair,
located in the line of the axis upon which the chair moves in rocking from front
to rear, substantially as and for the purposes herein before set forth.
18. The combination of the chair body and its supporting plunger; a ball and
socket joint connecting said parts, the two members of the joint having a groove
and nin connection with each other whereby they are restrained from rotation
relatively to one another horizontally or in the plane of the seat: a clamp or lock
for holding the members rigidly together a locking dog for locking the chair
against lateral rocking movement only and a single operating lever and
connections between the locking dog and the lever having sufficient slack to permit
the lever by a partial movement to operate the clamp to free the members, and
thus permit them to rock from front to rear, without disturbing the locking dog,
substantially as herein before set forth.
19. The combination with the chair body of the foot board carrying frame
hinged to the chair body the foot board hinged to the carrying frame, and rods
having their upper ends detachably jointed to the chair body and their lower ends
C

page_text: jointed to the foot board at points eccentric to the hinge between the foot board
and its carrying frame by half round bearings carried by said rods resting upon
journals or joint pins attached to and projecting inwardly from the interior
opposite sides of the foot board, whereby said foot board can at will be connected
to and disconnected from said rods, substantially as and for the purposes
herein before set forth.
20. The combination with the chair body, the vertically movable supporting
plunger therefor, and the plunger cylinder, of a ball and socket joint comprising a
ball to which the plunger is secured at a point laterally to one side of the vertical
axis of said ball, and a socket fitting the ball, and secured centrally to the
underside of the chair, substantially as and for the purposes herein before set
forth.
21. The combination of the chair body; the foot board carrying frame hinged
to the chair hody: the foot board, hinged to the carrying frame; controlling rods
having their upper ends jointed to the chair body and their lower ends detachably
jointed to the foot board and its carrving frame: the balancing spring
connected to the said rods; and stops attached to the said rods and the
footboard carrying frame respectively, substantially as and for the purposes
hereinbefore set forth.
22. In combination with the foot board, the auxiliary step supporting frame
hinged thereto and arranged and adapted, substantially as described to fold up
under the foot board, when during the descent of the foot board, it is pressed upon
or against the floor on which the chair stands, and to automatically unfold and
resume its position of use when relieved of that pressure, substantially as and for
the purposes herein before set forth.
23. In a dental chair and in combination with the seat frame and an arm rest,
and a support therefor hinged to the forward end of the seat frame upon a
transverse horizontal axis, so that said arm rest may be swung forward entirely
clear of the seat leaving the side of the seat frame without impediment to the
operator, and a locking device upon the seat frame, above the hinge point of the
arm rest support, and adapted to engage said support at a point between the hinge
and the arms cushion or arm rest proper, substantially as set forth.
24. In combination with the seat frame and arm rest support hinged thereto at
or near the front end of said frame upon a transverse horizontal axis, a bearing
on the seat frame against which the said support brings up and upon which it
rests when raised into its position of use, and a locking device on the seat frame
which engages said support at a point between the hinge and the arm cushion
⚫ or arm rest proper substantially as set forth.
25. The combination with the seat frame and the arm rest and its support, of a
hinge between the two consisting of a horizontal laterally projecting stud on the
one and a corresponding socket in the other to receive the stud, a cross pin in
the socket engaging a peripheral groove in the stud, the latter being also cut away
on one side at its inner end beyond the groove, and the arrangement being such
that the cut away portion of the stud will be opposite the cross pin when the
arm rest is swung forward and down upon its hinge, substantially as and for the
purposes hereinhefore set forth.
26. In combination, a seat frame, an arc shaped hinge member secured thereto
and located below the top of the seat, a back supporting frame provided at its
lower end with a concentric hinge member fitting the hinge member on the seat
frame, a back carried by and vertically adjustable on the back supporting frame,
and means for locking said back supporting frame, in its adjusted position.
27. In combination, a seat frame and an arc-shaped hinge member secured
thereto concave face uppermost and located below the top of the seat, a back
supporting frame having at its lower end a concentric hinge member fitting the
hinge member on the seat frame, a back carried by and vertically adjustable
upon said frame, and means for locking said frame in its adjusted position.
28. The back supporting frame having a guide way for reception of a vertically

page_text: adjustable chair back, and prolonged below the guide way in a portion curved and
formed to constitute one member of a concentric hinge, in combination with the
chair seat frame, the stationary concentric hinge member secured thereto, and
means for locking together the two members, substantially as hereinbefore set
forth.
29. In combination with, the chair seat frame and the back supporting frame
a concentric hinge connecting the same consisting of an arc-shaped stationary
member attached to the seat frame, a concentrically curved movable member
carried by the chair back frame and fitting and engaging the stationary member,
a spring actuated locking device for automatically locking the two members in
adjusted position, a releasing handle or knob mounted on the upper part of the
back supporting frame above the hinge, and connections between the locking
device and the handle whereby said device can be moved in a direction to unlock
the hinge member, substantially as hereinbefore set forth.
30. The stationary curved hinged member having a trough like form and
secured bottom uppermost to the chair seat frame, in combination with the back
supporting frame, provided with a concentrically curved hinged member fitting
between the sides of the stationary member, the two members being united by a
tongue and groove connection, in combination with a locking dog carried by the
movable hinged member and adapted to engage a rack on the inner face of the
stationary member, substantially as described.
31. In combination with the back supporting frame and the seat frame, the
two concentrically curved hinged members engaging and fitting and adapted to
slide one upon the other, and a spring pressed pad carried by the one and adapted
to exert constant pressure upon the other, substantially as and for the purposes
hereinbefore set forth.
32. The combination with a back supporting frame of a back pad carrier
mounted and vertically adjustable on said frame, a back pad hinged at its top
to the back pad carrier, and provided upon its face next the carrier with a rack
projecting towards the latter; and a pivoted dog or detent mounted on the carrier
in position to engage the rack, and provided with a finger adapted to engage a stop
on the rack to limit the movement of the back pad away from the carrier,
substantially as and for the purposes hereinbefore set forth.
33. A head rest supporting stem composed of sections united by a plurality of
hall and socket joints in combination with a handle located upon one of the end
sections, beyond the series of joints, and means controlled thereby for locking all
of said joints simultaneously and by one movement of the handle, substantially
as and for the purposes herein before set forth.
34. The combination with a chair back of a head rest supporting stem, mounted
and vertically adjustable as a whole thereon, and composed of sections, united by
a plurality of ball and socket joints, a lock for rigidly fastening the stem in its
position of vertical adjustment on the back, means for locking all of said joints
simultaneously, and a handle mounted upon the end section which carries the lock
and connected to and adapted to operate at one and the same time by any one
movement, the lock for the stem and the means for simultaneously locking all
of the ball and socket joints in said stem, substantially as and for the purposes
herein before set forth.
35. The combination with the head rest and the head rest supporting stem
composed of a plurality of sections jointed together, of joint locking or clamping
devices, the toggle lever and connections whereby said toggle lever is caused to
operate the clamping devices to lock or release all the joints simultaneously,
substantially as and for the purposes herein before set forth.
36. In a head rest stem composed of a plurality of sections united by ball and
socket joints, a section provided with a pressure transmitting spindle or rod
extending lengthwise of and through said section as well as through the ball
member of the joint carried by said section and longitudinally movable therein
o transmit locking or clamping pressure from one end of the section to a point

page_text: beyond its opposite end, substantially as and for the purposes hereinbefore set
forth.
37. In a head rest stem composed of a plurality of sections jointed together
end to end, section provided with a longitudinally movable pressure transmitting
rod extending lengthwise of and through the section including the male member
of the joint carried by said section, and means located at a point beyond said
section for exerting endwise pressure upon said pressure transmitting rod,
substantially as and for the purposes herein before set forth.
38. The head rest stem composed of sections united together by ball and socket
jeints, in combination with a toggle lever in the bottom section, means for pressing
said lever, a clamp for the ball of each ball and socket joint, and pressers and
motion transmitting spindles carried by and movable relatively to stem sections,
and acted on by the toggle lever to effect the simultaneous clamping of all the
ball and socket joints.
39. The combination of the head rest stem sections the ball and socket joints
uniting the same, the pusher in the lowermost section arranged to act upon and
clamp the ball which adjoins it in its socket, the pusher or presser at the upper
end of the middle section arranged to have a corresponding clamping action upon
the ball which it adjoins, a pressure transmitting spindle carried by and extending
longitudinally of the middle section and having its ends in contact with the upper
and lower clamping pushers or pressers respectively, and means for thrusting or
forcing the lowermost pusher in a direction to exert clamping action-the
combination being and acting substantially as and for the purposes herein before
set forth.
40. The back pad carrier provided with a head rest way having a forward
inclination from bottom to top relatively to the body of the carrier, in combination
with a head rest supporting stem mounted and vertically movable upon said way,
and a back pad hinged to said carrier at a point in rear of the upper section of
the head rest way, substantially as and for the purpose hereinbefore set forth.
Dated this the 11th day of February 1897.
BASIL MANLY WILKERSON.