Improvements in Dental Chairs.
Year: 1899

page_text: Improvements in Dental Chairs.
I, BASIL MANLY WILKERSON, of the City of Baltimore, 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 relates to dental chairs and consists in certain improvements
which will be hereinafter claimed.
In the accompanying drawings in which I have shown the preferred manner
of carrying my improvements into effect:-
Fig. 1 is a view in side elevation of the chair complete.
Fig. 2 is a top or plan view of the base portion of the chair with the chair-
body omitted.
Fig. 3 is a vertical central sectional view of the base portion of the chair on
the line 33 of Fig. 5.
Fig. 4 is a similar view on the line 4-4 of Fig. 5, some parts being in side
elevation.
Fig. 5 is a top or plan view of the base portion of the chair, with some parts
shown in horizontal section on the line 5-5 of Fig. 3.
Fig. 6 is a similar view, the section being taken on the line 6--6 of Fig. 3,
and with the operating lever shown in its normal position.
Fig. 7 is a similar view on the same sectional line, but with the parts in different
positions, the operating lever being in its position for elevating.
Fig. 8 is a similar view on the line 8-8 of Fig. 3, the operating lever being
shown in full lines in its elevating position and in dotted lines in its other
positions.
Fig. 9 is a similar view on the line 9-9 of said Fig. 3.
Fig. 10 is a vertical sectional view drawn on the line 10-10 of Fig. 7, of the
rotary supporting-frame or casting and the pedestal or base, with the supporting
and elevating mechanism omitted, and particularly showing the locking mechan-
ism between said rotary supporting-frame and said pedestal;
Fig. 11 is a horizontal section on the line 11-11 of Fig. 10;
Fig. 12 is a vertical section on the line 12-12 of Fig. 11; and
Fig. 13 is a side elevation of the upper end of the clamp-rod and its bell-crank
iever.
Fig. 14 is a view in side elevation of the rotary supporting-frame detached, and
Fig. 15 is a vertical section of the same on the line 15-15 of Fig. 8.
Fig. 16 is a vertical central sectional view on the line 3-3 of Figs. 2 and 5
of the telescopic supporting and elevating mechanism, the supporting-frame and
pedestal being omitted.
Fig. 17 is a horizontal section on the line 17-17 of Fig. 16;
Fig. 18 is a section through one member of the telescopic elevating mechanism
on the line 18-18 of Fig. 16; and
Fig. 19 is an inverted plan view of the lower end of said member.

page_text: Fig. 20 is a view in side elevation of the guide cylinder of the supporting and
elevating mechanism; and
Fig. 21 is a similar view of the same showing it turned at a right angle.
Fig. 22 is a central vertical sectional view of said cylinder on the line 22–22
of Fig. 23.
Fig. 23 is a plan or top view of said cylinder;
Fig. 24 is a cross section of the same on the line 24-24 of Fig. 21;
Fig. 25 is a cross section thereof on the line 25-25 of Fig. 22.
and
Fig. 20 is a top or plan view of the pump, its supporting casting and valves.
Fig. 27 is a vertical section of the same on the line 27-27 of Fig. 26.
Fig. 28 is a sectional diagrammatic view of the pump; valves and plunger
cylinder, the section being drawn on the lines 27-28.
Figs. 29 to 33, inclusive, (Sheet. 5) are separate views of the various parts of
the telescopic plunger clamping mechanism.
Fig. 34 is a plan or top view of the main operating lever, detached.
Fig. 35 is a view in side elevation of the same.
Fig. 36 is a section of the same on the line 36-36 of Figs. 34 and 35; and
Fig. 37 is a section on the line 37-37 of Fig. 34.
Fig. 38 is a view in side elevation of a dental chair showing my improved
leg and foot-rest section in its lowest as well as its highest position, and with
the back-rest section broken away.
Fig. 39 is a top or plan view of the dental chair with the back-rest section and
the upholstered seat pad omitted..
Fig. 40 is a similar view with the leg and foot-rest section omitted and also
showing a somewhat modified seat-frame.
Fig. 41 is a view in vertical central section of the chair with the base or sup-
porting portion omitted, and with a portion of the back-rest section and a portion
of the leg and foot-rest section also omitted.
Fig. 42 is a view in rear elevation of the main controlling rod of the leg and
foot-rest section detached.
Fig. 43 is a view in rear elevation of my improved back-rest section.
Fig. 44 is a central vertical sectional view of said back-rest section showing a
portion of the seat-frame of the chair to which said back-rest section is attached.
Fig. 45, (Sheet 16) is a view in side elevation of a modified form of foot-rest.
Fig. 46, (Sheet 18) is a view partly in plan and partly in horizontal section, of a
modified form of rock shaft for actuating the pawl of the leg and foot-rest section.
Fig. 47, (Sheet 18) is a detail sectional view showing one of the recesses for the
side arms of the foot-board supporting-frame.
Fig. 48 is a view in side elevation of the entire head-rest, including the head-
rest proper and its support or carrier.
Fig. 49 is a view in rear elevation of the same with the head-rest pads omitted.
Fig. 50 is a top or plan view of the head-rest proper.
Fig. 51 is a view in front elevation of the lower section of the head-rest support
or carrier.
Fig. 52 is a central vertical sectional view of the head rest support or carrier
Fig. 53 is a front or face view of the toggle lever of the head rest support or
carrier, detached.
My invention may be divided into four general parts, namely; (a) supporting
and elevating mechanism; (b) foot-board and foot-rest; (c) back-rest, and (
head-rest.
The supporting and elevating mechanism illustrated by Figs. 1 to 37, inclusive
of the drawings, Sheets 1 to 15, comprise a dental chair base of novel construction
in which is contained four distinct mechanisms which may be operated by or con-
trolled by a single foot-actuated operating-lever. These mechanisms are, first
horizontal rotating mechanism, comprising means for locking the chair-body in
any position to which it may be horizontally adjusted; second, elevating mechan
ism third, mechanism for clamping the vertically adjustable chair-body sup

page_text: porting plunger; and fourth, lowering mechanism. In addition to the base and
the said mechanisms, my invention also comprises a novel telescopic chair-body
supporting plunger, and certain details of construction, all of which will be
hereinafter full described.
BASE.
The base (see Figs. 1, 3, 4, 10, 14 and 15) is shown as consisting of a cylindrical
pedestal B having a closed bottom and serving as the liquid reservoir, and an
annular or disk portion B₁ for resting upon the floor. Rotatably fitted in said
base is a supporting-frame or casting A which supports and carries the entire
chair-body supporting and elevating mechanism. The supporting-frame (see
particularly Figs. 10, 14 and 15) consists of an outer or main cylindrical section A
and an inner cylindrical section A¹ connected to said outer cylinder and which
extends above the top of the same. The outer cylindrical section A of the sup-
porting-frame is formed at its upper end with an annular flange a² which rests
and turns upon the upper end of the pedestal B and has near its top and bottom
bearing surfaces a³ a which bear against corresponding surfaces on the interior
of the pedestal. By this construction the supporting-frame is supported within
the base and may be freely rotated therein to provide for the horizontal turning
movement or adjustment of the chair-body, which, as before stated, is supported
by way of said supporting-frame.
The two cylindrical sections A and A¹ of the supporting-frame are connected
by means of vertical webs a and a horizontal web or plate a¹ (see Figs. 9, 10-
and 15). The purpose of the horizontal web or plate a¹ is mainly to hold the
respective sections of the supporting-frame together and to strengthen the entire
structure, but it also admirably serves as a floor or base for a portion of the-
elevating and lowering mechanism and protects the oil in the reservoir from any
foreign matter that may fall into the base when the upper end of the same is
exposed.
A detachable cap or dome B2, preferably made in two sections (see Figs. 1, 2, 3
and 4), is suitably fitted upon the supporting-frame in such a way as to cover
the space between the sections of said supporting-frame, thus completely enclos-
ing the mechanism contained in the base. The lower end of the cap rests upon
the upper end of the outer cylinder A of the supporting-frame, while the upper
end of said cap surrounds the inner section A¹ of said frame, just below an
exterior flange or annular shoulder thereon, and the sections of the cap may.
be bolted together in any suitable manner. As will be more fully explained
hereinafter, the detachable cap is wholly independent of the elevating and lower-
ing mechanism contained in the base and is also independent of the operating-
lever for said mechanism, whereby when one or both sections of the cap are
removed, the entire mechanisms contained in the base are exposed to view, and
while thus exposed may be freely operated. When the cap is thus removed, the
horizontal web or plate a', as before stated, serves to prevent foreign matter from
falling into the oil in the reservoir beneath said web.
SUPPORTING-FRAME LOCKING MECHANISM.
In order to lock the chair-body in any position to which it may be horizontally
rotated and to prevent it from being accidentally turned, I have provided suitable
locking mechanism between the rotatable supporting-frame and the non-rota-
table base. This locking mechanism (see Figs. 10, 11, 12 and 13) may consist
of a vertical rod A2 mounted to turn in bearings and a inside the supporting-
frame, and means, actuated by the turning of said rod, for frictionally engaging
the pedestal to lock the supporting-frame thereto. In the present instance I have
shown this means as consisting of a clamp block or shoe A³ adapted to slide hori-
zontally in a bearing in said supporting-frame and in a notch or recess a in the
vod A2 near the lower end thereof, the outer surface of said block corresponding
to the curvature of the bearing surface of the pedestal between the same and the

page_text: .
lower end of the supporting-frame. The inner surface of the clamp block is
also curved and is borne upon by a flattened or cam surface a8 on the rod A²
formed by the inner wall of the recess a'. When the rod A2 is turned in one
direction its flattened or cam surface forces the clamp block tightly against the
pedestal and securely locks the rotatable supporting-frame to the non-rotatable
pedestal, thus preventing rotation of the chair-body. If desired a light plate-
spring a may be secured at al⁰ to the outside of the supporting-frame and fitted
in a groove in the outer or bearing surface of the clamp-block.to hold the same
in place when the supporting-frame is removed from the pedestal, whilst not
interfering with the free movement of said block. To the top of the rod A2 is
attached a bell-crank lever A4 (see Figs. 6 and 13) to one arm of which is secured
a coiled wire spring A5 which acts upon the lever with a tendency to turn the
rod A2 in a direction to force the clamp-block against the pedestal, as just
described, this being the normal position of the rod. The manner of turning the
rod for leaving the supporting-frame free to be rotated will be explained herein-
after. Obviously, various forms of clampng or locking devices other than the
particular clamp-block may be used in lieu thereof.
CHAIR-BODY SUPPORTING PLUNGER.
The mechanism for supporting the chair-body and by which the same may be
raised and lowered, is as follows:-(See Figs. 3, 4, 6, and 15 to 25 inclusive).
Rigidly connected to the supporting-frame A is an upright cylinder A6 which
will hereinafter be designated the fixed plunger cylinder. This plunger cylinder
is shown as having screw-threaded connection with a socket-piece A at the lower
end of the inner section A¹ of the supporting-frame. For convenience of manu-
facture I prefer to make the lower portion A10 of the inner section A¹ of the
supporting-frame separate and connect it to said frame by means of screws a¹².
(See Figs. 3 and 15). The socket-piece A' may be cast integral with the lower
portion A10 of the inner section A of the supporting-frame and it closes the
lower end of the fixed plunger cylinder A6. It is shown as being held in place
by means of webs 20, best shown in Fig. 26.
Fitted in the fixed plunger cylinder A6, and movable up and down therein is
the cylindrical member As of the vertically movable telescopic chair-body sup-
porting-plunger. A guide cylinder A is rigidly connected to the upper end of
and moves with the cylindrical member A8 of the telescopic plunger, and sur-
rounds and is adapted to move up and down upon the fixed plunger cylinder A6,
and also has bearing in the inner cylindrical section A¹ of the supporting-
frame A. Notches a (see Figs. 21, 22 and 24) are formed in the lower end of
the guide cylinder A and straddle the webs a20 of the socket-piece A7 when said
cylinder is in its lowest position, so that said webs do not interfere with the full
descent of the guide cylinder.
The piston member A" of the telescopic supporting-plunger, upon which mem-
ber the chair-body is mounted, as hereinafter explained, is preferably solid, and
is fitted to be moved up and down in the cylindrical member A8 of the plunger,
and also has bearing in the guide cylinder A at and near the top thereof.
Suitable packing a3 is provided at the top of the fixed plunger cylinder A6 for
making a liquid-tight connection between the inside of this cylinder and the
cylindrical member A8 of the telescopic plunger. The lower end of the piston
member A of the plunger is also provided with suitable packing a for making
it fit liquid-tight in the cylindrical member A8 of the plunger. I prefer that
this piston packing be constructed as follows:-The cup shaped leather pack-
ing a is flexible and is held in place some distance from the lower end of the
piston by means of a metallic head A15 the same diameter as the piston and secured
thereto by screws a². An annular groove or channel a27 is cut in the metallic
head of the piston behind the leather packing adjacent to and opening into
the groove in the metallic head in which the packing is fitted.
A vertical
port as is made in the metallic head and leads into the channel a27. When the

page_text: piston member of the plunger is being elevated and also when it is descending,
the oil in the plunger cylinder under pressure beneath the piston is forced
through the port a into the channel a27 and the cup shaped packing is expanded
against the cylindrical member A8 of the telescopic plunger, whereby the proper
close contact of the packing with said cylinder is ensured.
In order to relieve the chair from all jar and shock when the chair-body sup-
porting-plunger reaches the extreme of its up and down movements, I have pro-
vided said plunger with suitable buffing devices which will effectually cushion the
plunger at the end of its upward movement as well as at the end of its downward
movement.
Referring to Figs. 3, 16 and 19, it will be seen that the lower end of the piston
member A of the telescopic-supporting plunger is bored out centrally to form
an oil-chamber e, and a buffer-rod or plunger E is fitted to reciprocate in said
chamber. Said buffer-rod is held in place by means of a screw-plug closing
the lower end of the oil chamber e, the stem of the rod passing through a central
opening in said screw plug and the head of the rod abutting against said plug,
when the rod is in its lowest position. A spiral spring 12 is confined in the oil-
chamber e between the upper end thereof and the head of the buffer-rod and
serves to cause the buffer-rod to project beyond the lower end of the piston. The
screw plug E is formed with small holes e', and the diameter of the head of the
buffer-rod is slightly smaller than the oil-chamber of the piston, in order that oil
may pass between the plunger cylinder and the oil-chamber e, or channels or
grooves may be cut in the head of the buffer-rod for this purpose.
When the piston is in an elevated position relatively to the bottom of the
plunger cylinder A6 the spring E2 forces the buffer-rod downward, and the oil-
chamber is filled with oil, which enters through the openings e in the screw
plug E and passes through or around the head of the buffer-rod. When the
piston descends, just before the end of its down stroke, the buffer-rod strikes the
bottom of the plunger cylinder and is forced upward against the stress of
the spring E, and the oil in the chamber above the buffer-rod escapes back to the
plunger cylinder by way of the space between the head of the buffer-rod and the
walls of the chamber, and the openings e¹. The oil escapes from the oil-chamber
very slowly and affords a cushion for the buffer-rod which thereby cushions the
final movement of the piston, and relieves the chair from all jar or shock in its
descent.
Referring now to Figs. 21 and 22, one of the notches a" in the lower end of
the guide cylinder A of the telescopic supporting-plunger is provided with a
coiled spring e² which is seated in a socket opening into the top of said notch,
the spring projecting into said socket. When in the descent of the chair-body,
the guide cylinder A reaches its lowest position the spring e strikes against one
of the webs a20 and acts as a buffer to relieve said guide cylinder from jar.
The upward movement of the piston member All of the telescopic supporting-
plunger is limited by a shoulder a formed by the lower end of a longitudinal
groove in said piston member coming in contact with a stop on the upper
end of the guide cylinder A projecting into said groove. This stop is formed
by a clamp-block or shoe C8, further on to be explained. (See Figs. 3 or 16.)
Secured upon the lower edge of said clamp-block is a plate spring which
normally stands off from said clamp-block, and when said piston reaches the limit
of its upward movement in the guide cylinder A, instead of striking directly
against the clamp-block, or whatever stop may be used, the shoulder a is met
by said spring E³, and the piston is thus relieved of shock or jar.
A suitable stop lug, formed by a screw a23 (see Figs. 20 to 25, inclusive) is
placed on the outside of the guide cylinder A near the bottom thereof, and
serves to limit the upward movement of said guide cylinder by coming in contact
with the upper end of the inner section A¹ of the supporting-frame. A spring,
not shown, similar to the spring E³, should be provided for cushioning the guide
cylinder when it reaches the limit of its upward movement.

page_text: In this way not only is the telescopic supporting plunger cushioned at the
ends of its upward and downward movements, but the members or sections of the
In other words
plunger are likewise cushioned at the ends of their movements.
all the movable parts of the supporting-plunger which are adapted to strike
other parts are cushioned, whereby the operation of the supporting-mechanism
is noiseless and without shock or jar.
The upper end of the guide cylinder A may be bevelled off to form a trough-
like depression a24 around the piston A" adapted to catch any oil that may be
carried up by said piston.and which runs down therefrom. The oil which collects
in this depression may escape therefrom by way of the groove in, the piston
and a hole in the before-mentioned clamp-block C. If desired a pocket or
channel may be formed in the guide cylinder A near the upper end thereof
for the reception of any oil running down from the telescopic-plunger.
PLUNGER CLAMPING MECHANISM.
2
The mechanism for clamping the sections or members of the telescopic chair-
body supporting plunger together and for simultaneously clamping the plunger
as a whole to the supporting-frame, for the purpose of firmly supporting the
chair-body against vibration or shaking movement, is in some respects similar to
the mechanism shown, described and claimed in my Patent No. 10.496, A.D., 1897.
I do not wish to be understood as claiming herein anything shown or described
in said Patent.
The plunger clamping mechanism is best illustrated in Figs. 3, 5, 6, 7, 16,
17, 20 to 25, and 29 to 33 (Sheet 5), and in the present instance is shown as
consisting of a clamp bar C arranged parallel with the guide cylinder A of the
telescopic plunger, and loosely connected thereto near the top and bottom bý
screws cc, and a dowel pin 25. (See Figs. 5, 20, 22 and 25.) The inner surface
of this bar is curved transversely to correspond with the outer surface of said
guide cylinder A and is provided on said inner surface with a longitudinal pro-
jection or rib c', which bears against said guide cylinder in a longitudinal
groove a¹ therein, the clamp bar being adapted to have a slight horizontal rock-
ing movement on said rib c', as a fulcrum. A clamp-block or shoe C is fitted to
slide horizontally in a bearing in the guide cylinder A, the inner end of this
block projecting into a longitudinal groove a³ in the solid piston member All of
the telescopic plunger, and is borne upon by the clamp bar C. The front rounded
edge of one member C¹ of a toggle lever bears in a longitudinal groove 2 on the
outer surface of the clamp bar C and the outer member C2 of the toggle lever has
bearing in an adjustable fulcrum-piece C³. (See Figs. 3 and 5.) The adjustable
fulcrum-piece C3 is provided with a round shank C which passes through a long
tubular nut C screwing into an extension A12 of the supporting-frame section A',
this extension also serving to accommodate the clamp-bar C and its operating
toggle lever. That part of the long nut which projects outside of the sup-
porting-frame extension A2 is provided with wrench engaging surfaces C, and
a jam nut C7 is employed for locking the long nut in any position to which it may
be adjusted. The inner member C of the toggle-lever is formed with two lugs c³ ³
and a space ct between the lugs; and the outer member C2 of the toggle-lever is
formed with a cut away or bevelled portion on which is a lug adapted to
register with the space c' of the member C¹. (See Figs. 3 and 29 to 33.) This
formation provides a very strong toggle-lever without interfering with its free
movement. The outer member C2 is extended some distance below the inner
member and on its lower end is formed with a lug c which slides in a groove 8
in the top of a lever C. Said lever is provided with a pintle Co having bearing
in a socket on the supporting-frame, the lever turning on this pintle as a
fulcrum. The socket or bearing for the pintle of the lever C, is shown as being
formed in a block A13 secured to the outside of the cylinder A¹ of the supporting-
frame by screws c10. (See Figs. 3 and 14.) An adjustable bearing may be

page_text: provided for the top of the outer member C³ of the toggle-lever, and is shown as
consisting of a screw C15.
To the short arm C" of the lever C is connected one end of the coiled spring A5.
the opposite end of which is connected to the arm A' of the bell crank lever of
the mechanism for clamping the rotary supporting-frame to the non-rotating
pedestal, as herein before described. The said spring acts with a tendency to pull
the member C2 of the toggle lever in a direction to straighten out the same and
force the clamp-bar C inward against the block or shoe Cs with sufficient force to
clamp the piston member A" of the telescopic plunger in the guide cylinder A³
thereof and at the same time bind or clamp the said guide cylinder A9 in the
inner cylindrical section A' of the supporting-frame. The lever C is also pro-
vided with a long arm C¹ by which the lever may be rocked against the stress
of the spring A5 to bend or flex the toggle-lever and unclamp the telescopic
plunger.
It will thus be seen that the plunger clamping mechanism normally acts to
clamp the sections or members of the telescopic plunger together and the plunger
as a whole to the supporting-frame, whereby the chair-body is rigidly supported
against lateral vibration; that when the lever C9 is actuated to overcome the
action of the spring A5, as will be hereinafter described, the toggle-lever simul-
taneously unclamps the clamp-bar C and shoe C8, whereby the guide cylinder A³,
carrying with it the clamp-bar C, is free to be moved up and down in the sup-
porting-frame, and the piston section A" of the plunger is free to be moved up
and down in the guide cylinder; and that when the lever C is actuated to come
within the influence of the spring, the toggle-lever automatically acts to simul-
taneously clamp the members of the plunger together and to the supporting-
frame, in whatever position of vertical adjustment the plunger members may
occupy relatively to each other or to the supporting-frame.
The toggle-lever may be adjusted to exert more or less force against the clamp-
bar C by means of the adjusting nut C5, the member C2 of the toggle lever freely
sliding in or out in the groove of the lever C, without disturbing the pivotal
connection between the toggle lever and the supporting-frame, which connection
is by way of the pintle C10 of the lever C.
It should be understood that portions of my improved plunger-clamping
mechanism, such for instance as the toggle-lever, are not confined to telescopic
plungers, but are applicable to simple or non-telescopic plungers.
ELEVATING AND LOWERING MECHANISM.
The previously described telescopic chair-body supporting plunger is adapted
to be raised and lowered for the purpose of varying the vertical position or
adjustment of the chair-body supported thereby, by means, preferably, of
hydraulic elevating and lowering mechanism, as next to be described. (See
Figs. 4, 9, 26, 27 and 28).
The pump for imparting an upward movement to the telescopic plunger and
the valves for controlling the flow of oil between the oil reservoir, formed by
the pedestal B, and the pump, and between the pump and the fixed plunger
cylinder A, are preferably carried by a single casting D, having detachable con-
nection with the supporting-frame A.
The vertical pump cylinder D is shown as made in a separate piece having
Ecrew-threaded connection at its lower end at d with a socket or opening 12 in
the casting D; or if. preferred the pump cylinder may be cast integral with .the
said casting D. An oil inlet valve 13 seated in a screw plug 1) which closes the
lower end of the socket or opening 12 in the casting serves to admit oil from
the oil reservoir to the pump cylinder through an opening in the screw plug 14,
when the pump piston D5 is raised, and to prevent the return of oil to the
reservoir when said piston is depressed. A port or passage way in a portion
of the casting 1) communicates with a chamber in the casting and through
which all oil from the pump cylinder to the plunger cylinder and from the

page_text: plunger cylinder to the oil reservoir must pass. The upper end of this chamber d
is closed by a plug 16 screwed into the casting and forming a seat for an outlet
valve D' and a bearing for the stem d of said outlet valve. (See Fig. 27). The
outlet valve D is formed with a downwardly extending tubular projection d
which constitutes a bearing and guide for the stem d of a check valve 18
adapted to close the port or passage way between the chamber d³ and the pump
cylinder, for preventing the return of oil to said pump cylinder from the plunger
cylinder. The stem of the check-valve D8, it will be seen, slides in the tubular
bearing ds of the outlet valve, and automatically closes the passage way ² by
virtue of a spring & surrounding the stem of the valve D8 and bearing at its
opposite ends against the valve 18 and the projection of the outlet valve, this
spring also serving to normally close the outlet valve. The stem d of the outlet
valve is longitudinally corrugated, grooved or flattened at one or more places on
its sides, as at d³, to permit oil to pass from the chamber d³ to the oil reservoir
when the outlet valve is tripped to lower the chair-body. The upper end of the
outlet valve stem projects above the plug D and has fitted upon it a cap 19
having an outer annular flange which loosely surrounds the outside of the
upper end of the plug Do with a space between said flange and said plug. The func-
tion of the flanged cap D9 is to deflect downwardly the oil escaping from the
plunger cylinder by way of the outlet valve when the same is tripped to lower
the chair-body, and thus deaden the noise which would otherwise be made by the
oil issuing under pressure from around the valve stem.
The outlet valve may be tripped or opened for lowering the chair-body by
applying downward pressure to its stem through or by way of the cap Dº. The
means employed in the present organization for imparting this downward pressure
to the outlet valve will be explained further on.
Communication between the chamber and the plunger cylinder is made by
means of a passage way do in an off-set portion D10 of the casting 1) and a
passage way a partly in an off-set portion A13 of the lower portion A10 of the
supporting-frame and partly in one of the webs 20 of said lower portion A10.
The detachable supporting connection between the casting D and parts carried
thereby and the supporting-frame A may be made as follows:-The off-set D1º
of the casting D is fitted upon the off-set A13 of the supporting-frame in such a
way that the passage-ways 10 and a16 register, and afford communicating connec-
tion between the pump and the plunger cylinder A6. A screw-bolt D passes
through the off-set 110 and screws into the off-set A13, thus firmly clamping the
casting upon the supporting-frame and making a liquid-tight connection between
the passage ways do and a16 at the junction of the pump casting and the
supporting-frame.
By means of this construction the entire pumping mechanism including its
various valves and passage ways may be readily removed as a whole from the
base or pedestal B, for the purpose of cleaning or making repairs, without dis-
turbing other parts of the mechanism contained in the pedestal. To do this it is
only necessary to remove one or both of the detachable sections of the dome or
cap 12 for exposing the interior of the pedestal, and unscrewing the screw-bolt 1",
which it should be observed is located in a readily accessible position. By this
construction, also, the outlet valve and the check-valve for preventing the return
of oil to the pump cylinder from the plunger cylinder may be readily removed
without removing or disturbing other parts of the pump mechanism, or the cast-
ing upon which it is mounted. This may be accomplished by simply lifting the
flanged cap 19 from off the outlet valve stem, and unscrewing the screw plug De
by way of its wrench-engaging surface which is also located above the
position where it can readily be reached when the cap section B2 is removed. In
in a
pump
this way the entire pumping mechanism may be readily removed or placed in
position, or only the outlet valve D' and valve 108 be removed, if desired.
Lugs don the pump casting D may rest upon lugs or projections as on the

page_text: supporting-frame for giving additional support to said casting and the parts
carried thereby.
..
The pump above referred to and now to be described is of peculiar and novel
construction. The passage way opens into the side of the pump cylinder D' a
short distance above the bottom thereof and is preferably V-shaped in cross-
sectional area, or gradually narrows downwardly to an acute angle termination.
As the pump-piston D³, near the completion of its down-stroke, passes the passage
way d², the escape of the oil therethrough is gradually restricted, thus gradually
retarding the descent of the piston; and when the piston finally closes the
passage way d² some oil is confined between the bottom of the pump cylinder and
the piston; and acts as a cushion to prevent the sudden stoppage or arresting of
the piston. In this way it is practically impossible to jar the main operating
lever or the chair body when said lever is depressed to elevate the chair-body.
The pump-piston D is solid, is slightly longer than the pump cylinder and is
A stiff coiled
substantially the same size as the interior diameter thereof.
spring D surrounding the 'pump cylinder and piston and bearing at one end
against the pump casting D and at its other end against an annular shoulder d¹
on the top of the piston, serves to normally hold the piston in its upper position
and to return it to such position after the main operating lever has been relieved
of pressure of the foot.
Suitable packing is provided for the piston, said packing' being similar to the
packing used on the piston member of the telescopic plunger and consisting, in
this instance, of two cup-shaped leather disks D¹³ held in place upon the piston
by means of a metallic head 1 fitted snugly in the pump cylinder and connected
to the piston by screws 12, only one of which is shown in the drawings. (Fig. 27).
In order to secure a proper close contact between the piston packing and the
pump cylinder, an annular groove 13 is made in the metallic piston head 144
behind each cup or section of the packing, adjacent to and opening into grooves
in the piston head in which the leather cups are fitted. The lower groove d¹³
communicates with the pump cylinder beneath the piston by way of a port 14,
and a similar port 20 affords communication with the upper groove When
the piston descends oil under pressure beneath the piston is forced through the
port d into the groove 13 with the effect of expanding or forcing the lower
packing cup outwardly against the wall of the cylinder and in a similar way the
upper packing cup is expanded during the up-stroke of the piston.
The pump piston for a portion of its length above its packing is made of
smaller diameter than the interior of the pump cylinder, for the purpose of pro-
'viding an annular oil space 25 around the piston and between it and the cylinder,
the top and bottom of this space being formed, respectively, by the lower end
of the top or gland D of the cylinder and an annular shoulder do on the piston.
In the top of the piston is a recess or cavity which communicates with the
oil space through a vertical passage №¹ and a horizontal passage d¹º, both in
the piston, the passage 19 opening into the oil space 15 a short distance above
the shoulder d The cavity is intended to be filled or partly filled with oil
which passes to and from the oil space around the piston by way of the passages №18
and for the purpose of keeping this space always filled with oil.
When the piston is in its lowest position the oil space is lengthened out and
is filled with oil. As the piston rises and the oil space decreases by reason of
the shoulder d¹ on the piston approaching the top of the cylinder, the oil dis-
placed from the oil space is forced up into the cavity d through the communicat-
ing passages, this movement continuing until- the passage 19 has passed the
bottom of the cylinder top D15, thus shutting off the escape of the oil from the
oil space. The oil thus confined in the oil space serves to cushion the up-stroke
of the piston and prevent all jar or the sudden stoppage or arresting of the piston.
As the piston descends the oil flows back into the oil space from the recess in
the ton of the piston.

page_text: In a pump constructed as I have just described, the operation is exceedingly
smooth and soft, the pump-piston, and consequently its operating-lever, being
cushioned at the ends of both its upward and downward strokes; and the packing
between the piston and cylinder is always expanded or tightened during the up-
ward or passive stroke of the piston as well as during the downward or effective
stroke of the piston, it being understood that the port d20 opens into the oil
space 15.
OPERATING LEVER.
As before stated, a single foot-actuated operating lever F is employed for
actuating the pump for elevating the chair-body, for tripping the outlet valve
for lowering the chair-body for controlling the plunger clamping mechanism,
and for controlling the locking mechanism between the rotatable supporting-
frame and the non-rotating pedestal. The instrumentalities herein shown for
actuating and controlling these several mechanisms by a single lever these
several mechanisms having already been described-are now to be explained.
(See Figs. 3, 4, 5, 6, 7, 8, 30, 32, 34, 35, 36 and 37.)
The main operating lever F is pivoted to rock vertically about a horizontal
pivot which connects its inner end to an upright post which is swivelled
in a bearing F2 of the supporting-frame A, the operating-lever being movable
horizontally with said upright post. (See particularly Figs. 34, 35 and 36.) The
operating-lever, therefore, is capable of being rocked vertically for the purpose
of actuating the pump-mechanism, and moved horizontally into various positions
for the purpose of controlling the several other mechanisms above referred to.
The operating-lever is suitably curved to best adapt it for the purpose intended
and at its inner end is provided with a short arm or lever F3 extending substan-
tially in the same direction as the operating lever. On the underside of the
outer end of the short arm F3 of the operating lever is a socket f¹ (see particularly
Fig. 4), and a piston rod F having balls fa on its opposite ends, bears loosely in
the socket of the short arni of the operating lever, and in a socket in the
upper end of the pump piston D³. When the operating lever is depressed, as by
the foot, the pump-piston D5 is also depressed through the medium of the piston-
rod F. As before explained, the coiled spring D12 surrounding the pump
cylinder and piston serves to normally hold the piston in its upper position and
return it to such position after the main operating lever has been relieved of
pressure of the foot. The same spring, of course, serves to normally elevate the
main operating lever.
By this construction the pumping mechanism may be actuated, by vertically
rocking the operating-lever, to elevate the chair-body to any desired position.
The mechanism for tripping the outlet valve for lowering the chair-body, the
mechanism for controlling the telescopic plunger clamping mechanism, and the
mechanism for controlling the locking mechanism between the rotatable sup-
porting-frame and the non-rotating pedestal may be actuated or brought into
play by the horizontal turning movement of the operating-lever. These several
controlling mechanisms will now be described in the order just above named, it
being understood that owing to the loose ball-and-socket connection of the pump
piston rod F the operating-lever and its short arm F3 may be freely moved
horizontally for the purpose of controlling the mechanisms about to the described,
without disturbing or operating the pump mechanism.
The controlling mechanism for tripping the outlet valve D7 for lowering the
chair-body is as follows:-
Rigidly projecting from the horizontally swivelling post F¹ is a controlling
arm F5 which moves horizontally with the main operating-lever, but is not moved
when said lever is rocked vertically, the operating-lever rocking vertically about
the pivot without moving the post For the controlling arm F5, rigidly con-
nected thereto. This controlling arm, about midway its length, is provided with
an adjustable lug or projection shown as consisting of a screw F6, which may be

page_text: locked in its adjusted position by means of a set screw f³. (See Figs. 33, 34
and 35). This lug or projection is adapted to impinge, when the operating-lever
is moved the proper distance to the right, upon a roller bearing on the outer
end of a vertically rocking arm or lever F7 pivoted to a lug f* on the supporting-
frame and bearing near its outer end upon the cap D2 of the outlet valve. The
downward movement which may thus be imparted by the horizontal movement of
the operating-lever to the lever F through the controlling-arm F³ serves to de-
press the cap D' and trip the lowering valve D, as before described. The extent
to which the outlet valve may be opened by the operating-lever may be regulated
by adjusting the screw Fo of the controlling-arm, and the rate of descent of the
chair-body may thus be nicely regulated, as desired. The vertically rocking arm
or lever F may be slipped in place upon the lug f* when one section of the dome or
cap Ba is removed, a long lug f5 on this cap section serving to hold the arm
or lever in position when the cap section is in place. See Figs. 6 and 7.
The telescopic plunger-clamping mechanism is controlled by the horizontal
movement of the operating-lever through the medium of the same controlling
arm through which the movement of the operating-lever is imparted for
tripping the outlet valve for lowering the chair-body. For this purpose the con-
trolling arm F is provided at or near its outer end with a roller bearing fo which
is adapted to bear against the side of the long arm C12 of the lever C of the toggle
lever plunger clamping mechanism. The outer surface of the arm C2 against
which the roller f of the controlling arm bears, is of cam form, for the purpose
of imparting the movement of the controlling arm to the arm C12 and also for
imparting certain movements of said arm C¹² to said controlling-arm, under
certain conditions, as will soon be made plain. In Fig. 6 the parts are shown in
their normal or inoperative position with the roller bearing fe of the controlling
arm resting near a cam or shoulder 7 on the long arm C2 of the lever C³, and
the operating lever and the controlling arm F5 occupying a position to the left of
the position which they must assume when the chair-body is being elevated.
When in this position the controlling arm has no effect upon the lever C and
the spring A5 is free to act upon said lever to straighten out the toggle-lever and
thus bring the plunger clamping mechanism into action. By moving the operat-
ing-lever to the right of its normal position the roller bearing f of the con-
trolling-arm is caused to ride upon the arm C12 of the lever C until it rests
against a cam or shoulder f at one end of a depression f9 near the outer end of
said arm C, the parts then being in position for elevating the chair, this posi-
tion being illustrated in Fig. 7. This movement of the operating lever forces
the arm inwards and rocks the toggle-lever member C2 against the pulling
action of the spring A5 and relieves the clamp-bar C from the action of said
spring, whereby the telescopic plunger members are left free to be moved up or
down. The cam surface of the lever arm (12 is so proportioned as to yieldingly
hold the operating-lever in either its normal or its elevating positions, and it
will be obvious that movement of the operating-lever to the right of its elevating
position operates the outlet valve to lower the chair-body, as previously explained,
and at the same time the roller bearing facts upon the lever arm (12 in such a
way as to hold said arm in the position in which the plunger clamping mechanism
is maintained in its inoperative position while the chair-body is being lowered.
A stop or shoulder f10 at the outer end of the depressed portion of the lever
arm serves to limit the movement of the lever F5 and the operating lever to
the right. The instant the operating-lever is relieved from pressure the spring A³,
acting through the lever and controlling-arm F³, pulls it into its normal
position and throws the plunger clamping mechanism into locking position.
When in its normal position, the operating-lever should be locked against
downward movement so that it may be used as a foot-rest for the operator. This
may be accomplished by the short arm F3 of the operating-lever resting upon a
fixed portion of the supporting-frame as a lug on the section A¹ of the
supporting-frame, when said operating-lever is in its normal position. (See

page_text: Fig. 8). Upon moving the operating-lever into its position for. elevating, the
chair-body its short arm F3 clears the lug f" and leaves the lever free to be
rocked vertically.
:
The locking mechanism between the rotatable supporting-frame A and the non-
rotating pedestal B, is also controlled by the horizontal movement of the operat-
ing-lever through the medium of the controlling-arm F5. (See particularly
Figs. 6, 7, 10, 34, 35 and 36). This arm near its inner or fulcrum end is provided
with an adjustable stud f12 which screws into it and is locked in its adjusted
position by a set screw f¹³. The stud f12, when the operating-lever. is moved
horizontally to the left of its normal position, is adapted to strike against one
end of a push rod F8 mounted to reciprocate in a bearing lug on the section.A!
of the supporting-frame. The opposite end of this push rod bears against...the.
short arm F15 of the bell-crank lever A4 of the clamp rod A2 of the mechanism
for clamping the supporting-frame to the pedestal. Slight pressure on the push
rod, caused by sidewise movement of the operating-lever to the left of. its
normal position, serves to rotate the clamp-rod A2 in opposition to the pull of
the spring A5, to release the clamp block A³ and permit the supporting-frame and
chair-body to be freely rotated. When the operating-lever is relieved of pressure
the spring A5 acts through the medium of the lever C9 and controlling lever F
to automatically turn the clamp rod to lock the chair-body in its position of hori-
zontal adjustment, and to restore the operating-lever to its normal position.
The horizontal movement of the operating-lever to the left necessary for un-
clamping the clamping mechanism between the supporting-frame and pedestal
for permitting the chair-body to be rotated horizontally, may be performed without
disturbing or interfering with the adjustment of any of the other mechanisms of
the chair under the control of said operating-lever.
The operation of the operating-lever in performing its various functions may
be described as follows:-In Figs. 2 and 6 the operating-lever is shown in full
lines and in Fig. 8 in dotted lines marked "normal," as occupying its normal
position in which the chair-body is locked against rotation and the telescopic-
plunger firmly clamped, and the operating-lever is held against downward move-
ment. By moving the operating-lever to the right of its normal position into
the position shown in Figs. 7 and 8, the plunger clamping mechanism is auto-
matically released and the operating-lever is free to be rocked downwardly, but
the lowering valve and the supporting frame clamping mechanism are not dis-
turbed. After the chair-body has been elevated to the desired extent by vertical
rocking movement of the operating-lever, this lever should be moved to its normal
position to permit the plunger clamping mechanism to act and also to transform
the operating-lever into an operator's foot-rest. To lower the chair-body the
operating-lever is moved to the right, as far as it will go, into the position shown
in full lines Fig. 5 and dotted lines marked "Lowering" Fig. 8. This move-
ment simultaneously trips the lowering valve and releases the plunger clamping
mechanism, without disturbing the clamping mechanism between the supporting-
frame and the pedestal. Immediately upon releasing the operating-lever from
pressure of the foot it automatically moves back to its normal position, and the
lowering valve is closed and the telescopic plunger clamped. By moving the
operating-lever to a position to the left of its normal position, into the position
indicated by dotted lines marked "turning" Figs. 8 and 9, the clamping
mechanism between the supporting-frame and the pedestal is released and the
chair-body may be freely rotated horizontally, and immediately upon relieving
the operating-lever of pressure it automatically resumes its normal position and
the chair-body becomes locked in any horizontal position to which it may have
been adjusted.
I have shown and explained the operating-lever as automatically resuming its
normal position immediately after it has been relieved from pressure required to
move it to its position for tripping the outlet valve, but obviously the cam sur-
face of the arm (12 of the toggle lever may be so formed as to cause the operat-

page_text: ing-lever to automatically move to its position for elevating the chair-body, after
the outlet valve has been tripped. In fact this mechanism can readily be con-
structed to cause the operating-lever to act in any desired manner. For example
it can be constructed so that after the operating-lever has been moved to trip
the outlet valve and it is suddenly released it will fly back to its normal position,
but if gradually released it will simply move to its position for elevating the
chair-body.
It should be understood that the roller bearing fo of the controlling arm 15
striking against the shoulder f of the lever arm C2 arrests the movement of said
controlling arm, as well as the operating-lever, when the latter has been released
after tripping the outlet valve and also when said lever is moved from its elevat-
ing to its normal position; and that the spring A serves to cushion the parts
when the said roller bearing f strikes the shoulder f.
A plate spring F8 may be interposed between the vertically movable short
arm 3 of the operating-lever and the controlling-lever F for the purpose of
cushioning the said short arm F3 when the same at the end of its upward move-
ment strikes the controlling-arm. Said spring may be secured to the top of the
short arm F3, as plainly shown in Fig. 8.
The operating-lever F projects outside of the supporting-frame through an
opening in one of the sections of the dome or cap B2 and is suitably curved both
horizontally and vertically, and is provided on its outer extremity with a foot-
rest F⁹. It is best operated by the foot for elevating the chair-body by placing
the foot upon the rest F and applying downward pressure thereto with a step-by-
step or pumping motion, and for performing its other functions pressure should
be applied to the side of the rest to move the lever horizontally in one direction
or the other. This latter movement may be more conveniently accomplished by
the operator placing one foot on the floor with the side of his leg touching one
side of the foot-rest and pressing the rest to one side by inclining his leg in the
proper direction without lifting his foot. In order that the sides of the rest
may not hurt the leg of the operator when the same pressed against the rest, I
have shown the rest as being provided with stuffed or upholstered pads F10
secured to the sides thereof in any suitable manner. The top of the rest may,
if desired, be covered. by a rubber pad F", which will prevent the foot from
slipping.
.
Upon the operating-lever, inside the supporting-frame or rather the cap 'thereof,
is a sharp-edged disk or flange F12 for the purpose of arresting any oil that might
get upon the inner portion of the lever and thus prevent its escape to the outside
of the supporting-frame or pedestal. Should any oil get upon the inner portion
of the lever it will be met by the flange and drip off its edge into the interior of
the pedestal.
The operating-lever, it will be seen, has no connection whatever with the cap B²,
nor has any of the elevating mechanism, and when either or both of the sections
of said cap are removed the entire elevating mechanism is exposed to view. While
thus exposed the elevating mechanism may be operated and its action plainly
seen.
A chair-body H, is, as usual, mounted upon the telescopic plunger by way of a
yoke or cross-head G connected to the upper end of the piston 'member "A"
of the plunger.
:
FOOT-BOARD AND FOOT-REST.
I will now describe my improvements relating to the foot-board and foot-rest
portion of the chair, referring to sheets 16, 17 and 18, Figs. 38, 39, 40, 41,
42. 45, 46 and 47 of the drawings.
That portion of the chair usually termed the foot-rest section comprises a foot-
board, platform, or leg-rest, suitably connected to the seat-frame of the chair,
and a root-rest proper carried by said foot-board or platform."
The foot-board or platform in the present instance, as in my before mentioned

page_text: Patent No. 10,496 of 1897, is capable of being raised and lowered relatively to
the seat of the chair to accommodate persons of different stature. It is also
capable of being elevated to a level with the seat section of the chair, and is
maintained at all times practically in parallelism with said seat, so that when
the foot-board or platform is raised to the level of the seat, it will form practi-
cally an extension thereof, and when in such position it comes into play as a
leg-rest. The back-section and the head-rest section are likewise capable of
being adjusted to a level with said seat section of the chair, whereby when all
the sections of the chair-body are brought into alignment the chair is virtually
transformed into what is tantamount to a couch, or the "anaesthetic " position,
as it is called by dentists.
For the purpose of convenience all positions of the back and the foot-board
when the same are not in alignment will herein be referred to as the "operat-
ing" positions, because these positions provide only for dental operations. The
positions of these parts when in alignment or in approximate alignment will be
referred to as the "anaesthetic" position, because such position meets the require-
ments and incidents of anaesthesia.
As the foot-rest carried by the foot-board or platform normally occupies a
position above the level of said foot-board or platform, it is obviously desirable
when the chair is temporarily transformed into a couch, as above indicated, that
the foot-rest should also assume an inoperative position in alignment with the
other sections of the chair-body, or drop to or below the level of the foot-board,
where it will be out of the way and not interfere with the feet of a person
under the influence of an anaesthetic. Besides generally improving the construc-
tion of the foot-board and its operating mechanism, I have also provided mechan-
ism whereby whenever the foot-board is elevated to its uppermost position, the
foot-rest, as just stated, is caused to automatically drop to a level with the foot-
board, and whenever the foot-board is lowered the foot-rest automatically assumes
its normal operative position.
I will first proceed to describe the improved leg and foot-rest as follows:-
Curved side arms A. A constituting the supporting-frame of the foot-board are
hinged or pivoted at or near their upper ends at a a to the opposite inner sides
of the seat frame B of the chair near the front of said seat-frame.
The side arms are shown as being connected by a central plate, screen, or
apron A which may be cast integral with said arms or made separate therefrom
as may be desired.
A foot-board or platform C is hinged at its inner end to the lower end of the
side arms A. A at a¹ a¹. A foot-rest D is carried at the outer end of the foot-
board, and is pivoted thereto by way of its side-arms D¹ DT at d d, the foot-rest
being adapted to project above the foot-board at all times save when the foot-
board is in its uppermost position on a level with the seat of the chair, or when
it is independently dropped to or below the level of the foot-board, as will be
hereinafter explained.
A supplemental foot-rest D2 may be pivoted by way of its side arms D³ D³ to
the outer end of the foot rest at did, and is capable of being rocked into either
of two operative positions nearer to or farther away from the chair seat.
A controlling rod E preferably triangular in shape and of skeleton form, and
which will be herein referred to as the main controlling rod, is pivoted at its
upper broad end at ee to the lower ends of brackets E¹ E' secured to the inner
opposite sides of the seat frame B, and at its lower end the main controlling rod
is pivotally connected at e¹ to the lower end of a link E2 pivotally connected at
its opposite end to the pivot rod a¹ connecting the side arms A A and the foot-
board. The distance between the pivots a and c is the same as the distance
between the pivots a¹ and e¹. Notched lugs C¹ C¹ depending from the inner end
of the foot-board are adapted to engage the pivot bolt e¹ which unites the main
controlling rod and the link E3. Thus the main controlling rod may be said to
be pivotally connected to the foot-board at the point e¹, and the construction is

page_text: such that the parallelism of the foot-board relatively to the chair-seat is preserved
in whatever position of vertical adjustment said foot-board may be placed. At
the same time, owing to the peculiar construction of the pivotal connection be-
tween the main controlling rod and the foot-board, the latter may be folded up
against the supporting-frame and the foot-rest turned over and down upon the
chair seat without disturbing the pivotal connection between the supporting-
frame and main controlling rod and the foot-board. The purpose of this adjust-
ment is chiefly to enable the chair to be conveniently packed for transportation
and also for moving the foot-board out of the way when desired. When the
foot-board and foot-rest are folded up as just described, the notched lugs C¹ C¹
leave their bearing on the pivot el which is held in proper position by the link E
so that when the foot-board is again lowered to its operative position the notched
lugs will necessarily find their proper bearings.
A secondary controlling rod F is located beneath the foot-board and is sustained
in proper horizontal position, and is adapted to have a slight endwise sliding
movement at or near its inner end in a stirrup C2 on the under side of the
foot-board. The secondary controlling rod has pivotal connection at its outer
end with the foot-rest Da short distance below its pivotal connection d with said
foot-board by way of a lug or lugs on said foot-rest. The inner end of the
secondary controlling rod is shown as being enlarged to form a head F adapted
to bear against a rounded projection E3 of the main controlling rod, said projec-
tion extending a short distance forward of the pivot el of said main controlling
rod. By this construction it will be seen that as the head of the secondary
controlling rod bears against the projection of the main controlling rod the
foot-rest is caused to normally project above the surface of the foot-board in
operative position; that when the foot-board is raised to the level of the chair
seat to constitute a leg-rest, as before described, the movement of the projection E³
permits the secondary controlling rod to move inwardly whereby the foot-rest
is caused to drop to or below the level of the foot-board to its inoperative posi-
tion; and that when the foot-board is lowered the projection E3 acts upon the
secondary controlling rod to cause the foot-rest to automatically resume its opera-
tive position, above the level of the foot-board. This construction also allows of
the foot-board being folded up as before described, the head of the secondary
controlling rod being free to leave the projection E³ when the foot-board is folded,
and being assured of coming in proper contact with this projection when the foot-
board is lowered again.
In addition to automatically raising and lowering the foot-rest relatively to
the foot-board by movement of the latter, I have also provided means for enabling
the foot-rest to be dropped to or below the level of the foot-board independently
of the movement of said foot-board and in whatever position the same may
occupy.
The preferred manner of accomplishing this is as follows:-
Instead of pivoting the forward end of the secondary controlling rod directly
to the lug or lugs d² of the foot-rest, I have provided a toggle connection_as
follows: The lugs 2 are on opposite sides of the centre of the foot-rest and a
pivot rod G passes through them. Pivoted upon said rod G near the lugs &
are links G¹ through the opposite ends of which pass a rod G³, the forward forked
end of the secondary controlling rod being pivoted to said rod G³. When the
foot-rest is in its operative position above the foot-board, as shown in the lower
foot-board Fig. 38, the toggle connection is straightened out the links G¹ resting
against the under side of the secondary controlling rod, and the foot-rest cannot
be moved downwardly. By slightly depressing the secondary controlling rod by
means of its operating handle F2 the toggle connection is broken or opened, and
the foot-rest is permitted to drop below the upper surface of the foot-board into
an inoperative position, as shown in the upper foot-board, Fig. 38. A coiled
spring H connecting the foot-board and the secondary controlling rod serves to
assist in restoring the foot-rest to its upright operative position and to return the

page_text: toggle to its closed position which may be accomplished by simply grasping, the
foot-rest and lifting it. A. rubber plug or plugs may be secured upon the foot-
board, and when the foot-rest drops the lugs strike against these plugs,
whereby all noise and jar is prevented. The object in thus dropping the foot-
rest below the upper surface of the foot-board when the same is in its lowest or
medium positions, or in other words, when the foot-board, is in any of its
"operating" positions, is to place it beyond the reach of the feet of a patient
seated in the chair in order to prevent the patient from kicking or bringing undue
pressure to bear upon the foot-rest when undergoing painful operations; or when
under the influence of an anaesthetic. The operating handle of, the secondary
controlling rod may be depressed to drop the foot-rest either by hand or foot,
as desired.
..
In Fig. 45, I have shown a modification of the connection between the foot-
board and foot-rest for permitting the latter to be dropped, and in which the
toggle lever is omitted. This connection may be described as follows:-
Lugs are formed on the foot-rest as before, and are connected by a rod d³.
The outer ends of the secondary controlling rod F are formed with . lower
notches f, upper notches f², and suitable cam surfaces, as shown in the drawing.
When the rod d³ rests in the lower notches f¹ the foot-rest is in its upright
operative position. By depressing the secondary controlling rod F, as
before explained, the lower notches f¹ will leave the rod, and
the foot-rest will drop until the rod d³
comes to rest in the
upper notches 2, the foot-rest being thus held in its inoperative posi-
tion on or below the level of the foot-board. The foot-rest may be
restored to its normal operative position by simply lifting it as before, until the
rod rests in the lower notches f. It will be understood that the spring H
should be employed as in the preferred form. The rod acting upon the cam-
like surfaces of the notched secondary controlling arm provides for an easy and
gradual stopping of the foot-rest, which may thus be dropped without shock or
jar and without the employment of the rubber plugs f, shown in Fig. 38. It
will of course be understood that with the herein described organization of the
foot-board and foot-rest the foot-rest is automatically placed in an inoperative
position whenever the foot-hoard is moved to its uppermost or anaesthetic posi-
tion; and that the foot-rest may also be placed in a similar inoperative position,
when desired, even when the foot-board is in its lowest or any of its operating
positions. Obviously this latter adjustment of the foot-rest may be used in an
organization in which the automatic movement of the foot-rest is omitted.
The foot-board may be locked and sustained in any position to which it may
be vertically adjusted by means as follows:-
An
A pawl I pivoted to or between lugs or brackets a projecting from the central
plate or screen A¹ of the foot-board supporting-frame, is adapted to engage with
the teeth of a ratchet plate E connected to or formed with the main controlling
rod E. A weighted arm or extension I¹ of the pawl serves to normally hold the
pawl in engagement with the ratchet plate. The pawl is keyed upon a rock
shaft I having bearing at one end in said lugs or brackets a² and projecting to
one side of the supporting-frame in which its opposite end has bearing.
operating pedal or handle J is provided for the rock shaft I2 and is located on the
outside of the foot-board supporting-frame. Instead of securing the operating-
handle directly upon the rock shaft 12 upon which the pawl is keyed, I prefer to
key it upon another rock shaft J₁ parallel with the rock shaft I2 and having
bearing in a projection a³ of the side frame A. A lever J2 keyed upon the rock
shaft is connected with a lever I³ keyed upon the rock shaft 12 by means of a
link Ja, whereby the movement of the operating pedal may be transmitted to the
pawl I. The operating pedal or handle J which extends on opposite sides of the
rock shaft J¹, may be operated either by the hand or foot, and serves as the means
for actuating the pawl and also for raising and lowering the foot-board.

page_text: The weight of the foot-board and parts carried thereby is counterbalanced by a
coiled spring K which is connected at one end to a projection E³ on one of the
brackets E and at its opposite end is connected to the main controlling rod E.
The tendency of this spring is to pull the foot-board upwardly, whereby the
same may be raised and lowered with comparative ease...
When it is desired to raise the foot-board the operator's foot or hand is placed
upon the operating handle of the pawl J' and a slight pressure upon the inner
end of said handle serves to rock the pawl out of engagement with the ratchet,
and further downward and forward pressure upon the handle will elevate the
foot-board. Upon relieving the handle of pressure, the pawl, owing to the action
of its weighted arm, will immediately. engage the ratchet and lock the foot-board
in any position to which it may have been elevated. To lower the foot-board
the pawl is tripped, as before, and the foot-board allowed to descend to the desired
the
position. It will be observed that the operating-handle is located at or near
bottom of the foot-board supporting-frame practically on a level with the foot-
board in convenient reach of the operator's foot, and that when it is desired to
but slightly change the vertical position of the foot-board, it can most conveniently
be accomplished by means of the said operating handle. Obviously, however,
the foot-board may be elevated to any desired point by grasping it and lifting
it bodily.
Owing to the particular connection between the pawl I and its operating handle
or pedal, the pivot of said handle or pedal is located more to the rear of the
pivotal connection a between the supporting-frame and the seat frame when the
foot-board is in its lowest position than would be the case were said handle or
pedal secured directly upon the rock shaft I2 of the pawl. In this way a greater
leverage is attained and the foot board may be elevated with greater ease.
A similar result may be attained by the modified construction shown in Fig. 46
in which the link Ja is dispensed with and the pawl I is carried on the same
shaft J to which the operating handle J is secured, said shaft being disposed
obliquely relatively to the side arms A A, as shown.
The side arms A A of the foot-board supporting-frame are preferably extended,
as at A2, a short distance above the pivotal connection a of these arms with the
metallic seat-frame B, the object of this being to cover up the space which would
otherwise be left between the said arms and the seat-frame when the foot-board is
elevated to its nighest position. The upper extensions A2 of the side. arms
project into slots or recesses in the wood base portion or frame L of the
upholstered chair-seat L', which rests upon the metallic seat-frame B.
11
BACK-REST.
'
I will now proceed to describe my improved back-rest as follows: (referring to
Figs. 38 to 47, inclusive, sheets 16 to 20.)
The hinged connection between the back supporting-frame and the seat-frame
is substantially the same as that shown and described in my before-mentioned
Patent, No. 10,496, of 1897, as is also the locking mechanism for holding the
back supporting-frame in any position to which it may be inclined, but the means
for actuating said locking-mechanism is different.
'
The back-rest supporting-frame N consists of two connected side or guide
rails N N straight for the greater portion of their length, but at their lower
ends curved in the arc of a circle to form an arc-shaped hinge-member N³. This
arc-shaped hinge-member N2 is. adapted to fit and move in or upon a corresponding
arc-shaped hinge-member N³ fixed upon the seat-frame B. The arc-shaped hinge-
members are formed with suitable interlocking guide grooves and tongues to
guide and hold the parts in proper relation to each other. A pawl N4 is keyed
upon a rock-shaft N5, journalled upon the back supporting-frame in lugs n n,
the pawl being provided with teeth for engaging a series of notches n¹ on the
fixed hinge-member N³. A plate spring No secured to the pawl N' and bearing
against a portion of the back supporting-frame, serves to keep the pawl engaged

page_text: with the series of notches n¹, except when said pawl is purposely withdrawn
therefrom.
The improved means for actuating the pawl N for withdrawing the same from
locking engagement with the fixed hinge-member for permitting the back-frame
to be tilted backward and forward, is as follows:-
A bell crank controlling lever O is pivoted at o to one of the side rails N¹ of
the back supporting-frame near the top thereof with its long arm O¹ projecting
slightly beyond the side of the side rail of the supporting-frame to which it is
pivoted. To the inner or short arm 02 of the controlling-lever is connected one
end of a connecting-rod or link O3, the opposite end of which is connected to an
arm O keyed upon the rock-shaft N5 to which the pawl N is also keyed. Pres-
sure upon the long arm 0¹ of the controlling-lever rocks its inner or short
arm 0, which motion is transmitted to the arm 04 by the connecting-rod O³ and
the pawl N is rocked downwardly out of engagement with the fixed hinge-
member.
It should be observed that the controlling-lever 0 of the back-frame locking
mechanism is located at a point where the back-frame is grasped by the hands
of the operator when it is desired to change the angle or inclination of the same,
and that when the back-frame is so grasped, one hand of the operator covers the
projecting arm of the controlling-lever, and a slight and natural pressure of this
hand upon the controlling-lever quickly releases the locking mechanism, and the
back-frame may be rocked backward or forward as desired. When the desired
inclination or adjustment of the back-frame has been attained, the operator
simply releases his hold of the same and the locking mechanism automatically
acts to instantly lock the back-frame in its adjusted position. Thus the adjust-
ment of the back-frame may be quickly and easily effected by inclining it forward
as well as backward without the necessity of manipulating any handles, screws or
levers, save the rocking of the controlling-lever which, as before stated, may be
performed by the same movement of the hand required for grasping and moving
the back-frame.
A vertically-adjustable back-pad carrier or frame P is suitably mounted to be
moved up and down upon the back supporting-frame, and a back-pad P1 is hinged
to the top of said frame, but as the construction of these particular parts of the
chair form no part of my present invention, description of them is unnecessary.
For the purpose of quickly and automatically elevating the foot-board to its
uppermost position when it is desired to place the chair in its aforesaid anaes-
thetic position, I have provided mechanism whereby when the back-rest section
of the chair is lowered to a level with the chair seat the foot-board is automati-
cally raised to a level with said seat. I am aware that such a movement is not
broadly new, but I have devised novel and improved means for accomplishing it
which I will now describe.
A link R passing from front to rear of the seat frame of the chair is pivoted
at its forward end to the foot-board supporting-frame a short distance below its
pivotal connection a with the seat-frame B. Said link is shown as being pivoted
between lugs a' on the inner side of the central plate or screen A¹ of the foot-
board supporting-frame. The link is prevented from falling by means of a side
lug near its rear end resting and adapted to travel upon the curved flange or
ledges of a guide plate S secured to the seat-frame. The rear extremity of the
link is notched at ŕ for engagement with a stud n³ on one of the side rails N¹
of the back rest supporting-frame near the lower extremity thereof.
وو
Without further description it will be apparent that the back rest may be
adjusted or rocked back and forth within certain limits to secure all necessary or
desired "operating positions without affecting or moving the foot-board, and
that the foot-board may likewise be raised and lowered to secure various "operat-
ing" positions without affecting the back-rest. The moment, however, the back
is lowered to or beyond the limit of its "operating" positions its stud n³ comes in
contact with the notched end of the link R which transmits the continued down-

page_text: ward movement of the back rest to the foot-board, whereby the latter is raised
to the level of the chair seat simultaneously with the lowering of the back rest
to the level of said seat. After the back rest has been moved to a level with the
chair seat and the lever 0 released the back rest and of course the foot-board
are securely locked in position. When the back is again raised to the point
where its operating positions begin the foot board is automatically lowered to the
beginning of its medium or operating position, at which point the back and the
foot-board are again independently adjustable.
The guide S not only serves to prevent the link R from falling when its notched
end is not engaged by the stud n³ of the back rest, but it also maintains said
link in the proper position to ensure the contact or engagement of the stud and
notched link in whatever position they may happen to be when it is desired to
elevate the foot-board by means of the back-rest.
The number and arrangement of the teeth on the rack plate E of the main
controlling rod is such that the pawl does not act after the foot-board has been
elevated a certain distance, say about midway between its highest and lowest
positions. By this means the foot-board may be adjusted to and locked in any
desired operating position of vertical adjustment from its lowest to its medium
positions in which it is to be used as a foot-board or rest by its operating treadle
and locking pawl; but after the foot-board is raised to its highest position to
form a leg rest as previously explained, it will freely move to its medium position
when the back rest is raised to the beginning of its operating position.
SEAT-FRAME.
As shown in Fig. 39, the seat frame B of the chair is as usual journailed to
rock about trunnions of a yoke or cross head T connected to the upper end
of a chair body supporting plunger A". In Figs. 40 and 41 I have shown an
improved connection between the seat frame and the yoke or cross head. In this
improvement instead of journalling the yoke directly to the sides of the seat
frame, as is customary, it is journalled to trusses B₁ B₁ which extend from front
to rear of the seat frame near and substantially parallel with the sides of said
frame. These trusses B₁ B are bowed or curved upwardly, as shown in Fig. 41,
in order that their central portions to which the yoke is journalled, extend above
the top of the seat frame. The trusses are shown as being cast integral with the
seat frame, although if desired they may be made separate and bolted to the
seat frame.
This construction not only provides a stronger and more rigid seat frame, but
it permits of the use of a shorter yoke or cross head, which obviously has less
spring or yield than the comparatively long cross heads now in common use.
Moreover, this construction enables the trunnions to be located above the scat
frame B and between the frame L of the upholstered seat L', thus elevating the
trunnions and bringing them nearer the centre of weight of the chair-body and
patient, whereby the chair-body is more evenly balanced.
HEAD-REST.
That part of my invention relating to the head-rest (shown in Figs. 48 to 53
inclusive, sheets 21 and 22) consists of certain improvements in the head-rest
proper and also in the support or carrier therefor. The said support or carrier is
in some respects similar to the head-rest support or carrier shown, described and
claimed in my aforesaid Patent, No. 10,496 of 1897. The object of this part of
my invention is to improve the head-rest support or carrier shown in said patent
and at the same time provide a new and improved head-rest proper.
As in my before mentioned patent, the head-rest support or carrier consists of
a jointed stem composed of three sections S, S1 and S2 united together by
universal joints. The lower section S, which is tubular or hollow, is mounted and
adapted to slide up and down on a dove-tailed way P2 of the back-frame N, the
section being formed with a base portion grooved to fit upon and embrace the

page_text: dove-tailed way.
To the upper section S2 is attached the supporting bar T₁ of
the head-rest proper, which will be more particularly referred to hereinafter,
The intermediate section S¹ is connected to its two fellow sections by ball-and-
socket joints. The upper section $2 has a balls on its lower end which fits in a
socket on the upper end of the intermediate section $', this, socket being formed
by a sleeve s¹ screwed upon the section $ and by the concave head s². of an end-
wise movable presser rod S3 fitted in the tubular intermediate section S. The
lower end of this section S¹ has a ball 3 on its lower end which fits in a socket
on the upper end of the lower section S. This socket is formed by a sleeve
screwed upon the section S and the concaved head of an endwise, movable
push piece Sfitted in the upper tubular or recessed end of the section S. The
presser rod S3 passes through and slightly beyond the ball son, the intermediate
section S¹ and bears upon the concave surface of the head of the push piece, S.
Suitable mechanism is provided for clamping the head-rest carrier, upon the
dove-tailed way P2 and simultaneously clamping the ball-joints of the head-rest
carrier together, whereby the head-rest carrier may be made rigid and the same
locked to the back-pad carrier. This mechanism is shown as consisting of a
toggle-lever $5 which acts to cause the push-piece S to clamp the ball 3 in its
socket, the same movement being transmitted to the presser rod $3 to clamp the
balls in its socket, the toggle-lever at the same time clamping the lower section $
of the head-rest carrier to the dove-tailed way P2 of the chair back. The toggle-
lever S5 is placed in the section S in the position shown in Figs. 51 and 52 with
its opposite ends bearing at the top against the push-piece S and at the bottom
against an abutment s6 on the interior of this section. The end of the toggle-
lever which bears against the abutment is bevelled so that when the toggle-
lever is straightened this beveled or wedge-shaped end will be forced against the
dove-tailed way P2. A pressure screw S provided with an external operating
handle or knob s enters the section S 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 lever with the effect of forcing up
the push-piece S and thus locking both joints of the head-rest carrier and the
carrier to the chair back.
It is desirable when the pressure screw Se is operated to unclamp the joints
of the head-rest carrier for the purpose of adjusting the head-rest, that the
various joints of the carrier be self-sustaining; that is to say be yieldingly sup-
ported and yet not allowed to drop or move except when direct pressure is applied
to the head-rest or carrier. This self-sustaining adjustment or condition is re-
quired at all times for the universal or ball-and-socket joints of the carrier, when
the same is unlocked, but the joint between the vertically adjustable carrier and
the chair-back should be perfectly free when it is desired to adjust the carrier up
or down, yet this lock should be self-adjusting when the universal joints are being
adjusted. These important results are accomplished in the following manner :-
Fitted upon the lower end of the stem of the push piece 'S is a socketed slide
piece S7 adapted to slide upon the stem of said push piece inside of a recess
formed in the upper end of the lower section S of the head-rest carrier. One end
of the toggle-lever bears against the slide-piece for pushing the push-piece up-
wardly, and a spring surrounding the stem of the push-piece is confined between
the head of said push-piece and the upper end of the slide piece S7 and acts with
a tendency to force the push-piece and the slide piece apart. A shoulder 12 on
the slide-piece $7, adapted to abut against a shoulder s¹3 on the section S, limits
the downward movement of said slide-piece. A spring S8, preferably having a
coil in it, is secured at its opposite ends to the respective members of the toggle-
lever, for the purpose of holding said members together, without interfering with
their free movement, yet at the same time ensuring the bending or flexing of the
toggle lever when the same is not in action. The lower member of the toggle-
lever S has an opening s4 through it near its lower end, and a headed pin or
bolt projecting from the section S enters said opening. A spring $10 surrounds
$9

page_text: the pin and is confined between the head of said pin and a shoulder s" on the
toggle-lever. The object of this spring is to ensure the toggle-lever being re-
leased from frictional engagement with the dove-tailed way of the back-pad
carrier, when the pressure screw is operated sufficiently to allow of this movement.
From the above description it will be understood that by screwing the pressure
screw in tightly the toggle-lever is caused to firmly lock the carrier to the back-
pad carrier against vertical movement and to simultaneously firmly lock both
universal joints of the carrier; that by unscrewing the pressure screw to a certain
extent all of the joints of the carrier are in a self-sustaining condition, that is to
say, the spring is permitted to exert sufficient pressure on all the joints to
render them tight enough to maintain the carrier in any position to which it may
be moved, but leaving it in a condition to be adjusted by pressure applied to the
head-rest or its carrier. By unscrewing the pressure screw still farther, the
spring forces the slide piece S' downwardly until its shoulder s2 abuts against
the shoulder 13 of the carrier section S, when the springs cannot act upon the
toggle-lever. When in this condition the universal joints are still self-sustaining
as before, but the joint between the carrier and the chair-back is relieved of all
friction, and the carrier may be freely moved up and down, without disturbing
the adjustment of the universal joints.
The head-rest proper consists of two pads T T which are connected to the
supporting-bar T by means of compound or S-shaped clamp links T2 T2. (See
particularly Figs. 48 and 50). These links are each provided with eyes or
openings in their opposite ends which fit upon studs or pivots on the outer
opposite ends of the supporting-bar, and studs or pivots t' on the head-rest pads.
In order to clamp the head-rest pads in their adjusted position each link is pro-
vided with a clamp screw T3 having an operating handle or knob T and which
passes through an opening in one end of the link and through an opening in the
body of the link and screws into the opposite end of the link. Screws (2 screwing
in the links and entering slots, 3 in the studs t, serve to prevent the links from
accidentally coming off the studs, and at the same time limit the turning move-
ment of said links about said studs. The pads may be kept in place on the links
by means of a pin or spring in each link engaging an annular groove in each
stud of the pads. This construction enables the links to turn about their
pivotal connection with the supporting-bar in a line with the plane of said bar
or toward and away from each other, and the head-rest pads to turn about their
pivotal connection with the links, whereby a very wide range of adjustment of
the, head-rest is permitted. Another advantage of this construction is that the
pads are readily detachable from their clamp links and may be reversed.
While I have described and illustrated but a single embodiment of my present
improvements it will be quite obvious to those familiar with the art to which my
invention appertains, that this embodiment is susceptible of many variations and
modifications without departing from the spirit. or scope of my invention. Not
only can the details of construction be modified more or less, but some of the
mechanisms may be used without the others or in different relations and combina-
tions. I therefore wish it to be understood that my invention is not restricted
to the particular details of construction or the precise groupings or combina-
tions of mechanisms herein shown and described.
'
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
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1,.
".
1. The combination, in a dental chair; of the cylindrical pedestal having a
closed bottom and forming an oil reservoir, a supporting-frame consisting of an
outer cylindrical section and an inner cylindrical section, the said outer section
having supporting and rotating connection with said pedestal, and the inner
section extending above the top of the outer section and connected thereto by a
horizontal web located below the top of the. pedestal and above the oil in the

page_text: reservoir, and a detachable cap closing the space between the inner and outer
sections of the supporting-frame above said horizontal web, substantially as and
for the purpose described.
2. The combination, in a dental chair, of the supporting-frame consisting of
connected inner and outer cylindrical sections, the inner section extending above
the outer section, a chair-body supporting plunger mounted to move up and down
in the said inner section of the supporting-frame, plunger elevating mechanism
mounted inside the supporting-frame, and a cap detachably connected
with said supporting-frame, and closing the space between the inner and
outer sections thereof, said cap being independent of said elevating mechanism,
whereby when said cap is detached, the said elevating mechanism is exposed to
view and the operation of the same is not interfered with, substantially as
described.
3. The combination, in a dental chair, of a supporting frame having an inner
cylindrical section, a fixed plunger cylinder rigidly connected to said supporting-
frame, a cylindrical telescopic plunger member movable up and down in said
fixed plunger cylinder, a guide cylinder connected to the upper end of said
cylindrical plunger member and movable up and down therewith, said guide
cylinder surrounding the said fixed plunger cylinder and having bearing in the
upper end of said inner cylindrical section of the supporting-frame, a piston
member of the telescopic plunger fitted to move up and down in said cylindrical
member of said plunger, and also having bearing in said guide cylinder at the
top thereof, and a chair-body mounted upon the upper end of said piston member
of the telescopic plunger, substantially as and for the purpose set forth.
4. The combination, in a dental chair, of the non rotatable base, a supporting-
frame having bearing in said base and adapted to be horizontally rotated therein,
and means for automatically locking said supporting-frame to said base, substan-
tially as and for the purpose set forth.
5. The combination, in a dental chair, of the non-rotatable base, the chair-body
mounted thereon and adapted to be horizontally rotated relatively thereto, auto-
matic clamp mechanism for normally locking the chair-body to the base against
horizontal rotation, and means for releasing the automatic clamp mechanism for
permitting the chair-body to be rotated, substantially as set forth.
6. The combination, in a dental chair, of the non-rotatable pedestal, a support-
ing-frame having bearing in said pedestal and adapted to be horizontally rotated
therein, a clamp-rod mounted to turn in bearings in said supporting-frame, a
clamp actuated by said clamp-rod, a spring acting upon said clamp-rod for
normally causing said clamp to clamp said supporting-frame to the pedestal
against rotation therein, and means for turning said clamp-rod against the stress
of said spring for unclamping said supporting-frame and permitting the same
to be rotated, substantially as described.
7. The combination, in a dental chair, of the non-rotatable pedestal, a sup-
porting-frame having bearing in said pedestal and adapted to be horizontally
rotated therein, a clamp rod mounted to turn in bearings in said supporting-
frame, a clamp actuated by said rod, a bell-crank lever connected to said clamp-
rod, a spring connected to one arm of said bell-crank lever for causing said clamp
to normally clamp said supporting-frame to the pedestal against rotation, and a
controlling-lever for acting upon the other arm of said bell-crank lever for un-
clamping said supporting-frame and permitting the same to be rotated, substan-
tially as described.
8. The combination, in a dental chair, of the non-rotatable pedestal, a sup-
porting-frame having bearing in said pedestal and adapted to be horizontally
rotated therein, a vertical clamp-rod mounted to turn in bearings in said sup-
porting-frame and having a cam surface, a clamp block mounted to slide horizon-
tally in a hearing in said supporting-frame and adapted to bear against said
pedestal, said clamp block being borne upon by the cam surface of said clamp

page_text: rod, and means for actuating said clamp-rod for causing the clamp block to clamp
and unclamp the supporting-frame to and from the pedestal, substantially as
described.
9. In a dental chair-body support the combination of the plunger, the cylinder
in which said plunger is movable up and down, a buffer-rod fitted in the lower
end of said plunger, and means for normally projecting said buffer-rod from said
plunger, substantially as and for the purpose described.
10. In a dental chair-body support, the combination of the plunger formed
with an oil chamber in its lower end, the cylinder in which said plunger moves
up and down, a buffer-rod having a head movable up and down in said oil-
chamber, the oil being adapted to pass said head to and from said oil-chamber,
whereby when the buffer rod strikes the bottom of said plunger cylinder, the oil
confined in the oil-chamber gradually escapes and cushions the final downward
movement of the plunger, substantially as described.
11. In a dental chair-body telescopic supporting plunger, the combination of
the fixed plunger cylinder, the cylindrical plunger member movable up and
down therein, the guide cylinder connected to said cylindrical plunger member
and movable up and down therewith and surrounding said fixed plunger cylinder,
and a buffing-device on the lower end of said guide cylinder, substantially as and
for the purpose described.
12. In a dental chair-body telescopic supporting plunger, the combination of
the fixed plunger cylinder, the cylindrical plunger member movable up and down
therein, the guide cylinder connected to said cylindrical plunger member and
movable up and down therewith and surrounding said fixed plunger cylinder, a
buffing-device on the lower end of said guide cylinder, the piston member of the
plunger movable up and down in said cylindrical member and said guide cylinder,
and a buffing-device located between the top of said guide cylinder and the
bottom of said piston member, substantially as and for the purpose described.
13. The combination, in a dental chair, of a vertically movable chair-body sup-
porting-plunger, clamping mechanism therefor comprising a horizontally movable
toggle-lever, a spring acting upon said toggle-lever for causing the same to
normally clamp said plunger and means for unclamping said toggle-lever, the
said clamping mechanism acting to clamp the plunger against upward and
downward and lateral movement at all times except when acted upon by the
means for unclamping it, substantially as described.
14. The combination, in a dental chair, of a telescopic supporting-plunger,
separate locking devices for each member of said telescopic-plunger, a horizontally
movable toggle-lever for simultaneously operating said lecking devices, and
means for actuating said toggle-lever, substantially as and for the purpose set
forth.
13. The combination. in a dental chair, of a telescopic supporting-plunger,
separate clamping devices for each member thereof, a toggle-lever, a spring
acting upon said toggle-lever for causing the clamping devices to normally clamp
the telescopic supporting plunger, and means for simultaneously unclamping
said clamping devices, substantially as and for the purpose described.
16. The combination, with a chair-body supporting plunger, of clamping
mechanism therefor comprising a toggle-lever, the outer member of which is
composed of two parts having sliding connection with each other, and an adjust-
able fulcrum piece against which one part of said outer member of the toggle-
lever has bearing, substantially as and for the purpose described.
17. The combination, in a dental chair, of a telescopic supporting-plunger,
separate locking devices for each member thereof, a toggle-lever, one member.
of which is provided with two arms, a spring acting upon the toggle-lever
through one of its arms for causing the separate locking mechanisms to simul-
taneously grip the respective members of the telescopic plunger, and means for
acting upon the toggle-lever through its other arm for causing said locking

page_text: mechanisms to release the said plunger member, substantially as and for the pur-
pose set forth.
18. The combination, in a dental chair, of the supporting-frame, the telescopic
plunger movable up and down therein, the clanıp bar arranged parallel with
the outer member of the telescopic plunger, the clamp block fitted to move in an
opening in the outer member of the telescopic plunger to bear upon the inner
member thereof and be acted upon by the clamp bar, and a toggle-lever for
simultaneously causing the clamp bar and clamp block to clamp the members of
the plungers together and to the supporting-frame, substantially as and for the
purposes described.
19. The combination, in a dental chair, of the supporting frame, a telescopic
supporting plunger movable up and down in a cylinder of said supporting-
frame, a clamp bar arranged parallel with the outer member of said telescopic
plunger to which said clamp bar is connected in such a way as to be capable of
being rocked horizontally, means fór horizontally rocking said clamp bar "to
force it to clamp the outer member of the telescopic plunger to the said support-
ing-frame, and means for transmitting the movement of said clamp bar to the
inner member of said telescopic plunger, whereby when the clamp bar is actuated
the members of the telescopic plunger are simultaneously clamped in the support-
ing-frame in any position of vertical adjustment they may occupy; substantially
as described.
20. In elevating mechanism for dental chair, the combination of the pump
cylinder, and its top or gland, the piston movable up and down therein and
formed with an enclosed oil-space and an exposed oil-recess, and also having a
passage way between said oil-space and said oil-recess, the said passage way
opening into the oil-space a short distance above its lower end, whereby just
before the piston reaches the end of its upstroke the said passage way is closed
and the oil confined in the oil-space serves to cushion the piston at the end of its
upstroke, substantially as described.
21. The combination, in a dental chair, of a base, a detachable cap or dome for
the same, a plunger cylinder supported therein, an upright pump cylinder sup-
ported by the side of said plunger cylinder, a communicating passage way
between said cylinders, a valve containing plug screwing into the top of said
passage way and located in a plane above the top of the upright pump cylinder in
a readibly accessible position, a normally closed outlet or lowering valve con-
tained in said plug, and means for tripping said valve, whereby when the detach-
able cap or dome is removed the said valve containing plug is exposed and may
be readily detached, substantially as and for the purpose described.
22. The combination, in a dental chair, of the base, a detachable cap or dome
for the same, a plunger cylinder supported therein, an upright pump cylinder
supported by the side of said plunger cylinder, a communicating passage way
betwen said cylinders, a valve containing plug screwing into the top of said
passage way and located in a plane above the top of the upright pump cylinder in
a readily accessible position, a normally closed outlet or lowering valve con-
tained in said plug, means for tripping said valve, a valve for preventing return
of oil to the pump cylinder from said plunger cylinder also contained in' said
plug, whereby when the detachable cap or dome is removed the said valve con-
taining plug is exposed, and may be readily detached, substantially as described.
23. The combination, in a dental chair, of the base, a supporting-frame mounted
therein, a plunger cylinder fixed to said supporting-frame a casting having
detachable connection with said supporting-frame, a pump and its valves carried
by said casting, a passage way in said supporting-frame communicating with
the plunger cylinder, a passage way in said casting communicating with the pump,
said passage ways being adapted to register with each other when the casting is
in place, and a bolt passing through said casting into the said supporting-frame
for detachably connecting said casting to said supporting-frame, the head of said
bolt extending above the top of the pump in a readily accessible position, whereby

page_text: the casting, the pump and its valves may be removed as a whole from the base
without disturbing other mechanisms contained within said base, substantially
as described.
!
24. In elevating and lowering mechanism for dental chairs, the combination of
the outlet or lowering valve the stem of which projects above the top of the plug
in which the valve is mounted, and a flanged 'cap. secured to said valve stem.
above said valve plug, substantially as and for the purpose described.
25. In elevating and lowering mechanism for dental chairs, the combination.
of the outlet or lowering valve the stem of which projects above the top of the.
plug in which the valve is mounted, and a flanged cap secured to said valve stem.
above said valve plug, the flange of said cap loosely surrounding the top of said
valve plug, whereby the oil escaping from around the valve stem when the valve
is opened, strikes against the flanged cap and is thereby deflected downwardly
substantially as described.
26. In a dental chair, the combination of the base, a supporting-frame mounted
to rotate horizontally therein mechanism' for locking said supporting-frame to
said base, a vertically adjustable supporting plunger, clamping mechanism for.
the same, plunger elevating and lowering mechanism, and a single operating
lever for controlling all of said mechanisms, substantially as and for the pur-
poses described.
:
27. In a dental chair, the combination of the base, a supporting-frame mounted
to rotate horizontally therein, mechanism for locking said supporting-frame to
said base, a vertically adjustable supporting plunger, clamping mechanism for
the same, plunger elevating mechanism, and a single operating lever for con-
trolling all of said mechanisms, substantially as and for the purposes described.
28. In a dental chair, the combination of the base, a supporting-frame mounted
to rotate horizontally therein, mechanism for locking said supporting-frame to
said base, a vertically adjustable supporting plunger, clamping mechanism for
the same, plunger. lowering mechanism, and a single operating-lever for con-
trolling all of said mechanisms, substantially as and for the purposes described.
29. In a dental chair, the combination of the base, a supporting-frame mounted
to rotate horizontally therein, 'mechanism for locking said supporting-frame to
said base, à vertically adjustable supporting-plunger, elevating and lowering
mechanism therefor, and a single operating lever for controlling all of said
mechanisms, substantially as and for the purposes described.
30. In a dental chair, the combination of the base, a supporting-frame mounted
to rotate horizontally therein, mechanism for locking said supporting-frame to
said base, a vertically adjustable supporting plunger, mechanism for locking said
plunger, and a single operating lever for controlling said mechanisms, sub-
stantially as and for the purpose described.
31. The combination, in a dental chair, of the base, the supporting-frame sup-
ported by and adapted to rotate horizontally therein, mechanism for clamping the
supporting-frame to said base, the chair-body, supporting plunger vertically
adjustable in the supporting-frame, mechanism for elevating the supporting.
plunger, and a single lever for both operating the plunger elevating mechanism
and for controlling the mechanism for clamping the supporting-frame to the
pedestal, substantially as set forth.
$
32. The combination, in a dental chair. of the base, a supporting-frame mounted
to rotate horizontally therein, a vertically adjustable supporting plunger elevat-
ing mechanism for the same, automatic clamp mechanism for normally locking
said supporting-frame to said base, and means for releasing said automatic clamp
mechanism for permitting said supporting-frame to be rotated, said means being
under the control of the operating-lever of the plunger elevating mechanism,
substantially as and for the purpose described. .
33. In a dental chair the combination of the base, the supporting-frame, the
»lunger. plunger elevating mechanism, a post mounted upon said supporting-
frame and having horizontal turning connection therewith, and an operating

page_text: lever for said plunger elevating mechanism connected at its inner end to said
post by a horizontal pivot, whereby said operating-lever may be rocked vertically
independently of said post and be moved horizontally therewith, substantially
as and for the purposes described.
34. The combination, in a dental chair, of the vertically adjustable supporting
plunger, the fixed plunger cylinder, the pump, an operating lever for actuating
said pump by vertical movement, a communicating passage way between said
pump and said fixed plunger cylinder, an outlet valve in said passage way, a
pivoted arm bearing upon the stem of said outlet valve and adapted to be rocked
downwardly for tripping said outlet valve by horizontal movement of said operat-
ing-lever, substantially as described.
35. The combination, in a dental chair, of a vertically adjustable supporting
plunger, plunger clamping mechanism, plunger elevating mechanism; a lever
connected to said plunger clamping mechanism, a spring connected to said lever
for causing the plunger clamping mechanism to normally clamp the plunger, an
operating lever for the plunger elevating mechanism, and connections between
said operating lever and said lever of the plunger clamping mechanism, whereby
when the operating lever is moved into a position for operating the plunger
elevating mechanism, the plunger clamping mechanism is automatically un-
clamped, substantially as described.
36. The combination, in a dental chair, of a vertically adjustable supporting-
plunger, plunger clamping mechanism, plunger elevating mechanism and plunger
lowering mechanism,, a lever connected to said plunger clamping mechanism, a
spring connected to said lever for causing the plunger clamping mechanism to
normally clamp the plunger, a single operating-lever for the plunger elevating
and lowering mechanisms, and connections between said operating-lever and said
lever of the plunger clamping mechanism, whereby when the operating-lever is
moved to operate either the plunger elevating mechanism or the plunger lowering
mechanism, the plunger clamping mechanism is automatically unclamped, sub-
stantially as described.
37. The combination, in a dental chair, of the base, the supporting-frame
rotatably mounted therein, mechanism for clamping said supporting-frame to
said base, a vertically adjustable supporting plunger, clamping mechanism for
the same, plunger elevating mechanism, plunger lowering mechanism, a lever,
a spring connected to said lever for causing the supporting-frame clamping
mechanism and the plunger clamping mechanism to normally act, a single
operating-lever and connections, whereby when said operating-lever is moved in
one direction to operate either the plunger elevating mechanism or the plunger
lowering mechanism the plunger clamping mechanism is automatically un-
clamped and the clamping mechanism for the supporting-frame is undisturbed,
and when said operating-lever is moved in the opposite direction, said clamping
mechanism for the supporting-frame is unclamped, substantially as described.
38. In a dental chair, the combination of the base, the supporting-frame
mounted to rotate horizontally therein, mechanism for clamping the supporting-
frame to said base, a vertically adjustable supporting plunger, mechanism for
elevating said supporting plunger, and a single lever which operates said plunger
elevating mechanism when moved vertically and unclamps the supporting-frame
clamping mechanism when moved horizontally in one direction, substantially as
and for the purpose described.
39. The combination, in a dental chair, of the base, the vertically adjustable
chair-body supporting plunger, elevating and lowering mechanism therefor, a
single operating lever for controlling these mechanisms, said operating lever
having its pivotal and operative connections inside said base, substantially as
and for the purpose described.
40. The combination, in a dental chair, of the base, the vertically adjustable
chair-body supporting plunger, elevating, lowering, and clamping mechanism
therefor, and a single operating lever for controlling these three mechanisms,

page_text: said operating lever having its pivotal and operative connections inside said base,
substantially as and for the purpose described.
41. The combination, in a dental chair, of the base, the, supporting-frame
rotatably connected with said base, the vertically adjustable chair-body sup-
porting plunger, locking mechanism between the base and the supporting-frame,
plunger elevating, lowering and clamping mechanism, and a single operating
lever for controlling all of these mechanisms, said operating lever having its
pivotal and operative connections inside said base, substantially as and for the
purpose described.
42. An operating lever for dental chairs pivoted to rock vertically and turn
horizontally and provided with an arm which moves vertically with said lever,
and with a controlling-arm which moves horizontally with said lever but is not
affected by vertical movement of the same, substantially as and for the purpose
described.
43. The combination, in a dental chair, of a vertically movable chair-body
supporting-plunger, clamping mechanism therefor comprising a horizontally
movable toggle-lever, a spring acting upon said toggle-lever for causing the same
to normally clamp said plunger, and means under the control of the operating or
elevating lever of the chair for unclamping said toggle-lever, substantially as
described.
44. An operating lever for dental chairs having a flange thereon inside the
chair base or pedestal for the purpose of deflecting all oil on the inner portion
of the lever into the oil reservoir and preventing the same from reaching that
portion of the lever which projects outside of said base or pedestal, substantially
as described.
45. The combination, in a dental chair, of the vertically adjustable supporting
plunger, the pump for elevating said plunger, an operating lever for said pump,
and a piston rod having ball-and-socket connection with said operating lever and
also with the piston of said pump, whereby said operating lever may be moved
horizontally as well as rocked vertically, substantially as described.
46. The combination with the seat of a dental chair, of the foot-board sup-
porting-frame hinged thereto, the foot-board hinged to the lower end of said
frame, means for maintaining the parallelism of said foot-board reatively to
said seat when the former is vertically adjusted a foot-rest carried at the outer
end of the foot-board and normally occupying a position above the level of the
plane of the same, and means for automatically moving the foot-rest into a
position on a level with or below the upper surface of the foot-board when said
foot-board is moved into a position on a level with said seat, substantially as and
for the purpose described.
47. The combination with the seat of a dental chair, of the foot-board sup-
porting-frame hinged thereto, the foot-board hinged to the lower end of said
supporting-frame, a foot-rest hinged to the outer end of said foot-board and
normally occupying a position above the level of the same, a main controlling
rod pivoted to said seat and to said foot-board, a secondary controlling rod
pivoted to the main controlling rod and to the foot-rest, whereby when the foot-
board is raised to the level of the seat, the foot-rest is automatically moved into a
position on a level with the foot-board, and means for locking the foot-board
in any position to which it may be adjusted, substantially as and for the purpose
described.
48. The combination with the seat of a dental chair, of the foot-board_support-
ing-frame hinged thereto, the vertically adjustable foot-board hinged to the
lower end of said foot-board frame. mechanism for locking the foot-board in its
vertically adjusted position, and a lever located substantially on a line with the
plane of said foot-board for controlling said locking mechanism and by means of
which the foot-board may he raised and lowered, substantially as and for the
purpose described.
49. The combination with the seat of a dental chair, of a foot-board supporting-

page_text: frame hinged thereto, a vertically adjustable foot-board hinged to the lower end of
said supporting-frame, a controlling-rod pivoted to said seat and to said foot-
board, a rack upon said controlling-rod, and a rocking pawl carried by said support-
ing-frame, substantially as and for the purpose described.
50. The combination with the foot board of a dental chair, of a foot rest pivoted
to the outer end thereof, means for sustaining said foot rest in an upright opera-
tive position above the level of said foot board, and means whereby said foot-rest
may be caused to drop into an inoperative position to or below the level of said
foot-board, substantially as and for the purpose described.
51. The combination with the foot board of a dental chair, of a foot-rest pivoted
to the outer end thereof, and a toggle-lever connection between said foot-board
and said foot-rest, whereby when the toggle-lever is straightened out the foot-
rest is sustained in an upright operative position above the level of the foot-board
and when the toggle-lever is opened the foot-rest is permitted to drop to or below
the level of the foot-board into an inoperative position, substantially as and for
the purpose described.
..
52. The combination with the seat of a dental chair, of a foot
board supporting frame hinged thereto, a foot board hinged to the
lower end of said supporting-frame, a foot-rest pivoted to the outer end of said
foot-board, a main controlling-rod pivoted to said chair seat and to said sup-
porting-frame, a secondary controlling rod connected at one end with said main
controlling-rod, and a toggle-lever connection between the opposite end of
said secondary controlling rod and said foot-rest, whereby when said toggle-
lever connection is straightened out the foot-rest is normally sustained in an
upright operative position above the level of said foot-board and when said
foot-board is raised to its uppermost position on a level with said chair-seat the
foot-rest is automatically moved to a position on a level with or below the
surface of said foot-board, and when said toggle-lever connection is opened or
broken the said foot-rest drops to or below the level of the foot-board independ-
ently of the movement of said foot-board, substantially as described.
53. The combination, in a dental chair, of the foot-board, the foot-rest pivoted
to the outer end thereof and adapted to normally occupy an operative position
above the level of said foot-board. and a supplemental foot-rest pivoted to the
outer end of said foot-rest, and adapted to be turned into two operative positions
nearer to and farther away from the foot-board, by rocking it about its pivotal
connection with said foot-rest, substantially as and for the purpose described.
54. The combination, in a dental chair, of the metallic seat-frame, an uphol-
stered seat fitted thereon, and provided with a wood base having slots or recesses
in its opposite sides, a foot-board and side arms forming the supporting-frame
for said foot-board and pivoted to said metallic seat-frame, said side arms
extending a short distance above their pivotal connections with said, metallic
scat frame, said extensions being adapted to enter the slots or recesses in the
wood base of the upholstered seat when the foot-board is in any of its low
positions, substantially as and for the purpose described.
55. The combination, in a dental chair, of the seat, a back supporting-frame
hinged thereto and adapted to be rocked vertically, means for locking said back
supporting-frame in any position to which it may be rocked, and a controlling
handle pivoted to said back supporting-frame to rock transversely thereof, whereby
said locking means may be controlled by moving said lever transversely of the
back supporting-frame, substantially as and for the purpose described.
56. The combination, in a dental chair, of the seat, a back supporting-frame
hinged thereto and adapted to be rocked vertically, an automatic lock for nor-
mally locking said back supporting-frame in any position to which it may be
rocked, a controlling lever for said lock pivoted to said back supporting-frame
and having its handle projecting from the side thereof, whereby when the handle
of said controlling lever is pressed inward, the lock is released and the back
supporting-frame is free to be rocked vertically, substantially as described.

page_text: 57: The combination,-in a dental chair of the seat provided with a fixed arc-
shaped hinge-member having detent notches therein, a back supporting-frame
provided with an arc-shaped hinge-member having sliding connection with said
fixed hinge-member, a pawl pivoted to said back supporting-frame and normally
in engagement with the detent notches of said fixed hinge-member, a controlling
lever pivoted to said back supporting-frame near its upper end and having its
handle projecting from the side thereof, and a connection between said pawl and
said controlling lever, whereby when the handle of the latter is pressed inward
the pawl is disengaged from the notches of the fixed hinge-member, sub-
stantially as and for the purpose described.
58. The combination, in a dental chair, of the seat, a vertically adjustable
foot-board hinged to the front thereof, a foot-rest carried at the outer end of
said foot-board and normally occupying a position above the level of the same,
a back rest hinged to the rear of said seat frame, and connections between said
back rest and said foot-board and between said foot-board and said, foot-rest;
whereby the back rest and the foot-board may be independently adjusted to
various operating positions within certain limits, but when the back rest is
lowered to a level with the seat, the foot board is automatically elevated to a
level with said seat and said back rest, and the foot rest is automatically lowered
to or below the level of said foot-board, to bring the back-rest, the seat, the
foot-board and the foot-rest into alignment, substantially as and for the purpose
described.
59: The combination, in a dental chair, of the seat, a vertically adjustable
foot-board hinged to the front thereof, a back-rest hinged to the rear of said seat
and adapted to rock vertically, both the back-rest and the foot-board being
capable of adjustment to a level with said seat, a link pivoted to the foot-board
and provided with a side lug, and having its rear end notched, a fixed guide plate
having a curved flange or ledge upon which the said side lug of the link rests
and travels and a stud on the back-rest adapted to engage the notched end of
salink, whereby when the back-rest is lowered to a level with the seat the foot-
rest is thereby automatically elevated to a level with said seat, substantially as
and for the purpose described.
60. The combination, in a dental chair, of the seat-frame, trusses extending
from front to rear thereof and substantially parallel with the sides of said frame,
said trusses also extending above the top of said frame, a chair-body supporting-
plunger, and a yoke or cross head connected to said plunger, the seat-frame being
journalled to said cross head by way of the trusses, the journals being located
at a point above the level of the seat-frame, substantially as and for the purpose
described.
61. The combination of a head-rest supporting-stem or carrier composed of
sections, universal joints between the sections of said stem, a handle located upon
one of the sections, means controlled by said handle for locking all of said
joints simultaneously and by one movement of the handle, and means for yield-
ingly supporting the stem when the joints have been unlocked by the handle,
substantially as and for the purpose described.
62. In combination with a chair-back, a head-rest supporting stem or carrier
composed of sections, universal joints between the sections of said stem, a
vertically sliding connection between the lower section of said stem and said
chair-back. means for simultaneously locking said universal joints and said
vertically sliding connection, and means for yieldingly clamping said joints and
said connection, when said locking means are unlocked, substantially as and
for the purpose described.
63. In combination with a chair-back, a head-rest supporting-stem composed
of sections, universal joints between the sections of said stem, a vertically sliding
connection between the lower section of said stem and a chair-back, a handle
located upon said lower section, means under the control of said handle for simul-
taneously locking said universal joints and said vertically sliding connections,

page_text: means for yieldingly clamping said universal joints when said locking means
are unlocked, and means, also under the control of said handle, for either yield-
ingly clamping said vertically sliding connection or leaving the same free, sub-
stantially as and for the purpose described.
64. The combination with a chair-back, of a head-rest supporting stem com-
posed of sections, ball-and-socket joints between the sections of said stem, a
vertically sliding connection between the lower section of said stem and said
chair-back, means carried by said lower section for rigidly clamping the same
in its position of vertical adjustment on said chair back, a push piece mounted
in the upper end of said lower section for clamping the ball-and-socket joint
between said lower section and the section connected thereto, a slide piece located
between said push piece and said means for clamping the stem to the chair-back
for transmitting locking or clamping pressure from said clamping means to said
ball-and-socket joint, and a spring acting with a tendency to force said push
piece and said slide piece away from each other, substantially as and for the
purpose described.
65. The combination in a head-rest, of an adjustable supporting stem or
carrier, a supporting-bar adjustably connected midway its length to said support-
ing-stem or carrier, studs projecting at right angles from the opposite ends of
said supporting-bar, two clamp links each of which is fitted at one end to
swivel about the respective studs of the supporting-bar, whereby said links are
capable of being rocked in a line with the plane of said supporting-bar or toward
and away from each other, two head-rest pads each pivoted to the outer end
of the respective clamp links, whereby said pads are capable of being rocked in
the line of movement of said clamp links, and means for simultaneously clamping
and unclamping the pivotal connections of each clamp link and its respective
head-rest pad and stud of the supporting-bar, the clamping means for one link
being independent of the clamping means for the other link, substantially as
described.
Dated this 25th day of September AD 1800.
BASIL MANLY, WILKERSON.