Improvements in Dental Chairs.
Year: 1894

page_text: Date of Application, 12th June, 1894-Accepted, 14th July, 1894
Improvements in Dental Chairs.
I, ARTHUR WILLIAM BROWNE, of Prince's Bay, in the County of Richmond
and State of New York, United States of America, Manufacturer, 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 certain improvements, substantially such as hereinafter
described and claimed, in means for imparting a wide range of vertical adjustment
to the bodies of dental chairs and for maintaining them in any desired position of
adjustment.
In the accompanying drawings showing a suitable embodiment of my invention,
and modifications thereof, with the chair body omitted,
Fig. 1, Sheet 1, is a view in side elevation.
Fig. 2, Sheet 2, is a view in rear elevation.
Fig. 3, Sheet 3 is a view partly in plan, with various parts omitted, and partly
in section on the line 3 of Fig. 1.
Fig. 4, Sheet 3, is a detail view, partly in front elevation, and partly in section
on the line 4 of Fig. 3.
Fig. 5, Sheet 2, is a view partly in front elevation and partly in section on the
line 5 of Fig. 3.
Fig. 6, Sheet 1, is a plan view of the upper arms of the supplementary parallel
arms.
Fig. 7, Sheet 1, is a plan view of the lower arm of the main parallel arms, and
also showing partly in section a portion of the link or tension rod connecting the
supplementary parallel arms with the turning support.
Fig. 8, Sheet 1, is a plan view of said tension rod.
Fig. 9, Sheet 1, a plan view of a modification..
Figs. 10 and 11, Sheets 1 and 2, are side elevations showing portions of the
parallel arms with modifications of the means whereby the supplementary arms are
caused to rock about their jointed connection with the main arms.
Figs. 12 to 16, inclusive, Sheets 4 and 5, show another modification,
Fig. 12 being a view mainly in side elevation, some parts being in vertical section ;
Fig. 13 a rear elevation, with the elevating lever in section; Fig. 14 a view in
perspective of a portion of the raising and lowering mechanism, particularly
showing details of construction of the curved rack thereof; Fig. 15 a view on an
enlarged scale partly in plan, and partly in section on the line 4 of Fig. 12, showing
features of the mechanism for retarding descent of the chair body support; and
Fig. 16 a view in perspective of the detached rotary arms of the retarding
mechanism.
Referring now to Sheets 1, 2 and 3 of the drawings, it will be seen that a
recessed or hollow base A is provided with an internal annular ledge or shoulder a
constituting a seat upon which is supported a circular plate or disk B which is
adapted to turn horizontally and constitutes in connection with two standards B' B',
which are rigid therewith, a turning support for vertically adjustable mechanism
which carries the chair body. A ring A screwed to the base and overlapping the
disk B of the turning support serves to hold this disk down to its seat in the base.
Any suitable means permitting of the adjustment of the turning support whilst
serving to lock it against movement after adjustment may be employed.
The vertically adjustable mechanism for raising and lowering the chair body is

page_text: "
'
"
as follows: A set of parallel arms, in this instance two such arms C C (herein
after termed the main parallel arms) are jointed at their inner or rear ends to and
between the standards of the turning support by means of pivoting rods bb
passing through bearings of the arms, and through the standards to which they are
fastened. The lower arm C' of the main parallel arms C C¹ terminates at its rear
or inner end in a downwardly projecting curved extension C' rigid therewith and
constituting a lever for a purpose in turn to be explained. At their front or outer
ends the main parallel arms have connection with each other by way of links D D
to the upper and lower ends of which the arms are jointed by pivots cc cc. A
set of supplementary parallel arms shown as consisting of two pairs of such
arms E E F F have jointed connection with the main parallel arms by means of
the links D, D¹ and pivots c c c c at their front ends, whilst at their rear ends the
supplementary arms E E' F F1 are pivoted to a chair body carrier G at e e
and ff. At their front ends the supplementary arms E F terminate in
downwardly projecting extensions à d' curved or converging toward each other and
connected at their front extremities to constitute an actuating lever. A link or
tension rod H is jointed at one end to this actuating lever at h, and at its other end
to the standards B' B' of the turning support at h' ', this link rod being forked
at its inner or rear end so as to embrace the standards. For this link coupling H
a chain or equivalent jointed connection may be substituted. A suitable chair
body (not shown) is to be attached in well known way to the upper end of the
carrier G.
A reservoir I for oil or other liquid, and a horizontal cylinder I are carried by
the disk B of the turning support, with which they are rigid. A piston J adapted
to be moved horizontally in the cylinder is connected by the connecting rod J¹
with the extension or actuating lever C of the set of main parallel arms, the
connecting rod being pivoted at its opposite ends to the piston and said actuating
lever. The liquid reservoir is adapted to communicate with the cylinder in rear
of the piston by a liquid way or passage K at the side of the cylinder and provided
at or near its opposite extremities with spring-actuated valves kk. The valve l
when opened against the pressure of its spring admits liquid to the passage K, and
when the valve k is opened against the pressure of its spring liquid is allowed to
pass from this passage to the cylinder behind the piston. These valves are herein-
after termed the inlet valves. A liquid way or passage L at the side of the
cylinder opposite that at which the passage K is located is provided with a valve /
(hereinafter called the outlet valve) normally held closed by a spring. When this
valve is opened liquid is allowed to pass slowly from behind the piston, to the
reservoir by the passage L. A foot-actuated lever M pivoted over the horizontal
cylinder engages a rod or stem of the outlet valve land serves to trip, the valve
when the outer end of the lever is depressed. An elevating lever N pivoted at
to one of the standards of the turning support, is normally maintained in its
elevated or inoperative position by a spring, O. This lever is coupled by a
⚫ connecting rod or link p to a pump piston P working in its cylinder Q at the side
of the cylinder 11. The liquid passage K' is intersected by and communicates with
this pump cylinder. The reservoir has a slot in its top through which the
actuating lever C' projects for engagement with the connecting rod J.
From the above description it will be seen that when the elevating lever is
actuated to work the pump piston, liquid from the reservoir will be forced into the
cylinder behind its piston, thus forcing forward the cylinder piston and by its
connecting rod actuating the lever C of the set of main parallel arms to rock
upward their outer ends. The supplementary parallel arms are at the same time
elevated with the outer ends of the main parallel arms and are also caused to rock
about their pivotal connection therewith by means of the jointed coupling connection
between the turning support and the actuating lever of the set of supplementary
parallel arms. In this way the chair body carrier may be quickly elevated to any
desired extent. To gradually lower the chair body carrier the outlet valve is
tripped to permit of escape of the liquid from the cylinder behind its piston, and

page_text: thus allow this piston to be moved inward to the extent desired by the weight of
the chair body and its elevating mechanism.
It will be seen that by the employment of the horizontal reservoir, cylinder, and
piston, the elevating mechanism may be mounted upon its support low down or
near the floor upon which the support rests and yet admit of a desirable wide range
of vertical adjustment of the chair body.
My improvements may be modified in various ways whilst still retaining novel
features of my invention. When a range of vertical movement less than that
which may be imparted by the employment of the supplementary parallel arms in
addition to the main parallel arms will answer, the set of parallel arms which are
jointed directly to the support may be employed without the supplementary arms,
and the chair body carrier be jointed to the outer ends of the set of arms which are
jointed to the support; and this set of arms instead of consisting of two members
may consist of four members, two in place of each arm C C as will readily be
understood, whilst instead of the upper arms E F of the set of supplementary
parallel arms being made in two separate parts they may be in one piece as shown
by Fig. 9. Although it is preferable to have the support for the parallel arms
mounted upon the base so as to turn horizontally, the turning movement of this
support might be dispensed with and a rigid connection made between it and its
carrying base, in which event the chair body could be mounted to turn about the
upper end of its carrier in suitable well known way. Instead of the supplementary
parallel arms being provided with the actuating lever and controlling link H, other
equivalent means for causing them to rock about their jointed connection with the
main parallel arms may be provided, such, for instance, as shown by Fig. 10, in
which two gear segments RS meshing with each other are rigidly attached to or
formed with the outer ends of the arms E F, and C', respectively. In Fig. 11 the
actuating lever of the supplementary parallel arms is made shorter than elsewhere
shown, and the link H connects this actuating lever with the lower one (C¹) of the
main parallel arms instead of with the support.
In accordance with the improvements illustrated by Sheets 4 and 5 of the
accompanying drawings, a suitable pedestal or base, shown as composed of a plate A
and four legs A' A' A' A' screwed or bolted thereto, has secured to it a curved
standard A and a curved arm A'. The upper end of the vertical shaft B of a
worin B' is mounted to turn in a bearing a at the upper end of the base standard A³,
and this worm shaft is supported at its lower end as in turn to be explained.
Vertically adjustable parallel arms C C and C¹ C are jointed at their front ends
by pivots at c¹ to uprights C2 C3 of the base which are shown as formed with
the front legs A¹ A' of the base. The arms C C are shown as formed together or
rigidly connected with each other (see Fig. 14) and the arms C¹ C¹ except that
they are shorter are constructed similarly to the arms C C. These arms C C are
jointed by pivots at dd at their rear ends to a chair body carrier D. An
additional pair of short parallel arms D' D' are jointed by pivots at 'd' to the
chair body carrier at their rear ends, and have pivotal connection at their opposite
or front ends with the arms C C and C₁ C' by way of links D2 D2. Pivots bb
connect the links at their lower ends with the arms C¹ C³, and pivots bb connect
the upper ends of the links with the arms D' D' whilst midway the length of the
links they are jointed by pivots to the arms C C midway the length of these
arms. A curved rack E rigidly connected with the arms CC gears with the
worm B'.. Adjustably connected with the rack E is a similarly toothed and curved
auxiliary rack E' shown as lighter or thinner than the main rack. The connection
between these rack sections is such that the auxiliary rack may slide slightly
lengthwise upon the main rack. Screws or headed pins e e secured to the main
rack section engage slots e' el in the auxiliary rack section, and a pin on the main
section engages a slot f¹ in the auxiliary section and is connected by a
spring F
with a pin on the auxiliary section. It will be seen that the tendency of the spring
is to move the auxiliary rack section upward and thus cause the worm to be snugly

page_text: engaged by the rack sections, thus preventing rattling or loose motion between the
parts.
As will be understood, a suitable chair body is to be mounted upon the upper
end of its carrier D, and adapted to be vertically tilted and horizontally. turned, in
well known ways.
A foot-actuated elevating lever G pivoted at g to the base standard A³ carries a
pawl G which is pivoted at g₁ to the inner end of the lever and is adapted to
engage the rack and rock upward the parallel arms of the elevating mechanism
when the outer end of the lever is depressed by pressure of the foot upon the foot-
rest thereof. A spring acts upon the lever pawl to throw it into engagement
with the rack upon downward movement of the outer arm of the lever, and serves
also to elevate this arm of the lever when released from pressure of the foot. The
upward movement of the long arm of the lever is limited by contact of a shoulder /¹
on the pawl with the upper end of the base arm A, and the pawl is at the same
time rocked out of engagement with the rack.
To uphold the parallel arms and sustain the chair body in any position of
adjustment, mechanism is provided as next to be explained.
The rotary worm shaft is mounted at its lower end in a bearing provided in an
upright shaft H, and a flaring socket H' thereof, hereinafter termed the cone
socket or seat. The worm shaft is provided with a disk or circular projection I
with inclined periphery, its form being that of an inverted frustum of a cone, and
it is hereinafter called a cone as a bearing connection such as that between the
worm shaft and socket is usually termed a cone and socket bearing. This cone I
is adapted to be frictionally locked with the cone socket to prevent rotation of the
worm. The shaft H of the cone socket is mounted in a bearing shown as formed
in an upright J having supporting connection with the base and surrounded by a
vertically adjustable collar or sleeve K acted upon by a strong spring K¹ the
tendency of which is to move the sleeve upward if not occupying its normal or
elevated position in which it is supported by the spring. A foot-actuated tripping
lever L embraces the sleeve K, is pivoted thereto at kk, and is jointed to the base
standard A. The screw or headed pin by which the tripping lever is fulcrumed
passes through a slot in the lever so as to allow it slight endwise movement when
operated and so prevent cramping or binding of the sleeve K upon the bearing
upright about which it is supported and adapted to slide up and down. Upward
movement of the cone socket is prevented by a disk or collar m secured to its shaft
beneath its bearing. A cone and socket connection between the sleeve K and cone
socket H' is provided by the inclined or flaring upper end n of the sleeve and the
engaging inclined peripherial portion n' of the cone socket.
In the operation of the mechanism above described, actuation of the elevating
lever rocks the rack and parallel arms to lift the chair body and causes the worm
to rotate and the worm shaft at each actuation of the lever by downward movement
of its outer end is lifted slightly so as to disengage the worm shaft cone from its
socket to permit of free rotation of the shaft. Upon upward movement of the
lever after each downward stroke the pawl is disengaged from the rack and the
worm shaft descending slightly jams or wedges its cone in the socket H¹, so as to
prevent rotation of the worm shaft independently of the cone socket and its shaft,
whilst rotation of the cone socket and shaft is prevented by the cone and socket
connection at n n' between the sleeve K and cone socket, the parts being forcibly
jammed together by the spring K. Thus, it will be seen, the elevating mechanism
is upheld and the chair body maintained in the position to which it may be elevated.
To allow the parallel arms to rock downward to lower the chair body, the tripping
lever L is pressed downward at its outer end by the foot, thus compressing the
sleeve-upholding spring K' and relieving the sleeve K from its frictional connection
with the cone socket H¹ which is allowed to rotate with the worm shaft to lower
the chair body to the extent desired. It will be obvious that when the tripping
lever is actuated to lower the chair body the weight upon the parallel arms causes

page_text: the rack bar to rotate the worm in the opposite direction to that in which it is
rotated by the lifting lever, the worm being of suitable pitch to provide for its
being so actuated by the rack.
Suitable mechanism for retarding or rendering gradual the descent of the chair
body is provided; such mechanism, as in this instance shown, being as follows:
The disk m of the cone-socket shaft H is secured to a rotating carrier M having
arms or blades N adapted to slide end wise and revolve with their carrier in a pump
chamber formed by a casing O eccentrically to which the carrier is mounted.
A journal p projects downwardly from the underside of the rotary carrier M with
which it is rigidly connected, and into a bearing in the bottom of the pump casing
in which it is stepped or supported by an adjusting screw p¹. The pump casing O
is rigidly secured to the base. It will readily be seen that the worm shaft is
upheld by the base through the medium of the intervening mechanism.
reservoir P for oil or other suitable liquid is secured to the base beneath the
plate A thereof. A pipe Q projecting into the reservoir from the pump chamber
serves as an inlet through which liquid may be drawn or sucked into the chamber
by the rotation of the pump blades, and a valved pipe R serves as an outlet from
the chamber for the liquid. It will be seen that by adjusting the valve S of the
outlet pipe the escape of the liquid from the pump chamber back to the reservoir
may be controlled so as to offer more or less resistance to the rotation of the pump
blades.
A
In operation when it is desired to lower the chair body gradually or without shock,
it will be seen that with the valve of the outlet pipe suitably adjusted, and with
the weight of the elevating mechanism upon the rotary carrier of the pump blades
the resistance offered by the liquid to the rotation of the blades will regulate the
speed of lowering the chair body by controlling the speed of rotation of the worm.
During this operation it will of course be understood that the worm shaft is
frictionally locked with the shaft H which is fixed to the rotary carrier of the
pump blades.
.
It will be seen that by the employment of the short lower and upper parallel
arms, and the longer intermediate arms, with the links connecting the arms ample
space is provided for the worm, the base standard and other parts without
interfering with the movements of the parallel arms in raising and lowering the
chair body.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The combination, in a dental chair, of a set of parallel arms provided with
the actuating lever rigid with one of said arms, the support to which said arms
are jointed one above the other, the horizontal cylinder, its piston, the connecting
rod jointed to said actuating lever and piston, and the chair body carrier having
jointed supporting connection with said parallel arms and maintained at all times
in an upright position, substantially as set forth.
2. The combination, in a dental chair, of the main parallel arms linked together
5 at their outer ends, the support to which they are jointed, means for actuating
said arms, the supplementary parallel arms jointed to the linked ends of the main
parallel arms, means by which the supplementary parallel arms are caused to rock
about their jointed connection with the main parallel arms upon actuation of these
main arms and the chair body carrier jointed to the supplementary parallel arms
O and maintained at all times in an upright position, substantially as set forth.
3. The combination, in a dental chair, of the main parallel arms linked together
at their outer ends, the support to which they are jointed, means for actuating
these arms, the supplementary parallel arms having jointed connection with the
linked ends of the main parallel arms and provided with the actuating lever, the
5 coupling link making jointed connection between said actuating lever and support,

page_text: :
and the chair body carrier jointed to said supplementary arms and maintained at
-all times in an upright position, substantially as set forth.
4. The combination, in a dental chair, of the base, the horizontally turning
support carried thereby, a set of parallel arms jointed to said support and one of
which is provided with the actuating lever rigid with it, the .horizontal cylinder,
its piston, means for actuating the piston, the connecting rod jointed to said
actuating lever and piston, and the chair body carrier having jointed
supporting connection with said parallel arms and maintained at all times in an
upright position, substantially as set forth.
5. The combination of the base, parallel arms having jointed connection with
the base, the chair body carrier having jointed connection with the parallel arms,
the curved rack carried by the parallel arms between their jointed connections
with the base and chair body carrier, the elevating lever, and its pawl engaging
said rack, substantially as set forth.
6. The combination of the base, the worm and its vertical rotary shaft having
supporting connection with the base, the curved rack engaging the worm, the
parallel arms having jointed connection with the base and carrying the curved
rack, means for actuating the curved rack to raise it and the parallel arms, the
chair body carrier with which the parallel arms have jointed connection, and
means by which to prevent rotation of the worm and its upright shaft and so
prevent downward movement of the rack and parallel arms, substantially as set
forth.
7. The combination of the base, the chair body carrier, the short lower parallel
arms having jointed connection with the base, the longer intermediate arms having
_jointed connection both with the base and the chair body carrier, the short upper
parallel arms having jointed connection with the chair body carrier, the links
-connecting the upper, lower, and intermediate arms, and means for actuating and
for upholding the parallel arms, substantially as set forth.
8. The combination of the base, the rotary worm and its shaft provided with
the cone, the curved rack engaging the worm, means for actuating the rack to
raise it, the parallel arms carrying the rack and having jointed connection with
the base, means for supporting a chair body by the parallel arms; and the cone
-socket and its shaft having supporting connection with the base and with which
the worm shaft cone is adapted to be frictionally locked against rotation
independently thereof, substantially as set forth.
9. The combination of the base, the rotary worm and its shaft having supporting
-connection with the base, the curved rack engaging the worm, means for actuating
the rack to raise it, the parallel arms carrying the rack and having pivotal
connection with the base, means for supporting a chair body by the parallel arms,
and means by which to control the speed of rotation of the worm shaft to gradually
lower the elevating mechanism when it is permitted to descend, substantially as set
"forth.
10. The combination of the base, the rotary worm and its shaft provided with
the cone, the curved rack engaging the worm, means for actuating the rack to
raise it, the parallel arms carrying the rack and having jointed connection with
the base, means for supporting a chair body by the parallel arms, the cone socket
- and its shaft, the bearing for the cone socket shaft, the sleeve on this bearing
having the cone and socket connection with the cone socket shaft, the spring acting
on said sleeve, and the tripping lever, substantially as set forth.
11. The combination, in a dental chair, of the base, the chair body elevating a
mechanism provided with the curved rack, the shaft provided with the worm
engaging the rack of the elevating mechanism, means for actuating the rack, and
the mechanism by which the rotation of the worm is controlled in lowering the
-elevating mechanism, consisting of the pump chamber, the pump blades, their
rotary carrier with which the worm shaft has connection, the inlet and outlet pipes,
and the liquid-carrying reservoir, substantially as set forth.
12. The combination, in a dental chair, of the base, the worm and its shaft

page_text: having supporting connection with the base, parallel arms having jointed connection:
with the base, the sectional curved rack carried by said arms, and comprising the
main section, the auxiliary section adapted to slide thereon, and the spring.
connecting the rack sections, and means for actuating the rack, substantially as set.
forth.
D
304th day of Man 1001
ARTHUR WILLIAM BROWNE.