Improvements in Dental Chairs.
Year: 1891

page_text: Date of Application, 4th Aug., 1891-Accepted, 12th Sept., 1891
COMPLETE SPECIFICATION.
Improvements in Dental Chairs.
A communication from abroad by DEWELL STUCK, of Jay Street, Rochester, in the
County of Monroe and State of New York, United States of America.
I, GEORGE CECIL DYMOND, M. Inst. M.E., of the Agency for Foreign Patent
Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester both in the
County of Lancaster, and 323 High Holborn in the County of Middlesex, Patent
Agent, do hereby declare the nature of this invention and in what manner the same
s to be performed, to be particularly described and ascertained in and by the
ollowing statement :-
In the accompanying drawing,
Fig. 1 is a side elevation of my improved chair;
Fig. 2 is a partial section on line 2-2 of Figure 12;
Fig. 3 is a partial section on line 1-1 of Figure 4;
Fig. 4 is a partial plan, the seat and part of the foot rest being broken away;
Fig. 5 is a section on line 5---5 of Figure 4;
Fig. 6 is a partial section on line 6-6 of Figure 4;
Fig. 7 is a partial section on line 7-7 of Figure 6;
Fig. 8 is a partial section on line 8-8 of Figure 6 ;
Fig. 9 is a plan of the hydraulic jack;
Fig. 10 is a partial section on line 10-10 of Figure 12;
Fig. 11 is a partial section on line 11-11 of Figure 12;
Fig. 12 is a partial plan of the seat-raising mechanism, the elevating screw and
surrounding tubes being omitted;
Fig. 13 is a plan of the cover of the pan in the base;
Fig. 14 is a bottom plan of a wheel immediately below the cover showing a
clamping device ;
Fig. 15 is a similar view of a modification of the clamp ;
Fig. 16 is a plan of another clamping disk situated in a recess in the aforesaid
wheel;
Fig. 17 is a section on line 17-17 of Figure 15;
Fig. 18 is a partial plan of a modification of the device indicated in Figure 14.
Mechanism for raising the chair seat will be first described.
The reference letter a denotes the base of the chair, a' a standard or pedestal
supported thereon, and a² a cap or cover. a is a tube or plunger fixed to the chair
seat frame and movable through the cap a². a' is a screw fixed in the upper end of
the plunger, and has its main threads engaged by an internally threaded tube or
nut b, which latter at its foot is fixed to a wheel b', which is adapted to be clamped
by a device carried in wheel 62 to a pulley 63, whereby the wheel ' and the tubular
nut 6 are turned with the effect to raise the screw and seat frame.
a* denotes a stop on the foot of the plunger. is a telescoping guide tube,
and c an exterior tube fixed at its foot or like device to a disc c*, and at its top to
the pedestal by screws d. indicate packing between the several tubes. d is a
two part ring clamp operated by a lever d³, moved and locked by a screw d* working
through the wall of the pedestal.
The pulley is turned to move tube b and raise the screw a* and the chair seat
by a lever e having a fulcrum in the standard. The short arm of the lever has a
hook adapted to engage a link e', which normally is supported in the fork of a
standard e secured to the cover or disc c*. To the foot of this link is attached
a cord or chain e which passes about guide pulleys f and fl and is attached to the
aforesaid pulley 63. e is a chain attached to the latter pulley and extended around

page_text: the guide pulley f' and attached to its periphery. The cover is cut away at c to
permit the passage of the said chains. ex is a chain attached to the underside of
pulley and passed under guide pulley f³ up to the lower end of a stout spring f
When the long arm of the lever e is depressed, the pulley 63 is turned and spring f
put under tension sufficient to return these parts to their initial position when the
lever e is released. e is a lever pivoted in the standard and adapted to push the
link out of the hook on the end of lever e and allow the long arm of the lever to fall
to a vertical position. Its hook can be re-engaged with the link by simply lifting the
long or power arm of the lever.
During the descent of said lever e under pressure applied by the foot or other-
wise to its free end and the consequent relation of the pulley 3, said pulley is
clamped to the wheel & fast on the lifting tube or nut by means of the inter-
posed wheel 62, which carries in a recess on its upper face and at its exterior
part a wedge g situated between two series of rollers g' and adapted to be moved
to force a clamping block g³ against a shoulder in wheel &' by a pin g depending
from the bottom of the pulley b³. 6 is a pin fast on the wheel 2 which enters a
short slot in the pulley, whereby the relative movement of these parts is limited,
and is a stop that limits the backward movement of wheel 62.
It will be seen
that a slight forward movement of the pulley and of its pin 9' will clamp said
pulley to the wheel 1 and its attached lifting nut b, whereby the above described
depression of the lever e raises the chair seat. A slight reverse movement loosens
the wedge g and permits spring to turn back the pulley and elevate the lever
without affecting wheel 6' and the chair-seat lifting nut b.
is
The lifting nut and its attached wheel are clamped to the disc c*, which is
connected to the chair standard, by a clamping block h which is adapted to be
forced against a shoulder or flange on wheel by a block h². A roller
interposed between these blocks and a series of rollers / arranged at the inside
of block 2. These rollers and blocks are located in a recess in the upper side of
the cover c* near its outer edge, said recess being contracted in width toward one
end. The clamp is released automatically by the revolution of the wheel b.
blocks, however, can be first moved, that is directly by means of a crank arm
fast on a sleeve 3 supported to turn on a stud i fixed to a post 2. Upon said
sleeve are fixed arms to which are connected the springs j and j. These springs
normally hold the arm h* so as to press the blocks toward the narrow end of the
recess and clamp the wheel. If it is desired to release the wheel to lower the
The
seat by its weight, the clamp is directly released by means of a lever j³ fast on a
short shaft to which is fixed an arm to which the spring is secured, which
lever can be depressed with the effect to move the blocks toward the wide end of
the recess and release the clamp. indicates screws supported in the standard and
adapted to regulate the tension of the springs, and e denote thumb nuts provided
with means for attaching the springs.
As
It will be understood that the standard a¹ is supported on the base and can be
revolved thereon. K is a stop to prevent its being raised off from said base.
the ring d² can be clamped upon the plunger a³ which has a lug be fitting the
groove 6 in a³ and the tube c³ being fixed by screws d and key b' respectively to
the standard a¹ and the cover cx, which latter may by means of the above described
clamps be held fast to the pulley 63, all these parts so connected and the chair
seat also can be revolved together.
indicates a series of anti-friction balls arranged in a groove formed in the
bottom of a pan k² screwed into the base a, and is a cap or flange similarly
grooved and made fast on the solid extension of the lifting tube b.
k is a friction wheel having its center supported on cap k³ and adapted to be
automatically clamped to the wheel 6 by a disc located in a suitably formed
recess on its under side at its periphery. " are frictional flanges formed on
wheel and cover c*, as indicated. The disc is adapted to bear on both the
wheels and whenever it is moved toward the narrow end of the aforesaid
recess, as it will be (relatively) whenever the wheel 6' is turned in the opposite

page_text: direction, as occurs when the lifting nut is allowed to suitably rotate to permit
the chair seat to descend. The friction of the wheel is by this means added
to that of wheel 6 with the effect to retard the descent of the seat and obviate
a sudden movement or jar. 6¹ is revolved in the opposite direction as in raising
the seat, the disc will be in the wide end of its recess, and the said wheel moves
independently of the friction wheel. Preferably the pan k² is supplied with a fluid,
such as glycerine or oil.
In Figure 15 is shown a modification of the clamping device denoted by 12, the
recess to receive said device being also correspondingly modified and so that the
roller is adapted to act against the bodies of the wheels, as indicated.
Instead of the clamping disc and roller above described, other devices such as
a panel or ratchet might be used, see Figure 18. The gist of the invention in this
direction does not consist in the particular forms of this device, nor in the number
of the friction wheels or friction flanges.
Mechanism for supporting the chair seat in various angular portions is shown
in Figures 3, 4 and 6. In Figures 3, 4 and 6, are shown devices for supporting
the chair seat at various angles. The seat frame is denoted by m, and a cross
frame by ml. This latter frame has journals provided with bearings on the seat
frame and is fastened to the plunger a³ and screw a', as indicated. The lever m²
is pivoted to the seat frame at ³, and moves about said pivot in a horizontal
plane. m is a curved rack fixed to said lever. m³ are inward extensions of the
seat frame, one of which receives the lever pivot, and both of which guide the
lever: m is an extension of the lever which moves in a slot in the under side of
the seat frame flange and limits the movement of the lever, and also aids to keep
the lever steady. m is a pin on the cross frame m' that is made to engage any
desired recess in the rack to hold the seat frame in any particular plane to which
it may have been adjusted. The spring m³ acts to maintain the engagement
whenever the power end of the lever is released. By pressing on this end of the
lever with foot, hand, or knee, the tension of the spring may be overcome and the
rack swung away from the frame pin m' whereupon the seat may be tilted and
then locked in its new position by releasing the lever and permitting the spring
to act.
Mechanism for adjusting a foot rest and back is shown in Figures 4, 6, and 8.
The reference letter n denotes the back frame, which is pivoted to the arms n* of
the seat frame m at n'. The back frame n is further connected with the seat frame
by a bar n² pivoted to said latter frame at n³ and extending into a recess in the
back frame. n is a clamping block having an inclined face and movable in a
similarly shaped recess n³ formed in the back frame. The block is provided with
a screw threaded opening, which receives the rod no, which is provided with an
operating handle n'. The position of this handle indicated by full lines in Figure 4
corresponds to the position of the parts when the clamp is operative. The screw
rod n the foot of which bears at n upon the bottom of the recess n³ having been
suitably turned, the block n¹ is thereby moved up in the recess and pushed laterally
against the bar n² forcing it against the wall of the recess at o' (see Figure 4) by
means of the inclination of the opposite wall of said recess. To release the lock or
clamp, the handle n' is turned to the position indicated by dotted lines in Figure 4,
which has the effect to lower clamping block n' and relieve the bar n² of pressure
from said block. By these devices the back can be adjusted to any desired
position and clamped therein. 02 indicates a lug provided with a seat for a rubber
cushion g against which bar n² strikes when the back is lowered to its lowest position,
and is adapted to obviate jarring. o is a shoulder on n² adapted to engage n¹ when
the back is elevated to its highest position.
Numeral o denotes the main foot rest of a chair. At its rear upper and outer
part near the top of the upward extension of it is provided with pins or studs o, and
below at the foot of said extension it is provided with like studs 08, all of which fit
in blocks oº (see Figures 6 and 7) adapted to slide in grooves p and p¹ (see Figure 6)

page_text: formed in the inside of brackets p² pendent from the seat frame. The studs ở? and
its blocks are below the angle made by the two parts p and p¹ of each groove.
The rear of the foot rest is guided by the devices just described in such manner
that the outer end of the rest is tilted toward the seat as it is raised, and from the
seat as it is lowered.
23 indicates a foot lever for raising the seat. It is connected to a rod or bar p*;
which has bearings in boxes p³ secured underneath the foot rest. p indicates a
rod or bar supported in the brackets p2 and constituting a fulcrum for the foot
lever. It also holds the brackets firmly in their relative position and supports foot
rest lowering mechanism. The foot rest is raised by depressing the free end of
foot lever p³, the lever sliding freely over its fulcrum and the studs o' and o³ with
their bearing blocks sliding up in grooves p and p', as indicated.
p denotes a hydraulic jack adapted to lower the foot rest. It is connected
by a strap p to the cross bar p. The jack has two compartments as usual
one of which is a piston q provided with packing q¹. At its foot is an elastic
disc q held in place by a screw 93, these parts being of well known form.
The piston rod 9 is pivoted at 9 between offsetting lugs 9 on the foot rest.
9 denotes a valve having a seat in the diaphragm 9. 9 is a spring adapted
to hold the valve to its seat. This spring is conveniently coiled about a plug r
passed through the end of the valve chamber. This chamber communicates at
all times with the piston chamber. The valve stem has a bearing in and
passes freely through the diaphragm 2, and is arranged in the path of the
short arm of a lever 3 by which the valve may be opened. This lever is
pivoted to the hydraulic jack at 24 and is provided with an adjustable stop ³,
which is so located as to strike the partition or diaphragm 2 of the jack when
the short arm of lever is depressed. By this stop the extent of the movement
of the lever and valve in one direction is determined.
It will be obvious that when the foot is raised by the foot lever, as before
described, it will pull up the piston rod q and piston g, the jack being held
down by its connection with rod 26. The jack being supplied with glycerine,
oil, or other liquid, it will be drawn down into the valve chamber by the action
of the ascending piston, which also opens the valve and compresses its spring.
The fluid thus introduced under the elevated piston will sustain it and the foot
rest until the valve is opened by the operation of lever ³ to permit the fluid
to escape from under the piston. The lever is normally held out of contact
with the valve stem by the weight of its long arm. 7 is a cord, or like
connecting device adapted to raise the long arm of lever ³, and thereby open
the valve to permit the descent of piston q and of the foot rest. This cord
extends from the lever to the chair back passing preferably through the seat
frame and above the pivot n³ and through a suitable hole in frame m (see
Figure 4) along the back standard to its outer end where it is provided with
a handle or knot . By pulling this cord the lever can be raised and
the valve opened to permit the descent of the piston g and of the foot rest
connected thereto, as described. Upon releasing the cord from the hand the
weight of the long arm of the lever immediately lifts its short arm from the
valve stem and permits spring q° to close the valve and thereby arrest the descent
of the piston and foot rest. By this means the descent of the foot rest can be
very nicely regulated by simply opening the valve more or less as required
and without the use of the foot or the exercise of any material degree of
strength, and without the necessity of the operator leaving the head of his
patient, or of so exerting himself as to interfere with his proper work. And this
easy and exact lowering of the foot rest can be effected by the means described
whatever be the position of the adjustable back.
It may be observed that the handle for clamping the bar n² that connects the
back and the seat frame is located near the cord handle r', whereby the clamp and
the valve can be conveniently manipulated at suitable times to permit the desired

page_text: 10wering of the foot rest and the adjustment of the back, which may be simultaneous
or not, as desired.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. A chair having a screw attached to the bottom of its seat, the internally
screw threaded sleeve engaging said screw, devices for holding the seat and screw
against rotation, a resistance wheel fixed to the said sleeve, a reservoir containing
said wheel and resistance material, a pulley also fixed to said sleeve, a lever pivoted
in the standard, intermediate devices including a chain and guides therefor, whereby
the sleeve may be rotated by the lever and said intermediate devices, substantially
as set forth.
2. A chair having a screw attached to the bottom of its seat, the internally
screw threaded sleeve engaging said screw, devices for holding the seat and screw
against rotation, a resistance wheel fixed to said sleeve, a reservoir containing said
wheel and resistance material, and mechanism to revolve the sleeve, said sleeve
being supported from its bottom, substantially as set forth.
3. A chair having a screw attached to the bottom of its seat, the internally
screw threaded sleeve engaging said screw, devices for holding the seat and screw
against rotation, a resistance wheel fixed to the said sleeve, a reservoir containing
said wheel and resistance material, whereby the weight of the seat and its occupant
may cause the seat to descend without turning and whereby the descent may be
retarded by the turning of the sleeve and the wheel, and a friction brake for the
resistance wheel, substantially as set forth.
4. The combination of the chair body or seat the elevating screw secured
thereto and supporting said seat, the revolving sleeve provided with screw threads
which engage the screw, a resistance wheel secured directly to the sleeve, and a
liquid reservoir within the base of the chair, said wheel being adjusted to revolve
with equal freedom in either direction, and a plunger C secured to the seat,
substantially as set forth.
5. The combination of a chair body or seat, an elevating screw secured thereto,
a sleeve provided with screw threads engaging said screw, a lifting lever adapted to
raise the seat by revolving said sleeve, a friction clutch whereby the power of said
lever is communicated to the sleeve and mechanism to render the clutch inoperative
at will, substantially as set forth.
6. The combination of a chair body or seat, an elevating screw secured thereto,
a sleeve provided with screw threads engaging said screw, a lifting chain passed
around a part connected to said sleeve and adapted to rotate it, a lever and an
intermediate link connecting the chain and lever, and guide pulleys to direct the
chain, substantially as set forth.
7. The combination of a chair body or seat, an elevating screw secured thereto,
a sleeve provided with screw threads engaging said screw, a lifting chain passed
around a part connected to said sleeve and adapted to rotate it, a lever and an
intermediate link connecting the chain and lever, and guide pulleys to direct the
chain, said link being detachable from the lever and adapted to be automatically.
engaged therewith upon raising its power arm, and the link detaching lever adapted
to detach the link from the lifting lever, substantially as set forth.
8. In a dental chair, seat-lifting mechanism a pivoted pedal lever adapted to
automatically engage said mechanism, and a device to disengage the pedal lever
from the mechanism, said disengaging device being normally inoperative, the power
arm of the lever being free to fall to a substantially perpendicular position within
the circumference of the chair base whenever the disengaging device is intentionally
operated, substantially as set forth.
9. The combination with the movable seat supporting plunger c², of the stationary
base a, rotatable standard a' supported on the base, the divided clamp ring d² at
the upper end of the standard, clamping screw d' and the lever bearing both upon

page_text: the clamp ring and upon the base, whereby the plunger is secured in the standard,
and the standard is simultaneously prevented from turning on the base, substantially
as described.
10. In a dental chair and fixed to a revolving part thereof to retard its motion,
a resistance wheel having sections, a locking device between the sections adapted
to lock the said sections together when they are revolved in one direction and to be
automatically disengaged when they are revolved in the other, in combination with
a liquid holding pan, substantially as set forth.
11. In a dental chair, the combination with the seat frame provided with suitable
brackets of a foot rest, an hydraulic lowering jack having the piston cylinder
supported from said brackets, a valve chamber communicating with said cylinder,
valve operating devices and the piston connected to the foot rest, and mechanism
adapted to elevate the piston, substantially as set forth.
12. In a dental chair, the combination with the seat frame provided with suitable
brackets, of a foot rest, an hydraulic lowering jack having the piston cylinder
supported from said brackets, a valve chamber communicating with said cylinder,
valve operating devices, and the piston connected to the foot rest, and mechanism
adapted to elevate the rest and the piston, and a flexible valve-operating connection
extending to the chair back, substantially as set forth.
13. In a dental chair, the combination of the seat frame provided with brackets 13
connected by rod 6, said brackets having bent grooves, the hydraulic lowering jack,
embracing a cylinder, piston and valve chamber, pivotally connected to said rod, a
foot rest supported on said piston and provided with studs to enter the grooves, and
mechanism for raising the foot rest, substantially as set forth.
14. The combination with the seat frame of a chair provided with brackets
having a bent groove p p³ with a foot rest having pins adapted to enter and slide
in both parts of the groove and devices for raising and lowering the foot rest
substantially as set forth.
15. In a dental chair, the combination with the seat frame, of a foot rest
movably supported therein and provided with lowering mechanism, a cord or the
like attached to and adapted for operating the lowering mechanism, a chair back
frame hinged to the chair frame, a bar pivoted to the seat frame upon which said
chair back frame is adapted to be moved, said cord passing near the pivot of the
bar and fastened to said bar, a rod supported in the back frame and adapted to
move said cord and operate the lowering mechanism, and guide pulleys on the
chair back and rod for the cord, whereby the back and the rest may be raised or
lowered independently, substantially as set forth.
16. In a dental chair, the combination of the chair seat frame, and the back
frame hinged thereto, the foot rest adjustably supported from the seat frame with
lowering mechanism for said rest having an operating device with a handle
extending to the back frame, and a clamping mechanism, provided with a handle
the handles of the clamping and lowering mechanism being located in said back
frame and in proximity to each other, substantially as set forth.
17. In a dental chair, the seat frame, the back frame and the bar both hinged to
the seat frame and movable with respect to each other, and an elastic stop secured
to the back frame in the path of the bar and adapted to limit the downward
movement of the back frame, substantially as set forth.
18. In a dental chair, the seat frame, the back frame and the bar both hinged to
the seat frame and movable with respect to each other, and a stop on the bar
arranged in the path of a part secured to the back frame and adapted to limit the
upward and forward movement of the back frame, substantially as set forth.
A
1001
WM. P. THOMPSON & Co.,
Agents for the Applicant.