Improvements in and connected with Dental Chairs.
Year: 1894

page_text: Date of Application, 10th July, 1894-Accepted, 11th Aug.,
1894
COMPLETE SPECIFICATION.
Improvements in and connected with Dental Chairs.
A communication by DEWELL STUCK, of 33, Jay Street, Rochester, in the State
of New York, United States of America, Machinist.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.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, Civil Engineer, 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 :-
The invention has for its object to provide efficient means for raising and
lowering the seat of a dentist's chair that will permit a larger range of movement
than usual heretofore. In some cases a large range has been secured by extending
the raising and lowering mechanism through the floor that supported the chair.
Parallel seat supporting arms moved by power transmitted through gears have
been proposed and such arms have been raised and lowered by a liquid column
for the purpose named. The present invention utilizes a liquid column to directly
move the seat through a large range without employing the system of parallel
levers heretofore proposed and it consists in the construction hereinafter described
and particularly pointed out.
In the accompanying drawings
Figure 1 is a vertical section ;
Figure 2 is a transverse section on line 2-2 of Figure 1;
Figure 3 is a vertical section on line 3-3 of Figure 2, the chair base being
omitted.
Figure 4 is a plan of the seat frame and its support.
Numeral 1 denotes the chair base and 2 a liquid reservoir secured therein by
screws 3. Within this reservoir is removably fastened a cylinder 4 the screw
threaded and closed end or foot of which extends through the bottom of the
reservoir and is there fastened by a nut 6. 7 deuotes a packing between the
flange 8 of the cylinder 4 and the bottom of the reservoir 2. The upper end of
the cylinder extends through and is suitably held in an opening 9 in the top of the
base. Oil or other fluid is forced into the cylinder 4 through the port 91 and
allowed to escape through port 10 according as it is desired to raise and lower the
chair the devices for effecting these operations being of well known character.
the present instance the ports communicate with the cylinder below the level of
the bottom of the reservoir, the cylinder extending below said bottom, the
construction being such that piston 11 may also descend below said level to increase
the downward range of the seat movement.
In
The seat is moved vertically through the medium of a piston 11 and piston
rod 12. The upper end of the latter, which is preferably rounded, bears in a
similar socket 13 situated at the upper part of a recess 14, formed in the head 19 of
a part 20 of a telescoping guide or standard, said upper end being substantially in
the lower plane of the upholstered seat. The recess is of a size adapted to receive
the upper end of the cylinder 4.
The seat frame 15 is supported and adapted to turn on the trunnions 16 of a
cross bar 17 which rests as indicated at 18, 18, upon the head 19 of the telescoping
guide which consists of a solid bar 20 which is integral with the head 19 and a
tubular part 21 surrounding said bar and having in transverse section an oblong
and approximately lozenge shape. Within the tube 21 the bar is bifurcated and

page_text: provided with guide wheels or rollers 22 preferably eight in number journalled in
the limbs of the bar 20. These wheels are adapted to bear on suitable tracks 24
formed on the interior of the tube 21, and to guide the bar in its lengthwise
movements.
25 denote right and left hand screws adapted to slightly vary the relative
distance of the legs of the bar 20 for the purpose of causing the wheels to bear
with more or less force upon the tube as found desirable in practice and to
compensate for wear.
The tube 21 is guided by wheels 26 journalled in brackets 27 fixed to the interior
of the chair base. These are preferably eight in number and bear on tracks 28.
29 denotes a friction device which can be made to bear on wheels 26 with greater
or less force by means of screws 30 to compensate for wear and maintain a suitable
degree of friction. To permit the raising and lowering of the friction bar through
the slight distance required to vary the friction, the screws are arranged in an
inclined direction.
31 denotes a stop on tube 21 adapted to strike the upper part of the base and
prevent the further ascent of the tube and 32 is a stop fast on the bar 20 and
movable in a slot in the tube to limit both ascent and descent of the bar with
relation to the tube.
The bar 20 of the telescoping guide is adapted to be clamped to the cross bar or
seat frame support 17 by a screw 33 which can be turned to force a frusto-conical
washer 34 against a screw or other part 35 fast on the bar. 36 are lugs fixed on
said cross bar to support the fulcrum of a locking lever adapted to engage a rack
connected with the seat frame.
37 denotes a recess in an enlarged part of the cross bar 17 and extending
preferably through nearly or a little less than half a circle. The extension 14
of the head 19, in which the recess 14 is formed, is situated in the recess 37 and
limits the rotary motion of the seat frame support 17 upon the head 19.
The above described construction is such that the piston 11 can descend below
the bottom of the liquid reservoir and that the cylinder 4 may at such time reach
near to the upper plane of the seat support, the range of the chair seat movement
in vertical lines being only limited to the length of the cylinder, the telescoping
guide. and its stops being suitably arranged to permit the full movement.
The telescoping guide combined with the seat elevating piston affords a stable
support to the seat and suitably directs its movements in vertical lines notwith-
standing the fact that the center of gravity of the chair and its occupant is subject
to considerable change.
My correspondent is aware that a seat frame and a seat support have been
combined with a spring-held pin adapted to enter one of a series of holes to lock the
two in a position corresponding to the situation of said hole and he does not broadly
claim locking devices for this purpose but only the particular construction pointed
out which avoids the use of a spring and the necessity of holding the pin out of
engagement when the seat is rotated more than the distance between two holes and
also permits a finer adjustment of the seat. This special arrangement also provides
a Jock, above the lower plane of the seat bar, so as not to interfere with the lowering
of the seat to the lowest practicable point. He is also aware that a seat clerating
support has been combined with an attached cylinder partly immersed in a liquid
contained in another cylinder to retard the descent of the seat and operating as a
guide and be does not broadly claim devices of this nature.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent I declare that what I claim is :
1. In a dental chair seat-elevating mechanism comprising a cylinder extending to
the floor level, a piston adapted to descend to practically the same level, means
for elevating the piston, and a piston rod extending above the level of the
bottom of the seat frame cross bar, and said cross bar having a recess, whereby it

page_text: is adapted to descend below the top of the rod and cylinder, substantially as
set forth.
2. In a dental chair a base, a guide tube 21 a seat guiding bar 20 having a
recessed extension 14, the seat frame comprising the frame-supporting cross bar
having a recess opening 37 to receive said extension, a seat-elevating rod adapted
to enter the recess in the extension and devices for raising the rod, all combined.
substantially as set forth whereby the chair seat is guided, its vertical range enlarged,
and whereby its rotation is limited.
3. In a dental chair the combination of the base, the seat frame, a guide rod 20.
and a telescoping guide 21 each made movable in the base friction wheels inter-
posed between the telescoping parts and also between the guide 21 and the base said
latter guide having tracks for the wheels, and seat-elevating and -supporting
mechanism, substantially as set forth.
4. In a dental chair the combination of the base, the seat frame, a guide rod 20.
and a telescoping guide 21 each made movable in the base, friction wheels inter-
posed between the telescoping parts and also between the guide 21 and the base,.
said latter guide having tracks for the wheels, a friction device adapted to bear on
the wheels connected to the base, and seat-elevating and -supporting mechanism,
substantially as set forth.
5. In a dental chair the combination of a base 1, a seat-elevating cylinder
extending above the base, a piston rod, a recessed seat-frame bar, a guide rod 20
and a telescoping guide 21 each made movable in the base and the rod provided
with a flat head directly supporting the seat frame bar both bar and head being
recessed to permit the rod and cylinder to extend above the bottom of the cross
bar, all substantially as set forth.
6. In a dental chair the combination of the cross bar to support the seat
frame, a vertical bar supporting said cross bar, a headed bolt secured to the
top of the vertical bar and extending through the cross bar, a frusto-conical washer
adapted to bear upon the under side of the bolt head, and a screw situated in the
cross bar to force the washer against the head and lock the bars together, the
head, washer and screw being situated above the bottom of the seat frame,
substantially as set forth.
Dated this 9th day of July 1894.
WM. P. THOMPSON & Co.,
Agents.