Improvements in Dental Chairs.
Year: 1895

page_text: Date of Application, 2nd Apr., 1895-Accepted, 4th May, 1895
Improvements in Dental Chairs.
We, WILLIAM BRAYTON MANN, Doctor of Dental Surgery, and WILLIAM
TECUMSETH STILWELL, Broker, both of No. 21 Firemen's Building, in the City
of Baltimore and State of Maryland, United States of America, 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 :-
This invention relates to certain improvements in dental chairs where a fluid
column (such as oil) is employed to elevate the chair-body and a pump is employed
to impel or force the said fluid.
The accompanying drawings illustrate the improvements which constitute the
subject-matter of the invention.
Figure is a side elevation of an ordinary dental chair mounted on and raised by
means of our improvements.
Figure 2 is a vertical section of the pedestal and the elevating mechanism and
shows the improved construction thereof.
Figure 3 is a horizontal cross-section of the pedestal on line 3-3 of Figure 2.
Figure 4 is a side view on a larger scale of the valve-chamber and treadle.
Figure 5 is a horizontal cross-section of same.
Figure 6 is a view of the crank-shaft.
Figure 7 shows two views illustrating the action of the link connecting the crank-
shaft and ring-plate.
Figure 8 is a plan view of the ring-plate, and Figure 9 shows a modification and
is a vertical section of the elevating mechanism.
Figure 8 is a modification of the clamp device.
Figure 10 is a horizontal cross-section of the base on line 10-10 of Figure 9.
Figure 11 is a side view of the piston as seen from a transverse direction to the
view shown in Figure 9, and also shows a section of the oil-pan.
Figure 12 is a section of the cylinder and stand-pipe.
Figure 13 is a top plan view, on a larger scale, of the passage-way and supply-
valve from the pump-cylinder to the base of the piston.
Figure 14 is a side view of the parts shown in Figure 13 and also showing the
lever of the release valve by which the chair-body is lowered.
Figure 15 shows two views of the release valve of the modification.
Referring to the drawing the parts seen in Figures 1 to 8 inclusive, will first be
described.
The pedestal, A, exteriorly is cylindric and is supported on feet or a bell-shaped
base or broad rim, b; this base contains an oil-reservoir, B, formed by a bottom
pan, c, secured within the hollow base by bolts, c'. The lower surface of this plate
or pan should, by preference, like the broad base, b, rest upon the floor; the top of
the pedestal has a cover plate, d, suitably secured.
The pedestal contains two cylinders, D, and, E, one of these, D, is for the lifting.
piston, F, which supports the chair-seat or chair-body, C, and the other, E, is for
the pump-piston, G.
Figures 2, 4 and 5, show the valve-chamber, H, attached to the base of the
pump-cylinder, E, a vertical pipe, f, is in this chamber and opens into the pan, c, or
oil-reservoir, B; the lower end of this pipe is open having only a strainer, f³, in it
to prevent the passage to the pump of any dirt that may be in the oil; a check-
valve,, is at the upper end of this pipe and while allowing oil to pass into the
pump-cylinder, prevents its return from the pump-cylinder to the oil-reservoir.

page_text: The lower end of the lifting cylinder, D, at the side where it adjoins the pump
cylinder is open and communicates with the oil-reservoir, B. The stand-pipe, D',
in Figure 2 is screwed, at, g, into a central plate, c, of the pan and is stationary;
this pipe, D', extends upward through said cylinder, D, and its upper end, d,
projects above the top of the cylinder whereon the cover plate, d, sets; the lower
end of this stand-pipe has communication with the valve-chamber, H, which latter
communicates from the bottom of the pump cylinder, E. A check-valve, g', allows
oil to pass from the pump-cylinder into the valve-chamber and from thence the oil
flows by a passage, h, to the stand-pipe, D', but said check-valve prevents oil from
returning to the pump-cylinder.
The lifting piston, F, is shown in Figure 2 and is tubular and open at its lower
end and slips down over the stand-pipe, D', like a sleeve; it also enters and fits in
the cylinder, D, and thus the piston, F, moves up and down in the annular space, F',
between the cylinder and stationary stand-pipe. The upper end of the tubular
piston, F, is closed by a head, i, and a vent-hole into the said tube is closed by a
removable screw-plug, j, for a purpose hereinafter described. The lower end of the
tubular piston has a vertical slot, k, which takes over the passage, h, between the
pump-cylinder and stand-pipe, and thus when the piston is fully down its lower end
will rest upon the bottom plate or pan, c, of the oil-reservoir, thereby availing of
the utmost limit of lowering movement and resulting in having the chair-body as low
down as possible. On the other hand when the chair-body or seat is elevated to
the extreme limit the said slot, k, does not interfere with the piston giving effective
support to the said body or seat.
The pistor, F, itself has no packing to make a tight fit in the cylinder, D, but
the upper end of the stand-pipe, D', has a cup-packing, e, which tightly fits in the
bore of the tubular piston. The piston has a vertical groove, l, on its exterior
which, however, does not extend to its ends but stops short thereof, leaving a stop-
shoulder, at the lower end of the groove; a lateral pin or screw, l, is in the cover
plate, d, of the pedestal and the point-end of this screw projects into said groove ou
the piston. The piston thus prevented from rotating in the cylinder but is free
to raise and lower; the contact of the stop-shoulder, , with the screw; l', determines
the extreme limit of elevation of the piston.
A release or lowering valve, m, is in the chamber, H; this valve opens upwardly
against the pressure of the oil in the stand-pipe, D', and valve chamber, H, and is
kept to its seat normally by sa d pressure. This valve is shown in Figures 2, 4
and 5. A lever, I, is piroted by a screw-bolt, o, and one end takes under the
projecting end of the valve-stern, m³, (see Figures 2 and 4) the other end of this
lever projects through a slot, p, in the base and on the exterior has a foot piece, I'
By depressing this foot piece the release valve, m, will be opened and oil in the
valve-chamber, passage, h, and stand-pipe, D', will be discharged into the oil-
reservoir, B, and thereupon the piston, F, and chair-body will be slowly lowered.
The lowering will be slow because the valve port through which the oil has to
discharge is quite small.
A spring, g, bears against the valve lever, I, and normally supports it, and
prevents it from lifting the release valve, m.
The pump piston, G, is depressed or forced down by the lever, I, which is
arranged to give great power, and said piston is raised by the retracting spring, r.
A suitable pivot-pin, K, is fixed horizontally at one side of the pedestal, in this
instance it is screwed thereto; the pump lever, J, has its eye, s, mounted on this
pivot-pin; this lever extends alongside of and past the pedestal to the opposite
side; a slot, t, is in the side of the pump-cylinder, E, and a short arm, q', is attached
to the lever-eye, s, and projects through the said slot, t, into the cylinder, and a
link-bar, u, connects between the pump-piston, G, and the said short arm, g. This
short arm, 7, on the lever, J, is the direct means which forces the pump-piston, G,
down. The lifting spring, r, has its lower end attached to a pin, v', between two
ears on the short arm, q', and its upper end is attached to a cross-pin, v', which rests
in notches at the top of the cylinder, E. The spring, r, keeps the pump-piston, G,
1

page_text: normally raised; when it is being raised the pistou sucks the oil from the reservoir
up through the pipe, f, and check-valve, f', into the cylinder, E; when the
piston, G, is forced down by the lever, J, the oil in the pump-cylinder will be
forced through the check-valve, g', and passage, b, into the stand-pipe, J¹.
The upper end of the non-rotating piston, F, has a head with an L-shaped
flange, w, which is circular; a chair-seat base, N, has a circular opening at its
center provided with an annular flange, w', which is seated on the L-shaped flange, w,
and is rotatable thereon. To hold the seat-base, N, from rotation, we have
provided a special device shown in Figures 2, 6, 7 and 8. A clamp plate, P, is
loosely supported by pendent screws, 0, below the annular flange, w¹, so as to be
vertically-movable on said screws; this clamp-plate, which in Figure 8 has a ring
form, of course revolves with the seat-base, N, and takes below the stationary
L-shaped flange, wc, on the piston-head. Now it will be seen that if the clamp ring-
plate, P, is raised so as to bear up against the lower surface of the L-shaped
flange, w, the latter will thereby be clamped and consequently the seat base, N, will
be prevented from rotating. To, thus raise the clamp-plate a crank-shaft, P1, has
bearing in the seat-base and its inner end has an eccentric pin, ; the seat base, N,
has a vertical slot, ¹, and a link-bar, a, raises the clamp-plate; this link-bar
in Figure 8 has its upper end attached to the eccentric pin, passes down through
the slot, ', in the seat base and also through a slot, a³, in the ring-plate, P, and the
lower end of this link below the ring-plate has a pin, e. By a half-turn of the
crank, P, the link-bar, r², will be either raised or lowered as the case may be; if
raised, the ring plate, P, will be raised, as in the left-hand view of Figure 7, and
caused to bear up against the lower surface of the circular head flange, w, and
clamp it and hold the chair-body from rotating. When the ring-plate is lowered,
as in the right-hand view of Figure 7, the seat base is free to be rotated.
Instead of a link-bar and ring-plate separately constructed, a link-bar, a², and
clamp device, P2, as an integral piece may be used, as in Figure 8^.
The central plate, c³, of the pan, c, is fitted therein by means of a flange, c³, and
screws and, of course, a suitable packing to make the joint oil-tight. By removing
the bolts, c', of the pan, the screws in the flange of the central plate, and the
screws, d³, through the central plate into the lower end of cylinder, D, all the
mechanism may be removed.
The oil-reservoir is supplied with oil at the inlet port, a', and the pan has at one
side a hole which is closed by a plug, b. This plug and hole enables all the oil to
be drawn out of the pan when it is desired to remove the mechanism from
the base.
The vent-hole and plug, j, in the top of the piston heretofore referred to, are
useful when first charging the chair parts with oil and putting it in operative
condition. Before the chair-parts are charged with oil, the stand-pipe and the
tubular piston at its closed top contain air; now when the pump forces oil into the
bottom of the stand-pipe, the air referred to is compressed in the upper part of
the stand-pipe and as the forcing of oil continues and the piston, F, rises, this
compressed air would be in the tubular piston and would constitute an elastic
cushion on top of the column of oil. The result would be that the chair-body
or seat would be mounted on this elastic cushion and instead of being fixed and
etable would be yielding and movable-a condition unfit for dental operations.
The utility, therefore, of the vent-hole and plug, j, is to provide for the escape of
all the air contained in the stand-pipe and piston when the oil is being charged or
filled into said parts. When full of oil the vent-hole is closed by the plug and the
chair is then in operative condition.
The upper head of the piston, F, has on its lower side an annular groove or
chamber, y, see Figure 2, provided at one side with a ring parking, y', shown in
solid black. The cover plate, d, on top of the pedestal has an upward-projecting
curb or flange, D2, which is a continuation of the cylinder, D; when the piston, F,
and chair-body are fully down the curb or flange, D³, fits in the annular groove, y,
on the piston-head, as shown in Figure 2. It will be understood that when the

page_text: piston and chair-body are lowering, and as they approach the final or lowermost
point, this curb or flange, D', will take into the annular groove which contains air,
and as said groove is tight by reason of the packing-ring, y, the air is confined in
the groove and thus serves as a cushion to produce a soft and easy stop.
Referring to the modification shown in Figures 9 to 15 inclusive, the pedestal, A, oil-
reservoir, B, force pump, E, G, and lever, J, have the same construction and relation
as the same parts shown in Figure 2. The lifting cylinder, D, and pump-cylinder, E,
in this modification extend entirely across the interior of the pedestal; the stand-
pipe, D', in this case screws into the passageway, ', which communicates from the
pump-cylinder to the stand-pipe.
The release valve, m, is located in this passageway, and the lever, I, and its
foot-piece, I, open the release valve.
The tubular piston, F, in this modification has at its lower end two diametrically
opposite terminals, ; when the piston is fully down each of these terminals take
on an opposite side of the passageway, h, that is, they sit astride of the passageway;
this position is denoted by broken lines in Figure 13 and wholly shown in
Figure 11. By this construction of two terminals the lower end of the piston when
down may rest on the bottom of the oil-reservoir, and when up to the limit these
terminals fit the cylinder and stand-pipe and serve to give a rigid support to
the raised chair-seat.
The release valve, m, in this case is the same as in Figures 2, 4 and 5, but the
stem is slightly different in construction, having a groove in it instead of a plural
number as in the other, and the oil-pan in this case has no separate central plate in
its bottom.
From the foregoing description the operation of the chair will be readily
understood.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is,
-
1. In a chair, the combination of a pedestal, A; an oil-reservoir in the base of
the pedestal; a cylinder, D, for a lifting piston and enclosed in said pedestal and
having its lower end open into the oil-reservoir; a stationary stand-pipe, D', within
the said lifting cylinder and forming therein an annular space; a tubular lifting
piston, F, fitting in the annular space in said cylinder and having its upper end
closed; a pump-cylinder enclosed in said pedestal and communicating with the oil-
reservoir; a check-valved communication or passage from the pump-cylinder to
the said stand-pipe; and a release valve to allow the oil in the stand-pipe to escape
to the oil-reservoir.
2. In a chair, the combination of a pedestal, A; an oil-reservoir in the base of
the pedestal with the lower surface of the bottom plate of said reservoir substantially
on the same horizontal plane as the lower surface of the feet or rim of the pedestal;
a cylinder, D, for a lifting piston and enclosed in said pedestal and having its lower
end open into the oil-reservoir; a stationary stand-pipe, D', within the said lifting-
cylinder and forming therein an annular space; a pump-cylinder enclosed in said
pedestal; a check-valved passage from the pump-cylinder to said stand-pipe; a
tubular piston, F, fitting in the annular space in said lifting cylinder and having its
upper end closed and provided at its lower end with a slot which takes over the
said passage from the pump-cylinder to the stand-pipe, whereby, when the piston
is fully down, its lower end may rest on the bottom plate of the oil-reservoir.
3. In a chair, the combination of a pedestal, A; an oil-reservoir in the pedestal;
a stationary lifting cylinder, D, enclosed in said pedestal; a stationary stand-
pipe, D', within the lifting cylinder aud with the cylinder forming an annular
space a communication from the oil-reservoir whereby oil may enter the lower
end of said stationary stand-pipe; a tubular piston fitting in the annular space in
said lifting cylinder and having its upper end closed; and a vent-hole in the
upper end of said tubular piston-said hole being closed by a suitable plug.

page_text: 4. In a chair, the combination of a pedestal; an oil-reservoir in the pedestal; a
stationary lifting cylinder, D, enclosed in said pedestal; a horizontal cover
plate, d, on top of the pedestal and sitting upon the top extremity of the said
cylinder; a stationary stand-pipe, D', within the lifting cylinder and with the
cylinder forming an annular space, and having its upper end, , projecting above
the top of the lifting cylinder and above the said horizontal cover plate; and a
tubular piston which slips down over the said stand-pipe and fits in the said annular
space in the lifting cylinder.
5. In a chair, the combination of a pedestal, A; an oil-reservoir in the pedestal ;
a cylinder, D, for a lifting-piston and enclosed in said pelestal; a stationary stand-
pipe, D', within the said lifting cylinder and forming therein an annular space; a
tubular lifting piston, F, fitting in the annular space in said cylinder and having
its upper end closed; a pump-cylinder enclosed in said pedestal and communicating
with the oil-reservoir; a valve-chamber, H, attached to the base of the pump-
cylinder; a check-valved pipe from the oil-reservoir to the pump-cylinder; and a
passage or pipe from the said valve chamber to the stand-pipe.
6. In a chair, the combination of a pedestal having rim or feet the under surfaces
of which rest or seat upon the floor; an oil-reservoir formed by a bottom pan
secured within the said pedestal and the lower surface of the bottom of which is
substantially in the same horizontal plane as the undersurface of said rim or feet;
a stationary cylinder, D, enclosed in said pedestal; a stationary stand-pipe, D',
within the stationary cylinder and forming w.th said cylinder an annular space; a
tubular piston fitting in the annular space and having its upper end closed and
having its lower end, when the piston is fully down, resting on the said bottom pan
of the oil-reservoir.
7. In a chair, the combination of a pedestal; a non-rotatable vertically-movable
piston provided at its upper end with a circular head flange, w; a sent-base, N,
having an annular flange, w¹, seated on the said circular head flange and rotatable
thereon; a vertically movable clamping device below the said circular head
flange; a link-bar to raise the clamp device; and a crank-shaft operating the
link-bar.
8. The combination of a chair-body; a pedestal; a cylinder in the pedestal and
having at its upper end a curb; a lifting piston attached to the chair-body and having
an upper head provided on its lower sides with an annular groove, and said groove
having a packing-ring, y', guarding the entrance to the groove and forming there-
with an air-chamber into which latter the said curb enters when the chair-body
and piston are moving down to the final point, whereby the air in said chamber
serves as a cushion when the down movement stops.
Dated this 14th day of March 1895.
WILLIAM BRAYTON MANN.
WILLIAM TECUMSETH STILWELL.