Improvements in or relating to Dental Chairs.
Year: 1895

page_text: Date of Application, 21st May, 1895-Accepted, 14th Sept., 1895
Improvements in or relating to Dental Chairs.
A communication by FRANK RITTER, of Rochester, in the County of Monroe and
State of New York, United States of America, Manufacturer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S. M.I.M.E. of The Agency for
6 Bank Street
Foreign Patent Solicitors 6 Lord Street, Liverpool and
Manchester both in the County of Lancaster, 118 New Street, Birmingham
in the County of Warwick and 31 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 relates to dental chairs and has for its object to increase the utility
and simplicity of the construction of such chairs and the invention consists in the
construction hereinafter described and particularly pointed out.
In the accompanying drawing:
Figure 1 is partial elevation ;
Figure 2 is a partial central vertical section;
Figure 3 is a partial rear elevation partly in section ;
Figure 4 is a plan of a spittoon ;
Figure 5 is a plan of the chair, the seat being removed and the back frame
sectioned ;
Figure 6 is a section on line 6-6 of Figure 2;
Figure 7 is a section on line 7-7 of Figure 5 ;
Figure 8 is a section on line 8-8 of Figure 7;
Figure 9 is a partial section on line 9-9 of Figure 5;
Figure 10 is a central vertical section of the back frame;
Figure 11 is a plan of the head rest; and
Figure 12 is a plan of a modified head rest pad.
In Figures 1 to 6* are illustrated particular improvements in the steadying
rods, pedestal, piston cylinder and base.
Figure 1 is a partial vertical section;
Figure 2 is a transverse section on line 2-2 of Figure 1*;
Figure 3* is a similar section on line 3-3 of Figure 1*;
Figure 4* is a vertical section on line 4-4 of Figure 3* ;
Figure 5* is a sectional detail; and
Figure 6 is a partial section of a sectional base having an entire bottom.
Numeral 1 denotes a chair base. 2 is a pedestal rotatably supported on the
base. 3 denotes a seat frame and 4 its cross bar. 5 is a plunger rigidly secured
to the bar 4. This plunger is a piston rod and its foot is a piston adapted to be
raised by fluid pressure and to be lowered automatically.
The piston works in a fixed tube 6 which at its bottom communicates with an
oil reservoir and with a pump through suitable valved passages.
7 denotes a sliding steadying guide tube or cylinder which near its foot fits the
tube or piston cylinder 6. It also fits an opening in the top of the pedestal and has
a perforated cap 8 that fits the plunger. The main function of this sliding cylinder
is to support the plunger laterally and obviate shaking, especially when the
cylinder is locked as will be explained. The guide tube 7 has an exterior groove
71

page_text: to receive a key 711 see Fig., 2, fast on the pedestal to prevent the independent
rotation of the sliding guide tube.
9 indicates pendants or guide rods fixed to the cross bar preferably at each side
of the plunger. They are made movable through sleeves 10 rigidly fixed to the
steadying cylinder 7 by arms integral with its cap 8.
11 indicates locking devices seated in recesses formed interiorly in the sleeves 10
see Fig., 9, and adapted to be operated each by the foot of a steadying pendant 9
when it is pulled up against the bottom of the said device 11 with the effect to
force the inclined faces of the part 11 against similar faces in the sleeve, as
happens in the elevation of the chair seat frame. This lock becomes inoperative
by gravity at any time when the seat is free to descend.
The cylinder 7 is locked by similar device 12 bearing upon the interior of the
pedestal, see Fig., 2. 13 denotes a spring normally drawing down the locking
device 12 and making it operative. 14 is a treadle whereby the spring may be
overcome and the lock disengaged to permit the tube 7 to descend. The lock 12
is automatically released by the friction of the tube when said tube is drawn up as
elsewhere explained.
The seat is raised by pumping a suitable liquid under the piston which forces
up the plunger and seat frame. In the lowest position of these parts the pendent
guides 9 extend to near the top of the base as shown in Figure 1. When the
plunger and seat frame rise the pendants 9 are drawn up through the sleeves 10
until their lower ends push up and make operative the locking devices 11,
whereupon through the medium of the arms and cap 8, the ascent of the seat
frame and its cross bar continuing, the guide or steadying tube 7 is drawn up to
any desired height.
The chair seat is supported on a liquid column in usual manner. To lower it
a valve 15 is opened and the liquid is forced by gravity from under the supporting
piston or plunger into the oil reservoir 16. This valve is opened by the same lever
or treadle 14 which releases the lock 12, and simultaneously, so that the guide
tube 7 descends with the plunger. The downward movement of the seat releases
pendants 9 from the locks 11 and said pendants can move freely through their
sleeves, and must so move when tubes 7 are arrested, if that occurs before the seat
has reached its lowest level.
To enable the valve to be opened by the lever, as stated, a rod 17 connects these
parts in such manner that the lowering of the lever overcomes a spring which
normally closes the valve and pushes the latter down into its open position.
As usual in dental chairs the pedestal supporting the parts above described
rotates on the base and is provided with a lock such as a screw 18 see Figs., 2 and 3,
bearing against a friction block 19 situated between the base and the pedestal, and
carried by the latter.
Heretofore such locks have been made operative by a treadle which required to
be lifted by the foot to release the lock. This is objectionable for the reason that
the operation is liable to disturb the equilibrium of the operator who must not only
support himself upon a single foot but lift with the other. To avoid this the lever
is provided with a tread on each side of its axis so that the screw can be turned in
either direction by a downward pressure and does not endanger the stability of the
operator.
The chair is adapted for the use of children by a supplementary seat elevating
device to raise the seat so that a child sitting on it can make use of the head rest
in its lower position. 20 denotes a swinging frame pivoted at 21 in the seat frame
and pivotally connected at 22 with seat raising bars 23. On the rear end of one of
these is a foot piece 24 by which it is operated. The bars 23 bear each against a
friction pulley b, b₁ (see Figures 3 and 9) supported to turn on suitable screws or
studs fixed to the seat. By pushing on the pedal the frame 20 is swung forward
and bars 23 pushed forward and upwardly with the effect to raise the seat causing
it to tilt about the pivots 24. This also throws into operative position the child's
foot rest 25 having pivots at 26 and pivotally connected at 26¹ to said bars 23.

page_text: When not in use this foot rest is partially concealed in a pocket 27 formed in a
downward extension from the seat frame. To restore the level of the seat after
raising it as stated it can be tipped backwards.
The back frame is pivoted to the seat frame at 28 in usual manner. 29 indicates
a curved rack pivotally connected to the said back frame and adapted to move
through an opening in a stud or projection 30 fixed to the seat frame. The
concavity of the bar rests on or moves smoothly over a convex surface 31 formed
in this stud. 32 denotes a holding bar or catch normally forced into engagement
with the rack by a spring 33, see Fig., 5, and 34 is a lever or handle to aid in over-
coming the spring and withdrawing the bar, when it is desired to raise or lower the
back frame.
An upholstered back is pivoted to the back frame at 35 and it is held in any
desired position by a rack fixed to back and a holding pawl fixed to the frame.
The back frame comprises the outer part 36, see Figs., 1, 5 and 10, a main
sliding extension 37 and a two-part subsidiary extension, the rear or interior part
made of brass, is denoted by 38 and the other partially enclosing it by 39.
40 denotes a handle movable vertically in a slot in the outer part 36 and adapted
to lock the slide 37 in said part 36. The main extension 37 can be moved up or
down by means of this handle and then locked by simply turning the handle which
has a screw thread connection suitable for the purpose. The extension parts 38
and 39 are moved by the handle 41. They have each a slight independent
movement controlled by the cam ring 39" formed on said handle and fixed to
pin 47 which is virtually a part of slide or bar 38. This cam is arranged to bear
against a suitable beveled face of a sleeve 39111 loosely scated in the upper part of
a yoke 39 attached to or forming part of the slide or bar 39. By suitably turning
the cam handle 41 the parts 38 and 39 are oppositely moved and thus their feet or
inclined faces 42 are wedged together and against the main slide 37. This
operation also locks the head rest as will appear.
The beveled sleeve 3911 is provided with a vertical side-groove, to receive the
end of a screw a which is fitted in the upper part of the yoke 39¹ so as to prevent
the rotation of said sleeve, when turning the handle 41, of the ring-cam 39".
On the upwardly projecting portion of the sleeve 3911 is fitted a block 51 having
a conical upper surface, and a clamping-bar or cover 49 the latter having recesseil
upper and lower surfaces to receive respectively, the head of the pin 47 and the
conical part of the block 51, so that the parts may be securely clamped together by
turning the handle 41 and the cam forming part thereof.
The head rest comprises two upholstered pads 43 each pivotally supported by an
arm 44 terminating in a hemisphere.
70 denotes a block provided with a stem or point entered in a hole in the
arm 44 and held therein by a set screw 72. 73 indicates a pivot passing through
said block and through two ears fast on the pad 71 indicates stops on the block to
limit the movement of the pad about said pivot 73.
Referring to Figure 12 of the drawing, 74 denotes a valved inlet for charging a
pad cam with a fluid such as air or water to form a cushion for the head, which
may be substituted for the usual stuff cushion.
The two hemispheres of arm 44 are secured together by a pivot or screw 45 as
shown, and they together constitute the ball, of a ball and socket joint. This con-
struction permits the whole head rest to be adjusted in any direction and also
provides that the parts may be independently moved about said pivot 45 to or from
each other.
Heretofore these pads have been connected with their supporting arms by
means of ball and socket joints. These require to be locked after adjustment
and the joint and locking devices make the construction too complex for these
purposes. If pads are supported by ball and socket joints, locks are necessary
otherwise they are two unstable and they permit a nervous or timid patient to
dodge. They also necessarily involve a larger range of movement than desirable,
and do not limit it either in direction or extent as by this improvement, which

page_text: automatically operated when required for comfort, the permissible motion being
very small and in one desired direction only and the construction being such that
a startled patient will not push a pad from its adjusted position and cannot dodge.
The socket of the aforesaid joint is formed in the outer end of a compound head
rest bar consisting in the main of two horizontal members connected to each other
by a transverse headed pin or bolt 46 and joined to the back frame by a pin having
a head 47 which pin is fixed to the slide 38 of the back frame as shown. Each
member of the head rest bar comprises a hollow cover 49, 49¹ enclosing, respectively,
a separately movable beveled block 50, 55. The ball of the main head rest joint
is locked in any desired position by the relative endwise movements of said
parts 49 and 55 of the outer member of the bar.
To produce this effect, suitable pressure and a slight movement of various parts
is propagated from the handle 41 which is fixed to the pin 47. Upon slightly
rotating the handle and its cam in locking together the slides 38 and 39 said slides
are oppositely moved with the effect to force the head of the pin 47 towards the
frusto-conical block 51 whereby the cover 49 is securely clamped, and the parts 38
and 39 locked together, simultaneously with this movement the outer end of the
adjacent beveled block 50 is pressed against a correspondingly beveled sleeve 52,
supported on pin 46, by a key 53, thereby depressing said pin and causing same to
draw the cover 49' towards the conical sleeve 54, whereby the intermediate
beveled block 55 is pressed outward and thus made to clamp the ball, of the ball
and socket-joint.
Heretofore beveled parts adapted to produce a lateral pressure without devices
to exert positively a transverse pressure have been employed in compound head-
rest bars but the locking was not sufficiently secure.
In one instance the lock was made more secure by transverse ties or headed
pins but the action of these was dependent upon levers which were liable to be
broken by the great pressure to which they were necessarily subjected. The
present construction is simple and insures a secure lock without danger of
breakage. And it is also economical since less tooling of the parts are required
and only the covers 49 and the pin heads need be nickelled.
The pivot 73 that connects each pad to its supporting arm is parallel to the pad
lengthwise thereof and in an approximately central line and close to the pad. The
object of this construction is to provide for a small automatic tilting adjustment
of each pad to cause it to bear full against the head and avoid the discomfort
produced by contact with the edge of such a pad.
Heretofore spittoons supported upon brackets attached to dental chairs have
been provided with flexible water supply and waste tubes that extended from the
spittoon to a fixed point or fixed points in the floor. In such constructions the
tubes are liable to be thrown in the operator's way, or to be twisted or their
connections strained. To avoid these evils and support the flexible pipes or tubes
in a comparatively out of the way situation and with their lower ends supported in
and rotatable with the seat frame, telescopic tubes are provided, both for the water
supply and the waste, extending preferably from the seat frame cross bar to the
level of the floor.
55', see Figure 7, denotes a tube fixed to the cross bar and 56 a tube telescoping
therewith and having its foot fixed to a coupling 57 rotatably supported by a
water tight joint in a bowl 58, or the like, fixed to the floor. 59 indicates the
discharge opening which may be connected with a sewer or other suitable
receptacle.
60 denotes an inlet pipe for water and 61 a valve for opening and closing the
same. This pipe communicates with a semi-annular passage 62, a vertical
passage 63, an inlet 64 and with a pipe 65, see Fig., 8, fixed to and rotating with
the coupling 57. The pipe 65 telescopes with a pipe 66 see Fig., 6 fixed to the
cross bar like pipes 55 and 56, and all these pipes rotate with the chair seat frame
and with the pedestal. In addition to their other advantages they act as guides
and aid in preventing a shaky or unsteady condition of the seat frame and plunger

page_text: which is a consideration of especial importance in a chair providing for a large
range of movement in the class to which the present invention pertains.
The telescoping pipes are preferably connected by communicating flexible
pipes 67 with a spittoon supported by an extensible arm 68, see Fig., 3, movable
in a supporting sleeve 69 mediately supported on a swinging bracket in usual
manner. The construction is such that the bracket can be swung horizontally and
the sleeve 69 and its supporting rod moved vertically and the arm also swung on
said rod and further the spittoon can be moved to and fro from the rod by the
telescoping connection of its arm 68 and sleeve 69.
The flexible pipes 67 need descend but little if any below the chair seat frame
and can therefore be kept out of the way of the operator's feet under every
adjustment.
All these parts are connected to rotate with the chair seat frame and the
pedestal.
The modifications represented in Figures 1 to 6* will next be described.
In said figures, numerals 1 and 2 denote respectively upper and lower sections of
a chair base. These sections are secured to each other either by screws or like
means and support a pedestal 3 in usual manner. In section 1 of the base a
receptacle 4 for overflowed oil is provided by means of the inner wall 5 of the
annular base skirt 5', the bottom of the base being made relatively thin by
preference and situated below the main body of the said skirt. Chair bases are
made of cast metal and are liable to be broken in transportation or otherwise.
One object of this sectional construction is to limit such fractures to one part
of the base and obviate the necessity of replacing the entire base when broken.
A further object is to provide in the base a capacious receptacle for oil that
may be spilled or that may leak or overflow from the oil receptacle such as
indicated at 6.
This oil holder is fastened to the pedestal by screws 7 or other like means and is
recessed on several sides to provide room for telescoping liquid conveying pipes 8
and 9 and for steadying guide rods.
To permit said rods to descend to or near to the floor level, holes 13 may be
provided in the pedestal. The rods are composed of two sections 14 and 15, the
first of which is made fast to the cross bar of the seat frame. The other section 15
has a dovetailed or like connection to section 14 when the latter is raised or
lowered with the cross bar. 17, see Fig. 4*, denotes a stop to limit the independent
movement of section 14 in an upward direction and 18 is a groove that permits
this section to rise until said stop engages the shoulder at the top of the groove.
The section 15 is suspended by a flange 15¹, see Fig., 1×, upon the upper edge of a
sleeve 19 formed integral with or fixed to a bar or support 20' of a guiding and
steadying tube 21. 11 denotes a locking device situated between the sleeve 19 and
section 15 and made operative by the lifting effect of a plate or projection fixed on
the foot of section 15 when the parts are at their highest elevation.
The guide or steadying tube 21 has a bearing at 121 on the pedestal and also on
the piston cylinder 22. Within the latter and between it and the piston is a sliding
piston cylinder extension 23. It is adapted to be moved up by the piston whenever
the latter comes in contact with the ring or projection 24, whereupon it lifts it and
the said cylinder extension 23 to which the ring is fixed. This extension cylinder 23
can be lifted by the piston until stopped by the action of a stop 21' engaging a
groove in the steadying tube 21, see Fig., 5*.
25 is a packing to prevent oil which is forced under the piston from escaping
between the cylinders 23 and 22.
26 is a coupling cup whereby piston cylinder 22 is fixed to the bottom of the
oil holder. This cup extends to near the floor level and receives oil when forced
in by the pump to raise the piston. The parts being at their lowest elevation, the
oil passes through one or more perforations 27 in the foot of the movable cylinder 23
or in an elastic terminal thereof and ascends through a passage 28 in the packing.

page_text: When oil is pumped in, the piston is first forced up carrying the chair seat
or seat frame. The pumping continuing the piston engages the ring 24 and pulls
up the cylinder 23. By this means the piston and piston rod may be lifted
entirely above the level of the ordinary fixed piston cylinder 22, the cylinder 23
forming a movable extension of the same. The piston being permitted to descend
in usual manner can push said tube 23 down until the piston and the foot of tube 23
are near the floor as indicated in the drawing.
By this means a much higher elevation may be given to the seat with a piston
rod and fixed cylinder of a given length. This therefore provides that these parts
may be made shorter than heretofore and yet raise the seat as high or even higher
than usual. But such shortening of the piston rod and cylinder permits the chair
to be correspondingly lowered and this is an important object of the improvement,
namely, to provide a chair seat adapted to be raised as high as customary or if
desired higher, and yet permit it to be lowered beyond what is practicable in any
prior chair having a hydraulic lifting apparatus situated above the floor level.
By the ascent of the piston as just described the cross bar is raised with the
effect to pull sections 14 of the steadying rods up through the sleeves 19 until the
stops 17 engage sections 15 whereupon the latter are also pulled up until the pro-
jections at their lower ends operate the locking devices whereupon the bar 20 is
lifted pulling up the steadying tube 21 until it reaches the desired height or
is stopped by suitable means such as a key 21¹ engaging the lower end of a groove
therein, (see Figure 5*).
Some of the advantages of the improvement could be secured without extending
the sectional steadying guide rods 14, 15, down into the pedestal, but this enables
the chair provided with such rods to be lowered further than would otherwise be
practicable, unless the sections of the rods were increased in number. It is further
obvious that if the steadying rods were not made in sections but entire, the
openings to permit their descent within the pedestal would provide for lowering
the chair seat or seat frame having such steadying guides lower than would
otherwise be possible.
The means above described for increasing the range of movement of the
steadying rods co-operate with the extensible piston cylinder and they together
with the steadying tube provide that the chair seat may be moved both higher and
lower than heretofore practicable in this class of chairs without shaking or binding
and with a firm, easy and stable motion highly desirable in dental chairs.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondents, I declare that what I claim is :-
1. In a dental chair, the combination of a rotating pedestal, a seat supporting
plunger, steadying rods or guides fixed to the seat frame cross-bar in vertical
planes outside the top of the pedestal, and the rod-receiving sleeves, said parts
being supported by and rotatable with the pedestal, substantially as set forth.
2. In a dental chair, the combination of the seat supporting plunger, steadying rods
or guides fixed to the seat frame cross bar, and the rod receiving sleeves mediately
supported in the pedestal, locks normally inoperative and means for making them
operative by the ascent and contact of the said rods to lock the rods in the sleeves,
substantially as set forth.
3. In a dental chair, the combination of a rotating pedestal, a seat-supporting
plunger, steadying rods or guides fixed to the seat frame cross bar, and the rod
receiving sleeves, said parts being supported in and rotatable with the pedestal
and a steadying cylinder, said cylinder having bearings in the pedestal and
supporting said sleeves, substantially as set forth.
4. In a dental chair and in combination with a rotatable pedestal, a chair seat
frame having a cross-bar, a seat frame elevating and lowering plunger, parallel
rods attached to the cross bar and a supplemental guide, comprising a steadying

page_text: tube movably supported in the pedestal and provided with sleeves to receive said
parallel rods, all the parts being supported by and rotatable with the pedestal,
substantially as set forth.
5. In a dental chair, the base, the pedestal, the plunger supporting the seat, the
plunger or piston cylinder, the sliding steadying tube situated between and touching
both the pedestal and plunger tube and vertically movable with respect to each,
said steadying tube being connected to the seat frame independently of the plunger
by a sliding steadying rod and said rod fixed to the seat frame outside the top of
the pedestal to permit it to descend beside the same, all substantially as described,
whereby the stability of the seat is promoted.
6. In a dental chair, the combination of the pedestal, the plunger, the plunger
cylinder, and the sliding steadying tube situated between and bearing on the pedestal
and cylinder and movable with respect to each, with an automatically operating
locking device to lock the steadying tube and pedestal together and a lock-tripping
lever, substantially as described.
7. In a dental chair, the combination of the pedestal, the oil reservoir, the
planger, the plunger cylinder, the valved passage whereby oil may flow from the
cylinder to the reservoir, the steadying tube situated between and bearing on
the pedestal and cylinder and movable with respect to each, the device to
automatically lock said tube and pedestal together, the lock-tripping lever and a
connection between the lever and valve whereby the operation of the lever to
release the lock to permit the steadying tube to descend also opens the valve to
permit the plunger to descend, substantially as described.
8. In a dental chair, the combination of telescoping pipes one of which is fixed to
the cross bar of the seat frame, and the other fixed to a coupling rotatably supported
below the chair pedestal, a support for said coupling, and means for supplying
liquid to the pipes and coupling, said pipes being rotatable with the seat frame and
pedestal, and adapted to connect with a receptacle attached to the chair and
communicate with it and also with a conduit or receptacle below the chair,
substantially as set forth.
9. In a dental chair, in combination, the chair seat frame, the plunger
supporting said frame, the plunger cylinder, the rotating pedestal supporting
the plunger and cylinder, the rotatable coupling 57, supports for the couplings,
conduits for admitting a liquid to the pipes and coupling, the pair of telescoping
pipes, one of each pair being fixed to the seat frame and one to said coupling,
said pipes and all the parts rotating with the pedestal, substantially as set
forth.
10. In a dental chair, in combination the chair seat frame, the plunger, the
pedestal, the telescoping pipes, the coupling 57, said pipes extending from the
frame to the coupling and all the parts rotating with the pedestal, and a fixed bowl
or support independent of the chair and having a seat for the coupling, substantially
as set forth.
11. In a dental chair, the rotatable seat, devices for raising and lowering the
same, a spittoon, a vertically extensible pipe having connection and communication
with said spittoon and with a conduit fixed below the chair, all said parts except
the conduit being rotatable with the chair and with the raising and lowering devices,
substantially as set forth.
12. In a dental chair, the combination of the pedestal, two pairs of telescoping
pipes, one pipe of each pair being fixed in the seat frame cross bar and the other
pipe of each pair fixed to the coupling rotatably supported below the pedestal, said
coupling, a spittoon, and flexible pipes by which the spittoon and telescoping pipes
communicate, substantially as described.
13. In a dental chair, the combination of the pedestal, two pairs of telescoping
pipes, one pipe of each pair being fixed in the seat frame cross bar and the
other pipe of each pair fixed to the coupling rotatably supported below the
pedestal, said coupling, a spittoon, and flexible pipes by which the spittoon
and telescoping pipes communicate, said spittoon being mediately supported

page_text: from the chair seat frame by a horizontally sliding arm, substantiany
forth.
45 507
14. In a dental chair, the combination of the seat and pivotally supported seat
frame, with a swinging frame supported from the seat frame, and seat-elevating
bars pivotally supported in said frame, whereby the seat may be independently
raised, substantially as set forth.
15. In a dental chair, the combination of a seat and seat frame having a pivotal
support with a swinging frame supported from the seat frame, and seat-elevating
bars pivotally supported in said frame, whereby the seat may be independently
raised and a childs foot rest connected to said bars and pivoted to the seat frame
whereby the said rest may be moved into operative position simultaneously with the
raising of the seat, substantially as set forth.
16. In a dental chair, the combination of the back frame pivoted to the Beat
frame, the curved toothed bar fixed to the back frame, the seat frame provided with
the opening to receive the bar and a locking bar supported and movable in the
seat frame to engage the rack teeth and lock the back frame in any desired
position, said opening being below the top of the seat frame and the bar
curved from the back frame when vertically disposed toward its front whereby the
back can be lowered to or below the level of the seat and locked, substantially as
set forth.
17. In a dental chair, the head-rest bar support comprising the two bars 38
and 39 having formed thereon contiguous beveled surfaces for forcing the beveled
faces together and wedging one of the said bars between the other and the sliding
extension to lock the parts in place, substantially as set forth.
18. In a dental chair, the combination in a head rest of the pads each connected
by one arm with a hemisphere, said arms and hemispheres, a central pivot passing
through the ball formed by said hemispheres, a socket to hold the ball, and a
clamping device to lock the ball in its socket and its halves together, substantially
as set forth.
19. In a dental chair, the combination in a head rest, of the pad supporting
arms, the pads, each pad having a pivot 73 situated contiguous its back near its
longitudinal center and adapted to permit movement in the direction of one plane
only to provide for the automatic adjustment of the pad to the head, substantially
as set forth.
20. In a dental chair, the head rest supporting arms 44 having a jointed
connection with the chair back frame and provided each with a socket, the pad
supporting blocks having each a stem to enter one of said sockets, and set screws
whereby the head rest pads may each be independently adjusted and fixed to its
arm, substantially as set forth.
21. In a dental chair, the head rest supporting arms 44 having a jointed
connection with the chair back frame and provided each with a socket, the pad
supporting blocks having each a stem to enter one of said sockets, and set screws
whereby the head rest pads may each be independently adjusted and fixed to its
arm, said pads being separately pivoted in the blocks and provided with stops to
have a free limited movement to and from each other, substantially as set forth.
22. In a dental chair, a compound bar containing at one end a socket for the
ball and socket joint for the head rest, and comprising two covers 49, 49¹ pivoted
together by a headed pin, one of the said covers being pivotally connected by a
headed pin to the back frame, beveled biocks (51, 54) situated under said covers,
beveled sleeves (39, 52) surrounding the pins and freely movable thereon and
means for moving the sleeves on the pins to draw the same to the covers and
simultaneously crowd the blocks transversely to the pin whereby the ball is locked
in its socket at one end of the bar and the other end of the bar locked to the back
frame and the two members of the bar locked together by both lateral and vertical
pressure, substantially as set forth.
23. In a dental chair, a compound bar comprising two members each consisting
of a bar or cover 49 and beveled block 50 and also comprising a transversely

page_text: disposed pin bearing on the cover, beveled sleeves 3911, 52 freely movable on the
pins, and means such as a cam ring for tightening one of the pins against a cover,
said means being also adapted to push a block transversely of the pin, the con-
struction being such that the movement that positively tightens a pin on the cover
also crowds the several sleeves and blocks together and thereby tightens a second
pin on the cover and simultaneously transmits pressure to the end of the bar to
lock the head rest, substantially as set forth.
24. In a dental chair, the base, the rotary pedestal seated upon the base, and a
device to lock the base and pedestal together, said device consisting of a screw or
the like provided with an operating tread on each side of its axis both said treads
beng in a horizontal plane tiansverse to the pedestal whereby the device may be
either loosened or tightened by a downward pressure of the foot, substantially as
described.
25. In a dental chair, the base made in sections detachably secured together,
said sections consisting of an approximately horizontal part to rest on the floor and
a vertical cylindrical part to support the chair pedestal, said horizontal part com-
prising a skirt and a bottom, the skirt being raised above the bottom to enclose a
chamber for overflowed oil, substantially as described.
26. In a dental chair provided with a piston and fixed piston cylinder, the
movable cylinder extension and a packing to prevent oil from being forced
between the cylinder and movable cylinder extension and means whereby the
extension may be moved by the piston, said packing being secured to the foot of
the cylinder extension and provided with an opening to permit the passage of oil
to the piston and having also perforations for the oil to enter said passage when
the said extension is in its lowest situation, substantially as described.
27. In a dental chair, the oil-holder, the coupling cup screwed into the bottom
of said holder, the piston cylinder screwed into such cup, a movable piston cylinder
extension carrying a packing at its foot to pack the joint between it and the main
cylinder, said packing having perforations below the foot of the extension to permit
ingress of oil, substantially as described.
28. In a dental chair, the steadying guide rods made in sections connected to
slide one upon the other within a guide tube, one being fixed to the cross bar of
the seat frame and the other suspended in a bar 20, in combination with the cross
bar elevating piston, substantially as described.
29. In a dental chair, in combination steadying rods attached to the cross bar,
guiding sleeves for said rods, a pedestal having openings to permit the descent of
the rods and means for raising said cross bar, substantially as described.
Dated this 20th day of May 1895.
WM. P. THOMPSON & Co.,
Agents.