Improvements in Dental Chairs.
Year: 1895

page_text: Date of Application, 25th June, 1895-Accepted, 3rd Aug., 1895
Improvements in Dental Chairs.
1, 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, as hereinafter claimed, in means
for raising and lowering and maintaining in position vertically adjustable supports
for the bodies of dental chairs by the actuations of a single lever.
In the accompanying drawings which show a suitable embodiment of my improve-
iments with the chair body omitted,
Fig. 1 is a side elevation.
Fig. 2 is a view partly in plan and partly in transverse section.
Fig. 3 is a view partly in side elevation and partly in vertical section.
Fig. 4 is a view partly in front elevation and partly in vertical section, with
parts broken away and omitted.
Fig. 5 is a view on an enlarged scale partly in side elevation and partly in
vertical section, showing the mechanism in position for raising the chair body
support, preparatory to operating the lever by which this mechanism is actuated;
and Fig. 6 a similar view, with the mechanism in the position assumed by it when
the lever has been actuated to raise the support.
Fig. 7 is a view similar to Figs. 5 and 6 with the mechanism set for lowering the
chair body support; and Fig. 8 a similar view, with the mechanism in the
position assumed by it when the lever has been actuated preparatory to lowering
the support.
Fig. 9 is a view partly in plan and partly in horizontal section, with portions
broken away, showing details of construction; and Fig. 10 a view partly in side
elevation, and partly in vertical section.
Figs. 11 and 12 show separately the controlling rock shaft and its crank by
which the operation of the mechanism for raising and lowering the chair body
support is controlled.
Fig. 13 is a side view partly diagrammatric and partly in section showing the
controlling rock shaft and crank, with the rock shaft in the position to which it is
adjusted when the chair body support is to be raised; and Fig. 14 a similar
view with the rock shaft adjusted to the position to allow the chair body
support to be lowered.
Figs. 15, 16 and 17, show a modification of the raising, lowering, and upholding
mechanism and its controlling mechanism, Fig. 15 showing in elevation the modified
mechanism in position for raising the chair body support preparatory to operating
the foot-actuated lever; and Fig. 16 showing the parts as set for lowering
preparatory to operating the foot-actuated lever; whilst Fig. 17 is a view in
perspective of the cranked rock shaft by means of which the controlling mechanism
of the raising and lowering mechanism is actuated. In these views of the modified
mechanism the support carrier and various other parts are omitted.
A support A for a chair body is mounted so as to be vertically adjustable upon a
suitable supporting base or pedestal which as shown consists of the legs A¹ and the

page_text: hollow cylinder A² within and upon which cylinder is supported a carrier B in
which the support A is adapted to move up and down, these parts being assembled
substantially as in English Letters Patent, No. 4,662, of January 9, 1878, and as
explained in said Patent a lever B2 serves to actuate a clamp to lock the carrier B
against turning in the pedestal, and the support is vertically grooved or recessed
and provided in the recess with a row of teeth a to be engaged by pawls as in turn
to be explained.
A foot-actuated lever is made in two parts or sections-a main or outer part C
and a short curved inner part C'-which are jointed together by a vertical
pivot C2 passing through lugs or forks of the inner section and through the
inner end of the outer section of the lever near a horizontal pivot d by which the
lever is jointed by its inner section to the carrier B which is provided with
lugs D D for supporting this pivot. It will be seen that the lever (both sections
thereof) is adapted to rock or swing vertically and that its long arm or main section
may be swung horizontally to one side. The main arm of the elevating lever is
provided at its inner end with a cam which when this arm of the lever is moved
sidewise into the position in which it is shown by full lines in Fig. 9, acts upon a
clamping shoe made in two parts or sections D² ², and thus clamps the chair body
support A against lateral movement or vibration in any position to which it may
be adjusted in its carrier. With the exception that the clamping shoe is made to
engage a vertically extending groove or recess e in the support and thus lock the
support against turning in its carrier, this clamping shoe, and the lever so far as
described, are the same in construction and operation as set forth in my English
Patent No. 9,688 of May 17, 1894, and I do not herein claim any improvement set
forth in said Patent. When the clamping shoe is actuated the lever is locked
against vertical movement by engagement of its lateral lug E between stops formed
by projections (one only of which is shown) on the carrier lug D. and when the
lever is in the position in which it is shown by dotted lines Fig. 9, it is prevented
from moving sidewise in one direction by its lateral projection E', substantially as
in said Patent.
A pawl F is pivoted to the inner end of the sectional actuating lever and adapted
for engagement with the teeth of the vertically adjustable support A, and the lever
is overbalanced, a spring F1 having connection at its opposite ends with the inner
end of the lever and with the support carrier B being provided which acts with a
tendency to hold up the other end of the lever and maintain it in this position
when not actuated and restore it to such position after actuation. The lever-
carried pawl is pivoted by its hub or bearing F2 upon its journalf of the lever and
the pawl hub is provided with vertically extending flanges or projections fº¹ƒ'
constituting a guide-way sliding on the enlarged lower end or cross-head g of a pawi
controlling link G which is adapted to rock slightly in this guide way as the
actuating lever is operated, for a purpose in turn to he explained. An upholding
or detent pawl H adapted to engage with the teeth of the vertically adjustable
support, is carried by the support carrier, being pivoted at / to a bracket H' secured
to the support carrier. The link G is pivoted at its upper end to the upholding
pawl Hat g above the pivot of this pawl.
The throw or length of stroke of the lever pawl F is limited by stops at II',
shown as formed by the detachable cap J of the carrier B, with which the pawl
comes in contact on its up stroke, and by an inward projection of the carrier with
which the pawl hub comes in contact at the end of its lower stroke. See Fig. 3.
For a purpose in turn to be made obvious the length of stroke of the lever pawl
somewhat exceeds the pitch of the support teeth that is, the distance between
pawl-engaging shoulders of adjacent teeth is slightly shorter than the distance
travelled by the pawl at each actuation thereof by the lever.
To adapt the one actuating lever to operate to either raise or lower the chair
body support, pawl controlling or adjusting mechanism in addition to the before
described link G is provided as follows:-A rockshaft K is mounted in a bearing K'
provided in a detachable section L of the support carrier which section is screwed

page_text: in place. A crank armık at the inner end of this rockshaft is provided with
a pin engaging a slot in the pawl-controlling. link G. An actuating lever or
crank M is mounted loosely by a hub or short sleeve m on the rockshaft K which
is provided with a stop pin n which projects into a recess or cut-away.portion N of
the inner end of the hub m of the rockshaft lever. Shoulders o o' at the opposite
extremities of the recess N of the lever. hub serve to engage this lever with the
rockshaft by way of its stop pin.n.. A spring P has connection at one end, with the
support carrier by way of an arm; P₁ secured to the carrier, and at its opposite end
with a short crank arm or extension p of the inner end of the lever or crank handle M,
by way of a bent link pl. A washer or collar.n. pinued to the rockshaft outside
its. lever hub detachably secures, the lever in place. It will be seen that the
tendency of the spring P is to hold the shouldered hub of the crank lever: M in
contact with the stop. pin. n on the rockshaft, whether this lever be adjusted to the
position in which it is represented in Fig. 13, or to that in which it is shown
in: Fig. 14, and consequently the action of the spring, P on the rockshaft tends to
rock it and transmit the pull of this spring of the pawl controlling mechanism to the
link G by way of the crank pin k¹ of this controlling mechanism.
The operation of the raising and lowering mechanism is as follows:-To raise
the chair body support the lever or crank M of the pawl-controlling mechanism is
turned into the position in which it is represented by dotted lines Figs. 5, 6 and 13.
With..the main arm of the foot-actuated lever in its elevated position and the
support sustained by the upholding pawl H, it will be seen that by the action of
the spring P on the rockshaft K the crank pin k¹ engaging the slot of the link G is
made to exert pressure upon the upholding pawl in a direction such as to hold it
engaged with a tooth of the support, whilst at the same time the lower enlarged end
or cross head, of the link acting upon the guide way of the hub of the lever pawl
above the pivot of this pawl exerts a pressure upon this pawl in a direction such as
to cause its engagement with a tooth of the support when moved upward by the
lever. Upon downward movement of the long arm of the lever the. upholding pawl
yields, the lower end of the link G.rocking slightly in its guide way on the hub of
the lever pawl as the upholding pawl yields. When the lever pawl has been lifted
far enough to bring its axis of oscillation above the plane of contact of the link
end or cross-head with its guide way on this pawl it will be seen that the spring P,
acting through the rockshaft and its crank pin upon the link, tends to rock the
lever pawl away from the toothed support; but as the weight of this support and
the chair body (not shown) is at this time sustained by the lever pawl the force
exerted by the link actuating spring P is inadequate to disengage the pawl from
the support. The stop I which limits upward movement of the lever by acting
upon.. its pawl, serves also to ensure engagement of this pawl with the toothed
support during the finishing portion of the upstroke of the lever, so that in
event of failure of the link of the pawl controlling or adjusting mechanism to act
properly, the support would be sustained by the lever pawl. The stroke of the
lever pawl exceeding the pitch of the teeth of the support as before stated, it will
be seen that by the time of completion of the upstroke of the lever pawl the
upholding pawl is rocked by the action of the link of the pawl controlling or
adjusting mechanism into position (see Fig. 6) for engagement with a tooth of the
support just after the lever pawl starts on its downward stroke. When the
upholding pawl takes the weight of the support upon downward movement of
the lever pawl this latter pawl immediately rocks out of engagement with the
support. During the concluding portion of the down stroke of the lever pawl after
its axis of oscillation has been brought below the cross-head g of the link of the
pawl controlling mechanism, this mechanism acts with a tendency to engage the
pawl with the support, it will be seen, and by continuing to actuate the raising and
lowering lever the support may be elevated to the extent desired..
To lower the chair body support the lever M of the pawl controlling mechanism
is adjusted to the position in which it is represented by Figs. 7, 8 and 14, so that
the pull of the spring P upon the link G tends to move this link in the opposite

page_text: direction to that in which it is moved by the action of the spring when the pawl
controlling mechanism is adjusted for raising the support as just above explained.
Upon depressing the main arm of the foot-actuated lever, its pawl, being held out
of engagement with the toothed support, ascends freely or clear of the support until
the axis of oscillation of this pawl comes above the plane of contact of the link end
or cross-head with its guide way on the pawl hub, when by the action of the link
the lever pawl is swung into contact with the support and slightly before the time
of completion of its upstroke engages a tooth thereof. During this upward
movement of the lever pawl until after its engagement with a tooth of the support,
the weight upon the upholding pawl prevents its disengagement from the support
although the spring-actuated link G tends to trip this pawl at the time when this
link is acting upon the lever pawl to engage it with the support. After engagement
of the lever pawl with the toothed support the slight additional elevation of the
support releases the upholding pawl from weight of the support and it flies out of
engagement therewith. Upon the downward stroke of the lever pawl, during
which sufficient pressure is exerted upon the foot rest of the elevating and lowering
lever to prevent too rapid descent of the support, the upholding pawl remains out
of contact with the support until slightly before the completion of the downstroke
when the upholding pawl engages a tooth of the support and arrests its descent,
this engagement of the upholding pawl with the support being caused by the action
of the lever pawl upon the upholding pawl by a shoulder a¹ on the lever pawl
bearing against the upholding pawl to force it into position before the support is
released by the lever pawl; and, after this, just before the completion of its
downward stroke, the lever pawl flies out of engagement with the support. The
lowering operation may be repeated as required to adjust the support as desired.
Although the adjustable support A is shown as round and fitted so as to move
end wise in a turning carrier, I do not wish to be understood as confining my
improvements to such construction, as the support may be of any desired form,
rectangular or of other polygonal shape in cross-section; and any suitable
equivalent be employed for the carrier shown, and the carrier instead of being
adapted to turn horizontally may be stationary. My improvements may otherwise
be modified in various respects, whilst retaining essential features of my invention.
Figs. 15, 16 and 17, show modifications of my improvements. In these figs. the
pawl Qis pivoted at its heel to the inner end of the raising and lowering lever,
and the upholding pawl R is, as before, pivotally connected with the support
carrier which is not shown. Movements of the pawls away from the rack teeth
of the support A are limited by stops q and r. The modified pawl-controlling
mechanism is as follows:-An arm or lever S is pivotally connected midway its
length at s with the support carrier (not shown) so as to be capable of rocking
vertically. A curved slot s' extending lengthwise of this rocking lever S is
engaged by a pin or roller at one end of a link rod T which at its opposite end is
pivoted to a projection or lug T₁ of the raising and lowering lever above the
fulcrum pivot of this lever. The link rod has a slot at t and this slot is engaged
by the pin u of a crank U at one end of a rock shaft u' suitably mounted and
provided with the actuating lever or crank U. By turning the rockshaft by its
actuating lever the link rod T may be caused to rock the rocking lever S and
engage its slot at either end thereof, because of the engagement of the crank pin u
with the link slot t. A spring R₁ acting on the actuating lever U₁ serves to
yieldingly hold the rockshaft in either of its two positions of adjustment. A
rod V is pivoted at one end to the lever pawl Q near its pivotal connection with
the raising and lowering lever, and engages and is adapted to slide in an eye or
bearing Vat the lower end of the rocking lever S. Collars are adjustably
secured to the slide rod V at opposite sides of and at suitable distances from the
bearing V, and coiled springs V2 2 surrounding the slide rod bear at their opposite
ends, respectively, against the bearing and the collars vv. A rod W is pivoted to
the upholding pawl R near its pivot and is adapted to engage and slide in a
bearing X at the upper end of the slotted rocking lever S. This slide rod W, like
V

page_text: the slide rod V, is provided with adjustable collars ww', and springs x x³ interposed
between the collars and the slide rod bearing X.
To raise the toothed support, with the mechanism as modified, the rock shaft of
the controlling mechanism is adjusted so as to cause the parts to occupy the
positions in which they are represented by Fig. 15. Upon actuation of the lever
pawl by depressing the outer end of the raising and lowering lever, this pawl is
caused to engage a tooth of the support A and lift the support, releasing the
upholding pawl from weight so that it may be moved away from the support by the
action of the compressed slide rod spring . As the support is being lifted
the rocking lever S is rocked by means of the link rod T, the upper end of the
rocking lever moving toward the support and its lower end away from it. Thus
the springs V and of the respective slide rods are compressed. The action of
the spring upon the upholding pawl by way of the slide rod bears this pawl
against the rack of the support and moves it into position for engaging a rack tooth
slightly before the completion of the upstroke of the lever pawl. Shortly after the
commencement of the upward movement of the outer end of the raising and
lowering lever, the upholding pawl is engaged with a tooth of the support rack,
and by the action of the spring V upon the lever pawl through the slide rod V,
this pawl is first thrown out of engagement with the support rack, and then, as the
rocking lever is rocked by the link connecting it with the raising and lowering
lever, the springs and are gradually compressed, so that the former acting
through the slide rod V on the lever pawl moves it into contact with the support
rack. At the completion of its down stroke this pawl is left in the position in
which it is represented in Fig. 15 so that the lifting operation may be repeated.
To lower the toothed support--the rockshaft of the pawl controlling mechanism is
adjusted so as to cause the parts to occupy the positions in which they are repre-
sented in Fig. 16. The operation of the modified mechanism in lowering the
support will readily be understood from the above explanations and the description
of the operation of the preferred mechanism.
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 of the vertically adjustable chair body support provided with
the vertically extending groove or recess, the carrier for the support, the lever
composed of jointed sections, pivoted to the carrier and provided with the cam at
the inner end of its main section, and the sectional clamping shoe mounted to slide in
the carrier and the inner section of the lever, actuated by said cam and engaging
said groove or recess in the support when the lever is swung sidewise, substantially
as set forth.
2. The combination of the vertically adjustable toothed support, its carrier, the
raising and lowering lever jointed to the carrier, the lever pawl for engaging the
toothed support, provided with the guideway, the support upholding pawl supported
by the carrier, the controlling link pivoted to the upholding pawl at one end and at
its opposite end engaged by the guide way on the lever pawl, and means for main-
taining a yielding pressure upon the controlling link to actuate the pawls, substantially
as set forth.
3. The combination of the raising and lowering lever, its pawl provided with the
guide-way, the carrier to which the lever is pivoted, provided with the stops acting
upon said pawl and serving to limit the movements of the lever, the vertically
adjustable toothed support mounted in the carrier and with which said pawl is
adapted to be engaged, the support-upholding pawl supported by the carrier and
against which the lever pawl is adapted to strike, the controlling link pivoted to
the upholding pawl at one end and at its opposite end engaged by the guide way on
the lever pawl, and means for maintaining a yielding pressure upon the controlling
link to actuate the pawls, substantially as set forth.
4. The combination of the vertically adjustable toothed support, its carrier, the

page_text: raising and lowering lever jointed to the carrier, the lever pawl for engaging the
tootbed support, provided with the guide way, the support-upholding pawl
supported by the carrier, the controlling link pivoted to the upholding pawl at one
end and at its opposite end engaged by the guide way on the lever pawl, the rock-
shaft provided with a crank having a pin engaging a slot in said link, and supported
by the carrier, the crank or lever loosely mounted on the rockshaft, provided with
an extension or short crank, and adapted to be rocked on the rockshaft and be
engaged therewith in two positions of adjustment, and the spring acting on the
short crank or extension of the crank lever, substantially as set forth.
Dated this 9th day of May 1895.
ARTHUR WILLIAM BROWNE.
ARTHUR WILLIAM BROWNE.