Year: 1887

page_text: Date of Application, 18th Apr., 1887
Complete Left, 12th Jan., 1838
Complete Accepted, 17th Feb., 1888
I, CARL WITTKOWSKY, of Charlottenburg, near Berlin in the Empire of Germany,
Manufacturer, do hereby declare the nature of this invention to be as follows:-
This invention relates to an improved construction of wooden plates for the seats
and hacks of chairs so that they shall possess the necessary amount of elasticity or
spring action.
In order to effect this, it is necessary to impart to the wood a bent form, and this
has already been attempted but without success, the bending having been effected in
the direction of the chair's axis, or in a direction at right angles thereto. In both
cases the necessary horizontal peripheral surface was wanting, for fixing the seat plate
to the framing, so that either this fixing was imperfect, or if effected by the
application of great force, the elasticity of the seat was on the one hand diminished,
and on the other hand there was always a tendency of the plate to return to its
original form. It was endeavoured to overcome this defect by forming centrally on a
horizontal peripheral surface, which served for fixing to the chair frame, an inwardly
or outwardly curved seat or back surface. But even this did not supply the
deficiency, as, by this arrangement, the seat had no elasticity at all.
According to the present invention the desired object is attained, by providing
between the horizontal peripheral surface and the seat surface proper (or back
surface) which may be either curved or flat, an intermediate surface which has a
stronger and different curvature from that of the seat surface, if this be curved, so
that this intermediate surface constitutes the actual elastic part.
With this arrange-
ment the seat or back has its flat peripheral surface serving to fit it to the chair frame,
and it has also in the middle a seat or back surface which may either be flat or
inwardly or outwardly curved, and between these is an intermediate surface which
may either be a segment of a dome or be otherwise curved, which affords the seat or
back the required elasticity.
The elasticity obtained by this construction may, however, be greatly increased by

page_text: substituting for the separate flat peripheral surface and the elastic intermediate surface
a single strongly bent elastic surface which also affords the necessary spring action
and which on the one hand surrounds the plate forming the seat or the back surface,
(which may be either flat, concave or convex,) and which on the other hand bears
directly upon the chair frame, the dimensions of such curved surface being made
equal to the combined dimensions of the flat peripheral part and intermediate part
before described.
For fixing such elastic plates to the chair frame there are however required special
means of fixing for enabling them to be secured in such a manner as not to interfere
with their elasticity. There are two different descriptions of these arrangements, the
one or the other of which is employed according to whether the chair frames are
constructed on the old system for cane seats and backs, or whether they are specially
constructed for use with the above described plates, with special appliances for the
purposes of fixing.
For the first mentioned old construction of chair frames, the fixing of the plates is
effected by screwing a number of screws through the intermediate surface into the
chair frame, the holes, for this purpose formed in the said surface being somewhat
larger than the diameter of the screws, so that on depressing the central seat or back
surface, the entire elastic surface can partake of such motion while the heads of the
screws prevent the seat from moving away from the chair frame.
provide a more ornamental appearance, the heads of the screws and the slotted holes
may be covered in by the heads of large ornamental furniture nails driven into the
seats or backs.
In order to
In the case of chairs the frames of which are specially constructed for the application
of the said elastic plates thereto, a simpler mode of fastening is employed, dispensing
with the screws and nails. The framing, which may otherwise be constructed in the
usual manner, is for this purpose provided with a groove into which the elastic inter-
mediate surface, and also the peripheral surface enter. This groove may, for
convenience of insertion of the seat plate, be made of greater depth on one side
than is required for the size of the seat, so that the one edge of the latter is first
pushed into such deepened groove as far as it will go, after which the middle of the
seat is bent outwards convexly until its width is so much reduced that the other edge
thereof can be inserted into the other groove of the framing. The seat is then allowed
to resume its original form, whereby it will be made to pass to the full extent into the
groove.
As, on using such chairs, the pressure of the body upon the seat or back only tends
to fix the same more securely in the grooves of the framing, thus dispensing with all
other fixing devices, such as glue, nails, screws, and also, as, by this construction, the
edges of the seat are hidden, thus presenting a more sightly appearance and dispensing
with the necessity of finishing these edges as heretofore, it will be evident that this
construction of chairs is particularly advantageous.
In order to prevent the slipping to and fro and rattling of the seat in the grooves, a
strip of elastic material such as caoutchouc, tape, pasteboard &c. may be introduced
into the grooves whereby the seat plates will be held all the firmer, and these will in
their turn prevent the strips from coming out.
In the case of chairs that are of themselves elastic, as, for example, the Austrian
bent wood chairs, the introduction of the seats may be further facilitated by pressing
together the framing somewhat in one direction by means of screw clamps, so that it
assumes a more or less oblong form, and is thus extended in one direction so that the
seat can be readily inserted into the grooves without requiring to be bulged for this
purpose, after which the framing is allowed to resume its original shape. With
ordinary chairs, the one side of the frame may also be left open so as to allow the seat
to be slid into the grooves of the other part, after which the frame is closed up. This
arrangement however involves more work and is more expensive.
An essential advantage of the last described construction of the seat and back plates
is that they are much more elastic than the others.
The depression of the middle part can not only be effected down to the horizontal

page_text: face of the flexible peripheral surface, but also considerably further, that is to say,
into a downwardly or outwardly bulged position the opposite of that which the seat
originally occupied. To allow of this extent of motion, the surface of the frame on
which the seat rests, is formed with a downward incline permitting of double the
inclination that could be obtained by the horizontal surface.
The middle seat or back surface may either be of circular or polygonal configuration,
corresponding to that of the outer configuration of the seat, or it may be differently'
formed; it is produced in the well known manner by pressing the plate between male
and female dies of the required form. The plates may also be made either of single
thick sheets of veneer, or of two or more thinner sheets cemented together in the
well known manner.
The above described plates may also be engraved, perforated or otherwise
ornamented. With the second described construction, as there is no glueing
required, the plates may have a covering or cushion of fabric, leather &c.
Dated this 18th day of April 1887
ABEL & IMRAY,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
An Improved Construction of Elastic Seats and Backs for
Chairs or Seats.
I, CARL WITTKOWSKY of the City of Charlottenburg near Berlin, Kingdom of
Prussia, German Empire, Merchant 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 of an improved construction of elastic seats and backs for chairs or
seats refers to wooden plates, so that they shall possess the necessary amount of
elasticity or spring action.
In order to effect this, it is necessary to impart to the wood a bent form, and this
has already been attempted in the manner shown by the figures 1, 2 and 3, but
without success. By this known construction the bending having been effected, either
in the direction of the chairs axis, as shown in fig. 1 or in a direction at right angle
thereto, as shown in fig. 2. In both cases the necessary horizontal peripheral surface
was wanting for fixing the seat plate to the framing, so that either this fixing was
imperfect, or if effected by the application of great force, the elasticity of the seat was
on the one hand diminished, and on the other hand there was always a tendency of
the plate to return to its original form. It was endeavoured to overcome this defect
by forming centrally on a horizontal peripheral surface A, which served for fixing to
the chair frame an outwardly curved seat or back surface B as shown in fig. 3, in full
drawn lines, or an inwardly curved seat or back surface B as shown in dotted lines in
the same figure. But even this did not supply the deficiency, as, by this arrangement,
the seat had no elasticity at all.
According to the present invention the desired object is attained by providing
between the horizontal peripheral surface A and the seat surface proper (or back
surface) B, which may be either curved or flat, an intermediate surface C, which has a
stronger and different curvature from that of the seat surface, if this be curved, so
that this intermediate surface C constitutes the actuel elastic part. With this
arrangement shown in the figs. 4 to 9, the seat or back has its flat peripheral
surface A serving to fit it to the chair frame, and it has also in the middle a seat
or back surface B, which may either be flat (see the figs. 4 and 5) or inwardly curved
(see the figs. 6 and 7) or outwardly curved (see the figs. 8 and 9) and between these
is an intermediate surface C, which may either be a segment of a dome or be other-
wise curved, which affords the seat or back the required elasticity. The elasticity
obtained by this construction may however be greatly increased by substituting for
the seperate flat peripheral surface A and the elastic intermediate surface C a single
strongly bent elastic surface C, as shown in the figs. 10 to 14, which also affords the
necessary spring action and which on the one hand surrounds the plate B forming the
seat or the back surface (which may be either flat, concave or convex), and which on
the other hand bears directly upon the chair frame Z, the dimensions of such curved
surface C¹ being made equal to the combined dimensions of the flat peripheral part A
and intermediate part (hefore described with reference to the figs. 4 to 9.

page_text: For fixing such elastic plates to the chair frame there are however required special
means of fixing for enabling them to be secured in such a manner as not to interfere
with their elasticity. There are two different modifications of these arrangements,
the one or the other of which is employed according to whether the chair frames are
constructed on the old system for cane seats and backs, or whether they are specially
constructed for use with the above described plates with special appliances for the
purposes of fixing.
For the first mentioned old construction of chair frames, the fixing of the new
elastic plates is effected in the manner shown by the figs. 10 and 11, by screwing a
number of screws a through the intermediate surface into the chair frame Z the
holes for this purpose formed in the said surface being somewhat larger than
the diameter of the screws a, so that on depressing the central seat or back surface B,
the entire elastic surface C¹ can partake of such motion, while the heads of the
screws a prevent the seat from moving away from the chair frame Z. In order to
provide a more ornamental appearence the heads of the screws a and the slotted
holes can be covered in by heads c of large ornamental furniture nails driven into
the seats or backs..
In the case of chairs the frames of which are specially constructed for the
application of the new said elastic plates thereto, a simpler mode of fastening is
employed, dispensing with the screws and nails. The framing Z, which may other-
wise be constructed in the usual manner, is for this purpose (as shown in the
figures 12 and 13) provided with a groove D, into which enters the elastic inter-
mediate surface C which is here also the peripheral surface. This groove D may for
convenience of insertion of the new-elastic seat plate, be made of greater depth on one
side then is required for the size of the seat, so that the one edge of the latter is first.
pushed into such deepened groove as far as it will go (see at W fig. 14) after which
the middle of the seat B is bent outwards (see at X in the fig. 14.) that is to say
convexly, until its width is so much reduced that the other edge thereof (see at Y in
the fig. 14) can be inserted into the other groove of the framing. In this position.
which is shown in the fig. 14, the seat is then allowed to resume its original form by
leaving the pression at X whereby it will be made to pass to the full extent into the
groove D of the frame Z.
As on using the chairs of the last described constructions, the pressure of the body
upon the seat or back only tends to fix the same more securely in the grooves of
the framing, thus dispensing with all other fixing devices, such as glue, nails, screws
and also, as by this construction the edges of the seat are hidden, thus presenting
a more sightly appearance and dispensing with the necessity of finishing these as
theretofore, it will be evident that this construction of elastic seats or backs for chairs
is particularly advantageous.
In order to prevent the slipping to and fro and rattling of the seats or the backs
(after the constructions shown in the figures 10 and 12) in the grooves D, a strip of
elastic material such as caoutchouc, tape, pasteboard etc. may be introduced into the
grooves, whereby the seat plates will be held all the firmer and this will in their turn
prevent the strips from coming out.
In the case of chairs that are of themselves elastic, as for example, the Austrian
bent wood chairs, the introduction of the seats may be further facilitated by pressing
together the framing somewhat in one direction by means of screw clamps, so that
it assumes a more or less oblong form, and is thus extended in one direction. so
that the seat can be readely inserted on one side (see at W in the figure 14) into
the grooves without requiring to be bulged for this purpose, after which the framing
is allowed to resume its original shape. With ordinary chairs, the one side of the
frame may also be left open so as to allow the seat to be slid into the grooves of
the other part, after which the frame is closed up. This arrangement however
involves more work and is more expensive.
An essential advantage of the construction of the seat and back plates described
with reference to the figs. 10 to 14, is that they are much more elastic than the
others. The depression of the middle part B can by this construction not only be

page_text: effected down to the horizontal face of the flexible peripheral surface C¹, but also
considerably further, that is to say, into a downwardly or outwardly bulged position,
the opposite of that which the seat originally occupied. To allow of this extent of
motion, the surface of the frame Z, on which the seat rests, is formed with a downward
incline F, as shown in the figures 10 and 12" for the constructions formerly described
with reference to the figs. 10 and 12, which incline F is permitting of double the
inclination that could be obtained by the horizontal surface.
The middle seat or back surface B may either be of circular configuration, as
shown in the figs. 4, 6, 8 and 11 or with polygonal configurations as shown in the
figs. 5. 7, 9 and 13 corresponding to that of the outer configuration of the seat, or it
may be differently formed. It is produced in the wellknown manner by pressing the
plate between male and female dies of the required form. The plates may also be
made either of single thick sheets of veneer, or of two or more thinner sheets
connected together in the wellknown manner. The above discribed plates may also
be engraved, perforated or otherwise ornamented. With the second described con-
structions as there is no glueing required, the plates may have a covering or cushion
of fabric, leather etc.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed, I declare that what
I claim is:
1.) The construction of elastic wooden seats and backs to chairs, wherein the plane
surface A is connected with the seat or back proper B by means of a strongly bent
intermediate surface C, which affords the requisite spring action substantially as
berein described with reference to the figs. 4 to of the drawings.
2.) The construction of elastic wooden seats and backs to chairs, wherein the seat
or back proper B is combined with a single strongly bent peripheral surface C¹ which
affords the requisite spring action and at the same time forms the bearing surface for
connection with the chair frame, substantially as herein described with reference to
figs. 10 to 14 of the drawings.
3.) In combination with the construction of seats or backs referred to in the
proceeding claim, the use of screws a screwing into the chair framing and passing
through slotted holes in the part C₁ of the seat, the said screws being covered, or
not, with furniture nails c, substantially as herein described with reference to the
figs. 10 and 11 of the drawings.
4.) In combination with the elastic seats or hacks for chairs referred to in the
claim 2, the construction of the seat or back frames Z of the chairs with grooves D,
into which the edges of the part C₁ of the seat or back fit so as to be held therein
with a certain freedom of motion substantially as herein described with reference to
figs. 12 and 13 of the drawings.
5.) The arrangement of the inclined surface F on the seat and back frames Z of the
chairs referred to in the proceeding claims with a downward slope in order to allow
the elastic seat to assume an inverted position substantially as herein described with
reference to figs. 10ª and 12ª of the drawings.
Dated this 4th day of January 1888.
A. KUHNT & R. DEISSLER,
Attorneys.