U.S. patent application number 13/305925 was filed with the patent office on 2012-10-25 for one piece plastic chair.
This patent application is currently assigned to SEBEL FURNITURE LTD. Invention is credited to Michael Andrew FEWCHUK.
Application Number | 20120267934 13/305925 |
Document ID | / |
Family ID | 45218580 |
Filed Date | 2012-10-25 |
United States Patent
Application |
20120267934 |
Kind Code |
A1 |
FEWCHUK; Michael Andrew |
October 25, 2012 |
ONE PIECE PLASTIC CHAIR
Abstract
A one piece integrally formed moulded plastic chair (11) is
disclosed having a seat (2), backrest (3) and legs (4-7). A
U-shaped rib (19) extends between the upper regions of the rear
legs (6, 7) to cross-brace same. A gap (24) is proved between the
cross piece (20) of the rib (19) and the underside of the seat (2).
In use the seat (2) deforms to reduce the size of the gap (24)
under the weight of a sitter. This deformation thereby provides a
more comfortable seat.
Inventors: |
FEWCHUK; Michael Andrew;
(Eastwood, AU) |
Assignee: |
SEBEL FURNITURE LTD
Padstow
AU
|
Family ID: |
45218580 |
Appl. No.: |
13/305925 |
Filed: |
November 29, 2011 |
Current U.S.
Class: |
297/451.11 ;
297/452.14 |
Current CPC
Class: |
A47C 5/12 20130101 |
Class at
Publication: |
297/451.11 ;
297/452.14 |
International
Class: |
A47C 7/16 20060101
A47C007/16 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 1, 2010 |
AU |
2010 246 557 |
Claims
1. An injection moulded one piece plastic chair comprising: a seat
having a front region and a rear region, a pair of front legs, and
a pair of rear legs; wherein said seat and legs are integrally
connected to each other, the upper portions of said front legs are
interconnected by a first rib which projects from the underside of
said seat across substantially the width of said seat front region
and provides a support for said seat front region and a cross-brace
for said front legs; and the upper portions of said rear legs are
connected by a second substantially U-shaped rib which is located
below said seat rear region, which forms a cross-brace for said
rear legs, which extends across substantially the width of said
seat rear region, and which is connected with said seat only
adjacent said rear legs, so that a first opening is formed between
the underside of said seat and said second rib, whereby said rear
region of said seat can flex toward said second rib under the load
of the weight of a sitter.
2. The chair as claimed in claim 1 wherein the second rib is shaped
to have an increased stiffness relative to a planar rib moulded
together with said seat.
3. The chair as claimed in claim 2 wherein said second rib has at
least one portion of appreciable thickness in a front to rear
direction relative to said seat.
4. The chair as claimed in claim 3 wherein said second rib is at
least partially hollow.
5. The chair as claimed in claim 2 wherein said second rib has a
cross-sectional shape which is bent or curved or kinked.
6. The chair as claimed in claim 1 and having a backrest extending
upwardly from said seat rear region.
7. The chair as claimed in claim 6 and having a second opening
between said backrest and said seat whereby said backrest can flex
relative to said seat.
Description
BACKGROUND
[0001] The present invention relates to chairs and, in particular,
to integrally moulded, one piece plastic chairs.
[0002] When plastic chairs were originally fabricated several
decades ago, a plastic shell was moulded and this was screwed or
otherwise connected to a steel frame which formed at least the legs
of the chair. Such plastic shells did not include substantial
reinforcing ribs and were thus relatively flexible. The metal legs
were rigid and the shell could therefore flex relative to the frame
and legs.
[0003] In more recent times, one piece chairs where the seat,
backrest and legs of the chair are all simultaneously formed have
also been produced. These are the chairs with which the present
invention is concerned.
[0004] Such chairs are made by injection moulding and although the
moulds for such chairs are very expensive, the individual chairs
produced by such moulds are inexpensive and, if able to be sold in
sufficiently large numbers, more than pays for the cost of the
mould or tool. Educational institutions including schools and
universities are a large market for such chairs. A prior art chair
of this type is illustrated in FIGS. 1 and 2 and is known from
Australian Design Registration No. 316,934 (to which US Design
Patent No. D607,654 corresponds). As seen in FIG. 1, the prior art
chair 1 has a seat 2 and a backrest 3 and four legs 4-7 which are
respectively a left front leg 4, a right front leg 5, a left rear
leg 6 and a right rear leg 7.
[0005] As seen in FIG. 2, the upper portions of the front legs 4, 5
are joined by a front rib 8 and the upper portions of the rear legs
6, 7 are joined by a rear rib 9. This provides a strong cross brace
for each pair of legs. Both the front rib 8 and rear rib 9 extend
across the underside of the seat 2 and are integrally formed with
it. This has the consequence that the seat 2 is relatively rigid
and so provides a firm support for the sitter.
SUMMARY
[0006] The genesis of the present invention is a desire to provide
an essentially similar chair to that of the chair 1 but in which
the seat 2 exhibits some "give" or flexibility and so is able to
deform under the weight of a sitter. This has the consequence that
the seat 2 to some extent moulds itself to the shape of the sitter.
This has the result that the chair is more comfortable for the
sitter.
[0007] In accordance with a first aspect of the present invention
there is disclosed an injection moulded one piece plastic chair
comprising: [0008] a seat having a front region and a rear region,
a pair of front legs, and a pair of rear legs; [0009] wherein said
seat and legs are integrally connected to each other, the upper
portions of said front legs are interconnected by a first rib which
projects from the underside of said seat across substantially the
width of said seat front region and provides a support for said
seat front region and a cross-brace for said front legs; and [0010]
the upper portions of said rear legs are connected by a second
substantially U-shaped rib which is located below said seat rear
region, which forms a cross-brace for said rear legs, which extends
across substantially the width of said seat rear region, and which
is connected with said seat only adjacent said rear legs, so that a
first opening is formed between the underside of said seat and said
second rib, whereby said rear region of said seat can flex toward
said second rib under the load of the weight of a sitter
[0011] According to another aspect of the present invention there
is provided a method of deforming the seat of a one piece
integrally formed moulded plastics chair under load.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A preferred embodiment of the invention will now be
described, with reference to the accompanying drawings in
which:
[0013] FIG. 1 is a front perspective view of a prior art chair;
[0014] FIG. 2 is an inverted plan view of the chair of FIG. 1;
[0015] FIG. 3 is a perspective view from the underside looking from
the rear of the chair of the preferred embodiment;
[0016] FIG. 4 is a perspective view from the underside and looking
from the front of the chair of FIG. 3;
[0017] FIG. 5 is a side elevational view of the chair of FIGS. 3
and 4 with part of the view being a vertical cross-section;
[0018] FIG. 5A is an enlarged view the rib 19 of FIG. 5;
[0019] FIG. 6 is a side-elevational view similar to FIG. 5 but
illustrating the deformation of the seat under the load imposed by
a sitter; and
[0020] FIG. 7A-71 are each cross-sectional views similar to FIG. 5
but each illustrating a rib profile arrangement. In FIGS. 7A -71
the cross hatching utilized in FIGS. 5 and 5A has not been used so
as to not overburden the drawings.
DETAILED DESCRIPTION
[0021] In FIGS. 3-6, the chair 11 of the preferred embodiment is
illustrated with those portions of the chair 11 which are the same
as the chair 1 being allocated like designation numbers. Thus the
seat 2, backrest 3 and legs 4-7 are as before. In addition, the
front rib 8 which projects from the underside of the east 2 and
interconnects the front legs 4, 5 is also unchanged.
[0022] However, as seen in FIGS. 3 and 4, the rear rib 19 which
interconnects the rear legs 6, 7 is changed so as to be generally
arcuate or U-shaped having a cross piece 20 and a right upright 21
and a left upright 22. As a consequence of this construction, there
is a gap 24 between the upper edge of the cross piece 20 and the
lower surface of the seat 2.
[0023] As seen in FIG. 4, the lower forward edge of the rear rib 19
is provided with a thickened portion 25 to increase the rigidity of
the rear rib 19. Preferably the thickened portion 25 is hollow and
is formed by injecting gas into the thickened portion 25 thereby
reducing the amount of plastic contained in the rear rib 19 and
allowing the rib to cool rapidly after moulding. The thickened
portion 25 (which adds to the rigidity of the cross-brace between
the rear legs 6,7) compensates both for the material removed from
the rib 19 (relative to the rib 9 of FIG. 2) so as to create the
gap 24 and for the fact that the rib 19 is only connected to the
seat 2 by means of the uprights 21 and 22.
[0024] Turning now to FIGS. 5 and 6, it will be seen from FIG. 5
that with the chair 11 unloaded, the gap 24 between the seat 2 and
cross piece 20 of rib 19, is appreciable. However, as seen in FIG.
6, with the chair 11 loaded by the weight of the sitter, the seat 2
has moved downwardly thereby reducing the size of the gap 24. This
downward movement of the seat 2 allows the seat 2 to flex and to
conform to some extent to the shape of the body of the sitter. This
makes the seat 2 more comfortable and is thought to prolong sitter
concentration. By comparison the seat of the prior art chair 1 of
FIGS. 1 and 2 is not "flat" or smooth because the presence of the
rib 9 creates a corresponding inflexible ridge like undulation on
the upper surface of the prior art seat which can be
uncomfortable.
[0025] An unexpected benefit of the above described construction is
that since most of the rear rib 19 does not contact the under
surface of the seat 2, there is less likelihood for the upper
surface of the seat 2 to be blemished. Such blemishes are sometimes
caused by the existence of an integrally formed rib under the
surface of the seat 2 which can create differential rates of
cooling of the moulded plastic.
[0026] Turning now to FIGS. 7A-71, in each drawing is illustrated
one of a corresponding series of rib profiles 29-109 each of which
is a replacement for rib 19. Thus each of the ribs 29-109 can
operate in conjunction with the air gap 24 and provide a
sufficiently rigid cross-brace for the rear legs 6,7 because each
rib's stiffness is greater than a simple planar rib (such as rib
9). Each rib is illustrated in cross-sectional fashion in the same
manner as FIG. 5 save that the cross-hatching is omitted.
[0027] For rib 19, the increase in stiffness is achieved by a
single thickened region 25 which is preferably hollow. For rib
profile 29 of FIG. 7A, the increase in stiffness is achieved by a
kink or bend. For rib profile 39 of FIG. 7B, the increase in
stiffness is achieved by both a kink and a thickened region 35 in
the middle of the rib 39, the thickened region 35 again preferably
being hollow.
[0028] In FIG. 7C, the rib 47 is provided with a J-shaped profile
or cross-sectional shape to provide the increase in stiffness. In
both FIGS. 7D and 7E the rib profiles 59 and 69 respectively are
provided with a thickened region 55 and 65 which are respectively
of circular and approximately tear drop cross-sectional shapes.
Again, preferably both thickened regions 55 and 65 are hollow.
[0029] In FIGS. 7F and 7G, the corresponding rib profiles 79 and 89
are each provided with two thickened regions 75A, 75B and 85A, 85B
respectively. These thickened regions extend in the same direction
in FIG. 7F and in opposite directions in FIG. 7G. In FIG. 7H the
increase in stiffness is achieved by a double J (or S-shaped)
profile for the rib 99. In FIG. 71 the rib profile 109 is provided
with three thickened regions 125A, 125B and 125C.
[0030] It will be appreciated by those skilled in the plastic
moulding arts that the tool required to mould the chair of FIGS.
3-6 is more complicated than the tool required to mould the prior
art chair of FIGS. 1 and 2 with a conventional planar rib 9. This
is because retractable parts are required to form the gap 24.
Alternatively, conventional ejector mechanisms can be shaped to,
and thereby used to, form the gap 24.
[0031] The foregoing describes only some embodiments of the present
invention and modifications, obvious to those skilled in the
plastic moulding arts, can be made thereto without departing from
the scope of the present invention.
[0032] The term "comprising" (and its grammatical variations) as
used herein is used in the inclusive sense of "including" or
"having" and not in the exclusive sense of "consisting only
of".
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