Note: Descriptions are shown in the official language in which they were submitted.
~1~59~ .
Background of the Invention
This invention relates to wood flooring and
more particularly to an improved, dimensionally stable
wood flooring which is highly resistant to deterioration
` 5 because of variations in humidity and temperature.
` It is well known that wood flooring fillets
-`~ expand and contract significantly when exposed to
changes in temperature and humidity. This dimensional
instability has been a serious problem in wood floors,
especially those in which the wooa strips or fillets are
not secured to one another by means of a backing
material, but rather are adhered directly to a subfloor.
Such a floor is subject to buckling if inadequate space
is provided between the fillets so that upon expansion
they press unduly against one another. To prevent
buckling, some prior floors employed relatively lar~e
gaps between adjacent fillets. Not only are large gaps
unsightly, but they can become filled with dirt and
grit, efectively diminishing the available expansion
space. In other floors t especially those covering large
areas, adjacent tiles made up of a plurality of fillets
have been laid with their grains running in alternate
directions. Because woods expand and contract by
differing amounts in different directions with respect
to grain orientation, such a parquet arrangement limits
dimensional changes across the ~aps separating
contiguous tiles, thereby reducing the likelihood of
buckling.
One approach to solving the dimensional
instability problem has been to fill the gaps with a
flexib]e bonding material which has sufEicient
compressibility to accommodate the maximum change in gap
width. See, for example, U.S. Patent No. 3,36S,850 in
which the preferred bonding material is a blend of
chloroprene synthetic rubber, esterified rosin and an
antioxidant. Although this material remains flexible,
.,
~
~5984
-2-
it is of limited compressibility 50 that only a
relatively small portion of the gap thickness is
available for fillet expansion.
The limited compressibility and expandability
of the previously used gap filling materials have
several disadvantages. First, since much of the gap
width cannot be utilixed, the maximum amount of
expansion of a fillet for a given gap width must be
limited. One means of bounding expansion has been to
limit the maximum width of the fillet to approximately
one inch. Another means has been to orient the fillet
with respect to the wood grain so that the surface
adjacent to the gap is the flat grain face. It is known
that dimensional changes transverse to the flat grain
faces are less than for other grain orientations. A
third'way to control the amount of dimensional change is
to use woods with inherent dimensional stabili~y. Woods `1'
such as beech and gumwood have accordingly been avoided
in the past because they are less dimensionally stable
than other woods, such as oak and maple. Again, because
of the limited elasticity of the previously used'binding
material in the gap, high shear stresses develop between
fillets during expansion, requiring very rigid adhesive
to prevent the fillet from breaking away from the
subfloor. Each of these constraints imposed by the
prior gap-filling materials adds considerably to the
cost of the finished floor.
It is, therefore, an object of the present
invention to provide dimensionally stable wood flooring
having a highly compressible gap-filling mater'ial
between the wood fillets, that is, a material which can
be compressed to a small fraction of its unstressed
thickness.
It is a further object of the invention to
provide a gap filler that allows the use of wider
~5~
~illets or planks made up of multiple fillets, and eliminates
the need to alternate -the grain direction of adjacent planks,
especially advantageous in floors covering large open areas~
Other objects, features and advanta~es of the present
invention will become apparent in what follows.
Summary of the Inven-tion
Broadly speaking, the above objects are me-t by the
present invention which provides dimensionally stable wood
flooring comprising wood fillets separated by gaps, each fillet
having a width no greater than approximately t~o inches and each
gap having a width less than one-eighth inch-and larger than one- -
sixty-fourth inch, wherein each of the fillets (A) is elongated
in the direction of the wood grain; (B) has a subs-tantially
rectangular cross-section; (C) is axranged for being secured to
; a subfloor with an adhesive; and (D) further characterized in
that a compressible synthetic foam ma-terial fills the gaps and
joins the fillets together, the foam material having flexibili-ty,
compressibility and expandability sufficien-t to span continuously
the gaps under substantially all environmen-tal conditions of
expansion and contraction of the fillets when secured to a sub-
floor, and wherein -the foam material is a preformed sheet adapted
to fit into and fill the gaps between the fillets.
: The invention may also be seen as providing the
manufacture of dimensionally stable wood flooring for securing
to a subfloor and comprising wood fillets separated by gaps,
each illet being elongated in the direc-tion of the wood grain
and having a subs-tantially rectanyular cross-section, -the .im-
provement comprising the steps of (A) selecting a compressible
synthetic foam material in sheet form charac-terized by flexibill-ty,
compressibili-ty and expandab.ility sufficien-t to span continuously
the gaps under substantially all condi-tlons of environmental ex-
pansion and contrac-tion of -the fillets upon being secured -to a
subfloor, (B) in-troducing the sheet material i.nto the inter-
. ,
-`'-~" jr/~ - 3 -
~5913g
fillet gaps, and (C) adhering the sheet material to the fillets
to join the fillets into wood 100ring sheets.
Brief Des _ ption of the Drawings
` -- '
The invention disclosed herein may he better under-
stood with reference to the following drawings of which:
Fig. 1 is a partly exploded view of a preassembled
wood flooring tile embodying the invention; and
Fig. 2 is an end elevation view o-E the installed
flooring under the condition of extreme expansion.
Description of the Preferred Ernbodiments
:
Referring now to Fig. 1, a representative flooring
tile 10 has been partly exploded to show better an individual
wood fillet 18. In this figure, the wood grain runs along the
length of the fillet 18 and the fillet is cut so that the edge
grain surface 1s the wearing surface 20, that is, the lines 22
that demarcate the growth rings on the tree from which the
r fillets 18 are cut extend substantially between the upper and
lower surfaces of each fillet. Hence, the latera] surfaces 24
of each fillet are the flat grain surfaces~ It is to be stressed
that wood fillet 18 need not have been cut so that the lateral
surfaces 24 on each fillet are the flat
~' ' ' .
89L
; grain surfaces. Although it is advantageous to orient
the fillets in this way because dimensional stability
transverse to the grain lines 2~ is about twice the
dimensional stability along the grain lines, it is
S unnecessary to do so because the foam material filling
the gap according to this invention can accommodate
larger expansions of the fillets.
Again because the foam gap-filling material
can accommodate greater fillet expansion, individual
fillets made from dimensionally stable wood species can
- be up to two inches in width with a gap width between
fillets no greater than that in floors having narrower
fillets, e.g., gap widths in the range of 1/64 to l/16
inch. When, however, wider fillets are fashioned from
less dimensionally stable wood species, gaps between
adjacent fillets will be larger, up to approximately l/8
inch, to accommodate the expected greater dimensional
changes.
Referring now to Fig r 2, gaps 30 between
fillets 18 are filled with foam layer 26. Foam layer 26
may be formed in place or it may be made of a preformed
foam sheet bonded to the adjacent fillets. A suitable
material for forming foam layer 26 in place is a blend
~ of chloroprene synthetic rubber, esterified rosin, and
; 25 an anti-oxidant as disclosed in U.S. Patent ~oO
3,365,850, with a foaming agent such as bicarbonate of
soda added. This blend produces a hi~hly compressible,
closed cell foam. Foam layer 26 may also be cut from a
preEormed sheet of neoprene or polyethylene. A suitable
neoprene is number 4,002 manufactured by Tenneco
Chemicals, Inc., General Foam Division, Carlstadt, New
Jersey, and a suitable polyethylene sheet is Volara Type
E manufactured by Voltek, Inc. of Lawrence,
Massachusetts. When preformed sheet is used as foam
layer 26, a suitable adhesive is used to bond the
preformed sheet of foam to the adjacent wood fillets.
.
,
~125984
::
: Use of preformed foam materials simpllfies both the
manufacturing process and also the machinery required to
assemble the fillets within a single flooring tile.
Such use of preformed foam also substantially increases
the hourly output capacity of an assembly system,
~ thereby reducing production costs.
:
The fillets 18 are preassembled to form tiles
with a gap of 1/64 inch to 1/8 inch between contiguous
fillets. This gap width is generally sufficient to
accommodate the maximum dimensional change in fillet
width. With a gap width within this range, it has been
found that the foam layer 26 continuously spans and
substantially fills the gaps under all conditions o
fillet expansion and contraction. This is particularly
important in excluding dirt from the gaps under extreme
contraction.
~ .
As shown in Fig. 2r the tile is secured to the ~ .
suhfloor 16 with an adhesive 28 that holds the fillets
in place against the forces that develop durin~ the
20 dimensional changes due to temperature and humidity.
Because foam layer 26 disposed between adjacent fillets
18 is highly compressibley the forces which develop
between the individual fillets are not high. This
permits the use of a less rigid and less costly adhesive
25 28 such as standard rubber-based wood block adhesive to
secure the tiles to the subfloor. The use of a less
rigid adhesive imparts a greater degree of flexibility
to the tiles thereby permitting them to conform more
readily to irregularities in the subfloor 16.
Referring still to Fig. 2, the illustrated
fillets 18a, 18b, and 18c are shown under the condition
of maximum expansion as caused by high environmental
temperature and humidity, for example. Note, however,
that the gaps 30 still remain between adjacent fillets
35 and the continuous foam layers 26 separate the fillets~
. . ...
34
The dimensionally stable wood flooring
disclosed herein, therefore, comprises wood fillets
separated by a synthetic foam layer which is highly
compressible. Because the foam layer can accommodate
large amounts of compression, the wood fillets can be
wider than previously used or even be cut so that the
surface adjacent the gaps is a mixed grain or a flat
grain surface. Incorporating a foam layer also permits
the use of less dimensionally stable woods formerly
thought inappropriate for wood flooringg such as gum and
beechwood. Another advantage to be realized from the
invention herein is the capability to construct stable
floors of multiple fillets joined to form wide wooden
planks~ illustratively of seven inches in width, laid
substantially parailel and side-by-side, iOe., without
the requirement to alternate grain directions. The
~invention disclosed herein, therefore, permits lower
cost, yet dimensionally stable wood floors.
.
In view of the foregoing, it may be seen that
the objects of the present invention have been achieved
and other advantageous results obtained.
As various changes could be made in the above
preferred embodiments without departing from the scope
of the invention, it should be understood that all
matter contained in the above description or shown in
the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
.
What is claimed is:
