The invention pertains to a method of making a wood floor covering
which is flexible and can be laid on concrete with a mastic using
momentary pressure. Instead of the nominal 3/4-inch thickness of
conventional strip hardwood floors, the floor covering is only about
1/10-inch thick. The finish on the floor covering is sufficiently
wear-resistant so that for the life of the flooring the wood is
never subject to wear. The finish is applied in the factory as a
thermoplastic resin film which extends over the wood and spans the
joints between the wood blocks of which the flooring is composed.
In bonding the film a cushion is placed on the film, and heat is
applied to the assembly sufficiently high to soften or melt the
film. The blocks are kept from spreading apart by a constraining
means partly embedded in the back of the wood by pressure, and the
resin is chilled under pressure until it reaches room temperature
and is solidified. In a preferred form of the flooring, the finish
is the sole means for tying the blocks together, and the wood surface
1. The method of making a flexible wood floor covering which comprises
the steps of producing wood blocks from 1/16-inch to 3/16-inch thick,
assembling the blocks in edge-to-edge relationship, covering the
assembled blocks with a plastic resin film with an adhesive between
the film and the blocks, placing an elastic cushion on the film,
subjecting the assembly to heat adequate to soften the film, then
cooling the assembly under pressure to cause the adhesive to bond
the film to the blocks.
2. The method of claim 1 including placing a constraining means
between the assembled blocks and the supporting surface.
3. The method of claim 2 in which the plastic film is a vinyl-chloride
film in the thickness of from 3 to 15 mils.
4. The method of claim 1 in which the wood members are held together
only by the finish.
5. The method of claim 1 in which the wood blocks comprise two
layers of veneer bonded together with the grain of the plies crossing
at right angles.
6. The method of claim 1 in which one surface of the wood is subjected
to abrasion prior to said assembling step, thereby removing wood
from the softer portions of its surface.
7. A wood floor covering which consists of an assembly of wood
blocks of a thickness from 1/16-inch to 3/16-inch thick, held together
edge-to-edge primarily with a thermoplastic resin finish bonded
thereto by an adhesive and covering only one surface of the assembly
and spanning the joints between the blocks, the thickness of the
finish ranging from 3 to 15 mils.
8. The method of claim 1 in which the surface of the wood blocks
has been unevenly darkened by charring prior to said assembling
9. The method of making a flexible wood floor covering which comprises
the steps of providing wood blocks from 1/16-inch to 3/16-inch thick,
assembling the blocks in edge-to-edge relationship, bonding a transparent
wear-resistant film on the assembled blocks so that the film covers
the blocks and forms ridges projecting downward between the blocks
and revealing depressions between blocks at the surface.
BACKGROUND OF THE INVENTION
With the trend in the building industry in large cities toward
high-rise buildings, the need arises for a hardwood floor covering
which can be laid on concrete floors with an adhesive in the manner
in which conventional resilient floor coverings are installed, such
as vinyl tile or linoleum. Floor coverings on concrete follow the
surface of the underlying concrete, which must therefore be troweled
smooth. It must also be dry. To be a satisfactory floor covering,
it must not be thicker than other floor coverings, hence, not thicker
than 3/16-inch. A major purpose of the present invention is to produce
a thin hardwood floor covering suitable for covering concrete floors
in high-rise buildings.
Conventional strip flooring on concrete requires nailing strips
or sleepers embedded in the concrete to which the flooring can be
nailed. The flooring may also be nailed to a subflooring, such as
plywood, which in turn is nailed to embedded wood members. In the
form of plywood blocks, the flooring is sometimes laid on concrete
with an asphaltic mastic, which yields slowly when subjected to
SUMMARY OF THE INVENTION
One aim of the present invention is to produce a flexible wood
floor covering which can be bonded to subflooring in a manner resembling
the bonding of vinyl tile.
Another aim is to finish the floor covering with a finish that
is so durable and wear-resistant that it will not wear through for
the life of the floor, and need therefore never be renewed. The
wood itself is never subjected to wear. It can therefore be very
thin. Requirements other than wear resistance determine the minimum
thickness of the wood. The finish must also be vaporproof so that
the moisture content of the wood does not change appreciably after
Other objects of this invention will become apparent as the following
specification progresses, reference being had to the accompanying
drawing to illustrate the invention.
In the drawings:
FIG. 1 is a top plan view of the wood product;
FIG. 2 is an enlarged, fragmentary, cross-sectional view of the
product, showing the finish on the same; and
FIG. 3 is an enlarged, fragmentary, cross-sectional view of the
apparatus for forming the product.
The product of this invention, denoted by the numeral 10 may be
laid on concrete made smooth by troweling, but the resultant concrete
surface is rarely perfectly flat and free of grit that causes small
elevations in the floor covering. The floor covering must therefore
be sufficiently thick to prevent telegraphing of grit in or on the
The wood floor covering must be slightly flexible to follow the
contour of the subflooring so that the edges of adjacent sections
of the floor covering are flush and present no obstruction against
which a person may trip.
Inasmuch as the wood of the present invention is never subject
to wear, it can be much thinner than conventional strip flooring,
which is generally fully 3/4-inch thick. The wood of the present
invention is only about 1/10-inch thick. The invention therefore
effects great economy in the use of wood. The wood should, however,
not be thinner than about 1/16-inch to prevent any solid particles
such as specks of gravel in the surface of concrete from telegraphing
through. Moreover, very thin wood floor coverings lack the appearance
of solidity. This is the case if the wood is less than about 1/16-inch
The wood of the present invention can be a single ply of veneer,
or two plies of veneer bonded together, with the grain direction
of each ply perpendicular to that of the other. This construction
improves the dimensional stability and flexibility of the flooring.
Minimum thickness of wood consistent with the requirement of non-telegraphing
is also desirable so that wood strips that are slightly bent will
be held to the subflooring over their entire length without springing
away when freshly bonded with conventional flooring mastics. Strips
that are thicker than about 3/16-inch and are also bent lengthwise
are often difficult to hold down when freshly bonded, especially
when the subflooring is not perfectly flat.
The product of this invention can be made in various forms, for
example, as square tile, each consisting of four or more squares
of smaller size, held together by the finish. The small squares,
in turn, may consist of separate short blocks of wood placed edge-to-edge,
and held together with no connecting means other than the finish.
A herringbone pattern is another attractive floor design. The finish
must be elastic and tough, and resistant to abrasion. It must be
clear and follow surface roughness that may be present in unsanded
or abraded wood. Abrasion removes wood fibers from the softer areas.
A convenient flooring unit in the form of a square that can be
installed rapidly is 12 inches by 12 inches in size. Such a unit
may consist of four smaller squares, each square consisting of about
six or seven slats of wood. Four such squares (FIG. 1) are held
together by the film finish spanning the joints between the component
wood slats, as well as the joints between the squares. The slats
of one square are at right angles to the slats of adjacent squares,
as shown in FIG. 1.
The flooring may also be made in the form of wide, long planks
that are moderately flexible and sufficiently thin so that the flexibility
in the lengthwise direction is adequate for good bonding to prevent
springing away from the supporting floor while the bonding adhesive
is fresh. Wide, long planks may be composed of narrow wood strips
held together only by the finish spanning the joints. The floor
may also be produced in various parquetry patterns, each unit consisting
of a number of pieces of wood connected together in a pattern only
by the finish, or primarily by the finish.
The finish is applied to the wood in the form of a plastic film
that is transparent, thermoplastic, and waterproof. If previously
coated with an adhesive, it can be bonded to the wood while the
film is being heated, and then cooled under pressure. Cushioned
pressure may also be used, in which case the heat is transmitted
through an elastic cushion such as a sheet of synthetic rubber.
Bonding with cushion pressure improves the bond over that obtained
with flat plate pressure without a cushion because the film can
be firmly pressed into the depressions of a rough, unsanded wood
surface and is thereby well bonded to both the elevations and valleys
of rough wood. The surface is thereby completely finished and, being
rough, shows that the floor is made of real wood and is not a printed
wood grain substitute. Printed wood grain surfaces lack the flash
associated with genuine wood.
The resultant finish revealing the roughness of the wood is less
subject to noticeable scuffing than the scuffing on a smooth surface.
Individual blocks stand out. The joints between blocks are accentuated.
If wood strips are loosely placed together on a smooth supporting
surface with a thermoplastic film over the strips, and the softened
film is subjected to cushion pressure, the outward lateral thrust
of the compressed cushion or of the melted plastic that is squeezed
into the joints pushes the strips apart. We have found that such
spreading is prevented if a constraining means such as a wire screen
or a perforated plate is used in direct contact with the wood. When
subjected to pressure adequate to bond the film to the wood, such
a constraining means is partly embedded in the wood, preventing
adjacent strips or blocks from spreading apart. When the assembly
is cooled under pressure, the blocks remain in their position.
The loose placement provides spacer for the plastic to enter part
way into the joints. The plastic does not fill the joint and permits
hinge-like action at each joint when it has solidified. It does
not extend down far enough to prevent hinge action.
The film finish can be a durable thermoplastic of several types
appropriately plasticized, such as a vinyl or acrylic resin in a
thickness of from 3 to 15 mils. This contrasts to the thickness
of conventional varnish finishes which generally does not exceed
2 mils. Other films may also be used, of comparable durability,
thermoplasticity, clarity and flexibility. In appearance, the finish
may resemble a waxed surface and reveal the fact that it has been
forced part way into the joints as shown in FIG. 2.
A suitable vinyl is one commercialized by Union Carbide Corporation,
Chemicals and Plastics Division, 270 Park Avenue, New York, N.Y.,
under the name KDA 2216 clear. Another suitable vinyl is one known
as Ultron UL 28 1015 clear, marketed by Monsanto Chemical Company,
2710 Lafayette, Santa Clara, Calif. A suitable acrylic resin is
Korad C marketed by Rohm & Haas Company, 1920 South Tubeway
Avenue, Los Angeles, Calif.
A synthetic rubber sheet may be used as a cushion. The smoothness
of the rubber determines the smoothness of the finish on the wood.
This may therefore be glossy or mat. The heat-softened film is chilled
under pressure and retains the imprint of the elastic cushion.
The original thickness of the film is not changed greatly when
it is heated and caused to flow under the pressure of the rubber
A synthetic rubber cushion about 1/8-inch thick is sufficiently
thin to permit rapid transfer of heat to the film. The film is bonded
to the wood with an adhesive previously applied and dried on the
film or on the wood. The heated assembly, shown in FIG. 3 consisting
of the caul plates, a wire screen, the wood, the film and the cushion,
is transferred while hot to a cold press, where it is chilled under
A further improvement in the appearance of a flexible wood floor
covering made as described may be introduced by charring the surface
of rough wood blocks as by means of a hot roller at a temperature
high enough to scorch the wood. Such scorching is uneven and particularly
attractive in coarse textured wood such as oak. The scorched wood
is protected from wear by the plastic finish.
In installing the wood floor covering made as described, an adhesive
having the consistency of conventional mastics used for laying resilient
floor coverings is spread on the subflooring with a notched blade.
The adhesive so spread forms ridges that are subsequently flattened
when the floor covering described is placed on the freshly spread
adhesive and then subjected to pressure as by means of a heavy roller.
As the floor covering is finished in the factory, it can be put
into service immediately after installation.