This invention relates to tongue and groove joints. These joints are
particularly useful for joining pieces of laminate flooring. Glue in these joints
resists penetration of moisture.
Commercially available laminate flooring generally includes a wear
surface glued to a substrate. The wear surface generally is high-wear resistant
decorative laminate. The substrate generally is fibre board or particle board.
Each piece of laminate flooring generally has a groove along one end and one
side suitable for joining with a tongue along one side or end of an adjacent
piece of laminate flooring.
While such laminate flooring has found wide acceptance in Europe as
flooring, it is not substantially used in the United States. In part the reason may
be due to installation difficulties and the lack of moisture resistance in the joint
areas.
Laminate flooring is assembled by placing glue in the groove and
inserting the tongue of one piece into the groove of an adjacent piece. A
substantially complementary fit of a tongue and groove results in difficulty in
aligning the tongue and groove. Additionally, as the glue is absorbed into
substrate, the substrate swells, causing the groove to tightly squeeze the tongue.
This can make full insertion of the tongue into the groove extremely difficult.
Furthermore, as the tongue and groove are moved together, glue can be
compressed in the groove by the tongue in a piston fashion. This can increase
the difficulty in abutting the wear surfaces of adjacent laminate flooring pieces.
To overcome this assembly problem, laminate flooring manufacturers
offer special tools for assembling pieces of laminate flooring.
One such special tool is a hammering aid that has a flat surface and
complementary tongue and groove engaging surfaces. When difficulty is
encountered in abutting the wear surfaces of adjacent pieces, the hammering
aid is placed along the edge of the laminate. The flat surface of the hammering
aid is then struck with a hammer repeatedly to apply a force to the joint and
force the tongue and groove together.
However, even with the use of a hammering aid, a gap can remain
between adjacent pieces. The gap is unsightly and allows for damaging
penetration of moisture to the substrate. The problem with moisture
penetration into the joint is that it can cause the substrate to swell. Excess
swelling damages laminate flooring.
Laminate flooring with tongue and groove joints are difficult to
manufacture. The tight complementary fit between the tongue and groove
requires attention to be paid to cutting tolerances for the widths of the tongue
and groove. An interesting yet problematic phenomenon occurs during the
process of cutting the tongues and grooves. The cutting process itself
progressively dulls and wears the cutting blades. As the blades progressively
wear, grooves of later cut articles are progressively narrower than grooves of
earlier cut articles. Likewise, tongues of later cut articles are progressively
wider than tongues of earlier cut articles. Unfortunately, at some point, the
widths of the tongues and grooves are not within acceptable tolerances.
Thus there is a need in the art for an improved tongue and grooved joint.
There is a need for a tongue and groove joint that does not require special tools
for installation. There is a need for a moisture resistant tongue and groove
joint. These and other needs will become apparent to those of skill in the art
upon review of this specification, including its claims and drawings.
It is an object of the present invention to provide for an improved tongue
and grooved joint.
It is another object of the present invention to provide for a tongue and
grooved joint that does not require special tools for installation.
It is yet another object of the present invention to provide for a moisture
resistant tongue and groove joint.
These and other objects of the present invention will become apparent to
those of skill in the art upon review of this specification, including its claims
and drawings.
An article of the present invention has a planar, decorative wear surface,
a grooved edge and a tongued edge. The tongued edge has a tongue with a
planar lower surface positioned an index distance from and parallel to the
planar decorative surface. The grooved surface has a groove with a planar
lower surface positioned the index distance from and parallel to the planar
decorative surface. The upper surfaces of the tongue and groove are shaped
and sized such that upon joining two pieces of the article by positioning the
lower surfaces of the tongues and grooves together and moving the tongue of
one piece into the groove of another piece, liquid glue placed in the groove will
be squeezed out between the upper surfaces of the tongue and groove and
upwardly between the tongued and grooved edge toward the decorative
surfaces of the two pieces. This joint can be assembled without the use of
special tools and the glue acts as a barrier to water damage to substrate of
laminate flooring.
The tongue has a beveled surface extending from the end surface to the
upper surface of the tongue. The beveled surface can form an oblique angle to
the upper surface of the tongue. Preferably more than about one half and most
preferably more than about two thirds of the length of upper surface of the
tongue remains after the beveled surface is cut. A space for glue to be
squeezed through is provided between the upper surfaces of tongues and
grooves upon joining pieces of the article. A space for glue to be squeezed
through is also provided between a planar surface above the tongue and a
planar surface above the groove. The planar surface above the tongue forms a
right angle to the decorative surface. The planar surface above the groove
forms an acute angle to the decorative surface The acute angle can be about
82.5 to 87.5 degrees. A space is provided between a planar surface below the
tongue and a planar surface below the groove. The planar surface below the
tongue forms a right angle to the decorative surface. The planar surface below
the groove forms an acute angle to the decorative surface. The acute angle can
be about 82.5 to 87.5 degrees.
In order that the invention may be more readily understood and so
that further features thereof may be appreciated, the invention will now be
described by way of example, with reference to the accompanying drawings in
which;
Figure 1 is a side-view of the tongue and groove joint of the present
invention; Figure 2 is a side-view of an assembly step of the tongue and groove
joint of the present invention showing glue placed in the groove and the tongue
entering the groove; Figure 3 is a side-view of an assembly step of the tongue and groove
joint of the present invention showing the tongue in contact with glue in the
groove and the glue being squeezed out; Figure 4 is a side-view showing the tongue and groove of the present
invention being fully joined and glue squeezed out to the wear surface; and Figures 5 - 8 show the dimensions of an embodiment of the tongue and
groove joint of the present invention in English and Metric units.
The tongue and groove joint of the present invention is described with
reference to laminate flooring. However, the present invention is applicable to
other articles that can be joined with tongue and groove joints.
Features and functions of the tongue and groove joint of the present
invention are shown in side views of pieces of laminate flooring 10 on figures 1
to 4. A piece of laminate flooring 10 is shown on figure 1 with a rectangular
tongue 26 on a planar tongued edge 25. Another piece of laminate flooring 10
is shown on figure 1 with a rectangular groove 16 on a planar grooved edge 15.
Additional features of laminate flooring are decorative laminate 11,
substrate 13, and backer 14. The decorative laminate provides a wear surface
12. The tongue 26 and groove 16 are cut in the substrate. It is believed that
particle board, fibreboard or plywood can be suitable substrates 13 for laminate
flooring. A backer 14 is believed to be required when laminate flooring is to be
installed on a flexible pad. The backer 14 provides dimensional stability to the
laminate flooring and can be a moisture barrier. It is believed that a backer is
not required for laminate flooring that will be glued to an existing floor.
The tongue 26 and groove 16 are shown on figure 1 as having planar
lower surfaces, 28 and 18 respectively. These planar lower surfaces are
parallel with and an indexing distance from planar wear surface 12. Abutment
of the planar lower surface 28 of tongue 26 and the planar lower surface 18 of
groove 16 during the joining of the tongue and groove, as shown on figures 2
through 4, causes indexing of wear surfaces 12 of pieces of laminate flooring
10.
The tongue 26 and groove 16 are shown on figures 3 and 4 as having
planar upper surfaces, 27 and 17 respectively. These planar upper surfaces are
parallel and spaced apart. This space provides a flow path for glue to flow
during the joining of the tongue and groove joint of this invention.
The planar tongued and grooved edges, 25 and 15 respectively, above
and below the tongue 26 and groove 16 are shown on figure 4 as not being
parallel. The planar tongued edge 25 is cut at a right angle (90 degrees) to the
wear surface. The planar grooved edge 15 is cut at an acute angle (less than 90
degrees) to the wear surface. This provides a space above tongue 26 and
groove 16 for glue 20 to flow to the wear surface 12 of laminate flooring 1 0. It
is believed that this acute angle should be about 82.5 to 87.5 degrees. An acute
angle above about 87.5 degrees will not provide sufficient space for viscous
glue to flow to the wear surface 12. An acute angle of less than about 82.5
degrees will result in a larger space than required. Water absorbed by the
substrate from the excess glue could swell the substrate and separate the planar
tongued and grooved edges, 25 and 15 respectively. This also provides a space
below the tongue 26 and groove 16 for the substrate to absorb moisture and
swell without damaging the laminate flooring. It is believed that this swelling
will not apply pressure for separating the planar tongued and grooved edges, 25
and 15 respectively.
Tongue 26 is shown as having a beveled surface 30 extending from its
end surface 29 to its upper surface 27. The bevel is shown as cut at an oblique
(45 degree) angle to the upper 27 and end 29 surfaces of the tongue 26. The
beveled surface 30 can serve as a guide during the joining of tongue 26 and
groove 16.
Glue 20 is shown on figure 2 in the end 19 of groove 16. Glue 20, after
curing, adheres the tongue and groove joint together and acts as a barrier
against moisture penetration to the substrate 13. Commercially available wood
glues are suitable to adhere the tongue and groove joint together. Franklin
Titebond II Wood Glue, which is available from Franklin International of
Columbus, Ohio is believed to be suitable for joining laminate flooring.
Franklin Titebond II Wood Glue is believed to be a polyvinyl acetate emulsion
adhesive. When laminate flooring is installed on a flexible pad, it is believed to
be desirable for the glue to be somewhat flexible. It is thought that flexibility of
the glue, after curing, can better accommodate depression of laminate flooring
at the tongue and groove joint of this invention.
Additional features and functions of the tongue and groove joint of this
invention are shown on figures 2 through 4. As the tongue and groove of two
pieces of laminate flooring 10 are joined, tongue 26 applies pressure to liquid
glue 20 in groove 16. Glue 20 flows past beveled edge 30 and through space
31 between the upper surface 27 of tongue 26 and the upper surface 17 of
groove 16. The lower surfaces 28 of tongue 26 and the lower surface 18 of
groove 16 are abutted, thereby providing an impediment to glue flowing
between the lower surfaces 28 and 18 of the tongue and groove.
The beveled surface 30, as shown of figure 4, reduces the length of the
upper surface 27 of tongue 26 and the upper surface 17 of groove 16 as
compared to the lengths of the surfaces of a rectangular tongue. This is
believed to aid in glue 20 flowing, preferentially, between the upper surfaces of
tongue 26 and groove 16 during the joining of pieces of laminate flooring 10.
The abutment and length of the lower surfaces, 28 and 18 respectively, of
tongue 26 and groove 16 is also believed to aid in glue 20 flowing,
preferentially, between the upper surfaces of tongue 26 and groove 16 during
the joining of pieces of laminate flooring 10. Additionally, it is believed that
pressure created on the glue 20 during the joining of the tongue 26 and groove
16, as shown on figures 3 and 4, will be transmitted, in part, downwardly on
upper surface 27 and beveled surface 30 of tongue 26. This pressure can also
aid in glue 20 flowing, preferentially, between the upper surfaces of tongue 26
and groove 16 during the joining of pieces of laminate flooring 10.
The curing of the glue 20 involves the loss of solvent, water in the case
of Franklin Titebond II Wood Glue, to the substrate 13. Water causes swelling
of the substrate. It is believed necessary to limit the volume of glue 20 that will
cure by water or other solvent to the substrate 13. This is accomplished in the
embodiment of this invention as shown on figures 1 - 4 by limiting the distance
between (1) the end 19 of groove 16 and the end 29 of tongue 26, (2) the
amount of the tongue that is cut off in making beveled surface 30, (3) the space
31 between the upper surface 27 of tongue 26 and the upper surface 17 of
groove 16 and (4) the space 32 between planar tongued edge 25 and planar
grooved edge 15 above tongue 26 and groove 16, respectively.
It is believed that swelling of the substrate at the upper surfaces of the
tongue and groove, 27 and 17 respectively, aids in holding the tongue and
groove joint of this invention together. Therefore, it is believed that no more
than one half and preferably no more than one third of the upper surface 27 of
tongue 26 should be removed in cutting the beveled surface 30 on tongue 26.
The space between the upper surfaces of the tongue and groove should be
limited to the space required for glue to preferentially flow to the wear surface
12 when tongue 26 and groove 16 are joined. It is believed that excess space
can result in damage to laminate flooring. Glue loses water to the substrate 13
adjacent space 31 during the curing of the glue. Some swelling is beneficial for
producing a tight tongue and groove joint. However, excess swelling damages
laminate flooring.
Sufficient glue 20 should be placed in the end 19 of the groove 16 such
that a portion of the glue will flow to the wear surface 12 as the tongue and
groove joint of this invention is joined. Additional glue is not beneficial and
increases the cleanup efforts.
A laminate flooring embodiment of the tongue and groove joint of this
invention shown on figures 5 through 8. The dimensions of the features of
laminate flooring are preferred dimensions for the embodiment shown. The
tolerances are preferred tolerances for the embodiment shown. Dimensions and
tolerances are shown on figures 5 and 6 in inches. Dimensions and tolerances
shown on figures 7 and 8 in millimeters.
The tolerances for cutting the upper and lower surfaces of the tongue
and groove are different. It is shown on figures 5 - 8 that the lower surfaces, 28
and 18 respectively, of the tongues and grooves are cut to be 0.2 ± 0.0015
inches (5.08 ±0.0381 millimeters) from the wear surface 12. The upper surface
27 is cut for the tongue 26 to have a minimum width of 0.09 inches (2.286
millimeters) and to increase in width by up to 0.003 inches (0.0762 millimeters)
during the cutting of the tongue. The upper surface 17 is cut for the groove to
have a maximum width of 0.1 inches (2.54 millimeters) and to decrease in
width by up to 0.003 inches (0.0762 millimeters) during the cutting of the
groove. This provides a minimum space 31 between the upper surface 27 of
tongue 26 and the upper surface 17 of groove 16 of 0.004 inches (0.1016
millimeters).
While the illustrative embodiments of the invention have been described
with particularity, it will be understood that various other modifications will be
apparent to and can be readily made by those skilled in the art without
departing from the spirit and scope of the invention. Accordingly, it is not
intended that the scope of the claims appended hereto be limited to the
examples and descriptions set forth herein but rather that the claims be
construed as encompassing all the features of patentable novelty that reside in
the present invention, including all features that would be treated as equivalents
thereof by those skilled the art to which this invention pertains.
Additionally, while the present invention has been illustrated with
respect to laminate flooring, it is to be understood that the tongue and groove of
the present invention may be utilized in any application in which it is desired to
have a tongue and groove joint, including but not limited to flooring in general,
furniture, cabinets, countertops and wall panelling.
The features disclosed in the foregoing description, in the following
Claims and/or in the accompanying drawings may, both separately and in any
combination thereof, be material for realising the invention in diverse forms
thereof.