Foldable plastic product

A foldable plastic product, such as a floor mat (10), comprises a sheet of material including at least two panels (16, 17) having upper surfaces (11), lower surfaces (12) and sides (13) spanning the upper and lower surfaces and defining the thickness of the sheet. At least one bridge portion (18) is provided, the upper surface of which integrally connects the upper surfaces (11) of the panels (16, 17). The thickness (D) of the bridge portion (18) is less than the thickness of the sheet. At least one hinge portion (20) is provided having an upper surface (22) coincident with the bridge portion (18). The lower surface (21) of the hinge portion (20) integrally connects the lower surfaces (12) of the panels (16, 17). The hinge portion (20) is preferably formed of a material selected from the group of thermoplastic elastomers selected from the group consisting of thermoplastic polyurethanes and plasticized polyvinylchlorides having a Shore A hardness of between about 65 to about 80 durometer.

TECHNICAL FIELD 
This invention relates to a plastic product that is capable of being folded 
and to the process of making such a product. More particularly this 
invention relates to a plastic product, such as a floor mat or a chair 
mat, that can be folded upon itself through an arc of approximately 
180.degree. and yet be returned to its flat condition of normal use. 
BACKGROUND ART 
An elongated mat of plastic material is a well known product for use in 
homes and certain commercial applications as a protective overlay for 
carpeting. Generally such mats are used in association with chairs to not 
only protect the carpet against concentrated wear associated with movement 
of the chair, but also to facilitate ease of movement of the chair across 
the floor surface inasmuch as the chair is permitted to move across the 
mat as opposed to the carpet. 
These mats are commonly used in commercial application in conjuction with 
office services. Due to the length of the desks with which such mats are 
used, the mats often are required to be of a length which makes storage, 
shipping, and retail display in their fully elongated configuration 
impractical, difficult and costly. Over the years attempts have been made 
at improving such floor mats, with the purpose of eliminating their 
impracticability as the primary focus. That is, efforts have been made to 
develop plastic products that possess easy, durable and repeatable folding 
characteristics which can be made by simple and economical processes. 
These prior efforts, however, have failed to achieve this goal so that 
there remains a longfelt need in the market for such a product and an 
economical and simple method for making the same. 
Examples of such prior attempts include the device depicted in U.S. Pat. 
Nos. 4,448,625 and 4,476,174. These patents disclose a method of making a 
composite plastic product having an integrally laminated plastic strip 
extending transversely across the under surface of the mat and a slit 
extending through its upper surface downwardly to the plastic strip which 
facilitates folding of the mat. Such a solution, however, is undesirable 
because the slit extending through the upper surface of the mat can be 
construed by the user to be a defect, is unsightly, serves as a collection 
source for dirt and other minuscule particles thereby accentuating the 
unsightly nature thereof, and results in eventual failure of the mat. For 
example, since the slit is in the upper surface of the mat, the movement 
of the rollers of a chair over the slit causes repeated flexing of the 
joining plastic strip which will ultimately crack or otherwise fail. 
Moreover, the user is likely to be aware of the slit as his chair moves 
thereover. 
Another example of a prior attempt is the foldable plastic product depicted 
in U.S. Pat. No. 4,784,888. The product of that patent, preferably a chair 
mat, includes an elongate hinge extending in at least one of the length 
and/or width directions of the product between the product's sides. The 
hinge is created by the formation of an angled or curved slit 
configuration from the underside of the plastic product which is 
preferably in an L-shaped configuration. This solution is also undesirable 
because the L-shaped slit often leads to irregularities in the upper mat 
surface after repeated folding. Moreover, as with the mat of the other 
prior art, repeated movement of the chair rollers over the slit causes 
repeated flexing about the slit and ultimate cracking or other failure at 
the slit. 
In an effort to eliminate these problems, attempts have been made to 
produce a mat having a middle section made of a thinner material or of a 
more flexible material than the remaining portion of the mat. However, as 
yet, such mats have not been able to be produced to exhibit a uniformly 
hard surface, that is, one which does not yield to the forces placed upon 
the upper surface of the mat in the course of its normal use in the 
portion of the mat containing this different material. The most common 
problem experienced in the mats of this type is that the portion of the 
mat containing the different material yields and thereby results in the 
mat having a dip or uneven surface in that portion when a chair is rolled 
thereacross. Thereafter, such mats are unsuitable for their normal and 
intended use, that is, enabling a chair to roll across the upper surface 
without encountering changes in elevation. Moreover, the middle section of 
the more flexible softer material often will collect dirt rendering the 
mat unsightly. 
DISCLOSURE OF THE INVENTION 
It is therefore a primary object of the present invention to provide a 
foldable plastic product, such as a floor mat or chair mat that is capable 
of being folded upon itself approximately 180.degree.. 
It is another object of the present invention to provide a foldable plastic 
product, as above, in which such foldability is imparted to the product by 
virtue of an integrally formed living hinge. 
It is a further object of the present invention to provide a foldable 
plastic product, as above, in which the hinge thereof is easily formed by 
simple processing techniques. 
It is yet another object of the present invention to provide a foldable 
plastic product, as above, which does not require or include a slit or any 
like interruption to impart foldability to the product. 
It is a still further object of the present invention to provide a foldable 
plastic product, as above, possessing durable and repeatable folding 
characteristics. 
These and other objects of the present invention which will become apparent 
from the description to follow, are accomplished by the means hereinafter 
described and claimed. 
In general, a foldable plastic product, such as a floor mat includes a 
sheet of material including at least two panels having upper surfaces, 
lower surfaces and sides spanning the upper and lower surfaces and 
defining the thickness of the sheet. At least one bridge portion is 
provided, the upper surface of which integrally connects the upper 
surfaces of the panels. The thickness of the bridge portion is less than 
the thickness of the sheet. At least one hinge portion is provided having 
an upper surface coincident with the lower surface of the bridge portion. 
The lower surface of the hinge portion integrally connects the lower 
surfaces of the panels. The hinge portion is preferably formed of 
materials selected from the group consisting of thermoplastic 
polyurethanes, thermoplastic polyesters, natural and synthetic rubbers and 
plasticized polyvinylchlorides having a Shore A hardness of between about 
55 to about 85 durometer.

PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION 
A flexible plastic product accoring to the concept of the present invention 
is indicated generally by the numeral 10 and is shown as a sheet of 
material in the conventional configuration of a chair mat, however, it 
should be appreciated that all suitable configurations for any type of 
floor mat or like flexible plastic products are clearly within the spirit 
of the present invention. Chair mat 10 has an upper surface 11, a lower 
surface 12, and sides or edges 13 extending therebetween. Edges 13 define 
the thickness of mat 10 which typically ranges from about 0.100 inches to 
about 0.200 inches. 
As depicted in FIG. 1, upper surface 11 is generally planar, however, it 
may carry a decorative embossing or other surface configuration as are 
well known to those skilled in the art. Moreover, as is conventional, mat 
10 may include a ramped or sloped surface (not shown) extending about its 
peripheral edge so that, for example, the rollers of a chair supported by 
mat 10 can more easily roll from the floor upon which the mat rests onto 
upper surface 11 of mat 10. Additionally, mat 10 may be provided with 
protrusions or cleats 15 projecting downwardly from lower surface 12 which 
serve as grippers to engage an underlying carpet or other flooring 
material upon which mat 10 is placed. It should be appreciated that the 
presence of the sloped surface, the upper planar surface, and the 
protrusions 15 carried by lower surface 12 are not essential to the 
present invention with other designs or configurations clearly being 
within the scope of the present invention. 
With reference generally to FIGS. 1 and 2, upper surface 11 is shown as 
including panels 16 and 17 and a bridge 18 spanning the area between 
panels 16 and 17. Similarly, lower surface 12 includes the under surface 
of panels 16 and 17 integrally connected by a hinge 20. As depicted, hinge 
20 and corresponding bridge 18 extend transversely across the lower and 
upper surfaces, respectively, of mat 10, defining panels 16 and 17 on each 
side thereof. 
It should be appreciated that bridge 18 and hinge 20 do not have to be 
visually distinguishable from panels 16 and 17, and that the distinctions 
shown in the drawings are merely for illustrative purposes. Preferably, 
hinge 20, although of a different material as will be explained more fully 
hereinbelow, is preferably of the same clarity and texture as the 
remaining portions of mat 10, if mat 10 is constructed of a clear 
material. However, if mat 10 is constructed of an opaque material, hinge 
20 does not necessarily have to be of the same color and texture. 
While only one hinge 20 is depicted, thereby enabling the upper surfaces of 
panels 16 and 17 to be folded into a juxtaposed relationship for purposes 
of storage, display, handling, or shipping, additional hinges may be 
provided. For example, instead of the one hinge construction shown in the 
drawings two or more hinges may be utilized to enable mat 10 to be folded 
about itself several times or in alternative directions. 
As depicted in FIGS. 1 and 2, hinge 20 preferably is of a cycloid 
configuration wherein the base portion 21 of hinge 20 is coincident with 
the lower surface 12 of mat 10, that is, the lower surfaces of panels 16 
and 17. Arcuate surface 22 of hinge 20 extends into the thickness of mat 
10 and is coincident with the lower surface of bridge 18. Particularly 
bridge 18 extends a depth D from the upper surface 11 of mat 10 into the 
thickness of the mat. Dimension D can vary depending upon a number of 
factors including, among others, the particular plastic materials that are 
selected as well as the thickness of mat 10. For a mat 10 of thickness 
0.145 to 0.160 inches, dimension D can be from about 0.040 to about 0.070 
inches. Accordingly, the height of hinge 20 for a mat 10 having a 
thickness of 0.145 to 0.160 inches can vary between from about 0.080 to 
0.120 inches, and preferably between about 0.090 to 0.110. 
It has been found that foldability and performance of mat 10 are dependent 
on the magnitude of dimension D. When the magnitude of dimension D exceeds 
0.070 inches for a mat 10 having a thickness of 0.145 to 0.160 inches, 
foldability of mat 10 is impeded and becomes more difficult. On the other 
hand, when the magnitude of dimension D is less than 0.040, the bridge is 
likely to yield to loads placed on upper surface 11 of mat 10, such as the 
load created by a chair moving across mat 10. In such situations the mat 
loses its uniformity and a dip or groove is formed in upper surface 11 
thereof. 
Hinge 20 may also be of a trapezoidal shape, as illustrated in FIG. 3, or 
any other configuration suitable to impart the requisite foldability and 
durability characteristics. As will be discussed more fully hereinbelow, 
the precise configuration of hinge 20 is partially dependent upon the 
manner in which hinge 20 is formed, i.e., by coextrusion or by lamination. 
Preferably panels 16, 17 and bridge 18 are formed of any suitable clear or 
opaque plastic materials well known to those skilled in the art of making 
rigid, semi-rigid or flexible plastic products. One such material which is 
preferred is a semi-rigid polyvinylchloride (PVC). Particularly preferred 
are PVC's having a durometer as measured on the Shore D scale ranging from 
between about 50 to about 75, and more preferably about 60 to about 70 
durometer. 
Hinge 20 can be formed of an elastomer selected from, but not limited to, 
the group consisting of thermoplastic polyurethanes, thermoplastic 
polyesters, natural and synthetic rubbers and plasticized 
polyvinylchlorides having a Shore A hardness of between about 55 to about 
85 durometer. More preferably, such materials have a Shore A hardness of 
between about 65 to about 75 durometer. Particularly preferred are 
compounds having a Shore A hardness of 70+/-3 durometer. 
Such compounds have excellent adhesive compatibility with the materials 
used to form panels 16, 17 and bridge 18. Moreover, such compounds have 
been identified as being suitable to provide repeatable and durable 
foldability to mat 10 without the presence of any slit in the upper 
surface 11 or lower surface 12 of mat 10. 
A particularly preferable thermoplastic polyurethane is the commercially 
available series of thermoplastic compounds offered by B.F. Goodrich 
Company under the trade name ESTANE, which are ether type thermoplastic 
polyurethanes preferably having a Shore A hardness of 70 durometer. 
One particularly preferable form of plasticized polyvinylchloride is one 
having a medium density dispersion resin and dioctyl phthalate (DOP) as a 
plasticizer and having a Shore A hardness of between about 55 and about 85 
durometer. Other plasticizers which may be utilized include heptyl undecyl 
phthalate and diheptyl nonyl phthalate. 
A typical thermoplastic polyester is the commercially available series of 
thermoplastic compounds offered by Dupont under the trade name HYTREL 
having a Shore A hardness of 55 to 63 durometer. 
A typical synthetic rubber is the commercially available series of 
thermoplastic rubbers offered by Shell Oil Company under the trade name 
KRATON having a Shore A hardness of 55 to 85 durometer. Another synthetic 
rubber which could be utilized is the commercially available series of 
thermoplastic rubbers offered by Dupont under the trade name ELVALOY which 
are copolymers of ethylene and vinyl acetate having a Shore A hardness of 
55 to 85 durometer. 
To fold mat 10, the upper surface of panel 16 is juxtaposed with the upper 
surface of panel 17 as is illustrated in FIG. 4. Cleats or protrusions 15, 
carried by lower surface 12 of mat 10, then protrude outwardly when mat 10 
is in its folded position. However, if desired, mat 10 can be just as 
readily folded so that cleats 15 extend inwardly. As illustrated, chair 
mat 10 is thus folded substantially upon itself about an arc of 
180.degree., thereby being about one-half its original size facilitating 
storage, retail display, handling and/or shipping. 
Mat 10, as described above, may be formed by any conventional plastic 
forming process, such as extrusion, coextrusion or other methods of 
thermoforming. The sheet so formed may be then shaped by conventional 
cutting or molding equipment, and the resultant product folded about hinge 
20, or hinges formed therein, and appropriately stored or shipped. When 
unfolded, however, mat 10 will return to its normal flat, planar 
configuration. 
Mat 10 may also be formed by extruding components panels 16 and 17 and 
bridge 18, in a conventional manner, then passing the hot extrudate over a 
strip, or a tape, in the configuration of hinge 20, and feeding the 
composite material into a conventional calendering apparatus. Upon leaving 
the rollers of the calendering apparatus, the composite plastic sheet may 
be cut into predetermined lengths and appropriately shaped by conventional 
means. As in the previous description, the resultant mat 10 may be folded 
and appropriately stored or shipped. 
The following examples demonstrate the practice of the present invention. 
It is to be understood that these examples are utilized merely for 
illustrative purposes and are not to be considered as limitations of the 
present invention. 
EXAMPLE 1 
A thermoplastic polyurethane tape having a cycloid configuration and being 
0.100 inches thick by 2.00 inches wide was fed into the extrusion take-off 
rolls downstream of the die lip on the upper surface of a PVC mat 
extrudate for a 0.145 inch mat. The rolls were maintained at 150.degree. 
F. The resultant plastic sheet was then permitted to be cooled to room 
temperature, and then was cut at a predetermined length in the 
configuration of a chair mat. Mats so prepared have been rotary fatigue 
tested at 8 rpm with two foam underlay pads. Such testing demonstrated 
that failure, that is, stress cracking, eventually occurred outside of the 
hinge area demonstrating that there was no weakening of the product in 
view of the presence of the hinge. 
EXAMPLE 2 
The mat described in Example 1 was produced, using instead of the 
thermoplastic polyurethane tape, a plasticized polyvinylchloride tape 
having a Shore A durometer hardness of 75. Similar results to those 
described with respect to Example 1 were obtained. 
From the foregoing, it is apparent that the objects of the present 
invention have been fully accomplished. As a result of this invention, the 
improved foldable plastic product in the configuration of a chair mat 
substantially avoids the problems associated with prior art chair mats. 
Having thus described and exemplified the preferred embodiment of the 
present invention, it will be understood that such description and 
illustration is by way of example only and that such modifications and 
changes as may suggest themselves to those skilled in the art are intended 
to fall within the scope of the present invention, as limited only by the 
appended claims.