The present invention relates to a thermoplastic floor plank particularly useful for sea/land cargo container floors, truck and van floors, ship and boat decking, railway wagon floors, and platforms as well as a floors constructed with such plastic planks.

Container industry uses floor planks predominantly made of tropical hardwoods. Plywood made from tropical hardwoods such as apitong and keruing has been widely accepted by the container industry as the best material for container floors. Although tropical hardwood is most commonly used in container flooring applications, it has disadvantages in that it is expensive, is ecologically unfriendly due to the deforestations caused by excessive logging, is heavy and requires strict hygiene observance.

For these reasons and particularly due to rise in tropical wood prices brought up by severe restrictions imposed by relevant governments on logging tropical hardwoods and environmental pressures to replace tropical hardwoods by more environmental friendly materials ("green floors"), the container industry is forced to look for alternative materials to tropical hardwoods for container flooring applications. However, the move away from hardwoods has proved difficult.

Various materials are being considered by the container industry as possible replacement materials for tropical hardwoods but it is still unclear which, if any, alternative material will be favored by the container industry.

5 Softwoods such as Finnish and Scandinavian birch plywood, as long as its price is comparable to the price of tropical hardwoods, are considered by the industry as possible alternate flooring material. However, even though softwood is finding place in the container flooring market, it is unclear whether the softwood capacity exists to serve the mass market. Moreover, the use of softwoods is connected with the use of wood preservative materials which are often toxic and are undesirable in containers transporting food articles due to the risk of contaminating the transported food articles.

Rubberwood, properly treated and processed, is another possible tropical hardwoods replacement material considered by the container industry.. Although, rubberwood is a plantation wood, is environmental friendly and has been proven to be good replacement for ₂₀ apitong, the container industry is reluctant to accept 100 percent rubberwood floors. Moreover, it remains to be seen whether sufficient quantities of rubberwood can be grown to satisfy the demands of the container box building industry.

„ _c Bamboo is another possible tropical hardwoods replacement material considered by the container industry. No availability problems are associated with bamboo since it grows in 3-5 years, depending on the climatic conditions. Bamboo flooring can generate sufficient strength to compare it with tropical hardwood flooring. Bamboo flooring biggest

30 problem appears to be its weight and the fact that bamboo floor cannot be nailed down.

Although the search for viable alternatives to tropical hardwoods as container flooring materials has concentrated on the aforementioned alternative wood sources, other alternative materials such as plastic-coated laminated softwoods, metal/wood combinations,

and totally non-wood materials such as, metal/plastic combinations, metals (e.g., aluminum), plastics and waste textile materials have been considered but are believed as unlikely to be viable for years to come.

It has been reported that Dong Yang Chemicals, a South Korean company, and Envirodek, a U.K. company, have under development an all plastic flooring material (see, e.g., Cargo Systems September 1994, p. 37-39 and Cargo Systems August 1994, p. 55, respectively). However, there is no indication as yet of any use of such materials in commercial transportation container flooring applications.

French Patent No. 1 ,522,503 teaches that a matrix of foamed thermoplastic/thermoset material can be reinforced with wooden sticks, plastic extrudates, light metal tubes, reinforced plastic profiles and other reinforcing materials. The reinforcing materials may be linked to each other to form a continuous network (horizontally or at an angle) but it is essential that they also must adhere to the polymer matrix which makes separation and recycling very difficult.

French Patent No. 2,579,926 teaches the increasing use of thermoplastic profiles having hollow cell structure as products replacing wood or metal (e.g., for window, door, garage doors, fencing and other applications) since they do not rot, are corrosion resistant and can be colored in the mass. It further teaches that thermoplastic profiles can be reinforced. The reinforcement can be done by increasing the thickness

(this increases the use of material) of the profile or by providing a metal or wooden internal reinforcement (this results in the profiles weight and cost increase). It is also suggested to increase the elastic modulus of the thermoplastic profiles by incorporation of glass or other mineral fibers and fillers, thereby providing a composite material. However, the resultant products are expensive and difficult to convert to finished profiles by usual extrusion methods. The document also teaches that extruded thermoplastic profile may be reinforced and stiffened by including a reinforcing element designed to be anchored in the set thermoplastic profile. The adhesion between thermoplastic profile and reinforcing element may be obtained using surface undercuts,

perforation through the body of the thermoplastic profile, the use of adhesive, or heat sealing the reinforcing element to the thermoplastic profile. This type of reinforcing elements attachment to the thermoplastic profiles make separation and recycling very difficult tasks.

Planks of various configuration made of a plastic material for use in flooring, decking and scaffolding applications are known. See, for example, Japanese Utility Model Publication No. 125172; Japanese Patent Publication Nos. 1217/77 and 21154/80; U.S. Patent No.4,349,297; U.S. Patent No.4,496,029; U.S. Patent No. 5,009,045; and U.S. Patent No. 0 5,412,915.

However, none of the known plastic planks has been accepted by the transportation industry for use in flooring applications such as cargo container floors, and truck and van floors for various reasons. It is 5 evident that the container industry does not as yet have a viable alternative to tropical hardwood for flooring applications. The search for a viable alternative materials to tropical hardwoods for flooring applications is, therefore, continuing.

0 The present invention concerns an improved floor plank of extruded thermoplastic material which is light, easy to manufacture, has an improved flexural strength and rigidity, is hygienic, easy to maintain and recycle. The thermoplastic floor plank of this invention is particularly suitable for sea/land cargo container floors, truck and van floors, railway 5 wagon floors and platforms.

In one aspect, the present invention concerns a floor plank made of a thermoplastic material comprising plurality of hollow cells extending in a side-by-side arrangement lengthwise through the floor n plank and a reinforcing member securely positioned within at least one of the hollow cells.

In another aspect, the present invention concerns floors, decks, and platforms constructed with the thermoplastic planks of this invention.

We have now surprisingly discovered that a plank made of a thermoplastic material having plurality hollow cells extending in a side- by-side arrangement lengthwise through the thermoplastic plank and including a reinforcing member securely positioned inside at least one of the hollow cells so that the reinforcing member can neither rotate within nor slip out of the at least one of the hollow cells has improved properties due to the unexpected combination of high flexural strength and rigidity, long term performance and economical use of material. It is not essential that the reinforcing member be physically attached or adhered to the walls of the at least one of the hollow cells to be securely positioned inside the at least one of the hollow cells. However, if the reinforcing member is securely positioned inside the at least one of the hollow cells in such manner, it shall not be physically attached or adhered to more than one point of the wall of the at least one of the hollow cells to minimize or prevent failure under cyclical loads due to stress concentrations. If physically attached or adhered to the wall of the at least one of the hollow cells, it is preferred that the reinforcing member be physically attached or adhered to the wall of the at least one of the hollow cells at the end of the reinforcing member. Easy installation and separation of the reinforcing member from the thermoplastic plank due to the fact that it is not physically attached or adhered to more than one point of the wall of the at least one of the hollow cells ofthe thermoplastic plank is an additional advantage of this invention.

The embodiments of the present invention shown in the drawings and described herein in detail are to be considered an exemplification of the invention, and are not intended to limit the present invention to the embodiments illustrated. It should be noted that dimensional relationships between members of the illustrated embodiment may vary in practice or may have been varied in the illustrations to emphasize certain features of the invention.

Figs. 1 to 6 show a partial perspective view of different embodiments of the thermoplastic plank 1 of the present invention.

Figs. 7 to 9 show a partial perspective view of different embodiments of the floor 5 assembled from two or more thermoplastic planks 1.

Figs. 10A to 10D show different embodiments of the reinforcing member 3 useful in the present invention.

The thermoplastic plank 1 illustrated in Fig. 1 has plurality of rectangular hollow closed cells 2 extending in a side-by-side arrangement lengthwise through the thermoplastic plank 1 and the l-shaped 10 reinforcing member 3 securely positioned within some of the hollow closed cells 2 so that it can neither rotate within nor slip out of the hollow cell 2.

The thermoplastic plank 1 illustrated in Fig. 2 has plurality of 15 triangular hollow closed cells 2 extending in a side-by-side arrangement lengthwise through the thermoplastic plank 1 and the T-shaped reinforcing member 3 securely positioned within some ofthe hollow closed cells 2 so that it can neither rotate within nor slip out of the hollow cell 2.

20

The thermoplastic plank 1 illustrated in Fig. 3 has plurality of square hollow closed cells 2 extending in a side-by-side arrangement lengthwise through the thermoplastic plank 1 and the square-shaped reinforcing member 3 securely positioned within some of the hollow

25 closed cells 2 so that it can neither rotate within nor slip out of the hollow cell 2.

The thermoplastic plank 1 illustrated in Fig.4 has plurality of rectangular hollow open cells 2 extending in a side-by-side arrangement lengthwise through the thermoplastic plank 1 and the l-shaped reinforcing member 3 securely positioned within some of the hollow open cells 2 so that it can neither rotate within nor slip out of the hollow open cell.

The thermoplastic plank 1 illustrated in Fig. 5 has plurality of rectangular hollow closed cells 2 extending in a side-by-side arrangement lengthwise through the thermoplastic plank 1 , the l-shaped reinforcing member 3 securely positioned within some of the hollow closed cells 2 so that it can neither rotate within nor slip out of the hollow cell, and integral locking means 4A.4B extending along the length of the thermoplastic plank 1 on both side edges for locking adjacent thermoplastic planks 1 together side-by-side to form a floor.

The thermoplastic plank 1 illustrated in Fig. 6 has plurality of

10 rectangular hollow closed cells 2 extending in a side-by-side arrangement lengthwise through the thermoplastic plank 1 , the l-shaped reinforcing member 3 securely positioned within some of the hollow closed cells 2 so that it can neither rotate within nor slip out of the hollow cell, and , _c integral locking means 4C,4D extending along the length of the thermoplastic plank 1 on both side edges for locking adjacent thermoplastic planks 1 together side-by-side to form a floor.

Fig. 7 illustrates a floor 5 of the present invention comprising _2n three thermoplastic planks 1 assembled together in a side-by-side longitudinal contact.

Fig. 8 illustrates two thermoplastic planks 1 of this invention assembled together in a side-by-side longitudinal contact by the flange ₂₅ 4A / corresponding flange 4B connecting means to form partially assembled floor 5 of the present invention.

Fig. 9 illustrates two thermoplastic planks 1 of this invention assembled together in a side-by-side longitudinal contact by the tongue _ _n 4C / mating groove 4D connecting means to form partially assembled floor 5 of the present invention.

The thermoplastic plank illustrated in Figs. 1 to 6 is made of an extruded thermoplastic material, preferably reinforced with a filler such as calcium carbonate, talc, glass fibers, silicates, wood flour or any other suitable material.

There are plurality of hollow cells 2 extending in a side-by-side arrangement lengthwise through the thermoplastic plank 1. The hollow closed or open cells 2 can have various shapes such as, for example, rectangular, triangular and square shape as illustrated in Figs. 1, 2 and 3. The number and size of hollow cells 2 can be varied depending on the width of the thermoplastic plank 1 and the intended use ofthe thermoplastic plank. The hollow cells 2 can be close or open type cells. When open cells are used in the thermoplastic plank 1, the cells are opened at the bottom surface, i.e. , the side opposite the load bearing , _β surface, of the thermoplastic plank 1 because the load bearing surface of the thermoplastic plank 1 must be solid and substantially flat, as illustrated in Fig.4.

The reinforcing member 3, illustrated in Figs. 10A to 10D, . ,. made of a suitable material is securely positioned within at least one of the hollow cells 2. The reinforcing member 3 can easily be inserted into or removed from the hollow cell but can neither rotate within nor accidentally slip out of the hollow cell 2.

_2π If desired, the thermoplastic plank 1 can have integral locking means extending along the length of the thermoplastic plank 1 on both side edges for locking adjacent thermoplastic planks together side-by- side to form an assembled plastic floor. Locking means can be any suitable locking means known to a skilled person but it is preferred that

25 the locking means comprises a flange 4A formed on one side edge of the thermoplastic plank 1 and a corresponding flange 4B on the other side edge of the thermoplastic plank 1 (illustrated in Fig. 5) or a tongue 4C formed on one side edge of the thermoplastic plank 1 and a mating groove 4D on the other side edge of the thermoplastic plank 1

³⁰ (illustrated in Fig. 6). Each of the flange 4A and the corresponding flange 4B as well as the tongue 4C and the mating groove 4D of one thermoplastic plank 1 mate with the corresponding elements on adjacent flooring thermoplastic planks 1.

Thermoplastic materials suitable for the manufacture of the thermoplastic plank 1 as well as the extrusion techniques are well known in the art. Suitable thermoplastic materials include, for example,polyolefins and blends thereof, polyvinyl chloride, polystyrene, polymethyl methacrylate and copolymers of methyl methacrylate with acrylic acid and alkyl acrylates, polyoxymethylenes, polycarbonates, polyamides and polyesters which are preferably of a high molecular weight. Suitable polyolefins include polyethylene, polypropylene homopolymers and copolymers, and blends thereof. Polyethylenes such

_{1 Q} as high density polyethylene, ultra high molecular weight polyethylene, low density polyethylene, linear low density polyethylene are preferred thermoplastic materials. High density polyethylene and blends thereof particularly the one manufactured by the metallocene catalyst technology is preferred thermoplastic material. Suitable thermoplastic

15 materials and their preparation is described in U.S. Patent Nos. 3,616,018, 3,183,283, 3,392,213, 3,914,342 and 4,937,299; European Patent No. 0'129'368; Belgian Patent No. 533,362; and International Patent Publication Nos. WO 93/1 1940, WO 94/09060 and WO 94/171 12. Preferably, thermoplastic materials are reinforced with a filler such as, for

20 example, calcium carbonate, talc, glass fibers, silicates, mica, and wood flour.

The thermoplastic plank 1 of this invention is typically 2 m to 12 m, preferably 6 m to 12 m, long, 20 mm to 40 mm, preferably 25 mm to 35 mm high, and 100 mm to 300 mm, preferably 100 mm to 200 mm, wide and is produced by extrusion. It should, however, be appreciated that these dimensions can vary to suit the particular floor construction and proper plank dimensions will be readily determined by the skilled artisan ~ _ without undue experimentation. The width/height ratio of the thermoplastic plank 1 is typically greater than 2: 1. The thermoplastic plank 1 shall have substantially constant height and the load bearing surface of the thermoplastic plank 1 shall basically be a solid flat surface.

A reinforcing member of any shape known to a skilled person can be used as the reinforcing member 3 in the present invention. The

number and shape of the reinforcing members 3 used in the thermoplastic plank 1 will depend on the intended use of the plank and will readily be known to a skilled person. Some suitable reinforcing members 3 are illustrated in Figs. 10A to 10D. The l-shaped reinforcing member is the preferred reinforcing member 3. The reinforcing member 3 can conveniently be made of any known suitable material such as, for example, a fiber reinforced plastic material, an aluminum alloy, steel and magnesium alloy. Suitable fiber reinforced plastic materials are those which have significantly (more than a factor of 10) higher Young's Modulus than a thermoplastic material used for the manufacture of the thermoplastic plank 1. Fiber reinforced plastic materials suitable for the manufacture of the reinforcing member 3 used in the present invention are well known to a skilled person. These materials include fiber reinforced polyester resins and thermoplastic materials mentioned hereinabove reinforced with a fiber. The dimensions of the reinforcing member 3 are such that it fits snugly inside the hollow cell 2 without the need to be fastened to the walls thereof with a separate fastening means but , if desired, it can be fastened to no more than one point to the wall of the hollow cell 2, preferably at either end of the reinforcing member 3. A skilled person can easily determine proper dimensions ofthe reinforcing member 3. The reinforcing member 3 has no sharp edges to minimize the risk of cutting into the walls of the hollow cell 2.

Two or more thermoplastic planks 1 can be assembled together in a side-by-side longitudinal contact into the floor 5 of the present invention as illustrated in Figs. 7 to 9. The assembled floor 5 of the present invention can be fastened to a floor supporting structure of a sea/air cargo container, truck, van, ship, railway wagon and the like by a suitable fastening means, such as screws and clips. When fastening the floor planks 1 to the floor supporting structure, it should be taken care that the fastening means do not go through or are attached to the reinforcing members 3.

The thermoplastic plank 1 is particularly suitable for transportation container floors and represents a clear improvement over

planks conventionally used by the transportation industry in flooring applications due to its unique structure and unexpected combination of improved flexural strength and rigidity, long term performance, recyclability of materials, and light weight. Moreover, cargo container floors constructed of thermoplastic planks 1 are resistant to corrosion and chemicals, are hygienic and easy to maintain.

It should be understood that the present invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to those skilled in the art are included within the scope of the following claims.