The present invention relates to a locking joint for joining elements of a surface covering. The invention has particular, but not exclusive, application for flexible surface coverings. Such flexible surface coverings may, for example, be used for synthetic decking. Other applications of the present invention will be readily apparent to those skilled in the art in view of the advantages described herein.

Synthetic decking, especially for marine applications, already exists. There are however many problems with the present products. Some of these problems include separation of the joints between planks as the material contracts over time which is a characteristic of the plastics used. Most of the existing products make use of harmful solvent based adhesives for the joints, the application of which is also labour intensive. These products can produce a burning sensation on bare skin making them impossible to stand or lie on in hot climates especially as they become smooth surfaced, they become less anti-slip and can even cause an aquaplaning effect in very wetted conditions. The flexible nature of these decking materials and their design do not lend themselves to flat even application and an uneven finish results especially noticeable when wet. These products are also hard and have little or no cushioning to falls or knocks.

According to a first aspect of the present invention a surface covering comprises two or more covering elements, each covering element having a first part comprising a female member;

a second part comprising a male member for engagement with a female member,

the first part having a top surface and a basal surface, the basal surface extending beyond the top surface to provide an open recess for reception of the male member,

the second part having a top surface and a basal surface and a male member protruding therebetween, the female member and the male member providing an interference fit upon engagement.

Preferably the open recess extends between the top surface and the basal surface beneath the top surface to receive the male member beneath the top surface.

Preferably the top surface terminates adjacent the open recess in an inclined surface.

More preferably the first part is further provided with an abutment and the second part is provided with a recess, the abutment being accommodated within the recess upon engagement.

Still more prefereably one of the abutment and recess is provided with a protrusion, the other of the abutment and recess is provided with a groove, the protrusion being received within the groove upon

engagement. Preferably upon engagement of the male and female part a channel is formed in an upper part of the covering between the male and female parts

More preferably a sealing element is located in the channel. Preferably, upon engagement the sealing element is under compression.

Preferably the sealing element is formed as a co-extrusion with the female or male part of each covering element.

Preferably the sealing element is located on the male part above the male member. More preferably the sealing element is located in the channel subsequent to engagement.

Preferably the upper surface of at least one covering element is provided with one or more of a roughened surface, channels or grooves.

Preferably the lower surface of at least one covering element is provided with one or more of a roughened surface, channels or grooves.

Preferably each covering element is provided with ducts or channels extending along a length of the covering element.

Preferably at least one covering element is provided with at least one photovoltaic cell. More preferably, the at least one photovoltaic cell is retained in an upper surface of the covering element, or in which the photovoltaic cell is retained beneath a transparent or substantially transparent part of the covering element.

Preferably at least one covering element is provided with at least one lighting element.

Preferably at least one covering element is provided with one or more magnetic elements.

Preferably at least one covering element is provided with one or more stiffening elements.

Preferably the basal surface is provided with apertures extending therethrough.

According to a second aspect of the invention a joint comprises

a first part comprising a female member;

a second part comprising a male member for engagement with a female member,

the first part having a top surface and a basal surface, the basal surface extending beyond the top surface to provide an open recess for reception of the male member,

the second part having a top surface and a basal surface and a male member protruding therebetween, the female member and the male member providing an interference fit upon engagement. According to a third aspect of the invention a floor covering is provided comprising forming a covering surface according to the first aspect of the invention and securing the covering surface to the floor.

Preferably the covering elements are joined to one another by sliding. Optionally a lubricant may be provided to aid such sliding.

According to a further aspect of the invention a covering element is provided incorporating one or more from a number of photovoltaic cells (or strips), a lighting element, a magnetic element and a stiffening element.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure la is a sectional view of male and female joints of a locking joint in a surface covering in accordance with the present invention;

Figure lb is an illustration as to how covering elements having such joints may be slid together;

Figure lc shows a section of surface covering deformed to cover a nonlinear path;

Figure 2 shows in side section a further embodiment of the invention; Figure 3a shows in side section the joints of Figure 2 in an assembled condition;

Figure 3b shows in side section the joints of Figure 2 during assembly;

Figure 4 shows a sectional view of a further embodiment of a covering element for use in the present invention.

Figure 5 shows a sectional view of a further joint formed by covering elements in accordance with the invention;

Figure 6 show a sectional view of another joint formed by covering elements in accordance with the invention;

Figure 7 shows a perspective view of further adjacent covering sections forming a surface covering in accordance with the present invention;

Figures 8a, 8b and 8c illustrate further features of the covering elements.

Figure 9 shows a schematic perspective view of a surface covering incorporating photovoltaic cells; and

Figure 9a shows a further schematic view of a covering element incorporating a photovoltaic cell. Referring first to Figure la, there may be seen end portions of first and second covering elements 2, 4 which may be joined to form a surface covering. Each covering element 2, 4 is formed as an elongate strip having a length.

A first part of each covering element comprises a female member. A second part of each covering member comprises a male member for engagement with a female member. The first part has a top surface 6 and a basal surface 12, the basal surface 12 extending beyond the top surface 6 to provide an open recess 10 for reception of a male member. The second part has a top surface 21 and a basal surface 23 and a male member 22 protruding therebetween. The female member and the male member providing an interference fit upon engagement of adjacent covering elements.

In more detail the female joint comprises a first overhanging member 7 provided with an inclined or oblique surface 8, the open recess extending between the top surface 6 and the basal surface 12 beneath the top surface and provided with a curved receiving surface 10 beneath the overhanging member 7 and the basal surface terminating in an abutment in the form of upstanding tooth 14. The top surface can be seen to terminate adjacent the open recess with the inclined or oblique surface 8.

The male joint comprises a tongue having a first part 20 extending from the top surface 21 of the second covering element and a second part forming the male member 22 extending from a lower portion of the first part 20 such that a groove or notch 24 is formed between the second part 22 of the tongue and the rest of the second covering element. A free end of the second part is provided with a shaped edge 26.

When the first and second parts engage the tongue 22 is received within the open recess 22, the shaped edge 26 matching with the curved receiving surface 10 to form an interference fit. This has an advantage that the covering elements do not require the use of adhesive to be secured together to form the surface covering, thereby eliminating this harmful and labour intensive task.

In addition, the abutment 14 is accommodated within the recess 24 upon engagement.

The covering elements may be manufactured from any suitable material. Such materials include flexible plastics materials.

Upon engagement of the male and female part a channel is formed in an upper part of the surface covering between the male and female parts.

In use, a sealing element or strip 30 of a suitable material, such as a caulking material, is located in the channel. The sealing strip may be manufactured of any suitable material.

In Figure la the sealing strip 30 which the sealing strip is formed as a co- extrusion with the male part of the covering element. It is formed on the male joint between an upper surface of the second part 22 of the tongue and the first part 20 of the tongue. The sealing strip 30 has an oblique or inclined surface 32 forming a gap or recess 34 between the sealing strip 30 and a part of the upper surface of the second part 22 of the tongue.

The second element is conveniently joined to the second element in one of two ways. Firstly, the mating edges of adjacent covering members are aligned such that the oblique surface 8 of the female joint is received in the gap or recess 34 of the male joint (e.g. in the direction of arrow A). The covering elements 2,4 are then rotated with respect to one another such that the tooth 14 of the female joint engages the groove 24 of the male joint.

In the case of flexible covering elements this insertion assembly method means that additional covering elements can be added in confined spaces both due to the flexible nature of the covering elements and that lesser clearance is needed than if the elements need to be horizontally aligned before joining.

On manufacture the tongue is sized to be an interference fit with the female joint. In the case of flexible elements, the tooth 14 is able to deflect around the tongue into the groove 24.

Alternatively, whether the covering elements are flexible or rigid, the ends of adjacent covering elements may be aligned and the male joint fed laterally into the female joint to form the surface covering (Figure lb). Optionally a lubricant may be used to aid the sliding of the covering elements.

A floor covering can be provided comprising forming a covering surface as described above and securing the covering surface to the floor. A compressive or foam material can be attached to the underside of the covering surface to provide further shock absorption.

Preferably the covering elements are joined to one another by sliding. Optionally a lubricant may be provided to aid such sliding

The sealing strip 30 in this arrangement has several advantages.

Firstly, when the surface covering is mounted onto a surface, where the sealing strip is extruded with the covering element and is oversize for the channel formed on engagement, when the covering elements are brought together the sealing strip 30 is placed into compression causing a downward force to be exerted. This ensures the forming of a watertight seal between the adjacent covering elements. This also provides an opposing force to act against contraction of the covering elements over time. The material of the sealing strip may be softer or harder than the material of the covering elements. If the sealing strip is harder than the covering elements, the covering elements are compressed by the sealing strip to provide the force to ensure that force is exerted to retain the covering elements together. Further, while the joint is watertight it is not airtight, thereby allowing the under surface to 'breathe' as required. This has an advantage when applying the surface covering to certain surfaces such as wood, due to the possibility of retained moisture which may otherwise cause lifting of the surface covering as the moisture expands due to temperature fluctuation.

Alternatively, a sealing strip 30 can be formed in situ in the channel formed on engagement of the covering members subsequent to engagement. The sealing strip can be added either as a liquid and allowed to set or added as a preformed item. The sealing strip 30 may then be sanded or subject to other treatment to obtain a desired surface finish. The sealing strip 30 also provides for the formation of a surface seal.

In the case of flexible covering elements, the tightness of the joints formed means that a covering surface can be manufactured without the need for adhesive. This provides for a fast assembly. As a result of the tightness of the joint, the covering surface can be manufactured off site, and may be conveniently stored for example by rolling up of the covering surface.

The covering elements may be provided with a bonding sheet or equivalent to provide a bonding material to an underside of the covering element. The bonding sheet or equivalent may be double sided. As an alternative the bonding sheet may be applied to the rear of an assembled surface covering. When supplied to an installer, the assembler simply removes the back of the contact sheet and secures the covering element or surface covering to the recipient surface using the exposed bonding material.

The upper surface of the elements may be provided with tracks 50 (Fig. 8c) or other surface features to allow drainage of excess water. The features may be adjacent the joints between the covering elements.

Secondly, in use, covering elements formed of plastics material may contract over time. The sealing strip 30 locating within the channel is able to accommodate such lateral contraction while maintaining an effective seal.

To further protect against contraction of the covering elements, whether longitudinal, lateral or both, the covering elements may incorporate fibres, webbing or strands. These will also serve to restrict lateral or longitudinal expansion due to temperature fluctuations.

Where the covering elements are flexible, the covering elements may be distorted to form a curved covering surface. The lateral displacement between adjacent covering elements allows for the covering elements to form curved surface coverings. Figure lc shows a section of surface covering displaced around a curve away from an assembled straight form (dotted lines). The arrows B show the relative movement of the individual covering elements as the covering elements are curved. Figures 2 and 3 show a further embodiment of the present invention. Like reference numerals are used throughout to refer to like parts. In Figure 2 the female joint is as the previous embodiment. The sealing strip 30 is, however, triangular in section and mounted to a sloping surface of the upper part 20 of the tongue. The adjacent covering elements form a joint as shown in Figure 3a.

Figure 3b shows the covering element 4 carrying the male joint being flexed to enter the covering element 2 carrying the female joint. Figure 3b also shows a further optional protrusion 40 on the lower part of the male joint that can be received within a suitable mating groove 42 on an outer edge of the upstanding tooth 14, the protrusion 40 being received within the groove 42 upon engagement.

It will be understood that suitable profiling of the male and female joints can facilitate bending of the covering elements during the assembly process. For example, grooves, slots 54 (Fig. 8b) or hollow channels 52 (Fig. 8b) may be provided in the covering elements.

The hollow channels 52 may be used to convey gasses or liquids through the surface covering either to heat the surface or to cool the surface as required. Optimally a manifold may be provided at one end of the covering element to facilitate passage of the medium, whether liquid or gas into the covering element. In use, as noted, the lower surface of the covering elements 2,4 (and so of the surface covering formed by adjacent covering elements) may be secured to an underlying surface by adhesive. The underside may be provided with profiling to allow for excess adhesive to be accommodated as the surface covering is glued into position. The underside of the product can have a roughened, textured, embossed or laterally grooved characteristic with or without the described channelling, in order to provide a good 'key' for gluing.

Where slots, such as the shaped slots 54 of Figure 8a are provided, these may also serve to accommodate excess adhesive 56 when the surface covering is being secured to a surface to be covered. The use of shaped slots can allow for the formation of a key 58 to aid further in anchoring the surface covering to the surface being covered.

Channels, sufficiently large grooving or other shaped slots 54 allow for excess adhesive to travel laterally beneath the covering element allowing for a more flat and even application of the surface covering to a surface.

The dimensions of the shaped slots 54 can be such that a cushioning effect is achieved wherein air or soft material under the surface can be compressed under weight to cushion a fall or provide a more comfortable walking feel making the overall surface covering suitable for gymnasiums or around pools or child playing areas. Figure 4 shows a covering element 2 having a female joint to the right hand side and male joint to the left. The upper surface is provided with grooves 58 of varying separation to produce a wood grain effect. The grooves 58 may be formed during the manufacture of the covering element, or subsequently, for example by embossing or other suitable technique. The underside of the covering element is provided with larger slots or recesses 54 and with feet 55 between the recesses 54 themselves provided with a surface texture 59, for example to aid in securing the surface covering to an underlying surface using an adhesive.

Figure 5 shows a further embodiment of a surface covering joint in accordance with the invention. The male and female joints have been shaped such that a channel 57 is formed on the underside of the surface covering between the covering elements 2, 4. This channel allows for the accommodation of excess adhesive in the manner described above. Also shown by the dashed line is the sealing strip 30 before compression.

Figure 6 shows a further embodiment which in addition to the sealing strip 30 provided at the upper surface of the joint, a second sealing strip 36 is provided in a second channel formed at the lower surface of the joint upon engagement of the male and female part. It will be appreciated that the covering surface so formed is reversible. The upper and lower surfaces can be provided with differing surface finishes or surface effects so that alternatives may be provided for the respective surface finishes. It will be understood that one of the finishes that may be provided to a covering element is a completely smooth, flat or untextured surface.

Figure 7 shows a perspective view of a joint formed in accordance with the invention. An upper surface of a first covering element 2 is shown by way of example having a textured finish 60. An upper surface of a second covering element 4 is provided with a variety of illustrative features including inclined channels 62 and grooves 64. These features are provided to allow a reduced skin contact and to reduce the effect of bare skin on a heated surface covering. The additional surface area created by these features also allows for greater heat dissipation increasing this effect. These features are also selected to provide increased grip, and allow for effective dispersion of excess water to prevent aquaplaning. Such features will also take time to wear down to a smooth effect.

As can be seen in relation to Figure 7 the channels or grooves may be provided laterally across the covering elements as an alternative to being provided extending longitudinally.

Figure 9 shows how photovoltaic cells 70, or strips 72 of such cells can be incorporated into a surface covering. Such cells (or strips) may be incorporated into the manufacturing process of the covering elements, for example included in the extrusion process, or applied subsequently - for example the covering elements may be provided with a recess or other retaining profile into which the cells (or a strip of cells) can be positioned (as shown, for example, in Figure 9a). The covering elements can be provided with channels or other openings to accommodate wiring for the cells (or strips). These grooves may be sized to allow flexing of the covering element around a curve while retaining a photovoltaic cell within the covering element (Figure 9A). The flexing of the retaining profile allows the appearance of curved photovoltaic cells (or strips). Additional elements may be included within the grooves to hold the pholtovoltaic cells (or strips) in position.

The wiring for the photovoltaic cells (or strips) may be included within the covering element, running alongside the photovoltaic cells (or strips) within a retaining profile (preferably along an inner retaining profile when the covering element is curved) or in a gap formed between the photovoltaic cells (or strips) and a recess formed in the covering element. The gap under the cells (or strips) can be adjustable.

As an alternative, the cells (or strips) can be incorporated into the sealing strip 30.

It will be understood that the surface covering need only contain as many covering elements incorporating such photovoltaic cells (or strips) as are desired.

Alternatively the retaining profile may be use to retain a lighting element as noted below or other element to provide a desired visual effect. In an alternative embodiment, the covering elements may be formed of transparent material or incorporate transparent (or substantially transparent) portions. This allows for the surface covering to incorporate photovoltaic cells (or strips) within the covering elements, but beneath the upper surface of the covering elements, thereby protecting the photovoltaic cells (or strips) from damage.

Alternatively, a surface covering incorporating such covering elements with transparent regions could be overlaid onto an arrangement photovoltaic cells (or strips).

Similarly, the covering elements may overlie a lighting arrangement to allow light through. Alternatively, the covering elements may incorporate suitable lighting elements to allow for the bespoke forming of a lighting pattern or effect when the surface covering is assembled from the covering elements. The lighting elements may be formed with the covering elements or retained in the manner described above for the photovoltaic cells (or strips).

Magnetic elements may also be incorporated into the covering elements. For example, bar or strip magnets may be incorporated into the lower surface of one or more covering elements making up a surface covering. Such a surface covering has particular application for covering steel surfaces as it allows the surface covering to be secured in place, to provide a suitable exposed surface having the desired properties, yet may readily be lifted for inspection of the steel surface. It will also be appreciated that, where appropriate, the covering elements may incorporate stiffening elements. These may be incorporated during manufacture of the covering elements or more preferably, retained in suitable receiving grooves in the covering elements as required to provide the desired strengthening for a particular surface covering.