Edge Finished Resilient Tile, Method and Apparatus

The present invention is directed to an edge finished resilient tile, and a method and apparatus for producing the tile. In particular, the invention is directed to an edge finished resilient tile which has superior squareness and uniformity of size within each lot and from lot to lot. Due to the superior squareness and uniformity of size, a surface covering can be easily laid in which the tile edges are substantially indiscernible.

Resilient tile, particularly vinyl composition tile and vinyl tile, are typically produced by die cutting the individual tiles from a continuous sheet. The punch press which die cuts the tile, actually punches out the tile from the continuous sheet by tearing the tile composition under a blade. Therefore, rather than having a smooth cut edge, the tile edges are jagged.

Further, the squareness of the tile is dependent on the squareness of the punch as well as the straightness of the die cut edges. The unevenness of the edges is exacerbated if the tile is coated, particularly with a curtain coater, after being die cut.

These nonuniformities and unsquareness lead to unsightly seams when the individual tiles are laid up as a surface covering. These seams are typically about 0.010 inches wide and are readily discernible from distances of three feet or greater.

To overcome these disadvantages, some tile have been edge-finished by sanding or otherwise finishing the edges of a stack of tiles. However, such methods have not addressed the problem of accurately positioning the tiles in the stack or accurately aligning each stack. Therefore, While this method has improved the squareness and uniformity of the tiles, the seams of most prior art tile floors are still readily discernible.

It is an object of the invention to provide an apparatus and method for consistently producing an edge-finished resilient tile which has a squareness of within 0.005 inches and edge lengths within 0.005 inches of each other. Such tile can be laid up as a surface covering which has seams Which are substantially indiscernible at a distance.

It is another object to provide an apparatus and method for producing such edge finished tile at a rate of at least 10,000 tiles per hour. To achieve such an object, is the further object to provide an apparatus and method which allows the simultaneous edge finishing of a plurality of tiles.

The foregoing objects can be accomplished by positioning the tile to be edge finished on a continuous belt by contacting the tile edges with three reference points, maintaining the position with hold down means and moving the held down tile past an edge finishing means such as a cylindrical shaper router having the axis of rotation perpendicular to the plane of the tile.

FIG. 1 is a schematic representation, in plan, of apparatus to edge finish resilient tile in accordance with the present invention.

FIG. 2 is a schematic representation, in side elevation, of a link of the continuous belt of the apparatus of FIG. 1.

FIG. 3 is a schematic representation, in elevation, of the apparatus of FIG. 1.

As previously discussed, most resilient tile is presently die cut and installed without edge finishing the tile. While some tile is edge finished by sanding the edges with a belt sander, this method is slow and does not produce adequately square and uniform tile.

Resilient tile is presently die cut oversized. This is because after the die cut tile is coated with a wear layer and processed to adhere the wear layer to the tile, it shrinks. The amount of shrinkage depends upon such variables as the starting materials, uniformity of the tile composition in laying up the continuous sheet from which the tiles are die cut, and the processing temperatures and pressures. Therefore, in addition to the previously discussed problems of squareness and edge straightness, it has been difficult to obtain tile of uniform size.

As a result of the non-uniform size, squareness, edge roughness and edge straightness, surface coverings which are laid up with the tile of the prior art yield seams which are readily visible. Some manufacturers have addressed these problems by forming a stack of finished tile and sanding or otherwise finishing the edges. However, not only is this process time consuming and expensive, means have not been developed to accurately position the individual tiles in the stack or the stack with relation to the sander to obtain uniformly sized and square tile.

Tile which is within 0.005 inches of square as determined by ASTM Standard F540 and edges of length within 0.005 inches of a desired length have been obtained using the apparatus shown schematically in FIG. 1. The unfinished tile 1 is positioned on the continuous belt 3, held down by hold down rollers 5 and opposite edges 7 and 9 finished with routers 11. The tile 1 is accurately positioned on the continuous belt 8 by a stop means 13, dogs 15 and pusher means 17. The pusher means 17 is located generally opposite the stop means 13 and is spring loaded with a spring 19. The spring 19 has sufficient force to push the tile into contact with the stop means 13 and creates sufficient drag on the tile i to maintain the tile in contact with the dogs 15.

It is important that, as the edges 7 and 9 initially contact the stop means 13 and pusher means 17, the tile 1 be free to move relative to the continuous belt 3. As shown in FIG. 1, the contacting surfaces 23 of stop means 13 and 25 of pusher means 17 are convex to assist in positioning the tile 1. The preferred radius of curvature for the contacting surface 23 is found to be six inches for 9".times.9" tile and 12".times.12" tile. Preferably, the point of contact of surface 25 with edge 9 is at the trailing edge of surface 25. It has also been found desirable to have the point of contact of the pusher means 17 be slightly upstream from the point of contact of the stop means 13.

As shown in FIG. 1, before the trailing edge 27 passes the stop means 13 and pusher means 17, the leading edge 21 is contacted by the first set of hold-down rollers 6. Preferably, the first set of hold-down rollers are positioned to contact the leading edge 21 when the point of contact of the pusher means 17 is about 1/2 inch from disengaging the edge 9 and the point of contact of the stop means 13 is about 3/4 inch from disengaging the edge 7. To maintain the accurate positioning of the tile established by the dogs 15, stop means 13 and pusher means 17, it is important that the hold down rollers 5 have minimum play and exert sufficient pressure on the tile 1 to clamp the tile 1 to the continuous belt 3.

To compensate for variabilities in the length of the links 29 forming the continuous belt 3 and accurately position the tile 1 perpendicular to the direction of travel, the dogs 15 must be adjustable. A preferred embodiment is shown in FIG. 2. The dog 15 is secured to the link 29 by screws 31. The dog 15 is adjusted relative to link 29 by inserting or removing shims 33.

The ability to adjust the dogs 15 is particularly important during the second edge finishing step. After the two edges 7, 9 adjacent the trailing edge 27 are edge finished as shown in FIG. 1, the tile 1 is positioned on a second continuous belt with one of the finished edges 7, 9 becoming the trailing edge. The squareness of the finished tile is obtained by adjusting the dogs 15 to maintain the trailing edge perpendicular to the direction of travel.

Processing of the tiles can be increased by edge finishing a plurality of tiles simultaneously as shown in FIG. 3. To obtain the precise squareness and sizing obtained by the present invention, the individual tiles must be positioned on the conveyor belt 3 with each trailing edge in contact with both dogs 15 and with one edge adjacent to the trailing edge in contact with the stop means 13. This is accomplished by having independent spring loaded pusher means 17 and 18 contacting the individual tiles at the edge opposite the stop means 13. If a single pusher means contacted a plurality of the tiles, there is no assurance that each tile would be in contact with the stop means 13. In fact, it is most likely that the widest tile would contact the stop means while the remaining tile or tiles would only contact the two dogs and pusher means.

By using the above described apparatus, runs in excess of 20,000 resilient tile have been produced in which each tile is well within 0.005 inches of square and have sides of length well within 0.005 inches of each other. It is anticipated that runs in excess of 250,000 tiles with the specified squareness and size can be easily achieved when the process is utilized in a commercial production line. No known commercial tiles, particularly 9".times.9" or 12".times.12" tiles, have such consistent squareness and uniformity.