Anchor sheet

Abstract

An improved anchor sheet is described. The anchor sheet can be injection molded from polypropylene and can have a thickness of between 0.031 inches and 0.75. Such an anchor sheet can be molded with hooks and can have an attached resilient layer. Stems integral with the anchor sheet are used to form the hooks, and may be 1 mm high and 0.55 mm in diameter. The density of stems may be approximately 230 per square inch, or approximately 128,000 stems on a plate. An anchor sheet made in this way makes an excellent field of hooks when installed onto a supporting surface such as a floor. This field of hooks can take an overlying decorative covering such as pieces of loop backed carpet. When a resilient layer is attached, for example by ultrasonic welding, to the underside of the anchor sheet, between the anchor sheet and the floor, the anchor sheet can have the right degree of “give”, so that a user can experience some cushioning effect from the resilient layer below the anchor sheet, but with some level of rigidity so that the load of walking is transmitted across a larger surface and does not “dig” into the resilient layer.

Description

FIELD OF THE INVENTION

This invention concerns improvements to an anchor sheet having hooks across one side for use under carpets or other decorative coverings as described, for example in U.S. Pat. Nos. 6,306,477 (Pacione, Oct. 23, 2001), 6,298,624 (Pacione, Oct. 9, 2001), 6,395,362 (Pacione May 23, 2002), and PCT/CA 00/00681 (Pacione et al.), published under WO 00/74544 on Dec. 14, 2000. This application incorporates by reference the specifications of these earlier patent documents.

BACKGROUND OF THE INVENTION

The earlier Pacione cases generally disclose an anchor sheet which can be supplied in various shapes and sizes, with or without a pre-attached decorative covering. These earlier cases also describe how individual sheets can together form a contiguous mass of anchor sheet to provide a field of hooks which engage loops on the underside of an overlying flooring, particularly carpet pieces. Such a contiguous mass can be formed by attaching the anchor sheets directly together, either by overlapping or abutting or by the use of attachment devices aided by the bridging of neighbouring sheets by the overlying covering. Such mass can be free floating or attached to the floor.

As discussed in the earlier Pacione cases, the current inventor has invented an anchor sheet (in some contexts referred to as a hook plate or a module) which, when installed, acts to tie decorative covering together as a functional unit and to add mass and stability to such unit, particularly in the case of a unit having a flexible decorative covering such as a carpet. The anchor sheet may be substantially covered over one side with hooks for anchoring a decorative covering. The anchor sheet itself may be attached to an underlying substrate, such as a floor or wall, or it may be loose laid on a floor where the anchor sheet may have sufficient mass to prevent movement of the anchor sheet.

SUMMARY OF THE INVENTION

The present invention provides an improved anchor sheet having desirable characteristics when in place under a floor covering.

It is possible, generally even preferred, when using coverings in combination with the anchor sheet of the present invention to use a floor covering that includes little or no cushion layer as is often provided in carpet by a foam layer, e.g., as by urethane foam. The benefits of an anchor sheet of the present invention are most evident when it is used in combination with such a covering having little or no distinct cushioning layer in the covering.

An anchor sheet of the present invention provides an overlying plastic sheet and an underlying cushioning layer. An anchor sheet made up of a top plastic layer and underlying cushion has been generally previously described, as in U.S. Pat. Nos. 6,298,624, 6,306,477, and 6,395,362 and WO 00/74544.

In a broad aspect, the invention is an anchor sheet made up of a plastic sheet and an underlying resilient layer secured thereto. The plastic sheet has a thickness of between 1/16 inches and ¼ inches and having a flexural modulus (ASTM D790) of between 700 and 3600 MPa. The resilient layer has a compression force deflection (ASTM D3574-C) that is within about 30 percent of the compression force deflection of a low density polyethylene layer ⅜ thick and a density of 30 kg/m³. A value within about 30 percent of the compression force deflection of the indicated material can be up to 30 percent more than the value measured for the indicated material or down to 30 percent less than the value measured

When included as part of a carpet installation having an overlying carpet having no rubber or urethane foam layer, for example, an anchor sheet of the present invention provides a desirable “feel” or “give” as a person walks over the installation. With the present invention, a carpet having little or no internal resilient layer or cushion can be used, resulting in less stress on the carpet fibers and primary backing. The anchor sheet can also provide the required level of sturdiness so that furniture can be placed on or moved over the installation and is relatively resistant to puncture, under normal wear. The lower layer includes a suitable level of resiliency for installation atop, for example, a concrete floor of a newly constructed office building to suitably ride over imperfections therein.

Related to the invention(s) disclosed herein are invention(s) in the following U.S. provisional patent applications, all filed concurrently herewith and incorporated by reference:

• • U.S. Provisional Patent Application entitled “Carpet tile, installation, and methods of manufacture and installation thereof”. This application shows coverings that can be used with an anchor sheet of the present invention;
  • U.S. Provisional Patent Application entitled “System and methods of manufacturing hook-plates”. This application shows a method for manufacturing an upper plastic layer that can be used as the upper portion of the present invention;
  • U.S. Provisional Patent Application entitled “Ultrasonic welding of resilient layers to plates”. This application shows a method for securing a cushioning layer of the present invention to the upper plastic layer;
  • U.S. Provisional Patent Application entitled “Floor covering having a removable decorative inlay”. This application shows a particular covering arrangement that can be used with the present invention; and
  • U.S. Provisional Patent Application entitled “Anchor sheet positioning and connection system”. This application shows ways and means for connecting anchor sheets to each other.

In a further aspect of the invention the sheet has a resilient layer made from low-density polyethylene.

If polypropylene is used for the anchor sheet and with a resilient layer made of low-density polyethylene, the preferred thickness of the anchor sheet is about 0.125 inches. Further experimentation has shown the preferred size of the anchor sheet and the preferred way of connecting the anchor sheets together is as follows. It has been found that one size of anchor sheet of approximately 24″×24″ square (taking into account some possible geometric variation along the edges, usually the corners, to accommodate devices for attaching neighboring sheets to each other) is preferred with an overlap/underlap area provided between adjacent sheets, so that the sheets overlap to form a planar surface. However, with a connector disclosed in the above-detailed application entitled “Anchor sheet positioning and connection system”, no connection of the sheets to the floor, or directly to each other at the overlap area, is necessarily required.

Other additional features of the preferred anchor sheet are additional aspects of the invention disclosed herein and are described below and outlined in the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further understood from the following detailed description of an embodiment of the invention, with reference to the drawings in which:

FIG. 1 shows an anchor sheet in simplified form with an underpad according to this invention:

FIG. 2 shows an anchor sheet in plan view having overlapping edges in addition to the cutaway portions for the cornerpieces;

FIG. 3 shows a cornerpiece to be used with certain geometric shapes of anchor sheets;

FIG. 4 shows an embodiment with two differently configured anchor sheets;

FIG. 4 a shows another embodiment with two differently configured anchor sheets;

FIG. 4 b is a section through line 4b-4b of FIG. 4a;

FIG. 5 is a section through line 5-5 of FIG. 4;

FIG. 6 is a section through line 6-6 of FIG. 4; and

FIG. 7 shows an embodiment of an interlocking anchor sheet.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, an anchor sheet 1 is provided. Anchor sheet 1 is placed on or attached to a surface such as floor (not shown). In the present embodiment, anchor sheet 1 is in the shape of a square. Anchor sheet 1 may alternatively be configured in any shape that can be conveniently abutted with another piece to create a floor pattern such as, for instance, a rectangle, a hexagon or an octagon or a mixture thereof. Generally, the preferred shape will be an equilateral polygon, but a rectangle or any other shape may also be used as appropriate. Typically, a shape will be chosen which allows a planar surface to be created out of a single major piece. Such shape can have a countersink along one edge to receive an overlapped portion of an adjacent similar sheet. However, different shapes can be used, having any number of edge areas which are countersunk from the top surface. Additional sheets can be put into this area. In FIG. 1, anchor sheet 1 contains a top surface layer having hooks 4 countersunk area 7 which can be used by an overlap portion of an adjacent sheet of the same or different shape or for an attachment piece.

Anchor sheet 1 may also include a cushion or resilient layer 5, which is attached to a side of anchor sheet 1 opposite to hooks 4. When installed, resilient layer 5 is located between anchor sheet 1 and the underlying floor. In this configuration, resilient layer 5 provides resilience to the anchor sheet when a downward force is applied thereto. Similarly, if an overlayment or cover, such a decorative covering (not shown), is attached to or supported by anchor sheet 1, then the decorative covering will be similarly cushioned. The decorative covering may be a carpet overlaid on top of the anchor sheet. Resilient layer 5 may also be used to add mass to anchor sheet 1 to inhibit movement thereof. Furthermore, resilient layer 5 may be manufactured to have a greater coefficient of friction with the floor than anchor sheet 1 in order to reduce movement of resilient layer 5 (and, by connection, anchor sheet 1 and the decorative covering) relative to the floor. However, it should be emphasized that cushioning is not necessary for anchor sheet 1 to function, but such cushioning can have at least the advantages described above, depending on the characteristics of the overlayment and the intended use of anchor sheet 1.

The anchor sheet is relatively rigid in the sense that it is not tape or cloth like. Anchor sheet 1 can have the right degree of “give”, so that a user can experience some cushioning effect from resilient layer 5 below the anchor sheet, but with some level of rigidity so that the load of walking is transmitted across a larger surface and does not “dig” into resilient layer 5. This “give” is a product of the combination of the “stiffness” common of the anchor sheet and the “compressibility” of the resilient layer. To achieve a “feel” it is possible to have a more stiff anchor sheet and a more compressible resilient layer or it is possible to have a less stiff anchor sheet and less compressible resilient layer. However, all of the preferred combinations shown will work, subject to the application and the personal preference of the user.

Hooks 4 of top surface layer 3 attach to the loops of an overlying carpet (not shown). Hooks 4 can be attached to sheet 1 by any convenient means, but injection molding is preferred. It is possible for the hook material to be a different plastic or polymer material, and even applied as a film with adhesive, since hooks 4 may need to be relatively more resilient and flexible than the anchor sheet 1 itself. In this case, a laminate anchor sheet 1 rather than unitary construction can be used. Hooks 4 have stems 1 mm high and 0.55 mm in diameter with a stem density of approximately 230 stems per square inch of top surface layer 3. The ratio of stem height to diameter is preferably about 2:1, and may be as great as 10:1. The stem diameter may be in the general range of 0.3 to about 0.9 mm. Stem diameters of as small as 0.1 mm have been found to be acceptable.

When the density of hooks 4 is approximately 230 per square inch, nearest-neighbour hooks are spaced about 1.8 mm from each other, and are arranged in a grid of equilateral triangles so that each hook has six nearest neighbours. In this configuration, there are approximately 128,000 stems on a 24 by 24-inch anchor sheet 1. Sheets having as many as 330 stems per square inch may be used as well. While a single anchor sheet 1 may be installed, in the preferred embodiment, an anchor sheet subfloor comprising two or more anchor sheets 1 is installed (as illustrated, in part, in FIG. 2).

As seen in FIG. 1, anchor sheet 1 has a thickness A. The appropriate thickness A will depend on the intended use of the anchor sheet, and may vary with the type of overlayment to be used. The preferred thickness A will generally not be less than 0.062 inches. One preferred thickness A is about 0.125 inches, but the thickness A may preferably flooring (not shown) is replaced, or where a thick anchor sheet needs to be used to create a level surface with an adjacent surface.

The appropriate thickness of resilient layer 5 may also vary depending on the intended use of the anchor sheet, and the type of overlayment to be used. For many uses, the preferred thickness of resilient layer 5 may be about 0.375 inches. A preferred total thickness when resilient layer 5 is combined with an anchor sheet of thickness A, is about 0.5 inches, not including the height of hooks 4 of anchor sheet 1. When thickness A of anchor sheet 1 is about 0.125 inches and anchor sheet 1 includes resilient layer 5 of about 0.375 inches thick, a desirable walkability of the anchor sheet/resilient layer combination may be achieved.

In the above-described configuration, the material costs for the anchor sheet and resilient layer may be generally less than other configurations. For example, use of a thicker anchor sheet may increase costs. More material is required to increase the thickness of the anchor sheet because it is generally more dense than the resilient layer. Conversely, an increase in the thickness of the resilient layer is generally less expensive, but, depending on the magnitude of the increase, the walkability of the anchor sheet/resilient layer combination may be negatively affected. The use of the aforementioned thicknesses may also serve to achieve a level of durability of the anchor sheet/resilient layer combination without unduly increasing manufacturing costs.

If the combined thickness of the anchor sheet and resilient layer is greater than about 0.5 inches, the use of such anchor sheet combination may be limited in some installations. For example, a thicker anchor sheet and resilient layer combination may obstruct or interfere with a door or other nearby feature when the anchor sheet is installed.

Referring again to FIG. 1, cutaway from thickness A is a countersunk area A which circle. When combined with similar abutting anchor sheets aligned along sides 9 and 11, a ¾ circular cut out area is formed. A fourth anchor sheet diagonally opposite anchor sheet 1 forms a complete circle having a circular cut out area and could have a “hole” 14, as described below. Typically, the cut-out area will be such that the width of the anchor sheet at 13 will be approximately half of the total thickness A of the anchor sheet. However, the width of the anchor sheet at 13 may be other than approximately half the total thickness A. In addition, there can be a second area 14 which is cut away from the corner (the apex of the angle formed by the two sides of the square). This second area 14 also has a geometric shape (in this example, a ¼ of a circle) so that, when combined with other anchor sheets, the anchor sheet edges are aligned so that their corners meet at the virtual intersection of the four corners, and a second smaller circle is formed in the completed anchor sheet structure.

Thus, a circular cut away area 14 within a second larger circular cut out area 7 is created when four similar anchor sheets abut each other, as shown in FIG. 2. A complementary corner piece or attachment device 31 can then be added which will match the shape and thickness of the reduced thickness portion and the shape and thickness of the cutaway area (see FIG. 3). Corner piece 31 can be attached to area 7 by glue or other permanent attachment, or by detachable attachment such as pressure sensitive adhesive or a hook and loop, or post and hole type. Fastening devices such as hook and loop or a screw or nail may be used to attach the corner pieces to a floor to hold the anchor sheet to the floor at only a few discrete points by use of the corner pieces, with or without direct attachment to the anchor sheets. However, it is not necessary to attach any part of the anchor sheet 1 or corner piece 31 directly to the floor. A preferred “snap-fit” attachment system is described, among others. in the above-detailed application entitled “Anchor sheet positioning and connection system”. With this form of attachment relative movement between anchor sheets can be achieved, although the anchor sheets are attached directly to each other. It will also be appreciated that area 7 can have any shape or size in relation to the size of the anchor sheet and attachment piece 31 can be correspondingly bigger.

FIG. 2 shows an arrangement of anchor sheets 1 and corner pieces 31 where there is a plurality of overlapping anchor sheets 111. In this example, anchor sheets 111 are squares. Except as noted herein, anchor sheets 1 and 111 have similar characteristics, and the description of one generally applies to the other (e.g., materials used for manufacture). Unlike the embodiment in FIG. 1, anchor sheets 111 do not abut each other in one plane only. Rather, anchor sheets 111 have an underlay area 15 in which there is a lower portion edge 16. Underlay area 15 is indicated in FIG. 2 by a grid marking, but underlay area 15 is part of anchor sheet 111. Underlay area 15 is configured to lie under overlap area 19 on an adjacent sheet 111. Overlap area 19 extends on two sides of each sheet 111, and underlay area 15 extends on the other two sides. Overlap area 19 overlaps the underlay area 15 of each sheet 111, for instance, along an area 20 (the area between the top abutment edge at the dotted line). Overlap and underlay areas 19 and 15 may be configured to extend from anchor sheet 111 by a similar amount. This enables underlay area 15 to generally support overlay area 19. However, the degree of overlap need not be complete. For example, overlap area 19 may extend a fraction as far as underlay area 15. Such unmatched overlap can affect the degree of support provided at overlap area 20. In an embodiment, each of overlap area 19 and underlay area 15 may extend from sheet 111 by two inches, and preferably extend by one inch, to form a generally uniform overlap thereof in area 20. The thickness of the overlap area 19 may be approximately half the thickness of thickness A.

An area of reduced thickness 21 is formed in the general vicinity of where the apex of underlay edges 15. The cutout is centered over the area of abutment for instance lower portion edges 16 of anchor sheets 111. The cutout is not centred over the corner line of abutment 25 created by the overlap edges extending over the area of overlap 19. In addition to the reduced thickness area 21 (similar to area 7 in FIG. 1) there is a cutaway area 23.

It is possible to use an embodiment by providing a reduced thickness area along any edge (or portion of an edge) of a modular anchor sheet, having a cut away area within the reduced thickness area to provide a countersink for use with the attachment devices described. A reduced thickness area surrounding a cut away area may also be located anywhere in the interior of an anchor sheet for use of an attachment device at that interior point. However, this is generally not preferred, unless the attachment device is to be attached to the floor because an attachment device at an interior point can obviously not connect two anchor sheets together.

If an overlapping arrangement is used, the extent of underlay edges 15 and overlap 19 need not be along more than one side, nor need it be along an entire side. Overlap may occur at just a portion of one side enough to permit portions of co-operating anchor sheets 1 to overlap. Similarly, the particular shape of such overlapping pieces may be varied as long as the overlap is sufficient to achieve the functions described herein.

In one embodiment, anchor sheets 1 are square, of similar size and shape, and have sides in the range of 24 to 48 inches, although anchor sheets outside of this range may also be used.

Anchor sheets 111 may be made of an extruded or injection molded material in which the two pieces are thermally bonded so as to form the overlap 19 and underlay area 15. Sheets 111 may be cut by a gauge or jig. Anchor sheet modules 111 may be die cut. The layer of hooks may be thermally bonded to the surface of the top sheet. Alternatively, the injection-molded using a one- or two-step or multi-step process mold, using materials such as polypropylene or polyethylene.

The overlap 19 and underlay 15 areas of the sheets 111 may be provided with means for detachable or permanent attachment, or the underlay areas 15 of an adjacent sheet may simply lie underneath and support the overlap areas 19 without any form of attachment. Preferably, however, any attachment provides for relative movement between adjacent sheets. The snap fit arrangement described in the above-detailed application entitled “Anchor Sheet Positioning and Connection System” could be suitable. Possibly, the sheets 111 may also be made with corresponding registering bumps and indentations (not shown) in the overlap 19 and underlay 15 portions of sheets 111 to assist in retaining sheets 111 together and in alignment during installation.

In cases where hook and loop systems or hooks are provided for, the hooks may be temporarily covered by a hard slip covering as discussed in U.S. Pat. No. 6,306,477, or a soft covering as disclosed in U.S. Pat. No. 4,822,658 to temporarily prevent premature engagement of the hooks to the loops.

Anchor sheet 111 may alternatively be configured to work in conjunction with one or more differently configured anchor sheets. For example, a first type of anchor sheet (not shown) could be constructed to have complementary corner pieces (such as 31 in FIG. 3) attached or integrally molded to the corners thereof. A second complementary anchor sheet, such as anchor sheet 111 would receive the corner pieces in a similar manner as described for the preferred embodiment. Alternatively, two or more anchor sheets could be configured to have an interlocking keystone or jigsaw puzzle like shape. An example of an interlocking keystone anchor sheet 111′″ is illustrated in FIG. 7. If such an arrangement is used, then thereof to inhibit separation and bending of adjacent anchor sheets away from their common plane. However, the keystone male in portion 41 could be made smaller than the opening so that some relative movement between the sheets could be possible while still being interlocked.

Referring to FIGS. 4 to 6, anchor sheets 111′ (shown in white and light grey) and 111″ (shown in dark grey) are different yet configured to be complementary to one another. The shading of sheets 111′ and 111″ in FIG. 4 is done merely to distinguish the two configurations. These anchor sheets are arranged, positioned, or connected to one another in a similar manner as described for the preferred embodiment. These anchor sheets differ from the preferred embodiment in that anchor sheet 111′ has only an underlay areas 15′ which co-operate with overlay areas 19″ of anchor sheet 111″. The dashed line in FIG. 4 shows the extent of the underlay area 15′ of anchor sheet 111′. FIGS. 4a and 4b illustrates a similar arrangement wherein anchor sheet 111′″ serves to connect anchor sheets 111′.

Referring again to FIG. 1, the thickness A is ⅛ of an inch, and the thickness of the anchor sheet at 13 is 1/16 of an inch. (Similarly, the overall thickness of anchor sheet 111 may be ⅛ of an inch, with the thickness of the underlay area 15 being 1/16 of an inch.) The thickness of the resilient layer 5 is in the range from approximately ¼ of an inch to ⅜ of an inch, depending on the desired resiliency and amount of surface traffic. Hooks 4 of top surface layer 3 have a density that may range from about 160 to 1200 hooks per square inch, and may be as high as 2000 hooks per square inch. The preferred density is approximately 230 hooks per square inch.

The preferred materials for anchor sheet 1 and resilient layer 5 are polypropylene and polyethylene. The preferred plastic material for anchor sheet 1 is polypropylene, such as ExxonMobil PP7805 E2 copolymer grade for compounding or injection molding. Accutuf® has a melt flow index of 100, a tensile yield strength of 4100 psi, a flexural modulus of 250×10³ psi. PP7805 E2 has a melt flow index of 80 @ T=230° C., F=2.16 kg), and a tensile strength at yield of 33 MPa (50 nm/min). Other plastics may be used such as those sold as STAMYLAN (TM) P 112MN40, with an ISO 1873 indication of PP-H or other thermoplastic materials. Stamylan (TM) has a melt flow index of 50 169 T=230° C., F=2.16 kg), a flexural modulus of 1900 MPa, proportional strength of 35 MPa, ultimate strain of greater than 50%, and a density of 910 kg/m³ and a melting point of approximately 160° C. Other polypropylenes such as those having lower or higher melt flow indexes, for example, 80 or 100, may also be used. It will be appreciated that other materials may also be used in the injection process, including polyethylene terephthalate, nylon and other polymers. In general, the plastic from which the sheet is manufactured has a flexural modulus of between 1200 and 2600 MPa (ASTM D790), or a flexural modulus of between 1300 and 2500 MPa, or a flexural modulus of between 1400 and 2400 MPa, or a flexural modulus of between 1500 and 2300 MPa, or a flexural modulus of between 1600 and 2200 MPa, or a flexural modulus of between 1700 and 2100 MPa, or a flexural modulus of between 1800 and 2000 MPa.

In a preferred embodiment, resilient layer 5 is made from low density polyethylene with a density of approximately 30 kg/m³. Other foams having a suitable compression force deflection test may be used, and are of a suitable material such as polyurethane or rubber. The preferred foam has a compression force deflection (ASTM D3574-C) which is the same or very near to that of the disclosed polyethylene foam that is ⅜ inches thick and has a density of 30 kg/m³.

ASTM standards referred to herein are available from ASTM International. 100 Barr

ASTM D3574, Test C, is the compression force deflection test (50% compression) as set out in designation D 3574-01 on Jan. 22, 2003. The value obtained in the test is that set out as the standard, i.e., 50 mm by 50 mm by 25 mm in thickness.

Flexural modulus is determined according to ASTM D790 at a temperature of 23° C.

In alternative embodiments, anchor sheet 1 is made of thin polycarbonate or polyester. For thick covering materials such as stone or ceramic, anchor sheet 1 may be as thick as ¼ of an inch or even greater. Thickness may vary depending upon the covering material and the stability requirements for any covering such as carpet. It is also possible for anchor sheet 1 to be made of thin sheet metal, carbon fibres or some form of polymer.

Anchor sheets 1 may be any size convenient for sale, transportation or installation, typically in the range of 12 inches by 12 inches square to 36 inches by 36 inches square. As noted, anchor sheet 1 is an approximately 24 inches by 24 inches square. In an alternative embodiment, anchor sheet 1 is an approximately 25 inches by 25 inches square.

Anchor sheets 1 may be manufactured using some convenient method such as the injection moulding and coining method disclosed in the above-detailed patent application entitled “System and Methods of Manufacturing Hook Plates”. The referenced application discloses that, in order to manufacture an anchor sheet or hook plate, injection molding is used. The hook plate manufactured by the molding apparatus (not shown) may be a square that is 24 by 24 inches, and has ⅛ of an inch thickness. Stems integral with the hook plate are used to form the hooks, and may be 1 mm high and 0.55 mm in diameter. The density of stems may be approximately 230 per square inch, with a distance between stems of 1.8 mm arranged in a regular triangle, or approximately 128,000 stems on a plate.

The polypropylene material is injected into the mold at a temperature of approximately 280° C. and a pressure of approximately 150 bar, while the mold is internally cooled to a temperature of approximately 60° C. Under these constraints, the injection time is approximately 2 seconds, the holding time is approximately 12 seconds, the cooling time is approximately 35 seconds, and the ejection time is approximately six seconds, for a total cycle time of approximately 55 seconds. Due to the large number of small stems being molded across the plate, it is important that the work-piece be ejected from the mold before the shrinkage of the work-piece is sufficient to shear the stems as they sit in the array of cavities in the mold. In the molding process of the present description, the total holding and cooling time is approximately 47 seconds, and it has been found that letting the hook plate cool for longer than this time results in shearing of the stems from the rest of the hook plate under the given pressure conditions for the material. Also, with the large number of small stems being molded across the plate, it is important that the hook plate be ejected from the mold at approximately the same time across the entire work-piece. Air ejectors may be used for this purpose.

Once the hook plate is removed from the mold, it is allowed to passively cool to room temperature. This step is not necessary if the subsequent coining parameters are adjusted to compensate. When removed from the mold, the hook plate will have a surface temperature of approximately 60° C.

The stems are coined into an array of mushroom-headed hooks by engaging a heated coining plate onto the tops of the array of stems, melting (or softening) the tops of the stems and deforming them into a mushroom-head shape. A generally planar coining plate may be engaged by lowering it to uniformly apply pressure to the tops of the stems.

The coining plate is preferably made of steel, and is heated electrically. The contact surface of the coining plate is relatively flat and smooth, having no substantial designed cavities therein for forming the heads.

The coining plate is heated above the melting temperature of the material of array of stems, and is then lowered so that the coining surface engages the tops of array of stems. This causes the plastic in tops of array of stems to become molten and deform, creating an array of mushroom heads or hooks.

Placed beneath the uncoined plate is a compressible resilient layer made of any resilient material that is more resilient and compressible than the material of the work-piece being coined. While not essential, the resilient layer provides a cushioning effect underneath the uncoined hook plate. Initially the downward force of the coining plate onto the stems and the heat transfer thereto is not sufficient to significantly cause the stem-heads to deform, as the resilient layer begins to compress, until the elastic resistance of resilient layer and the heat transfer are sufficient to alter the shape of the stem heads, thereby causing the stems to form an array of hooked heads. The resilient layer may lessen any effect which might be caused by the coining surface of the coining plate not being parallel with the stem heads. This causes the stems to form the heads at substantially the same time, thereby producing generally uniform hooks for the hook plate.

Numerous modifications, variations, and adaptations may be made to the particular embodiments of the invention described above without departing from the scope of the invention, which is defined in the following claims.

Claims

1. An anchor sheet for underlying a floor covering, the sheet comprising: (a) a plastic sheet having a thickness of between 1/16 inches and ¼ inches and having a flexural modulus (ASTM D790) of between 700 and 3600 MPa; and (b) a resilient layer secured to a first side of the plastic sheet and having a compression force deflection (ASTM D3574-C) that is within about 30 percent of the compression force deflection of a low density polyethylene layer ⅜ inches thick and a density of 30 kg/m3.

2. The anchor sheet of claim 1 wherein in the plastic sheet is an injection-molded thermoplastic.

3. The anchor sheet of claim 1 wherein the plastic is polyethylene.

4. The anchor sheet of claim 1, wherein the plastic sheet has a thickness of between about ⅛ inches.

5. The anchor sheet of claim 1, wherein a second side of the plastic sheet is covered by hooks integrally molded therewith.

6. The anchor sheet of claim 6, wherein the hooks having a density between 160 hooks per square inch to 1200 hooks per square inch, or approximately 230 hooks per square inch, or approximately 330 hooks per square inch.

7. The anchor sheet of claim 1, wherein the resilient layer comprises, or consists essentially of, polyethylene.

8. The anchor sheet of claim 1, wherein the plastic sheet has a flexural modulus of between 1200 and 2600 MPa, or a flexural modulus of between 1300 and 2500 MPa, or a flexural modulus of between 1400 and 2400 MPa, or a flexural modulus of between 1500 and 2300 MPa, or a flexural modulus of between 1600 and 2200 MPa, or a flexural modulus of between 1700 and 2100 MPa, or a flexural modulus of between 1800 and 2000 MPa.

9. The anchor sheet of claim 1, wherein the anchor sheet is a square and having an outer planar dimension in the range of between approximately 12 inches by 12 inches and approximately 36 inches by 36 inches.

10. The anchor sheet of claim 9, wherein the anchor sheet is approximately 24 inches by 24 inches.

11. An anchor sheet comprising: a sheet with a first and second surface; the sheet being made of a polypropylene; hooks projecting from said first surface; and a resilient layer made of low density polyethylene attached to the second surface; wherein the sheet has a thickness between 0.062 inches and 0.50 inches.

12. The anchor sheet of claim 11, wherein the sheet has a thickness of approximately 0.125 inches.

13. The anchor sheet of claim 12, wherein the sheet is injection molded.

14. The anchor sheet of claim 3, wherein the anchor sheet is a square in the range of approximately 12 inch by 12 inch to approximately 36 inch by 36 inch.

15. The anchor sheet of claim 14, wherein the anchor sheet is approximately 24 inch by 24 inch.

16. The anchor sheet of claim 13, wherein the first surface bears a field of hooks, the hooks having a density between 160 hooks per square inch to 1200 hooks per square inch.

17. An anchor sheet shaped to have a substantially flat square lower layer part having an underside covered in a resilient layer and a substantially flat square upper layer part of the same size as the lower layer part having an upper side substantially covered in hooks in which the upper layer part is offset from the lower layer part an equal amount along two adjacent edges to expose two adjacent portions of the lower layer part and in which countersunk holes are formed through the anchor sheet centred on the corners formed by the lower layer part wherein, the sheet has a total thickness between 0.020 inches and 0.75 inches in its thickest part.

18. The anchor sheet of claim 17, wherein the sheet has a thickness between 0.062 and 0.75 inches in its thickest part.

19. The anchor sheet of claim 18, wherein the sheet has a thickness of approximately 0.125 inches at its thickest.

20. The anchor sheet of claim 19, wherein the sheet is injection moulded.

21. An anchor sheet for use in a subfloor for detachable attachment to a decorative covering, the anchor sheet comprising: an upper surface having a means for detachable attachment to the decorative covering; a lower surface opposite the upper surface, the lower surface being covered with a resilient layer; a recess of a first shape reducing the thickness of the anchor sheet in a first area; and a complete cut through the anchor sheet of a smaller second area within the first area of a second shape; wherein the sheet has a thickness between 0.020 inches and 0.75 inches.

22. The anchor sheet of claim 21, wherein the sheet has a thickness between 0.062 and 0.75 inches in its thickest part.

23. The anchor sheet of claim 22, wherein the sheet has a thickness of approximately 0.125 inches at its thickest.

24. The anchor sheet of claim 21, wherein the sheet is injection molded.

25. An anchor sheet comprising: a sheet with a first surface and a second surface; the sheet being made of one of a polypropylene and a polyethylene, and a resilient layer attached to the second surface; wherein the first surface bears a field of hooks, the hooks having a density between 160 hooks per square inch to 1200 hooks per square inch.

26. The anchor sheet of claim 25, wherein the field of hooks has a density of approximately 330 hooks per square inch.

27. The anchor sheet of claim 25, wherein the anchor sheet is a square in the range of approximately 12 inch by 12 inch to approximately 36 inch by 36 inch.

28. The anchor sheet of claim 27, wherein the resilient layer has a thickness between ¼ of an inch and ⅜ of an inch.

29. The anchor sheet of claim 28, wherein the sheet has a thickness between 0.020 inches and 0.75 inches.

30. The anchor sheet of claim 29, wherein the sheet has a thickness between 0.062 inches and 0.75 inches.

31. The anchor sheet of claim 30 wherein the sheet is 0.125 inches thick.

32. An anchor sheet for use in a subfloor for detachable attachment to a decorative covering, the anchor sheet comprising: an upper surface having a means for detachable attachment to the decorative covering; a lower surface opposite the upper surface, the lower surface being attached to a resilient layer; one of an overlay and an underlay area located adjacent an edge of the anchor sheet, wherein the anchor sheet has a reduced thickness in the area, and the area is configured to overlap with the other of an overlay and underlay area of a complementary anchor sheet; and wherein the anchor sheet has a maximum thickness of between 0.020 inches and 0.75 inches.

33. An anchor sheet for use in a subfloor for detachable attachment to a decorative covering, the anchor sheet comprising: an upper surface having a means for detachable attachment to the decorative covering; a lower surface opposite the upper surface, the lower-surface being attached to a resilient layer; and one of a male and female feature defined in the anchor sheet and located adjacent an edge of the anchor sheet, the feature being configured to interlock with the other of male and female feature of a complementary anchor sheet.

34. The anchor sheet of claim 33, wherein the feature is keystone-shaped.

35. The anchor sheet of claim 33, wherein the feature is jigsaw puzzle piece-shaped.

36. An anchor sheet comprising: a first layer of a polypropylene sheet of between 0.062 inches and 0.50 inches; and a second layer of polyethylene foam of a density of at least 20 kg/m3 and of thickness of between ¼ inches and ⅜ inches.

37. The anchor sheet of claim 36 in which the anchor sheet provides for countersunk areas at least along one edge.