Patent Application
20050200051
1. Field of the Invention
This invention relates to a method of, and an apparatus for, molding a composite modular plastic tile with edge interlock elements, and more particularly, to a method and apparatus for molding a composite polymeric tile comprised of a planar substrate and a preformed lamina covering the substrate wherein the lamina is bonded to the substrate during the formation process.
2. Background Discussion
The process of plastic injection molding employing an injection molding machine is a conventional process for molding modular polymeric floor tiles with exposed edge male-female interlock elements on all edges thereof, as disclosed, for example, in U.S. Pat. No. 6,303,318 to Ricciardelli et al., assigned to the same assignee as the instant invention. As illustrated in
As disclosed in U.S. Pat. No. 6,303,318, the tile may be composed of a material of recycled, granulated carpet fiber and carpet backing material to which a polymeric plasticizer is added to increase molding plasticity and product resiliency prior to the feeding of the matrix in molten form into the closed and co-acting mold halves of a two-cavity injection molding machine. As disclosed in the '303 patent, this granulated material is primarily composed of polyvinyl chloride that can be readily molded under the heat and pressure available in a two-cavity injection molding machine. Polyvinyl chloride tiles have been produced by such machines which are typically comprised of horizontally aligned respective fixed and movable mold platens having horizontally aligned cavities therein for respectively molding the lower and upper portions of the tile after being driven together, held closed and fed molten plastic. The molten plastic matrix material is typically injected into the fixed plastic platen half of the injection molding machine by an extruder at a temperature of approximately between 100-400 degrees Celsius, and preferably at a temperature of approximately between 125-175 degrees Celsius and most preferably at a temperature of approximately 150 degrees Celsius and subjected to a pressure of between 1,200 and 1,500 pounds per square inch (PSI). The extruder is arranged to provide material to the closed mold cavity and molds the tile with exposed interlocks on all edges. Coolant material, having a temperature of approximately between 20-60 degrees Celsius, and preferably about 40 degrees Celsius, is transferred through coolant tubes that are embedded in the fixed platen to accelerate solidification of the matrix prior to opening the movable mold and the subsequent removal of the completely molded tile.
The operation involving the opening and closing of the movable platen half is controlled by bi-directional valves coupled to a hydraulic cylinder having an internal, translatable piston with its piston rod connected to an end of the movable platen opposite its cavity face. The drive force applied by the hydraulic cylinder to the movable platen to hold the two platens in abutment and the mold cavity closed during injection of the molten matrix therein typically approximates 200 tons. The mold cavity in the movable platen is typically designed to mold the top surface portion and a minor thickness proportion of the tile that may be embossed with a pattern of coin-like protrusions to provide the tile with greater slip resistance. Conversely, the fixed platen is typically designed to mold the remaining portion of the tile body, and both platens incorporate opposed contacting edgings of interlock molding elements for molding there-between the alternating male and female edge interlock elements on all of the tile edges.
As will be apparent, plastic tiles may be fabricated of recycled materials utilizing waste scrap that would otherwise likely be deposited in landfills, and therefore, it is advantageous solely from an environmental viewpoint to provide greater user acceptability of these products. By adhering, for example, a decorative, additional surface lamina on the tile, acceptability of the tile for various flooring applications is likely to be increased.
Conventional processes for adhering a lamina onto a plastic substrate involves the process of laminating the preformed plastic tile components; one example is a planar base or substrate component and the second, a top lamina appropriately colored or otherwise utilization-enhanced plastic sheet. The two performs are typically laminated together by applying heat and pressure to the superimposed components comprising the composite tile sufficient to effect thermal adhesion therebetween. Since adhesion is required between the opposing and interior surfaces of the previously molded substrate and lamina, the prior art processes are inherently inefficient because they require tile reapplication of external heat and pressure to both component members for a period sufficient to heat and soften the interfacing surfaces of both to achieve adhesion.
In accordance with this invention, the method of this invention is implemented by a two-platen injection molding apparatus having open and closed sides; the first platen being stationary and the second platen being drivable against and away from the first platen. The second platen incorporates a second mold cavity half with an inwardly recessed pocket portion that is sized and shaped to receive and position a lamina component there on with the platens open. The first platen incorporates a first cavity half aligned opposite the second cavity and recessed to mold the underlying substrate component from molten polymeric material that is injected into the first cavity.
The mold platens are constructed to provide two pairs of interlock element molding strips; one pair being a substantially identical mirror image of the other with the interlock molding elements of the one pair of strips projecting toward the plane of the lamina and the molding elements of the other pair of strips projecting away from that plane.
With the platens and their cavities driven closed, molten substrate material is injected into the fixed, first cavity and is directed against the lamina surface facing that cavity to effect a thermal bonding therewith and the substantially simultaneous formation of the interlock element pairs on the substrate around the lamina edges.
In accordance with one embodiment of the invention, placement of lamina in the second movable mold and removal of the laminated composite from the first, fixed mold is performed by a robotic arm that is movable between the open platens.
Accordingly, another embodiment of the present invention is directed to an injection molding apparatus for making a modular interlocking composite plastic tile of a substrate with preformed planar plastic lamina laminated thereto, comprising:
The following is a brief description of the drawings that form a part of this disclosure in which:
The tile 10 is a layered composite comprised of a planer lamina upper portion 11 that is superimposed upon a generally planar and parallel lower portion, or substrate, 12. The substrate 12 has a generally smooth upper surface. The substrate 12, is molded with a first and a second pair of the interlock-configured edge strips 14A, 14B and 16A, 16B, respectively, extending laterally outwardly from a central region of the substrate 12. Each pair of the strips 14A, 14B and 16A, 16B is molded along with the central region of the substrate 12 in the injection molding apparatus 18,
The male-female elements 19, 20, respectively, on the first edge pair 14A, 14B and the male element 21 and female element 22 on the second edge pair 16A, 16B project generally perpendicularly from opposite respective sides of the substrate. Thus, as shown in
The two pairs of somewhat resilient interlock elements 19, 20 and 21, 22 are substantially mirror images of one another so as to mate and thereby physically interlock with inverted, substantially identical and equally resilient pairs of edge interlocks on contiguous tiles without the use of adhesives.
As mentioned above, the substrate 12 may be composed of a granular matrix of PVC waste carpet scrap, various other thermoplastic matrices, utilizing for example, virgin PVC or other polymeric compositions of the polyolefin groups are also suitable materials for injection molding of the substrate and for the virtually simultaneous adhesion to the lamina 11. A typical substrate 12 has an average cross-sectional thickness of about 0.10 to 0.50 inches and preferably about 0.25 inch, and a top surface planar and devoid of protuberances. The substrate shape is generally determined by end user requirements and typically the substrate is molded to mount a square-shaped lamina 11 that simulates a variety of square-shaped floor products, such as square ceramic, stone or marble tiles or wood squares.
As disclosed in co-pending U.S. application Ser. No. 09/884,638, by Thomas E. Ricciardelli, filed Jun. 19, 2001 and assigned to the assignee of the present application, which is hereby incorporated by reference in its entirety herein,
The substrate component may also have an overall rectangular configuration with staggered ends to simulate the staggering of juxtaposed wood planks of a wood floor. In both of the embodiments disclosed in the patent applications, the lamina is preformed to cover, and thereby conceal, the downwardly projecting pair of interlock edges 16A, 16B with the interlock elements 21, 22 thereon, but leaves the edge strips 14a, 14B and their upwardly, projecting pair of interlock elements 19, 20 exposed to effect a mating engagement with substantially identical, inverted and downwardly facing pair of substrate interlocks on a substantially identical, superimposed interlock tile edges of a substantially identical tile.
Conversely, the concealed downwardly-facing interlock elements 21, 22 of the second pair of interlock edge strips 16A, 16B matingly engage underlying upwardly-projecting interlocks of other contiguous tiles (not shown). Because a pair of the lamina edges of both rectangular and square shapes are coextensive with the mating edge pairs of the contiguous tiles, the tiles typically will substantially abut one another to simulate linear grout lines or wood grooves.
The lamina 11 is preferably preformed of a sheet of plastic material and pre-cut to a desired size to cover the top surface of the substrate 12 contiguous to the edges thereof with the exception of first edge pair of the interlock strips 14A, 14B, which are exposed for subsequent interlocking purposes. The lamina 11 is typically composed of a thin, flexible sheet of polyvinyl chloride (PVC), or other polymeric material with suitable properties, having a thickness ranging from approximately 0.002 inch to 0.150 inch and more particularly from approximately 0.004 inch to 0.125 inch, and a weight of approximately 0.05 pounds per square inch to 0.50 pounds per square inch and preferably about 0.10 pounds per square inch. The lamina may be composed of materials other than plastic provided that thermal bonding with the substrate material can be effected in the injection molding apparatus 18. As will be apparent, the lamina is typically opaque and provided with a decorative appearance by color printing, sublimation or photographic techniques, which will be apparent to those skilled in the art.
A prior art injection molding apparatus of the type disclosed in U.S. Pat. No. 6,303,318 is designated by the numeral 18 in
The platen 24 has molten plastic injected into it from a heated extruder 28 under the control of a flow control valve 38. With a second control valve 50 driven to its open state, the piston 42 drives a predetermined quantity of the molten plastic in a heated hydraulic cylinder 40 sufficient to mold the tile through a conduit 43, and hence into the closed mold cavity where the tile is molded with through-edge type interlock elements thereon, as illustrated in U.S. Pat. No. 6,303,318.
Having described a prior art injection molding process and apparatus, the process of this invention, as outlined by the flow diagrams of
The apparatus 60 comprises a fixed platen 62 with a mold cavity 64 for molding the flat bottom portion 12,
The cavity 68 is recessed into the face 70 of the platen 60 to a depth of typically twice the thickness of the lamina 11 and the lamina 11 is seated in the cavity with close edge tolerances of approximately 1 millimeter or less. Thus, for an exemplary lamina 11 of about 0.125 inch in thickness, the cavity has a depth of about 0.150 inches and the lamina 11 is placed with its top surface flat against the flat cavity base 72 and its bottom surface facing the cavity 64. The depth of cavity 64 is typically about twice that of the cavity 68, or in the exemplary case, about 0.300 inches. The depth differential offsets the parting line of the closed mold along the abutting interface of the platen faces 69, 70 from the interface between the bottom surface of the lamina 11 seated in the cavity 68 and the substrate material bonded thereto, which bonding occurs in the cavity 68 along a plane parallel to and inwardly of the edge 70 and the mold parting line, as shown in
As seen in
Spaced around the periphery of the cavity base 72 and centrally thereof are a plurality of recessed suction cup elements 85, each having a flush screen or diaphragm 89 attached to the base 72 by screws 89A and commonly connected together by interior suction conduits 86 formed in the platen 66. The conduits 86 are coupled to a central conduit 86A that is connected to a flexible hose or conduit 87 by a fluid-tight coupling 88 that can move with the platen 66 and is coupled to a source of vacuum pressure 90,
To mold the first and second oppositely projecting pairs of interlock elements 14A, 14B and 16A, 16B, respectively, the corresponding first and second element forming strips on each respective platen are correspondingly formed with their interlock element patterns arranged to project in opposite directions on their respective platens. The right-angled element-forming strip for molding the first pair of downwardly facing interlock elements underlying the lamina edges are on the fixed platen face and the right-angled interlock element strip for molding the second pair of interlock elements of inverted-mirror image design and disposed laterally outwardly of their corresponding right angled lamina edges are on the movable platen face. To mold the tile 10 with its specific interlock edge structures, it is a preferred embodiment that the substrate material, that is typically black in color, does not flow around the edges of the lamina and adhere to the top surface edges of the lamina. The lamina is seated with only slight edge clearances of, for example, approximately between 0.0005 inch and 0.002 inch and more typically approximately 0.001 inch in the cavity of the movable platen and the corresponding interlock molding strips on the fixed platen are positioned laterally inwardly of the moveable platen cavity walls. Conversely, the second pair of right-angled cavity walls of the moveable platen are equally closely adjacent the inside edges of the two molding strips that form the second pair of the exterior interlocks so that molten substrate material injected against the bottom lamina surface 12 is impeded from flowing around the second pair of lamina edges and onto the top surface of the lamina during the injection molding process.
The interlock feature patterns are typically formed into the platen faces during the manufacture of the platens and may have the particular locking structure illustrated in
To mold the base interlock structure of the tile 10, the cavity sidewalls 76, 77,
Conversely, and with reference to
As discussed above, the first pair of interlock element molding strips is cast on the fixed platen 62 as mirror images of the second pair of interlock molding strips on the second platen 66 when viewed in plan, thereby producing the patterns of tile interlock elements illustrated in
Accordingly, a preferred embodiment of this invention employs a robotic arm 100,
With the platens 62 and 66 in the open position, the control circuitry 101 is energized to raise the arm 100 and thereby lift the plates 110, 111 from their depicted midway position between the platens 62, 66 to a location adjacent but outside of, the apparatus 60. The control circuitry 101 then activates the arm 100 to rotate counterclockwise, as viewed in
During the interim period the molding operation described herein is completed so that the molded tile 10 is retained in the cavity 64 and the platen 66 driven rearward by operation of the control 29 and cylinder 30 to open the mold and expose the laminated tile 10 in the cavity 64. The arm 100 is lowered by the control 101 until the plates 110 and 111 are again horizontally opposite the cavities 64 and 68, respectively, with the lamina 11 gripped by the plate 111 and positioned centrally of the cavity 68 and with the plate 110 positioned directly opposite the molded tile. The control circuitry 101 is then energized to cause the arm 100 to drive the plate 110 toward the right as viewed and into the cavity 64 until the plate contacts the tile in that cavity. The valve 116 is opened by a signal from the vacuum control circuit 119, and applies a vacuum pressure to the cavitated tile through the plate 110 apertures. The control circuitry 101 then activates the arm 100 to move until the preform lamina on the plate 111 is seated in the cavity 68 with its top surface against the cavity base 72.
The valve 91 is then energized to open and apply vacuum pressure from the source 90 to the cavity base 72 thereby retaining the lamina in the cavity 68. Substantially simultaneously, valve 117 is energized to close and remove vacuum pressure from the plate 111 and the lamina thereagainst and the arm 100 returned to its initial position,
The empty plate 111 and the plate 110 carrying the molded tile 10 are then moved upwardly and outwardly of the platens by the arm 100 to a prescribed floor area, not shown, adjacent the apparatus, whereupon the valve 116 is closed to release the vacuum and the tile carried by the plate. The valve 117 is opened to condition the plate 111 for picking up and transporting another lamina from the stack. The arm 100 may be rotated to stack the laminated tile prior to the release of the vacuum.
The valve 91 may also be selectively energized by signals from the vacuum control 119 so that vacuum is only applied to the cavity 68 during the time interval when the lamina is being held flush against the carrier base 72. Coolant is circulated through the coolant tube 45 to expedite adhesion between the lamina and the substrate during this interval. As the platens separate to release the tile, horizontal ejector pins, not shown, may be mounted inwardly of the cavity base 72 are cammed outwardly by platen movement to push the laminated tile outwardly toward the fixed cavity 64 where it resides until the suction plate 110 is moved opposite the cavity 64, whereupon similar ejector pins, also not shown, in the platen 62 are driven outwardly to push the laminated tile 10 outwardly to release it from the cavity 64 for pick-up by the plate 110.
While the apparatus 60 utilizes the movable platen as the mold half for the lamina, the arrangement could be reversed with the fixed platen constructed to seat the lamina and the moveable platen adapted to receive the molten substrate from the extruder 40,
Additionally, the substrate matrix may be a different color than the preformed lamina 11 and thus should the robotic arm 100 fail to center the lamina 11 in the cavity 68 with all of its edges sufficiently close to the cavity sidewalls 74, 75, 76 and 77, molten substrate may flow around the lamina edges and deposit substrate material on the top surface of the lamina. In order to inhibit this deposition, as illustrate in
Thus, it will be understood by those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention as defined in the following claims.
