Antimicrobial, molded laminate shopping cart part and method of manufacturing same

Abstract

An antimicrobial, molded laminate shopping cart part and method of manufacturing same are provided. The part, such as a small child seat, includes a structural carrier made from a thermoplastic resin and having an outer surface. The part further includes a formed plastic film sheet having upper and lower surfaces. The lower surface is bonded to the outer surface of the carrier. The film sheet includes an outer clear plastic layer including at least one antimicrobial agent disbursed throughout the plastic layer. The antimicrobial agent exhibits controlled migration through the clear plastic to the outer surface of the clear plastic layer.

Claims

1. A method of manufacturing an antimicrobial molded laminate shopping cart child seat, the method comprising: providing a formed plastic pre-painted film sheet having top and bottom surfaces and providing a warning or advertisement, the top surface being covered by a clear plastic layer, the clear plastic layer having an outer surface and comprising at least one antimicrobial agent dispersed throughout the clear plastic layer, wherein the antimicrobial agent exhibits controlled migration throughout the clear plastic layer to the outer surface of the clear plastic layer, the plastic pre-painted film sheet including one or more layers of color in contact with a layer of polyvinylidene fluoride overlaying and protecting the one or more layers of color, wherein the clear plastic layer is in contact with and protects the layer of polyvinylidene fluoride; placing the film sheet in a mold cavity of an injection mold having a shape defining the shopping cart child seat; and injecting a thermoplastic resin into the mold cavity of the injection mold at a temperature and pressure sufficient to melt the bottom surface of the film sheet to generate a structural carrier for the film sheet, the carrier including an attachment portion for removably attaching the seat to a shopping cart, the generation of the structural carrier creating sufficient pressure and heat to bond the structural carrier to the bottom surface of the film sheet to form the molded laminate seat.

2. A method of manufacturing an antimicrobial molded laminate part, wherein the part comprises a shopping cart child seat, the method comprising: providing a painted film sheet including at least one layer of printing, a layer of polyvinylidene fluoride applied over the at least one layer of printing, and an acrylic clear coat layer in contact with and overlaying the layer of polyvinylidene fluoride, the acrylic clear coat layer includes an anti-microbial agent dispersed throughout the acrylic clear coat layer, wherein the antimicrobial agent exhibits controlled migration throughout the acrylic clear coat layer to an outer surface of the acrylic clear coat layer; forming the painted film sheet and acrylic clear coat layer in a vacuum forming mold to form a preform; cutting the preform to form an applique preform having top and bottom surfaces, the top surface being the clear plastic layer; placing the applique preform in a mold cavity of an injection mold having a shape defining the molded laminate part; and injecting a thermoplastic resin into the mold cavity of the injection mold at a temperature and pressure sufficient to melt the bottom surface of the film sheet to generate a structural carrier, wherein the thermoplastic resin is injected with sufficient pressure and heat to melt a bottom surface of the applique preform and bond the structural carrier to the applique preform to form the shopping cart child seat.

3. The method of claim 2 wherein the painted film sheet is selected from the group consisting of: polyurethane, and polycarbonate.

4. The method as claimed in claim 2, wherein the film sheet is a pre-painted film sheet which provides a warning or advertisement.

5. The method as claimed in claim 2, wherein the polyvinylidene fluoride comprises more than 50 percent of the total thickness of the film sheet.

6. The method as claimed in claim 2, wherein the part comprises a shopping cart child seat.

7. The method as claimed in claim 2, wherein the total thickness of the film sheet is less than 1.0 mils.

8. The method as claimed in claim 2, wherein the structural carrier includes an attachment portion for removably attaching the part to a shopping cart.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of one embodiment of a prior art plastic shopping cart;

(2) FIG. 2 is an exploded view of the plastic shopping cart shown in FIG. 1;

(3) FIG. 3 is a top plan view of a prior art plastic child seat for use in a shopping cart, such as the shopping cart of FIGS. 1 and 2 and having a warning printed thereon;

(4) FIG. 4 is a top plan view of a plastic child seat for use in a shopping cart such as the shopping cart of FIGS. 1 and 2 and manufactured in accordance with at least one embodiment of the present invention;

(5) FIG. 5 is a view, partially broken away and in cross section, taken along lines 5-5 of FIG. 4;

(6) FIG. 6 is a schematic view, partially broken away and in cross section, of a conventional injection molding system which may be utilized to make plastic parts or components of the present invention; a mold of the system is depicted in an open position with a formed plastic film sheet placed between two mold halves of the mold;

(7) FIG. 7 is a view similar to the view of FIG. 6 with the mold depicted in a closed position, with the film sheet placed in a mold cavity between the two mold halves;

(8) FIG. 8 is a view similar to the view of FIGS. 6 and 7 depicting the mold cavity with the molten resin injected therein to form the structural carrier for the film sheet and the resulting part; and

(9) FIG. 9 is a block diagram flow chart illustrating various method steps for manufacturing the plastic part or component.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(10) As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

(11) Referring now to FIGS. 4 and 5, there is illustrated an antimicrobial, molded laminate shopping cart part, such as a small child seat, generally indicated at 60, constructed in accordance with at least one embodiment of the present invention. The part 60 is antimicrobial in the sense that a clear coat plastic covering layer 62 of a formed film sheet, generally indicated at 64, has at least one antimicrobial agent dispersed throughout the layer 62.

(12) Antimicrobial is equivalent to antibacterial, antifungal, antiviral, antiparasitic, microbicidal, and microbistatic. Most antimicrobial agents control microorganism growth by penetrating the microorganism's thin cellular walls, thereby interrupting the organism metabolic function, and finally killing said organism.

(13) A part having antimicrobial properties includes any material that kills or inhibits growth of a microorganism.

(14) A microorganism corresponds to bacteria, fungi, archea and protists and most typically the microorganism is unicellular.

(15) Dispersed throughout corresponds to the dispersal of a species, e.g., an antimicrobial agent, homogeneously or heterogeneously throughout the clear plastic layer. For example, the antimicrobial agent may be homogeneously dispersed throughout the finish such that the concentration of antimicrobial agent at the surface is substantially the same as the concentration at any other sampling location in the layer. Heterogeneous dispersal corresponds to more antimicrobial agent at one sampling location in the layer relative to some other sampling location in the layer. For example, there may be more antimicrobial agent at the surface relative to other sampling locations or there may be islands of more concentrated antimicrobial agent throughout the layer.

(16) The film sheet 64 is a thin membrane composite having a thickness of less than 0.5 millimeters.

(17) The film sheet 64 is preferably pre-painted. The film sheet 64 is preferably a polyester sheet such as Mylar, a polyurethane or polycarbonate sheet.

(18) The part 60 also includes a structural carrier 66 which may be formed from a thermoplastic resin such as polyolefin, polycarbonate, tee tpe, sebs tpe, and a mixture of polycarbonate and acrylonitrile/butadiene/styrene (ABS). The corresponding film layer or sheet 64 is compatible with the plastic of the structural carrier so that diffusion between contact surfaces occurs in the method of the present invention as described hereinbelow. The carrier 66 includes an attachment portion 67 for removably attaching the part 60 to the shopping cart.

(19) The film sheet 64 preferably has the following coatings placed on a membrane 68, layer 70 of acrylic color in mating contact with the membrane 68 and a layer 72 of polyvinylidine fluoride (PVDF) with the acrylic clear coat 62 to protect the film from damage and to provide film elasticity, chemical resistance, stain resistance, weathering and UV protection. In the most preferred embodiment, PVDF comprises about 72% of the total pre-form thickness which is less than 1.0 mils and is preferably about 0.2 mils.

(20) Referring now to FIGS. 6 through 8, there is illustrated a conventional injection mold, generally indicated at 76, of a system for making a plastic component pursuant to the present invention. With such a system there is included an injection molding machine, having a nozzle for injecting predetermined amounts or shots of molten resin. The injection molding machine includes a hydraulic screw ram which is disposed in a bore formed in a barrel of the injection molding machine. The ram plasticizes and advances resin towards the nozzle. Upon complete plasticization of the resin, the screw ram is hydraulically advanced towards threaded portions of the barrel to inject molten plastic through the nozzle, as is well known in the art.

(21) As depicted in FIG. 6, opposing surfaces of mold parts 78 and 80, respectively, of the mold 76 define a mold cavity 82 with the formed film sheet 64 disposed therein. FIG. 6 illustrates an open position of the mold 76 and FIG. 7 illustrates a closed position of the mold 76.

(22) As illustrated in FIG. 6, there is a depiction of a one-piece film sheet 64 which is first placed in the mold cavity 82 in the open position of FIG. 6. Thereafter, as depicted in FIGS. 7 and 8, the structural carrier 66 is molded in the mold 76 of the plastic injection molding system to form a completed unitary laminate plastic component.

(23) In an alternative embodiment, the mold 76 can be modified to produce a plastic component or part with embossed lettering. This embossed effect is achieved by etching into the mold 76 the desired pattern or letters so that the letters have at least a 0.5 millimeter radius on the edge of the letter, or else the film sheet 64 may tear and stretch.

(24) The unique features of the laminate plastic components or parts are 1) a stiff inner material to support the intended application; 2) reduction and/or elimination of paint problems such as drips, runs, spits, dry spray, light coverage and gloss and improved color match and paint adhesion; 3) reduced molding scrap due to splay, flow marks and minor surface imperfections, which can be completely covered by the film sheet 64; and 4) increased durability of the resulting plastic laminate components.

(25) Referring now to FIG. 9, there is illustrated in a block diagram flow chart form various method steps for forming the part 60 of the present invention.

(26) At block 100, a painted film sheet composite is initially provided.

(27) At block 102, the painted film sheet composite may be placed in a vacuum mold (not shown) which is operated to form a pre-form if the film sheet 64 is to have anything other than a planar shape. If the film sheet 64 is to have a planar shape, then block 102 can be skipped.

(28) At block 104, after the film sheet 64 or pre-form has been removed from the vacuum mold (if needed), the pre-form is cut to form the part 60 which may provide a warning as in FIG. 3 or an advertisement as in FIG. 4.

(29) At block 106, the film sheet 64 or pre-form is inserted into the plastic mold 76.

(30) At block 108, molten plastic is injected into the mold 76 through its injection aperture at a temperature and pressure sufficient to melt the bottom surface layer of the film sheet 64 or pre-form.

(31) At block 110, the part 60 is cooled to a temperature beneath the softening point of both resins.

(32) At block 112, the mold 76 is opened and the completed part 60 is removed.

(33) While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.