BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a roll of stacked liner sheets and a substrate sheet (master PAD roll) ready for thermoforming.
FIG. 2 is a sectional side view of a tray sheet section positioned between heaters prior to thermoforming.
FIG. 3 is a sectional side view of a heated tray sheet section positioned in a thermoforming apparatus prior to thermoforming.
FIG. 4 is a sectional end view of a thermoformed tray system prior to ejection from the thermoforming apparatus.
FIG. 5 is a detailed sectional side view of a segment of a stack of liner sheets and a substrate sheet.
FIG. 6 is a top view of a preferred tray system.
FIG. 7 is a top view of an alternative preferred tray system.
FIG. 8 is a side view of an alternative tear tab assembly.
FIG. 9 is a side view of another alternative tear tab assembly.
FIG. 10 is a side view of yet another alternative tear tab assembly.
FIG. 11 is a side view of yet another tear tab assembly.
FIG. 12 is a side view of a pad of liner sheets.
FIG. 13 is a sectional side view of a stamping apparatus and a pad of liner sheets.
FIG. 14 is a side view of a stack of substrate and sheets.
FIG. 15 is a sectional side view of a stack of substrate and sheets in preparation for molding into a female cavity mold.
FIG. 16 is a sectional side view of a stack of substrate and sheets molded into a female cavity mold.
DETAILED DESCRIPTION OF THE INVENTION
In the following description, terms such as horizontal, upright, vertical, above, below, beneath, and the like, are used solely for the purpose of clarity in illustrating the invention, and should not be taken as words of limitation. The drawings are for the purpose of illustrating the invention and are not intended to be to scale.
As illustrated in FIGS. 1 and 5, tray sheet 10, comprised of a plurality of liner sheets 12 and a bottom substrate sheet 14, is shipped to the thermoformer as a roll 16.
As illustrated in FIG. 2, tray sheet 10 is pulled via the thermoforming machine from roll 16 and positioned within a thermoforming apparatus comprised of upper and lower heaters 22 and 23 to heat the sheet to a moldable state. While both ovens can be heated simultaneously, they also may need to be adjusted independently of one another. The heated sheet is then pulled further to a position over a vacuum source 24 as illustrated in FIG. 3. A female mold 26 conforming to the desired shape of the tray system is positioned in communication with vacuum source 24. Heated sheet segment 10 is lowered onto mold 26 and a vacuum is drawn on mold 26 with vacuum source 24, shaping sheet segment 10 to the interior contours of mold 26 as shown in FIG. 4. The molded tray system is then cooled and ejected from mold 26, and edge trimmed if desired.
The resultant product is a thermoformed tray system comprised of a substrate sheet in the shape of the desired tray, with a plurality of liner sheets stacked thereon and held in place by adhesive layers, both natural or man made, between the liner sheets and the lowermost liner sheet and the upper surface of the substrate sheet. All sheets are molded into the shape of the desired tray.
A preferred tray 30 is illustrated in FIG. 6. Tray 30 is comprised preferably of a horizontal, flat central shelf 32 with ridges 34 to remove excess paint from a paint roller rolled across shelf 32, down ramps 40 and paint wells 36 and 38 on opposite sides of ramps 40. Tear tab 42 can be located anywhere on the perimeter of all liner sheets, or all or part of the entire perimeter of the liner sheet can form a tab 43 for use in separating the liners. An alternative tray configuration is illustrated in FIG. 7, showing the addition of feet 44 for added stability.
Various other means may be used to include tabs to facilitate separation of the tapes. For example, as shown in FIG. 8, the layers of liner sheets 50 may be stepped during the converting process where the substrate 52 and liner sheets 50 are formed into a roll. The resulting look will be like steps 54 on the edges, allowing the consumer to see the edges of all the layers.
In another alternative shown in FIG. 9, the liner sheets 60 may be “strip coated” before it is made into the roll form. That is, adhesive is applied to the body of the liner sheets 60, except for the area of the tabs 62. Thus, the liner sheets 60 have adhesive except for the edges (e.g., ½″), either on one side or both sides of the liner sheets. The end result is the edges of the paint tray will have no adhesive on the “tabs” 62, allowing the consumer to identify and begin peeling the layers.
Yet another alternative as shown in FIG. 10, is to use actual separate tabs 70 on the edges of the liner sheets 72 to distinguish between layers. The separate tabs 70 could be tape/film of plastic or paper (e.g. ¾″ wide, with or without adhesive) to be applied on the ends of the protective tape on either the top or bottom preferably the bottom (this side of the protective tape has the adhesive). This tape/film could be of various colors and designs and will serve as an aid for the consumer to pull apart the layers of liner sheets 72.
Yet another alternative is shown in FIG. 11, using actual separate tabs 56 on the edges of the liner sheets 66 to distinguish between layers, however tabs 56 are applied on opposing edges of sequencing liner sheets 66, while liner sheets 66 are shifted, creating a pitter patter effect with tabs 56 hidden underneath top liner sheets 66 until top layer is removed. The separate tabs 56 could be tape/film of plastic or paper (e.g. ¾″ wide, with or without adhesive) to be applied on the ends of the protective tape on either the top or bottom, preferably the bottom (this side of the protective tape has the adhesive). This tape/film could be of various colors and designs and will serve as an aid for the consumer to pull apart the layers of liner sheets 66.
While the invention is described primarily in terms of the manufacture of a paint tray with a stack of thermoformed sheet liners conforming to the interior dimensions of the paint tray, it will be apparent that the broad concept of the invention can be modified for other applications. For example, as illustrated in FIGS. 12 and 13, instead of simultaneously shaping the substrate that forms the tray or other product and the liner sheets, the substrate can be initially formed into the tray, or the tray can be otherwise manufactured. A pad of liner sheets 80 can then be formed within the tray. That is, a mold of the image of the product, e.g., paint tray 82, is suspended above the product (e.g. paint tray in plastic or metal) and sandwiched in between is a continuous roll of liner sheets 80. The paint tray will be moving along a conveyor 84 and when the paint tray is nested opposing the mold image of the product 86, the two parts are “stamped” together, thus creating the finished product with the pads of liner sheets.
In another alternative illustrated in FIGS. 14-16, multiple layers of plastic sheets 90 having the same thickness, instead of liner sheets/protective tape, can be thermoformed simultaneously, in order to make multiple products. Applied applications for this would be various containers such as plastic egg cartons, cookie trays (e.g., Oreo), Jello containers, blister packs, rigid paint tray liners etc. The substrate is a more rigid material, while the liner sheets/protective tape is more stretchable and pliable, such as a garbage bag. The plastic sheets 90 in this process are of a lesser thickness than the paint tray of 0.030″, but not as thin as the liners of protective tape.
This latter process ideally uses about 3 to 6 layers in roll form. Currently the maximum thickness to thermoform (in roll form) effectively is around 0.050″. A coating, adhesive barrier, release agent, or film will be applied to or placed in between the sheets where needed and in any combination to prevent the sheets from melting/bonding together in the thermoforming process, and for allowing the finished products to be separated easily (e.g., a form of silicone may be introduced between the layers of sheets while a zone coat of adhesive (e.g., 1 inch wide) may be applied along the edge of the substrate). This adhesion allows for easier transport of the roll of sheets by keeping the material together in roll form more effectively. Multiple sheets of approximate thickness 0.010″ each are stacked together with a barrier/adhesion between each layer. The multi-sheet layers are rolled together and then sold to various thermoforming companies. Ultimately time and money are saved by the thermoformers, allowing them to be more efficient. Sheets 90 are thermoformed by being drawn or pressed into a mold 92 having the desired cavity shape.
Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.
Patent Application
20070246474
