Patent Application
20070275209
a and 1b show cross sectional views of an embodiment of the invention having semi-spherical suction cups.
a through 3g show cross sectional views of embodiments of the invention with different shapes and heights of suction cups.
a shows a top view of a plastic tape with semi-spherical suction cups on one side.
b through 6d show cross sectional views of tape with different sizes of suction cups.
a shows a top view of an embodiment of the invention using tapes with suction cups.
b shows a cross sectional view of the embodiment of
a and 9b show cross sectional views of an embodiment of the invention with suction cups without tapes attached to one side and both sides, respectively.
a through 10f show different patterns for an embodiment of the invention having a skid-resistant discontinuous coating on the plastic sheet.
a and 11b show cross section views of the embodiment of
a and 12b show cross section views of the embodiment of
n alternative to the method of
The present invention comprises skid-resistant (may also be called slip-resistant, non-slip, non-skid, anti-slip, anti-skid, skid-proof, slip-proof, skid-free, slip-free, etc.) plastic (or polymer) sheets that can reduce or overcome the problem of slippage and hence reduce the bodily injuries as well as equipment damage. Various ways to achieve or obtain skid-resistance in single plastic sheets are described.
The first embodiments of the invention, as shown in
Referring to
Suction cups (2) are formed as part of the sheet (1). Upon initial force (pressure), such as a person stepping on it or the legs of a furniture piece or ladder being placed on it, or any vehicular traffic, etc., the suction cups (2) are deformed and the air inside the cups is forced out. This action creates vacuum or low pressure area inside the cups which provides a suction force that acts to adhere (or stick) the sheet to the surface it is against (floor, wall, flat furniture surface, etc.) and prohibits (or resists) it from slipping. The suction (or vacuum) action created will increase with increased force, e.g., heavier person stepping on it, or with plurality of suction cups, or with larger size suction cups.
The suction cup (2) design can be imparted on one side or on both sides (preferable) of the sheet depending on the application and need.
The shapes and heights of the suction cups may be different as shown in
The spacing of the suction cups, in either direction (longitudinal—along the length of the sheet and widthwise), will depend on their depth (height), shape and size (diameter) as well as the type of the polymer and thickness of the sheet used. For suction cups with higher depth and/or larger sizes, the spacing between them may be increased. Typical spacing could be between 12 mm (½ in) to 50 mm (2 in) apart in both directions (longitudinal and widthwise direction). Typical diameter of the cup may vary between 3 mm (0.12 in) to 6 mm (0.25 in). However, suction cups smaller than 3 mm (0.12 in) or larger than 6 mm (0.25 in) in diameter will work for many applications.
The cups may be spaced randomly in both directions (longitudinal and widthwise) or in any desired pattern. The circular area surrounding the suction cup might be made glossy smooth (flat), for better (or complete) contact with the smooth surfaces it will be in contact with (e.g. laminate flooring, wooden flooring, tiled flooring and other smooth floorings or another plastic sheet) and to retain the suction effect for longer term. In addition to the suction action, the roughness created by the suction cup pattern will also help the skid-resistant dust protective plastic sheet reduce the slippage.
The embossing/engraving will be done according to the shape, height and the spacing of the suction cups. The newly extruded plastic/polymer sheet will pass through the nip of these rollers creating the suction cup design.
The rollers may or may not be heated, depending on the necessity. If the newly extruded sheet is hot enough, the rollers may not be needed to be heated. However, heated rollers may make it easier to form the suction cups. The temperature will depend on the type of polymer used and the speed of the operation.
In another version of manufacturing, shown in
In either of the cases discussed above, the process could be completed in one step when the rollers (42)(43) or molds (142)(143) are operated in line (simultaneously) with the extrusion machine (41), as shown in
In another embodiment of the sheets with suction cups, as shown in
b through 6d show a cross-section of the tape (60) at one of the suction cups. As shown in these figures, the cups (62)(63) and (64) may be varied in height and diameter.
The attaching (bonding) of the tape (with the suction cups) to the plastic sheet, lengthwise, might be accomplished by the use of adhesive, heat (thermal) bonding, ultrasound or any other possible method that will achieve good bonding.
a shows the plastic sheet (70) with the tapes (60) attached.
Such tapes with suction cups may be easily produced by injection molding or by using simple molds. Currently some bath mats with suction cups at the bottom are commonly produced and used.
If the plastic sheet (70) and the tape (60) (with the suction cups (61)) are made using same or chemically similar materials (e.g. PE, PP, etc.), it is easier to heat (thermal) bond them together; particularly during the extrusion of the sheet. It is also possible to bond two different materials (plastics/polymers), although a little harder, depending on their chemistry. For example, if one of the materials is non-polar such as PE (all varieties), PP (all varieties), PET or other polymers, there may be problems in bonding it to the other material. For such polymers, techniques such as corona discharge and atmospheric pressure plasma (also called open air plasma) can be easily applied to make their surface polar. These techniques incorporate oxygen and nitrogen containing chemical groups thus changing the surface characteristics of the polymers to more polar, improving their chemical bonding capability. The chemical bonding in such cases may be covalent or hydrogen bonding. Using such techniques it is possible to modify the surface of the plastic sheet to specifically suit the chemistry of the skid-resistant material. This allows the skid-resistant plastic and the tape to bond well. Atmospheric pressure plasma and corona treatments can be applied on line, during the extrusion of the sheet and their cost should be minimal.
The tape (60) (with the suction cups (61)) may be attached on one side or both sides of the plastic sheet depending on the necessity and the application of the sheet. A cross section of a skid-resistant dust protective sheet (70) with tapes (60) attached to both sides is shown in
The spacing between the tapes on the plastic sheet and the placing of (distance between) the suction cups on the tape can be varied as desired. The size (diameter) and the depth (height) of the suction cups can also be varied as desired. In general, thinner skid-resistant dust protective sheets may use suction cups with smaller diameters and smaller depth (heights). Thicker skid-resistant dust protective sheets may use more suction cups per unit area or suction cups with larger diameters or larger depth. The circular area surrounding the suction cup outside edge might be made glossy smooth (flat) for better contact with the smooth surfaces it will be in contact with (e.g. laminate flooring, wooden flooring, tiled flooring and other smooth floorings or another plastic sheet) and to retain the suction action effectively over longer periods.
It may also be possible to attach suction cups without the use of the polymer tape. In such cases, the cups may be directly attached or bonded to the sheet on one side or both sides.
The suction cup design will also allow these skid-resistant dust protective sheets to be installed on vertical surfaces (e.g. walls or furniture). Once a small pressure is applied against these skid-resistant dust protective sheet and the suction cups (vacuum) are activated, the sheets will remain in place until pulled apart when desired. Conventional plastic sheets currently being used do not have such mechanism and readily fall off such vertical surfaces unless taped or somehow attached or held.
In other embodiments of the skid-resistant dust protective sheets of the invention, as shown in
The discontinuous skid-resistant coating may take various forms, as shown in
The skid-resistant discontinuous coating, although very thin, will have some thickness of its own and hence will project above the surface of the sheet.
The presence of the discontinuous coating of the skid-resistant properties, results in a significant increase in the coefficient of friction of the plastic on that side. This additional friction capability imparts the sheet with the skid-resistance characteristics. The discontinuous design of the skid-resistant material will provide a textured surface.
A host of elastomeric skid-resistant materials including but not limited to amorphous olefin polymers, urethanes, copolymers, various ethylene propylene copolymers, propylene 1-butene copolymers, higher propylenes, terpolymer analogs, ethylene vinyl acetate copolymers (hot melt or water based emulsions) styrene-butadiene, (hot melt or water based emulsion) cellulose acetate butyrate (hot melt), ethyl cellulose (containing plasticizers applied as hot melt), a variety of acrylics, natural rubber, variety of high tack rubber based adhesives, variety of synthetic rubber hot melts, and several other hot melts can be used for this purpose. All varieties of the materials mentioned above are commercially available. Since the skid-resistant material does not cover the entire surface of the plastic sheet, the cost can be controlled with the design.
To reduce the cost of the skid-resistant coating materials even further, a variety of fillers or combinations of fillers may be added to them. These include calcium carbonate, a variety of clays and other inexpensive materials that are commercially available in fine particle form. The fillers may be added such that the material properties, especially the coefficient of friction, will not be altered significantly.
The dots/squares and other shapes and grid or other patterns and designs of the skid-resistant material can be achieved through spraying or roller printing such as those commonly used printing machines employed in textile processing. Special ink jet type digital printers may also be used.
Skid-resistant material coating on both sides is preferred for better performance. Also, when it is desirable to cover areas that are larger than the width of the plastic sheet, the skid-resistant material coating present on both sides will make it easier to put two sheets side-by-side with small overlapping of the two sheets. The skid-resistant material coating from both sheets coming in contact should be sufficient to keep them together (attached) without needing any additional tape to join them. The same technique may be used to apply the coating on the other side of the plastic sheeting. The process may be carried out simultaneously or sequentially.
For some plastic (polymers) sheets surface treatment might be necessary to achieve good bonding between the skid-resistant coating material and the plastic sheet. Some surface treatments such as those described in the next paragraph or others may be useful in improving the plastic sheet/skid-resistant material bonding. This is especially true when non-polar polymeric materials such as PE, PP, PET, etc., which have very low surface energy, are used for the sheet along with high surface energy skid-resistant coating materials. In such cases, the skid-resistant coating material will not spread on the plastic sheet as desired. Instead the skid-resistant material will bead up and will not bond effectively with the sheet. Even if the two are bonded initially, the bond may not last long. The skid-resistant material may come apart with friction such as rubbing action.
As mentioned in the previous paragraph, one of the problems with non-polar materials such as PE (all varieties), PP (all varieties), PET and several other polymers, is that they are difficult to bond to any other material. For such polymers, techniques such as corona discharge and atmospheric pressure plasma (also called open air plasma) can be easily applied to make their surface polar. These techniques incorporate oxygen and nitrogen containing chemical groups thus changing the surface characteristics of the polymers to more polar, improving their chemical bonding capability. The chemical bonding in such cases may be covalent or hydrogen bonding. It is also possible to modify the surface of the plastic sheet to specifically suit the chemistry of the skid-resistant material. This allows the skid-resistant material to spread on the sheet evenly, as desired, rather than bead as well as bond well. Some of these treatments can also make the sheet surface slightly rougher by etching it, providing adequate mechanical bonding with the skid-resistant coating material. A variety of gases (air, oxygen, nitrogen, argon, ammonia, etc.) or mixtures may be employed in plasma treatment, the easiest and the least expensive being air. Although some plasma require vacuum, atmospheric pressure plasma and corona treatments can be applied on line, during the extrusion of the sheet and their cost could be minimal.
The sheets may be color coded (for thicknesses) for easier identification. The color/dye/pigment may be added to the sheet (polymer) itself or the skid-resistant material. The sheets may be conveniently sold in 20 to 50 (or higher) meter/yards and 2 to 5 (or higher) meter/yard width.
Since the sheets will be impermeable, they will also be impervious to any liquids, e.g. water and oil based liquids.
Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.
