Patent Application
20060210766
High performance backcountry articles, such as camping mattresses/pads and tents, need to be light in weight and compact in size so a backpacker or mountaineer can minimize the weight they must carry. In order to keep the user on a camping pad and the pad stationary on sloped surfaces, it should be constructed of high friction materials on both the top and bottom of the pad. Alternatively, or in addition to this, having a floor of a tent structure that also has low-slip properties is considered desirable: not only do pads stay in place better, but any object placed on the floor will also benefit from such an enhanced friction surface.
Current non-slip, high friction or low-slip fabrics are constructed of high bulking textured yarns. DuPont, Inc. makes appropriate fabrics of this type, under the brand name Supplex®. The loose or random nature of some of the filaments provides enough texture to increase the surface friction of the woven fabric. However, because textured yarn is used on both sides of the mattress/pad surface, weight is increased everywhere. Moreover, the loose yarn does nothing to increase the mechanical strength of the textile. In addition, to make a fluid impervious mattress/pad from textured fabric, a relatively large amount of polymeric coating must be applied to the inside surfaces of the fabric, further increasing weight. In general, the nature of the current art for creating high friction mattress/pad fabric creates the undesirable side effect of increasing the base fabric's weight from 30-60%. This consequence runs contrary to the stated goal of providing a mattress/pad solution having minimal weight properties.
Similar consequences occur with respect to tent floors. The overall weight of a tent is of great concern to backpackers, however, providing a slip-resistant tent floor is also considered highly desirable, given the generally non-level or irregular surfaces upon which the tents are erected.
The need for lightweight, slip-resistant fabrics and similar materials extends beyond those applications described above. Additional applications include technical outerwear such as snow and climbing clothing (bibs, jackets and pants), knee and elbow pads, tablecloths and mats, fabric friction tape (e.g., bicycle handlebar tape) and other applications wherein low weight and increased slip-resistance in a high longevity product are desirable.
The invention is directed to a material deposition treatment that can be applied to at least a user contacting side of a flexible substrate to increase the coefficient of friction between the user, or an article worn by the user, and the substrate without appreciably increasing the overall weight of the substrate or a structure incorporating the substrate. The material deposition treatment may rely upon the physical properties of the deposited material, such as the area, shape, density, topology or profile of the material, upon the mechanical properties of the material, or upon combinations thereof to enhance the friction of the substrate. The invention is therefore directed to methods for creating such a material deposition treatment and articles produced thereby.
Methods according to the invention are broadly characterized as selectively applying a friction enhancing coating to a flexible substrate where the selective application comprises a plurality of “elements”, preferably in the form of repeating patterns. The flexible substrate comprises at least one of nylon, polyester, acetate, poly/cotton, aramid, Lycra®, Vectran®, polypropylene, Nomex®, or Spectra®. The coating comprises at least one of acrylics, epoxies, polyvinyl chlorides, polyolifins, neoprenes, polyurethanes, butyls, Hypalon®, nitrites, Viton®, polyethylenes, polypropylenes, polystyrenes or silicones, all of which may include the incorporation of silica and/or any aggregates. The methods for applying the coating to the substrate comprises planar screening, rotary screening, reverse rolling, direct spraying, transfer coating or rotogravure transferring.
In a preferred method, rotogravure printing is used due to its ability to deposit polymeric elements with highly raised profiles (the height above the substrate being coated). A cross-linked polyurethane compound is a preferred coating due to its adhesive ability, durability, acceptability of pigments, and easily controlled viscosity, amongst other properties.
The product resulting from practicing the methods of the invention is a durable and lightweight article incorporating a plurality of “elements” (raised geometric shapes) corresponding to the template used during the material deposition process. Depending upon the mode of material deposition, the template can be a physical item such as a screen or drum, or can be data such as used with a CNC direct spraying apparatus. Thus, a treatment creating a plurality of raised geometric shapes that cover 25% of a textile's outer surface area can result in an article having increase of overall weight of less than 10%. Applying the right polymer to a typical coated nylon taffeta fabric used in self-inflating mattresses will yield a product that has a 30%-40% reduction in the weight compared to the previous state-of-the-art non-slip fabrics, and is significantly lighter than any textured mattress fabrics currently available.
A preferred process for applying the raised geometric shapes to a woven fabric material used in self-inflating mattresses uses a hot melt rotogravure line applying a plurality of cross-linked polyurethane “elements” to one side of a nylon taffeta fabric. The pattern of the gravure roll is infinitely variable so those patterns can be matched to different substrates, although in this embodiment the pattern comprises spaced-apart truncated domes. Additionally, it is found that the height or profile of the shapes is important to maximizing friction with the least amount of added weight. Moreover, the polyurethane should be sufficiently cross-linked so that the pattern is retained during a mattress manufacturing process such as is described, for example, in U.S. Pat. No. 4,025,974, which is incorporated herein by reference. Cross-linking also provides abrasion resistance and durability. As noted above, additives and pigments can be added to the base coating for color as well as to increase friction.
It will be appreciated that articles resulting from the processes described herein have a plurality of variables, all of which may be modified to produce a desired result. With respect to the selective application of a coating, each “element” has three primary properties that affect its contribution to the increased coefficient of friction possessed by the treated substrate: the element footprint (i.e., the two dimensional area of the element at the coating-substrate interface), the element height (e.g., topology and cross sectional profile considerations), and the element composition.
Turning then to the several figures, wherein like numerals indicate like parts, and more particularly to
The field density of elements 40 is generally driven by an enhanced friction factor versus an increased weight factor. Variables to be addressed include the weight density of the coating compound and the volume of each element. Thus, the field density range can be from as little as 5% of the available panel area to as much as 90%. Moreover, each element can be minimized if a large number is used, or can be maximized if few elements are used to achieve the desired enhancement versus weight combination. If dome-shaped elements are used, preferably densities range from about 187 elements per square inch (29 elements per square centimeter) to about 382 elements per square inch (59 elements per square centimeter). In addition, each element can be compact, such as a dome, or elongate, such as a line (linear or otherwise).
Also affecting friction performance is the elevation profile and topology of each element.
Thus, it should be understood that any given element can possess each form of apex exclusively or in combination. Logically, any given element can also possess a plurality of apexes, in addition to other structure, as is illustrated in
Of particular applicability of element 40 is with respect to inflatable mattresses or pads. In these articles, a resilient material is sandwiched between two flexible panels where the resilient material is substantially bonded to the inside surfaces of the panels, and the panel perimeters are sealed to one another, thereby establishing a fluid impervious chamber. A valve is established between the chamber and the environment to regulate the influx and efflux of air into and from the chamber. At least one panel outer surface is treated according to the treatment methods described herein to create a friction enhanced inflatable mattress or pad. The treatment may take place prior to the construction of the mattress or pad, or may take place thereafter.
This is a continuation-in-part application that claims benefit, under 35 USC §120, of co-pending International Application PCT/US04/23165, filed on 19 Jul. 2004, designating the United States, which claims foreign priority benefits under 35 USC §119 (a) to U.S. Provisional Patent Application No. 60/488,454, filed 18 Jul. 2003, which applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60488454 | Jul 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US04/23165 | Jul 2004 | US |
| Child | 11335164 | Jan 2006 | US |
