Gas Impermeable, Elastically Deformable Laminate and Inflatable Articles Formed Therefrom

The present invention generally relates to inflatable articles formed of a laminate that is gas impermeable and elastically deformable, and particularly relates to a laminate used in forming a buoyancy compensator vest that is more comfortable to the user due to an ability to use lower inflation pressures.

Divers usually wear jackets, or vests, to achieve neutral or slightly positive buoyancy at various depths. The vest typically includes a buoyancy compensator chamber which the diver can selectively pressurize from the diver's air tank in order to adjust buoyancy under water. The buoyancy compensator normally also has an associated pressure relief valve.

Various diving vests with buoyancy compensators are known, such as described by U.S. Pat. No. 4,016,616, issued Apr. 12, 1977, inventor Walters; U.S. Pat. No. 4,561,853, issued Dec. 31, 1985, inventors Faulconer and Langton. However, previous buoyancy compensator devices have tended to be tight, highly inflated in use, and rather uncomfortable, particularly because during exposure to wave impact air is forced out of the associated relief valve which usually means that the chambers are typically inflated to a high pressure level.

One approach to increasing diver comfort has been to provide a soft backpack with a liquid-filled bladder that can be secured to a buoyancy compensator, such as is described by U.S. Pat. No. 4,952,095, issued Aug. 28, 1990, inventor Walters. Another approach (a life jacket design) is described by U.K. Patent Application 8725209, published May 25, 1988, in which relatively flat inflatable panels are described.

However, diver comfort remains an objective for which improvements continue to be sought for diving applications.

Accordingly, it is one object of the present invention to provide a laminate that is substantially gas impermeable and elastically deformable and that can be formed into a wide variety of inflatable articles having different stretch and strength needs, particularly relatively high pressure inflatables having good cycle life.

In one aspect of the present invention, an article comprises a laminate that includes an elastomer layer capable of repeated two-dimensional stretch and retraction. Opposed to the elastomer layer is a first substantially gas impermeable layer, and the two layers are substantially continuously adhered to one another and maintained in laminated form by adhesive means.

In a particularly preferred embodiment of the inventive article, the laminate forms an elastically deformable surface for receiving and containing gas therein, such as buoyancy gas as part of a SCUBA diver's vest, a dry suit or a semi-dry suit. Other embodiments for the inventive laminates include various inflatable articles, such as rafts and kayaks, automobile safety bags, diving suits, swimming learning vests, aircraft and life saving jackets and vests, medical therapeutic containers, waders, and the like.

FIG. 1 illustrates, in cross-section, a laminate embodiment of the invention;

FIG. 2 is a perspective of a buoyancy compensator with which the inventive laminate is useful; and

FIG. 3 is a sectional view in the direction of lines 3--3 of FIG. 2 showing a chamber for containing buoyancy compensating gas.

Laminates of this invention include an elastomer layer, a substantially gas impermeable layer, and adhesive means for adhering the layers to one another, and can be used to form all or part of a wide variety of articles. With reference to FIG. 1, a laminate embodiment 10 is illustrated with elastomer layer 12, first opposed substantially gas impermeable layer 14, and adhesive means 16 for substantially continuously adhering layers 12, 14 to one another and to form a substantially gas impermeable and elastically deformable surface (actually, two surfaces illustrated as surface 18a and surface 18b). Adhesive means 16 is also for maintaining layers 12, 14 in laminated form when the laminate is repeatedly stretched, such as during inflation.

Suitable elastomers for forming elastomer layer 12 include materials formed by elastomeric fibers, such as spandex fibers, in woven, non-woven, or knit fabrics, which can further include one or more of materials such as nylon and polyester or ether based polyester.

Preferred fibers are selected from the group consisting of polyester elastomers, polyester/polyether elastomers, polyamide/polyester/polyether elastomers, polyester/polyurethane elastomers, polytetramethylene terephthalate and polyester/polyurethane elastomers. More preferably, the fibers are polyester/polyether elastomers. Preferred polyester/polyether elastomers are described in U.S. Pat. Nos. 3,763,109, 3,766,146, and 3,651,014. Polyester/polyether elastomers and polyester/polyurethane elastomers are available commercially from E. I. du Pont de Nemours and Company under the trademarks Hytrel and Lycra.

A particularly preferred material for elastomeric layer 12 is polyester. Among the various suitable commercially available materials that may be used as elastomer layer 12 are, for example, stretchable Nomex fabric the thread of which is available from du Pont and Antron Cordura mixed with spandex fibers ("Spandura"), also available from du Pont. Fabric weight may vary, depending upon particular applications, with a preferred fabric weight range being on the order of about three ounces to about twenty-five ounces per square yard, and particularly preferred being about two and one-half ounces to about sixteen ounces per square yard for forming components of SCUBA diving apparatus, such as a buoyancy compensator.

The first opposed substantially gas impermeable layer 14 is preferably a continuous polymeric film. Gas transmission properties are generally a function of film thickness, with films of about 0.5 mils PET (polyethylene terephthalate), for example, typically having an oxygen transmission of about 7 cc/100 in.sup.2 /day Because the film should be substantially gas impermeable in forming the inventive laminate, a film thickness of at least 1 mil, more preferably at least about 2.5 mils thickness is preferred, with preferred thicknesses typically being between about 7 mils to about 30 mils, more preferably about 7 mils to about 16 mils. Such films are flexible, yet provide substantial strength in preparing inventive laminates.

Also, films with reduced permeability to vapors (that is, films that are substantially gas impermeable for a variety of applications contemplated by this invention) can themselves be composites, such as where one layer is a flexible polymer, such as a polyurethane, polyethylene, ether polyurethane, or polypropylene, while another layer is coated on or coextruded and serves as a barrier layer. Barrier layers can generally be viewed as substantially organic based or substantially inorganic based. For example, U.S. Pat. No. 3,442,686, issued May 6, 1969, describes a film composite in which silicon oxide coatings are deposited on polymers to serve as a barrier layer. This produces barrier coatings on even quite thin polymer films of oxygen transmission rate properties on the order of about 0.2 cc/100 in.sup.2 /day and similar water vapor transmission rate properties.

The layers 12 and 14 are bonded, or continuously adhered, and maintained in laminated form (that is, do not delaminate) even when the laminate is repeatedly stretched and retracts, such as to accommodate substantial volume increases due to elastic deformations in response to elevated pressures. Thus, the laminate has a good elastic limit for the various applications contemplated without permanent deformation occurring.

The substantially gas impermeable layer, as has been described, will tend to also have some stretchability, but it is believed to be the elastomer layer that primarily provides the necessary two-dimensional stretch and the essential retraction properties so that the inventive laminate can be repeatedly stretched and retract following elastic deformations in use due to elevated pressures. The particular strength and amount of stretchability desired will depend upon the particular application. However, in forming buoyancy compensators one normally encounters elevated pressures in the range of about 0.5 psi to about 8 psi, which can be readily accommodated by a laminate in accordance with this invention.

The adhesive means, or adhesive layer, 16 continuously adheres layers 12, 14 such as by melt bonding or by adhesive bonding, for example by thermal lamination on hot rolled calendaring equipment. Suitable adhesive materials are commercially available, for example, from laminators or combiners, such as Kenyon Laminating Group (Peacedale, R.I.) and Uretek (New Haven, Conn.). A particularly preferred inventive laminate is formed of 100% polyester tubular knit with adhesive from Polyurethane Specialties Co. (Lindhurst, N.J.) through Kenyon Laminating Group, using a 10 mil thick polyurethane ether based film. An adhesive with good resistance to UV, salt water, and within a preferred range of modulus (stretch) between 6,000-10,000 is Uretek, style # nylon 16-71.

Particularly preferred adhesive materials for adhesive bonding are liquid polyether urethanes (which can be dissolved in methyl ethyl ketone). For example, such an adhesive material can be substantially continuously spread on film layer 14 and thereafter elastomeric fabric 12 added and adhered in a heat calendar process. Application can be by known techniques, such as by reverse roll head, by floating head, or by knife over roll head. The latter is particularly preferred. The depth at which a solubilized adhesive, such as an ether based polyurethane dissolved in MEK, penetrated the layer to which it is applied is controllable by the time when cure is commenced. The resultant laminates are preferably RF weldable for preparation in a variety of forms.

Where even greater strength is required for a particular application, then an additional layer (not illustrated), also preferably gas impermeable and also preferably polymeric, may be added so that the additional layer either is sandwiched between or on either side of the elastomer layer and the gas impermeable layer. This additional layer is preferably adhered in the sandwiched relationship by the same or a different adhesive process as the previously described laminates. For example, adhesive material 16 can be a solvent based adhesive while the second layer can be calendar heat bonded (that is, fused) to film 14.

In the various applications for inventive laminate 10, either surface 18a or surface 18b can be exposed to the elevated pressure for inflation, although the polymeric layer will typically be exposed to the elevated pressure while the elastomeric layer (defining surface 18a) will be exposed to touch or be adjacent to a wearer's skin for purposes of comfort.

Turning to FIG. 2, a buoyancy compensator 20 is illustrated having opposed walls 22, 24 and with which the inventive laminate is usefully employed. For example, either all or part of wall 22 or all or part of opposed wall 24 can be made from inventive laminate 10.

With reference to FIG. 3, both walls 22, 24 are illustrated as formed from inventive laminate 10 where buoyancy compensator 20 is illustrated as being formed with chamber 25 between the two walls 22, 24. Thus, as illustrated, the buoyancy compensator 20 can be of a single bag construction. In addition, the buoyancy compensator 20 can be of the type (not illustrated) well known to the art by having a double bag, or double wall, where the outer bag generally provides for the maintenance of pressure within the buoyancy compensator while the inner bag, or bladder, provides a maintenance of the air therein in a sealed relationship.

In one particularly preferred embodiment, wall 24, which is in contact with the diver's body includes a soft, strong 100% polyester with a suede-like finish. The opposed wall 22 is formed from the inventive laminate 10. The walls 22, 24 are preferably affixed one to the other to form a chamber for receiving pressurized air, but affixation can also be by various heat sealable processes (such as tape and glue or a vulcanizing hand process).

The buoyancy compensator 20 typically has a waist portion 26, which terminates in attachable belt portion 28. The belt 28 has buckles 30 and 32 (or other fastening means) in order to secure the waist portion 26 around a user's waist. Waist portion 26 will preferably be formed of a woven neoprene in combination with a nylon stretch material, which has neutral buoyancy in water. This material is also preferably used for the shoulder portions 34, 36.

Shoulder portions 34 and 36 define a neck area 38. A harness 40 (illustrated generally at the back) is constructed to receive a backpack (not illustrated) which snugly fits in harness 40 to provide lumbar support and to cradle the SCUBA air tank 50. The air tank 50 has a valve and a regulator, generally shown as valve and regulator 52. The valve and regulator 52 serve to provide breathing gas to the diver wearing buoyancy compensator 20.

Tube 56 is connected to an inflation system 58. The inflation system 58 has a mouthpiece 62 through which a user can inflate the buoyancy compensator orally. Inflation system 58 may comprise a soft-touch power inflator 64, oral inflation button 65, a rapid exhaust valve 66, and an overpressure relief valve 68 which all work together as inflation system 58 and which are preferably surrounded in a protective material, such as a soft elastomer, that conforms to the user's hand and protects the mechanical parts from wear and tear. The soft touch inflator 64 permits control of the air entering the buoyancy compensator 20, while the rapid exhaust valve 66 is readily opened by pulling down on the inflator tube 56. The overpressure relief valve 68 is preferably integrated into the inflation system 58 to allow air to escape quickly in the event of overpressuring the buoyancy compensator 20.

Because the inventive laminate 10 is elastically deformable, the portions of such a buoyancy compensator 20 formed from the inventive laminate are more comfortable to the user due to an ability to use lower inflation pressures, particularly because during exposure to wave impact the elastically deformable surface (such as surface 18a and surface 18b) will tend to deform and the garment itself does not need to be inflated to the typical high pressure levels to compensate for wave action. That is, the deformability feature allows larger wave impact without losing air from a chamber formed by the inventive laminate. This results in a substantially more comfortable garment and the uncomfortable "squeeze" sensation of highly inflated prior art buoyancy compensators is avoided.

Particularly preferred inventive laminate constructions permit volume increases due to elastic deformation on the order of up to about 100 percent in response to elevated pressures, such as within the range of about 0.3 psi to about 5 psi. As will be appreciated, chambers formed by the inventive laminates 10 will be resistant not just to elevated pressures, but more generally will perform as a substantially gas impermeable membrane for pressure difference with respect to the pressures imposed on surfaces 18a, 18b. That is, laminate 10 is substantially gas impermeable even with the pressure difference between a hypothetical pressure P.sub.a (to which surface 18a would be exposed) and a hypothetical pressure P.sub.b (to which surface 18b would be exposed). Thus, inventive laminate 10 could be used to form part or all of a diving suit where the internal suit pressure and the external pressure due to water are adjusted to neutral buoyancy over a pressure difference range beginning at about 0 psi and upwards. Cycle tests with different laminates suggest upper pressure difference values to about 100 psi can be accommodated. Where the inventive laminate 10 is forming a membrane between fluids with one fluid in liquid or solid form, then the elastically deformable surface of the laminate can have a volume variable in response to variable fluid densities, such as in medical therapeutic containers where expansion can be due to a liquid-to-solid transformation.

Again with reference to FIG. 1, typical and preferred aspects of buoyancy compensator 20 include shoulder areas 34 and 36 that are adjustable by means such as buckles 80 and 82 on adjustment straps. The shoulder areas 34,36, as well as pockets and soft backpack, can be RF welded to save labor cost of sewing with the new laminate 10. Additional attachments, fasteners, and the like features as are well known to the art may be included with the buoyancy compensator 20. For example, hooks, straps, loops, buckles, and the like are usefully included (but not illustrated).

The walls 22 and 24 are shown with a sealed periphery 84. As earlier noted with reference to FIG. 3, this seals the outer edges to form an interior chamber 25 between the walls 22 and 24. Buoyancy compensators of the invention can have a plurality of chambers, preferably where such chambers are interconnected and thus at the same pressure.

Returning to FIG. 2, heatset areas 86 can take a variety of forms, shapes, and locations on the article and can be provided by radio frequency (RF) welding, ultrasonic welding, thermal heatsealing, or any other suitable sealing process, so that the buoyancy compensator walls 22 and 24 are brought into connection with each other at desired areas of the article to better fit or conform to a user's shape, to accommodate attachments, and the like. Also, the conformation of the buoyancy compensator is retained by the various heatset areas to prevent undue expansion during dives.

As will be readily understood, the inventive laminate 10 can be desirably utilized in preparing other articles, particularly other inflatable articles, such as rafts and kayaks, automobile safety bags, diving suits, swimming learning vests, aircraft and lifesaving jackets and vests, medical therapeutic containers, waders, and the like. Other buoyancy compensator vests are also known to the art, such as snorkel buoyancy compensators, for which inventive laminate 10 is readily and desirably adapted.

Aspects of the invention will now be further illustrated.

Testing was performed on various laminate 10 embodiments of the invention. Cycle testing was performed by forming laminate 10 embodiments into pressurized air containing chambers (such as illustrated by FIG. 3), and then repeatedly filling and evacuating the chambers with pressures by a machine that can fill to 20 psi and can evacuate to subatmospheric. An overpressure valve permits positive pressure variations up to 100 psi. Chambers formed from various laminates were initially screened, and then selected laminates were tested at over 10,000 cycles of input (1.5 psi) and exhaust.

A burst test was also used in which pressurized air was input into the chambers up to rupture. Laminates were further subjected to a wash test in which four inch by four inch laminate pieces were subjected to heavy cycle, standard washing machine washing for 50, 100, or 150 cycles and then examined for wear, possible delamination, and color degradations. Ten out of fifty cycles included bleach, and about one-third of the cycles were with hot water, another about one-third with warm water, and a final about one-third with cold water. All cycles included conventional laundry detergent at manufacturers' suggested use levels.

Laminates were yet further subjected to impact tests where a drop weight plate machine with a fifteen pound drop weight was used to impact the laminate rapidly and to apply uneven stress to different local areas on chambers formed from the laminates. The laminate forming chambers were then visually inspected for any weaknesses due to the impact tests.

Preferred laminates of this invention perform well under the just described cycle, burst, wash, and impact testing. Several preferred laminate 10 embodiments of the invention, all successfully passing the tests as above described, were prepared as follows.

A laminate embodiment was prepared from 100% knit polyester (style 5270, commercially available from Flynt Amtex, Inc.) weighing 3.9 ounces per square yard, and having a 75% stretchability (both length and width). Adhesive used was obtained from Polyurethane Specialties Co. through Kenyon Laminating Group and Eurotech Incorporated. The substantially gas impermeable layer was 10 mils polyurethane film. The polyester knit and polyurethane film were laminated by means of the adhesive through a heat calendar process, and the resulting laminate gave excellent testing results.

A second laminate embodiment giving good testing results was formed in a similar manner with a nylon and spandex fabric (6 oz., 120 warp, and 80 fill) and either 7 mils or 16 mils polyurethane film.

Yet another laminate embodiment with good test results used Antron Cordura and spandex (7 oz., 120 warp, and 95 fill) as the elastomer layer, while the first substantially gas impermeable layer was 10 mils polymeric film with a second layer being sandwiched between the elastomer layer and first layer by means of adhesive. The second, sandwiched layer can be a stretchable (spandex knit) ballistic type fabric (such as used in bullet-proof vests).

A fourth embodiment was prepared where the inventive laminate was formed from 100% stretch polyester as elastomer and adhered to 10 mils polyurethane film. This laminate was then used to form one wall of a chamber while the other wall was formed from a 10 mil polyurethane film adhered to a non-stretch polyester suede. The two walls were joined into the pressurized, air containing chamber by means of a welded joints.

It is to be understood that while the invention has been described above in conjunction with preferred specific embodiments, the description and examples are intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims.