US3787908A

US3787908A - Incompressible, conformable structure containing cellular particles

Info

Publication number: US3787908A
Application number: US00158889A
Authority: US
Inventors: W Beck; N Sweeny
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1971-07-01
Filing date: 1971-07-01
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29

Abstract

The disclosed cushioning means comprises a flexible-walled container filled with a flowable liquid and, suspended in the liquid, tiny cellular particles having a low density. The cellular particles reduce the density of the liquid fill and also improve its thermal insulative properties. A viscosity modifier is preferably added to the flowable liquid fill to provide better dimensional stability characteristics, as compared to a conventional water bed.

Description

United States Patent 1191 Beck et a]. 1 Jan. 29", N74

[5 INCOMPRESSIBLE, CONFORMABLE 3.585.356 6/1971 Hall 5/348 STRUCTURE CONTAINING CELLULAR 1,907,41 l 5/1933 Timony 15/3 PARTICLES Inventors: Warren R. Beck, Saint Paul;

Norman P. Sweeny, North Oaks, both of Minn..

Minnesota Mining and 'Manufacturing Company, Saint Paul, Minn.

Filed: July 1, 1971 Appl. No.: 158,889

Assignee:

us. 01. 5/348 WB, 5/91 1m. 01. ..A47c 27/08 Field Of Search.. 5/348, 349, 350, 91, 348 WB; 15/3; 259/95; 106/40; 260/25 B; 297/284 References Cited UNITED STATES PATENTS 9/l971 Von Heck 297/284 Primary Examiner-B0bby R. Gay Assistant Examiner-Andrew Calvert Attorney, Agent, or Firm-Alexander, Sell, Steldt &

- DeLaHunt 5 7 ABSTRACT The disclosed cushioning means comprises a flexiblewalled container filled with a flowable liquid and, suspended in the liquid, tiny cellular particles having a low density. The cellular particles reduce the density of the liquid fill and also improve its thermal insulative properties. A viscosity modifier is preferably added to the flowable liquid fill to provide better dimensional stability characteristics, as compared to a conventional water bed.

13 Claims, 2 Drawing Figures PAIENTED 2 9 974 5Kv/ m g W may,

. 1 v INCOMPRESSIBLE, CONFORMABLE STRUCTURE CONTAINING CELLULAR PARTICLES FIELD OF THE INVENTION This invention relates to incompressible, conformable products-e.g., cushioning means such as mattresses, pillows, and the like. An aspect of this invention relates to cushioning means with a liquid center such as water beds. A further aspect of this invention relates to the inclusion of a significant concentration of cellular particles in the liquid center or fill liquid and means to keep this concentration substantially uniform throughout any cross section of the cushioning means.

DESCRIPTION OF THE PRIOR ART In the late 1960s, it was suggested that an inflatable vinyl chair could be filled with liquid starch or gelatin to provide a cushioning means which would conform exactly to the shape of the human body. Liquid starch and gelatin proved to be unworkable fill materials which were not readily adaptable for providing the desired results. However, it was found that plain water confined within a flexible vinyl envelope did provide a very effective cushioning means. A recent embodiment of the water-filled vinyl cushion is the so-called water bed, which is typically a vinyl bag enclosing at least 500 lbs. (230 kg) and up to about 2500 lbs. (1140 kg.) of water. The water bed provides a degree of comfort which is difficult to obtain by any other means, with the possible exception of a carefully designed air mattress.

Although the water bed concept has had considerable public acceptance, even-the most expensive and carefully designed water bed structures have problems, both from the standpoint of the user and the furniture dealer. First, the weight of water contained within the vinyl bag or other flexible outer covering is considerable. The typical bedroom is not designed to contain a bed weighing nearly a ton or more. Second, the water contained in the water bed mattress tends to absorb heat from its surroundings and cause the user of the bed-to feel chilled. For comfort, it is often necessary to provide a water bed with an electric water heater. Third, many users of water beds'are disturbed by a rippling and sloshing effect; although there is no air space within the water bed mattress, the enclosed water is nevertheless mobile and free to move in several directions. This rippling and sloshing effect is a problem that would be encountered even if a low viscosity fill liquid other than water were used, and the use of a non-liquid fill would sacrifice one of the principal advantages of the water bed concept; i.e., when a water bed is installed, the ernpty mattress can be brought to the site of installation in collapsed form and filled with water on the job. Needless to say, solid and semi-solid fill materials which are not flowable and cannot be pumped are ordinarily inappropriate for use in the water bed concept due to the importance of this on-the-job assembly technique. Furthermore, even semi-solids are not as conformable to the body as a water bed mattress.

Hollow, uni-cellular filler particles comprising a solid wall of a glassy silicate, a ceramic, or a rigid synthetic resin enclosing a hollow space comprising a gas or other fluid have been available in the market place for several years. Examples of such hollow fillers are disclosed in Veatch et al., US Pat. No. 2,797,201, issued June 1957, Veatch et al., U. S. Pat. No. 3,030,215, issued Apr. 1962, and Beck et al., U. S. Pat. No. 3,365,315, issued Jan. 1968. These hollow fillers have been used in gelled sealing liquids according to Canadian Patent 571,519, published Mar. 3, 1959, and in resilient cellular materials suitable for use in upholstered structures according to Merriman et al., U. S. Pat. No. 3,300,421, issued Jan. 1967. The Merriman et al. structure contemplates, in effect, a rubber latex foam loaded with rigid cellular particles. Apparently, it has never been suggested that the Veatch et al. or Beck et al. hollow filler particles could be utilized in a truly incompressible, conformable liquid composition capable of being pumped as a fill material for a cushioning means of the water bed type.

Accordingly, this invention contemplates an incompressible, conformable structure or cushioning means containing a conformable liquid mixture capable of being pumped which is lower in density, less heat absorptive, and less inclined to ripple and slosh about within its flexible walled container than is water. This invention further contemplates a .water bed construction filled witha continuous liquid phase containing suspended hollow, cellular (preferably unicellular), liquid-impervious filler particles. This invention further contemplates a water bed type of construction which can be assembled and filled at the site of use and can be disassembled and emptied for transport to a different site of use, which has more advantageous density, heat insulative, and dimensional stability characteristics than aconventional waterbed, but which neverthelessjprovides the comfort. of an incompressible, conformable liquid n11 material. I

SUMMARY OF THE INVENTION Briefly, this invention involves filling a flexible walled container with an incompressible, conformable mixture capable of being pumped, having a density less than 1.0 grams per cubic centimeter, said mixture comprising a continuous liquid phase and, suspended therein, hollow, cellular, water-impervious filler particles less than about 5 .millimeters in diameter, which particles-have an average true particle density less than 0.6 grams per cubic centimeter. The hollow filler particles comprise v a solid wall completely enclosing a fluid-containing core, the fluid being preferably gaseous. The amount of filler particles contained in the flowable mixture is large enough to significantly reduce the density of the mixture, but not so large as to prevent the mixture from being incompressible and conformable at room temperature, therefore maintaining the mobility of the filler particles within the mixture. Accordingly, less than about 65 percent by volume of hollow unicellular filler particles should be used, but if the concentration of filler particles in the mixture falls below at least about 30 volume percent, the reduction in density will not be sufficiently advantageous to justify the use of the hollow filler particles. In fact, for most applications, the concentration of hollow filler is preferably greater than 40 volume percent. The liquid phase of the liquid mixture preferably comprises water thickened with less than about 5 percent by weight of asuitable thickening agent or viscosity modifier. Thixotropic agents, antidusting agents, and fungicides can also be included in the liquid mixture,-as will be explained subsequently.

DESCRIPTION OF THE DRAWING This invention can be more clearly understood by referring to the accompanying drawing, wherein FIG 1 is a perspective view of a water bed installation made according to this invention, with parts broken away to show the internal structure of the bed.

FIG. 2 is a perspective view of a different embodiment of the invention shown in section, to illustrate its internal structure.

As can be seen from FIG. 1, water bed comprises a mattress 13 and high strength support means 11. Mattress 13 comprises a rubberized fabric container means comprising an outer fabric 23 and an inner rubber liner 21', rubber liner 21 containing within it a low density fill material 16 comprising a continuous aqueous phase 17 and microbubbles 15 (shown, for convenience of illustration, greatly enlarged and in a much sparser concentration than would normally be used in this invention) substantially uniformly suspended within aqueous phase 17. A particulate, amine-treated bentonite clay is present in aqueous phase 17 to prevent microbubbles 15 from rising to the top of mattress l3 and increasing the concentration in this portion of mattress 13 to the point where mattress 13 becomes stiff and board-like. Thus, the concentration of microbubbles 15 in fill material 16 is substantially uniform throughout any crosssection of mattress 13. The concentration of the aminetreated bentonite clay in aqueous phase 17 is large enough to impart false body to fill material 16, thereby preventing excessive rippling or sloshing in mattress 13 when the bed is in use. However, fill material 16 can still flow like a fluid when subjected to pumping action or suction. If an excessive concentration of the treated clay is used, the surface of mattress 13 can actually become relatively stiff, like a stiff mud.

The microbubbles 15 reduce the density of the mattress 13 by up to about 50 percent. Microbubbles 15 also reduce the heat capacity of mattress 13, thus alleviating the coldand clammy feeling that a water bed mattress canacquire and obviating the need for an electrical heater. Even the combined use of microbubbles l5 and the thickening agent does not thicken aqueous phase 17 to the point where it is no longer flowable or at least pumpable. Accordingly, aperture means 25 permits onthe-site filling of mattress 13 with a liquid fill comprising aqueous phase 17 and microbubbles 15. For filling, aperature means 25 in mattress 13 is provided with removable, replaceable fillcap 27. Drain means 29 is provided in support means 11 and mattress 13 to permit collapse of mattress 13, thus greatly reducing the weight of bed 10, should the bed have to be moved. It is generally necessary to apply some type of suction to withdraw fill material 16 from mattress 13 through aperture 25 or drain means 29. However, even without suction, a considerable portion of fill material 16 will spontaneously flow out drain means 29 under the influence of gravity.

Drain means 29 can, if desired, be coupled with a valve (not shown) in the bottom wall of mattress 13 to facilitate draining or filling of mattress 13. For on-site assembly and installation of bed 10, it is advantageous to fill mattress 13 from the bottom, via such a valve arrangement, while leaving aperture means 25 open to permit air to escape during filling.

A particularly significant feature of bed- 10 of FIG. 1 is that support means 11 raises mattress 13 off the floor. This elevation of mattress 13 is made possible by the weight reduction obtained from the use of microbubbles 15. Without microbubbles l5, fill material 16 could be too heavy for support means 11.

FIG. 2 illustrates the usual type of water bed installation 30 where support means 31 does not elevate mattress 33 off the floor'or other base, but merely helps to contain it and give it dimensional stability. Mattress 33 comprises, however, the same type of microbubbles 35 (also shown greatly enlarged and in lower-than-normal concentration) and aqueous phase 37, contained within a similar rubberized fabric envelope or wall 43. Dip tube 49 permits filling of mattress 33, and during the filling operation, cap 47 can be removed from vent 45 to permit escape of air.

DETAILED DESCRIPTION OF THE INVENTION Several methods for manufacturing and installing cushions or beds made according to this invention can be used. For small cushions and pillows, a flexible walled container can be filled with a liquid center containing the microbubbles and can be distributed as such. For larger structures such as water beds, an onsite installation method can be used, for example:

I. A mattress can be filled with dry microbubbles and shipped to the site of installation. Water can be forced into the mattress on the site or a thickened liquid can be separately shipped and likewise forced into the mattress.

2. An empty mattress (e.g. a collapsed but inflatable vinyl bag or rubberized fabric bag) can be shipped to the site of installation; a fully formulated fill liquid, e.g.

comprising microbubbles, water, thickener, and other additives can be separately shipped and pumped into the empty mattress on the site.

3. Method (2), above, can be modified to the extent that the fill material is not fully formulated; e.g., dry microbubbles can be shipped to the site and mixed up with, for example, water or thickened waterat the site. In this and other methods, the dry microbubbles are preferably treated with a'rn inor amount (a few percent by volume) of a binder such as polyvinyl acetate or methyl cellulose. With this binder treatment, the fully formulated liquid fill material, if accidentally spilled,

will leave a solid residue which can be easily disposed of rather than a dust-like deposit which could become randomly dispersed throughout a large area. Whenever organic material is present, either as the hollow filler particles or as the binder, it is preferred to also add a terial.

The use of a binder such as methyl cellulose has the advantage that the binder will also serve as a viscosity modifier for the aqueous liquid. Other suitable viscosity modifiers for aqueous liquidsare the hydrous clays, e.g., hydrophilic magnesium aluminum silicates such as bentonite, particularly Wyoming bentonite, and hydrophilic colloids and gums such as Carbopol 941 (trademark). Good thixotropic effects are achieved with amine-treated bentonites, e.g., Bentones" (trademark) such as Bentone LT, which are preferred for use in this invention. These treated bentonites are commercially available and are made by reacting the clay particles with primary, secondary, tertiary, or quaternary amines of the formula R R R N or R,R R R NX, where R R R and R are aliphatic groups or hydrogen and X is a suitable anion. Amine treatments of this type are described in a U. S. Pat. to Hauser, No. 2,531,427, issued Nov. 28, 1950. The viscosity modifier preferably comprises less than 5 wt. percent of the continuous liquid phase, more preferably 0.1 3 percent by weight. This concentration of viscosity modifier provides both uniformity and stability of suspension of the cellular filler particles in the liquid phase, without unduly reducing the mobility of the filler particles. For non-aqueous liquid fill systems, colloidal silica and fine asbestos are suitable viscosity modifiers.

Aqueous liquids (including mixtures of water with other liquids) should normally be used in the fill liquid, particularly in view of the importance of low toxicity and flammability in typical cushioning uses; however, for very specialized uses requiring very low density or the like, low density organic liquids are permissible, though not preferred.

The cellular filler particles suspended in the liquid fill material of this invention can be multicellular, similar to the cellular glass nodules described in U.S. Pat. No. 3,354,024, issued Nov. 21', 1967 and U.S. Pat. No. 3,510,392, issued May 5, 1970, but unicellular particles are preferred. These cellular particles should be less than 5 mm. in diameter and are preferably rounded, i.e., spherical or ellipsoidal in shape. The roundness facilitates mobility in the liquid phase, particularly in high particle concentrations such as 60 volume percent. The void space or spaces in each particle should be wholly enclosed by an outer wall comprising, preferably, a glassy or polymeric material such that the void spaces, which are preferably filled with a gas such as CO S or the like, cannot be permeated by (and are inert toward) liquids such as water. On the other hand, a minimum of wall material should be used, consistent with adequate strength and impermeability, to keep the density of the particles as low as possible.

Organic polymeric and glassy or inorganic materials suitable for forming the'walls of hollow or cellular particles are disclosed in, for example, U. S. Pat. No. 2,797,201, issued June 25, 1957 and u. s. Pat. No. 3,365,315, issued Jan. 23, 1968. The preferred unicellular particles are substantially hole-free and spherical microbubbles ranging in size from 1 to 500 microns, preferably 300 microns, and ranging in true particle density from about 0.05 to about 0.6 g/cc. Wall thicknesses (less than about 5 percent of the diameter of the unicellular microbubbles) can be on the order of a half micron. The glass (at least 40 wt. percent SiO at least 5 wt. percent alkali metal'oxide, and at least one other oxide) microbubbles made according to U. S. Pat. No. 3,365,315 have extraordinary liquid impermeability,

low density, chemical inertness, and high resistance to isostatic pressures and hence are preferred for use in this invention. These microbubbles are commercially available as .3M brand Glass Bubbles, the preferred commercial embodiment being the B B Series of about 0.1 0.4 g/cc density, e.g. BlSB and B258, and the B-A Series, e.g., B22A and 812A.

Though less preferred, organic polymeric or resin microspheres are operative in this invention, as pointed out previously. The preferred resin microspheres have walls derived from phenolaldehyde polymers, epoxy resins, or polyvinylidine chloride polymers (including co-polymers, terpolymers, etc.). Other inorganic-type microbubbles or microspheres operative in this invention include those made from sodium silicate and from ceramics, e.g., vitrified compositions containing materials such as feldspar, silica, kaolin, or alumina. Any of the afore-mentioned wall materials can be caused to form a complete spherical or ellipsoidal enclosure around a gaseous core such as CO or S0 thus providing a particle with a true particle density well below 1.0 g/cc, e.g., 0.05 0.6 g/cc. Thus, when a suitable liquid such as water is the primary constituent of the liquid phase of the fill material, a room-temperature flowable liquid having a density less than 1.0 g/cc is obtained by suspending the cellular particles in the liquid phase.

The concentration of the suspended cellular particles should be at least about percent by volume of the liquid fill material in order to provide a truly helpful reduction in the weight of the cushioning structure. Concentrations greater than 65 volume percent severely 7 reduce the mobility of even spherical cellular particles and thus interfere with the comfort of the user. The preferred range of cellular particulate filler concentration is 60 percent by volume, maximum mobility and weight reduction being obtained in the vol. percent range. Surprisingly, even in this 50 60 vol. percent range, an aqueous liquid fillmaterial of this invention, containing up to 5 percent by weight of a viscosity modifier, is flowable enough at room temperature to be pumped in or out of a water bed.

The flexible-walled containers used to contain the low density liquid fill material can comprise vinyl film, rubberized fabrics (e.g., a latex rubber film covered with textile), polyester films, polyester/polyolefin film laminates, or the like. Typical film or laminate thicknesses range from 1 40 mils (0.025 1.0 mm), preferably at least 20 30 mils (0.5 0.75 mm). Baffle means can be included within the flexible-walled container to further reduce the mobility of the liquid fill material, but such means are ordinarily not preferred for use in this invention, except for very specialized uses, e.g., mattresses for tiltable hospital beds.

The following non-limiting Examples illustrate the principle and practice of this invention.

EXAMPLE 1 The following formulation was used to make a liquid fill material for a cushion:

Made according to U.S. Pat. No. 3,365,315; density range (average): 0.200.25 g/cc, as determined by air compression pycnometer', size: between 20-120 microns; strength: 400 psi (28 kg/cm) required to collapse 20 vol. of bubbles in water by isostatic pressure.

be 0.58 g/cc. The polyester bag was heat sealed and laid flat on a table. It was found that the glass bubbles remained mobile within the bag and had the properties of a stable suspensoid, i.e., the bubbles have no apparent tendency to pack near the upper surface of the bag.

3. A structure according to claim 1 wherein said continuous liquid phase contains a viscosity modifying agent.

4. A structure according to claim 1 wherein said structure further comprises a support means for providing dimensional stability for said liquid-impermeable A similar formulation was prepared from 49.8 vol. I

percent H 0, 50 vol. percent of the .B25B" bubbles and 0.2 vol. percent (i.e., 1 wt. percent of the aqueous phase) of Bentone LT (trademark of National Lead Co.) having a density of 0.62 g/cc. and, after sealing in a polyester bag, was found to have very similar properties, including excellent suspension stability.

EXAMPLE 2 The following formulation was prepared as in Example 1:

Properties similar to B25 B Glass Bubbles, but nominal average particle density is only 0.20 g/cc.

The density of this formulation was 0.60 g/cc. The suspension stability and mobility of the bubbles, after sealing in a polyester bag, were found to be very good.

The same formulation, but without the Bentone LT, was found to have poor suspension stability. A polyester bag containing this unmodified water/glass bubble mixture became stiff and not particularly suitable for use as a cushion due to packing of glass bubbles just under the upper surface of the bag. The use of 0.25 percent by weight of the"Bentone reduced this packing problem somewhat but did not provide a completely stable suspension.

What is claimed is:

1. An incompressible, conformable structure comprising:

a liquid-impermeable flexiblewalled container containing therewithin a room-temperatureincompressible, conformable mixture, said mixture being capable of being pumped and having a density less than 1.0 gram per cubic centimeter, said mixture comprising a continuous liquid phase and, suspended therein in an amount accounting for at least 30 volume-percent of the mixture, hollow, liquid-impervious filler particles comprising a-solid wall completely enclosing a fluid-containing core, s id filler particles being less than about 5 mm. in diameter and having an average true particle density less tha n 1.0 gram per cubic centimeter and less than the density of said continuous liquid phase, the amount of said filler particles contained in said mixture being insufficient to prevent the pumpability and conformability of said mixture at room temperature.

2. A structure according to claim 1 wherein said continuous liquid phase comprises water and said filler particles have a true particle density less than 0.6 gram per cubic centimfitfir.

flexible-walled container.

5. An article of furniture comprising 1. a cushioning means, said cushioning means comprising (a) a liquid-impermeable flexible-walled container, and, contained therewithin, (b) a roomtemperature-incompressible, conformable mixture capable of being pumped and having a density less than 1.0 gram per cubic centimeter, said mixture comprising a continuous aqueous liquid phase and, suspended therein in an amount accounting for at least 30 volume-percent of the mixture, hollow substantially spherical unicellular liquid impervious particles l-500 microns in diameter having a true particle density less than 0.6 gram per cubic centimeter, and less than the density of said contin uous liquid phase, and the amount of said particles contained in said mixture being insufficient to prevent the pumpability and conformability of said mixture at room temperature, and 2. a frame means forsupporting said cushioning means. 6. Article according to claim 5 wherein said frame means is a bed frame, and said cushioning means is a mattress provided with an aperture means for introducing or removing a liquid material.

7. A structure according to claim 1 in which said wall of the tiller particles comprises glass.

8. A structure according to claim 1 in which the tiller particles are spherical unicellular particles.

9. A structure according to claim 8 in which said wall of the filler particles comprises glass.

10. An incompressible, conformable structure comprising:

a liquid-impermeable flexible-walled container containing therewithina room-temperatureincompressible and conformable mixture, said mixture being capable of being pumped and having a density less than 1.0 gram per cubic centimeter, said mixture comprising a continuous liquid phase that contains a viscosity modifying agent and, suspended therein in an amount accounting for at least 30 volume percent of the mixture, hollow,

rounded liquid-impervious filler particles comprising a solid glass wall completely enclosing a fluidcontaining core, said filler. particles being less than about 5 mm. in diameter and having an average true particle density less than 0.6 gram per cubic centimeter and less than the density of said continuous liquid phase, the amount of said filler particles contained in said mixture being insufficient to prevent the pumpability and conformability of said mixture at room temperature.

11. A structure of claim 10 in which the particles are spherical unicellular particles.

12. A structure of claim 10 in which the particles account for between 40 and 60 volume-percent of said mixture.

13. A structure of claim 10 in which the particles account for at least 50 volume-percent of said mixture.

Claims

2. a frame means for supporting said cushioning means.
2. A structure according to claim 1 wherein said continuous liquid phase comprises water and said filler particles have a true particle density less than 0.6 gram per cubic centimeter.
3. A structure according to claim 1 wherein said continuous liquid phase contains a viscosity modifying agent.
4. A structure according to claim 1 wherein said structure further comprises a support means for providing dimensional stability for said liquid-impermeable flexible-walled container.
5. An article of furniture comprising
6. Article according to claim 5 wherein said frame means is a bed frame, and said cushioning means is a mattress provided with an aperture means for introducing or removing a liquid material.
7. A structure according to claim 1 in which said wall of the filler particles comprises glass.
8. A structure according to claim 1 in which the filler particles are spherical unicellular particles.
9. A structure according to claim 8 in which said wall of the filler particles comprises glass.
10. An incompressible, conformable structure comprising: a liquid-impermeable flexible-walled container containing therewithin a room-temperature-incompressible and conformable mixture, said mixture being capable of being pumped and having a density less than 1.0 gram per cubic centimeter, said mixture comprising a continuous liquid phase that contains a viscosity modifying agent and, suspended therein in an amount accounting for at least 30 volume percent of the mixture, hollow, rounded liquid-impervious filler particles comprising a solid glass wall completely enclosing a fluid-containing core, said filler particles being less than about 5 mm. in diameter and having an average true particle density less than 0.6 gram per cubic centimeter and less than the density of said continuous liquid phase, the amount of said filler particles contained in said mixture being insufficient to prevent the pumpability and conformability of said mixture at room temperature.
11. A structure of claim 10 in which the particles are spherical unicellular particles.
12. A structure of claim 10 in which the particles account for between 40 and 60 volume-percent of said mixture.
13. A structure of claim 10 in which the particles account for at least 50 volume-percent of said mixture.