Adjustable Mattress For Pregnant Mothers

Abstract

A body resting on a mattress is uniformly supported because a layer of substantially non-resilient but flowable material below the top resilient layer of the mattress distributes itself to conform to the general contour of the body. The flowability of the non-resilient material is controlled. The mattress may have the envelope that contains the non-resilient flowable material divided into compartments with means to alter the support given by each compartment, and said means may be programmed so the mattress massages the body.

Description

BACKGROUND OF INVENTION

The human body is of irregular contour, and this is particularly true of pregnant mothers. When the body lays on a relatively hard flat surface those surfaces of the body that are farthest from its head-to-foot axis make contact and bear the full load of the body, and the unit load on these areas being relatively high the blood circulation near these areas is impaired so that the body becomes distressed and must change position frequently to obtain some temporary relief. This problem is particularly acute for pregnant mothers who in advanced pregnancy cannot comfortably lay on their stomach or sides. Mattress materials of plant fibers, animal hair and feathers have been used since ancient times and some modern mattresses combine similar materials with metal springs in various configurations to attempt to achieve a more comfortable sleeping posture for the body but these spring arrangements are generally expensive, unadjustable and are so large that they do not effectively conform to the sharp irregularities of the body's contour. A mattress in which the support to the body is unadjustable is seldom satisfactory because when it is too soft the heavy parts of the body sink deep into the mattress which distorts the body, obstructs easy movement and in summer time can be unbearably hot. When a mattress is too hard it defeats its purpose.

SUMMARY

In accordance with the present invention a structure is made of an envelope, at least part of which is flexible and of low stretchability, in which is confined a substantially non-resilient flowable material, the flowability of which is controlled by controlling the force with which the structure, and envelope, resist the further motion of the flowable material, and a resilient material on which the body to be supported rests, covering at least one flexible surface of the envelope. The structure may be sub-divided into separate compartments in which different flowability characteristics of the flowable material may be maintained, or, alternately, in which the flowability of the flowable material in each compartment may be continuously or intermittently altered by altering the volume of the envelope either mechanically or by altering gas pressure or liquid pressure in the envelope compartment thus causing the slightly elastic envelope to increase in volume or decrease. This altering of the flowability of the flowable material by altering the volume of the envelope wherein the flowable material is contained may be done by programming means to provide the desired conformability of the structure to an irregularly contoured externally applied load. The programmed altering of the external mechanical pressure on the envelope or the altering of gas pressure or liquid pressure in the envelope causes motion of the structure and massages the body. Mattresses, pillows, furniture, body braces, shipping containers and other items can be made in accordance with this invention.

IDENTIFICATION OF DRAWINGS

FIG. 1 is a schematic showing a bed mattress consisting of an envelope containing non-resilient flowable material and a layer of resilient material.

FIG. 2 is a sectional view of a portion of FIG. 1.

FIG. 3 is a diagram of an arrangement of non-resilient rounded particles and the forces acting on them.

FIG. 4 is a sectional view of a portion of FIG. 1 with an irregularly contoured body reclining on the mattress.

FIG. 5 is a sectional view of a mattress in which a predetermined volume of a resilient material is included in the envelope.

FIG. 6 is a sectional view of a mattress having a plurality of compartments.

FIG. 7 is a sectional view of a mattress in which the envelope is in a container.

FIG. 8 is a sectional view of a mattress with mechanical means for adjusting the flowability of the non-resilient material.

DESCRIPTION OF EMBODIMENTS

A mattress of FIG. 1 includes an envelope 10, at least one surface of which is flexible and of low stretchability, containing substantially non-resilient flowable material and a layer of resilient material 12.

FIG. 2 is a sectional view of FIG. 1 showing the envelope 10, the layer of resilient material 12 and the non-resilient flowable material 11. The shape of the envelope, the elasticity of the material from which the envelope is made, and the quantity of non-resilient flowable material in the envelope may be selected to obtain the desired flowability of the flowable material for a predetermined load to be supported by the mattress.

It has been discovered that a substantially non-resilient flowable material of discrete particles having rounded contours has the property of flowing readily when a pressure at one part of the mass of flowable material is higher than another part up to the point where there is only a small difference between the force with which one particle tries to move in a given direction and the force with which another particle lying in its path resists that motion and under these conditions these particles lock into position and cease to flow. This is illustrated and explained in the diagram of FIG. 3 where an arrangement of five spherical substantially non-resilient particles in a single plane are illustrative of what occurs in a large mass. Although spherical particles are used in the illustration the phenomena is similar with particles that are not spherical but are well rounded. When a force F1 is applied B tends to move A in the direction of the force but the motion of A is resisted by the force F2 transmitted through D. A does not move when F1 and F2 are equal as the particles are then in a fluid-like situation where the " pressure" is uniformly distributed throughout the mass. When a force, such as the weight of a reclining body, is applied in one part of an envelope containing a mass of non-resilient spherical particles the particles adjacent to where the weight is applied are subjected to a much higher force tending to move them than the forces tending to resist such motion, and for example, F1 in the illustration would be much higher than F2 and A would move, and push D ahead of it, in the direction of force F1 until further motion of D is restrained with a greater force than previously, as would occur for example when D was forced deeper into a resilient material, until finally the force resisting the further motion of D would approach in magnitude the force impelling A towards D and further motion of D and of A would cease. As described above the action is consistent with that of a perfect fluid, that is one in which there are no shearing forces. To understand the functioning of this invention it is very important to note that in FIG. 3 there are other forces that give unique characteristics to the flowability of the substantially non-resilient flowable material and these are the forces, similar in magnitude to F2 which press spheres E and C respectively against A and consequently tend by static friction at the interface to prevent the motion of A in the direction of D even when the force F1 is greater than F2. Consequently in an extended system of spheres each subject to the same force F2 at all interfaces there can be no motion of a sphere such as A due to increasing the force on a sphere such as B from F2 to F1 until F1 is greater than F2 plus four k F2 where k is the static coefficient of friction between spheres such as E and A and where this coefficient k is about 0.5, a common value of the coefficient of friction for dry wood on dry wood, F1 must be substantially greater than 3 times F2 before there will be motion of A, and for values of F1 between F2 and 3 times F2 there will be no motion and the position of the spheres will be stationary and in effect locked. If the spheres are wood and they are wet with water or oil k is about 0.25 and F1 must substantially exceed 2 times F2 before there will be motion. This action resembles that of thixotropic materials. Although FIG. 3 shows a symetrical arrangement of spheres which would not ordinarily occur in a mass of spheres the principles that determine action in a random mass of spheres are the same. In accordance with this invention the force resisting motion of the spheres, corresponding to F2, is the inverse of the property herein referred to as "flowability," and is controlled in various ways including, but not limited to (1) using an envelope of predetermined stretchability and predetermined shape, or alternately (2) including in the envelope a predetermined quantity of a material of predetermined resiliency, or alternately (3) the combination of (1) and (2), or alternately (4) in combination with (1), (2) or (3) applying to the envelope an external mechanical force, either constant or varying, sufficient to control the flowability of the flowable material or (5) which may be used in combination with (1), (2), (3) or (4) altering the coefficient of friction between the particles constituting the non-resilient flowable material.

FIG. 4 is a sectional view of a portion of FIG. 1 with an irregularly contoured body 13 reclining on the mattress illustrating how the non-resilient flowable material 11 flows to take the general contour of the body resting upon the mattress before the flowable material 11 locks up and maintains its position and illustrating how, after this has occurred the resilient material 12 provides a substantially uniform support to all parts of the reclining body 13.

FIG. 5 is a sectional view of a mattress in which a predetermined volume of a resilient material 14, such as but not limitqd to a volume of flexible open cell urethane foam or a gas impervious envelope filled with pressurized gas, is included in the envelope 10 that contains the non-resilient flowable material 11 and a layer of resilient material 12. In a preferred embodiment of this invention by proper selection of the stretchability of the envelope and proper selection of the volume and the resiliency of resilient material 14 enclosed inside the envelope, and by proper distribution of this resilient material 14 inside the envelope 10 along the top inside surface of the envelope 10 the resilient material also performs the function of the layer of resilient material 12 which is normally outside of the envelope 10 and in this case the layer of resilient material 12 outside of the envelope may be reduced in thickness or even eliminated.

FIG. 6 is a sectional view of a mattress having an envelope 10 with partitions 15 and 16 of flexible substantially non-stretchable material bonded to the inside of the envelope 10 and dividing it into separate compartments 17, 18 and 19, each compartment containing non-resilient flowable material 11, and predetermined volumes 20, 21 and 22 of resilient materials which are selected in combination with the shape and elasticity of the envelope and the volume of non-resilient flowable material in each compartment to give in each of the compartments separately the desired flowability of the flowable material for that compartment and the desired support by that compartment to the reclining body.

FIG. 7 is a sectional view of a mattress in which the envelope containing the non-resilient flowable material 11 is composed of a rigid frame 23 to which is secured along the top edge of the rigid frame a sheet of flexible material 24 which may be thick enough to have significant resilient properties and thus achieve the combined functions of (a) an envelope surface, (b) a volume of resilient material included in the envelope, and (c) a layer of resilient material on top of the envelope. In a variation of this arrangement the frame 23 may be of a relatively thick resilient flexible material having substantially the same thickness, flexibility and resiliency as the sheet of flexible material 24. For some applications it may be advantageous in the arrangement of FIG. 7 to also use a flexible envelope to enclose the flowable material 11, or, alternately, to enclose all of the structure shown in FIG. 7.

FIG. 8 is a sectional view of a mattress in which an envelope 10 containing non-resilient flowable material 11 is itself contained in a rigid frame 23 to the top edge of which is affixed a layer of resilient material 12, a plunger 25 is arranged so that it can be adjustably advanced into a part of the volume occupied by the envelope 10 so that the particles of flowable material in the envelope are forced to move upward against the constraining action of the envelope 10 and the constraining action of the layer of resilient material 12, this constraining action increasing the pressure between the flowable particles and reducing their flowability by the desired amount.

An example of a mattress similar to FIG. 2 has a 2 inch thick resilient layer of open cell urethane foam of 3 pounds per cubic foot density on the top surface of an envelope of 0.050 inch butyl rubber. Instead of urethane foam it is feasable to use foam rubber, sisal fibers, cotton, wool, horse hair, feathers or other cushioning materials. Instead of butyl rubber, it is feasable to use any textile or flexible sheet material of plastic, rubber, leather or similar products. The envelopes dimensions when filled are, for a single mattress, about seven feet long, four feet wide and six inches thick. The envelope is filled to these dimensions with a non-resilient flowable material which is hard-wood spheres having a diameter of three-eighths inch. Instead of hard-wood spheres it is feasable to use hollow or solid rounded particles of any organic, metal, ceramic, glass or plastic material having a load bearing capacity of at least about 3 pounds per square inch, and of any size from about one-sixteenth inch to about 1 inch. To enhance the flowability of the particles of flowable material it may be advantageous to at least partially coat the particles of flowable material with; a thin film of an elastomer such as, but not limited to, tetrafluoroethylene or neoprene rubber; graphite flakes; molybdenum disulphide flakes; or grease.

An example of a mattress similar to FIG. 6 has a 1 inch thick layer of open-cell urethane foam of 3 pounds per cubic foot density on the top surface of an envelope of nylon textile. The overall envelope dimensions when filled are 7 feet long, 4 feet wide and 7 inches thick. The partitions are parallel to the four foot dimension, are bonded to the top sides and bottom of the envelope so that the flowable material cannot readily pass from one compartment to another. The partitions are located so that the center compartment is 4 feet wide by 1 foot long and 7 inches deep. Each of the other compartments are 4 feet wide by 3 feet long by 7 inches deep. Inside the center compartment and adjacent to the inside top surface of the envelope is a pad of open-cell flexible urethane foam having a density of 4 pounds per cubic foot and normal dimensions of 4 feet by 1 foot by 2 inches thick. This center compartment is filled with hollow cellulose acetate balls one half inch in diameter in such quantity that with all the surfaces of the envelope and the partitions held flat at their nominal dimensions the pad of urethane foam in the compartment is compressed to half its normal thickness, or one inch. Inside each of the two other compartments is a pad of open cell flexible urethane foam adjacent to the inside top surface of the envelope having a density of 2 pounds per cubic foot and normal dimensions of 4 feet by 3 feet by 3 inches thick. Each of these compartments is filled with hollow cellulose acetate balls three eighths of an inch in diameter in such quantity that with all the surfaces of the envelope and the partitions held flat at their nominal dimensions the pad of urethane foam in each compartment is compressed to two thirds of its normal thickness, or two inches.

An example of a mattress similar to FIG. 7 has a supporting frame that is an open top box made of 2 inch thick plywood and having internal dimensions of 7 feet long by 4 feet wide by 8 inches deep. The inner surfaces of the box are lined with a sheet of one eighth inch thick flexible urethane foam to reduce the noise from movement of the plastic balls. The box is filled with balls of acetate that have been coated with tetrafluoroethylene to reduce the friction between the balls. Instead of coating the balls with tetrafluoroethylene they may be lubricated with flake molybdenum disulphite or a liquid such as oil or water. Across the top of the box and secured to the top edges of the box so that the plastic balls cannot leak out is a layer of open-cell flexible urethane having a density of 3 pounds per cubic foot a length of 7 feet and 4 inches, a width of 4 feet, 4 inches and a thickness of 2 inches. In a variation of this example the wooden box may be replaced by open-cell flexible urethane foam having a density of three pounds per cubic foot and the same dimensions as the wooden box and a flexible envelope may enclose the complete structure.

An example of a mattress similar to FIG. 9 has a supporting frame that is an open top box made of 11/2 inch plywood having internal dimensions of 7 feet long by 4 feet wide and 8 inches in height in which are set three separate flexible envelopes made of 0.030 inch neoprene-rubber, each having a width of 4 feet and a height of 8 inches and the center envelope having a length of 11/2 feet and the two outer envelopes each having a length of 23/4 feet so that the combined length of the three envelopes is 7 feet. Across the top of the three envelopes is a layer of open-cell flexible urethane foam of 2 pounds per cubic foot density 7 feet long by 4 feet wide by 2 inches thick. In the center envelope adjacent to the inner top surface is a piece of 2 pound per cubic foot density open-cell flexible urethane foam which has been sealed in a gas and liquid impermeable flexible cover of 0.020 inch neoprene rubber and having the overall dimensions of 4 feet wide by 11/2 feet long and 3 inches thick. In the other two envelopes are similar units except each having the dimensions of 4 feet wide by 23/4 feet long by 3 inches thick. Each of the envelopes is filled with a flowable material in sufficient quantity so that with all exterior surfaces of the envelope held flat at its nominal dimensions the 3 inch thickness of urethane foam in the envelope is compressed to 11/2 inches. In the bottom of each of the envelopes is sealed a liquid or gas entry means that is connected by pipes to a reversible hydraulic pump that draws liquid from a reservoir and forces it under pressure into the envelope, or alternately, removes liquid from the envelope and returns it to the reservoirs. A pressure indicating means is connected to the piping adjacent to the liquid entry means of the envelope to indicate the pressure in the envelope and signal it to the control box which then actuates to control the electric motor that drives the hydraulic pump so as to increase or decrease the gas pressure in the envelope in accordance with a predetermined program. With the air removed from the voids between the particles of flowable material in each envelope, the voids are filled with liquid to make the system operational. When the liquid in an envelope or envelopes is to be maintained at the same pressure for long periods, the liquid serving principally as a lubricant for the flowable particles, the pumping and programming means are not required.

Claims

The invention claimed is:

1. A structure consisting essentially of the combination of:

a. a flexible envelope having walls of a sheet material of relatively slight stretchability that are sufficiently free of pores as to retain the contents of the envelope, said envelope comprising at least one compartment

b. a flowable substantially non-resilient material having thixotropic properties filling the envelope

c. a means for controlling the flowability of the flowable material whereby the flowable material locks in position and does not flow when the desired shape of the flowable material has been obtained

d. a sheet of resilient material interposed between the flowable material and the body to be supported by the structure.

2. The structure of claim 1 in which there are a plurality of compartments in each of which separately a predetermined flowability of the flowable material may be established.

3. The structure of claim 1 in which the flowable material is composed primarily of sphere-like pieces of a substantially non-resilient material.

4. The structure of claim 1 in which the flowable material is lubricated by the particles of the flowable material having a thin coating oa an elastomer or materials yielding lower coefficient of friction than that of the flowable material on itself.

5. The structure of claim 1 in which the flowable material is lubricated by a liquid that fills or partially fills the voids between the particles of the flowable substantially non-resilient material.

6. The structure of claim 1 in which the sheet of resilient material is flexible urethane foam.

7. The structure of claim 1 in which the sheet of resilient material is inside the flexible envelope.

8. The structure of claim 1 in which all surfaces of the envelope are covered with resilient flexible material on either the outer surfaces of the envelope or on the inner surfaces of the envelope.