Title:
INSOLE STRUCTURE
United States Patent 3724106


Abstract:
An insole structure for footwear comprised of upper and lower surfaces which form one or more internal cavities within the body of the structure, the cavities so formed containing a fluid such as water, air or a gel, providing thereby a durable and comfortable means for cushioning and supporting the feet inside footwear such as shoes, sandals, slippers and/or boots. The present invention may find embodiment in (i) a flexible contoured insole designed for insertion into conventional footwear or (ii) in footwear having the invented insole structure built into and made and integral part thereof. The shape, location, height, etc., of the cavities can be designed to achieve particular therapeutic objectives such as the support of weak arches.



Inventors:
MAGIDSON H
Application Number:
05/158018
Publication Date:
04/03/1973
Filing Date:
06/29/1971
Assignee:
MAGIDSON H,US
Primary Class:
International Classes:
A43B17/02; A43B17/03; (IPC1-7): A43B13/38
Field of Search:
36/44,29
View Patent Images:
US Patent References:
3589037FOOT CUSHIONING SUPPORT MEMBER1971-06-29Gallagher
3449844PROTECTIVE INNER SOLE1969-06-17Spence
3120712Shoe construction1964-02-11Menken
2762134Cushioning insoles for shoes1956-09-11Town
2677906Cushioned inner sole for shoes and meth od of making the same1954-05-11Reed
2477588Hydraulic insole1949-08-02Dumm
2221202Cushion foot support for shoes1940-11-12Ratcliff
2084517Pneumatic insert for shoes1937-06-22Vogel
1869257Insole1932-07-26Hitzler
1712387Insole for shoes1929-05-07Kajiyama



Foreign References:
GB856622A
Primary Examiner:
Guest, Alfred R.
Claims:
I claim

1. An insole adapted for insertion into a conventional article of footwear comprising:

2. The insole of claim 1 wherein said structure has a plurality of perforations located in portions thereof displaced from said internal cavity, said perforations being adapted to enable the circulation of air through said structure.

3. In an article of footwear, and integral thereto, an insole comprising:

4. In an article of footwear having an inner sole, an insole providing cushioning and support to the foot of a wearer comprising:

Description:
BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of footwear, and more particularly to insoles and innersoles for foot cushioning and/or supporting structures.

2. Prior Art

The use of insoles for enhancing the comfort of footwear is not new. The prior art shows a number of such structures. One type of insole disclosed by the prior art is the foamed rubber thermoplastic insole designed to be inserted into the wearer's footwear. This type of insole is typically comprised of a sheet of cushioning material (e.g., foamed rubber) layered with one of a pair of relatively thin outer sheets of suitable material. In another structure of this type the cushioning material may be fully enclosed within an outer structure. Regardless of their variations, insoles of this type all suffer from the Same disadvantage, to wit: the deterioration and/or compression of the cushioning material and the resultant loss of resilience thereof. In some cases the cushioning material may even desintegrate, rendering the insoles useless as well as uncomfortable due to lumps and voids therein.

Another type of prior art insole is the medicated insole having encapsulated within an outer structure one or more medicating materials such as (i) foot powder or (ii) rupturable plastic capsules containing scented, cooling, germicidal and/Or fungicidal substances. Insoles of this type typically have an upper section made of a porous material in order to allow the powder or other appropriate substance to pass through to the user's feet. These insoles have the disadvantage of higher cost because of the necessary inclusion therein of the consumable material. The prior art discloses means for replenishing the supply of powder or other consumable material in this type of insole. As a result, however, the user must bear the cost of continual replacement of the material in order to continue to use the insoles. On the other hand, some of the structures disclosed by the prior art provide no means for replenishing the consumable material. In these cases, when the consumable is depleted, the entire insole becomes useless and must be replaced.

A further disadvantage of medicated insoles is they provide little cushioning of the feet. This is because they are conceived and designed primarily as dispensers of powder or other medicated substances and not as foot cushioners. In the first place, powders and small plastic capsules have little resilience; secondly, because of internal shear forces, powder and plastic capsules cannot rapidly and uniformly distribute the pressure applied by the weight of the user. As a result, insoles of this type lack good cushioning characteristics.

The present invention overcomes these shortcomings of the prior art by disclosing a novel structure which utilizes a fluid, such as, for example, water, as the cushioning medium encapsulated within one or more cavities within the body of the structure. Unlike the prior art insoles which use foamed rubber or foamed thermoplastic material, the fluid used in the present invention does not deteriorate or compress under the temperature, pressure, and Moisture conditions to which insoles are subjected. In addition, unlike the medicated insoles, the Present invention does not utilize or rely upon relatively expensive and consumable materials in order to have a comforting effect upon the feet. And, further, the use of a fluid as the cushioning medium results in a more comfortable insole than that which is possible when powder or small plastic capsules are used. This result is attributable to the well knoWn physical property Of fluids under pressure, to wit: the property of distributing the applied pressure uniformly and almost instantly throughout the fluid. Thus, the encapsulated fluid immediately redistributes itself within its cavities so that (i) the upper section of the insole conforms to the contour of the bottom surface of the user's foot where these surfaces are in contact; and (ii) the supporting force provided by the fluid is applied uniformly over the contacting surface of the user's foot. As a result of this property of fluids, the present invention provides a highly comfortable sensation to the user, a sensation which has heretofore not been achievable.

SUMMARY OF THE INVENTION

The present invention is a novel insole structure which cushions and supports the user's feet during the wearing of footwear such as shoes, sandals, an integral and/or boots. The present invention insole can either be an integral part of the item of footwear or a separate structure designed for insertion into footwear.

The present invention is comprised of upper and lower contoured surfaces which together form one or more internal cavities within the body or the structure. The cavities so formed contain a suitable fluid, such as water, which serves as the cushioning and supporting medium of the insole. The fluid within the cavities is entrapped; since it is normally unable to escape, the fluid lasts for the life of the insole structure. The fluid filled cavities can be located so as to provide support to particular portions of the foot.

The invention insole structure achieves its unique cushioning and supporting effect by utilizing the well known property of fluids; i.e., the property of distributing applied pressure uniformly and almost instantly throughout the fluid. Thus, when the user's weight is applied to the invented structure the fluid in the cavities immediately redistributes itself therein causing the upper surface of the insole to conform to the bottom contour of the user's foot where these surfaces are in contact, while, at the same time, supporting the foot with uniform pressure over its contacting surface. The effect is a pleasantly cushioned but firm sensation of comfort While wearing footwear.

The benefits of the present invention are not limited to providing comfort to wearer's of footwear. The invented insole structure can also have a therapeutic effect upon feet which are not healthy in one or more respects. The shape, location, contour and height of the cavities, and the elasticity of the insole material can be selected so as to provide the degree of cushioning and support which is desired to those portions of the foot where it is needed. For example, the invented insole can readily be configured to provide support to weak arches.

In practicing the present invention embodiments thereof can be either structurally independent of the item of footwear or an integral part of it. In the former case the invented insole is contoured to be inserted into and to fit properly in a corresponding sized shoe, slipper, etc.

Embodiments of the present invention which are structurally independent of the footwear are comprised of relatively thin upper and lower contoured surfaces made of a flexible non-porous material, such as polyethylene, vinyl or elastomeric plastic. In some embodiments of this type, the upper surface is flat and has an outer contour which conforms to the contour and style of the footwear into which it is to be inserted. The lower surface also has an outer contour conforming to that of the footwear. However, the lower surface is not flat, but configured to provide one or more raised (three-dimensional) regions. It is the raised regions of the lower surface which in combination with the upper surface, form the internal cavities of the invented insole structure. In other structurally independent embodiments of the present invention the lower surface is flat while the upper surface provides one or more raised regions which, together with the lower surface, form the internal cavities. One application of the latter embodiment would be found in an insole structure configured to provide support to the arch of the foot.

The present invention also contemplates structurally independent embodiments which can be characterized as partial insoles; i.e., insoles configured to cushion and support only one portion of the wearer's foot such as the heel, arch, or ball. Typically such partial insoles have a single fluid-filled cavity and an outer contour which conforms to the portion of the foot for which they are adapted.

Those embodiments of the present invention which are configured to fit within an item of conventional footwear must necessarily be relatively thin. A preferred overall thickness is about 1/8 inch; however, this constraint is not necessarily applicable in the vicinity of the arch of the foot.

With respect to embodiments of the present invention which are structurally part of the footwear, there are two which are preferred. The first is comprised of upper and lower surfaces of a flexible non-porous plastic, such as polyethylene, vinyl or elastomeric plastic, each surface being cemented and/or sewn into the structure of the item of footwear during the construction process. The two surfaces form one or more cavities with the body of the structure in which a suitable fluid is contained to provide the desired cushioning and support. In a second preferred embodiment of the type, the inner sole of the item of footwear is utilized as the lower surface of the invented insole structure. Accordingly, the inner sole has formed in its upper region one or more compartments which, in combination with the upper surface, form the fluid-containing cavities of the structure. The compartments are typically located so that the cushioning and support provided by the fluid is applied to one or more portions of the foot as desired. The upper surface of the insole structure is disposed on top of the inner sole of the item of footwear and cemented and/or sewn therein, sealing the compartments in the inner sole and thereby forming the inner cavities. The fluid contained in these inner cavities provides the cushioning and support of the user's foot which is characteristic of this invention. As in other embodiments of the present invention, the upper surface is typically a flat piece of flexible non-porous material such as polyethylene vinyl or elastomeric plastic.

The user's foot interfaces with the top of the upper surface of the structure. Consequently, in order to enhance the comfort of using the invented insole, preferred embodiments include a moisture-absorbing fabric or other suitable covering secured to the top of the upper surface for the purpose of reducing the build-up of a moisture during use.

The fluid which is encapsulated in the cavities within the body of the structure is a suitable non-compressible fluid such as water, air or a gel. The viscosity of the fluid is a variable, the selection of which enables the designers to achieve a range of effects relative to the "feel" of the insole. The cavities are typically filled with the fluid up to the ambient barometric pressure; i.e., without causing any stretching of the flexible plastic material comprising the surfaces of the structure. Stretching of this material does occur, however, when the user's weight is applied to the insole, since there must be a redistribution of the fluid within the cavities.

In some applications, such as where support of the arch is sought, increased firmness may be required at a particular area of the insole structure. To achieve greater firmness, the fluid in a particular cavity can be maintained at a no-load pressure which is greater than the ambient air pressure. As a result, the elastic material comprising the structural surfaces will be stretched somewhat, even under no-load conditions. When the user's weight is applied to the insole, there will be less elasticity and, consequently, greater firmness.

It can be seen therefore, that by selecting the viscosity of the fluid, the pressure of the fluid in the cavities, and the elasticity of the material comprising the surfaces of the structure, the designer can achieve a broad range of support and cushioning effects in practicing this invention. In addition, the shape, contour, location and height of the cavities are variables which, by appropriate selection, enable a wide range of design objectives to be achieved.

Embodiments of the present invention can be made by plastic forming and footwear construction techniques which are known in the art. Plastic forming techniques suitable for making the flexible plastic surfaces of the invented insole structure include injection molding, vacuum molding and blow molding processes. Insertion of the fluid into the cavities can be accomplished while the upper and lower surfaces of the structure are being joined together, or afterwards by appropriate injection and sealing techniques.

Thus, it is an object of the present invention to provide a relatively inexpensive insole structure which comfortably cushions and supports the user's feet when wearing footwear.

It is still another object of the present invention to provide an insole structure which can be configured to have a therapeutic effect upon the feet of the user.

It is still yet another object of the present invention to provide a structure which is adapted for insertion into conventional footwear.

A further object, of this invention is to provide a structure which is built into and made an integral part of footwear.

Other objects novel features and advantages of the present invention will become apparent upon making reference to the following detailed description and the accompanying drawings. The description and the drawings will also further disclose the characteristics of this invention, both as to its structure and its mode of operation. Although preferred embodiments of the invention are described hereinbelow, and shown in the accompanying drawing, it is expressly understood that the descriptions and drawings thereof are for the purpose of illustration only and do not limit the scope of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings in which are illustrated preferred embodiments of the present invention:

FIG. 1 is a top perspective view of a first embodiment of the present invention, showing an insole which is configured to be inserted into conventional footwear.

FIG. 2 is a cross-sectional view of the insole structure of FIG. 1 taken along lines 2--2 of FIG. 1.

FIG. 3 is a cross-sectional view of the insole structure of FIG. 1 taken along lines 3--3 of FIG. 1.

FIG. 4 is a longitudinal cross-sectional view of another embodiment of the present invention, showing a therapeutic shoe adapted to support the wearer's arches.

FIG. 5 is a transverse cross-sectional view of the shoe of FIG. 4 taken along lines 5--5 of FIG. 4.

FIG. 6 is a longitudinal cross-sectional view of still another embodiment of the present invention, showing a shoe having fluid filled compartments in its inner sole.

FIG. 7 is a top perspective view of a further embodiment of the present invention showing a single cavity insole partial insole adapted to cushion and support the ball of the foot.

FIG. 8 is a top perspective view of another embodiment of the present invention showing a single cavity partial insole adapted to cushion and support the arch of the foot.

FIG. 9 is a top perspective view of a further embodiment of the present invention showing a single cavity insole partial insole adapted to cushion and support the heel of the foot.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 1-3 a first embodiment of the present invention is described, generally designated by the reference numeral 8. This first embodiment is an insole structure which is adapted for insertion into an item of conventional footwear, such as shoes, boots, slippers and/or sandals. It is comprised of an upper surface 10 and a lower surface 12 made of a flexible, non-porous polyethylene, vinyl or elastomeric plastic. In this first embodiment 8, the upper surface 10 and lower surface 12 are separate sections joined together by a suitable cement or other means for joining plastic materials. However, it should be understood that the present invention also contemplates embodiments wherein the upper and lower surfaces 10 and 12 comprise a continuous and integral structure. The upper surface 10 and the lower surface 12 have outer contours which comform to the contour and style of the footwear into which embodiment 8 is to be inserted during use. Upper surface 10 is a flat piece of material, while lower surface 12 has raised contoured regions 12a, 12b, 12c and 12d. When joined together surfaces 10 and 12 form cavities 14a - 14d in which a suitable non-compressible fluid 14' is contained (FIG. 2). Thus, it is clear that in embodiments wherein surfaces 10 and 12 are separate members, their union must be such that a suitable seal is formed. In embodiment 8, the fluid 14' contained in cavities 14a - 14d provides cushioning and support to the various portions of the foot, namely; the toes, ball, instep and heel respectively. The present invention contemplates embodiments having more or less than four cavities, as well as cavities at different locations and of different shapes and contours. In addition, this invention also contemplates embodiments having a flat lower surface and a raised upper surface, the reverse of embodiment 8, as well as embodiments whose upper and lower surfaces each have raised regions. An embodiment of the latter type is depicted in FIG. 4 and described more fully hereinbelow.

A suitable moisture-absorbing fabric covering 16, preferably cotton, is disposed over the entire top of upper surface 10. Thus, during use, the user's feet come into contact with covering 16 instead of the plastic material comprising upper surface 10. Covering 16 absorbs the moisture normally generated in footwear and thereby, enhances the comfort to be derived from use of the invented insole. Covering 16 may be cemented to the top surface of section 10 or joined by other suitable techniques known in the art. FIGS. 2 and 3 depict the covering 16 cooperatively engaged by a lip 18 extending around the periphery of upper surface 10 and is similar to that described in applicant's U.S. Pat. No. 3,599,353 issued on Aug. 17, 1971. Lip 18 is an integral part of upper surface 10 and provides additional means for securing the covering 16 to the top of surface 10. Lip 18 will also prevent the edge of covering 16 from fraying or otherwise becoming disengaged. The extent to which the covering 16 is secured by the lip 18 is best seen by reference to FIGS. 2 and 3. The preferred length of lip 18, that is, the extent to which it overlaps covering 16, is about 1/32 inch. Although covering 16 can be any suitable moisture-absorbing fabric, it is preferable that the fabric have a backing of flexible plastic on the side interfacing with the top of upper surface 10. Such backing would enhance the adhesion of covering 16 to surface 10.

Walls 13a, 13b, 13c, and 13d of raised regions 12a - 12d respectively are configured at an angle, with reference to the vertical, which ensures that they collapse under the weight of the wearer's feet; i.e., by configuring the walls 13a - 13d at such an angle, they are prevented from providing their own rigid structural support. As the angle of the walls 13a - 13d approaches the vertical, the walls 13a - 13d tend to act increasingly as rigid support members. At the proper angle, typically in the region of 45°, the walls smoothly give way under the user's weight and enable the insole support to be provided by the fluid 14'.

Since embodiment 8 is adapted for insertion into conventional footwear, an overall thickness of about 1/18 of an inch is preferred.

The fluid 14' can be water or other appropriate liquid, air or a gel having a suitable viscosity. The fluid 14' is the cushioning and supporting medium of the invented insole. When the weight of the user's foot is applied to the upper section 10, fluid 14' in the cavities 14a-14d immediately redistributes itself therein until the upper surface 10 conforms to the contour of the bottom surface of the user's foot whenever these surfaces are in contact. In addition, since it is a property of fluids to distribute applied pressure uniformily throughout the fluid, uniform support is applied to the user's foot over its contacting surfaces. As a result the user's weight is supported uniformly over a greater area of his feet than is the case with non-fluid supporting means. Thus, a firm, but pleasantly cushioned sensation of comfort is achieved while wearing footwear.

The viscosity of fluid 14' and the elasticity of the plastic material comprising surfaces 10 and 12 determine to a great extent the "feel" of the invented insole; in addition, the no-load pressure at which fluid 14' is maintained in cavities 14a - 14d is a variable which has an effect upon the firmness, and therefore the "feel," of the insole. As the no-load pressure of fluid 14' increases above the ambient atmospheric pressure, the flexible plastic material comprising surfaces 10 and 12 is stretched. To the extent there is such non-load stretching, there is a corresponding decrease in the ability of the material to stretch further when the user's weight is applied to the insole. Consequently, the user's weight is supported at a higher pressure applied over a smaller area of his feet, resulting in a firmer feeling of support. In some applications in which this invention may be practiced, greater firmness at a particular portion of the insole is desirable, such as where the insole is used to support the user's arches. Such an application is more fully described hereinbelow with respect to a second embodiment of the invention.

The benefits of the present invention are not limited to enhancing the comfort of conventional footwear. The invention can be practiced so as to provide a therapeutic benefit for certain foot problems. For example, consider a user who has a sensitive area on the sole of his foot due to a callous or a cut. Since the present invention is better adapted than conventional insoles to uniformly distribute the applied pressure over a larger area of the foot, there is an immediate benefit to such a user by virtue of the fact that less pressure is applied to the sensitive area. In addition, an embodiment of the present invention can be designed which even further reduces the pressure applied to the sensitive area. For example, by providing a donut-shaped raised region on the upper surface of the insole structure, a region coming into contact only with the area of the user's sole surrounding the sensitive area, the pressure on the sensitive area can be reduced substantially.

Another therapeutic application of the present invention relates to the support of weak arches. With reference to FIGS. 4 and 5, a second embodiment, a therapeutic shoe 30 configured for use by persons with weak arches, is described. In this embodiment the insole structure is an integral part of the shoe 30 and is incorporated therein during the process of shoe construction. The insole structure is comprised of an upper surface 32, having a raised contoured region 32c in the vicinity of the arch, and a lower surface 34 having raised regions 34a, 34b, and 34d. Surface 34 is disposed upon the inner sole 35 and is secured thereto, as well as to the structure of shoe 30, by conventional techniques known in the art. Surfaces 32 and 34 are made of a flexible plastic material such as those disclosed hereinabove. When joined, they form cavities 36a - 36d which contain a fluid 36' in the same manner as described above with reference to the embodiment shown in FIG. 2. Of particular interest in this, second embodiment 30 is the raised region 32c of surface 32 which forms cavity 36c. It is shaped to conform to the normal contour of the arch of a human foot and is located with respect thereto. The fluid 36' in cavity 36c is preferably one having a high viscosity. The no-load pressure of fluid 36' in cavity 36c and the elasticity of the plastic material comprising surface 32 can be selected by those skilled in the art so that the insole structure in the vicinity of the user's arch provides firm support thereto.

A moisture-absorbing covering 38 is preferably disposed upon the top of surface 32 and secured thereto, as well as to the structure of shoe 30 by means known in the art.

The manner in which the insole structure of this second embodiment 30 provides cushioning and support to the user's feet is the same as that described above with respect to the first embodiment. As is the case with respect to the first preferred embodiment described hereinabove, walls 37a, 37b and 37d of raised regions 34a, 34b and 34d are at an angle with respect to the vertical, typically 45°, which ensures that they smoothly give way under the user's weight and thereby not provide their own rigid structural support.

A third preferred embodiment, of the present invention is shown in FIG. 6, the insole being disposed within shoe structure 40. In this embodiment, as in the second embodiment, the present invention insole structure is an integral part of the shoe 40 and is incorporated therein during the process of manufacturing the shoe 40.

An inner sole 42 of the shoe 40 is utilized to provide the lower surface of the insole structure. Compartments 44a - 44d are configured in the upper region of the inner sole 42 to a depth of about 1/8 of an inch. The area, shape and location of the compartments 44a - 44d are selected to provide cushioning and support to particular portions of its foot. In this preferred embodiment of the present invention 40, four compartments are depicted so that cushioned support is provided to the toes, ball, instep and heel respectively. An upper surface 46 is disposed over the inner sole 42 and secured thereto, as well as to the structure of shoe 40, by methods known in the art. Surface 46 is made of a flexible plastic material, preferably of one of the kinds described above. The joining of surface 48 to inner sole 42 seals the compartments 44a - 44d which become the internal fluid 44' filled cavities characteristic of the invented insole structure. The manner in which the above described structure provides cushioned support to the user's feet is the same as has been described with respect to the first embodiment.

A moisture-absorbing covering 48 is preferably disposed upon the top of surface 46 and secured thereto, as well as to the structure of the shoe 40.

An additional feature which is preferable in the embodiments of the present invention is the presence of air holes or channels 90 in the insole structure at locations which do not effect the structure's capability to contain the fluid in the cavities therein. The purpose of such air holes or channels is to enable the circulation of air within the item of footwear; i.e., to enhance the ventilation of its inner regions.

The present invention also contemplates embodiments, structurally independent of the footwear, which can be characterized as partial insoles; i.e., insoles configured to cushion and support only one portion of the user's foot. These partial insoles are inserted into the item of footwear at the locations at which they are adapted for use. With reference to FIGS. 7-9 those preferred forms of the partial insole embodiments of this invention are shown. In FIG. 7 insole 50, adapted to support and cushion the ball of the foot, is shown. It has a single fluid-filled cavity formed, as in the other embodiments, by upper and lower surfaces, the lower surface having a single raised region 52 with sloping walls 54. In FIG. 8 an insole 60, adapted to support and cushion the arch of the foot, is shown. It too has a single fluid-filled cavity similar in construction to that of insole 50. FIG. 9 depicts a similar single cavity insole 70 adapted to support and cushion the heel. These three embodiments also contemplate the addition of a moisture-absorbing fabric, secured to the top of the upper surface, to enhance the user's comfort by reducing the build-up of excess moisture.

The plastic surfaces which comprise the invented insole structure can be produced by conventional plastic forming techniques such as injection molding, vacuum molding or blow molding. When either injection molding or vacuum molding processes are utilized, the upper and lower surfaces are typically separate elements and must be joined together with leakproof bond. This can be accomplished by methods and materials known in the art. The fluid which is encapsulated in the cavities formed within the body of the insole structure can be encapsulated during the process of joining the upper and lower section of the structure, or afterwards, by known fluid injection and sealing techniques.

With reference to FIGS. 1-3, a fabric covering 16 was described, secured to the top of upper surface 10 along its edges by a lip 18 of upper surface 10. This configuration can be produced during the injection molding of the upper surface 10 in a similar manner to that described in applicants U.S. Patent identified hereabove. Prior to injecting the plastic material into the mold, the covering 16 is inserted into the mold, the outer edge of which extends approximately 1/32 of an inch into the area that will be permeated with the injected plastic. Thus, when the plastic material is injected, the lip 18 will form around the outer edge of the covering 16, thereby securing it to the top of the upper surface 10.

The insole structure which is structurally independent of the item of footwear, i.e., the first preferred embodiment disclosed above, lends itself to production by the techniques of blow molding. By this method, an integral structure is formed. This has the advantage of eliminating the steps of bonding separate upper and lower surfaces; and further, it eliminates the risk of fluid leakage due to defective bonding. Blow molding an insole adapted for insertion into footwear, of course, is done while the plastic material is in a semi-molten state. After the structure is molded, and while the plastic is still semi-molten, the upper and lower surfaces are joined in the areas between the raised regions by the application of heat and pressure. In this manner separate sealed internal cavities are formed. The fluid is injected into the cavities by means of an appropriate injection apparatus, after which the hole caused during injection is heat sealed.

Other embodiments, modifications and extensions of this invention will become apparent to those skilled in the art. All such variations which basically rely on the teachings which this invention has advanced are considered within the spirit and scope of this invention.