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Claims  |
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What is claimed is:
1. An inflatable cushion comprising: a flexible rectangular base formed
from a flexible material and having corners; air cells attached to and
projecting outwardly from the base to form an array, with the air cells
likewise being formed from a flexible material, the interiors of the air
cells further being in communication through the base for equalizing the
pressure within the air cells, each air cell when deflated having four
laterally directed projections with each projection having closely spaced
side walls, the side walls of adjacent projections being connected near
the center of the air cell to form depressions in the sides of the air
cell, the air cells being arranged on the base in an array with the
depressions of adjacent air cells facing each other, the air cells when
the pressure within them is increased being adapted to expand such that
the side walls of their projections move outwardly away from their centers
and thereby eliminate the depressions and such that the side walls along
opposing depressions in adjacent air cells are adapted to come into
contact; and a cover including a retaining section that underlies the base
and a covering section that is attached to the retaining section and
extends over and around the array of air cells, the covering section being
formed from an elastic fabric, the corners of the rectangular base being
projected through the cover.
2. An inflatable cushion comprising: a flexible base containing connecting
channels; and inflatable fluid cells attached to and projecting outwardly
away from the base to form an array of fluid cells, the connecting
channels of the base opening into the interiors of the fluid cells for
generally equalizing the pressure within the fluid cells, each fluid cell
having a center axis about which it is symmetrical and when deflated
having a pedestal at which the fluid cell is connected to the base, with
the pedestal being of rectangular shape and enclosing a generally,
rectangular opening that leads from the base into the interior of the
cell, each fluid cell when deflated further having four fins which project
away from the base and also extend laterally away from the center of axis
of the cell toward the corners of the pedestal, but do not extend beyond
the pedestal so that the fluid cell is widest at its pedestal when
deflated, each fin having a pair of closely spaced side walls which are
connected along an edge that generally aligns with the corners of the
pedestal, the side walls of adjacent fins being further connected to each
other near the center axis of the fluid cells to form depressions in the
sides of the fluid cell, the dimension of the fluid cell along its center
axis being greater than the width of the fluid cell at its pedestal, the
fluid cells being arranged in the array with the depressions of adjacent
fluid cells facing each other, so that when the pressure within the fluid
cells is increased the side walls of the fins on each fluid cell move
outwardly away from the center axis for the cell to eliminate the
depressions in the fluid cells and the side walls of adjacent fluid cells
come into face-to-face contact.
3. A cushion according to claim 2 wherein each fluid cell when deflated has
four pedestal walls that are located between the depressions and the base
and are inclined with respect to the base to form the pedestal on the
base, the pedestal walls also being adapted to move outwardly away from
the center axis of the fluid cell when the pressure within the fluid cell
is increased.
4. A cushion according to claim 2 wherein the edges of the fins for each
fluid cell curve toward the center axis of the fluid cell remote from the
base when the fluid cell is deflated.
5. A cushion according to claim 2 wherein each fluid cell includes an end
wall and the curved edges of the fins merge into the end wall.
6. A cushion according to claim 2 wherein the fluid cells are arranged in
the array on closely spaced rows, each fluid cell being in two rows with
the one row being perpendicular to the other row.
7. A cushion according to claim 2 wherein the pedestals of the fluid cells
form a square opening into the base.
8. A cushion according to claim 2 wherein the pedestals of each fluid cell
have walls that are inclined with respect to the center axis of the cell
such that the pedestal possesses a generally pyramidal configuration.
9. A cushion according to claim 8 wherein the inclined walls of the
pedestal for each fluid cell lie between the depressions for that fluid
cell and the base.
10. A cushion according to claim 2 wherein the fluid cells are arranged in
horizontal and transverse rows, and the fluid cells are oriented such that
the margins of the rectangular openings at the pedestals are parallel to
the rows.
11. A cushion according to claim 2 wherein the depressions for each fluid
cell are located beyond the pedestal for that fluid cell and the fins for
the cell are attached to the pedestal.
12. An inflatable cushion comprising: a first flexible sheet; a second
flexible sheet attached to the first sheets and having rectangular
openings arranged in longitudinal and transverse rows with the margins of
the openings being parallel to such rows, the first and second sheets
being joined together along their peripheries such that an impervious seal
exists in the region of the peripheries, the sheets also being joined
together within the confines of the peripheries so that the sheets cannot
be significantly separated in that region, yet such that the openings are
connected by channels that are essentially between the two sheets, whereby
the openings are in communication with each other; and flexible fluid
cells attached to the second sheet around the rectangular openings therein
and projecting away from the second sheet, each fluid cell having a center
axis and when deflated including four fins which extend outwardly away
from the center axis toward the corners of the opening at which the cell
is located, with each fin having a pair of closely spaced walls which
merge at an edge, the edges of the fins aligning with the corners of the
opening and extending away from the opening where the edges converge, so
that the fins extend no further laterally than the opening for the fluid
cell on which they are located, the dimension of each fluid cell along its
center axis being greater than the width of the rectangular opening around
which the fluid cell is attached to the second sheet, the side walls of
adjacent fins on each fluid cell further being connected to each other
near the center axis for the cell to form depression in the sides of the
fluid cell, whereby the depressions of any fluid cell will open toward the
depressions in cells that are adjacent to that cell, the fluid cells when
the pressure within them is increased being adapted to expand such that
the side walls of their fins move outwardly away from the center axes of
the cells to eliminate the depressions in the cells, all such that the
side walls at opposing depressions of adjacent fluid cells come into
contact.
13. The cushion according to claim 12 wherein the fins of each fluid cell
at their upper ends curve inwardly toward the axis of the fluid cell.
14. The cushion according to claim 12 wherein the fluid cells are formed
integral with the second sheet.
15. The cushion according to claim 12 wherein when the fluid cells are
inflated, the side walls of the fluid cells will expand outwardly between
the fins so that the fins are less pronounced and the side walls of
adjacent fluid cells will contact each other and the upper ends of the
fluid cells will provide a supporting surface.
16. A cushion according to claim 12 wherein each fluid cell when deflated
further includes a pedestal which is attached to the second sheet around
the opening in the second sheet at which the fluid cell is located, and
the fins for the fluid cell are attached to and extend away from the
pedestal.
17. A cushion according to claim 16 wherein the pedestal has at the ends of
the depressions in the sides of its fluid cell inclined walls that slope
toward the second sheet such that the pedestal has a generally pyramidal
configuration.
18. A cushion according to claim 12 wherein the outside edges of the fins
for each deflated fluid cell converge to a dome on the deflated fluid
cell.
19. A cushion according to claim 12 wherein the openings in the second
sheet are square. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
This invention relates in general to cushioning devices and more
particularly to cushions having a multiplicity of inflatable cells.
Conventional cushioning devices for supporting the human body, such as the
typical mattress, seat cushion or padded back rest, do not distribute the
weight of the supported body evenly over the area of the body that is in
contact with the cushioning device. For example, in the case of a mattress
the buttocks or hips, and likewise the shoulders, sink further into the
mattress than the lumbar region of the back. Since most conventional
cushioning devices exert a supporting force that is proportional to the
amount they are deflected, those portions of the body which sink deepest
into the cushioning device experience a resisting force per unit area that
is considerably greater than those body portions that deflect the
cushioning device only slightly. For those individuals who are confined to
beds or wheel chairs for extended periods of time the unequal distribution
of supporting forces can lead to extreme discomfort and can even be
debilitating in the sense that bed sores often develop at the skin areas
where the supporting force is greatest.
While cushions which derive their cushioning properties from inner springs
or foam material are quite common and inexpensive to manufacture, they
suffer the inability to distribute loads or restoring forces evenly. On
the other hand, some very specialized cushions are available which
distribute the supporting forces more evenly and indeed generally
uniformly over the entire supported area. These cushions employ a series
of air cells which are extended generally perpendicular from a base and
are, therefore, oriented generally perpendicular to the contacting surface
of the body that they support. Moreover, all of the cells are
interconnected and, therefore, exist at the same internal pressure
irrespective of the extent of deflection. Since the ends of the cells
actually contact the supported body, it is desirable to have the cells
arranged quite closely for this enables the ends of the cells to resemble
a generally continuous surface. Perhaps the most refined air cell cushions
currently available are disclosed in U.S. Pat. Nos. 3,870,450 and
4,005,236. The air cells of these cushions are molded in a fluted
configuration, each with seven or eight fins, so that when the cells are
inflated they will expand laterally into contact with each other and their
ends will collectively form a generally uniform supporting surface.
While cushions of the type disclosed in U.S. Pat. Nos. 3,870,450 and
4,005,236 provide uniform load supporting characteristics, they are
difficult and expensive to manufacture, owing primarily to the large
number of fins in each cell. These fins on occasion prevent the latex from
distributing uniformly over forms used in the dipping operation by which
the cushions are made, and this results in a high rejection rate. The
problem seems to reside primarily in the small form radii created by the
numerous fins, for air bubbles tend to collect in the radii and cause
discontinuities in the latex film that builds up on the form. Also, the
numerous fins impede stripping the dipped parts from the forms. Also, the
numerous fins on each mold produce an overall cell configuration which
tends to experience its greatest wear on the top of the air cell, as well
as significant wear along its sides where it contacts other air cells.
Furthermore, the cushion, by reason of its multifluted cells, is difficult
to clean.
SUMMARY OF THE INVENTION
One of the principal objects of the present invention is to provide a
cushion which exerts its supporting forces on a supported body generally
uniformly through a multiplicity of interconnected air cells. Another
object is to provide a cushion of the type stated in which the air cells
are easily formed in a simple dipping operation. A further object is to
provide a cushion of the type stated in which the air cells are arranged
in rows both longitudinally and transversely in the cushion. An additional
object is to provide a cushion of the type stated which is easily cleaned.
Still another object is to provide a cushion of the type stated which is
durable. Yet another object is to provide a dipping form for producing a
cushion of the type stated, with the form having relatively large radii
which deter air bubbles from collecting when the form is dipped. These and
other objects and advantages will become apparent hereinafter.
DESCRIPTION OF THE DRAWINGS
In the accompanying drawings which form part of the specification and
wherein like numerals and letters refer to like parts wherever they occur:
FIG. 1 is a perspective view of a cushion constructed in accordance with
and embodying the present invention, the cover of the cushion being broken
away to show the cells in a deflated condition;
FIG. 2 is an elevational view of the cushion taken along line 2--2 of FIG.
1;
FIG. 3 is a plan view taken along line 3--3 of FIG. 2;
FIG. 4 is a sectional view taken along line 4--4 of FIG. 2;
FIG. 5 is a sectional view taken along line 5--5 of FIG. 3;
FIG. 6 is an elevational view of the cushion with the air cells inflated;
FIG. 7 is a plan view of the cushion taken along line 7--7 of FIG. 6 and
likewise showing the air cells inflated;
FIG. 8 is an elevational view of a dipping form on which the air cells are
formed;
FIG. 9 is a plan view of the dipping form taken along line 9--9 of FIG. 8;
and
FIG. 10 is a sectional view of an air cell similar to FIG. 5, but without a
pedestal.
DETAILED DESCRIPTION
Referring now to the drawings, a cushion A (FIG. 1) basically includes a
base 2, and a multiplicity of air cells 4 projecting from the base 2
generally parallel to each other. The air cells 4 are the same size and
configuration and are arranged in transverse and longitudinal rows to form
an array of rectangular configuration. One or more of the air cells at a
corner of the cushion A is provided with a tube 6 through which air may be
introduced into the cushion for inflating its air cells 4. The tube 6, in
turn, contains a manually operated valve 8. Within the base 2 adjacent air
cells 4 are connected in the sense that their interiors are in
communication with each other, so that when the air cells 4 are inflated
through the tube 6 all will exist at the same pressure. Similarly, should
a load deflect some of the air cells 4 more than the others, the pressure
within all of the air cells 4 will nevertheless equalize. Thus, the
cushion A will exert a generally uniform force, or more accurately
pressure, on the surface area of any body supported on it, even though
that body may be of complex and irregular contours and deflect some of the
air cells 4 more than others. By reason of these characteristics, the
cushion A is ideally suited for use as a mattress, a portion of a
mattress, a seat cushion, or a back rest.
Each air cell 4 is symmetrical about a center axis X that is perpendicular
to the base 2 and in its deflated configuration, that is the configuration
in which is it formed, includes (FIGS. 2-5) a pedestal 10 and four
projections or fins 12 which extend upwardly from the pedestal 10, the
fins 12 being arranged at 90.degree. intervals around the axis X. The
pedestal 10 is pyramidal and as such has four sloping side walls (FIG. 5).
Where it merges into the base 2 it is square (FIGS. 3 & 4). The fins 12
extend out to the corners of the pyramidal pedestal 10, and each fin 12
has spaced apart side walls 14 which are parallel and along the outside of
the fin 12 these walls 14 are connected by a convex edge wall 16. The side
walls 14 of adjacent fins 12 merge at concave connecting walls 18. Thus,
each air cell 4 has a depression 20 opening out of each of its four sides,
there being a different depression 20 above each of the four inclined
walls that comprise the pedestal 10. The connecting walls 18 extend
upwardly from the upper end of the pedestal 10 and are straight throughout
most of their length. The convex edge walls 16, on the other hand, extend
upwardly from the corners of the pedestal 10 and thus originate at the
base 2. For much of their length the convex edge walls 16 are straight,
but near their upper ends they, in contrast to the concave walls 18, curve
inwardly toward the axis X. At the upper end of the air cell 4 the convex
edge walls 16, the side walls 16 and the connecting walls 18 all merge
into a dome 22 which is the top of the air cell 4 (FIGS. 2 & 5).
The air cells 4 are arranged on the base 2 in longitudinal and transverse
rows (FIG. 1) and the margins of the pedestals 10 for these cells lie
parallel to the rows. Thus, for each air cell 4 two of the margins on its
square pedestal 10 are parallel to the longitudinal rows and two are
parallel to the transverse rows. The fins 12, being extended to the
corners of the pedestals 10, are of course oriented at 45.degree. with
respect to the rows. The spacing between the longitudinal rows and the
transverse rows is equal.
The filling tube 6 extends outwardly from the fin 12 on an air cell 4 at
one of the corners of the cushion A, so that it is easily accessible for
inflating the air cells 4. The tube 6 contains the valve 8.
The base 2 consists of an upper sheet 26 and a lower sheet 28 (FIGS. 2 & 5)
which are cemented together between the rows of air cells 4 and also along
the periphery of the cushion A. The upper sheet 26 is formed integral with
the air cells 4 and is therefore interrupted by the pedestals 10 for the
air cells 4. Thus, viewed from beneath, the upper sheet 26 has a plurality
of square pockets which represent openings into the air cells 4. The lower
sheet 28, on the other hand, is continuous and closes these openings.
In addition, the base 2 contains communicating strips 30 which extend along
each of the longitudinal rows of air cells 4 and also along the two
endmost of the transverse rows. The strips 30 are centered with respect to
the rows along which they extend, and they prevent the upper and lower
sheets 26 and 28 of the base 2 from bonding together where they lie. As
such, they provide small connecting ducts or channels 32 between the
individual air cells 4 along the rows in which they lie, and it is through
these channels that adjacent air cells 4 in the longitudinal rows and in
the endmost transverse rows communicate. The channels 32 do not collapse,
and the communication that they provide is controlled in that a restricted
flow rate between cells 4 is provided. The communicating strips 30
terminate at the endmost air cells 4 in their respective rows and do not
extend out into the peripheral region that surrounds the array of air
cells 4. Here the two sheets 26 and 28 are bonded firmly together,
preferably by a rubber cement, to form an air-tight seal along the
periphery of the cushion A. The bonds in the spaces between the rows of
air cells 4 do not isolate adjacent air cells 4, but instead prevent the
two sheets 26 and 28 from separating when the cushion A is inflated, and
thus these bonds serve to maintain the base 2 flat when the cushion A is
inflated.
The air cells 4 together with the upper sheet 26 of the base 2, all of
which are integral, are formed by repeatedly dipping a form 34 (FIGS. 8 &
9) in a latex bath, and with each dipping more latex adheres to the form
34. The dipping is repeated until the latex on the form 34 reaches the
desired thickness, whereupon the latex material that has accumulated on
the form 34 is stripped from the mold 34. The resulting shape is the air
cells 4 and the upper sheet 26 of the base 2, with the former projecting
from the latter.
The dipping form 34 includes (FIGS. 8 & 9) a flat plate 36 and mandrels 38
arranged in longitudinal and transverse rows on the plate 36. The mandrels
38 correspond in configuration and position to the air cells 4, and thus
each has a pyramidal pedestal 40, fins 42, flat side surfaces 44 and
convex edge surfaces 46 along the fins 42, concave connecting surfaces 48
between the fins, and a dome 50. One of the corner mandrels 38 also has a
cylindrical boss 52 projected laterally from one of the fins 42, and it is
about this boss that the filling tube 6 is formed. The form 34 is dipped
into a latex bath with its plate 36 oriented at about 45.degree., allowed
to remain for a minute or two, and then withdrawn. Since the concave
surfaces 48 between the fins 42 on the mandrels 38 have relatively large
radii, air does not tend to collect at these locations. Smaller radii, on
the other hand, are more likely to trap air in the form of bubbles which
remain during the dipping. These bubbles result in a weakness or perhaps a
void at the radius, and the resulting air cells are therefore more likely
to leak. The inclined surfaces of the pedestal 10 also serve to prevent
entrapment of air, since they eliminate deep pockets within the form 34.
The cushion A is assembled by laying the upper sheet 26 over a support
plate containing apertures which are spaced to accommodate the air cells
4, with the air cells 4 projecting downwardly through the apertures. This
presents the normal bottom of the upper sheet 26 upwardly. Then a rubber
cement or other bonding agent is applied to the exposed surface of the
upper sheet 26. Next the communication strips 30 are laid over the
inverted upper sheet 26, care being exercised to center them with respect
to the rows of air cells 4. However, no rubber cement is applied to the
strips 30.
In addition one surface of the lower sheet 28 is coated with a rubber
cement or other bonding agent. Then with the upper sheet 26 and air cells
4 supported on the apertured plate, the lower sheet 28 is inverted,
aligned with the upper sheet 26 on the apertured plate, and then forced
tightly against the upper sheet 26. The rubber cement or bonding agent on
the two sheets 26 and 28 bonds, joining the two sheets tightly together,
except in the regions of the strips 30 where the small communicating
channels 32 exist. This completes the base 2.
Finally the joined together sheets 26 and 28 and the integrally formed air
cells 4 are removed from the apertured plate and the base 2 is trimmed.
When the valve 8 in the filling tube 6 is open, the air cells 4 assume the
configuration in which they are molded, that is the pedestal 10, the fins
12 and the depressions 20 are all distinctly present. However, when the
cushion A is inflated, as it must be in order to be used, the side walls
14 of the fins 12, as well as the concave walls 18 between the fins 12 and
the inclined walls of the pedestal 10 move outwardly, and each air cell 4
assumes a somewhat square cross-sectional configuration (FIGS. 6 & 7). In
so doing, the side walls 14 of the fins 12 and the concave walls 18 lose
their identity and become part of a flat side wall 54, and the depressions
20 are no longer present. Indeed, the flat side walls 54 formed by the
displaced fin walls 14 and the concave connecting walls 18 contact their
counterparts which they face on the adjacent air cells 14, notwithstanding
the spacing that formerly existed between the rows of air cells 4. The
additional surface areas afforded by the fins 12 permits adjacent air
cells 4 to expand laterally into the voids that originally separated them,
and here the air cells 4 contact each other. The location of the fins 12
at the corners of the air cells 4 together with the arrangement of the air
cells 4 in rows with their pedestals 10 marginally aligned permits the air
cells 4 to retain the square configuration when inflated and, indeed,
permits them to occupy substantially the entire area within the confines
of the rectangular array, so that no voids exist in that array, even at
the corners of the air cells 4. Thus, the domes 22 together with the
curved portions of the arcuate edge walls 16 for the fins 12 and the
adjacent portions of the fin side walls 14 form enlarged dome-shaped ends
56 which are relatively flat and bear against the supported body. Since
the air cells 4 when inflated are packed so closely together, their
dome-shaped ends 56 collectively form a surface that is generally
continous across the array. It is this surface on which the supported body
rests.
To prepare the cushion A for use, air may be pumped into it until it is
somewhat over inflated. Then the pump is detached from the filling tube 6
and the valve 8 in that tube is closed. Next, the user rests upon the
cushion A in the posture he would assume when normally using it. This
deflects some of the air cells 4 toward the base 2 or at least drives the
dome-shaped ends 56 toward the base 2. Usually most of the air cells 4 are
distorted somewhat, but some more than others. Even so, the interiors of
all of the air cells exist at the same pressure. Once upon the cushion A,
the user opens the air valve 8 slightly and allows some of the air to
escape, and as a consequence the user sinks deeper into the array of air
cells 4. The air valve 8, however, is closed before any of the air cells 4
bottom out. Indeed, when the valve 8 is closed, at least one inch of space
should exist between the base 2 and the dome-shaped ends 56 of the air
cells 4 having the greatest deflection. By sinking still further into the
array of air cells 4, the limit being when at least one of the cells 4
bottoms out, the support provided by the air cells 4 is distributed over a
greater area on the supported body, and thus decreases in terms of force
per unit area. Of course, the supporting force is substantially equal when
considered on a unit area basis, even though some air cells are deflected
more than others, this being by reason of the fact that all of the air
cells 4 are in communication through the base 2 and therefore exist at the
same pressure.
To provide greater continuity to the supporting surface provided by the
dome-shaped ends 56 of the air cells 4, the cushion A may be contained in
a cover 60 (FIG. 1) that surrounds the array of cells 4 on the cushion A.
The cover 60 further protects the air cells 4 and confines the air cells 4
of the outer rows so that they exhibit less tendency to deflect outwardly.
The cover 60, which is optional, includes retaining section 62 which lies
beneath the base 2 of the cushion A and covering section 64 which is
attached to the retaining section 60 and extends around and over the array
of air cells 4.
The retaining section 62 is cut from a fabric that has little, if any,
elasticity. It contains a large open area through which the base 2 is
exposed, but it is continuous along the periphery of the base 2 with which
its margins register, except that its corners are cut off, leaving beveled
edges 66 beyond which the corners of the base 2 project. The covering
section 64 is cut from an elastic fabric that stretches in both of the
directions that the fabric thread passes. It is connected to the retaining
section 62 along stitching 68 at the periphery of the retaining section
62, except that the stitching 68 does not extend along the beveled edges
66. Thus, the covering section 64 is detached from the retaining section
62 at the beveled edges 66, leaving slits through which the corners of the
base 2 project. The slit at one of the corners further accommodates the
filling tube 6. In its corner regions the covering section 64 is provided
with vertical stitches 70 which are about as long as the air cells 4 are
high. These enable the covering section 64 to fit snugly over and around
the array of air cells 4 without gathering at the corners of the array.
Since the covering section 64 has two-way stretch characteristics, it
yields to conform to the contours of the body supported on the air cells
4, all without imposing shear or other restoring stresses of any
significance. The retaining section 62, being located beneath the base 2
of the cushion A, keeps the covering section 64 in place over and around
the array of air cells 4.
The communicating strips 30 need not be separate elements of the base 2,
but instead they may be formed integral with either the upper sheet 26 or
the lower sheet 28. Irrespective of whether they are integral or separate,
the strips 30 may be arranged such that some cells 4 are totally isolated
from other cells 4 and of course must be inflated through a different
filling tube 6. This divides the cushion A into separate compartments or
sections, which in turn may be used to position the user or counteract
certain external forces applied to the user. For example, when the cushion
A is used for the driver's seat of an automotive vehicle, such as a truck,
its air cells 4 may be arranged in sections so that the cells 4 along the
sides of the cushion are capable of being inflated to a greater pressure
and height than the ones at the center of the cushion A. This positions
the user over the center section and enables the side sections to resist
forces caused by the acceleration encountered in cornering. Of course,
when the cushion A contains several independent sections, each must be
adjusted to acquire the desired immersion depth.
The pyramidal base 2 and its sloping surfaces are present primarily to
eliminate deep pockets in the form 34 on which the air cells 4 are
produced, for deep pockets, particularly when presented downwardly tend to
trap air along the mandrels 38 and the resulting air bubbles cause
discontinuities in the latex coating that covers the mandrels 38. Where
dipping with the plate 36 at 45.degree. is employed, all of the inclined
surfaces may be eliminated except the one that is presented downwardly on
the mandrel 38 when the form 34 is dipped. In that case, the resulting air
cell 4 has only one sloping surface at its pedestal 10, and most of the
side walls 14 for the fins 12 rise directly from the upper sheet 26.
The air cells 4 may also be formed in a cavity mold, in which case the
pedestal 10 may be eliminated altogether (FIG. 10). Thus, the side walls
14 for all of the fins 12 would rise directly from the upper sheet 26 of
the base 2, as would the concave connecting walls 18. Rotational molding
and injection molding may be used to form the air cells 4 without
pedestals 10, both of these processes using cavity molds.
This invention is intended to cover all changes and modifications of the
example of the invention herein chosen for purposes of the disclosure
which do not constitute departures from the spirit and scope of the
invention.
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Description |
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