Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to an insole footbed cushion
of the type which, for example, may be used in an athletic shoe.
Athletic shoes are becoming increasingly popular and
the public is becoming increasingly demanding with regard to
these shoes, particularly their comfor-t and shock absorption
characteristics. As shoes must inevitably be produced in
standard sizes, it is often difficult ~or a discerning customer
to find a satisfactory shoe if his foot size is nat close to
that of a standard last. In such a case, the role of the insole
cushion becomes ver~ important because the customer is able
to modify a standard shoe to meet his requirements more exactly.
Even to a customer whose foot does fit the standard shoe size,
an insole cushion can improve comfort and shock absorption.
Furthermore, it can be replaced at minimum cost when worn or
soiled without requiring the purchase of new shoes.
Various forms of insole cushions are known. One
such form is made by continuously spreading latex foam sheets
onto a textile backing. The foaming is produced by mechanical
means and leads to large and open cells. These readily absorb
liquid and wear tests have shown that crumbling o~ the foam
is a common type of failure for this form of insole cushion.
Furthermore, considerable capital investment is required to
make such insole cushions. Such insole cushions were also ~?
generally flat and would tend to move around within the shoe
unless they were cut exact~y to the right size.
Various other forms of insole cushions have been
tried, although these would suffer from the dlsadvantages of
high cost, movement in the shoe, poor shock absorption or high
water retention. Insole cushions are very low cost items and
it is extremely important to be able to employ mass production
techniques, while at the same time providing an insole cushion
not suffering from these disadvantages.
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Accoraingly, the present invention provides an insole
cushion comprising 2 layer of resilient closed cell foam plas-
tics material compression molded ~rom a sheet of the material to
form a generally planar main region adapted to lie against a
shoe insole and having in a heel region thereof an upwardly
flared marginal portion shaped to fit around a wearer's heel.
The upwardly flared marginal portion in the heel re,
gion not only increases wearer comfort but also renders the
size of the insole less critical for any particular shoe size.
If the main region of the insole cushion is slightly too small
for the shoe, the upwardly flared marginal portion wedges
against the upstanding walls of the shoe upper in the heel re~
gion. This firmly holds the insole cushion in place within
the shoe and thus reduces any tendency for it to slip around
during use. Furthermore, it also helps to mold the insole
cushion around the wearer's heel and improve comfort.
The closed cell structure of the plastics material
reduces surface water absorption and also helps to ensure better
compressibility and recovery during use.
The plastics material is preferably low density poly-
ethylene or EUA (ethylene vinyl acetate copolymer) or a mixture
thereof having a microcellular structure. This helps to mini-
mize cell collapse during compression molding thereby to improve
still further the compressibility of the finished product.
Desirably, the upper surface of the insole cushion
is covered with a layer of terry cloth to improve comfort and
also to absorb water. The layer of terry cloth may be cemented
to plastics sheets prior to compression molding.
The invention will now be described in more detail,
by way o~ e~ample anl~, with Xe~erence to the accompan~ing draw-
ings, in whi~c~
~ i5 an underneath vie~ o a preform for making
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insole cushions;
Pig. 2 iS a longitud~nal section taken along the line
II-II of Fi~. l;
Fiy. 3 is a perspective view of a completed insole
cushion.
The insole cushion blank shown in Fig. 1 is made in
the foll4wing manner. Firstly, a large sheet of low density
foamed resin having a microcellular structure is provided~
The resin is formed from the following composition:
Parts
Ultrathene 637 (trademark) 90.00
Alathon 3175 (trademark) 10.00
Zinc oxide 1.00
Stearic acid 1.00
Cellmic CAP 124 (trademark) 10.00
Perkadox 14/40 (trademark) 4.5
116.5
Curing 8 minutes - 160 C
The foamed resin has the following properties:
Expan~ion 120%
Specific Gravity 0.066
Hardness IRHD ~28
Split Tear Stress N/2.5 cm 14,5
A layer of terry cloth 2 is then bonded to the foamed
resin sheet by uslng any suitable known cement. Blanks of the
general shape of the preform shown in Fig. 1 are then diecut
from the sheet and at the same time provided with a central
slit 3 extending part way into the blank.
The sheets from which the blanks are cut have a
thickness o~ ~pp~oximatel~ 0.6 cm.
The ~lanks are then preheated at 12nC for 3 minutes
and then preformed in a cold mold for 1 minute to provide the
preform 1. The cold mold is preferably a bladder mold of the
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type described in our copending application serial No. 329,544
filed on Jul~ 9, 1979.
Prior to trimming, the molded preform has the shape
shown in Fig. l. The preform comprises two insole cushion
forms having a generally planar main region 4 with an upwardly
flared marginal portion 5 extending around a heel region of
the insole cushion. The marginal portion 5, in the embodiments
shown, is also shaped at 6 to extend under the arch of a wearer's
foot and form an arch support.
During molding embossed lines 7 are impressed on the
preform 1. In the embodiment shown, three arcuate lines are
shown corresponding to three different shoe sizes. To complete
the manufacture of an insole cushion, thè preform is trimmed
to form two complete insole cushions. It is trimmed around
one of the lines 7 to provide the desired size and around the
dotted line llto remove excess material from the preform.
The rear portion of the main region ~ is defined, on
the underneath of the insole, by the contour 8 separating the
planar psrtion of the insole cushion from the upwardly flared
marginal portion 5. This contour is of such a size that it
will fit into any shoe having a size corresponding to any one
of the lines 7. The rear portion lies against the insole of
the shoe, but an accurate fit is not critical ~ecause if it
slightly too small, the marginal flared portion engages the
upstanding walls of the heel region of the shoe upper and
preventsmovement of the insole cushion within the shoe. A
front portion of the main region 4 is defined by the periphery
of the insole cushion which is cut along one of the lines 7
according to the shoe size.
Three different sizes of insole cushions can there-
fore be made from the preform l simply by cutting along any
one of the lines 7 and trimming the remaining portion of the
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preform as desired. This is achieved because, owing to the
presence of the upwardly flared marginal portion 5, an exact
fit of the rear portion of the main region 4 is not critical.
In the embodiment described, the toe region 9 of the
completed insole cushion has a thickness of about .3 cm which
increases to about .4 cm in a region 10 adjacent the arch
support region 6. The region 10 of slightly increased thickness
provides a metatarsel cushion for the foot of the wearer. The
arch support region 6 is convexly curved and shaped to fit
comfortably under the arch region of the wearer's foot.
Because of its simple construction, the described
insole cushion can be manufactured cheaply using mass production
techniques. The molding of a preform from which a number of
insoles to fit different sized shoes can be made simply by
trimming helps further to reduce the cost of manufacture. It
is not necessary to mold an insole cushion separately for each
possible shoe size. The flared marginal wall 5 not only
increases wearer comfort b~ partly surrounding the heel and
also providing a metatarsal cushion and arch support, it also
ensures that the insole cushion is firml~v wedged against the
walls of the upper of the shoe and therefore movement of
the insole cushion within the shoe is avoided.
It is indeed extremely surprising that such an insole
cushion can be molded from a foamed plastic material. Generally,
it would be thought that the cells of foamed plastic would
collapse on compression and that it would not be posslble to
provide sufficient resilience in a single layer of compressed
foam plastic to form an effective insole cushion. Surprisingly,
it has been found that, provided the closed cell structure is
employed, such plastics material can be compression molded
to give the desired three dimensional shape of the insole
cushion. The resulting compressed product still has good
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resilience and shock absorption properties. Advantageously,
the material has a microscoplc cell size which minimize cell
collapse during compression and ensures optimum resilience
sf the compressed product, and a compression set of approximately
50%.
The plastics material employed has some degree of
cross linking to make is partially thermosetting, although it
also retains some degree of plasticity.
The optimum average cell size for the microcellular
plastics material is .02 to .05 mm.
..
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