Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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S~ped Support Insert for Shoes
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The invention concerns a shaped shoe part or foot and arch
support consisting of a closed-cell, cross-linked foam polyolefin
with a surface structure adapted and conforming to the human foot
and with zones of different elasticities.
German Gebrauchsmuster 76 27 371 discloses a support of this type
with orthopaedic properties. In order to give this support ~ones of
different elasticities, it has been necessary to bond individual partsof foam
plastic together. This results in a~rupt transitions between zones of
different elasticity, and manufacture has proved unduly expensive.
One object of this invention is to develop a shaped shoe part as a
foot and arch support for incluslon during manufacture oE the shoe or for
insertion into the finished shoe, which will have excellent orthopaedic prop-
erties and at the same time can be manufactured~in a comparatively simple manner.
~ore particularly in accordance with the invention there is
provided, a shaped foot support for shoes comprising, a closed-cell
cross-linked foam polyolefin with a surface structure adapted to the
underside of the human foot and having zones of different elasticities,
the foam polyolefin being structured as one piece and the ~ones of
different elasticities being distributed over the surface and merging
smoothly into one another. The foam polyolefin may have lower elasticity
in regions of relatively high orthopaedic loading and vice versa. The
elasticlty of the foam polyolefin may vary 1nversely as its density with
the elasticity rising as the density falls. Preferably, the density
varies within the range of 0.07 to 1 kg/dm . More preferably, the
range may be 0.1 to 0.4 kg/dm . The foam polyolefin may have an insole -
attached to it which may be of a fibrous material of natural or synthetic
fibres united with a bondiny agent. The foam polyolefin may be provided
with a surface lining.
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The new shaped shoe part can particularly advantageously be
produced by a combined heat and pressure treatment from a homogeneously
structured blank of foam plastic of predetermined climensions. The
process of shaping is determined substantially by the mutual overlapping
of the different zones of compressibility, or elasticity, of the foam
plastic piece. At the same time, the elasticity can be influenced by
the intentional introduction of material in chosen regions of the
article.
The accompanying drawing illustrates a specific embodimen~ of ;
the new shaped shoe part 1 by way of example.
The different zones of the ar-ticle are illustrated in the drawins
by specifying their densities, but it should be understood that the
boundaries between the different zones merge continuously into each
other, so that the article forms one monolithic piece. It is evident
that in the new shoe part the foot is supported principally in the -
regions of the heel 2 and of the ball 3 of the foot, where the denslties
are highest and the elasticity is least tthe elasticity varying inversely
as the density). ~t the same time, however, the new shoe part has the
remainder of its upper surface in contact with the under side of the
foot, exerting differing elasticity or softness over the foot and arch
region ~ depending on the anatomical relationships to the support. By
supporting the foot in the boundary zones 5, a distinct improvement in
overall foot support is achieved, and chaffing or similar effects that
have hitherto been common can be avoided. The invented shoe part is
distinguished by an exceptionally low overall weight and by complete
physiological acceptability. It shows no chemical aging phenomena and
does not interfere with the normal dissipation of perspiration.
~ By including a surface lining on the shaped shoe insert,not
; only can its external appearance be improved, but also its elastic
behaviour. Generally, both the upper and the lower sides can be lined,
and,mechanically speaking, a sandwich structure is thus produced.
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For example, for sports shoes, a particularly good overall stability can
be achieved ~y such sandwich structuring, without the necassity of having
to accept any appreciable worsening of the support characteristics by
comparison with unlined shaped shoe par-ts. It is possible, and
in many cases, expedient, to line the underside of the foam piece directly
with an insole of normal construction. In fashion styled shoes, the use
of a fibrous material of natural or synthetic fibres united with a bonding
agent has proved excellent as such an insole.
The following example illustrates a process of manufacture of
a new insert:
A flat sheet of a closed cell foamed crosslinked polyethylene
with a density of 0.9 kp/dm and with a thiokness of 10 mm had a leather
fiber material containing a binder and of a thickness of 1 mm Elame-adhered
to its underside. A blank was stamped from this sheet material with the ~;
outer contours conforming to a pre-determined shape for a foot support for
shoes and was exposed both above and below for three minutes to an infrared
surface heat~r at a distance of 30 cm. The foam and the leather-fiber ~
material were brought by this treatment to a semi-plastic condition which
~;; extended into the central zone of the bIank. ;
The heated blank was then placed in the lower part of a cooled
metal-forming tool or press which immediately shaped the upper surface of
the blank to the desired finished form for the foot support which was
retained after cooling.
~n accordance with the anatomical shape of the human foot,~the ~ ~`
finished support had a thickness varying between 2 and 11 mm such that the
greatest density of the support was in the region of the heel and the ball
of the foot. The density of the support was greatest in the areas of least
; thickness where it had the greatest load capaclty and least relative
elasticity. The article was immediately ready for use.
While the support is, .in gen~ral, made from a uniform sheet, it
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may, in some instances, be desirable to subject the blank to a milling
process in certain areas for reducing ~he amount of material present in
those areas, for instance, in the region of the heel and the ball of the
foot~ This allows the finished article to accommodate to extremes of
orthopedic requirements as well as to allow the realization of particular
effects dictated by fashion styling. It is of particular advantage that
the bearing properties of the support can be modified by the thermoplastic
flow which occurs during forming, or by the above-mentioned milling pre-
treatment so that the mechanical pre-treatment need only be relatively
rough while still producing a very accurately formed and dimensioned final
product. While the milling proce~s allows the removal of thermoplastic
in areas where it is desired, it is also possible to add or inject
additional thermoplastic material in the regions where additional density
of material may be required over and above that achieved simply by the flow-
forming which occurs in the shapiny tool.
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