U.S. patent application number 11/271150 was filed with the patent office on 2007-05-17 for multi-material molded shell for footwear.
This patent application is currently assigned to Columbia Sportswear North America, Inc.. Invention is credited to Daniel S. Laska.
Application Number | 20070107257 11/271150 |
Document ID | / |
Family ID | 38039255 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070107257 |
Kind Code |
A1 |
Laska; Daniel S. |
May 17, 2007 |
Multi-material molded shell for footwear
Abstract
A shell for a boot or other footwear includes a first section of
molded of a first thermoplastic material and a second section
molded of a second thermoplastic material and integrally bonded
with the first section. The first and second thermoplastic
materials preferably have different material properties, such as
color, hardness, or density, to enhance the aesthetic and/or
functional design of the footwear. Methods of making molded
multi-material shells and footwear including such shells are also
disclosed.
Inventors: |
Laska; Daniel S.; (Portland,
OR) |
Correspondence
Address: |
STOEL RIVES LLP
900 SW FIFTH AVENUE
SUITE 2600
PORTLAND
OR
97204-1268
US
|
Assignee: |
Columbia Sportswear North America,
Inc.
Portland
OR
|
Family ID: |
38039255 |
Appl. No.: |
11/271150 |
Filed: |
November 11, 2005 |
Current U.S.
Class: |
36/4 |
Current CPC
Class: |
A43B 7/12 20130101; B29D
35/146 20130101; A43B 1/0027 20130101; A43B 5/002 20130101 |
Class at
Publication: |
036/004 |
International
Class: |
A43B 1/10 20060101
A43B001/10 |
Claims
1. A shell to which a sole and an upper of an article of footwear
are attached, comprising: a first section of a first molded
thermoplastic material; and a second section of a second molded
thermoplastic material different from the first molded
thermoplastic material, the second section being integrally joined
with the first section along an interface therebetween to form a
shell of unitary construction.
2. The shell of claim 1 in which the first and second thermoplastic
materials are different colors.
3. The shell of claim 1 in which the first and second thermoplastic
materials are different hardnesses.
4. The shell of claim 1 in which the first and second thermoplastic
materials are different densities.
5. The shell of claim 1 in which the first section comprises a
collar.
6. The shell of claim 1 in which the second section is over-molded
around the first section.
7. The shell of claim 1, in which the shell includes a flange to
which the upper is attached.
8. The shell of claim 1, in which the shell is waterproof.
9. The shell of claim 1, in which: the first thermoplastic material
is a first TPU material having a first density; and the second
thermoplastic material is a second TPU material having a second
density different from the first density.
10. The shell of claim 9, in which the second density is greater
than the first density.
11. An article of footwear including the shell of claim 1.
Description
TECHNICAL FIELD
[0001] This application relates to footwear and, more particularly,
to molded thermoplastic shells for footwear and methods of molding
such shells.
BACKGROUND OF THE INVENTION
[0002] Waterproof winter boots and other kinds of footwear
sometimes include a semi-rigid molded plastic shell in the
configuration of a slipper, to which an outsole may be molded,
glued, or stitched. An insole and/or foot bed may be inserted
inside the shell to provide cushioning. Finally, a flexible fabric
or leather upper including lacing eyelets is typically stitched or
glued along the rim of the shell to complete the boot or other
article of footwear.
[0003] U.S. patent application Ser. No. 10/889,586 of Laska et al.,
filed Jul. 12, 2004, which is incorporated herein by reference,
describes a molded shell for footwear and a method of molding the
shell around a skirt of the upper to provide a strong molded
connection between the shell and the upper.
[0004] The present inventor has recognized a need for improvements
in footwear and molded shells, in particular, for providing an
enhanced aesthetic appearance or improved flexibility
characteristics for enhanced comfort.
SUMMARY
[0005] In accordance with embodiments disclosed herein, a shell for
a boot or other footwear includes a first molded thermoplastic
section and a second molded thermoplastic section integrally bonded
with the first section. The first section may be pre-formed by
molding a first thermoplastic resin in a first mold or by other
means, then inserted into a second mold in which the second section
is formed by over-molding a second thermoplastic resin into
integral chemical and/or mechanical engagement with at least a
portion of a perimeter of the first section to form a unitary
structure. In alternate embodiments, the first and second sections
are formed simultaneously or sequentially in a single mold, during
one or more mold cycles. An outsole and an upper are preferably
attached to the shell after it has been molded.
[0006] The physical properties of the first thermoplastic material,
such as color, hardness, elasticity, and others, may differ from
the physical properties of the second thermoplastic material,
thereby forming a shell having regions of different colors,
hardnesses, elasticity, or other properties. In one embodiment a
generally U-shaped collar of a first material of a first color
extends from the medial ankle region forward, over the instep, and
rearward to the lateral ankle region. A second section of the
shell, including the toe box, lower sidewalls, heel region and
underfoot portion, is formed of thermoplastic material of a second
color. The material of the second section may provide enhanced
insulation capabilities and an aesthetically pleasing color
contrast from the first portion.
[0007] The multiple material shell concept can also be extended for
shells of three or more different molded materials.
[0008] Additional aspects and advantages will be apparent from the
following detailed description of preferred embodiments, which
proceeds with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a front-top-lateral side perspective view of a
boot including a shell according to a preferred embodiment, wherein
the stippling indicates color;
[0010] FIG. 2 is a rear-lateral side perspective view of the boot
of FIG. 1 with regions broken out to show detail;
[0011] FIG. 3 is an exploded assembly view of the boot of FIG. 1
with the upper omitted and showing detail of an insole, the shell,
and an outsole of the boot;
[0012] FIGS. 4-7 are a pictogram showing steps for molding the
shell of FIG. 3, including inserting a preformed plastic collar
section of the shell into the mold (FIGS. 4-5), closing the mold
around the collar and a core of the mold (FIGS. 5-6), and, after
injecting a material to form a second section of the shell, opening
the mold and removing the shell (FIG. 7);
[0013] FIG. 8 is a cross section view of the mold of FIGS. 4-7
showing cross sectional detail of the molded shell;
[0014] FIG. 9 is a cross section view of the mold and shell of FIG.
8 taken along lines 9-9 of FIG. 8;
[0015] FIG.10 is a cross section view of the mold and shell of FIG.
8 taken along lines 10-10 of FIG. 8; and
[0016] FIG. 11 is a cross section view of the mold and shell of
FIG. 8 taken along lines 11-11 of FIG. 8.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0017] Throughout the specification, reference to "one embodiment,"
"an embodiment," or "some embodiments" means that a particular
described feature, structure, or characteristic is included in at
least one embodiment. Thus appearances of the phrases "in one
embodiment," "in an embodiment," or "in some embodiments" in
various places throughout this specification are not necessarily
all referring to the same embodiment.
[0018] Furthermore, the described features, structures,
characteristics, and methods may be combined in any suitable manner
in one or more embodiments. Those skilled in the art will recognize
that the various embodiments can be practiced without one or more
of the specific details or with other methods, components,
materials, etc. In other instances, well-known structures,
materials, or operations are not shown or not described in detail
to avoid obscuring aspects of the embodiments.
[0019] With reference to FIGS. 1-3, a boot 10 according to a
preferred embodiment includes a shell 20 to which an upper 24 of
boot 10 is attached via a flange 28 (FIG. 2) of a shell 20. Upper
24 may be made in any suitable manner and is preferably assembled
primarily of soft fabric, leather, or synthetic material
components. Upper 24 may be attached to shell by adhesives,
stitching, taping, molding, heat bonding, or any other means. A
sole 30, including a cushioning midsole 32 and an wear-resistant
outsole 34, is attached to shell 20 opposite upper 12 by any
suitable method. However, it may be preferably to glue or mold the
sole 30 to shell 20, to preserve a waterproof aspect of the shell
that might otherwise be compromised by a stitched attachment. Prior
to its attachment to upper 24 and sole 30, shell 20 is formed by a
molding process, a preferred embodiment of which is described below
with reference to FIGS. 4-7. An insole 46 (FIG. 3) may be inserted
into shell 20, after it is made, to provide cushioning and arch
support.
[0020] With reference to FIGS. 2 and 3, shell 20 comprises a first
molded thermoplastic section 40 and a second molded thermoplastic
section 42. The first section 40 is preferably preformed as a
U-shaped collar (open at the heel) in a preliminary injection
molding operation. The second section 42 is then preferably
overmolded onto first section 40 in a second injection molding
operation, i.e., an over-molding operation described below with
reference to FIGS. 4-7. The first and second sections 40, 42 are
preferably formed of two different thermoplastic materials that are
selected to be chemically compatible so as to form a chemical bond
at their interface 48. A chemical bond helps to strengthen the
semi-rigid shell 20 and to form a unitary waterproof structure that
is resistant to separation, tearing, or leaking at the interface
48. Compatibility of the materials of the first and second sections
40, 42 may also result in a mechanical bond at the interface 48,
due to re-melting of the material of first section 40 during the
over-molding of second section 42 and attendant mixing of the two
materials at the interface. Without forgoing the desired chemical
compatibility, the first and second materials may comprise two
different formulations and colors of thermoplastic material.
[0021] Shells 20 according to the present disclosure may have two
or more regions of different colors, hardnesses, elasticity,
surface finish, strength, insulating capability, and other physical
properties. The particular combinations of properties and colors
are virtually unlimited, and subject only to the availability of
chemically compatible materials having the desired properties.
[0022] The physical properties of the first thermoplastic material
of first section 40, preferably differ from the physical properties
of the second thermoplastic material of the second section 42 in a
manner that results in improved footwear performance
characteristics. For example, first section 40 may be formed of a
material having a light color and low hardness for fashion and
enhanced flexibility across the instep, while the second section 42
may be formed of a darker material having a higher hardness to
provide scuff resistance and hide dirt and scuffs lower on the boot
10, where the shell 20 is more likely to contact soil, rocks, and
other objects. The contrasting dark and light bands of shell 10 can
be achieved without expensive painting or gluing operations.
[0023] In one embodiment, the first section 40 is formed of a first
material comprising a medium hardness thermoplastic elastomer, such
as a thermoplastic polyurethane (TPU) having a durometer of
approximately 80 Shore A. One suitable high-density TPU material
for first section 40 is sold under the name ELASTOLLAN.RTM. S80 by
BASF Corporation. The second section 42 may be formed of a second
material comprising a harder TPU having a durometer of
approximately 85 Shore A. A suitable hard TPU material is sold
under the name AVALON.RTM. 85AB by Huntsman Chemical Company
(formerly ICI Plastics). The coloring of the materials may
preferably be due to colorants mixed with the resin, which will not
bleed or separate.
[0024] The first section 40 may be pre-formed by molding a first
thermoplastic resin in a first mold or by other means, then
inserted into a second mold. With reference to FIG. 4, first
section 40 may comprise a preformed collar 50 that is inserted on a
mold core 54 or into a cavity of a mold 60 (FIG. 5) for forming
second section 42. Collar 50 may take any suitable shape. In the
embodiment shown, collar 50 extends from the medial ankle region
forward, over the instep, and rearward to the lateral ankle region.
In other embodiments, the first section comprises panels or
components of other shapes and configurations. In some embodiments,
the first section 40 comprises two or more pieces that are both
inserted into mold 60 at the same time for over-molding the second
section 42 thereto. Skilled persons will appreciate that the
thicknesses, positions, and widths of various regions of the
sections of different materials can be customized to achieve
desired design and performance attributes, such as flexibility,
lateral stability, comfort, weight, and others.
[0025] After first section 40 has been inserted into mold 60 or
onto core 54, the mold 60 may be closed as depicted in FIG. 5. Mold
60 may preferably include a dam 64 comprising a small sharp rib
extending within the cavity of the mold and positioned to come into
contact with or press against a lower perimeter region of collar 50
adjacent where interface 48 will be formed when second section 42
is molded. Dam 64 helps to achieve a crisp transition between the
first and second materials by preventing the second material of
second section 42 from flowing around first section 40 during the
molding step. Dam 64 may preferably extend along the entire lower
perimeter of first section 40, as depicted by the broken line
numbered 64 in of FIG. 8.
[0026] As shown in FIG. 6, when mold 60 is closed, a cavity 70 is
formed around first section 40. The cavity includes a toe box
region 72, lower sidewalls 74, a heel region 76 and underfoot
region 78, which, when filled with the thermoplastic material, as
depicted in FIGS. 7 and 8, will form corresponding regions of the
second section of the shell 20.
[0027] A part line 80 of the mold runs along a portion of the lower
perimeter of first section 40 to correspond with dam 64 for at
least a portion of the length of shell 20. FIGS. 8-11 show the
placement of part line 80 and dam 64 in greater detail. Strategic
placement of part line 80 can help minimize mold flash and result
in an aesthetically pleasing shell 20, devoid of part lines along
the top of the shell.
[0028] In an alternative embodiment, the molding process is
repeated one or more times to add third or further shell sections,
so that shell may comprise three or more sections of different
molded materials. In still other embodiments, the first and second
sections are formed simultaneously or sequentially in a single
mold, during one or more mold cycles. In yet other embodiments the
first and second sections are formed by a co-molding process.
[0029] It will be obvious to those having skill in the art that
many changes may be made to the details of the above-described
embodiments without departing from the underlying principles of the
invention. The scope of the present invention should, therefore, be
determined only by the following claims.
* * * * *