Note: Descriptions are shown in the official language in which they were submitted.
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Field of the Invention
This invention relates to a lift or sole con-
struction for a shoe, in which the lift attached to the
bottom of the heel of either a man's shoe or woman's
shoe is molded into a single piece from two resin
layers and which displays excellent advantages with
regard to both health and wearing comfort.
Background of the Invention
Accompanying the trends of recent years
toward more diversified consumer needs and greater
health awareness, there have also been changes made in
the constructions used Eor shoe heels. The lifts or
soles attached to the bottom oE shoe heels have alway~
been easily ~ubject to wear, and the replaceability of
those lifts has been an important problem. Iron ring
lifts, hard rubber, and other constructions were origi-
nally used for the lifts on women's shoes, but there
were problems with such matters as wear resistance,
and recently the most common material used for lifts
has come to be urethane resin, which features excellent
wear re~istance. However, the change to this material
did not eliminate the need for replaceability. Espe-
cially on high-heeled shoes, the largest proportion of
the weight of the wearer is exerted upon the lifts
attached to the bottom of the heel, and because of the
small surface area, these lifts are subject to severe
wear and thus require replacement frequently. In the
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past, because it has been difficult to replace li ~ ~7 8
other than at a shop ~pecializing in shoe repair, the
result was a shortening of the life of the product.
For this reason, heel device~ have been proposed for
which it is possible for the lift to be replaced rela-
~ively easil~ without requiring any special skill, such
as that described in laid open in Japanese Utili~y
Model Publication Sho. 63-4407.
Incidentally, even if the lifts of the prior
art differ as to whether or not replacement is easy,
the entire lift is still molded into a solid piece from
urethane re~in or a similar substance.
The following problems occ~lrred as a result
of the lifts of the prior art being molded into a solid
piece from a ~ingle layer of resin:
(1) If the lift was molded into a solid piece
from hard urethane resin, the impact shock -
from walking on a hard floor surface would
reverberate to the head of the wearer, thus
~0 presenting problems with regard to both
health and wearing comfort.
(2) In addition, the lifts were often colored
black (colored with carbon black) in order to
present a slim appearance from a design as-
pect, and this could result in marks being
made on the floor surface while walking.
(3) Further~ore, If the entire lift was mol~e~ 7
into a solid piece from soft resin in consid-
eration of the health aspect, the manner in
which the weight of the wearer was applied
while walking could cause the lift to tilt
sideways, thus presenting the danger of the
wearer twisting an ankle.
In consideration of the factors described
above, it is a general object of this i.nvention is to
provide a lift construction which increases the product
value of the shoe, by molding a replaceable lift into a
single piece from two resin layers, upper and lower,
and, moreover, by selecting resins having properties
which are suitably matched to the various needs.
Summary of the Invention
A shoe lift constructed in accordance with
this invention comprises a replaceable lift attached to
the bottom of the heel of the shoe. The lift is molded
from two resin layers, upper and lower, and, in addi-
tion to one of these two resin layers ~eing molded froma hard resin and the other being molded from a rela-
tively soft resin, in order to mold the upper and lower
resin layers into a single piece, connecting holes are
formed in one of the layers and connecting projections
are formed in the other layer. In addition, in this
composition, the upper layer i8 a nylon resin layer and
the lower layer is a urethane resin layer.
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With the composition described above, by
molding the lift into two layers, upper and lower, it
is possible to mold the upper and lower layers from
resin layers having properties which are suitably
matched to the various needs. In other words, if one
of the upper and lower layers is molded from a hard
resin layer and the other from a relatively soft resin
layer, the shock-absorbing action of the soft resin
layer prevents the impact force from the floor from
~0 reverberating to the head of the wearer, thus both
improving the health aspect and also providing good
wearing comfort. In addition, the hard resin layer
makes it possible to ensure sufficient rigidity for the
entire lift, thus eliminating the danger of the wearer
twisting an ankle as a result of the manner in which
the weight of the wearer is applied while walking which
might cause the lift to tilt sideways. Furthermore, it
is possible to select different coloring for the upper
and lower layers, and in particular, if the lower layer
is a urethane resin layer, a bright, natural color can
be easily used, thus making it possible to prevent
marking of a floor surface.
Brief Description of the Drawinqs
The following is a description of an embodi-
ment of the invention, given with reference to the
figures of the accompanying drawings, wherein:
Fig. 1 is a perspective view of the heel part
of a shoe incorporating the present invention;
Fig. 2 is an enlarged side view of the heel'~ 0
part with some parts in section;
Fig. 3 shows four diagrams (a), (b), (c) and
(d) in schematic form, of steps in molding a shoe lift;
Figs. ~(a) and 4(b) are a pla:n view and a
perspective view of the lower layer of the lift showing
an example of the connecting projections;
~igs. 5(a) through 5 (G) are plan ~iews of the
lower layer of the lift showing various styles of
10 connecting projections; and ~:
Figs. 6(a) and 6(b) show additional embodi- :
ments of the lift construction.
Detailed Description of the Invention
Although the shoe in the embodiment shown in
Figs. 1 and 2 is a type of a woman's shoe, the inven-
tion is also equally applicable to a man's shoe. The
shoe comprises a shoe body 1, a heel body 2 made of, in
this specific example, rigid plastic which p~ojects
from the bottom rear of the shoe body 1, and a two-lay-
er molded lift 3 which is attached to the bottom ofthis heel body 2 and which will be described later.
The heel body 2 may also be molded into two separate
layers, upper and lower.
The heel body 2 described above i~ attached
as a continuous single piece to the bottom of the shoe
,
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body 1, and a wedge-shaped notch 4 (see Fig. 2) whi ~ 7 g~
tapers in the inward and downward direction is formed
at the bottom of the heel body 2. In addition, an
insertion hole 5 is formed in the center part of the
bottom of the heel body 2. The hole 5 i9 substantially
perpendicular to the bottom surface 2a of the body 2.
metal mounting fixture 6 which projects upwardly from
the top of the horseshoe-shaped lift 3 extends into
this insertion hole 5, so that, as shown in Fig. 2, the
heel body 2 and the lift 3 are connected together as a
single piece. The mounting fixture 6 has a head or
flange 6a at its bottom, and this flange 6a is embedded
into the lift 3 so that the mounting fixture is secured
to the lift 3 as a single piece. In addition, multiple
vertical grooves are formed into the circumference of a
shank or insertion part 6b of the mounting fixture 6
for the purpose of increasing the adhesio~ and also
preventing the lift 3 from turning. The hole 5 and the
insertion part 6b have mating cross-sectional shapes
and the part 6b is sized to fit tightly in the hole 5.
The notch 4 is used when removing a worn lift 3 from
the heel body 2 in order to replace it. In other
words, by inserting the tip of a screwdriver or similar
tool D into the notch 4 as indicated by the imaginary
lines in Fig. 2, the lift 3 can be pried loose and
removed from the heel body 2 by the principle of lever-
age. It should be noted that, because the notch 4 is
provided on the inward-facing side of the bottom of the
heel body 2, even if, for example, there is no outer
covering ~wrapping) around the heel, it is not espe-
,
ciall~ visible from the outside, and thus there is noimpairment to the appearance of the shoe.
The following is a detailed explanation of
the lift construction of this invention.
As shown in Fig. 2, the lift 3 i9 molded from
two resin layers, an upper layer 3A and a lower layer
3B. In other words, the lift 3 is not a solid piece
made entirely of a single resin, as in the prior art,
but is comprised of two resin layers, the upper layer
3A and the lower layer 3B, which divide it vertically
into two approximately equal halves. For example, of
the upper and lower layers, one layer is molded from ~
hard nylon resin, and the other layer is molded from ~-
relatively softer urethane resin. Rather than using
two different resins for the upper an~ lower layers, it
is also possible to mold both the upper and the lower
layers from the same resin, for example, urethane. If
different resins are used for the upper and lower
layers, it becomes easy to provide each layer with the
mechanical properties which meet the corresponding
needs required of that layer. Of course, even if both
layers are molded from the same resin, it is also
possible to allot different hardnesses or other proper-
ties to the upper and lower layers. The reason why a
relatively soft resin layer is used for one of the two
layers is that, by providing that layer with a shock-
absorbing function, the impact shock generated while
walking on a hard surface does not reverberate to the
head of the wearer, thus improving the health aspect, 2
weariny comfort, etc.
In addition, the reason for specifically
using a urethane resin layer for the lower layer 3B is
that, because the black coloring (colored with carbon
black) used in order to present a slim appearance couId
result in marks being made on the floor surface whi.le
walking, this is prevented by allotting urethane resin
for the lower layer and utilizing its bright, natural
color.
Furthermore, the reason for composing either
the upper layer or the lower layer from a hard resin is
that, if the upper layer 3A and the lower layer 3B were
both molded into a single piece from the same ~oft
resin, the entire lift 3 would lack rigidity, and the
manner in which the weight of the wearer is applied
while walking could cause the lift to tilt sideways,
thus presenting the danger that the wearer may twist an
ankle; however, by composing a layer which comprises
one-half of the lift from a hard resin layer, it is
possible to provide the rigidity required for the
entire lift, thus eliminating such danger.
By molding the lift into two layers, upper
and lower, in this way, it becomes possible to appro-
priately select resins having properties which aresuitably matched to the various needs and to allot them
to the upper and lower layers, and, in particular,
because it is possible to mold the two layers from
different resins, it thus becomes possible to achieve a
lift which has multiple composite function~. 2
The upper and lower resin layers which com-
prise the lift construction of this invention are not
connected together into one piece by adhesive, but are
composed so as to form a single piece by a male-female
dovetail type of connection in the molding stage, as
will be described later. In other words, as shown in
Fig. 2, multiple connecting projections 3b are formed
so that they project from the top of the resin layer of
the lower layer 3B and fit into connecting holes 3a
formed in the resin layer of the upper layer 3A in
order to connect the two layers together into one
piece. The reason for using this type of connection is
that, although connection by adhesive might be con~id-
ered i~ ord~r to utilize the good adhesion of the two
layer~ if urethane resin layers are used for both the
upper and lower layers, if this method were used,
adhesive material could protrude from the adhesion
surfaces, thus impairing the external appearance. In
addition, another reason is to make it possible to also
use nylon resins or the like having poor adhesion
properties as one of the resins which compose the
material oE the lift.
- 25 With the lift construction of this invention
as described above, it is possible to manufacture it by
injection molding. The ~ollowing i9 a description of
the lift molding method based on the schematic diagrams
shown in Fig. 3.
In step (a) of Fig. 3, the mounting fixture 6
described earlier is first placed and secured in t
prescribed location in a die (female die) 7 having
projections 7a of trapezoidal cross-sections inside it.
A male die or cover 8 is set in place on the die 7,
forming a cavity 3A' which forms the upper layer of the
lift inside the dies. Then, after the dies 7 and 8 are
secured, the prescribed molten resin (for exam~le,
urethane resin~ is injected in through an injection
port 8a. The flange 6a is exposed on its top and
bottom sides. When this resin is injected, the molten
resin also flows into the space between the flange 6a
of the mounting fixture 6 and the die 7, thus embedding
and securing the mounting fixture 6 in the resin.
After the resin has been in;ected and solidi-
fied, the dies are opened and a molded piece which
corresponds to the upper layer of the lift plu9 the
fixture 6 is released from the dies.
Due to the trapezoidal shape of the projec-
tions 7a, parts of this molded piece are thus formedinto trapezoidal cavities 3a having a reverse taper,
i.e. the connecting holes 3a.
In step (b), the molded piece which corre-
sponds to the upper layer 3A of the lift i9 then placed
inside a different female die 9 and a cover die 8 is
placed in position in the same way as just described,
as shown in step (c).
With reference to step (c), the inside of
this die is formed with a cavity 3B' for the purpos~ ~f~
molding the lower layer 3B oE the lift. The layer 3A
is placed on a flat bottom surface 9a of the cavity
3B', and the shank of the mounting fixture 6 extends
downwardly into a hole 9b in the die 9 at the bottom of
the cavity 3B'. The side walls 9C of the cavity 3B~
fit snugly against the outer sides of the layer 3A.
After the dies 8 and 9 are secured, molten resin (for
example, nylon resin) is injected in through the injec-
tion port 8a. This nylon resin also fills the connect-
ing holes:3a ha-vin~ a trapezoidal cross-section with a
reverse taper which were formed in the resin of the
upper layer 3A. After the injected resin solidifi.es,
the dies are opened, the molded piece is released and
removed from the dies, and thus the molded lift of this
invention shown in step (d) is obtained.
Because the connecting holes 3a mentioned
above are formed with a reverse-taper trapezoidal
cross-section, when they become filled by the lower
layer resin, reverse-taper connecting projections 3b
are formed. Thus a dovetail type of connection between
the layers is formed, thereby forming or connecting the
resin layer of the lower layer 3B into essentially one
piece with the resin layer of the upper layer 3A in
such a manner that it i9 almost impossible for them to
become separated. In this lift construction, the
connecting holes 3a are formed as through holes in
order to make it possible to open the dies. For the
shape or positioning of the connecting projections 3b
which fit into the connecting holes 3a, for example, as
shown in Fig. ~, conically shaped or mushroom-shaped2~7
connecting projections 3b are formed on the surface of
the horseshoe-shaped lower layer 3B in approximately
three or four locations according to the amount of
surface area. In addition, as shown in Fig. 5, avoid-
ing the space occupied by the flange 6a of the mounting
fixture 6, it is also possible to form a continuous
U-shaped connecting projection 3b (Fig. 5(a)) or to
form two longitudinal or lateral elongated connecting
projections 3b (Figs. 5(b) and 5(c)).
In Fig. 6, if insert dies are used in order
to make it possible to open the dies, it then becomes
possible to connect the lift into one piece without
using through-holes for the connecting holes as is the
case in the embodiment explained above. Fig. 6(a)
shows an example of screwhead-shaped connecting projec-
tions 3b, and Fig. 6(b) shows an example of knob-shaped
connecting projections 3b. In either case, in the same
way as in the embodiment described above, the upper and
lower layers are composed in such a manner that it is
impossible for them to become separated.
A shoe lift according to this invention has
numerous advantages as follows:
5 (1) By molding the lift in two layers, upper and
lower, it is possible to select resin materi-
als having properties which are suitably
matched to the various needs and to allot
them to the upper and lower layers. In other
words, if one of the upper and lower layers~ ~ 8
is molded from a hard resin and the other :
layer from a relatively soft resin, it is
possible to obtain a lift construction which ~:
has advantages with regard to both health and
wearing comfort, with none of the impact :
shock from the floor re~erberating to the
head of the wearer, while at the same time
ensuring sufficient rigidity for the entire :
lift.
(2) It is possible to use different coloring for
the upper and lower layers, and, in particu-
lar, if the lower layer is molded from ure-
thane resin and a bright, natural color lg
used, it is possible to prevent marking of
the floor surface.
(3) Because it is possible to mold the two-layer
lift construction of this invention into one
piece as an injection-molded product, it is
possible to obtain a lift having a beautiful
finish and a high product value at a reason-
able cost.
