Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates in general to the
footwear industry and in particular to improvements in work
shoes and boots and the protection afforded thereby to a wearer
thereof. The invention is related to that shown and claimed in
copending Canadian Application Serial No. 374,968, filed April 8,
1981 and assigned to the assignee of the present invention.
BACKGRO~'D OF THE INVENTION
Protective footwear, such as work boots and shoes,
has been ~anufactured for many years. Such footwear usually
has a protective steel toe cap and may be provided with either
a spring steel arch support or shank and/or a stainless steel
protective mid~sole which protects the arch, ball and toe regions
of the foot from nails or other sharp objects which might
penetrate the sole of the boot. In order to save sole material,
which is relatively expensive, such footwear usually has a heei
plug or filler which is positioned in the heel and reduces the
amount of sole material in the heel portion.
Some problems associated with the manufacture of work
footwear, as detailed hereinafter, relate to the material and
composition of the heel plug, the strength of the shank and/or
mid-sole, and the location of these parts in the sole area
during boot production.
r,7ith respect to the heel plug the material thereof has
in the past been a laminated paperboard or fiberboard material
and the plugs have been die cut from large sheets of the
laminated material. Due to lateral compression of the material
during die cutting the composition tends to flake. The resulting
flakes can migrate to the outer surfaces of the heel and arch
area during production and can then require additional repair
steps to remove blemishes caused thereby.
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Shanks, usually produced from heat treated spring
steel, are used to strengthen the arch area and thus must be
accurately located to serve their intended purpose. Once the
sole has set it is difficult, if not impossible, to detect any
dislocation of a shank. Such dislocation results in factory
rejects or wearer discomfort if not detected at the factory.
One of many past attempts at rectifying this problem involved
the clinching of the shank to the bottom of the insole. This
results in damage to the metal last on which the footwear upper
is attached.
Protective mid-soles are not without their problems
as well. They are difficult to properly locate during
production; they do not always provide complete coverage to the
sole area of the boot; and they may not provide sufficient
rigidity to a boot if a shank is not used in conjunction therewith.
Some attempts have been made to use a steel shank in combination
with thé stainless steel-mid-sole but, unless a layer of an
appropriate material is placed between these metal components,
unacceptable "squeaking" due to the components rubbing together
~0 can result. Furthermore, since the shank is harder than the
mid-sole, repeated flexing of the sole during use can cause the
shank to wear through the mid-sole and perhaps then through the
sole of the boot or shoe.
It is important to realize that safety footwear is
- r~latively expensive, resulting from the cost of the special
components used therein and the care needed in manufacture.
High standards must be maintained to provide the wearer with
maximum comfort and protection. Experience has shown that a
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junction with heel fillers having the af,orementioned upwardly
projecting rib or other connecting meanst whereby a "unitary"
heel filler and protective mid-sole assembly can be pla,ced in
the protective footwear.
PriQr art mid-soles ha~e yaried in overall con-
figuration from units barely covering the.sole area to unlts
covering the overall sole an,d heel area~ This latter configur-
ation is a waste of expensive material since no additional pro-
tection is really achieved when the heel area is covered. The
most important areas to be protected are the arch and ball areas,
with the arch area being the most vulnerable to penetration.
Broadly speaking, the problems of the prior art
are overcome by the present inyention which provides a protective
mid-sole for location in the sole of an,article of footwear compris-
ing a plate member generally conforming in plan and elevation to
the contours of the sole an~d having heel., arch and ball portions,
the plate member being provided in the arch portion thereof with
yenerally longitudinally oriented and downwardly projecting strength-
ening rib means formed integrally therewith.
' Furthermore the present invention can be $een as pro-
viding a protective mid-sole for location in the sole of an article
of ~ootwear comprising a plate member generally conforming in plan
and elevation to the conto~rs of the sole and having heel, arch
and ball portions, the plate member being provided in the arch por-
t,ion thereof with a generally longitudinally oriented and downward-
ly projecting strengthening rib formed integrally therewith, and
in the heel portion with apertured locating means.
The protective mid-sole used in the present invention
1S standardized ,in overall configuration and extends rea.rwardly
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.18~person wearing protective footwear tends to become careless
as to where he places his foot while working as he relies on
his footwear to protect him. If the footwear does not provide
maximum protection the wearer is operating with a false sense
of security.
Many of the aforementioned problems are overcome by
the invention disclosed and claimed in the related Canadian
patent application referred to hereinabove. The invention of
that applciation contemplates first of all the use of a moulded
heel filler to replace the prior art laminated heel plug. The
heel filler of that application may be advantageously provided
with location means in the form of projections on the bottom
surface or through holes to locate and anchor the heel filler
during the sole production step. Also the heel filler of that
application may be provided with means, such as an upwardly project-
ing rib, which can receive a slotted end of a shank or protective
mid-sole so as to properly locate the shank or mid-sole in the
boot sole relative to the heel filler.
The shank, as described in that application, is usually
provided with a central longitudinally extending rib or ribs
which further strengthen the heat treated spring steel.
~dditionally the shank at one end is provided with the afore-
mentioned slot or other co-operating locating mechanism for
attachment to the heel filler.
SUMMARY OF THE INVENTION
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l'he present invention is directed primarily to the
protective mid-sole per se which, by itself, demonstrates
specific advantages over prior art mid-soles. Furthermore the
protective mid-sole of this invention may be utilized in con-
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so as to overlie the forward portion of the heel filler or
plug, thereby bringing the slot therein, if used, into registry
with the locating rib or projection on the heel filler. The
mid-sole has a central rib extending longitudinally in the arch
area to reduce the flexibility of the boot in this region. The
central rib projects downwardly so that a nail or other sharp
object penetrating the sole of the boot or shoe will be deflected
to one side by the rib, thereby greatly reducing the chance of
forced penetration of the mid-sole. With such a ribbed mid-sole
there is no longer the necessity of providing a separate shanX
as in the past when additional arch support was desired.
By utilizing the protective mid-sole and the heel
filler in combination better work footwear is produced. With the
heel fillér there will be a much smaller percentage of production
re~ects and there will be less possible wear on production equip-
ment. The unit cost of a boot or shoe will be less due to a
reduction in cost of the heel filler over the prior art and due
to a reduction in sole material since the heel filler can be
larger than the prior art heel plug. By using the heel filler
in conjunction with a protective mid-sole connected thereto there
will be fewer problems in locating these elements in the sole
during production. Furthermore the accurately located ribbed
mid-sole provides greater strength to the footwear and the
standardized length and coverage of the mid-sole provides greater
protection to the boot or shoe wearer. Standardizing also reduces
lnventory problems as footwear will be designed to meet the shape
of the mid-sole rather than vice versa, as is presently happening.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 shows the sole portion of a prior art work
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boot in cross-section.
FIGURE 2 shows a plan view of a prior art heel plug
and protective mid-sole.
FIGURE 3 shows a perspective view of the heel filler
described and claimed in the aforementioned related application.
FIGURE 4 shows a perspective view of the protective
mid-sole of the present invention.
FIGURE 5 shows a side view of the protective mid-sole
of the present invention.
FIGURE 6 shows the protective mid-sole of the present
invention assembled to a heel filler of the aforementioned
application.
DESCRIPTION OF THE PREFER~ED EMBODIMENT
Figure 1 illustrates in cross-section the sole portion
of a common work boot, the boot being designated by reference
number 20. The illustrated boot is but one example of the many
configurations offered on the market today and is intended only
to show how some manufacturers presently attempt to provide
reasonable protection for a wearer. The boot includes a
protective high carbon steel toe cap 22 covered interiorly and
exteriorly by leather layers 24 and 26 respectively. At the
heel and ankle area, various layers of leather, constituting
portlons of the outer boot 28, the inner boot 30 and the heel
reinforcement 32 are shown in part. The inner sole 34 is con-
structed of reconstituted leather or other "breathable" material.
The external sole 36 includes a heel portion 38, an
arch portion 40, a ball portion 42 and a toe portion 44. The
heel and ball portions have corrugations 45 or other friction-
enhancing means Oll the underside thereof.
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As seen in Figure 1 the sole 36 is provided internally
with a heel plug 46 and a protective sole piece 48. The heel
plug 46 in the past has been formed as a compressed laminate of
paperboard material such as is sold under the trademark "Homosote".
Such material is provided as a large sheet and the plugs are die
cut therefrom. The die cutting operation is not completely
clean, however, as discussed hereinabove, and the paperboard
material tends to flake or leave bits of "dust" clinging thereto
which can be detrimental to subsequent processes. The protective
- 10 sole piece 48 is typically formed of type 301 stainless steel
and conforms generally to the outline of the outer sole in the
arch, ball and toe regions. The protective sole piece 48 is
intended to protect the foot of the boot wearer from nails or
other sharp objects which might penetrate the sole 36 in the
arch, ball or toe regions. The heel plug affords some
protection but its primary purpose is to fill in a portion of the
heel 38 so that the amount of material used to mould the sole,
in the heel region, can be reduced.
There are essentially two processes by which the
soles of work boots are secured to the leather uppers. In the
first process a gummy rubbery material is placed in a mould which
conforms to the outline of the outer sole 36 and which also
defines the outer configuration, including corrugations, etc.
After the rubbery material has partially cured, the heel plug
46 and the protective sole piece 48 are placed, by hand, on the
material already in the mould; additional material is added; and
the upper including the inner sole 34 is brought into contact
with the rubbery material by way of a last. The rubbery material
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is then vulcanized under high heat and pressure to completely
set the material, secure the upper to the sole, and in essence
encapsulate the heel plug 46 and the protective sole piece 48 in
the sole 36.
The second method`involves an injection moulding
process which requires prelocation of the upper, heel plug and
protective sole piece prior to the moulding step.
,, In both of the above described methods there is little
- absolute control over the final position and orientation of
the heel plug and/or the protective sole piece. These items
have been known to drift from their set positions to their final
positions as much as one-half inch. This of course is very
detrimental and can result in failures and/or factory rejects.
Also, the aforementioned problem with the die cut laminated
paperboard heel plugs is manifested at the moulding stages as
the flakes tend to migrate to the outer surface of the heel or
arch areas of the sole. When this happens the flakes must be
ground away from the sole surface and a filler compound
smoothed over the ground area to improve the appearance of the
; 20 sole.
Some of the flaking problems have been overcome by
using a laminated fiberboard material for the heel plug but such
material substitution has resulted in higher cost of production
as the fiberboard material is more expensive than the older
paperboard material.
The heel filler of the aforementioned application over-
comes the various heel plug problems of the prior art and is
illustrated in Figures 3 and 6 of the drawings. Figure 3 shows
a one-piece moulded heel filler 50 which is larger in all
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dimensions than the prior art heel plugs 46, which is lighter in
weight and is less expensive to produce. The heel filler 50 is
advantageously moulded by conventional means of a blown or
e~panded polyethylene material. Other plastics including both
thermosets and thermoplastics may be used. In addition to the
advantages outlined above, the configuration of the heel filler
50 provides additional advantages not available with the prior art.
With reference to Figure 3 the heel filler 50 has
a peripheral side surface 52 which corresponds generally in
transverse cross-section to the cross-section of the heel 38 in
which it will reside. The transverse cross~sectional dimensions
of the heel filler 50 are greater than those of the prior art
heel plug 46 which it replaces and this will result in a saving
in the rubbery material constituting the heel portion 38 of
the boot sole.
Furthermore the upper surface of the heel filler 50
is formed as a step whereby there is a first upper surface 54
which is adjacent the side and rear side walls of the heel
filler. A raised portion 56 rises above the surface 54 and is
defined by side wall 58. The surface 54 provides a convenient
locating and receiving surface for the lowermost ends of the
portions 28, 30 and 32 of the upper during the lasting or
moulding step when the upper is secured to the sole.
As shown in Figure 6 the rear bottom portion of the
heel filler may be bevelled as at 57 so that more sole
material is provided in the bottom rear area of the heel, which
area is most prone to wear during walking. The forward wall 59
of the heel filler may be curved as shown in Figure 3, flat,
or of any other desired shape.
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The heel filler 50 may be advantageously provided,
if desired, with through holes 60 which extend from the top
surface of the raised portion through to the bottom surface of
the heel filler. When the sole is finally formed, whether
through vulcanizing or injection moulding, the material of the
sole can flow into the bores 60 to help locate and rigidify
the heel filler 50 in position. Additionally the bores 60
themselves aid in rigidifying the heel filler. Since the heel
filler is desirably formed in a blow moulding or expansion
process the interior of the heel filler will be somewhat porous.
However, at any surface a "skin" of the material will form, which
"skin" increases the resistance of the moulded articles to
compressive failure. The through bores 60 will increase the
amount of "skin" as a "skin" will form thereabout and thus
the resistance to failure of a heel filler having such bores
will be greater than that of a heel filler not so provided.
The heel filler as des~ribed hereinabove will have
greater utility than, and is an improvement over, prior art
heel plugs and can be used, as described, as a direct replacement
for such heel plugs in any shoe or boot which can make use of
such a filler or plug.
The greatest advantage can be achieved, however, if
the heel filler is used in conjunction with other elements
such as the protective mid-sole of the present invention, to be
described hereinbelow.
In work boots which use a protective mid-sole such
as 48, advantages can be achieved with an improved mid-sole 62
illustrated in Figures 4 and 5, especially when the mid-sole 62
is used in conjunction with the previously described heel filler
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50. As seen in perspective in Figure 4 the mid-sole 62 is
formed as a plate member having a periphery which, like that of
mid-sole 48, conforms to the outline of the sole portions 40, 42
and 44 in plar. and is shaped as required to conform to the shape
of the sole in elevation as shown in Figures 1 and 5. ~owever, mid-
sole 62 is longer than mid-sole ~8, having a rear or heel
portion 64 which extends rearwardly a sufficient distance to
overlie the forward portion of the heel filler 50. This heel
portion 64 is provided with a longitudinally extending slot 66.
This slot fits over, in a close interference fit therewlth, an
elongated projection 68 formed on the top surface of the heel
filler 50 as shown in Figures 3 and 6. With the mid-sole
connected to the heel filler in this manner the assembly operator
only has to concern himself with properly locating a single
element (made up of two parts) in the mould or rubbery material,
rather than with two separate units. Even though a pre-assembly
step is required the overall saving in time and rejected or
spoiled unit greatly outweighs the cost of the pre-assembly step.
Additionally the mid-sole 62 is advantageously provided
with a generally longitudinally extending and downwardly pro-
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jecting rib 70 (Figure 6) which strengthens the mid-sole 62 in
the arch portion and eliminates the necessity of a separate
arch support or shank. On the upper surface of the mid-sole 62
the rib 70 appears as a groove 72. By having the rib 70 face
downwardly the rib 70 will deflect the point of a nail, or other
sharp object, away from an orientation which might otherwise
cause penetration of the mid-sole. If the rib 70 were to face
- upwardly the resulting groove in the underside of the mid-sole 62
would actually guide the sharp object more into a detrimental
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penetrating orientation.
It should also be mentioned that during the vulcaniza-
tion or injection moulding step when the upper is attached to
- the sole, the ~leat used in that step and the pressure applied
by the last will tend to melt that portion of the locating
projection 68 which initially rises above the mid-sole 62 so
as to positively secure the two parts together as in a
rivetting or staking operation.
While the greatest advantages are achieved by the
previously described combination of the mid-sole 62 with the
heel filler 50 is it clear that the present invention could be
used on its own, without being associated with the heel filler
of the aforementioned related application. Mid-soles used by
themselves need not be provided with the slot 66 although the
rib 70 would be necessary in order to achieve the desired
degree of safety. Such a mid-sole could be used in a shoe or
boot assembly that has no heel filler or heel plug per se or
in an assembly that uses either a prior art heel plug or a
moulded heel filler, as described in the related application,-
which has no locating projection, such as 68.
Furthermore if the heel filler 50 has a different
form of locating projection, such as a transverse rib or a
plurality of circular projections, it would be necessary to
form the mid-sole with appropriate corresponding locating
apertures in the heel portion 64, replacing the longitudinal
slot 66 as required.
Notwithstanding the aforementioned location and
assembly advantages of this invention over the prior art and
without altering the concept, an alternative method of pre-
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assembly is possible. The heel filler, as previously described
but absent the protruding locating means on the top surface
thereof, can be pre-assembled with a protective mid-sole ~
by means of insert moulding at the time the heel filler itself
is moulded from plastics material. This generally involves
positioning the mid-sole by mechanical or other means in the
mould prior to injection moulding the heel filler. This process,
carried out by the component manufacturer, is commonly des-
cribed as "insert moulding". The final mid-sole with heel
filler assembly, is integral and functlons in exactly the
same way as an assembly of separate components as described
hereinabove.
Another variation in the aorementioned inventlon which
results in an improved product involves coating the stainless
steel mid-sole with an adhesive material such as is available
unaer the trademark "CHEMLOK 250"available from Hughson Chemicals.
This material is vulcanizable and will securely bond the mid-
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sole to the sole material during a vulcanizing boot-forming step.
A mid-sole bonded in this manner will not shift at all in its
position. It is also conceivable that the mid-sole could be
formed to advantage from materials other than stainless steel,
one such possibility being KEVLAR (trademark of E.I. du Pont de
Nemours and Company).
The preferred embodiments of the present invention
have been described hereinabove. It is understood that other
variations from the described embodiments could occur to a
person skilled in the art without departing from the spirit of
the present invention. Hence the protection to be afforded the
present invention should be dçtermined from the claims appended
hereto in conjunction with the foregoing disclosure.
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