CA1118594A - Protective mid-sole for footwear - Google Patents

Abstract

ABSTRACT
A protective mid-sole for use in footwear such as safety boots or shoes is described. The mid-sole conforms in plan and elevation to the contours of the footwear sole and has heel, arch and ball portions. In the arch portion a generally longitudinally oriented and downwardly projecting rib is provided, the rib strengthening the mid-sole in the arch area and serving to deflect sharp objects away from the vulnerable arch area. The heel portion of the mid-sole may be provided with apertured locating means such as a slot for securing the mid-sole, via an appropriate projection, to a heel filler carrying the projection so as to improve the assembly of a heel filler and mid-sole in the sole of the footwear.

Description

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.

~d/ -1--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 pg/~ - 4 -' ~, ~ ,-" :-~ . , .

.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-sd/

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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 Bd/ -5-'':
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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 sd/

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 sd/ -8-" ' ' .
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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 sd/ -10-~, i8~
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-;i, , 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 sd/ -11-' . -:

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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-sd/ -12-. . ~ , I

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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-: .
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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Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS;

1. A protective mid-sole for location in the sole of an article of footwear comprising a plate member generally conforming in plan and elevation to the contours of the sole and having heel, arch and ball portions, said plate member being provided in the arch portion thereof with generally longitudinally oriented and downwardly project-ing strengthening rib means formed integrally therewith.

2. The mid-sole of claim 1 wherein apertured locat-ing means are provided in said heel portion for reception of a corresponding locating projection extending upwardly from a heel filler member locatable in the heel of said footwear.

3. The mid-sole of claim 1 or 2 wherein said plate member is formed from stainless steel.

4. The mid-sole of claim 1 or 2 wherein said plate member is moulded from a suitable plastics material.

5. A protective mid-sole for location in the sole of an article of footwear comprising a plate member generally conforming in plan and elevation to the contours of the sole and having heel, arch and ball portions, said plate member being provided in the arch portion thereof with a generally longitudinally oriented and downwardly projecting strengthen-ing rib formed integrally therewith, and in the heel portion with apertured locating means.

6. The mid-sole of claim 5 wherein said locating means is adapted to receive a corresponding mating pro-jection extending upwardly from a heel filler locatable in the heel of said footwear.

7. The mid-sole of claim 1, 2 or 5 wherein said plate member is coated on at least one surface thereof with a vulcanizable adhesive material.

8. The mid-sole of claim 5 or 6 wherein said plate member is formed from stainless steel.

9. The mid-sole of claim 5 or 6 wherein said plate member is moulded from a suitable plastics material.

10. The mid-sole of claim 2, 5 or 6 wherein said locating means is a slot extending generally longitudinally within said heel portion.

11. The mid-sole of claim 2, 5 or 6 wherein said locating means is a slot extending transversely within said heel portion.

12. The mid-sole of claim 2, 5 or 6 wherein said locat-ing means is a plurality of circular holes located within said heel portion.