Boot and shoe making – Processes – Miscellaneous parts
Reexamination Certificate
1998-01-30
2001-03-27
Patterson, M. D. (Department: 3728)
Boot and shoe making
Processes
Miscellaneous parts
C012S1420MC, C036S0170PW, C036S0170PW, C036S019500
Reexamination Certificate
active
06205604
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to an improved welt used in the production of shoes. The welt is precemented with an adhesive that can be activated during the shoe production process.
BACKGROUND OF THE INVENTION
Traditionally, a leather welt has been stitched to a shoe upper, which was in turn attached to the shoe sole, for comfort and longevity of the shoe. Today, with the advent of unit soles, uppers are attached to the sole by cement; to preserve the traditional appearance, a separate welt is attached to the unit sole around the periphery of the upper. This welt may also increase the strength of the bond between the upper and the sole of the shoe, since the welt is cemented on both sides.
The separate welt is most commonly in the form of a vinyl (or other plastic) strip, which is stitched (or cemented) to the upper, and is cemented and/or stitched to the sole. The cement is usually applied in the form of a viscous liquid to the surface of the welt, which is then placed in contact with the sole or with both sole and upper to form a bond.
It has been suggested that manufacturing costs could be reduced by precoating the welt with a solid adhesive, which could be activated to form a bond when in contact with the sole or both the sole and upper. For example, the welt can comprise a layer of a thermoplastic polymer. Such a welt can be placed in contact with the sole (and optionally the upper), and heat can be applied to soften the thermoplastic and cause it to activate and bond with the sole (and upper). This method avoids the use of dangerous aromatics and volatile cements, and reduces the amount of tooling used in shoe manufacture. Thus, it would be expected to be less expensive than the traditional process.
A precoated welt of this type (manufactured by a coextrusion process), was briefly manufactured and sold by Rextrude, Inc., in the early 1980's. This welt was found not to form a sufficiently strong bond with the shoe, however. Further, it was found that coils of precoated welt would sometimes self-adhere during transport, particularly when left for long periods in semitrucks in the hotter regions of the country. An enclosed truck bed can reach temperatures as high as 140° F. in the summer in some parts of the U.S. Because of these problems, precoated welts were abandoned by the industry.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a precemented welt capable of forming a strong bond with a shoe sole or with both a sole and an upper when placed in contact therewith and subjected to activating conditions. It is a further object to provide such a welt having activating conditions which are unlikely to be attained unintentionally during storage or shipping of the welt material.
As used herein, “activating conditions” are conditions which cause a solid cement material to adhere to other materials with which it is placed in contact. For the thermoplastic cement materials recommended for the preferred embodiments of the invention described below, an activating condition will usually be a condition of high temperature, suitable to cause softening of the thermoplastic material. Other types of activating conditions are also contemplated within the scope of the invention, such as the presence of solvents or resins. The cement material is said to “bind” to the contacting material when it is subjected to activating conditions.
In one aspect, the invention comprises a precemented welt comprising a body member and a surface layer, the surface layer capable of binding when exposed a temperature of at least 225° F. for a time of at least 30 seconds. The surface layer may be an aromatic polyurethane elastomer such as MORTHANE® PA07. The bond formed with typical sole materials by exposing the welt to activating conditions may have a strength of 30 psi (pounds per square inch) or more.
®“MORTHANE” is a registered trademark of Morton International, Inc.
In another aspect, the invention comprises a precemented welt having a body member and a surface layer, where the surface layer comprises an aromatic polyurethane elastomer. The surface layer may be capable of forming a bond with typical sole materials having a strength of 30 psi or more. The surface layer may be selected so that exposing the welt to air at 140° F. does not constitute an activating condition.
In a further aspect, the invention comprises a precemented welt comprising a solid surface layer capable of forming a bond when subjected to activating conditions, where the solid surface layer is capable of forming a bond having a strength of at least 30 psi. The surface layer is selected so that exposing the layer to air at 140° F. does not constitute an activating condition.
In another aspect, the invention comprises a method of making a precemented welt. The method comprises coextrusion of the structural material of the welt with a thermoplastic polymer capable of binding to a contacting material when exposed to activating conditions. The polymer is selected so that exposure to air at 140° F. does not constitute an activating condition. The bond formed by exposing the welt to activating conditions may have a strength of 30 psi or more. The polymer may be selected so that activating conditions include exposing the welt to temperatures of at least 225° F. for a period of at least 30 seconds.
REFERENCES:
patent: 1952329 (1934-03-01), McKenna
patent: 2117824 (1938-05-01), Rogers
patent: 3824643 (1974-07-01), Decoulos
patent: 4095543 (1978-06-01), Gassman
patent: 4390678 (1983-06-01), LaBelle et al.
patent: 5608000 (1997-03-01), Duan et al.
patent: 5820719 (1998-10-01), Strickland et al.
patent: 5885679 (1999-03-01), Yasue et al.
Choate Hall & Stewart
Patterson M. D.
Rextrude Co.
LandOfFree
Precemented welt does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Precemented welt, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Precemented welt will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2441976