US3786580A

US3786580A - Inner boot and method for forming the same

Info

Publication number: US3786580A
Application number: US00093964A
Authority: US
Inventors: M Dalebout
Original assignee: KIPP AND CHRISTIAN; TANNER GOLD AND TRASK
Current assignee: KIPP AND CHRISTIAN; TANNER GOLD AND TRASK
Priority date: 1968-05-02
Filing date: 1970-12-01
Publication date: 1974-01-22
Anticipated expiration: 1991-01-22

Abstract

An inner boot for use within an outer shell which includes a flexible inner liner sized to receive the foot of an individual, an outer liner positioned about the inner liner to form a substantially closed compartment between the liners and attached to the inner liner with connecting means for maintaining filling material within the compartment and for passing gas out of said compartment when said filling material is injected thereinto. A filling tube can be provided in communication with the compartment for injecting a resin elastomer reaction mixture into said compartment.

Description

United States Patent 1191 Dalebout Jan. 22, 1974 1 INNER BOOT AND METHOD FOR 3,325,920 6/1967 Werner et al. 36/2.5 AL FORMING THE SAME 3,377,721 4/1968 Johnson 36/25 AL 3,521,385 7/1970 Dalebout 36/25 AL [75] Inventor: Melvin W. Dalebout, Salt Lake City,

Utah Primary Examiner-Patrick D. Lawson 1 Asslgnees n r Gold & Trask; 1 1 and Attorney, Agent, or Firm-David v. Trask; William s.

Christian Britt; Richard F. Bojanowski [22] Filed: Dec. 1, 1970 21 Appl. No.1 93,964 57 ABSTRACT Related US. Application Data Continuation-impart of Ser. No. 8,547, Feb. 4, 1970, Pat. No. 3,581,412, which is a continuation-in-part of Ser. No. 726,094, May 2, 1968, Pat. No. 3,521,385.

US. Cl. 36/2.5 AL, 12/142 P Int. Cl. A43b 00/00 Field of Search 36/25 R, 2.5 AL, 71;

References Cited UNITED STATES PATENTS 6/1967 Robinson 36/25 AL An inner boot for use within an outer shell which includes a flexible inner liner sized to receive the foot of an individual, an outer liner positioned about the inner liner to form a substantially closed compartment between the liners and attached to the inner liner with connecting means for maintaining filling material within the compartment and for passing gas out of said compartment when said filling material is injected thereinto. A filling tube can be provided in communication with the compartment for injecting a resin elastomer reaction mixture into said compartment.

27 Claims, 6 Drawing Figures PAIENTEUJAHZZIQH SHEEI 1 OF 2 INVENTOR. Melvin W. Dalebom CW His Attorney PATENTEUJANP? m4 sum 2 0F. 2

JF/G. 5 20" m in;

INVENTOR. Melvin W Dalebout lF/G. 6

His Attorney INNER BOOT AND METHOD FOR FORMING SAME RELATED PATENT APPLICATIONS This application is a continuation-in-part of my copending US. Pat. application, Ser. No. 8,547, filed Feb. 4, 1970, now Pat. No. 3,581,412, said copending application being a continuation-in-part of Ser. No. 726,094, filed May 2, 1968, now issued US. Pat. No. 3,521,385.

BACKGROUND OF THE INVENTION One of the most difficult problems that arises in connection with ski boots and the like is that of snugly fitting the boot to the foot of an individual without subjecting the foot and ankle to painful irritation because the boot fits too tightly. Attempts have been made to overcome this problem by using moldable pads in the boot such as described in U.S. Pat. No. 3,374,561, or by filling isolated compartments in the boot with small discrete particles or semi-resins which flow to conform with the shape of the individuals foot such as described in U.S. Pat. Nos. 3,325,920 and 3,377,721. However, in all such previous attempts only a portion of the inner boot has been form-fitted to the shape of the wearers foot, i.e., generally, the portion of the boot that conforms with the sides of the foot and the lower ankle. Accordingly, the foot can still shift within the boot unless the boot is closed very tightly about the foot. This means that portions of the boot that do not conform to the shape of the individuals foot can exert substantial pressures on the foot thereby creating sources of pain.

Accordingly, it is the principal object of this invention to provide an inner boot for substantially rigid outer sheels, such as ski boot shells, having an interior liner which is custom fitted to the shape of an individuals foot and preferably an exterior liner shaped to conform with the interior shape of the outer shell.

Another object of the invention relates to a method for forming the inner boot.

BRIEF DESCRIPTION OF THE INVENTION In its broadest form the invention relates to the inner boot which includes a flexible inner liner sized to receive the foot of an individual; a flexible outer liner positioned about the inner liner forming a substantially closed compartment between the liners said outer liner being attached to the inner liner with connecting means for maintaining filling material within the compartment and for passing gas out of said compartment when it is filled with said material.

In another embodiment of the invention, the filling material is a resin elastomer reaction mixture.

In another embodiment of the invention the connecting means comprises spaced stitches.

In yet another embodiment of the invention, the resin elastomer reaction mixture is injected into the compartment between the inner and outer liners when the individuals foot is positioned within the inner liner and air entrapped in said compartment is urged out of said compartment through the connecting stitches.

In still another embodiment of the invention, the inner liner of the inner boot is a closed cell foam pad with a stretch fabric material secured to the pads surface and the outer liner is an elastic member which is urged by the filling material to substantially conform with the interior of the outer shell.

BRIEF DESCRIPTION OF THE DRAWINGS So that the invention will be more readily understood and carried into effect reference is made to the accompanying drawings, which are offered by way of example only and are not to be taken as limiting the invention, the scope of which is defined by the appended claims which are intended to embrace equivalent structures and processes.

FIG. I is a side view of the inner boot of the invention with an elongated filling tube attached thereto for injecting a liquid resin elastomer reaction mixture into the compartment between the boots liners.

FIG. 2 is a top view of the inner boot of the invention.

FIG. 3 is a sectional view taken in the plane of line 3-3 of FIG. 1 looking in the direction of the arrows.

FIG. 41 is a partial sectional view of a segment of the inner boots wall showing the construction of the wall.

FIG. 5 is a sectional view taken in the plane of line 5--5 of FIG. 2 looking in the direction of the arrows. FIG. 6 is a sectional view taken in the plane of line 66 of FIG. 3 looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to the drawings, inner boot 10 of this invention is shown in FIGS. 1 and 2. As illustrated, the inner boot is preferably a high top one that can be sized to receive the entire foot and lower ankle of an individual. The ankle cuff portion 12 of the boot I0 is preferably sized to extend beyond the top edge of the outer boot shell in which the inner boot is used to protect the ankle from contacting any portion of the outer boot shell. While the inner boot 10 can be used with any outer boot shell, it is preferred to use a substantially rigid shell such as described in my US. Pat. No. 3,521,385.

Inner boot includes an outer liner 14 and an inner liner 16 which are connected together proximate the top edge 18 of the boots ankle cuff 12 to form a compartment 20 between the

liners

14 and 16. Compartment 20 extends substantially about the entire foot and preferably the lower ankle of an individuals foot when said foot is placed within the inner boot. Inner liner 16 and, preferably outer liner 14 are constructed from a flexible material such as a suitable plastic, leather, fabric, or the like, so that the liners can be urged to a predetermined shape when compartment 20 is pressure filled with a resin elastomer of the type hereinafter described. Most preferably, outer liner 14 is constructed from a thin walled stretchable material molded as a unitary structure in the form of a boot or shoe. Materials such as neoprene, rubber latex, or the like, are useful for this purpose. As shown in FIG. 3, inner liner 16 is somewhat smaller than outer liner 14 so that the outer liner can be urged snugly against the interior of the outer boot shell while inner liner 16 is urged to conform with the shape of a foot or mandrel positioned within the inner boot 10. The ankle cuff and instep portions of inner boot 10 are split at 22 so that an individual can easily place his foot into the bower portion of the boot. A conventional tongue can also be provided within the boot beneath said split in the ankle cuff for sealing purposes, or padding, hereinafter described, can be built into the inner boot which does away with the need for a tongue.

To minimize friction on the foot of the user of the inner boot of this invention, a layer of protective material such as described in U.S. Pat. No. 3,449,844 is positioned over the interior face of inner liner 16, or preferably, said protective layer is used as the inner liner 16. Protective layers of the type described in said Pat. No. 3,449,844 include a closed call foam base 24 preferably having a two-way stretch fabric 26 bonded to the bases interior face, i.e., the face of the base 24 which is positioned adjacent to an individuals foot positioned in the inner boot. Base 24 is an elastic closed cell foam such as neoprene, closed cell rubber, poly vinyl chloride, rubber latex, vinyl foam, and the like. Stretch fabric 26 provides a slick surface between the protective pad and the foot of a person using the boot. Any fabric and/or weave can be used having a coefficient of friction lower than that of foam base 24 which is capable of a two-way yield or stretch so that motion is imparted through the fabric to the foam base. The best example of a fabric of this type which does not impede base movement in stretch nylon, also known as elastic nylon. Fabric 26 is bonded to foam base 24 with a rubbery adhesive so that the elastic characteristics of the fabric or the foam are not destroyed when the fabric is bonded to base 24.

As indicated the instep and ankle cuff slit 22 in inner boot 10 can be sealed with a conventional shoe tongue, not shown in the drawings, or an instep flap 30 and an ankle cuff flap 32, each preferably made of leather or the like, can be used for this purpose. When such flaps are used it is preferred to provide a layer of relatively soft padding 34 along the opposite side edges of slit 22 as shown in FIG. 5. Padding 34 is secured to inner liner 14, preferably within compartment 20, to cover the area of the foot normally covered with a tongue member. The padding can, of course, be used in the ankle cuff portion 12 of inner boot 10 as well as any other portion thereof where desired. The thickness and type of padding can be varied to obtain a predetermined softness.

When a thin walled stretchable outer liner 16 is used it is preferred to secure a fabric tape 36 along the edges of the outer liner 16, i.e., along slit 22 and around the ankle cuff portion of the liner, that are stitched to inner liner 14. The fabric tape bonded to the outer liner 16 prevents the outer liner from rupping when it is stitched. Also, to add strength to the outer liner and to give it a finished appearance a leather facing 38 can be applied to the outer liner adjacent to slit 22.

The upper end 18 of inner boot 10 is preferably finished by lapping inner liner 14 around an elongated foam strip such as the one-half round member 40 shown in FIG. 6 and then sewing inner liner 14, outer liner l6, and flap 32 together in a conventional fashion with stitches 42. As an alternative, an elastic cuff can be sewed to the boots upper end 18 for sealing purposes. The elastic cuff can be formed from any relatively soft elastic material such as stretch nylon, or the like.

The filling material of this invention is preferably a resin elastomer suitable for forming a resilient form, i.e., one that is capable of being bent and compressed and then return to substantially its original shape. Polyurethane elastomers are particularly useful filling materials. Such elastomers are formed by curing liquid reaction mixtures of organic polyisocyanates and organic polyols in the presence of a catalyst and, optionally, a filler. When a suitable catalyst is used the curing reaction occurs at ambient temperature and pressure conditions.

Suitable organic polyols for preparing the polyurethane elastomers include a simple polyols such as ethylene glycol, or glycerol, as well as, polymeric polyols such as polyester polyols and polyalkylene ether polyols. Preferably, the organic polyols is a polyalkylene ether polyol such as described in U.S. Pat. Nos. 3,249,855 and 3,201,136.

Typical suitable organic polyisocyanates for preparing poly-urethane elastomers include aliphatic polyisocyanates such as hexamethylene diisocyanate, pentamethylene diisocyanate, etc; cycloaliphatic polyisocyanates such as cyclohexyl 2,4 diisocyanate, 4, 4'- methylene bis (cyclohexyl iso-cyanate), etc., and; aromatic polyisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4-methylene bis (phenylisocyanate), l,5-naphthalene diisocyanate, 4,4',4"-triphenylmethane triisocyanate, polyalkylene polyaryl polyisocyanates disclosed in U. S. Pat. No. 2,683,730, etc.

The proportions of organic polyisocyanate and organic polyol employed in the polyurethane forming reaction can be varied somewhat depending on the particular characteristics of the polyurethane product desired. In preparing urethane elastomers according to the preferred embodiment of the invention, an amount corresponding to a NCO: OI-I ratio of about 0.9: l-l .411 is used.

Useful compounds which function as cold curing catalysts are, for example, certain organo-tin compounds of tetravalent tin, which may be defined as the organotin compounds having at least one tin to chalcogen valence bond. Representative groups of these tin catalysts are the organo-tin oxides, hydroxides, carboxylates i (e md),

| SI1--O"C")1 alcoholates l V or combinations thereof. Representative examples of effective tin catalysts of this group are dibutyl tin diacetate, dibutyl tin di-2-ethyl hexoate, dibutyl tin oxide, dibutyl tin monomethoxy methyl maleate, dibutyl tin sulfide, tributyl tin 2-ethyl hexoate, monobutyl tin tri-2- ethyl hexoate, triphenyl tin hydroxide, bis-(tributyl tin) oxide, bis-(tributyl tin) tetrapropenyl succinate, bis- (tri-butyl tin) n-nonyl succinate, and bis-(tributyl tin) malonate.

Another group of cold curing catalysts for liquid hardenable polyurethane reaction systems of the type herein described are represented by the soluble organic acid salts or leads, bismuth, antimony, mercury, tin, and particularly their fatty acid salts. Representative of these metal salts are those of the fatty acids which are soluble in the glycol and urethane reaction mixture. A preferred group of catalysts are the lead salts such as lead octoate (lead di-2-ethyl hexoate), lead naphthenate and similar lead drying salts.

As indicated, a filler can be added to the urethane forming reaction mixture to alter the properties of the elastomer. For example, even very small amounts of finely divided inert fillers will increase the load bearing characteristic of the elastomer. Any suitable finely pulverized organic or inorganic material or combination of materials which are inert to reaction with the elastomer forming reactants, may be incorporated into the polymer. Typical example of suitable fillers include expanded mica, cork, perlite, attapulgite, calcium silicate, kaolin, magnesium tri-silicate, talc, zinc sulfide, red lead oxide, barium sulfate, bentonite, calcium fluoride, halloysite, titanium dioxide, aluminum silicate, amorphous silica, etc.

I The amount of filler used in generally not critical and can be varied over a broad range and, as indicated, depends to a considerable extent upon the particular properties and characteristics desired in the final elastomer product. Generally, the filler is added in amounts of between about ten percent and sixty percent by weight of the total reaction mixture.

Specific examples of the method of producing polyurethane elastomers suitable for use in this invention are disclosed in US. Pat. Nos. 3,429,855 and 3,201,136, which patents are incorporated herein by reference in their entirety.

The inner boot of this invention is custom fit to the foot of an individual by placing the boot in an outer support shell and thereafter closing the shell about the inner boot with the individual s foot positioned therein. Optionally, a mandrel corresponding to the shape of the foot and lower ankle of an individual can be positioned within the boot. A liquid resin elastomer reaction mixture of the type herein described in then injected under pressure into compartment until the compartment is substantially filled. When this occurs, inner liner 16 is snugly urged to a position adjacent to the individuals foot and lower ankle, or mandrel, and outer liner 14 is urged against the interior surface of the outer support shell. To expedite filling an elongated fill ing tube 28 is secured to liner 14 in communication with compartment 20. Preferably, the filling opening in liner 14 is positioned proximate the upper portion of the inner boots ankle cuff 12 above the top of the upper surface of the outer support shell. However, an opening can be provided in the outer support shell at any appropriate position therein through which the filling tube passes.

When fitting the inner boot 10 it often is desirable to provide an enlarged area for the individuals toes so that they can freely move within the boot. When this is desired an appropriately sized covering can be positioned over the toes before the individuals foot is placed within the boot. Accordingly, after the filling material has been injected into the inner boots compartment 20, the toe covering can be removed and there results an enlarged compartment for the toes. This step can, of course, be omitted when an appropriately sized mandrel is used for fitting purposes.

It is to be noted that unless means are provided for air and gases of reaction to escape from compartment 20 when it is filled with the filling material the material will not completely fill compartment 20. Accordingly, it is preferred to connect liners l4 and 16 of inner boot 10 by, for example, sewing them together with spaced stitches 42 in a fashion which allows the air and other gases within compartment 20 to escape between the stitching. However, the stitches should be sufficiently tight to prevent the filling material from passing in any large quantity therethrough. When air pockets are formed within compartment 20 the air can be withdrawn with a conventional hypodermic needle.

The individual components of the elastomer reaction mixture can be prepackaged so that they can be easily mixed together in a proper reaction mixture. For example, a three package system can be used for polyurethane elastomers wherein a predetermined quantity of a polyisocyanate, a polyol and a curing catalyst are packaged in separate containers. When an inner boot it) is to be pressure filled with an elastomer, the separate packages containing the reaction components are emptied into a container and mixed into a substantially homogeneous reaction mixture. Preferably the reaction mixture is whipped as it is mixed to entrain air bubbles therein which reduce the weight of the elastomer when it cure hardens and also increases its insulating property.

After compartment 20 has been filled to the desired extent the resin elastomer is allowed to cure harden. This can be done at ambient conditions or, optionally, the curing rate can be accelerated by elevating the temperature of the inner boots environment. Preferably, the boot 10 is filled with a resin elastomer that will substantially cure harden in less than minutes and most preferably, in about 10 to 45 minutes from the time the resin reactants are mixed together. After the reaction mixture has cured filling tube 28 is severed proximate its point of connection to outer wall 14. A patch can then be secured to the outer wall over the severed filling tube for appearance purposes.

I claim:

1. in combination with an outer shell, an inner boot adapted to be custom fit to the foot of an individual positioned within said outer shell, said inner boot comprising a flexible inner liner sized to receive the foot of said individual; an outer liner positioned about said inner liner to form a substantially closed compartment between said inner liner and said outer liner, the outer and inner liners being attached together with connecting means for substantially maintaining filling material within said compartment and for exhausting gases out of said compartment when said filling material is passed into said compartment; and filling means in communication with said compartment for injecting filling material into said compartment.

2. The combination of claim 1 wherein said connecting means comprises spaced stitches.

3. The combination of claim 2 wherein said inner boot is sized to enclose the foot and lower ankle of said individual.

4. The combination of claim 2 wherein said filling means comprises an elongated tube.

5. The combination of claim 4 wherein said elongated tube is secured to the ankle cuff portion of said outer liner at a position above the top edge of the ankle cuff of the outer boot shell.

6. The boot of claim 3 wherein said inner liner and said outer liner of said inner boot surrounds the entire foot and lower ankle of said individual.

7. The boot of claim ll wherein said outer liner is formed from a thin walled stretchable sheet material.

8. The boot of claim 7 wherein said thin walled stretchable sheet material is latex rubber.

9. The boot of claim 7 wherein said outer liner is formed as a unitary structure in the proximate shape of a boot.

10. The combination of claim 9 wherein said inner liner of said inner boot comprises a closed cell foam sheet having a two-way stretch fabric bonded to the face of said sheet positioned adjacent said foot of said individual.

11. An inner boot for use within an outer shell and adapted to be custom fit to the foot of an individual which comprises a flexible inner liner sized to receive said foot of said individual; an outer liner positioned about said inner liner to form a substantially closed compartment between said inner liner and said outer liner, the outer and inner liners being attached together with connecting means for substantially maintaining filling material within said compartment and for exhausting gases out of said compartment when said filling material is passed into said compartment; and filling means in communication with said compartment for injecting filling material into said compartment.

12. The inner boot of claim 11 wherein said connecting means comprises spaced stitches.

13. The inner boot of claim 12 wherein said inner boot is sized to enclose the foot and lower ankle of said individual.

14. The inner boot of claim 12 wherein said filling means comprises an elongated tube.

15. The inner boot of claim 12 wherein said inner liner of said inner boot comprises a closed cell foam sheet having a two-way stretch fabric bonded to the face of said sheet positioned adjacent said foot of said individual.

16. The inner boot of claim 12 wherein said outer liner is formed from a thin walled stretchable sheet material.

17. The inner boot of claim 16 wherein said sheet material is latex rubber.

18. The inner boot of claim 13 wherein said outer liner of said inner boot surrounds the entire foot and lower ankle of said individual.

19. The inner boot of claim 12 wherein a relatively soft pad is secured to said inner liner to cover the instep portion of the individuals foot.

20. A method for custom fitting an article of footwear to the foot of an individual which comprises providing an outer shell with an inner boot within said outer shell, said inner boot including an inner liner sized to receive the foot of said individual and an outer liner positioned about said inner liner to form a substantially closed compartment between said inner liner and said outer liner, the outer and inner liners being attached with connecting means for substantially maintaining filling material in said compartment and for exhausting gases out of said compartment; injecting a filling material into said compartment when a form the shape of an individuals foot is positioned within said inner liner to exhaust gases out of said compartment through said connecting means and to urge said inner liner substantially adjacent to and about said form of said individuals foot and to urge said outer liner substantially against the interior sidewalls of said outer boot shell.

21. The method of claim 20 wherein said filling material is a liquid resin reaction mixture and said reaction mixture is cured in said compartment while said form of said individuals foot is positioned within said inner liner.

22. The method of claim 20 wherein the form the shape of said individuals foot is said individual's foot.

23. The method of claim 21 wherein said resin reaction mixture is aerated prior to injecting said reaction mixture into said compartment.

24. The method of claim 21 wherein said resin reaction mixture is a polyurethane resin reaction mixture.

25. The method of claim 22 wherein a toe covering is positioned over the toes of said individuals foot when said foot is positioned within said inner liner of said inner boot to provide an enlarged area for the toes of said individuals foot in said inner boot.

26. The method of claim 24 wherein said polyurethane resin reaction mixture is prepared prior to injecting said mixture into said compartment by mixing together separately packaged quantities of a polyisocyanate, a polyol and a curing catalyst.

27. A method of custom fitting a boot to a mandrel corresponding to the foot of a wearer or to the foot of the wearer comprising,

providing an outer boot shell made of a substantially rigid material with an injection opening and vent opening,

providing a flexible, double-wall liner for the boot shell, the inner wall of which approximates the surface of the mandrel or foot of the wearer and the outer wall of which has injection and vent openings therein adapted to register with the injection and vent openings in the boot shell,

inserting a mandrel or foot of the wearer in the liner,

inserting the liner into the boot with the injection opening on the liner registering with the injection opening of the boot and the opening on the liner registering with the vent opening of the boot, closing the boot about the liner,

injecting through the injection opening of the liner an uncured foaming resinous material mixed immediately prior to injection with a catalyst, the components of the resinous material reacting to produce an elastomeric foam which expands to fill the space between the inner and outer walls of the liner and which causes the outer wall of the liner to conform substantially to the inner surface of the shell of the boot and the inner wall of the liner to conform substantially to the mandrel or foot of the wearer, the forming gas generated in the liner by mixing of the catalyst and resin venting to the atmosphere through the vent opening, and

allowing the foam resin adequately to cure in the liner prior to removal of the mandrel or foot of the wearer.

Claims

7. The boot of claim 1 wherein said outer liner is formed from a thin walled stretchable sheet material.

17. The inner boot of claim 16 wherein said sheet material is latex rubber.

19. The inner boot of claim 12 wherein a relatively soft pad is secured to said inner liner to cover the instep portion of the individual''s foot.

20. A method for custom fitting an article of footwear to the foot of an individual which comprises providing an outer shell with an inner boot within said outer shell, said inner boot including an inner liner sized to receive the foot of said individual and an outer liner positioned about said inner liner to form a substantially closed compartment between said inner liner and said outer liner, the outer and inner liners being attached with connecting means for substantially maintaining filling material in said compartment and for exhausting gases out of said compartment; injecting a filling material into said compartment when a form the shape of an individual''s foot is positioned within said inner liner to exhaust gases out of said compartment through said connecting means and to urge said inner liner substantially adjacent to and about said form of said individual''s foot and to urge said outer liner substantially against the interior sidewalls of said outer boot shell.

21. The method of claim 20 wherein said filling material is a liquid resin reaction mixture and said reaction mixture is cured in said compartment while said form of said individual''s foot is positioned within said inner liner.

22. The method of claim 20 wherein the form the shape of said individual''s foot is said individual''s foot.

25. The method of claim 22 wherein a toe covering is positioned over the toes of said individual''s foot when said foot is positioned within said inner liner of said inner boot to provide an enlarged area for the toes of said individual''s foot in said inner boot.

27. A method of custom fitting a boot to a mandrel corresponding to the foot of a wearer or to the foot of the wearer comprising, providing an outer boot shell made of a substantially rigid material with an injection opening and vent opening, providing a flexible, double-wall liner for the boot shell, the inner wall of which approximates the surface of the mandrel or foot of the wearer and the outer wall of which has injection and vent openings therein adapted to register with the injection and vent openings in the boot shell, inserting a mandrel or foot of the wearer in the liner, inserting the liner into the boot with the injection opening on the liner registering with the injection opening of the boot and the opening on the liner registering with the vent opening of the boot, closing the boot about the liner, injecting through the injection opening of the liner an uncured foaming resinous material mixed immediately prior to injection with a catalyst, the components of the resinous material reacting to produce an elastomeric foam which expands to fill the space between the inner and outer walls of the liner and which causes the outer wall of the liner to conform substantially to the inner surface of the shell of the boot and the inner wall of the liner to conform substantially to the mandrel or foot of the wearer, the forming gas generated in the liner by mixing of the catalyst and resin venting to the atmosphere through the vent opening, and allowing the foam resin adequately to cure in the liner prior to removal of the mandrel or foot of the wearer.