Foot-fitting insert for ski boot or the like
United States Patent 3925916

A flexible insert for a boot comprises a foot-fitting liner with a core of elastomeric sheet material sandwiched between two skins. At least part of the core is an open-celled foam polymer in an air-impervious envelope, preferably of heat-sealable plastic.

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International Classes:
B32B5/18; A43B5/04; (IPC1-7): A43B19/00
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Primary Examiner:
Lawson, Patrick D.
Attorney, Agent or Firm:
Ross, Karl Dubno Herbert F.
I claim

1. An insert for a boot; comprising a foot-fitting liner of flexible sheet material including an elastomeric core sandwiched between two skins, at least part of said core having a multiplicity of interstices filled with air, said skins including a fabric impregnated with an air-impervious mass to form an airtight envelope about said part.

2. An insert as defined in claim 1 wherein said part consists essentially of an open-celled foam polymer.

3. An insert for a boot, comprising a foot-fitting liner of flexible sheet material including two juxtaposed skins bonded to each other along a plurality of closed seams encompassing separate areas, and an elastomeric core of open-celled foam polymer sandwiched between said skins in each of said areas, said skins forming an air-impervious envelope about each core whereby air in the cells of each core has limited mobility within the envelope but cannot escape therefrom.

4. An insert as defined in claim 3, further comprising a solid elastomeric layer sandwiched between said skins in parts of said liner outside said areas.

5. An insert as defined in claim 3, wherein said areas extend along opposite sides of said liner across the region of the ankle.

6. An insert as defined in claim 5, further comprising a resilient pad on said liner overlying a fraction of each area in the region of the ankle.

7. An insert as defined in claim 3 wherein said skins include a fabric.

8. An insert as defined in claim 7 wherein said fabric is impregnated with an impervious mass along said part.

9. An insert as defined in claim 7 wherein said envelope consists of thermoplastic layers overlain by said fabric.


My present invention relates to a foot-fitting insert for a ski boot or the like, adapted to be received in the boot as a permanent or removable liner.


Liners of this type are especially desirable in the case of integrally molded ski boots which must allow for a certain internal clearance in order to give the foot of the skier the necessary mobility. The inserted liner is thus designed to fill up that clearance without unduly restricting the motion of the foot, serving at the same time as a thermal insulator.

Boot liners are known which comprise a sealed envelope filled with a pasty mass, being displaceable inside the envelope to adapt itself to the shape of the foot. Aside from the high cost of such liners, their effectiveness is limited to certain temperature ranges below which the mass tends to harden and above which it becomes excessively liquid. Such liners are therefore not satisfactory for ski boots which are worn both indoors and outdoors so as to be subject to major temperature variations.

Also not fully satisfactory are liners in which the flowable mass has been replaced by air pockets. Although the usefulness of such a boot insert is not substantially affected by changes in temperature, the air in the pockets tends to yield in the presence of concentrated stress as caused by protrusions on the foot of the user, or possibly on extraneous objects when the insert is to be extracted from the boot to serve as after-ski footwear.


It is, therefore, the object of my invention to provide an improved insert of this description which avoids the aforestated disadvantages and can be used as either a permanent or an extractable liner for a ski boot.


I realized this object, in accordance with my present invention, by constructing a foot-fitting liner from flexible sheet material including an elastomeric core sandwiched between two skins, these skins forming an air-impervious envelope about at least a part of the core which has a multiplicity of interstices filled with air. This enveloped part consists, pursuant to a further feature of my invention, of an open-celled foam polymer such as, for example, polyurethane.

The air-impervious envelope may consist of heat-sealable thermoplastic material, either as a self-supporting foil or an an impregnant of a skin-forming fabric layer, to enable all-around closure of the envelope by thermal fusion.


The above and other features of my invention will now be described in detail with reference to the accompanying drawing in which:

FIG. 1 is a longitudinal sectional view of a ski boot lined with an insert according to my invention;

FIG. 2 is a side-elevational view of the insert of FIG. 1 without the boot;

FIGS. 3 and 4 are cross-sectional detail views respectively taken on the lines III -- III and IV -- IV of FIG. 2; and

FIG. 5 is a view similar to FIG. 4, illustrating a modification.


An integrally molded ski boot 1, FIG. 1, is provided with an insert 2 which may be removable therefrom to serve as an after-ski shoe. Insert 2 is a foot-fitting liner of flexible sheet material with an elastomeric core 4, 4a sandwiched between two skins comprising a pair of fabric layers 3 which may be adhesively bonded thereto. Two major lateral areas A of the insert (one on each side), extending over the region of the ankle, are bounded by a closed seam 7 forming a sealed envelope for the core portion 4a, FIGS. 4 and 5, which consists essentially of an open-celled foam polymer. In FIG. 4 the envelope is formed by two thermoplastic layers 6, e.g. of polyethylene, fusion-bonded to each other along the seam 7 and overlain by the fabric layers 3. FIG. 5 shows the fabric layers 3 themselves impregnated with resin, e.g. a polyester, to form the airtight envelope around the open-celled core portion 4a, the seam 7 being here produced by fusion of the impregnants with omission of the plastic layers 6.

As further shown in FIG. 1, a pair of elastic pads 8 (one on each side) may be juxtaposed with the insert 2 in the region of the ankles for additional protection, the material of these pads being substantially denser than that of the core portion 4a. Pads 8 may consist of the same solid (i.e. nonfoamed) elastomeric material as the core portions 4 surrounding the area A, e.g. polyurethane. Any lateral pressure acting upon this pad will be distributed by the resilient core 4a over the entire area A for effective cushioning of the foot without materially impeding its mobility.

Naturally, other areas or possibly the entire insert could be provided with the highly elastic core 4a sealed within an airtight envelope.

Since the air in the interstices of the core 4a cannot migrate freely within the envelope but can shift only to a limited extent, it will not be completely extruded from a region subjected to localized lateral stress so that continued mechanical as well as thermal protection is assured for the entire foot clad with the insert. This insert, accordingly, can also be worn indoors on the foot without the boot 1.

My improved insert 2 can be produced at greatly reduced cost, compared to the conventional liners referred to above, and can be sealed along the boundary 7 with very little effort. This enables high-rate mass production with conventional equipment.

Although polyurethane has been mentioned as an example of a foamable plastic material of low thermal conductivity and good mechanical stability, both on shelf and in use, other materials in this class can be employed for the same purpose.