CA2030562A1 - Flexible heated sole for footwear, containing heat-accumulating materials of changing state - Google Patents

Abstract

In a flexible heated sole for articles of footwear containing heat-accumulating material of which the state changes at a melting point of >40·C, the material (15) is held internally of the sole (35) together with a heat source which, when activated, brings about the change from solid to liquid state; in the liquid state, the material possesses the capacity to absorb a notable quantity of thermal energy, which is gradually restored as heat to the foot of the wearer over a generous period of time.

Description

WO 90tl2516 2 ~ ~ f3 3 ~

A flex-blo heated sole for footwear, containing heat-ac~umulating materials of changing state The discomfort of cold feet is one suffered by many people. It is a problem experienced ~y those with poor circulation, and those who work in cold and damp conditions, or in sedentary or static types or 05 occupation.
The prior art embraces a variety of heated footwear designs: footwear heated by means of gas, by the introduction and extraction of heat sources, by means of exothermic materials, and of materials heated by pressure received from the wearer's feet.
Other designs feature electric heating by means of resisrances enveloped in refractory mater-al, ror exampie ceramic. Such designs have met with scant commercial success, and for reasons that are simply identified: the impossibility of their large scale industrial implementation, their high cost, their lack of effectiveness and practical advantages.
Accordingly, the object of the present invention is to overcome the drawbac~s mentioned above through the embodiment of a sole featuring much lower costs ~ ~ 3 o ~ ~ ~ PCT/~ W~2 of application than those of the pric.r art~ ease of azsembly of it~ component parts! and significant practical advantages in use. ~oreover ! the sole is filled with ~ heat accumulating material capable of 05 changing state! which ~eeps the footwear warm for an e:;tended period of time even after the heating energy supply has been disconnected. The fle;~ible sole containing the heat accumulating material possesses a structure giving maximum flexibility !
and is notably lightweight. ~lso! the flexible heated sole can be applied to all types of footwear ~slippers, shoes, boots~ ski-boDts etc.).
The invention will now be described in detail, by way of example, with the aid of the accompanying drawings! in which:
-fig 1 is a longitudinal section through a flesible -~
sole filled with heat-accumulating material ! warmed by an electric heater embodied as a resistance located internally of the sole;
-fig 2 is a longitudinal section through a flexible sole filled with heat-accumulating material ! warmed by means of a thermal conductor connected to an external electric heater;
-fig 3 shows an e:sternal electric heater to which the thermal conductor of fig B is connected;

SU~STtTUTE SWEEr ,.

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W0 ~ 16 '~ 3 G ~ ~ ~ PC~ 0/~W~2 -fig 4 illustrates the structure of an electric heater embodied as a resistance;
-fig S illustrates a 220/l2~ electrical transformer for the electric heater, with relative c~nnections 05 -fig 6 illustrates a cord by means of which to supply the electric heater with power direct from a 12v source;
-fig 7 i5 a view from beneath Df the monolithic part of the sole, t~ which an outer sole is bonded ultimately~ illustrating the arrangement of a plurality of cavities;
-fig 8 illustrates the flexible heated sole in a simplified longitudinaI section, highlighting certain of its functions;
l~ -fig 9 illustrates the fles:ible heated sole in a simplified longitudinal section, highlighting certain other functions, -fig lO illustrates a method of uniting the sole to the upper using a plain stitch;
-fig ll illustrates a method of uniting the sole to : the upper using a stitched and folded seam, -fig 12 illustrates the fitment of accessories;
-fig 13 illustrates application of the flexible heated sole to a rigid structure such as a sk.i-Z5 boot;

S~ ITIITE SHEEr ,..... .

wo 90/12516 PCI/IT90/00042 3 ~

-figl4 illustrates a indicator light connected to a temperature contr~l;
-fig 1' illustrates a pr~tectivs plug for the ~ocket connector of the electric heater! in a first t~pe 05 of embodiment;
-fig 16 illustrates a protective plug for the socket connector o~ the electric heater, in a second type of embodiment.
~ccording tG the present invention, a flexible heated sole 3S for footwear c~mprises a monolithic part 11 performing the functions of a support, a heat insulator, and a reservoir 36 destined to be filled with a heat-accumulating m~terial 15.
The monolithic part 11 cf the sole 35 is moulded, lS hence easy and inexpensive to produce, and can thus be fashioned in plastic material pos,es-ing notable flexibility and lightness (expanded polyurethane, rubber, etc...~; in addition! cavities lZ are formed in the monolithic moulding 11 to render the structure of the sole 35 still more flexible and comfortable.
13 denotes an outer layer of material (e.g. rubber, leather, PVC, other plastics etc.) applied to the tread of the monolithic part 11 of the sole 35, ZS which possesses flexible and non-slip properties.

~UE~STITUTE SHEET

W0 ~tl~16 ~ 3 ~ PCT/~0/~2 The monolithic part 11 of the sole 35 incorporates a plur~lity of reservoirs 36, each contalning material 15 with a high capacity for accumulating heat, the surfaces 36a o~ which are coated with an 05 impermeable substance 14. The impermeable layer thus formed serves to prevent the slightly porous monolithic part 11 of the sole 35 from absorbing small quantities of the heat-accumulating material when the material 15 i5 in the liquid state~ as lQ this would ieopardize the notable fle:sibility of the sole at the moment when the material 15~ hence the entire sole 35~ begins to cool.
In ~he sole of fig 1, the reservoirs 36 accommodate an electric heater 16 consisting in an electrical resistance 16a powered at 12 volts~ a temperature control 17 and a thermal stabilizer lB.
The heat-accumulating material 15 contained in the reservoirs 36 possesses the capacity to absorb a notable quantity of heat produced by a source of thermal energy and to continue giving off the heat stored in this way over a considerably extended peri~d ~4...6 hours). The material 15 remains solid at ambient temperature~ and the moment in which the temperature is raised to me}ting point ~from 40 C
Z5 upwards~ depending on the exact material adopted)~

~;U~STITUTE SHEEI' WO ~ 16 2 ~ PCT/r~/0~2 its state changes to liquid; it is in this fluid condition that the heat-accumulating material 15 absorbs heat to maximum capacity. On disconnecting the source of thermal energy, which i9 an electric 05 heater 16 or 42 in the examples illustrated, the heat-accumulating material 15 begins a slow cooling process, with maximum thermal hysteresis being reached at the moment when resolidification begins to occur.
Heat-accumulating materials 15 adopted in embodying the flexible heated sole 35 for footwear, according to the invention, are: hydrated salts, hydrocarbons and chemical compounds. Hydrocarbons possess a high capacity for heat accumulation, and for thermal and electrical insulation, and are exceedingly light;
hydrated salts possess fundamentally the identical properties of hydrocarbons, and have the advantage of lower cost.
An electric heater 16 immersed in hydrated salts must necessarily be insulated by means of a plastic material 19 able to withstand high temperatures, such as polytetrafluoroethene; unlike hydrocarbons, hydrated salts conduct electricity and will corrode metals. At all events, both hydrocarbons and salts are easily obtainable, non-toxic and inexpensi~e.

W0 ~/1~16 ~ ~ i3 5 ~ ~ PCT/r~/~W~2 The electric heater 16 of fig 1 operates at low vc,ltage (12`~); acccrdingly, fc,otwear provided with the flexible sole 35 can be connected with equal ease to the dsmestic a.c. supply (220V~, thrcugh a 05 small transformer 21 (fig 5), and to lZV supplies as commonly prcvided in motor vehicles, boats etc.
by way of a power cord and plug-in connector 24 (fi~ 6).
The heater 16 is preset in such a way that it will not R~ceed 70 C, in order to prevent decc,mposition of the heat-accumula'ing material 15 and avoid any overheating of the impermeable coatjng 14 and the material from which the monolithic part 11 cf the sole ~5 is fashioned. In the example of fig 1, the heater 16 is an electrical resistance 16a made up of one or more metal strands 20~ woven together in order to ensure strength and a mark.ed degree of flexibility tfig 4); a variety c.f metals might be used for the resistance 16a (constantan, nick.el-chrDmium alloy, etc.).
When the heat-accumulating material 15 utili7ed is a conductor of electricity, the coating of plastic material 19 ~fig 4) permits of obtaining a fluid-tight encapsulation of the immersed resistance 16a Z5 while leaving its flexibility unaffected; such a SUI~STITUTE SHEE1~

W0 ~/1~16 2 ~ . PCT/r~ W~2 soluticln is uncbtainable, by contra~t, in the case of refractory-wc,und metal-clad resi=tances ~e.g. a~
used for washing machines~ hot water tanks etc.).
The heat-accumulating material 15 i5 melted by the 05 immersed resistance 16a in a short period of time (10...2-~ min~ the resistance 16a being positioned in the reservc,irs 36 in such a way as to effect a uniform melt of the material 15.
The electrical resistance 16~ 42 is provided with a miniature temperature contrcl 17, 47 preset to a given maximum temperature ancl serving as a safety device. In the event that the wearer should forget or fail to disconnect the heater from the power supply, the temperature control 17, 47 will operate by breaking the heater circuit and activating a visual indicator 22 mounted tc, the e:~terior c,f the sole 35 in the case of fig 1, and of the heater 42 in that of of fig 2, signifying that the ma:~imum temperature setting has been reached. In the event that the heater remains connected to the pc,wer supply~ the temperature control 16, 42 will cut in again at a preset temperature.
In fig l, 25 denotes a socket at the rear end of the monolithic part 11 of the sole 35 through which Z5 power is supplied to the heater 16, by plugging in :: SU~STITUT~ SHEEr , ~ ,, W0 ~/1~16 ~ 3 ~ 5 ~ ~ PCT/r~ 2 a cc,nnect~r Z6 attached to one end of a cord 23;
the remaining end ~,f the cDrd i3 connected to a tran-former 21, and the transfc,rmer in turn to a mains plug Z8 ~fig 5).
OS ~lternatively, 12V power can be supplied direct to the heater 16 without the need for transformers, utili2ing the came socket 25 and connector 26~ and a cord Z~ as in fig 6, of which the plug 24 i5 a type suitable for insertion into the cigar lighter socket of a motor vehicle.
With the plug-in connector 26 removed, the socket 2S is prDtected by a plug that keeps out dirt and lends a more elegant appearance to the footwear.
The reservoirs 36 cf heat-accumulating material 15 intercommunicate by way of passages 2~ affording access also to the electric heater 16~ in the case of fi~ 1~ or tc, the thermal conductor 4~ in that of fig 2. ~eing mcre capacious than the forwardmost reservoir for technical and practical reasons, the rear reservoir holds a greater quantity of the heat-accumulating material 15 and thus absorbs more heat. To the end of ensuring a uniform distribution of heat during the cooling process~ use is made of a thermal stabilizer 18 which in the example of the Z5 drawings is embodied as a flexible metal possessing SV~;TIl VTE SHEEr WO ~/1~16 2 ~ 3 i~ PCT/r~/~H~2 high thermal conducti~ity.
30 denotes a layer of flexible, tough, compact and impermeable material applied by welding or adhesive bonding to the top side of the monolithic part 11 OS of the sole 35, which is of just a few millimetres thickness in order to facilitate the transmission of heat from the material 15 to the foot of the wearer. The rear part of the layer 30 is covered over with a reinforcement 31 fashioned in material possessing rigidity and strength, which serves to relieve the rear end of the flexible heated sole 35 beneath the wearer's heel ~the part of the foot which exerts greatest pressure~. The reinforcement material 31 is glued to the layer denoted 30, and a lS further layer 32 of compact foam rubber, or of a material possessing similar properties, is glued in turn to the top side of the reinforcement 31; this additional layer 32 ser~es to render the insole of ~he footwear comfortable and anatomical, cushioning the step and attenuating the warmth at the rear end so as to keep the foot from overheating.
33 denotes a heel piece fashioned in a breathing material (e.g. leather, fabric), with which the foot of the wearer makes contact.
34 denotes the upper, being the remainder of the ..
.
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.

W0 ~/1~16 ~ l7 ~ PCT/~0/~W~2 article of footwear as distinct frcm the fle;:ible heated sole 35, which will be fashioned in fle~ible and breathing material, e:~cept in the case of ski boo~s.
05 Fig 2 illustrate- the ~alne fle:~ible heated sole 35 containing heat-accumulating materials 15, capable of changing state and with a melting point of over 40 C, for which the heating procesc i5 different tc that described thus far. In fig l, the electric heater 16 is located inside the sole 35, immersed in the heat-accumulating material 15 occupying the reservoirs 36; by contrastl the reservoirs 36 in fig 2 accommodate a flexible metal element 4C~ of high thermal conductivity with branches 38 giving a uniform distributic,n of heat. The rear end of the thermal conductor 40 is connected to a rigid metal element 41 of high thermal conductivity~ which may be fashioned in the same material as the fle~ible element 40, but rigidly~ in order to avoid problems when plugging in the relative connector ~fig 3).
The electric heater 42 comprises a hollow metal element 43 of high thermal conductivity embodied such that the heater 42 is able to fit faultessly over the rigid element 41 when inserted into the Z5 socket 44 at the rear end of the sole 3~ ~fig 2).

SU13STITUTE SHE~

, WO ~/1~16 ~! 3(~` ~ ~ ~ P~T/~0/~W~2 A powerful electrical resistance 45 cperated off 220V is wound around the hollow element 43 and invests i~ with heat; the resistance is protected and insulated, thermally and electrically, by a 05 material 46 serving to prevent unpleasant scalding.
48 denotes a pin that inserts into the socket 49 automatically when the heater 42 is located in the socket opening 44 at the rear of the sole 35. The pin 48 serves to connect the temperature control 47 with a detector 50 placed lnside the reservoirs 36 and in contact with the heat accumulating material;
the temperature of the material 15 is sensed by the detector 50 and relayed to the temperature control, which causes the heater to cut out automatically at the prescribed maximum temperature.
The electric heater 42 is completed by a structural component 51 in plastic material, and connected to the 220V a.c. power supply by way of a cord 23 and a plug 28. Thermal and physical factors dictate that the conductor 40 transmits more heat into the heel end of the sole than the toe, and to balance and render the heat uniform throughout the entire -:
sole 35 of the footwear, the conductor 40 is coated with an insulation 52, 53 that decreases gradually in thickness the farther away it extends from the ' . ~ .
. . '- - ~ ' ` I

W0 ~/12516 ~ ~ 3 ~ PCT/r~ W~2 point at which the conductor 4~) is couplQd to the heater 42.
54 denotes a plug in shockproof material~ serving to conceal the socket 44 and avoid the entry of 05 dirt.
The external surface of the monolithic part 11 of the sGle 35 affords points where a connection is made with the interior; these accommodate the indicator 22, the socket 25 (fig 1), or in the case of the e~ternal heater 421 the opening 44 (fig Z), and a filler plug 55 throuqh which the reservoirs are filled with the heat-accumulating material 15 (see fig lZ).These points connect tne reservoirs 36 with the e:~terior, and therefore must be stopped tight in order to prevent any escape of the heat-- accumulating material 15. ~ccordingly, the relative accessories 22, 25, 44, 55 are embodied with sets of projecting peripheral fins 56 that grip the wall of the relative hole ~figl2 shows the hole 57 which Z0 receives the filler plug 55).
Figs 8 and 9 illustrate the fle::ible capabilities of the sole 35, which not only are given by virtue of the structure of the sole 35, but are favoured also by inclusion of the cavities 12, which allow a notable degree of bend in the footwear, including SU~STITUTE SHE~

WO ~/125l6 ~a3~5~ PCT/~0/0~2 the reservoirs 3~ containing the heat-accumulating material 1J~ especially at the points denoted 6~
(emboclied as webs separating the reservoirs), and thus prevent unwanted drawbacks such as a break in 05 the monolithic part 11 of the sole 35, and rupture of the reservoirs 36 themselves.
FiglO illustrates the external part of the fle:~ible heated sole 35 and the upper 34, and more e~actly, the stitch 61 which unites the one to the other.
The çtitch 61 reflects a more reliable option than simply sticking the two parts tDgether, given that a glued join tends to come unstuck with time.
Fig 11 illustrates a further methccd cf stitching, suitable for slippers etc., in which the upper 34 and the covering 6Z of the sole 35 are stitched together in a reversed rib 63; more exactly, the covering 62 of the sole 35 is united to the upper in a reversed stitch, and its bottom skirt then secured and glued between the monolithic part 11 of ZO the sole 35 and the tread 13.
Notwithstanding its flexible structure, the heated sole 35 for footwear, containing material 15 that is heat-accumulating and capable of changing state, can equally well be accommodated internally of a rigid structure such as a ski-boot ~fig 13).

SUE~STITUT SHE~

Claims (15)

1. WO 90/12516 PCT/?T90/00042 AMENDED CLAIMS
   [received by the International Bureau on 24 September 1990 (24.09.90) ;
   original claims 1-3, 7-11 amended;
   new claims 13-15 added; other claims unchanged (4 pages)]
   
   A flexible heated sole for footwear, containing a heat-accumulating material of changeable state, of the type comprising a heating element (16,40) immersed into heat-accumulating material (15), characterized in that it comprises :
   - a heat-insulating monolithic part (11) in flexible, light material;
   - at least a reservoir (36), directly formed in the upper surface of the monolithic part (11);
   - a heat-accumulating material (15) capable of changing state with a melting point of over 40 °C
   and contained in the reservoir (36);
   - points (60) of the monolithic part (11) which raise from the inside of the reservoir (36) and determine correspondent portions of flexibility in the sole;
   - a flexible, impermeable layer (30) applied on the top side of the monolithic part (11) and of said points (60) designed to close the reservoir (36) and to allow the foot to lean.
2. 2) A sole as in claim 1, wherein the said points (60) laterally delimit a plurality of reservoirs (36) which are crossed by the heating element (16, 40) WO 90/12516 PCT?T90/00042 inserted in passages (29) formed in said points (60) which define, on the upper side, the portions supporting the flexible layer (30).
3. 3) A sole as in claim 1, wherein the heating element (40) is a thermal conductor receiving the heat from a separated electric heater (42) stably connectable but removable.
4. 4) A sole as in claim 3, wherein the thermal conductor (40) consists in a flexible metal element occupying a longitudinal position internally of the sole (35) and affording branches (38) by which thermal energy is distributed uniformly to the heat-accumulating material (15).
5. 5) A sole as in claim 3, wherein the electric heater (42) is provided with a temperature control (47) piloted by a detector (50) that is positioned in direct contact with the heat-accumulating material (15) and designed to sense a maximum temperature prescribed for the heat-accumulating material.
6. 6) A sole as in claim 4, wherein the thermal conductor (40) is coated in a heat insulation (52, 53) that decreases gradually in thickness with the increase in distance from the print at which the conductor (40) is connected to the electric heater (42).
7. 7) A sole as in claim 2, wherein the reservoirs (36) intercommunicate by way of the passages (29).
8. 8) A sole as in claim 2, wherein the heating element (16, 40) is flexible.
9. 9) A sole as in claim 1, wherein the heating element (16) is provided with a temperature control (17) placed in direct contact with the heat-accumulating material, which is designed to sense the temperature of the heat-accumulating material and pilot the the operation of the electric heater (16) directly.
10. 10) A sole as in claim 2, wherein at least a more capacious reservoir is provided, on whose top side, on the flexible layer (30), at least a further layer (32) is applied to attenuate the passage of the warmth coming from the heat-accumulating material (15) contained in the larger reservoir (36) and directed towards the foot.
11. 11) A sole as in claim 1 incorporating a plurality of cavities (12), formed in said points (60) and designed to give greater flexibility and enhance the lightness of its structure.
12. 12) A sole as in claim 1, wherein the reservoirs (36) connect with the external environment by way of a hole (57) that permits of filling the reservoirs with the heat-accumulating material (15), and is sealed hermetically by means of plug (55) of which the shank (55a) exhibits a plurality of projecting peripheral fins (56) that interact positively with the walls of the hole (57).
13. 13) A sole as in claim 1, wherein the heat-accumulating material (15) consists in hydrated salts and the heating element (16, 40) is coated with plastic materials (19).
14. 14) A sole as in claim 1, wherein the heat-accumulating material (15) consists in hydrocarbons.
15. 15) A sole as in claim 1 with such dimensions as to be exactly contained in a rigid footwear and to form a direct support of the foot.