A FLEXIBLE HEATED SOLE FOR FOOTWEAR, CONTAINING HEAT-ACCUMULATING MATERIALS OF CHANGING STATE

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 DEG 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: A flexible heated sole for footwear, containing heat-accumulating materials of changing state The discomfort of cold feet is one suffered by many people. It is a problem experienced by those with poor circulation, and those who work in cold and damp conditions, or in sedentary or static types of 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 resistances enveloped in refractory material, for example 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 drawbacks mentioned above through the embodiment of a sole featuring much lower costs of application than those of the prior art, ease of assembly of its component parts, and significant practical advantages in use. Moreover, the sole is filled with a heat accumulating material capable of changing state, which keeps the footwear warm for an extended period of time even after the heating energy supply has been disconnected. The flexible sole containing the heat accumulating material possesses a structure giving maximum flexibility, and is notably lightweight. Also, the flexible heated sole can be applied to all types of footwear (slippers, shoes, boots, ski-boots 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 flexible 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 external electric heater to which the thermal conductor of fig B is connected; SUBSTITUTE SHEET -fig - illustrates the structure of an electric heater embodied as a resistance; -fig 5 illustrates a 220/1ΞV electrical transformer for the electric heater, with relative connections; -fig 6 illustrates a cord by means of which to supply the electric heater with power direct from a 1ΞV source; -fig 7 is a view from beneath of the monolithic part of the sole, to 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 longitudinal section, highlighting certain of its functions; -fig 9 illustrates the flexible heated sole in a simplified longitudinal section, highlighting certain other functions; -fig 10 illustrates a method of uniting the sole to the upper using a plain stitch; -fig 11 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 ski- boot; SUBSTITUTE SHEET -figl - illustrates a indicator light connected to a temperature control; -fig 15 illustrates a protective plug for the socket connector of the electric heater, in a first type of embodiment; -fig 16 illustrates a protective plug for the socket connector of the electric heater, in a second type of embodiment. According to the present invention, a flexible heated sole 35 for footwear comprises a monolithic part 11 performing the functions of a support, a heat insulator, and a reservoir 3ό destined to be filled with a heat-accumulating material 15. The monolithic part 11 of the sole 35 is moulded, hence easy and inexpensive to produce, and can thus be fashioned in plastic material possessing notable flexibility and lightness (expanded polyurethane, rubber, etc...); in addition, cavities 12 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, which possesses flexible and non-slip properties. SUBSTITUTE SHEET The monolithic part 11 of the sole 35 incorporates a plurality of reservoirs 36, each containing material 15 with a high capacity for accumulating heat, the surfaces 36a of which are coated with an 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 is in the liquid state, as this would jeopardise the notable flexibility of the sole at the moment when the material 15, hence the entire sole 35, begins to cool. In the 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 stabiliser IB. 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 period (4... hours). The material 15 remains solid at ambient temperature, and the moment in which the temperature is raised to melting point (from °C upwards, depending on the exact material adopted), SUBSTITUTE SHEET 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 is an electric 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 inexpensive. The electric heater 16 of fig 1 operates at low voltage (12V); accordingly, footwear provided with the flexible sole 35 can be connected with equal ease to the domestic a . c . supply (220V), through a small transformer 21 (fig 5), and to 12V supplies as commonly provided in motor vehicles, boats etc. by way of a power cord and plug-in connector 24 (fig 6) . The heater 16 is preset in such a way that it will not exceed 70 °C, in order to prevent decomposition of the heat-accumulating material 15 and avoid any overheating of the impermeable coating 14 and the material from which the monolithic part 11 of the sole 35 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 marked degree of flexibility (fig 4); a variety of metals might be used for the resistance 16a (constantan, nickel— chromium alloy, etc.). When the heat-accumulating material 15 utilised 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 while leaving its flexibility unaffected; such a SUBSTITUTE SHEET B solution is unobtainable, by contrast, in the case of refractory-wound metal—clad resistances (e.g. as used for washing machines, hot water tanks etc.). The heat-accumulating material 15 is melted by the immersed resistance 16a in a short period of time (10...20 min) , the resistance 16a being positioned in the reservoirs 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 control 17, 47 preset to a given maximum temperature and 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 to the exterior of the sole 35 in the case of fig 1, and of the heater 42 in that of of fig 2, signifying that the maximum temperature setting has been reached. In the event that the heater remains connected to the power supply, the temperature control 16, 42 will cut in again at a preset temperature. In fig 1, 25 denotes a socket at the rear end of the monolithic part 11 of the sole 35 through which power is supplied to the heater 16, by plugging in SUBSTITUTE SHEET a connector 26 attached to one end of a cord 23; the remaining end of the cord is connected to a transformer 21, and the transformer in turn to a mains plug 2B (fig 5). Alternatively, 12V power can be supplied direct to the heater 16 without the need for transformers, utilising the same socket 25 and connector 26, and a cord 23 as in fig 6, of which the plug 24 is a type suitable for insertion into the cigar lighter socket of a motor vehicle. With the plug-in connector 26 removed, the socket 25 is protected by a plug that keeps out dirt and lends a more elegant appearance to the footwear. The reservoirs 36 of heat-accumulating material 15 intercommunicate by way of passages 29 affording access also to the electric heater 16, in the case of fig 1, or to the thermal conductor 40 in that of fig 2. Being more 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 stabiliser IB which in the example of the drawings is embodied as a flexible metal possessing SUBSTITUTE SHEET high thermal conductivity. 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 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 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 serves to render the insole of the 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 article of footwear as distinct from the flexible heated sole 35, which will be fashioned in flexible and breathing material, except in the case of ski boots. Fig 2 illustrates the same flexible 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 process is different to that described thus far. In fig 1, the electric heater 16 is located inside the sole 35, immersed in the heat-accumulating material 15 occupying the reservoirs 36; by contrast, thε reservoirs 36 in fig 2 accommodate a flexible metal element 40 of high thermal conductivity with branches 38 giving a uniform distribution 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 flexible 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 socket 44 at the rear end of the sole 35 (fig 2). SUBSTITUTE SHEET A powerful electrical resistance 45 operated off 220V is wound around the hollow element 43 and invests it with heat; the resistance is protected and insulated, thermally and electrically, by a 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 inside 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 point at which the conductor 40 is coupled to the heater 42. 54 denotes a plug in shockproof material, serving to conceal the socket 44 and avoid the entry of dirt. The external surface of the monolithic part 11 of the sole 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 external heater 42, the opening 44 (fig 2) , and a filler plug 55 through which the reservoirs are filled with the heat-accumulating material 15 (see fig 12).These points connect the reservoirs 36 with the exterior, and therefore must be stopped tight in order to prevent any escape of the heat- accumulating material 15. Accordingly, 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 receives the filler plug 55). Figs 8 and 9 illustrate the flexible 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 SUBSTITUTE SHEET the reservoirs 36 containing the hεat-accumulating atεrial 15, especially at the points denoted 60 (embodied as webs separating the reservoirs) , and thus prevent unwanted drawbacks such as a break in thε monolithic part 11 of the sole 35, and rupture of the resεrvoirs 36 themselves. FiglO illustrates the external part of the flexible heated sole 35 and the upper 34, and more exactly, the stitch 61 which unites the one to thε othεr. The stitch 61 reflects a more reliablε option than simply sticking the two parts together, given that a gluεd join tends to come unstuck with time. Fig 11 illustrates a further method of stitching, suitable for slippers etc., in which the upper 34 and the covering 62 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 securεd and glued between the monolithic part 11 of the sole 35 and the tread 13. Notwithstanding its flexiblε structurε, thε hεatεd solε 35 for footwear, containing matεrial 15 that is hεat-accumulating and capablε of changing statε, can equally well bε accommodated internally of a rigid structure such as a ski-boot (fig 13) . U

Claims: Claims 1) A flexible heated sole for footwear, containing a heat-accumulating material of changeable state, of the type comprising an electric heater (16, 42) located internally of the sole (35) and designed to warm the heat-accumulating material (15) , characterized in that the heat-accumulating material (15) changes state at a melting temperature in excess of 40 * C. 2) A sole as in claim 1, wherein the electric heater (16) is positioned in direct contact with the heat- accumulating material (15) . 3) A sole as in claim 1, wherein the electric heater (42) is stably connectable to and removable from a thermal conductor (40) positioned in direct contact with the heat-accumulating material (15) . 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) 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) 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 point at which the conductor (40) is connected to the electric heater (42) . 7) A sole as in claim 1, wherein the heat-accumulating material (15) is contained in intercommunicating reservoirs (36) formed internally of the sole (35) , of which the surfaces (36a) are treated with an impermeable substance (14) designed to prevent any infiltration of the heat-accumulating material (15) into the sole (35) . 8) A sole as in claim 2, wherein the electric heater (16) consists in an electrical resistance (16a) distributed uniformly along the sole (35) and occupying the heat-accumulating material (15) in its entirety. 9) A sole as in claim 2, wherein the electric heater (16) is provided with a temperature control (17) placed in direct contact with the heat-accumulating material (15) , which is designed to sense the temperature of the heat-accumulating material and pilot the operation of the electric heater (16) directly. 10) A sole as in claim 1, further comprising a thermal stabilizer (18) embodied in flexible metal, which is designed to ensure a uniform distribution of temperature throughout the heat-accumulating material (15) . 11) A sole as in claim 1, incorporating a plurality of cavities (12) designed to give greater flexibility and enhance the lightness of its structure. 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) A sole as in claim 1, further comprising an externally located visual indicator (22) serving to provide evidence of arrival at a prescribed maximum temperature of the heat-accumulating material (15) .

Inventors: BARBARESI FRANCO, PASCUCCI CLAUDIO, BARBARESI, FRANCO, PASCUCCI, CLAUDIO
Applicants: BARBARESI FRANCO, PASCUCCI CLAUDIO, BARBARESI, FRANCO, PASCUCCI, CLAUDIO
Application year: 1990
Main classification: A43B7
IPC codes: A43B7, A43B13