Note: Descriptions are shown in the official language in which they were submitted.
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
,.
, ~ , ,, ~ -.` .
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
..
.
'' "' :
.
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
14
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~
