FIELD OF THE INVENTION
[0001] The present invention relates to footwear and, in particular, it deals with a liquid
water impervious but water vapor permeable footwear having means for electrostatic
discharge to the ground.
BACKGROUND OF THE INVENTION
[0002] There are many industrial applications where operators make use of antistatic and/or
conductive footwear capable of transmitting an eventual charge accumulated during
a certain working time with the aim of avoiding accidents that may arise from electrostatic
discharge. For example, such footwear is mandatory for working on oil platforms and
in numerous other applications where flammable or explosive materials are handled.
It is known to use for that purpose a piece of footwear having an outsole of an antistatic
and/or conductor material with wires or other conductor members connecting the midsole
to the outsole for discharging to the ground electricity that may accumulate on the
cloth during work.
[0003] Also known in the art is footwear internally lined with a layer of a liquid water
impermeable but water vapor pervious material, such as porous, stretched PTFE which
contributes to a free respiration of the foot while preventing liquids on the outside
from getting into the footwear.
[0004] These shoes are very practical, and it would be advantageous to make use of these
properties in antistatic and/or conducting footwear. With this object in view, there
was provided a footwear comprising an internal lining of an liquid water impervious
water vapor permeable material and an antistatic midsole connected to the outsole
through appropriate conductors. This solution requires, however, that the lining of
the liquid impervious material be perforated for the passage of such conductors. As
such, the perforations need to be sealed and thus make it difficult to obtain good
results that would remain unchanged with time.
[0005] In use, the footwear, hence the layer of a liquid water, breathable material, is
subjected to numerous repeated bending, abrasion, and the like so that the seal is
rapidly destroyed, and liquids can get into the interior of the shoes after a short
while.
SUMMARY OF THE INVENTION
[0006] It is the goal of this invention to eliminate the above-mentioned disadvantage and
to provide footwear in which a midsole of an antistatic material is connected to an
outsole by means of a plate or tape made of a conductor material that extends upward
along the lining of an upper in the rear zone, is bent over to the outer surface of
the lining, and is then connected to an antistatic grip sole.
[0007] This tape is then covered with a protective ribbon that is stitched to the lining,
whereby an electrical continuity is ensured between the midsole and the outsole without
the need to perforate the protective layer and without exposing the tape of a conductor
material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
Figure 1 schematically shows a piece of footwear according to the invention in vertical
section;
Figure 2 is a detail of Fig. 1 showing conductor means for connection;
Figure 3 is a detail of a piece of footwear according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The invention is characterized by a particular construction of parts allowing the
interior of the footwear to be connected to the ground without the need to perforate
a layer of impervious and transpirable material.
[0010] More specifically, footwear, according to the invention, comprises an antistatic
insert connected through a copper plate or a plate of another conductor material to
a zone located between a midsole and an outsole which is also antistatic, wherein
the plate of a conductor material covered with a protective ribbon extends rearward
to the lining of the footwear to be positioned between the lining and the upper.
[0011] As described above, a strip of a conductor material is completely hidden. At the
same time, it is not necessary to perforate the impervious transpirable material of
the footwear to connect the midsole to the antistatic outsole.
[0012] With reference to the drawings, a piece of footwear according to the invention comprises
an upper 1, a outsole 2 made of an antistatic and/or conductor material, and a midsole
3 inserted between the outsole and the inner lining of the shoe.
[0013] According to the invention, the interior of the footwear, in the zone of the upper
and the midsole, is lined with a layer 4 of a liquid water impermeable but water vapor
pervious (breathable) material, in particular, with a layer of porous, stretched polytetrafluoroethylene.
[0014] An antistatic insert or insole 5 is provided inside the footwear and is connected
to a bus or similar conductor material 6, e. g., to a plate or bus made of copper
of another appropriate conductor material.
[0015] Bus 6 is connected to midsole 3 at a point adjacent to the rear portion and extends
upward along the rear side of the lining where it is covered with a protective tape
or ribbon 8 made of leather or another appropriate material. Bus 6 is then bent back
at the top edge of the upper and extends along the outer surface of the lining between
the lining and the upper, also in the rear portion of the shoe.
[0016] In this manner, the bus of a conductor material can extend from the interior of the
footwear where it is connected to midsole 3 to the outside between the outsole and
midsole while remaining protected by the lining all the way through.
[0017] The end of bus 6 is then bent to be positioned between the lining and the midsole
in contact with the antistatic grip sole.
[0018] As described above, an electric connection is established between the midsole and
the antistatic grip sole without the need to perforate the inner lining 4 made of
an impervious transpirable material and without exposing the bus.
[0019] In addition, the same leather ribbon that serves to protect bus 6 is also used to
prevent the heel from abrading the bus during walking thus eliminating the adverse
effect of such abrasion and the risk of the bus breakage.
[0020] It will be apparent that dimensions and materials used may vary depending on specific
application.
1. Footwear constructed to discharge electrostatic charges to the ground, comprising
an internal lining of a liquid water impermeable and water vapor permeable material,
an insole made of an antistatic material positioned in the interior of the footwear,
and means for connecting said antistatic insert to a grip sole of the footwear, characterized
by the fact that said means comprise a conductor member that extends along the lining
of the upper upward to the collar of the shoe and is then bent over downward to bring
its end in contact with said outsole.
2. The footwear of Claim 1, characterized by the fact that said means comprise a bus
or a similar member of a conductor material that extends upwardly along the interior
rear side of the lining, is bent and then extends downward while remaining in permanent
contact with the outer rear part of the lining of the upper to be clamped at the grip
sole.
3. The footwear of Claims 1 and 2, characterized by the fact that said bus of a conductor
material is covered with a protective ribbon.
4. The footwear of Claim 1, characterized by the fact that said conductor means extend
outside the lining.