Antistatic shoe

Abstract: An antistatic shoe (1) which comprises a sole (2) at which there are provided, in the heel and tip regions, two or more connected seats (3, 4). The seats accommodate at least one insert (6) made of conducting plastics which is connected to the ground and, by means of a conducting plate (10), to an insole (12).

Description: The present invention relates to an antistatic shoe. Antistatic shoes are currently commercially available which can discharge to the ground the electrostatic charge accumulated by a person on his body. The most common situation is a passenger leaving a car that has just come to a halt. If he touches the car body, the passenger can be affected by an electric shock which is unpleasant although substantially harmless. This discharge occurs only if the person is insulated from the ground, for example by wearing a pair of shoes with a sole made of rubber or other insulating material. The need is thus felt of a type of shoe which allows the charge that has accumulated on the car during motion to discharge to the ground through the body of the traveler without the traveler being aware of anything or being affected in any way by the event. Current antistatic shoes offer an undeniable solution to this problem, although they suffer drawbacks which are described hereinafter. First of all, the technique and the method for producing the antistatic shoes entail a lot of work and accordingly also affect manufacturing costs. A conventional antistatic shoe is in fact constituted by a small coil of conducting metal wires, for example made of copper, which are usually located proximate to the heel, above the rubber sole. Several individual wires extend from the coil, each wire being arranged in a very small hole located in a preset region of the sole. The wires, by passing through the corresponding holes, reach the lower surface of the sole, where they are upset. In this way, a first electrical bridge through the sole is provided. The coil is further electrically connected to a metal tab which passes through a slot formed in the insole or inner sole inside the upper and ends in an upward region with a first metallic plate which is arranged horizontally. At the metallic plate, proximate to the region of the heel of the overlying insole, two slots are provided in which two flexible conducting wings are made to slide; the wings are folded downward and are connected to an overlying second metallic plate. In this way the accumulated electric charge can discharge to the ground, by flowing through the body of the user down to the heel and then through the second metal plate and the corresponding wings connected to the first metal plate. Immediately thereafter, the electric current flows through the tab and the underlying coil and discharges to the ground by means of the individual wires monolithically connected to said coil. This method for manufacturing antistatic shoes is evidently complicated, leading to an increase in manufacturing times and costs. Moreover, in these conventional antistatic shoes, over time the sole inevitably wears, and so do the metal wires, and the holes become clogged, often leading to a sharp decrease in the efficiency of the shoe. Other conventional antistatic shoes have different mechanisms for conduction through the sole, using metallic pins or similar elements, which pass through the insole or inner sole associated with the upper and reach the lower surface of the sole. In some embodiments there is a single grounding point at the heel: this leads to the drawback of not eliminating the problem when, as often occurs, only the tip of the shoe is placed on the ground, for example when leaving a car. GB-A-558 340 discloses an antistatic shoe having an insole and an out-sole both provided with a hole or opening at the heel and ball portions. The insole openings are filled with plugs of electro-conductive rubber including downwardly extending portions or with separate discs of electro-conductive rubber. The out-sole holes are filled with electro-conductive rubber in order to protrude to the ground. Above the out-sole openings there are layers of electro-conductive rubber which are preferably integral with the rubber material filling the respective sole openings. Finally, also the whole shoe heel 32 is formed of electro-conductive rubber. FR-A-2255026 discloses an antistatic shoe comprising an insole with conducting elements positioned on either sides and electrically connected by sewing using a metallic thread, an outer sole through which extend conducting plugs that are part of a conducting layer intermediate the insole and the outsole. FR-A-2754982 discloses a method of making antistatic soles for shoes, comprising an upper layer of conductive material provided with pads which traverse a lower layer. The aim of the present invention is to solve the above-described drawbacks, by providing a device which allows to obtain a simplified shoe manufacturing process which leads not only to an economic advantage but also to an improvement in the quality of the product. Within the scope of this aim, an object of the present invention is to provide a shoe which allows to solve the problem of grounding in the safest and most durable manner for the user. Another object is to provide a shoe whose sole offers maximum uniformity of its components, without having metallic elements such as nails, pins or coils which can cause discomfort, especially over time and as the sole deteriorates. These and other objects which will become better apparent hereinafter are achieved by an antistatic shoe according to the present invention, which comprises the features of claim 1. Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a particular embodiment thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein: Figure 1 is a partially sectional side view of the upper and of the underlying sole with an insert, according to the present invention; Figure 2 is a bottom view of the sole with two protrusions for ground discharge; Figure 3 is a side view of the upper and of a second embodiment of the sole with the corresponding insert. The embodiment represented, which comprises one through seat in the sole, is not part of the invention. Figure 4 is a bottom view of the second embodiment of the sole with the corresponding grounding component. With reference to the above-cited figures, the reference numeral 1 designates an upper of a conventional type in which the foot of the user is inserted. The reference numeral 2 designates a sole in which at least two through seats 3 and 4 are formed respectively at the tip and at the heel; the seats are connected one another by means of a channel 5 and are adapted to accommodate a complementarily shaped insert 6 made of conducting plastic material. The insert 6, which is longitudinally elongated, has a central body 7 which is arranged in the channel 5; two protrusions, designated by the reference numerals 8 and 9, are provided at the ends of the body 7, are preferably cylindrical or prism-shaped, are shaped complementarily to the seats 3 and 4, respectively, and are therefore located at the toe or heel region of the sole or at both regions. The insert 6 is kept in place by the mutual thermal bonding of parts of the respective elements made of plastics. A metal plate 10, preferably made of copper, is arranged in a suitable opening 11 formed in the inner sole or insole, designated by the reference numeral 12, which is arranged inside the upper 1; the lower surface of the metal plate 10 rests on the underlying protrusion 9 of the insert 6. Operation is as follows: with reference to Figure 1, the electrical charge is propagated through the body of the user down to the heel, which is connected to the insert 6 by means of the metallic plate 10. Since the insert has conducting properties, immediate and simple discharge to the ground occurs when the front protrusion 8 or the rear protrusion 9 makes contact with the ground. It has thus been observed that the present invention has achieved the intended aim and objects, an antistatic shoe having been provided which is adapted to discharge to the ground, through the user, the electrostatic charge accumulated for example by a car during travel. Since the insert 6 is made of plastics, walking is optimum, as the insert follows the deformation of the sole. The invention is of course susceptible of numerous modifications and variations within the scope of the appended claims. As shown in Figures 3 and 4, it is possible to associate with an upper 101 a sole 102 which has, in a downward region, a channel 105 which runs from the toe region to the heel region. A complementarily shaped insert 106 made of conducting plastic material is arranged in the channel 105 and has, in the end adjacent to the heel region, one or more protrusions, designated by the reference numeral 120, which are directed toward the inner sole 112. The protrusions are connected to the upper by means of appropriate complementarily shaped holes, designated by the reference numeral 121, so as to maintain contact with a metal plate 110 which is accommodated in a complementarily shaped seat, designated by the reference numeral 111, which is formed in the inner sole 112 of the upper 101. The materials employed, as well as the dimensions that constitute the individual components of the present invention, may of course be the most pertinent according to specific requirements. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims: An antistatic shoe comprising a sole (2), and an insole or inner sole (12), comprising through seats (3, 4) which are formed respectively at the tip and at the heel of the sole (2), the seats (3, 4) being connected one another by means of a channel (5) and being adapted to accommodate a complementarily shaped insert (6), made of conducting plastic material, which insert is connected to the ground and comprises a central body (7) arranged in the channel (5) and protrusions (8, 9) provided at the end of the central body (7) and shaped complementarily to the seats (3,4); characterised in that : a metal plate (10) is arranged in an opening (11) in a region of the heel of the insole or inner sole (12), a lower surface of the metal plate (10) resting on one of the underlying protrusions of the insert (6). The shoe according to claim 1, characterized in that said insert (6) associated with said channel (5) and said seats (3, 4) is kept in place by mutual thermal bonding of parts of the respective plastic elements. The shoe according to one or more of the preceding claims, characterized in that it has a sole on the lower surface of which there is provided at least one channel which affects both the tip region and the heel region. The shoe according to claim 3, characterized in that a complementarily shaped insert made of conducting plastics is arranged in said channel and has, at its end that affects the heel region, one or more upward protrusions. The shoe according to claim 4, characterized in that said one or more upward protrusions are connected, by means of suitable shaped holes, to said metal plate accommodated in a complementarily shaped seat formed in said insole or inner sole.

Inventors: BALDIN FRANCESCO, BALDIN, FRANCESCO
Applicants: CALZATURIFICIO FRAU S P A, THERMOSHOE S N C DI BALDIN & C, CALZATURIFICIO FRAU S.P.A., THERMOSHOE S.N.C. DI BALDIN & C.
Application year: 2000
Main classification: A43B7
IPC codes: A43B7