ANTI-NBC (NUCLEAR, BIOLOGICAL OR BATERIOLOGICAL, CHEMICAL) OVERSHOE AND ITS MANUFACTURING PROCESS

Abstract: The invention is characterised in that it comprises a textile insert (1) which is completely permeated by and embedded in the mixture (2) and is made inseparable from the latter by means of moulding and vulcanisation in an injection-moulding press wrth a closing pressure of approxi­ mately 200 atmospheres. This insert is embedded in the mixture in an asymmetric­ al manner, as a result of which externally the insert is covered with a thick layer of rubber, whereas internally the mixture permeates beyond the insert on account of the moulding pressure and reaches a reduced thickness of 0.1mm. Thus, unlike those of the prior art, anti-NBC over­ shoes are obtained which have an ergonomic shape, are without joints, and hence are practically impermeable to NBC aggressive agents, and which have excellent mechanic­ al characteristics. They are used, in particular, for protection against the attacks of chemical, biological and bacteriological agents and for protection against thermonuclear radiation.

Description: The development of nuclear technologies and their varied applications, along with the preparation of new chemical, biological or bacteriological aggressive agents, has brought about a need for suitable garments or articles which can be worn by authorised personnel whilst performing repairs, overhauls and maintenance work, by the civil population in the event of accidents or catastrophes and by the special civil defence corps in the course of their duties and during decontamination operations. Furthermore, in a manner consistent with the threat of an NBC war, the General Staffs of the armed forces of the technologically advanced countries have commissioned the various research institutes and specialised companies to undertake product research and development studies in this direction, that is regarding how to defend oneself and, if necessary, neutralise an NBC threat. In this respect there may be cited the specifications of NATO, which in 1977 was already issuing precise instructions to its member countries, namely that the troops should be provided with equipment constituting an effec tive form of defence for resisting chemical, biological and bacteriological attacks and for entering the scene of the action, without danger, after thermonuclear attacks. In particular, various models of overshoes have been produced, which tend to guarantee impermeability with respect to NBC aggressive agents and at the same time possess the required degree of mechanical strength. Models (from Canada, Great Britain, Belgium and Italy) were produced by means of a process involving a rubberised fabric; the latter, suitably cut, was glued and shaped on an aluminium last and the whole assembly was vulcanised in an autoclave. In Germany, for example, an overshoe has been produced by means of compression moulding; this article has a very low mechanical strength which does not satisfy in any way the conditions stipulated in the specifications. From FR-A-1 413 536 it is known to manufacture a shoe in form of a boot made of a mixture based on vulcanised rubber forming a layer without any internal and external joints and having internal and external surfaces without any interruption of the surface continuity. On the inside of the layer a textile insert is bonded to the mixture. The textile insert, which during manufacturing of the shoe is fitted on a male part of a mould for receiving the moulded mixture on its outside surface, is made so as to cover the larger part of the mould without undergoing deformation and without forming interspaces between the individual threads, so that the rubber material is practically prevented from penetrating into the textile insert. A shoe is therefore obtained in which the textile insert constitutes a sort of internal sock having the purpose of forming an internal lining rather than a shoe reinforcement. Such a shoe has therefore limited strength characteristics and is not suitable for use as an anti-NBC overshoe. For use against aggressive agents there has been suggested by DE-B-T 9697 V/61a a material made of woven synthetic polyammide fibres or like fibres and provided on one or both sides with a covering of vulcanised butyl rubber. Such a material is particularly indicated for overgarments requiring considerable flexural adaptability in addition to the capacity of resisting against agressive agents. Apart from vulcanising a rubber material on one or both sides of a textile material, this prior art document does however not give any suggestions for providing an overshoe having anti-NBC characteristics. The present invention aims at providing an overshoe and an associated manufacturing process, described below, which avoid the disadvantages of the prior art: overshoes with joints which have low reliability as regards the risk of leaks and/or having low mechanical strength, complex and costly manufacturing processes. According to the present invention there is provided an anti-NBC overshoe made of a mixture based on a vulcanised rubber forming a layer without any internal and external joints and having internal and external surfaces without any interruption of the surface continuity, and comprising internally of the layer of the mixture a textile insert bonded to the mixture, characterized in that the textile insert is completely embedded and permeated by the mixture in an off-centre position with respect to the layer formed by the mixture, the mixture having on the outside of the textile insert a thickness of at least 2 mm and on the inside of the textile insert a thickness of about 0.1 mm. The anti-NBC overshoe according to the present invention possesses high characteristics as regards quality since it has an external surface without joints, i.e. there is no interruption of the surface continuity, and a reinforcing insert completely embedded and permeated by the mixture of vulcanised rubber; as a result, the overshoe remains practically impermeable without losing the necessary mechanical characteristics and hence satisfies the conditions required. The manufacturing process according to the invention, which results in improved economy and speed of production and makes it possible to obtain easily overshoes which have superior quality characteristics, impermeability and resistance, comprises the following operations: a) Fitting of a textile insert onto the male part of an overshoe shaped injection mould; b) Closing of the mould and consequent tensioning of the textile insert which thus adheres completely to the said male part; c) Injection under high-pressure of a rubber-based mixture into the mould by means of an injection press so as to make a layer of mixture penetrate from outside beyond the above-mentioned textile insert, which is thus completely permeated by and embedded in the rubber mixture; d) Vulcanisation, in the mould, of the mixture until completion, after which mixture and insert are intimately bonded, thereby giving rise to an inseparable whole. There now follows a description of a particular embodiment of the invention, with reference also to its production cycle, in relation to the Figures of the attached drawings, without, however, detracting in any way from the general nature of the subject of the invention itself. Figure 1a is a side elevational view of a particular embodiment of the overshoe. Figure 1b shows a plan view of the anti-NBC overshoe which is the subject of the invention, seen from the sole, the said sole being provided with anti-slip pattern and relief. Figure 1c shows a cross section of the overshoe at the level of the instep. Figure 2 shows a flow chart of the process for manufacturing the anti-NBC overshoe, broken down into its most important operations. The anti-NBC overshoe, in the characteristic embodiment of Fig. 1a, is shaped in an ergonomic manner so as to allow it to be easily put on or taken off, the cross-section 3 of entry, or respectively the length of the leg portion 9, being about 9/16, or respectively 3/4, of the cross-section, or length, of the sole 11. The toe 5 of the overshoe is thus extremely short, whereas a bulge at the heel 6 further facilitates introduction, or removal of the foot once inside. In practice an overshoe is obtained in which the cross-section at the instep 7 and the cross-section at the upper end of the leg portion 9 are very similar in size to the area of the upper 4. The height of the leg portion 9 can be chosen as required, in accordance with the various requirements, from the foot 10 of the anti-NBC overshoe. The anti-NBC overshoe is fixed to the leg of the wearer by means of a cord or lace which passes through holes 8 in the upper edge of the leg portion 9 and which has precisely the function of fastening the overshoe to the leg of the wearer. The sole 11 has a special relief pattern to prevent slipping (Fig. 1b). Structurally, the overshoe which is the subject of the invention (Figures 1a and 1c) comprises a textile insert 1 which is made of polyamide fabric and has been specially woven and prepared and which is completely permeated by and embedded in a mixture 2 based on butyl or nitrile rubber to which KOEDUR has been added. This insert 1, which is completely permeated by the mixture and embedded in it in the manner of a core, is off-centre with respect to the said mixture in the sense that it is arranged asymmetrically with respect to the layer formed by the said mixture. Externally the covering layer on the insert, which insert has a thickness of 0.3 ± 0.1 mm, can reach a thickness of 2 ± 0.1 mm on the leg portion 2.3 + 0.1 mm on the toe and 3.2 (+0.4, -0.2) mm on the sole, whereas inter nally the layer of mixture, which has penetrated through the textile insert during the injection-moulding operation, reaches the thickness of 0.1 ± 0.02 mm. The overshoe thus consists completely of rubber on the outside and is without joints, whereas the insert is permeated by the mixture which extends inside by a thin layer beyond the insert, the insert and mixture, after vulcanisation, thereby forming a whole which is intimately bonded and inseparable. In this way a high, almost total degree of impermeability is guaranteed, whilst excellent mechanical characteristics are retained. There now follows a detailed description of the production cycle (Figure 2). Moulds are made from tempered AQ 50 steel suitable for treatment by nitriding. The moulds are intended for injection moulding and consist of: a male part shaped at an angle of 75° jaws a cover Due to the special shape of the male part, the textile insert can be introduced and the finished product removed despite the almost complete inelasticity. The textile insert 1 is made of polyamide fabric woven with 12 beating-up operations both for the warp and for the weft and is prepared from pieces of cloth which are hollow-punched at 45° with respect to the direction of the beating-up; thus the elasticity required to compensate for the variability of the article is produced and perfect adaptability to the male part of the mould is ensured. The mixture for moulding the anti-NBC overshoe is based on a butyl or nitrile rubber to which KOEDUR has been added. The textile insert is fitted onto the open male part and, when the mould is closed, is tensioned and adheres perfectly to the male part. The mixture is injected at a pressure of approximately 200 atmospheres so as to make a layer of about 0.1 mm penetrate beyond the textile insert, which is thus completely permeated by and embedded in the rubber and hence is inseparable from the latter once the vulcanisation process has been completed. At the end of the cycle the overshoe consists completely of rubber on the outside and is without joints. Anti-NBC overshoes are thus obtained which are particularly suited for protection against NBC aggressive agents and which can be used by the civil population, by civil defence personnel in the event of an NBC catastrophe, by specialists who operate, repair, overhaul and maintain NBC plants and by troops in the event of an NBC threat or conflict.

Claims: Anti-NBC overshoe, made of a mixture (2) based on a vulcanised rubber forming a layer without any internal and external joints and having internal and external surfaces without any interruption of the surface continuity, and comprising internally of the layer of the mixture (2) a textile insert (1) bonded to the mixture (2), characterized in that the textile insert (1) is completely embedded and permeated by the mixture (2) in an off-centre position with respect to the layer formed by the mixture (2), the mixture (2) having on the outside of the textile insert (1) a thickness of at least 2 mm and on the inside of the textile insert (1) a thickness of about 0.1 mm. Anti-NBC overshoe according to claim 1, characterized in that the cross-section of the leg portion (9) is about 9/16 of that of the sole (11) and in that the upper edge (3) of the leg portion (9) is provided with holes (8) for a lace or cord for fixing the overshoe to a wearer's leg. Process for manufacturing an anti-NBC overshoe according to Claim 1 or 2, characterised in that it comprises the following operations: a) Fitting of a textile insert (1) onto the male part of on overshoe shaped injection mould; b) Closing of the mould and consequent tensioning of the textile insert (1) which thus adheres completely to the said male part: c) injection under high pressure of a rubber-based mixture (2) into the mould by means of an injection press so as to make a layer of mixture penetrate from outside beyond the above-mentioned insert (1), which is thus completely permeated by and embedded in the rubber mixture (2). d) Vulcanisation, in the mould, of the mixture (2) until completion, after which mixture (2) and insert (1) are intimately bonded, thereby giving rise to an inseparable whole. Process according to Claim 3, characterised in that the textile insert (1) is made of polyamide fabric with 12 beating-up operations both for the warp and for the weft and is prepared from pieces of cloth which are hollow-punched at 45° with respect to the direction of the beating-up so as to produce the elasticity required to compensate for the variability of the article and so as to ensure perfect adaptability to the male part of the mould. Process according to Claim 3 or 4, characterised in that the mixture for injection-moulding of the anti-NBC overshoe is based on butyl rubber to which KOEDUR has been added. Process according to Claim 3 or 4 characterised in that the mixture for injection-moulding of the anti-NBC overshoe is based on nitrile rubber to which KOEDUR has been added. Process according to one of Claims 3 to 6 characterised in that the mixture is injected with a closing pressure of the injection-moulding press equal to about 200 atmospheres, so as to obtain the penetration of a layer of mixture of at least 0.1 mm of thickness beyond the textile insert and on the inside of the latter, in addition to the external covering of the same. Use of the anti-NBC overshoe according to Claim 1 or 2 for protection against nuclear radiation and attack by chemical, biological and bacteriological aggressive agents. Use of the anti-NBC overshoe according to Claim 1 or 2 in preparation for or following a NBC catastrophe.

Inventors: FABBRO, ORESTE
Applicants: SGE SOCIETA' GENERALE ELASTOMERI S.P.A.
Application year: 1985
Main classification: A62B17
IPC codes: A62B17, A43B3