An antistatic hose for conveying fluids

0001The present invention relates to an antistatic hose for conveying fluids comprising at least one conductive layer, and preferably intended for the chemical/pharmaceutical and food sectors.

0002At present various types of conductive hoses are known in which the conductive layer may be positioned either on the inside (in contact with the fluid conveyed) or on the outside (in contact with the external environment).

0003For example, patent <patcit id="pcit0001" dnum="EP707169A"><text>EP 707 169</text></patcit> refers to a hose in which a conductive layer of plastic or elastomeric material covers an inner layer which forms the duct for the fluid, and in which a narrow electrically-conductive strip extends longitudinally along the hose. Moreover, said strip is at least partly in contact with the conductive layer and is homogeneously inserted in a spiral shape in the film which forms the inner layer.

0004Patent <patcit id="pcit0002" dnum="EP999396A"><text>EP 999 396</text></patcit> refers to an antistatic hose with a wall made of elastomeric materials to which conductive particles are added. In this case the hose has a thin outer layer which is not conductive and which covers the conductive wall, except for a spiral portion. The Document <patcit id="pcit0003" dnum="US3825036A"><text>US 3 825 036</text></patcit> discloses an antistatic hose according to the preamble of claim 1.

0005However, the conductive hoses currently used have several disadvantages.

0006It should be remembered that the hoses are often used in systems together with moving parts. Therefore, the hoses have to be moved over the floor by dragging (in particular when hoses are full of product they are very heavy).

0007Despite the fact that in most applications the floors are smooth, hoses with an outer surface made of elastomeric material tend to wear due to friction. This phenomenon is particularly evident in the case of dark coloured hoses when they are dragged, leaving a coloured mark on the floor.

0008The wear phenomenon is aggravated by the fact that the elastomeric material adheres well to the ground, increasing friction.

0009This disadvantage is particularly problematic in those production environments (such as in the pharmaceutical and/or food industry) in which cleanliness is essential.

0010Moreover, hoses made of elastomeric material cannot resist all chemical attacks. As a result, the hoses should be used in environments in which they come into contact with a single product or with two or more products of a similar chemical nature.

0011Secondly, the use of elastomeric materials for hoses built on a mandrel, makes the hose difficult to clean, due to the fact that the surface is not smooth because of the cloth finish.

0012In this situation the technical need of the present invention is to provide an antistatic hose for conveying fluids which overcomes the above-mentioned disadvantages.

0013In particular, the technical need of this invention is to provide an antistatic hose for conveying fluids which guarantees not only sufficient conduction, but also a high level of resistance both to wear and to attack by chemical substances.

0014The technical need of the present invention is also to provide an antistatic hose for conveying fluids which has a reduced external friction coefficient, facilitating dragging.

0015A further technical need of the present invention is to provide an antistatic hose for conveying fluids which is easy to clean.

0016The technical need specified and the aims indicated are substantially achieved by an antistatic hose for conveying fluids as described in the claims herein.

0017Further characteristics and advantages of the invention are apparent from the detailed description which follows, with reference to the accompanying drawing, which illustrate preferred embodiments of the antistatic hose for conveying fluids by way of example and without limiting the scope of application, and in which: <ul id="ul0001" list-style="dash" compact="compact"><li><figref idref="f0001">Figure 1</figref> is a side view of a section of hose which has an outer wall made in accordance with the present invention.</li></ul>

0018With reference to the accompanying drawings, the numeral 1 denotes as a whole an antistatic hose for conveying fluids according to the present invention.

0019The hose 1 has at least one conductive layer 2 comprising both a first, conductive material 3 and a second, non-conductive material 4.

0020The first, conductive material 3 forms a basic matrix in which medium sized blocks 5 of the second, non-conductive material 4 are inserted (<figref idref="f0001">Figures 1</figref> and 2).

0021In this way the first, conductive material 3 forms a continuous conductive path 6 extending along the entire length of the hose 1.

0022At least one of the two materials 3, 4 but advantageously both, is a thermoplastic material.

0023In the case of the first material 3, conductive particles such as carbon black are added to the thermoplastic material.

0024In the preferred embodiment, the thermoplastic material is polyethylene, preferably with an ultrahigh molecular weight (UPE).

0025In the embodiment illustrated, the first material 3 and second material 4 have different colours. In particular, the first material 3 has a dark colour approaching black (due to the presence of the carbon black), whilst the second material 4 has a light colour approaching white.

0026As illustrated in the accompanying drawings, the blocks 5 of the second material 4 form a plurality of isolated patches, unevenly distributed in the basic matrix consisting of the first, conductive material 3.

0027A similar distribution may, for example, be obtained with a process for formation of the conductive layer 2 (process preceding steps for production of the actual hose 1 which may occur with any known method, for example by working on a mandrel) which includes first the formation of an even layer of the first material 3, then the addition to this layer, during a calendering step, of medium sized blocks 5 of the second material 4. This step preferably takes place at a temperature corresponding to the softening point of the thermoplastic material so that the blocks 5 of the second material 4 can integrate and fuse with the first material 3 but without processes involving mixing of the two materials 3, 4.

0028The addition of the blocks 5 of the second material 4 occurs in an uneven way, but with a predetermined proportion relative to the first material 3.

0029In this way, in the resulting conductive layer 2, the second material 4 is distributed in the matrix of the first material 3 in an uneven and irregular way.

0030Advantageously, the non-conductive material 4 represents more than 50% of the total material in the conductive layer 2.

0031The conductive layer 2 described above is used to make the outer surface of the hose 1, as illustrated in the accompanying drawing.

0032To preserve the flexibility of the hose 1, the conductive layer 2 is less than 1 mm thick, and preferably less than 0.2 mm thick.

0033The present invention may be applied to any type of hose 1, whether a hose 1 made of rubber, a multilayer hose 1 with or without textile and/or metal inserts, etc.

0034Finally, the hose 1 is preferably intended in particular for applications with fluids at medium - low pressures.

0035The present invention brings important advantages.

0036Firstly, the antistatic hose for conveying fluids disclosed guarantees not only good conduction, but also a high level of resistance both to wear and to attack by chemical substances.

0037On one hand, if the outer surface is made of a plastic conductive layer as described above, since there is a low friction coefficient it is easier to drag over the ground, increasing its resistance to wear compared with hoses made with a basis of elastomeric materials.

0038Moreover, a conductive layer of plastic material of the type describe above, resistant to chemical attack, can allow on one hand use of the hose in environments with an aggressive atmosphere or in contact with any type of fluid, and on the other hand allows hose cleaning using any product without the risk of ruining it.

0039It should also be said that the present invention is relatively easy to produce and the cost of implementation of the invention is not very high.

0040The invention described can be subject to modifications and variations without thereby departing from the scope of the claims.