GB1584843A

GB1584843A - Process and device for the continuous production of elastomeric hoses with reinforcement structure

Info

Publication number: GB1584843A
Application number: GB27827/77A
Authority: GB
Original assignee: Industrie Pirelli SpA; Pirelli SpA
Current assignee: Industrie Pirelli SpA; Pirelli and C SpA
Priority date: 1976-07-15
Filing date: 1977-07-04
Publication date: 1981-02-18
Also published as: AU2703377A; AR211189A1; DE2727318A1; SE7708111L; DE2727318C2; JPS5929421B2; BE856837A; AU513251B2; NL7707428A; ES460836A1; FR2358259A1; FR2358259B1; IT1064856B; SE423201B; JPS5313683A

Description

(54) PROCESS AND DEVICE FOR THE CONTINUOUS PRODUCTION OF ELASTOMERIC HOSES WITH REINFORCEMENT STRUCTURE (71) We, INDUSTRIE PIRELLI SpA, an Italian Company of Centro Pirelli, Piazza Duca d'Aosta No. 3, 20100 Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention refers to a process for the continuous production of elastomeric hoses with a reinforcement structure, and more particularly to a process for the continuous vulcanisation of these hoses.

In addition, the invention refers to a device to carry out the process mentioned.

Various processes are known, according to which the elastomeric hoses with reinforcement structure are placed inside an autoclave for vulcanisation.

In such processes, the hose, which is supported internally by fluid under pressure, is forced against a lead sleeve which covers it temporarily, and, under the effect of the pressure and the heat, is vulcanised, with the optside surface pressed against the lead sleeve.

Subsequently, when the hose has been removed from the autoclave, the lead sleeve is cut away.

According to other known methods, the hose, which has been coiled up, is placed in the autoclave supported internally by a flexible spindle, and with a fabric sleeve on the outside which is able to withstand the pressures during vulcanisation.

Subsequently, when vulcanisation is complete, the flexible spindle and the sleeve are removed.

The processes mentioned are based on discontinuous production stages, and in particular, removal of the sleeve is laborious and often causes obvious, unacceptable marks on the elastomeric layer covering the hose, as a result of the tools used.

An object of the present invention is to provide an improved continuous production of reinforced elastomeric hoses.

In accordance with one aspect of the present invention a continuous process for the production of elastomeric hose with reinforcement structure comprises the stages of extruding an elastomeric layer, providing a reinforcement structure and covering the reinforcement structure with elastomeric material, characterised by the stages of a) continuously feeding the unvulcanised hose in the direction of its longitudinal axis and supporting the hose internally with fluid under pressure; b) winding with a fabric winding strip around the unvulcanised hose; c) vulcanising the hose being fed by applying heat directly to the winding strip, the winding strip being directly in contact with the wall of the vulcaniser, right from the start of the vulcanising stage, and for at least part of that stage, and d) unwinding the winding strip from the hose.

This process is particularly suitable for the production of reinforced elastomeric hoses when both a good quality product and a high rate of production are required.

Preferably the stage b) comprises winding around the unvulcanised hose a winding strip consisting of a fabric which reduces in length when subjected to the action of heat.

In fact, it has been found that by applying heat without intervening layers of air to a fabric strip, preferably which reduces in length when subjected to the action of the heat, right at the start of vulcanising the hose, there is a radial force transmitted uniformly to the elastomeric layers of the hose beneath, the said force being equilibrated by the pressure of the fluid inside the hose.

Consequently, as the forces in play are considerable, the outside surface of the hose is pressed perfectly, continuously and more or less instantaneously, against the coils of the strip and the elastomeric covering layer is then free from pores and has a uniform outside diameter.

Preferably, the strip is nylon fabric.

In a preferred embodiment, the process is characterised by the fact that a radial com pressing is applied directly to the winding strip at the same time as the heat, right at the start of the vulcanising stage, and for at least part of that stage. This process considerably improves the appearance of the hose, as it has been found that the compression action fa yours heist absorption by the winding strip, resulting in its contraction and pressing of the outside surface of the hose.

On the other hand, the compression action mentioned in no way limits the rate of hose feed during vulcanisation as the use of nylon for the winding strip, i.e. a material which is known to possess a low coefficient of friction, reduces any hindrance to the hose feed to a minimum.

! It can be seen from the above that the process according to the invention not only makes it possible to obtain a vulcanised product with a superior, or at least equivalent external appearance compared with that obtained with the discontinuous processes already known, but also makes it possible to achieve continuous production of hoses of good quality, in long length, and extremely quickly.

Preferably, the process according to the invention is characterised by the fact that the hose is wound with a strip of nylon, or similar fabric, bathed with water.

This embodiment of the process favours even more the immediate contraction of the winding strip, and improves the pressing of the external elastomeric covering of the hose.

Another preferred embodiment of the process is characterised by the fact that the winding strip is wound in contiguous coils which overlap for part of their width measured in the direction of the hose axis.

In this case-still being preferable-the continuous coils overlap for half their width.

In accordance with a further aspect of the present invention a device for the continuous production of elastomeric hose with reinforcement structure comprises an extruder, means for applying the reinforcement structure, means for covering the reinforcement structure with elastomeric material, and means for continuously feeding the hose, characterised by the fact that it additionally comprises a winding device for winding a fabric strip round the unvulcanised hose, a vulcaniser with at least a first -cylindrical chamber, the diameter of which is equal at most to the diameter of the unvulcanised hose covered with the winding strip of the said fabric, an unwinding device for unwinding the said strip from the vulcanised hose and means for introducing and maintaining fluid under pressure inside the hose.

Preferably the device is characterised by the fact that the length of the first chamber of the vulcanising device is at least equivalent to 60% of the total length of the vulcanising device.

The invention will be more clearly understood from the fdllowing detailed description which is given as an example and is therefore not limitative, with reference to the enclosed diagrammatic illustrations, where: Figure 1 shows a longitudinal view of the device according to the invention; Figure 2 shows a longitudinal section of part of a crude hose before it is.vulcanised using the device in Figure 1; Figure 3 shows a partial longitudinal section of the vulcanising device, and 'Figure 4 shows a partial- perspective view of the unwinding device which is part of the device in Figure 1.

The continuous process for the production of hoses according to the preferred embodiment of the invention, is as follows.

A first layer of elastomeric material,- - e.g. rubber, constituting the core of the hoses extruded with an extruder, and longitudinal threads or cords are supplied to the extruder's extrusion head, which are gradually taken up and incorporated into the rubber core.

At the same time, a reinforcement structure, consisting of synthetic fabric threads-or cords, for example, is wound round the hose in a spiral arrangement.

This reinforcement structure could be of any other known type, i.e. with artificial fabric threads or cords, or, for example, with metal wires or cords, in a spiral arrangement, or even with non-woven fabrics based on artificial or synthetic materials.

During the extrusion stage mentioned, and in the subsequent stages, the hose is fed continuously in the direction of its longitudinal axis, using any feed system, and supported internally by fluid under pressure, e.g. air.

In a subsequent stage, an elastomeric covering layer is extruded on the body already formed, or a sheet of elastomeric material is wound round the hose with contiguous coils which overlap for half their width.

At this point, the hose is complete in its parts, i.e. core, reinforcement structure to withstand feed and operating stresses, external protective covering consisting of a sheet of elastomeric material, for example, wound round in coils.

It is well defined how the processes mentioned for extruding the core, for making the reinforcement structure, and for applying the covering layer, can be of any known type, and as these processes are not included within the scope of the invention, they are not described in detail.

In the subsequent stages, the hose, which is still unvulcanised, is fed continuously for vulcanisation.

Before proceeding with vulcanisation a strip of nylon is wound round the hose. The contiguous coils of the said strip overlap for half the width of each coil, measured in the direction of the hose axis. This strip is bathed with eater beforehand in order to favour regular distribution of the coils on the hose.

In the subsequent stage, the hose, covered with this winding strip, is continuously vul canised.

Immediately at the start of this stage, heat is applied directly and pressure applied in a radial direction to the outside surface of the winding strip, resulting in a compression action which is applied uniformly to the elas tomeric layers underneath, until there is an equilibrating counter force applied by the air under pressure inside the hose.

Therefore, right from the start of the vulcanising stage, the outermost elastomeric layer provided in an embodiment of the invention is pressed against the winding strip.

Consequently, the subsequent vulcanising stage-the outermost elastomeric layers of the hoses having been compacted, and the pores formed in these layers, removed-can take place without it being necessary to apply pressures in a radial direction to the winding strip, i.e. only by applying the heat which is strictly necessary to complete vulcanisation of all the elastomeric layers of the hose.

It results from the above that the feed rate of the hose is high, because the radial pressure which is applied to the winding strip is limited tothe initial vulcanising stage only, and even during this period, the hindrances affect- -ing hose- feed' are minimum because' the winding strip, being nylon, creates minimum friction against the walls of the vulcanising unit, within which the wrapped hose moves.

In the subsequent stage, the winding strip is gradually removed from the vulcanised hose, which is then taken up on a suitable drum, in the usual way.

The- device for the continuous production process of elastomeric hoses with reinforce ment structure is now illustrated in Figure 1 relating to the text.

The device 1 (Figure 1) is described below in connection with the production of a hose 2 (Figure 2) consisting of a preliminary elasto meric layer 3, in whidh ldngitudinal fabric threads 4 are embedded, a reinforcement structure made up of at least one fabric cord 5, in a spiral arrangement, and a sheet of elastomeric material 6, the contiguous coils of which overlap for half their width (Figure 2).

The hose illustrated in Figure 2 is produced by means of a device which basically consists of (see Figure 1) an extruder 7, designed to extrude the preliminary elastomeric layer 3 and to embed longitudinal threads 4 in it, a distribution rotor 8, designed to wind fabric cord 5 round the preliminary elastomeric layer 3, a winding device 9 to wind elastomeric, e.g. rubber, sheet 6.

The extruder 7, distribution rotor 8 and winding device 9 are of a known type and do not constitute the innovatory part of the invention In particular, :the extruder 7 and distri bution rotor 8 can be similar to those descri bed in U.K. Patent No. 1,145,684 of the Applicant.

Basically, the device consists of means for supporting the hose internally, a winding device 91 designed to wind the strip of fabric, which reduces in length when subjected to the action of heat, round the crude hose, a vulcan iser 10 with at least one section 11 (Figure 3) into which the hose passes, in direct contact with wall 111, and an unwinding device 12 (Figure 1).

The means for supporting the hose intern ally consist of air under pressure introduced (Figure 1) with tubing T at the head of ex truder 7 when the first elastomeric layer of the hose, ,is being extruder.

The winding device 91 consists of a cage 13, which is coaxial with, and roates round the unvulcanised hose, the said cage has an arm 14 which supports a bobbin 15 on which a continuous strip - of nylon N, already moistened with water, has been wound. - This winding machine is arranged in such a way in relation to the hose feed that the contiguous coils of the strip overlap for half their width 1.

The vulcaniser 10 has first section 11 which, according to a preferred embodiment (Figure 3), consists of a first cylindrical chamber (Figure 3) having a through bore 17, the diameter of which is smaller than the external diameter of the hose already wound with the nylon strip. In the example described, the length of this first section is equal to 60% of the total length of the vulcaniser, and the internal, circular walls 111, having a smaller diameter than the hose, perform the function of applying a mechanical pressure to, the winding strip.

The remaining part of vulcaniser 10 con sists of (Figure 3) a second cylindrical cham ber 18, with a second pipe 19, the axis of ,which is in alignment with the axis of pipe 17, and which has a larger diameter.

The vulcaniser also has means of heating Figure 3) consisting of steam V circulating in a cylindrical vessel 20 which is arranged round, and in contact with, the first and second chamber 11 and 18.

In particular, the pipes in the vulcaniser can be covered with a material having a low coefficient of friction, such as polytetra fluororethylene, for example.

The unwinding device 12 consists of (Figure 1) a cage 21, which is coaxial with and rotates round the hose, a rotation arm -22 which is an integral part of the cage, a bobbin 23 connected to arm 22, the said bobbin being rotated round its axis by any suitable, known gear system (not illustrated) to take up the nylon strip.

The unwinding device 12 has another component which is essential for unwinding the strip coils, which consists of an unwinding regulating bar 24 which is an integral part of cage 21, and parallel to the hose axis.

This bar is designed to support the nylon strip as it unwinds, and has a point 26 which is inserted whilst the cage rotates between the elastomeric sheet 6 of hose 2 and the coil of nylon strip 27 (Figure 4) which has to be unwound.

The function of the device is as follows: with particular reference to Figure 1, hose 2, being in its unvulcanised state, consisting of preliminary elastomeric layer 3, reinforcement structure 4, 5, elastomeric covering sheet 6, is fed from left to right of Figure 1 by any feed force F.

During this feed process, hose 2 is covered by means of winding device 91 by a strip of nylon already moistened with water and wound on so that its coils overlap for half their width. This overlapping is important so that the hose is continuously and totally covered with material having a low coefficient of friction.

Subsequently, hose 2, still being fed along its axis, enters vulcaniser 10, passing into first chamber 11, where the winding, consisting of the strip of nylon, is subjected simultaneously to a radial compression, due to the restricted diameter of walls 111 of the vulcaniser, and to an intense heat in direct contact with walls 111, heated by steam V (Figure 3) which circulates inside vessel 20, and then into second chamber 18, without pressure acting from the outside to the inside of the hose, which vulcanisation is completed.

The introduction of hose 2 into first chamber 11 is helped by the action of winding device 91 which, (Figure 1), being immediately up-line of vulcaniser 10, supports the weight of the unvulcanised hose by means of the strip of nylon under tension between bobbin 15 and the coils already wound round the sheet of the elastomeric material 6 which constitutes the external covering of hose 2.

In addition, as the nylon strip is wound round the hose under tension, it offers the further advantage of counteracting any expansion of the walls of the unvulcanised hose which might occur, due to an excess of air pressure inside the hose, for example.

Therefore, unvulcanised hose 2 arrives at the vulcaniser inlet in the best possible condition, i.e. without inflection or expansion of the walls, and as it is continuously wound with the nylon strip, it moves in contact with the walls of first chamber 11 with minimum friction.

This consideration is important, because, since there are minimum hindrances affecting hose feed in the vulcaniser, the tension can be increased, and therefore the feed rate of the hose without the risk of breaking the longitudinal fabric reinforcements of which it consists, due to excessive tension.

In particular, therefore, with the absence of considerable hindrances affecting hose feed, and consequently, the absence of the risk of breaking the longitudinal reinforcements, it is possible not to increase the diameter nor the number of longitudinal threads of the hose in order to withstand not only the operating pressures, but the feed stresses too.

At the outlet of vulcaniser 10, hose 2 (Figure 1) passes through the centre of cage 21 of unwinding device 12, and the nylon strip N is gradually removed from it.

Unwinding device 12 operates in the following manner (Figure 4): Cage 21 is operated in order to make arm 22 rotate round the hose axis, and bobbin 23 rotates in the opposite direction to the nylon strip winding; in addition, bobbin 23 is made to rotate round its own axis K in order to take up the coils gradually unwound from the hose.

This movement which, in itself, would be suitable for unwinding coils which are placed simply in abutment, is not sufficient for unwinding overlapped coils, as the coil being unwound 28 (Figure 4) would be strongly counteracted by continuous coil 27 which is on top of it and still wound round the hose.

The unwinding device relating to the device according to the invention resolves this problem in that the unwinding regulator bar 24 rotates with cage 21 with point 26 always inserted between sheet of the elastomeric material 6 covering the hose and coil 27 above, at the same time keeping part of its length always under contiguous coil 28 being unwound.

In other words, the outer surface of the bar acts as a transmission pulley for the strip of nylon subjected to the tension applied by take-up bobbin 23.

As can be easily understood, this bar 24 permits regular, automatic unwinding of the overlapping nylon coils.

At the end of the unwinding operations, the hose 2 is continuously taken up in a known way and coiled round a suitable drum (not illustrated).

As a result of the strong pressing action applied in the first chamber 11 of the vulcaniser, the elastomeric material of the hose is not cracked in any way, the outside surface is uniform and the external diameter is the same for the complete length of the hose.

Although only some embodiments of this invention have been illustrated and described, it is understood that all possible embodiments available to a man skilled in the art are included within its scope, such as, for example, the use of fabrics other than nylon for the winding strip which react in a similar way when subjected to the action of heat.

It is also understood that the process and the device can also be applied to the pro due tion of different types of elastomeric hoses.

Claims

WHAT WE CLAIM IS:-

1. Continuous process for the production of elastomeric hose with reinforcement structure comprising the stages of extruding an elastomeric layer, providing a reinforcement structure and covering the reinforcement structure with elastomeric material, characterised by the stages of: a) continuously feeding the unvulcanised hose in the direction of its longitudinal axis and supporting the hose internally with fluid under pressure; b) winding a fabric winding strip around the unvulcanised hose; c) vulcanising the hose being fed by applying heat directly to the winding strip, the winding strip being directly in contact with the wall of the vulcaniser, right from the start of the vulcanising stage, and for at least part of that stage, and d) unwinding the winding strip from the hose.

2. Continuous process for the production of elastomeric hose with reinforcement structure, comprising the stages of extruding an elastomeric layer, providing a reinforcement structure, and covering the reinforcement structure with elastomeric material, characterised by the stages of a) continuously feeding the unvulcanised hose in the direction of its longitudinal axis and supporting the hose internally with fluid under pressure; b) winding around the unvulcanised hose a winding strip consisting of a fabric which reduces in length when subjected to the action of heat; c) vulcanising the hose being fed by applying heat directly to the winding strip, the winding strip being directly in contact with the wall of the vulcaniser, right from the start of the vulcanising stage, and for at least part of that stage, and d) unwinding the winding strip from the hose.

3. Process in accordance with claim 1 or claim 2, characterised by the fact that, at the same time as the heat a radial compression is applied directly to the winding strip, right from the start of the vulcanising stage, and for at least part of that stage.

4. Process in accordance with any one of claims 1 to 3, characterised by the fact that the hose is wound with a winding strip of the said fabric, moistened with water.

5. Process in accordance with any of the previous claims, characterised by the fact that the said strip is wound on in contiguous coils which overlap for part of their width, measured in the direction of the hose axis.

6. Process in accordance with claim 5, characterised by the fact that the contiguous coils of the said strip overlap for half their width, measured in the direction of the hose axis.

7. Process for the production of elastomeric hose substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

8. A device for the continuous production of elastomeric hose with reinforcement structure comprising an extruder, means for applying the reinforcement structure, means for covering the reinforcement structure with elastomeric material, and means for continuously feeding the hose, characterised by the fact that it additionally comprises a winding device for winding a fabric strip round the unvulcanised hose, a vulcaniser with at least a first cylindrical chamber, the diameter of which is equal at most to the diameter of the unvulcanised hose covered with the winding strip of the said fabric, an unwinding device for unwinding the said strip from the vulcanised hose and means for introducing and maintaining fluid under pressure inside the hose.

9. Device in accordance with claim 8 characterised by the fact that the length of the first chamber of the vulcaniser is at least equal to 60% of the total length of the vulcaniser.

10. Device in accordance with claim 8 or claim 9, characterised by the fact that the unwinding device has a cage which rotates round the hose and is coaxial with the hose, an arm on the cage designed to support a bobbin to take up the coils of the winding strip, means for rotating the bobbin round its own axis, an unwinding bar connected to the cage, parallel to the hose axis, designed to support the coil being unwound and taken up by the bobbin, and with its point inserted under the overlapped coil of the hose which is contiguous with the coil being unwound.

11. Device for the continuous production of elastomeric hose substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

12. Flexible hose of elastomeric material with reinforcement structure, produced according to the process of any of the claims 1 to 7 and/or with a device in accordance with any of claims 8 to 11.