GB2025892A - Reinforced tubular articles - Google Patents

Abstract

A method of and apparatus for the production of a reinforced tubular article employs a rotatable roller (1) and a fixed mandrel (3) which are spaced apart so as to define a nip (4) therebetween. A strip (5) of reinforced polymeric material is fed through said nip and caused to wind helically around the fixed mandrel (3) by the action of the rotatable roller (1) so as to form a tubular article (7) the wall thickness of which is equal to size of the nip (4) A carrier strip (11) of low friction material may be employed to assist movement of the reinforcing strip (5) over the fixed mandrel (3), and said movement may be further assisted by arranging the rotatable roller in skewed relation relative to the fixed mandrel. Furthermore, the roller and mandrel may be angled relative to one another such that the width of the nip (4) decreases along the length of the mandrel. <IMAGE>

Description

SPECIFICATION Reinforced tubular articles This invention relates to a method and apparatus for producing reinforced tubular articles such as hose.

According to one aspect of the present invention a method of producing a reinforced tubular article comprises helically winding a strip of reinforced polymeric material such that successive turns are in contact with one another, said strip being fed through the nip defined by a rotatable roller and a fixed mandrel and caused to wind around the fixed mandrel by the action of the rotatable roller, the width of the nib being equal to the desired wall thickness of the tubular article.

Preferably the strip of reinforcement material has an initial thickness greater than the width of the nip, and is compressed by said nip.

According to a further aspect of the present invention an apparatus for the production of a reinforced tubular article comprises means for feeding a strip of reinforced polymeric material helically through the nip between a rotatable roller and a fixed mandrel, the width of the nip being equal to the desired wall thickness of the tubular article.

The coefficient of friction between the surface of the mandrel and the surface of the reinforced tubular article should be less than 1, preferably less than 0.5, more preferably less than 0.25.

The polymeric material may comprise a thermoplastic rubber (e.g. an ABA styrenebutadiene block copolymer or a blend of a high ethylene content EPDM with polypropylene and/or polyethylene), a vulcanisable rubber (e.g.

ethylene/propyiene rubber, ethylene/propylene/diene rubber, nitrile rubber, polychloroprene rubber, polyisoprene rubber and SBR), a thermosetting plastics material (e.g. a peroxide cross-linkable ethylene/vinyl acetate copolymer) or a thermoplastic plastics material (e.g. polypropylene, polyethylene and polyvinyl chloride) or a blend of any of these and may contain bonding ingredients (e.g. aldehyde condensation resin forming ingredients suchas resorcinol and hexamethylene tetramine).

The reinforcement may comprise a thermoplastic rubber (e.g. a blend of a high ethylene content EPDM with polypropylene and/or polyethylene), a vulcanisable rubber, a thermosetting plastics material (e.g. a glass reinforced polyester or epoxy resin), a thermoplastic plastics material (e.g.

polypropylene, polyethylene, poly(vinyl chloride) polycarbonate or an aliphatic polyamide, such as nylon), fibrous material (e.g. carbon, glass, steel, carbon or polyester) or a blend of any of these. If fibrous material is used in the reinforcement it may be in a discontinuous fibred form orientated in the direction of the strip of polymeric material and may be pretreated e.g. treated unregenerated cellulosic fibres (available as Santoweb from Monsanto). Preferably the ratio of length:diameter of the fibrous material used in more than 5:1 and more preferably more than 10:1.

The reinforcement may be in a mono filament form, e.g. rodlike, or of multifilament form e.g. in a cabled, stranded or yarn construction.

The strip of reinforced polymeric material may be produced by extruding the polymeric material around the reinforcement by means of a cross head die. The cross-section of the reinforced strip may for example be square, rectangular, or circular and that of the reinforcement may for example be square, rectangular or circular. Other cross sectional shapes such as parallelogramatic section may be used, the facing surfaces of succesive turns being of substantially complementary shape.

Particularly wherein the strip is substantially rectangular in cross-section it may incorporate more than one reinforcement element. As the strip is helically wound around the mandrel, adjacent coils should adhere to each other by means of e.g.

tack or melting or adhesive.

In the final reinforced tubular article preferably all components are bonded together and any vulcanisable or theremosettable compositions vulcanised or thermoset respectively. For example where the reinforced polymeric material includes a plastics composition and a vulcanisable rubber composition, said compositions may be fusion bonded together. That is, the completed tubular article may be heated so as to vulcanise the rubber composition (e.g. in an autoclave, fluid bed, salt bath or microwave unit) at a temperature above that which will melt the plastics so as to effect a bond. Alternatively the rubber composition can be vulcanised at a temperature below that which will melt the plastics and then the temperature can be raised to melt the plastics and thus bond the composite.

The diameter of the tubular article is determined primarily by the stationary mandrel but may be varied relative thereto by adjusting the speed of the incoming reinforced polymeric strip relative to that of the rotating roller. In addition the reinforcement in the strip should be sufficiently rigid at the process temperature so as to be able to be tensioned in order to control the hose diameter.

The longitudinal axis of the mandrel and roller, being also the rotational axis of the roller, may be parallel or at a small acute angle to each other.

The-axes may be angled such that the; nip between the roller and mandrel decreases along the length of the mandrel from the end at which the strip is applied. The angle selected will depend in part on the length of the mandrel, and difference between the initial thickness of the strip and width of the nip; typically the angle will lie in the range 0 to 20.

The axes may be additionally or alternatively be skewed relative to one another such that the axis of the roller lies substantially perpendicular to the strip material in the nip between the roller and mandrel. Typical skew angles envisaged lie in the range ao to 100, though other angles could be used.

The temperature of the mandrel and roller may be controlled as desired depending on the hose materials being used.

Means may be provided for reducing friction between the surface of the mandrel and the surface of the tubular article e.g. a solid means such as a carrier strip, a liquid means or a gaseous means. A carrier strip may be used, either continuous or not, and it may be removed from the reinforced tubular article at any stage or not at all.

Suitable strip materials include polytetrafluoroethylene (Teflon)(Registered Trade Mark), cellulose acetate, and polyethylene terephthalate (Melinex (Registered Trade Mark)).

Preferably the width of the carrier strip is about the same width as that of the strip of reinforced polymeric material.

If desired a further layer or layers can be applied to the reinforced tubular article e.g. by a conventional wrapping technique.

Several embodiments of the invention will now be described by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a side view of apparatus according to the present invention; Figure 2 is a plan view of the apparatus of Figure 1; Figure 3 is a cross-sectional view along line B-B of Figure 1; Figure 4 is a cross-sectional view along line A-AofFigure 1; Figure 5 is a cross-sectional view in detail of the strip of reinforced polymeric material as shown in Figure 4; Figure 6 is a perspective view of the mandrel of Figure 1; Figure 7 is a cross-sectional view of another embodiment of the present invention;; Figure 8 is a cross-sectional view of a modified form of part of the apparatus of Figure 4, and Figures 9 and 10 each show side views of further embodiments of the present invention A rotatable roller 1 (driven in the direction indicated by the arrow by means e.g. friction or gears not shown) and a fixed mandrel 3 supported by means of an arm 2, define therebetween a nip 4 which is selected to be equal in width to the desired wall thickness of the tubular article. Forice is applied by means not shown to press the roller 1 against the mandrel 3 at position 6.

The reinforced tubular article 7 is made from a strip 5 of reinforced polymeric material initially having a circular cross-section as shown in Figure 3, but which is squeezed to a rectangualr crosssection (see Figure 5) in the nip 4 as the tubular article 7 is formed. The initial diameter of said strip is greater than the width of the nip 4. A crosshead die 8 (see Figure 2) feeds the strip 5 into the nip 4. Figure 6 shows the mandrel 3 which has holes 9 and 10 through which may be fed a carrier strip 11 from a spool 1 2 (see also Figure 1).

In use of the apparatus a thermoplastic rod 1 3 of circular cross-section is passed through the cross-head die 8 where it receives an extruded covering 14 of a vulcanisable rubber composition, its cross-section being still circular. The thus formed strip 5 is then passed through the nip 4 onto the carrier strip 11, and is pushed around the outside of mandrel 3 by the action of the rotating roller 1. Flange 1 5 at one end of the rotating roller 1 prevents movement of the strip 5 away from the formed tubular article 7; the tubular article 7 moves in the opposite direction as shown by the arrow in Figure 2. The rubber in the finished tubular article 7 can then be vulcanised and the carrier strip 11 can be removed or left in place as lining or additional reinforcement.Figure 5 is a cross-sectional view of the strip 5 after passing through nip 4 and being combined with the carrier strip 11 which becomes at least temporarily adhered to the strip covering 14.

In the embodiment shown in Figure 7, a rotatable roller 36 (driven in the direction of the arrow by means e.g. friction or gears not shown) and a fixed mandrel 35 define therebetween a nip which is equal to the desired wall thickness of the tubular article and less than that of the strip 33 to be fed through it. A carrier strip 34 is fed to the inside of the mandrel 35 from a spool (not shown).

In use of the apparatus the strip 33 is passed through the nip and around the inside of the mandrel 35 by the action of the rotating roller 36.

The rotating roller 36 may either have a flange (as in Figures 4 to 6) to prevent the tubular article from moving in the wrong. direction and to govern the width of the nip, or may be used in conjunction with the arrangement shown in Figure 8.

In Figure 8 an alternative to the flange arrangement of Figure 4 is shown. This comprises a rotating roller 37 mounted on an arm 38 and pressing against the rotating roller 31 to prevent the tubular article moving in the wrong direction.

A stop 39 prevents the two rollers 31, 33 touching.

In a further embodiment illustrated in Figure 9 a reinforced hose is constructed on apparatus comprising a non-rotatable hollow mandrel 43 and rotatable die roller 42 which are supported so as to define therebetween a nip equal in width to the required thickness of the resulting hose.

The mandrel 43 is substantially similar to that shown in Figure 6 and is formed with a slot 49. A strip 44 of melinex 50, optionally coated with rubber 51 (see inset on Figure 9), may be fed from inside the mandrel and through said slot so as then to pass helically around the outer surface of the mandrel and act as support for other hose forming components.

Upstream of the slot the mandrel is surrounded by a rotatable creel 45 which carried a series of circumferentially spaced bobbins that provide axial hose reinforcement.

In use of the apparatus a strip of reinforcement material 41 of substantially ribbon like form is applied to the mandrel substantially in line with the slot. The strip 41 is transported helically along the length of the mandrel and through the nip by means of a melinex strip the rubber coating 51 of which becomes bonded to the strip 41, during subsequent vulcanisation thereof. Cords from the creel 45 are fed to between the melinex strip 44 and reinforcement strip 41; said creel is rotated at a speed which matches that of the reinforcement strip and thus the cords form an axially extending reinforcement in the finished hose.

In contrast to the earlier described embodiments of the invention, in accordance with this embodiment the reinforcement strip comprises a strip of rubber having a plurality of mutually parallel spaced apart reinforcement elements, e.g. cords, embedded therein. The reinforcement strips described in U K P 1356791 have been found to be particularly suitable.

Figure 10 shows a variation of the embodiment described with reference to Figure 9. In this embodiment the creel is positioned downstream of the slot and forms an axially extending reinforcement between a first strip reinforcement layer and a second strip reinforcement layer which is formed by helical winding at a position downstream of the creel.

It has been found that a particularly important feature of the present invention is the use of a driven roller to move the reinforcement strip around the mandrel. It has been found that this significantly assists movement of the strip mandrel around the mandrel.

Claims (13)

1. A method of producing a reinforced tubular article comprising helically winding a strip of reinforced polymeric material such that successive turns are in contact with one another, said strip being fed through the nip defined by a rotatable roller and a fixed mandrel and caused to wind around the fixed mandrel by the action of the rotatable roller, the width of the nip being equal to the desired wall thickness of the tubular article.

2. A method according to claim 1 wherein a carrier strip of low friction material is employed to assist movement of the strip of reinforced polymeric material over the mandrel.

3. A method according to claim 1 or claim 2 wherein the strip of reinforced polymeric material comprises a reinforcement core of plastics composition embedded in a vulcanisable rubber composition which can be vulcanised at a temperature below that which will melt the plastics.

4. A method according to any one of the preceding claims, wherein the strip of reinforced polymeric material has an initial thickness greater than said width of the nip.

5. Apparatus for the production of a reinforced tubular article comprising means for feeding a strip of reinforced polymeric material helically through the nip between a rotatable roller and a fixed mandrel, the minimum width of the nip being equal to the desired wall thickness of the tubular article.

6. Apparatus according to claim 5 wherein a carrier strip of low friction material is provided to assist movement of a strip of reinforced polymeric material over the mandrel.

7. Apparatus according to claim 5 or claim 6 wherein the longitudinal axis of the mandrel is angled relative to the longitudinal axis of the roller.

8. Apparatus according to claim 7 wherein said axes are skewed relative to one another at an angle in the range - to 100.

9. Apparatus according to claim 7 or claim 8 wherein said axes are angled such that the nip between the roller and mandrel decreases along the length of the mandrel.

10. Apparatus according to claim 9 wherein said angle lies in the range 0 to 20.

11. Apparatus according to any one of claims 5 to 10 and incorporating a creel assembly rotatable substantially in unison with movement of the strip of reinforced polymeric material around the mandrel.

12. A method of producing a reinforced tubular article substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

13. Apparatus for the production of a reinforced tubular article substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.