Thin rubber hose and its production method

Abstract

An impermeable rubber hose is thinned for the purpose of reducing weight and costs. A rigid resin film is used as an intermediate layer. When the resin film is gradually rolled up into a cylindrical shape from a planar shape and fed to an extrusion head and rubber is simultaneously extrusion-molded inside and outside the cylindrical film, the film produces a break or a twist to make extrusion molding difficult. It is an object of the present invention to make simultaneous extrusion molding possible even in such a condition. To attain the above object, a thermoplastic resin film ( 5 ) which forms an intermediate layer ( 2 ) and of which the melting point is lower than the vulcanizing temperature is formed in a long belt-shape. Slits ( 7 ) are provided at fixed intervals on the right and left long side sections ( 8, 8 ) of the film ( 5 ) in the longitudinal direction. When the resin film ( 5 ) is fed into an extrusion head ( 10 ) to be rolled up into a cylindrical shape, because both the long side sections ( 8, 8 ) of the film ( 5 ) are formed as weak sections by the slits ( 7 ), the film ( 5 ) adsorbs a strain when bent and is bent in a circle, thereby allowing the right and left long side sections ( 8, 8 ) to overlap at an overlapping section ( 6 ). In this condition, rubber is simultaneously extrusion-molded inside and outside the film and then, vulcanized to weld the overlapping section ( 6 ), thereby eliminating the slits ( 7 ).

1 . A method for producing by extrusion molding a thin rubber hose having a resin film as an intermediate layer with an inner rubber layer and an outer rubber layer laminated inside and outside the resin film, the resin film consisting of a long belt-shaped film having a weak section provided in advance on the long sides of the film, wherein the resin film is rolled up into a cylindrical shape so that the two long sides overlap, comprising the steps of: 
 feeding a long, belt-shaped resin film of which the long sides are provided with a weak section in advance into an extrusion head to be rolled up and bent into a cylindrical shape so that the two long sides overlap;    extruding rubber inside and outside the resin film for integration and extrusion-molding a raw rubber hose of which the intermediate layer is the resin film; and    heating the raw rubber hose to a predetermined temperature for vulcanization.    
   
   
       2 . The method for producing the thin rubber hose according to  claim 1 , wherein the resin film is a thermoplastic resin and the overlapping section is integrally welded simultaneously with vulcanization.  
   
   
       3 . The method for producing the thin rubber hose according to  claim 1 , wherein the weak section is composed of a plurality of slits cut inwardly from the edge sections of the long sides, and the inward end of each slit is inclined toward the feeding direction of the resin film or is provided perpendicular to the longitudinal direction of the resin film.  
   
   
       4 . The method for producing the thin rubber hose according to  claim 3 , wherein the slits are respectively provided on both long sides and provided in a positional relation in which they do not overlap when the two long sides overlap.  
   
   
       5 . The method for producing the thin rubber hose according to  claim 3 , wherein the slits are respectively provided on the two long sides in a positional relation in which they overlap when the two long sides overlap.  
   
   
       6 . The method for producing the thin rubber hose according to  claim 1 , wherein the weak section is composed of a plurality of punched holes.  
   
   
       7 . The method for producing the thin rubber hose according to  claim 1 , wherein the weak section is formed by thinning one or both of the long side sections which overlap.  
   
   
       8 . The method for producing the thin rubber hose according to  claim 1 , wherein the rubber is mixed with a thermoplastic resin and after vulcanizing the raw rubber hose, this hose is reheated to about the melting temperature of the mixed thermoplastic resin to give a predetermined shape.  
   
   
       9 . The method for producing the thin rubber hose according to  claim 7 , wherein thinning is realized by a taper shape in which the thickness is gradually reduced toward an end section.  
   
   
       10 . A method for producing a thin rubber hose by extruding an inner layer rubber and an outer layer rubber inside and outside an intermediate layer made of a film of a substantially cylindrical shape, comprising the steps of: 
 rolling a belt-shaped film into a substantially cylindrical shape to allow a pair of edge sections, one on each side in the lateral direction of the film, to overlap to form an overlapping section and feeding the film into an extrusion head; and    extruding the inner layer rubber and the outer layer rubber inside and outside the film while decompressing and drawing the overlapping section within the extrusion head.    
   
   
       11 . The method for producing a thin rubber hose which has an intermediate film layer according to  claim 10 , wherein the film is fed into the extrusion head while being rolled up from a planar shape to a substantially cylindrical shape at the inlet of the extrusion head.  
   
   
       12 . The method for producing a thin rubber hose which has an intermediate film layer according to  claim 10 , wherein the film is shaped into a substantially cylindrical shape in advance before fed into the extrusion head.  
   
   
       13 . The method for producing a thin rubber hose which has an intermediate film layer according to  claim 10 , wherein the film is composed of a thermoplastic resin or an inorganic material such as metal, or a laminated structure combining them.  
   
   
       14 . The method for producing a thin rubber hose which has an intermediate film layer according to  claim 10 , wherein the film bending load is 400 N or more when the film width is 100 mm and the film thickness is 0.05 mm.  
   
   
       15 . The method for producing a thin rubber hose according to  claim 10 , wherein each of the pair of edge sections overlapping at the overlapping section is tapered so that they are thinned toward the end in the lateral direction thereof.  
   
   
       16 . A method for producing a thin rubber hose provided with an intermediate layer by extruding an inner rubber layer and an outer rubber layer inside and outside the intermediate layer of a substantially cylindrical shape within an extrusion head, comprising the steps of: 
 forming a pipe serving as the intermediate layer in advance;    providing the pipe with a cut line in the axial direction;    feeding the pipe into the extrusion head, cutting the pipe open; and    rounding the pipe again within the extrusion head to allow the cut line sections to directly or indirectly overlap, thereby forming the cylindrical-shaped intermediate layer.    
   
   
       17 . The method for producing a thin rubber hose provided with an intermediate layer according to  claim 16 , wherein the bending load of the intermediate layer is 400 N or more for a film of 100 mm width and 0.05 mm thickness.  
   
   
       18 . The method for producing a thin rubber hose provided with an intermediate layer according to  claim 16 , wherein the inner rubber layer and the outer rubber layer are extruded, decompressing and drawing in the overlapping section.  
   
   
       19 . The method for producing a thin rubber hose provided with an intermediate layer according to  claim 16 , wherein the intermediate layer is formed in a bellows-shape.  
   
   
       20 . A method for producing by extrusion molding a thin rubber hose having an inner rubber layer and an outer rubber layer laminated respectively inside and outside a resin film serving as an intermediate layer, the intermediate layer having a circular cross section and forming an overlapping section by allowing a pair of side sections, which divide the intermediate layer in the circumferential direction, to overlap, wherein at least one of the two sides forming the overlapping section on the surface side is thinned to eliminate a step in the overlapping section on the surface side, comprising the steps of: 
 thinning at least one of two long side sections of a long belt-shaped resin film;    rounding the resin film to be fed into an extrusion head so that the two long sides of the resin film overlap to form an overlapping section where no step is produced at least on the surface side;    bending the resin film into a cylindrical shape within the extrusion head; and    extruding rubber inside and outside the resin film.    
   
   
       21 . A method for producing by extrusion molding a thin rubber hose having an inner rubber layer and an outer rubber layer laminated respectively inside and outside a resin film serving as an intermediate layer, the intermediate layer having a circular cross section and forming an overlapping section by allowing a pair of side sections, which divide the intermediate layer in the circumferential direction, to overlap, wherein at least one of the two sides forming the overlapping section on the surface side is thinned to eliminate a step in the overlapping section on the surface side, comprising the steps of: 
 rounding a long belt-shaped resin film to allow the two long side sections to overlap;    forming the resin film into a cylindrical shape which has an overlapping section where a step is produced at least on the surface side;    eliminating the step on the surface side by a subsequent process; and    extruding rubber inside and outside the cylindrical resin film.