Mold for molding foamed tube for tire, and method of manufacturing foamed tube for tire

Abstract

A mold for molding a foamed tube for a tire is formed from a first mold and a second mold. Each mold has an annular concave portion for tube molding, and joining faces which are continuous with the annular concave portion and are formed at an inner side and an outer side, in a radial direction, of the annular concave portion. Each of the joining faces of the first mold and the joining faces of the second mold has horizontal joining faces provided adjacent to the annular concave portion in a direction orthogonal to an axial direction at a radially inner side and a radially outer side of the annular concave portion, and an inclined joining face provided continuously with the horizontal joining face so as to be inclined with respect to the horizontal joining face at one of an inner side and an outer side in the radial direction.

1 . A method of manufacturing a foamed tube for a tire, comprising the steps of: 
 (a) filling a foaming-agent-containing rubber composition, which generates gas when heated, into at least the annular space of a mold comprising: 
 a first mold having a first annular concave portion which molds one side, in an axial direction, of the foamed tube for a tire; and  
 a second mold having a second annular concave portion which molds another side, in the axial direction, of the foamed tube for a tire,  
   wherein when the first mold and the second mold are combined in the axial direction, the first annular concave portion and the second annular concave portion form an annular space for molding the foamed tube for a tire,    the first mold has first joining faces which are connected to the first annular concave portion and which are positioned at an inner side and an outer side, in a radial direction, of the first annular concave portion, and the first joining faces include horizontal joining faces provided adjacent to the first annular concave portion in a direction orthogonal to the axial direction at the inner side and the outer side, in the radial direction, of the first annular concave portion, and inclined joining faces each provided continuously with a respective one of the horizontal joining faces so as to be inclined with respect to the horizontal joining face at one of an inner side and an outer side in the radial direction,    the second mold has second joining faces which are connected to the second annular concave portion and which are positioned at an inner side and an outer side, in the radial direction, of the second annular concave portion, and the second joining faces include horizontal joining faces provided adjacent to the second annular concave portion in a direction orthogonal to the axial direction at the inner side and the outer side, in the radial direction, of the second annular concave portion, and inclined joining faces each provided continuously with a respective one of the horizontal joining faces so as to be inclined with respect to the horizontal joining face at one of an inner side and an outer side in the radial direction, and    the first mold and the second mold have configurations which complementarily complete one another via the first joining faces and the second joining faces; and    (b) heating and vulcanizing the foaming-agent-containing rubber composition.    
   
   
       2 . A method of manufacturing a foamed tube for a tire, comprising the steps of: 
 (a) preheating one of a first mold and a second mold, the first mold having a first annular concave portion which molds one side, in an axial direction, of the foamed tube for a tire, the second mold having a second annular concave portion which molds another side, in the axial direction, of the foamed tube for a tire, wherein    when the first mold and the second mold are combined in the axial direction, the first annular concave portion and the second annular concave portion form an annular space for molding the foamed tube for a tire,    the first mold has first joining faces which are connected to the first annular concave portion and which are positioned at an inner side and an outer side, in a radial direction, of the first annular concave portion, and the first joining faces include horizontal joining faces provided adjacent to the first annular concave portion in a direction orthogonal to the axial direction at the inner side and the outer side, in the radial direction, of the first annular concave portion, and inclined joining faces each provided continuously with a respective one of the horizontal joining faces so as to be inclined with respect to the horizontal joining face at one of an inner side and an outer side in the radial direction,    the second mold has second joining faces which are connected to the second annular concave portion and which are positioned at an inner side and an outer side, in the radial direction, of the second annular concave portion, and the second joining faces include horizontal joining faces provided adjacent to the second annular concave portion in a direction orthogonal to the axial direction at the inner side and the outer side, in the radial direction, of the second annular concave portion, and inclined joining faces each provided continuously with a respective one of the horizontal joining faces so as to be inclined with respect to the horizontal joining face at one of an inner side and an outer side in the radial direction, and    the first mold and the second mold have configurations which complementarily complete one another via the first joining faces and the second joining faces;    (b) positioning and placing, within the annular concave portion of the mold which is preheated, a foaming-agent-containing rubber composition which generates gas when heated;    (c) combining and closing the first mold and the second mold;    (d) heating the molds and carrying out vulcanization of the rubber composition; and    (e) after carrying out heating for a predetermined period of time, opening the molds and removing the rubber composition.    
   
   
       3 . A method of manufacturing a foamed tube for a tire according to  claim 2 , wherein said step (c) of combining and closing the first mold and the second mold includes a step of airtightly joining the horizontal joining faces of the first joining faces and the horizontal joining faces of the second joining faces when closing the molds.  
   
   
       4 . A method of manufacturing a foamed tube for a tire according to  claim 3 , wherein said step (d) of heating the molds and carrying out vulcanization of the rubber composition includes a step in which gas is generated by the foaming agent, innumerable independent air bubbles are formed in the rubber composition, and an internal pressure of the rubber composition rises.  
   
   
       5 . A method of manufacturing a foamed tube for a tire according to  claim 4 , wherein said step (e) of, after carrying out heating for a predetermined period of time, opening the molds and removing the rubber composition, includes: 
 a step in which the rubber composition swells suddenly substantially simultaneously with opening of the molds, and first, the rubber composition enters into a gap between the horizontal joining faces of the first mold and the horizontal joining faces of the second mold;    a step in which the foamed rubber composition which has entered into the gap between the horizontal joining faces abuts the inclined joining faces at the outer sides and stops; and    a step in which the swelled, foamed rubber composition is pushed by its own swelling force against the inclined joining faces and remains within the molds until the molds are completely opened, and therefore, the rubber composition can be prevented from protruding out to an exterior of the molds before the molds are completely opened.