Device and product of pressing two mold portions together and controlling an internal pressure so as to create a hollow cone

Abstract

A method and device for the manufacture of a hollow cone ( 37 ) with a cone tip ( 31 ) whereby a parison of viscous material ( 35 ) is molded into the shape of the hollow cone. An escape space ( 11 ) becomes accessible to the material in the vicinity of a cone tip to be formed. The moment the pressure present in the material in the vicinity of the cone tip to be formed exceeds a previously defined value. Breaking-off of the cone tip during or after molding is prevented by this. The hollow cone is suitable inter alia for use in a cathode ray tube.

1 . A method of manufacturing a hollow cone provided with an open side and a cone tip remote from the open side, whereby a parison of viscous material is brought into a first mould part after which the parison of material is moulded into the desired shape of the hollow cone by means of a second mould part, characterized in that an escape space for the material becomes accessible in the vicinity of the cone tip to be formed and adjoining the first mould part the moment the pressure present in the material in the vicinity of the cone tip to be formed exceeds a previously defined value.  
     
     
         2 . A method as claimed in    claim 1   , characterized in that the escape of the material into the escape space is prevented by means of a gas pressure applied in the escape space until the pressure present in the material has become greater than the gas pressure.  
     
     
         3 . A method as claimed in    claim 2   , characterized in that after the parison of material has been introduced into the first mould part, the parison is kept floating in the first mould part by means of the gas pressure until moulding starts.  
     
     
         4 . A method as claimed in    claim 2    or    3   , characterized in that the formed cone is pressed from the first mould part by means of the gas pressure after moulding.  
     
     
         5 . A method as claimed in    claim 2   ,    3    or  4 , characterized in that the gas pressure is adjustable during the manufacture of the hollow cone.  
     
     
         6 . A device suitable for carrying out the method as claimed in    claim 1   ,    2   ,  3 ,  4  or  5 , which device is provided with a first and a second mould part which are displaceable relative to one another, characterized in that the device is provided with an escape space with closing possibility which merges into the first mould part.  
     
     
         7 . A device as claimed in    claim 6   , characterized in that the escape space is provided with a gas pressure connection.  
     
     
         8 . A device as claimed in    claim 7   , characterized in that the escape space is funnel-shaped, a comparatively large open side of the escape space merging into the first mould part and a comparatively small open side of the escape space being connected to the gas connection.  
     
     
         9 . A cone manufactured by the method as claimed in    claim 1   ,    2   ,  3 ,  4  or  5 .  
     
     
         10 . A cathode ray tube provided with a cone as claimed in    claim 9   .