Double-wall plastic produce container having ventilation holes therein, and mold for the manufacture thereof

Abstract

In this ventilated double-wall plastic container, each hole structure has a central hole surrounded by a solid flange extending along the inside wall of the double-wall structure. The hole structure also has a spacer portion connecting the solid flange to the outside wall of the double-wall structure. The wall segments of the hole structure between the spacer portion and the flange and between the spacer portion and the outside wall of the container define angles that are either obtuse angles or right angles. In another aspect, the mold for manufacturing the double-wall container has spaced-apart inside and outside metal walls, a plurality of openings in the outside metal wall, and hole-forming inserts mounted in the openings and projecting toward the inside wall. A projecting surface on each of the hole-forming inserts defines with the inside wall a space of even thickness surrounding a pin at the centre of the insert.

1 . A double-wall plastic container having a double-wall structure comprising a first and second spaced-apart walls, and ventilation holes therein;
 each of said ventilation holes having a hole structure comprising a central hole surrounded by a flange made of solid plastic, and spacer means connecting said flange to said first wall, wherein segments of said spacer means connected to said flange and to said first wall define angles of 90° or more.   
   
   
       2 . The double-wall plastic container as claimed in  claim 1 , wherein said flange extends perpendicularly from said central hole. 
   
   
       3 . The double-wall plastic container as claimed in  claim 2 , wherein said central hole has a diameter and said flat flange has a width of about three times said diameter. 
   
   
       4 . The double-wall plastic container as claimed in  claim 3 , wherein said first and second walls have a similar wall thickness and said flange has a flange thickness of at least 0.75 times said wall thickness. 
   
   
       5 . The double-wall plastic container as claimed in  claim 4 , wherein said flange extends along and flush with said second wall. 
   
   
       6 . The double-wall plastic container as claimed in  claim 1 , wherein said spacer means has a conical shape. 
   
   
       7 . The double-wall plastic container as claimed in  claim 1 , wherein said spacer means has a spherical shape. 
   
   
       8 . The double-wall plastic container as claimed in  claim 1 , further having ribs therein, and one of said ventilation holes is located in one of said ribs, and said spacer means define sides of said rib. 
   
   
       9 . A double-wall plastic container having a double-wall structure comprising a first and second spaced-apart walls, and ventilation holes therein;
 each of said ventilation holes having a hole structure comprising a central hole surrounded by a flange made of solid plastic and extending along and flush with said first wall at a right angle from an axis of said central hole, said flange having a width of about three times a diameter of said central hole; and   spacer means connecting said flange to said second wall, wherein segments of said spacer means connected to said flange and to said second wall define obtuse angles.   
   
   
       10 . The double-wall plastic container as claimed in  claim 9 , wherein said first and second walls have a similar wall thickness and said flange has a flange thickness of at least 0.75 times said wall thickness. 
   
   
       11 . The double-wall plastic container as claimed in  claim 9 , wherein said flange has a disc-like shape. 
   
   
       12 . A mold for molding a ventilated, double-wall container by a rotational molding process;
 said mold comprising spaced-apart inside and outside walls;   an opening is said outside wall;   a hole-forming insert mounted in said opening;   said hole-forming insert having a pin extending therefrom and against said inside wall, and a projecting surface extending toward said inside wall and defining with said inside wall a space of even thickness surrounding said pin.   
   
   
       13 . The mold as claimed in  claim 12 , wherein said space of even thickness extends perpendicularly from said pin. 
   
   
       14 . The mold as claimed in  claim 12 , wherein said hole-forming insert comprises a compression spring mounted therein against an end of said pin for pushing said pin against said inside wall. 
   
   
       15 . The mold as claimed in  claim 13 , wherein said projecting surface has a spherical shape, a conical shape or a cylindrical shape. 
   
   
       16 . The mold as claimed in  claim 14 , wherein said hole-forming insert comprises a threaded hollow plug adjustably mounted therein and said pin and said spring are mounted inside said threaded hollow plug. 
   
   
       17 . The mold as claimed in  claim 12 , wherein said projecting surface makes obtuse angles with said outside wall and with said space of even thickness. 
   
   
       18 . The mold as claimed in  claim 12 , wherein said hole-forming insert comprises a bar-like trapezoidal body defining said projecting surface. 
   
   
       19 . The mold as claimed in  claim 13 , wherein said space of even thickness has a width of about three times a diameter of said pin. 
   
   
       20 . The mold as claimed in  claim 13 , wherein said space of even thickness has a disc-like shape.