Gas-permeable plug and method for manufacturing the same

Abstract

A gas-permeable plug is adapted to be inserted in an insertion hole formed through a part of a casing in an inward-outward direction. The gas-permeable plug has a plug body and a permeable sheet including therein countless minute permeable pores. The plug body is injection molded from a material having rubber-like elasticity and the permeable sheet is integrally bonded to a sheet bonding portion by an anchor operation such that when the plug body is injection molded, at the sheet bonding portion, a part of a heat-melted liquid resin enters the minute permeable pores and/or the permeable gaps in irregular directions by the injection molding pressure and is solidified.

1 . A method for manufacturing a gas-permeable plug, including a plug body that is substantially ring-shaped or cylindrical and has a vent hole formed through a center portion in an inward-outward direction, with an injection mold that includes a first mold and a second mold which form a cavity therebetween when closed together, the method comprising: 
 setting a gas permeable and liquid impermeable sheet having a plurality of minute permeable pores directed in irregular directions and/or a plurality of fine permeable gaps directed in irregular directions at a molding position of the vent hole of the plug body in one of the first mold and the second mold when the injection mold is open;    closing the first mold and the second mold together, and sandwiching and fixing a center portion of the gas permeable and liquid impermeable sheet between a molding surface of the first mold and a molding surface of the second mold while an outer peripheral portion of the gas permeable and liquid impermeable sheet is located in the cavity; and    molding the plug body by injecting a resin that is a heat melted liquid into the cavity under a predetermined injection molding pressure, mechanically bonding the outer peripheral portion of the gas permeable and liquid impermeable sheet and the resin integrally, whereby the resin enters the minute permeable pores and/or the permeable gaps by the predetermined injection molding pressure, and allowing the resin to solidify.    
   
   
       2 . A method according to  claim 1 , wherein the minute permeable pores and/or the permeable gaps of the gas permeable and liquid impermeable sheet have irregular shapes.  
   
   
       3 . A method according to  claim 1 , wherein the closing of the first mold and the second mold together includes compressing an annular portion of the gas permeable and liquid impermeable sheet inside of the outer peripheral portion of the gas permeable and liquid impermeable sheet.  
   
   
       4 . A method according to  claim 3 , wherein the compressing of the annular portion of the gas permeable and liquid impermeable sheet does not compress an inside portion of the gas permeable and liquid impermeable sheet inside of the annular portion.  
   
   
       5 . A method according to  claim 3 , wherein the compressed annular portion has a thickness in a range of 90% to 5% of a thickness of the annular portion prior to compression.  
   
   
       6 . A method according to  claim 3 , wherein the molding of the plug body does not cause the resin to flow to the inside portion of the gas permeable and liquid impermeable sheet.  
   
   
       7 . A method according to  claim 1 , wherein the injecting of the resin includes heating the outer peripheral portion of the gas permeable and liquid impermeable sheet, and compressing the outer peripheral portion of the gas permeable and liquid impermeable sheet due to the predetermined injection molding pressure.  
   
   
       8 . A method according to  claim 1 , wherein the resin is a thermoplastic elastomer resin.  
   
   
       9 . A method according to  claim 8 , wherein the resin is an olefin type thermoplastic elastomer resin.  
   
   
       10 . A method according to  claim 1 , wherein the resin includes resin materials having mutual miscibility with the gas permeable and liquid impermeable sheet.  
   
   
       11 . A method according to  claim 1 , wherein the injecting of the resin includes forcibly pressing the resin into the minute permeable pores and/or the permeable gaps with the predetermined injection molding pressure and a dwelling pressure of several hundred to several thousand Newton per cm2.  
   
   
       12 . A method according to  claim 1 , wherein the gas permeable and liquid impermeable sheet is a single sheet body.  
   
   
       13 . A method according to  claim 1 , wherein the gas permeable and liquid impermeable sheet includes a laminated sheet having a backing sheet, the backing sheet having the plurality of minute permeable pores directed in irregular directions and/or the plurality of fine permeable gaps directed in irregular directions.  
   
   
       14 . The method according to  claim 1 , further comprising, after the molding of the plug body, inserting a reinforcing body in the plug body.  
   
   
       15 . The method according to  claim 14 , wherein the reinforcing body is formed of a harder material than the plug body.  
   
   
       16 . A method according to  claim 2 , wherein the closing of the first mold and the second mold together includes compressing an annular portion of the gas permeable and liquid impermeable sheet inside of the outer peripheral portion of the gas permeable and liquid impermeable sheet.  
   
   
       17 . A method according to  claim 16 , wherein the compressing of the annular portion of the gas permeable and liquid impermeable sheet does not compress an inside portion of the gas permeable and liquid impermeable sheet inside of the annular portion.  
   
   
       18 . A method according to  claim 16 , wherein the compressed annular portion has a thickness in a range of 90% to 5% of a thickness of the annular portion prior to compression.  
   
   
       19 . A method according to  claim 16 , wherein the molding of the plug body does not cause the resin to flow to the inside portion of the gas permeable and liquid impermeable sheet.  
   
   
       20 . A method according to  claim 2 , wherein the injecting of the resin includes heating the outer peripheral portion of the gas permeable and liquid impermeable sheet, and compressing the outer peripheral portion of the gas permeable and liquid impermeable sheet due to the predetermined injection molding pressure.  
   
   
       21 . A method according to  claim 2 , wherein the resin is a thermoplastic elastomer resin.  
   
   
       22 . A method according to  claim 21 , wherein the resin is an olefin type thermoplastic elastomer resin.  
   
   
       23 . A method according to  claim 2 , wherein the resin includes resin materials having mutual miscibility with the gas permeable and liquid impermeable sheet.  
   
   
       24 . A method according to  claim 2 , wherein the injecting of the resin includes forcibly pressing the resin into the minute permeable pores and/or the permeable gaps with the predetermined injection molding pressure and a dwelling pressure of several hundred to several thousand Newton per cm2.  
   
   
       25 . A method according to  claim 2 , wherein the gas permeable and liquid impermeable sheet is a single sheet body.  
   
   
       26 . A method according to  claim 2 , wherein the gas permeable and liquid impermeable sheet includes a laminated sheet having a backing sheet, the backing sheet having the plurality of minute permeable pores directed in irregular directions and/or the plurality of fine permeable gaps directed in irregular directions.  
   
   
       27 . The method according to  claim 2 , further comprising, after the molding of the plug body, inserting a reinforcing body in the plug body.  
   
   
       28 . The method according to  claim 27 , wherein the reinforcing body is formed of a harder material than the plug body.