Patent Publication Number: US-4549668-A

Title: Lid with vent valve

Description:
Lids of this kind with vent valves, of silicone rubber, as known hitherto, are not suitable for products which cause the vent valve to swell up. Swelling causes the vent valve to become ineffective and then the required security is not presented. 
     It is the problem of the invention to indicate a lid having a vent valve of the stated kind which is suitable even for packings of gas-evolving products which otherwise effect swelling of the vent valve. More especially the vent valve is to be stable against the actions of all kinds of organic peroxides. The vent valve is to be able stably to possess a uniformly reproducible opening pressure between 0.05 and 0.2 bar. Finally the vent valve is to fit into ordinary caps, especially screw caps. 
      A combination of (relatively soft) polyethylene for the bush and/or the retaining ring and (relatively hard) polypropylene for the valve ball, and likewise this combination with converse association, are especially preferred here. 
    
    
     The invention will be described hereinafter by means of an example of embodiment with reference to the accompanying drawings, wherein: 
     FIG. 1 shows the vent valve in the installed condition, 
     FIG. 2 shows the vent valve according to FIG. 1 in exploded representation, 
     FIG. 3 shows the detail X in FIG. 2, 
     FIG. 4 shows the retaining ring. 
    
    
     In the present example of embodiment the vent valve 2 is inserted into a screw cap 4. On the inner side of the cap 4 there is an annular collar 6 flush surrounding a bush 8 of polyethylene. Axially through the bush 8 there extends a passage 10 which widens by way of a conical stage 14 towards a hole 12 in the crown of the cap 4. A valve ball of polypropylene lies in the conical stage 14. A retaining ring 20 of polyethylene is seated in an annular shoulder 18 of the bush 8 which surrounds the axial passage 10 close to the hole. A compression spring 22 of V4A steel is arranged between the retaining ring 20 and the valve ball 16. If the axial passage 10 has a diameter of 2 mm. in its narrow region and a diameter of 5.9 mm. in its wide region, the valve ball 16 has a diameter of 5 mm. and the compression spring has a diameter of 5.6 mm. and four turns with a wire diameter of 0.5 mm. and finally in the unstressed condition a length of 5.6 mm., the opening pressure of the valve lies stably between 0.05 and 0.2 bar. 
     The circumferential surface 24 of the annular shoulder 18 is provided with a protruding annular detent flange 26 for reception in a corresponding annular groove 28 in the circumferential surface 30 of the retaining ring 20. 
     A section 32 of the bush 8 adjoining the cap 4 tapers conically in the direction towards the cap 4 from a diameter 34 which is somewhat larger than the diameter of the inner surface of the annular collar to the diameter of the inner surface of the annular collar. 
     For assembly, the bush 8 with the valve ball 16 and the compression spring 22 is pressed flush into the annular collar 6. If the cap is screwed on to a vessel with a gas-evolving product, in the case of excess pressure the valve ball 16 is pressed against the compression spring 22 and thus the axial passage 10 is opened to the hole 12. 
     Vent valves of the kind as described were stored over three months in TBPEH and then, still unswollen, proved stably to have a reproducible opening pressure between 0.05 and 0.15 bar. 
     The conical taper of the bush permits its simple introduction into the annular collar 6 and nevertheless a firm seating in the annular collar 6.