Air-evacuable bag with double-layered valve film and method for manufacturing same

Abstract From the Canadian patent

An air-evacuable bag has a one-way valve therein having two layers of valve film neither of which is the sidewall of the bag. By forming the one-way valve of smooth double- layered valve film, unwanted air gaps caused by textured surfaces in the sidewalls of the bag are avoided thereby minimizing air leakage back into an evacuated bag. A method for the manufacture of such air-evacuable bags incorporates a roll supplying a first valve film layer a roll supplying a first sidewall layer a roil supplying a second valve film layer and a roll supplying a second sidewall layer. As the film coming off the first valve film layer roll passes the roll supplying the first sidewall layer both the …