Abstract: Medical bags composed of plastic sheets jointed at their edges and a fluid charging/discharging tube sealed between the edges of the sheets have suffered, due to the use of a mold having smooth and straight land conforming with the surface of the tube, various problems such as formation of burrs by the displaced molten plastic material on the inner side of the product bag, weakening or generation of pinholes around the free end of the tube attributable to excessive thinning of the sheets and so forth. According to the invention, these problems are overcome thanks to the use of a mold which has a central first land of an inside diameter slightly smaller than the sum of the tube diameter and thicknesses of sheets and at least one additional land provided at each side of the first land, the additional lands having inside diameters increasing successively and slightly greater than that of the first land.

Abstract: Medical bags composed of plastic sheets jointed at their edges and a fluid charging/discharging tube sealed between the edges of the sheets have sufferred, due to the use of a mold having smooth and straight land conforming with the surface of the tube, various problems such as formation of burrs by the displaced molten plastic material on the inner side of the product bag, weakening or generation of pinholes around the free end of the tube attributable to excessive thinning of the sheets and so forth. According to the invention, these problems are overcome thanks to the use of a mold which has a central first land of an inside diameter slightly smaller than the sum of the tube diameter and thicknesses of sheets and at least one additional land provided at each side of the first land, the additional lands having inside diameters increasing successively and slightly greater than that of the first land.