A method for producing a cross bottom sack

摘要

1,193,676. Block-bottomed bags. WINDMÍLLER & HÍLSCHER. 28 July, 1967 [3 Aug., 1966], No. 34869/67. Heading B8K. [Also in Division B5] A tube blank I (Fig. 1) for a crossed-bottom bag secured by a dry pressure-sensitive adhesive which sticks only to itself, is cut at the ends to expose parts of the inside surfaces of the end flaps to receive the adhesive. In the blank illustrated the lower wall is extended at 3, and the upper wall at 11, while the opposed walls at each end are correspondingly recessed. An adhesive with a volatile solvent is then applied at the hatched areas on both sides of the blank and is allowed to dry before the blanks are stacked. The blank ends are subse quently opened to diamond form, as shown in Fig. 3, a valve sleeve 18, coated with the same adhesive, is secured in place, and the bottoms closed in the usual way. This results in the outer exposed surfaces having a coating of adhesive which can either receive a cover sheet or which may be inactivated, for example by talcum powder or by a solution of water and alcohol with a wetting agent. Alternatively, the adhesive may be printed in a pattern which leaves the exposed surfaces of the bottom free. A suitable adhesive for polyolefin sheeting is a mixture of isocyanate modified polyesters with free hydroxyl groups and isocyanate resins in a solvent. The sheeting may be first subjected to a corona discharge. The transverse cuts by which the bag blank is separated from a web are preferably first formed as perforations, those parts 9, 10 (Fig. I) which coincide in the two walls being subsequently cut while the non-coincident perforations 11, 12 are pulled apart by accelerating rollers. Where the blanks are cut from extruded lie-flat tubing, the perforations are made by apparatus including a carriage floating inside an opened portion of the tubing. Where the blank is cut from tubed flat web, the perforations may be made before the web is tubed. The seam in the tubed web may be by a heatactivated adhesive. The web may be multi-ply.