Manufacturing container or tube from paper; or other manufacturi – Container making – Pliable container
Patent
1991-07-11
1992-09-29
Kisliuk, Bruce M.
Manufacturing container or tube from paper; or other manufacturi
Container making
Pliable container
493227, 493926, 493933, B31B 174
Patent
active
051510766
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a flexible intermediate bulk container (FIBC) for lifting, transportation and storing of bulk material. The FIBC is formed from a hose-like blank. One half-length portion of the blank is turned inside out and thread onto or pulled over the other half-length portion, thus forming inner and outer sacks having a common base or separate bases.
By a flexible container as employed herein is meant a container for lifting, transportation and storing of bulk material such as powderous or granular fertilizer, ground or unground grain, Portland cement, coal, etc., in quantities of several hundred kilos per container.
There are previously known sack-like containers for the above-mentioned type. U.S. Pat. No. 3,789,897 describes a FIBC comprising inner and outer sacks which are formed from a hose-like blank where one half-length portion of the blank is turned inside out and threaded onto the other half-length portion. In the fold formed between the inner and outer sacks at the top end of the container, there is placed a rope for drawing together the filling section of the container. The same type of system is used at the base of the container.
For lifting of such container, along the circumference thereof is arranged a set of separate lifting loops each passing through slots in the inner and outer sacks below the rope. The container is therefore complicated to construct and expensive to manufacture. In addition, a draw-back of such container is that there exists considerable stress concentration in the areas where the lifting loops are attached to the inner and outer sacks. This stress can result in rupture during lifting of the container. The carrying capacity is thus limited by the construction, and is described as being between 600-1000 kg.
A second type of double-walled container is known from NO U.S. patent application Ser. No. 871,705. The main disadvantage of this container is its complicated and labor intensive manufacturing method.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method of manufacturing a flexible container, where the container construction is simplified and improved so that the manufacturing costs are reduced and that the load carrying capacity is increased two to three times without the need to increase the quality of the container material.
A special feature of the invention is that the hose-like blank of material used for the container is provided with two or more longitudinal slots or openings separated by the same distance around the circumference of the hose-like blank. One half-length portion of the hose-like blank is rotated with respect to the other half-length portion around the longitudinal axis of the blank and that one half-length portion is turned inside out and threaded onto the other half-length portion. Thus, the material in the areas between the slots or openings forms two or more integrated lifting loops.
The integrated lifting loops are extensions of the walls of the inner and outer sacks and extend in parallel from the inner sack to the outer sack. During lifting of the container according to the invention, the forces will be distributed evenly and uniformly, i.e. without stress concentrations, to the walls of the inner and outer sacks. The rotation also ensures that the material of lifting loops are rotated. The material of the lifting loops is kept together and the loops themselves extend in parallel, thus forming a single lifting eye.
By comparing the container according to the invention and the container according to the above mentioned U.S. patent, several advantages are obtained:
Containers can be made with larger carrying capacity by using the same quality of material, i.e. the ratio of carrying capacity/material weight increases.
The manufacture of flexible containers is simpler with fewer manufacturing steps and parts. In U.S. Pat. No. 3,789,897, separate lifting loops and ropes for drawing together sections at the top and bottom are employed and
REFERENCES:
patent: 3106140 (1963-10-01), Baker
patent: 4191229 (1980-03-01), Skaadel et al.
patent: 4710967 (1987-12-01), Petschner
Kisliuk Bruce M.
Lavinder Jack W.
Norsk Hydro a.s.
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