STITCHED VALVE BAG AND PROCEDURE FOR MAKING SAME

Abstract: The invention concerns a stitched valve bag and a procedure for manufacturing stitched valve bags from a material web run in tubular form. The valve bag (30) is provided at both ends with a stitched seam (38), and the bag (30) has in one corner a valve member (34') constituting a valve opening. In the longitudinal direction of the mantle part (31) of the bag (30) has at one end (32) at a distance from the corner of the bag been made an incision (36) longitudinal to the mantle (31). The portion between the incision (36) and the corner has been folded to become a valve member (34'), along a folding line (35) extending substantially from the bottom of the incision (36) obliquely to the margin of the mantle part (31). On the side beyond the incision (36) the bag end (32) has for improved strength been folded double before stitching said end of the bag.

Description: The invention concerns a stitched valve bag provided with a stitched seam at both ends and said bag having in its corner a valve member constuting a valve opening. The invention concerns a procedure for manufacturing stitched valve bags from a material web run in tubular form, said bags being provided at both ends with a stitched seam and said bags having in their corner a valve member constituting a valve opening. The bag made as taught by the invention is intended to be used as a so-called cement bag or equivalent. Bags of the kind described above, paper bags in particular, have previously been manufactured, for instance, in the following way. A full-width paper web is run in tubular shape with desired dimensions, the bag blank in tubular form comprising a mantle part which is open at both ends. Prior to cutting the bag blank off, an incision is made for the valve member on one end of the blank in the machine direction, i.e., in the longitudinal direction of the blank, and a certain part of the material is removed from this end in connection with the cut-off operation. Folding of the valve member or the corner of the valve opening is then performed, whereafter the valve end and bottom of the bag may be stitched closed. This procedure of prior art, and the bag manufactured according to this procedure, is embarrassed by a number of drawbacks. It is a significant drawback that in the manufacturing of the bag wasted pieces are cut off and have to be discarded, the removal of which is often difficult in practice and which cannot be utilized in any way whatsoever: being wast material, they have to be thrown away. Furthermore, the stitched seam on the side of the bag's valve end detracts from the strength of the bag because the material in the vicinity of the seam has not been "anchored" in any way. Moreover, a bag of this kind, when subjected to stress, tends to fail at the valve-end stitches and the material in the bag will then escape through the stitched seam. Another valve bag manufactured by a procedure of prior art is formed in that the paper web is run in tubular form of desired dimensions, the bag blank in tubular form comprising a mantle part with both ends open. Next, one open end of the tubular bag blank can be stitched closed, and folding of the valve opening corner can be performed on the other end of the bag blank. It is thus understood that no incision in the machine direction for forming the valve on the bag is associated with this manufacturing method. When the corner of the valve opening has been folded, the valve end of the bag can be stitched closed. The drawback of a bag made by this procedure is that the valve will be short and therefore the bag does not close properly. The object of the invention is to achieve an improvement over the technique of prior art. The more detailed object of the invention is to provide a stitched valve bag which has greater strength and better tightness at its valve end than any bags produced heretofore. It is a further object of the invention to teach a procedure by which a bag of said kind is manufactured without involving any extra work steps in the procedure. Still one object of the invention is to provide a procedure which enables the length of the valve member on the valve bag to be adjusted in a simple manner. The bag of the invention is mainly characterized in that at one end in the longitudinal direction of the mantle part of the bag, at a distance from the corner of the bag, has been made an incision longitudinal to the mantle, the portion between this incision and said corner having been folded, to become a valve member, along a folding line extending substantially from the bottom of said incision obliquely to the margin of the mantle portion, and that on the side beyond said incision the end of the bag has, for improved strength, been folded double before stitching said end of the bag. The procedure of the invention is mainly characterized in that said material web is cut up into bag blanks of predetermined length, these blanks comprising a mantle part open at both ends, that on one open end of the mantle part at a distance from the corner of the bag blank is made in the machine direction, i.e., in the longitudinal direction of the mantle, an incision which delimits a valve blank from said end of the bag blank, that folding of the valve blank to become a valve member is carried out, as well as folding said end of the bag blank double at a distance determined by said incision from said bag blank end, and that stitching of both ends of the bag blank is carried out, whereby a completed bag is obtained. At the same time, the length of the valve member that is formed within the bag can be steplessly adjusted by changing the length of the incision. With the procedure of the invention and with a bag manufactured according to the procedure several advantages over designs of prior art are achieved, of which for instance the following may be held forth. The bag of the invention is easy to manufacture by mechanical means. The procedure of the invention is even simpler than previous procedures because no piece of material has to be removed from the bag blank. As a result, savings in economy are also achieved since the material can be more completely utilized. The bag manufactured by the procedure of the invention has greater strength than those of prior art because the material of the bag's valve end, which used to be discarded, is now made use of towards improving the strength of the bag's valve end. Since the stitched seam of the valve end will have good strength, the bag can be made using even one single material course (several courses may naturally equally be used). When two material courses are used, the inner course is for instance paper, and the outer, so-called reinforcing material is for instance a course woven of some plastic material. Furthermore, it is possible by changing the length of the valve to produce by the procedure of the invention a bag with better tightness than by any method of prior art. The invention is described in detail in the following, referring to some advantageous embodiments of the invention, presented in the figures of the attached drawing, but to which the invention is not meant to be exclusively confined. Figs 1A and 1B present, as seen from above, a paper bag of prior art. Figs 2A and 2B present, as seen from above, two alternative embodiments of the material web associated with the manufacturing of the bag depicted in Figs 1A and 1B. Figs 3A and 3B present, as seen from above, another bag of prior art. Fig. 4A presents, as seen from above, the valve end of a bag according to the invention, prior to folding the corner of the valve member. Fig. 4B presents, as seen from above, the valve end of a bag according to the invention, with the corner of the valve member folded. Fig. 4C presents, as seen from above, the valve end of a bag according to the invention, fully stitched. Fig. 5 presents, as seen from above, the material web of which the bag of the invention is made. The valve bag of prior art, presented in Fig. 1A, has been generally denoted with reference numeral 10. Reference numerals equivalent to those in Fig. 1A are used in Figs 1B, 2A and 2B. The valve bag 10 comprises a mantle part 11, an upper part 12 and a lower part 13. In one corner of the upper part 12 of the bag 10 has been formed a valve member 14. In Fig. 1A, the bag 10 is shown in the stage where it has already been cut, but the valve member 14 has not been folded. In Fig. 1B the valve member 14 is shown, folded along the folding lines 15. The folds of the valve bag 10 carry the reference numeral 17. In Fig. 1B has also been indicated, with interrupted lines, the stitched seam 18, with which the upper part 12 of the bag is stitched closed after the valve member 14 has been folded. Of course, a similar stitched seam 18 is also applied in the lower part 13 of the bag. The mantle 11 of such a bag 10 of prior art usually consists of a plurality of material thicknesses, e.g. of the triple material thickness. The bag 10 of prior art, described above, can be made on a material web e.g. in two ways, as depicted in Figs 2A and 2B. As shown in Fig. 2A, the bag 10 may be made in that the full-width paper web is run to tubular shape of desired dimension, by cutting the web along the dotted lines indicated with reference numeral 13a, and which go to form the lower part 13 of the bag 10. Next, in order to form the valve member 14, an incision 16 running in the machine direction, i.e., parallel to the mantle part 11, is made at one end of the bag blank, this incision extending up to the transversal line 12a, marked with a dotted line, and this forming the upper part 12 of the bag 10. Along said line 12a is thereafter made a cross-cut, whereby the waste piece 19 is removed from the bag blank. The valve member 14 is then folded along the folding lines 15, and the upper part 12 and lower part 13 of the bag are stitched closed with the stitched seam 18. In practice, the cuts 13a, 12a and 16 are often made in one work step. In the manufacturing mode of Fig. 2B, the waste piece 19 is smaller of its size than in the procedure of Fig. 2A, but implementation of the procedure of Fig. 2B is more difficult. In the procedure of Fig. 2B, the paper web may be cross-cut, for forming the bag 10, only at one end of the bag 10 with a transversal cut 13b. It is thus understood that this cut 13b will produce, on the material web, the lower parts 13 of two consecutive bags. On a material web as shown in Fig. 2B, the upper parts 12 of two consecutive bags face each other and therefore the cut 12b cannot be carried at one go right across the material web. Another valve bag of prior art, depicted in Figs 3A and 3B, has been generally denoted with reference numeral 20. The bag 20 comprises a mantle part 21, an upper part 22 and a lower part, not depicted in the figure. The folds of the bag 20 carry the reference numeral 27. A valve member 24 is formed in one corner of the upper part 22 by folding one corner of the upper part 22 along the folding lines 25, whereafter the bag 20 is ready for being stitched. In Fig. 3B has been indicated the stitched seam 28, and a similar stitched seam is of course also provided in the lower part of the bag 20. The bag 20 according to Figs 3A and 3B is rather much simpler to manufacture than the bag 10 of Figs 1A-2B. The bag 20 according to this embodiment is manufactured by cutting the material web to tubular lengths of desired dimension, whereby the bag blank in tubular form comprises a mantle part 21 with both ends open. In the upper part 22 of the bag is formed a valve member 24 by folding one upper corner of the bag along the folding lines 25, whereupon the upper part 22 of the bag is stitched closed with the stitched seam 28, and the lower part with a similar seam. The bag is then fully completed. With the bags of prior art described in the foregoing is associated the drawback that the material lying in the vicinity of the stitched seam 18,28 in the upper part 12,22 of the bags is in no way "anchored". Therefore, such a bag 10,20 of prior art is likely under stress to fail at the stitched seam 18,28, whereby the material in the bag escapes through the seam. Of course, the bag 10 of Figs 1A-2B could be anchored by folding double the upper end 12 before stitching the valve end of the bag and performing the stitching only thereafter. The blank for the bag 10 formed in this manner would, however, have to be longer than that of Figs 1A-2B by the length of the folded part, with the result of greater material waste and even higher manufacturing costs. The bag 20 of Figs 3A-3B could likewise be anchored in similar manner, but this too would require the use of a longer blank. Moreover, making the fold would be exceedingly difficult in practice when a bag as in Figs 1A-2B and 3A-3B is made of a plurality of material courses. In Figs 4A-4C is presented the manufacturing of the valve end of a bag 30 according to the invention, and Fig. 5 illustrates the way in which the bag blank is taken from the material web. As can be seen in Fig. 5, the material web has been run in tubular form and it has been cross-cut to given dimensions along the lines 32a and 33a. In this same connection is made a longitudinal incision 36 for the valve blank 34 in the upper part 32 of the bag blank, in the machine direction, i.e., longitudinal to the mantle part 31 of the blank. Forming the valve member 34' of the bag 30 and "anchoring" the valve end is effected in the way depicted in Figs 4A-4C. The bag 30 of said figures comprises a mantle part 31, a lower part, or bottom part not depicted in these figures, and an upper part 32. In the upper part 32 has been made, in the way just described, an incision 36 in the machine direction for the valve blank 34. The folds of the bag 30 carry the reference numeral 37. Said incision in the machine direction, 36, has been carried up to the folding line 39 of the valve end, which corresponds to the upper part 12 of the bag 19 shown in Fig. 1A. Different from the bag shown in Fig. 1A, the bag blank is not cut along the folding line 39 in the design of the invention; instead, the upper part 32 of the bag is folded along said line 39 in order to reinforce the valve end of the bag 30. As can be seen in Fig. 4B, the valve blank is folded, to become a valve member 34', along the folding lines 35, and thereby the forming of the valve member 34' is completed. When the valve member 34' has been fully folded, the above-mentioned folding of the upper part 32 of the bag 30 along the folding line 39 is carried out, as shown in Fig. 4C. The valve end of the bag 30 and its lower part 33 are then stitched closed with stitched seams 38. The valve end of the bag 30 of the invention can thus be anchored in the way just described, by folding double the upper part 32 of the bag 30. Through this, the strnegth of the valve end of the bag 30 is substantially improved, so that the bag 30 may even be made using one single material course if this should be required. When using several material courses, the bag may be manufactured either of paper or equivalent altogether, or by using, in one of the courses at least, various reinforcing materials, e.g. woven fabric material or equivalent. The reinforcing material has to be of a kind which endows the bag 30 with adequate strength, and the reinforcing material may moreover be treated in a way preventing moisture penetration, in which case it will also constitute a moisture protection for the bag 30. The woven fabric material cannot become unravelled in the vicinity of the stitched seam 38 at the valve end of the bag because the upper part 32 of the bag has been folded double. It is obvious, of course, that the lower part 33 of the bag may equally be folded double in like manner, although in that case a longer bag blank will be needed. The invention is not critical as regards the succession in which cross-cutting, incision, valve folding and stitching of upper and lower part are performed. In the foregoing the invention has been described by way of example with reference to the figures of the attached drawing. By this it is not intended, however, to confine the invention to concern merely the examples presented in the figures: numerous modifications are feasible within the scope of the inventive idea defined by the claims following below.

Claims: 1. A stitched valve bag (30) provided at both ends with a stitched seam (38), and said bag (30) having in one corner a valve member (34') constituting a valve opening, characterized in that in the longitudinal direction of the mantle part (31) of the bag (30) has at one end (32) at a distance from the corner of the bag been made an incision (36) longitudinal to the mantle (31), the portion between said incision (36) and said corner having been folded to become a valve member (34'), along a folding line (35) extending substantially from the bottom of said incision (36) obliquely to the margin of the mantle part (31), and that on the side beyond said incision (36) the bag end (32) has for improved strength been folded double before stitching said end of the bag. 2. Procedure for manufacturing stitched valve bags of a material web run in tubular form, said bags (30) being provided at both ends with a stitched seam (38) and said bags (30) having in one corner a valve member (34') constituting a valve opening, characterized in that said material web is cut up into bag blanks of given length and comprising a mantle part (31) open at both ends (32,33), that at one open end (32) of the mantle part (31) at a distance from the corner of the bag blank is made in the machine direction, i.e., in the longitudinal direction of the mantle (31), an incision (36) which delimits a valve blank (34) from said end of the bag blank, that folding of the valve blank (34) to become the valve member (34') and double folding of said end (32) of the bag blank are performed at the distance from said end (32) of the bag blank determined by said incision (36), and that stitching of both ends of the bag blank is carried out, whereby a completed bag (30) is obtained. 3. Procedure according to claim 2, characterized in that the length of the valve member (34') on the valve bag (30) is adjusted by changing the length of the incision (36).

Inventors: KOSKINEN, ERKKI, RANTANEN, KEIJO
Applicants: OY W. ROSENLEW AB
Application year: 1986
Main classification: B65D30
IPC codes: B65D30