FR2586650A1 - Bags, starting material, and process and machine for manufacturing them - Google Patents

Abstract

The invention relates to a starting material for bags, as well as the bags produced by means of the latter, a sheet or a film intended for forming the walls 14 of the bag being folded in order to constitute the folded and closed upper part 11 of each bag. A zip-like closure strip 17 comprises a member 18 housed within the upper fold of the bag and marginal parts of the member 18 supporting reclosable profiles 19, 20 of the zip-like closure, at least one of the marginal parts remaining unattached with respect to the wall of the bag. A tear thread 33 may be carried by the zip-like closure strip and especially by its member 18. The bag may comprise a starting tab for the tear thread. The invention also describes a process for producing the starting material constituting the bag, and a machine for obtaining it.

Description

 Bags, basic product, process and machine for making them.

 The invention relates to the art of manufacturing plastic bags equipped with a zipper and more particularly relates to a new and improved bag, the basic product and a method and a machine for making such bags. .

Plastic bags equipped with zippers in one piece with these are described in US Pat.
Re 28 959. The one-piece extrusion of the thin film of the bag and the larger cross-sectional mass of the zipper profiles causes manufacturing problems, particularly with regard to the speed of manufacture. Increased production and the resulting manufacturing savings are important for a market that has become very competitive. Constant efforts are therefore made to improve them and lower manufacturing costs.

 US Patent 3,543,343 discloses another example of extruded profiles integrally on a tubular film. In addition, this patent describes the equipment of a freshly extruded tubular film with complementary profiled closure strips, which are manufactured separately. The extruded profiles in one piece have the drawbacks already described in connection with the patent Re 28 959. The fixing of the individual closure strips is a complicated matter, and the problem of obtaining a reasonable degree of accuracy of the alignment of the Individually fixed zipper strips also arise.

 In addition, U.S. Patent 3,543,343 discloses the feature of attaching a tear wire or cord to the top fold of the base product separately from the integral film structure of the zipper. No indication is provided as to how the end of the pull cord should be manipulated to open a bag.

 US Patent 4,101,355 discloses fusing or adhesive bonding zipper strips which have complementary profiles adapted to interlock with one another by folding the strips along a fold line. Central. But this patent does not teach the attachment of the entire base or base product to both sides of the profile, i.e. the side strips of the sides of each strip on the film base product of the bag.

 US Pat. No. 4,341,575 shows an arrangement similar to that of US Pat. No. 4,101,355 but is limited to securing the entire base of the zipper strip, including the side edges of the sides, to the film of the bag.

 US Patent 4,430,070 discloses fastening a minor region of each of the base portions of the zipper strips directly to the back of their profiles, thereby providing a hinged attachment of the profiles to the inner side of the bag. Each of the complementary bands of the zipper is independently connected to the film constituting the body of the bag, being spaced from the open end of the bag.

 An important object of the present invention is to provide a new and improved bag, a basic product for the manufacture of the bag, a method and a machine for obtaining folded upper edges of the bags, having a zipper fastened accurately according to which precedes the parts of the zipper profiles are disengaged from the film constituting the walls of the bag, and the profiles are accurately and permanently aligned with respect to one another and the edges to be pulled to open. the zipper are automatically of structure, that is to say of thickness, heavier than that of the walls of the bag, which facilitates the opening of the profiles and ensures that no tearing takes place at the junction between the zipper and the film, as they are always kept tight and assembled during the opening operation of the profiles, that is to say opening the bag.

 To this end, the present invention provides a bag comprising an upper portion, opposed sides, a bottom and opposed walls, a one-piece fold connecting the walls to the top of the bag, the walls being secured together along opposite sides of the bag and the walls being initially separated from each other along the bottom to form an opening for filling the bag with the opening, after which the opening is closed, and a closure strip at folded slide having complementary separable profiles along its opposite marginal portions, an intermediate folded chord connecting the marginal portions, the folded chord being accommodated in the upper fold of the bag, means securing the chord to the fold, and the marginal portions being not fixed and remaining free, on at least the totality of the width of the profiles, with respect to the walls, so that these walls can deviate from the parts m arginales and profiles.

 The present invention also provides a novel and improved high speed process, and a machine, for making the basic product of the bag as well as for making the bags.

 In addition, the present invention provides a novel and improved arrangement of the bag tear wire for bags of the general type in question.

Other objects, features and advantages of the invention will become apparent upon reading the following description of a representative embodiment, in conjunction with the accompanying drawings, although variations and modifications may be made without reference to the accompanying drawings. depart from the spirit and the scope of the new concepts implemented in this description, drawings in which ::
FIG. 1 is a partial illustrative sectional view of a bag embodying the invention,
FIG. 2 is a cross-sectional view showing the basic product used to manufacture the bag of FIG. 1,
FIG. 3 is a view similar to that of FIG. 2 but showing a modified structure of the zipper,
FIG. 4 is a view similar to that of FIG. 3 but showing a tear strip incorporated in the structure of the zipper,
FIG. 5 is a partial illustrative view showing how the bags comprising the tear strip of FIG. 4 are adapted to their manufacture,
FIG. 6 is a partial view showing the operation of the tear strip to open the bag,
FIG. 7 is a schematic illustration of the manufacturing device of the basic product for producing a bag according to the present invention,
FIG. 8 is a partial detailed sectional view on a larger scale, substantially along line VIII-VIII of FIG. 7,
FIG. 9 is a partial illustrative view of a modified structure of the bag implementing the inveation,
FIG. 10 is a cross-sectional view showing how the base product of the bag of FIG. 9 is adapted to its manufacture,
Fig. 11 is a cross-sectional view of another modification of the basic product used to make the bag and showing how it is suitable for manufacture,
Fig. 12 is a cross-sectional view of another modification of the base product used to make the bag and illustrating a method for making it;
FIG. 13 is a schematic view showing the test results when a bag made according to FIG. 1 is tested by subjecting it to an internal pressure by means of air, and
Fig. 14 is a similar schematic view showing that the bag of Fig. 9 responds to a test in which it is subjected to internal pressure by means of air.

 Referring now to FIGS. 1 and 2, a bag 10 has an upper portion 11, opposite sides 12 (only one of which is shown, but with the opposite side being a replica of the side being shown), a bottom 13 and Opposite walls 14. The walls 14, which are advantageously made from a thin plastic film such as polyethylene or the like, are fastened together, for example by heat welding, along the opposite sides 12 of the bag and are initially separated from each other along the bottom 13, as shown by the dashed lines of Figure 1 to form an opening for filling the bag, after which the opening is closed for example by welding hot. A one-piece fold connects the walls 14 to the upper portion 11 of the bag.

 A folded zipper band 17 is accommodated in the fold 15 of the bag. The zipper strip comprises a chord 18 with complementary and separable profiles 19 and 20 along its opposite marginal portions 21. The chord 18 is bent and received in the bend 15 and secured, for example, by hot melt welding to 22, by an adhesive or the like.

 As shown in Figure 1 and more exaggerated in Figure 2, the marginal portions 21 and the profiles 19 and 20 are fully detached and free from the walls 14, so that the latter can deviate from the marginal parts and This is particularly advantageous if it is to be certain that the zipper 17 remains closed even when the walls of the bag are considerably inflated to the outside when the contents have been poured into the bag, since any stress likely to be directed towards the upper part of the bag by the walls of the bag is located in the upper fold 15 and in the folded chord 18 housed and fixed inside, releasing the stress applied to the zipper 17. When the bag has been opened, for example by cutting the upper portion 11, as indicated in dashed lines, the resulting pulling edges can be manipulated to pull and / or Screw the zipper 17, that is, pulling and separating the profiles in mutual engagement 19 and 20. To close the zipper 17, it suffices to press the profiles 19 and 20 against each other. other to embroider them in one another. Of course, this is facilitated when the zipper 17 is made of an extruded plastic such as polyethylene or any other suitable plastics material.

Although the profiles 19 and 20 are, as shown in FIGS. 1 and 2, of the single arrow-shaped type with a complementary groove, the invention can also be adapted to complementary profiles in the form shown in FIG. Figure 3 where the complementary profiles 23 which are shown are of the type with grooves and multiple ribs, generally hook-shaped.For the rest, the base product used for the manufacture of the bag of Figure 3 is generally similar to the basic product used for making the bag of Figures 1 and 2 in that the profiles 23 are supported by the opposed marginal portions 24 on opposite sides of the intermediate frame 25 of a zipper strip 27 which is secured by means 28 to the walls 29 of the bag adapted to be folded along a region 30, in the same manner as the fold 15 formed in Figure 1. However, to facilitate a flexion With respect to the chord 25 along its central longitudinal axis, it is possible to form a fold 26 which projects from the plane of the chord away from the sections 23, as can be noted by the slight bulge 26a. In this case, the profiles are accurately assembled when the frame 25 is folded along its fold line. Naturally, the fold 26 can also be constituted in the frame 18 of FIG. 2 if desired
FIG. 4 is similar to FIG. 3 but shows an attachment band 31 comprising an intermediate frame 32 provided with a cord or tear wire 33. In this case, the frame 32 of the fastening strip has similar to the other forms of the invention which are described, opposed marginal portions 34 supporting multiple rib and groove profiles 35 of a separable zipper. The frame 32 is fixed by a suitable fixing means 37 on a longitudinal region 38 of the walls 39 of the bag, leaving the marginal portions 34 and the profiles 35 free with respect to the walls 39 of the bag. According to a desirable construction, the wire 10 is attached to the surface of the frame which is opposite the interconnected sections of the zipper when the base product of the bag is folded in the manner shown in FIGS. 5 and 6. Preferably, the stripping wire 23 is at least partially embedded in the adjacent surface of the frame 32. This can be achieved during the extrusion of the fastening strip 31 or thereafter.

If desired, the chord 32 may have a longitudinal fold similar to the bend 26 of Figure 3 and the wire 33 may be disposed in this bend.

 When bags 40 are made with the material described in connection with FIG. 4, the walls 39 of the bag are folded towards each other along the region 38, so that the rib 32 of the web 31 of the zipper is similarly folded and that the profiles of the zipper engage one another in the desired manner. At their bottom ends 41, the bags 40 are kept open until filled.

 For the convenience of filling, the bags 40 may be kept in the form of a string by being connected to one another by one or more integral fasteners, in the present case being in the form of a fastener 42. adjacent to the lower ends 41 and a fastener 43 advantageously provided at the folded upper ends of the bags and comprising the cord or the tear wire 33. In this case, the bags 40 are held apart from each other by their edges by means of a separation slot 44, the clips 42 and 43 forming bridges through the slot.

Advantageously, the fasteners 42 and 43 are formed concurrently with the fusion welding of the welding lines 45 which close the sides, along the adjacent sides of the bags. To separate the bags from one another, the fasteners 43 and 42 are cut along a center line
S. The upper fastener 43 therefore constitutes respective starting tabs 47, in line with the folded upper ends of the bags and more particularly containing an extension of the stripping wire 33. The result is that when one breaks a tab 47 and when pulling the tear wire 33 fixed on it upwards, the folded upper part of the bag, including the folded chord 32, can be easily opened by tearing, as indicated at 48 in FIG. 6 , so as to open the bag which can then be closed by means of the zipper 31.

 To obtain the basic product for the manufacture of the bag of the type described, the method and the machine shown by way of example in FIGS. 7 and 8 may be used. The film 14, 29, 39, as the case may be, which forms the wall of the bag, is advantageously fed from a prefabricated roll 50 to a support table 51 along which the material is drawn by means of nip rollers and drive 52. At the level of the roller 50 or the table 51, the zipper strip 17, 27, 31, as the case may be, is fed from a suitable source and joined to the strip 14, 29, 39.Although the roll 50 comprises a prefabricated film material and that the slide fastener tape 17, 27, 31 is a prefabricated tape that can be pulled from a roll (not shown), both, or only the film or zipper tape, can be derived directly from 'an extrusion apparatus and pelymerises or partially pol ymerized in the production line reaching the junction point described. A means such as a guide and a joining roll 53 guides the strip of the zipper so as to join it to the film.

 Once the film and the strip of the zipper have been assembled, the guide means 54 accurately guides the band of the slide fastener relative to a welding device 55 which may be constituted by an electronic heating element, an ultrasonic horn, a wheel or the like. The guide means 54 comprises two complementary plates 57, each of which has an overhead holding plate 58 mounted on a support 59 fixed to a suitable frame (not shown) of the apparatus. The plates 57 are elongated in the machine direction or production path and serve as holding devices which overhang the zipper profiles along the opposite marginal portions of the zipper strip. precise guiding of the zipper strip as it circulates longitudinally with the film constituting the walls of the bag, each of the plates 58 comprises a downwardly-depending guiding cheek 60 cooperating with the adjacent inner edges of the thus forming a simple and effective means for guiding the zipper on and along the film for attachment to the latter.

The plates 58 and cheeks 60 also serve as heat shields against heating the profiles and marginal portions of the ribs of the zipper strips. This makes it possible to be certain that only the intermediate portion of the ribs of the zipper strips will be heated and fused to the film constituting the walls of the bag. In addition, heating means that attach the zipper to the film can also be simple and require a minimum of adjustment.

 In an adjacent region and downstream of the guide means 54 and the fusion welding means 55, the zipper band which is now secured and the film is folded for example by a fold line forming roll 61. and guide plates 61a, and the rollers 52 which cooperate with them to cause the zipper profile sections to engage. This latter operation is facilitated by the respective guide grooves 62 of the rollers 52, which are arranged to receive the regions of the zipper profiles. Downstream of the folding, driving and guiding rollers 52, the basic product constituting the folded bag may be welded transversely as shown at 63 by means of fusion welding bars 64 or the like.

 As shown, bags 10, 40, where appropriate, which are completed, inverted and open-bottomed, are oriented so that their open bottoms are ready to be filled. This filling can be performed in an adjacent downstream station, or the base product used for the manufacture of the bags can be rolled and the bags subsequently filled in a bag filling station.

 It has been found that even greater resistance could be obtained in the separation or opening of the zipper against internal pressures in the bag by virtue of the structure shown by way of example for bag 65 (FIG. 9) which may be desirable for certain applications. In a manner similar to that of the bag illustrated in FIG. 1 or FIG. 5, the bag 65 comprises an upper closure ply 67, side walls 68, vertical and opposite edges 69 closed by welding and a lower end which is provided with a closing weld line 70 when the bag has been filled.A slide fastener 71 includes a rib 72 which is secured within the fold 67 by a means 73 which is shown by way of example under form of a hot-welding line, but which may be an adhesive if it is preferred. The opposite marginal portions 74, 74b of the frame 72 support respective slide fastener profiles 75 and 77, which are complementary in shape and can be nested within each other. In this case, one of the profiles of the zipper that supports the marginal tab 74a is not connected to the panel 68 constituting the adjacent wall of the bag, while the opposite marginal 74b is attached from its edge and over the entire width of the profile 77 of the zipper to the adjacent panel 68 constituting the wall of the bag, as indicated in 73a.

 As shown in FIG. 10, the junction between the zipper 71 and the base product 68 constituting the walls of the bag is adapted to be performed in substantially the same manner as that described with reference to FIGS. 7 and 8, with a slight modification consisting essentially in the fact that instead of applying the fusion energy to the upper part of the assembly, to connect the parts, it is applied from below as will be explained. The strip base product 68 constituting the bag walls and the base product web of the slide fastener 71 are joined to each other and run longitudinally along a support means comprising a table 51 '. Retaining and guiding means 79 cooperate with the tape 71 of the zipper after its assembly to the film 68 constituting the walls of the bag. A retaining panel 80 overhangs the band 72. Lateral and angular guide cheeks 81 cooperate with the adjacent edges of the zipper sections 75 and 77 to maintain the accuracy of the longitudinal movement of the slide fastener 71, and cheeks 82 generally extending horizontally overhang the profiles 75 and 77.

 To secure the slide fastener 71 to the film 68, there is provided a means 83 desirably in the form of an electronic heating element, an ultrasonic horn, a hot air nozzle or the like, which concentrates the fusion energy in a slot 84 of the table 78. This slot 84 is arranged to expose the film 68 to the application of the fusion energy at the point where it comes into contact with the frame 72 of the zipper and with the marginal portion of the zipper that supports the profile 77, leaving the profile 75 which supports the marginal portion unexposed to the application of the fusion energy. The fusion junction 73 and 73a is then made continuously as the film and slide fastener assembly passes through the slot 84. Otherwise, the apparatus for producing the basic product of the bag and dividing it into sections of bags can be substantially in accordance with what has been described with reference to Figure 7.

 Another modification is shown in FIG. 11 which, in fact, combines the techniques of FIGS. 8 and 10. The table 51 "includes a slit 84 of concentration of the fusion energy, which exposes only the portion of the marginal portion 74b of the frame of the zipper which supports the profile 77, so as to anchor this region of the marginal portion 74b of the zipper on the film 68 by means of the fusion energy provided by a device 85. By Moreover, the rest of the apparatus shown in Figure 11 may be substantially the same as that of Figure 8, and the same description applies to the parts of Figure 11 which are designated by the same references. the fixing of the portion of the profile 77 of the zipper and the chord 72 of this zipper is substantially the same as that described for FIGS. 9 and 10, in that the chord 72 is fixed by fusion, as indicated at 73 ', all its width except the marginal portion 74a, while the marginal portion 74b which supports the profile 77 of the zipper is partially bonded at 73a'.

 According to another modification which is shown in FIG. 12, the marginal portion 74b of the zipper which supports the profile 77 of this zipper comprises an extension edge 87 which is fused to the film 68 constituting the walls of the bag. as shown at 88, thereby obtaining substantially the same effect as that described for the bag structure of FIG. 9. In other words, the marginal portion 74b which supports the slide fastener profile 77 is attached to the film 68 while the marginal portion 74a which supports the profile 75 of the zipper remains unsecured. A device 85 for producing fusion energy which is concentrated on and through the extending edge 87 of the frame 68 is adapted to make the joining and the fusing attachment 88.For the rest> the apparatus shown is substantially the same as the apparatus of Figure 8, and the same description applies to elements that are identified by the same reference numerals.

 Tests have shown that a substantially improved resistance to the opening of the zipper is achieved by internal pressures within the bag by the measurements described with reference to FIGS. 9 to 12.

 Referring to FIG. 13, a bag made substantially in accordance with FIG. 5 was tested by inflating it until the internal pressure separated the profiles from the zipper. It has been found that an air pressure of 1 kg was required to separate the profiles from the zipper. Furthermore, it took an air pressure of 1.750 kg to separate the zipper profiles of a bag consisting substantially of Figures 9 to 12, by inflating as shown in Figure 14. An observation of the bags both tests showed that equal pulling and separating force was applied to the slide fastener for the test of Figure 13, while a pulling and separating force applied to only one side of the closure zipper appeared to be the case for the test of Figure 14.

 It will be observed that if it is necessary to connect not fusion-compatible materials but incompatible materials to form the film boring the bag and the zipper band, for example in the case where the film is made of a material such as propylene which is not melting compatible with polyethylene used for the zipper strip, adhesive fastening of the zipper strip to the film, using now known techniques. Naturally, of course, at least one of the marginal portions of the frame of the zipper strip, including the entire zipper profile on it, remains unsecured to the film constituting the walls of the bag. , so as to maintain a relationship of freedom between this marginal portion of the frame and the film which provides excellent resistance to traction exerted on the zipper in the direction of its opening by forces internal to the bag. As is known, the film constituting the walls of the bag may also be single layer or multilayer, whichever is preferred.

 It will be appreciated that variations and modifications can be made without departing from the spirit and scope of the novel concepts of the present invention.

Claims (32)

 Bag (10) comprising an upper portion (11), opposite sides (2), a bottom (13) and opposed walls (14), a one-piece fold (15) connecting the walls (14) at the top (11) of the bag, the walls (14) being attached to each other along said opposite sides of the bag and the walls being initially separated from each other along said bottom (13). ) to constitute a filling opening of the bag through said opening, after which this opening is closed, characterized in that it comprises a zipper strip (17) comprising complementary profiles (19, 20) and separable along its marginal portions (21), an intermediate folded chord (18) and connecting said marginal portions (21), said folded chord being accommodated in said upper fold (15) of the bag, means securing said chord to said fold, and at least one of said marginal portions being unfixed and free, on at least all of the width of the profile relative to the adjacent wall, so that the wall can deviate from said marginal portion and its profile.  2. The bag of claim 1, characterized in that the two marginal portions are not fixed and feel free on at least all of the width of the profiles they support relative to the adjacent walls of the bag, so that both walls of the bag can deviate from said marginal portions and profiles they support.  3. Bag according to claim 1, characterized in that the other of said marginal portions is attached at least in part to the adjacent wall of the bag, so that the profile supported on said other marginal part is held against the adjacent wall of the bag .  4. The bag of claim 1, characterized in that the other of said marginal portions comprises an edge extending beyond its profile, and said extending edge is firmly fixed to the region of the wall adjacent thereto.  5. Bag according to claim 1, characterized in that said chord comprises a tear wire (33).  6. Bag according to claim 1, characterized in that said bag comprises a starting tab (47) extending from at least one of said sides, - line with said upper part and comprising inside an extension said tear wire.  7. Bag according to claim 1, characterized in that said frame comprises a longitudinal fold (26) for positioning said profiles to cooperate accurately when the entire zipper is closed.  8. Bag according to claim 7, characterized in that a tear wire (33) is embedded in said fold.  9. Bag according to claim 1, characterized in that it consists of a bag forming part of a bag clevis, and said bags are connected to each other along their sides.  Bag and sack of bags according to claim 9, characterized in that connecting ties (42, 43) connect the bags to each other keeping them separated.  11. Bag comprising opposite walls, a closed upper part, opposite sides and a bottom, characterized in that it comprises a tear wire extending along the closed upper part of the bag, and a starting tab extending from at least one of the sides of the bag and including an end extension of said tear wire to facilitate manipulation of said tear wire to tear open said upper portion of the bag.  Bag according to claim 11, characterized in that said upper part comprises a one-piece fold connecting said walls, a folded strip of a slide fastener comprising complementary and separable profiles along its opposite marginal parts, the zipper strip being accommodated in said upper ply of the bag and said sections being interlockably engageable with one another, and said stripping wire being supported by said zipper strip.  A basic product for making bags, each comprising opposing walls secured together along opposite sides of the bag and opening to the bottom of the bag for filling, and comprising a fold connecting the upper portions of the walls characterized in that it comprises a zipper strip having complementary and separable profiles along its opposite marginal portions and an intermediate chord connecting said marginal portions, means securing said chord to said sheet material within said fold, and at least one of said marginal portions being not fixed and being free with respect to the adjacent wall so that this wall can be spaced from said marginal portion and the section which supports.  14. Basic product for making bags according to claim 13, characterized in that said marginal portions are not fixed and are free, over at least the entire width of the profiles they support, relative to the adjacent walls of the bag, so that the two walls of the bag can deviate from said marginal portions and profiles they support.  The basic product according to claim 13, characterized in that the other of said marginal portions is firmly attached at least in part to the adjacent wall of the bag, so that the profile which is supported on said other marginal portion is held against the adjacent wall of the bag.  A base product according to claim 13, characterized in that the other of said marginal portions comprises an extension edge beyond its profile, and said extension edge is firmly attached to the region of the wall which is adjacent thereto .  The base product of claim 13, characterized in that said means for attaching said chord to the sheet material within said fold comprises fusion welding of the chord and sheet material within the fold.  18. Basic product according to claim 13, characterized in that said chord supports a tear-off wire.  19. Basic product according to claim 13, characterized in that said chord comprises a longitudinal fold which facilitates the precise bending of the chord in the fold.  20. A method for producing a basic bag product, characterized in that it comprises providing a bag wall sheet, providing a zipper strip having complementary profiles on its opposed marginal portions and an intermediate chord connecting the marginal portions, attaching said chord to the sheets constituting the walls of the bag, holding at least one of said marginal portions unsecured and free relative to the adjacent sheet of the wall of the bag, in such a way that this wall sheet can separate from said marginal part, and the fold of the sheet constituting the walls of the bag along the fixed chord, so that the zipper strip is housed inside the fold thus produced. .  21. The method of claim 20, characterized in that it comprises the realization of said fixing by fusion welding of said frame on the sheet constituting the walls of the bag.  22. The method of claim 22, characterized in that it comprises maintaining the two marginal portions unfixed and free relative to the sheet constituting the walls of the bag, so that the wall sheet can deviate from the two parts marginal.  23. The method of claim 20, characterized in that it comprises the resistant attachment of at least a portion of the other of said marginal portions to the adjacent sheet which constitutes the walls of the bag in the region at the rear of the profile supported by said other marginal portion.  24. The method of claim 20, characterized in that the other of said marginal portions comprises a rim extending beyond the profile supported by said other marginal portion, and fixing said extension edge on the sheet region constituting the walls. of the bag which is adjacent to said prolonged edge.  25. The method of claim 20, characterized in that it comprises the equipment of said chord with a tear wire.  A machine for making a bag base product, comprising means for supporting a bag wall sheet, means for providing a slide fastener strip with a frame and complementary profiles that can be releasably engaged with one another. in the other along the opposite marginal portions of said strip, means for engaging with said profiles and guiding said strip to assemble with said sheet, means for securing said strip to said sheet leaving at least one one of said free and non-fixed marginal portions with respect to said sheet so that the sheet can move away from said marginal portion, and means for folding said sheet along said frame and accommodating said strip within the fold thereby got.  27. Machine according to claim 26, characterized in that said fixing means comprise welding means using a melting energy.  28. Machine according to claim 27, characterized in that it comprises the combination of means for guiding and protecting against heat, between which said fixing means act to perform the welding by a fusion energy of said frame on said sheet .  29. Machine according to claim 26, characterized in that said fixing means are constituted and arranged to fix the other of said marginal portions along the rear of the profile supported by it on the adjacent portion of said sheet.  30. The method of claim 26, characterized in that the other of said marginal portions comprises an edge extending beyond the profile supported by the other marginal portion, and means for securing said edge in extension to the region of said leaf that is adjacent to it.  31. The method of claim 26, characterized in that said folding means comprises a device for forming a fold line and a folding device.  32. The method of claim 26, characterized in that it comprises means for transversely welding the folded strip and the zipper strip to form sections of bags.