Apparatus for making multiple plastic bags with reclosable fastener thereon

The invention relates to a machine for the continuous manufacture of a plastic strip product from which, after welding and cutting along lines transverse to the strip, bags can be obtained, the width of which is reduced. equal to the spacing between said lines, and on the two edges of the openings of which are fixed closure strips provided with coupling members of complementary shapes.

More particularly, the invention relates to a machine ^J for placing and processing a sheet forming the walls of plastic bags and closure strips;

such bags, and also to fix the closure strips on the sheet by means of continuous high speed hot sealing means, for example by ultrasonic;

Such a machine for providing improved bags must be capable of being implemented in production! continues at high speed and be associated with ex- operations. [trusion. <

In the manufacture of plastic bags of the kind;

above, the bags usually have a folded bottom and;

I side edges welded to each other. Flexible closure strips, capable of being coupled, are welded to the upper edges of the bags, intended to form their opening, thereby making it possible to obtain bags which can be opened and then closed. '

Closure bands can be of various types, such as those described in U.S. Patent No. 2,780,261 to Svec et al. According to this patent, the walls of the bags are formed by a thin, lightweight plastic sheet which is extruded separately. closure bands. These bands are extruded according to a process which produces ribs and grooves of complementary shapes and carefully chosen dimensions, so that they can mate when pressed against each other, and that they can be mated. can separate when pulled in two opposite directions. These bands have ribbon-shaped parts which are welded to the sheet.

It has been found that the bags in question can be produced by a double operation, that is to say that two web products, intended for the manufacture of the bags, can be formed simultaneously on either side of a line. longitudinal section of a central assembly of closure strips. By cutting transverJFa / RL

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dirtily following equidistant lines and welding along the length of the material thus produced, two bags are formed simultaneously, repetitively. Because the cost of the bags is a function of the speed at which they can be made, it is important that the length of the products from which they are made can be made smoothly and quickly, at industrial and industrial production speeds. a sure way. Failure to assemble the closure strips with the sheet would result in leaks and in the production of bags which could not be properly closed and reopened, due to misalignment of the closure strips. Likewise, the amount of heat required to assemble the closure strips to the sheet has an effect on the weld. If the amount of heat is insufficient, the seal is improperly formed, as a result of which the bag may leak, or even the tape of the closure strip may peel off the sheet like a skin. . If, on the contrary, the amount of heat is too high, the plastic material may melt and holes may appear in the walls of the bags.

It is also important that the closure strips and the sheet are oriented accurately with respect to each other. If the foil is not properly placed, with respect to the tape-shaped part of the closure strips, good sealing cannot be achieved and the rough protruding edges of the plastic material inside the bag may. forming crevices in which the contents of the bag can become trapped or, if they are outside the bag, these ridges run the risk of being torn and pushed aside by an inattentive user who would mistakenly mistake these ridges for opening lips of the closure strips.

In the method of manufacture described, the closure strips and the foil constituting the walls of the bag are produced separately by an extrusion process and assembled shortly thereafter according to a line production process comprising the continuous welding of the bags. bands on the sheet.

• Until now, bags with closure strips were manufactured in a single operation which required, in addition to transverse welding, the attachment of the closure strips to the bag, during the manufacturing operation, by welding 40 intermittently covering the tape of the closure strips

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6.7.73 - 6 + 5 + 6 on the sheet, which reduced the speed of the operation and;

welding safety. This resulted from the fact that each cycle!

i welding started with a heat production time ί and then a. cooling time of the weld for-r · 5 mée before the operation can be repeated. This prevented the closure bands and the sheet from being attached to each other in a continuous fashion as they were extruded.

In addition, the heat could never be precisely controlled because, as has been indicated, it varied continuously during its cycle. In the case of the present invention, once the optimum extrusion speed^:has been achieved, the heating means necessary to join the closure strips and the sheet can be adjusted and maintained at a determined setting with a suitable degree of precision. The invention also has the advantage of making it possible to use the most advantageous plastics with regard to the transparency and the resistance of the bag, for the sheet and for the closure bands, when a slippage and formation of suitable profiles. In general, the characteristics required of plastics are not the same for the closure bands and for the sheet, and the one-off production methods of the sheet and the bands usually give rise to a compromise. , which does not allow optimal conditions to be obtained. On the contrary, when the closure strips and the sheet are extruded separately, the most advantageous extrusion, cooling and control methods for each of them can be used, thereby increasing the speeds at which they can be manufactured. compared to those to which they can be made in one piece.

Under these conditions, one of the best ways to make resealable closure strip bags is to join the strips and the sheet when extruded separately, in a continuous and secure manner, and to process. then in bags the product which constitutes the assembly of the sheet and the bands. After this assembly, the material is put into rolls, intended to be shipped to a processing industry where the bags are then formed by sectioning and transverse welding of the product. It is therefore important, for the industry which initially produces the product,

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,) xi that this is carried out in a way which allows its winding and storage. j

An object of the invention is therefore to develop a per- machine! designed, for the continuous manufacture of a strip product, which allows the production of closure strip bags and which is capable of working at industrial extrusion speeds and provides a product of precise dimensions and of good quality for the production. manufacture of bags.

Another object of the invention is to develop a machine 10 for forming, in a continuous and simultaneous manner, two web products intended for the manufacture of bags, which can work at industrial extrusion speeds, eliminating them. There is no possibility of the formation of holes by melting the plastic material and ensuring a solid and optimum attachment of the closure strips to the plastic sheet.

Yet another object of the invention is to develop a machine. ne which uses tubular sheathed sheet, folded sheet or flat sheet and which can simultaneously fix the anterior and posterior closure strips by one and the same continuous production operation.

Other aims, advantages and characteristics of the invention will emerge better from the description below of some of its embodiments, taken by way of illustration but not at all. limitative, with reference to the accompanying drawings in which:.

- the figure. 1 is a sectional and perspective view of a bag made from a product according to the invention and provided with closure strips capable of being closed ;;

- Figure 2 is a schematic plan view of a machine according to the invention for the manufacture of products 30 for making bags; j

- Figure 3 is a vertical sectional view along the line III-III of Figure 2; '

- Figures 4 to 10 are vertical sectional views • of the machine of Figure 2, in various locations along the length of the machine, indicated by the cutting lines referenced in corresponding Roman numerals in Figure 2;

- Figure 11 is a partial perspective view of the machine of Figure 2;

- Figure 12 is a perspective view of a variant 40 of a machine according to the invention;

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- Figure 13 is a vertical sectional view along the i line XIII-XIII of Figure 2, showing another embodiment -। i sation of the invention; '¹

- Figure 14 is a fragmentary perspective view. 5 showing a support means;

FIGS. 15 and 16 are sectional views showing an embodiment of the invention according to which a flat sheet and a single closure strip are used; and

- Figure 17 is a sectional view showing a stage of the construction of the bag subsequent to those of Figures 15 and 16.i

Figure 1 shows a bag of the type formed from the product produced using a machine according to the invention.

This bag constitutes the finished product and the continuous strip product intended to make the bag is mostly rolled before being transformed into bags during a final operation carried out by a bag-making company.

The bag, made of a thin plastic sheet. such as polyethylene, has a folded bottom 10. On the upper edges of the bag are fixed closure strips 11 20 and 12. The front strip 11 is fixed to the front or top wall 10_a of the bag by at least one heat seal , in · 13, and the rear band 12 is fixed to the upper edge of the rear or lower wall 10b by a weld;

hot, in 14. By the indication of front or upper parts and of rear or lower parts, it is intended to identify respectively the various elements of the bag and of its closure bands, but it goes without saying that during the operation of the bag. the machine the web product (s) can be processed in different positions and that the reference to certain positions should be regarded as relative. Likewise, the closure strip 11 may have different shapes from those shown in FIG. 15.

The front or top closure strip 11 has a ribbon-shaped side part 15, by means of which it is fixed to the front wall 10_a of the bag. The posterior or lower closure strip 12 also has a ribbon-shaped side part, 16, by means of which it is. attached to the upper edge of the rear wall 10b of the bag. The anterior band 11 also has a thick marginal part, 40 and 18 in which ribs and grooves are formed, JFa / RL '

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6.7.73 - 6 + 5 + 6 'intended to engage in grooves and for- ribs;

my corresponding carried by a thickened marginal part 17j of the posterior band.

A continuous length of web product is formed on either side of a longitudinal seam line and is intended to be severed centrally to form bags, two by two. To form these bags two by two, the strip products are welded and then cut transversely according to;

equidistant lines, distributed over the length of the products in ί 10 stripes. The appearance of the products from which simul- | simultaneously two bags by transverse sectioning and by welding i is shown in figure 10.i

As seen in Figure 2, a continuous length of ^s'thin plastic tubular sheath 21, intended to form the walls of the bags, is introduced into the machine, for example. from a feed roll or extrusion machine not shown.

The tubular sheath first passes to a cutting station; page in which are arranged blades 24 and 25, located at a certain distance from each other, as seen in figure 5. These blades cut a strip 26 in the center of the upper wall 21a, so as to form an interstice, as can be seen in FIG. 6. This cutout forms edges 27 and 28i intended to constitute the upper edges of the anterior walls:

res of opposing bags. The front or top closure strips must be attached to these edges. In some cases, to avoid loss of material, it may be desirable to cut a single slit in the tubular sheath and spread the edges apart to form edges 27 and 28. '

According to another embodiment of the invention, the ban-;

of the closure device can be applied to the surface of a flat strip, as shown in Figure 15.

. The cutting blades 24 and 25 are carried on a bro-. 35 ehe 29 and continuously cut the tube 21, which is fed into the machine, for example by being pulled forward at a continuous speed by a drive roller (not shown), on which the or strip products | are rolled up; such a roll is placed at station E. When the tubular sheath passes through the machine, it begins with '

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6.7.73 - 6 + 5 + 6. '' go through the cutting station A, then an application station B where the upper closure strips are placed on the edges of the tubular sheath, then a separation station B ^ where the upper closure strips are separated from the in5 strip further, and finally a welding station C where the closure strips are fixed in a continuous manner on the edges of the sheet, after which it passes through an assembly station D, where the closure strips are coupled.

At the application station B is provided a guide roller 10 34 placed above the tubular sheath and having grooves 34a and 34b which guide the upper profiled closure strips 31 and 32 for their positioning above the edges. 27 and 28. These profiled strips are placed so that the edges 31 and 32 of their ribbon-shaped part (fig15 re 7) cover the edges 27 and 28 of the plastic sheet. Precise orientation is required, as the ribbon-shaped parts are welded to the sheet by continuous hot welding means, such as ultrasonic welding heads which are capable of ensuring a seamless welding operation. make holes in the plastic sheet. The weld formed between the marginal parts of the closure strips and the sheet can be carried entirely by the edges of the sheet and by the tape-shaped parts, so that the entire overlap area can be used for welding. avoids any protruding edges, above or below the weld.

Underneath the sheet is placed a support roll 35 and the rollers 34 and 35 rotate at the same linear speed as the sheet.

On the setting roller 34 is also fed a lower closure strip 36, which is fixed to the lower central part 21b of the sheet. The strip 36 passes through the opening formed between the edges 27 and 28 of the sheet and is applied, downwards, against the lower central part 21J, as seen in Figures 7 and 8. This lower or posterior closure strip 36 has profiles 36a ^ and 36b on its edges and a ribbon-shaped part 36 £ at its center. This part 36c is intended to be welded to the central lower wall 21b of the sheet, according to a wide weld, and when the bags are formed, a longitudinal cut is effected.

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6.7.73 - 6 + 5 + 6 killed in the middle of the weld, so that half of the, strip 36 will go with each bag .।

The sheet is then brought above and below one! support 40 which has upper support surfaces and | lower for the leaf. The ribbon-shaped portions of the upper closure strips 31 and 32 and the edges of the upper side walls 27 and 28 of the sheet pass between continuous heat sealing means 41 and 42 and the upper surface of the support 40, to be welded. Below the support 40 are further continuous heat sealing means 43 which welds the central ribbon-shaped portion 36c 'of the lower or posterior closure strip to the center of the lower wall 21b of the. sheet. The welds formed are shown below the marginal portions 31a and 32a and below the central portion 36 £ in Figure 9.

Various welding mechanisms can be used. One type which can be used preferentially is an ultrasonic welding station and the assembly described is assumed to be equipped with such equipment. Each of the continuous hot welding means 41, 42 and 43, if ultrasonic means are used, comprises a welding head powered by an ultrasonic generator, itself powered by a source of electrical energy. This head can move downwards to apply to the overlapping parts of the plastic material. The application of mechanical vibrations at ultrasonic frequency by the welding head is carried out for a period of time sufficient for.

cause fusion between the contacting surfaces and these layers are held in their relative positions for a time sufficient for the plastic to solidify properly. An ultrasonic frequency of 20,000 Hz is considered optimal, but other frequencies can be used. A controller is provided to adjust the frequency and intensity of the energy applied to the sheet and to the tape-like portions of the closure strips. When the speed of the sheet is increased or decreased, the frequency can be increased or decreased, and then be maintained at an optimum value, so as to allow the weld to form evenly and completely. The welding heads are brought into contact with the plastic material, which they hold 40 against the support, and the vibrations pass through the plasJFa / RL material.

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6.7.73 - 6 + 5 + 6 tick up to the contact surfaces between the layers to be joined. At the location of these surfaces in contact, the intense vibration of one of the surfaces with respect to the other j produces, by friction, enough heat to cause:

melting the plastic material, provided that the material 'which is below the head and which is in contact with | this remains there for a sufficient time for the merger to take place.

The plastic layers can be of different thicknesses, as can happen when changing the thickness of the sheet without changing that of the tape-shaped portion of the closure strips. Likewise, due to the fact that the cha-.

is generated between the surfaces of the layers themselves, they can be welded to their extreme edges. Because the energy transmitted to the plastic can be controlled by fine-tuning the frequency of the ul- vibrations. trasonores, immediate control can be obtained, as a function of the travel speed of the sheet, which speed constitutes the final control quantity. ,

The sheet, after leaving the separator support "passes.

at station D where the anterior closure bands 31 and 32 are · pressed, so as to mate with the posterior band 36;

as shown in figure 10. For this purpose, a collating and pressure roller presses the bands downwards so that their ribs and grooves mate. The roller 50 has annular channels 51 and 52 which align the bands 31 and 32 and press them to ensure their mutual engagement (FIG. 10).

Figure 11 shows the support 40 in more detail; it has a rounded front end 40ji, in the form of a beak, which is smooth, so as to ensure the separation of the lower band and the upper bands 31 and 32. The upper surface 40b of the support 40 is smooth, so as to support the . sheet and the bands 31 and 32, so that the continuous hot welding heads-41 and 42 can be pressed against the tape-shaped parts 31a. and 32ëi and against the edges 27 and 28 of the sheet, to form the continuous weld. Likewise, the lower surface 40 £ of the support 40 is smooth, so that the welding heads 43 can form the desired weld, by joining the lower sheet and the ribbon-shaped part 36c:

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6.7.73 - 6 + 5 + 6 lower closing strip 36.

If ultrasonic means are used for welding, due to the fact that the weld is formed in this case by the transmission of vibration energy, the support 40, shown in figure 14, is divided into two parts: a part upper 40f. and a lower part 40g. These parts are separated by an acoustic insulating material 40h.

Fig. 12 shows another kind of support, 60. Continuous hot welding means 64 secure the lower closure strip 36 to the lower sheet 21b, lowering them from its upper part and trapping the bottom. sheet and the strip between this support and a lower support 61a. For this, the support 60 is provided with a longitudinal notch in its rear edge, so that between the projecting parts 60a and 60b there is an opening 60α through which the continuous hot welding means 64 pass. The lower support 61a also supports the sheet, and a plate 61 is placed below the support 60 and below the assembly roller 62 which presses the closure strips 20 against each other, between the plate 61. and the assembly roller 62.

The support 61a and the plate 61 can be made in one piece.

In FIG. 13, a support 70 comprises guide members providing additional guidance of the closure strips. In the lower surface of the support 70 are formed grooves 70ei and 70b for the parts serving for the actual closing of the strip 36. Plates 75 and 76, located below the support, help to support the sheet 21.

At the upper part of the support are provided guide members 71 and 72 with L-shaped section. These members are fixed to the support by means of wing screws 73 and 74 and form channels for guiding the parts serving for the closure of the strips 31 and 32. These guide channels hold the strips in place with a precise orientation for their passage past the continuous hot welding means 41 and 42.

Figure 15 illustrates an arrangement in which a planar sheet is used instead of a tubular sheath. It goes without saying that the principles explained in connection with the description of the preceding figures can also be used with a flat sheet, 40 so that the sides of the sheet are folded towards the inJFa / RL

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6.7.73 - 6 + 5 + 6. 11. . 'térieur, their edges coming to locations 27 and 28 of Figure 2, instead of cutting a strip in a tubular sheath. Likewise, instead of cutting a strip in a tubular sheath, it is possible to leave only a single slit in it and then spread the edges of this slit apart.

In FIG. 15, the flat sheet is shown in the form of a laminated product 80 comprising several layers of which only an inner layer 80.a and an outer layer 80b have been shown. The outer layer 80b may be made of a protective sheet and the inner layer 80a of a plastic sheet intended to seal the bag. A strip 90 having profiled parts 84 and 85 of complementary shapes is attached to the sheet 80. The sheet is fed continuously into a machine such as that described above, but having a support 83 below the sheet and seal heads 86, 87 and 88 above the sheet. These heads may also be of the ultrasonic type, to provide continuous heat sealing between the web 90 and the sheet 80. The welds are formed at 89, 90 and 91, as the sheet and the web pass continuously through the machine.

In the embodiment of Fig. 16, a laminate sheet 93 is provided, but the profiled parts which engage with each other are carried by separate bands. The bands 94 and 95 are affixed to the sheet so as to constitute an additional cover. These bands respectively carry a male profile 96 and a female profile 97.

As the sheet 93 and the webs 94 and 95 laid thereon are continuously fed through the machine, seal heads 99, 100, 102 and 103 seal the webs to the sheet. Welds are formed at 94a and 94b for strip 94, and at 951 and 95b for strip 95. The welding heads apply pressure to the sheet then supported by a support 98 disposed below. The sheet is then folded back at 106, one edge of its edge being folded over the other, as indicated by arrow 109, and separate bags are formed by transverse welding and severing of the folded sheet.

The lower edges remain separated after transverse welding and severing, and the bag is then filled with the product it is intended to contain. Then, to complete 40 the bag, the ends of the sheet 93a. and 93b are brought to JFa / RL ”

0594 -2052-3 / 73 6.7.73 - 6 + 5 + 6 '12 alignment as shown in Figure 17 and are heat welded by welding means 108, against a plate 110.

It should be noted that perfected bags are thus obtained, owing to the welding process and the structure of the weld shown in Figures 15 and 16. The profiled elements are in fact carried by separate bands and the bands. are attached to the bag over an extent which does not go beyond these profiled parts. In other words, areas 96a. and 97a. Figures 16 and 17, located directly below the profiled parts, are not fixed to the sheet. This allows for additional flexural flexibility of the rib of the male section 96 and the groove of the female section 97, which helps to prevent them from separating under the action of the torsional and tensile stresses which are normally exerted on the tube. bag. The flexible profile bands 94 and 95 act as hinges in the small area located directly at the base of the profiles, where they are not fixed. In addition, the profiled strips are firmly and completely fixed on the sheet, so that no leakage can occur.

As goes without saying and - as it follows moreover already from the foregoing, the invention is in no way limited to those of its modes of application and embodiments which have been more especially considered; on the contrary, it embraces all the variants. _