Abstract:
A method for automatically making bags equipped with matching closure profiles comprising the steps of: unwinding a supply of at least a film for forming the bag walls; unwinding a supply of closure assembly comprising a W-shaped support sheet, constituting an inner U-shaped tear band provided on its inner surface opposite respectively the matching closure profiles, and the external lateral webs extending beyond the closure profiles and the U-shaped inner band, the closure assembly being further pre-equipped with a series of sliders actuating the closure profiles distributed over the length of the unwinding closure assembly; and fixing the resulting closure assembly via the external lateral webs on the film forming the bag walls.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of bags having complementary closure strips designed to enable a user to perform a series of successive opening and closing operations. 
     Numerous types of bag and/or closure strip have already been proposed for this purpose. 
     By way of non-limiting example, reference can be made to the following documents: U.S. Pat. No. 4,929,255, U.S. Pat. No. 4,892,414, EP-0 562 774, EP-0 395 362, U.S. Pat. Nos. 5,382,094, 5,181,583, EP-0 728 665. 
     More precisely still, the present invention relates to the field of bags in which the closure strips are opened and closed by means of a slider. 
     Various types of bag and slider-operated closure strip have also been proposed. 
     By way of example, reference can be made on this point to the following documents: EP-0 051 010, EP-0 102 301, and EP-0 479 661. 
     BACKGROUND OF THE INVENTION 
     Bags having slider-actuated closure strips offer the huge advantage, compared with bags that do not have a slider, of being easy to handle. 
     The slider makes it easier to separate the strips in order to open such bags, and conversely makes it easier to engage the strips in order to close such a bag. All that needs to be done for this purpose is to move the slider in translation along the strips. 
     Attempts have indeed been made to facilitate the handling of strips that do not have a slider, in particular by providing ribs on the walls of bags fitted in this way, the ribs making it easier to locate the strips by touch. Nevertheless, those dispositions do not give full satisfaction compared with slider-fitted bags. Firstly, making such ribs complicates the production installation. Secondly, such ribs do not provide location and actuation that are as easy as those provided by a slider. 
     However, in practice, it is observed nowadays that bags fitted with slider-actuated closure strips have not been the subject of major industrial development. 
     This seems to be due in particular to the fact that it is difficult to make use of slider-actuated closure strips on conventional machines for forming and/or filling bags automatically. Sliders gives rise to extra thickness which makes it very difficult for automatic machines to move strips and/or films fitted therewith. 
     As described in documents EP-0 051 010, EP-0 102 301, and EP-0 479 661, that is why proposals in the past have been made to add sliders to the strips after the closure strips have themselves been fixed on the film(s) making up a bag. However, those proposals generally require equipment that is rather complex for delivering the sliders, opening them, and then closing them on the closure strips, with the slider being accurately positioned relative to the closure strip, and as a general rule doing so on a continuous traveling line. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is now to propose novel means for automatically making bags that include slider-actuated opening and/or sealing strips. 
     According to the present invention, this object is achieved by an automatic method of manufacturing bags that is characterized by the fact that it comprises the steps consisting in: 
     supplying at least one moving film adapted to form bag walls; 
     supplying at least one moving closure assembly comprising a W-shaped support sheet constituting both an internal channel-section tamperproofing tape provided on its facing internal surfaces with respective complementary closure strips, and also external lateral webs extending beyond the closure strips and the internal channel-section tape, the closure assembly also being prefitted with a series of sliders for actuating the closure strips and distributed along the length of the closure assembly as fed; and 
     fixing the closure assembly formed in this way, via the external lateral support webs to the film forming the bag wall. 
     As explained below, the method of the present invention makes it possible to eliminate the drawbacks of the previously-known means. 
     Firstly, because of the internal channel-section tamperproofing tape, the present invention makes it possible to guarantee initial sealing of the bags and makes it possible to inspect and spot easily any untimely opening or attempted opening of such bags. 
     In addition, and above all, because of the presence of the lateral external support webs which project considerably beyond the sliders, the present invention makes it possible to locate the sliders away from the fixing zone (preferably implemented by heat-sealing jaws) for fixing the closure assembly on the film constituting the bag. 
     The present invention also makes it possible to deliver bags either in the open state or in the closed state depending on requirements. 
     The present invention also relates to a machine for automatically manufacturing bags by implementing the above-specified method, and bags obtained thereby and to the closure assembly for performing the method. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other characteristics, objects, and advantages of the present invention will appear on reading the following detailed description and from the accompanying drawings, in which: 
     FIG. 1 is a diagrammatic section view of a closure assembly of the present invention; and 
     FIG. 2 shows an automatic machine for forming, filling, and sealing bags in accordance with the present invention. 
     FIG. 3 shows an automatic machine in accordance with the present invention for making bags that travel horizontally as similarly shown in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As mentioned above, the present invention relates to using an automatic machine to manufacture reclosable bags having slider-actuated closure strips. 
     The present invention can be applied to machines for automatically manufacturing bags equally well regardless of whether travel through the machines is horizontal or vertical. 
     In addition, the present invention applies equally well to machines for automatically manufacturing bags that are filled during a step subsequent to manufacture, and possibly geographically separated from the manufacturing site, and to machines for manufacturing, filling, and sealing bags at a single location and during successive steps. 
     Thus, the present invention applies preferably, but in non-limiting manner, to machines for automatically forming, filling, and sealing bags, and most advantageously to such machines where bags travel vertically. 
     A description of such machines for automatically forming, filling, and sealing bags that travel vertically can be found in the following documents: U.S. Pat. Nos. 4,894,975, 5,400,565, 5,111,643, 4,909,017, 4,617,683. 
     Essentially, and as shown in accompanying FIG. 2, it is recalled that such machines generally comprise: a forming throat  100  which receives as input a film  110  in the flat state taken from an unreeler  112  and which delivers at its outlet the film  110  shaped into a tube; a filling chute  120  which opens out into the forming throat  100 , and consequently into said tube; longitudinal heat-sealing means  130  for closing the tube longitudinally; and means  140  suitable for sequentially generating a first transverse line of heat-sealing before a product is introduced into the tube via the filler chute  120 , and then a second line of transverse heat-sealing after the product has been introduced into the tube, thereby sealing a package around the product. 
     As mentioned above in the context of the present invention, the machine for automatically forming bags also receives a closure assembly  10  which comprises, as shown in FIG. 1, a W-shaped support sheet  20  constituting firstly an internal channel-section tamperproofing tape  22  provided on its facing inside surfaces  23  and  24  with respective complementary closure strips  30  and  40 , and secondly external lateral webs  26  and  28  which extend beyond the closure strips  30  and  40  and the internal channel-section tape  22 , the closure assembly  10  also being prefitted with one of a series of sliders  50  for actuating the closure strips  30  and  40 , which sliders are distributed along the length of the closure assembly as delivered. 
     The closure strips  30  and  40  can be implemented in a wide variety of ways. They preferably comprise respective complementary male and female section members. The structure thereof is not described in greater detail below. 
     Similarly, the sliders  50  can be implemented in a wide variety of ways. Preferably, as shown in FIG. 1, each slider comprises a soleplate  52  which carriers two side flanges  54  and  56  on one of its faces together with a central separator rib  58  which co-operates with the side flanges  54  and  56  to define two passages which converge or diverge (depending on the direction considered) for receiving respective ones of the strips  30  and  40 . The structure of sliders suitable for use in the context of the invention is not described in greater detail below. 
     The pitch at which sliders  50  are disposed on the closure assembly  10  is equal to the size of the bags that are to be formed. 
     As shown diagrammatically in FIG. 2, this closure assembly  10  is preferably fed longitudinally and is fixed (preferably by heat-sealing) via said external lateral webs  26  and  28  to the free edges of the film  110  that has been shaped into a tube. 
     Still more precisely, the external support webs  26  and  28  are most preferably heat-sealed to the film  110  via their free segments  26   a  and  28   a  situated beyond the central channel-section tape  22 . 
     In addition, and preferably but in non-limiting manner, the external webs  26  and  28  are heat-sealed to the film  110  using the above-mentioned means  130  which perform longitudinal heat-sealing of the film. 
     The closure assembly  10  is cut to the size of a bag by conventional cutting means, preferably associated with the means for transverse heat-sealing  140 , thereby separating bags individually. 
     Also and preferably, the closure strips  30  and  40  are mutually engaged (in the closed position) while they are being fixed to the film  110 . This disposition guarantees that the closure assembly  10  is positioned properly and accurately on the film  110 . 
     Nevertheless, the closure strips  30  and  40  can subsequently be separated by moving the sliders  50  by means of an appropriate tool, should that be necessary. 
     Where appropriate, it is also possible to provide lines of heat-sealing  60  at constant pitch to bond together the complementary closure strips  30  and  40  prior to feeding them to the machine for automatically forming bags. The pitch of these lines of heat-sealing  60  is equal to the size of the bags. Under such circumstances, the closure strips  30  and  40  are mutually engaged (closed) between the slider  50  and one of the lines of heat-sealing  60 , and they are disengaged (opened) between the slider  50  and the other adjacent line of heat-sealing  60 . 
     Nevertheless, such lines of heat-sealing  60  are not always essential. Naturally, implementations that avoid using such lines of heat-sealing present the advantage of avoiding any need for the position of the closure assembly to be identified relative to the film. 
     In a variant, a line of weakness or precut can be provided in the central channel-section tape  22 , e.g. in a middle portion thereof. Such a precut line is represented diagrammatically by reference  25  in FIG.  1 . 
     The sheet  20  supporting the strips, and the film  110  used in the context of the present invention, can be implemented in a wide variety of ways. It can be constituted merely by a single film of thermoplastic material, or by a composite film of thermoplastic material, i.e. a film built up by juxtaposing layers of different kinds, or indeed a composite film, e.g. constituted by plastic-coated paper or by a metal-coated film. 
     Naturally, the present invention is not limited to the particular embodiments described above, but extends to any variant within the spirit of the invention. 
     In the description above, the closure assembly  10  is fed longitudinally, i.e. the closure assembly  10  is fed in the same direction as the film  110 . However, in a variant, it is possible to envisage feeding the closure assembly  10  in a direction which extends transversely to the travel direction of the film  110 . The person skilled in the art is aware of numerous machines that operate by feeding closure strips transversely. That is why this disposition is not described in greater detail below. When closure strips are fed transversely to the travel direction of the film  110 , it is possible either to feed the closure assembly in the form of an individual segment precut to the size of a bag, or else in the form of a continuous strip which is cut in situ to the size of a bag. In another variant which is particularly suitable to making bags with travel taking place horizontally, the bags are made from two films respectively constituting the two main walls of a bag. 
     In yet another variant, it is possible to envisage fixing the closure assembly  10  to the film  110  by means other than the longitudinal jaws  130 . 
     The complementary closure strips  30  and  40  can be fitted, e.g. by means of adhesive or heat-sealing, to the support sheet  20 , or they can be integrally formed with the support sheet  20 , e.g. by molding. 
     In a non-limiting embodiment, the width of the external lateral webs  26  and  28  can be about 25 mm to 40 mm. In addition, in a variant, the external lateral webs  26  and  28  can be heat-sealed over their entire width to the film of bags. In which case, the segments referenced  26   a  and  28   a  in FIG. 1 coincide with the webs  26  and  28 .