Machine and working cycle for making plastic bags with a zip fastener and device for positioning them.

p0001The present invention relates broadly to a machine for manufacturing bags in plastic consisting of two superposed sheets welded along their side edges, the base remaining open or being closed by a line of welding or bending, these bags being equipped with mating profile elements extending along the edges of their opening and which can be coupled by elastic deformation by pressure under the effect of the sliding of a slider, said machine comprising inter alia in known manner , downstream of an extruder producing the sheets, on the one hand an apparatus installation automatic sliders, operational position, on the profiled elements that s'étendent coupling to the edges of two sheets superposed longitudinal scrolling, and secondly a welding blade and clean cut to be made at the desired rate, and this during periodic stops of the travel of the sheets, the transverse welding lines forming the side edges of the bags.

p0002Currently, some types of plastic bags are prepared from sheets of such material and have two opposite walls in principle welded by their side edges, a fold of the sheet or other welding line forming the bottom, unless the bags are supplied with an open bottom. Opposite the bottom s'étendent, along the edges of the bag opening, two profiled elements, namely one on each wall, which elements have shapes-com "complementary and can thus s'accoupler by deforming elastically by pressure under the effect of the sliding of a slider, which allows conveniently to the user to open or close the bag so repetitive, simply by moving the cursor along said elements. the slider is stopped at each end by a weld point at the location where both profiles are flattened and secured, near the side edges of the bags.

p0003These bags are produced continuously at high speed by an extrusion process, the principle généraldefabri-cation consisting essentially scrolling two superimposed sheets moving in the direction of their length, sheets on which a blade welding and cutting down to perform at the desired rate (depending on the speed of travel of the sheets and the width desired for bags), and this during a stop of the scrolling, transverse welding lines forming the side edges of bags.

p0004Said coupling profile elements may be extruded simultaneously with the sheet and form an integral part thereof, or be made separately and be reported continuously on the respective longitudinal edges, by welding or gluing.

p0005An appropriate device, such as for example the one that is the subject of the French patent application filed on behalf of the plaintiff October 14, 1980 under n_° 80 21974 'automatically laying said slides, coming in operational position, said coupling style profile elements on each bag width. This pose automatic sliders s'effectue-course also at the rate desired, upstream of position welding and cutting transverse leaf.

p0006This being so, the problem of positioning each slider along the length of said coupling profiled elements, given the fact that the machine must be able to deliver variable width bags. To prevent some sliders are positioned at the location where it is planned to perform the welding points mentioned above, which would be the cause of an operating incident, it is usually necessary when moving a bag width to a width different, moving the unit laying sliders to change the distance which separates the blade aforementioned welding and cutting, and to ensure that this distance remains an exact multiple of the width of the bags. Otherwise, in fact, the sliders may be positioned at locations in the width of the bags that décaleraient progressively towards one of the side edges thereof, which would lead inevitably to the incident operating supra.

p0007One of the purposes of the present invention is to avoid the inconvenience of having to move more or less frequently the slider placement device, which is relatively heavy and bulky, and to ensure that it can be fixed, while avoiding too, automatically and safely, the risk of any operating incident.

p0008For this purpose, a machine of the general type indicated at the beginning is in accordance with the present invention, characterized in that it further comprises, between said apparatus for laying sliders and said blade welding and cutting, a positioning device automatic said sliders on said profiled elements coupling, adapted to bring them to a given distance from the intended location for said transverse welding lines, regardless of the intended width for said bags.

p0009This prevents any risk of a cursor distributed by the device to pose "grave" in the space provided for welding said lines cross, and therefore any risk of happening incident type operation consisting in that welding blade and cutting crushes a cursor.

p0010In this way, the slider placement device may be fixed, which may be particularly advantageous when it is intended that this device works on sheets scrolling at least a part of the path is vertical, an arrangement which makes it simpler and more reliable the supply means of the apparatus sliders, since they then move by gravity into a vertical chute.

p0011Thus, an additional feature of a machine according to the invention may consist in that said slider placement device is stationary and operates on a vertical part of the path of scrolling leaves.

p0012The present invention also relates, more particularly, the structure and mode of operation of said automatic positioning device of the sliders.

p0013According to one characteristic of the invention, in this respect, the apparatus is characterized in that it essentially comprises a frame, a passage to allow scrolling of said elements coupling profiles which extend along the edges longitudinal two superposed sheets and, on either side of said passage, two facing rollers mounted at the free ends of two pivoting arms and adapted, among other movements, either to move apart from the other, to give free passage to a slider mounted on said profiled elements, or to move towards each other, and temporarily prevent this passage, which, the travel of the sheets continuing_"causes a longitudinal displacement, of determined amplitude of said slider on said members.

p0014It is thus possible automatically and conveniently move the sliders at a determined location of the space between the pitches of two lines of welding and successive transverse cut, which avoids absolutely reliable way the disadvantages described above.

p0015Such cursors positioning apparatus of the present invention has other interesting features, which will be more specifically described below, and in particular means for the delivery of finished bags open or closed, as well as perform a test the proper functioning of each slider.

p0016One embodiment of a positioning device sliders according to the invention will now be described by way of non-limiting example, with reference to the figures of the accompanying drawing in which:<ul><li>- Figure 1 is a plan view and partial schematic of this apparatus;</li><li>- Figure 2 is an axial sectional view through the line II-II of Figure 1; and</li><li>- Figure 3 shows diagrammatically the drive rollers of the device.</li></ul>

p0017In the various figures, what we can call the unit's chassis has been referenced 1 and the two rollers, forming between them a passage for the coupling profiles, 2. These rollers, which are rotatable about axis 2a, and comprise a groove 2b are each mounted at the free end of an arm 3 mounted to pivot about an axis 4. the other end of arm 3 is connected by a connecting rod 5 to a common axis 6 secured to a moving support 7. the axes hingedly connecting the arms 3 to the rods 5 have been referenced 8.

p0018Position, in abutment, of the movable support 7 relative to the chassis 1 can be adjusted by rotating a knurled knob 9 mounted on the end of a screw 10 screwed into the bracket and whose free end comes abut, at 11, on one end of the chassis 1. a against nut 12 allows, after adjustment, and by clamping the wall 13 of the support 7, to fix the position of the screw 10 with respect to support 7.

p0019By these means, it is possible to adjust the degree of maximum nip of the two rollers 2 one on the other.

p0020The displacement of the movable support 7, which will control the pivoting of the links 5 and the levers 3, and consequently the opening and closing of the rollers 2, is produced by a pneumatic cylinder 14 fixed relative to the frame 1 and whose threaded end 15 of piston rod, on which also a estmonté 16 against adjusting nut, is screwed into said support. Automatically controlling the supply of the cylinder of the ram 14 is effected by means of a solenoid valve and any means suitable sensors (not shown), this according to the progress and scheduled downtime superposed sheets of material plastic scroll (in the direction of arrow F), which have been referenced 17 and carry on their free longitudinal edges of the profiled elements coupling 18 (of Figure 2, a slider mounted in operational position on the profiles 18 been referenced 19).

p0021As for the axes of articulation 4, they are fixed to a carriage 20 slidably mounted on the chassis 1. The sliding of the carriage 20 relative to the frame 1 is provided on each side by lateral wings 21, with restraint provided by the via two lateral grooves 22 of the frame, on each of which slides the head 23 of a screw 24 fixed in said carriage 20.

p0022Finally, and for a purpose that will be seen subsequently, the carriage 20 can be locked elastically on the chassis 1 by the rounded end 25, biased outwardly by an internal spring, an elastic lock screw 26 to nut 27 fixed on the carriage 20, this end can come to occupy one of two notches 28 or 29 of the frame 1.

p0023That is, the operation of the apparatus which has just been described is as follows: a slider 19 having come into the position shown in Figure 3, the actuator 14 has been ordered, during the previous cycle time, so that the plunger is retracted to the maximum in his body, which brought the mobile support 7 in position before stop shown in Figure 2. the rounded end 25 of the resilient latch 26 then occupies the slot 29.

p0024This movement of the support 7 moving forward, ç'est ie downwards, provoked the maximum approximation of the two rollers 2 towards each other as a result of pivoting of the links 5 and arm 3; these rollers then prevent the passage forward said cursor 19, which remains locked behind the rollers 2, while the leaves 17 continue to scroll in the direction of the arrow F. The location of the line of welding and cutting cross rear leaf thus advance to the cursor 19, which thus find themselves on the corresponding bag when finished, close the rear end of the connection profiles 18.

p0025In Figure 3, the rollers and the various axes of the system are in the position to which references that refer to them, and which are the same as in the other figures, are assigned to the index 1 (and so on: 2 , 3 and 4 for the following time of the operating cycle).

p0026At this time, stopping the leaves 17 is produced by an electric brake acting on the rollers, with production of a control signal of the second cycle time: the cylinder rod 14 and spreads out the support Mobile 7 Chassis 1 , which causes the opening of rollers 2 (their axes come 2a 2 in Figure 3).

p0027When the rollers are fully open and that the arms 3 are then blocked (in the position of Figure 1), a further actuation of the actuator 14 causes a displacement of the carriage 20 rearwardly, that is, ie upwards, the rounded end 25 of the resilient latch 26 leaving 29 slot chassis to occupy the slot 28. the system is then arrived at the third time of the cycle of operation (indices 3 references in Figure 3).

p0028The rollers 2 (axes in position 2a₃) Are then always in the open position, but behind the slider 1_'9.

p0029The cylinder 14 is then controlled in opposite direction, which causes the closing of the rollers 2 behind the cursor 19. The rollers are then in the position 2a₄ of Figure 3 (fourth cycle time).

p0030The rollers 2 being closed on the profile 18, the pivot arms 3 are again blocked and further operation of the actuator 14 can no longer that return the carriage 20 forward, that is to say towards the position he occupied during the first cycle time, the rounded end 25 of the latch spring 26 this time leaving the slot 28 of the frame to return to the notch 29.

p0031During this forward movement of char iot 20 with the rollers 2 closed (leaves 17 still being stopped), the slider 19 is slightly moved forward on the profiles 18, causing their coupling on a short length.

p0032This arrangement has the advantage of testing the functioning cursor 19 which, if faulty or improperly engaged on the profiles 18 is ejected, which allows easy and quick identification of the fault. Moreover, this leaves enough space at the rear end of the profiles 18 (behind the cursor) for performing the welding point on the profiles, this solder constituting a stop for the slider on the future bag.

p0033After which, having returned to the first cycle, the leaves are re-scrolling and system operation starts the same way.

p0034One can get open bags (with the exception of the short length closed at the back, he just mentioned), if rollers 2 being closed up, do not cause inter-engagement profiles coupling 18 during the first cycle. Indeed, when the slider is blocked by the rollers 2 in position 2_. and that the sheets are advanced, the slider causes a disengagement of the profiles 18, which are coupled at the installation of sliders device.

p0035By acting on the knob 9, however we can ensure that in the closed position to the maximum pinch rollers 2 sufficiently profiles 18 during the first cycle to induce mating. We then get completely closed bags.

p0036It is thus seen that the invention allows to obtain bags open or closed, variable widths without having to change the distance between the device installation sliders blade welding and cutting, with cursors whose functioning has been tested, and which are always located at a determined distance from the rear end of the strips, on each bag.

p0037As goes without saying and as results already from the foregoing, the invention is not limited to those of its modes of application and embodiments which have been more especially envisaged; it embraces, on the contrary, all variants.