The present invention refers to a station of application of segments of opening/closing strip on plastic web films suitable to form bags.
With reference to the enclosed
These bags are equipped with a strip element (or segment) welded to a wall of the bag (generally on the inner face) and able to give the characteristic of being easily openable and reclosable to the bag itself: on the bag, in fact, strip elements are arranged having a tear thread that, when pulled, tears up the bag along an opening line; to enable the reclosure thereof, the bag (or the strip element fastened thereto) is provided with an adhesive band that suitably uncovered allows the reclosure thereof.
These strip elements require that punchings for accessing the element and for starting the tear are provided in appropriate positions on the wall of the bag.
A station of the specified type is known for example from EP 1 584 562 A1 and comprises, essentially, punching means of predefined areas of the plastic film for the access to areas of the strip segments through the film and welding means of the strip segments at intervals on the plastic film, wherein the punching means and the welding means are positioned in the station along the flow path of the film to act in sequence on the same zone for punching the film and for welding the segments in the predetermined points of the film, keeping the film stationary between the punching operation of the film itself and the corresponding welding operation of a strip segment on the film.
In particular, in the station according to the aforesaid document EP 1 584 562 A1, the welding means comprise two welding opposed surfaces, mutually movable towards each other with interposition of the plastic film and of the strip segment to be welded to the film, and the punching means comprise on one face of the film at least one punch movable towards the surface of the film and on the opposite face of the film contrast means, which are movable between an operative position, in which are interposed between one of the welding surfaces and the corresponding face of the film to make abutment with the punch, and a non-operative position outside the interposition, to permit the approach of the welding surfaces and the welding of the strip segment on the film that is interposed between them.
Although functioning, the station of application described in EP 1 584 562 A1 shows some recognized drawbacks.
A first drawback of the station of application according to EP 1 584 562 A1 resides in the fact that the punch is provided movable towards the surface of the film through (or, anyway, near to) one of the welding surfaces.
The consequent heating of the punch causes therefore a rapid wear of the relevant contrast means and of the punch itself.
Furthermore, the fact that the contrast means of the punch, when they assume the operative position, are interposed between one of the welding surfaces and the corresponding face of the film, while, when they assume the non-operative position, are arranged outside the interposition, complicates the structure and the operation of the station itself, limiting the operational performance thereof.
Furthermore, in the aforesaid station, the means causing the operative motion of the welding means and of the punching means comprise actuators, for example pneumatic, that for their own structure do not allow to reach the accuracy and the operational rhythm necessary for a correct and efficient operation of the station itself.
The present invention, starting from the knowledge of the aforesaid drawbacks according to the prior art, aims to overcome them.
In particular, an object of the invention is to provide a station of application of segments of opening/closing strip on plastic web films suitable to form bags allowing to substantially limit the wear of the punch and of the relevant contrast means.
Another object of the present invention is to provide a station of the specified type allowing to avoid, during the processing, the interposition of the contrast means of the punch between one of the welding surfaces and the corresponding face of the film, simplifying the structure of the station itself and increasing the operational performance thereof.
A last but not least object of the present invention is to provide a station of the indicated type allowing to avoid the use of actuators to cause the operative motion of the welding means and of the punching means, improving the accuracy and the speed of the operational rhythm of the station for a more correct and efficient operation.
In view of these objects, the present invention provides a station of application of segments of opening/closing strip on plastic web films suitable to form bags, having the features of the attached first claim, to which reference is made for presentation brevity.
Further advantageous technical features of detail of the station of application according to the invention are described in the relevant dependent claims.
The aforesaid claims, as hereinafter defined, are considered to form integral part of the present description.
The present invention, together with its objects and advantages, will become more evident from the following detailed description, concerning a preferred embodiment of the station of application herein exclusively claimed, given by way of illustrative, but not limiting, example, with reference to the enclosed drawings tables, also given only by way of example, in which:
Firstly with reference to
Said station S comprises a framework I having a substantially portal structure, through which a plastic film in continuous strip form (not shown), intended to form a bag for the packaging of products, is fed and made to pass. Said plastic film is unwound, upstream, from a coil (also not shown), which is rotating supported through a rotating reel A (
With C feeding means of a suitable continuous strip (not shown) in a direction transverse to the feeding direction of said plastic film are denoted. Said feeding means C are arranged laterally to the framework I and comprise a coil C1 rotating supported with respect to a horizontal axis, oriented in a direction substantially orthogonal to that of the axis of the reel A.
From said coil C1 (for example with a sliding gear actuating a tensioning brake) the continuous strip is unwound toward a punching and welding area Z (
In said inner area Z of the framework I with two operating units U1, U2 are provided, upper and lower respectively, i.e. arranged from opposite sides (above and below) with respect to said plastic film, angularly rotating about respective axes substantially parallel to that of the reel A and mutually opposed.
In particular and with reference also to
a shaft U11, placed in an upper position with respect to said plastic film, stationary supported with respect to the framework I and selectively rotated in opposite directions (in an angular range of ±180° by a respective brushless electric motor with reducer U12, fixed with respect to the framework itself;
a shaft U21, placed in a lower position with respect to said plastic film, vertically mobile supported in said framework I, with alternate approaching and removal motion with respect to said upper shaft U11, by support means sliding in corresponding vertical rectilinear guides fastened to said framework. Said shaft U21 is rotated, for example in opposite directions (in an angular range of ±180°, by a respective brushless electric motor with reducer U22, fixed with respect to said support means. The axes of the aforesaid two shafts U11, U21 are parallel to each other and to that of the reel A and are substantially contained in the same vertical plane;
said upper operating unit U1, which is integral in rotation with respect to said upper shaft U11 and has a body of a substantially rectum parallelepiped general shape, ideally inscribed in a cylinder whose axis coincides with that of said shaft U11 and which fixedly supports, respectively:
a1) on a first side face, tray or storing means U13 for loading and temporarily retaining a strip segment cut to size, wherein said strip segment is oriented in the direction of the axis of the shaft U11, which substantially coincides with the direction of application of the segment itself on the underlying plastic film;
b1) on a second side face opposite (with respect to the axis of U11) to said first face, plate means to contrast the punching U14;
c1) on a side face intermediate between said first and second faces, the first plate means with thermowelding surface U15, and
said lower operating unit U2, which is integral in rotation with respect to said lower shaft U21 and has a body of a substantially rectum parallelepiped general shape, ideally inscribed in a cylinder whose axis coincides with that of said shaft U21 and which fixedly supports, respectively:
a2) on a first side face, punching means U22 with two substantially “half-moon” punches U22.1;
b2) on a second side face opposite (with respect to the axis of U21) to said first face, second plate means with a thermowelding surface U23, and
gripper means P (
It will be noted that the lower shaft U21 with the relevant lower unit U2 is vertically mobile supported in said framework I, with alternate approaching and removal motion with respect to the upper shaft U11, through an underlying camshaft, stationary and having axis parallel and contained in the same vertical plane with respect to that of the lower shaft U21.
Said camshaft is rotated by a respective brushless electric motor with reducer U31, fixed with respect to the framework I.
Said camshaft supports two eccentric, fixed and cooperating with corresponding sliding blocks with cam-followers provided in said support means of said lower shaft U21; said sliding blocks are guided in corresponding rectilinear vertical guides fixed in the framework I.
In the enclosed
In the station S according to the present invention, as will become more evident hereinafter, plastic film and strip segment are joined in line, according to a configuration always resulting from the arrangement of
The upper unit U1 and the lower unit U2 of the station S are initially spaced from each other and a plastic film in continuous strip form (not shown and, as mentioned, intended to form bags) is interposed between them, which film is suitably fed through the station S while remaining stationary during the whole running cycle described hereinafter.
Step 1 (
The tray means U13 of the upper unit U1 are arranged in a horizontal plane with their suction surface facing upward. The gripper means P lay on said tray U13 a strip segment (not shown), which is therein retained by suction.
Furthermore, the plate means to contrast the punching U14 of the upper unit U1 are arranged immediately above the plastic film.
In this step, the lower unit U2 of the station S has the punching means U22 facing the overlying plastic film.
Step 2 (
The upper unit U1 with shaft U11 is maintained stationary, while the lower unit U2 with shaft U21 is raised, by the cam means driven by the motor U31, until the two punches U22.1 of the punching means U22 cut the plastic film and are in abutment with the contrast plate means U14 of the upper unit U1. Two “half-moon” punches are thus made on the film itself.
Subsequently (this operation is not shown in the drawing), the lower unit U2 with shaft U21 is lowered, by the cam means driven by the motor U31, carrying out an inverse stroke to the raising one.
The upper unit U1 is solidly rotated with the shaft U11 around the axis thereof at an angle (here taken as positive) of +180° (also this operation is not shown in the drawing), so to bring the suction surface of the tray U13 immediately above the plastic film. Upon completion, the suction action of the vacuum pump means is stopped and the strip segment is laid by gravity on the plastic film, exactly in line in the area of the two “half-moon” punchings.
Step 3 (
The upper unit U1 is solidly rotated with the shaft U11 around the axis thereof at a negative angle of −90° (i.e., the aforesaid shaft U11 carries out a partial rotation, preferably inverse to the previous one), in such a way to place the first plate means with thermowelding surface U15 immediately overlying the plastic film in the area thereof having the two “half-moon” punchings.
At the same time, the lower unit U2 is solidly rotated by 180° with the shaft U21 around the axis thereof, so as to place the second plate means with thermowelding surface U23 immediately underlying said area with punchings of the plastic film and the punching means U22, opposite to the second plate means with thermowelding surface U23 themselves, facing downwards.
The lower unit U2 with shaft U21 is then raised, by the cam means driven by said motor U31, until the second plate means with thermowelding surface U23 press, for the necessary time, the aforesaid area of the plastic film, on which the strip segment is arranged in line, against the first plate means with thermowelding surface U15 of the upper unit U1.
The thermowelding is thus made on the plastic film of said strip segment positioned, in said area of the plastic film, in line with said two “half-moon” incisions.
Step 4 (
Finally, the lower unit U2 is lowered again, by the cam means driven by the motor U31, carrying out an inverse stroke to the raising one and it is subsequently solidly rotated by 180° with the shaft U21 around the axis thereof, so as to rearrange the punching means U22 facing the overlying plastic film.
In its turn, the upper unit U1 is further solidly rotated with the shaft U11 around the axis thereof at a negative angle of −90°, in order to rearrange the tray means U13 in a horizontal plane with their suction surface facing upward.
The two units U1 and U2 are thus brought back to the initial arrangement and, after the plastic film has been advanced of the desired length and the suction of the vacuum pump means through the suction surface of the tray U13 is restored, the running cycle of the station S can be repeated.
The above-described running cycle of the station S is carried out in an automated way under the control of a software program performed by programmable logic control (PLC) means.
As results from the foregoing, the invention provides a station of application of segments of opening/closing strip on plastic web films intended to form bags, which allows to achieve the following main advantages:
since the punching means are arranged far from the welding means, the rapid wear of the former and of the relevant contrast means due to heat induced by the latter is avoided;
the punching contrast means do not interpose between one of the welding surfaces and the corresponding face of the film; therefore, the structure and the operation of the station are simplified and the operational performance is increased;
the means causing the operative motion of the welding means and of the punching means do not comprise any actuators, in particular pneumatic ones, but cam means and cam-followers driven by electric motorization means. This fact allows to operate, in the station according to the invention, with high accuracy and operational rhythm, achieving a correct and efficient operation of the station itself.
Basing on what above illustrated, it is therefore understood that the station of application of segments of opening/closing strip on plastic web films suitable to form bags, which is the subject of the present invention, achieves the objects and realizes the advantages previously mentioned.
A further advantage of the present invention concerned the improved accessibility to all the component parts of the machine, thus simplifying any interventions of maintenance and/or shape or die replacement and adjustments (e.g. set-up) in general.
Finally, it is clear that several other variants may be made to the station of application in question, without departing for this from the novelty principles inherent in the inventive idea, as well as it is clear that, in practical embodiments of the invention, the materials, the shapes and sizes of the illustrated details may be whichever, depending on the needs, and may be replaced with other technically equivalent.
Where the construction features and the techniques mentioned in the subsequent claims are followed by reference signs or numbers, those reference signs have been introduced with the sole purpose of increasing the intelligibility of the claims themselves and, consequently, they have no limiting effect for the interpretation of each element identified, by way of example only, by such reference signs.
Number | Date | Country | Kind |
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MI2012A000286 | Feb 2012 | IT | national |
Filing Document | Filing Date | Country | Kind |
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PCT/IB2013/000280 | 2/25/2013 | WO | 00 |