Patent Application
20140141954
The present invention refers to a machine for producing bags of flexible material, intended for example for producing bags suitable for containing sterile medical products, pharmaceuticals, foods and yet more.
In order to produce bags and packets of flexible material, there are known machines called welders or “bag makers” that normally operate from one or more films of suitable material, for example plastic or thermoplastic, fed forwards by one or more respective rollers or cylinders, known as “calendars”.
The flexible material, plastic or not, is thus fed towards a subsequent welding group, provided with one or more upper welding bars or plates and one or more corresponding lower welding bars or plates. The upper and lower welding bars or plates are heated and act on the film according to a vertical alternate movement, pinching such a film along one or more linear portions. The intervention of the upper and lower welding bars or plates is defined in the field as “stroke”.
Downstream of the welding group corresponding cutting groups are positioned to separate apart the single bags just welded. The bags thus obtained are finally collected in piles or rolls in the last work station of the machine. Once the piles or rolls of bags are complete, in the preselected number, such bags are picked up by handling groups to be packaged inside corresponding boxes or similar containers.
In detail, a typical welding group of a machine for producing bags of flexible material can comprise a single lower welding plate and a single upper welding plate, of a shape and size compatible with the shape and size of the lower welding plate. At least one of the welding plates, like for example the upper welding plate, is mobile with an alternate motion along a plurality of vertical guiding columns. The alternate motion of such a welding plate is usually generated by one or two motors arranged at the welding plate itself.
The bodies of the lower and upper welding plates are typically manufactured from aluminium, since there is a need to both distribute the heat uniformly along all the plates, and to be able to have considerable rigidity, in particular in terms of the mobile welding plate, which acts on the thermoplastic film in the entire area to be welded. The aluminium must, moreover, be suitably worked and smoothed to ensure surface linearity.
During the operation of the machine, the movement together and apart of the upper welding plate and the lower welding plate can cause imbalances due to the imperfect distribution of weights on the mobile welding plate and to the not perfectly linear movement of the mobile welding plate itself. It should be observed that apparently small imbalances in weight, of the order of a few kilograms, and/or misalignments of a few hundredths of a millimetre in the contact between the lower and upper welding plates can generate inadequate welding lines. An imperfect welding of the perimeter edges causes particular problems in some types of bags, like for example those intended to contain sterile medical products, which must respect precise and strict quality standards.
In addition, the movement together and apart of the upper welding plate and lower welding plate is controlled and guided by complex transmission mechanisms that are biased by high inertias (accelerations, stopping, motion inversions, new accelerations, etc.) and made to rotate at high speeds. The current welding groups of machines for producing bags of flexible material thus tend to wear out quickly, with consequent possibilities of breaking and needing to stop the machine.
Finally, due to the considerable weight of the aluminium body that forms the mobile welding plate, the removal of such an aluminium body with respect to the structure of the machine is problematic, which may need to be carried out for example for maintenance operations or to modify the format of the bags being produced on the machine itself.
The purpose of the present invention is therefore to make a machine for producing bags of flexible material, intended for example for producing bags suitable for containing sterile medical products, pharmaceuticals, foods and yet more, which is able to solve the aforementioned drawbacks of the prior art in an extremely simple, cost-effective and particularly functional manner.
In detail, a purpose of the present invention is to make a machine for producing bags of flexible material that is able to ensure a movement that is as linear and homogeneous as possible of the mobile welding plate of the relative welding group.
Another purpose of the present invention is that of making a machine for producing bags of flexible material in which it is possible to identify in real time and immediately correct not just possible malfunctions of the motorised means and of the motion transmission mechanisms of the mobile welding plate, but also possible misalignments and imbalances, even by a small amount, in the vertical alternate movement of such a mobile welding plate.
A further purpose of the present invention is to make a machine for producing bags of flexible material in which it is possible to reduce the inertias and the forces that impact upon the motorised means and on the motion transmission mechanisms of the mobile welding plate.
Yet another purpose of the present invention is to make a machine for producing bags of flexible material in which it is possible to easily remove and equally easily remount the aluminium body that forms the mobile welding plate.
These purposes according to the present invention are accomplished by making a machine for producing bags of flexible material, intended for example for producing bags suitable for containing sterile medical products, pharmaceuticals, foods and yet more, as outlined in claim 1. Further characteristics of the invention are highlighted by the dependent claims, which are an integral part of the present description.
The characteristics and advantages of a machine for producing bags of flexible material according to the present invention will become clearer from the following description, given as an example and not for limiting purposes, referring to the attached schematic drawings, in which:
With reference to the figures, a preferred embodiment of a machine for producing bags of flexible material according to the present invention is shown, wholly indicated with reference numeral 10. The machine 10 is provided with a plurality of distinct work stations arranged in line, in other words arranged in sequence one after the other, which allow the bags to be made from one or more films of flexible material, like for example plastic or thermoplastic.
The machine 10 firstly comprises a reel-holder group 12, which rotatably supports an upper reel 14 and a lower reel 16, one above the other and having parallel axes, which respectively feed a first film of flexible material and a second film of flexible material.
The films coming from the unwinding of the respective upper 14 and lower 16 reels are positioned one above the other and are thus introduced, downstream of the reel-holder group 12, through a welding group 18, provided with at least one upper welding plate 20 and at least one corresponding lower welding plate 22. The upper 20 and lower 22 welding plates are heated and are provided with corresponding linear welding tracks. The upper 20 and lower 22 welding plates thus act on the films according to a vertical alternate movement, pinching such films along one or more linear portions.
Downstream of the welding group 18 there is a longitudinal cutting group 24 and a transversal cutting group 26, which separate from one another the single bags just obtained further to the welding operation on the films. The bags thus obtained can finally be gathered in piles or “stacks” in a stacking group 28 arranged downstream of the longitudinal 24 and transversal 26 cutting groups.
In detail, with reference in particular to the welding group 18 (
The upper welding plate 20 is constrained at the top to moving means consisting of a plurality of screws 36, preferably four of them arranged on the vertices of a rectangle, which slide vertically inside respective female screws 38 formed through a cover 40 fixed to above the vertical guiding columns 32. According to the invention, each screw 36 is moved vertically inside the respective female screw 38 by a respective motor 42 integral with the cover 40. Preferably, all of the motors 42 are identical to one another and are arranged in an equidistant manner from the respective screws 36, so as to make uniform both the load, and the thrust action on the upper welding plate 20. In this way it is possible to obtain a movement that is as linear and homogeneous as possible of the upper welding plate 20 with respect to the lower welding plate 22. However, it is possible the use of motors 42 that are different to one another, just as it is also possible for such motors 42 to be arranged at different distances from the respective screws 36.
Each motor 42 is operatively connected to the respective screw 36 through corresponding motion transmission means, like for example a toothed belt 44 arranged between each motor 42 and the respective screw 36. Each motor 42 is also operatively connected to an electronic control unit (not shown) capable of managing the functioning of all motors 42. The electronic control unit is thus capable of activating simultaneously and in perfect synchrony all motors 42, as well as of maintaining all functioning parameters controlled in order for the movement of the upper welding plate 20 to always be regular and uniform.
The lower welding plate 22 is provided with one or more sensor means 46, for example consisting of load cells, capable of instantly detecting, for each “stroke” that the upper welding plate 20 performs on the lower welding plate 22, the compression load measured at each point of force that such an upper welding plate 20 imparts on such a lower welding plate 22. There are preferably at least three load cells 46 (four in the embodiment shown in the figures) and they can be advantageously arranged between the lower welding plate 22 and the base 30.
The load cells 46 are operatively connected to the electronic control unit to send to such an electronic control unit the signals relative to the compression load, measured at all points of force, derived from each “stroke” that the upper welding plate 20 performs on the lower welding plate 22. The aforementioned signals, detected during the pressure or welding step, are interpreted by the electronic control unit to independently manage the functioning of each single motor 42. For example, if the signals were indicative of an anomalous compression load, or one that is not uniformly distributed over all the surface of the lower welding plate 22, the electronic control unit would immediately modify the position parameters of one or more motors 42 to rebalance the correct alignment of the upper welding plate 20. If needed, the electronic control unit could immediately stop all the motors 42 to avoid potential damages to the entire welding group 18.
Preferably, each screw 36 can be provided with control means of its current position, which must coincide with the controlled position and with the current position of all of the remaining screws 36. Such control means are operatively connected to the electronic control unit and can consist, for example, of an angular position transducer 48, or “encoder”, provided with a respective gearing 50 connected to each screw 36. Such control means 48 and 50 thus operate to verify the perfect synchronisation of the simultaneous movement of the screws 36, consequently ensuring the homogeneity of movement of the upper welding plate 20. If the control means 48 and 50 are present, the electronic control unit is configured to intervene by instantly blocking all of the motors 42 in the condition in which the signals sent by such control means 48 and 50 are indicative of an anomalous movement of one or more of the respective screws 36.
With reference in particular to
The welding element 54 is supported by a horizontal guiding rod 56 constrained to the supporting plate 52. In the operating configuration of the upper welding plate 20, the welding element 54 is made integral with the horizontal guiding rod 56 through corresponding fixing means 58. For safety reasons, also considering its considerable weight, the welding element 54 is also made integral directly with the supporting plate 52 through a plurality of blocking screws 60.
If it were necessary to remove the welding element 54 from the supporting plate 52, firstly the blocking screws 60 would have to be loosened or removed, and then the fixing means 58 that stably constrain the welding element 54 to the horizontal guiding rod 56 would have to be loosened. The welding element 54 would at this point be in the condition of being able to slide horizontally along the horizontal guiding rod 56, but without the danger of falling onto the lower plate 22. The horizontal guiding rod 56 thus allows the workers with the task of removing the welding element 54 to not have to manually support such a welding element 54 while the respective blocking screws 60 are loosened or removed.
It has thus been seen that the machine for producing bags of flexible material according to the present invention achieves the purposes highlighted earlier.
The machine for producing bags of flexible material of the present invention thus conceived can in any case undergo numerous modifications and variants, all of which are covered by the same inventive concept; moreover, all of the details can be replaced by technically equivalent elements. In practice, the materials used, as well as the shapes and sizes, can be whatever according to the technical requirements.
The scope of protection of the invention is therefore defined by the attached claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| MI2012A 001943 | Nov 2012 | IT | national |
