"MEANS FOR CONTROLLING THE SIDE WELDING JAWS OF HORIZONTAL PACKAGING MACHINES"

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TECHNICAL FIELD

This invention concerns means for controlling the sealing jaws of horizontal packaging machines designed to produce fluid-tight packages, in particular packages with a zip closure.

More specifically, this invention refers to highspeed horizontal packaging machines for packaging products by means of synthetic film, which make it possible to automatically obtain packages that can be subsequently closed, being equipped with a zip closure.

These machines can be used in the food and chemical industries in order to produce consistent batches of packages ready to be transported and marketed.

BACKGROUND ART

The background art includes horizontal packaging machines for the packaging of products, generally food products but also other types of products.

These machines generally comprise a supporting frame including a protective guard for a packaging unit, a movement device that allows the positioning of products at one end of the frame, a conveyor unit designed to transfer the products from the movement device towards the packaging unit and an extractor unit to pick up the packaged products.

According to a well-known technique, the packaging unit comprises a roller around which the synthetic film, normally polyethylene-based, is wound. This film is unwound by means of an appropriate unwinding device and

wrapped around a tunnel or shaping device on which it is continuously sealed.

The products to be packaged are conveyed inside the tunnel or shaping device continuously or intermittently, while the sealed film is pulled over the outside of the tunnel.

At the tunnel exit is a sealing and cutting device designed to seal the side flaps which will form the base of the packages and to separate the packages from the remaining film still wrapped around the tunnel.

Longitudinal sealing takes place at the level of the tunnel by means of a pair of heated pads that seal the flaps of the film joined together during the infeed of the film . The machine is also equipped with a cutter designed to separate the packages so that the bottom seal of a package normally coincides with the upper closure of the immediately preceding package .

This machines foresees the unwinding of the film by means of the joint action of an unwinding unit and two pairs of infeed rollers, one upstream and one downstream of the sealing and cutting unit, with the simultaneous positioning of a pair of long elements designed to form a zip closure so that the package can be reused after being opened.

The pair of long elements is positioned on the film just upstream of the first pair of infeed rollers so that the sealing and cutting device can form a package with a zip closure that is guaranteed by the adhesion of the long elements. in some cases, the machine is equipped with an electronic device to control the speed of this unit and the rotation speed of the infeed rollers, if the two speeds are different at the portions of film that will

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subsequently be cut, there will be discontinuity in the two long elements forming the zip closure which will itself be discontinuous.

Problems have been encountered regarding the use of electronic controls for speed adjustment, since these controls take up a considerable amount of space on the machine as well as being difficult to maintain and set up.

Another problem is represented by the fact that the positioning of numerous sources of movement, such as unwinding units and pairs of infeed rollers, upstream of the sealing and cutting unit, often causes folds in the film and the long elements, with consequent machine down time for repositioning of the film. The patent EP 1.413.521 filed by the same applicant, proposes a pouch sealing machine or horizontal packaging machine which, to overcome some of the problems described above, foresees the positioning, downstream of the sealing unit on the packaging machine, of a power-driven film infeed roller equipped with means for gripping and infeeding each individual package produced.

According to this solution, the sealing unit comprises a pair of platforms, on opposite sides of the film and the pair of long elements being infed, each platform being equipped with a pair of sealing pads as well as idle film-guide rollers.

Immediately downstream of the sealing unit, the machine is equipped with a cutting device for just the pair of long elements forming the zip in order to obtain portions of film which separate one package from the next, without zips.

This solution, which did resolve some of the problems described above, foresees that the outer

- - surface of the roller is equipped with side sealing jaws equipped with sealing and cutting devices, these jaws guaranteeing, in the closed position, both the side seal of the film and the separation of each package from the next by drawing the film forward.

These jaws are arranged on the roller in such a way as to allow their reciprocal movement which, closing like a book on the package, is enabled by the use of an oscillating feeler element which, prompted by special pins positioned at the level of each gripper jaw, allows the movement to be synchronized with the film infeed.

This solution, however, presents the problem that, since the feeler element has to be prompted numerous times during the infeed of the packages to be sealed and cut, its efficiency is inversely proportional to the increase in film infeed speed and to the frequency of feeler element prompting.

As can be imagined, it follows that the functioning of the feeler element will be optimal up to a fairly limited infeed speed, while at higher film infeed speeds the control mechanism is subject to jamming and malfunctioning caused by a frequency that the device is unable to maintain.

The feeler element is also subjected to a movement that produces a continuous annoying and sometimes deafening noise, which is harmful to the workers and to the quality of the workplace.

DESCRIPTION OF THE INVENTION This invention proposes to provide means for controlling the sealing jaws of a horizontal packaging machine for producing fluid-tight packages, that is able to eliminate or at least reduce some of the problems described above.

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This invention also proposes to provide means for controlling the alignment of the sealing jaws of a horizontal packaging machine, that are able to guarantee increased productivity of the sealing and cutting jaws, further reducing production and machine down times, also succeeding in using jaw control means that are perfectly- functional even at high speeds.

This is achieved thanks to means for controlling the alignment of the sealing jaws of a horizontal packaging machine for producing fluid-tight packages with the features described in the main claim.

The dependent claims describe advantageous embodiments of the invention.

The means according to the invention for controlling the sealing jaws of a horizontal packaging machine for producing fluid-tight packages according to the invention substantially consist of an alignment device with a servomotor which comprises a rotor with several protrusions, each of which supports a roller designed to intercept each alignment device for each sealing and cutting jaw.

The rotation of this rotor is commanded and controlled in synchronization with the movement of the jaws by means of a servomotor, connected to appropriate means of transmission, controlled in turn by an electronic control unit.

DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become evident on reading the following description of one embodiment of the invention, given as a non-binding example, with the help of the accompanying drawings in which: figure 1 is a side view of a packaging machine

equipped with means for controlling the sealing jaws according to the invention; figure 2 shows a detailed view of the means according to the invention for controlling the sealing jaws and of their means for automatic alignment on the basis of the infed packages.

DESCRIPTION OF ONE EMBODIMENT

Referring first to figure 1, the reference number 10 indicates in general a horizontal packaging machine, in particular a horizontal packaging machine for producing fluid-tight packages 11.

In the embodiment shown in figure 1, the machine 10 comprises: a roller 12 around which synthetic film 13 is wound, a unit 14 for the longitudinal sealing of the film

13, a power-driven roller 15, positioned downstream of the sealing unit 14, designed to pull the film 13 towards a conveyor belt 16 for the accumulation and sorting of the formed packages 11.

The outer surface of the roller 15 is fitted with a plurality of side sealing jaws 17 equipped with cutters, preferably equally spaced at an angle, but with the possibility of sliding on the roller 15 to vary the distance between them in accordance with the size of the product to be packaged.

In the closing position, the jaws 17, ensure both the side sealing of the film 13 and the separation of each package 11 from the next, cutting the film 13 at the point of the seal.

As can be seen in figure 1 and, more specifically in figure 2, each jaw 17 comprises an inner fixed section 18 and a swing type oscillating mobile outer

section 19, or arm.

The function of the mobile arm 19 is to remain in the raised position, in contrast to a spring, with respect to the roller 15 and to move down only when, during rotation of the roller 15, each infed package has to be sealed and cut.

Each jaw 17 is allowed to shift on the roller 15, to move to the correct distance from with respect to the next jaw, by means of a pin 20, protruding from the fixed sector 18 of the jaw parallel to the rotation axis of the roller.

Each of the pins 20 is engaged by a rotor, indicated overall by 21, which is positioned parallel to the rotation axis of the roller 15 and at the side of roller, above the centre and slightly back with respect to the film infeed direction.

The rotor 21 presents a plurality of protrusions 22 each supporting an idle roller.

In the example shown, the rotor 21 has five protrusions, forming a sort of star with the respective idle rollers positioned at the apexes.

The rotor 21 is rotated by means of its connection to a servomotor 23 equipped with a drive pulley 24 that turns a belt 25 connected to the rotor 21. The controlled speed drive of the servomotor 23 determines the angular movement of the rotor 21, in such a way that the idle rollers positioned at each apex 22 intercept the pin 20 of each of the jaws 17.

Since the speed of the angular movement of the rotor is controlled, it allows each idle roller to press its respective pin 20 so as to move the jaw to the exact preset distance from the previous jaw already in the working position.

It can be seen in figure 2 that the rotor 21 is

- - fitted precisely in the area in which the line of jaws 17 on the roller 15 must be adjusted to ensure that each jaw moves to the exact position near the arrival point of the portions to be sealed and cut. The rotation speed of the rotor 21 can be calibrated exactly to allow the movement of the jaws 17 at the most appropriate moment, simply by adjusting the servomotor 23, which can also be connected to an electronic control unit or to the machine PLC. The invention is described above with reference to a preferred embodiment. It is nevertheless clear that the invention is susceptible to numerous variations, within the framework of technical equivalents.