WO2021181289A1

WO2021181289A1 - Thermosealing unit for packaging machines with volumetric flow partialising device

Info

Publication number: WO2021181289A1
Application number: PCT/IB2021/051974
Authority: WO
Inventors: Aaron HEER
Original assignee: Heer Aaron
Priority date: 2020-03-11
Filing date: 2021-03-10
Publication date: 2021-09-16
Also published as: IT202000005182A1

Abstract

Heat sealing unit (U) for product packaging machines (P) contained in a tray (V), comprising: a lower bell (1) and an upper bell (2) mutually movable, means (4a, 4b) for heat sealing a film (f) to a tray (V), a vacuum source (7) and suction points (6a, 6b) connected to the vacuum source (7) to create vacuum inside the lower and upper bells, further comprising a vacuum partialising device (8) interposed between said vacuum source (7) and first and second suction points (6a, 6b) respectively of said lower and upper bells (1, 2).

Description

THERMOSEALING UNIT FOR PACKAGING MACHINES WITH VOLUMETRIC

FLOW PARTIALISING DEVICE

Technical Field

The present invention relates to a heat sealing unit with a continuous volumetric flow partialising device for packaging machines, for example machines for packaging products in a container or tray by means of a film heat-sealed to the tray.

In particular, the partialiser of the invention is designed to be applied to packaging machines in which the film is made to adhere under vacuum to the product to obtain the so-called “skin effect” or for machines which perform heat sealing in a controlled atmosphere through the introduction of a gas into a packaging unit previously subjected to vacuum.

Background art

Currently, packaging machines are known comprising a heat sealing unit divided into two chambers, one upper and one lower, which sealingly overlap during the heat sealing step, being separate from the packaging film.

During the heat sealing process, one or both of the chambers can be subjected to more or less forced vacuum.

Depending on the type of packaging to be carried out, it may be necessary to obtain the same degree of vacuum in both chambers, for example before the reintegration with gas in the case of heat sealing in a controlled atmosphere, or to have a main vacuum in one of the two chambers, for example to adhere the film to a hot wall of a chamber before the film cutting step.

In different steps it may be desirable to alternate or balance the vacuum in the lower and upper chambers.

The systems of known type therefore have many drawbacks because they do not allow the balancing to be varied during the different steps of the packaging process, thus limiting the possible operations which can be carried out in the heat sealing unit.

Object of the Invention

The present invention is therefore intended to overcome the drawbacks of the already known solutions and to provide a heat sealing unit provided with a flow partialiser in packaging machines equipped with an upper chamber and a lower packaging chamber, which allows a continuous, fast and flexible management of the volumetric flow entering and exiting the lower and upper chambers. Summary of the invention These objects have been achieved by realising a volumetric flow partialiser for packaging machines according to at least one of the appended claims.

A first advantage is that it is possible to obtain an effective management and balance of the vacuum in the heat sealing unit and the continuous adjustment of the pressure difference between the two chambers which can be performed based on the vacuum reached.

A further advantage is that it is possible to perform, without structural modifications, different working steps in the same heat sealing unit which require different vacuum conditions, for example the feasible adjustment in the unit of the invention makes it possible to provide an automatic adjustment of the flow partialiser which avoids manual modifications having to be performed on the vacuum management system when switching from packaging in controlled atmosphere mode to packaging with a "skin" effect.

List of Drawings

These and other advantages will be better understood by anyone skilled in the art from the description below and the accompanying drawings, given as a non limiting example, in which:

- fig. 1A schematically shows a heat sealing unit in a conventional packaging machine;

- fig. 1 shows a partialising device according to the invention applied to a heat sealing unit of a packaging machine;

- figs. 2a-2c show a detail of three different configurations of the partialiser of fig-1 ;

- fig. 3 shows a partialiser according to the invention in greater detail;

- figs. 4a-4d respectively show: a perspective view, a view from above, a rear view in partial and front section of a partialising device of a heat sealing unit of a packaging machine; - fig. 5a-5c show three operating configurations of the partialiser of fig.4, respectively in the vacuum position only of the lower chamber, only of the upper chamber and with 50% partialisation.

With reference to the attached drawings, a heat sealing unit U according to the invention is described, intended for use in packaging machines of products P contained in a tray V, by heat sealing a film f at the peripheral edge 5 of the tray or container.

The described unit comprises a lower bell 1 and an upper bell 2 which can be sealingly overlapped so as to define a heat sealing chamber 3 inside which the heat sealing process of the film to the tray occurs, for example by heat sealing bars 4a, 4b.

The lower and upper bells are mutually movable between a non-operating offset position, in which the film f can be passed between the two bells, and a sealed operating position in which the bells are separated by the film (f) which thus defines two distinct regions communicating with a vacuum source, for example a vacuum pump, through the respective suction points 6a, 6b which, in the example described, connect the vacuum source 7 to the lower bell 1 and upper bell 2.

According to the invention, and with particular reference to figure 1 , the unit U comprises a vacuum partialising device 8) interposed between the vacuum source 7 and the suction points 6a, 6b of the lower and upper bells 1 , 2.

The partialiser 8 is equipped with adjustment means 9 to partialise between the lower and upper bells the vacuum created by said source and thus determine the best operating conditions depending on the packaging process to be implemented.

In the illustrated embodiment, the adjustment means 9 comprise a three-way valve connected to the source 7 and to the lower and upper bells, operable by an actuator 10 between a maximum partialisation position towards the lower bell and a maximum partialisation position towards the upper bell and capable of continuously partialising the volumetric flow between the lower and upper bells. Preferably, the three-way valve is shaped with a first outer hollow sleeve 11 provided with two openings 12, 13 communicating respectively with the suction points 6a, 6b and inside which a second inner sleeve 14 integral with the movement of the control stem 19 of a linear actuator 10 sealingly slides between two end positions.

The inner sleeve 14 has a cavity 34 which communicates at one end 32 with the vacuum source 7 and is provided with openings 15, 16 which in use face the openings 12, 13 of the outer sleeve 11 so as to each define a suction port 17, 18 of variable dimensions between a maximum dimension and a minimum or no dimension, and vice versa the other at the position assumed by the inner sleeve 14 in the sliding thereof between the end positions.

Figures 2a-2c show, by way of example, the partialiser with the inner sleeve 14 in the extreme rightward position with suction completely towards the upper bell (fig.2a), in the extreme leftward position with suction completely towards the lower bell (fig.2b), and in the central position (fig.2c) with suction or 50% partialised emission towards the two bells.

With reference to figure 3, a three-way partialisation valve is illustrated in which the openings 12, 13 of the outer sleeve 11 consist of holes inclined with respect to the axis “a” of the sleeve and communicate with the suction points 6a, 6b by blocks 38, 35 in turn provided with holes 39, 40 which are aligned and of the same diameter as the openings 12, 13, sealingly fixed to the cylinder 11 by gaskets 33. At one end, the cylinder 11 further includes a block 37 fixed to the cylinder 11 by a head gasket 36.

In this embodiment, the openings 15 16 of the inner sleeve 14 are also obtained by drilling the same diameter and inclination of the openings 12, 13 and the sleeve 14 is equipped with an end fitting 40 for connection to the actuator 10. Preferably, the unit U further comprises at least one pressure sensor 21 , 22 applied to detect the internal pressure in at least one of said lower and upper bells 1 , 2.

A filter 23 and a safety valve 24 may also be interposed in the line between the partialiser valve 8 and the vacuum source 7.

With reference to figures 4-5, a further preferred embodiment of a partialiser 80 is illustrated, provided with a three-way rotary valve capable of reducing the response time or the speed in creating the desired vacuum level in the bells. In this example, the flow partialising device 80 is interposed between the vacuum source 7 and the suction points 60a, 60b respectively of the lower and upper bells 1 , 2 and the flow adjustment means 90 to partialise the inflows and outflows comprise a three-way rotary valve operable continuously by a rotating actuator 100 between the maximum partialisation position towards the lower bell (fig.5a) and the maximum partialisation position towards the upper bell (fig.5b) passing, for example, from an intermediate partialisation position of 50% (fig.5c).

In more detail, the partialiser 80 comprises a casing 81 , preferably with an opening lid 95, within which a chamber 82 is realised communicating through respective openings 84, 85, 86 with the vacuum source 7 and the suction points 60a, 60b of the upper and lower chambers.

Inside the chamber 82 a rotating shutter 87 can sealingly rotate, comprising three ducts 88, 89, 91 in fluid communication with each other and which during the rotation of the shutter face the openings 84-85 of the vacuum source 7 of the suction points 60a, 60b, putting them in communication.

Preferably, the ducts 89-91 are in the form of radial branches.

The shutter 87 is moved by an actuator shaft 100, mounted on the casing 81 for example on a bearing 83, so as to communicate the shutter branches 88-91 with the openings 84-86 of the chamber 82.

Depending on the position assumed by the shutter, the vacuum source 7, through the branches 88-91 , can therefore be selectively communicated exclusively with the lower chamber as shown in figure 5a, exclusively with the upper chamber as shown in figure 5b or with both by partialising the vacuum, for example at 50%, as shown in figure 5c or with other degrees of partialisation selected according to the needs of the packaging process.

The unit of the invention may be applied to different types of packaging processes.

By way of example, it may be applied to packaging in a controlled atmosphere or with a “skin” effect or which determines a substantial adhesion of the film on the product. In the first case, the heat sealing process involves a step of creating the same degree of vacuum in both bells and subsequently reintegrating with the introduction of gas (e.g., 02 or C02) in at least one of said lower and upper bells of the chamber 3 through at least one reintegration valve 20 communicating with a suction point 6a and/or 6b.

In particular, two valves 20, 30 may be provided for the reintegration of air between the upper chamber and the partialiser and for the reintegration of gas in the lower chamber, respectively.

Subsequent to the reintegration or creation of a controlled atmosphere in the chamber 3, the film is thus heat sealed and cut at the edges of the tray.

In the second case, represented by way of example in fig. 1a, the heat sealing unit is provided inside the lower and upper bells 1 , 2, respectively, with a lower mould or tank 25 with a housing 26 for the tray and an upper heat sealing plate 27 which can be superimposed on the mould 25.

The heat sealing means comprise first and second heat sealing bars 4a, 4b respectively associated with the mould and the plate and which in operation can be mutually placed side by side at the peripheral edge of the tray V.

In different embodiments and types of film used (flat or single-folded), the bars 4a, 4b may be arranged in an “L” or “C” shape at different peripheral edges so as to be able to completely seal the open flaps of the film at the tray.

In order to obtain the “skin” effect, the plate 26 can be provided with a heated wall 29 equipped with holes 30 communicating with the upper bell 2 useful in combination with the pressure in the lower chambers which pushes the film into contact with the upper plate to suck and retain the film (f) in contact with the wall 29 in the presence of main vacuum in the upper bell 2 until the softening of the film is obtained and therefore, during the reintegration step, for the re- introduction of gas into the upper chamber.

After heating the film, the process includes a reintegration step with the introduction of air into the upper chamber through the holes 30 (possibly part of the air can also be introduced into the lower chamber) and then the heat sealing step, for example by sealing and cutting bars, for example by peripheral blades 45, of a type known per se, outlined in fig.1 a. Still with reference to the machine of fig.1 A, in a possible packaging process the following steps can be included, given by way of example

1 ) Start: partialiser configured to partialise at 50%-50% between the two chambers.

This initial balancing has the purpose of preventing the film from being “sucked’Vpushed too violently against the welding plate at the start and preventing the film from being damaged;

2) Step of reaching the set vacuum (99% vacuum). In this step the partialiser operates so that there is always a little bit more vacuum in the upper chamber in order to keep the film in contact with the heating plate 29.

3) Maintenance step, for a certain time the pump keeps the set vacuum to allow the film to further heat;

4) As soon as the film has the desired temperature, the partialiser can move and create slightly more vacuum in the lower chamber where the product is located, allowing the film to rest gently on the product;

5) When the partialiser is in the desired step, the air is reintegrated.

In a further operating example, the following configurations of the partialiser may be implemented, which will vary depending on the vacuum level reached to achieve and maintain a difference of 1% of the vacuum with prevalence in the upper chamber.

Vacuum Level 0%

Partialiser opening: (upper 55%-45% lower)

Vacuum Level 50%

Partialiser opening: (upper 60%-40% lower)

Vacuum Level 90%

Partialiser opening: (upper 65%-35% lower)

Vacuum Level 95%

Partialiser opening: (upper 75%-25% lower)

Vacuum Level 98%

Partialiser opening: (upper 90%-10% lower).

The invention provides important advantages due to the fact that it is possible to obtain an effective vacuum management and balance in the heat sealing unit and the continuous adjustment of the pressure difference between the two chambers which can be performed according to the vacuum achieved.

In particular, in the initial suction step of the air present in the tank (lower and upper chamber), the partialiser of the invention allows the control of the flow out of the lower and upper chamber ensuring a very fast and flexible management of the degree of desired, absolute and relative vacuum of each chamber. Furthermore, subsequently, when a step of re-introducing or re-integrating air or gas is implemented, the partialiser allows independent control of the flow into the lower and upper chambers so as to create precisely controlled overpressure in the desired chamber so that the overpressure control must be precise and vary according to the packaging desired. For example, in the particular case of a “skin” effect machine, in order to obtain a good effect the overpressure must be high, but at the same time it is useful to be able to reduce it in the case of “skin” packages of foods in “weak” trays such as cardboard or expanded PS. On the contrary, in the case of packaging in a controlled atmosphere it is desirable to avoid an excessive pressure difference to prevent the film from moving and being marked by the sealing plate. Further, an overpressure with respect to the atmospheric pressure in the package is useful in counteracting the collapse of the package due to the absorption of C02 in the food (especially beef).

A further advantage is that it is possible to include an automatic adjustment of the flow partialiser which avoids manual modifications to be performed on the vacuum management system when switching from packaging in controlled atmosphere mode to packaging with a “skin” effect using the same heat sealing unit.

These application examples are given by way of example, but it is understood that the unit of the invention may also be used in different packaging processes which require the realisation of vacuum conditions in two bells of a sealing chamber of a film to a tray.

The present invention has been described according to preferred embodiments, but equivalent variants can be conceived without departing from the scope of protection granted.

Claims

1. Heat sealing unit (U) for packaging machines of products (P) contained in a tray (V), comprising: a lower bell (1), an upper bell (2) which can be fluid-sealingly superimposed on the lower bell to define a heat sealing chamber (3), the lower and upper bells being mutually movable between a non operative offset position and a sealed overlapping operating position in which the lower bell and the upper bell are separated from the film (f), means (4a, 4b) for heat sealing a film (f) to a peripheral edge (5) of a tray (V) at said operating position of the bells (1 , 2), at least one vacuum source (7) suction points (6a, 6b) connected to the vacuum source (7) to create vacuum inside at least said lower bell and/or said upper bell characterised in that it comprises a flow partialising device (8, 80) interposed between said vacuum source (7) and first and second suction points (60a, 60b) respectively of said lower and upper bells (1 , 2) and provided with adjustment means (9, 90) for independently partialising the inflows and outflows into and from the lower and upper bells based on the vacuum level created by said source.

2. Unit according to claim 1 , wherein said adjustment means (9, 90) partialise said flows continuously.

3. Unit according to claim 1 or 2, wherein said adjustment means (9, 90) comprise a three-way valve connected to the source (7) and to the lower and upper bells (1, 2) which can be operated by means of an actuator (10, 100) between a maximum partialisation position towards the lower bell and a maximum partialisation position towards the upper bell.

4. Unit according to claim 3, wherein said three-way valve comprises a first outer hollow sleeve (11) provided with at least two openings (12, 13) communicating respectively with the suction points (6a, 6b), inside which a second inner sleeve (14) communicating with the vacuum source (7) and provided with openings (15, 16) facing said openings (12, 13) of the outer sleeve (11) flows tightly between two end positions so as to each define a suction port (17, 18) of variable dimensions between a maximum dimension and a minimum or no dimension, and vice versa, at the sliding of the inner sleeve (14) between said end positions.

5. Unit according to claim 4, wherein said inner sleeve (14) is integral with the movement of the control stem (19) of a linear actuator (10).

6. Unit according to claim 3, wherein said partialiser (80) comprises a casing (81), a chamber (82) is realised communicating through respective openings (84, 85, 86) with the vacuum source (7) and the suction points (60a, 60b) of the lower and upper bells (1 , 2), inside the chamber (82) being able to rotate a rotating shutter (87).

7. Unit according to claim 6, wherein said shutter (87) comprises three radial branches (88, 89, 91) in fluid communication with each other, the shutter (87) being moved by an actuator shaft (100) so as to selectively communicate the branches (88-91) of the shutter with the openings (84-86) of the chamber (82) depending on the angular position assumed.

8. Unit according to one of the preceding claims, comprising at least a reintegration valve (20, 30) communicating with a suction point (6a, 6b) for the introduction of air or gas into at least one of said lower and/or upper bells.

9. Unit according to any one of the preceding claims, comprising at least one pressure sensor (21 , 22) applied to detect the internal pressure in at least one of said lower and upper bells.

10. Unit according to one of the preceding claims, comprising a filter (23) interposed between the source (7) and the partialiser (8).

11. Unit according to one of the preceding claims, comprising a safety valve (24) interposed between the source (7) and the partialiser (8).

12. Unit according to one of the preceding claims, comprising at least a lower mould (25) with a housing (26) of at least a tray (V) and an upper heat sealing plate (27) which can be superimposed on the mould (25), said mould (25) and said plate (26) being arranged inside the lower and upper bells (1, 2), respectively, at least in said operating position, wherein said heat sealing means comprise first and second heat sealing bars (4a, 4b) associated respectively with the mould (25) and the plate (26) and which can be mutually placed side by side at at least a portion of the peripheral edge of the tray (V).

13. Unit according to claim 12, wherein said plate (26) is provided with a heated wall (29) equipped with suction holes (30) communicating with the upper bell (2) to retain the film (f) in contact with the wall (29) in the presence of vacuum in the upper bell (2).