DE SCRIPTION

Background and summary of the invention

The present invention relates to a device for welding o f packages for packaging machines , which can also be used in a process for production o f packages under vacuum, and therefore also in machines which are provided with tanks or chambers for the vacuum.

As is known, packaging machines can be horizontal or vertical, o f a manual or automatic type, and are used to obtain finished packs of bulk products . In automatic packaging machines , a certain quantity o f bulk pro duct is introduced into a ho llow tubular element which provides the form o f the package to be obtained. Around this tubular element there is wound a film made o f p lastic material which is drawn downwards, and is subj ected to longitudinal welding by means o f welding means . When this longitudinal welding has been comp leted, the film which will form the pack o f product must b e welded in a transverse direction, in order to close the top and bottom o f the packs . In machines which are under vacuum, at the exit from the tubular forming element each package must be introduced into a tank or chamber for the vacuum.

Downstream from the tubular forming element, devices are provided for transverse welding o f the top and bottom o f the p acks , and for separation o f them. These devices can have very large dimensions, they may have a low level o f efficiency, and they require complicated actuating means for movement o f the welding heads , including in the case o f application o f these devices to the machines which are under vacuum, in which it is necessary to guarantee the air tightness o f the tank or chamber for the vacuum.

The obj ect o f the present invention is thus to provide a device for welding o f packages for packaging machines , which, by means of the use of a single actuating motor, makes it possible to transform the rotary motion of this motor into alternating linear motion o f the welding bars, such as to move them away and bring them clo ser, optionally also at a variable speed. Thanks to double-lever actuating means, this device is particularly compact and efficient, and can be used with major structural advantages also inside tanks or chambers for the vacuum of packaging machines which are under vacuum.

This object is achieved by the present invention by means of a device for welding of packages for packaging machines according to Claim 1.

Brief description of the drawings

Other advantageous characteristics of the present device for welding of packages for packaging machines are the subject of the dependent Claims.

Further characteristics and advantages of the present invention will be better understood in the course of the following description, which is considered by way of non-limiting example with reference to the attached drawings, in which:

- Figure 1 illustrates a first view in lateral elevation of a first embodiment of a device for welding of packages for packaging machines, which, according to the present invention, is provided with double-lever actuating means, and is in a first, open position with the welding bars at the maximum distance from one another;

- Figure 2 illustrates a view from above of the present device in Figure 1, in the open position;

- Figure 3 illustrates a second view in lateral elevation of the first embodiment of the present device, in a completely closed position, and with a minimum distance or gap between the welding bars;

- Figure 4 illustrates a view from above of the present device in Figure 3, in the closed position;

- Figure 5 illustrates a first view from above of a second embodiment of the present welding device provided with double-lever actuating means, and in a first open position with the welding bars at the maximum distance from one another;

- Figure 6 illustrates a view in lateral elevation of the double-lever actuating means of the present device in Figure 1, in the position in Figure 5;

- Figure 7 illustrates a second view from above of the second embodiment of the present device, in a second, closed position, with the welding bars at the minimum distance from one another; and

- Figure 8 illustrates a view in lateral elevation of the double-lever actuating means of the present device in Figure 7 in the closed position in Figure 7.

Description of the preferred embodiment of the invention

With reference to these appended drawings, and with particular reference to Figures 1 and 2 of the drawings, 15 indicates a chamber for the vacuum of a packaging machine which is under vacuum, for example a device for the production of packages under vacuum such as that described in patent application GE2011 A000006 which belongs to the holder of the present application. This chamber 15 for the vacuum, which is illustrated partially and schematically, comprises a lower container 16, which for example has a rectangular form, and an upper box-shaped frame 17. This frame 17 is provided in its upper part with a first opening 18, which can be closed hermetically by a sliding cover 19, and it is provided in its lower part with a second opening 20 for the passage of the packages to the lower container 16, which is provided with means, not illustrated, which can create the vacuum inside the chamber 15, and therefore put each package under vacuum. Each of the packages which reaches the chamber 1 for the vacuum, see for example the package P which is illustrated in Figure 2, is welded completely at the bottom, whereas at the top it has been welded partly. The final welding of the top of each of the packages is carried out by means of two welding bars 5 and 5', which are aligned transversely and are opposite one another. These bars are actuated by means of a device for transmission of motion, comprising a support structure 1 for two pairs of parallel horizontal guides 2 and 2'. This support structure 1 is entirely contained inside the chamber 15 for the vacuum. A pair of slides or runners 3 and 3' slide on the guides 2 and 2'. Each of these runners 3 and 3' is substantially a rectangular plate which is provided with four through holes, see for example the through hole 103, in which the two pairs of guides 2 and 2' are inserted. The runner 3 and the runner 3' positioned on each guide 2 and 2' translate simultaneously and in directions opposite to one another, then they are moved away from one another, or are brought closer to one another. The runner 3', which, looking at the Figures is disposed on the right-hand side of the device, is in a specular position, relative to a median plane M of the device, in relation to the runner 3 which is placed on the left-hand side. The runner 3' which is situated on the right-hand side supports a first plate 4', substantially in the form of an "L", which is placed in a specular position, relative to the median plane M, in relation to a second plate 4, which is substantially in the form of an "L", and is supported by the runner 3 which is situated on the left-hand side of the device. Each of these plates 4 and 4' supports respectively one of the said welding bars 5 and 5', which must be translated in one direction or the other. These bars 5 and 5' are also in a specular position relative to the median plane M of the device. Each of the slides 3 and 3' is connected by means of a small plate 6 and 6' provided with a corresponding pin 7 and 7' to a first final part of a corresponding arched lever: the pin 7 is connected to the free final first part 108 of a first arched lever 8, whereas the pin 7' is connected to a free final first part 108' of a second arched lever 8'. These final first parts 108 and 108' of the arched levers are in diametrically opposite positions. These arched levers 8 and 8' can have the form of an arc of a circumference, an arc of an ellipse or the like, and they are preferably the same. Each of these arched levers 8 and 8' comprises a second final part 208 and 208' which is connected to a support plate 9, in this case with a circular form. The second final part 208 of the arched lever 8 is connected to this plate 9 by means of a pin 10, around which this lever 8 can rotate, whereas the second final part 208' of the arched lever 8' is connected to the plate 9 by means of a pin 10' around which this lever 8' can rotate. The pins 10 and 10' and therefore the final parts 208 and 208' of the levers 8 and 8' are located in the vicinity of the periphery of the said plate 9, and in diametrically opposite positions relative to the plate. This support plate 9 is connected centrally to the shaft 11 of an electric motor 12, which is secured to a wall of the box-shaped frame 17 of the chamber or tank 15 for the vacuum. In the situation in Figures 1 and 2, the present device is illustrated in the open position, in other words with the welding bars 5 and 5' at the maximum distance L from one another, and therefore in this situation the package P can easily pass through the free space left between the said bars 5 and 5'.

In Figures 3 and 4, the present device is illustrated in the closed position, in other words with the welding bars 5 and 5' at the minimum distance from one another. In this situation, if the present device is applied to a device for production of packages under vacuum, such as that described in patent application GE2011 A000006 belonging to the holder of the present application, these bars 5 and 5' complete the welding of the top of the package P in the preceding Figures. In fact, this package reaches the chamber 15 for the vacuum with the bottom completely welded and with the top partially welded, and it is suitably positioned inside the lower container 16 of the said chamber 15. In this stage, the cover 19 hermetically closes this chamber 15 for the vacuum.

By means of the present welding device with double-lever actuation, the two welding bars 5 and 5' can pass at the required speed from the open position to the closed position, and vice versa. For example, in order to pass from the open position in Figures 1 and 2 to the closed position in Figures 3 and 4, in which the welding bars 5 and 5' complete the welding of the top of the package, the motor 12 is actuated such that the shaft 11 makes the plate 9 rotate by approximately 90° in the direction of the arrow R in Figure 1. Simultaneously with the rotation of the plate 9, there is also synchronous rotation of the arched levers 8 and 8' around the respective rotation pins 10 and 10', in the direction opposite that of the direction R of the support plate 9. When this rotation of the plate 9 is completed, the end parts 208 and 208' of the levers 8 and 8' will also have rotated by 90° in the direction of the arrow R, whereas the final parts 108 and 108' of the levers, and therefore the welding bars 5 and 5', will have been brought closer to one another (in this respect compare Figures 1 and 3 and Figures 2 and 4). In the passage from the open position to the closed position or vice versa, one of the two levers passes below the other. In this case the arched lever 8' passes below the lever 8, and thus the levers 8 and 8' can cross one another, naturally without any interference with one another. In order to pass from the closed position to the open position, when the bars 5 and 5' have completed the welding of the top of the package, it will be necessary to actuate the motor such that the plate 9 completes a rotation of approximately 90° in the direction of the arrow R' in Figure 3, opposite to the direction of the arrow R in Figure 1. As can be seen, when the rotation is completed, the rotation pins 10 and 10' of the final parts 208 and 208' of the respective arched levers 8 and 8' are still in a diametrically opposite position on the plate 9.

Depending on the dimension and form of the arched levers, as well as on the distance between the corresponding mobile parts, the angle of rotation which is imparted by the motor 12 to the plate 9 can be other than 90°.

The speed of bringing closer and moving away of the welding bars 5 and 5' is variable for the same speed of rotation of the motor 12, and in particular the speed of initial bringing closer, as well as that of final moving away in the opposite phase, of these two bars 5 and 5', is high, whereas when the bars are at a sufficiently close distance, there is distinct slowing down of their bringing closer, until the situation of minimum distance in Figures 3 and 4 is reached. Consequently these bars 5 and 5' are brought quickly closer to the package edges to be welded, whereas when these bars reach the vicinity of the said edges and come into contact with them, they will undergo distinct deceleration, so as to have adequate time to carry out the welding. In the same manner, whilst they are being moved away, these bars 5 and 5' will have substantially a first, relatively slow phase of detachment from the edges of the package, and a second, relatively fast phase of moving away from one another, such as to allow the package to pass through the bars which are once more in the open position, as in Figures 1 and 2.

Figures 5 and 6 illustrate a second embodiment of the present device applied to automatic packaging machines for production of packages, which device is not under vacuum, and comprises a support structure 21 in which the two horizontal and parallel guides 2 and 2' are provided. In this packaging machine, each package P which is obtained from a tubular forming element, not illustrated, must be welded transversely to the top and bottom, and also the packages in sequence must be separated from one another. It will be appreciated that the support structure 21 is provided with a central aperture 23 for the passage of each package P. In this case, the plates 4 and 4' support double welding bars 22 and 22'. The bar 22 comprises an upper 122 and lower 222 welding head between which there is provided a seat 322 for accommodation of a tool, not illustrated, for cutting and separation of one package from another in the packaging process. This cutting tool will be provided with corresponding actuators which allow it alternately to exit from the said seat 322 and return into it. The bar 22' also comprises two welding heads 122' and 222', which are aligned transversely to the heads 122 and 222 of the bar 22. Between these heads there is provided a seat 322' in which there is accommodated a counter-blade, not illustrated, which can co-operate with the cutting tool which emerges from the seat 322 of the bar 22. The double-lever actuating means of these bars 22 and 22' are altogether similar to those described for the first embodiment of the device, and therefore the same numbers correspond to the same elements as those described in Figures 1 - 4. To each of the plates 4 and 4' there is also connected an element 24 and 24' for support of a device for folding the edges of plastic material film of two opposite sides of the top or bottom of the package, and preferably the two short sides of the package. This folding device comprises two folding plates 25 and 25' which can be brought closer to one another and moved away from one another in the longitudinal direction, i.e. in the direction at right-angles to the transverse direction of alternate sliding of the bars 22 and 22' along the guides 2 and 2'. Each of the two plates 25 and 25' is provided with a suitably pointed end in order to fold the edges of the top or bottom of the package P, and a pin 26 and 26' is positioned on the plates. This pin 26 and 26' is accommodated inside a cam track 27 and 27' which is connected to the respective support element 24 and 24'.

In order to pass from the open position in Figures 5 and 6 to the closed position in Figures 7 and 8, in which the welding bars 22 and 22' carry out the welding of the top of a particular package, the welding of the bottom of the successive package, and the separation of these packages, the motor 12 is actuated such that the shaft 11 rotates the plate 9 by approximately 90°, similarly to the situation seen in Figure 1. Simultaneously with the rotation of the plate 9, there is synchronous rotation of the arched levers 8 and 8' around the respective rotation pins 10 and 10', in the direction opposite the direction of rotation of the support plate 9. When this rotation of the plate 9 is completed, the end parts 208 and 208' of the levers 8 and 8' will also have rotated by 90°, whereas the final parts 108 and 108', and therefore the welding bars 22 and 22', will have been brought closer to one another. Substantially, by means of a single rotation of the motor 12 in one direction and for a limited angle, there is simultaneous transverse translation which brings the welding bars 22 and 22' closer in the direction of the arrows B and B' in Figure 5, and at the same time simultaneous longitudinal translation which brings the two folding plates 25 and 25' closer to the edges of the short sides of the package in the direction of the arrows A and A' in Figure 5. In order to pass from the closed position to the open position, when the bars 22 and 22' have completed the welding of the top of a package, the welding of the bottom of a successive package, and the separation of the packages, it will be necessary to actuate the motor such that the plate 9 completes a rotation of approximately 90° in the direction opposite the one previously described.