WO2009135747A1

WO2009135747A1 - Carousel-type automatic packaging machine of products in bags

Info

Publication number: WO2009135747A1
Application number: PCT/EP2009/054399
Authority: WO
Inventors: Roberto Talacci
Original assignee: Perfect Pack S.R.L.
Priority date: 2008-05-08
Filing date: 2009-04-14
Publication date: 2009-11-12
Also published as: EP2288549B1; EP2288549A1; ITMC20080070A1; PL2288549T3; ES2427266T3

Abstract

The present invention relates to a carousel-type automatic packaging machine (m) of products in bags (s), comprising a series of pairs of grab pliers, each of them being designed to grab a single bag (s) and installed in saddles (4) used to move it through the various filling and sealing stations (sr).

Description

Carousel-type automatic packaging machine of products in bags.

The present patent application for industrial invention relates to a carousel-type automatic packaging machine (m) of products in bags (s), comprising a series of pairs of grab pliers, each of them being designed to grab a single bag and installed in saddles used to move the bag through the various filling and sealing stations.

Machines of this type are used to fill bags of any shape or size with powders, liquids or tissues, and to seal each bag.

Following is a diagrammatic description of the current constructive layout of the said automatic machines and relevant support means for the pairs of pliers, in order to point out the drawbacks

In the said packaging machines, each bag to be filled is grabbed by a pair of pliers, designed to support it in vertical position, adjacent to the bag supported by the pair of pliers in immediately preceding or subsequent position. In the case of a standard rectangular bag, it can be said that each bag is grabbed by a pair of pliers in the two upper corners or, more precisely, on top of the vertical right and left side. As soon as it is grabbed, the bag is transported along a series of stations in order to be first filled and then sealed The first station opens the bag in order to fill it with the content, which can be either of solid or liquid type, as mentioned above.

When the bag is in vertical transportation position, each bag is composed of two sheets with identical size, a front sheet and a back sheet, joined on three sides, and precisely on the opposite pair of vertical sides and on the lower horizontal side.

The two upper horizontal sides of the two sheets that are not joined are first separated in order to fill the bag and then moved close and joined in order to seal the content that was previously inserted in the bag.

In order to open the bag, starting from the condition in which the two upper sides of the two sheets are aligned and engaged one against the other one, the two grab pliers make an advance travel in order to open the mouth of the bag.

After filling the bag, the pliers make a separation travel until they reach their initial distance, in such a way that the upper sides of the two sheets return in close position before reaching the sealing station, in which the mouth of the bag is sealed. The said pairs of pliers are installed on corresponding support saddles that can support two or more pliers, according to the model of saddle.

In case of saddles that support two pliers only, the pliers can move closer or farther, being evident that each pair of pliers supports only one bag.

Saddles that support four pliers are known, which have the same configuration as the saddles with two pliers, except in that each saddle supports two pairs of pliers in order to support two bags.

Special saddles are known, in which a pair of bags is grabbed by three pliers, of which one is a central fixed pliers, and two are lateral mobile pliers; the only difference of this type compared to the one described above consists in that the central fixed pliers must be provided with two opposite jaws, one rightwards and one leftwards, in order to cooperate with the right-hand mobile pliers and the left-hand mobile pliers, respectively.

For the sake of simplicity, the description of the invention continues with reference to a saddle that supports three pliers, it being understood that the invention may be applied, with the same efficacy and the same advantages, to saddles that support one pair of pliers only or multiple pairs of pliers.

As mentioned above, a saddle for three pliers, of known type, comprises a central fixed pliers and two lateral mobile pliers, designed to translate simultaneously in opposite directions, in order to increase or decrease their distance from the central pliers In this way, each saddle can support two bags in adjacent coplanar position, which are supported by the central pliers on the side facing the centre of the saddle, and by the corresponding lateral pliers on the side facing the lateral side of the saddle More precisely, the central pliers is provided with a pair of opposite jaws, in such a way that the pliers can grab a first bag on the right and a second bag on the left, while the lateral pliers are provided with a pair of jaws that face the central pliers

The three pliers are in parallel direction and each pair of jaws comprises a mobile jaw and a fixed jaw.

Moreover, the saddle is provided with actuation means of the mobile jaw of each pliers, which are designed to push the mobile jaw forward, moving it away from the fixed one, and bring it back to closing position.

The said machines of known type are also provided with adjustment means designed to adjust the distance between all pairs of mobile pliers from the corresponding fixed pliers since, after choosing the size of the bags to be packaged, all mobile pliers must be separated from the central fixed pliers of a predefined value suitable to the size of the bag to be packaged.

For evident volume reasons, in all automatic packaging machines the said saddles are mounted according to a closed, preferably circular, arrangement to minimise the total volume of the machine, which is consequently identified as "carousel machine".

In the most typical case of machines with carousel structural configuration, each saddle is fixed to a revolving articulated coupling, one next to the other one, in such a way that the rotation of the articulated coupling results in the simultaneous movement of all the saddles.

It must be noted that the pliers are fixed on the saddle with the jaws facing the outside of the carousel, in such a way that the back of the pliers and the back of the saddle face the centre of the carousel. Therefore, the three pliers of each saddle are not in parallel position to the sets of three pliers of the adjacent saddles; in fact, the longitudinal axis of - A -

each lateral pliers forms, with the longitudinal axis of the adjacent lateral pliers, a convergence angle that varies according to the number of saddles arranged around the circumference of the said articulated coupling.

In view of the above, the longitudinal axes of two adjacent lateral mobile pliers, which belong to two adjacent saddles, converge towards the centre of the carousel, in such a way that the distance between the back end of two adjacent lateral mobile pliers, supported by corresponding adjacent saddles, is by far lower than the distance of the jaws situated in the front ends of the same pliers. With reference to the current models of carousel machines, additional drawbacks consist in the fact that all the filling devices of the bags are situated in external position to the saddles and therefore also in external position to the bags grabbed by the pliers.

For this reason, it is currently necessary to provide a series of support surfaces under the bags, in order to support the filling devices

The said surfaces are situated under the filling stations of the bags, with the risk of being easily dirtied because of the inaccurate distribution from the nozzle, and also because of the accidental breakage of the bags during filling. Another drawback caused by the external position of the said support surfaces with respect to the saddles consists in the increased radial volume of the machine.

Moreover, it must be noted that the current models of carousel packaging machines are provided with two handling devices of the mobile pliers, one being designed to adjust the distance between the pliers according to the width of the bag to be filled, and one being designed to open the bag.

More precisely, the said adjustment means of the distance of the mobile pliers consist in two concentric rings with identical diameter on which the mobile pliers designed to support the bags are mounted.

With each set of three pliers comprising a right-hand mobile pliers and a left-hand mobile pliers, all the right-hand pliers are currently supported by the said first ring, and all the left-hand pliers are supported by the said second ring.

The said rings must be rotated in opposite direction in order to adjust the distance between each pair of pliers, thus increasing or decreasing the distance between all the pairs of pliers.

The devices designed to open the bag consist in oscillating supports, one for each pliers, which are oscillated by means of a cam system.

More precisely, each pliers is supported by a support bracket that oscillates with respect to a vertical axis, which is actuated by a cam system in such a way that when the bag reaches the filling station, the bag is opened by getting the supporting pliers closer; after filling, the bag is brought back to its original position, by oscillating the pliers in opposite direction by the same rotation angle. The purpose of the present invention consists in devising a carousel- type packaging machine of products in bags, in which the devices used to open the bag coincide with the devices used to adjust the distance between each pair of pliers.

These and other purposes have been achieved by the packaging machine of the invention, whose main characteristics are illustrated in the first claim.

The machine of the invention provides for the installation of a series of saddles on a revolving articulated coupling, each saddle supporting a fixed pliers in the centre and a pair of mobile pliers on the sides, being designed to make advance and withdrawal travels, sliding along a transversal track that supports them.

The said mobile pliers are actuated by means of a worm-type mechanism, which is actuated by adjustment devices situated on the back of the frame. The adjustment devices are designed both to adjust the distance and to open the bag inside each pair of pliers. Moreover, the said saddle is provided with a flange used to fix it on a revolving articulated coupling situated in external position on an innovative central structure with basket-like configuration, which supports the control devices of the handling devices of the mobile pliers. For major clarity the description of the saddle that supports the pliers according to the present invention continues with reference to the enclosed drawings, which only have an illustrative, not limiting purposes, wherein:

- figures 1A, 1 B and 1 C are views from different angles of an automatic packaging system of products in bags, in which the carousel-type machine of the invention is used;

- figures 2 and 3 are a perspective view and a plan view of the carousel machine of the invention, respectively;

- figure 4 is an axonometric rear view of the saddle used in the carousel machine of the invention to support the pliers used to grab the bag; - figure 5A is an exploded view of the fixed pliers mounted in the centre of the saddle of figure 4, seen from an angle perpendicular to the longitudinal axis;

- figure 5B is an exploded view of one of the two mobile pliers mounted on the two sides of the saddle of figure 4, seen from an angle perpendicular to the longitudinal axis;

- figure 6 is a top view of the set of three pliers of the saddle of figure 4.

With reference to figures 1A, 1 B and 1 C, the carousel-type packaging machine (M) of the invention is designed to be used in a system (I), of known type, which also includes devices designed to make packaging bags starting from reels (B) of film, in such a way to automatically feed the machine (M) with a series of bags (S) arranged on a vertical plane and designed to be taken by the said machine (M) by a series of pairs of pliers designed to grab each bag (S) at the lateral ends of the upper opening. More precisely, the said pairs of grab pliers are mounted on a series of identical saddles (1 ) that are moved automatically, with intermittent advance travel, under the filling devices, of known type, of the bags (S).

With reference to figure 4, each saddle (1 ) is provided with a central frame (2) with a lower flange (3) for anchoring above a revolving articulated coupling (4). The frame (2) supports a coaxial pair of identical transversal threaded bars (5) with horizontal axis that protrude from both sides of the frame (2) and are driven into rotation by means of a mechanism that comprises a worm in orthogonal position to the threaded bars (5), with head (6) protruding on the back of the frame (2). The frame (2) is centrally provided with a seat for insertion of the body

(7) of the fixed central pliers (PF) that must be positioned with axis (D-D) in horizontal position and perpendicular to the axis (F-F) of the said coaxial pair of transversal bars (5).

The fixed pliers (PF) is firmly anchored to the frame (2) with suitable means (8) that consist in screws and corresponding threaded holes according to a preferred embodiment.

With reference to figure 2, the body (7) of the central pliers (PF) is provided with an annular flange (9) with holes (9a) that receive screws (10), which engage inside threaded holes obtained directly on the front of the frame (2).

The frame (2) is frontally provided with a transversal bar (1 1 ) in parallel position to the axis (F-F) of the threaded bars (5), having the same length.

The transversal bar (1 1 ) acts as guide track for the opening and closing travels of the two lateral mobile pliers (PM).

With reference to figure 5, each lateral pliers (PM), as well as each fixed pliers (PF), has an empty body (7, 12), in which a stem (13) is inserted and slides, with the tip (13a) frontally protruding from the body (7, 12), and the head (13b) of the stem (13) protruding on the back. A return spring (14) is positioned between the head (13b) of the stem

(13) and the back of the body (7, 12) and pushes the stem (13) towards the back of the pliers (PM or PF).

Each pliers (PM or PF) is frontally provided with a fixed jaw (15, 15M) composed of a plate fixed on the front of the body (7, 12), which is provided with a central hole in which the stem (13) of the pliers (PM or PF) slides, being provided on the tip (13a) with a mobile jaw (16, 16M) that is interfaced with the corresponding fixed jaw (15, 15M).

The stem (13) is laterally provided with a radial pin (13c) designed to slide inside a slot (7a, 12a) internally obtained on the body (7, 12), which acts as cam for the said pin (13c), in such a way that during the advance travel of the stem (13), in addition to translating forward with respect to the body (7, 12), the stem (13) is forced to make a 90° rotation with respect to its axis that coincides with the axis (A-A; D-D) of the pliers (PM or PF).

When the pliers (PM or PF) is actuated to determine the opening of the mobile jaws (16 and 16M), the spring (14) is compressed and the mobile jaw (16, 16M) makes a forward roto-translation, being joined to the tip (13a) of the stem (13).

With reference to figure 4, all the three pliers (PM or PF) have the same structural configuration, except for that the fixed pliers (PF) is provided in external position on the body (7) with an annular flange (9) firmly fixed to the frame (2), and the annular flange (17) obtained in external position on the body (12) of the two mobile pliers (PM=PR) is fixed to a sleeve (18) obtained above a slide (19) that can translate laterally with respect to the central frame (2) and allows the mobile pliers (PM=PR) to move closer or farther with respect to the fixed pliers (PF). The slide (19) is provided with a threaded hole in which the threaded bar (5) is engaged; it being evident that, by rotating both threaded bars (5) simultaneously, the two mobile pliers (PM) slide along the transversal bar (1 1 ), getting closer or farther with respect to the central pliers (PF) according to the rotation direction of the threaded bars (5). With reference to figures 5A and 5B, each body (12) of the collapsible mobile pliers (PM=PR) has a longitudinal axis (A-A) that coincides with the axis of the stem (13) that slides inside it and actuates the mobile jaw (16M).

Each pair of jaws of a fixed pliers (PF) identifies a single grab plane (Pf), and each pair of mobile pliers (PM) identifies a grab plane (Pa).

With reference to figure 6, it can be noted that the plane (Pf) of the fixed pliers (PF) is aligned with the plane (Pa) of the two corresponding mobile pliers (PM).

With reference to figure 4, a horizontal plate (50) is fixed on the frame (2), facing the back of the saddle (1 ), under which a track (51 ) is fixed, on which a saddle (52) slides to push forward the stems (13) of the pliers (PM and PF) simultaneously, opening the mobile jaws (16 and 16M).

More precisely, the saddle (52) has an overturned L-shaped section, whose horizontal wing (52a) is provided with means (52d) designed to cooperate with the guide and slide track (51 ), while a revolving roller (53) with vertical axis is provided on the back of the vertical wing (52b). The length of the vertical wing (52b) is practically identical to the length of the transversal bar (1 1 ) and the front side (52c) is parallel to axis (F-F).

The front side (52c) of saddle (52) is interfaced with the head (13c) of the stems (13) of the pliers (PM and PF) supported by the saddle (1 ), allowing the stems (13) to move forward as soon as the saddle (52) is actuated and pushed forward.

As mentioned above, when the stem (13) is pushed forward, it makes a roto-translation with respect to its axis (A-A; D-D) and the mobile jaw (16 or 16M) is separated from the fixed jaw (15 or 15M). Since the head (13b) of the stem (13) is joined to the stem (13) and it makes a roto-translation, a revolving ball (13d) is mounted in idle on the head of each stem (13) to avoid excessive friction.

With reference to figures 2 and 3, it can be noted that each saddle (1 ) is fixed on a revolving articulated coupling (4) situated in external position in a central tower (21 ).

As shown in fig. 3, eight saddles (1 ) as the ones illustrated above are anchored with screws on the articulated coupling (4), and the central tower (21 ) has a cage-like structure, composed of a series of eight vertical uprights (22), which are identical and regularly spaced, connected on top by an annular plate (23) with regular octagonal external profile and circular internal profile.

A cover panel (24) with rectangular shape is inserted and screwed between each upright (22).

With reference to fig. 3, two of the cover panels (24) support on the back an electrical motor (26) with shaft in radial direction with respect to the articulated coupling (4) and laying on a horizontal plane.

The shaft drives a screwdriver into clockwise or anti-clockwise rotation, as necessary, whose tip (27) protrudes frontally from the cover (24) and is of flat type.

The flat tip (27) of the said screwdriver, in idle position, is always horizontal, and consequently the shaft of the electrical motor always makes angles equal to an entire multiple of 180°.

With reference to fig. 2, when the articulated coupling (4) is stopped, the tip (27) of the screwdriver is inserted into the seat (6a) obtained on the head (6) of the worm of the adjustment device mounted on the saddle (1 ) that momentarily stands in front of the tip (27) of the screwdriver.

When the articulated coupling (4) is stopped, the electrical motor (26) actuates the tip (27) of the screw, rotating it for a predefined number of times, and always going back to horizontal position before the articulated coupling (4) starts to move again. Although Fig. 3 shows two electrical motors (26) that correspond to two adjustment stations (SR) of the distance of the mobile pliers (PM), multiple adjustment stations (SR) may be necessary according to the different bags to be filled.

With reference to fig. 3, one of the cover panels (24) supports on the back a jack (28) with stem in radial direction with respect to the articulated coupling (4) and laying on a horizontal plane. The jack (28) is fixed to the panel (24) in such a way that the tip protrudes frontally from the panel (24), interfering with the roller (53) of the saddle (1 ) that momentarily stands in front of it.

As soon as the articulated coupling (4) stops, one of the saddles (1 ) stops in front of the actuator (28) that corresponds to the jaw opening-closing station (SG).

The advantage of a structure with central tower (21 ) and interchangeable cover panels (24) consists in the simplicity and inexpensiveness of changing the number and position of the adjustment stations (SR) as necessary, as well as the number of the jaw opening-closing stations (SG); it being evident that the said change only requires the installation of a new electrical motor (26) or a new jack (28), as illustrated above, in one of the cover panels (24).

In order to guarantee that the distance selected between the pairs of mobile pliers (PM) is not subjected to undesired changes during the movement of each saddle (1 ), between the two adjustment stations (SR), in external position on the structure with central tower (21 ), a guide track for the head (6) of the adjustment screw is fixed.

As shown in fig. 2, the track consists in an annular series of arched segments (29) with maximum thickness identical to the thickness of the tip (27) of the screwdriver; the said annular series of segments (29) is arranged along a circumference concentric to the articulated coupling (4).

The track (29) is positioned on a plane that coincides with the plane of the tip (27) of the screwdriver when the articulated coupling (4) is stopped. Moreover, the track (29) is positioned inside the seat (6a) obtained on the head (6) of the worm for the entire time in which each saddle (1 ) moves between an adjustment station (SR) and the following one, to avoid accidental rotations of the head (6) of the screw, which would correspond to undesired translation travels of the mobile pliers (PM).

Claims

1 ) Carousel-type automatic packaging machine of products in bags, comprising a series of pairs of pliers, each pair being designed to grab a bag (S) in vertical position on the lateral sides of the upper opening, wherein:

- the said pairs of grab pliers move forward and stand, with intermittent motion, under a series of filling devices, of known type, arranged along the circumference of said carousel machine;

- each pair of pliers has at least one mobile pliers (PM), and both pliers are provided with a body (7, 12), a fixed jaw (15, 15M) and a mobile jaw (16, 16M) that is interfaced with the corresponding fixed jaw (15, 15M);

- each pliers has a longitudinal plane (A-A; D-D) in horizontal and perpendicular position to the grab plane (Pf and Pa), on which the mobile jaw (16, 16M) and the fixed jaw (15, 15M) engage one against the other; - each mobile pliers (PM) is supported by means that allow for translation along an axis (F-F) horizontal and parallel to the grab plane (Pa);

- each pair of pliers is simultaneously actuated by means designed to move the mobile jaws; machine characterised in that each pair of pliers is supported by a frame (2) and in that the said means that support each mobile pliers (PM) and allow for translation along a horizontal axis (F-F) parallel to the grab plane (Pa) consist in:

- a threaded transversal bar (5) that protrudes laterally from the frame (2) and is rotated by a mechanism that comprises a worm with head

(6) protruding on the back of the frame (2);

- a corresponding transversal bar (1 1 ) joined to the frame (2), which is arranged on the same side of the frame from which the threaded bar (5) protrudes, and arranged in parallel position to axis F-F. - a support slide (19) for the sleeve (18), which is supported by the transversal bar (1 1 ) with possibility of sliding and has a threaded hole that engages with the thread of the threaded bar (5).

2) Machine according to the above claim, characterised in that the machine comprises an electrical motor (26) with shaft in radial direction with respect to the articulated coupling (4), which drives a screwdriver into clockwise or anticlockwise direction, with flat tip (27) always horizontal in idle position; it being provided that when the articulated coupling (4) is stopped, the tip (27) of the screwdriver is inserted in the seat (6a) obtained on the head (6) of the worm of the adjustment device mounted on the saddle (1 ) that momentarily stands in front of the tip (27) of the screwdriver.

3) Machine according to any of the above claim, characterised in that the frame (2) is provided on the back with a track (51 ) with a sliding saddle (52) designed to actuate the mobile jaws (16 and 16M) of each pair of pliers. 4) Machine according to the above claim, characterised in that the track (51 ) is positioned under a horizontal plate (50) fixed on the frame (2) and facing backwards.

5) Machine according to claims 3 and 4, characterised in that the saddle (52) has an overturned L-shaped section, with horizontal wing (52a) provided with means (52d) designed to cooperate with the guide and slide track (51 ), while a revolving roller (53) with vertical axis is provided on the back of the vertical wing (52b).

6) Machine according to the above claim, characterised in that the length of the vertical wing (52b) is practically identical to the maximum distance that can be reached by the pliers (PM) mounted on the frame (2) and in that the front side (52c) of the saddle (52) is parallel to axis (F-F).

7) Machine according to claims 5 or 6, characterised in that it comprises a jack (28) with horizontal stem in radial direction with respect to the articulated coupling (4), and with tip that pushes forward during the forward travel and actuates the trolley (52) of the saddle (1 ) that stands in front of it.

8) Machine according to claims 5 or 6, characterised in that it comprises a jack (28) with horizontal stem in radial direction with respect to the articulated coupling (4), and with tip that interferes during the forward travel with the roller (53) of the saddle (1 ) that stands in front of it.

9) Machine according to any of the above claims, characterised in that it comprises a guide track for the head (6) of the adjustment screw, which consists in an annular series of arched segments (29) with maximum thickness identical to the one of the tip (27) of the screwdriver and arranged along a circumference concentric to the articulated coupling (4); it being provided that the track (29) is positioned on a plane that coincides with the plane of the tip (27) of the screwdriver when the articulated coupling (4) is stopped and the track (29) is positioned inside the seat (6a) obtained on the head (6) of the worm.

10) Machine according to any of the above claims, characterised in that the articulated coupling (4) is situated in external position on a central tower (21 ). 1 1 ) Machine according to the above claim, characterised in that the central tower (21 ) has a cage-like structure, composed of multiple identical and regularly spaced vertical uprights (22), in the same number as the saddles (1 ) fixed on the articulated coupling (4).

12) Machine according to the above claim, characterised in that the uprights (22) are connected on top by means of an annular plate (23) with regular octagonal external profile, having as many sides as the vertical uprights (22).

13) Machine according to claims 1 1 or 12, characterised in that a cover panel (24) with rectangular shape is inserted and screwed between each upright (22). 14) Machine according to claim 13, characterised in that at least one of the cover plates (24) supports the electrical motor (26) in such a way that the tip (27) of the screwdriver protrudes on the front of the panel. 15) Machine according to claim 13 or 14, characterised in that at least one of the cover panels (24) supports a jack (28) with horizontal stem in radial direction with respect to the articulated coupling (4) and with tip protruding on the front of the panel. 16) Machine according to any of claims 9 to 15, characterised in that the annular series of arched segments (29) is fixed in external position on the structure with central tower (21 ).

17) Machine according to any of the above claims, characterised in that each pliers has an empty body (7, 12) in which a stem (13) is inserted and slides, with the tip (13a) frontally protruding from the body (7, 12), and the head (13b) of the stem (13) protruding on the back.

18) Machine according to the above claim, characterised in that a return spring (14) is positioned between the head (13b) of the stem (13) and the back of the body (7, 12) and pushes the stem (13) towards the back of the pliers.

19) Machine according to any of claims 17 or 18, characterised in that each pliers is frontally provided with a fixed jaw (15, 15M) composed of a plate fixed on the front of the body (7, 12), which is provided with a central hole in which the stem (13) of the pliers slides, supporting on the tip (13a) a mobile jaw (16, 16M) that is interfaced with the corresponding fixed jaw (15, 15M).

20) Machine according to any of claims 12 to 19, characterised in that the stem (13) is laterally provided with a radial pin (13c) designed to slide inside a slot (7a, 12a) obtained inside the body (7, 12), which acts as cam for the said pin (13c), in such a way that during the advance travel of the stem (13), in addition to translating forward with respect to the body (7, 12), the stem (13) makes a 90° rotation with respect to its axis (A-A; D-D).

21 ) Machine according to any of the above claims, characterised in that each pair of pliers is mounted on a frame (2) joined to a revolving articulated coupling (4) actuated by an electronic control unit.

22) Machine according to the above claim, characterised in that the frame (2) supports only one pair of pliers, with a first fixed (PF) and a second mobile (PM) pliers.

23) Machine according to claim 21 , characterised in that the frame (2) supports only one pair of pliers, both being mobile pliers (PM).

24) Machine according to claim 21 , characterised in that the frame (2) supports three pliers, a fixed central pliers (PF) and two lateral mobile pliers (PM), it being provided that the jaws (15 and 16) of the central pliers (PF) have two pairs of grab surfaces, a pair facing to the right and a pair facing to the left, which cooperate with the jaws (15M and 16M) of the right-hand lateral mobile pliers (PM) and the jaws (15M and 16M) of the left-hand mobile pliers (PM) on the left side, respectively, in order to support two bags (S).

25) Machine according to the above claim, characterised in that the frame (2) is provided with a central seat for insertion of the body (7) of the fixed central pliers (PF), which is positioned with axis (D-D) in horizontal position and perpendicular to axis (F-F) and is firmly anchored to the frame (2) with suitable means (8).

26) Machine according to the above claim, characterised in that the means (8) consist in an annular flange (9) provided with holes (9a) that receive screws (10) engaged inside threaded holes directly obtained on the front of the frame (2).

27) Machine according to any of claims 17 to 26, characterised in that the head (13b) of the stem (13) is provided with a revolving ball (13d) in idle.

28) Machine according to any of the above claims, characterised in that the frame (2) is obtained in a saddle (1 ) provided with a lower flange (3) for fixing above the revolving articulated coupling (4).