MXPA00003403A - Device for producing a scoring line in the cylindrical wall of a plastic cup, particularly of a plastic cup for closing a container, and machine using said device - Google Patents

Abstract

A device for producing a scoring line in the cylindrical wall of a plastic cup, comprising:a mandrel (8), provided with elements for positioning and retaining a cup applied thereon;a plurality of jaws (24), an end whereof is articulated to the mandrel (8) so as to oscillate on radial planes;respective circular arc-shaped blades (30) being applied to the opposite end of the jaws and being arranged on a plane which is perpendicular to the axis of the mandrel;actuation elements for the jaws being further provided, as well as elements for actuating the mandrel (8) with respect to the actuation means so as to actuate the arc-shaped blades (30) radially from a position which is external to the cup (11) to a position for engaging the wall of the cup at which the blades (30) form a scoring line in the wall.

Description

DEVICE FOR PRODUCING A CUT LINE IN THE CYLINDRICAL WALL OF A PLASTIC CUP, PARTICULARLY A PLASTIC COVER FOR CLOSING A CONTAINER. AND MACHINE USING SAID DEVICE 5 TECHNICAL FIELD The present invention relates to a device for producing a cutting line in the cylindrical wall of a plastic cup and to a machine using said device. The invention is used in particular in the so-called tamper evident caps composed of a cup and an obvious alteration ring that emerges from the rib of the cup and in which the cutting line between the cup wall and the evident alteration ring allows to separate the cup from the evident alteration ring when the cover is unscrewed from the container to which it has been applied.

BACKGROUND OF THE INVENTION The machines that use devices to produce a cutting line between the cup and the alteration ring evident in the screw caps for closing containers are already known. These devices consist essentially of a circular cutter against which the cover is rolled to produce a cutting line that makes the ring of alteration evident ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the lid is unscrewed from the container. To achieve the bearing of the lid, it is placed on a mandrel that follows a path that is concentrically external to the circular cutter and presses the wall of the lid against the sharp edge of the cutter. Such devices are described, for example, in EP-533 633 and in the patents of E.U.A. 3,824,941, 3,861, 551, 4,343,754 and 4,904,435. A device with the features of the preamble of claim 1 is known from DE-A-1 482 603. Conventional devices face certain substantial disadvantages which can be attributed substantially to the fact that they are highly sensitive to variations in the external and internal form of the device. the cup. In addition, it is commonly the case that the cut is not carried out perfectly due to the fact that the cover can slide on the mandrel and thus could not complete its rotation on the cutter.

DESCRIPTION OF THE INVENTION The purpose of the present invention is to provide a device that allows to solve the disadvantages mentioned above of conventional devices. This purpose is achieved with a device for producing a cutting line in the cylindrical wall of a plastic cup according to the present invention, which has the features described in claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS The additional features and advantages of the present invention will become apparent from the following detailed description based on the accompanying drawings, in which: Figure 1 is a sectional view of a device according to the invention, about how to produce a cutting line on a screw cap to close containers; Figure 2 is a sectional view, taken along the plane ll-ll of Figure 1; Figure 3 is a view of the device of the invention in the cutting position; Figure 4 is a sectioned view of a second embodiment of the device; Figure 5 is a sectional view, taken along a vertical plane, of a machine composed of a plurality of devices arranged in a carousel configuration; Figure 6 is a sectioned view, taken along a vertical plane, of another carousel type machine; Figure 7 is a view of a further embodiment of the device applied to a machine of the type shown in Figure 5; Figure 8 is a view of another embodiment of the device applied to a machine of the type shown in Figure 5; Figure 9 is a sectional view, taken along the plane IX-IX of Figure 8.

DETAILED DESCRIPTION OF THE INVENTION With reference to figures 1, 2 and 3, the device according to the present invention is generally designated with the reference number 1 and is formed by a cylindrical body 2, called a receptacle onwards, so to be agreed upon in the description, which it comprises a bottom 3 and a cylindrical wall 4. The receptacle 2 is centered and fixed by means of screws 5 to a support structure 6 so that its axis A is vertical. The internal cavity of the receptacle 2 constitutes a seat 7 for the sliding of a cylindrical mandrel 8. At the end of the mandrel 8 coming out downwards, a rod 9 is provided for centering a plastic lid 10 composed of a cup 11 and a ring 11. obvious alteration 12 that emerges from the rib of the cup 11. The cup 11 is internally threaded to be screwed onto the mouth of a container, and the obvious alteration ring 12 has internal projections which, once the cap has been screwed on, they are coupled under an external collar formed below the mouth of the container. ^ as? & ^? mt ^ ?, The device 1 allows forming a cut line between the cup 11 and the obvious alteration ring 12 to allow separation of the cup 11 from the obvious alteration ring 12, which is retained by the collar of the container when the cover is unscrewed. A cavity 12a for receiving a screw 13 is formed in the bottom 3. The screw 13 is screwed in the mandrel 8 through a hole 14 which is formed in the bottom of the cavity 12a and has a diameter smaller than the head of the screw 13. The screw head 13 locks against the mandrel 8 a bushing 15 which is guided in the hole 14. In this way, the mandrel can carry out axial strokes, with respect to the receptacle 2, which are limited by the connection, against the bottom of the cavity 12a, of the head of the screw 13, which then acts as a stroke limiter. An axial blind hole 16 is formed in the mandrel 8 and is open toward the bottom 3. The hole 16 houses a spring 17 that rests against the bottom 3 through the interposition of a spacer bushing 18. A threaded rod 19 is screwed in the bottom 3, inside the receptacle 2, it exits axially through the bushing 18 and the spring 17 and is locked in a rotatable manner by means of a nut 20. The bar 19 is suitable for splicing against the bottom of the blind hole 16 to determine the position of the mandrel inside the seat 7. Three recesses 21 are formed on the outside of the mandrel and are angularly spaced at 120 °. A limb 23 is articulated in each recess by means of a pivot 22 and a clamp 24 is engaged ^^^^^^^^^^^^^^^^^ S ^^^^^^^^ g ^^^^^^^ fc ^^^^^ rigidly to it. The jaw 24 is formed by a sector that is substantially conical and has an inclined outer surface converging towards the bottom of the seat 7. By means of springs 25 interposed between the jaws 24 and the mandrel 8, the sectors are kept in contact against the inner rib 26 of the wall 4 of the receptacle 2. Conveniently, the internal rib 26 has a bevel that is complementary to the bevel of the outer surface of the jaws 24 and is cambered to form, together with the jaws, a line of circumferential contact. Each jaw 24 has, in a downward region, an arch-shaped seat 28 in which a block 29 is provided to retain a blade 30 that is disposed substantially on a plane that is perpendicular to the axis A of the mandrel 8. Two screws 31 pass through the block 29 and the blade 30 and hold the blade in the seat 28. Each blade 30, see figure 2, has a cutting edge 32 which has the shape of a circular arc whose radius is substantially equal to the radius of the lid 10 and has a plurality of notches 33 having a preset mutual distance. As will be explained more clearly hereinafter, the blades 30 are designed to cut through the cylindrical wall of the lid to separate the obvious alteration ring 12 from the cup 11, except for bridges that join the obvious alteration ring 12 with the cup 11 and which are formed not cutting in the notches 33. A radial seat 34 is formed in the blocks 29 to lock ^^^^^^^ t ^^^^^^^^ A ^? tmt ^^^^ t ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 35 is inserted there. The sharp edge of the cutter rests on a radial plane passing through the axis A of the mandrel 8 and is aligned with the sharp edge 32 of the respective arc-shaped blade 30. The cutter 35 is retained in the seat 34 by a screw 36 which is screwed from the outside through the clamp 24. The cutters 35 are arranged at a level such that when the arc-shaped blades 30 cut the wall of the lid , the cutters 35 cut transversely through the evident alteration ring. The described device operates as follows. In the initial conditions, the mandrel 8 is in a lowered position with respect to the receptacle 2, and the jaws 24 are kept separated against the internal rib 26 of the receptacle 2 by the springs 25. The lid 10 that will be cut, after having been arranged on a lifting device 37, it is lifted by the lifting device and centered on the rod 9. As the lifting device 37 continues its upward stroke, the impulse applied against the rod 9 causes the lifting of the mandrel 8 in contrast to the elastic reaction applied by the spring 17. During the lifting of the mandrel 8, the jaws 24 are joined against the rib 26 and are thus forced to move mutually closer to the mandrel 8 and cause the coupling of the blades 30 against the wall of the top 10, thus causing the cut S? * Peripheral of said lid at the level where the evident alteration ring 12 is separated from the cup 11. The penetration of the blades 30 into the wall of the lid 10 is determined by the joining of the bar 19 against the bottom of the blind hole 16 and is adjusted by screwing or unscrewing the bar 19 so that the obvious alteration ring 12 remains attached to the cup only on the bridges formed by the notches 33 while, by virtue of the cutters 35, the ring of evident alteration It is perforated transversely to facilitate its breaking when the lid is removed after being applied to a container. The invention described is susceptible to numerous modifications and variations. The number of the blades 30 and of the cutters 35 is chosen according to the needs. For example, it is possible to provide four blades 30 associated with respective jaws, each blade covering an angle of 90 °. In addition, the cutters 35 can also be omitted from the device, for example if the obvious alteration ring, after breaking, should remain attached to the container. Figure 4 is a view of one embodiment of the invention in which the device has been modified to form plastic discs starting from a cup 38 having a bottom 39 and a cylindrical peripheral wall 40. The difference with respect to the embodiment of the preceding figures is substantially the fact that an annular cutter 41a is provided in the rod 9 of the mandrel 8 which internally cuts the cup along the peripheral region of the bottom 39, to separate a disk that can be used as a Lining for lids or for other purposes. Figure 5 is a view of a modality comprising a plurality of devices 1 for providing a carousel type machine. The machine comprises a vertical arrow 41 which is connected to a motor drive means and is rotatably supported in a sleeve 42 which is raised from a support base 43. In the upper part of the arrow 41 a disk 44 is provided. which supports a plurality of devices 1 which are mutually equidistant in angular form, and which are arranged concentrically around the arrow 41. The disk 44, by means of a sleeve 45, is coupled in a rigid and rotating manner to a flange 46 which is wedged on the arrow 41 above the sleeve 42. A tray 47 is fixed to the sleeve 42 on the flange 46 and is designed to receive the caps arriving from a feed channel 48. A star member 47a is disposed on the tray 47 and is rigidly coupled thereto. The star element 47a is peripherally provided with seats 49 which are aligned with the respective devices 1 and into which the caps are transferred. which arrive from the channel 48. The seats 49 are aligned with openings 49a of the tray 47 and with respective holes 50 which are formed in the flange 46 and are parallel to the arrow 41. The respective bars 51 are guided in the holes 50 and constitute the lifting devices for The lugs 51 have, at their lower end, two free rollers 52 and 53 which are diametrically opposed and whose axis of rotation is radial with respect to the arrow 41. The outer roller 52 of the two rollers 52, 53 engages a vertical guide 54 which is attached to the peripheral region of the flange 46, exits downwards and prevents the respective bar from rotating in the seat 50 but allows it to slide axially. The internal roller 53 in turn engages a slot 55 of an axial cam 56 which is rigidly coupled to the support base and which runs around the sleeve 42. With the machine described, the covers 10, fed in succession from the channel 48 and transferred in the seats 49 of the star element 47a, which rotates at par with the machine, are transferred on the receiving tray 47 and placed in the openings 49 that are on the upper parts of the bars 51, which are at your lowest career limit in this step. When turning the machine, each lifting device 51, actuated by the cam 56, lifts the respective lid until it connects against the rod 9. Then, as the lifting device continues to rise, the blades 30 close on the lid 10 and the peripheral cut is formed as described above with reference to Figure 1. When the cut is completed, the lifting device 51 is lowered, allowing the mandrel 8 to follow its movement by means of the spring 17. Simultaneously with the descent of mandrel 8, spring 25 uncouples the blades 30 from the lid, which once they have been released on the tray 47 can be removed laterally from the seats by means of conveyor elements. Figure 6 also shows an application of the device for forming a carousel machine that is different from the previous one because instead of lifting the lid 10 the devices 1 are lowered. The machine of figure 6 comprises a vertical arrow 57 which is connected to motorization means and is rotatably supported on a support base which is not shown. A sleeve 58 is wedged over the arrow 57 and is provided with a rim 59 in which a plurality of bushings 60 are provided which are angularly equidistant about the arrow 57. The receptacles 2 of the respective devices 1 can slide in the bushings 60. Tray 61 for receiving the caps is attached to the lower end of the sleeve 58 together with the corresponding star 61a, which is provided with seats 61 within which the covers 10 are transferred by a feed channel which is similar to that designated with the reference number 48 in the embodiment of the machine shown in FIG. Figure 5. A kind of drum 62 is attached to the upper end of the sleeve 58 and is provided with axial guides 63 which are aligned with the bushings 60. Sliding blocks 64 respectively can slide in the guides 63 and are connected to the receptacles 2 of the respective devices 1 by means of bars 65. Conveniently , couplings ^^^^^^^^^^^ j ^^^^^^^^^ a flexible 66 are provided between the bars 65 and the sliding blocks 64 to allow small mutual movements. The respective free rollers 67 exit inwardly from the sliding blocks 64 and engage the slot 68 of an axial cam 69 which is centered and fixed on the collar 70 of a sleeve 71 in which the upper portion of the arrow 57 is supported rotatable The sleeve 71 and therefore the cam 69 are made stationary with respect to the arrow 57 by means of a clamp type connection 72 to the machine frame. It is evident from figure 6 that when turning the arrow 57, the cam 69 drives the sequential descent of the devices 1, in such a way that the rods of the mandrels 8 couple the respective covers 10 that will be cut. When the rod 9 of a device has made contact against the bottom of the respective lid, the cam 69 drives the further descent of the device, which causes the movement of the mandrel 8 with respect to the receptacle 2, thereby closing the jaws 24 and cutting the lid perimetrically. By continuing to rotate the machine, the cam 69 drives the lifting of the device 10, so that the spring 17 can push the mandrel 8 outwards again, allowing the jaws 24 to open and let the blades disengage from the lid, which can then be left on the tray 61 for removal. Figure 7 illustrates a further embodiment of a machine of the Ú &-** > --a - «-« e? i-fc? - »ari-taa type shown in figure 5, but provided with devices 1 such as that of figure 4 to form plastic discs. The machine in figure 7 can of course also be used to cut lids to close containers. With respect to the above devices, the differences in the embodiment of FIG. 7 attempt to reduce the friction and consist of the fact that the mandrel 8 is guided in the receptacle 2 by means of a ball bearing in the form of a sleeve 73 and also because in order to operate the jaws 24, bearings 74 are provided which are supported on extensions 75 of the wall 4 and are in contact with the conical outer surface of the jaws 24. Advantageously, instead of the threaded rod 19, an adaptive shim 76 is provided which makes it possible to adjust the level at which the blades 30 act. Finally, the reference number 77 designates a duct carried on the support surface of the cup. 38 and is connected to a suction source for retaining the discs on top of the bars 51. Another embodiment of the machine of Figure 5 is shown in Figures 8 and 9, and allows each device to determine the angular position of the device. the cover 10 with respect to a cutter 35 (see figure 9). This requirement originates in case the lids 10 in which the evident alteration ring 12 is provided are provided with internal flaps 78 which are separated by spaces 79 and must remain attached to the cup 11 after the break along the the cutting lines, formed by the blades 30 and by the cutters 35, when the lid 10 is unscrewed from the container. This is done to avoid having to remove, with a subsequent operation, the obvious alteration ring that has remained attached to the neck of the container, or for reasons of recycling of materials, since the material of the lid is different from the material of the container. In the embodiment of FIGS. 8 and 9, the rod 9 has a peripheral groove 80 in which the circular sectors 81 are coupled; said sectors being centered in a seat 82 of a disk 83 which is fixed to the lower end of the mandrel 8 by means of screws 84. The sectors 81 are crossed by fixing screws 84a which are screwed into the disk 83. The rod 9 has a outer set of teeth 85 whose angular distance is equal to the distance of the spaces 79 between the flaps 78 of the lid 10. Further, in the rod 9 a blind hole 86 is provided having a threaded portion in which a ring is screwed 87. The ring 87 has a flange 88 with which it is locked against a shoulder of the hole 86 and an axial seat 89 in which a pivot 90 provided with a collar 91 is guided. A spring 92 acts on the pivot 90 and, by connecting it against the bottom of the hole 86, it keeps the collar 91 in contact against an internal splice of the hub 87. When the collar 91 rests on the inner splice of the ring 87, the end of the pivot 90 exits axially to the outside of the arrow 90.

The angular arrangement of the teeth 85 and their shape is such that they are allowed to enter the spaces 79 when the lid is placed on the rod 9. To ensure that the obvious alteration ring 12 remains attached to the cup 11 also after the lid has been removed from the container, some portions 93, 94 of two adjacent blades 30 are removed so that the wall of the lid in front of them remains intact. The obvious alteration ring 12 is opened forming a single cross-sectional line with a single cutter 35 disposed at one end of the portion 93. In this way, when the lid is unscrewed from the container, the apparent alteration ring can be broken starting from the position of the cutter 35. To place each cover 10 on the respective rod 9 in the desired angular position with respect to the cutter 35, on the upper part of the corresponding bar 51 there is provided a coaxial pin 95 which supports, by means of bearings 96, a bushing 97 provided with an external set of teeth 98. In the upper part of the bushing 97, a seat 99 is provided for housing a tray 100 which constitutes a support base for a cover 10. By means of the drive from the bar 51 by the cam 56, the bushing 97 is raised from a lowered position to receive a cover on the tray 100 to a position for coupling the rod 9. To allow the teeth 85 of the rod 9 to enter the spaces 79 between the flaps 78, the set of teeth 98, during the upward stroke of the bushing 97, is engaged with a driving element that is capable of causing the bushing 97 to rotate. The driving element is formed, for example, by a ring 101 with internal teeth which is fixed to the exterior of the devices 1. The profiles of the teeth 98 are configured to avoid violent impacts when the engagement with the teeth occurs 85. In a further embodiment, the elem The actuator is formed by a gear which is rotatably supported on the central shaft 41 and which is constantly engaged with the set of teeth 85 of the bushing 97. The wheel is controlled by a drive cam whose profile is such as to make it the bushing 97 rotate gradually. By means of the machine of FIGS. 8 and 9, in a first step of the lifting action a relative rotation occurs between the lid 10 and the bushing 97 until the teeth 85 engage the spaces 79, while in a second step of the lifting action, as a consequence of the relative movement between the jaws 24 and the receptacle 2, the evident alteration ring is cut peripherally and transversely. By means of the downward stroke, the pivot 90, by means of the impulse applied by the spring 92, causes the separation of the cover of the rod 9 and its positioning on the tray 100.

Claims (11)

NOVELTY OF THE INVENTION CLAIMS

1. - A device for producing a cutting line in the cylindrical wall of a plastic cup, particularly a cover (10) that is designed to close a container and that is composed of a cup (11) and a ring of obvious alteration (12) exiting from the rib of the cup, comprising: a cup retention means (8) which is provided with retention means for positioning and retaining a cup (11) applied thereon; a plurality of jaws (24), hinged to oscillate on planes resting radially with respect to said axis (A); respective circular arc-shaped blades (30) being applied to said jaws (24) and being arranged on a plane that is perpendicular to said axis (A) of said mandrel (8); furthermore, jaw drive means (2) for said jaws (24) are provided to actuate said blades in the form of an arc (30) radially from a position that is external to said cup (11) to a position for coupling the cylindrical wall. said cup (11) wherein said blades (30) form a cutting line in said wall, characterized in that said cup retaining means are constituted by a mandrel (8) that is supported in such a way that it is slidable along its own axis (A), said jaws (24) being articulated (22) at a first end thereof in said mandrel (8), and said blades in arc shape (30) being applied at the opposite end of the jaws (24), and because mandrel drive means (37) are further provided to drive said mandrel (8) for movement thereof with respect to said drive means jaw (2) and to cause then, in cooperation with the jaw drive means (2), the oscillation of said jaws (24) and the actuation of said arc-shaped blades (30).

2. The device according to claim 1, further characterized in that said drive means are constituted by a receptacle element (2) forming a seat (7) for sliding said mandrel (8), said receptacle element has a rib (26) that acts as a splice for said jaws (24), so that the radial movement of said blades (30) is activated when said mandrel (8) is actuated with respect to said receptacle element (2), said jaws (24) being formed by sectors whose outer surface is substantially conical, springs (25) being disposed between said mandrel (8) and said jaws (24) and being suitable for maintaining the conical outer surface of said jaws (24) in contact against the rib (26) of said receptacle element (2).

3. The device according to claim 1, further characterized in that said drive means are formed by a receptacle element (2) forming a seat for sliding said mandrel (8), said receptacle element (2) has a wall in which bearings (74) are supported on planes that are radial with respect to the axis (A) of said mandrel (8), said jaws (24) being formed by sectors whose outer surface is substantially conical and in contact with said bearings (74), to drive the radial movement of said blades (30) when said mandrel (8) is actuated with respect to said receptacle element (2), springs (25) being disposed between said mandrel (8). ) and said jaws (24), said springs being adapted to maintain the conical outer surface of said jaws (24) in contact against said bearings (74).

4. The device according to claim 1, further characterized in that each of said jaws has a seat (28) to receive a block (29) to fix a blade (30).

5. The device according to claim 4, further characterized in that said block (29) has a seat (34) for a cutter (35) whose sharp edge rests on a plane that is radial with respect to said mandrel (8), is aligned with the cutting edge of said blades (30) and is suitable for cutting said evident alteration ring (12) transversely.

6. The device according to claim 5, further characterized in that the cutting edge of said blades (30) has notches (33) are suitable for forming bridges to join the evident alteration ring (12) to the cup (11). ) after forming the cutting line.

7. The device according to claim 1, further characterized in that said mandrel (8) has a rod (9) to place said cup (11) having an annular cutter (41a) suitable for cutting the bottom of said cup ( eleven ).

8. A machine comprising the device according to claim 1, further characterized in that it comprises: a vertical arrow (41) that is rotationally driven; a disc (44), which is rigidly and rotatably coupled to the upper part of said arrow (41) and supports a plurality of said devices (1) that are angularly equidistant and are arranged concentrically around said arrow (41); a tray (47) for receiving the caps (10) that is rotatably and rigidly coupled to said arrow (41) under said devices; a flange (46) that rotates rigidly with said arrow (41) below said tray (47); a plurality of seats (50) and openings (49a) that are formed in said flange (46) and in said tray (47) respectively, said seats (50) and openings (49a) being vertically aligned with respective devices (1); respective bars (51) being guided in said seats (50) and said openings (49a), said bars being controlled by an axial cam (56) which is arranged in a stationary configuration about said arrow (41); said bars (51) being driven in succession by said cam (56) to carry out an active stroke and a return stroke between a lowered position and an elevated disposition, said active stroke being suitable to cause the lifting of the caps (10). ) from said receiving tray (47), centered on the respective mandrels (8), the = MSC v¡ &? &? ¡hißíti ^ uSÍ? lifting the mandrels (8) and driving the blades (30) to produce a cutting line around the lid; said return stroke being adequate to cause the placement of the cut caps (10) on said receiving tray (47).

9. A machine comprising the device according to claim 1, further characterized in that it comprises: a vertical arrow (41) that is rotationally driven; a flange (59) that rotates rigidly with said arrow (41) and is provided with a plurality of bushings (60) that are parallel to said arrow, are angularly equidistant and are arranged concentrically around said arrow; a plurality of devices (1) slidably guided within said bushings (60); a tray (61) for receiving the caps that rigidly rotates with said arrow (41) below said devices (1); a drum (62) which is rotatably fixed to said arrow (41) and is provided with a plurality of guides (63) which are parallel to said bushings (60); respective sliding blocks (64) being slidable in said guides (63), each sliding block being connected to a respective device (1), said sliding blocks being controlled by an axial cam (69) that is stationary about said arrow said sliding blocks (64) being driven in succession by said cam (69) to carry out an active stroke and a return stroke between a lowered position and a raised position; said active stroke being suitable for determining the centering of said mandrels (8) on the respective caps (10) arranged on said receiving tray (61) and the actuation of the blades (30) to produce the cutting line around the caps; said return stroke being suitable to cause the lifting of said devices (1) and the uncoupling of said mandrels (8) from said covers (10).

10. The machine according to claim 8, further characterized in that said rod (9) has an external set of teeth (85) which is composed of teeth whose angular distance and shape are such that they engage in spaces (79) of the evident alteration ring (12) formed by flaps (78) that come out inside the lid (10), and because in the upper part of each of said bars (51) there is disposed a bushing (97) rotatably supported it is provided with a seat (99) for positioning a lid (10), actuating elements (98, 101) being provided to make said bushing (97) rotate, during the positioning of said lid (10) on said rod (9). ), so as to determine the angular positioning of said lid (10) with respect to said rod (9) and the coupling of the external set of teeth (85) of said rod (9) in said spaces (79).

11. The machine according to claim 10, further characterized in that said drive elements are constituted by a set of teeth (98) that is externally formed to said bushing (97) and is controlled by a drive gear (101) .