SEAMING UNIT AND METHOD FOR SEAMING A THIN-WALLED NON-CYLINDRICAL CAN

Description

The invention relates to the field of seaming containers, in particular metal containers intended to receive food products. The invention relates more specifically to a method for seaming so-called “shaped” cans—i.e. the body of which is not a right cylinder-made of thin steel.

BACKGROUND OF THE INVENTION

Seaming makes it possible to produce sealed junctions by winding and crushing a peripheral edge of a metal can and of its cover. The different steps of a seaming are reminded of in FIG. 1. A seaming unit is known from patent application FR3054148, comprising a first plate rotatably mounted about a first axis on a chassis and connected to first means for driving in rotation. A first lever provided at a first end of a first thumbwheel is pivotably mounted on the first plate at a first pivot point to describe a first circular trajectory of the first pivot point about the first axis along a first diameter. A second plate is rotatably mounted about the first axis and is connected to second means for driving the second plate in rotation.

A second end of the first lever is connected to the second plate at a second connecting point to describe a second circular trajectory of the second connecting point about the first axis along a second diameter, such that the first thumbwheel follows a third seaming trajectory along the seam in the can. Introducing an angular offset between the first plate and the second plate during their rotations makes it possible to enable the distance separating the first axis of the first end from the second lever to vary, and thus to move the first thumbwheel along the third seaming trajectory. Such a seaming unit makes it possible to modify the seaming trajectory and to adapt it to various can formats and shapes, without needing to intervene on the unit which represents a significant advancement regarding current mechanical cam seaming machines. The accurate controlling of the position of the first thumbwheel notably improves the quality of the seaming and consequently decreases rejects due to a seaming defect. This device has demonstrated a significant improvement in the quality of seamings for cans for which the wall has a thickness of around twenty to twenty-five tenths of a millimetre. However, this improvement is less perceptible for thin-walled cans, the thickness of which is less than twenty tenths of a millimetre. The option of effectively seaming thin-walled cans represents a strong economical challenge, in that it would make it possible to decrease the weight and the cost of each can.

AIM OF THE INVENTION

The invention aims, in particular, to improve the quality of the seamings on thin-walled cans.

SUMMARY OF THE INVENTION

To this end, a method for seaming a seam in a thin-walled can using a seaming unit is provided, comprising:

• • a first plate rotatably mounted about a first axis on a chassis and connected to first means for driving in rotation;
  • a first lever provided at a first end of a first thumbwheel is rotatably mounted on the first lever about a first articulation point, and which is pivotably mounted on the first plate at a first pivot point to describe a first circular trajectory of the first pivot point about the first axis along a first diameter;
  • a second plate rotatably mounted about the first axis and which is connected to second means for driving the second plate in rotation. A second end of the first lever is connected to the second plate at a first connecting point, to describe a second circular trajectory of the first connecting point about the first axis along a second diameter. The method according to the invention comprises the following steps:
  • selecting a can shape to be seamed;
  • determining a third seaming trajectory;
  • determining a value of the first diameter so as to obtain a first angular clearance of the first lever about the first pivot point during the movement of the first thumbwheel along the third seaming trajectory, such that the first displacement is less than sixty degrees;
  • implanting the first pivot point on the first plate, such that the first pivot point describes the first circular trajectory about the first axis along the first diameter;
  • controlling the first means for driving in rotation and the second means for driving in rotation, such that the first thumbwheel follows a third seaming trajectory along the seam in the can.

The inventor has been able to observe that decreasing the displacement of the first lever would enable a better accuracy in the positioning of the first thumbwheel and a decreasing of the reject volume during the seaming of the cans, particularly thin-walled cans, the wall thickness of which is less than twenty-five hundredths of a millimetre.

Decreasing the seaming reject volume is even more marked when the first diameter is chosen, such that the first angular clearance is less than forty-five degrees.

Reducing the seaming reject volume is even more marked when the method comprises the additional step of determining a first length of a first lever arm separating the first pivot point from the first articulation point, so as to reduce the first angular clearance of the first lever about the first pivot point during the movement of the first thumbwheel along the third seaming trajectory, and adjust the value of the third diameter along the second length of the second lever arm. Advantageously, the first length of the first lever arm is between forty and sixty millimetres.

A simple implementation is obtained when the step of determining a value of the first diameter comprises the following steps:

• • determining a first distal point of the third seaming trajectory located at the greatest distance from the first axis;
  • determining a first straight line tangent to the third seaming trajectory at the first distal point;
  • determining a first distance separating the first axis from the first pivot point when the first thumbwheel is applied on the first distal point and that a second straight line connecting the first articulation point and the first pivot point is parallel to the first tangent straight line;
  • determining a first proximal point of the third seaming trajectory located at the lowest distance from the first axis;
  • determining a third straight line tangent to the third seaming trajectory at the first proximal point;
  • determining a second distance separating the first axis from the first pivot point when the first thumbwheel is applied on the first proximal point and that a fourth straight line connecting the first pivot point and the first connecting point is parallel to the third tangent straight line;
  • establishing a value of the first diameter at the average value of the first and of the second distance.

The quality of the seaming is further improved when, the first lever comprising a first lever arm separating the first pivot point from the first articulation point and a first actuation arm separating the first pivot point from the first connecting point, the method comprises an additional step of selecting a first angle extending between the first lever arm and the first actuation arm so as to reduce the first angular clearance of the first lever about the first pivot point during the movement of the first thumbwheel along the third seaming trajectory.

Such a determination can be led to using the following steps:

• • determining a second angle delimited by the first lever arm and a straight line orthogonally cutting the axis Oy and passing through the first pivot point when the first thumbwheel is applied on the first distal point and that the first pivot point is located on the first trajectory;
  • determining a third angle delimited by the first lever arm and fourth straight line orthogonally cutting the axis Oy and passing through the first pivot point when the first thumbwheel is applied on the first proximal point and that the first pivot point is located on the first trajectory;
  • establishing a value of the first angle at a value corresponding to half the sum of the second angle and of the third angle.

Advantageously, the first diameter is between one hundred and twenty and two hundred and twenty millimetres, preferably between one hundred and forty and two hundred and ten millimetres.

It is possible to reduce the seaming time, when the seaming unit also comprises:

• • a second lever provided at a third end of a second thumbwheel rotatably mounted on the second lever about a second articulation point, and which is pivotably mounted on the first plate at a second pivot point to describe a fourth circular trajectory of the second pivot point about the first axis along a third diameter;
  • a third plate rotatably mounted about the first axis and third means for driving the third plate in rotation. A fourth end of the second lever is connected to the third plate at a second connecting point, to describe a fifth circular trajectory of the second connecting point about the first axis along a fourth diameter. The method comprises the additional steps of:
  • defining a sixth seaming trajectory;
  • determining a value of the third diameter so as to obtain a reduced second angular clearance of the second lever about the second pivot point during the movement of the second thumbwheel along the sixth seaming trajectory, which is less than sixty degrees;
  • implanting the second pivot point on the first plate, such that the second pivot point describes the fourth circular trajectory of the second pivot point about the first axis along the third diameter;
  • controlling the first means for driving in rotation and the third means for driving in rotation, such that the second thumbwheel follows the sixth seaming trajectory.

A particularly marked reduction of the reject volume is obtained, when the method comprises the following additional steps:

• • determining a second length of a second lever arm separating the second pivot point from the second articulation point so as to further reduce the second angular clearance of the second lever about the second pivot point during the movement of the second thumbwheel along the sixth seaming trajectory, and
  • adjusting the value of the third diameter along the second length of the second lever arm.

Advantageously also, the second length of the second lever arm is between forty and sixty millimetres.

A particularly effective simple implementation of the method of the invention is made when the step of determining a value of the third diameter comprises the following steps:

• • determining a second distal point of the sixth seaming trajectory located at the greatest distance from the first axis;
  • determining a fifth straight line tangent to the sixth seaming trajectory at the second distal point;
  • determining a third distance separating the first axis from the second pivot point when the second thumbwheel is applied on the second distal point and that a sixth straight line connecting the second articulation point and the second pivot point is parallel to the fifth tangent straight line;
  • determining a second proximal point of the sixth seaming trajectory located at the lowest distance from the first axis;
  • determining a seventh straight line tangent to the sixth seaming trajectory at the second proximal point;
  • determining a fourth distance separating the first axis from the second pivot point when the second thumbwheel is applied on the second proximal point and that an eighth straight line connecting the second pivot point and the second connecting point is parallel to the seventh tangent straight line;
  • establishing a value of the third diameter at the average value of the third and of the fourth distance.

Advantageously, the first diameter and/or the fourth diameter is between one hundred and twenty and two hundred millimetres.

The cycle time is improved when the method comprises the additional step of adding a first release distance to the value of the first diameter and/or a second release distance to the third diameter.

Preferably, the first and/or the second release distance is between two and five millimetres.

Advantageously also, the second lever comprises a second lever arm separating the second pivot point from the second articulation point and a second actuation arm separating the second pivot point from the second connecting point, the method comprising an additional step of selecting a third angle extending between the first lever arm and the first actuation arm so as to reduce the second angular clearance of the second lever about the second pivot point during the movement of the second thumbwheel along the sixth seaming trajectory.

The invention also relates to a seaming unit comprising:

• • a first plate rotatably mounted about a first axis on a chassis and connected to first means for driving in rotation;
  • a first lever provided at a first end of a first thumbwheel is rotatably mounted on the first lever about a first articulation point, and which is pivotably mounted on the first plate at a first pivot point to describe a first circular trajectory of the first pivot point about the first axis along a first diameter;
  • a second plate rotatably mounted about the first axis and which is connected to second means for driving the second plate in rotation, wherein a second end of the first lever is connected to the second plate at a first connecting point, to describe a second circular trajectory of the first connecting point about the first axis along a second diameter. The seaming unit comprises an assembly comprising the first plate and the first lever which is arranged to be deposited from the seaming unit without requiring the second plate and/or the first drive means to be dismounted. The first plate comprising a first pivot point positioned on the first plate, such that the first pivot point describes the first circular trajectory about the first axis along the first diameter, the first diameter having been determined according to any one of the methods described above.

Other features and advantages of the invention will emerge upon reading the following description of particular non-limiting embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is made to the accompanying drawings, in which:

FIG. 1 is a figure representing the different steps of a seaming;

FIG. 2 is a schematic, vertical cross-sectional view of a seaming head according to a first embodiment of the invention;

FIG. 3 is a schematic, planar view of the seaming head of FIG. 2;

FIG. 4 is a schematic view of a second step of the method according to the invention;

FIG. 5 is a schematic view of a fifth step of the method according to the invention;

FIG. 6 is a schematic view of a twelfth step of the method according to the invention;

FIG. 7 is a schematic view of a thirteenth step of the method according to the invention;

FIG. 8 is a schematic, planar view of a seaming head according to a second embodiment of the invention;

FIG. 9 is a schematic, vertical cross-sectional view of a seaming head according to a second embodiment of the invention;

FIG. 10 is a schematic view of a twelfth step of the method according to the invention;

FIG. 11 is a schematic view of a thirteenth step of the method according to the invention;

FIG. 12 is a schematic, planar view of a seaming head according to a sixth embodiment of the invention;

FIG. 13 is a schematic, planar view of a seaming unit according to a seventh embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In reference to FIGS. 1 to 5, the seaming unit according to the invention, generally referenced 1, is intended for the seaming of a bottom 90 on a body 91 of a shaped can 92 along a seam 93. The seaming unit 1 comprises a seaming head 2 mounted on a chassis 3. The seaming head 2 comprises a first plate 10 rotatably mounted about a first axis Oy, in this case, a vertical axis. The first plate 10 is driven in rotation about the first axis Oy by a first gear servomotor 11, which drives in rotation, using a first gear train 12, a first hollow shaft 13 constrained to rotate the first plate 10. The first hollow shaft 13 is rotatably mounted about a mandrel-bearing shaft 4 secured to the chassis 3 and provided at one of its ends with a mandrel 5 to immobilise a movement of the bottom 90 in a horizontal plane. The seaming head 2 also comprises a second plate 20 rotatably mounted about the first axis Oy. The second plate 20 is driven in rotation about the first axis Oy by a second gear servomotor 21, which drives in rotation, using a second gear train 22, a second hollow shaft 23 constrained to rotate the second plate 20. The second hollow shaft 23 extends about the first hollow shaft 13 and is rotatably mounted about the latter. The first gear servomotor 11 and the second gear servomotor 21 are both connected to a computer 70.

A first lever 50 is provided at a first end 51 with a first winding thumbwheel 52 which is rotatably mounted on the lever 50 about a first articulation point 51.1. The first lever 50 is pivotably mounted on the first plate 10 at a first pivot point 53 to describe a first circular trajectory 54 of the first pivot point 53 about the first axis Oy along a first diameter D1. Thus, the first pivot point 53 travels through a first circular trajectory 54 of first diameter D1 during a rotation of the first plate 10 of three hundred and sixty degrees about the first axis Oy.

A second end 55 of the first lever 50 is connected to the second plate 20 at a first connecting point 56, to describe a second circular trajectory 57 of the first connecting point 56 about the first axis Oy along a second diameter D2. The lever 50 therefore has a first lever arm 58 of first length L58 which separates the first pivot point 53 from the first articulation point 51.1. The lever 50 also has a first actuation arm 59 of second length L59 which separates the first pivot point 53 from the first connecting point 56. Introducing an angular offset between the first plate 10 and the second plate 20 makes it possible to modify the position of the first thumbwheel 52, such that the first thumbwheel 52 follows a third seaming trajectory, in this case a winding trajectory 95, along the seam 93 of the can 92.

The method according to the invention will now be described in reference to FIGS. 1 to 5.

According to a first step, a can shape to be seamed is selected, in this case, a rectangular-shaped can 92 of length L equal to one hundred and ten millimetres and of width 1 equal to sixty millimetres. According to a second step, the seaming trajectory 95 is determined. The seaming trajectory 95 for such a can 92 is known and generally corresponds to a homothety of centre located on the axis Oy of the seam 93 once seamed and the ratio k of which is determined according to the number of winding/crushing passes and of the profile of the first thumbwheel 52. For illustration purposes, it will be considered that the first thumbwheel 52 is a winding thumbwheel which performs the winding of the seam 93 in one single pass.

According to a third step represented in FIG. 4, a first distal point 94 of the third seaming trajectory 95 located at the greatest distance from the first axis Oy is determined.

According to a fourth step, a first straight line Td94 tangent to the third seaming trajectory 95 at the first distal point 94 is determined. According to a fifth step, a first distance D94 is determined separating the first axis Oy from the first pivot point 53 when the first thumbwheel 52 is applied on the first distal point 94 and that a second straight line D53-51.1 connecting the first articulation point 51.1 and the first pivot point 53 is parallel to the first tangent straight line Td94.

According to a sixth step represented in FIG. 5, a first proximal point 96 of the third seaming trajectory 95 located at the greatest distance from the first axis Oy is determined.

According to a seventh step, a third straight line Tp96 tangent to the third seaming trajectory 95 at the first distal point 96 is determined. According to a seventh step, a second distance D96 is determined separating the first axis Oy from the first pivot point 53 when the first thumbwheel 52 is applied on the first proximal point 96 and that a second straight line D51.1.1-53 is parallel to the third tangent straight line Tp96. According to an eighth step, the value of the first diameter D1 is established at the average value of the first distance D94 and of the second distance D96.

According to a ninth step, a first release distance d1 is added to the value of the first diameter D1, the release distance d is, in this case, five millimetres.

According to a tenth step, the first pivot point 53 is implanted on the first plate 10, such that the first pivot point 53 describes the first circular trajectory 54 about the first axis Oy along the first diameter D1.

According to an eleventh step, the computer 70 controls the first gear servomotor 11 and the second gear servomotor 21, such that the first thumbwheel 52 follows the third seaming trajectory 95 along the seam 93 of the can 92.

The angular clearance observed of the first lever 50 about the first pivot point 53 for such a can 92 and a lever arm of forty-five millimetres is around forty degrees for a standard format can known as “quarter club”.

According to a second embodiment, the method comprises an additional step, prior to the tenth step, of selecting a first length L58 of the first lever arm 58, so as to reduce the first angular clearance of the first lever 50 about the first pivot point 53 during the movement of the first thumbwheel 52 along the third seaming trajectory 95. Determining the first length L57 can be made, graphically using working drawings, by iteration or by any other method known to a person skilled in the art. The first diameter D1 is then calculated once more as described for the first embodiment.

The inventor has discovered that the best results in terms of seaming quality were obtained when the first length L58 of the first lever arm 58 was between forty and sixty millimetres and that the first diameter was between one hundred and forty and two hundred millimetres.

Optionally, it is possible to also adjust the second length L59 of the first actuation arm 59.

According to a third embodiment represented in FIGS. 6 and 7, the method comprises additional steps of selecting a first angle β1 extending between the first lever arm 58 and the first actuation arm 59 so as to reduce the first angular clearance of the first lever 50 about the first pivot point 53 during the movement of the first thumbwheel 52 along the third seaming trajectory 95. Thus, according to a twelfth step, a second angle α1 is determined, delimited by the first lever arm 58 and a fourth straight line D53 orthogonally cutting the axis Oy and passing through the first pivot point 53 when the first thumbwheel 52 is applied on the first distal point 94 and that the first pivot point 53 is located on the first trajectory 54 (FIG. 6). According to a thirteenth step, a third angle α2 is determined, delimited by the first lever arm 58 and the fourth straight line D53, when the first thumbwheel 52 is applied on the first proximal point 96 and that the first pivot point 53 is located on the first trajectory 54 (FIG. 7). According to a fourteenth step, a value of the first angle β1 is established at a value corresponding to half the sum of the second angle α1 and of the third angle α2.

According to a fourth embodiment represented in FIGS. 8 to 11, the seaming unit 1 also comprises a second lever 60 provided at a third end 61 of a second crushing thumbwheel 62 rotatably mounted about a second articulation point 61.1. The second lever 60 is pivotably mounted on the first plate 10 at a second pivot point 63 to describe a fourth circular trajectory 64 of the second pivot point 63 about the first axis Oy along a third diameter D3.

Thus, the second pivot point 63 travels through a fourth circular trajectory 64 of third diameter D3 during a rotation of the first plate 10 of three hundred and sixty degrees about the first axis Oy.

The seaming head 2 also comprises a third plate 30 rotatably mounted about the first axis Oy. The third plate 30 is driven in rotation about the first axis Oy by a third gear servomotor 31, which drives in rotation, using a third gear train 32, a third hollow shaft 33 constrained to rotate the third plate 30. The third hollow shaft 33 extends about the second hollow shaft 23 and is rotatably mounted about the latter. A fourth end 65 of the second lever 60 is connected to the third plate 30 at a second connecting point 66, to describe a fifth circular trajectory 67 of the second connecting point 66 about the first axis along a fourth diameter D67 about the first axis Oy along a second diameter D2. The lever 60 therefore has a second lever arm 68 of second length L68 which separates the second pivot point 63 from the second articulation point 61.1. The lever 60 also has a second actuation arm 69 of second length L69 which separates the second pivot point 63 from the second connecting point 66. Introducing an angular offset between the first plate 10 and the third plate 30 makes it possible to modify the position of the second thumbwheel 62, such that the second thumbwheel 62 follows a sixth seaming trajectory, in this case a sixth crushing trajectory 97, along the seam 93 of the can 92.

According to a twelfth step, represented in FIG. 10, a sixth seaming trajectory 97 is defined, in this case, a first crushing pass trajectory. According to a thirteenth step, a second distal point 98 of the sixth seaming trajectory 97 located at the greatest distance from the first axis Oy is determined.

According to a fourteenth step, a fifth straight line Td98 tangent to the sixth seaming trajectory 97 at the second distal point 98 is determined. According to a fifteenth step, a third distance D98 is determined separating the first axis Oy from the second pivot point 63 when the second thumbwheel 62 is applied on the second distal point 98 and that a sixth straight line D61.1-63 connecting the second articulation point 61.1 and the second pivot point 63 is parallel to the fifth tangent straight line Td98.

According to a sixteenth step represented in FIG. 11, a second proximal point 99 of the sixth seaming trajectory 97 located at the lowest distance from the first axis Oy is determined.

According to a seventeenth step, a seventh straight line Tp99 tangent to the sixth seaming trajectory 97 at the second proximal point 99 is determined. According to a fifteenth step, a fourth distance D99 is determined separating the first axis Oy from the second pivot point 63 when the second thumbwheel 62 is applied on the second proximal point 99 and that the sixth straight line D61.1-63 is parallel to the seventh tangent straight line Tp99. According to an eighteenth step, the value of the third diameter D3 is established at the average value of the third distance D98 and of the fourth distance D99.

According to a nineteenth step, a second release distance d2 is added to the value of the third diameter D3, the second release distance d2 is, in this case, five millimetres.

According to a twentieth step, the second pivot point 63 is implanted on the first plate 10, such that the second pivot point 63 describes the fourth circular trajectory 64 about the first axis Oy along the third diameter D3.

According to a twenty-first step, the computer 70 controls the first gear servomotor 11 and the third gear servomotor 31, such that the second thumbwheel 62 follows the sixth seaming trajectory 97 along the seam 93 of the can 92.

The angular clearance observed of the second lever 60 about the second pivot point 63 for such a can 92 and a lever arm of forty-five millimetres is around forty degrees for a standard format can known as “quarter club”.

According to a fifth embodiment, the method comprises an additional step, prior to the twentieth step, of selecting a second length L68 of the second lever arm 68, so as to reduce the second angular clearance of the second lever 60 about the second pivot point 63 during the movement of the second thumbwheel 62 along the sixth seaming trajectory 97. Determining the second length L68 can be made, graphically using working drawings, by iteration or by any other method known to a person skilled in the art. The third diameter D3 is then calculated once more as described for the third embodiment.

The inventor has discovered that the best results in terms of seaming quality were obtained when the second length L68 of the second lever arm 68 was between forty and sixty millimetres.

The second angle β2 separating the second lever arm 68 and a second actuation arm 69 extending between the pivot point 63 and the connecting point 66 can also be optimised according to the same method as that used for determining the first angle β1 of the first lever 50.

According to a sixth embodiment represented in FIG. 12, the seaming head 2 comprises a third lever 40 and a fourth lever 80. The third lever 40 is identical to the first lever 50 and has a fifth end 41 provided with a third winding thumbwheel 42. The third lever 40 is pivotably mounted on the first plate 10 at a third pivot point 43 diametrically opposite the first pivot point 53 to describe the first trajectory 54 during the rotation of the first plate 10 about the first axis Oy. The sixth end 45 of the third lever 40 is connected to the second plate 20 at a third connecting point 46 to describe the second trajectory 57.

The fourth lever 80 is identical to the second lever 60 and has a seventh end 81 provided with a fourth winding thumbwheel 82. The fourth lever 80 is pivotably mounted on the first plate 10 at a fourth pivot point 83 diametrically opposite the second pivot point 63 to describe the fourth trajectory 64 during the rotation of the first plate 10 about the first axis Oy. The eighth end 85 of the fourth lever 80 is connected to the third plate 30 at a fourth connecting point 86 to describe the fifth trajectory 67. Such an arrangement makes it possible to reduce by two, the seaming time of a can with respect to the third embodiment of the invention.

According to a seventh embodiment represented in FIG. 13, the first plate 10 is fixed to the first shaft 13 using a plurality of screws 14. This particular arrangement makes it possible to proceed with depositing the first plate 10 and the first lever 50 in the form of a manipulable coherent assembly of a block without needing to dismount the second plate 20 and/or the first gear servomotor 11.

The deposition of the assembly comprising the first plate 10 and the first lever 50 is performed by depositing the screws 14 then by causing the sliding of the first plate 10 parallel to the axis Oy. During this movement, a fourth shaft 15 secured to the second plate 20 and which is received in a housing 16 of the first plate 10 to release the first connecting point 56 from the housing 16.

Naturally, the invention is not limited to the embodiment described, but covers any variant coming within the scope of the invention as defined by the claims.

In particular:

• • although, in this case, the seaming unit comprises a mandrel, the invention also applies to other types of support of the bottom, like for example, a roll evolving along the first fold of the bottom facing the winding and crushing thumbwheels;
  • although, in this case, the control unit comprises an electronic computer, the invention also applies to other types of electronic control unit, like for example, a control unit using logic doors, a microprocessor, an FPGA or other;
  • although, in this case, the first, second and third plates are rotatably mounted about a vertical axis, the invention also applies to other orientations of the axis of rotation of the plates, like for example, a horizontal or any orientation;
  • although, in this case, the first, second and third plates are driven in rotation by gear servomotors, the invention also applies to other first, second and third means for driving the first, second and third plates in rotation, like for example, hydraulic or pneumatic motors;
  • although, in this case, the seaming unit comprises two levers bearing a winding thumbwheel, the invention also applies to a seaming unit comprising a different number of levers bearing a winding thumbwheel, like for example, more than two levers bearing a winding thumbwheel;
  • although, in this case, the seaming unit comprises two levers bearing a crushing thumbwheel, the invention also applies to a seaming unit comprising a different number of levers bearing a crushing thumbwheel, like for example, more than two levers bearing a crushing thumbwheel;
  • although, in this case, the plates are connected to the pinions by hollow shafts, the invention also applies to other types of connection in rotation, like for example cages, rods, or magnetic connections;
  • although, in this case, the gearings linked to each of the gear servomotors are located at different heights, the invention also applies to other solutions making it possible to avoid interferences, like for example, hollow axial motors, belt or cable assemblies;
  • although, in this case, the pivots of the first and second levers are located on circles of different diameter, the invention also applies to other configurations, like for example, lever pivots positioned on circles of identical diameters;
  • although, in this case, the shaped can is of substantially rectangular cross-section, the invention also applies to the seaming of other can shapes, like for example, round, square, hexagonal cross-sectional cans, or polygonal cross-sectional cans, the number of sides of which can be equal to three or more;
  • although, in this case, the invention has been described in reference with the seaming of a can bottom on a can bottom, the invention also applies to other seaming types, like for example, the seaming of a junction seam between two walls;
  • although, in this case, the seaming unit comprises a winding thumbwheel and a crushing thumbwheel, the invention also applies to a seaming unit comprising one single thumbwheel to wind and seam the seam along different trajectories;
  • although, in this case, determining the first and the third diameter has been done using the measurement of a proximal point and of a distal point, the invention also applies to other methods for determining a diameter, making it possible to optimise the angular clearance of the first (respectively second) lever, such as the iterative calculation, a CAD simulation, a graphic method;
  • although, in this case, a determination of the first diameter has been described prior to determining the length of the first lever arm, the invention also applies to a determination of the length of the first lever arm prior to determining the first diameter;
  • although, in this case, selecting the first angle is done by graphic determination and calculating the half-sum of two angles measured for distal and proximal positions, the invention also applies to other types of additional step of selecting a first angle extending between the first lever arm and the first actuation arm, so as to reduce the first angular clearance of the first lever about the first pivot point during the movement of the first thumbwheel along the third seaming trajectory, like for example, a digital analysis, a determination involving a three-dimensional modelling, a determination by standard deviation or other statistical processing;
  • although, in this case, the winding operations are performed in one single pass of one single winding thumbwheel, the invention also applies to seaming operations performed in several passes of one or more thumbwheels, like for example, two passes of a winding thumbwheel and a pass of two clamping thumbwheels;
  • although, in this case, the release distance is equal to five millimetres, the invention also applies to other release distance values, like for example, less than five millimetres, more than five millimetres, and preferably a release distance of between two and five millimetres;
  • although, in this case, a first plate has been described, connected to the seaming unit by screwing on the first hollow shaft and a fourth shaft secured to the second plate and slidingly mounted with respect to the first plate, the invention also applies to other ways of constituting an assembly comprising the first plate and the first lever, which enables the deposition of the assembly without dismounting other elements, like for example, a connection of the first plate to the seaming unit by pins and/or a fourth shaft secured to the first plate and slidingly mounted on the second plate.

Although, in this case, the description deals with embodiments comprising several technical features described together, these are not necessarily linked to one another, and each have a technical effect which provides a specific advantage to the invention, which justifies the autonomous features not leading to modifications of other features of an embodiment can be individually copied from one embodiment to another, in order to give the latter the specific advantage which is linked to it.