JP6884052B2 - Can bottom molding method - Google Patents

Description

The present invention relates to a can bottom molding method in which a can bottom is molded (bottom reforming).

In recent years, there has been a demand for weight reduction of cans such as aluminum cans, and it is effective to reduce the thickness (wall thickness) of the cans. However, if the thickness of the can is simply reduced, the bottom of the can is likely to be deformed such as bottom growth and buckling. Bottom growth is a phenomenon in which the annular convex portion (rim) of the bottom of a can is deformed due to an increase in the internal pressure of the can containing the contents. When bottom growth occurs, the height of the can (total length in the can axis direction) changes, which causes manufacturing and shipping defects. Further, the buckling is a phenomenon in which the dome portion of the bottom of the can is inverted when the internal pressure of the can exceeds the compressive strength.

For the purpose of preventing such deformation of the can bottom, for example, bottom reform processing (bottom profile reformer processing, BPR processing) by a can bottom forming apparatus as shown in Patent Document 1 below has been proposed.
The can bottom molding apparatus includes a can bottom molding unit having a star wheel that holds the can body of the can, a spindle shaft (spindle center shaft) that extends so as to coincide with the can shaft of the can held by the star wheel, and a star wheel. It also includes a rotating shaft to which a can bottom forming unit is attached, and a drive motor that rotates the rotating shaft around its central axis.
Further, the can bottom forming unit reciprocates in the radial direction with respect to the top support member that supports the open end of the can body of the can held by the star wheel, the bottom support member that supports the can bottom, and the can bottom. It also includes a pressing roller that rotates around the spindle axis to press the inner peripheral wall of the annular convex portion of the can bottom and to form a groove-shaped concave portion extending in the circumferential direction.

The drive motor rotates (revolves) the star wheel, the can held by the star wheel, and the can bottom forming unit (hereinafter, abbreviated as the can bottom forming unit and the like) around the central axis of the rotation axis. The drive motor also rotates (revolves) the pressing roller around the spindle shaft (around the can shaft of the can held by the star wheel) via a gear mechanism or the like. The pressing roller is rotatable around the central axis of the pressing roller. Therefore, when the pressing roller is pressed against the inner peripheral wall of the annular convex portion and revolved around the spindle axis as described above, The pressing roller rolls on the inner peripheral wall while rotating (rotating) around its central axis.

In this way, the can bottom molding unit or the like revolves around the central axis of the rotation axis, and the pressing roller revolves around the spindle axis of the can bottom molding unit to revolve the bottom of the can held by the star wheel. Processing is applied and recesses are formed. By forming the concave portion in the bottom of the can, the strength of the bottom of the can is increased, and deformation of the bottom growth, buckling, etc. is suppressed.

U.S. Pat. No. 5,704,241

The conventional can bottom molding apparatus has the following problems.
For example, by increasing the rotation speed of the drive motor, it is possible to increase the speed at which the can bottom forming unit or the like is rotated around the central axis of the rotation axis, and to improve the production efficiency. However, when the rotation speed around the central axis of the rotation axis of the can bottom forming unit or the like is increased, the rotation speed around the spindle axis of the pressing roller is also increased accordingly, and as a result, the pressing roller is accompanied by an increase in centrifugal force around the spindle axis. Due to the extension of the link mechanism and the influence of speed dependence, the depth (molding amount) of the concave portion formed on the bottom of the can becomes deep.

That is, since the depth of the recess changes according to the speed at which the can bottom molding unit or the like is rotated around the central axis of the rotation axis, the pressure resistance strength of the can bottom changes depending on the operating speed of the device, and the quality of the can varies. Occurs. Specifically, the deeper the depth of the recess, the higher the pressure-resistant strength of the can bottom, and the shallower the depth of the recess, the lower the pressure-resistant strength of the can bottom. For example, when the amount of change in the depth of the recess is 0.5 mm (the amount of change in the BPR inner diameter (diameter) is 1.0 mm), the pressure resistance strength of the can bottom changes by about 130 kPa.

The present invention has been made in view of such circumstances, and is formed on the can bottom regardless of the operating speed of the device (corresponding to the rotation speed around the central axis of the rotation axis of the can bottom molding unit or the like). It is an object of the present invention to provide a can bottom forming method capable of stabilizing the processing accuracy of the concave portion to be formed.

One aspect of the present invention is a dome portion that is recessed upward in the can axis direction in the can bottom of a can that has a can body and a can bottom and has a bottomed tubular shape, and an outer peripheral edge portion of the dome portion. An annular convex portion extending downward along the can axis is formed, and at least one of the inner peripheral wall and the outer peripheral wall of the annular convex portion is pressed by a pressing roller. A can bottom molding method in which the pressing roller is rolled to form a concave portion extending in the circumferential direction in the annular convex portion, and the star wheel holding the can body of the can is held by the star wheel. A can bottom molding unit having a spindle shaft extending so as to coincide with the can shaft of the can, and a rotation shaft to which the star wheel and the can bottom molding unit are attached are rotated around the central axis of the rotation shaft. The ratio of the second rotation speed for rotating the pressing roller included in the can bottom molding unit to the first rotation speed to be rotated around the spindle axis is changed according to the magnitude of the first rotation speed. It is characterized by that.

In the can bottom molding method of the present invention, a rotation speed at which a star wheel, a can held by the star wheel, and a rotation shaft to which a can bottom molding unit (hereinafter referred to as a can bottom molding unit) is attached is rotated around its central axis. The ratio (speed ratio) of the rotation speed (second rotation speed) for rotating the pressing roller around the spindle axis to the (first rotation speed) is set to the first rotation speed (of the device) of the can bottom forming unit or the like. It is changed according to the magnitude of (corresponding to the operating speed).

Therefore, for example, when the first rotation speed of the can bottom forming unit or the like is increased for the purpose of improving the production efficiency, the ratio of the second rotation speed of the pressing roller to the first rotation speed is decreased. As a result, the second rotation speed of the pressing roller can be maintained within a predetermined range. On the contrary, when the first rotation speed of the can bottom forming unit or the like is lowered, the ratio of the second rotation speed of the pressing roller to the first rotation speed is increased to increase the pressing roller. The second rotation speed of the above can be maintained within a predetermined range.

That is, the speed ratio between the speed at which the can bottom forming unit or the like revolves around the central axis of the rotation axis and the speed at which the pressing roller revolves around the spindle axis can be inversely proportional to the first rotation speed. Therefore, regardless of the first rotation speed of the can bottom forming unit or the like, the second rotation speed of the pressing roller can be kept within the desired range. As a result, the depth (molding amount) of the recess formed in the can bottom is stabilized, and the pressure resistance strength of the can bottom is stably increased. Therefore, deformation of the bottom growth, buckling, etc. at the bottom of the can is surely suppressed.

From the above, according to the present invention, it is possible to stabilize the processing accuracy of the recess to be molded on the can bottom regardless of the operating speed of the device (corresponding to the rotation speed around the central axis of the rotation shaft of the can bottom molding unit or the like). it can. That is, regardless of the speed of operation, the processed quality of bottom reform processing can be stabilized, and good quality cans with stable quality can be manufactured.

Further, in the can bottom molding method, when the first rotation speed is increased, the ratio of the second rotation speed to the first rotation speed is decreased, and the first rotation speed is decreased. In this case, it is preferable to increase the ratio of the second rotation speed to the first rotation speed.

Further, in the can bottom molding method, a first drive motor for rotating the rotation shaft around the central axis of the rotation shaft and a second drive motor for rotating the pressing roller around the spindle shaft are provided. The ratio of the second rotation speed to the first rotation speed may be set by the ratio of the motor rotation speed of the second drive motor to the motor rotation speed of the first drive motor.

In the above configuration, the first drive motor rotates (revolves) the rotating shaft and the can bottom forming unit attached to the rotating shaft around the central axis of the rotating shaft. Further, the second drive motor rotates (revolves) the pressing roller around the spindle axis. Then, the ratio of the second rotation speed of the pressing roller to the first rotation speed of the can bottom forming unit or the like is the ratio of the motor rotation speeds of the first drive motor and the second drive motor that are independent of each other (rotation speed ratio). Set by.

Specifically, the motor rotation speed of the first drive motor is determined by the frequency of the power supply input to the first drive motor, and the motor rotation speed of the second drive motor is the frequency of the power supply input to the second drive motor. Is determined by. Therefore, by controlling the frequency ratio between the first drive motor and the second drive motor, the above-mentioned "ratio of the second rotation speed to the first rotation speed" can be set accurately and easily.

For example, when the operating speed of the apparatus is frequently changed, for example, the type of can to be molded is frequently changed, it is preferable to use the above configuration. That is, if the second drive motor is connected to the pressing roller and the second rotational speed of the pressing roller is kept within a predetermined range regardless of the first rotational speed of the can bottom forming unit or the like, the present invention described above. The effects of the above can be easily obtained without the need for troublesome parts replacement work (replacement / adjustment of the gear mechanism, etc.).

Further, in the can bottom forming method, the drive motor for rotating the rotating shaft around the central axis of the rotating shaft and rotating the pressing roller around the spindle shaft is provided, and the above-mentioned said with respect to the first rotation speed. The ratio of the second rotation speed may be set by adjusting at least one of the reduction ratio between the drive motor and the rotation shaft and the reduction ratio between the drive motor and the pressing roller. Good.

In the above configuration, the drive motor rotates (revolves) the rotation shaft and the can bottom molding unit attached to the rotation shaft around the central axis of the rotation shaft, and rotates the pressing roller around the spindle shaft (revolution). ). When the first rotation speed of the can bottom forming unit or the like is changed, the reduction ratio of the gear mechanism or the like (reduction mechanism) between the drive motor and the rotation shaft, and between the drive motor and the pressing roller By adjusting at least one of the reduction ratios of the gear mechanism and the like (reduction mechanism), the ratio of the second rotation speed to the first rotation speed is changed.

Specifically, for example, when the motor rotation speed of the drive motor is increased to increase the first rotation speed of the can bottom forming unit or the like for the purpose of improving production efficiency, the deceleration between the drive motor and the rotation shaft is reduced. By adjusting at least one of the ratio and the reduction ratio between the drive motor and the pressing roller, the ratio of the second rotational speed to the first rotational speed is reduced to reduce the second rotation of the pressing roller. The speed can be maintained within a predetermined range. On the contrary, when the motor rotation speed of the drive motor is reduced to reduce the first rotation speed of the can bottom molding unit or the like, the reduction ratio between the drive motor and the rotation shaft and the reduction ratio and the rotation shaft are reduced. By adjusting at least one of the reduction ratios between the drive motor and the pressing roller, the ratio of the second rotational speed to the first rotational speed is increased, and the second rotational speed of the pressing roller is set within a predetermined range. Can be maintained.

Therefore, while using one (common) drive motor to revolve around the central axis of the rotating shaft of the can bottom forming unit and the like and around the spindle axis of the pressing roller, the can bottom forming unit and the like are second. Regardless of the rotation speed of 1 (corresponding to the operating speed of the device), the depth (molding amount) of the recess formed in the can bottom can be stabilized, and the pressure resistance strength of the can bottom can be stably improved. In this case, since one drive motor is sufficient, the running cost can be reduced.

According to the can bottom molding method of the present invention, the processing accuracy of the recess to be molded on the can bottom can be stabilized regardless of the operating speed of the apparatus.

It is a vertical cross-sectional view which shows the vicinity of the bottom of a can. It is sectional drawing which shows the structure of the can bottom molding apparatus. It is a figure which shows the X part of FIG. 2 in an enlarged manner. It is a figure which shows the Y part of FIG. 2 in an enlarged manner. It is a figure which shows the Z part of FIG. 2 in an enlarged manner. It is sectional drawing which shows the vicinity of the bottom spindle of the can bottom molding apparatus enlarged. It is sectional drawing which shows the vicinity of the bottom spindle of the can bottom molding apparatus enlarged. It is a top view which shows the vicinity of the bottom spindle of the can bottom molding apparatus enlarged. It is sectional drawing which shows the vicinity of the top spindle of the can bottom molding apparatus enlarged. It is sectional drawing which shows the vicinity of the top spindle of the can bottom molding apparatus enlarged. It is a top view which shows the vicinity of the top spindle of the can bottom molding apparatus enlarged. It is a graph which shows the relationship between the operation speed and the BPR inner diameter in the Example and the comparative example of this invention. It is a graph which shows the relationship between the operation speed, the BPR inner diameter and the pressure resistance strength in the Example of this invention.

Hereinafter, the can bottom molding apparatus (bottom reform apparatus) 10 according to the embodiment of the present invention and the can bottom molding method (bottom reform method) using the same will be described with reference to the drawings. In addition, the drawings used for explaining the embodiments of the present invention may be shown by enlarging, emphasizing, or excerpting the main parts in order to make the features of the present invention easy to understand, and the dimensions of each component. The ratio etc. are not always the same as the actual ones.

First, the can 50 that is molded by the can bottom molding apparatus 10 of the present embodiment will be described.
As shown in FIGS. 1 and 10 (a) and 10 (b), the can 50 has a can body (wall) 51 which is a peripheral wall of the can and a can bottom (bottom) 52 which is a bottom wall of the can. It has a bottomed tubular shape in preparation. The can 50 of the present embodiment is an aluminum can made of an aluminum alloy material or the like, and the inside thereof is filled with contents such as beverages, and a can lid (not shown) is wrapped around the open end of the can body 51. It is sealed by. That is, the can 50 is a can body used for a so-called two-piece can.

The central axis of the can body 51 and the central axis of the can bottom 52 are arranged coaxially with each other, and in the present embodiment, these common axes are referred to as can axes.
Further, the direction in which the can shaft extends (the direction along the can shaft) is referred to as the can shaft direction. Of the can axis directions, the direction from the can bottom 52 toward the open end of the can body 51 is referred to as upward, and the direction from the open end of the can body 51 toward the can bottom 52 is referred to as downward.
The direction orthogonal to the can axis is called the radial direction. Of the radial directions, the direction closer to the can shaft is called the inner side in the radial direction, and the direction away from the can shaft is called the outer side in the radial direction.
Further, the direction of orbiting around the can axis is called the circumferential direction.

Unless otherwise specified, various shapes of the can 50, such as “concave”, “convex”, “dented”, and “protruding”, used in the present embodiment are exposed to the outer surface (outer surface of the can, which is exposed to the outside) of the can 50. It represents various shapes on the surface).
Further, in the vertical cross-sectional view (longitudinal view including the can shaft) of the can 50 shown in FIGS. 1 and 10 (a), 10 (b) and the like along the can axis direction, the "shape of each part of the can 50 is described. Line shapes such as "arc", "curve", "straight line", and "tangent" represent various line shapes on the outer surface of the can 50 unless otherwise specified.

Of the cans 50, the upper end portion of the can body 51 is an open end portion that opens to the outside of the can 50. The contents are filled into the can 50 through this open end. At the open end of the can body 51, a neck portion 53 whose diameter decreases toward the top is formed.

The can bottom 52 is connected to a dome portion 55 that is recessed upward in the can axis direction and an outer peripheral edge portion of the dome portion 55, projects downward in the can axis direction, and is along the circumferential direction around the can axis. It is provided with an annular convex portion (rim) 56 extending from the surface.
The annular convex portion 56 has a ground contact portion (nose portion) 59 that protrudes most downward on the can bottom 52, an inner peripheral wall (counter portion) 57 that is adjacent to the radial inner side of the ground contact portion 59, and a diameter of the ground contact portion 59. An outer peripheral wall (heel portion, chime portion) 58 adjacent to the outside in the direction is provided.

In the present embodiment, the can bottom molding apparatus 10 described later forms a groove-shaped recess 60 that is recessed outward in the radial direction and extends along the circumferential direction on the inner peripheral wall 57 of the can bottom 52 of the can 50. As shown in FIG. 1, the concave portion 60 has a concave curved shape in a vertical cross-sectional view including the can shaft of the can 50.
In the present embodiment, the can (work) before the concave portion 60 is formed is indicated by reference numeral W, and the can after the concave portion 60 is formed is indicated by reference numeral 50.

Next, the can bottom molding apparatus 10 shown in FIGS. 2 to 11 will be described.
The can bottom forming apparatus 10 forms a concave portion 60 as shown in FIG. 1 by pressing at least one of the inner peripheral wall 57 and the outer peripheral wall 58 among the annular convex portions 56 of the can bottom 52 of the can W. .. In the example of the present embodiment, the concave portion 60 is formed in the inner peripheral wall 57 by performing the bottom reforming process on the inner peripheral wall 57 of the annular convex portion 56.

As shown in FIG. 2, the can bottom forming apparatus 10 includes an apparatus frame 11 which is a base of the apparatus, a rotating shaft 12 rotatably supported by the apparatus frame 11 via a bearing, and the rotating shaft 12. A star wheel (turret) 13 that is attached and has a plurality of pockets for holding the can W of the work on the outer circumference, and a plurality of can bottoms that are attached to the rotating shaft 12 and are provided corresponding to each pocket of the star wheel 13. The first drive motor 41 that rotates the molding unit 14, the star wheel 13, the can bottom molding unit 14, and the rotating shaft 12 around the central axis O of the rotating shaft 12, and the pressing roller 20 of the can bottom molding unit 14, which will be described later. The second drive motor 42 is provided around the spindle shaft C of the can bottom forming unit 14 (around the can shaft of the can W held by the star wheel 13).

The first drive motor 41 is connected to the rotating shaft 12 via a driving force transmission member including a reduction mechanism such as a gear mechanism. The first drive motor 41 rotates the rotating shaft 12 with respect to the device frame 11 around its central axis O, so that the star wheel 13 integrally provided on the rotating shaft 12 and the plurality of can bottom forming units 14 Is rotated (revolved) around the central axis O of the rotating shaft 12.

The star wheel 13 has a disk shape or a columnar shape. The central axis of the star wheel 13 is arranged coaxially with the central axis O of the rotating shaft 12. On the outer circumference of the star wheel 13, a plurality of concave curved pockets corresponding to the shape of the outer peripheral surface (convex curved surface) of the can body 51 of the can W are formed at equal intervals in the circumferential direction around the central axis O. ing. In each pocket of the star wheel 13, the can body 51 of the can W is held by air suction or the like by an air suction means (not shown).

The can bottom forming unit 14 has a spindle shaft (spindle central shaft) C extending so as to coincide with the can shaft of the can W held by the star wheel 13. The can bottom forming unit 14 has a top spindle 15 arranged above the can axis direction of the can W held in the pocket of the star wheel 13 and integrally provided on the rotating shaft 12, and the can bottom forming unit 14 in the can axis direction of the can W. It includes a bottom spindle 17 that is arranged below and is integrally provided on the rotating shaft 12. The top spindle 15 and the bottom spindle 17 are arranged so as to face each other with a pocket of the star wheel 13 and a can W held in the pocket sandwiched between them and separated from each other in the spindle axis C direction, which is a common axis.

The top spindle 15 has a top support member 16 that supports the open end of the can body 51 of the can W held in the pocket of the star wheel 13. The bottom spindle 17 reciprocates in the radial direction with respect to the bottom support member 18 that supports the can bottom 52 of the can W held in the pocket of the star wheel 13 and the can bottom 52, and rotates around the spindle shaft C. The annular convex portion 56 has a pressing roller 20 for forming a concave portion 60 extending in the circumferential direction.

The spindle shaft C of the top spindle 15 and the central shaft of the top support member 16 and the central shafts of the spindle shaft C and the bottom support member 18 of the bottom spindle 17 are the can shafts of the can W held in each pocket of the star wheel 13. On the other hand, it is arranged coaxially. Each spindle shaft C corresponding to each pocket of the star wheel 13 extends parallel to the central axis O of the rotating shaft 12.

As shown in FIGS. 4 and 10 (a) and 10 (b), the top support member 16 has a topped tubular shape and includes a peripheral wall and a top wall. The top support member 16 can abut on the upper end (open end) of the can body 51 of the can W to support the open end of the can body 51. Specifically, the neck portion 53 of the can body 51 comes into contact with the peripheral wall of the top support member 16. Further, in the illustrated example, a guide member is fitted in the open end portion of the can body 51, and the can body 51 is also supported from the inside in the radial direction thereof. Instead of bringing the neck portion 53 of the can body 51 into contact with the peripheral wall of the top support member 16 as described above, the upper end opening edge of the can body 51 is brought into contact with the top wall of the top support member 16. You may.

As shown in FIGS. 4 and 7 (a) and 7 (b), the bottom support member 18 has a bottomed tubular shape and includes a peripheral wall and a bottom wall. The bottom support member 18 can abut on the bottom 52 of the can W and the lower end of the can body 51 to support the vicinity of the bottom 52 of the can. Specifically, the lower end portion of the can body 51 is fitted in the peripheral wall of the bottom support member 18. Further, the ground contact portion 59 of the can bottom 52 and the outer peripheral wall 58 come into contact with the bottom wall of the bottom support member 18.

As shown in FIGS. 2, 3, 6 (a), 6 (b) and 8, the bottom spindle 17 includes a bottom cam follower 19. The bottom cam follower 19 is engaged with the bottom cam 27 integrally provided on the device frame 11. In the example of the present embodiment, the bottom cam 27 is arranged on the radial outer side of the rotating shaft 12, and is a cylindrical cam extending around the central axis O of the rotating shaft 12.

That is, the can bottom molding device 10 includes a bottom cam mechanism 28 including a bottom cam follower 19 and a bottom cam 27 that engages with the bottom cam follower 19. Then, the bottom cam mechanism 28 reciprocates the bottom support member 18 with respect to the can W in the can axis (spindle axis C) direction.

Specifically, the bottom cam 27 of the bottom cam mechanism 28 forms a predetermined trajectory whose position along the central axis O direction changes toward the direction of the central axis O of the rotating shaft 12. By guiding the bottom cam follower 19 along this trajectory, the bottom cam follower 19 reciprocates within a range of a predetermined stroke L1 along the spindle axis C direction. Further, the bottom support member 18 connected to the bottom cam follower 19 also reciprocates within a range of a predetermined stroke L1 along the spindle axis C direction.

Further, as shown in FIGS. 2, 4 and 7 (a) and 7 (b), the bottom spindle 17 approaches and separates from the annular convex portion 56 of the can bottom 52 in the radial direction, and the annular convex portion A pressing roller 20 that presses at least one of the inner peripheral wall 57 and the outer peripheral wall 58 of 56 and is rolled around a can shaft (spindle shaft C) to form a concave portion 60 extending in the circumferential direction on the annular convex portion 56. I have.
In the present embodiment, the pressing roller 20 can reciprocate in the radial direction with respect to the inner peripheral wall 57 of the can bottom 52, and the inner peripheral wall 57 is pressed from the inner side to the outer side in the radial direction. By rolling on the can axis along the circumferential direction, a groove-shaped recess 60 extending in the circumferential direction is formed on the inner peripheral wall 57. That is, the pressing roller 20 rotates around the central axis of the pressing roller 20 while revolving around the can axis (spindle axis C) in a state of being pressed by the inner peripheral wall 57 of the can bottom 52.

The pressing roller 20 is a molding die made of, for example, a cemented carbide. The pressing roller 20 has a disk shape, a cylindrical shape, or a columnar shape, and its central axis extends parallel to the spindle shaft C. The pressing roller 20 is provided in the bottom support member 18 of the bottom spindle 17 so as to be rotatable around the central axis and slidable in the radial direction orthogonal to the central axis.

The bottom spindle 17 is provided with a link mechanism including a link portion 22 and the like for sliding the pressing roller 20 in the radial direction. The pressing roller 20 is connected to the molding cam follower 21 via a link portion 22 or the like.
As shown in FIGS. 3 and 6 (a) and 6 (b), the molding cam follower 21 is engaged with the molding cam 29 integrally provided on the apparatus frame 11. In the example of the present embodiment, the molding cam 29 is arranged on the radial outer side of the rotating shaft 12, and is a cylindrical cam extending around the central axis O of the rotating shaft 12.

That is, the can bottom molding device 10 includes a molding cam mechanism 30 including a molding cam follower 21 and a molding cam 29 that engages with the molding cam follower 21. Then, the molding cam mechanism 30 reciprocates the pressing roller 20 with respect to the can W in the radial direction orthogonal to the can shaft (spindle shaft C). In the illustrated example, the bottom cam 27 and the molding cam 29 are integrally formed on one cylindrical member.

Specifically, the molding cam 29 of the molding cam mechanism 30 forms a predetermined trajectory whose position along the central axis O direction of the rotating shaft 12 changes toward the direction of the central axis O. By guiding the molding cam follower 21 along this trajectory, the molding cam follower 21 reciprocates along the spindle axis C direction within a predetermined stroke L2 larger than the stroke L1. Then, the pressing roller 20 reciprocates within a range of a predetermined stroke L1 along the spindle axis C direction, and due to the action of the link portion 22 or the like (link mechanism), the difference between the stroke L2 and the stroke L1 (L2-L1). ), The linear motion in the spindle axis C direction is converted into a radial slide motion orthogonal to the spindle axis C, and the linear motion is also reciprocated in the radial direction within the range of the stroke.
As a result, the pressing roller 20 can press the inner peripheral wall 57 of the annular convex portion 56 of the can bottom 52 held by the bottom support member 18 from the radial direction.

As shown in FIGS. 2, 3 and 6 (a) and 6 (b), the can bottom forming apparatus 10 is arranged coaxially with the central axis O of the rotating shaft 12, and the central axis O with respect to the rotating shaft 12 A drive gear 23 that can rotate around and a driven gear 24 that meshes with the drive gear 23 and is coaxially arranged on the spindle shaft C (the can shaft of the can W held by the star wheel 13) and connected to the pressing roller 20. , Is equipped.

The drive gear 23 has a circular ring shape or a cylindrical shape, and a rotating shaft 12 is inserted therein. The drive gear 23 is rotatably attached around the central axis O on the radial outer side of the rotating shaft 12 via a bearing provided on the outer periphery of the rotating shaft 12.
The driven gear 24 is provided on each bottom spindle 17, and all the driven gears 24 mesh with one drive gear 23. That is, the driven gear 24 is a planetary gear that is arranged on the outer circumference of the drive gear 23, which is a sun gear, at equal intervals, and rotates while revolving around the drive gear 23.

In FIG. 2, the second drive motor 42 is connected to the drive gear 23 via a drive force transmission member including a reduction mechanism such as a pulley, a belt, a sprocket, and a gear mechanism.
In the example shown in FIG. 2, a connecting gear 44 that is integrated with the drive gear 23 and is rotatable around the central axis O around the rotating shaft 12 is provided. Specifically, the drive gear 23 is arranged at the first end (one end) along the central axis O direction of the cylindrical body through which the rotating shaft 12 is inserted, and the second end (the other end). A connecting gear 44 is arranged in the portion), and these are integrated with the central axis O as a common axis (that is, coaxially).

Further, between the connecting gear 44 and the second drive motor 42, there is a connecting gear 45 that meshes with the connecting gear 44, a sprocket 47 that is integrated with the connecting gear 45 via a shaft 46, and a sprocket 47 and a second. A sprocket 48 provided between the drive motor 42 (also between the sprocket 47 and the first drive motor 41, as will be described later) is provided. The shaft 46 is supported by a bearing (not shown) of the device frame 11, and is a first end portion (one end portion; an end portion located inside the device frame 11) along the central axis direction of the shaft 46. ), And a sprocket 47 is arranged at the second end (the other end; the end located outside the device frame 11).
The rotational driving force of the second drive motor 42 is transmitted to the drive gear 23 via the sprocket 48, the sprocket 47, the shaft 46, the connecting gear 45, and the connecting gear 44.

The second drive motor 42 rotates the drive gear 23 around the central axis O with respect to the device frame 11, so that the driven gear 24 that meshes with the drive gear 23 is driven relative to the drive gear 23. It rotates around the spindle shaft C while revolving around the outer circumference of the gear 23. Further, when the driven gear 24 is rotated around the spindle shaft C, the pressing roller 20 connected to the driven gear 24 supports the can W held by the star wheel 13 and the bottom support member 18 thereof. On the other hand, it rotates (revolves) around the spindle axis C.

In the present embodiment, the rotation direction of the rotating shaft 12 with respect to the device frame 11 around the central axis O and the rotation direction of the drive gear 23 with respect to the device frame 11 around the central axis O are set to be opposite to each other. That is, the rotation direction of the rotation shaft 12 that is rotationally driven around the central axis O by the first drive motor 41 and the rotation direction of the drive gear 23 that is rotationally driven around the central axis O by the second drive motor 42 are mutually exclusive. The opposite.

Further, in the present embodiment, the connection between the pressing roller 20 and the second drive motor 42 can be switched to the connection between the pressing roller 20 and the first drive motor 41, and the first drive motor 41 spindles the pressing roller 20. It can rotate around the axis C. Specifically, the can bottom forming apparatus 10 is provided with a shaft-shaped connecting member 43 capable of connecting the first drive motor 41 and the drive gear 23. Then, the rotational driving force of the first drive motor 41 is transmitted to the drive gear 23 via the connecting member 43, the sprocket 48, the sprocket 47, the shaft 46, the connecting gear 45, and the connecting gear 44.

As described above, when the second drive motor 42 and the drive gear 23 are connected and the driving force of the second drive motor 42 is transmitted to the pressing roller 20, for example, the connecting member 43 is removed to connect the second drive motor 42. The connection state between the first drive motor 41 and the drive gear 23 via the member 43 is released.
Further, when the first drive motor 41 and the drive gear 23 are connected and the driving force of the first drive motor 41 is transmitted to the pressing roller 20, the first drive motor 41 is driven via the connecting member 43. The connection state between the second drive motor 42 and the drive gear 23 is released by connecting the gear 23 and removing the belt member that connects the motor pulley of the second drive motor 42 and the sprocket 48, for example.

As shown in FIGS. 2, 5, 9 (a), 9 (b) and 11, the top spindle 15 includes a top cam follower 25. The top cam follower 25 is engaged with the top cam 31 integrally provided on the device frame 11. In the example of the present embodiment, the top cam 31 is arranged on the radial outer side of the rotating shaft 12, and is a cylindrical cam extending around the central axis O of the rotating shaft 12.

That is, the can bottom molding device 10 includes a top cam mechanism 32 including a top cam follower 25 and a top cam 31 that engages with the top cam follower 25. Then, the top cam mechanism 32 reciprocates the top support member 16 with respect to the can W in the can axis (spindle axis C) direction.

Specifically, the top cam 31 of the top cam mechanism 32 forms a predetermined trajectory whose position along the central axis O direction changes toward the central axis O of the rotating shaft 12. By guiding the top cam follower 25 along this trajectory, the top spindle 15 reciprocates within a range of a predetermined stroke L3 along the spindle axis C direction. However, the top support member 16 of the top spindle 15 is brought into contact with the open end of the can body 51 of the can W in the middle of the stroke L3, and after the contact, the action of the elastic member 26 (contraction due to elastic deformation). Further stops the forward movement toward the can W. Therefore, the stroke L4 of the top support member 16 shown in FIGS. 4 and 10 (a) and 10 (b) is set smaller than the stroke L3.
That is, in FIGS. 4 and 10 (a) and 10 (b), the top spindle 15 includes an elastic member 26, and the elastic member 26 faces the top support member 16 toward the can W in the can axis (spindle axis C) direction. To be urged to.

Next, a can bottom molding method using the can bottom molding apparatus 10 will be described with an example of operation.
The rotary drive force transmitted from the first drive motor 41 causes the rotary shaft 12 to rotate around its central axis O. Along with this, the star wheel 13 attached to the rotating shaft 12, the can W held by the star wheel 13, and the can bottom forming unit 14 provided on the rotating shaft 12 corresponding to the can W also rotate around the central axis O. It is rotated (revolved).

Correspondingly, for molding the bottom cam 27 of the device frame 11, the bottom cam follower 19 of the bottom spindle 17 engaged with the bottom cam 27, and the molding cam 29 of the device frame 11 and the bottom spindle 17 engaged with the molding cam 29. By the action of the cam follower 21, the bottom spindle 17 and its bottom support member 18 move forward (approach) in the spindle axis C direction toward the can W held in the pocket of the star wheel 13. That is, the bottom spindle 17 moves along the spindle axis C direction toward the top spindle 15 side (upper in the can axis direction; the same applies hereinafter) by the stroke L1. As a result, the bottom support member 18 is brought into contact with the can bottom 52 of the can W.

Specifically, the bottom wall of the bottom support member 18 comes into contact with the ground contact portion 59 and the outer peripheral wall 58 of the can bottom 52 of the can W from the spindle axis C direction. Further, the lower end portion of the can body 51 is fitted into the peripheral wall of the bottom support member 18. Further, the pressing roller 20 provided in the bottom support member 18 is arranged close to the can bottom 52 of the can W. Specifically, the outer peripheral edge portion (flange portion) of the pressing roller 20 is arranged to face the inner peripheral wall 57 of the annular convex portion 56 of the can bottom 52 from the inside in the radial direction.

Further, the can W in which the top spindle 15 and its top support member 16 are held in the pockets of the star wheel 13 by the action of the top cam 31 of the device frame 11 and the top cam follower 25 of the top spindle 15 that engages with the top cam 31. It moves forward (approaching) in the direction of the spindle axis C toward. That is, the top spindle 15 moves along the spindle axis C direction toward the bottom spindle 17 side (downward in the can axis direction; the same applies hereinafter) by the stroke L3. As a result, the top support member 16 is brought into contact with the open end of the can body 51 of the can W.

Specifically, in the middle of the stroke L3, the neck portion 53 at the open end of the can body 51 comes into contact with the peripheral wall of the top support member 16. After the top support member 16 comes into contact with the open end of the can body 51 in this way, the elastic member 26 elastically deforms according to the amount of forward movement of the top spindle 15 thereafter, so that the top support member 16 Further forward movement toward the bottom spindle 17 side along the spindle axis C direction is stopped. As a result, the top support member 16 moves toward the bottom spindle 17 side along the spindle axis C direction by a stroke L4 smaller than the stroke L3.
In the present embodiment, the bottom support member 18 is brought into contact with the can bottom 52 and the top support member 16 is brought into contact with the open end of the can body 51 at substantially the same time. is there.

Then, as shown in FIG. 4 and the like, the can W is sandwiched by the bottom support member 18 and the top support member 16 from both sides in the spindle axis C direction. At this time, the can W is supported by both support members 16 and 18 in a state of being pressurized in the can axis direction (spindle axis C direction) by the restoring deformation force of the elastic member 26.

Next, the molding cam follower 21 moves forward toward the top spindle 15 along the spindle axis C direction according to the difference (L2-L1) between the stroke L2 and the stroke L1. At this time, the link portion 22 (link mechanism) connected to the molding cam follower 21 slides the linear motion of the molding cam follower 21 in the spindle axis C direction in the radial direction orthogonal to the spindle axis C. Convert to. As a result, the pressing roller 20 connected to the link portion 22 is moved outward in the radial direction, and the outer peripheral edge portion (flange portion) of the pressing roller 20 is the inner peripheral wall 57 of the annular convex portion 56 of the can bottom 52. And presses the inner peripheral wall 57.

Further, the drive gear 23 is rotated around the central axis O by the rotational drive force transmitted from the second drive motor 42 (or the rotational drive force transmitted from the first drive motor 41 via the connecting member 43). The driven gear 24 that meshes with the drive gear 23 is rotated around the spindle shaft C. Along with this, the link portion 22 and the pressing roller 20 connected to the driven gear 24 rotate (revolve) around the spindle shaft C. As a result, the pressing roller 20 rolls around the inner peripheral wall 57 of the annular convex portion 56 (rotates while revolving), and the inner peripheral wall 57 has a groove-shaped recess 60 extending along the circumferential direction. It is molded.
In the present embodiment, the pressing roller 20 in a state of pressing the inner peripheral wall 57 of the annular convex portion 56 is rotated around the spindle axis C (around the can axis) by one or more rotations, so that the inside of the annular convex portion 56 is formed. A ring-shaped recess 60 extending over the entire circumference in the circumferential direction is formed with respect to the peripheral wall 57.

Here, the rotation speed at which the star wheel 13, the can bottom forming unit 14, and the rotation shaft 12 are rotated around the central axis O of the rotation shaft 12 is defined as the “first rotation speed”. The first rotation speed revolves the star wheel 13, the can W held by the star wheel 13, and the can bottom forming unit 14 (hereinafter abbreviated as the can bottom forming unit 14 and the like) around the central axis O of the rotating shaft 12. It is the speed to make it. When the first rotation speed of the can bottom forming unit 14 or the like is increased, the number of cans W of the work supplied to the pocket of the star wheel 13 per unit time and the number of cans 50 that are subjected to bottom reform processing and discharged from the pocket. That is, the processing amount of the molding process can be increased. As described above, since the processing amount of the molding process by the can bottom molding apparatus 10 depends on the first rotation speed of the can bottom molding unit 14 and the like, the first rotation speed can be paraphrased as "the operating speed of the apparatus". Can be done.
Further, the rotation speed at which the pressing roller 20 included in the can bottom forming unit 14 is rotated around the spindle shaft C (around the can shaft) is defined as a "second rotation speed". The second rotation speed is the speed at which the pressing roller 20 revolves around the spindle shaft C.

Then, in the present embodiment, the ratio of the second rotation speed of the pressing roller 20 to the first rotation speed of the can bottom forming unit 14 and the like is changed according to the magnitude of the first rotation speed. .. Specifically, when the first rotation speed of the can bottom forming unit 14 or the like is increased, the ratio of the second rotation speed of the pressing roller 20 to the first rotation speed is decreased. Further, when the first rotation speed of the can bottom forming unit 14 or the like is lowered, the ratio of the second rotation speed of the pressing roller 20 to the first rotation speed is increased.

In the present embodiment, the first rotation speed of the can bottom forming unit 14 and the like is determined according to the motor rotation speed of the first drive motor 41. Further, the second rotation speed of the pressing roller 20 is determined according to the motor rotation speed of the second drive motor 42. Therefore, the ratio of the second rotation speed to the first rotation speed is set by the ratio of the motor rotation speed of the second drive motor 42 to the motor rotation speed of the first drive motor 41.

The motor rotation speed of the first drive motor 41 is determined by the frequency of the power supply input to the first drive motor 41. Further, the motor rotation speed of the second drive motor 42 is determined by the frequency of the power supply input to the second drive motor 42.
That is, although not shown, the can bottom molding apparatus 10 of the present embodiment adjusts the power frequency of the first frequency converter and the second drive motor 42, which can adjust the power frequency of the first drive motor 41. A possible second frequency converter and a control unit for controlling the first and second frequency converters are provided. Then, the control unit changes the ratio (speed ratio) of the second rotation speed of the pressing roller 20 to the first rotation speed of the can bottom forming unit 14 or the like according to the magnitude of the first rotation speed.

After the bottom 52 is bottom-reformed to form the recess 60, the pressing roller 20 first retracts inward in the radial direction from the inner peripheral wall 57 in the reverse procedure of the above. Further, the top spindle 15 and the bottom spindle 17 move backward (separately) with respect to the can W in the spindle axis C direction, respectively, and the support state of the can W by the top support member 16 and the bottom support member 18 is released.

In this way, the can bottom forming device 10 performs bottom reform processing on the can bottom 52 of the can W, and a recess 60 is formed in the can bottom 52. The can 50 in which the recess 60 is formed is transferred to a subsequent process of the can bottom molding apparatus 10.

In the can bottom molding apparatus 10 of the present embodiment described above and the can bottom molding method using the same, the rotation speed (first) of rotating the rotary shaft 12 to which the can bottom molding unit 14 and the like are attached around the central axis O thereof. The ratio (speed ratio) of the rotation speed (second rotation speed) for rotating the pressing roller 20 around the spindle shaft C to the rotation speed of the can bottom forming unit 14 and the like is the first rotation speed (of the device). It is changed according to the magnitude of (corresponding to the operating speed).

Therefore, for example, when the first rotation speed of the can bottom forming unit 14 or the like is increased for the purpose of improving the production efficiency, the ratio of the second rotation speed of the pressing roller 20 to the first rotation speed is set. By lowering it, the second rotation speed of the pressing roller 20 can be maintained within a predetermined range. On the contrary, when the first rotation speed of the can bottom forming unit 14 or the like is lowered, the ratio of the second rotation speed of the pressing roller 20 to the first rotation speed is increased. The second rotation speed of the pressing roller 20 can be maintained within a predetermined range.

That is, the speed ratio between the speed at which the can bottom forming unit 14 or the like revolves around the central axis O of the rotating shaft 12 and the speed at which the pressing roller 20 revolves around the spindle shaft C is inversely proportional to the first rotation speed. Can be done. Therefore, regardless of the first rotation speed of the can bottom forming unit 14 and the like, the second rotation speed of the pressing roller 20 can be kept within the desired range. As a result, the depth (molding amount) of the recess 60 formed in the can bottom 52 is stabilized, and the pressure resistance strength of the can bottom 52 is stably increased. Therefore, deformation of the bottom growth, buckling, and the like on the can bottom 52 is reliably suppressed.

From the above, according to the present embodiment, the recess 60 to be molded into the can bottom 52 is processed regardless of the operating speed of the device (corresponding to the rotation speed around the central axis O of the rotating shaft 12 of the can bottom forming unit 14 or the like). The accuracy can be stabilized. That is, regardless of the speed of operation, the processed quality of bottom reform processing can be stabilized, and a good quality can 50 with stable quality can be manufactured.

Further, in the present embodiment, the first drive motor 41 rotates (revolves) the rotary shaft 12 and the can bottom forming unit 14 or the like attached to the rotary shaft 12 around the central axis O of the rotary shaft 12. Further, the second drive motor 42 rotates (revolves) the pressing roller 20 around the spindle shaft C. Then, the ratio of the second rotation speed of the pressing roller 20 to the first rotation speed of the can bottom forming unit 14 or the like is set to the ratio of the motor rotation speed of the second drive motor 42 to the motor rotation speed of the first drive motor 41 ( Set by (rotation speed ratio).

Specifically, the first drive motor 41 and the second drive motor 42 are independent of each other, and the motor rotation speed of the first drive motor 41 is determined by the frequency of the power supply input to the first drive motor 41. The motor rotation speed of the second drive motor 42 is determined by the frequency of the power supply input to the second drive motor 42. Therefore, by controlling the frequency ratio between the first drive motor 41 and the second drive motor 42, the above-mentioned "ratio of the second rotation speed to the first rotation speed" can be set accurately and easily. it can.

For example, when the operating speed of the apparatus is frequently changed, for example, the type of the can W to be molded is frequently changed, it is preferable to use the above configuration. That is, if the second drive motor 42 is connected to the pressing roller 20 and the second rotational speed of the pressing roller 20 is kept within a predetermined range regardless of the first rotational speed of the can bottom forming unit 14 or the like. The above-described effects of the present embodiment can be easily obtained without the need for troublesome parts replacement work (replacement / adjustment of the gear mechanism, etc.).

Further, in the present embodiment, the can bottom forming unit 14 and the like are rotated (revolved) around the central axis O, and the rotating direction of the rotating shaft 12 around the central axis O and the pressing roller 20 are rotated (revolved) around the spindle axis C. Since the rotation directions of the drive gear 23 around the central axis O are set to be opposite to each other, the following effects are obtained.
That is, in this case, when the can bottom forming unit 14 or the like is rotated in the first rotation direction (for example, clockwise) of the central axis O of the rotary shaft 12, the drive gear 23 is the first of the central axis O rotations. It is rotated in two rotation directions (for example, counterclockwise). As a result, unlike the present embodiment, for example, when the drive gear 23 is non-rotatably fixed to the device frame 11, the rotation speed of the driven gear 24 meshing with the drive gear 23 around the spindle shaft C is compared with the rotation speed. In the present embodiment, since the rotation speed (second rotation speed) around the spindle shaft C of the driven gear 24 that meshes with the drive gear 23 increases, the second rotation speed of the pressing roller 20 connected to the driven gear 24 is increased. You can speed up. That is, the ratio of the second rotation speed to the first rotation speed described above can be set based on the state in which the second rotation speed of the pressing roller 20 is increased. Therefore, the molding speed of the recess 60 in the can bottom 52 can be increased, and even when the operating speed of the device (the first rotation speed of the can bottom molding unit 14 or the like) is increased, the production efficiency can be improved. It can be surely planned.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention, for example, as described below.

In the above-described embodiment, the first drive motor 41 rotates the can bottom forming unit 14 and the like and the rotary shaft 12 around the central axis O of the rotary shaft 12, and the second drive motor 42 pushes the pressing roller 20 into the spindle shaft. It was supposed to be rotated around C, but it is not limited to this.
For example, when the operating speed of the device is changed infrequently, by using the connecting member 43 shown in FIG. 2, the can bottom forming unit 14 and the like and the rotating shaft 12 are used only by the first drive motor (drive motor) 41. May be rotated around the central axis O of the rotating shaft 12, and the pressing roller 20 may be rotated around the spindle shaft C. Then, the ratio of the second rotation speed of the pressing roller 20 to the first rotation speed of the can bottom forming unit 14 and the like is set as the reduction ratio between the first drive motor 41 and the rotation shaft 12 and the first drive motor. At least one of the reduction ratios between 41 and the pressing roller 20 is adjusted and set.

That is, in the above configuration, when the first rotation speed of the can bottom forming unit 14 or the like is changed, the reduction ratio of the gear mechanism or the like (reduction mechanism) between the first drive motor 41 and the rotation shaft 12 and the reduction ratio, and By adjusting at least one of the reduction ratios of the gear mechanism and the like (reduction mechanism) between the first drive motor 41 and the pressing roller 20, the ratio of the second rotation speed to the first rotation speed is changed.

Specifically, for example, when the motor rotation speed of the first drive motor 41 is increased to increase the first rotation speed of the can bottom forming unit 14 or the like for the purpose of improving production efficiency, the first drive motor 41 is used. The ratio of the second rotation speed to the first rotation speed by adjusting at least one of the reduction ratio between the rotation shaft 12 and the reduction ratio between the first drive motor 41 and the pressing roller 20. Can be reduced to maintain the second rotational speed of the pressing roller 20 within a predetermined range. On the contrary, when the motor rotation speed of the first drive motor 41 is reduced to reduce the first rotation speed of the can bottom forming unit 14 or the like, the first drive motor 41 and the rotation shaft 12 are used. By adjusting at least one of the reduction ratio between the first drive motor 41 and the reduction ratio between the first drive motor 41 and the pressing roller 20, the ratio of the second rotation speed to the first rotation speed is increased. The second rotation speed of the pressing roller 20 can be maintained within a predetermined range.

Therefore, one (common) drive motor (first drive motor 41 in the above example) is used to revolve around the central axis O of the rotating shaft 12 of the can bottom forming unit 14 and the like, and the spindle shaft C of the pressing roller 20. The depth (molding amount) of the recess 60 formed in the can bottom 52 is determined regardless of the first rotation speed (corresponding to the operating speed of the device) of the can bottom forming unit 14 or the like while revolving around. It can be stabilized and the pressure resistance of the can bottom 52 can be stably improved. In this case, since one drive motor is sufficient, the running cost can be reduced.

Further, in the above-described embodiment, the pressing roller 20 presses the inner peripheral wall 57 of the annular convex portion 56 of the can bottom 52 and rolls around the can shaft (spindle shaft C) to form a diameter on the inner peripheral wall 57. It was decided to form a groove-shaped recess 60 that is recessed outward in the direction and extends along the circumferential direction to perform bottom reform processing, but the present invention is not limited to this. For example, the pressing roller 20 presses the outer peripheral wall 58 of the annular convex portion 56 of the can bottom 52 and rolls around the can axis, recesses inward in the radial direction of the outer peripheral wall 58, and extends along the circumferential direction. The groove-shaped recess 60 may be formed and bottom reforming may be performed. Alternatively, the pressing roller 20 is pressed and rolled against both the inner peripheral wall 57 and the outer peripheral wall 58 of the annular convex portion 56 of the can bottom 52, respectively, and the concave portion 60 is formed in the inner peripheral wall 57 and the outer peripheral wall 58, respectively. May be good.

Further, in the above-described embodiment, the can bottom molding apparatus 10 and the can bottom molding method form the recess 60 with respect to the can bottom 52 of the can W used for the can body of the two-piece can. It is not limited to. For example, a recess 60 may be formed on the bottom of a bottle can in which the open end of the can body is necked or screwed by a bottle necker (bottle can manufacturing apparatus). Alternatively, the recess 60 may be formed with respect to the bottom of the DI (Drawing & Ironing) can produced in the process of manufacturing the bottle can. The DI can is a can body (that is, the outer diameter of the can body 51 is the can bottom 52) in which the neck portion 53 is not formed at the open end of the can body 51 of the can W described in the above embodiment. It is a can body that is constant from the connection part to the opening end part).

In addition, each configuration (component) described in the above-described embodiments, modifications, and notes may be combined as long as it does not deviate from the gist of the present invention, and addition, omission, replacement, and other configurations may be added. It can be changed. Further, the present invention is not limited by the above-described embodiments, but is limited only by the scope of claims.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to this embodiment.

[BPR inner diameter confirmation test based on operating speed]
The operating speed of the can bottom molding device 10 (corresponding to the first rotation speed around the central axis O of the rotating shaft 12 of the can bottom molding unit 14 or the like) and the BPR inner diameter of the can bottom 52 of the bottom reformed can 50 (corresponding to the first rotation speed around the central axis O of the can bottom molding unit 14 or the like). A confirmation test was conducted on the relationship with the maximum diameter of the inner peripheral wall 57, that is, the maximum inner diameter of the concave portion 60 of the annular convex portion 56).

A plurality of operating speeds of the device were set between 800 and 1800 cpm. In addition, "cpm" represents the number of cans made per minute (the number of cans to be bottom-reformed) of the device. Specifically, for example, when the number of pockets of the star wheel 13 is 12, the operating speed when the star wheel 13 rotates 100 times per minute is 1200 cpm.

In the embodiment of the present invention, the first drive motor 41 rotates (revolves) around the central axis O of the rotating shaft 12 of the can bottom forming unit 14 and the like, and the second drive motor 42 rotates around the spindle shaft C of the pressing roller 20. It was decided to rotate (revolve). Further, the motor rotation speed of the first drive motor 41 and the motor rotation speed of the second drive motor 42 can be controlled separately by the control unit. Then, the ratio of the second rotation speed of the pressing roller 20 to the first rotation speed (speed ratio) according to the magnitude of the first rotation speed (operating speed of the device: cpm) of the can bottom forming unit 14 or the like. :%) Was changed.

Specifically, as shown in Table 1 described later, when the first rotation speed (operating speed) of the can bottom forming unit 14 or the like is 1200 cpm, the second of the pressing roller 20 with respect to the first rotation speed. The speed ratio of the rotation speed was set to 100% (reference value). Then, when the first rotation speed is lowered from 1200 cpm, the speed ratio of the second rotation speed is increased from 100%, and when the first rotation speed is increased from 1200 cpm, the speed ratio is increased. The speed ratio of the second rotational speed was lowered below 100% so that the (actual) second rotational speed of the pressing roller 20 was within a predetermined range.
More specifically, the control unit, the first frequency converter, and the second frequency converter make it possible for the motor rotation speed of the second drive motor 42 (motor power supply) to be relative to the motor rotation speed of the first drive motor 41 (motor power supply frequency). The ratio of (frequency) was defined as the above ratio (speed ratio).

On the other hand, in the comparative example, the connecting member 43 is used, and only the first drive motor 41 rotates (revolves) around the central axis O of the rotating shaft 12 of the can bottom forming unit 14 and the like, and around the spindle shaft C of the pressing roller 20. It was decided to rotate (revolve). Further, the reduction ratio between the first drive motor 41 and the rotating shaft 12 and the reduction ratio between the first drive motor 41 and the pressing roller 20 are not changed (that is, both reduction ratios are fixed). .. Therefore, the ratio (speed ratio:%) of the second rotational speed of the pressing roller 20 to the first rotational speed (operating speed of the device: cpm) of the can bottom forming unit 14 or the like is the ratio of the can bottom forming unit 14 or the like. It is constant regardless of the magnitude of the first rotation speed.

Specifically, as shown in Table 2 described later, the second rotation speed with respect to the first rotation speed covers the entire range of the first rotation speed (operating speed) of 800 to 1800 cpm of the can bottom forming unit 14 and the like. The speed ratio was fixed at 120%. Therefore, if the first rotation speed of the can bottom forming unit 14 or the like increases, the second rotation speed of the pressing roller 20 also increases in proportion to this. Further, if the first rotation speed of the can bottom forming unit 14 or the like decreases, the second rotation speed of the pressing roller 20 also decreases in proportion to this. The reason why the speed ratio is set to 120% is that the molding amount (depth) of the recess 60 is secured even at the minimum operating speed of 800 cpm, and the pressure resistance strength of the can bottom 52 after BPR processing is maintained.

Then, in each of the examples and comparative examples of the present invention, the bottom 52 of the can bottom was subjected to bottom reform processing, and the inner diameter of the BPR after forming the recess 60 was measured. At each operating speed, the inner diameter of the BPR was measured by arbitrarily extracting 20 cans, and the average value, the maximum value, the minimum value, the standard deviation (σ), and 3σ were confirmed.
The confirmation results of the examples of the present invention are shown in Table 1 below, and the confirmation results of the comparative examples are shown in Table 2 below. Further, FIG. 12 shows the relationship between the operating speed and the BPR inner diameter.

From the results of Table 1 and FIG. 12, in the embodiment of the present invention, the BPR inner diameter of the can bottom 52 is substantially constant regardless of the operating speed of the device (first rotation speed of the can bottom forming unit 14 or the like). Therefore, it was confirmed that the variation in the inner diameter of BPR was remarkably suppressed. That is, it was found that the molding amount (depth) of the recess 60 formed in the can bottom 52 is constant regardless of the operating speed.
On the other hand, from the results of Table 2 and FIG. 12, it was found that in the comparative example, the BPR inner diameter of the can bottom 52 changes greatly depending on the operating speed of the device. Specifically, for example, when comparing the case where the operating speed is 800 cpm and the case where the operating speed is 1800 cpm, the BPR inner diameter has changed by about 0.3 mm.

[Confirmation test of BPR inner diameter and pressure resistance strength by operating speed]
Next, using the examples of the present invention, a confirmation test was conducted on the relationship between the operating speed, the BPR inner diameter, the pressure resistance strength, and the like. Specifically, under the same conditions as in the embodiment of the present invention in the above-mentioned "confirmation test of BPR inner diameter by operating speed", bottom reform processing is performed on the can bottom 52 at each operating speed of 800 cpm, 1300 cpm, and 1800 cpm. The BPR inner diameter, bottom depth (dome depth), pressure resistance strength, and bottom growth (can bottom elongation deformation amount) after forming the recess 60 were measured. The number of cans for measuring each operating speed was 20 cans arbitrarily extracted, and the internal pressure at the time of bottom growth measurement was 618 kPa.
The confirmation results are shown in Tables 3 to 5 and FIG. 13 below.

From the results of Tables 3 to 5 and FIG. 13, it was found that in the examples of the present invention, the BPR inner diameter, bottom depth, pressure resistance strength and bottom growth were substantially constant at each operating speed. That is, regardless of the operating speed of the device, the processing accuracy of the recess 60 formed in the can bottom 52 can be stabilized, and a good quality can 50 having no variation in the pressure resistance strength of the can bottom 52 and the like can be manufactured. It was confirmed that it could be done.

According to the can bottom molding method of the present invention, the processing accuracy of the recess to be molded on the can bottom can be stabilized regardless of the operating speed of the apparatus. Therefore, it has industrial applicability.

10 Can bottom molding equipment (bottom reform equipment)
12 Rotating shaft 13 Star wheel (turret)
14 Can bottom forming unit 16 Top support member 18 Bottom support member 20 Pressing roller 41 First drive motor (drive motor)
42 2nd drive motor 50 can 51 can body 52 can bottom 55 dome part 56 annular convex part (rim)
57 Inner peripheral wall (counter section)
58 Peripheral wall (heel part, chime part)
60 Recess C Spindle shaft (can shaft)
O Central axis W can (work)

Claims (4)

On the bottom of a can that has a can body and a can bottom to form a bottomed cylinder,
The dome part that dents upward in the can axis direction,
An annular convex portion that is connected to the outer peripheral edge of the dome portion, projects downward in the can axis direction, and extends along the can axis is formed.
A can bottom molding method in which at least one of the inner peripheral wall and the outer peripheral wall of the annular convex portion is pressed by a pressing roller, and the pressing roller is rolled to form a concave portion extending in the circumferential direction on the annular convex portion. hand,
A star wheel holding the can body of the can, a can bottom molding unit having a spindle shaft extending so as to coincide with the can shaft of the can held by the star wheel, and the star wheel and the can bottom molding unit. With respect to the first rotation speed for rotating the rotation shaft to which is attached around the central axis of the rotation shaft.
A can bottom molding method in which the ratio of a second rotation speed for rotating the pressing roller included in the can bottom molding unit around the spindle axis is changed according to the magnitude of the first rotation speed. The can bottom molding method according to claim 1.
When the first rotation speed is increased, the ratio of the second rotation speed to the first rotation speed is decreased.
A can bottom molding method for increasing the ratio of the second rotational speed to the first rotational speed when the first rotational speed is decreased. The can bottom molding method according to claim 1 or 2.
A first drive motor that rotates the rotating shaft around the central axis of the rotating shaft, and
A second drive motor that rotates the pressing roller around the spindle axis is provided.
A can bottom molding method in which the ratio of the second rotation speed to the first rotation speed is set by the ratio of the motor rotation speed of the second drive motor to the motor rotation speed of the first drive motor. The can bottom molding method according to claim 1 or 2.
A drive motor for rotating the rotating shaft around the central axis of the rotating shaft and rotating the pressing roller around the spindle shaft is provided.
The ratio of the second rotation speed to the first rotation speed is at least one of the reduction ratio between the drive motor and the rotation shaft and the reduction ratio between the drive motor and the pressing roller. Can bottom molding method to adjust and set.

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