METHOD FOR SEAMING PACKED CANS

Abstract: Improvements are made on the known method for seaming packed cans in the prior art, which consists of the steps of clamping a can body (4) and a lid (5) between a lifter (3) having a same rotary axis (12) as a chuck (2) rotated by drive means and adapted to drive itself or to be driven at the same speed as the aforementioned chuck, rotationally driving the entire assembly while applying a compression force thereto, and thereafter pressing a groove portion (6) of a roll (1) from the outside to an edge portion (5a) of the lid to wrap up and deform the edge portion, whereby a sealing property of the seaming portion can be insured. The improvements reside in that seaming is effected by pressing the groove portion of the aforementioned roll to the edge portion of the lid with the rotary axis (11') of the aforementioned roll kept inclined with respect to the rotary axis (12) of the aforementioned chuck.

Description: The present invention relates to a method for seaming packed cans, which is available in a can seamer for packed cans in which aluminium cans, iron cans and the like are used for packing beer, coffee, juice or the like. Description of the Prior Art: An automatic can seamer for packed cans representing the most relevant prior art was proposed in Laid-Open Japanese Utility Model Specification No. 60-171640 (1985). Explaining the operation of the proposed device with reference to Fig. 3, a can body 4 was placed on a lifter 3 having a same rotary axis 12 as a chuck 2 that was driven by a drive mechanism, after a lid 5 has been placed on the same can body 4 the lifter 3 was pushed up so that the lid 5 and the can body 4 might be clamped by the chuck 2 and the lifter 3 and subjected to a compressing force, also the lid 5, the can body 4 and the lifter 3 were integrally rotated by driving the chuck 2, thereafter a groove 6 of a roll 1 was pressed against an edge portion 5a of the lid 5 to wrap up and deform the edge portion 5a as shown in Fig. 5, thereby a flange edge 4a of the can body 4 was also wrapped up and deformed according to the aforementioned deformation of the lid edge portion 5a, eventually seaming was effected in such manner that a perfectly folded mouth edge 4a of the can body 4 was pinched between the edge portion 5a and a lid periphery 5b as shown in Fig. 6, and thereby lid fixing was achieved. In this prior art method, a rotary axis 11 of the roll 1 and the rotary axis 12 of the chuck 2 are parallel to each other, and the roll 1 moves from the outside in the direction perpendicular to the rotary axis 12 so that it may successively press the edge portion 5a of the lid 5. In the above-described device in the prior art, a successive working process was employed, in which the roll 1 was brought close to the edge portion 5a of the lid 5 from the outside in the direction perpendicular to the roll rotary axis 11 and the chuck rotary axis 12 to press the edge portion 5a, and the edge portion 5a was wrapped up to be deformed. The larger the overlap width h of the can (Fig. 6) is, the better becomes the sealing property between the can and the lid and the better is the appearance of the can. However, in order to enlarge this overlap width h , it is required that when the lid 5 is placed on the can body 4 and they are compressed by the lifter load as clamped between the chuck 2 and the lifter 3, the seaming portion of the lid 5 on the side of the can body 4 should bend exactly at the very base portion 7 thereof where the lid 5 and the can body 4 comes into contact with each other to hold a sufficient "body hook" (fold length) ℓ . However, in the above-mentioned seaming device in the prior art, since the structure of the roll 1 to be moved so as to successively press the edge portion 5a of the lid 5 was such that it moved from the outside in the direction perpendicular to the rotary axis 12 of the can to press the edge portion 5a, in order to exactly bend the edge portion 5a at the very base portion 7 thereof, a considerably large lifter load that is a compressing force acted between the lifter 3 and the chuck 2 was necessitated. Accordingly, unless a large lifter load was applied, it was difficult to insure a sealing property by enlarging the overlap width h of the seaming portion between the edge portion 5a of the lid 5 and the flange edge 4a of the can body 4. Therefore, in the prior art, in the case of aluminium cans it was necessary to select the aforementioned lifter load at about 80 kg. And a can wall thickness of 0.12 mm or more was necessary in order that buckling of the can may not be caused by the lifter load of about 80 kg. Accordingly, the arrangement and structure of the roll 1 in the above-described known device in the prior art involved the problem that it was impossible to contemplate reduction of a can material cost by thinning the can wall thickness to the above-mentioned thickness of 0.12 mm or less. Moreover, sometimes fine creases would be produced along the periphery of the seaming portion, and so, there was also the problem that these creases would stick into the can body, resulting in deterioration of a sealing property. SUMMARY OF THE INVENTION: It is therefore one object of the present invention to provide a novel method for seaming packed cans, which is free from the above-mentioned shortcomings inherent to the known method for seaming packed cans in the prior art. A more specific object of the present invention is to provide a method for seaming packed cans, in which even if a lifter load is made small as compared to the known method in the prior art, a sufficient overlap width of the seaming portion can be held, hence a sealing property at the seaming portion can be insured, and accordingly, even if a can wall thickness is made thin as compared to that in the prior art, buckling of the can would not be generated. This object is solved by a method according to claim 1. According to the present invention, owing to the above-mentioned characteristic feature that seaming is effected by pressing the groove portion of the roll to the edge portion of the lid with the rotary axis of the roll kept inclined with respect to the rotary axis of the chuck, the location of the edge portion of the lid coming into contact with the groove of the roll would change from the upper portion of the lid flange to its side portion and then to its lower portion as the lid and the can body rotate, hence wrapping deformation of the edge portion of the lid would proceed smoothly, thereby folding deformation of the edge portion of the can body that is secondarily resulted from the wrapping deformation of the lid edge portion, becomes easy, and therefore, successive seaming work for the can flange can be achieved perfectly even with a smaller lifter load than that applied in the prior art. Accordingly, even in the case of cans having a thinner wall thickness than that in the prior art, seaming work for a can flange can be effected without generating buckling of the can, and so, a can material cost can be reduced by the amount corresponding to the thinned thickness. Furthermore, according to the present invention, creases would not be produced along the periphery of the lid at the seaming portion in distinction from the prior art method, and a sufficiently large overlap width at the seaming portion can be realized. The above-mentioned and other objects, features and advantages of the present invention will become more apparent by reference to the following description of preferred embodiments of the invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: In the accompanying drawings: Fig. 1 is a front view showing an inclined state of a roll in a method for seaming packed cans according to a first preferred embodiment of the present invention; Fig. 2 and 3 is a side view showing one example of an automatic can seamer for packed cans in the prior art; Figs. 4, 5 and 6 are enlarged partial cross-section views showing the successive working steps for a seaming portion between a can body and a lid in the prior art; Fig. 7 is a perspective view showing a contact location between an uninclined roll and a lid in the prior art; Fig. 8 is a perspective view showing a contact location between an inclined roll and a lid according to the present invention; and Fig. 9 is a diagram showing a relation between a preset lifter load and a body hook. DESCRIPTION OF THE PREFERRED EMBODIMENTS: Now, the present invention will be described in greater detail with reference to the accompanying drawings, in which Fig. 1 shows a first preferred embodiment of the invention. Referring to Fig. 1, reference numeral 1 designates a roll having a groove 6, numeral 2 designates a chuck, numeral 3 designates a lifter, numeral 4 designates a can body, numeral 5 designates a lid, numeral 12 designates a rotary axis of a chuck, and the structures of the respective members are identical to those shown in Fig. 3. The method illustrated in Fig. 1 is different from the prior art method shown in Fig. 3 in that the groove 6 of the roll 1 is pressed to an edge portion 5a of the lid 5 with an rotary axis 11′ of the roll 1 kept inclined with respect to the rotary axis 12 of the chuck 2. The arrangement of the roll 1 shown in Fig. 1 is such that seaming work is effected by pressing the groove 6 of the roll 1 to the edge portion 5a of the lid 5 with the rotary axis 11′ of the roll 1 kept inclined with respect to the rotary axis 12 of the chuck 2 on a tangential plane of a cylindrical surface having its center axis located on the rotary axis 12. More particularly, starting from the state where the rotary axis 11′ is placed in parallel to the rotary axis 12 with the surface of the roll 1 kept in contact with a cylindrical surface having its center axis aligned with the rotary axis 12, the rotary axis 11′ is inclined leftwards as viewed in Fig. 1 on a tangential plane of the cylindrical surface. It is to be noted that while the rotational direction of the rotary axis 11′ of the roll 1 is the direction for the roll 1 to depress the lid 5 in the illustrated case, the roll 1 could be rotated in the opposite direction, and in this case the rotational direction is the direction for the roll 1 to push up the lid 5. Now, explaining the operation of the above-described arrangement, the can body 4 having the lid 5 placed on its mouth portion and the lid 5 are clamped between the lifter 3 and the chuck 2 as applied with an appropriate lifter load, and when the chuck 2 is rotated about the rotary axis 12 by drive means not shown, the chuck 2, the can body 4 and the lifter 3 rotate integrally in the same direction. On the other hand, the roll 1 successively approaches to the lid 5 while being rotated in the direction of an arrow about the roll rotary axis 11′ by separate drive means not shown, it presses the groove 6 to the edge portion 5a of the lid 5, and thereby the seaming portion of the can body 4 and the lid 5 is subjected to successive working, starting from the state shown in Fig. 4, through the state shown in Fig. 5 into the state shown in Fig. 6. The contact locations 8 between the wrapping deformation portion 5a and the roll 1 during this seaming work would align on the same radial line portions as shown in Fig. 7 in the event that the rotary axis 12 of the roll 1 does not incline, whereas in the event that the rotary axis 12 inclines, as the seaming portion and hence the lid 5 rotationally proceeds the contact portions 8 would change from the upper portion of the radial lines through its side portion to its lower portion as shown in Fig. 8, and so, wrapping deformation of the can lid edge portion 5a would proceed smoothly. Consequently, folding of the can flange portion becomes deep as a secondary result of the deformation of the can lid edge portion 5a, and a sufficient body hook ℓ can be realized. Furthermore, the seaming method according to the present invention can be practiced even by pressing the groove 6 of the roll 1 to the edge portion 5a of the lid 5 with the rotary axis 11' of the roll 1 inclined in any arbitrary direction with respect to the rotary axis 12 of the chuck 2 in combination with the inclination according to the first preferred embodiment illustrated in Fig. 1 and in most cases this combined method is employed. It is to be noted that a possible range of the inclination angle of the rotary axis 11' with respect to the rotary axis 12 in the above-described respective embodiments, is 1 - 6° and an appropriate range thereof is 3 - 4°. A diagram in Fig. 9 shows the correlation between a preset load of the lifter 3 taken along an abscissa and a body hook ℓ taken along an ordinate, in the case where the seaming roll 1 is inclined in the direction of a lever being pressed to the can body 4 in a rotary motion type can seamer that is employed in many seaming lines. An inclined roll 1 having the width of the groove 6 broadened by about 5% as compared to that in the prior art, was employed, and data for a roll having an inclination angle of 3° and that having an inclination angle of 4° are shown. With regard to the direction of inclination, mainly the rotary axis 11' of the roll 1 is inclined with respect to the rotary axis 12 of the chuck 2 within a tangential plane of a cylindrical surface having its center axis aligned with the rotary axis 12, as shown in Fig. 1. As seen from Fig. 9, a preset load for the lifter 3 that is necessary for obtaining the same body hook ℓ could be reduced by 5 - 15 kg as compared to the prior art method. As explained in detail above, according to the present invention, owing to the fact that seaming is effected by pressing the groove portion of the roll to the edge portion of the lid with the rotary axis of the roll kept inclined with respect to the rotary axis of the chuck, the location of the edge portion of the lid coming into contact with the groove of the roll would change from the upper portion of the lid flange to its side portion and then to its lower portion as the lid and the can body rotate, hence wrapping deformation of the edge portion of the lid would proceed smoothly, thereby folding deformation of the edge portion of the can body, becomes easy, and therefore, successive seaming work for the can flange can be achieved perfectly even with a smaller lifter load than that applied in the prior art. Accordingly, even in the case of cans having a thinner wall thickness than that in the prior art, seaming work for a can flange can be effected without generating buckling of the can, and so, a can material cost can be reduced by the amount corresponding to the thinned thickness. Furthermore, according to the present invention creases would not be produced along the periphery of the lid at the seaming portion in distinction from the prior art method, and a sufficiently large overlap width at the seaming portion can be realized.

Claims: A method for seaming packed cans consisting of the step of clamping a can body (4) and a lid (5) between a lifter (3) having a same rotary axis (12) as a chuck (2) rotated by drive means and adapted to drive itself or to be driven at the same speed as said chuck (2) and said chuck (2), rotationally driving the entire assembly while applying a compression force thereto, and thereafter pressing a groove portion (6) of a roll (1) from the outside to an edge portion of the lid to wrap up and deform the edge portion, whereby a sealing property of the seaming portion can be insured; characterized in that seaming is effected by pressing the groove portion (6) of said roll (1) to the edge portion of the lid with the rotary axis (11') of said roll (1) kept inclined with respect to the rotary axis (12) of said chuck (2) on a tangential plane of a cylinder surface having its center axis located on the rotary axis (12).

Inventors: TAKAGI, KOICHI NAGOYA MACHINERY WORKS MITSUBISHI, TAURA, YOSHIHARU C/O TAKASAGO TECHNICAL INST., YUZAKI, YOSHINORI HIROSHIMA TECH. INST.MITSUBISHI
Applicants: MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1989
Main classification: B21D51
IPC codes: B21D51