PRODUCTION APPARATUS FOR PRODUCING EXTERNAL CAN OF DRY ELEMENT BATTERY

Abstract: A production apparatus produces an external can of a dry element battery. The production apparatus comprises a notch forming mechanism (2) supplied with a plate shaped base material (7) which becomes the external can of the dry ele­ ment battery for forming notches (7a, 7b, 7c) at predeter­ mined positions of the base material, a forming mechanism (4) for forming the base material which is formed with the notches into a cylindrical shape with a joint portion loca­ ted at a lower side, a turning mechanism (5) for turning the base material (7) which is formed to the cylindrical shape so that the joint portion faces up, a laser welding unit (6) for irradiating a laser beam from above the turned base material so as to join the joint portion by a laser welding and form the external can of the dry element battery, and a feeding mechanism (10, 15, 25, 40) for successively feeding the base material to the notch forming mechanism, the for­ ming mechanism the turning mechanism and the laser welding unit.

Description: The present invention generally relates to production apparatuses for producing external cans of dry element batteries (cells), and more particularly to a production apparatus which produces an external can of a dry element battery by using a laser welding to weld a joint portion. Such an apparatus, having the features recited in the preamble of claim 1, is described for example in document EP-A-0 208 564. Recently, cylindrical dry element batteries have changed from a type which has a paper outer packaging to a type which has a metal outer packcaging. As a result, the performance of the cylindrical dry element battery has greatly improved due to better resistance against liquid leak and better resistance against expansion. Accordingly, various production apparatuses have been proposed to produce the metal outer packaging of the cylindrical dry element battery. In the present specification, the metal outer packaging will hereinafter be referred to as an external can. Conventionally, a production apparatus which produces the external can is similar to a production apparatus which is used to produce a cylinder of a general three-piece can. Such a production apparatus generally comprises a forming mechanism for forming a plate shaped base material into a cylindrical body, and a joining device for joining confronting edges of the cylindrical body. The forming mechanism employs a roll forming method to form the cylindrical body, and the joining device employs a certain joining or bonding method to join the confronting edges of the cylindrical body. Recently, there is a proposal to join the confronting edges of the cylindrical body by a laser welding. When the laser welding is employed to join the confronting edges of the cylindrical body, no projection is formed at the joint. For this reason, the capacity of the battery is not reduced at the joint portion. As a result, the life of the battery can be extended, and the mechanical strength and the resistance against the liquid leak can be improved. When forming the cylindrical body by the roll forming, it is desirable that the joint portion where the confronting edges meet is positioned at a lower side. The forming mechanism which employs the roll forming method comprises an upper forming roll and a lower forming roll which has a diameter larger than that of the upper forming roll, and the lower forming roll is driven. Hence, the forming roll having the large diameter must be arranged at a height position which is higher than a position where the base material is supplied in order to position the joint portion at an upper side. When the forming roll having the large diameter is arranged at a high position, mechanisms and devices for dribing this forming roll must also be provided at the high position. But when the mechanisms and devices having large size and weight are concentrated at the high position of the production apparatus, there is a problem in that the safety of the production apparatus becomes poor. In addition, the position where the forming of the base material takes place becomes hidden by the forming roll which has the large diameter, and there is a problem in that an operator cannot confirm the forming state of the base material. Therefore, the joint portion of the cylindrical body which is formed by the roll forming is generally positioned at the lower side for the various reasons described above. On the other hand, when making the laser welding, it is desirable for safety reasons that a laser beam is emitted downwardly. If the laser beam were emitted upwardly and a slight gap exists at the joint portion of the cylindrical body, the laser beam will pass through the gap and advance upwardly of the production apparatus. This may cause an unexpected accident. Hence, it is desirable that the laser beam is emitted downwardly, but in this case, the joint portion of the cylindrical body must be positioned at the upper side. Therefore, the joint portion of the cylindrical body which is formed by the roll forming is conventionally positioned at the lower side owing to the arrangement of the forming rolls. On the other hand, the laser welding which brings out the various features described above cannot be employed because it is undesirable and dangerous to emit the laser beam upwardly of the production apparatus. For these reasons, a seam welding is conventionally employed as a method which can weld the joint portion which is positioned at the lower side. Accordingly, it is a general object of the present invention to provide a novel and useful production apparatus for producing external cans of dry element battery, in which the problems described above are eliminated. This apparatus is defined by the combination of features of independent claim 1. Another and more specific object of the present invention is to provide a production apparatus for producing an external can of a dry element battery, comprising a notch forming mechanism supplied with a plate shaped base material which becomes the external can of the dry element battery for forming notches at predetermined positions of the base material, a forming mechanism for forming the base material which is formed with the notches into a cylindrical shape with a joint portion located at a lower side, a turning mechanism for turning the base material which is formed to the cylindrical shape so that the joint portion faces up, a laser welding unit for irradiating a laser beam from above the turned base material so as to join the joint portion by a laser welding and form the external can of the dry element battery, and a feeding mechanism for successively feeding the base material to the notch forming mechanism, the forming mechanism, the turning mechanism and the laser welding unit. According to the production apparatus of the present invention, it is possible to employ both the forming rolls to form the base material into the cylindrical shape and the laser welding to weld the joint portion of the base material which has the cylindrical shape, because the production apparatus is provided with the turning mechanism. As a result, it is possible to produce the external cans of the dry element batteries with a high productivity. Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings. FIG. 1 is a plan view showing an embodiment of a production apparatus according to the present invention; FIG. 2 is a side view showing the embodiment of the production apparatus according to the present invention; FIGS. 3A through 3G are diagrams for explaining the forming of an external can from a base material; FIG. 4 is a side view showing a forming mechanism which is assembled within the embodiment of the production apparatus according to the present invention; FIGS. 5A and 5B are a cross sectional view and a side view respectively showing a turning mechanism which is provided in an embodiment of a production apparatus according to the present invention; and FIG. 6 is a diagram for explaining a driving system of the embodiment of the production apparatus according to the present invention. A description will be given of an embodiment of a production apparatus for producing an external can of a dry element battery according to the present invention. Fig. 1 shows a plan view of the embodiment of the production apparatus according to the present invention, and Fig. 2 shows a side view of the embodiment of the production apparatus according to the present invention. In Figs. 1 and 2, a production apparatus 1 generally comprises a notch forming mechanism 2, a preforming mechanism 3, a forming mechanism 4, a turning mechanism 5, a laser welding unit 6, various feeding mechanisms and the like. The production apparatus 1 forms a plate shaped base material 7 shown in Fig. 3A into an external can 8 of a dry element battery shown in Fig. 3G. A description will now be given of the mechanisms and devices constituting the production apparatus 1 by referring to the production steps of the external can 8. The base materials 7 are stacked on a stacker 9 which is positioned at a left portion of the production apparatus 1. In this state, each base material 7 is simply a press formed plate (sheet) which corresponds to one dry element battery as shown in Fig. 3A. When the production apparatus is started, the base materials 7 which are stacked on the stacker 9 are successively fed out one by one by a first feeding mechnism 10 to each of the mechanisms which will be described hereunder. The first feeding mechanism 10 has a carrier bar 11 which as a long stroke, and the base material 7 is moved in a direction X when the carrier bar 11 moves in the direction X. The base material 7 is first fed to the notch forming mechanism 2 by the first feeding mechanism 10. The notch forming mechanism 2 has a pair of upper and lower metal dies (not shown) which form notches 7a, 7b and 7c at three positions of the side edges of the base material 7 as shown in Fig. 3B. The notches 7a and 7b are formed so as to facilitate the bending of upper and lower portions of the external can 8 to the inside thereof in a step which is not carried out by the production apparatus 1. The notch 7c is formed to ensure safety when the dry element battery is erroneously used. The base material 7 which is formed with the notches 7a through 7c by the notch forming mechanism 2 is then fed to the preforming mechanism 3 by the first feeding mechanism 10. The preforming mechanism 3 has a pair of upper and lower preforming rollers 12 and 13 as shown in Fig. 6. Both side edge portions of the lower preforming roller 13 has a diameter slightly greater than the remaining portion of the lower preforming roller 13. For this reason, when the base material 7 shown in Fig. 3B passes between the upper and lower preforming rollers 12 and 13, side edge portions 7d and 7e of the base material 7 are bent slightly upwards as shown in Fig. 3C. The side edge portions 7d and 7e of the base material 7 are bent beforehand so as to improve the shape of the cylinder when the base material 7 is afterwards formed into the cylindrical shape. lf the external can 8 were formed without bending the side edge portions 7d and 7e of the base material 7 beforehand, the welded joint portion will project outwardly and it will be impossible to obtain a true cylindrical shape. The base material 7 which is formed with the notches 7a through 7c and is subjected to the preforming is fed by the first feeding mechanism 10 to a horizontal feed base 14. The first feeding mechanism 10 has the function of transporting the base material 7 in the direction X from the stacker 9 to the horizontal feed base 14. A horizontal feeding mechanism 15 is provided in a vicinity of the horizontal feed base 14. This horizontal feeding mechanism 15 also has a carrier bar 16, and the base material 7 shown in Fig. 3D which is transported to the horizontal feed base 14 is transported in a direction Y as the carrier bar 16 moves in the direction Y. The forming mechanism 4 is provided on a downstream side of the horizontal feeding mechanism 15 along the direction Y in which the base material 7 is transported. The forming mechanism 4 is shown in Fig. 4 on an enlarged scale. The forming mechanism 4 generally comprises feed rolls 17 and 18, a guide mechanism 19, forming rolls 20 and 21, a driving mechanism 22 and the like. The base material 7 which is transported in the direction Y by the horizontal feeding mechanism 15 is fed further in the direction Y by the feed rolls 17 and 18 and reaches the forming rolls 20 and 21. In this state, the base material 7 is fed to the forming rolls 20 and 21 with a high positioning accuracy because the base material 7 is guided by the guide mechanism 19. The upper forming roll 20 has a diameter smaller than the diameter of the lower forming roll 21, and the lower forming roll 21 with the large diameter is rotated by the driving mechanism 22. The upper forming roll 20 rotates counterclockwise while the lower forming roll 21 rotates clockwise in Fig. 4. When the base material 7 is fed to the forming rolls 20 and 21, the base material 7 is guided by a steel deflector 23 and moves in a direction A while being formed into a cylindrical shape. The base material 7 then makes contact with a steel blank stopper 24 and the base material 7 is formed into the cylindrical shape shown in Fig. 3E. Owing to the structure of the forming mechanism 4, a joint portion 24 where the two confronting edges of the base material 7 meet is positioned on a lower side. The joint portion 24 shown in Fig. 3E is the portion which is welded in a latter step. If the cylindrical shape were to be formed so that the joint portion 24 becomes positioned on an upper side, the forming roll 21 having the large diameter and the driving mechanism 22 which drives this forming roll 21 must be arranged at a high position of the forming mechanism 4. But as described before, such an arrangement causes problems in that the safety of the production apparatus becomes poor and the position where the forming of the base material 7 takes place becomes hidden by the forming roll 21 which has the large diameter thereby making it difficult for an operator to confirm the forming state of the base material 7. According to this embodiment, the base material 7 which is formed to the cylindrical shape as indicated by a one-dot chain line in Fig. 4 is guided by a carrier cylinder 30 and fed to the turning mechanism 5 while maintaining the state where the joint portion 24 is positioned on the lower side. Returning now to the description of Fig. 1 and 2, a second feeding mechanism 25 is provided at an upper portion of the forming mechanism 4 and the turning mechanism 5. The second feeding mechanism 25 is shown in detail in Fig. 2. The second feeding mechanism 25 has a pair of pulleys 26 and 27, a belt 28 which is fit on the pulleys 26 and 27, and a plurality of hooks 29 which are provided on the belt 28 for engaging and feeding the base material 7 which has the cylindrical shape. The base material 7 which is formed to the cylindrical shape by the forming mechanism 4 is guided by the carrier cylinder 30 and is fed in the direction X by the second feeding mechanism 25 to the turning mechanism 5. The turning mechanism 5 constitutes an essential part of the present invention. The turning mechanism 5 turns the position of the base material 7 so that the joint portion 24 faces upwardly. Figs. 5A and 5B show the turning mechanism 5 on an enlarged scale. The turning mechanism 5 has a simple construction comprising a turning cylinder 31, a transmitting shaft 32, a driving mechanism 33 and the like. As will be described later, a rotational force of a motor 34 is transmitted to the driving mechanism 33, and this rotational force is changed into an intermittent rotation by an intermittent mechanism which is built into the driving mechanism 33. This intermittent rotation is transmitted to the transmitting shaft 32 via a belt 35. A helical gear 36 is provided at an upper portion of the transmitting shaft 32, and the helical gear 36 meshes a helical gear 37 which is provided on the turning cylinder 31. Hence, the turning cylinder 31 rotates 180° intermittently at predetermined intervals. The turning cylinder 31 is provided coaxially to the carrier cylinder 30. Accordingly, the base material 7 which is fed in the direction X along the carrier cylinder 30 by the second feeding mechanism 25 is fed from the carrier cylinder 30 to the turning cylinder 31. In this state, the base material 7 must pass by a base 38 which holds the transmitting shaft 32 and the turning cylinder 31, but the joint portion 24 of the base material 7 which is formed to the cylindrical shape is positioned at the lower side. Hence, the transmitting shaft 32 and the base 38 are arranged so that the transmitting shaft 32 and the base 38 relatively pass between a gap which is formed at the joint portion 24 of the base material 7 as the base material 7 is fed. In addition, the portions of the transmitting shaft 32 and the base 38 which fit into the gap at the joint portion 24 of the base material 7 is made narrow as indicated by B in Fig. 5B so as not to excessively spread the gap at the joint portion 24 and deform the cylindrical shape. Next, a description will be given of the operation of the turning mechanism 5. The base material 7 which is formed to the cylindrical shape as described above is fed to the turning mechanism 5 by the second feeding mechanism 25, the Patter and the driving mechanisms (22, 33) being mechanically synchronized as will be described later. Hence, when the base material 7 is fed to the turning mechanism 5, the driving mechanism 33 which operates intermittently is in a non-driving state where the turning mechanism 5 is not driven and the base material 7 is fed to the turning cylinder 31 which is stationary. When the base material 7 is loaded onto the turning cylinder 31, the driving mechanism 33 starts to drive the turning mechanism 5 and the turning cylinder 31 rotates 180°. Accordingly, the base material 7 is turned so that the joint portion 24 faces up as shown in Fig. 3F. In this state, the mechanisms are mechanically synchronized so that the second feeding mechanism 25 is not driven. When the base material 7 is turned in the above described manner, the driving of the second feeding mechanism 25 starts and the base material 7 which has the joint portion 24 positioned at the upper side is fed to a carrier cylinder 39 which is located at the downstream side of the turning cylinder 31 along the direction X. The carrier cylinder 39 is shown in detail in Fig. 2. A third feeding mechanism 40 is provided at a lower portion of the carrier cylinder 39. The third feeding mechanism 40 has a construction similar to that of the second feeding mechanism 25 and comprises pulleys, a belt, hooks and the like. The base material 7 is fed towards the laser welding unit 6 by the third feeding mechanism under the guidance of the carrier cylinder 39. A butting mechanism 41 for eliminating the gap at the joint portion 24 of the base material 7 is provided in front of the laser welding unit 6. The butting mechanism 41 comprises a plurality of attachments 42 through 45 which are arranged on both sides of the carrier cylinder 39, and the attachments 42 through 45 are driven by chains 46 and 47. The base material 7 which is formed to the cylindrical shape and has the confronting edges which are made to butt each other by the butting mechanism 41 is fed to the laser welding unit 6. For example, the laser welding unit 6 is a CO₂ laser welding unit and is designed to emit a laser beam downwardly for safety reasons. The laser welding unit 6 is arranged at a position so that the laser welding unit 6 confronts the joint portion 24 of the base material 7 which is fed in the direction X. The laser welding unit 6 welds the joint portion 24 of the base material 7 by the laser welding and forms the external can 8 shown in Fig. 3G. The laser welding of the joint portion 24 of the base material 7 is made possible because the turning mechanism 5 is provided in the production apparatus 1. As described before, the laser beam used in the laser welding must be emitted downwardly for safety reasons and the joint portion 24 of the base material 7 must be positioned at the upper side when the base material 7 is fed to the laser welding unit 6. On the other hand, when forming the base material 7 which has the form of a plate into the cylindrical shape, the joint portion 24 is inevitably positioned at the lower side due to the characteristics of the forming rolls 20 and 21. According to the embodiment, it is possible to realize the production apparatus 1 which brings out both the fine characteristics of the forming rolls and the fine characteristics of the laser welding. In addition, the construction of the turning mechanism 5 is simple as described above in conjunction with Figs. 5A and 5B, and the construction of the production apparatus 1 will not become complex by the provision of the turning mechanism 5. The mechanisms and devices of the production apparatus 1 described heretofore are driven by a single driving motor 34. Fig. 6 shows an essential part of a driving system of the production apparatus 1. As shown in Fig. 6, the rotational force of the motor 34 is divided into two by a gear box 48. One output of the gear box 48 is used to drive the preforming mechanism 3. The other output of the gear box 48 is used to drive the notch forming mechanism 2, the forming mechanism 4, the turning mechanism 5, the horizontal feeding mechanism 15, the second feeding mechanism 25 and the like. Although not shown, the other feeding mechanisms 10 and 40 are also driven by the motor 34. Also shown in Fig. 6 are a cam 49 for driving the metal die of the notch forming mechanism 2, a cam 50 for driving the carrier bar 16 of the horizontal feeding mechanism 15, and an intermittent mechanism 51 for intermittently driving the second feeding mechanism 25. By driving the driving system of the production apparatus 1 by the single motor 34, it is possible to reduce the number of required motors, reduce the power consumption of the production apparatus 1, and reduce the cost of the production apparatus 1. In addition, it is possible to simplify the control system of the production apparatus 1 by mechanically synchronizing the driving of the driving system.

Claims: A production machine (1) for producing external cans (8) of dry element batteries from plate-shaped blanks (7), the machine comprising: a blank stacker (9) providing a supply of plate-shaped blanks (7), a roll forming station (4) for forming the blanks (7) into virtually a cylinder having a longitudinal gap (24) defined by two confronting edges (7d, 7e) of the blank (7), a laser welding station (6) providing a downwardly emitted laser beam for joining said confronting edges, and feeding means (10, 15, 25, 40) for feeding said blanks (7) from the blank stacker (9) to the roll forming station (4) and to the laser welding station (6) in succession, characterized in that said roll forming station (4) is of the type providing said longitudinal gap (24) at a lower position of the formed cylinder, and in that a turning station (5) is arranged between said roll forming station (4) and said laser welding station (6), said turning station (5) having rotable cylinder receiving means (31) connected with an intermittent driving mechanism (33) for turning each cylinder about its axis to bring said longitudinal gap (24) to an upper position before feeding the cylinder onward to the laser welding station (6). A production machine (1) as claimed in claim 1, characterized in that a preforming station (3) is arranged preceding the roll forming station (4), comprising roller means (12, 13) for preforming said edges (7d, 7e) of the blanks (7) determined to define said longitudinal gap (24). A production machine as claimed in claim 1 or 2, characterized in that a single motor (34) is provided for driving at least said feeding means (25), said roll forming station (4) and said driving mechanism (33) of the turning station (5) in synchronism. A production machine as claimed in any of claims 1 to 3, characterized in that a butting mechanism (41) is provided for butting said confronting edges (7d, 7e) at each cylinder prior to welding in said laser welding station (6).

Inventors: IHARA, SHINICHI, ITOH, JYOJI
Applicants: SOUDRONIC AG
Application year: 1989
Main classification: B21D51
IPC codes: B23K26, H01M2, B21D51