Abstract:
A sealing method for battery containers which employs a first fixture to engage with the outer peripheries of edges of an opening of a container made from metal sheets, in order to define a shape of the opening of the container; then a second fixture is inserted into an inner space of the container from its opening, so that the edges of the opening of the container are shaped due to the ductility and malleability properties of metal sheets, and lateral surfaces of the container are made flat; lastly, a cover is placed on the opening of the container to have the container sealed by a welding means. The sealing method can restore an original shape of the container from a deformed state by using the fixtures, so that an entire sealing process for battery containers can be executed by automation in order to save labor costs.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to a sealing method for battery containers and more particularly to fixtures by which a shape of a container formed from metal sheets can be adjusted automatically, and an original shape of the container can be restored from a deformed state, so that an entire sealing process for battery containers can be executed by automation. 
     2. Related Art 
     Because of breakthroughs in materials technology for lithium batteries, secondary batteries have become a power supplies source (e.g. lithium iron phosphate oxide) for devices which require large electricity consumption such as electric bikes and electric wheelchairs. The power storage quantity and power supply quantity of non-aqueous electrolytic secondary lithium batteries are larger than those of conventional lithium battery. 
     Because of breakthroughs in materials technology for lithium batteries, lithium batteries have become a power supply source (e.g. lithium iron phosphate oxide) for devices which require large electricity consumption such as electric bikes and electric wheelchairs. The power storage quantity and power supply quantity of non-aqueous electrolytic secondary lithium batteries are larger than those of conventional lithium battery. The battery container of the aforementioned secondary lithium battery is usually a metal container made of aluminum. Generally, the metal container is a container made of aluminum or stainless steel with at least one end having an opening; after an anode and a cathode, and a separator are installed in the metal container, the opening of the container is covered by a cover placing on its top, and then the opening of the container and the cover are sealed by using various sealing techniques so as to ensure a long-term and stable sealing of the battery interior to prevent moisture and air from penetrating. 
     Referring to  FIG. 1 , typically, a secondary battery  10  contains a plurality of battery cells  50  (three battery cells are shown in the drawing for an example) disposed inside a container  20  (a rectangular battery container is used as an example). Each of the battery cells  50  is composed of an anode layer, a separating layer and a cathode layer which are stacked together, and the battery cells  50  are conductively connected to electrode ends  40  disposed on a cover  30 . The container  20  is made of metal sheets including one of stainless steel, nickel-plated steel, aluminum, and aluminum alloy. 
     Currently, for sealing of the secondary battery  10  (a rectangular battery container is used as an example), longitudinal side edges  21  and transverse side edges  22  of an opening of the container  20  are welded together with longitudinal side edges  31  and transverse side edges  32  of the cover  30  by using a welding device. Typically, a laser welding technique is used for sealing, and the technique uses an intense light source (typically a nitrogen-filled lamp) to actuate a laser resonant cavity of a yttrium iron garnet (YIG bar) to emit a single-frequency light (λ=1.06 mm), and it is focused into a beam by resonance and refraction, then the focal point is pointed at connecting portions of the longitudinal side edges  21 ,  31 , and the transverse side edges  22 ,  32  of the container  20  and the cover  30  respectively, so that the corresponding edges are welded together into one body. As a result, an objective for welding and sealing of the cover  30  with the container  20  is achieved. 
     It should be noted that, in conventional sealing processes of the secondary battery  10 , because the container  20  is made of metal sheets, thus the longitudinal side edges  21  and surfaces  23  below the longitudinal side edges  21  can be easily concavely deformed during shipping and handling; furthermore, the transverse side edges  22  and the longitudinal side edges  21  can also be easily deformed and cannot be maintained vertical to each other when a large quantity of the containers  20  are stacked on each other. Manpower has to be relied on during the sealing process of the secondary battery  10  because of the deformation problems of the container  20  mentioned above; therefore, the shapes of the containers  20  have to be adjusted manually before the battery cells  50 , which are conductively connected to the electrode ends  40  of the cover  30 , can be placed inside the container  20  by workers, and the connecting portions of the longitudinal side edges  21 ,  31 , and the transverse side edges  22 ,  32  of the container  20  and the cover  30  have to be made flat, before proceeding with sealing by laser welding. 
     SUMMARY OF THE INVENTION 
     In order to solve the abovementioned drawbacks, the present invention provides a sealing method for battery containers, by using fixtures, the shape of a container formed from metal sheets can be adjusted automatically, and the original shape of the container can be restored from a deformed state, so that the sealing method is provided for automatically placing battery cells into the container. 
     Another objective of the present invention is achieved by automatically disposing battery cells into a container and flattening the connecting portions between the edges of the container and the cover, so that the sealing process can be automatically performed by a laser welding in order to save labor costs. 
     In order to achieve the abovementioned objectives, the present invention discloses a sealing method for battery containers of secondary batteries. A cover is placed on an opening of a container formed from metal sheets, then by using a welding means, the cover and corresponding edges of the container are welded together so as to seal the cover and the container, and the sealing method includes: 
     Using a first fixture to engage with the outer periphery of edges of an opening of a container to define the shape of the opening of the container; then a second fixture is inserted into an inner space of the container from its opening, and then the second fixture is drawn out from the inner space of the container, so that the shape of the opening of the container is fixed, and the lateral surfaces of the container are made flat due to the ductility and malleability properties of metal sheets; after the cover is placed on the opening of the container, the cover and the container can then be welded together by using a welding means. 
     In one embodiment, the second fixture comprises a front end portion and a back end portion, a sectional area of the front end portion is smaller than that of the back end portion, and an area of the opening of the container in which the shape of the opening is defined; a maximum sectional area of the back end portion of the second fixture inserted into the inner space of the container is not smaller than the area of the opening of the container in which the shape of the opening is defined. 
     In one embodiment, the first fixture can be further engaged with the lateral surfaces of the container to fix the shape of the opening of the container and the flatness of the lateral surfaces of the container. 
     A third fixture can be further used to flatten periphery surface of the cover, so that the periphery surfaces of the cover and the container are on a same plane. 
     When the cover is placed on the opening of the container, the periphery surface of the cover and the edges of the opening of the container are on a same plane; that is, the dimensions of the opening of the container and the cover are the same, so that a welding means can be performed for sealing by welding onto the top. 
     In one embodiment, when the cover is placed on the opening of the container, the periphery surface of the cover are located lower than the edges of the opening of the container; that is, the dimension of the cover is slightly smaller than that of an inner circumference of the opening of the container, so that a welding means can be performed for sealing by welding internally. 
     In one embodiment, when the cover is placed on the opening of the container, a lower circumference of the cover is closely connected to the edges of the opening of the container; that is, the dimension of the cover is the same as that of an outer circumference of the opening of the container, so that a welding means can be performed for sealing by welding laterally. 
     The advantages of the present invention lie in that: it can be applied to that the battery containers require alignment before welding in a manufacturing process. Due to the ductility and malleability properties of metal sheets, fixtures are used to adjust the shape of the container formed from metal sheets. Therefore, the sealing method of the present invention can be automated to solve the problems of following: the deformation of transverse and longitudinal side edges which are unable to maintain vertical to each other due to stacking and the concavely deformed longitudinal side edges or the lateral surfaces below the longitudinal side edges during shipping and handling. The present technique employs fixtures to automatically adjust the shape of the container formed from metal sheets, and to restore an original shape of the container from a deformed state, so that the battery cells can be automatically placed inside the container, and the connecting portions of the edges of the container and the cover are made flat for sealing by using a laser welding means, therefore an entire sealing process for the battery container can be executed automatically in order to save labor costs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a secondary battery; 
         FIG. 2  is an illustration of a first fixture according to one embodiment of the present invention; 
         FIG. 3  is an illustration of a first fixture according to another embodiment of the present invention; 
         FIG. 4  is a first illustration of a second fixture according to one embodiment of the present invention; 
         FIG. 5  is a second illustration of a second fixture according to one embodiment of the present invention; 
         FIG. 6  is an assembling illustration of a cover and a container according to one embodiment of the present invention; 
         FIG. 7  is a first illustration showing a welding area of a cover and a container according to one embodiment of the present invention; 
         FIG. 8  is a second illustration showing a welding area of a cover and a container according to one embodiment of the present invention; 
         FIG. 9  is an illustration of a cover being flatly pressed according to one embodiment of the present invention; 
         FIG. 10  is a first illustration of a cover and a container being welded together according to one embodiment of the present invention; 
         FIG. 11  is a first sectional view of a second fixture according to one embodiment of the present invention; 
         FIG. 12  is a second sectional view of a second fixture according to one embodiment of the present invention; and 
         FIG. 13  is a second illustration of a cover and a container being welded together according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiment and the accompanying drawings, but should not be construed as limitations thereof. 
     The present invention discloses a sealing method for battery containers and the sealing method can be applied to secondary batteries. A cover is placed on an opening of a container formed from metal sheets. Then, by using a welding means, the cover and corresponding edges of the container are welded together. Sealing of a rectangular battery container is used as an example below, and the method can be applied to any welding techniques which require alignments for processing the battery containers. 
     Referring to  FIGS. 2 to 7 , a first fixture  200  is used to engage with the outer periphery of edges of an opening  120  of a container  110 ; that is, longitudinal side edges  121  and transverse side edges  122  of the opening  120  as shown in  FIG. 2 , so as to define a shape of the opening  120  of the container  110 , to adjust deformation of the longitudinal side edges  121  and the transverse side edges  122  (which are not vertical to each other as shown in  FIG. 2 ) caused by piling up of the containers  110 , and also to fix the shape of the opening  120  of the container  110  for subsequent processes. In addition, by using a first fixture  210 , an engaging area with the container  110  can be enlarged, and the engaging area may include lateral surfaces  123  of the container  110  as shown in  FIG. 3 , so that the first fixture  210  can not only fix the shape of the opening  120  of the container  110  but keep the flatness of the lateral surfaces  123 . 
     After the first fixture  200  is engaged with the periphery of the opening  120  of the container  110 , a second fixture  300  is inserted into an inner space of the container  110  from the opening  120  as shown in  FIG. 4 , and then the second fixture  300  is drawn out from the inner space of the container  110  as shown in  FIG. 5 . Due to the ductility and malleability properties of metal sheets, the edges of the opening  120  of the container  110  are shaped (e.g. the transverse side edges  122  and the longitudinal side edges  121  are made vertical to each other), and the lateral surfaces  123  of the container  110  are made flat. The second fixture  300  comprises a front end portion  310  and a back end portion  320 . The sectional area of the front end portion  310  is smaller than that of the back end portion  320  and the opening  120  of the container  110 , and the sectional area of the back end portion  320  of the second fixture  300  must not be smaller than the area of the opening  120  of the container  110  in which the shape of the opening  120  is defined. It is shown in the figures as an example that the maximum sectional area and the shape of the back end portion  320  are the same as those of a cover  150 . 
     Accordingly, even though the longitudinal side edges  121  and the lateral surfaces  123  below the longitudinal side edges  121  or the opening  120  of the container  110  may be concavely deformed during handling and transportation, an original shape of the container  110  can still be restored from a deformed state by inserting the front end portion  310  of the second fixture  300  into the inner space of the container  110  such that the shape of the container  110  formed from metal sheets can be adjusted by the back end portion  320  of the second fixture  300  due to the ductility and malleability properties of metal sheets. 
     Lastly, the cover  150  which is conductively connected to at least one battery cell  130  (three battery cells  130  are used as an example as shown in the figures) is placed on the opening  120  of the container  110  as shown in  FIG. 6 . Typically, two electrodes  140  made of metal are penetrated through the cover  150  for electrically connected to an anode and a cathode of the battery cells  130  respectively. Practically, any conventional structures for electric connection of the cover  150  and the battery cells  130  can be applied, that is, any types of electrode which can go through the cover. 
     The battery cells  130  which are conductively connected to the cover  150  are disposed in the inner space of the container  110 , and the cover  150  is placed on the opening  120  of the container  110 . In addition, since the periphery surface of the cover  150  and the edges of the opening  120  of the container  110  are located at a same plane, a laser  400  is used for welding and sealing the cover  150  with the container  110  by a laser welding means from top as shown in  FIG. 7 . A metal layer  151  (commonly used metals such as copper, aluminum, etc.) of the cover  150  at the periphery surface thereof and the corresponding edges (the longitudinal side edges  121  and the transverse side edges  122 ) of the container  110  are welded together so that sealing of the battery container is achieved. The laser welding technique for sealing is of prior arts and is not an emphasis of the present invention; therefore it will not be explained further in details. 
     Referring to  FIG. 8 , alternatively, after the first fixture  200  is detached from the container  110 , the laser  400  is used for welding and sealing. The metal layer  151  of the cover  150  at the periphery surface thereof and the corresponding edges (the longitudinal side edges  121  and the transverse side edges  122 ) of the container  110  are welded together so that sealing of the battery container is achieved. 
     Referring to  FIG. 9 , in one embodiment, before the cover  150  is placed on the opening  120  of the container  110 , a third fixture  500  can be further used. The periphery surface of the cover  150  may be pressed by the third fixture  500  so as to flatten the periphery surface of cover  150 . When the cover  150  is placed on the opening  110  of the container  120 , the periphery surface of the cover  150  and the edges (the longitudinal side edges  121  and the transverse side edges  122 ) of the opening  120  of the container  110  are located at a same plane; therefore it is more convenient to use the laser  400  to perform welding and sealing operations, so that the metal layer  151  of the cover  150  at the periphery surface thereof and the corresponding edges of the container  110  are welded together, and sealing of the battery container is achieved. 
     Referring to  FIG. 10 , in one embodiment, when the cover  150  is placed on the opening  120  of the container  110 , a lower circumference of the cover  150  is closely connected to the edges (the longitudinal side edges  121  and the transverse side edges  122 ) of the opening  120  of the container  110 ; that is, the dimension of the cover  150  is the same as that of the opening  120  of the container  110 , then the laser  400  is used to weld the metal layer  151  of the cover  150  at the lateral sides thereof with the corresponding edges of the container  110  together from lateral sides, and sealing of the battery container is achieved. 
     A rectangular battery container is used as an example in the invention. However, it is not limited thereto, and the opening of the container does not have to be rectangular; if the first fixture is an oval shape (to correspond with a design of the cover), or a rectangular shape with beveled edges, the second fixture can also be designed to match the cover and the first fixture, so that the shape of the opening of the cover can be changed. 
     Referring to  FIGS. 11 to 13 , a pressing portion  321  can be formed on the back end portion  320  of the second fixture  300 . In one embodiment, a sectional area of the pressing portion  321  can be slightly larger than the area of the opening  120  of the container  110  as shown in  FIG. 11 , so that after the second fixture  320  is disposed in the inner space of the container  110  from the opening  120  and a notch  111  is formed near the opening  120  of the container  110  as shown in  FIG. 12 ; this is an advantage for positioning of the cover  150  on the opening  120  of the container  110 , for example, tightly contact between the cover  150  and the container  110  can be confirmed by slightly pressing on the cover  150 . In the embodiment, the cover  150  is placed on the opening  120  of the container  110 , and the periphery surface of the cover  150  are located lower than the edges (the longitudinal side edges  121  and the transverse side edges  122 ) of the opening  120  of the container  110 ; that is, the cover  150  is slightly smaller than the dimensions of an inner circumference of the opening  120  of the container  110 , then the laser  400  is used to weld the metal layer  151  of the cover  150  at the periphery surface thereof with the corresponding edges of the container  110  together by welding internally, and sealing of the battery container is achieved. 
     Note that the specifications relating to the above embodiments should be construed as exemplary rather than as limitative of the present invention, with many variations and modifications being readily attainable by a person of average skill in the art without departing from the spirit or scope thereof as defined by the appended claims and their legal equivalents.