Abstract:
A method and apparatus for preparing connecting straps and end terminals for lead batteries by filling selected cavities of the mold is disclosed. The mold has cavities for casting connecting straps and an end terminal. Molten lead is filled up to an amount of lead sufficient to fill the preselected cavities of the mold. The content of the mold is brought together with inverted plate lugs of grouped battery plates to fuse the plate lugs together with the content of the mold prior to solidification. The method and apparatus includes a first mold block having at least three mold cavities in an upper face thereof, whereby at least two preselected cavities of the at least three mold cavities are translationally aligned to be filled with lead.

Description:
TECHNICAL FIELD 
     This disclosure relates to lead-acid batteries and, more particularly, to a method and apparatus for delivering molten lead or a lead alloy to the cast-on-strap molds used in the manufacture and assembly of lead-acid batteries. 
     BACKGROUND OF THE INVENTION 
     Electrochemical storage batteries, and in particular, lead sulfuric acid storage batteries are ubiquitous in automotive applications. These batteries have electrochemical cells developing about 2.1 Volts each. Generally, six of these cells are connected in series to produce the 12 Volt battery known as a SLI (starting, lighting, ignition) battery common in automobile systems. 
     The cell elements comprise a series of alternating positive and negative plates with separators positioned therebetween. The electrical connections for the positive plates, and the negative plates as well, are typically made by a strap which connects the lugs of individual plates together. The straps are made of a wide variety of molten lead, or, more usually, lead-based alloys. 
     Various machines have been developed and used over the years to cast the straps onto the cell elements in a semi-continuous manner. Such machines have often been termed “cast-on-strap machines”. Generally, cast-on-strap (COS) machines require inserting the cell element upside down into a mold for the strap. The lug elements for the respective plates are thus positioned in a mold containing the requisite molten lead or molten lead alloy, and the molten material is allowed to solidify. The cell element is then removed with the cast-on-strap in place. 
     Typically in COS machines, stacked battery plates and separators for a plurality of cells making up a lead-acid storage battery have the respective connection lugs on the positive and negative plates of each cell interconnected by a cast-on strap and an intercell connecting post or terminal post cast as an integral portion of each strap. These casting operations are accomplished simultaneously with the cells inverted but otherwise oriented as they are to be in the finished battery structure. Stacked cell elements are clamped with the plate lugs extending downward. A plurality of properly oriented mold cavities (e.g., 12 cavities for a 12V battery) are preheated then molten lead is poured or flows into each mold cavity. The clamped cell assemblies are positioned to immerse a portion of the plate connecting lug on each plate in the molten mass in an appropriate connector strap cavity. The cavities are then chilled, as by flowing water through the body of the mold, and when the molded straps and posts solidify adequately they are extracted from the mold with the plates fused thereto. 
     Mold expense is a significant factor in machines of the type under consideration. It has been difficult to obtain suitable castings in which mold forms can be produced. The variety of cell and terminal arrangements required for lead-acid batteries has further complicated mold construction. Furthermore, the simultaneous casting operation discussed above necessitates large expensive molds and large casting machines. 
     In accordance with the above, it is desirable to improve mold assemblies for battery strap and post cast-on machines. It is further desired to decrease cycle time of battery strap and post cast-on machines while reducing the cost and size of mold assemblies and casting machines. 
     SUMMARY OF THE INVENTION 
     A method and apparatus for preparing connecting straps and end terminals for lead batteries by filling selected cavities of one or two molds is disclosed. A first mold includes five mold cavities in an upper face thereof, whereby at least two preselected cavities of the five mold cavities are translationally aligned to be filled with lead to form a first strap/post terminal configuration while another at least two preselected cavities of the first mold form a second strap/terminal configuration. A second mold includes five mold cavities in an upper face thereof that form third and fourth strap/post terminal configurations depending on which two cavities are selected and translationally aligned to be filled with lead. The first and seconds molds form four different strap/post configurations for connecting individual cells formed from the two molds in a multi-cell battery. In another embodiment, a single mold includes five cavities in an upper face thereof, whereby at least two preselected cavities of the five mold cavities are selected to form a selected strap/terminal configuration. The single mold forms four different strap/post configurations for connecting individual cells formed from the two molds in a multi-cell battery. 
     In another embodiment, a method for casting straps onto storage battery plates is disclosed. The method includes providing a source of molten lead, receiving a first mold block having five mold cavities in an upper face thereof in a first molding station, whereby at least two preselected cavities of the five mold cavities are filled with lead, translating the mold block to align each of the at least two preselected cavities with the source of molten lead, and translating the battery plate group or the mold block toward a battery plate group to dip lugs of the group into the at least two preselected cavities and allow solidification of the molten lead producing a molded cell for placement in a multi-cell battery. 
     The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following brief description of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the exemplary drawings, which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several figures: 
     FIG. 1 is a partially broken away schematic perspective view of the operating elements of the apparatus in which the mold assemblies of this disclosure are utilized; 
     FIG. 2A is a top view of one exemplary mold having five cavities for allowing flow of lead therethrough that cast straps in a first configuration for a cell in a battery; 
     FIG. 2B is a top view of an exemplar complementary mold of FIG. 2A having five cavities that cast straps in a second configuration for another cell of the battery; 
     FIG. 2C is a side view of the mold of FIG. 2A illustrating U-shaped flanges in the first configuration extending from straps formed by the cavities; 
     FIG. 2D is a side view of the mold of FIG. 2B illustrating U-shaped flanges extending from straps formed by the cavities; 
     FIG. 3 is a plan view of a 12V battery having six cells similar to those shown in FIGS. 2A-D illustrating electrical communication between contiguous cells through opposite polarity terminal connection with an intercell connector; 
     FIG. 4A is a top view of an alternative exemplary mold having five cavities for allowing flow of lead therethrough that cast straps in a first set of configurations for a cell in a battery; 
     FIG. 4B is a top view of an alternative exemplar complementary mold of FIG. 4A having five cavities that cast straps in a second set of configurations for a cell of the battery; 
     FIG. 5 is a top view of yet another exemplary single mold having five cavities for allowing flow of lead therethrough that cast straps/terminals in four configurations for a cell in a battery; and 
     FIG. 6 is a plan view of another 12V battery having six cells similar to those shown in FIG. 3 illustrating placement of molded cell configurations formed with the mold of FIG.  5  and electrical communication between contiguous cells through opposite polarity terminal connection with an intercell connector. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A small cast-on strap (COS) machine in which the mold assembly  12  of this disclosure is utilized is shown generally at  10  in FIG. 1 as comprising a cast-on station  14  having a transfer station  16  for unloading lead-acid battery cells resulting from mold assembly  12 , a lug burnishing station  20 , a lug fluxing station  18 , and a transfer mechanism  22  in operable communication with a rotable receptacles  30  disposed on a periphery portion of cast-on station  14 . Transfer mechanism  22  also allows transfer to perform burnishing and fluxing operations at stations  20  and  18  and also loads the rotating receptacles  30 . In addition, transfer mechanism  22  unloads the rotating receptacles  30  for further processing of resulting battery cell elements at transfer station  16 . Cast-on station  14  is in further operable communication with two molding stations  26 ,  28 . Controls (not shown) for the COS machine  10  are automatically or semi-automatically operated to advance mold assemblies  12  produced at cast-on station  14  through other processes, such as cooling, by rotating cast-on station in a counter-clockwise direction, for example. Transfer mechanism  22  transfers elements through the burnishing, fluxing and then on cast-on station  14 . Cast-on station  14  is configured to receive molding assembly  12  on cast-on station  14  for advancement to the molding stations  26 ,  28  of cast-on station  14  in proper timing and sequence to result in casting cell strap and post terminals on the lugs of the positive and negative battery plates  32  disposed in molding assembly  12  for each cell to connect those respective lugs electrically and mechanically and to form intercell connector lugs or battery terminal posts (not shown) in appropriate spatial relationship for latter placement in a battery case. 
     The COS machine includes a drive means (not shown) for operable rotation of cast-on station  14 . Stacks of interleaved positive and negative battery plates  32  with suitable separators are mounted with their lugs extending downward and clamped together, typically by a machine operator actuating manual controls. When all plates  32  are aligned and stacked, the stack is elevated by transfer mechanism  22  and advanced at a level to carry the lugs  34  through a rotating burnishing brush in burnishing station  20 . The stack then advances to a position above fluxing station  18 , is stopped and lowered to dip the lugs  34  in a fluxing solution. It is then raised and permitted to drain. 
     At an appropriate point in the cycle of machine control, the mold assembly  12  is preconditioned for casting. The stack is then advanced in its elevated condition from the fluxing station  18  to the cast-on station  14 . In a preferred embodiment, transfer mechanism  22  is a robot configured to provide suitable transfer functions outlined above. The cast-on station  14  rotates toward molding stations  26 ,  28  to immerse lugs  34  in molding assembly  12  for injecting molten lead in selected mold cavities for the connector straps and post terminals. It will be appreciated that although injection of lead is discussed, other methods to fill the mold cavities can be used. For example, mold assembly is optionally filled by, but is not limited to, dipping or by selectively pouring molten lead in the mold cavities. 
     Coolant is circulated through jackets around the mold cavities to freeze the posts and straps and when an appropriate temperature has been achieved the cast post and strap are extracted from their molds by simultaneous operation of extractors driven by a knock-out plate in synchronism with the stack elevator. The cell unit with straps and post terminals are then rotated along in one of receptacles  30  to the transfer station  16  where, for example, the machine operator releases the molded cell from the mold assembly  12 . In one arrangement a molded cell is then inserted into a case where individual cells are later electrically and mechanically joined via the straps to form intercell connections. 
     The cast-on process outlined utilizes a mold filling technique referring to FIGS. 2A-2D. Two different configurations of mold assemblies  44  and  46  are depicted for injection of molten lead in two of five cavities  42  for each mold assembly  12 . FIGS. 2C and 2D are cross sectional side views of mold assemblies  44  and  46  shown in FIGS. 2A and 2B, respectively. Each mold produces at least one cell of a battery (not shown). When it is desired to inject the mold cavities  42 , a lead injection machine (not shown) at molding stations  26 ,  28  is used is to inject molten lead into at least two mold cavities  42 , preferably simultaneously to decrease cycle time. 
     It will be appreciated from the preceding discussion that a substantial degree of precision of control of thermal conditions are required at the cast-on station  14 . The cavities must be cooled sufficiently to solidify the metal for extraction in the form of straps and possibly a post terminal. The molten metal in the cavities cannot be so hot at the time the lugs  34  are immersed that they detrimentally affect the overlying cell assemblies as by melting the plates  32 , separators between the plates, or the lugs  34  above the region of immersion. 
     One form of an exemplary mold assembly  12  which affords three different configurations for a cell is shown in FIGS. 2A and 2C generally at  44 . A second form of an exemplary mold assembly which affords one more alternative configuration for a cell and a total of three different configurations is shown in FIGS. 2B and 2D generally at  46 . By filling two contiguous cavities  42  of the five cavities  42  in each mold assembly, three different configurations for each mold  44 ,  46  result depending on which two contiguous cavities  42  are selected. It will be understood that each mold assembly is translatable up and down relative to FIGS. 2C and 2D, as well as being translatable in left and right directions as shown relative to FIGS. 2A-2D for selecting two of the five cavities to be filled. 
     Referring to FIGS. 2A-2D, and  3 , mold cavities  42  in six individual molds assemblies  12  for a six cell battery  48  are shown including cavities for a negative terminal post  51 , a first cell negative strap  52  and a positive strap  53 , a second cell positive strap  54  and negative strap  55 , a third cell negative strap  56  and positive strap  57 , a fourth cell positive strap  58  and negative strap  59 , a fifth cell negative strap  61  and positive strap  62 , a sixth cell positive strap  63  and negative strap  64 , and a positive terminal post  65 . The cavities  51  and  65  for the terminal post are continuous with the cavities  52  and  63  of the first and sixth cells for the connector straps of the appropriate polarity. All other connector strap cavities include an intercell connector post cavity  66  adjacent a similar post cavity for the strap of opposite polarity for the next cell whereby the connection of adjacent connector posts connect the battery cells in series electrically. Intercell connector post cavity  66  molds a U-shaped flange  68  that extends substantially perpendicular from one end of a molded strap  53 - 62 , and  64 . U-shaped flange  68  is long enough for electrically joining contiguous straps of opposite polarity by, welding, for example. 
     In one embodiment and still referring to FIGS. 2A-D and  3 , it will be recognized that six cells forming battery  48  in FIG. 3 optionally includes three cells formed using mold assembly  44  and the other three cells formed using mold assembly  46 . More specifically, the first cell ( 1 ) of battery  48  is formed by injecting the two leftmost cavities of mold assembly  44  in FIG. 2A, forming negative terminal post  51 , first cell negative strap  52  and positive strap  53 . The second cell ( 2 ) is optionally formed by injecting either the two rightmost cavities  42  of mold assembly  44  in FIG. 2A or a pair of contiguous cavities contiguous to the two right most cavities  42 , forming second cell positive strap  54  and negative strap  55 . The third cell ( 3 ) is optionally formed by injecting either the two rightmost cavities  42  of mold assembly  46  in FIG. 2B or a pair of contiguous cavities  42  contiguous to the two right most cavities  42 , forming negative strap  56  and positive strap  57 . The fourth cell ( 4 ) is optionally formed by injecting either the two rightmost cavities  42  of mold assembly  44  in FIG. 2A or the pair of contiguous cavities  42  contiguous to the two right most cavities  42 , forming positive strap  58  and negative strap  59 . The fifth cell ( 5 ) is optionally formed by injecting either the two rightmost cavities  42  of mold assembly  46  in FIG. 2B or the pair of contiguous cavities  42  contiguous to the two right most cavities  42 , forming negative strap  61  and positive strap  62 . The sixth cell ( 6 ) is formed by injecting the two leftmost cavities  42  in FIG. 2B, forming positive strap  63  and negative strap  64 , and positive terminal post  65 . By translating mold assemblies  44 ,  46  in right and left directions, two of the five cavities  42  may be selected to inject molten lead to provide the desired strap/post configuration for each cell of battery  48  using two molds in three cycles. 
     Still referring to FIGS. 2A-2D, the mold assemblies  12  further include end bosses  69  and  71 , ends  72  and  73  and sides  74  and  75 . A mounting cavity  77  is provided in each of the bosses to enable the molding assembly to be clamped in the cast-on station  14  by means (not shown). 
     After filling is complete, for example, as determined by a timer set for the rate of molten metal flow, the molten metal solidifies in the preselected cavities and mechanically and electrically joins the isolated straps to corresponding lugs. The resulting cell unit is extracted from the mold assembly  12  and transferred for further processing. Six cell units are disposed in a 12 V battery case having flanges  68  aligned with holes in the cell partition walls within the battery case. Contiguous flanges  68  are then electrically connected, e.g., by welding, to complete a series connection between adjacent cells. 
     Referring now to FIGS. 4 a  and  4   b,  the two exemplary embodiments of molds  44  and  46  shown in FIGS. 2A and 2B are reproduced schematically as molds  144  and  146 , respectively. Molds  144  and  146  are schematic representations of molds  44  and  46  illustrated in FIGS. 2A and 2B each mold having five cavities  142 . In an exemplary embodiment, molds  144  and  146  allow twelve cell elements for use with two batteries to be molded in three cycles as opposed to molding six cells elements for use in one battery in three cycles using molds  44  and  46  discussed above. 
     In an exemplary embodiment and referring to FIGS. 4A and 4B, the first four or four left most cavities  142  of each mold  144  and  146  is filled with molten lead in the first and third cycles of three cycles to provide eight cell elements of the twelve cell elements needed to complete two batteries. Four of the eight cells are the outermost cells with post terminals while the other four are intermediary cell elements, two for each battery. In the second cycle, the last four or four rightmost cavities of each mold  144  and  146  as depicted are filled with molten lead to provide four more intermediary cell elements. 
     The cycle time is the same as described above with molds  44  and  46 , however, by filling four instead of two cavities at each cycle, battery production is doubled. It will be recognized that the above process necessitates a larger COS machine and may be more complex than that described with a three cavity mold  44 ,  46 , however, using two five cavity molds provides another choice for matching production requirements to available equipment and tooling investment. 
     In yet another alternative embodiment and referring to FIG. 5, an exemplary embodiment of a single five cavity mold  246  is depicted. Mold  246  is similarly configured to mold  146  illustrated in FIG. 4B, except for a fifth and rightmost cavity  242  of mold  246  is configured to mold a terminal post with a strap connector. In this manner, if the first two and leftmost cavities are filled with molten lead, a cell configuration shown in cell  6  of FIG. 3 results. Likewise, if the last two or rightmost cavities are filled with molten lead, a cell configuration shown in cell  1  of FIG. 3 results. Cells  2  and  4  are configured by filling the second and third cavities of mold  246 , while cells  3  and  5  of FIG. 3 are configured by filling the third and fourth cavities of mold  246 . 
     Using mold  246 , six cell elements are produced for use in a single battery in six cycles where two of the five cavities are injected with lead at each cycle to form a single cell element. Alternatively, six cell elements may be produced for use in a single battery in four cycles using mold  246  as described below. 
     Referring to FIGS. 5 and 6, injecting the first and second cavities of mold  246  provides an “A” configuration having a post terminal for a first cell of battery  248 , shown in cell  1  of FIG.  6 . It will be recognized that battery  248  in FIG. 6 is similarly configured to battery  48  in FIG. 3 although rotated 180°. Injecting the second and third cavities of mold  246  results in a “B” configuration for a second and fourth cell of battery  248 , shown in cells  2  and  4  of FIG.  6 . Injecting the third and fourth cavities of mold  246  results in a “C” configuration for use in the third and fifth cells of battery  248 , shown in cells  3  and  5  of FIG.  6 . Injecting the fourth and fifth contiguous cavities of mold  246  results in a “D” configuration having another post terminal for use in the sixth cell of battery  248 , shown in cell  6  of FIG.  6 . 
     Still referring to FIGS. 5 and 6, an exemplary method is outlined for molding six cell elements for battery  248  in four cycles. In a first cycle, the first four or four leftmost cavities of mold  246  are filled resulting in an A configuration and a C configuration. Both A and C configuration cells are rotated −90° for placement in battery  248  as first and third cell elements, shown in cells  1  and  3  of FIG. 6, respectively. In a second cycle, the last four or four rightmost cavities of mold  246  are filled providing a B configuration and a D configuration. The B configuration molded cell clement is rotated −90° while the D configuration molded cell element is rotated +90° for placement in battery  248  as the second and sixth cell elements, shown in cells  2  and  6  of FIG. 6, respectively. In a third cycle, the second and third cavities of mold  246  are filled providing another B configuration. This second B configuration molded cell element is rotated −90° for placement in battery  248  as a fourth cell element, shown in cell  4  of FIG.  6 . In the final fourth cycle, the third and fourth cavities of mold  246  are filled providing another C configuration. This second C configuration molded cell element is rotated −90° for placement as a fifth cell element in battery  248 , shown in cell  5  of FIG.  6 . 
     It will be understood by one skilled in the pertinent art that the apparatus and method discussed above for use in manufacturing cells of a 12 V battery is optionally employed in the manufacture of cells for use in a 36 V battery. A 36 V battery includes a battery housing or case defining a receiving area that is configured to receive and engage eighteen cells. Each cell has a plurality of positive plates each having a positive tab portion or lug depending outwardly from a periphery, a plurality of negative plates each having a negative tab portion or lug depending outwardly from a periphery, and a nonconductive separator disposed in between the plurality of positive plates and the plurality of negative plates. The tabs or lugs for the plates are analogous to lugs  34  of battery plates  32  discussed above in reference to a 12 V battery. 
     Accordingly, the above described method and apparatus affords casting straps to individual cells for use in a battery with a smaller and less expensive mold, as well as allowing a smaller COS machine to be employed because of the smaller mold. In addition, each mold provides at least two configurations for use in connecting lugs of contiguous cells of a battery depending on the cavities selected to fill with molten lead. The above described method and apparatus allows more flexibility and allows a single COS machine to mold the totality of cells to be employed in a battery. By using two COS machines in conjunction with 2 molds, cycle time can be gained. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the apparatus and method have been described by way of illustration only, and such illustrations and embodiments as have been disclosed herein are not to be construed as limiting to the claims.