Abstract:
An apparatus for delivering a predetermined volume of lead to a mould includes a housing defining a lead reservoir having a lead outlet defined in its base and in communication with the reservoir. A runway is provided beneath the base, spaced from the base and generally parallel thereto. A block is provided slidably mounted between the base and the runway and defining a through cavity having the predetermined volume for receiving lead from the outlet in a first position and for releasing the lead in a second position. A mechanism is provided for reciprocating the block between the first and second positions. A cast on strap machine is also disclosed. A lead delivery apparatus comprising a delivery chute is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for delivery of a predetermined volume of lead to a mould and in particular, but not exclusively, to such apparatus for use in manufacturing cast on straps during the manufacture of batteries. 
     2. Description of the Related Art 
     In the manufacture of batteries, particularly for example lead acid batteries, it is known to cast straps and other formations onto the lugs of battery plates so as to, for example, form a connection between a set of plates within a cell of the battery. Such straps are generally cast by filling a mould cavity with lead and dipping lugs into the cavity prior to the cooling of the lead. Typically, the mould cavities are filled by allowing lead to flow into channels at the sides of the cavities and spill over a weir into the mould. An example of such a moulding apparatus is shown in the Applicant&#39;s earlier application WO94/16466. In order to ensure a good connection between the lugs and casting, the lead must remain hot until the lugs are in position. However, in order to minimize cycle time in production, the lead must be cooled as quickly as possible once the plates are in position. 
     It is important that the volume of lead is carefully controlled during strap casting as excess lead (for example as a result of mould features such as weirs) will have an impact on both the cost and weight of the final battery produced. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Embodiments of the invention seek to provide an apparatus which may provide consistent measuring of lead and/or provide delivery of lead with minimal cooling during transit to the mould and/or enable unimpeded access to the mould by the plates. 
     According to a first aspect an apparatus for delivering a predetermined volume of lead to a mould includes a housing defining a lead reservoir having a lead outlet defined in its base and in communication with the reservoir; a runway beneath the base, spaced from the base and generally parallel thereto; a block slidably mounted between the base and the runway and defining a through cavity having the predetermined volume for receiving lead from the outlet in a first position and for releasing the lead in a second position; and a mechanism for reciprocating the block between the first and second positions. 
     This apparatus enables a single controlled volume of lead to be delivered accurately to an outlet location. In addition to ensuring a consistent volume of lead being delivered to a mould, the apparatus may also ensure that the lead can be delivered from the reservoir with minimal heat loss. 
     The cavity may have an upper inlet which is aligned with the lead outlet in the first position. The cavity may have a lower delivery port which can deliver lead in the second position. The cavity may be substantially ceiling-less, for example, the upper inlet of the cavity may be sized and shaped to match the lead outlet in the base of the housing. Alternatively, the cavity upper inlet may be smaller than the outlet in the base of the housing such that it lies within the outlet in the first position. Such an arrangement has been found to ensure that dross does not form within the cavity of the block but will instead float up the top of the reservoir from which it can be easily skimmed. 
     The runway may be provided with an opening at the second position. Alternatively, the runway may be arranged to stop short of the second position. The opening or runway end may be arranged to guide lead which is released from the cavity. 
     The housing may define a bleed opening, which may be aligned in the second position for allowing the ingress of gas into the upper part of the cavity in the second position. Thus, advantageously the bleed opening assists with smooth delivery of the volume of lead when the block is in the second position. 
     The block may further include a passageway, for example a through hole, for connecting the reservoir to a lead supply when the block is in the first position. The lead supply may, for example, be a constant head lead supply. 
     The apparatus may further comprise a drive mechanism for reciprocating the block. For example, the drive mechanism may comprise a crank mechanism. 
     The facing surfaces of the block and the reservoir may form a seal therebetween. The facing surfaces of the block and the runway may form a seal therebetween. At least one of the, or each, pair of facing surfaces may be provided with a graphite coating. The base of the housing and the runway may be arranged at an incline such that any lead leakage is directed in a predetermined direction. A gully may be provided at the edge of the runway to contain any such leakage. 
     In some embodiments the lead may be released directly from the block at the second position into a mould. Alternatively, the apparatus may further comprise a chute defining a lead passageway for extending between the second position and a mould fill position. A passageway may be arranged to ensure that the turbulence of the flow of lead into the mould is minimized and ensure a quick and clean fill of the mould cavity. The passageway may include a channel and a gap at the mould fill position and the chute may further comprise a wall on the opposite side of the gap to the channel for directing lead downwards as it debouches from the channel. The channel may be an open channel, for example a half pipe channel. 
     The apparatus may further comprise a moveable support for supporting the chute and arranged to move the chute between a lead delivery position and a rest or store position (for example, the moveable support may be a carriage). 
     The block may comprise a plurality of cavities. For example, a plurality of cavities may be provided in which each cavity may be arranged to deliver a predetermined volume of lead to a different section of the mould (for example to form different straps). The cavities may have different volumes (for example one cavity may be for a strap and another may be for a strap including a post). Multiple cavities could be fed from a single reservoir. The reservoir may have a single lead outlet or could be provided with a lead outlet for each cavity. 
     The runway may be provided with a blind hole which is aligned with a cavity (and may, therefore, also be aligned with the inlet) when the block is in the first position. The cavity may be sized and shaped to match the outlet of the cavity (such that the blind hole may coextensive with the cavity when the block is in the first position). The blind hole may be arranged to provide a sump below the cavity for receiving lead. Advantageously, the provision of a sump helps to resist the build up of dross on the sealing surface between the runway and block. 
     The housing may be provided with a cover to define an enclosed ullage above the reservoir. Advantageously, the ullage may be filled with an inert gas which reduces or eliminates the formation of dross on the surface of the lead. Therefore, the housing may further include an inlet for the provision of an inert gas to the ullage. The bleed opening may be in communication with the ullage such that inert gas is drawn into the cavity during delivery of the lead. Advantageously, this has been found to reduce build up of lead oxides on the walls of the cavity which would otherwise cause “decay” in the measured volume of the cavity. 
     A lead delivery apparatus may comprise a plurality of apparatuses according to an embodiment of the invention. For example, a lead delivery apparatus may comprise at least two blocks linked together to reciprocate together. 
     According to a further aspect of the invention, there is provided a cast on strap machine including a mould comprising a mould block defining a plurality of mould recesses and an apparatus in accordance with an embodiment of the invention. 
     In some embodiments a block may be provided with a plurality of through cavities each having a predetermined volume for receiving lead from an outlet in a first position and for releasing the lead in a second position. For example, the cavities may each have a predetermined volume to match that required for a particular mould recess. 
     According to a further embodiment of the invention, there is provided a lead delivery apparatus comprising a delivery chute which, in use, defines a passageway between a lead delivery device and a mould wherein the chute is moveable between a lead delivery position, in which at least a portion of the chute is positioned over a mould, and a store position in which the chute does not overlie the mould. 
     The store position may be arranged to be below the plane of the upper mould surface. 
     The chute may be arranged to move across the surface of the mould before being displaced in a direction which is substantially perpendicular to the plane and the mould surface. For example, the chute may be translated across the surface of the mould from the first position in which it is positioned over the mould to a second position in which the chute does not overlie the mould and may then further move in a direction which is substantially perpendicular to the plane and mould surface to reach the store position. Alternatively the chute may be moved by a rotational movement. 
     At least part of the movement of the chute may be linked to the movement of a jig box which is arranged, in use, to bring a part into contact with the lead in the mould. For example, the chute may move across the surface of the mould before being moved below the level of the mould in conjunction with the movement of the jig box. 
     Whilst the invention has been described above, it extends to any inventive combination of features set out above or in the following description or drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       Specific embodiments of the invention will now be described in detail by way of example only and with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic cross-section view of a cast on strap machine according to an embodiment of the invention; 
         FIG. 2  is a schematic view of the embodiment of  FIG. 1  in the reservoir and cavity fill position; 
         FIG. 3  is a schematic view of the embodiment of  FIG. 1  in a lead delivery position; 
         FIG. 4  is a schematic view of embodiment of  FIG. 1  immediately after lead delivery and with the chutes in their first retracted position; 
         FIG. 5  is a schematic view of the embodiment of  FIG. 1  with the battery plates brought into contact with the mould and the chutes in their fully retracted position; 
         FIG. 6  is a schematic view of the embodiment of  FIG. 1  as the straps are ejected; 
         FIG. 7  is a schematic view of a mechanism for use in embodiments of the invention; and 
         FIG. 8  is a schematic view of a multiple cavity block for use in embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A cast on strap machine  1  in accordance with an embodiment of the invention is arranged to provide liquid lead into the mould cavities of a mould  50  before tabs  82  of a set of battery plates  80  are moved into position by a jig box  70  with the tabs  82  within the mould cavities and the lead can solidify so as to form straps connecting the tabs. A lead delivery apparatus  5  is provided for delivering a predetermined volume of lead to the mould  50 . The lead delivery apparatus  5  generally comprises a housing  2 , which defines an inlet reservoir  4 , a block  10 , a mechanism  20 , a runway  30  and a chute  40 . The lead delivery apparatus  5  is connected to a lead supply  60 . It will be noted that in the illustrated embodiment a pair of identical lead delivery apparatus are provided to deliver to opposing sides of the mould  50  (and fed from a common lead supply  60 ). It will be appreciated that this will depend upon the type of mould to be formed and therefore the invention may be used in a single or multiple arrangements. For clarity, the following description will describe the operation of only a single side of the apparatus but it will be appreciated from the figures that the two sides operate in an identical fashion (albeit with their motions mirrored). 
     The housing  2  defines a lead reservoir  4  in its interior and is generally arranged to have an open upper surface such that dross which accumulates maybe easily skimmed from the lead in the reservoir. An inlet  8  is provided for the supply of lead and an outlet  6  is provided in the base of the reservoir. 
     The housing may further be provided with a cover  3  which encloses the reservoir  4  but which is spaced apart from the lead fill level of the reservoir. As such an ullage  4   b  (i.e. an unfilled space) is defined above the reservoir  4 . A gas inlet  9  is provided at the rear of the housing  4  which extends into the ullage  4   b  such that, in use, the ullage  4   b  may be filled with an inert gas (for example pure nitrogen or argon). Typically, the gas will be introduced at atmospheric pressure (so as not to effect the flow of lead) but with a flow rate which is sufficiently high to expel the air from the ullage  4   b.    
     The housing is further provided with a bleed opening  7  which (as described in below) is arranged to be aligned with the through cavity  12  when the block  10  is in the second position. The bleed opening  7  is in fluid communication with the ullage  4   b  of the housing  2 . 
     Spaced apart from, and below, the housing  2  is a runway  30  which is arranged parallel to the lower surface of the housing and defines a slot therebetween which is shaped and sized to receive a block  10 . The runway is provided with a through hole  34  aligned with the inlet  8  on the housing  2  and a blind recess  36  in alignment with the outlet  6  of the housing  2  (the blind recess  36  will form a sump as described below). The runway  30  is sloped relative to the horizontal such that it&#39;s inward (i.e. closest to the mould  50 ) end is higher than its rearward end. This ensures that any lead which escapes during operation of the machine will run away from the mould  50 . Adjacent to the rearward (and lowermost) point of the runway  30  there is provided a gully  39  (which may be formed as part of the runway  30  or the lead supply pipe  66   a ,  66   b  which is positioned below the runway) for catching any lead leakage. The gully may be arranged to return the lead to the lead supply  60 . 
     The block  10  is provided with a through cavity  12  and a through hole  18 . In the non-displaced position of the block  10  the through hole  18  is aligned with the inlet  8  and through hole  34  to form the inlet path to the lead reservoir  4 . In the same position, the through cavity  12  is aligned with the outlet  6  of the lead reservoir  4  and the blind hole  36  of the runway  30  such that lead from the reservoir will enter the blind hole  36  and cavity  12 . 
     The mechanism  20  comprises a crank mechanism attached to the block  10  and arranged (as described below with reference to  FIGS. 2 to 5 ) to move the block between its neutral position and a lead delivery position. 
     A chute  40  is provided which defines a passageway  42  which, in use, is arranged to deliver lead from the block  10  to the mould  50 . The passageway  42  defines an inclined pathway for the lead and is provided with radiused corners to ensure smooth flow and minimise turbulence of the lead. The chute is provided with a moveable support  48  which is arranged to move the chute between a delivery position and a retracted position (as will be described in more detail with reference to  FIGS. 2 to 5 ). A wall  44  is provided at the end of the chute  40  proximal to the mould  50  and a gap  45  is provided between the passageway  42  and wall  44 . The gap  45 , thus, forms an outlet to the chute  40 . 
       FIG. 2  shows the apparatus in its starting position in which the block  10  is aligned such that the through cavity  12  is below the outlet  6  of the lead reservoir  4  and the through hole  18  is aligned with the inlet  8  of the lead reservoir  4 . Thus, lead will flow from the constant head lead supply  60  (as shown in  FIG. 1 ) through supply pipes  66   a  and  66   b  (which may typically be heated) and hole  34  in the runway  30  into the reservoir  4 . The reservoir will be maintained at a fill level defined by the head of the lead supply  60  (which is defined by a weir  64 ). As the through cavity  12  is in fluid communication with the lead reservoir  4 , a predetermined volume of lead will fill the cavity  12  and an additional volume of lead will enter the blind hole  36  so as to provide a sump below the cavity  12 . It will be noted that in this step the chutes  40  are already in the delivery position in which the passageway  42  is below the end  32  of the runway  30  and the gap  45  which defines the outlet of the chute is positioned above the mould recess of the mould  50 . 
     To commence filling of the mould, the mechanism  20  is actuated to slide block  10  relative to the housing  2  and runway  30 , as shown by the arrows A in  FIG. 3 . The actuation mechanism will be described in more detail with reference to  FIG. 7  below, but may be any convenient mechanism which provides a reciprocating action of the block  10 . The block  10  slides inwards towards the chute  40  until it reaches its second position (as shown in  FIG. 3 ) in which the delivery port  16  of the through cavity  12  is aligned with the end  32  of the runway  30 . In this position the bleed opening  7  provided in the housing  2  is in fluid communication with the inlet of the through cavity  12  such that gas may be drawn into the upper portion of the through cavity  12 . This arrangement helps to avoid any vacuum effect which may hinder the release of the lead within the through cavity  12 . Further, since the bleed opening  7  is in fluid communication with the ullage  4   b  the gas drawn into the cavity is inert gas. Advantageously, this has been found to reduce or avoid the formation of lead oxides on the surfaces of the through cavity  12  which would otherwise (over the course of many cycles) reduce the volume defined by the through cavity  12 . This will, therefore, reduce the downtime required for cleaning and maintenance of the machine. 
     The end  32  of the runway  30  and the outermost portion of the open passageway  42  are arranged to provide a gradual downward transition to guide the lead onto the chute with minimal turbulence which could otherwise result in splashing. The lead passes along the downwardly curved passageway until reaching the gap  45  which provides the outlet to the chute  40 . The wall  44  ensures a clean downwardly directed delivery of the lead into the mould cavity  50  with any lead which overshoots the gap  45  striking the wall and being downwardly directed back through the gap  45 . 
     Once the lead pouring has completed, the block  10  returns to its first position in which the through cavity is aligned with the outlet  6  of lead reservoir  4  (moving in the direction of arrows B shown in  FIG. 4 ). In this position the reservoir is again in fluid communication with the lead supply such that the level of the reservoir will be replenished and the through cavity  12  will be refilled. At this stage the chute  40  is retracted from its lead delivery position by being moved away from the mould  50  towards the housing  2 . The chute is moved by rotation of the moveable support  48  in the direction shown by arrows C, resulting in the chute  40  moving in the direction of arrows D. A cut-out  38  is provided in the lower surface of the runway  30  to accommodate the initial movement of the chute. The cut-out is a stepped portion in the lower surface and may for example be a slot of substantially equal width to that of the chute. 
     As shown in  FIG. 5 , the battery plates  80  are brought into position above the mould  50  by a downward motion (in the direction of arrow E) until the tabs  82  of the plates lie within the mould cavity (which now contains molten but cooling lead). A mechanical connection is provided between the moveable support  48  of the chute  40  and the jig box  70  such that the chutes move down (as shown by arrow F) below the upper surface of mould  50  in conjunction with the movement of the battery plates  80  towards the mould  50 . This is advantageous since the chute  40  will be hot (and may typically be heated to ensure the required delivery temperature of the lead is achieved) and may help to avoid any damage to the battery plates (or, more specifically, to the separators between the battery plates). This arrangement may, for example, enable the height of the tabs  82  to be reduced and/or may eliminate the need for providing a cooling air supply over the mould  50  as is known in conventional arrangements. 
     Finally, as shown in  FIG. 6 , the battery plates  80  are moved away from the mould  50  by the jig box  70  (in the direction of arrow H) and eject the formed straps with the tabs  82 . In conjunction with the movement of the jig box  70  the chutes  40  are moved upwards (in the direction of arrow G) and rotated inwards (in the direction of arrow I) to return to the delivery position. 
       FIG. 7  shows a mechanism  20  suitable for use in embodiments of the invention. The mechanism comprises a drive motor  100  arranged to rotate a crank  110  which is connected via a lever arm  120  to the block  10 . It will be noted that a plurality of blocks  10   a ,  10   b  and  10   c  may each be connected to a common mechanism for actuation in use. Each block  10  is associated with a separate housing  2   a ,  2   b  and  2   c  defining an independent lead reservoir, each of which is in fluid communication with the feed line  66   a ,  66   b . A simple connection may be provided between the block  10  and the mechanism  20 , for example a bar  21  and hook arm  22  arrangement, such that the block  10  and mechanism  20  may easily be disconnected for example to clean the block, housing or runway, or to replace the block (for example, to provide a block with a different capacity through cavity  12 ). 
     In some embodiments it may be desirable to provide a plurality of through cavities in a single block  210  as shown in  FIG. 8 . Each cavity  212   a  and  212   b  may have a different predetermined volume depending on the mould feature for which the lead is acquired. For example, a larger mould cavity  212   a  may be provided for forming a post detail while a small mould cavity  212   b  may be provided for forming a strap. The cavities  212   a  and  212   b  may be suitably shaped such that their delivery ports and are of a standard profile such that no modification is required to the chute  40 . 
     All of the invention has been described above with reference to one or more preferred embodiments. It will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims. 
     For example, the skilled person will appreciate that while the embodiment above has been primarily described in relation to the forming of straps, other formations may also be cast onto the lugs of battery plates (for example posts) and that a cast on strap machine may be used for the formation of any such formations without departing from the scope of the invention. 
     In some embodiments it may be advantageous to provide a plurality of cavities  12  arranged to deliver lead to a single mould cavity. For example, this may be desirable for relatively large mould cavities. The plurality of cavities could be in multiple blocks or in single multiple cavity block (of the type shown in  FIG. 8 ) For example, each cavity may measure a separate volume of lead and the total volume of the cavities may provide the volume required for the particular mould cavity. The cavities may for example deliver to different areas of a single mould cavity to ensure an even distribution of lead.