Lead delivery apparatus

A lead delivery apparatus for a cast on strap machine is arranged to deliver a predetermined volume of molten lead to a mould. The apparatus includes a first needle valve, a second needle valve, and a housing. The housing includes a reservoir having an inlet and an outlet. The reservoir inlet is in fluid communication with a molten lead supply. The reservoir is supplied with molten lead during use such that the molten lead in the reservoir is maintained at a constant height. A volume block has an inlet, an outlet and a through cavity and the volume block inlet is in fluid communication with the reservoir outlet. The through cavity together with the second needle valve defines the predetermined volume of molten lead received from the reservoir.

FIELD OF INVENTION

The present invention generally relates to the forming of battery components and in particular, but not exclusively, to such apparatus for use in manufacturing cast on straps during the manufacture of batteries. More specifically the invention relates to a lead delivery apparatus for a cast on strap machine arranged to deliver a predetermined volume of molten lead to a mould.

BACKGROUND OF INVENTION

In the manufacture of batteries, particularly for example lead acid batteries, it is known to cast connectors known as “straps” and other formations onto the “lugs” (or “tabs”) of battery plates. For example, straps are formed to provide a connection between a set of plates within a cell of the battery. Straps are generally cast using a “cast on strap machine” in which a mould cavity is filed with molten metal (normally molten lead) before the lugs of a group of battery plates are dipped into the cavity prior to the cooling of the lead. The mould for forming such straps general comprises a plurality of cavities each configured to form a separate strap across a “pack” or “group” comprising a plurality of battery plates. The mould may for example include a series of generally paired cavities spaced along the length of the mould such that each pair of cavities can form a positive and negative strap for a single group of batteries (and with the mould, therefore, forming a plurality of groups spaced along the length in a single process).

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's earlier published European patent EP0630526. 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 minimise 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 measured and controlled during strap casting, because 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.

The Applicants previously proposed a further battery moulding apparatus in published UK Patent Application GB2507485, which was later improved upon in UK Patent Application GB2536295. In both of these arrangements a reciprocating sliding block is used to provide an accurately measured volume of lead for each cavity of a mould.

Embodiments of the present invention seek to provide a new battery moulding apparatus and provide an alternative to the arrangement proposed in GB2536295 which may, for example, improve the measuring of molten lead delivered into the mould.

SUMMARY OF INVENTION

According to the first aspect of the present invention there is provided a lead delivery apparatus for a cast on strap machine arranged to deliver a predetermined volume of molten lead to a mould, comprising:a first needle valve;a second needle valve;a housing, the housing comprising:a reservoir comprising an inlet and an outlet,the reservoir inlet being in fluid communication with a molten lead supply,the reservoir being supplied with molten lead during use such that the molten lead in the reservoir is maintained at a constant height, andthe reservoir outlet being defined in a lower portion of the reservoir and being selectively openable and closable by the first needle valve;a volume block comprising an inlet, an outlet and a through cavity,the volume block inlet being in fluid communication with the reservoir outlet, the volume block inlet located below the reservoir outlet,the through cavity together with the second needle valve defining the predetermined volume of molten lead received from the reservoir via the reservoir outlet, andthe volume block outlet being selectively openable and closable by the second needle valve;

wherein the first needle valve is selectively moveable between a first position and a second position, such that in a first position the reservoir outlet is closed and the flow of molten lead between the reservoir and the volume block is prevented, and in a second position the reservoir outlet is open, such that the flow of molten lead between the reservoir and the volume block is permitted until an equilibrium position has been reached, which defines the predetermined volume; and

wherein the second needle valve is selectively moveable between a first position and a second position, such that in a first position the volume block outlet is closed and the flow of molten lead between the volume block and a mould is prevented, and in a second position the volume block outlet is open, such that the predefined volume of molten lead is permitted to flow between the volume block and the mould.

Advantageously, the present invention provides a lead delivery apparatus which comprises needle valves to control the flow of molten lead from the supply, through the reservoir and volume block, and into the mould. Advantageously, as will become apparent, the profile of the second needle valve provides an improved seal between the volume block and the mould which significantly reduces leaking, and thus reduces the volume of lead wasted.

The molten lead may be at least partly flowable from the reservoir into the volume block, and also from the volume block into the mould, due to gravity.

The first needle valve and the second needle valve may be angled relative to each other.

The first needle valve may be angled at around 20 degrees to the horizontal axis of the housing. Preferably, the second needle valve is substantially perpendicular to the horizontal axis of the housing.

According to a second aspect of the present invention there is provided a lead delivery apparatus for a cast on strap machine arranged to deliver a predetermined volume of molten metal to a mould comprising:a housing defininga reservoir having an inlet in fluid communication with a molten lead supply and an outlet;a volume block having an inlet in fluid communication with the reservoir outlet and an outlet for providing a predetermined volume of molten lead to a mould and a metering cavity defined therebetween;

wherein the housing defines a sealed ullage space extending over the molten lead within the reservoir and

the metering cavity of the block is in fluid communication with the ullage space; and

a supply of inert gas in fluid communication with the ullage space.

The features of the lead delivery apparatus of the second aspect of the invention are the same as described above with regards to the first aspect of the invention.

The first and/or second needle valves may each comprise a gas seal, such as a Nitrogen seal, located at the intersection between the first and/or second needle valves and the housing.

The first needle valve may comprise an elongate body and a sealing portion. The sealing portion may have a profile corresponding to the profile of the reservoir outlet. The sealing portion may comprise a flat end positioned flush with an end of the reservoir outlet. Preferably, the end of the reservoir outlet corresponds to the volume block inlet.

The second needle valve preferably comprises an elongate body and a seat engaging portion. The seat engaging portion may comprise a first section having a profile corresponding with the profile of the volume block outlet, such that the first section and the volume block outlet interlock when the second needle valve is in the first position to prevent the flow of molten lead between the volume block and the mould.

The seat engaging portion preferably comprises a second section protruding beyond the volume block outlet when the second needle valve is in the first position. The volume block outlet may be located within a recess on an exterior surface of the volume block. The second section preferably protrudes into said recess when the second needle valve is in the first position.

In some embodiments, the second needle valve may be made of stainless steel or carbon steel. In such embodiments, at least a portion of the second needle valve may comprise a metal nitride coating. For example, at least the first and/or second sections of the seat engaging portion may comprise a metal nitride coating. At least a part of the surface of the through cavity may also comprise a metal nitride coating. The volume block outlet may also comprise a metal nitride coating. The metal nitride coating may be one or more of: Titanium Nitride, Chromium Nitride, Chromium Aluminium Nitride, and Titanium Aluminium Nitride.

It may be an advantage of embodiments of the present invention that the metal nitride coating can help to reduce friction of the surfaces on which the coating is applied, which helps to prevent or at least reduce the amount of molten lead sticking to these surfaces, e.g. the surface of the second needle valve, the surface of the through cavity and/or the volume block outlet.

In another embodiment, the second needle valve may be made of titanium. In such embodiments, a metal nitride coating may not be required. It may be an advantage of embodiments of the present invention that making the second needle valve out of titanium can itself help to reduce friction of the surface of the second needle valve, which in turn helps to prevent or at least reduce the amount of molten lead sticking to the surface of the second needle valve.

The second section may comprise an elongate portion and a substantially tapered portion. The substantially tapered portion may extend along the longitudinal axis of the elongate portion. In an embodiment, the substantially tapered portion may be inverted, and extend internally within the elongate portion. The internally extending tapered portion may form a cavity within the elongate portion.

In an alternative embodiment, the substantially tapered portion may extend externally away from the elongate portion. The externally extending tapered portion may protrude into said recess when the second needle valve is in the first position such that the second section is fully confined within the recess. The elongate portion preferably protrudes beyond the volume block outlet by at least around 0.5 mm to around 1 mm.

The elongate body preferably comprises an upper section furthest from the seat engaging portion having a greatest diameter. The elongate body also preferably comprises a lower section located between the upper section and the seat engaging portion having the same greatest diameter or one or more relatively different diameters, such as relatively smaller diameters. When the second needle valve is in the first position, the part of the through cavity immediately surrounding the upper section may have a diameter which provides a narrow clearance gap between the upper section and said part of the through cavity. The narrow clearance gap may define a metering space.

The second needle valve may be removable and interchangeable with a different second needle valve. The volume block may also be removable and interchangeable with a different volume block. Each different volume block may have a different volume defined by its through cavity. Each different through cavity together with each different second needle valve may define a different predetermined volume of molten lead received from the reservoir via the reservoir outlet.

The predetermined volume of molten lead received from the reservoir via the reservoir outlet may be from 0.06 kg up to 0.25 kg. The predetermined volume of molten lead may be changed by removing the second needle valve and replacing with a different needle valve having a different profile and/or removing the volume block and replacing with a different volume block having a different sized through cavity.

Preferably, the reservoir comprises an inert atmosphere, such as Nitrogen, above the molten lead. Furthermore, the volume block may also comprise an inert atmosphere, such as Nitrogen, above any molten lead in the through cavity. When the second needle valve is in the second position, the volume of inert atmosphere in the through cavity may increase as the volume of molten lead in the through cavity decreases.

The reservoir inlet may be constantly open, such that the molten lead is constantly replenished and maintained at said constant height.

According to a third aspect of the present invention there is provided a lead delivery apparatus for a cast on strap machine arranged to deliver a predetermined volume of molten lead to a mould, comprising:

a needle valve comprising an elongate body and a seat engaging portion; and

a volume block comprising an inlet, an outlet and a through cavity,the volume block inlet being in fluid communication with a supply of molten lead,the through cavity together with the needle valve defining the predetermined volume of molten lead received from the supply, andthe volume block outlet being selectively openable and closable by the needle valve;

wherein the elongate body comprises an upper section furthest from the seat engaging portion having a greatest diameter, and a lower section between the upper section and the seat engaging portion having the same greatest diameter or one or more relatively different (e.g. smaller) diameters; and

wherein when the volume block outlet is closed by the needle valve, the part of the through cavity immediately surrounding the upper section has a diameter which provides a clearance gap between the upper section and said part of the through cavity.

The features of the lead delivery apparatus of the third aspect of the invention are the same as described above with regards to the first and second aspects of the invention.

Advantageously, as will be explained further in the examples, the clearance gap is narrow, and may provide a more accurate measurement of the predefined volume due to an improvement in the tolerance. The clearance gap may also help to prevent the needle valve from sticking, thus reducing the risk that the volume block outlet will not fully open and release the full predefined volume of molten lead. Furthermore, the clearance gap may also help to prevent a vacuum effect within the through cavity, which could otherwise hinder the release of molten lead from the through cavity into the mould.

The clearance gap may define a metering space. The lead delivery apparatus may further comprise a reservoir comprising an inlet and an outlet. The reservoir may be supplied with molten lead during use such that the molten lead in the reservoir may be maintained at a constant height. The molten lead may be flowable from the reservoir to the volume block until the level of molten lead in the volume block is substantially the same as the constant height level of molten lead in the reservoir.

Said level of molten lead in the volume block is preferably located within the clearance gap.

According to a fourth aspect of the present invention there is provided a lead delivery apparatus for a cast on strap machine arranged to deliver a predetermined volume of molten lead to a mould, comprising:

a needle valve comprising an elongate body and a seat engaging portion; and

a volume block comprising an inlet, an outlet and a through cavity,the volume block inlet being in fluid communication with a supply of molten lead,the through cavity together with the needle valve defining the predetermined volume of molten lead received from the supply, andthe volume block outlet being selectively openable and closable by the needle valve;

wherein the seat engaging portion comprises a first section having a profile corresponding with the profile of the volume block outlet, such that the first section and the volume block outlet interlock when the volume block outlet is closed by the needle valve; and a second section protruding beyond the volume block outlet when the volume block outlet is closed by the needle valve.

The features of the lead delivery apparatus of the fourth aspect of the invention are the same as described above with regards to the first, second and third aspects of the invention.

Advantageously, the interlock feature between the needle valve and the volume block outlet may help to provide a tighter seal between the volume block and the mould, compared to known lead delivery apparatuses. Furthermore, the tight fit between these features can help to “squeeze” out any remaining molten lead from the base of the through cavity and into the mould. This can help to ensure the correct predetermined volume is being released into the mould, within the improved tolerances. It may also be an advantage of embodiments of the present invention that the part of the needle valve protruding beyond the volume block outlet can help to prevent tails of molten lead from forming on the protruding part by “flicking” them off and into the mould due to the force of the needle valve closing the volume block outlet.

The seat engaging portion preferably comprises a first tapered portion, a second tapered portion, the first and second tapered portions connected by an elongate portion. The first section may comprise the first tapered portion and a substantial part of the elongate portion. The second section may comprise the second tapered portion and the remaining part of the elongate portion.

The second tapered portion may extend along the longitudinal axis of the elongate portion. The second tapered portion may extend internally into the elongate portion, forming a cavity within the elongate portion. The second tapered portion may alternatively extend externally away from the elongate portion.

The remaining part of the elongate portion preferably protrudes beyond the volume block outlet from around 0.5 mm to around 1 mm.

According to a fifth aspect of the present invention there is provided a cast on strap machine comprising:

a lead delivery apparatus as substantially described herein;

a battery plate positioning device;

a mould comprising a plurality of mould cavities; and

a mould loading apparatus arranged to move the mould between an in use configuration and a configuration in which the mould is external to the cast on strap machine to allow access to the mould.

Whilst the invention has been described above, it extends to any inventive combination set out above, or in the following description or drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2show a lead delivery apparatus10for a cast on strap machine arranged to deliver a predetermined volume of molten lead into a mould. The lead delivery apparatus10comprises a housing19having a removable cover36, and comprising a reservoir30and a volume block20. A first needle valve40extends through the housing19and the reservoir30, whereas a second needle valve50extends through the housing19and the volume block20.

The reservoir30comprises an inlet31and an outlet32. The inlet31(as seen in the cross-section ofFIG. 1) is located in the base of the reservoir30, and is fluidly connected to a feedpipe12via a riser18. The feedpipe12comprises a supply pipe16and a heater pipe14which in use will heat the feedpipe12in order to keep the lead molten so it can easily flow from the source to the reservoir30. During use, the reservoir30is supplied with molten lead33. The molten lead33in the reservoir is continually replenished during use and maintained at a constant height34(at a constant lead fill level) at all times. This is achieved by keeping the reservoir inlet31open, so that the reservoir30is in constant fluid communication with the molten lead supply (which is a ‘constant head’ lead supply).

The cover36encloses the reservoir30but is spaced apart from the lead fill level34of the reservoir30, thus creating an ullage space35above the molten lead33. The ullage space35comprises an inert atmosphere, such as Nitrogen, which helps to prevent the build up of oxides (which may otherwise form on the surface of the lead and accumulate on parts of the lead delivery apparatus).

The reservoir outlet32is located in a lower corner of the reservoir30and comprises a bore which fluidly connects the reservoir30to the volume block20. As will be described in more detail below, the reservoir outlet32is selectively openable and closable by the first needle valve40.

The volume block20comprises an inlet22, an outlet24and a through cavity26. The inlet22is in fluid communication with the reservoir outlet32via the bore, such that the end of the bore closest to the volume block20corresponds to the volume block inlet22.

The exterior surface of the volume block20comprises a recess28. The outlet24is located within the recess28, such that it is set back from the exterior surface of the volume block20. As will be described in more detail below, the volume block outlet24is selectively openable and closable by the second needle valve50.

The through cavity26fluidly connects the volume block inlet22and the volume block outlet24. The through cavity26also defines a predetermined volume of molten lead33to be received from the reservoir30via the reservoir outlet32. The middle portion of the through cavity26has the largest diameter, and has a substantially circular cross-section (when viewed from above).

As will be described in more detail below, the predetermined volume of molten lead can be from 0.06 kg up to 0.25 kg. The second needle valve50is interchangeable with needle valves having different profiles (as can be seen, for example, by comparingFIG. 2andFIG. 7). The volume block20is also interchangeable with volume blocks having different sized through cavities (as can be seen inFIGS. 10 and 11). The predetermined volume metered by the apparatus corresponds to the difference between the volume of the through cavity26and the volume occupied by the second needle valve50in its closed position. For example, a narrower profile (a smaller diameter) will increase the available space within the through cavity26for filling with molten lead, thus increasing the predetermined volume. Advantageously, having an interchangeable volume block and an interchangeable second needle valve allows the apparatus to process a wide range of battery sizes.

The ullage space35above molten lead33in reservoir30extends into the volume block20. In use, the molten lead25in the through cavity26is filled to a pre-determined level (which is where the lead level in the both the through chamber and the reservoir are in equilibrium). The Nitrogen in ullage space35is then drawn into the through cavity26and accommodates the area27above said equilibrium level.

At the intersection between the housing19and the first needle valve40, there is a Nitrogen seal41. This helps to prevent the Nitrogen within the ullage space35from escaping and potentially being replaced with Oxygen rich air. It is a known problem that Oxygen can cause the lead to oxidise, thus causing oxides to form and build up within the reservoir. Over time, the build up of oxides can cause a reduction in the available volume within the reservoir for filling with molten lead.

The first needle valve40extends through the housing19and into the reservoir30at an angle of around 20 degrees to the horizontal axis of the housing19. Advantageously, having the first needle valve at an angle to the horizontal axis of the housing, helps to keep the Nitrogen seal away from the molten lead in the reservoir. Furthermore, a vertical first needle valve would require a much larger volume block and through cavity, which would take up more space.

The first needle valve40comprises an elongate body42and a sealing portion44. The sealing portion44has a profile corresponding to the profile of the bore of the reservoir outlet32, that is the sealing portion44is partially tapered. The sealing portion44also comprises a flat end, which in use when the first needle valve40closes the reservoir outlet32, is positioned flush with an end of the bore of the reservoir outlet32.

In use, the first needle valve40is moveable between a first or extended position (shown inFIG. 2) and a second or retracted position (shown inFIG. 3). In the first position the reservoir outlet32is closed and the flow of molten lead33between the reservoir30and the volume block20is prevented. In the second position the reservoir outlet32is open, permitting the flow of molten lead33between the reservoir30and the volume block20. The reservoir outlet32remains open until the predetermined volume has been reached.

The second needle valve50extends through the housing19and the volume block20, and is substantially perpendicular to the horizontal axis of the housing19. The first needle valve40and the second needle valve50are angled relative to each other, such that the volume block inlet22is located below the reservoir outlet32.

At the intersection between the housing19and the second needle valve50, there is a Nitrogen seal51. This helps to prevent the Nitrogen within the area27from escaping and potentially being replaced with Oxygen, thus having the same consequences as detailed above. In this case, the build up of oxides will cause a reduction in the available volume within the through cavity, thus the through cavity will not be able to accommodate the predetermined volume of molten lead required for filling a particular mould. During the cast on process, the only time that Oxygen comes into contact with the molten lead is after it has been released into the mould.

The second needle valve50comprises a seat engaging portion53and an elongate body52. The seat engaging portion53comprises a first section54and a second section55. The first section54has a profile corresponding with the profile of the volume block outlet24, that is there is a first tapered portion57, followed by a substantial part of an elongate portion59(seeFIG. 3). This allows the first section54and the volume block outlet24to interlock or engage in use when the second needle valve50closes the outlet24. The profile of the second section55comprises the remainder of the elongate portion59followed by a second tapered portion58(seeFIG. 3). In this embodiment, the second tapered portion58extends away from the elongate portion59towards a point. The widest part of the second tapered portion58is at the base of the elongate portion59, with the narrowest part, the tip of the second tapered portion58, located externally from the elongate portion59along a longitudinal axis of the second needle valve50.

In use, when the second needle valve50closes the outlet24, the elongate portion59of the second section55protrudes by around 1 mm beyond the volume block outlet24and into the recess28. In use, the tip of the second tapered portion58is located in line with the exterior surface of the volume block20, as shown inFIG. 2.

The elongate body52comprises an upper section52awhich is located furthest from the seat engaging portion53. The greatest diameter of the second needle valve50is along the upper section52a. The elongate body52also comprises a lower section52bwhich is located between the upper section52aand the seat engaging portion53. The lower section52bhas the same diameter as the upper section52ain this embodiment, but in other embodiments, such as that shown inFIGS. 7 and 8, the lower section can have one or more different diameters. In fact, an advantage of embodiments of the present invention may be that the second needle valve is removable and interchangeable. This can allow the second needle valve ofFIG. 2to be replaced with the second needle valve ofFIG. 7, for example. As previously mentioned, the narrower diameter(s) of the lower section creates more available space in the through cavity to fill with molten lead from the reservoir.

When the second needle valve50closes the outlet24, the part of the through cavity26immediately surrounding the upper section52aof the second needle valve50has a diameter only slightly greater than the diameter of the upper section52a. This creates a narrow clearance gap56between the upper section52aand the through cavity26. Such a clearance gap56defines a metering space, which advantageously improves the tolerance of the predetermined volume. For example, by providing the clearance gap in line with the fill level of the reservoir, the equilibrium level will be located within the region of the clearance gap, thus any changes in volume of the reservoir will only affect the predetermined volume in the volume block by an insignificant amount, thus improving the accuracy of the measured predetermined volume.

In use, the second needle valve50is moveable between a first or extended position (shown inFIG. 3) and a second or retracted position (shown inFIG. 5). In the first position the volume block outlet24is closed, thus preventing the flow of molten lead between the volume block20and the mould (not shown). In a second position the volume block outlet24is open, permitting the predefined volume of molten lead to flow between the volume block20and the mould.

FIG. 3shows the first stage of the process. Initially, both the first and second needle valves40,50are in their respective first positions, such that there is no flow of molten lead between the reservoir and the volume block, nor the volume block and the mould. The reservoir30is then filled with molten lead33from the supply until the lead fill level34is reached.

The first needle valve40is then moved into its second/retracted position, such that molten lead33is allowed to flow between the reservoir30and the volume block20. Since the reservoir outlet32is located above the volume block inlet22, the molten lead33flows from the reservoir30into the volume block20, (and also from the volume block20into the mould) at least partly due to gravity.

The molten lead33flows into the through cavity26, and fills up the through cavity26until the levels reach equilibrium and thus the predetermined volume is reached. As the molten lead33is flowing out of the reservoir30and into the through cavity26, the feedpipe12continually replenishes the molten lead33within the reservoir, thus maintaining the molten lead33at the lead fill level34at all times.

The predetermined volume corresponds with the lead fill level34. Therefore, the molten lead33flows from the reservoir30to the volume block20until the level of molten lead level25in the volume block20is substantially the same as the lead fill level34in the reservoir30. The level25in the volume block20is located within the clearance gap56. Advantageously, this may improve the tolerance of the volume measurements because if the lead fill level34of the molten lead33in the reservoir30were to increase, the level of molten lead25in the volume block will also increase. However, the volume of molten lead required to increase the lead fill level34in the reservoir30is much greater then the volume of molten lead required to increase the level25in the volume block by the same amount. Therefore, any changes in the volume of the reservoir30will only affect the predetermined volume in the volume block20by an insignificant amount (such as a difference of only tenths of a gram).

It may be an advantage of embodiments of the present invention that there is no seal provided between the reservoir and the volume block. It is difficult to provide a lead seal in such a location, however the inventors of the present invention have taken full advantage of these difficulties and designed the lead delivery apparatus to function without a seal. For example, not providing such a seal allows the balancing of the lead levels in the reservoir and the volume block, which are carefully defined such that a predetermined volume of molten lead is provided to the moulds. Furthermore, a lack of sealing allows Nitrogen to be drawn into at the top of the through cavity from the reservoir to fill the ullage space above the molten lead. Not only does this help to prevent the build-up of oxides, but drawing in Nitrogen at the top of the through cavity can also help to push the molten lead out of the through cavity and into the mould.

FIG. 4shows the second stage of the process, whereby the through cavity26has been filled with molten lead to the level25corresponding to the lead fill level34in the reservoir30. Once the levels25,34have stabilised, the first needle valve40is moved to its closed/extended position. The corresponding and interlocking profiles between the volume block outlet24and the seat engaging portion53provides a tight seal which helps to mitigate the risk of molten lead leaking from the through cavity26, which is a known problem with known lead delivery apparatus.

FIG. 5shows the third stage of the process. With the first needle valve40in its closed/extended position, the second needle valve50is then moved to its open/retracted position. In this position, the volume block outlet24is open, and the molten lead within the through cavity26can now drain out of the volume block20and into the mould (not shown).

As the volume of molten lead25in the through cavity26decreases, the volume of the area27increases. Therefore, as the molten lead drains out of the volume block20, it is replaced with an inert atmosphere, such as Nitrogen which is drawn in to the top of the through cavity via a gas inlet (not shown) provided at the rear of the housing19and/or from the ullage space35above the reservoir30. Advantageously, drawing Nitrogen in at the top of the through cavity can help to push the molten lead out of the through cavity and into the mould. This arrangement helps to avoid any vacuum effect which may hinder the release of the lead from within the through cavity.

A further advantage of embodiments of the present invention is that the narrow gap helps to prevent the second needle valve seizing or sticking within the through cavity.

FIG. 6shows the final stage of the process, whereby all the molten lead within the volume cavity26has been released, and second needle valve is subsequently moved into its first/extended position to close the volume block outlet24.

The volume block outlet24and the seat engaging portion53fit tightly together due to their corresponding profiles. Therefore, as the second needle valve50is closes, any remaining molten lead within the through cavity26is essentially “squeezed” out. Furthermore, the profile of the second section55of the seat engaging portion53(the elongate portion and the tapered portion) protruding beyond the volume block outlet24and into the recess28causes the remaining molten lead to be forcefully flicked off the end of the second section. This helps to prevent a “tail” of molten lead hanging from the second section. Advantageously, the profile of the seat engaging portion53helps to minimise the amount of molten lead remaining within the through cavity26, thus helping to increase the accuracy of the volume of lead dispensed into the mould.

Since the second section55of the seat engaging portion53does not extend beyond the confines of the recess28, the recess28acts as a shroud for the tapered portion. This can help to not only protect the end of the needle valve, but also help to ensure the molten lead is flicked off into the mould.

Making the second needle valve out of titanium helps to reduce the surface friction of the second needle valve. Alternatively, if the second needle valve is made from stainless steel or carbon steel, then a metal nitride coating can be applied to the surface of the second needle valve, in particular the second section of the seat engaging portion, to reduce the surface friction. The ability to flick the molten lead off into a mould is greatly improved as the amount of friction provided by the surface of the second needle valve is reduced.

FIG. 7shows an alternative embodiment of the lead delivery apparatus110. This embodiment comprises a volume block120and a second needle valve150with a different, narrower, profile then the second needle valve50shown inFIGS. 2 to 6. The second needle valve of the present invention is interchangeable with other second needle valves having different profiles and dimensions, however, the apparatus works in exactly the same way as described above inFIGS. 3 to 6.

The second needle valve150comprises a seat engaging portion153and an elongate body152. Similar to the previous embodiment, the seat engaging portion153comprises a first section154and a second section155which are exactly the same as described above. The first section154comprises a first tapered portion157and a substantial part of an elongate portion159, and the second section155comprises a second tapered portion158and the remaining part of the elongate portion159.

The elongate body152comprises an upper section152awhich is located furthest from the seat engaging portion153. As before, the greatest diameter of the second needle valve150is along the upper section152a. The elongate body152also comprises a lower section152bwhich is located between the upper section152aand the seat engaging portion153. In this embodiment, the lower section152bhas a single smaller diameter than the upper section152a, giving the second needle valve150a narrower profile. Having a narrower profile creates more available space in the through cavity126to fill with molten lead from the reservoir. This increases the predetermined volume accommodated in the through cavity126, and subsequently released into the mould. This is particularly beneficial if, for example, the cast on strap machine was required to process larger batteries, because larger straps would need to be cast on which would require larger moulds and a larger predetermined volume. As will be described in more detail inFIGS. 9 and 10, an alternative or additional method of altering the predetermined volume accommodated by the through cavity is to interchange the volume block with a different volume block having a different sized through cavity, that is a through cavity with different dimensions.

A further advantage of embodiments of the present invention may be that the second valve needle is removable and interchangeable, because this allows the apparatus to process different sized batteries without having to substantially change the set-up of the machine. It is a very quick and simple procedure to remove one second needle valve and replace it with another which meets the requirements of the batteries to be processed.

FIG. 8ashows the same embodiment asFIG. 7, andFIG. 8bshows a close up of the relationship between the seat engaging portion153of the second needle valve150and the volume block outlet124. The same relationship applies to all embodiments of the second needle valve (e.g.50,150), and as such this has previously been described above inFIGS. 1 and 2, and will not be described again here.

FIGS. 9, 10 and 11all show a further embodiment of a second needle valve250located within a volume cavity226. However, the apparatus works in exactly the same way as described above inFIGS. 3 to 6.

The second needle valve250comprises a seat engaging portion253and an elongate body252. The seat engaging portion253comprises a first section254and a second section255. The first section254comprises a first tapered portion257and a substantial part of an elongate portion259, and the second section255comprises a second tapered portion258and the remaining part of the elongate portion259.

In contrast to the embodiment shownFIGS. 2 to 8, the second tapered portion258extends internally into the elongate portion259. The second tapered portion258forms a cavity within the elongate portion259, as is best shown inFIG. 9. The cavity is typically machined using a centre drill, which gives the cavity its tapered shape. The widest part of the cavity258is at the base of the elongate portion259, with the narrowest part, the tip of the second tapered portion258, located internally within the elongate portion259. The elongate portion259of the second section255protrudes into the recess228by 1 mm as before, but the second tapered portion258does not extend into the recess228.

In use, the second needle valve250works in exactly the same way as second needle valves50and150. Advantageously however, the profile of the second section255has been found to further reduce the amount of molten lead sticking to the surface of the second section in use, which may be because there is a smaller surface area onto which the molten lead could potentially stick. Such a profile may help to further prevent “tails” of molten lead hanging from the second section.

As mentioned above, if a different pre-determined volume is required, for example for moulding different sized battery straps, this can be achieved by switching the second needle valve for one having a different profile, and/or switching the volume block for one having a different through cavity dimensions.

FIGS. 10 and 11show two different volume blocks220and320. Through cavity326is shown to have larger dimensions (e.g. a larger diameter) compared to through cavity226, thus through cavity326has a larger volume than through cavity226.FIGS. 10 and 11also show two different second needle valves250and350. Second needle valve350has a larger profile, that is a larger diameter, than second needle valve250. Both second needle valves250and350comprise a seat engaging portion253and353as shown inFIG. 9, and operate in the same way as described above.

FIG. 11shows that the combination of volume block320with second needle valve350has a larger overall predetermined volume compared to the combination of volume block220with second needle valve250. Thus, in this example, two different strap sizes can be moulded and cast on to different size batteries.

Typically, interchanging the volume block can provide a change of around 0.1 kg in the predetermined volume of the through cavity; and interchanging the second needle valve can provide a change of around 0.06 kg in the predetermined volume of the through cavity. Therefore, switching the volume block provides a course adjustment of the volume, whereas switching the second needle valve provides a finer adjustment of the volume.

It may be an advantage of embodiments of the present invention that having the option of interchanging the second needle valve and/or the volume block will provide the user with a much greater range of predetermined volumes to select from, thus the lead delivery apparatus is able to mould and cast on straps for a wide range of battery sizes.

Although the invention has been described above with reference to an exemplary embodiment, 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, whilst embodiments have been described as having a single reservoir associated with a single volume block it will be appreciated by the skilled person that the invention is not limited to such an arrangement, for example a single reservoir may be provided with more than one outlet to supply a plurality of volume blocks.