Die casting generally involves the transfer of molten metal from a vessel through a conduit to a mould. A further mould is then introduced to the casting position and the process repeated. the volume of metal required for a cast is usually quite low. In general, one vessel is linked to one casting position.

For casting to give the desired quality of product it is necessary for the metal to be kept under carefully controlled conditions. To achieve this it is possible to use a holding furnace as the vessel and so provide heat input to that vessel as required. This requires a substantial number of such furnaces and each represents a large capital cost. The other possibility is to only have a relatively small volume of molten metal in the vessel at a point in time, use the majority of it up before it deviates significantly from the desired conditions and regularly top it up by transferring metal to it having the desired condition. That metal is transferred from a large holding furnace by means of a ladle or other container which moves a batch of the material at a time. This reduces the capital cost, but increases substantially the operating cost and difficulty.

Existing casting apparatus also faces problems in terms of the method it uses for transferring molten metal from the vessel into the conduit which links it to the mould. One technique used is to apply an elevated air pressure to the top surface of the metal in the vessel and so force it down within the vessel and up a stalk whose end is submerged within the metal. The top of the stalk is not exposed to the elevated air pressure. From the top of the stalk the metal flows out into a launder and then into the mould. This method faces problems as the metal flow through the stalk is low and hence is prone to cooling and blockage. Additionally the air pressure encourages air bubbles to form in the metal and this impair the quality of the cast achieved. Other approaches use a pump which is submerged within the molten metal to force the metal up the stalk and into the launder.

Submersion of the pump in such hostile conditions is problematic and necessitates expensive pump design and substantial maintenance.

The present invention has amongst its aims to simplify and/or reduced the cost of casting operations. The present invention has amongst its aims to improve the

controllability of casting operations. The present invention has amongst its aims the provision of improved delivery of the metal from the vessel to the mould. The present invention has amongst its aims the provision of improved quality cast products.

According to a first aspect of the invention we provide casting apparatus, the apparatus including a first conduit connected to a first pump, a second pump connected to a further conduit, the first and second pumps being connected by a junction conduit provided between them, the junction conduit also being connected to a spur conduit, at least one of the pumps being reversible in terms of its pumping direction.

According to a second aspect of the invention we provide a method of casting, the method including drawing metal through a first conduit using a first pump connected to it, the metal being pumped into a junction conduit, in a circulating mode, the metal passing through the junction conduit into a second pump, pumping in the same direction as the first pump, the metal then entering a further conduit which is connected to the second pump, in a casting mode, the pumping direction of the second pump being the reverse of that in the circulating mode, the first and second pumps combining to pump metal along a spur conduit connected to the junction conduit.

Preferably the pumping direction of the second pump is reversed again to return to circulating mode from casting mode. In circulating mode a metal free mould may be introduced to a moulding location. In casting mode metal may be introduced to the mould.

In circulating mode the mould with metal in may be removed and replaced with a further metal free mould.

The first and/or second aspects of the invention may be further provided from amongst the following options, possibilities and features.

The first and/or second pumps may be electromagnetic pumps. Preferably both pumps are of the same type. Preferably both pumps are of the same capacity.

The first conduit may be connected directly or indirectly to the first pump. The pump may be connected directly or indirectly to the junction conduit. The junction conduit

may be connected directly or indirectly to the second pump. The second pump may be connected directly or indirectly to the further conduit.

The junction conduit may be a T-shaped junction. Preferably the first and second pumps are connected to the ends of the cross of the T. Preferably the spur conduit is connected to the stem of the T.

Preferably the spur conduit or at least a part thereof is elevated compared with the junction conduit and/or first and second pumps. The junction conduit path leading to the spur conduit and/or the spur conduit may be provided with a valve to inhibit undesired flow of metal along the spur conduit. The influence of gravity may be relied upon to inhibit undesired flow of metal along the spur conduit.

The spur conduit preferably leads to one or more casting locations and/or moulds.

According to a third aspect of the invention we provide casting apparatus, the apparatus including a vessel holding a reservoir of molten metal, an outlet conduit leading to a first pump, the outlet conduit from the pump being connected by one or more other conveying elements to an inlet conduit to the vessel, the outlet conduit from the vessel, first pump, outlet conduit from the pump, one or more other conveying elements and inlet conduit forming a ring main through which molten metal is circulated, the one or more other conveying elements including a junction conduit leading to a casting location outside of the ring main, a further pump or an induction heater.

According to a fourth aspect of the invention we provide a method of casting, the method including providing a volume of molten metal in a vessel, drawing molten metal from that vessel through an outlet conduit to a first pump, passing the metal through the pump outlet conduit and on through one or more other conveying elements to an inlet conduit to the vessel and back into the vessel, the outlet conduit from the vessel, first pump, outlet conduit from the pump, one or more other conveying elements and inlet conduit forming a ring main through which molten metal is circulated, the method further including passing the metal through a junction conduit to a casting location outside the ring main using the junction conduit as one of the one or more other conveying components, pumping the metal using a further pump as one of the one or more conveying elements

and/or heating the metal using an induction heater as one of the one or more conveying elements.

The third and/or fourth aspects of the invention may be further provided from amongst the following options, possibilities and features.

The first and/or further pumps may be electromagnetic pumps. Preferably both pumps are of the same type. Preferably both pumps are of the same capacity.

The outlet conduit may be connected directly or indirectly to the first pump. The pump may be connected directly or indirectly to the pump outlet conduit and/or one or more conveying elements, such as a junction conduit, pump of induction heater. The inlet conduit may be connected directly or indirectly to the vessel.

A plurality of conveying elements in the form of junction conduits may be provided. The junction conduits preferably lead to casting locations. The junction conduit may be a T-shaped junction. Preferably the first and second pumps are connected to the ends of the cross of the T. Preferably a spur conduit is connected to the stem of the T.

A plurality of other conveying elements in the form of further pumps may be provided. Preferably one or more further pumps are provided at locations around the ring main. Preferably one or more further pumps are provided around the ring main to maintain metal velocity and/or achieve efficient pumping of the metal.

One or more induction heaters may be used to maintain the metal temperature above a level. The one or more induction heaters may be spaced around the ring main.

One or more induction heaters may particularly be provided at locations remote from the vessel.

The ring main may act as the metal supply route for a plurality of casting locations, and more particularly 20 or more such locations. The ring main may be long, for instance over 10m long, or even over 30m long, in terms of the distance travelled between leaving the vessel and returning to the vessel along the ring main. Preferably the ring main has a larger capacity than the spur conduits.

According to a fifth aspect of the invention we provide casting apparatus, the apparatus including a vessel holding a reservoir of molten metal, an outlet conduit from the vessel connected to a pump, the pump withdrawing metal from the vessel, the pump being

connected to a further conduit, one end of the outlet conduit extending into the vessel, below the level of molten metal in the vessel in use, the end of the conduit connected to the pump and the pump itself being above the vessel, and hence above the level of the molten metal in use, the pump being an electromagnetic pump.

According to an sixth aspect of the invention we provide a method of casting, the method including providing a volume of molten metal in a vessel, submerging one end of an outlet conduit from the vessel below the level of the metal in the vessel, the other end of the outlet conduit being connected to a pump, withdrawing metal from the vessel using the pump, the metal being fed to a further conduit connected to the pump, the end of the conduit connected to the pump and the pump itself being above the level of the molten metal, the pump being an electromagnetic pump.

The fifth and/or sixth aspects of the invention may be further provided from amongst the following options, possibilities and features.

The submerged end may extend at least 20cm below the surface of the molten metal and more preferably at least 50cm. Between 5 and 50% of the length of the outlet conduit may be submerged in the metal. The outlet conduit may be a stalk. The outlet conduit may be linear. The outlet conduit is preferably vertically provided, for instance within +/-10 degrees of the vertical.

The pump may have an axis and preferably that axis is also substantially vertically provided.

Preferably the further conduit leads directly or in directly to one or more casting locations and/or moulds.

The pump maybe at least 50cm and more preferably at least 100cm above the level of the metal.

According to a seventh aspect of the invention we provide casting apparatus, the apparatus including a vessel holding a reservoir of molten metal, an outlet conduit from the vessel connected to a pump, the pump outlet being connected to a further chamber, the further chamber being connected to a conduit leading to one or more casting operations.

According to an eighth aspect of the invention we provide a method of casting, the method including providing a volume of molten metal in a vessel, pumping molten metal from the vessel through a pump and into a further chamber for a period of time, switching off the pump or reversing the pump so as to allow the flow of material from the further chamber back into the furnace and repeating this cycle, wherein during casting metal is fed from the further chamber through an outlet conduit to casting operations.

The seventh and/or aspects of the invention may be further provided from amongst the following options, possibilities and features.

Preferably the further chamber is provided within a refractory block. Preferably the block is adjacent to the pump. Preferably the outlet from the pump enters the further chamber substantially horizontally. Preferably the outlet conduit from the further chamber exits the further chamber substantially vertically. The further chamber may be provided with a dome shaped upper portion and/or lower portion. Preferably the further chamber provides a homogenous and/or at temperature reservoir of metal for casting purposes.

The pump may be used to pump metal from the vessel/furnace into the further chamber for a period of between 10 seconds and 60 seconds before being turned off or reversed. A period of between 10 and 120 seconds may be allowed for the metal to flow back from the further chamber into the vessel/furnace. Preferably the cycle of pumping out of the vessel/furnace into the further chamber and allowing flow back from the further chamber into the vessel/furnace is repeated whenever a casting operation is not occurring.

Preferably during a casting operation, a higher level of metal throughput through the pump is used. Preferably metal is pumped from the vessel/furnace through the further chamber throughout a casting operation. Preferably metal within the conduit leading from the further chamber is returned to the vessel/furnace when casting operations stop.

Any of the aspects of the present invention may include features from amongst the following features, possibilities and options.

The vessel may be a furnace, holding furnace, ladle or crucible.

The molten metal may be aluminium, potentially together with one or more additional components.

The conduits may be of metal and/or may be refractory lined. The pumps may have a through passage of metal and/or be refractory lined. The conduits and/or through passage are preferably of circular cross-section.

Any of the first, third, fifth and seventh apparatus aspects of the invention may be combined in a casting apparatus with the features of one or more of the other of the first, third, fifth and seventh aspects of the invention, for instance in the following ways. Similar combinations may be made of the second, fourth, sixth and eighth aspects of the invention in terms of their method steps.

The casting apparatus may be provided according to a first preferred embodiment, second preferred embodiment, third preferred embodiment or fourth preferred embodiment and more particularly according to a combination of any two of those embodiments or more preferably according to a combination of any three of those embodiments and ideally a combination of all four embodiments.

In the first preferred embodiment of the casting apparatus, the casting apparatus may provide a first conduit connected to a first pump, a second pump connected to a further conduit, the first and second pumps being connected by a junction conduit provided between them, the junction conduit also being connected to a spur conduit, at least one of the pumps being reversible in terms of its pumping direction ; wherein a withdrawal pump is connected to a vessel holding a reservoir of molten metal by an outlet conduit, the outlet conduit is connected to a ring main which leads back to the vessel, the first pump, second pump and junction conduit being a part of the ring main, the spur conduit leading to one or more casting locations away form the ring main; and/or wherein a return pump is connected to an inlet to the vessel to return unused metal to the vessel, the return pump being a part of the ring main; and/or wherein an outlet conduit has one end submerged below the level of metal in a vessel, the outlet conduit is connected to a pump, the pump withdraws metal form the vessel, the pump being connected directly or indirectly to the ring main, the end of the conduit connected to the pump and the pump itself being above the vessel, and hence above the level of the molten metal in use, the pump being an electromagnetic pump.

In a second preferred embodiment of the casting apparatus, the casting apparatus may include a vessel holding a reservoir of molten metal, an outlet conduit leading to a first pump, the outlet conduit from the pump being connected by one or more other conveying elements to an inlet conduit to the vessel, the outlet conduit from the vessel, first pump, outlet conduit from the pump, one or more other conveying elements and inlet conduit forming a ring main through which molten metal is circulated, the one or more other conveying elements including a junction conduit leading to a casting location outside of the ring main, a further pump or an induction heater; wherein the one or more conveying elements include a conduit connected to a first pump, a second pump connected to a further conduit, the first and second pumps being connected by a junction conduit provided between them, the junction conduit also being connected to a spur conduit, at least one of the pumps being reversible in terms of its pumping direction; and/or wherein a return pump is connected to an inlet to the vessel to return unused metal to the vessel, the return pump being a part of the ring main; and/or wherein an outlet conduit has one end submerged below the level of metal in a vessel, the outlet conduit is connected to a pump, the pump withdraws metal form the vessel, the pump being connected directly or indirectly to the ring main, the end of the conduit connected to the pump and the pump itself being above the vessel, and hence above the level of the molten metal in use, the pump being an electromagnetic pump.

In a fourth preferred embodiment of the casting apparatus, the casting apparatus may include a vessel holding a reservoir of molten metal, an outlet conduit from the vessel connected to a pump, the pump withdrawing metal from the vessel, the pump being connected to a further conduit, one end of the outlet conduit extending into the vessel, below the level of molten metal in the vessel in use, the end of the conduit connected to the pump and the pump itself being above the vessel, and hence above the level of the molten metal in use, the pump being an electromagnetic pump; wherein the outlet conduit leads to at least one of the casting locations through a first pump, junction conduit and spur conduit, a second pump being connected to the junction conduit and to a further conduit, at least the second pump being reversible in terms of its pumping direction to either direct metal to the spur conduit or to return metal to the vessel; and/or

wherein the withdrawal pump is connected directly or indirectly to a ring main which leads back to the vessel, the ring main feeding metal directly, or more preferably through one or more spur conduits to one or more casting locations; and/or wherein a return pump is connected to an inlet to the vessel to return unused metal to the vessel, the return pump being a part of the ring main.

Various embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings in which:- Figure 1 illustrates a casting system according to one embodiment of the present invention, particularly for conveying metal to a mould; Figure 2 illustrates a casting system according to a second embodiment of the invention, particularly for circulating molten metal for use in casting; Figure 3 illustrates a casting system according to a third embodiment of the invention, particularly for introducing metal from a vessel into a conduit; Figure 4 illustrates a side view of a furnace, pump and chamber arrangement according to a fourth embodiment of the invention; and Figure 5 illustrates a plan view of the arrangement of Figure 4.

Conventionally, metal is pumped from a vessel into a conduit and then flows to a mould either under the influence of gravity or under the influence of the pump. A single vessel, which contains the reservoir of metal from which metal is drawn for casting, is usually connected to a single conduit and leads to a single mould or small number of moulds. Problems with this arrangement exist.

In a first form of the present invention, molten metal 1 is circulating through a conduit 3. The conduit flows into a first pump 5, then through a junction conduit 7, then through a second pump 9 and on to a further conduit 11. The junction conduit 7 has a spur conduit 13 leading away from it and that spur conduit 13 leads to one or more moulds 15.

In circulating mode, metal flows through the conduit 3, first pump 5, through junction conduit 7, onto second pump 9 and then further conduit 11, without any appreciable metal entering spur conduit 13. The spur conduit 13 may rise vertically from the junction conduit 7 to resist metal entering it.

When it is desired to cast, the metal needs to be pumped into the spur conduit 13 and hence to the moulds 15. This is achieved, casting mode, by operating the first pump 5 in the same way, but by reversing the direction of the flow produced by the second pump 9.

Thus the circulating flow passes along conduit 3, through pump 5, into junction conduit 7, but passes up the spur conduit 13 as flow into the second pump 9 is opposed totally by the reverse direction in which it now pumps. The metal thus flows to the moulds 15.

Once the desired amount of metal has been fed to the moulds 15 then the system is returned to circulating mode. The pumping direction for second pump 9 is reversed again therefore and the metal flows through from A to B as a result. Additionally, unused metal in the spur conduit 13 is drawn back into circulation and the risk of cooling and solidifying metal in this spur conduit 13 is avoided as a result.

Electromagnetic pumps are particularly suited for use as the second pump 9 which under goes reversals in pumping directions. Such pumps are particularly suited to pumping happily in either direction, with even performance in either direction and with quick reversal of flow when needed. The current fed to the pump simply needs to be reversed. It is preferred that electromagnetic pumps are used for the first pump 5 too. The use of two identical pumps allows them to readily balance one another and achieve controlled fed of the metal into the spur conduit 13 in casting mode.

In the Figure 2 illustration a beneficial set up for circulating molten metal is provided. This set up could be combined with the arrangement illustrated in Figure 1 readily.

The set up provides a single large capacity holding furnace 20. The use of a single furnace reduces capital cost compared with using a number of smaller furnaces and also allows a larger volume of metal to be stored, with consequential benefits in terms of homogeneity of metal for casting.

Metal 22 from the furnace 20 is extracted via conduit 24 and passes through pump 26. Again it is preferred that this and the other pumps are electromagnetic pumps. The metal 22 passes on from the pump 26 into conduit 28 and on round the ring main 30 before returning to the furnace 20. At a number of locations around the substantial length of the ring main 30 further pumps 32 are provided. These maintain the circulation of the metal within the ring main 30. For very large ring mains, top up heat may be introduced at a location remote from the furnace 20 using an induction heater 34. At a large number of

locations around the ring main 30 junctions 38 are provided which lead to spur conduits 40 and in turn to one or more moulds 42. Open and close able valves 44 may be provided at the junctions 38 to encourage metal flow into the spur conduit 40 for casting purposes.

The technique of Figure 1 could of course be used to switch between circulating mode and casting mode.

A casting system provided in the manner illustrated in Figure 2 offers substantial advantages in terms of easy distribution of homogeneous metal throughout a large casting plant in a very safe manner.

As an alternative technique for introducing metal into circulation the casting system illustrated in Figure 3 can be used. In this case, rather than draw metal 60 out through the side of the furnace 62, a hollow stalk 64 is provided, the end of which 66 is submerged below the level of metal 60 in the furnace 62. To draw the metal 60 out of the furnace 62 the stalk 64 leads to a pump 68, preferably an electromagnetic pump. This pumps the metal 60 up and out of the furnace 62 and into the circulating conduit 70. The pump 68 is well removed from the metal and so suffers none of the problems of submerged pumps. As no air over pressure is being used as the driving force for the metal bubble formation is eliminated.

Again this aspect of the casting system could be used alone or could be incorporated within a casting system including the features of Figure 1 and/or 2.

In the side view of Figure 4 a furnace 400 is provided. This has a sloping floor 402 to promote the flow of material towards the inlet 404 of a pump 406. The outlet 408 from the pump leads into a chamber 410. Material is fed into the furnace 400 using inlet 412. The chamber 410 is connected to a riser 414 which leads to casting operations.

When awaiting a casting operation the pump 406, on low power, is used to pump molten metal from the furnace 400 into the large chamber 410. The pump is then switched off and the level is allowed to settle. The process is then repeated. This allows for the re- circulation of metal to and fro between the furnace 400 and the chamber 410. This maintains the heat and other desirable properties in the metal in the chamber 410.

When casting is desired, the pump is used in a forward direction at a higher power. This transfers material through the chamber and up the casting neck 414 to the casting operations. The arrangement provided offers a quicker response in casting and reduces risks of freezing. The casting systems of the present invention are particularly suited for use in relation to aluminium casting, but can equally well be applied in relation to other materials.