WO2021044111A1

WO2021044111A1 - Casting apparatus

Info

Publication number: WO2021044111A1
Application number: PCT/GB2020/000073
Authority: WO
Inventors: Peter Michael HAIGH
Original assignee: Castings Technology International Limited
Priority date: 2019-09-04
Filing date: 2020-09-04
Publication date: 2021-03-11
Also published as: GB202200732D0; GB2586818A; GB2601253A; GB2601253B; GB201912691D0

Abstract

Apparatus is provided for casting solid objects. A mould has a recess defined in its top surface, and has a cavity with a sprue that opens into the recess. A plug having a closed top end is immovably attached to the mould and located at least partially within the recess. A receptacle to hold liquid feedstock has an aperture in its base, and the top end of the plug is of a reciprocal shape to the aperture such that it can seal the aperture. The receptacle is supported by a frame. The mould may be moved towards the crucible so that the plug seals the aperture, and moved away from the crucible to allow melted feedstock to flow out of the aperture and into the sprue.

Description

Casting apparatus

CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority from UK Patent Application No. 19 12

691.1.

BACKGROUND OF THE INVENTION

The present invention relates to casting objects using molten feedstock. Casting is a process whereby materials, often metals, are melted in a furnace and poured into a mould. When casting using expensive metals, it is important that none be wasted. Additionally, there are risks involved with manual handling of the apparatus.

It is an object of the invention to provide a method of casting in which no feedstock may be lost, and in which the casting can be carried out within a furnace or without manual handling.

It is known to tip-pour melted feedstock into moulds. However, this carries a risk of spillage and injury. An alternative is bottom-pour receptacles.

Bottom-pour receptacles, such as crucibles and ladles, have an aperture in the bottom. The aperture may be covered by a sliding strip underneath. This strip must be removed so that the feedstock can exit the receptacle. During this process, feedstock may stick to the strip and be lost. It may also drip off the strip, causing wastage and potentially harming operatives.

Another method of sealing a bottom-pour receptacle is using a rod having a plug on the end, that sits in the crucible or ladle. This rod must be lifted to allow the feedstock to exit the receptacle. However, the necessity of moving the rod prevents the apparatus from being operated inside a furnace, and again carries a risk of harm when the rod is lifted, due to splashing.

BRIEF SUMMARY OF THE INVENTION According to an aspect of the present invention, there is provided apparatus for casting solid objects, comprising a mould having a recess defined in its top surface, and having a cavity with a sprue that opens into said recess; a plug having a closed top end, immovably attached to said mould and located at least partially within said recess; and a receptacle to hold liquid feedstock having an aperture in its base, wherein said top end of said plug is of a reciprocal shape to said aperture such that it can seal said aperture.

According to a further aspect of the invention, there is provided a method of forming a solid object, in which: a mould has an internal cavity with a sprue, and a recess defined in its top surface into which said sprue opens; a plug is attached to said mould within said recess; and a receptacle is mounted above said mould such that an aperture in the base of said receptacle is sealed by the top end of said plug; said method comprising the step of: moving said mould downwards and away from said receptacle, such that said plug is removed from said aperture; whereupon liquid feedstock within said receptacle flows out of said aperture, into said recess and into said sprue in order to fill said cavity.

Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings. The detailed embodiments show the best mode known to the inventor and provide support for the invention as claimed. However, they are only exemplary and should not be used to interpret or limit the scope of the claims. Their purpose is to provide a teaching to those skilled in the art. Components and processes distinguished by ordinal phrases such as “first” and “second” do not necessarily define an order or ranking of any sort.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Figure 1 illustrates components of apparatus for casting;

Figure 2 illustrates a plug shown in Figure 1 ;

Figure 3 is a cross section of the assembled apparatus shown in Figure 1 ;

Figure 4 is a cross section of the apparatus shown in Figure 1 in a furnace; Figure 5 is a cross section of the apparatus in use; and

Figure 6 details a method of creating a cast item using the apparatus of

Figure 1.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 1

Components of apparatus 100 embodying the invention are shown in Figure 1.

A mould 101 defines an internal cavity in the shape of an item to be cast. Mould 101 also defines a recess 102 in its top, within which is a sprue leading to the cavity as will be shown in Figure 2. Attached to mould 101, in the recess 102, is a plug 103 with a tapered profile.

Apparatus 100 further comprises a cylindrical crucible 104. In this Figure, the mould and the crucible are shown separated for ease of illustration, but as will be shown in Figure 2 they are placed together in use.

In use, crucible 104 is supported by frame 105, which comprises a circular support portion 106, defining a central aperture 107 in which crucible 104 is supported by shoulder 108 that runs around the circumference of the crucible. Frame 105 further comprises four support legs 109 (of which three are visible) attached to a base 110.

Figure 2

Plug 103 is shown in Figure 2. It comprises a plug portion 201 and a port portion 202. Plug portion 202 is tapered from the plug portion to a first end 203 to provide a seal in an aperture having a reciprocal shape. First end 203, at the top of the plug, is closed, and the rest of plug portion 201 is solid although it may be hollow.

Port portion 202 is hollow, and comprises a cylindrical wall 204 defining an internal void, as will be shown in Figure 3. Second end 205, at the bottom of port portion 202, is open. Around the circumference of port portion 202 are three ports through wall 204, of which ports 206 and 207 are visible in this Figure.

Plug 103 also includes attachment means for attaching to mould 101. In this embodiment, the bottom part of wall 204 has an external helical thread 207 around its circumference, designed to screw into a reciprocating internal thread in sprue 305, as can be seen in Figure 3.

Figure 3

A cross section of the assembled apparatus 100 is shown in Figure 3. A scissor jack 301, in a lowered position, is placed on base 110 of frame 105, and mould 101 is placed on scissor jack 301. Mould 101 is of two parts, a top part 302 and a bottom part 303. Both parts together define cavity 304, which has the negative shape of the item to be cast. Sprue 305 is joined to cavity 304 and opens into recess 102, allowing for filling of the cavity with feedstock. If cavity 304 is of a complicated shape, it may be necessary for mould 101 to be made from more than one part. However, it is preferable that there is no joining point between parts within recess 102, as this could lead to feedstock running between the parts instead of down sprue 305.

Plug 103 is screwed into top part 202 of mould 101 directly above sprue 305, which is in the centre of recess 102. As shown in Figure 2, plug 104 comprises solid plug portion 201 and hollow port portion 202, comprising wall 204 defining internal void 306. Ports 206 and 207 are shown through wall 204. There is therefore a flow path from recess 102 through the ports, out of the second end 205, and into sprue 305.

Crucible 104 is supported by support portion 106 of frame 105, on shoulder 108. In the base of crucible 104 is defined an aperture 307, of a reciprocal shape to the top of plug 103.

Mould 101 and crucible 104 are co-located such that plug 103 is directly below aperture 307. Recess 102 is shaped and sized so that the base 308 of crucible 104 fits inside it. In this embodiment the assembled apparatus 100 is around 30cm high, and therefore manually moveable.

Thus there is provided a mould having a recess defined in its top surface, and having a cavity with a sprue that opens into the recess and a plug immovably attached to the mould and located within the recess.

There is also provided a receptacle, which in this example is crucible 104, to hold liquid feedstock. It has an aperture in its base, and the top end of the plug is of a reciprocal shape to the aperture such that it can seal the aperture. There is also provided a support, which in this example is frame 105, to hold the receptacle.

There is also provided moving means for moving the mould towards and away from the receptacle, which in this example is scissor jack 301.

Figure 4

To use apparatus 100, scissor jack 301 is operated to elevate mould 101, moving plug 103 into aperture 307, until the aperture is sealed as shown in cross-section in Figure 4. Feedstock to be melted is placed in crucible 104, and the entire apparatus 100 is placed in furnace 401. Plug 103 seals aperture 307 so that the feedstock does not flow out when it melts. The feedstock is shown in this Figure as molten feedstock 402, after the furnace has been operated.

Furnace 401 is a vacuum furnace that operates by induction. A port 403 is provided through the wall 404 of the furnace. This port is permanently sealed, and provides various inlets and outlets, for example to exhaust air and fill with an inert gas such as argon, and to provide electrical power and control to the various components. In particular, scissor jack 301 requires power and control, provided by line 405. Jack 301 is connected to line 405 after the apparatus is placed in the furnace. Alternatively, the frame and the scissor jack may be permanently in place in the furnace, and the mould and crucible placed inside before operation. Other components of induction furnace 401 are standard and will be understood by those skilled in the art. Other types of furnace may also be used.

Apparatus 100 is configured so that an item may be cast without the need for the introduction of any item through the wall 404 of furnace 401. Therefore, furnace 401 does not include a port that can be opened and closed. Such ports need to be cooled, often by water, in order to withstand the heat of the furnace. However, ports that are permanently sealed, such as port 403, do not need to be cooled. Furnace 401 therefore does not require a cooling system, which increases the safety of the furnace. However, in other embodiments, a furnace with a cooling system may be used.

Once apparatus 100 is in furnace 401, the furnace is operated to raise the temperature to a specific point for a specific amount of time, depending on the type and the volume of the feedstock. After the temperature has been raised for the set amount of time, it is assumed that the feedstock 402 is melted and ready to be poured into mould 101.

Figure 5

During the mould-filling procedure, furnace 401 may be switched off, or may be still operational in order to keep feedstock 402 at a high temperature.

Scissor jack 301 is operated remotely to lower mould 101. Crucible 104 is prevented from moving downwards by shoulder 108 sitting on frame 105, and therefore plug 103 is removed from aperture 307. This allows melted feedstock 402 to flow around plug portion 201 into recess 102. The feedstock then flows through the ports through wall 204, out through second end 205, and into sprue 305, thus filling cavity 304. One path taken by feedstock 402 is shown by dashed line 501 , although it should be appreciated that the feedstock will flow through all three ports, and may partially fill recess 102 before flowing into the sprue, depending on the viscosity of the feedstock and the size of the ports.

Thus, use of this apparatus provides a method of pouring melted feedstock from the bottom of a crucible into a mould, without the need to tip the crucible, to operate a sliding strip, or to introduce any external object into the furnace. The only moving part is the scissor jack, which can be operated remotely and which does not come into contact with the feedstock. There is no risk of spillage or loss of feedstock 402, because its path flows from the crucible directly into the mould, and the crucible fits into the recess so that any splashes will stay within the recess.

However, as the crucible is not a sealed fit in the recess, recess 102 is preferably of a large enough volume (excluding the volume occupied by plug 103) to hold all of melted feedstock 402, thus avoiding the potential for overflow.

In an alternative arrangement, the crucible does not fit within the recess but remains above the mould at all times, with the plug being either elongated or elevated relative to the embodiment described herein. In this case the recess would need to be deeper, to avoid the feedstock splashing out of the mould.

Once feedstock 402 has all flowed into cavity 304 and furnace 401 has cooled sufficiently, apparatus 100 can be removed from the furnace. The mould is then removed from the apparatus to cool, before removal of the item from the mould and further processing of the item. If another item is to be cast, a new mould is put in place and the process is restarted.

As an alternative to the small apparatus 100, the apparatus may be large and contained within an industrially-sized furnace. In that case, the above-described components would be similar save for scale. The crucible and its support could remain in place in the furnace, with moulds being placed as required.

Other arrangements of the crucible, plug and mould are envisaged. For example, sprue 305 could be in another position in the recess rather than in the centre, as long as the opening to the sprue is not located higher than the rest of the surface of the recess, so that the melted feedstock drains into the cavity. The location of the sprue may be dictated by the shape of the cavity within the mould.

Further, the plug need not be located directly over the sprue. Its position is dependent upon the way it is attached to the mould. For example, the plug could comprise a plug portion only, and the attachment means could be extending members, such as legs, that are attached to the top of the mould or the sides of the recess, so that the plug portion is held above the surface of the recess. The legs could be inserted into the mould before it is dried and fired, or apertures could be formed in the mould to hold the legs. In such an arrangement, the feedstock would flow over the plug, into the recess, and directly into the sprue without passing through the plug again. The plug could therefore be in any part of the recess, whether or not directly above the sprue. In this example the plug would still be partially within the recess, although not in contact with the surface of the recess. Raising the plug completely out of the recess would increase the risk of feedstock splashing out of the mould, and would therefore not be suitable for this apparatus.

Other methods of attaching the plug to the mould are also envisaged; any arrangement in which the plug is immovably attached would be suitable, as long as when the mould and receptacle are moved apart, the plug stays attached to the mould and breaks the seal with the receptacle.

Any suitable method of moving the mould can be used. The choice could be determined by the size of the mould; for example a large mould might need a more substantial jack, such as a hydraulic platform. Alternatively, the entire floor of the furnace could be arranged to move.

As a further alternative arrangement, the crucible could be arranged to move upwards, rather than the mould moving downwards. This could be done by moving the entire frame upwards. In this type of arrangement the mould would need to be prevented from moving upwards by some means. However, moving the mould downwards is preferred, as this means gravity assists in breaking the seal formed by plug 103. A further alternative is that the receptacle above the mould is a ladle rather than a crucible. In this case, the ladle and the mould would not be placed in a furnace. The material would be melted in a separate crucible, and poured via a trough into the ladle.

Figure 6

An overview of the method of creating a cast item, using apparatus 100 or similar, is shown in Figure 6.

At step 601 , a mould with a suitable cavity having a plug attached to it, a crucible, a frame and a jack are obtained. At step 602, the crucible is placed in the frame, and at step 603 the mould is placed on the jack below the crucible.

At step 604 the jack is raised to raise the mould so that the plug seals an aperture in the bottom of the crucible. At step 605 feedstock is heated in the crucible, either by placing the apparatus in a furnace or otherwise.

At step 606 the jack is lowered, lowering the mould and removing the plug from the aperture, allowing the molten feedstock to flow into the cavity.

At step 607 further processing of the item is carried out, such as allowing the mould to cool before removing the item and machining it.

Claims

1. Apparatus for casting solid objects, comprising: a mould having a recess defined in its top surface, and having a cavity with a sprue that opens into said recess; a plug having a closed top end, immovably attached to said mould and located at least partially within said recess; and a receptacle to hold liquid feedstock having an aperture in its base, wherein said top end of said plug is of a reciprocal shape to said aperture such that it can seal said aperture.

2. Apparatus according to claim 1 , wherein: said plug further comprises an outside wall defining an internal void; said wall has ports defined therein giving access to said internal void; and the bottom end of said plug is open; such that a flow path is defined from the outside of said plug through at least one of said ports and out of said bottom end.

3. Apparatus according to either of claims 1 or 2, wherein said plug is located above said sprue.

4. Apparatus according to any of claims 1 to 3, wherein the bottom end of said plug is formed with an external helical thread, and said mould defines an aperture having a cooperating internal thread, such that said plug is attached to said mould by being screwed in.

5. Apparatus according to any of claims 1 to 3, wherein the bottom end of said plug is formed with extending members that are attached to said mould.

6. Apparatus according to claim 1 , further comprising a support to hold said receptacle.

7. Apparatus according to claim 6, wherein said recess is shaped such that the base of said receptacle fits into the top of said recess.

8. Apparatus according to either of claims 6 or 7, wherein said support is a frame configured to fit over said mould, with an aperture defined in the top of said frame and configured to fit around said receptacle; and said receptacle comprises external support members to rest on said frame.

9. Apparatus according to any of claims 6 to 8, further comprising moving means for moving said mould towards and away from said receptacle.

10. Apparatus according to claim 9, wherein said moving means is a scissor jack located underneath said mould.

11. Apparatus according to any of claims 6 to 10, wherein said receptacle is a crucible.

12. Apparatus according to claim 11 , further comprising a furnace containing said mould and plug, said support, said receptacle, and said moving means.

13. Apparatus according to any of claims 6 to 10, wherein said receptacle is a ladle.

14. Apparatus according to either of claims 9 or 10, wherein said mould is located on top of said moving means, said receptacle is mounted in said support, the base of said receptacle is within said recess, and said aperture is directly above said plug.

15. A method of forming a solid object, in which: a mould has an internal cavity with a sprue, and a recess defined in its top surface into which said sprue opens; a plug is attached to said mould within said recess; and a receptacle is mounted above said mould such that an aperture in the base of said receptacle is sealed by the top end of said plug; said method comprising the step of: moving said mould downwards and away from said receptacle, such that said plug is removed from said aperture; whereupon liquid feedstock within said receptacle flows out of said aperture, into said recess and into said sprue in order to fill said cavity.

16. A method according to claim 15, wherein: said plug further comprises an outside wall defining an internal void; said wall has ports defined therein giving access to said internal void; and the bottom end of said plug is open; such that the path for said liquid feedstock from said recess to said sprue passes through said plug, via at least one of said ports, said internal void, and said bottom end.

17. A method according to either of claims 15 or 16, wherein said plug is located above said sprue.

18. A method according to any of claims 15 to 17, wherein said plug is attached to said mould using a screw fit at the bottom end of said plug.

19. A method according to any of claims 15 to 17, wherein said plug is attached to said mould by members extending from said bottom end attached to said mould.

20. A method according to claim 15, wherein said receptacle is mounted above said mould using a support frame.

21. A method according to claim 15, wherein the base of said receptacle is smaller than said recess such that it fits into said recess.

22. A method according to any of claims 15 to 21 , wherein said mould is placed on a scissor jack, and said step of moving said mould comprises lowering said scissor jack.

23. A method according to any of claims 15 to 22, further comprising the earlier steps of: placing said mould underneath said receptacle such that said plug is directly beneath said aperture; moving said mould towards said crucible so that the top of said plug seals said aperture.