WO2009040503A1

WO2009040503A1 - Apparatus for investment casting and method of investment casting

Info

Publication number: WO2009040503A1
Application number: PCT/GB2008/003171
Authority: WO
Inventors: Richard Stanley Goodwin; Kongsak Termpittayavej
Original assignee: Goodwin Plc
Priority date: 2007-09-24
Filing date: 2008-09-19
Publication date: 2009-04-02
Also published as: GB2452997A; JP2010540252A; CN101815592A; GB2452994A; EP2212040A1; GB0718637D0; BRPI0817229A2; GB0719889D0

Abstract

Described is a method of preparing an investment casting mould, said method comprising: providing a sleeve; blocking an open end of said sleeve by fixing a water permeable material over it; and providing a water absorbent material on a side of said water permeable material opposite to said sleeve, wherein said water absorbent material is held together and constructed and arranged to ensure fluid communication between said water absorbent material and the inside of said sleeve. Also described is an object for use in removing water from an investment casting slurry in a sleeve, wherein at least a portion of an outer surface of said object is water permeable thereby to provide fluid communication from outside of said object with a water absorbent material of said object, said object comprising a sealing feature for sealing the container onto an end of a sleeve.

Description

APPARATUS FOR INVESTMENT CASTING AND METHOD OF INVESTMENT CASTING

This invention relates to investment casting. In particular the invention relates to an object for use in removing water from an investment casting slurry in a sleeve and to a method of preparing an investment casting mould.

Lost wax investment casting has been in use for centuries. A model of the product to be produced (for example an item of jewellery) is created in wax or similar material. This is attached to a wax tree and placed in a sleeve, for example a container or a flask. The rest of the container is then filled with a ceramic slurry which is then solidified. Heat can be used to melt the wax which then leaves behind a mould into which material may be cast. The mould can be broken off once the cast material has itself solidified. The present invention provides an object for use in removing water from an investment casting slurry in a sleeve, wherein at least a portion of an outer surface of said object is water permeable thereby to provide fluid communication from outside of said object with a water absorbent material of said object, said object comprising a sealing feature for sealing the object onto an end of a sleeve.

The present invention provides a container for use in removing water from an investment slurry and containing a water absorbent material, said container comprising a sealing feature for removably sealing the container onto an end of a sleeve and an indentation portion for projecting into the bottom of the sleeve when the sleeve is sealed to the container.

The present invention provides an object for use in removing water from an investment casting slurry in a sleeve, wherein at least a portion of an outer surface of said object is water permeable thereby to provide fluid communication from outside of said object with a water absorbent material of said object, said object comprising a through hole so that the object can be placed on a projection such that said water absorbent material surrounds the projection when the projection extends through the object.

The present invention further provides a method of preparing an investment casting mould, said method comprising: providing a sleeve; blocking an open end of said sleeve by fixing a water permeable material over it; and providing a water absorbent material on a side of said water permeable material opposite to said sleeve, wherein said water absorbent material is held together and constructed and arranged to ensure fluid communication between said water absorbent material and the inside of said sleeve.

Specific embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 illustrates, in cross-section, a method of investment casting not in accordance with the present invention, but is generally how the process is currently carried out;

Figure 2 illustrates, in cross-section, an investment casting method in accordance with a first embodiment;

Figure 3 illustrates, in cross-section, an investment casting method in accordance with a second embodiment;

Figure 4 illustrates, in cross-section, an investment casting method in accordance with a third embodiment;

Figure 5 illustrates, in cross-section, an investment casting method in accordance with a fourth embodiment; Figure 6 illustrates, in cross-section, an investment casting method in accordance with a fifth embodiment;

Figure 7 illustrates, in cross-section, an investment casting method in accordance with a sixth embodiment;

Figure 8 illustrates, in cross-section, an investment casting method in accordance with a seventh embodiment;

Figure 9 illustrates, in cross-section, an investment casting method in accordance with an eighth embodiment;

Figure 10 illustrates, in cross-section, an investment casting method in accordance with a ninth embodiment; Figure 11 illustrates, in cross-section, an investment casting method in accordance with a tenth embodiment; and

Figure 12 illustrates, in cross-section, an investment casting method in accordance with an eleventh embodiment.

Over the past 50 years or more, Jewellery lost wax investment castings in Gold Silver and brass have been cast in a moulding material that is nominally made from a mixture of silica, cristobalite and plaster. The plaster content is used to achieve the setting ( solidification ) of the investment powder slurry when it is cast around the wax tree. It does - this by absorbing the water and as a result expands as the plaster crystals grow. It is necessary to make an easy flowing slurry investment moulding powder so that it will easily flow around the very fine wax detail that is on many Jewellery, medical and industrial lost wax investment castings. For it to be easy flowing there is the need for a water content of between 25 and 45 parts per 100 parts by weight of powder.

For Gold, Silver and brass castings, the burning out of the wax from the flask is normally carried out at 700⁰C plus or minus 80⁰C and metal is poured into the flask at a temperature of between 500 and 740°C. However for stainless steel, Cobalt, Platinum and high Palladium Platinum investment castings, the burn out is at a considerably higher temperature and the metal is cast into the sleeve at 850 to 1000⁰C. This higher sleeve temperature is needed to avoid chilling of the higher melting point metal - Platinum has a melting point of 1773 °C as compared to Gold that melts at 1063°C.

Due to the higher sleeve temperatures needed, it is no longer possible to utilise plaster in the investment powder recipe as the plaster breaks down at temperatures above 800⁰C.

Accordingly investment powder recipes for Platinum , Platinum alloys such as Palladium/Platinum, Platinum Rhenium and steels such as Cobalt and stainless steels are made up primarily of silica or a mixture of silica and cristobalite with additives in the 0.5 to 2.5% region to create the solidification of the investment powder slurry when it is poured around the wax tree in the sleeve.

This present invention is in respect to a mechanism of removing the water from investment powders that do not contain plaster or at least contain less than about 10% or less than about 6.0% or about 4.0% plaster. Without significant quantities of plaster in the investment powder slurry (5% to 28%), there is a need to absorb away the moisture from the slurry mix in a steady controlled manner whilst the chemical additives solidify the silica slurry.

One technique is illustrated in Figure 1 which is generally used world wide for high temperature casting powders. In this method a sleeve or flask 10 (the sleeve 10 may have any cross-sectional shape (through it is usually circular) and can have any height) is put on to a water permeable material 20 i.e. a material which is porous to water (such as pulp/or other water absorbent mat). This material may be between lmm and 4mm thick. The water permeable material 20 is sealed to the flask 10, for example using liquid wax 40. A purpose of the water permeable material 20 is to contain the slurry in the sleeve. The -A- wax tree 30, is stuck with wax to the centre of the water permeable material 20. This can be done before or after attaching the sleeve 10 to the water permeable material 20. This assembly is then sat on top of a loose pile (10mm to 30mm thick) of water absorbent material 60 such as silica or plaster or other absorbent powder. This water absorbent material 60 may even be the actual moulding material complete with additive.

The liquid slurry 50 is then poured into the sleeve 50. The slurry solidifies in between 45 and 120 minutes. The drawback is that it is very messy and log winded due to having to seal the joint between the flask and the mat with wax and due to having to clear up and throw away the powder the assembly was sitting on. There is also a health hazard associated with using silica powder due to silicosis caused by breathing in fine particles of silica. This problem is exacerbated in hot countries where fans are used for cooling in the factories.

The present invention avoids or alleviates at least some of these drawbacks by providing a method of preparing an investment casting mould. The method comprises providing a sleeve 10. Then an open end of the sleeve 10 is blocked by fixing a water permeable material over it. Preferably the fixing comprising sealing. An object comprising a water absorbent material is provided on a side of the water permeable material opposite to the sleeve. The water absorbent material is held together. For example the water absorbent material may be in a bag, or it may be of a loose material which has been compressed, for example wood or paper pulp or castable water absorbent material particularly one which is sized to fit into the bottom of the sleeve (e.g. has a circular cross- section with a diameter of between 9 and 7cm (the standard diameters of sleeves are 4 and 6 inches)). Such a water absorbent material object may also be placed in a (reusable) container. Therefore the water absorbent material is held together, for example by being compressed together and/or by being in a container. The container preferably completely surrounds the water absorbent material. The container is preferably designed and/or made of a material which does not allow the water absorbent material to pass through. At least a portion of a surface of the object comprising the water absorbent material or a wall of the container is water permeable thereby to provide fluid communication between the water absorbent material and the inside of the sleeve. Thus, the water absorbent material is contained so that the chance of the water absorbent material escaping is reduced. Furthermore, the cleanliness of the process is increased as all the water absorbent material is kept together. If the water absorbent material is in powder form and contained in a container, preferably the pores or through holes in the water permeable portion of the container wall have a smaller maximum diameter than the average or smallest minimum diameter of powder particle. The water absorbent material is provided sealed against water penetration before use, for example in a water impermeable package. The seal can be broken just prior to use ensuring that the water absorbent material remains fresh during transport from its place of manufacture to the place of use.

Preferably the water permeable portion of the object is the water permeable material which is fixed over an end of the sleeve. This reduces the number of components and can ease assembly of the system. For example, the invention may provide an object for use in removing water from an investment casing slurry in a sleeve. At least a portion of an outer surface of the object may be water permeable thereby to provide fluid communication from outside of said object with a water absorbent material of said object. The object may further comprise a sealing feature for sealing the container onto a sleeve in an orientation in which the water permeable portion is in contact with the investment casting slurry in the sleeve. Thus, the number of steps in manufacturing a mould is vastly reduced. In order to use such a container, the wax tree 30 with attached articles 35 is simply placed on the water permeable portion of the container. In one embodiment the object comprises an indentation portion which projects into the sleeve and provides a base for the trunk of the wax tree to be inserted. A sleeve 10 is then placed over the wax tree 30 and sealed to the object using the sealing feature of the object. The sealing feature of the object is preferably designed to withstand the hydrostatic forces which are present when the slurry 50 is poured into the sleeve 10. This can prevent water and/or slurry before it has set from escaping between the sleeve and the object. Preferably the sealing feature is constructed and arranged to be watertight with a hydrostatic pressure of at least 6cm of water, preferably 10cm, more preferably 15cm and even up to about 30 or 40cm. Such an arrangement further reduces the mess associated with producing a mould and can eliminate mould flaws associated with water and/or slurry leaking out around the edge. In some embodiments the sealing feature comprises an elastic material. This is a cheap and simple sealing feature which also has high tolerance for different sleeve 10 sizes.

The sealing feature may make use of a radially compressive force. Such a sealing feature is preferable because it does not require any features on the sleeve 10 to be present in order to fix the container to the sleeve 10.

In one or more embodiments the side walls of the container are stiff enough to resist compression by the sealing feature. This eases the design and manufacture of the object, particularly when an elastic and/or radially compressing sealing feature is used. In the case that the object comprises a container, it may be preferable to provide the container walls, other than the water permeable portion, as an integral piece. This can aid in manufacture. For example, the parts of the container other than the water permeable portion may be formed of (injection) moulded plastic. In one embodiment the fixing component is integral with side walls of the container. The side walls of the container are usually co-planar or parallel to the side walls of the sleeve 10. This arrangement can aid in the manufacture and assembly of the container. Furthermore, this arrangement can provide extra strength and/or ease of attachment to the sleeve 10.

Examples of material used for the water permeable portion include wood pulp formed cardboard, vermiculite, a perforated plate a woven material, a non-woven fabric etc. A water permeability of at least 0.25 cc/cm²/hour at a water head of 0.5 cm is preferable.

The water absorbent material described herein can be, for example, silica or plaster or other absorbent powders as described above. Further examples are wood or paper pulp or vermiculite. Preferably these materials have a water absorbency capacity of at least 100% by weight. Preferably the water capacity is more than 110%, 120%, 130%,

150% and 200% or even more. This will provide flexibility in terms of the suitability of a given container for various sleeve 10 heights for a given diameter.

Seven specific embodiments will now be described in detail with reference to

Figures 2-6. It will be understood that features of one embodiment can be applied to other embodiments as appropriate.

First Embodiment

A first embodiment is illustrated in Figure 2.

An object or container or canister of the present invention may have the following attributes: 1) a porous upper surface 85.

2) a base and top (lid) and side walls that contain absorbent material 70. 3) A fixing component or sealing mechanism between the top of the water absorbent container or canister 90 and the casting sleeve or flask 10 that it is joined to. (This may be part of the container or canister 90 or a separate item.)

4) A water absorbent filler/material 70, preferably inert hazard free fine grade vermiculite, but it could be ground silica, plaster, silica gel or other water absorbent material. Or a solid block of water absorbent material such as pulp. The base and sides of the canister may be water permeable and/or absorbent like the top or they may be waterproof made from a plastic or polymer material or similar or as a water absorbent core The volume of the water absorbent material in the canister (along with the water absorbent capacity of the lid, sides and base of the canister) should be at least large enough to soak away the unwanted water from the slurry in the flask. The higher the capacity in terms of water absorbency, generally the higher the rate of solidification of the slurry in the flask. A water absorbency capacity of between 1 10% and 250% by weight is preferred to provide flexibility of flask height for a given diameter. Only about 60% of the water needs to be removed from the slurry in this way; the remainder is removed in the wax burn out furnace.

The setting process of the slurry in the sleeve/flask 10 does not require all the moisture to be removed as residual moisture (approx 40% of the initial water content) can be driven off during the wax burn out cycle. The need is for enough moisture to be absorbed such that the slurry in the sleeve/flask 10 solidifies and is strong enough for the sleeve/flask 10 to be put in a burnout furnace without the solid powder matrix around the wax tree 30 fracturing in the handling process.

As shown in Figure 2, in the first embodiment the wax tree 30 is placed and/or fixed onto a water permeable material 20 (in the same way as in Figure 1). Also as in Figure 1, a (reusable) sleeve 10 is placed over the wax tree 30 onto the water permeable material 20 and sealed thereto using wax 40. The seal is made by a circumferential seal or bead of wax or other similar sealing compound that seals between the sleeve and the water permeable material around the bottom end of the sleeve 10 and between the sleeve 10 and the water permeable material 20. This whole assembly is then placed on a container 90 which contains a water absorbent material 70. The container 90 has at least a portion 85 of a wall 80 which is water permeable. The water permeable portion 85 is placed at least partly in register with the water permeable material 20 such that the water absorbent material 70 is in fluid communication with the inside of the sleeve 10.

The sleeve 10 of the described embodiments has a circular cross-section. Sleeves 10 come in standard diameters. The cross-section need not be circular and the cross-section could be something different, for example square. Also, the sleeve 10 is shown as having a top open end and bottom open end. In fact the sleeve may have a bottom end closed by a water permeable material. Also, the cross-section of the sleeve 10 may vary along the length of the sleeve. The top end may be tapered.

The shape of the container 90 shown in Figure 2 is idealised. Other shapes may be suitable. For example, the manufacturing process of the container may result in seams or other joints sticking out from the container 90. The container may, for example, be formed of two sheets fixed one on top of the other. In that case only the top sheet could be water permeable and the bottom sheet could be waterproof. Slurry 50 is then added into the flask and the drying process begins when the water absorbent material 70 absorbs water from the slurry 50. The water from the slurry passes through the water permeable material 20 as well as the water permeable portion 85. The container and or absorbent block outside radial shape could be round, oval, triangular, square, 5 sided, hexagonal, or a different many sided.

In this embodiment the weight of the sleeve 10 and slurry 50 hold the sleeve 10 to the container 90.

In the embodiment of Figure 2 the parts of the wall 80 of the container 90, not including the water permeable portion 85, are preferably waterproof. This is not necessarily the case. For example the walls 80 of the container 90 may all be made of the same or similar material. That might make manufacture easier. However, ensuring that the wall 80 of the container 90 which are not the water permeable portion 85 are waterproof has advantages. For example, water will not leak out of the container 90 and the chance of water absorbent material 70, once saturated with water, being lost from the container 90 are also decreased.

The container 90 of the Figure 2 embodiment is flexible and is pressed into the shape illustrated in Figure 2, in use. This eases transportation because the container 90 can assume any shape and thereby occupy a small volume. However, the container 90 may be stiff, as with the other described embodiments. Containers 90 with water absorbent material 70 may be placed in individual packaging. Such packaging is preferably is water impermeable so that the water absorbent material 70 does not absorb water between manufacture and use. A single package may contain one or more containers 90. Alternatively or additionally a seal against water penetration of a different form could be provided. For example a removable or breakable seal could be glued over the top of the container 90 over the water permeable portion 85. The seal could then be removed (e.g. broken or peeled off) prior to use.

Second Embodiment

A second embodiment is illustrated in Figure 3. The second embodiment is the same as the first embodiments except as described below.

In the second embodiment, the use of both a water permeable material 20 and a container 90 is eliminated. This is done providing the water absorbent material in substantially solid and/or rigid form (e.g. in a block). That is, the water absorbent material 70 is not in powder form, but is shaped. That is, the water absorbent material may be formed as an object for use in removing water from an investment casting slurry sleeve. The object may be of wood or paper (or similar material) pulp, for example. Alternatively the object may be made of a compacted powder or fibrous water absorbent material. The object need not be made of just one material and could, for example, be made of layers. This form of water absorbent material could be used with any other embodiment. Particularly with embodiments four to seven. This has the advantage that the other parts of the object (namely the container) can be reused. As with other embodiments, the water absorbent material may be reusable. That is, after drying of the slurry, the water absorbent material, with absorbed water, can be dried (for example by heating) and then reused. Preferably the object is elastically compressible in the radial direction so that, as described below, the body itself acts as a sealing feature for sealing the object onto the end of the sleeve 10.

In the second embodiment the object is sized and shaped to fit into the end of the sleeve 10. Preferably the object fits tightly into the sleeve, thereby sealing between the outer surface of the object and the inner surface of the sleeve 10. Thus the size and the shape of the object can be seen as a sealing feature allowing sealing of the object to the sleeve with the water absorbent material in fluid communication with the slurry 50 in the sleeve 10.

It is possible to complete the seal between the sleeve and the object using a bead of glue or wax 41 circumferentially between the object and the sleeve. Alternatively an extra component such as a sealing feature of embodiment six can be used. This is also illustrated in Figure 4 described below.

However, preferably no such extra component is used. It is the elasticity of the object itself which forms the tight seal. That is, the object has a diameter, at rest, greater than that of the inner diameter of the sleeve. When inserted into the sleeve, a compression force is applied to the object and the outward force generated by the compression then works between the object and the sleeve to seal. The shape of the object may be such as to aid in its insertion into the sleeve. For this purpose the object may be tapered. In use it is then pushed as far as possible into the sleeve to form the seal. In such a tapered embodiment it is not necessary for the object to be elastic, though that is preferable. The elasticity may be provided by an additional elastic material surrounding the object and, in use, in contact with the inner surface of the sleeve.

In an alternative arrangement, a lip may be formed on the object to that contact is additionally or solely between the outer surface of the sleeve and the object. In the case of sole contact between those two surfaces, the shape of the object can be similar to that of the container 90 of Figure 6.

The at least a portion of the top surface of the object (to which the wax tree 30 is attached) is water permeable. This brings the water absorbent material into fluid communication with the slurry. In one embodiment a separate water permable material (e.g. in the form of a layer) and which can also be water absorbent can be formed or placed on the top of the water absorbent material. This might be desirable if the object would otherwise be vulnerable to penetration by the slurry.

Third Embodiment

A third embodiment is illustrated in Figure 4. The third embodiment is the same as the second embodiment except as described below. In the Figure 4 embodiment, the top outer surface of the object comprising the water absorbent material is shaped to fit inside the sleeve 10. That is, a step is formed in -l ithe object. The smaller diameter is about that of the inner diameter of the sleeve, and the larger diameter is about that of the outer diameter of the sleeve 10. The very top portion may have the characteristics of the sealing feature of the object of the second embodiment (e.g. elastic, tapered etc.). A seal 330, for example in the form of an o-ring or washer or glue or wax may additionally be provided. The seal 330 sits on the Hp formed by the change between the minimum and maximum diameters.

As mentioned above, Figure 4 illustrates the optional feature of a radial inward force generating band 210 (in dashed lines) such as is described in detail in the sixth embodiment. Such a band 210 can be part of the sealing feature and can help in making the seal between sleeve 10 and the object tight enough to reach the desired level of watertightness.

A further optional feature is illustrated in Figure 4. That is an indentation portion 72 which extends further into the sleeve 10 than the rest of the top surface of the object. The indentation portion forms the base of the wax tree 30 (so that the mould is funnel shaped). The rest of the tree is attached to the top of the indentation portion 72 (which is in the shape of a truncated cone). The indentation portion 72 may have a hole in its top surface for receiving an end of the tree 30. This avoids the need for glue or other adhesive to attach the wax tree to the water permeable portion. The indentation portion can be integral, but need not be. Furthermore, it need not be water permeable or water absorbent. An indentation portion may form part of any embodiment. For example it may be formed on the top 100 or the water permeable material 20.

Fourth Embodiment

A fourth embodiment is illustrated in Figure 5. The fourth embodiment is the same as the first embodiment except as described below. In the Figure 5 embodiment the object comprises a container 90. The container

90 is comprised of side walls 120, a bottom 110, and a top 100. The top and bottom may be in the form of plates or they may have a different form, for example a sheet. The top 100 is formed at least in part as a water permeable portion. There is no equivalent to permeable material 20 of Figures 1 and 2. The bottom 110 may be water impermeable or water permeable. The top and bottom 100, 110 are preferably held by side walls 120 but they may also be somehow fixed in a different way, for example by glue. The side walls 120 are generally in the shape of a pipe. They preferably have the same (outer) cross-section as the sleeve 10. The side walls 120 can also comprise a bottom lip 122. The bottom lip 122 holds the bottom plate 110 in place. Between the top and bottom 100, 110 is the water absorbent material 70. As with all other embodiment, the water absorbent material 70 may be in any form. It could be in powder form, or it could be a solid object as in the second and third embodiments. In that case a separate top 100 may not be necessary as the top of the object can have the necessary properties. The object would not necessarily need to be fastened to the container. The container could be reusable with a new object comprising the water absorbent material or the object itself could also be reused. A reusable object could be dried inside or outside of the container 90. The container 90 could be used with several objects. The top 100 can either be glued in place or can sit in a recess on the inner surface of the side walls 120, for example. Such an arrangement is described and illustrated in relation to the fifth embodiment.

As can be seen, the side wall 120 extends above the top 100 to form a sealing feature 125 which can also be seen as a fixing component. The sealing feature 125 is sized such that it can be in contact with the outer surface of the bottom end of the sleeve 10. Preferably the material of the fixing component is elastic. In this way it is possible for it to be arranged to generate a readily compressive force. In this way a good seal between the container and the sleeve 10 can be generated. The sealing feature 125 therefore projects from the top of the container 90. The sealing feature 125 projects from the edge of the container 90 beyond the top 100 of the container. The top 100 of the container is the water permeable portion of the container. At rest the internal cross-sectional shape of the sealing feature 125 is the same, preferably smaller than the outer cross-sectional shape of the bottom of the sleeve 10. The sealing feature 125 is preferably elastically resilient to deformation radially outwardly. Preferably the sealing feature is elastic. Preferably the sealing feature exerts a radially compressive force onto the sleeve 10 when the container 90 is attached to the sleeve 10.

The material of the side walls 120 is preferably a polymer. Other materials may be suitable. Metal side walls may be suitable; the container can then be heated, for example during drying of the absorbent material. The side walls 120 could be, for example, an injection moulded component. The compressive force generated by the sealing feature 125 on the sleeve 10 is preferably enough to ensure that the container is attached to the sleeve 10 in such a way so that hydrostatic pressure generated by water in the slurry 50 does not lift the sleeve 10 from the container. Preferably the seal generated by the sealing feature has the properties described above. However, it is possible that further items are provided in order to increase the strength of the fixation and/or seal between the container and the sleeve 10. For example, an adhesive could be used. Alternatively or additionally a further clamping means could be used. For example a clamping means could include an elastic band positioned around the sealing feature 125 to increase the compressive force on the sleeve 10. Alternatively the clamp could extend longitudinally around the sleeve 10 and the container 90 to hold them together.

As can be seen, the sealing feature 125 has a tapered edge. In this way the internal diameter of the container decreases as distance away from the edge towards the bottom plate 110 increases. This increases the ease of inserting the sleeve 10 into the container.

The container of the second embodiment is relatively stiff. The top and bottom 100, 110 may however be flexible (e.g. made of sheet material). Alternatively they could be made thicker to aid in manufacture.

Fifth Embodiment

A fifth embodiment will now be described with reference to Figure 6. The fifth embodiment is the same as the fourth embodiment except as described below.

As with the fourth embodiment, the fifth embodiment comprises a container which is preferably comprised of materials which mean that the container is rigid. In the fifth embodiment the bottom 110 is provided integrally with the side walls 160.

As can be seen in Figure 6, a recess 167 (which is annular) is provided on an inner surface of the side wall 160. Edges of the top 100 sit in the recess 167. If the side walls 160 are formed of a elastic material, such as plastic, after the water absorbent material 70 has been placed in the container, the top (plate) 100 can be pushed into the container and snapped into the recess 167. The details of the sealing feature 165 of the Figure 6 embodiment are similar to those of the Figure 5 embodiment.

Sixth Embodiment A sixth embodiment is illustrated in Figure 7. The sixth embodiment is the same as the third embodiment except as described below.

In the sixth embodiment the sealing feature 210 may be separate from the container 90. The container 90 is formed in a similar way to that of the sixth embodiment except that the side walls 200 do not extend beyond the top 100. It will be appreciated that the container could be formed in other ways, as with the other embodiments, and for example could be similar to the construction of the container of the Figure 5 embodiment. That is, a bottom 110 could be provided which is not integrally formed with the side walls 200. In the Figure 7 embodiment the top 100 is fixed to the side walls 200. This may be by glue or other means. Alternatively or additionally, the whole of the container 90 could be made of the same material.

The fixing component 210 is provided as an elasticated sleeve. That is the sealing feature 210 is formed of a band of elastic material and is in the shape of an annulus with an internal diameter which, without any applied force, is smaller than the external diameter of the container and the sleeve 10. The sealing feature may be made of synthetic or natural rubber or any other elastic material.

Incidentally, the container 90 has an outer diameter which is substantially the same as the outer diameter of the sleeve 10. Thus, when the sleeve 10 and container are lined up, the sealing feature 210 can be placed over the join between the sleeve 10 and the container thereby to fix the container to the sleeve.

The container of the Figure 7 embodiment may be provided with the sealing feature separately or already attached to the top of the container.

In a further variation, the sealing feature 210 could be provided as an adhesive tape or the like. In that case the tape would not be in the form of an annulus but would be in the form of a longitudinal strip which is long enough to pass around the circumference of the sleeve 10 and the container 90. Alternatively it may not be necessary to have adhesive tape around the entire circumference and enough force to resist the hydrostatic pressures may be achievable by only having the fixing component 210 in the form of adhesive tape in discreet locations around the circumference of the sleeve 10 and container 90. This is particularly the case if a seal 330 is used or the sealing feature comprises other parts, such as in the second and third embodiments. A further alternative would be to have a clamp as described in relation to the second embodiment which extends between the top longitudinal edge of the sleeve 10 and the bottom of the container 90. This clamp could be reused along with the sleeve 10 and a new container 90 during preparation of a next mould.

Seventh Embodiment

A seventh embodiment is illustrated in Figure 8. The Figure 8 embodiment is the same as the fifth embodiment except as described below.

In the fifth embodiment, instead of using a radially compressive force to fix the container to the sleeve 10, the sealing feature comprises a mechanical interlock. One way in which this can be achieved is by a thread 310 on the container 90 which allows the container 90 to be screwed onto a thread 320 formed on the bottom edge of the sleeve 10. A washer 330 or O-ring may be provided between the top 100 and the end of the sleeve 10. The washer 330 is annular. The washer 330 can ensure the watertight integrity of the join between the threads 310, 320. An alternative to having threads 310, 320 is the provision of a bayonet type fitting. In a bayonet type fitting at least one projection is provided on the outer surface of the sleeve 10. A slot is provided in the side wall of the container which extends beyond the top plate 100. The projection slides into the slot during assembly. Relative rotation of the container 90 relative to the sleeve 10 is then effective to move the projection into a position in the slot which does not allow the sleeve 10 to move substantially away from the container 90. One way of achieving this is to provide the slot with an L-shape so that the projection travels down from the top of the L to the base of the L and then along the base. One, two, or more projections and corresponding slots may be provided. It may be advantageous to provide a biasing force in this embodiment. Such a biasing force would be for pushing the sleeve 10 away from the container 90 to hold it in place and prevent rotation. Such a biasing force could be provided, for example, by a washer 330. As will be appreciated, features from one embodiment can be used in other embodiments.

Eighth Embodiment An eighth embodiment is illustrated in Figure 9. The eighth embodiment is the same as the third embodiment except as described below.

In the eighth embodiment, a container 90 (such as the container of the fourth embodiment) is used. A projection from the bottom 110 forms the indentation portion 72 which is part of the container. The water absorbent material surrounds a base of the indentation portion 72. That is, the water absorbent material 70 is in the shape of an annulus and thereby surrounds the indentation portion 72. The indentation portion 72 extends from the bottom 110 of the container 90 through the water absorbent material 70 to form the indentation portion 72. The indentation portion 72 could be separate from the rest of the container 90. It could, for example, be glued onto the container. The indentation portion could be made of polymer. The top 100, if present, may have a central through hole for the indentation portion to protrude through. Alternatively the top 100 may be shaped (or shapeable). The water absorbent material 70 can be reusable or disposable after one use. The mouth of the container is extra wide in this embodiment. That is the inner diameter of the container is greater at the top than lower down. Actually the inner diameter at the top is greater than the outer diameter lower down. The edge curls outwards to make insertion easier. This feature can be used in other embodiments too. The side walls of the container flair out at the upper end to widen the mouth of the container.

Ninth Embodiment

A ninth embodiment is illustrated in Figure 10. The ninth embodiment is the same as the eighth embodiment except as described below.

Although it is clear from the foregoing description that it is possible for the indentation portion 72, bottom 1 10, sides 120 and sealing feature 125 to be made from an integral component, this is illustrated for clarity in Figure 10. In Figure 10, those components are made from a single piece of material, for example a plastics material or a rubber like material or rubber. This component is similar to the Figure 6 embodiment, particularly in relation to the sealing feature and side walls. The single piece of material is re-usable. The water absorbent material 70 is a separate insert. It is annular. In other words it has a through hole. The through hole is in the shape of a truncated cone. The water permeable top 100 can be fixed to the water absorbent material 70, or may be separate. The top 100 can even be of the same material as the water absorbent material 70. The water absorbent material 70 may or may not be reusable. The water absorbent material 70 may be unitary, for example made of wood or paper pulp etc..

A similar effect can be achieved by placing an insert such as the one illustrated in Figure 4 into a container such as a container of any one of Figures 5-8.

Preferably the fit of the water absorbent material 70 is such such that, in use, little, if any, water leaks between the indentation portion 72 and the inner surface of the water absorbent material 70. That is a seal is created between the water absorbent material 70 and the indentation portion 72. Similarly, it is preferred that no water leaks between the side walls 120 of the container and the water absorbent material 70.

One way of reducing the chance of liquid leaking between the indentation portion 70 and the water absorbent material is to ensure that the slope of the inner surface of the water absorbent material is shallower than the slope of the indentation portion 72. In this way it can be ensured that the water absorbent material contacts the indentation portion 72 at the top of the water absorbent material 70 rather than at the bottom, close to the bottom 110 of the container. Of course the slope of the inner surface of the through hole of the water absorbent material 70 and the indentation portion 72 could be the same.

Tenth Embodiment

A tenth embodiment is illustrated in Figure 11. The tenth embodiment is the same as the ninth embodiment except as described below.

The tenth embodiment allows a water absorbent material in powder form to be used. This can be done whilst still avoiding the mess and health hazard associated with use of powder. As can be seen from Figure 11, an object comprising the water absorbent material 70 is provided. The water absorbent material 70 is contained in a dish 600. In plan the dish is circular. The dish 600 defines the through hole through which the indentation portion 72 sits. The surface of the dish 600 which defines the through hole is sized and shaped in the same way as in the tenth embodiment. The material of the dish may be a plastics or metal material. The top of the dish 600 is sealed with a water permeable material top 100. Inside the dish 600 is water absorbent material, preferably in powder form. One form of water absorbent material is vermiculite. The water permeable material top 100 can be glued onto or pressed into the dish 600. This latter embodiment is easier to re-use - see below. hi a vertical cross-section taken through a central axis of the dish 600 (as is the case in Figure 11), the dish has a cross-sectional shape of two trapezium. Of the two parallel lines of the trapezium, the upper most line is longest. One of the non parallel lines of the trapezium is generally or nearly perpendicular to the two parallel lines. This geometry results in the surface forming the through hole having the shape of a truncated cone. However, it will be appreciated that other shapes may be suitable. For example, the indentation portion 72 may be in the shape of a pyramid or a hemisphere or a progressional shape curved towards the tree. The indentation portion 72 may have side surfaces which are at any acute angle to the bottom 110 of the container. The base of the indentation portion 72 can have any shape in plan including, but not limited to, a triangle, a square a circle a hexagon etc. Non symmetric shapes in plan as well as vertical cross-section are also possible. Indeed the shape of the indentation portion 72 may not be regular in vertical cross-section. The base portion of the indentation portion 72 could be a hemisphere, for example, with a cone shape on top.

In the embodiment of Figure 11 , the container 90 comprising the side walls, bottom and indentation portion could be re-used many times. Each time the container is used, a new object comprising the dish 600, water absorbent material 70 and top 100 is inserted into the container. After use the combination of the dish 600, water absorbent material 70 and top 100 could be disposed of. Alternatively they could be dried and reused.

Eleventh Embodiment

An eleventh embodiment is illustrated in Figure 12. The eleventh embodiment is the same as the tenth embodiment except as described below.

In Figure 12 the sleeve has been omitted and only the object comprising the water absorbent material 70 and the container 90 is illustrated.

The bottom 110 of the container 90 has at least one through hole 700. For example there maybe four through holes 700 in the bottom 110 of the container 90. These four through holes could be positioned evenly around the circumference of the container 90. The through hole 700 has two purposes. The first purpose is to enable a tool or an operator's finger to press through the through hole 700 from underneath the container 90 onto the dish 600 thereby to help remove the dish 600 from the container 90. The second purpose for the through hole 700 is to allow gas to be drawn out of the object comprising the water absorbent material 70 and thereby out of the sleeve 10. Gas is removed from the investment casting slurry by placing the whole assembly comprising the sleeve 10 and container 90 in a vacuum chamber. By having through holes 700 in the bottom 110 of the container 90 gas and/or liquid can be drawn out of the inside of the assembly and avoids gas in the container 90 being sucked out through the slurry in the sleeve 10. The very purpose of vacuuming is to remove gas from the slurry. A plurality of further through holes 710 can be provided in the bottom of the dish

600. The through holes 710 in the bottom of the dish 600 can be smaller than the through holes 700 in the bottom 110 of the container 90. This is because they do not need to be sized to allow a tool or an operator's finger to pass through them; the through holes 710 in the bottom of the dish 600 are simply to ensure that the inside of the dish 600 is in fluid contact with the outside of the container 90 so that the vacuum can draw gas and/or liquid out of the sleeve 10 and container 90 rather than through the slurry in the sleeve 10.

In order to ensure that all of the through holes 710 in the bottom of the dish 600 are in fluid contact with at least one through hole 700 in the bottom 110 of the container 90, a groove 720 may be present on the inner surface of the bottom 110 of the container 90. In this way, the dish 600 is supported by the bottom 110 of the container 90 and there is also fluid contact between the through hole 700 in the bottom 110 of the container 90 and the through hole 710 in the bottom of the dish 600.

In order to ensure that the water absorbent material 70 in the dish 600 does not fall out through through holes 710, a porous barrier 730 (for example paper) can be placed in the bottom of the dish 600. The barrier 730 is also in the shape of an annulus, to match the profile of the bottom of the dish 600.

In order to ensure that it is easy to place the sleeve 10 and container 90 in a vacuum chamber and to ensure that the inside of the sleeve 10 and container 90 is open to the vacuum, feet 740 can be present on the bottom of the container 90. When the container 90 is placed in the vacuum chamber, the container can stand on the feet 740 and this allows a gap between the bottom 110 of the container 90 and the surface on which the container 90 has been placed to be present. This allows gas and/or liquid to be extracted through the through holes 700 in the bottom 110 of the container 90. Through holes and/or feet 740 and/or grooves 720 and/or a porous barrier 730, as necessary, can be provided in any of the other embodiments if gas would otherwise not pass out of the slurry through the absorbent material 70 when the assembly is placed in a vacuum. In particular the embodiments of Figures 2 and 5-11 may benefit from these features. An alternative is to provide through holes 700, 710 in a sidewall of the container 90 and dish 600 so that no feet 740 are needed.

Claims

1. An object for use in removing water from an investment casting slurry in a sleeve, wherein at least a portion of an outer surface of said object is water permeable thereby to provide fluid communication from outside of said object with a water absorbent material of said object, said object comprising a sealing feature for sealing the object onto an end of a sleeve.

2. The object of claim 1, further comprising a container, said container containing said water absorbent material.

3. A container for use in removing water from an investment slurry and containing a water absorbent material, said container comprising a sealing feature for removably sealing the container onto an end of a sleeve and an indentation portion for projecting into the bottom of the sleeve when the sleeve is sealed to the container.

4. The object of claim 2 or container of claim 3, wherein said sealing feature comprises a portion which projects from an end of a side wall of said container.

5. The object of claim 2 or container of claim 3, wherein said sealing feature extends from an edge of said container.

6. The object of any one of claims 2, 4 or 5 or container of any one of claims

3-5 wherein container walls other than said water permeable portion are integral, preferably injection moulded.

7. The object of any one of claims 2, 4, 5 or 6, or container of any one of claims 3-6 wherein said sealing feature is integral to side walls of said container.

8. The object of any one of claims 2, 4, 5, 6 or 7, or container of any one of claims 3-7 wherein said at least a portion of a wall of said container forms said water permeable portion.

9. The container of any one of claims 3-8, wherein said water absorbent material is in the shape of an annulus and surrounds a base portion of said indentation portion.

10. The object of any one of claims 1 , 2 and 4-8, further comprising an indentation portion which projects beyond said water permeable outer surface away from said water absorbent material.

11. The object of claim 10, wherein said indentation portion is part of said water absorbent material.

12. The obj ect of any one of claims 9-11 or the container of any one of claims 3-8, wherein said indentation portion comprises a recess for the insertion therein of a base of a wax tree.

13. The object of any one of claims 1 or 10-12, wherein said sealing feature comprises side walls of said object sized and shaped for insertion into said sleeve under radial compression.

14. The object of any one of claims 1 or 10-13, wherein said sealing feature seals to inner side walls of said sleeve by a biasing force generated by the elastic compressibility of said object.

15. The object or container of any one of claims 1-12, wherein said sealing feature makes use of a radially compressive force.

16. The object or container of claim 17, wherein said object has side walls or said container has side walls, said side walls being stiff enough to resist compression by said sealing feature.

17. The object or container of any one of claims 1-12, wherein said sealing feature comprises a screw fixing.

18. The object or container of according to any one of the preceding claims, wherein said sealing feature is constructed and arranged to be watertight to a hydrostatic pressure of at least 6cm of water.

19. The object or container of any one of the preceding claims, wherein said sealing feature comprises an elastic material.

20. The object or container of any one of the preceding claims, further comprising a washer for contact between said object and a sleeve when said container is sealed to a sleeve to thereby improve the seal.

21. The object or container of any one of the preceding claims, wherein said water absorbent material is comprised of a unitary component.

22. The object or container of any one of the preceding claims, wherein said sealing feature extends around said water permeable portion.

23. The object or container of any one of the preceding claims, wherein said sealing feature is removable from said object.

24. The object or container of any one of the preceding claims, wherein said sealing feature is constructed and arranged such that when it seals the object to a sleeve, the water absorbent material is in fluid communication with an inside of the sleeve.

25. An object for use in removing water from an investment casting slurry in a sleeve, wherein at least a portion of an outer surface of said object is water permeable thereby to provide fluid communication from outside of said object with a water absorbent material of said object, said object comprising a through hole so that the object can be placed on a projection such that said water absorbent material surrounds the projection when the projection extends through the object.

26. The object of claim 25, wherein a surface of said object defining said through hole is substantially in the shape of a truncated cone.

27. The object of claim 25 or 26, wherein said through hole is co-axial with a central axis of said object.

28. The object of any one of claims 25-27, wherein said object, in plan, is substantially circular.

29. The object of any one of claims 25-28, wherein said water absorbent material is contained in a dish, said dish defining said through hole.

30. The object of claim 29, wherein an opening of said dish is closed by a water permeable material which forms said water permeable portion.

31. The object of any one of claims 25-30, wherein said water absorbent material is a powder.

32. The object or container of any one of the preceding claims, wherein said water absorbent material is dryable such that said object can be reused.

33. The object or container of any one of the preceding claims, wherein said water absorbent material is at least one of: plaster, silica, wood pulp, paper pulp, vermiculite.

34. The object or container of any one of the preceding claims, wherein said water permeable portion has a permeability of at least 0.25 cc/cm²/hour at a water head of 0.5 cm.

35. The object or container of any one of the preceding claims, wherein said water permeable portion is comprised of a material selected from the group: wood pulp, formed cardboard, Vermiculite formed shape, a perforated plate, a woven material, a non- woven fabric, a castable water absorbent material, a plastics or polymer material.

36. The object of any one of claims 1, 10-12 or 25-28, wherein said object is comprised of a unitary component.

37. The combination of a container according to claim 3 or any claim dependent on claim 3 and the object of claim 25 or any claim dependent on claim 25.

38. The object or container or combination of any one of the preceding claims, wherein said object further comprises a removable or breakable seal to seal said water absorbent material against water penetration, for example said object is in a water impermeable package.

39. An investment casting sleeve and an object, or container or combination according to any one of the preceding claims.

40. The investment casting sleeve and object, or container or combination according to claim 39, wherein said sleeve has features used by said sealing feature for fixing said object to said sleeve with a mechanical interlock.

41. A method of preparing an investment casting mould, said method comprising: providing a sleeve; blocking an open end of said sleeve by fixing a water permeable material over it; and providing a water absorbent material on a side of said water permeable material opposite to said sleeve, wherein said water absorbent material is held together and constructed and arranged to ensure fluid communication between said water absorbent material and the inside of said sleeve.

42. The method of claim 41 , wherein said water permeable material is a surface of said water absorbent material.

43. The method of claim 41 or 42, wherein said water absorbent material is comprised of a unitary component.

44. The method of claim 41 or 42, wherein said water absorbent material is held together by a container, which container has at least a portion of a wall which is water permeable.

45. The method of claim 44, wherein said water permeable portion of said container is the water permeable material which is fixed over an open end of the sleeve.

46. The method of claim 41, further comprising placing an object of claim 25 or any claim dependent on claim 25 into a container of claim 3 or any claim dependent on claim 3 and sealing said container onto said sleeve using said sealing feature.

47. The method of claim 41 , wherein said water absorbent material is the water absorbent material of an object, or container or combination of any one of claims 1 to 38 or the object, or container or combination and sleeve are an object, or container or combination and sleeve according to claim 39 or 40.

48. A container substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

49. A method substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.