METHOD, APPARATUS AND FEEDER SLEEVES FOR THE PRODUCTION OF CASTING MOULDS

Abstract: A method, apparatus and feeder sleeves are described for producing casting moulds having feeder sleeves incorporated therein in instances when the mould pattern plate or the cope mould are not accessible. Two part feeder patterns having a lower part (la) and an upper part (l) and feeder sleeves (6) whose lateral surface tapers from the bottom and to the top end of the sleeve are used. For moulds having a side feeder the lower part of the pattern (la) produces a depressed seating sur­ face (2) for the feeder sleeve (6) in the drag mould and the upper part (l) which has substantially the same taper as the taper of the feeder sleeve (6) and dimensions greater than the corresponding dimensions of the lateral surface (9) of the feeder sleeve (6) produces a cavity in the cope mould. The cope and drag moulds are closed in such a manner that the central vertical axis of the cavity in the cope mould is in line with the central vertical axis of the feeder sleeve (6), and there is a gap (7) between the wall (8) of the cavity and the outer lateral surface (9) of the sleeve. When metal is cast into the mould the sleeve (6) floats up and sits firmly and is sealed against the wall (8) of the cavity. For moulds having a top feeder the lower part of the pattern produces a depressed seating surface for a core whose upper surface has means for locating and centering the feeder sleeve.

Description: This invention relates to a method, apparatus and feeder sleeves for the production of casting moulds. The use of feeder sleeves of exothermic and/or heat-insulating material in sand moulds for metal casting is well known, and several methods for incorporating feeder sleeves, which may be open at both ends or closed at one end, are practised. In one method a feeder sleeve is located prior to moulding on a support fixed firmly to a casting pattern, or when the mould is to have a side feeder on a support fixed firmly to an extension of the casting pattern. After moulding the support is removed so as to produce a feeder cavity surrounded by the sleeve, which is held firmly in place. Either open or closed feeder sleeves may be incorporated in moulds using this method. In another method cylindrical feeder sleeves or tapered feeder sleeves having a smaller diameter at their bottom end are inserted from above into a cavity formed by locating a loose feeder pattern on the casting pattern, or in the case of a side feeder on an extension of the cast­ ing pattern, moulding and then upwardly removing the loosefeeder pattern. Both open and closed riser sleeves may be used in this method. In another method a tapered riser sleeve is inserted into a cavity formed by a tapered pattern dummy having longitudinal recesses, the sleeve being held firmly in place by ribs of moulding sand produced by the recesses. In order to incorporate feeder sleeves into casting moulds having a horizontal parting line, and consisting of a cope mould and a drag mould, it is necessary that either the casting pattern or the cope mould is accessible. There are however automatic moulding plants in which, for reasons of safety, the casting pattern is not accessible whilst the plants are operating, and where for reasons of design or safety the cope mould is also not accessible for the subse­ quent incorporation of feeder sleeves. Because of this limitation, only so-­ called natural feeding techniques can be prac­ tised for the production of castings in such moulding plants. When using such techniques, feeder patterns are fixed to the pattern plate, and after moulding and removal from the mould they produce feeder cavities, surrounded by mould­ ing sand and connected to the casting, which has to be fed. Natural feeders in comparison with in­ sulated and/or exothermically heated feeders of the same size, produced by incorporating feeder sleeves into the casting mould using the methods described above, have the disadvantage that they cool more quickly. In order to achieve the same solidification time as insulated or exothermi­ cally heated feeders, natural feeders must have a larger volume. For the commercial production of castings however this is a technical and economic disadvantage. The object of the present invention is to create a method by means of which foundry moulds incorporating feeder sleeves can be pro­ duced even when the pattern plate and cope mould are not accessible. According to the invention there is provided a method for the production of a metal casting mould comprising a cope mould and a drag mould and having, incorporated therein, a feeder sleeve whose outer lateral surface tapers from the bottom end of the feeder sleeve to the top end the method comprising (l) providing a two part feeder pattern consist­ ing of a lower part and an upper part, the lower part having means for locating and centering the feeder sleeve in the mould, and the upper part having a lateral surface having substantially the same taper as the taper of the feeder sleeve and dimensions greater than the corresponding dimen­ sions of the outer lateral surface of the feeder sleeve (2) fixing the lower part of the feeder pattern to a drag mould pattern plate and the upper part of the feeder pattern to a cope mould pattern plate (3) compacting particulate moulding material around the two parts of the feeder pattern and removing the two parts of the feeder pattern so as to produce a drag mould and a cope mould (4) locating the feeder sleeve in the mould and (5) closing the cope and drag moulds in such a manner that the central vertical axis of a cavity produced in the cope mould by the upper part of the pattern is in line with the central vertical axis of the feeder sleeve, and there is a gap between the wall of the cavity in the cope mould and the outer lateral surface of the feeder sleeve. In one embodiment of the invention the method comprises (l) providing a two part feeder pattern consist­ ing of a lower part and an upper part, the lower part having means for producing a depressed seat­ ing surface for the feeder sleeve in the drag mould, and the upper part having a lateral surface having the substantially same taper as the taper of the feeder sleeve and dimensions greater than the corresponding dimensions of the outer lateral surface of the feeder sleeve (2) fixing the lower part of the feeder pattern to a drag mould pattern plate (3) compacting particulate moulding material around the lower part of the feeder pattern (4) removing the lower part of the feeder pattern so as to produce in the drag mould the depressed seating surface for locating and centering the feeder sleeve (5) seating the feeder sleeve on the depressed surface (6) fixing the upper part of the feeder pattern to a cope mould pattern plate (7) compacting particulate moulding material around the upper part of the feeder pattern (8) removing the upper part of the feeder pattern so as to produce in the cope mould a cavity and (9) closing the cope and drag moulds in such a manner that the central vertical axis of the cavity in the cope mould is in line with the central vertical axis of the feeder sleeve, and there is a gap between the wall of the cavity in the cope mould and the outer lateral surface of the feeder sleeve. As the cavity produced in the cope mould by the upper part of the two part feeder pattern is larger in all its dimensions than the feeder sleeve located in the drag mould the feeder sleeve does not come into contact with the walls of the cope mould cavity when the cope mould and the drag mould are joined together. As a result the sleeve is not displaced when the cope and drag moulds are joined together and moulding material cannot be rubbed off the cavity wall and fall into the mould or the mould runner. The air gap which is deliberately pro­ duced around the external surface of the feeder sleeve must be sealed when metal is cast into the mould otherwise molten metal would flow around the feeder sleeve and gases produced during cast­ ing, for example by combustion of the feeder sleeve, would not be able to escape to the atmos­ phere. The flow of metal around the feeder sleeve is avoided because during casting the feeder sleeve floats up with the rising cast metal and its tapered outer surface sits firmly and is sealed against the wall of the similarly tapered cavity in the cope mould. In order to allow for slight variations from the nominal dimensions of a particular feeder sleeve when producing large quantities of that sleeve the upper part of the feeder pattern may be such that its lateral surface is in all its dimensions larger than the corresponding dimen­ sions of the outer lateral surface of the feeder sleeve by more than three times the standard deviation from the mean of those dimensions. In order to produce the required depressed seating surface for the feeder sleeve in the drag mould the lower part of the two part feeder pattern may contain a plate having a thickness corresponding to the desired depth of the depression, and to allow for production varia­ tions in feeder sleeves of a particular nominal size the lateral dimensions of the plate prefer­ ably correspond to the dimensions of the outer lateral surface of the feeder sleeve at the bottom end of the feeder sleeve plus three times the standard deviation from the mean of those dimensions. In addition to the plate for producing the depressed seating surface for the feeder sleeve the lower part of the two part feeder pattern preferably also contains in one piece parts for producing a feeder base, a feeder neck and optionally a feeder ingate. Partial penetration of molten metal be­ hind the feeder sleeve due to dimensional varia­ tions resulting from the production method used for making the sleeves can also be prevented by providing the sleeve with a rim at its bottom end and using a two part feeder pattern whose upper part has a similar rim at its bottom end. By making the thickness of the rim at the base of the feeder sleeve smaller than the total thickness of the plate in the lower part of the feeder pattern and the rim at the base of the upper part of the feeder pattern contact between the rim on the feeder sleeve and the cope mould when the cope mould and drag mould are joined together is prevented, and the feeder sleeve can float upwards with the rising metal on casting and provide an additional seal on the upper face of the rim. In another embodiment the feeder sleeve may have at its bottom end one or more lateral openings. These openings are located above the feeder neck and the feeder ingate after the feeder sleeve has been set in the drag mould so that the cast metal which flows from the ingate into the feeder base and through the feeder neck into the casting does not come into contact with the feeder sleeve until the end of mould filling when the upwards flotation of the feeder sleeve takes place. Thereby it is ensured that the cast metal does not displace prematurely and flow be­ hind the feeder sleeve standing loosely in the casting mould thus preventing subsequent accurate upward flotation. At the same time with this form of feeder sleeve the cast metal flowing into the mould past the lower edge of the feeder sleeve does not produce any turbulence and washoff which would influence the success of casting. The foregoing description of the in­ vention concerns a method, as well as feeder patterns and feeder sleeves for carrying out the method, in order to feed a casting from side feeders. Dependent on the position of a casting in the mould it is possible to define for all castings top and side surfaces. Side feeders are cavities located next to and connected by means of a feeder base and a feeder neck to the side surfaces of the casting cavity in the mould, as a rule close to the mould parting line between the cope and drag mould. In some cases it is however necessary that feeders are located directly on the top surface of a casting, and this practice is known as top feeding. The method of the invention can be adapted to top feeding practice by locating a core in the drag mould and locating the feeder sleeve on the core. According therefore to another embodi­ ment of the invention the method comprises (l) providing a two part feeder pattern consist­ ing of a lower part and an upper part, the lower part having means for producing in the drag mould a depressed seating surface for a core and the upper part having a lateral surface having sub­ stantially the same taper as the taper of the feeder sleeve and dimensions greater than the corres­ ponding dimensions of the outer lateral surface of the feeder sleeve (2) fixing the lower part of the feeder pattern to a drag mould pattern plate (3) compacting particulate moulding material around the lower part of the feeder pattern (4) removing the lower part of the feeder pattern so as to produce in the drag mould the depressed seating surface for locating and centering the core. (5) seating a core having an upper and lower sur­ face and one or more apertures extending from the upper to the lower surface, the upper surface hav­ ing means for locating and centering the feeder sleeve, on the depressed surface in the drag mould (6) seating the feeder sleeve on the upper sur­ face of the core about the locating and centering means (7) fixing the upper part of the feeder pattern to a cope mould pattern plate (8) compacting particulate moulding material around the upper part of the feeder pattern (9) removing the upper part of the feeder pat­ tern so as to produce in the cope mould a cavity and (l0) closing the cope and drag moulds in such a manner that the central vertical axis of the cavity in the cope mould is in line with the central vertical axis of the feeder sleeve, and there is a gap between the wall of the cavity in the cope mould and the outer lateral surface of the feeder sleeve. When molten metal is cast into the mould the feeder sleeve floats up and seals it­ self against the wall of the cavity in the cope mould while the core remains firmly in position. The bottom part of the feeder pattern no longer contains the elements necessary for side feeding practice such as the feeder sleeve seating surface, the feeder base and the feeder neck but only one or more centering parts which, in the moulded up condition produce depressions in the drag mould for locating the core. The core which may have one or more centering rims on its lower side is set into the depressions in the drag mould and bridges over the walls of a casting cavity which is lying in the drag mould. So that the solidifying casting can be fed from above through the core the core contains one or more breaker core­like apertures located above the top surface of the casting. Furthermore, the core contains in its upper face a feeder sleeve seating surface and centering means such as one or more rims for the feeder sleeve which is to be located on the surface. The feeder sleeve may be fixed on to the core by means of internal or external center­ ing. Preferably the lateral dimensions of the centering rim which locates the feeder sleeve correspond to the average lateral dimensions of the feeder sleeve at its bottom end plus a maxi­ mum of three times the standard deviation for external centering or minus a maximum of three times the standard deviation for internal center­ ing. The upper part of the feeder pattern has at its base a surrounding rim whose dimensions conform to the external dimensions of the core plus a maximum of three times the standard devia­ tion from the mean of the respective core dimen­ sions so that the portion of the core which projects into the cope mould is tightly enclosed at its outer perimeter when the cope and drag moulds are closed together. As a result the cover core is not able to float upwards with the rising cast metal during casting. The lateral surface of the upper part of the feeder pattern is in all of its dimensions larger than the corresponding dimensions of the outer lateral surface of the feeder sleeve by more than three times the standard deviation from the mean dimensions. In addition to the methods described for producing a casting mould containing a feeder sleeve the invention also includes two part feeder patterns, cores and feeder sleeves as described herein. The invention is illustrated with reference to the accompanying drawings in which:- Figures l, 2 and 3 show a front view, side view and a top plan view respectively of a two part feeder pattern according to the invention for producing a side feeder cavity in a casting mould Figure 4 shows schematically a section through a closed casting mould produced using the feeder pattern of Figures l 3 and through a feeder sleeve standing in the drag mould, before casting Figure 5 shows in a manner analagous to Figure 4 the position of the feeder sleeve after casting Figure 6 shows schematically a section through a closed casting mould and through a feeder sleeve standing in the drag mould, before casting, the mould having been produced using a two part feeder pattern whose upper part has a surrounding rim, and the feeder sleeve also hav­ ing a surrounding rim Figure 7 shows in a manner analagous to Figure 6 the position of the feeder sleeve after casting Figure 8 shows a view from below of a feeder sleeve with lateral openings at its bottom end Figure 9 is a vertical section along the line A - B of the feeder sleeve shown in Figure 8 Figure l0 shows schematically a section through a closed casting mould and the feeder sleeve with openings shown in Figures 8 and 9 standing in the drag mould, before casting Figure ll shows a drawing in section of a feeder sleeve with surrounding rim and open­ ings according to the invention Figure l2 and l3 show a front view and a top plan view respectively of a two part feeder pattern according to the invention for producing a top feeder in a casting mould Figure l4 shows schematically a vertical section through a closed casting mould containing a core located in the mould and having means for internal centering of a feeder sleeve, before casting Figure l5 is analagous to Figure l4 except that the core has means for external center­ ing of the feeder sleeve and Figure l6 shows schematically a vertical section through the mould shown in Figure l4, after casting. The feeder sleeve has floated up­ wards whilst the core has been held firmly in its position. Referring to Figures l - 5, the parting line of a two part feeder pattern is drawn in between the feeder pattern upper part l and the feeder pattern lower part la. In use the feeder pattern lower part la is fixed to a drag pattern plate; the feeder pattern upper part l is fixed centrally and symmetrically with the axis of the lower part la on to a cope pattern plate. The feeder pattern upper part l has an outer surface which tapers from bottom to top at a desired angle. The feeder pattern lower part la con­ tains in one piece a seating surface 2 for a feeder sleeve 6, a feeder base 3, a feeder neck 4 and a feeder ingate 5. The seating surface 2 for the feeder sleeve 6 is produced by means of a plate 2a of desired thickness which is part of the lower part of the feeder pattern la. The plate 2a overlaps outwardly with and projects into that section of the feeder pattern forming the feeder neck 4, the feeder base 3 and the feeder ingate 5. The outer lateral dimensions of the seating surface 2 of the feeder pattern corres­ ponds to the dimensions of the outer lateral surface at the bottom end of the feeder sleeve plus a maximum of three times the standard devia­ tion from the mean of those dimensions. The feeder neck 4 after casting joins the feeder base 3 with the casting. The feeder ingate 5 is connected on the pattern plate with the running system (not shown). In Figure 4 the feeder sleeve 6 stands in the drag of a closed casting mould on the feeder sleeve seating surface 2 and the out­ side surface of the feeder sleeve is surrounded on all sides by an air gap 7. The air gap is deliberately created by the fact that the upper part l of the two part feeder pattern l/la is larger in all of its dimensions than the feeder sleeve 6 located on the seating surface 2 in the drag mould. In particular, the lateral surface of the upper part l of the feeder pattern is larger than the corresponding dimensions of the outer lateral surface of the feeder sleeve by more than three times the standard deviation from the mean of those dimensions. In this way contact with wall 8 of the cavity in the cope mould by the feeder sleeve 6 when the cope mould and drag mould are closed together is avoided. Furthermore the feeder sleeve 6 is not displaced, and no moulding sand can be dislodged and fall into the feeder base 3, from which during pouring it could be washed into the casting. As shown in Figure 5, after the mould has been filled with molten metal the feeder sleeve has floated up­ wards and its outside surface 9 has been firmly seated and sealed against the similarly tapered wall 8 of the surrounding cavity in the cope mould. Referring to Figures 6 and 7 a cope mould is produced using a feeder pattern whose upper part l possesses at its bottom end a sur­ rounding rim which forms a ring shaped cavity ll. As shown in Figure 6 feeder sleeve 6a has at its bottom end where it sits on the feeder sleeve seating surface 2 a surrounding rim l0, and the outside surface 9 of the feeder sleeve 6a is surrounded on all sides by an air gap 7. The thickness of the surrounding rim l0 is smaller than the total thickness of the plate 2a of the lower part la of the feeder pattern and the surrounding rim of the upper part l of the feeder pattern so that the surrounding rim l0 is not touched by the cope mould when the two mould parts are closed together. Figure 7 shows the feeder sleeve 6a in position after floating as it would be after the mould has been filled. During the course of production of feeder sleeves some dimensional variations due to factors of the production method may occur, and as a result, for example, the outside surface of the feeder sleeve may not be exactly smooth and may not have at all points on its surface the desired taper. If such a feeder sleeve is used it can occur after the sleeve has floated that the outer surface 9 of the feeder sleeve only seats firmly against the tapered walls 8 of the surrounding cavity in the cope mould over part of its area, and as a result only achieves a partial seal. For such cases the embodiments of the invention shown in Figures 6 and 7 are particularly suitable because an additional and effective sealing surface is created on the upper edge l2 of the surrounding rim l0 of the feeder sleeve 6a. Referring to Figures 8 - l0 a feeder sleeve 6b has two lateral openings l3 located essentially diametrically opposite one from the other at its bottom end. The feeder sleeve 6b is located on the seating surface 2 in such a manner that the openings l3 are located above the feeder neck 4 and above the feeder in-gate 5. As a result during casting the full section of the feeder neck 4 and the feeder in-gate 5 is available so that the cast metal flowing into the feeder base 3 and from there into the casting cavity does not come into contact with the lower edge of the feeder sleeve 6b until the feeder sleeve 6b floats upwards with the rising cast metal at the end of filling the mould. In this manner any washing effect or tubulence by the cast metal on the lower edge of the feeder sleeve 6b is minimised. This becomes clear by a compar­ ison of Figures 6 and l0, and it can be seen from Figure l0 that the feeder neck 4 and the feeder ingate 5 are no longer constricted and that the ability of the feeder sleeve to float upwards and seal is not affected. Referring to Figure ll a feeder sleeve 6c has both a surrounding rim l0 and lateral openings l3 at its bottom end. As in the case of the feeder sleeve 6a shown in Figures 6 and 7 the surrounding rim l0 has a thickness which is smaller than the total thickness of the plate of the bottom part of the feeder pattern and the surrounding rim of the top part of the feeder pattern with which the sleeve is to be used. Referring to Figures l2 - l6 the part­ ing line of a two part feeder pattern is indicated between the feeder pattern's upper part l′ and the feeder pattern's lower part la′. The feeder pattern's lower part la′ consists of one or more centering means l3 and is fixed to a drag pattern plate, and after moulding a depression is formed in the drag mould and serves as a means of cen­ tering for a core l4 which is to be located therein. The feeder pattern's upper part l′ possesses at its bottom end a surrounding rim ll′ which conforms in its dimensions to the external dimensions of the core l4 plus a maximum of three times the standard deviation from the mean of the respective core dimensions. Above the rim ll′ the feeder pattern's upper part has an external surface 9′ tapering from bottom to top at a desired angle. In Figure l4 the core l4 spans over casting wall l5 which is lying in the drag mould. The core l4 is fixed with its centering rim l4a in the drag mould depression which was formed by the centering means l3 of the feeder pattern's lower part la. The core l4 has above the cast­ ing wall l5 a breaker core-like aperture l4b through which feed metal flows into the casting due to the solidification shrinkage of the casting. Further the core l4 also has on its upper face a surrounding rim l4c as a means of centering for the feeder sleeve 6. The feeder sleeve 6 stand­ ing on the core l4 in the enclosed casting mould is surrounded around its external surface by an air gap 7. The air gap is produced by the fact that the lateral surface of the upper part l′ of the two part feeder pattern l′ + la′ is in all of its dimensions larger than the outer lateral surface of the feeder sleeve 6 located in the drag mould on the core l4. In this manner contact with the walls 8 of the cavity in the cope mould by the feeder sleeve 6 when the mould parts are closed together is avoided. Furthermore the feeder sleeve 6 is not displaced and no moulding sand is rubbed off to fall into the drag mould. In Figure l4 the feeder sleeve 6 is centered inter­ nally by means of the centering rim l4c of the core l4. Figure l5 shows a modified form where the core l4 possesses at its outside edge a centering rim l4d by means of which the feeder sleeve 6 is centered by its external surface. When using such a core l4 the rim ll′ on the upper part of the feeder pattern l′ must be correspondingly shaped. Figure l6 shows that after the mould of Figure l4 has filled the feeder sleeve has floated upwards and has seated itself firmly so as to form a seal between its external surface 9 and the similarly tapered walls 8 of the surrounding cavity of the cope mould.

Claims: 1. A method for the production of a metal casting mould comprising a cope mould and a drag mould and having, incorporated therein, a feeder sleeve whose outer lateral surface tapers from the bottom end of the feeder sleeve to the top end characterised in that the method comprises (l) providing a two part feeder pattern consist­ ing of a lower part and an upper part, the lower part having means for locating and centering the feeder sleeve in the mould, and the upper part having a lateral surface having substantially the same taper as the taper of the feeder sleeve and dimensions greater than the corresponding dimen­ sions of the outer lateral surface of the feeder sleeve (2) fixing the lower part of the feeder pattern to a drag mould pattern plate and the upper part of the feeder pattern to a cope mould pattern plate (3) compacting particulate moulding material around the two parts of the feeder pattern and removing the two parts of the feeder pattern so as to produce a drag mould and a cope mould (4) locating the feeder sleeve in the mould and (5) closing the cope and drag moulds in such a manner that the central vertical axis of a cavity produced in the cope mould by the upper part of the pattern is in line with the central vertical axis of the feeder sleeve, and there is a gap between the wall of the cavity in the cope mould and the outer lateral surface of the feeder sleeve. 2. A method according to claim l charac­ terised in that the lower part of the feeder pattern has means for producing a depressed seating surface in the drag mould for locating and centering the feeder sleeve. 3. A method according to claim 2 charac­ terised in that the lateral surface of the upper part of the feeder pattern is in all its dimen­ sions larger than the corresponding dimensions of the outer lateral surface of the feeder sleeve by more than three times the standard deviation from the mean of those dimensions. 4. A method according to claim 2 or claim 3 characterised that the lower part of the feeder pattern contains a plate having a thickness corres­ ponding to the desired depth of the depressed seating surface for the feeder sleeve. 5. A method according to claim 4 charac­ terised in that the lateral dimensions of the plate correspond to the dimensions of the outer lateral surface of the feeder sleeve at the bottom end of the feeder sleeve plus three times the standard deviation from the mean of those dimensions. 6. A method according to claim 4 charac­ terised in that the lower part of the feeder pattern also contains parts for producing a feeder base, a feeder neck and optionally a feeder ingate. 7. A method according to any of claims 4 to 6 characterised in that the feeder sleeve and the upper part of the feeder pattern each have a rim at their bottom end and the thickness of the rim at the bottom end of the feeder sleeve is smaller than the total thickness of the plate in the lower part of the feeder pattern and the rim at the bottom end of the upper part of the feeder pattern. 8. A method according to any of claims 2 to 7 characterised in that the feeder sleeve has at its bottom end one or more lateral open­ ings. 9. A method according to claim l charac­ terised in that the lower part of the feeder pattern has means for producing in the drag mould a depressed seating surface for a core, a core having an upper and lower surface and one or more apertures extending from the upper to the lower surface, and the upper surface having means for locating and centering the feeder sleeve,is seated on the depressed surface in the drag mould and the feeder sleeve is seated on the upper surface of the core about the locating and centering means. l0. A method according to claim 9 charac­ terised in that the core has on its lower sur­ face one or more rims which are set into depres­ sions produced by the lower part of the feeder pattern. 11. A method according to claim 9 or claim l0 characterised in that the upper surface of the core has one or more rims for centering the feeder sleeve. 12. A method according to claim ll charac­ terised in that the feeder sleeve is located by an internal centering rim. 13. A method according to claim l2 charac­ terised in that the lateral dimensions of the centering rim correspond to the average lateral dimensions of the feeder sleeve at its bottom end minus a maximum of three times the standard deviation. 14. A method according to claim ll charac­ terised in that the feeder sleeve is located by an external centering rim. 15. A method according to claim l4 charac­ terised in that the lateral dimensions of the centering rim correspond to the average lateral dimensions of the feeder sleeve at its bottom end plus a maximum of three times the standard deviation. 16. A method according to any one of claims 9 to l5 characterised in that the upper part of the feeder pattern has at its base a surrounding rim whose dimensions conform to the external dimensions of the core plus a maximum of three times the standard deviation from the mean of the respective core dimensions. 17. A method according to any of claims 9 to l6 characterised in that the lateral surface of the upper part of the feeder pattern is in all of its dimensions larger than the correspond­ ing dimensions of the outer lateral surface of the feeder sleeve by more than three times the standard deviation from the mean dimensions. 18. A two part feeder pattern characterised in that it comprises a lower part comprising a plate and an upper part having a lateral surface which tapers from the bottom end to the top end of the upper part. 19. A two part feeder pattern according to claim l8 characterised in that the lower part also contains parts for producing a feeder base, a feeder neck and optionally a feeder ingate. 20. A two part feeder pattern according to claim l8 characterised in that the plate com­ prising the lower part has on its base a rim. 2l. A two part feeder pattern according to any of claims l8 to 20 characterised in that the upper part has at its bottom end a surrounding rim. 22. A feeder sleeve characterised in that it has an outer lateral surface which tapers from the bottom end of the sleeve to the top end and at its bottom end a surrounding rim. 23. A feeder sleeve characterised in that it has an outer lateral surface which tapers from the bottom end of the sleeve to the top end and at its bottom end one or more lateral openings. 24. A core characterised in that it has an upper surface and a lower surface, and one or more apertures extending from the upper surface to the lower surface and that both the upper and the lower surfaces have one or more rims.

Inventors: FRIEDRICHS, MICHAEL, SCHOPP, HELMUT
Applicants: FOSECO INTERNATIONAL LIMITED
Application year: 1986
Main classification: B22C9
IPC codes: B22C9