Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/10—Cores; Manufacture or installation of cores
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
  • B22C7/02—Lost patterns
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
  • B22C7/06—Core boxes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/02—Sand moulds or like moulds for shaped castings
  • B22C9/04—Use of lost patterns
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/10—Cores; Manufacture or installation of cores
  • B22C9/103—Multipart cores

Definitions

• the present invention relates in general to the technology for producing cast parts. En particular, it relates to gravity chills and low-pressure processes that use cores to obtain inside cavities in the casting.
• a typical example of such casting process is that used for obtaining engine cylinder heads, where internal cores are necessary for obtaining the water jacket for the engine cooling water, the intake and exhaust ducts, and any other secondary cavity.
• the main difficulty consists in perfectly collimating the inside of the part to be cast, that is the cores, with the outside, that is the chill, so as to obtain the required dimensional accuracy.
• the cores are obtained in corresponding moulds, called core boxes, and then they are normally pre-asse bled in the proximity of the chill.
• the group of pre-assembled cores is collected by automatic devices (grippers and jigs) and laid (assembled) into the chill. At this point it is possible to cast the molten metal which will fill the volume comprised between the sand cores and the chill.
• Sand projections are obtained onto the cores to keep the core group assembled in the desired position. Such prints are laid into the chill and do not constitute part of the object resulting from the casting.
• cores for intake and exhaust ducts of an engine cylinder head whose surfaces form the end shape of the casting
• such cores are inserted into the water jacket core and during the step of moving the cores group to the chill, if the assembly is performed manually they are free due to the effect of the gaps that will be occupied by the metal thickness. Then, they laid by gravity into the lower zone of the corresponding passages provided into the water jacket core. When the duct cores are in contact with the drag (lower base) of the chill, they get the final position.
• the ducts cores are held into suitable positions relative to the water jacket by a special automatic device, but normally only by the side of the flange coupling to the intake and exhaust manifolds.
• the water jacket core box interior must also be provided with all of the other parts resulting from the outside thickness of
• the problem of making the duct cores pass through the openings obtained in the water jacket cores is solved by dividing the latter horizontally into two halves, which are then attached to each other by an adhesive after inserting the ducts.
• Lost Foam Another casting process, called Lost Foam, consists in realising multiple polystyrene sectors using special dies. Once such sectors have been attached to one another, they match the part to be cast.
• the polystyrene model thus obtained is coated and then put into a container, which is then filled by vibration with common sand or a similar material.
• the molten metal is poured into the container. As polystyrene burns, it is replaced by the metal, so as to form the desired casting.
• Object of the present invention is to obviate the disadvantages of the prior art mentioned above, by proposing a new casting procedure which allows obtaining higher quality castings, thereby reducing the number of the cast scrap due to dimensional defects, and further introducing new design prospects.
• Another object of the invention is to provide a casting procedure which allows a perfect relative positioning between each core and an easy insertion of the cores into the mould or into another core, whichever their shape.
• Another object of the finding is to provide a casting procedure which allows a considerable simplification of the core boxes, that is, without any complex shapes, undercuts and connected moving parts, and which is therefore cheaper, more reliable and easier to maintain.
• Another object of the invention is to provide a chilling casting process for engine cylinder heads which allows obtaining cores for intake and exhaust ducts without any deformation on the outside thickness and with the most varied and complex shapes, which may result in better engine performance and ecologically more advanced engines as regards exhaust gases, as allowed by the new casting technology.
• Yet another object of the invention is to provide a casting procedure for engine cylinder heads which allows embedding inserts for the ducts into the casting, made of a material capable of standing the heat generated by the molten metal in order to obtain perfectly smooth ducts which should contribute to improving the engine efficiency.
• FIG. 1 shows sand and polymerised resin cores for realising the intake and exhaust ducts of an engine cylinder head
• FIG. 2 shows a section view of the core boxes for moulding the cores of Fig. 1 , in a variant with inserts around the intake and exhaust ducts;
• FIG. 3 shows the duct cores with inserts obtained with the core box of Fig. 2;
• - Figure 4 shows a section of the duct cores inserted into the die for their coating with foamed material;
• FIG. 5 shows the group of valve seats and duct cores coated with foamed material
• FIG. 6 shows the water jacket core box still empty
• FIG. 7 shows the core box (f ⁇ g.6) with the group of duct cores of Fig. 5 inserted therein;
• FIG. 8 shows the group of cores, valve seats and foamed coating obtained by moulding the water jacket core in the core box of the previous Figure, with the valve guides inserted into the coating;
• FIG. 9a and 9b show two enlarged details of the core assembly scheme, where black parts denote the difference in the shape and volume of the water jacket dimensions that can be obtained by the casting procedure under discussion compared to the current art;
• the present invention relates to a casting procedure for obtaining castings provided with inside cavities.
• cavities are obtained by laying in a mould, such as a chill, intended to receive the molten metal, one or more cores made or sand and polymerised resin or other material.
• cores are previously obtained into special moulds, called core boxes.
• core boxes In the case of more cores, these are obtained separately, each into a relative core box, and then they are assembled each other before being laid
• the cores are usually provided with complementary projections and cavities, called positive and negative prints, to support one another, and with other sand projections intended to lay into the suitable seats into the chill, which do not form part of the casting.
• the procedure according to the present invention provides for coating one or more cores made of sand or other material with a layer of foamed material, such as polystyrene, only in the shaped zones, using a special die and then laying them into the chill.
• foamed material such as polystyrene
• the core coating material is intended to dissolve in contact with the casting metal, which replaces it thereby determining the required casting thickness, so that the finished casting surface will be determined by the quality of the core surface.
• the main core box In order to receive the secondary cores already coated with foamed material, the main core box will be empty at the shapes of said secondary cores since shapes and thickness are replaced by the cores and by the coating layer. As a consequence, the main core box is much easier and cheaper to be realised since it allows eliminating any inside undercut and any moving parts required to realised the containments of secondary cores.
• the main core box only has the outside prints of the secondary cores, which will be pre- assembled into the same. Following the moulding of the main core box with sand and polymerised resin, a single monolithic body is obtained, already assembled and exhibiting a considerable geometric accuracy, consisting of the main core and of the secondary cores, which are integral with the main
• inserts consisting of heat resistant material, such as metal or composite material, and intended to be embedded into the
• the main core box is capable of receiving both sand cores or inserts coated with foamed material.
• inserts of metal or other material are to be embedded into the casting, and these inserts have an inside void and where such void is corresponding to the core design, they must be laid into a specific core box which only considers the insert thickness in
• such core wilt also prevent the molten material from penetrating into the
• the casting designer is provided with a new technology that allows obtaining castings which can even embed other adjacent parts currently casted separately, according to the constraints of the current traditional casting technology.
• Such new technology can also be used for obtaining stiffening
• the die is constructed with all core print seats equal to the core
• the casting procedure described is especially but not exclusively adapted to be applied to a chill casting process of
• the main core 11 is the water jacket core
• secondary cores mainly are those relating to the
• valve seats onto the outside diameter are embedded, whereas inside they will be aligned on the conical edges of the duct cores.
• the valve seats 14, 15 must have the proper machining stock on the inside diameter.
• the outside diameter of the valve seats is realised with a taper equal to the inside one, and such taper is required for the coating material to support and held into position the valve seats during further handling, up to the assembly into the chill or die. The metal will then finally block the valve seats onto the casting.
• valve guides 16", 17" can be automatically inserted into the suitable seats 16', 17' obtained in the foamed material.
• Special sealing members are applied to the junctions between foamed material and upper half water jacket core box in order to prevent sand infiltrations
• valve guides will be solid (without central holes) since mechanical machining for inserting the valve stems is performed with valve guides embedded into the casting. Among the other things, this allows preventing the use of traditional stiffening bosses around the valve guide into the duct cores.
• valve guides wilt be provided with a negative circular groove at the portions embedded in the foamed material, which will hold into position the valve guides in the casting metal when the latter replaces the foamed material.
• valve guide In the upper portion of the valve guide there is often another core 21 for the oil gallery, as in the case shown in fig. 10, or a core for the tappet compartment, which realises the risers (casting metal feeding during the shrinkage by cooling).
• the upper end of the valve guides will always be guided into a suitable seat realised into said upper core 21 or into the tappet compartment core, and therefore blocked into the correct position, even when the casting metal has dissolved or is dissolving the foamed material around the valve guides, without making the same valve guides collapse.
• the vatve guides are inserted and stopped into suitable seats 22 obtained in the duct cores (Fig. 3).
• the monolithic group comprising the water jacket core 11 , the secondary cores, the valve seats, the valve guides, the foamed material along with other cores, such as
• the molten metal will dissolve and replace
• Fig. 10 shows the same assembly scheme described above, but where the duct cores consist of metal hollow inserts 23 (or made of another material capable of standing the heat generated by the casting metal), filled with sand and polymerised resin having a support function as welt as serving
• the inserts end against the valve seats whereas as
• the intake ducts may be connected to one
• Such chamber may even reach the intake manifold coupling flange and form a single chamber integral with the same manifold, without implying any problems of assembly with the water jacket.
• Such concept may also be extended to inserts made of another material and embedded into the casting.
• the head designer will have a wide freedom of design since the current design constraints are eliminated, such as the forced passage of the ducts through the water jacket.
• the water jacket compartment can be realised with more rounded design
• outside duct core thickness is also free from deformations, with a constant and perfect thickness exactly as drawing specification.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Cylinder Crankcases Of Internal Combustion Engines (AREA)

Applications Claiming Priority (3)

Publications (1)

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  • 2002-10-04 IT IT000088A patent/ITBS20020088A1/it unknown
  • 2002-12-09 DE DE20221850U patent/DE20221850U1/de not_active Expired - Lifetime
  • 2002-12-09 RU RU2005109149/02A patent/RU2306194C2/ru not_active IP Right Cessation
  • 2002-12-09 JP JP2004544685A patent/JP2006502009A/ja active Pending
  • 2002-12-09 EP EP02808016A patent/EP1545811A1/en not_active Ceased
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  • 2002-12-09 CA CA002500794A patent/CA2500794A1/en not_active Abandoned
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• 2006
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