Patent Grant
6929052
The invention relates to a method and an apparatus for uphill casting/low-pressure casting, especially of light metal alloys, with a casting furnace lying below a casting table, having a riser pipe and a mouth opening of the riser pipe and having a mould with an underlying pouring-in opening and having a slide valve closure for the pouring-in opening, forming a flow-through channel which for casting takes on a substantially straight, longitudinal course.
Compared with gravity casting, uphill casting has the substantial advantage of a smooth controlled casting process. By this means the entrance of air bubbles and oxidation skin which is associated with any turbulence of the melt during casting is avoided. When using core packages as moulds, the separation and entrainment of moulding material in the gate and in the runner can be avoided which otherwise leads to a deterioration in the quality of the castings.
A disadvantage with uphill casting is that in general it is necessary to wait for the solidification process of up to 15 minutes duration before the mould just filled can be removed and the next mould can be brought over the casting furnace. In order to rectify this disadvantage, it has already been proposed that moulds should be closed directly after the low-pressure casting in the pouring-in opening and removed immediately from the riser pipe.
It is known from CH 415 972 that moulds for low-pressure casting can be provided with an underlying shut-off valve and a feeder head positioned thereover, below the mould cavity. The shut-off valve consists of a slider plate lying inside a pouring-in channel with a flow-through opening which is displaced transversely with respect to the pouring-in channel. The feeder head has a volume-displacing slider piston. Although the feeder head is heatable, after closure of the shut-off valve there may be some solidification of the melt in the flow-through opening of the slider plate, which requires separate removal of the plug there formed before the next casting process.
The object of the following invention is to further improve a method and an apparatus of said type.
The solution lies in a method for uphill casting/low-pressure casting in which for shut-off in the slide valve closure, two opening sections of the flow-through channel directly adjacent one to the other are displaced with respect to one another transversely to the longitudinal course of the flow-through channel directly after casting with still liquid melt in the pouring-in opening, so that an overlying opening section remains in open communication with the pouring-in opening free from undercut and an underlying opening section remains in open communication with the mouth opening of the riser pipe, wherein the opening sections are completely offset with respect to each other. A corresponding apparatus according to the invention is characterised in that the slide valve closure is placed on the casting table and comprises two mutually displaceable plates, each having a flow-through opening, wherein the plates can brought into overlap with their flow-through openings for casting and the plates are displaceable towards each other for shut-off so that the flow-through opening in the upper plate is in open communication with the pouring-in opening free from undercut and the flow-through opening in the lower plate is in open communication with the mouth opening of the riser pipe, while the sections of the flow-through opening are completely offset with respect to each other.
With the method according to the invention and the apparatus according to the invention, a method is provided especially suitable for small castings in which it is not necessary to separate the riser pipe from the slide valve closure during successive casting processes so that any air access to the melt level in the riser pipe can be largely excluded. This particularly applies if, after shut-off, the melt in the riser pipe is only lowered so far that at least the lower longitudinal section of the flow-through channel is emptied of melt, to avoid any sticking of melt to the upper slide plate. Here it can especially be provided that after shut-off, the melt in the riser pipe is only lowered to slightly below the mouth opening of the riser pipe and that during lowering of the melt, the riser pipe is acted upon by protective gas at the mouth opening.
In a preferred embodiment, the process sequence is distinguished by the fact that the mould itself as an entity is displaced together with the upper longitudinal section of the flow-through channel of the slider unit. In order to accelerate the process sequence, it is hereby provided that the melt should be actively cooled inside the pouring-in opening and if necessary, also inside the upper longitudinal section of the flow-through channel at the latest after shut-off, i.e., the displacement of the longitudinal sections of the flow-through channel towards to one another. In this case, a mould is then removed from the slide valve closure immediately after solidification of the melt in the upper longitudinal section of the flow-through channel and in the pouring-in opening of the mould. It is thus not necessary to wait for solidification of the entire casting. In order to avoid shrinkage caritation during the complete solidification, either a subsequent active pressure application from above or a rotation of the mould through 180° after lifting is to be proposed. The effortless removal of the mould results from the undercut-free configuration of the upper section of the flow-through channel in which an easily demouldable plug forms on the casting. This is achieved by the flow-through opening in the upper plate and if necessary, jointly with this the pouring-in opening of the mould, expanding continuously upwards, especially having an upwardly expanding conicity.
The apparatus according to the invention is especially constructed such that the plates are held in a cassette fixed to the casting table and the upper plate is held in a holder displaceable in the cassette, on which the mould can be placed. This holder can especially be inserted in a sliding carriage guided in the cassette on which it is supported in a spring fashion.
A suitable mould can have a lower cylindrical connecting piece which forms the pouring-in opening and which fits into a connecting-piece insert or a connecting-piece receptacle in the holder for the upper plate which is aligned towards the flow-through opening in the upper plate. Here especially the front face of the cylindrical connecting piece of the mould can be positioned flush onto the upper plate and if the mould's own weight is too low, can be braced against this to produce an effective seal. In order to accelerate the sequence of the casting processes as specified above, there are provided as cooling devices a coolant ring at the connecting-piece insert or the connecting-piece receptacle in the holder of the upper plate and a cooling chamber below or in the lower plate. The coolant feed pipe to the coolant ring must be elastic in this case in order to be able to equalize the movements of the sliding carriage or the holder. The actuating device for the sliding carriage can be arranged directly on the cassette. The mould can be designed as a permanent mould or consist entirely of mould material. The connection between the riser pipe and the slider unit can be such that the riser pipe passes through the casting table in an opening and abuts with a contact plate directly against the stationary lower slide plate. However, it is also possible that there is inserted securely in the casting table a sprue bushing which lines the opening in the casting table and is clamped against the lower slide plate in a sealing fashion and that the riser pipe abuts with a contact plate against the lower edge of this sprue bushing. It is preferably provided that the flow-through opening in the lower plate and, if necessary, jointly with this, the parts forming the flow-through channel adjacent thereto in the downward direction as far as the mouth of the riser pipe, jointly expand continuously downwards, especially having a downward-expanding conicity so that when the melt level in the riser pipe is allowed to drop, no melt residue is caught in the flow-through channel.
The riser pipe can be axially elastically and angularly moveably joined to the casting furnace via a metal bellows connection while the casting furnace is held such that it is moveable in height to allow docking of the riser pipe at the casting table and separation of the riser pipe from the casting table. With the same type of axial elastic and angular moveable connection between the casting furnace and the riser pipe by means of a metal bellows, the casting table can also be moveable in height in kinematic permutation in order to accomplish said docking and separation between the riser pipe and the casting table.
Insofar as uphill casting/low-pressure casting according to the invention is discussed heretofor, this initially relates to methods and apparatus wherein a controllable gas pressure is applied to the melt level in the sealed furnace, which makes the melt in the riser pipe rise or fall. Also included however are other methods and apparatus which can controllably convey the melt in the riser pipe, e.g. magnetic pumping arrangements at the lower end of the riser pipe in the casting furnace.
The uphill casting/low-pressure casting is hereinbefore related to a perpendicular gate of the moulds wherefrom are derived the corresponding designations upper plate/upper section of the flow-through opening, lower plate/lower section of the flow-through opening. The subject matter of the invention is not departed from, however, if moulds having horizontal gates are used, wherein the term “upper” is logically to be replaced by “mould-side” and the term “lower” is logically to be replaced by “riser pipe side” with a horizontally aligned flow-through direction but otherwise unchanged geometry and kinematics.
Details of the apparatus according to the invention are described in the following with reference to the drawings, wherein
The two figures are first described jointly. A slider unit 13 is screwed onto a casting table 11 having a flow-through opening 12. In the flow-through opening 12 of the casting table 11 is inserted a sprue bushing 15 which at the same time forms a connection for the riser pipe of a casting furnace not shown. Inside the sprue bushing 15 there is provided an undercut-free opening 16 down to the riser pipe. The slider unit 13 comprises a cassette 17 which is screwed directly onto the casting table 11. For its part this cassette 17 has a lower opening 18 which is flush with said opening 16. In the opening 18 there is inserted a sealing ring 14 which abuts against the sprue bushing 15 in a sealing fashion. In the cassette 17 there is inserted a lower slide plate 19. The lower slide plate 19 is held via a thrust piece by a screw 21 screwed into the cassette 17. Inside the cassette 17 a holder 22 is held horizontally displaceably. In the holder there is inserted an upper slide plate 23 which has an upper flow-through opening 24 of the slider unit. The holder 22 is arranged at a sliding carriage 25 which is held by guide rails 26 in the cassette 17. Inserted in the sliding carriage 25 are compression spring domes 30, 31 whose pressure cylinders 32, 33 press the holder 22 downwards so that the slide plates 19, 23 abut onto each other with pre-stressing and fit in the cassette 17. Attached to the cassette 17 is an adjusting cylinder unit 28 which acts via a rod 29 on the sliding carriage 25 so that the holder 22 can be displaced horizontally in the cassette 17.
The lower slide plate 19 has a lower flow-through opening 20, the upper slide plate 23 has an upper flow-through opening 24. In coaxial assignment to the upper flow-through opening 24 the holder 22 has a connecting-piece projection 34 and the sliding carriage 25 has a connecting-piece receptacle 35. Also inserted in the connecting-piece projection 34 is a cooling ring 36 shown in enlarged detail, which can be supplied with cooling air via a compressed-air line 37. The cooling ring 36 has inwardly directed air outlet openings 38. In the lower slide plate 19 there is constructed a cooling chamber 39 which is supplied with cooling air via another compressed air line 40. Inserted in the connecting-piece projection 34 and the connecting-piece receptacle 35 is a mould 41 having a downward-pointing sprue connecting piece 42 which sits on the upper slide plate 23. The mould 41 is sealed by a lid 43. The sprue channel 44 of the mould 41 is flush with the upper flow-through opening 24 and jointly with this, is undercut-free in the upward direction, and especially is constructed as conically opening. The mould 41 can be a permanent mould or a sand mould or a core package.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP01/07823 | 7/7/2001 | WO | 00 | 5/29/2003 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO02/04143 | 1/17/2002 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3529753 | Mack | Sep 1970 | A |
| 3627018 | Costello et al. | Dec 1971 | A |
| 3905419 | Tenner | Sep 1975 | A |
| 3980125 | Portalier | Sep 1976 | A |
| 5524700 | Gosch | Jun 1996 | A |
| Number | Date | Country |
|---|---|---|
| 26 46 187 | Apr 1978 | DE |
| 207675 | May 1993 | HU |
| 61-3653 | Jan 1986 | JP |
| 1-241352 | Sep 1989 | JP |
| WO 0204148 | Jan 2002 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20040250978 A1 | Dec 2004 | US |
