TECHNICAL FIELD

The invention relates to methods as stated in the pre¬ ambles of the claims 1, 9, 12 and 13 of closing the inlet in a mould after non-gravity casting with a non-ferrous alloy of green-sand moulds in a mould-string plant.

BACKGROUND ART

The international patent application WO 93/11892 relates to a method and a casting device for non-gravity casting with a light-metal alloy of green-sand moulds in a mould- string plant like the "Disamatic" moulding plant manu¬ factured and marketed by Applicants. In this known method, the light-metal alloy is pumped by means of an electro¬ magnetic pump from a heated reservoir through a heated ceramic tube into a bottom inlet disposed in the parting surface between the moulds, thus filling the mould. To prevent the metal from flowing out from the mould, the inlet must be closed before the nozzle of the casting device is removed from the inlet, and this specification indicates three different ways of achieving this, viz. :

1) A core provided with a through-going opening is disposed movably parallel to the outer surface of the mould in a guideway in the mould opposite the mould inlet so that the opening in the core during casting of the mould can be brought to lie aligned with said inlet, while the core after full-casting of the mould is displaced so that a compact part of the core is aligned with the inlet and closes it. The specification shows and describes both a horizontally and a vertically displaceable core.

95/32826 PC17DK95/ 00204

A drawback of this closing method is that during the dis¬ placement of the core, the nozzle of the casting device must abut sealingly against the latter with a certain force, thus at least hampering the displacement of the core.

2) After full-casting of the mould, the inlet of the latter is closed by pressing a metal plate obliquely from above down through the mould material encompassing the inlet of the mould, thus closing the inlet. As the pumping direction of the electromagnetic pump is reversed immediately before withdrawing the nozzle of the casting device from its sealing abutment around the inlet opening in the mould, there is a risk that the metal being pumped back carries along with it moulding sand having been torn loose during the pressing-down of the metal plate. During casting of the next mould, this moulding sand will then be pumped into this mould and may cause defects in the casting.

In both above-mentioned methods of closing the inlet of the mould, the nozzle of the casting device is withdrawn from the mould after casting the latter during the step- wise advancement of the mould string, then to be moved forward in abutment against the inlet of the succeeding mould in the mould string for casting said succeeding mould.

3) In this closing method, the nozzle of the casting device is pressed constantly against the side of the mould string, and a cutting edge is disposed at the mould string upstream of the nozzle, said cutting edge "planing" a groove in the side of the mould string, in which groove the nozzle and a chill plate mounted downstream of it

are displaced during the stepwise movement of the mould string. During the casting of a mould, the chill plate covers the inlet of the previously filled mould and cools the metal within the inlet to solidification, thus causing the inlet to be closed. This closing method requires rather complicated equipment with means for controlling the force with which the nozzle is pressed against the side of the mould string, as well as the cooling of the chill plate.

DISCLOSURE OF THE INVENTION

The object of the invention is to provide improved methods of closing the inlet in moulds of the kind described by casting the moulds by means of the known method and with the known casting device and including the object of especially avoiding the drawbacks mentioned under 1) and 2) , and to suggest further alternative methods hereof.

A first method of closing the inlet by using a movable element in accordance with this invention is set forth in the characterizing clause of claim 1.

The movable element may be composed of any material capa¬ ble of resisting the temperature influence and the ero- sion from the cast metal, e.g. of cured core sand, ceramic material or metal.

By placing the element in a recess of suitable dimensions disposed in at least one of the mould parting surfaces, it is gripped between the mould parts in such a manner that the frictional force to be overcome in order to displace the element inwardly into the mould is greater than the requisite force to press the nozzle of the cast¬ ing device against the element to create a seal during

casting of the mould. A further resistance to displacement of the element can e.g. be achieved, if the element is provided with at least one groove about at least a part of its circumference, said groove co-operating with a complementary projection located in at least one mould part, as in that case, the shear strength of this pro¬ jection has to be overcome before the element can be moved inwardly into the mould. Also other measures obvious to a skilled person for increasing the resistance of the element to displacement inwardly into the mould may be possible.

Alternative advantageous embodiments of the methods ac¬ cording to the invention, the effects of which are ex- plained in the following detailed portion of the present specification, are set forth in claims 2-16.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in more detail in the following detailed portion of the specification with reference to the drawings, in which

Figure 1 diagrammatically illustrates the previously mentioned known method of bottom filling with a light- metal alloy of green-sand moulds in a mould-string plant, Figures 2a - 2d illustrate a first method according to the invention of closing the inlet by means of a movable element before (2a and c) and after (2b and d) , respec¬ tively, closing of the inlet shown in vertical section through the mould parting surface, Figures 3a, b and c show vertical cross-sections through three modifications of the movable element shown in Figure

2 ,

Figures 4a - 4d in the same way as in Figure 2 illustrate a second embodiment of the method represented in Figure

2 before (4a and c) and after (4b and d) , respectively, the closing of the inlet,

Figures 5a and b in the same way as in Figures 2 and 4 illustrate a further method according to the invention of closing the inlet by means of a plate before and after, respectively, closing of the inlet,

Figures 6a and b in the same way as in Figures 2, 4 and 5 illustrate yet another embodiment of the method repre¬ sented in Figure 5 before and after, respectively, closing of the inlet,

Figures 7a and b in the same way as in Figures 2 and 4-6 illustrate a third method according to the invention of closing the inlet before and after, respectively, closing the same, and Figures 8a to 8e in the same way as in Figures 2 and 4-7 illustrate a fourth method according to the invention of closing the inlet, a metal tube being used during casting of the mould and subsequently being blocked in three different ways.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 1 diagrammatically illustrates the method of cast¬ ing green-sand moulds in a mould-string plant known from the international patent application WO 93/11892. This comprises a moulding machine - generally designated 1 - similar to the "Disamatic"-moulding machine manufactured and marketed by the Applicants and dealt with in U.S. patent specification No. 3,008,199, whose mode of opera¬ tion is described in the previously mentioned interna- tional patent application and for this reason only dealt with broadly in this specification.

Box-less mould parts 2 made from loose green sand, i.e. sand with moist clay as binder, supplied from a hopper 3

to a moulding chamber defined between a pattern located on a movable piston 5 and a pattern located on a movable and upwardly pivotable counter-pressure plate 5 in a down¬ wardly pivoted position (not shown) of the counter-pres- sure plate 5. In the moulding chamber, the green sand is compacted by the piston 4 to form a mould part 2, the counter-pressure plate 5 is conveyed forward and pivoted upwards to the position shown in Figure 1, after which the mould part 2 is conveyed by the piston 4 to abut against the mould string formed by previously produced mould parts 2, said mould string being conveyed a distance corres¬ ponding to the thickness of a mould part in the direction indicated by an arrow A. In the mould string, the front side of a mould part 2 together with the rear side of the previous mould part 2 defines a mould cavity 6 being cast with a light-metal alloy 7 through a bottom inlet, in general designated 8, and situated in or at the parting surface between two mould parts 2, by means of a casting device in general designated 9.

The casting device 9 consists of a heated reservoir 10 for the molten metal, in which an electromagnetic pump 11 is submerged, via a heated ceramic tube 12 pumping the molten metal up to a nozzle 13 which is in tight-fitting abutment around the casting opening to the inlet or the runner 8.

It will be appreciated that the casting of the mould cavity 6 must take place while the mould string is sta- tionary, i.e. within the intervals between each time the piston 4 advances the mould string through a distance cor¬ responding to the thickness of a mould part 2 in the direction of the arrow A.

After casting of the mould cavity 6 the inlet 8 must be closed, after which the nozzle 13 can be retracted, pos¬ sibly while reversing the pump 11, so that after the next movement of the mould string in the direction of the arrow A, the nozzle is ready to be brought into tight- fitting abutment around the casting opening to the runner 8 against the next mould cavity 6 in the mould string.

What has been described up to this point solely relates to the art known from the previously mentioned interna¬ tional patent application, and the runner is shown here as opening into the bottom of the mould cavity 6. It will be understood, however, that with non-gravity casting, the runner may also open into the mould cavity at some other location along its height. The non-ferrous alloy used is not necessarily a light-metal alloy.

Figures 2a and b illustrate a first embodiment of a first method according to the invention of closing the inlet 8 by means of a displaceable element 14. The element 14, which may e.g. be made from cured core sand or ceramic material or from metal, is cylindrical and has a through- going circular-cylindrical passage 15 and is preferably disposed symmetrically around the parting surface between two mould parts 2 - it may, however, border on this part¬ ing surface in such a manner that it is fixedly held by friction with the moulding sand, and in such a manner that it projects somewhat from the (lateral) surface of the mould string. On its surface encompassed by the ould- ing sand or on a part of this surface, the element 14 may possibly comprise at least one groove co-operating with projections formed in either or both of the mould parts 2. As shown in Figure 2a, during casting of the mould in the direction of the arrows shown, the outer,

plane end of the element 14 is in tight-fitting abutment against the nozzle 13 of the casting device 9, the element 14 being retained in the moulding sand with a force ca¬ pable of resisting the sealing pressure in this step being exerted on the element 14 by the nozzle 13.

When the mould has been filled completely, a considerably greater pressure is exerted on the element 14 by means of the nozzle 13, causing the element to be displaced inwardly into the mould to the position shown in Figure 2b, in which the plane inner end of the element 14 is brought into tight-fitting abutment against a plane sur¬ face 16 in the inlet 8, said plane surface 16 being pa¬ rallel to the inner end surface of the element 14. This causes closing of the inlet 8, and the nozzle 13 may be withdrawn as mentioned previously.

Figures 2c and d illustrate a modification of the embodi¬ ment shown in Figures 2a and c, in which the plane surface 16 in the inlet 8 is replaced by a recess or a seat 16' for the plane inner end of the element 14, providing a more reliable seal. Moreover, the internal cavity or the passage 15 in the element 14 is filled with a sieve-like material 15• capable of retaining possible solid matter and/or slag in the metal being cast, resulting in a final casting without such impurities. The sieve-like material must, of course, be able to resist influences from the metal being cast.

Figures 3a, b and c show three embodiments of the cross- section of the element 14 in Figures 2a and b. In Figure 3a the element has a circular-cylindrical outer surface and is placed symmetrically around the mould parting sur¬ face 17. In Figure 3b the outer surface of the element

has a square cross-section, and the element 14 is placed symmetrically around the mould parting surface 17 with two of its outer surfaces parallel to it. In Figure 3c the outer surface of the element 14 has a trapezoidal cross- section, and the entire element 14 is situated in one mould part in such a manner that the longer parallel side of the trapezoidal cross-section lies in the parting surface 17.

Figures 4a and b represent another embodiment of the method illustrated in Figure 2. In Figure 4a, the element 14" is retained as explained above, around the element 14 in Figure 2a and has a circular-cylindrical outer suface and an internal circular-cylindrical passage 15" which, however, is closed at the internal end by a wall 18. In the circumferential wall of the element 14" and imme¬ diately adjacent to the end wall 18 there are two openings 19 situated diametrically opposite each other, said ope¬ nings as shown in Figure 4a opening into an annular part 20 of the inlet 8, said annular part 20 encompassing the innermost part of the element 14". Within the end wall 18 the mould has a circular-cylindrical cavity 21 of sub¬ stantially the same diameter as that of the element 14" and with an axial extent somewhat greater than the thick- ness of the end wall 18 plus the axial extention of the openings 19.

After the mould has been filled by means of the nozzle 13 of the casting device as shown in Figure 4a in the direction indicated by arrows through the passage 15", the openings 19, the annular part 20 and the inlet 8, during which the end wall 18 of the element 14" exhibits a con¬ siderably higher resistance against erosion than the plane moulding-sand surface 16 or the seat 16' in the

embodiment of Figure 2, the element 14" is by means of the nozzle 13 pressed into the mould to the position shown in Figure 4b, in which the openings 19 are situated en¬ tirely within the cavity 21, and the annular part 20 of the inlet 8 is closed by the outer surface of the element 14". The nozzle 13 can then be withdrawn as explained previously.

In a modification of this embodiment shown in Figures 4c and d, a sieve-like material 20' is placed in the annular part 20 of the inlet 8 encompassing the element 14" and the openings 19 in the latter, said sieve-like material being capable of retaining solid matter and/or slag in the cast metal in a similar manner as the sieve-like a- terial in the modification of the first embodiment shown in Figures 2c and d.

Figures 5a and b illustrate a first embodiment of a second method according to the invention, in which the closing of the inlet takes place by means of a plate, which might be a metal plate as known from the state of the art refer¬ red to initially, but which might also consist of some other suitable material, e.g. a ceramic material. At this location adjacent the casting inlet, the inlet or the runner 8 has a downwardly inclined part 8• , across and substantially at right angles to which a plate 22 is located in oppositely disposed grooves in the mould parts 2. The plate 22 has a through-going opening 23, which in the casting position of Figure 5a is aligned with the downwardly extending part 8 ¹ of the runner 8, as the plate 22 in this position protrudes somewhat from the outside of the mould. After filling of the mould via the nozzle 13 with metal in the direction indicated by arrows, the plate 22 is moved into the mould to the position

shown in Figure 5b, so that it bars or closes the inclined part 8' of the runner 8, enabling the nozzle 13 to be withdrawn as mentioned above without the metal flowing out from the mould.

In the embodiment of this method illustrated in Figures 6a and b, the part 8" of the runner adjacent the casting inlet extends substantially vertically over at least a part of its length, and the plate 22' is placed in oppo- sitely disposed grooves in the mould parts 2 and extends at right angles to the vertical part of the duct 8", i.e. substantially horizontally. The plate 22' has a through- going opening 23', which in the casting position shown in Figure 6a is aligned with the duct 8", and in this position the plate 22' protrudes somewhat from the out¬ side of the mould below the nozzle 13. After filling of the mould, the plate 22' is pushed into the latter to the position shown in Figure 6b, in which it bars the runner part 8" and hence causes a closure of the mould inlet so that the nozzle 13 can be withdrawn as explained above.

In the third method according to the invention illustrated in Figures 7a and b, the part 8"' of the runner 8 adjacent the casting inlet extends obliquely, downwardly, and op¬ posite said part 8"' a recess 24 is provided in the out¬ side of the mould, the bottom of said recess extending parallel to the obliquely downwardly extending runner 8 ^I . After filling the mould by means of the nozzle as shown in Figure 7a, a piston 25 is pressed against the bottom of the recess 24 in such a manner that the moulding sand adjacent the piston 25 between the bottom of the recess 24 and the duct 8"' is pressed into the latter in the shape of a plug 26 locking the duct 8"' and consequently

95/32 26

12 closing the inlet to the mould. The nozzle 13 may then be withdrawn optially after reversing the pump 11, since - due to the downwardly inclined extension of the duct 8" ¹ - there is only a small risk of mould-sand particles from the plug 26 being sucked into the pump.

In the fourth embodiment of the method according to the invention of closing the inlet, as illustrated in Figures 8a to 8e, the outermost part of the runner 8 adapted to receive in abutment the nozzle 13 consists of a metal tube 27 secured in the mould. After filling the mould as shown in Figure 8a, the metal tube 27 is barred, either by placing cooling elements 28 around the metal tube 27 as shown in Figure 8b, said cooling elements cooling the tube 27 and the metal within it to make the latter soli¬ dify in the tube 27 as a plug closing the inlet of the mould, or by squeezing the metal tube 27 as shown in Figure 8c between a pair of jaws 29 so as to close the inlet of the mould, or as shown in Figures 8d and e by having the metal tube 27 opening into an expanded portion of the inlet 8, which portion contains a check-valve ball 30 and is partially barred at its downstream end by means of a pin 31 embedded into the mould-sand. During casting the metal may as shown in Figure 8d pass freely past the ball 30 resting against the pin 31, while - when casting is interrupted - the check-valve ball 30 closes the opening of the tube 27 as shown in Figure 8e.