EP0021282B1 - Apparatus for introducing molten metal into a centrifugal casting installation for tubes and other cylindrical objects - Google Patents

Abstract

In a centrifugal casting apparatus, the rate of flow of molten iron poured into the mold is controlled by varying the inclination of the feed channel. In particular, at the end of the casting operation, the supply of liquid to the feed channel is cut off and the upstream end of the feed channel is progressively raised. This can be controlled automatically by a cast iron level detector adjacent the pouring spout. In this manner, localized thickness defects in a series of pipes can be corrected. Furthermore, pipes of constant thickness throughout their length can be provided without the need to vary the translational speed of the feed channel or vary the rate of pivoting of the ladle of molten liquid.

Description

The present invention relates to the centrifugation of pipes or other tubular bodies of cast iron. It relates more particularly to centrifugal casting according to the De Lavaud process, in which liquid iron is poured into a rotary shell via a pouring channel supplied by a ladle while causing relative longitudinal movement between this channel and the shell, and the supply of the cast iron channel is interrupted before the spout has reached the outlet end of the shell.

From patent DE-C-704037, a casting device is known according to the De Lavaud method in which two interlocking pipes are cast simultaneously, a pair of pouring channels in a pair of centrifugation shells, the channels and the shells being twinned. This patent poses the problem of simultaneously feeding the shells and in particular, at the start of casting, before the relative axial movement between the channels and the shells, the ends with interlocking so as to introduce into these ends the same quantity of cast iron and thus obtain twin pipes with the same sockets, with the same dimensions.

According to this patent DE-C-704 037, this problem of simultaneous introduction of the same quantity of cast iron into the two interlocking ends is essentially resolved by providing along each pouring channel several retaining dams provided with regulation orifices casting jets. In addition, to further perfect the result, the twin channels are tiltable around horizontal articulations provided upstream, in the vicinity of the ladle, and have a variable inclination, even during casting, and in any case only during the casting of the sockets, that is to say before the relative axial displacement of each channel with respect to each shell, in order to regulate the speed of flow of the cast iron.

Starting from this prior principle of articulation of a pouring channel in order to vary its inclination, the Applicant has posed the problem of completely emptying the pouring channel of its usual remainder of cast iron which solidifies into a tongue . Such a tab indeed has the drawback of consuming superfluous melting energy and of requiring an elimination operation before the next casting.

This problem is solved, according to the invention, by a casting device for a De Lavaud type centrifuge machine, of the aforementioned type with articulated channel, with variable inclination, and of the type comprising an approximately horizontal beam in door-to-door position. false supporting a pouring channel of approximately the same length, this device being characterized in that the channel is articulated on the beam in the vicinity of its pouring spout and in that the upstream end of the beam is fixed to a carriage mobile on which is articulated one end of a jack.

Thanks to this device, it is possible to raise the pouring channel at the end of casting, towards the end of the relative axial displacement of the channel and of the casting shell, and not, as in the cited earlier patent DE-C-704 037, at the start of casting, before the relative axial displacement in translation, and it is possible to thus strongly modify the inclination of the pouring channel between a non-inclined position relative to the axis of the shell at the start of casting, when the pouring spout is located inside the interlocking end of the casting shell, and a strongly inclined position at an acute angle relative to the axis XX of the casting shell, at the end of casting, when the spout is located inside the plain end of the shell. In other words and more simply, it is possible to incline the pouring channel sufficiently with respect to the axis of the shell to empty it of all the remaining liquid iron.

This possibility of large inclination of the pouring channel with respect to the axis of the shell is only possible for sufficiently large shell diameters, for geometric reasons of the size of the inclined channel inside the shell. In addition, these characteristics are particularly advantageous for the casting of pipes of large diameters, because of the appreciable economy of liquid cast iron which they provide.

These characteristics and advantages are not found in the prior patent DE-C-704 037 concerning the centrifugal casting of pipes of small diameters with small variations in inclination of a casting channel with respect to its centrifugation shell.

Other details will appear during the description which follows.

• la Fig. 2 est une vue schématique analogue à plus grande échelle du dispositif de coulée de cette installation;
• la Fig. 3 est une vue correspondant à la Fig. 2 montrant le canal en position soulevée;
• les Fig. 4 et 5 sont respectivement des coupes prises suivant les lignes 4-4 de la Fig. 2 et 5-5 de la Fig. 3;
• les Fig.6 et 7 sont des vues partielles, respectivement en élévation latérale avec arrachement et en bout suivant la ligne 7-7 de la Fig. 6, d'une variante de l'invention relative à un canal monobloc;
• la Fig. représente schématiquement un dispositif de régulation conforme à l'invention.

In the accompanying drawing, given only by way of example, FIG. 1 is a schematic view in side elevation and in partial section, on a small scale, of an installation for casting pipes of large diameters, provided with a casting device according to the invention;

• Fig. 2 is a similar diagrammatic view on a larger scale of the casting device of this installation;
• Fig. 3 is a view corresponding to FIG. 2 showing the channel in the raised position;
• Figs. 4 and 5 are respectively sections taken along lines 4-4 of FIG. 2 and 5-5 of Fig. 3;
• Figs. 6 and 7 are partial views, respectively in side elevation with cutaway and at the end along line 7-7 of Fig. 6, of a variant of the invention relating to a one-piece channel;
• Fig. schematically represents a regulating device according to the invention.

The centrifuge installation shown in Figs. 1 to 5 comprises a machine 1 for centrifuging pipes 2 of interlocking cast iron having a diameter of, for example, between 600 and 2000 mm. These numerical values of diameters are given for information only and are not limitative. To judge the size of this machine 1 and the pipes 2 to be poured, a human silhouette 3 is shown next to the machine.

The machine 1 essentially comprises a rotary shell 4 for molding an approximately horizontal axis X-X housed in a casing 5 and carried by rollers 6 of which at least one is a motor. The rollers 6 are carried by a fixed frame 7 parallel to the axis X-X.

The shell 4 is supplied with liquid iron by a casting device 8 which will be described in detail below. This casting device comprises a carriage 9 movable in translation on the frame 7 parallel to the axis XX, so as to be able to introduce a channel-beam assembly 10 into the shell up to the most distant end thereof, which is provided with a socket 11.

The casting device 8 is itself supplied with cast iron by a tilting casting ladle 12, shown partially, the tilting axis of which is fixed.

In the extension of the casing 5, on the other side of the device 8, the installation comprises an extraction device 13 essentially consisting of a rolling track 14 parallel to the axis XX on which two support carriages 15 roll, 16 and an extractor carriage 17, and a lifting device 18. The device 13 may in particular be of the type described in patent FR 74.23701.

The assembly 10 comprises a support beam 19 of great inertia and a composite channel 20. The beam 19 is fixed by its upstream end to the carriage 9 and extends cantilevered towards the centrifugation machine 1. The free end of this beam has two horizontal lateral cylindrical studs 21, perpendicular to the axis XX and located in the extension of one another.

The channel 20 consists of a cradle 22 in which a pouring chute 23 fitted upstream of a weir 24 and downstream of a pouring spout 25 and composed of a certain number of successive segments. As a variant, the chute 23 could moreover be in one piece.

The cradle 22 extends downstream to the pouring spout 25. A little upstream thereof, it externally comprises two cylindrical lateral half-eyelets 26 corresponding respectively to the upper part of the pins 21 of the beam 19 and based on these. Immediately downstream of the carriage 9, a yoke 27 projects under the cradle. A double-acting jack 28 is articulated on the one hand to this yoke, on the other hand to another yoke 29 provided at the front of the carriage 9.

Thus, the composite channel 20 is mounted tilting around its downstream end between a roughly horizontal low position shown in FIGS. 1 and 2 and a high position inclined by an angle ce to the horizontal, shown in FIG. 3. These two extreme positions correspond respectively to the fully retracted state and to the fully extended state of the jack 28.

The casting device 10 also includes a flow control device shown diagrammatically in FIG. 8. This regulating device comprises a detector 30 of the level of the cast iron in the vicinity of the pouring spout 25 connected to a spool valve 31 with two positions controlling the supply of the jack 28 with pressurized fluid. The detector 30 is an inductor connected by electric wires 32 to a pilot electromagnet 33 acting on the distributor's counter 31 against a return spring 34.

The inductor 30 is mounted outside the channel spout, and therefore out of direct contact with the cast iron. It essentially consists of a coil sensitive to the presence of cast iron at a given level N, below which it maintains a supply of electric current on line 32 and below which it cuts this supply. In the first case, pressurized fluid is sent to the lower chamber of the jack 28, which causes the inclination of the channel 20; in the second case, this fluid is sent to the upper chamber of the jack 28 to bring the channel 20 back to its low position. In each case, the unpowered chamber of the jack is discharged.

The pilot device 33 is also equipped with a timer 33a capable of cutting off the supply of electric current when a displayed time has elapsed.

The casting of a pipe 2 (Fig. 1, and 3) by means of this installation takes place as follows.

Before casting, the carriage 9 moves in translation in direction f until the pouring spout 25 of the channel 20 is inside the interlocking end 11 of the shell 4 driven in rotation around axis XX. It is at this moment that the liquid iron is poured into the weir 11 through the pocket 12 and that it begins to flow into the shell. The carriage 9 then sets off again in translation in the opposite direction (arrow g) so as to make the spout 25 run the entire length of the shell until it exits through the plain end thereof.

During all this return movement, the inclination of the channel 10 can be varied if necessary by means of the jack 28 to modulate the rate of cast iron poured by the spout 25 at any point of the shell. This is how if we notice on the centrifuged pipes an excess thickness or a thinning well localized and always in the same place, we can remedy it by instantly increasing the inclination of the channel (for a thinning) or by decreasing it instantly ( for an extra thickness) at the moment when the beak 25 reaches the point of the shell where the irregularity to be corrected takes place, then by bringing the channel at its usual inclination, and this keeping constant both the tilting speed of the bag 12 and the translation speed of the carriage 9. This correction does not involve the regulating device of FIG. 8.

It should be noted that this mode of temporary variation of the device poured into the shell is made possible by the presence of the enlarged weir 24, which acts as a buffer with variable capacity to a certain extent between the pocket 12, which provides a constant flow fluid, and the chute 23 proper.

When the spout of the channel 20 reaches a point in its course situated towards the plain-tipped end of the shell 4, the supply of pig iron through the pocket 12 in the weir 24 is stopped. Still without modifying the speed of translation of the carriage 9, the jack 18 is then actuated again so as to gradually increase the inclination of the assembly 10 in order to deposit a constant quantity of cast iron throughout the shell 4, that is to say - say so that the flow rate at the pouring spout 25 remains constant until the latter leaves the shell.

During this phase of the casting, the assembly 10 rocks around the two journals 21 of the beam 19. The increase in the inclination of the channel 20 compensates for the lack of supply upstream, so that the end with plain end of the rotary shell receives the same turns of liquid iron, under the same thickness, as before the interruption of the supply. It follows that the centrifuged pipe 2 has a plain end of the same thickness and the same inclination of turns as its current part, and that the quality of this pipe is regular until the plain end.

It is easily understood that this increase in the inclination can be controlled automatically by the device of FIG. 8, which intervenes, after the interruption of the supply of the weir 24, as soon as the level of the cast iron drops in the vicinity of the pouring spout 25. When the pouring spout 25 comes out of the shell, the channel 20 is almost emptied of its liquid iron. The jack is retracted, for example under the control of the chronometer 33a, to lower the assembly 10 and return it to the normal low rest position of the cradle 22 on the support beam 19 for the next casting.

Since the speed of translation of the carriage 9 has not been slowed down at the end of the casting process, the manufacturing cycle is shortened, and the control of the movement of the carriage 9, which is carried out at constant speed throughout the race, is simplified. In addition, during casting, the slightest variation in the inclination of the channel instantly results in a precise correlative variation in the flow rate poured into the shell.

The almost total absence of iron solidified in rod or strip in the channel, after casting, allows savings on the consumption of iron, on the melting energy of this iron, on the time necessary for the ejection of the cast iron rod from channel 20 and maintenance of this channel.

Figs. 6 and 7 illustrate a variant of the invention in which the pouring chute 23a is in one piece and devoid of support cradle. In this case, the half-eyelets 26 are carried directly by this chute.

Claims (1)

1. Casting device (8) for a centrifugal casting machine for carrying out a method of manufacturing a tubular body (2) by centrifugation of the type in which molten cast iron is poured into a rotary mould (4) by means of a casting channel (20) supplied from a casting ladle (12) whilst bringing about relative longitudinal movement between this channel and the mould and the supply of cast iron to the channel being interrupted prior to the pouring spout (25) having reached the outlet end of the mould, this device of the type comprising a substantially horizontal cantilevered beam (19) supporting the casting channel (20) of substantially the same length and of the type in which the channel (20) is articulated with a view to varying its inclination during casting, being characterised in that the channel (20) is articulated on the beam (19) in the vicinity of its pouring spout (25), the upsteam end of the beam (19) being fixed to a movable carriage (9) on which one end of a jack (28) for the inclination of the channel is articulated.

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