WO 2005/102563 PCT/F12005/000198 1 CLOSURE OF THE DISCHARGE CHANNEL OF A METAL CASTING VESSEL The invention relates to a cock arrangement that is fitted in the bottom of a metal casting vessel provided with an opening, consisting of a channel body, through 5 which a channel runs, continuing the bottom opening, and the side of which is pro vided with a rotationally symmetrical recess extending transversely through the channel, and of a rotatable closure body, which is fitted in the recess and which comprises a transverse hole at the depth of the channel, which hole closes or opens the channel when the closure body is rotated. 10 Previously, for a closure of the casting conduit that starts from the bottom of a mol ten metal-containing casting vessel, a plug was used, which was raised and low ered and which was coupled to a lifting rod extending over the surface of molten metal. One difficulty was to make the plug catch the casting hole, when the conduit was closed after lowering the molten metal. Furthermore, the plug wore quickly in 15 use. Because of these problems, the plugs of casting holes have later on been re placed with sliding closure units, as described in the published patent application FI 92022, among others. The sliding closure unit consists of a horizontal plate that is rotated around a vertical axis and located against the lower end of a vertical 20 casting conduit, the plate comprising an opening, which can be brought next to the end of the conduit, whereby the conduit is open, and which can be rotated aside from the conduit, whereby the conduit is closed. The plate that forms the sliding closure unit is supported by a large frame, through which the rotating of the plate takes place. Such an arrangement is difficult to manufacture, cumbersome and 25 unreliable in use. Closing valve-type solutions similar to the invention have also been suggested. These are known from publications GB 183 241 (Figs. 1 and 2), US 4 905 876 (Fig. 5), US 4 913 324 (Figs. 1 and 4) and US 4 557 462 (Fig. 3), among others. However, their problem is that they do not function at high temperatures. Thus, US 30 4 557 462 suggests the use of a closing valve mainly for running light alloys that are easy to melt. The purpose of the invention is to provide a cock arrangement, which is fitted in the bottom of a metal casting vessel containing an opening, and which does not have the disadvantages of the closures mentioned above but which also functions 35 well at the high temperatures required by metal casting.
WO 2005/102563 PCT/F12005/000198 2 As mentioned above, the cock arrangement according to the invention consists of a channel body, through which the channel that continues the bottom opening of the metal casting vessel runs, and the side of which has a rotationally symmetrical recess that extends transversely through the channel. A rotatable closure body is 5 fitted in the recess, comprising a transversal hole at the depth of the said channel which can be turned in the same or another direction with respect to the channel to open and close the cock. The improvement of the cock arrangement is achieved so that the end of the closure body is hinged to the bottom of the recess and the contact surface between the closure body and the recess is rotationally symmetri 10 cal and smaller than the rotation surface of the recess. The concept "hinged" means that the end of the closure body is fitted in the bottom of the recess so that when rotated, the closure body otherwise remains essentially in place. The contact surface between the closure body and the recess refers to a surface that has a contact between the outer surface of the closure body and the 15 inner surface of the recess, when the end of the closure body is fitted in the bottom of the recess. Thus, it has been recognized that a closing valve-type metal casting cock func tions well at high temperatures, if the hole of the closure body is kept in alignment with the discharge channel of the melt and its sealing surfaces are symmetrical 20 and have small surface areas. The closure body is, for example, a cylinder or a cone, the end of which is hinged to the bottom of the recess of the channel body, the recess being identical in shape. The hole of the closure remains easily in alignment with the channel of the channel body. When the hole is aligned with the channel in this way, a considerably smaller contact surface between the pin and 25 the recess can be used compared with the rotation surface of the recess. Due to the small contact surface, heat transfer is under control and the temperature of the control devices will not increase excessively. The sealing contact surface is preferably from 10 to 80%, most preferably from 20 to 70% of the rotation surface. The contact surface is typically located in an area 30 that begins from the bottom and ends in a point in the recess that is between the channel and the outer edge of the recess. In the point where the sealing contact surface ends, the radii of rotation of the re cess and the closure body typically diverge, so that the radius of rotation of the closure decreases with respect to the radius of rotation of the recess, for example. 35 The recess and the closure body are preferably shaped like a truncated cone so that the contact surface therebetween is in the shape of a truncated cone that ex- WO 2005/102563 PCT/F12005/000198 3 pands from the bottom of the recess to its outer edge. Typically, the conical inner surface of the recess continues from the bottom to the edge, whereas the conical outer surface of the closure body shortly after the hole by decreasing the inclina tion of the conical surface, for example. 5 The rotational movement of the closure body of the cock arrangement according to the invention for opening and closing the channel can be provided by means of a shaft rod, which is joined to the closure body, and an actuator, such as a hydraulic motor, which rotates the rod through a lever arm. Metals, which can be cast by the cock arrangement according to the invention, 10 include cast iron, steel, aluminium, zinc, gold and other precious metals. The channel body and the closure body are suitably made of a refractory ceramic material, such as corundum or some other aluminium oxide-based mixture. The closure body is preferably provided with a coating, such as boron nitride, which provides air tightness. In addition to their fire resistance, ceramic materials are 15 characterized in their dimension stability that is due to a minor thermal expansion, enabling small tolerances in the dimensioning of the elements of the cock. The surface coming into contact with the recess of the closure body is preferably lubricated before installation, whereby good tightness is achieved and it is easy to rotate the closure body. 20 In the following, the invention is described in detail with the aid of an example and with reference to the appended figure that presents a cock arrangement according to one embodiment of the invention. Plate 1 is part of the bottom of the metal casting vessel that is provided with an opening, molten metal being provided above the plate. A cock arrangement 2 is 25 fitted thereto. The cock arrangement 2 comprises a channel body 3 that is like a mouth brick, and the molten metal coming from the hole of the plate 1 flows through the channel 4 of the channel body. The side of the channel body 3 also has a hollow recess 5 with the shape of a truncated cone, extending transversally through and past the channel 4. 30 The cock arrangement 2 also has a rotatable closure body 6, which is fitted in the said recess 5 and is, thus, partly of the same conical shape. The closure body 6 has a transversal hole 7 with respect to its length, its axis essentially seizing or joining the axis of the channel 4. The end 8 of the closure body 6 is hinged to the bottom 9 of the recess. In this way, the clearance of the closure body 6 and the 35 recess 5 from the bottom all the way past the channel 4 and the hole 7 is accurate WO 2005/102563 PCT/F12005/000198 4 and will not change according to the temperature, because the guiding surface is near the clearance at the same temperature. The contact surface that seals the closure body 6 and the recess 5 extends from the bottom 9 of the recess 5 all the way past the channel 4 and the hole 7. It ends 5 at the point 11 of the recess 5, which is between the channel 4 and the outer edge 10 of the recess 5. It preferably ends closer to the channel 4 than to the outer edge 10. The contact ends so that the inclination of the closure body 6 decreases from the point 11 outwards. Thus, the outer surface of the closure body 6 does not remain in contact with the inner surface of the recess 5 in the outer area, wherein 10 the temperatures of the surfaces differ from one another to a larger extent. It is obvious to those skilled in the art that various applications of the invention are not limited to the example presented above but can vary within the appended claims. For example, it is possible to place several superimposed mouth bricks under the casting vessel, together forming the discharge channel for the molten 15 metal. An improvement to the bottom cock of a metal casting vessel is synergistically pro vided by the above combination, wherein the end of the closure body is hinged to the bottom of the recess and, at the same time, the rotational contact surface is radically reduced. The new solution provides a better result than the previous clos 20 ing valves and sliding closure units.