Conventionally there is a permanent mold casting machine that manufactures casting products by pouring the molten metal from a holding furnace via a stoke into a cavity that is formed within the horizontally split molds that consist of the upper and lower molds.
For example, the permanent mold casting machine disclosed in the publication of the Japanese Patent Application, Publication No. S63-273561, belongs to this type of machine. In this permanent mold casting machine, the upper mold is attached to the lower surface of the upper mold base. It is movable up and down and is supported by four supporting frames that are installed around a holding furnace placed on a base table, wherein both (1) contacting the upper mold with the lower mold so as to form a product cavity between the upper mold and the lower mold that is disposed on the lower mold base that is fixed to the supporting frames, and (2) lifting the upper mold so as to form the space for setting of a core and for taking out products between the upper and lower molds, are carried out by the operation of lifting and lowering the upper mold base alone.
The permanent mold casting machine of the conventional structure as described above has a long distance for an upper mold base to travel when it is lifted or lowered. So, the four supporting frames must be very high. Accordingly the supporting frames are apt to bend if they are to support a large weight. Further, when the upper mold and the lower mold are separated, a large load presses the supporting frames. As a result, the supporting frames are apt to bend when the upper mold is opened (mold opening), causing the upper mold to slide in a horizontal direction so that the casting product that is lifted with the upper mold may interfere with the lower mold and be damaged or the washing that is disposed on the lower mold may come off. These problems are particularly conspicuous when the upper and the lower molds have a number of product cavities or complex product cavities. Further, the distance of travel of the upper mold base is long such that the hydraulic cylinder and hydraulic unit that lift and lower the upper mold base should have higher capacities. They become expensive.
In view of these problems, the present invention provides a method to move an upper mold in a permanent mold casting machine and the permanent mold casting machine used for the method, wherein the contact of the upper mold with the lower mold and its separation from the lower mold are carried out by means of a mold clamping mechanism, to which the upper mold is attached, so that the upper mold can carry out the scheduled work even if the distance of travel of the lifting and lowering frame becomes longer, and wherein, further, forming the space for setting of a core and for taking out a product between the upper and lower molds is achieved by the lifting of the mold clamping mechanism, and the upper mold (see the publication of Japanese Patent Application, Publication No. 2004-255406).
However, for the method and the permanent mold casting machine of Publication No. 2004-255406 a hydraulic cylinder and hydraulic unit having higher capacities are not required because of the use of the mold clamping mechanism. But the actuator of the mold clamping mechanism is required to generate a greater power than that required to lift the mold clamping mechanism and the upper mold so that the lifting and lowering frame should not be moved by the force generated at the time of the mold opening. There still remains a problem. Namely, the method and the permanent mold casting machine used for the method must have a very high capacity, especially if the actuator is operated by an electric cylinder, thus making it difficult to increase the speed of the machine.