GB1588592A - Casting apparatus - Google Patents

Description

(54) CASTING APPARATUS (71) We, HONDA KWZOKU GIJUTSU KABUSHIKI KAISHA, a corporation of Japan, of 1620, Aza Kamegafuchi, Ooaza Matoba, Kawagoe-shi, Saitama-ken, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to casting apparatus.

In the past so-called "low pressure casting apparatus" has widely been known in which molten metal stored in a closed crucible is transferred into a mold, placed on top thereof, under the pressure of gas blown into the crucible. Such casting apparatus has a number of advantages over conventional gravity casting apparatus, including an exceedingly high yield of molten metal due to the fact that there is no need for any riser system on the mold used. and ease of automation. On the other hand, the known apparatus has involved various disadvantages as follows: First, as the molten metal in the crucible is consumed or replenished, the lift distance of molten metal, from the level in the crucible to the cavity in the mold placed on top thereof, varies to a large extent.

This results in variations in casting quality, causing more or less change in pouring pressure and other casting conditions even with a fixed gas-blowing condition. Secondly, any leakage of gas blown into the crucible naturally causes some variation in pouring conditions, and the high temperature of the crucible and the sugstantial extent of its seal area make it extremely difficult to maintain any perfect airtightness of the crucible for an extended period of use.

Thirdly, the known apparatus necessitates the use of an elongate sprue pipe or socalled "stork tube", which must be held at all times in communication with the interior of the crucible below the level of the molten metal therein. This not only causes a tendency for oxides of molten metal to adhere to the inner wall of the sprue pipe and then to separate therefrom to flow into the mold during the pouring operation, but also involves the danger that a portion of the sprue pipe, especially that portion thereof which is dipped in the molten metal, partly dissolves out into the latter.

It will be apparent that such phenomena adversely affect the quality of castings obtained.

According to the present invention there is provided a casting apparatus comprising a base; a heating furnace pivotally secured to the base for vertical tilting movement; a crucible accommodated in the furnace and having a first portion adjacent the pivot connection of the furnace with the base and having an open top closed by a sprue plate formed with at least one sprue hole, and a second portion remote from the pivot connection of the furnace with the base and having its top formed with a gas blow hole and a replenishing hole for the supply of molten metal to be cast; a mold set on the sprue plate and interiorly communicating at all times with the crucible through the sprue hole(s) in the sprue plate; an oil-hydraulic cylinder connected between the furnace and the base for controllably tilting the furnace about the pivot connection thereof with the base at any desired speed thereby to cause molten metal held in the crucible to flow down under gravity into the mold at an optimum rate; and gas blower means connected with the gas blow hole for blowing, after the tilting of the crucible, gas into the crucible above the level of molten metal therein thereby to apply pressure to the level surface of the molten metal in the crucible.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a side elevational view, in cross section, of a casting apparatus; Figure 2 is a view similar to Figure 1, showing the apparatus in pouring position; Figure 3 is a front elevational view, in cross section, of the apparatus shown in Figure 1; and Figure 4 is a fragmentary cross-sectional view taken along the line IV-IV in Figure 3.

Referring to Figures 1 to 3, reference numeral 1 indicates a holding furnace provided on one side with a burner 2 and in which furnace a closed crucible 3 is accommodated. The crucible 3 is fixedly secured to the furnace 1 by means of a number of clamps 4 (only one of which is shown in Figure 1) and the front and rear (first and second) portions of the crucible 3 are closed at the top, respectively, by a top wall comprising a sprue plate 11 and a fixed cover 12. The fixed cover 12 is formed, for replenishment of molten metal, with an opening which is closed by a removable cover 13. The sprue plate 11 is formed oF a base plate 1 lea and an overlaying thermally insulating plate- 1 ib. As shown, sprue blocks 14 are embedded in. the insulating plate 1 lib. Reference numeral 16 indicates sprue holes extending through the sprue blocks 14 and the base plate 1 la, which holes are normally in direct communication with the interior space of the crucible 3 above the level of molten metal 5 therein, as shown in Figures 1 and 3.

Reference numeral 6 indicates a moldsupporting frame which is fixed to the top of the crucible 3 by means of an appropriate number of clamps 15 and 15' to surround the sprue plate 11. A pair of aligned pivot shafts 6a and 6b extend from the sides of the mold-supporting frame 6 and are rotatably supported by respective bearings 9 which. are mounted on top of a pair of upstanding support colums 8 provided on a platform base 7 of the apparatus.

In this manner, the structure including the furnace 1 and crucible; 3 is- mounted on the platform base 7 for free vertical tilting movement. Reference numeral 10 indicates an oil-hydraulic tilting actuator pivotally supported at its base end on the platform base 7, the actuator rod being pivotally connected åt its distal end with the riddle portion of thts mold-supporting frame 6 on one side thereof. With this arrangement, it will readily be noted that the furnace 1 can be tilted together with. the crucible 3 from the horizontal position shown in Figure 1 to any desired inclined position about the common axis of the bearings 9, as illustrated in Figure 2.

The casting mold 17 is arranged in the casting apparatus and consists of a lower and an upper mold section 17a and 17b.

The lower mold section 17a is fixedly mounted on the mold-supporting frame 6 so.that the cavity in the mold section is held in commuication with the sprue holes 16 formed in the sprue plate 11. The moldsupporting frame 6 is provided with a plurality of upstanding guide posts 19 on the top of which a stationary plate 21 is fixedly mounted. A movable plate 20 is also mounted on the guide posts 19 intermediate the ends thereof for vertical sliding movement. Reference numeral 22 indicates an oil-hydraulic actuator mounted on the stationary plate 21 and operatively connected with the movable plate 20 to serve the purpose of raising and lowering the latter along the guide posts 19. The upper mold section 17b of the mold 17 is fixedly mounted on the underside of the movable plate 20. In Figure 2, reference numeral 23 indicates a casting formed in the mold 17.

As shown in Figures 3 and 4, the upper mold section 17b is provided on opposite sides thereof with slidable inserts 17c the inner end faces of which are inclined inwardly downward so that, at the end of casting operation, when the upper mold section 17b is raised apart from the lower mold section 17a, the casting 23 remains securely held in the upper mold section 17b. To serve the purpose of releasing the casting 23 from the upper mold section 17b, ejector pins 24 are provided which extend through the mold section l7b and are fixed at the top to an ejector plate 25, which is actuated by knockout pins 26 extending downwardly from the stationary plate 21.

As shown in Figures l and 2, the fixed cover 12 of crucible 3 is formed with a gas inlet or blow hole 27 with which a gas blower means 29 is connected through the medium of a gas pipe 28. The gas blower means 29. operates at an appropriate time in the cycle of casting .operation. The gaseous medium employed in the system should be an inert gas - such as nitrogen gas. In Figures 1 and 2, reference numeral 30indicates a thermocouple arranged in the crucible 3 to determine the temperature of the molten metal 5.

.Description will next be made of the operation as illustrated. At first, when the crucible 3 is in horizontal position, the oil-hydraulic actuator 22 is energized to extend downwardly so that the movable plate 20 is lowered to place the upper mold section 1 7b in mating contact with the lower mold section 17a. Following this mold setting operation, the oil-hydraulic actuator 10 is extended, as shown in Figure 2, to tilt the structure including the furnace 1, the crucible 3 and the set mold 17 pivotally about the axis of the bearings 9.

Simultaneously with this, the molten metal in the crucible 3 flows under gravity into the mold 17 through the sprue holes 16.

It is here to be noted that, since the mold 17 is progressively tilted with the flow of molten metal into the mold, air previously held in the mold is expelled smoothly through the joint area between the mold sections and thus an effective replacement of the air by the molten metal is ensured.

It is also to be noted that the pouring rate and other casting conditions can be precisely controlled as desired simply by adjusting the tilting speed of the crucible 3 and hence the mold 17 thereon.

After this pouring of the molten metal, gas is blown into the crucible by operation of the gas blower device 29 so that gas pressure is exerted upon the surface of molten metal 5 in the crucible 3 and is transmitted to the molten metal in the mold 17 to act thereon "as a metal loading pressure. The loaded or pressurized state of molten metal in the mold 17 is maintained until the molten metal solidifies so that a casting 23 of unusually compact and uniform structure, substantially without blow holes or shrinkage cavities, is obtained.

Subsequently, the gas blower device 29 is rendered inoperative to reduce the pressure in the crucible 3 and the oil-hydraulic actuator 10 is retracted to restore the com lined furnace and crucible structure 113 to its normal horizontal position. Simultaneously with this, the oil-hydraulic actuator 22 is retracted to move the upper mold section 17b upwardly through the medium of the movable plate 20 so that the casting 23, held on the upper mold section 17b by means of the slidable inserts 17c, is raised apart from the lower mold section 17a. Subsequently, the slidable inserts 17c are retracted outwardly while the movable plate 20 continues to rise so that the knockout pins, abutting against the top surface of the ejector plate 25, hold the latter against further rising movement. As a result, the ejector pins 24 are pushed downwardly through the rising upper mold section 17b into the mold cavity on the underside thereof, thus ejecting the casting 23 downwardly out of the upper mold section 17b.

To summarize, molten metal held in the closed crucible flows under gravity into a mold set on the crucible as the latter is tilted and this not only enables smooth replacement by molten metal of the air previously held in the mold, but also makes it possible precisely to set the desired pouring conditions, free of any factor of external disturbance, simply by controlling the tilting speed of the crucible. Accordingly production of castings that are particularly stabilized and of uniform quality tends to be ensured at all times. In addition, the pouring/casting operation can be re peated, from one replenishment of the crucible, simply by repetitively tilting the crucible and hence operation can be readily automatized. Further, as gas is blown into the crucible after the molten metal has been poured into the mold, and as the gas pressure induced in the crucible is all directed through the mass of molten metal into the mold as a metal loading pressure, stable production of high-quality castings is facilitated with many fewer blowholes or shrinkage cavities than is the case with conventional low pressure casting apparatus in which gas is blown into the crucible under substantially the same pressure as used in the present apparatus. It will be apparent that, like conventional low-pressure casting apparatus, the present apparatus is advantageous in that the yield of molten metal is especially high on account of the fact that no riser system is required for molds used and that the quality of products is not effected in any adverse manner even if there be more or less gas leakage from the crucible.

Further, since the present apparatus is arranged so that, as long as the crucible is held horizontal, the sprue hole or holes in the mold set thereon islare in direct communication with the air space in the crucible above the surface of molten metal, the molten metal, when the crucible is tilted, reaches the sprue hole(s) directly.

On account of this, any trouble as caused in ordinary low-pressure casting apparatus by the use of a stork tube for passage of molten metal to the mold is minimised and molten metal can be poured into the mold under optimum conditions to form quality castings with ease as long as the crucible has an appropriate number of sprue holes formed in its top wall at proper locations.

WHAT WE CLAIM IS:- 1. A casting apparatus comprising a base; a heating furnace pivotally secured to the base for vertical tilting movement; a crucible accommodated in the furnace and having a first portion adjacent the pivot connection of the furnace with the base and having an open top closed by a sprue plate formed with at least one sprue hole, and a second portion remote from the pivot connection of the furnace with the base and having its top formed with a gas blow hole and a replenishing hole for the supply of molten metal to be cast; a mold set on the sprue plate and interiorly communicating at all times with the crucible through the sprue holes in the sprue plate; an oil-hydraulic cylinder connected between the furnace and the base for controllably tilting the furnace about the pivot connection thereof with the base at any desired speed thereby to cause molten metal held in the crucible to flow down under gravity into the mold at an optimum rate; and gas blower means connected with the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. through the joint area between the mold sections and thus an effective replacement of the air by the molten metal is ensured. It is also to be noted that the pouring rate and other casting conditions can be precisely controlled as desired simply by adjusting the tilting speed of the crucible 3 and hence the mold 17 thereon. After this pouring of the molten metal, gas is blown into the crucible by operation of the gas blower device 29 so that gas pressure is exerted upon the surface of molten metal 5 in the crucible 3 and is transmitted to the molten metal in the mold 17 to act thereon "as a metal loading pressure. The loaded or pressurized state of molten metal in the mold 17 is maintained until the molten metal solidifies so that a casting 23 of unusually compact and uniform structure, substantially without blow holes or shrinkage cavities, is obtained. Subsequently, the gas blower device 29 is rendered inoperative to reduce the pressure in the crucible 3 and the oil-hydraulic actuator 10 is retracted to restore the com lined furnace and crucible structure 113 to its normal horizontal position. Simultaneously with this, the oil-hydraulic actuator 22 is retracted to move the upper mold section 17b upwardly through the medium of the movable plate 20 so that the casting 23, held on the upper mold section 17b by means of the slidable inserts 17c, is raised apart from the lower mold section 17a. Subsequently, the slidable inserts 17c are retracted outwardly while the movable plate 20 continues to rise so that the knockout pins, abutting against the top surface of the ejector plate 25, hold the latter against further rising movement. As a result, the ejector pins 24 are pushed downwardly through the rising upper mold section 17b into the mold cavity on the underside thereof, thus ejecting the casting 23 downwardly out of the upper mold section 17b. To summarize, molten metal held in the closed crucible flows under gravity into a mold set on the crucible as the latter is tilted and this not only enables smooth replacement by molten metal of the air previously held in the mold, but also makes it possible precisely to set the desired pouring conditions, free of any factor of external disturbance, simply by controlling the tilting speed of the crucible. Accordingly production of castings that are particularly stabilized and of uniform quality tends to be ensured at all times. In addition, the pouring/casting operation can be re peated, from one replenishment of the crucible, simply by repetitively tilting the crucible and hence operation can be readily automatized. Further, as gas is blown into the crucible after the molten metal has been poured into the mold, and as the gas pressure induced in the crucible is all directed through the mass of molten metal into the mold as a metal loading pressure, stable production of high-quality castings is facilitated with many fewer blowholes or shrinkage cavities than is the case with conventional low pressure casting apparatus in which gas is blown into the crucible under substantially the same pressure as used in the present apparatus. It will be apparent that, like conventional low-pressure casting apparatus, the present apparatus is advantageous in that the yield of molten metal is especially high on account of the fact that no riser system is required for molds used and that the quality of products is not effected in any adverse manner even if there be more or less gas leakage from the crucible. Further, since the present apparatus is arranged so that, as long as the crucible is held horizontal, the sprue hole or holes in the mold set thereon islare in direct communication with the air space in the crucible above the surface of molten metal, the molten metal, when the crucible is tilted, reaches the sprue hole(s) directly. On account of this, any trouble as caused in ordinary low-pressure casting apparatus by the use of a stork tube for passage of molten metal to the mold is minimised and molten metal can be poured into the mold under optimum conditions to form quality castings with ease as long as the crucible has an appropriate number of sprue holes formed in its top wall at proper locations. WHAT WE CLAIM IS:-

1. A casting apparatus comprising a base; a heating furnace pivotally secured to the base for vertical tilting movement; a crucible accommodated in the furnace and having a first portion adjacent the pivot connection of the furnace with the base and having an open top closed by a sprue plate formed with at least one sprue hole, and a second portion remote from the pivot connection of the furnace with the base and having its top formed with a gas blow hole and a replenishing hole for the supply of molten metal to be cast; a mold set on the sprue plate and interiorly communicating at all times with the crucible through the sprue holes in the sprue plate; an oil-hydraulic cylinder connected between the furnace and the base for controllably tilting the furnace about the pivot connection thereof with the base at any desired speed thereby to cause molten metal held in the crucible to flow down under gravity into the mold at an optimum rate; and gas blower means connected with the

gas blow hole for blowing. after the tilting of the crucible, gas into the crucible above the level of molten metal therein thereby to apply pressure to the level surface of the molten metal in the crucible.

2. A casting apparatus substantially as hereinbefore described with reference to the accompanying drawings.