GB2323804A

GB2323804A - Molten metal supply

Info

Publication number: GB2323804A
Application number: GB9806820A
Authority: GB
Inventors: Hirotake Usui; Kazuya Matsuura; Yoshiaki Matsuda; Yuji Maeda; Syozo Minami; Masao Shibutani; Toshio Hashioka
Original assignee: Ryobi Ltd
Current assignee: Ryobi Ltd
Priority date: 1997-03-31
Filing date: 1998-03-30
Publication date: 1998-10-07
Also published as: GB9806820D0; JPH10272550A

Abstract

A molten metal supplying method capable of performing a simple and time-saving shot, and a compact molten metal supply device having a reduced number of components and capable of reducing the shot cycle are provided. A float 5 connected to a float drive unit 6 is immersible in molten metal 4 held in a holding furnace 2. A supply conduit 3 is connected between the holding furnace 2 and an injection sleeve 17. The sleeve has an injection gate 17a at a position equal to a constant surface level (CL) of the molten metal in the holding furnace immediately before injection. Further, are provided a surface level sensor 8 for detecting the constant surface level and generating the constant surface level signal, and a control unit 9 transmitting a drive signal to the float drive unit in response to the detection signal so as to downwardly move the float by a predetermined amount in order to supply a predetermined amount of molten metal into the injection sleeve.

Description

MOLTEN METAL SUPPLYING HETHOD AND MOLTEN METAL SUPPLY DEVICE The present invention relates to a molten metal supplying method and a molten metal supply device for supplying a molten metal in a holding furnace into an injection sleeve through a supply conduit.

For supplying a molten metal into an injection sleeve in a die-casting method, various methods referred to as a direct supply method have been proposed and put into prac tice in which the molten metal in the holding furnace is directly supplied into the injection sleeve.

For example, a molten metal supply device disclosed in Japanese Patent Application Kokai No. Sho 63-119965 includes a holding furnace for holding a molten metal1 a float immersible into the molten metal retained in the holding furnace, a surface level sensor for detecting a surface level of the molten metal in the holding furnace, a float driving unit for vertically moving the float, a supply conduit connected between the holding furnace and an injection sleeve for supplying the molten metal in the holding furnace into the injection sleeve, and an electromagnetic pump provided at the supply conduit for drivingly feeding the molten metal toward the injection sleeve. The float drive unit is operated for vertically moving the float so as to constantly provide a predetermined surface level of the molten metal in the holding furnace0 and a suction head of the electromagnetic pump is held at a constant level to provide a constant amount of outlet of the molten metal toward the injection sleeve.

With this arrangement, the surface level is controlled by the surface level sensor and the float. However, the electromagnetic valve used as the molten metal supplying means is actuated after the surface level control by the vertical movement of the float. Therefore, molten metal supplying cycle may be prolonged, and an expensive apparatus results.

Japanese Patent Application Kokai No.Sho-56-105864 discloses a molten metal supply device having a holding furnace, a float, a float drive unit, and a slide valve slidably movable for opening and closing a molten metal outlet in the holding furnace. With this arrangement, it would be impossible to completely close the molten metal outlet by the slide valve. If the molten metal leakage occurs at the outlet, accuracy in supply amount of the molten metal into the injection sleeve is greatly lowered.

A molten metal supply device disclosed in Japanese Patent Application Kokai No. Sho-57-88963 includes a holding furnace, a float immersible into the molten metal retained in the holding furnace, a float drive unit for vertically moving the float, a supply conduit connected to an injection sleeve for supplying the molten metal in the holding furnace into the injection sleeve, a supply cylinder/piston mechanism disposed to partition the holding furnace and connected to the supply conduit, and a valve for selectively introducing the molten metal into the supply cylinder. Surface level of the molten metal is controlled by the vertical movement of the float. The valve is moved to introduce a predetermined amount of the molten metal into the cylinder, and then the piston is driven to supply the predetermined amount of the molten metal into the injection sleeve through the supply conduit.

According to this arrangement, an entire device is intricate due to a separate provision of the supply cylinder. Further, opening and closing motion of the valve for the holding furnace is required, to prolong the molten metal supplying cycle.

Further, Japanese Utility Model Publication No. Hei-744377 discloses a molten metal supply device provided with a holding furnace holding the molten metal, a float immersible into the molten metal retained in the holding furnace for controlling the surface level of the molten metal, a com- pression furnace having a sealed structure and provided in the holding furnace, a valve for selectively communicating the compression furnace with the holding furnace, a compres sion mechanism for compression within the compression furnace, and a supply conduit connecting between the compres sion furnace and the injection sleeve. The float is vertically moved while opening the valve to make the surface level in the holding furnace into alignment with a predetermined level, and then, the valve is closed and the compres sion is applied into the compression chamber to supply the predetermined amount of the molten metal into the injection sleeve.

According to the disclosed device, entire shot cycle is prolonged due to the valve opening and closing operation.

Further, entire device becomes bulky and complicated due to the provision of the compression furnace and the compression mechanism.

Japanese Patent Application Kokai No. Hei-8-281412 discloses a molten metal supply device provided with a holding furnace, a partition wall for dividing the holding furnace into a holding chamber and a supply chamber fluid- com- municatable therewith, a supply conduit connecting the supply chamber with the injection sleeve for supplying the molten metal in the supply chamber into the injection sleeve of a die-casting device, a shut-off means movable between its communication position and its blocking position for selectively communicating and blocking the holding chamber with and from the supply chamber. a surface level detection means for detecting a predetermined surface level of the molten metal in the holding furnace, a first immersion body movable in a vertical direction in the holding chamber and moved downwardly until a predetermined surface level is detected when the shut-off means is at its communication position for introducing the molten metal in the holding chamber into the supply chamber, and a second immersion body movable in a vertical direction in the supply chamber and moved downwardly when the shut-off means is at its blocking position for introducing the molten metal in the supply chamber into the injection sleeve. A bellows is provided which separates the molten metal in the supply chamber from an atmosphere and which is movable interlockingly with the second immersion body. An inert gas application means is fluidly connected to an interior of the bellows for introducing an inert gas into the bellows. The inert gas application means maintains the supply chamber at an atmospheric pressure only when the shut-off means is at its communication position.

According to this device, a complicated and bulky device results, which problems would be the same as those of the Japanese Patent Application Kokai No. Sho57-88963 and the Japanese Utility Model Publication No. Hel7-44377.

As described above, according to the molten metal supply device, in addition to the mechanism including the float for adjusting the surface level of the molten metal in the holding furnace irrespective of the amount of the molten metal in the holding furnace, the mechanism, such as pneumatic pressure mechanism, the additional float and the supply cylinder mechanism for supplying the molten metal into the injection sleeve is also required, and/or the valve for selectively blocking the molten metal passage is provided. Accordingly, bulky and complicated device results, and a great numbers of mechanical components are required. Furthermore, as described above, the problem of the leakage of the molten metal, and prolongation of the shot cycle may occur due to the employment of the valve.

It is therefore, an object of the present invention to provide a molten metal supplying method capable of performing a simple and time-saving shot cycle.

Another object of the present invention is to provide a molten metal supply device having a reduced number of com- ponents and capable of reducing the shot cycle.

These and other objects of the present invention will be attained by a molten metal supplying method for supplying a molten metal in a holding furnace into an injection sleeve connected to the holding furnace through a supply conduit by a vertical movement of a float immersible into the molten metal in the holding furnace, the method including the steps of vertically moving the float, and then downwardly moving the float. In the vertically moving step, the float is vertically moved until a surface level of the molten metal in the holding furnace becomes coincident with a constant surface level which is equal to a level immediately before an injection gate of the injection sleeve. In the downwardly moving step, the float is downwardly moved by a predetermined distance for supplying a predetermined amount of the molten metal into the injection sleeve only through the supply conduit, after the surface level of the molten metal reaches the constant surface level.

In another aspect of the present invention, there is provided a molten metal supply device including a holding furnace for holding a molten metal, a float immersible into the molten metal held in the holding furnace, a float drive unit for vertically moving the float, a supply conduit connecting between the holding furnace and the injection sleeve for feeding the molten metal in the holding furnace to the injection sleeve, a surface level sensor for detecting a constant surface level of the molten metal in the holding furnace and generating a constant surface level detection signal, and a control means transmitting a driving signal to the float drive unit in response to the detection signal to downwardly move the float by a predetermined distance in order to supply a predetermined amount of the molten metal to the injection sleeve only through the supply conduit.

The injection sleeve has an injection gate open at a level equal to the constant surface level in the holding furnace at a state immediately before the injection.

The present invention will be more clearly understood from, the following description, given by way of example only, with reference to the accompanying drawings in Which: Fig. 1 is a schematic cross-sectional view showing a molten metal supply device according to a first embodiment of the present invention; Fig. 2 is a schematic view for description of a preparatory state for the molten metal supply in the molten metal supply device according to the first embodiment of the present invention: Fig. 3 is a schematic view for description of a supplying state for supplying the molten metal to an injection sleeve in the molten metal supply device according to the first embodiment of the present invention: Fig. 4 is a schematic view for description of a state immediately after the supply of the molten metal to the injection sleeve in the molten metal supply device according to the first embodiment of the present invention: Fig. 5 is a schematic view for description of a downwardly moving state of a float for the next preparation for the molten metal supply in the molten metal supply device according to the first embodiment of the present invention; and, Fig. 6 is a schematic cross-sectional view showing a molten metal supply device according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED RBOD1MENTS A molten metal supplying method and molten metal supply device according to one embodiment of the present invention will be described with reference to Figs. 1 through 5.

Fig. 1 shows a layout of a die-casting machine 11 and a molten metal supply device 1. The die-casting machine 11 has a metal mold provided with a fixed die holder 12 holding a fixed die 13 and a movable die holder 15 holding a movable die 14. A mold cavity 16 is defined by the fixed die 13 and the movable die 14. An injection sleeve 17 is fixed to the fixed die holder 12. An interior of the injection sleeve is in communication with the mold cavity 16 through a runner portion 18.

An injection gate 17a is formed in the injection sleeve 17, and a plunger tip 19 is reciprocally slidably movably provided in the injection sleeve 17. The plunger tip 19 is adapted to selectively open and close the injection gate 17a by the reciprocal sliding movement. That is, when the plunger tip 19 is positioned at its retracted position, the injection gate 17a is open as shown in Figs. 1 through 3, so that a molten metal can be filled into the injection sleeve through the injection gate 17a. If the plunger tip 19 is moved ahead, the molten metal supplied in the injection sleeve is introduced into the mold cavity 16, and at the same time, an outer peripheral surface of the plunger tip 19 closes the injection gate 17a to shut off the introduction of the molten metal into the injection sleeve.

The molten metal supply device 1 is fluidly connected to the injection gate 17a of the injection sleeve 17. The molten metal supply device 1 includes a holding furnace 2 for holding the molten metal. The holding furnace 2 is formed with a molten metal outlet port 2a. A supply conduit 3 is provided for connecting the molten metal outlet port 2a to the injection gate 17a. The injection gate 17a of the injection sleeve 17 is positioned at a vertical level approximately the same as a molten metal surface level in the holding furnace 2. That is, the vertical level of an open end of the injection gate 17a is coincident with a constant surface level described later in a state where the plunger tip is at its retracted position.

A float 5 immersible into the molten metal 4 is provided in the holding furnace 2, and a float driving unit 6 is connected to the float 5 for moving the float 5 in a vertical direction thereby controlling the surface level 4a of the molten metal or supplying a predetermined amount of the molten metal 4 into the injection sleeve 17 upon downward movement of the float 5. A heater 7 i8 immersed in the molten metal 4 in the holding furnace 2 for maintaining a temperature of the molten metal at a predetermined temperature. A surface level sensor 8 is provided for detecting a predetermined height of the surface level 4a (constant surface level CL) and generating a constant surface level detection signal. The constant surface level CL is a surface level of the molten metal in the holding surface 2 and is a surface level coincident with a level immediately below the open end of the injection gate 17a by way of the fluid communication through the supply conduit 3. By the vertical movement of the float 5, an arbitrary surface level 4a can be coincident with the constant surface level CL.

The float driving unit 6 and the surface level sensor 8 are electrically connected to a control unit 9. In the control unit 9, a constant surface level can be set, and at the same time, a descending distance of the float 5 from the constant surface level, and the descending distance corresponding to an amount of the molten metal necessary for one shot, can be computed. Thus, the control unit 9 trans mits a driving signal to the float driving unit 8 in response to the constant surface level detection signal generated from the surface level sensor 8 for moving the float downwardly by a predetermined distance.

With this arrangement, if the plunger tip 19 is at its retracted position, the injection gate 17a is open. During this state, the float drive unit 6 moves the float 5 downwardly until the surface level a becomes coincident with the constant surface level CL, that Is, until the constant surface level detection signal is generated from the surface level sensor 8. In accordance with a sinking volume of the float 5, the surface level is changed in the vertical direction. When the constant surface level detection signal is generated, the surface level of the molten metal in the supply conduit 3 reaches a level immediately below the open end of the injection gate 17a of the injection sleeve 17 as shown in Fig. 2. On the other hand, if a new molten metal is supplemented into the holding furnace 2 by a molten metal supplementing mechanism (not shown), the float is moved upwardly in accordance with the increase in supplementing amount to bring the surface level into coincident with the constant surface level. This is a preparatory state for injection.

The float drive unit 6 is driven continuously from the preparatory state so as to sink the float 5 by a predetermined amount Into the molten metal 4 as shown in Fig. 3. The descending distance corresponds to an amount of the molten metal necessary for one shot, and the distance is provisionally computed in the control unit 9. In accordance with the downward movement of the float 5, surface level in the holding furnace 2 is elevated, and simultaneously. the molten metal is supplied into the injection sleeve 17 through the injection gate 17a. Thus, a predetermined amount of molten metal can be supplied into the injection sleeve 17 through the supply conduit 3. In this way, the adjustment of the surface level of the molten metal and the supply of the molten metal into the injection sleeve are performed without any timed interruption and by the identical mechanism. Ac cordingly, contrary to the conventional device, variation in the supply amount of the molten metal due to the leakage of the molten metal through a valve does not occur. Consequently, highly accurate molten metal supply can be achieved.

When the predetermined amount of the molten metal is filled in the injection sleeve 17. the plunger tip 19 is moved in its advancing direction as shown in Fig. 4, 50 that the molten metal in the inject ion sleeve 17 is filled in the mold cavity 16 through the runner portion 18. In this case, the plunger tip 19 closes the injection gate 17a to block communication between the supply conduit 3 and the injection sleeve 17.

Then, as shown in Fig. 4, the float 5 is moved upwardly to the position shown in Fig. 2 in order to coincide the surface level with the constant surface level CL for the next shot. In accordance with the ascent movement of the float 5, the surface level 4a in the holding furnace 2 is lowered, and at the same time, the surface level at a position immediately below the injection gate 17a is also lowered. In this case, the lowered amount corresponds to the supplying amount of the molten metal into the injection sleeve 17 in the previous shot. Then, as shown in Fig. 5, the float 5 is moved downwardly for performing detection of the constant surface level.

As described above, the supply of the molten metal in tithe injection sleeve 17 can be performed only by the vertical movement of the float. Thus, consecutive operation shown in Figs. 2 through 5 can be performed continuously within a short period, to thus reduce the shot cycle.

A molten metal supply device according to a second embodiment of the present invention will next be described with reference to Fig. 6. The second embodiment pertains to a modification to the float and the float drive unit of the first embodiment. That is, in the second embodiment, a float is divided into an inner float 5A and an outer float 5B provided coaxially therewith. The outer float 5B has an inner peripheral surface defining an inner cylindrical space portion, and the inner sleeve 5A is movable slidably with respect to the inner peripheral surface. A volume of the in ner sleeve 5A is extremely smaller than that of the outer sleeve SB. A float drive unit includes an inner float drive unit 6A for driving the inner float 5A, and an outer float drive unit 6B for driving the outer float SB. The inner and outer floats 5A and 5B are movable in a vertical direction independent of each other or in synchronism with each other.

With this arrangement, for making the surface level into coincidence with the constant surface level, both the inner and outer floats 5A and 5B are simultaneously moved downwardly in such a manner that the inner float 5A is positioned in the inner cylindrical space of the outer float 5B.

Then, only the inner float SA is moved downwardly so as to supply the predetermined amount of the molten metal into the injection sleeve 17. By this operation, a smaller amount of molten metal can be precisely supplied into the injection sleeve. That is, during the supplying operation, it is unnecessary to move the float having a large volume. Accordingly, turbulence of the molten metal in the holding furnace can be prevented. Further, operation control to the inner float 5A can be performed easily, since the latter has a smaller mass providing the smaller inertia, thereby facilitating the control of the molten metal supply amount. In the molten metal supply device according to the second embodiment, the float is divided into the inner float and the outer float, and these inner and outer floats can be driven integrally with or independently of each other. Therefore, 8 reduced amount of the molten metal can be supplied with high accuracy, and corrugation at the surface level of the molten metal can be eliminated, and further, easy drive control to the float results.

According to the molten metal supplying method of the present invention, the step of coinciding the surface level of the molten metal with the constant surface level and the step of supplying the predetermined amount of the molten metal into the injection sleeve are carried out by only a continuous vertical movement of the float. As a result, molten metal supplying cycle can be performed with a reduced time period, and a molten metal supplying control can be facilitated.

Further, according to the molten metal supply device of the present invention, only the continuous vertical movement of the float is required in order to coincide the surface level of the molten metal with the constant surface level and to supply the predetermined amount of the molten metal into the injection sleeve. As a result, molten metal supplying cycle can be reduced, and the molten metal supply ing control can be facilitated. Further, a valve for blocking a molten metal passage is not required. Therefore, the problem of the molten metal leakage does not occur, to thus maintain the molten metal supplying amount with high accu racy. Furthermore, the electromagnetic valve for pressurizingly feeding the molten metal is not required. As a result, entire mechanism is simplified, and a compact molten metal supply device results.

While the invention has been described in detail and with reference to the specific embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. For example, in the depicted embodiment, a start timing of the downward movement of the float 5 after the detection of the constant surface level is contiguous with the preparatory state of injection.

However, the downward movement can be started in accordance with an injection start signal transmitted from the die casting machine 11.

Further, in the depicted embodiment, upward movement of the float 5 during injection (Fig. 4) and the downward movement of the float 5 for bringing the surface level into coincidence with the constant surface level (Fig. 5) are performed independently. However, it is possible to only move the float 5 upwardly by a computed amount in such a manner that the upwardly moving distance of the float corresponding to the predetermined supply amount of the molten metal into the injection sleeve 17 and the downwardly moving distance of the float 5 in Fig. 5 are provisionally taken into consideration as parameters in the computation.

Furthermore, an arbitrary desired amount of the molten metal can be supplied by detecting the supply amount of the molten metal into the injection sleeve 17 as a result of computation based on the sink volume of the float 5 and elevated distance of the surface level, and by synchronizing the detected supply amount with the closing timing of the injection gate 17a by the plunger tip 19. In this case, it is unnecessary to provisionally compute the downwardly moving distance of the float 5.

Furthermore, in the illustrated embodiment, downwardly moving distance of the float corresponding to a desired supply amount is computed after the surface level reaches the constant surface level. However, a RAM is connected to the control unit for storing a table containing the relationship between the desired supply amount and the downwardly moving distance of the float. With reference from the table, downwardly moving distance corresponding to a set supply amount can be retrieved.

Claims

1. A molten metal supplying method for supplying a molten metal in a holding furnace into an injection sleeve connected to the holding furnace through a supply conduit by a vertical movement of a float immersible into the molten metal in the holding furnace, the method comprising the steps of: vertically moving the float until a surface level of the molten metal in the holding furnace becomes coincident with a constant surface level equal to a level immediately before an injection gate of the injection sleeve: and downwardly moving the float by a predetermined distance for supplying a predetermined amount of the molten metal into the injection sleeve only through the supply conduit, after the surface level of the molten metal reaches the constant surface level.

2. The molten metal supplying method as claimed in claim 1, wherein the downwardly moving step is performed in contiguous with the vertically moving step.

3. A molten metal supply device comprising: a holding furnace for holding a molten metal; a float immersible into the molten metal held in the holding furnace; a float drive unit for vertically moving the float; a supply conduit connecting between the holding furna ce and the injection sleeve for feeding the molten metal in the holding furnace to the injection sleeve; a surface level sensor for detecting a constant surface level of the molten metal in the holding furnace and generating a constant surface level detection signal; a control means transmitting a driving signal to the float drive unit in response to the detection signal to downwardly move the float by a predetermined distance in order to supply a predetermined amount of the molten metal to the injection sleeve only through the supply conduit, the injection sleeve having an injection gate open at a level equal to the constant surface level in the holding furnace at a state immediately before the injection.

4. The molten metal supply device as claimed in claim 3, wherein the float is divided into an inner float and an outer float; and wherein the float drive unit comprises an inner float drive unit and an outer float drive unit for driving the inner and outer floats independent of each other or in synchronism with each other.

5. A molten metal supplying method substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.

6. A molten metal supply device constructed and arranged substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.