Abstract:
A method and apparatus is disclosed for the preparation of a semi-solid material in a mixing sleeve of a casting apparatus, the semi-solid material formed from a molten material after a mixing and a cooling thereof in the mixing sleeve wherein a handling of the semi-solid material is minimized.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to the formation of a semi-solid material and more particularly to a method and apparatus for the preparation of a semi-solid material in a mixing sleeve of a casting apparatus, wherein the semi-solid material is formed from a molten material after a mixing and a cooling thereof in the mixing sleeve and prior to being transferred to the shot sleeve. 
       BACKGROUND OF THE INVENTION 
       [0002]    In a typical die casting process, a molten material is introduced to a shot sleeve of a casting apparatus. The molten material is then forced into a die and cast into a desired object. However, use of a molten material may not be desired or feasible and a semi-solid material is used. Typically, to form a semi-solid material a molten material is electromagnetically stirred and cooled in a separate cooling sleeve. The semi-solid material may also be electromagnetically stirred and cooled in a separate ladle cup. The semi-solid material is then transferred to the shot sleeve before being forced into the die. 
         [0003]    Stirring and cooling the semi-solid material in a separate cooling sleeve or ladle cup requires a high level of temperature control of the molten material and the semi-solid material. The properties of the molten material may also require modification prior to mixing and cooling to facilitate the high level of temperature control. Furthermore, stirring and cooling the semi-solid material in a separate cooling sleeve or ladle cup requires that a robot or other automated device be utilized to transfer the semi-solid material to the shot sleeve. Such robots and devices may be extremely expensive and lengthen the cycle time of the casting process. Mechanical issues may also arise with the robot or automated device. 
         [0004]    It would be desirable to develop a method and apparatus for forming a semi-solid material in a shot sleeve wherein a handling of the semi-solid material minimized. 
       SUMMARY OF THE INVENTION 
       [0005]    Concordant and congruous with the present invention, a method and apparatus for forming a semi-solid material in a shot sleeve wherein a handling of the semi-solid material minimized, has surprisingly been discovered. 
         [0006]    In one embodiment, the casting apparatus comprises a mixing sleeve having a mixing cavity formed therein for receiving a molten material; a shot sleeve having a shot sleeve cavity formed therein, the shot sleeve cavity in fluid communication with the mixing sleeve cavity; an electromagnetic circuit adapted to produce an electromagnetic current for mixing the molten material in the mixing sleeve cavity; and a cooling sleeve disposed adjacent the mixing sleeve, the cooling sleeve causing the molten material in the mixing sleeve cavity to cool as the electromagnetic current causes a mixing of the molten material until the molten material forms a semi-solid material. 
         [0007]    In another embodiment, a mold for casting comprises a mixing sleeve having a mixing sleeve cavity formed therein for receiving a molten material; a shot sleeve having a shot sleeve cavity formed therein, the shot sleeve in fluid communication with the mixing sleeve cavity; a means for causing the molten material to flow into the mixing sleeve cavity of the mixing sleeve; an electromagnetic circuit positioned adjacent the mixing sleeve, the electromagnetic circuit adapted to produce an electromagnetic current, for mixing the molten material in the mixing sleeve cavity; and a cooling sleeve disposed adjacent the mixing sleeve, the cooling sleeve causing the molten material in the mixing sleeve cavity to cool as the electromagnetic current causes a mixing of the molten material until the molten material forms a the semi-solid material. 
         [0008]    The invention also provides a method of forming a semi-solid material in a shot sleeve cavity comprising the steps of providing a casting apparatus comprising a mixing sleeve having a mixing sleeve cavity formed therein for receiving a molten material therein, a shot sleeve having a shot sleeve cavity formed therein for receiving a semi-solid material therein, a means for causing the molten material to substantially fill the mixing sleeve cavity, an electromagnetic circuit for producing an electromagnetic current for mixing the molten material, and a cooling sleeve; positioning the electromagnetic circuit and the cooling sleeve adjacent at least a portion of the mixing sleeve; introducing the molten material into the casting apparatus; energizing the electromagnetic circuit to produce an electromagnetic current in the molten material in the mixing sleeve cavity, wherein the electromagnetic current causes a mixing of the molten material; and causing the cooling sleeve to cool the molten material as the electromagnetic current mixes the molten material until the semi-solid material is formed. 
     
     
       DESCRIPTION OF THE DRAWINGS 
         [0009]    The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
           [0010]      FIG. 1  is a cross-sectional view of a shot sleeve apparatus according to an embodiment of the invention; 
           [0011]      FIG. 2  is a cross-sectional view of the shot sleeve apparatus of  FIG. 1  during a pouring of a molten material; 
           [0012]      FIG. 3  is a cross-sectional view of the shot sleeve apparatus of  FIG. 1  after the molten material has been poured; 
           [0013]      FIG. 4  is a cross-sectional view of the shot sleeve apparatus of  FIG. 1  during a mixing of the molten material; 
           [0014]      FIG. 5  is a cross-sectional view of the shot sleeve apparatus of  FIG. 1  during a movement of a semi-solid material into a shot sleeve; 
           [0015]      FIG. 6  is a cross-sectional view of the shot sleeve apparatus of  FIG. 1  during an injecting of the semi-solid material into a die; 
           [0016]      FIG. 7  is a cross-sectional view of the shot sleeve apparatus of  FIG. 1  during a removal of a cast object from the die; 
           [0017]      FIG. 8  is a cross-sectional view of a shot sleeve apparatus according to another embodiment of the invention; 
           [0018]      FIG. 9  is a cross-sectional view of the shot sleeve apparatus of  FIG. 8  during a mixing of a molten material. 
           [0019]      FIG. 10  is a cross-sectional view of a shot sleeve apparatus according to another embodiment of the invention; 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical. 
         [0021]      FIG. 1  shows a shot sleeve apparatus  10  including a mixing sleeve  12  forming a mixing sleeve cavity  14 , a means for causing  16  a molten material  18  (shown in  FIGS. 2-4 ) to substantially fill the mixing sleeve cavity  14 , a cooling sleeve  20 , an electromagnetic circuit  22 , a gate  24 , a thermocouple  26 , and a shot sleeve  28  forming a shot sleeve cavity  30 . The molten material  18  can be any castable material such as aluminum, for example. 
         [0022]    The mixing sleeve  12  forms the mixing sleeve cavity  14  which includes an inlet  32  and an outlet  34 . The inlet  32  provides fluid communication between an exterior of the mixing sleeve  12  and the mixing sleeve cavity  14 . The outlet  34  provides communication between the mixing sleeve cavity  14  and the shot sleeve cavity  30 . The gate  24  is adapted to close the outlet  34 . The plunger  16  is slidably disposed in the mixing sleeve cavity  14 . In the embodiment shown, the mixing sleeve  12  has a horizontal orientation. It is understood that the mixing sleeve  12  may have a vertical orientation or an angled orientation, as desired. 
         [0023]    In the embodiment shown, the means for causing  16  the molten material  18  to substantially fill the mixing sleeve cavity  14  is a plunger  36 . The plunger  36  includes a rod  38  and a body  39  having a tip  40 . The tip  40  of the plunger  36  is configured such that it may be slidably positioned in the mixing sleeve cavity  14  and the shot sleeve cavity  30 . The tip  40  is adapted to form a seal with an inner wall  42  of the mixing sleeve  12  and an inner wall  44  of the shot sleeve  28 . It is understood that the means for causing  16  the molten material  18  to substantially fill the mixing sleeve cavity  14  may be any device capable of causing the molten material  18  to fill the mixing sleeve cavity  14 , as desired. 
         [0024]    A cooling sleeve cavity (not shown) is formed by the cooling sleeve  20 . The cooling sleeve  20  contains a fluid (not shown) and is positioned between the electromagnetic circuit  22  and a portion of the mixing sleeve  12 . It is understood that the cooling sleeve  20  may be positioned anywhere on the shot sleeve apparatus  10 , such as between the electromagnetic circuit  22  and the portion of the mixing sleeve  12  or adjacent a portion of the shot sleeve  28 , as desired. The configuration of the cooling sleeve  20  used depends on the size, shape, surface area, and wall thickness of the mixing sleeve  14  and the shot sleeve  28 . Further, the configuration of the cooling sleeve  20  used also depends on the molten material  18  used and a desired cooling rate of the molten material  18 . In the embodiment shown, the fluid is water. It is understood that other fluids may be used such as a water-glycol mix or any other fluid, or multipurpose solid-liquid convection medium, for example. The fluid used depends on the desired cooling rate of the molten material  18 , the properties of the fluid, and other similar factors. 
         [0025]    The electromagnetic circuit  22  is adapted to produce an electromagnetic current as indicated by the arrow A in  FIG. 4 . It is understood that the electromagnetic circuit  22  may be any electromagnet such as a solenoid or toroid, for example. As shown, the electromagnetic circuit  22  is positioned immediately adjacent the cooling sleeve  20 . It is understood that the electromagnetic circuit  22  may be positioned anywhere on the shot sleeve apparatus  10 , where the electromagnetic current flows toward the molten material  18  in the mixing sleeve cavity  14 . 
         [0026]    The gate  24  is disposed between the mixing sleeve cavity  14  and shot sleeve cavity  30  to militate against the flow of molten material  18  and semi-sold material  36  from the mixing sleeve cavity  14  to the shot sleeve cavity  30 . As shown, the gate  24  is adapted to be slidably removed from a position between the mixing sleeve cavity  14  and the shot sleeve cavity  30 . Other structures may be used such as a valve, for example, to selectively militate against flow and permit flow between the mixing sleeve cavity  14  and the shot sleeve cavity  30 . It is understood that the gate  24  may be produced from any conventional material, as desired. 
         [0027]    The thermocouple  26  is disposed in the mixing sleeve  12  and extends into the mixing sleeve cavity  14 . It is understood that the thermocouple  26  may be disposed anywhere on the apparatus  10  as desired, such as partially disposed in the mixing sleeve cavity  14 , partially disposed in the shot sleeve cavity  30 , and coupled to the gate  24 , for example. The thermocouple  26  may be any conventional thermocouple known in the art. 
         [0028]    The shot sleeve  28  includes an inlet  48  and an outlet  50 . The inlet  48  is in communication with the outlet  34  of the mixing sleeve  12 . The gate  24  is disposed between the outlet  34  of the mixing sleeve  12  and the inlet  48  of the shot sleeve  28 . The second outlet  50  is in fluid communication with a die cavity  52  formed in a cover die  54  and an ejector die  56 . The die cavity  52  may have any shape, as desired, to form a desired cast object. In the embodiment shown, the shot sleeve  28  has a horizontal orientation linearly aligned with the mixing sleeve  12 . It is understood that the shot sleeve  28  may have a vertical orientation or an angled orientation, or other orientation, as desired. Although the mixing sleeve  12  and the shot sleeve  28  are aligned linearly in the embodiment shown, it is understood that other configurations can be used as desired. 
         [0029]    In use, the molten material  18  is produced in a furnace (not shown) or other heating device. Typically, the molten material  18  is then introduced to the shot sleeve apparatus  10 . The molten material  18  is poured from a ladle  19  in the mixing sleeve cavity  14  of the mixing sleeve  12  through the first inlet  32 , as shown in  FIGS. 2 and 3 . It is understood that other structures can be used to introduce the molten material  18  into the mixing sleeve cavity  14 . 
         [0030]    As shown in  FIG. 4 , the plunger  36  is then caused to move to a position which causes the molten material  18  to substantially fill a portion of the mixing sleeve cavity  14 . The plunger  36  militates against the flow of the molten material  18  or the semi-solid material  46  toward the rod  38  of the plunger  36 . It is understood that the plunger  36  may also be utilized to transfer the semi-solid material  46  from the mixing sleeve cavity  14  to the shot sleeve cavity  30  and a die cavity  52 , as desired. Once the portion of the mixing sleeve cavity  14  has been substantially filled with the molten material  18 , the electromagnetic circuit  22  is energized to provide the electromagnetic current A to the molten material  18 . The electromagnetic current causes a mixing of the molten material  18  to occur in the mixing sleeve cavity  14 . The amount of electromagnetic current A required to be produced by the electromagnetic circuit  22  depends on the amount of molten material  18  in the portion of the mixing sleeve cavity  14 , the material properties of the molten material  18 , an amount of mixing desired, and the rate at which the molten material  18  is to be mixed. Concurrent with the energization of electromagnetic circuit  22 , the fluid is caused to flow to the cooling sleeve  20 . The fluid in the cooling sleeve cavity of the cooling sleeve  20  causes the molten material  18  in the mixing sleeve  12  to begin cooling. A temperature of the molten material  18  in the mixing sleeve  12  is measured by the thermocouple  26 . The simultaneous mixing and cooling of the molten material  18  in the mixing sleeve  12  causes the material properties of the molten material  18  to change until the semi-solid material  46  is formed. The mixing and cooling of the molten material  18  continues until a desired temperature is reached. The electromagnetic circuit  22  is then de-energized to stop the mixing. The desired temperature is determined based on the properties of the molten material  18  used and the desired properties of the semi-solid material  46  to be formed. It is understood that the cooling step and mixing step may occur at the substantially same time or at different times, as desired. 
         [0031]    After the desired temperature is reached and the electromagnetic circuit  22  is de-energized, the gate  24  and the thermocouple  26  are retracted and the plunger  36  is caused to slidingly move in the mixing sleeve cavity  14  and cause the semi-solid material  46  to move into the shot sleeve cavity  30 , as shown in  FIG. 5 . While the plunger  36  is positioned in the shot sleeve  28 , a control system (not shown) adjusts the speed and pressure of the plunger  36  to inject the semi-solid material  46  into the die cavity  52 , as shown in  FIG. 6 . The control system may be any conventional system including devices, such as a timer, a switch, and a thermocouple, for example. 
         [0032]    As shown in  FIG. 7 , once the semi-solid material  46  in the die cavity  52  has solidified and cooled to a desired temperature, the ejector die  56  is opened and the desired cast object can be removed therefrom. It is understood that the ejector die  56  may be opened using an automated device as known in the art, or the ejector die  56  may be opened manually. Once the desired cast object is removed from the die cavity  52 , typical open dwell activities such as cleaning and machining of the desired cast object can be conducted. 
         [0033]      FIG. 8  shows a shot sleeve apparatus  60  according to another embodiment of the invention including a plunger  62 , a mixing sleeve  64  forming a mixing sleeve cavity  66 , a means for causing (not shown) a molten material  68  to substantially fill the mixing sleeve cavity  66 , a cooling sleeve  70 , an electromagnetic circuit  72 , a thermocouple  74 , and a shot sleeve  76  forming a shot sleeve cavity  78 . 
         [0034]    The plunger  62  includes a rod  80  and a body  81  having a tip  82 . The tip  82  of the plunger  62  is sized such that it may be slidably positioned in the mixing sleeve cavity  66  and the shot sleeve cavity  78 . The tip  82  is adapted to form a seal with an inner wall  84  of the mixing sleeve  64  and an inner wall  86  of the shot sleeve  76 . 
         [0035]    In the embodiment shown, the means for causing the molten material  68  to substantially fill the mixing sleeve cavity  66  is gravity. It is understood that the means for causing the molten material  68  to substantially fill the mixing sleeve cavity  66  may be any device or force capable of causing the molten material  68  to fill the mixing sleeve cavity  66 , such as a plunger, for example. In the embodiment shown, the mixing sleeve  64  has an angled orientation. It is understood that the mixing sleeve  64  may have a vertical orientation or a horizontal orientation, as desired. 
         [0036]    The cooling sleeve  70  forms a cooling sleeve cavity (not shown) which is in fluid communication with a fluid (not shown). As shown, the cooling sleeve  70  is positioned between the electromagnetic circuit  72  and a portion of the mixing sleeve  64 . It is understood that the cooling sleeve  70  may be positioned anywhere on the shot sleeve apparatus  60 , such as between the electromagnetic circuit  72  and the portion of the mixing sleeve  64  or adjacent a portion of the shot sleeve  76 , as desired. The configuration of the cooling sleeve  70  used depends on the size, shape, surface area, and wall thickness of the mixing sleeve  64  and the shot sleeve  76 . Further, the configuration of the cooling sleeve  70  used also depends on the molten material  68  used and a desired cooling rate of the molten material  68 . In the embodiment shown, the fluid is water. It is understood that other fluids may be used such as a water-glycol mix or any other fluid, or multipurpose solid-liquid convection medium, for example. The fluid used depends on the desired cooling rate of the molten material  68 , the properties of the fluid, and other similar factors. 
         [0037]    The electromagnetic circuit  72  is adapted to produce an electromagnetic current as indicated by the arrow B in  FIG. 9 . It is understood that the electromagnetic circuit  72  may be any electromagnet such as a solenoid or toroid, for example. As shown, the electromagnetic circuit  72  is positioned adjacent the cooling sleeve  70 . It is understood that the electromagnetic circuit  72  may be positioned anywhere on the shot sleeve apparatus  60 , where the electromagnetic current flows toward the molten material  68  in the mixing sleeve cavity  66 . 
         [0038]    The thermocouple  74  is disposed in the mixing sleeve  64  and extends into the mixing sleeve cavity  66 . It is understood that the thermocouple  74  may be disposed anywhere on the apparatus  60  as desired, such as partially disposed in the mixing sleeve cavity  66  and partially disposed in the shot sleeve cavity  78 , for example. The thermocouple  74  may be any conventional thermocouple known in the art. 
         [0039]    The shot sleeve  76  includes an inlet  88 . The inlet  88  is in fluid communication with the shot sleeve cavity  78  and the mixing sleeve cavity  66 . The first inlet  88  is also in fluid communication with a die cavity  90  formed by a cover die  92  and an ejector die  94  when the ejector die  94  is positioned adjacent the cover die  92  and shot sleeve  76 . The die cavity  90  may have any shape, as desired, to form a desired cast object. In the embodiment shown, the shot sleeve  76  has an angled orientation with respect to horizontal. It is understood that the shot sleeve  76  may have a horizontal orientation or a vertical orientation or other orientation, as desired. Although the mixing sleeve  64  and the shot sleeve  76  are aligned linearly in the embodiment shown, it is understood that other configurations can be used as desired. 
         [0040]    In use, the molten material  68  is produced in a furnace (not shown) or other heating device. The molten material  68  is then introduced to the shot sleeve apparatus  60 . The molten material  68  is poured from a ladle  69  through the inlet  88 , as shown in  FIG. 8 . The means for causing the molten material  68  to substantially fill the mixing sleeve cavity  66  in the embodiment shown is gravity. The molten material  68  flows to the mixing sleeve cavity  66  and substantially fills a portion thereof. 
         [0041]    Once the portion of the mixing sleeve cavity  66  has been substantially filled with the molten material  68 , the electromagnetic circuit  72  is caused to provide the electromagnetic current B to the molten material  68 . The electromagnetic current causes a mixing of the molten material  68  to occur in the portion of the mixing sleeve cavity  66 . The amount of electromagnetic current B required to be produced by the electromagnetic circuit  72  depends on the amount of molten material  68  in the portion of the mixing sleeve cavity  66 , the material properties of the molten material  68 , an amount of mixing desired, and the rate at which the molten material  68  is to be mixed. Concurrent with the energization of the electromagnetic circuit  72 , the fluid is caused to flow through the cooling sleeve  70 . The fluid in the cooling sleeve cavity of the cooling sleeve  70  causes the molten material  68  in the mixing sleeve  64  to begin cooling. A temperature of the molten material  68  in the mixing sleeve is measured by the thermocouple  74 . The simultaneous mixing and cooling the molten material  68  in the mixing sleeve  64  causes the material properties of the molten material  68  to change until a semi-solid material (not shown) is formed. The mixing and cooling of the molten material  68  continues until a desired temperature is reached. The electromagnetic circuit  72  is then de-energized to stop the mixing. The desired temperature is determined based on the properties of the molten material  68  used and the desired properties of the semi-solid material to be formed. It is understood that the cooling step and mixing step may occur at the substantially same time or at different times, as desired. 
         [0042]    After the desired temperature is reached and the electromagnetic circuit  72  is de-energized, the thermocouple  74  is retracted, and the plunger  62  is caused to slidingly move in the mixing sleeve cavity  66  and cause the semi-solid material to move through the mixing sleeve cavity  66  and into the shot sleeve cavity  78  as described for  FIGS. 1 through 7 . While the plunger  62  is positioned in the shot sleeve  76 , a control system (not shown) adjusts the speed and pressure of the plunger  62  to inject the semi-solid material into the die cavity  90 . The control system may be any conventional system including devices, such as a timer, a switch, and a thermocouple, for example. 
         [0043]    Once the semi-solid material in the die cavity  90  has solidified and cooled to a desired temperature, the ejector die  94  is opened and the desired cast object can be removed. It is understood that the ejector die  94  may be opened using an automated device as known in the art, or the ejector die  94  may be opened manually. Once the desired cast object is removed from the die cavity  90  typical open dwell activities such as cleaning and machining of the desired cast object, for example can be conducted. 
         [0044]      FIG. 10  shows a shot sleeve apparatus  60 ′ according to another embodiment of the invention. Repeated structure from  FIGS. 8 and 9  have the same reference numeral and a prime (′) for clarity. A description and use thereof is not repeated. The molten material  68 ′ may be introduced into the shot sleeve apparatus  60 ′ with the ladle  69 ′ or with a metal pump (not shown), or a vacuum sucker tube (not shown). 
         [0045]    From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.