Patent Publication Number: US-6981541-B2

Title: Casting Furnace

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This invention relates to furnaces for use in melting and molding metals often referred to as casting. More particularly, this invention relates to a casting furnace incorporating a mold insertion and withdrawal system that operates adjacent to the mold and mold support thereby eliminating the need for a pit thereunder housing such a system. Specifically, the invention is a casting furnace with a mold insertion and withdrawal system attached thereto and incorporating an offset mold elevator for moving a mold from a mold loading chamber to a melt processing chamber while eliminating the need for a pit. The system further incorporates a readily removable chill plate on which the mold rides, and an overhead material feed system. 
     2. Background Information 
     Casting furnaces are used to melt metals such as chrome alloy, super alloy, titanium, and nickel-based castings or other like materials whereby the molten metals are poured into molds in the shape of the desired end product. This overall process is known as casting. During casting, one of the necessary operations is the insertion of the molds into the furnace prior to use, and the removal of the molds from the furnace after use. 
     A typical system for performing this process includes a furnace with a melt processing chamber coupled to a mold loading chamber whereby some form of a withdrawal cylinder is positioned directly under a plate or base that supports the mold. The plate is used to lift the mold into and out of the melt-processing chamber of the furnace. The withdrawal cylinder is a cylinder actuated in and out of an elevator tube positioned beneath the lowest point that the plate must actuate to during the use of the mold, whereby this elevator tube is positioned within a furnace pit where it extends into the pit and/or through a hole within the pit and into the ground or foundation on which the furnace sets, or into some form of an area below the furnace. 
     Although these systems operate generally in the intended manner, certain disadvantages and problems exist. First, the furnace may only be located where a pit or similar chamber beneath the furnace may be provided to house at least the elevator tube. Second, extra costs are incurred to build or modify such a building due to additional foundational costs associated with the pit requirement. Third, a pit is a confined space and thus it is difficult to maintain, improve, fix and/or operate the parts of the withdrawal cylinder and/or furnace positioned therein. 
     Furthermore, the withdrawal cylinder or elevator tube is very susceptible to major damage in the event of a mold breakout or overflow. This is particularly true since the cylinder is located directly under the mold or in close proximity to the mold whereby molten material during a breakout or overflow contaminates substantially all parts positioned below the mold including the withdrawal cylinder or elevator tube. This contamination often causes significant damage to seals, housings, and other parts as well as requiring significant clean-up of the harden metal thereon or replacement of many parts of the system. 
     It is also noteworthy that the mold elevator shaft in current systems is typically a hydraulically actuated, precision ground and polished chrome design to satisfy the water cooling requirements. Such a design is expensive. 
     For these and other reasons, it is thus very desirable to provide an improved mold withdrawal system. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is an improved casting furnace with a pit-less mold insertion and withdrawal system incorporating an offset elevator, and the method of use thereof. 
     Specifically, the invention is a furnace for melting and pouring molten material into molds. The furnace includes a melt-processing chamber including a melting pot from which molten material may be poured. The furnace also includes a mold support on which a mold is seated, the mold support moveable vertically along a first axis into and out of the furnace chamber, and an elevator mechanism, offset from the first axis, for raising and lowering the mold support into and out of the melt processing chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the invention, illustrative of the best modes in which the applicant has contemplated applying the principles, are set forth in the following description and are shown in the drawings and are particularly and distinctly pointed out and set forth in the appended claims. 
         FIG. 1  is a front elevational view of the present invention of the furnace incorporating a mold chamber with an offset mold elevator therein with a chill plate thereon, a furnace chamber, and an overhead system for providing material to be melted; 
         FIG. 2  is an enlarged front sectional view of the mold chamber portion of the invention as shown in  FIG. 1 ; 
         FIG. 3  is an enlarged top plan view of the mold chamber portion of the invention as shown in  FIG. 2 ; 
         FIG. 4  is an enlarged sectional view taken along line  4 — 4  in  FIG. 3  of the offset ball bushing track and ball screw drive system in the chamber shown in  FIGS. 2 and 3 ; 
         FIG. 5  is an enlarged view of the bottom portion of the offset ball bushing track and ball screw drive system in the chamber shown in  FIG. 4 ; 
         FIG. 6  is an enlarged sectional view taken along line  6 — 6  in  FIG. 5 ; 
         FIG. 7  is an enlarged sectional view taken along line  7 — 7  in  FIG. 6 ; 
         FIG. 8  is an enlarged view of the quick-change chill plate and the seat it seats within where the plate is unseated; 
         FIG. 9  is the same enlarged view as  FIG. 8  of the quick-change chill plate and the seat it seats within except the plate is seated but coolant hoses are not connected; 
         FIG. 10  is the same enlarged view as  FIG. 9  of the quick-change chill plate and the seat it seats within except the plate is seated and coolant hoses are connected; 
         FIG. 11  is an enlarged partial sectional view taken along line  11 — 11  in  FIG. 6 ; 
         FIG. 12  is the front elevational view of the present invention as shown in  FIG. 1  except the mold is elevated into the furnace chamber; and 
         FIG. 13  is the same front sectional view of the mold chamber portion of the invention as shown in  FIG. 2  except the mold is elevated as in  FIG. 12 . 
     
    
    
     Similar numerals refer to similar parts throughout the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     An improved casting furnace for melting metal and pouring the molten metal into molds is the present invention as is shown in the Figures although other embodiments are contemplated as is apparent from the alternative design discussions herein and to one of skill in the art. Specifically, the described embodiment of the improved furnace is indicated generally at  20  as shown in  FIGS. 1–13 . This furnace is designed to be of a pit-less variety whereby a mold insertion and withdrawal system  22  moves a mold  24  from a mold loading chamber  26  into and out of a melt processing or furnace chamber  28 . Overall, the furnace  20  includes a frame  30  including legs  40  and cross supports  42 , the mold loading chamber  26  and the melt processing chamber  28  with an access passage  32  therebetween, the mold insertion and withdrawal system  22  including a mold support  34  vertically moveable within the mold loading chamber  26  by a drive system  36 , and an overhead material provider  38  which includes a melt charge feeder chamber, a melt induction coil, a melt power supply, various vacuum components, and controls. 
     Frame  30  is a standard rigid structure of sufficient strength and rigidity to support the melt-processing chamber  28 , which is positioned on cross supports  42 . Frame may be any design, construction or configuration made out of any material that is sufficient to allow it to support the furnace  20 , the overhead material provider  38  and any material therein, as well as a mold substantially filled with a molten load. Frame  30  and mold loading chamber  26  are positioned on the ground G which may be a factory floor. There are no pits or other cavities within the floor for housing any portion of the furnace or any mold insertion or withdrawal system. 
     Mold loading chamber  26  defines an enclosed compartment or environment in which the mold  24  is inserted to be processed. In one embodiment, the mold loading chamber  26  is a square or similar shaped box-like structure with a plurality of sides including a bottom  50 , ends  52  including one of which may include an access door, and a top  54 . As noted an access door is provided in one of the ends to move the mold into and out of the entire system. In addition, a valve gate  56  is defined in access passage  32  of top  54 . A valve gate open and close mechanism  58  opens and closes the valve gate  56  when desired. Valve gate mechanism  58  includes a first pivot rod  60 , a first arm  62 , a second pivot rod  64 , a second arm  66 , a third pivot rod  68  and an elongated bar  70  with an elongated slot  72  therein. 
     In accordance with one of the features of the invention, the mold insertion and withdrawal system  22  includes mold support  34  on which mold  24  sits all of which is offset from the drive system  36  that moves the mold vertically within the mold loading chamber  26  into the furnace chamber  38 . Specifically, as best shown in  FIG. 10 . mold support  34  includes a chill plate  80  with a seating ring  82  on the bottom surface thereof defining an outer diameter, a hollow cylindrical seat  84  defining an inner diameter capable of receiving the outer diameter of the seating ring  82  therein, and a bracket  86  with a first end  88  capable of securing the seat  84  therein and a second end  89  securable to a collar as defined below of drive system  36  by brackets  91 , plates  93  and  95 , optional spacers  97  and bolts  99 . The mold support  34  may also include a height adjuster  90  including threaded bushings  92  secured to the bracket  86 , threaded rods  94  threadably adjustable within the bushings  92 , and a plate  96  secured to the upper ends of the rods  94  so as to be adjustably moveable upward to provide a higher stop for the mold  24  to sit on than the top rim of the seat  84  although the ring  82  will still be aligned partially within the seat. The height adjuster is also usable as a balancer whereby one or more, but less than all, of the multiple threaded rods are adjusted through the threaded bushings resulting in a tilting action of the plate  96  which once above the top rim of the seat  84  provides a more properly balanced or level seat. 
     The chill plate  80  is a cooling plate, which may be of a variety of designs. In the embodiment shown, the chill plate  80  is an upper plate  100  sandwiched together with a lower plate  102  whereby at least one channel is defined therebetween to receive cooling or chilled fluid. Specifically, the lower plate  102  includes a fluid entrance fitting  104  and a fluid exit fitting  106  with a fluid ports extending into the lower plate to a fluid passage extending therebetween in the mated area between the lower and upper plates. These fluid fittings and ports receive the cooling or chilled fluid such as water or another coolant. 
     The chill plate  80  is interchangeable with over chill plates by a quick disconnecting of fluid hoses from the fittings  104  and  106  followed by a lifting of the chill plate  80  and specifically its seating ring  82  from the hollow cylindrical seat  84 . A different chill plate is then seated onto the seat  84 , and the fluid hoses are connected to the fittings on the new chill plate. 
     A baffle system  108  is provided into the chill spool assembly. The baffle system includes a plurality of baffles that readily allow for in process changing thus enabling the use of a conformal design. This equates to tightly baffled parts that minimize diagonal view factors thus resulting in maximized temperature gradient and enhanced process control. In an alternative embodiment, stacked baffles may be also be used. 
     Drive system  36  of the mold insertion and withdrawal system  22  is an offset mold elevator that in the embodiment shown is of a ball bushing track and ball screw drive design. Specifically, as best shown in  FIG. 2-6 , the drive system  36  holds the mold support  34  so as to move a mold thereon up and down within the mold chamber  26 . The drive system  36  includes a top plate  110 , a bottom plate  112 , a ball screw  114 , an upper guide mount  116 , a lower guide mount  118 , a ball follower  120 , a center plate  122 , a plurality of guide rods  124 , I-beam support plates  126 , a collar  128 , upper bellows  130 , lower bellows  132 , multiple slidable guides  134 , a shade or water-cooled sliding-way cover  136 , and a drive motor  138 . 
     Ball screw  114  is drivably attached to drive motor  138  and is seated at each end in central apertures in top plate  110  and bottom plate  112 , respectfully, and extends therebetween. Guide mounts  116  and  118  secure the ball screw  114  in place while allowing it to rotate in central apertures in top plate  110  and bottom plate  112 , respectfully, as driven by drive motor  138  connected approximate the top plate  112 . The guide mounts  116  and  118  include an internal cylindrical passage with bearings, bushings and/or seals to allow the ball screw (not threaded at the ends where the mounts are located) to freely rotate, while the area in between the mounts is threaded thereby driving the ball follower  120  when the ball screw  114  is rotated by the drive motor. 
     In the embodiment shown, the plurality of guide rods  124  total four and are equally disbursed around the ball screw  114  as best shown in  FIG. 7 . As shown, each of the guide rods  124  includes a cylindrical portion  140 , an elongated neck portion  142 , and an elongated planar plate  144 . The guide rods  124  are grouped into two pairs, where each pair is connected together by I-beam support plates  126  as shown in  FIG. 7 . These guide rods provide for smooth and balanced movement of the ball screw and attached mold support  34 . 
     Ball follower  120  includes a threaded inner passage that is threaded onto the ball screw  114 . Ball follower also includes a disk that extends outward and defines a ledge  148 . Center plate  122  is connected to and/or rides on ledge  148  of the ball follower  120  such that movement of the ball follower up and down causes movement of the plate  122 . Collar  128  is connected to the plate  122  as best shown in  FIG. 4  whereby the collar is rigidly connected to the second end  89  of the bracket  86  of the mold support  34 . As a result, any movement of the ball screw  114  is directly correlated to the ball follower  120 , center plate  122 , collar  128 , bracket  86 , seat  84 , ring  82 , chill plate  80  and thus the mold  24  seated thereon. 
     Multiple slidable guides  134  as best shown in  FIG. 6  assist the collar  128  in maintaining proper alignment with the ball follower  120 . The upper bellows  130  extend from the top plate  110  to the collar  128 , and the lower bellows  132  extend from the collar  128  to the bottom plate  112 , and both bellows function to enclose the ball screw system for safety reasons. 
     Cover  136  is preferably transparent and attached to the collar  128  or bracket  86  so as to slide therewith. This cover is provided for safety reasons as well as to protect the drive screw and associated parts from furnace dust and debris. The cover, which is water-cooled, also protects the drive screw from heat given off from the hot mold. 
     Melt processing chamber  28  defines an enclosed compartment or environment in which raw materials are melted so as to flow whereby the molten materials are poured into the mold  24  that is inserted into the furnace from mold chamber  26 . More specifically, valve gate  56  as defined above is a gate selectively sealing access passage  32  of top  54  in mold loading chamber  26  thus selectively opening and closing a port or access between the mold loading chamber  26  and the melt processing chamber  28 . 
     Within the melt processing chamber  28  is a melting furnace  160  that is movably mounted so as to be moveable to receive ingots from valve  200 , and pivotally mounted so as to be able to pour molten material into the mold  24 . The melting pot includes some form of heating element as is well known in the art. Ingots or other raw material bars are provided by overhead material provider  38  whereby these materials are melted in the melting furnace  160  via an induction coil located therearound. Once the materials are sufficiently molten, valve gate  56  is opened and a mold  24  is elevated as described below such that the mold moves from the  FIG. 1  position to the  FIG. 12  position and is ready to receive the molten material by pivoting the furnace  160  to pour the material into the mold. 
     Melt processing chamber  28  as shown in one embodiment in the FIGURES is a cylindrical drum  164  laid on its side with a window  166  connected to the door  56 . Melt processing chamber  28  also includes one or more view windows  170 , a vacuum poppit valve  180 , an access plug  190 , and a valve  200  for controlling material flow. Valve  200  is a vacuum isolation valve that isolates the melt charge feeder  24  from the melt chamber  28 . 
     The overhead material provider  38  is connected to the melt-processing chamber at valve  200 . In addition to valve  200 , provider  38  includes a motor  202 , drive shaft or screw  204 , supports  206  and  208 , a guide rod  210 , guide supports  212  and  214 , a drive body  216 , a drive cylinder  218 , a sleeve  220 , a feed spoon  222 , a melt charge feeder chamber  224  with a door  228  therein, a material passage or port  229  with a valve  200  therein, and a support frame  230 . 
     Motor  202  is connected to drive shaft  204  so as to drive or turn the shaft within supports  206  and  208  which are affixed to frame  230  and contain bushings to allow for turning of the shaft therein. Guide rod  210  is affixed to guide supports  212  and  214  which are affixed to supports  206  and  208 . Drive body  216  includes a threaded port receiving the threaded drive shaft  204  and another port receiving the smooth walled guide rod  210 , whereby turning of the drive shaft  204  causes linear movement along the drive shaft by the drive body  216  which is further guided by the guide rod  210 . Drive body  216  in turn drives drive cylinder  218 , which is rigidly connected thereto, through sealable sleeve  220  such that head  222  on the opposite end of cylinder  218  drives ingots or the like into passage  229 . 
     In operation, all external chamber doors and valves are closed. The desired vacuum is provided to the furnace. Valve  200  is closed. The vacuum within the melt charge feeder  224  is released, and door hatch  228  is opened so that melt charge material to be melted is loaded into the melt charge feeder chamber  224  on feed spoon  222 . The door hatch  228  is closed, and a vacuum is returned to the melt charge feeder  224 . Induction melt furnace  160  is tilted to a horizontal position and lined up with port  229 . Valve  200  is then opened and melt charge is driven through the material port  229  and inserted into the melt furnace  160 . Specifically, drive motor  202  drives screw  204  to turn causing drive body  216  to move thereby pushing drive cylinder  218  and feed spoon  222  on the opposite end thereof. The melt charge material is thus driven into the material port  228 . Feed spoon  222  is then retracted and valve  200  closed. The melt furnace  160  is rotated into a vertical position. The induction power supply is turned on to melt the charge feed material. If necessary, some previous steps may be repeated to provide additional charge feed material to be melted. 
     Either in parallel with the above process or in sequence after, a mold is provided. Specifically, valve gate  56  is closed or verified to be closed. The vacuum in the mold-loading chamber  26  is released. Mold loading chamber door  52  is opened to allow insertion of a mold  24  into the chamber  26 . Once the mold is inserted and properly placed in the chamber on mold table  80 , the door  52  is closed and the vacuum returned. Once the melt charge is melted and casting is desired, valve gate  56  is opened. This occurs via valve gate open and close mechanism  58 . First pivot rod  60  is driven to turn or pivot by a motor. This causes first arm  62  to pivot clockwise on  FIG. 2  which pushes the second pivot rod  64  and attached second arm  66  downward such that third pivot rod  68  slides in elongated slot  72  in elongated bar  70 . All of this motion causes valve gate  52 , which is connected to first arm  62 , to open by pivoting downward to the position shown in  FIG. 12 . The mold  24  may now be moved into the chamber  28 . Motor  138  drives drive screw  114  to rotate causing ball follower  120  that is threaded thereon to move. Any movement of the ball screw  114  is directly correlated to the ball follower  120 , center plate  122 , collar  128 , bracket  86 , seat  84 , ring  82 , chill plate  80  and thus the mold  24  seated thereon. Upward driving of the drive screw  114  causes the mold to move upward into the chamber as shown in  FIG. 12 . Specifically, the motor  138  drives drive screw  114  to rotate causing ball follower  120  that is threaded thereon to move. Thus the hot mold is moved into the melt chamber into a casting position. Melt furnace  160  is titled at a controlled rate to cause pouring of the molten melt charge into the mold  24 . The mold elevator  36  is retracted by a downward driving of the drive screw  114  that causes the mold to move downward back into the mold loading chamber  26  as shown in  FIG. 2 . Valve gate  56  is then closed by a reverse action that was used to open it. Thereafter, the mold may be removed by breaking the vacuum, and opening the mold loading chamber door  52 . The mold is removed, and the entire process may be repeated non-stop until the end of a melt campaign, or a shut down for maintenance or other reasons. 
     Accordingly, the pit-less mold withdrawal system incorporating an overhead trolley is simplified, provides an effective, safe, inexpensive, and efficient device which achieves all the enumerated objectives, provides for eliminating difficulties encountered with prior devices, and solves problems and obtains new results in the art. 
     In the foregoing description, certain terms have been used for brevity, clearness and understanding; but no unnecessary limitations are to be implied therefrom beyond the requirement of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed. 
     Moreover, the description and illustration of the invention is by way of example, and the scope of the invention is not limited to the exact details shown or described. 
     Having now described the features, discoveries and principles of the invention, the manner in which the pit-less mold withdrawal system incorporating an overhead trolley is constructed and used, the characteristics of the construction, and the advantageous, new and useful results obtained; the new and useful structures, devices, elements, arrangements, parts and combinations, are set forth in the appended claims.