US3050794A

US3050794A - Furnace ladling apparatus

Info

Publication number: US3050794A
Application number: US838585A
Authority: US
Inventors: George W Holz
Original assignee: Lindberg Engineering Co
Current assignee: Lindberg Engineering Co
Priority date: 1959-09-08
Filing date: 1959-09-08
Publication date: 1962-08-28
Anticipated expiration: 1979-08-28
Also published as: CH365487A; GB913269A

Description

Aug. 28, 1962 G. w. HOLZ FURNACE LADLING APPARATUS 2 Sheets-Sheet 1 Filed Sept. 8, 1959 5 A fl INVENTORI ATTORNEYS.

Aug. 28, 1962 G. W. HOLZ FURNACE LADLING APPARATUS Filed Sept. 8, 1959 2 Sheets-Sheet 2 AT7URNEVS.

United States Patent 3,950,794 FURNACE LABELING APPARATUS George W. Holz, Chicago, liL, assignor to Lindberg Engineering Company, Chicago, Ill, a corporation of Illinois Filed Sept. 8, 1959, Ser. No. 838,585 2 Claims. (Cl. 22-79) This invention relates to furnace ladling apparatus and more particularly to apparatus for forcing molten metal from a furnace chamber through a discharge tube and to a desired point of use such, for example, as a die casting machine.

A number of different furnace ladling devices have been devised for forcing molten metal from the chamber of a melting or holding furnace to a desired point of use, such as a die casting machine. Many of such devices employ a discharge tube extending upwardly at an angle to the vertical to a point above the molten metal in the chamber and discharging adjacent to one side of the chamber. Molten metal discharged from the tube is conducted by a launder or similar discharge device to the mold of a die casting machine, or the like. Examples of highly desirable types of ladling devices of this general character are disclosed in the patent to Edstrand, No. 2,846,740 and my co-pending application, Serial No. 838,584, filed September 8, 1959.

In such apparatus and particularly when the apparatus is so constructed that molten metal may stand in the discharge tube above the level of molten metal in the chamber between successive shots, there is a tendency for the metal in the upper part of the discharge tube to freeze or to cool to a mushy consistency in the event there is a long interval between shots. Thus, any delay due to difficulties with the die casting machine, or the like, may result in the freezing or partial freezing of the metal in the discharge tube, making it difficult to restart the operation.

It is one of the objects of the present invention to provide a furnace ladling apparatus in which the ladling or discharging operation may be effected with the discharged metal being returned to the furnace chamber to prevent undue cooling of metal in the discharge tube.

Another object is to provide furnace ladling apparatus in which a ladling or discharging operation is effected automatically after a predetermined time interval of in operation and in which normal ladling or discharging operation resets the time interval.

According to a feature of the invention, a timer operative after a predetermined interval controls a movable launder, or similar discharge device, to position it to return molten metal to the furnace chamber and then initiates a ladling or discharging operation so that metal standing in the discharge tube will be returned to the furnace chamber and will not be allowed to cool to any undesired extent. The timer is reset by each normal ladling or discharging operation so that the return cycle will not be initiated unnecessarily.

The above and other objects and features of the invention will be more readily apparent from the following description when read in connection with the accompanying drawings, in which:

. FIGURE 1 is a diagrammatic view with parts in section showing a furnace equipped with ladling apparatus embodying the invention;

FIGURE 2 is a circuit diagram of the fluid circuits for the furnace; and

FIGURE 3 is a wiring diagram of the control apparams.

The furnace, as indicated generally in FIGURE 1, may be any desired type of metal melting or holding furof the crucible.

3,e5;,794 Patented Aug. 28, 1962 nace having a furnace body, indicated generally at it formed of refractory material and defining a chamber 11 to hold molten metal, indicated at 12. In operation of the furnace, as shown, it is contemplated that the level of molten metal therein will'vary from the level 13 illustrated to a lower minimum level indicated by the dot-dash line 14. In this respect, the furnace illustrated is similar to that more particularly described and claimed in my co-pending application referred to above, although the features of the present invention could be applied to furnaces ofother types utilizing dilferent types of ladling or discharging devices.

In the furnace illustrated, molten metal 12 in the furnace chamber is adapted to flow into a crucible 15 which is submerged at its lower end in the molten metal in the chamber and which is provided with a vertically elongated inlet passage 16 terminating at its upper end in an inlet opening 17 in the upper part of the crucible. At its lower end, the passage 16 opens into the molten metal in the furnace chamber and the passage is of such a vertical length that when the crucible is subjected to discharging pressure the head of metal above the lower end of the passage will always be sufficient to prevent the pressure from blowing out through the passage. A discharge tube 18 communicates with the lower part of the crucible below the inlet opening 17 and extends upwardly at an acute angle to the vertical to terminate above the maximum level of molten metal in the chamber and adjacent to one side of the chamber.

To fill the crucible and to discharge molten metal therefrom, the crucible is alternately subjected to vacuum and discharging pressure supplied by a pump or blower 19. The inlet of the pump or blower 19 is connected by a conduit 21 to a selector valve 22, which may be moved to different positions to connect the blower inlet either to atmosphere, as in the position shown, or to the upper end The blower outlet is connected in alternate paths through an adjustable reducing valve 22 and through a direct conduit 23 to a selector valve 24 which may connect either of the two paths through the valve 22 to atmosphere or to the upper end of the crucible.

In operation, the valve 22 is first turned to a position from that shown in which it connects the blower inlet to the crucible and the blower outlet to atmosphere. Under these conditions, the crucible is subjected to vacuum and molten metal will be drawn through the inlet passage 16 into the crucible to a level slightly above the inlet opening 17. After filling, the valve 22 may be returned to the position shown so that with the valve 24 in the position illustrated the crucible will be subjected to a relatively low intermediate pressure to force the molten metal in the crucible to the level of the inlet opening with the metal in the inlet passage dropping below the level in the crucible itself, as shown. When the level in the furnace chamber exceeds the level of the inlet opening 17, the intermediate pressure may be atmospheric, as disclosed in my co-pending application referred to above, but when the level in the furnace chamber may exceed the level of the inlet opening an intermediate positive pressure .is necessary to depress the level in the inlet passage to a point below the inlet opening.

For a discharging operation, the Valve 24- is moved to connect the conduit 23 directly to the upper part of the crucible to subject the crucible to a pressure high enough to force the metal therein above the outlet opening through the discharge tube 18. By regulating the amount of discharging pressure supplied and the time during which the crucible is subjected to that pressure, an accurately measured discharge or shot can be effected.

The metal forced out of the discharge tube 18 is normally received in a launder 25 which is mounted above 53 to connect the pressure the side wall of the furnace chamber adjacent to the upper end of the discharge tube and is conducted thereby to a pointoutside of the furnace chamber. In a conventional operation, the launder would conduct the molten metal to the inlet sprue of a die casting machine or other mold. 7

According to the present invention, 'a launder 25 is movably mounted so that it can move between a position shown, in which it will conduct the-molten metal outside of the furnace chamber, to a second position illustrated in dotted lines in which it will return molten metal discharged into it to the furnace chamber. For this purpose, the launder is pivotally mounted at 26 on an arm 27 supported by a bracket 28 on the side of the furnace body. A connecting rod 29 is slidably supported by the bracket 23 and is connected through a link 31 with the outer end of the launder spaced irom the pivot 25. The connecting rod 29 is connected to a fluid cylinder 32 by which it may be moved vertically to'tilt the launder between the two positions illustrated. When the launder is in the dotted line position shown, metal discharged into it from the dischargetube will return to the furnace chamber so that molten metal cannot stand an excessive amount of time in the discharge tube and thereby be cooled to an undesirable extent.

The fluid controls for operating the discharge apparatus and the launder. are illustrated diagrammatically in FIG- URE 2. As shown in thi-sfigure, the inlet conduit 21 for the blower 19 is connected to one port 33 of a plunger type valve which is provided with three

additional ports

34, 35 and 36. The valve has a plunger 37 for'med with cross ports and parallel stra ght-through ports, as shown, and is shifta-ble longitudinally ifrom its neutral position illustrated in which all of the ports are closed to a lefithand position in which the ports 33 and 34 are connected and

ports

35 and 36 are connected to a right-hand position in which ports 33 and 36 are connected and

ports

34 and 35 are connected. The valve is shifted to its lefthand position by a solenoid 38 and to its right-hand position by a solenoid 39 and will occupyits neutral position, as shown, when both of the solenoids are tie-energized. The port 36 is connected through a conduit 41 to the upper part of the crucible 15, the port 34 is open to atmosphere and the port 35 is connected through a conduit 42 and an adjustable pressure regulator 43 to the blower outlet; 'The blower outlet is also connected through a pressure regulator 44 and a solenoid shut-off valve 45 to the conduit 41 to supply a positive intermediate pressure thereto. Additionally, the conduit 41 may be connected to atmosphere through a filter 46, a flow regulating needle valve 47 and a solenoid shut-oil valve 48 to supply atmospheric pressure to the crucible as the intermediate pressure, when desired.

The fluid motor 32 is supplied with operating pressure from any convenient source through a supply conduit 49 through a reversing valve 51 which may be identical to the control valve 3437. The valve 51-is operated by

solenoids

52 and 53 to be shifted to the left by the solenoid 52 to connect the pressure to the upper part of the cylinder 32 and to 'be shifted to the right'by the solenoid to the lower part of the cylinder 32. V

The ladling apparatus is controlled preferably through an electrical controlcircuit, as shown in FIGURE 3, which is powered from any suitable source of electric current, the opposite leads of which are indicated at 54 and 55. A double master control switch is provided having

contacts

56 and 57 which are operated simultaneously and which normally occupy the position shown When the apparatus is shut down. These contacts may be moved manually to the left to start the operation.

The blower 19 is driven by a motor 58, which is connected directly to the lead 55 and through the control switch contact 56 to the lead 54. The motor, when energized, closes two normally open motor switches M81 and normally open, being closed temporarily whenthe a NSlthe switch MSI shunting the control switch 56. starter switch 59 is in series with the motor 58 and=1s ing button 61 therefor is manually depressed. I

The control switch 57in the open switchposition closes a pair of back contacts'which'connect a lead 62 between the'lower contacts of switch 56 and switch M51 to a lead.

v 63. 'When the control switch is closed, the contacts 57 connect the lead 62 toa lead 64. The starter switch. has a second switch section 65 which is normally closed and which is temporarily opened when the starter button is depressed to interrupt the lead 64.

The complete system, as shown, comprises three timer units lTR, ZTR and-3TR. The timer lTR includes a pair of

switch sections

66 and 67 which are normally closed,

as shown, and which are opened after the timer is run a a predetermined interval of time. The timer ZTR operates a similar pair of switches 68 and 69 and the timer 3TB.

operatesa single switch 71. The timer 3TR is additional ly connected inseries with a switch 72 which may be in terlocked with the casting mechanism, such'as the die casting machine, to be closed when the dies of the machine are fully closed in a condition to receive molten metal and to be open at other times. i l

The control system comprises five relays 3CR, 4CR, SCR, 6CR and 7CR The relay 3CR is connected in parallel with the solenoid 69 and is adapted to, be energized through normally closed relaycontaots 5CR3 and 7CR4 and a line 7-3 which is energized through the motor switches M81 and M82. The relay SCR is in parallel with the solenoid 45 or, in case the intermediate pressure is atmospheric, with the solenoid 43 and through either of the normally open relay switches 4CR1 or 5CR4 and the normally closed switch 7CR4. The relay 6CR' is energized through an emergency stop switch 74 and either of two paths, one of which includes a reset limit switch 75 and normally open contacts SCRS in series and the other of which includes normally open contacts GCRI and 3CR1 in series, The relay 7CR is in parallel with the solenoid 38 and may be energized either trom line 73 through timer motor switch 71 and a limit switch 76,

which is operated by tilting of the launder 25, or through 1 p the lead 63 and the limit switch 76., The limit switch 76 is in the position shown when the launder is in the'tull line position of FIGURE 1 and is moved to contact the lead 63 when the launder is tilted up to the dotted line position of FIGURE 1. The relay 4CR is energized directly from the lead 54 through the control switch 56 and normally closed contacts 5CR6 when the control switch is closed.

To start up an operation, the control switch is closed and the starter switch is temporarily closed to energize the motor 58. As motor switches M81 and M82 will close and will remain closed as long as the motor is energized to complete the motor circuit horn the lead 54 through the motor switches M81 and M32, the timer switch, 66 to the lead 55. At the same time, the timer ZTR will be energized through the lead 73, normally closed contact 7CR2 and switch 69.

this purpose an electrode 77 is mounted in the crucible and terminates slightly above the maximum desired level of molten metal therein. in the secondary winding of a transformer 78 whose primary winding is in series with the relay 4CR and the other side of the secondary winding of the transformer is grounded to the molten metal. When the levellin the crucible is low thesecondary winding of the transformer operatsoon as the motor is energized, the

The electrode 77 is connected 78 will be open-circuited and the impedance of the transformer primary winding will limit current flow through the relay 4CR to a value insuflicient to operate the relay. However, when the metal in the crucible reaches the dc sired level, current will pass from the electrode 77 to the metal, short-circuiting the transformer secondary and reducing its primary impedance sufficiently to allow operation of the relay 40R.

As soon as the relay 4CR is energized, it will close the normally open contact 4CR1 to energize the relay SCR and the solenoid 45. Energizing of the relay 5CR will close the normally open contacts 5CR1 and SCRZ to energize the solenoid 52 thereby to move the fluid motor 32 downward and tilt the launder to the full line position shown in. FIGURE 1. At the same time, the normally closed contact 5CR3 will open to de-energize the relay 3CR and the solenoid 39. The normally open contact 5CR4 will close to shunt the contacts 4CR1 thereby to maintain the relay SCR energized. The normally open contact 5CR5 will also close, conditioning the circuit to energize the relay 6CR when the reset limit switch 75 is closed.

Energizing of the solenoid 45 will open the corresponding valve and will supply to the crucible the relatively low intermediate pressure regulated by the regulator 44. In the case where the maximum liquid level is below the level of inlet opening 17, the solenoid valve 48 may be substituted for the solenoid valve 45 in the circuit so that at this time the crucible will be subjected to atmospheric pressure. In either event, the level in the crucible will drop to the condition shown in FIGURE 1 wherein the main portion of the crucible is filled to the level of the inlet opening 17 and the level in the vertical passage 16 is slightly below the level of opening 17. At this time, the apparatus is in condition to effect a ladling or discharging operation.

When the die casting machine is open for ejection of a completed casting, it will close the reset limit switch 75 to energize the relay 6CR which is interlocked through the normally open contacts 6CR1 and the normally closed contacts 3CR1. Provision of the reset limit switch 75 prevents a double shot in the die casting machine and is desirable when the ladling apparatus is supplying a machine of this type.

When the dies of the die casting machine are again closed and locked, ready to receive an additional shot, the switch 72 will be closed and the timer 3TR will be energized to move the switch 71 downward to complete a circuit to the solenoid 38 and relay 7CR through the switch 71 and the limit switch 76 which is then in the position illustrated. Energizing of the relay 7CR will open the normally closed contact 7 CR4 to de-energize the relay SCR and the solenoid 45.

Energizing of the solenoid 38 will shift the valve 37 to the left to connect the outlet of the blower 19 through regulator 43 and the selector valve to the upper part of the crucible to subject the crucible .to high discharge pressure. This discharging operation continues for an interval determined by the timer 3TR and until the timer 3TR has timed out and opened the switch 71. Opening of this switch will de-energize the relay 7CR and the solenoid 38 to return the valve 37 to its centered position, as shown. At this time, the apparatus is ready for refilling and the relay 30R will again be energized through the switch contacts 5CR3 and 7CR4 to repeat the cycle as described above. At any time in the cycle when it is desidered to stop the operation for any reason, the emergency stop switch 74 may be opened to tie-energize the timer STR thereby opening the switch 71 and returning the apparatus to the beginning of a discharge cycle.

When it is desired to shut down the ladling apparatus as, for example, at the end of a day, the control switches 56 and 57 will be moved to the oflE position, as shown. Because of the lag in the motor circuit, the switchesMSl and M82 will remain closed and the motor will be energized through the switch 66 of the timer 1TR.

As soon as the main control switch is moved to its off position, the solenoid 53 will be energized through the contacts SCRl, which are then closed, and the back contacts of the main control switch 57. Energizing of the solenoid 53 will throw the valve 51 to the right to supply pressure to the lower end of the fluid motor 32, thereby elevating the launder to the dotted position shown in FIGURE 1. When the launder is so elevated, it will throw the switch 76 to the left and will energize relay 7CR and solenoid 38 through the lead 63 and the contacts 57.

Energizing of the solenoid 38 will shift the valve plunger 37 to the left to subject the crucible to high discharge pressure. At this time, the metal in the crucible will be forced out through the discharge tube into the launder 25 and will be directed by the launder back into the furnace chamber.

At the same time, the timer 1TR will be energized through the normally open contact 7CR1 and the timer contact 67. The timer ZTR will remain energized through the normally open contact-7CR3 and the control switch section 57.

After all of the molten metal in the crucible has been forced out the timer 1TR will time out to open the

switches

65 and 67 thereby stopping the timer and deenergizing the motor 58. As soon as the motor is deenergized, the motor switches M81 and M82 will open removing all of the power from the circuit. Timers lTR and 2TR will reset, leaving the apparatus in its initial condition ready for restarting by closing the main control switch. It will be noted that at this time the level of metal in the crucible and in the discharge tube can never exceed the level of metal in the furnace chamber so that there will be no tendency in the crucible or discharge tube to cool and solidify or partially solidify. The apparatus will therefore be left in a rest condition in which it would remain, for example, over night.

According to the present invention, the apparatus will automatically-shut down if the interval between ladling or discharging cycles exceeds a predetermined interval which would tend to produce freezing or partial freezing of the metal in the crucible or discharge tube above the level of the metal in the furnace chamber. In this operation, assuming that the apparatus is in condition for discharge or ladling cycle, as soon as the switch 72 is closed the relay 5CR will be energized through the contacts 5CR4 and 7CR4 and the timer ZTR will be energized through the normally closed contact 7CR2.

Unless a ladling or discharge cycle is started by closing of the switch 72, the timer 2TR will time out to open the switch 69 and move the switch 68 to the upper contact shown. This will energize the solenoid 53 through the contacts 5CR1, switch 68, switch 65 and lead 64. Energizing of the solenoid 53 will operate the valve 51 to swing the launder up to the dotted line position which will swing the limit switch 76 to its left-hand position, as before. will energize the relay 7CR and the solenoid 38 to cause metal to be pumped or forced out of the crucible and back into the furnace chamber, as described above. This operation will continue until the timer lTR times out at which time the motor will be de-energized, the motor switches M51 and M82 will open and the apparatus will be placed in its inoperative or rest position subject to being restarted by momentarily closing the starting switch 59.

It will be seen, therefore, that with the present apparatus the apparatus is not allowed to remain for an excessive period of time in a condition in which the metal might freeze or partially freeze in the crucible or discharge tube. In the event of any long delay due to diificulty with the die casting machine, or the like, the apparatus will automatically shut itself down at the end of a predetermined time interval and will remain in a safe shut down condition until it is again restarted.

This- While one embodiment of the invention has been shown and describedherein, it will be understood that it is illusto the appended claims.

What is claimed is; V a J 1 l. Furnace ladling apparatus comprising; in combination with a furnace body formed with a chamber to contain molten metal, a crucible in the chamber, means defining a vertically elongated inlet passage opening'into the crucible above its bottom and into the chamber below the minimum operating levelofmolten metal therein, a discharge tube communicating with the lower part of the crucible below opening of theinlet passage into the crucible and discharging above the maximum level of molten metal in' the chamber adjacent to the top and one side of the chamber, fluid pressure means to subjectgthe crucible to vacuum to draw molten-metal into it through the inlet passage and thereafter to apply pressure to the crucible to force moltenmetal therein out the discharge tube, a launder mounted adjacent to the upper end of the discharge tubeto receive molten'metal from the discharge tube and movable from one position in which it directs molten metal,

outside of the chamber to a second position in'which the molten metal is returned to the chambenmeans to move the launder from one of said positions to the: other, a primarycontrol to operate the forcing means while the launder is in said one'position to discharge moltenmetal from the furnace, and control means to move the launder from said one position to said second position and thereafter to operate the fluid pressure means to apply forcing pressure to the crucible toforce' molten metal through the discharge tube into the launder and back into the fur'-' nace chamber, the control means including time responsive means operable after a predetermined time interval,

means controlled by operation of the time responsive.

means to operate the control means, and means operated by the primary control to reset the time responsive means whereby if the primary control is operated more frequently than said predetermined time interval the time responsive meanswill not operate.

2. Furnace ladling apparatus comprising a furnace body formed with a chamber to contain'molten metal, a dismolten metal in the chamber and: adjacent to the top and.

one side thereof, means to'force molten metal from the- 1 chamber through the discharge tube, a launder mounted.

adjacent tothe upper end of the discharge tube receiving;

molten metal from the discharge tube and movable to oneposition in'which it directs the molten metal to a point. outside of the chamber and a second position in which it causes the molten metal to return to the chamber, a primary control to operate the forcing means While the, launder is in said one position to dischargemolten metal. from the furnace, time responsive means operable after a predetermined time interval, mean-s controlled byoperation of the time responsive means to move the launderto said second position and to operate the forcing means: to force molten metal through the discharge tube into the launder and back into the furnace chamber, and means. operated by the primary control to reset the time responsive meanswhereb'y if the primary. control is operated more frequently than said predetermined time interval thev time responsive means will not operta-te but'if the primary control is not operated the timing means will operate to discharge molten metal through the discharge'tube before excessive cooling of the moltenfmetal in the discharge tube can occur.

References Cited in. the file of this patent UNITED STATES PATENTS