US3191247A

US3191247A - Furnace ladling apparatus

Info

Publication number: US3191247A
Application number: US838584A
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: 1965-06-29
Anticipated expiration: 1982-06-29
Also published as: GB917298A; CH364585A

Description

United States Patent O This invention relates to furnace ladling apparatus and more particularly to an apparatus for discharging molten ,metal in measured quantities from a furnace chamber.

The problem of ladling molten metal from a furnace chamber in accurately measured shots has long been a difficult one.

An extremely satisfactory solution to this problem is provided in the patent to Elmer E. Edstrand, No. 2,846,- 740. As disclosed in that patent, molten metal flows into a closed crucible through a vertically elongated inlet tube opening into the upper part of the crucible and is forced from the crucible through a discharge tube by subjecting the crucible to a relatively high discharge pressure. As an inital step the crucible may first be subjected to a low intermediate pressure to depress the level of molten metal in the inlet tube to a point below the inlet opening so that an accurately measured charge is retained in the crucible and the inlet tube is made of suflicient length to prevent the high discharge pressure from blowing past the molten metal therein.

It is one of the objects of the present invention to provide a furnace ladling apparatus, more particularly of the type disclosed and claimed in Edstrand Patent No. 2,846,740, which is operative over a relatively Wide range of fiuctuations in level of molten metal in the furnace chamber.

Another object is to provide a furnace ladling apparatus in which the crucible is first subjccted to vacuum to draw molten metal through the inlet tube into the crucible even though the level of metal in the furnace chamber is below the inlet opening. The crucible is then subjected to an intermediate pressure to depress the level of molten metal in the inlet tube to a point below the inlet opening and finally to a high discharge pressure to force molten metal ,the molten metal reaches an excessive level therein by rnelting a fusible vent closure.

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:

r FIGURE l is a sectional View with parts shown diagramatically of a furnace ladling apparatus embodying the invention;

FIGURE 2 is a partial view similar to FIGURE 1 showing an alternative arrangement;

FIGURE 3 is a partial section of a safety vent; FIGURE 4 is a diagram of the fluid circuit; and FIGURE 5 is a wiring diagram of the control circuit. The ladling apparatus as shown in FIGURE 1 is used with a metal melting or holding furnace having a body of refractory material formed with spaced chambers i i 11 and 12 adapted to hold molten metal. The chambers &191347 Patented June 29, 1965 are connected by subnerged channels 13 which are surrounded by a primary unit 14 consisting of a magnetic core carrying a primary winding to be energized by alternating current. While one well-known type of furnace is illustrated, it will be apparent that the ladling appa'atus, as described hereinafter, might be used with any other desired type of furnace containing molten metal.

in the two-chamber type furnace, as shown, the chamber 11 preferably constitutes a charging chamber and the molten metal is ladled from the chamber 12. For this purpose a crucible 15 formed of refractory material is mounted in the chamber 12 with its lower portion submerged in the molten metal therein. The molten metal during operation of the furnace will normally fluctuate between a maximum level as shown at 16 and a minimum level shown at 17. The crucible 15 is closed by a cover 18 to which a conduit 19 is connected to supply air or gas under pressure thereto for ladling the metal therefrom.

Metal enters the crucible 15 through a vertically elongated inlet tube 21 which may be integrally formed in one wall of the crucible. The tube 21 terminates in an inlet opening 22 which is at a level above the maximum metal level 16. At its lower end the tube 21 opens into the furnace chamber and it is made of a vertical height such that the maximum pressure in the chamber will not blow past the molten metal therein during a discharging operation.

Metal is discharged from the crucible through an outlet opening 23 in the lower part thereof and well below the inlet opening 22. A discharge tube 24 communicates with the outlet opening 23 and extends upward therefrom to a height above the maximum metal level 16 and through an opening in the furnace side wall. An adjustable launder 25 may be provided to receive metal from the discharge tube and to conduct it to a casting machine. To vary the pressure within the crucible, the Conduit 19 is connected through a three-way selector valve 26 selectively to the inlet of a blower 27 or to the outlet of the blower or to an atmospheric vent 28. The valve 26 may be turned manually or by any desired type of automatic control mechanism selectively to its three different positions to dischar e a shot of molten metal from the furnace chamber.

With the liquid level in the furnace chamber at a point between the

levels

16 and 17 and with the crucible vented to atmosphere no metal can flow into the crucible. As a first step in the operation the valve 26 is turned to the position shown to connect the crucible to the suction connection of the blower 27 with the discharge of the blower being vented to atmosphere through the valve and the vent 28. At this time, the crucible will be subjected to a vacuum sufiicient to raise molten metal from the furnace chamber through the inlet tube 21 to fill the crucible.

After the crucible is filled to a level slightly above the inlet opening 22, the valve is turned 45 degrees clockwise to vent the crucible to atmosphere through the vent 23. At this time, the level of metal in the inlet tube will drop to the same level as the level in the furnace chamber but all of the molten metal in the crucible below the inlet opening will be retained therein. Under these conditions, the levels will appear substantially as shown in FIG- URE 1.

To etlect discharge of the metal the valve 26 is turned a further 45 degrees clockwise to connect the crucible to the high pressure discharge of the blower with the blower inlet being connected to atmosphere. At this time the crucible is subjected to a high discharge pressure which may be controlled to efiect discharge of metal at the desired rate but which in any event is insufcient to blow past the head of metal in the inlet tube 21. This .superatmospheric pressure.

is effective; an accurately measured quanttyor shot ,of 'metal will be discharged. Upon completion of one discharge operation the valve is returned to the position shown and the cycle is repea'ted for subs'equent shots.,

crucihle itself below,

In the alternative apparatus shown in FIGURE 2, all i parts except the pressure controllingparts areidentical totcorresponding parts in FIGUREI and are indicated ,by the same reference numerals. In this constructon,

the inlet opening 22 lies at a' level beneath the maximum* metal level. intthe furnace chamber and above the minimum metal level 17. The `pressure .Conduit '19is connected through a two-position valve 31 either to the' suction side of a blower 32 or to a Conduit 33 supplying in the normal or starting position of the valve 31, as shown, the conduit 19 is conj power leads,

'manual shut -off valve 57 maybe provided in the atmospheric vent line' to close it when desired. Pressure gauges 58 and 59 may be provided in the line 52 and at a point between. the regulating valve 43 and solenoid shut-oil valve 49 to indicate the pressures therein.

The operation of the' apparatus' may be controlled through a circuit, asillustreted in PIGURE 5, energized from a source of electrical power whose opposite sidcs 'are indicated by the lin'es ol and 62. A nanually operable control switch63 may be mountedin one of the shown as &Lwhich may be closed manually to energize thecircuit ready for" operation. The lead 61 ,below the control switch 63 is connected through a manually operable starting switch 64 with a motor ,65 for driving the blower 27. A holding circuit ss is connected around the starting switch vthrough a normally open t motor switch 67 which is closed when the motor is energized to holdthe motor in operation 'until the control nected to the suction side of the blower and theconduit 33 is vented through an atmospheric'vent 34. The dis charge side of the'blower ?vz-is connected either through. a pressure reducing valve 35 or directly through ,a selector valve 36 to the conduit 33. o v

In operation, when theliquid level is at the maximum point 16 the metal from the furnace chamber can flow by gravity through the inlet tube and to the .crucible.

Hou/ever, with the

valves

31 and 36 in the position shown,

the 'crucihle will be -subjectedftovvacuum during charging e i so that even though the metal' level in the chamber falls ,to the minimum' point 17, the metal will still be drawn' through the inlet tube into the crucible to fill it. As the second step in the process, the valve' 35 is in the position shown and the valve 31 is turned 90 degrees to connect the inlet of the blower 32' toatmosphere ?and connect the outlet tube 33 to the Conduit 19. At this time a switch '63 is 'again opened. The lead 61- isconnected through the motor switch 67 to a lead 63 fOl'll which a plurality of relay circuits are energized. ,As shown, there The relay ICR is energized through normally'closed Contacts ?CR-l and SGR-1 andthe solenoid 45 is connected in parallel with this' relay, as shown. The relay 4CR is cnergized through a direct lead 69 from the control switch 63' through a normally closed contact CR-' and a transformer prirnary winding 71. The, Winding 71 is magnetically coupled to a secondary Winding 72 which which extends into the crucible and terminatcs above the is adjusted to be just sufficient to depress the level off molten metal in the crucible to or very slightly below the inlet opening so that .when the pressure is appliedthe crucible itself will be filled below the level of the inlet opening and all eXcess metal in the, crucible will be forced' back through the inlet tube into the furnace, chamber;) For a discharge operation, the valve %is turned 90 de,- grees counterclockwise to connect the blower outlet pres-` sure directly to the crucible to force the molten metal therefroin through the discharge tube 'the sameas in the embodiment of FIGURE 1. i

FIGURE 4 illustrates diagranniatically the fluid circuit '31 in FIGURE 2. The valve '38, asshown, has four spaced

ports

39, 40, 41 and 42 communication between' which is controlled by a 'shiftable plunger 43 having cross bores and angular bores thereiu, as shown. "The plunger is shifted by two -

solenoids

44 and 45 in opposite directions and' when both solenoids are de-energized will occupy a neutralpostion, as shown, in which all ol the ports are closed. I v y Theloutlet side of the purnp or blower 27 is 'connected through a Conduit i-6 and a pressure regulator 47 to the valve port 41. The blower outletis further connected maximum 'level of moltenmetal therein. When the metal 'eaches the maximum level desred. in the crucible, a sparkfwll jum;) across 'from the rod 73 to the molten metal 'in the crucible and will short the secondary winding 72 thereby increasing'the current flow through the thelevel reaches a predeterrnined high value.

The relay 5CR and the solenoid 54 are connected in parallel 'and are energized through the normally closed contactTCR-l and either of two normally open Contacts 4CR+1 or 5CR-2. i

Therelay (SGR is energized through a normally closed emergency stop switch 75 and either through normally closed contact 3CR-ll and normally. open contact ecin-i in series or through normally-open contact 'SGR-4 and normally open reset limit" switch 76 in series. The soienoid i iandrelay 'TCR are connected in parallel and are controlled' by a normally open 'switch 77 of a timer indicate-.d generally at 78 which includes a timing motor 79. 'The timing motor '79 isconnected in arallel with the relay CR through a limit switch 81.

i In operation of the ladling apparatus, as shown in FIG- through a pressure regulator 48, 'a solenoid operated r shut-oli valve 49 anda manual shut-off valve 51 with a' Conduit 52 which is connecte'd to the top of the' crucible as, for example, through the pipe 19. The Conduit 52 and the crucible are .also connectedthrough a conduit 53- with the valve port 42. v v

The Conduit 152 and the crucible may be vent ed to atmos phere through a solenoid valve 54, a, needle valve 55', by which the rate of flow is controlled, and a filter 56. A

' 70 i i i r FEGURE 4. Inthis position'of the plunger, the blower 5 and assuming'that'the furnacechamber is filled with molten metal toa level betweenthe maximum and minimum limits, the operation is started by closing the control switch 63 andmomentarly closing the starting switch 64 to energze' the' blower 'motor 65; As soon as the motor tain-the system in operation. At this stage, the relay 3CR is' energizedithrough the normally closed contacts 7CR-1 i and SGR-1 and the 'solenoid 45 is simultaneously energzed to shft the valve plunger (33 to the right, as seen `in outlet is connected throughjthe valve ports 41 and 40 to jatmosphere and the bloweriinle t is 'connected through `'valve ports 39 and 42 and-thetconduits 53 and 52 to the 1 upper part ofthe crucible to subject the crucible to vacuum. Molten metal from the furnace chamber will flow into the crucible until the level therein reaches a point sufliciently high to cause a spari: from the rod 73 to the molten metal in the crucible thereby increasing the current flow through the transformer primary 71 and energizing the relay t-CR.

This closes the normally open contact 4CR-1 to energize the relay SCR and the solenoid 54 to open the conduit 52 and the crucible to atmosphere so that the level therein can fall to the condition illustrated in FIGURE 1. The relay SCR and solenoid 54 are maintained energized through the contact SGR-2 and the relay 3CR and solenoid 45 are de-energized by opening of the contact SGR-1.

The apparatus is now in condition for a pumping cycle, but before this can 'be initiated it is desirable that a die cast or permanent mold machine, into which the molten metal is to be pumped, open for ejection of the last completed casting. This operation will close the reset limit switch 76 and will energize the relay CR through the reset limit switch and the Contacts SCR which are then closed. This feature prevents a double shot being pumped into the casting machine before it is in condition to receive additional molton metal.

When the dies of the die casting machine are fully closed, the switch 81 will be closed thereby and the timer motor 79 will be energized. As soon as the timer motor is energized the switch 77 Will close and will remain closed until the timer motor has timed out the desired cycle. Closing of the switch 77 will energize the solenoid 44 and the relay 7CR which will open the normally closed contact 7CR-1 to de-energize both relays SCR and 6CR, as well as the solenoid 54, to reclose the atmospheric vent valve. When the solenoid 44 is energized, it will shift the valve plunger 43 to the left to interconnect ports 39 and 40 and ports 41 and 42. At this time, the inlet of the blower 27 will be connected to atmosphere and the blower outlet will be connected through the regulator 47 and valve ports 41 and 42 to the crucible to subject it to high pumping pressure.

The pumping pressure will be maintained for the interval for which the timer motor '79 is set and at the end of this time interval, the switch 77 will open to de-energize the solenoid 44 and the relay 7CR. This returns the apparatus to its initial condition, ready for a further cycle and cycling in the manner described will be continued as long as the casting machine is operated and molten metal is available in the furnace chamber. It will be understood that automatic operation under control of the die cast machine through the switches 76 and 81 could be replaced by manual operation, if desired.

Emergency stop switch 75 may be operated at any time to stop the pumping at any point in the automatic cycle and when this switch is open, the system will return to its initial condition ready for a subsequent operation.

For operation under the conditions illustrated in FIG- URE 2 in which the intermediate pressure, instead of being atmospheric, is a relatively low positive pressure, the solenoid valve 49 may be connected in the control system in place of the solenoid 54 with the valve 57 being closed and the valve 51 being open. This operation will be identical to that above described except that instead of opening the valve 54, the valve 49 will be opened to supply the desired intermediate pressure, as determined by the regulator 48, to the crucible.

As a safety feature in the event the system should fail, for any reason, and vacuum in the crucible should continue to raise the molten metal level therein to a dangerously high level, a safety vent as shown in FIGURES 1 and 3 may be provided. This safety vent comprises a pipe extending through and sealed into the top of the crucible and terminating at its lower end within the crucible at a level slightly above the maximum expected level therein, but below a level which would be dangerous. As shown in FIGURE 3, the lower end of the pipe 85 is closed by a thin diaphragm 86 of fusible material, such as aluminum, which is secured in place by a cap 87. If the liquid level in the crucible should reach the level of the fusible material 86, this will be melted by the heat of the molten metal and will vent the crucible to` atmosphere through the pipe 85. In thi-s way, a dangerously high level in the crucible is prevented under all conditions.

While two embodiments of the invention have been shown and described in detail, it will be understood that these are for the purpose of illustration only and are not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claim.

What is claimed is:

Furnace ladling apparatus comprising a furnace body defining a chamber adapted to hold molten metal and vented to atmosphere, a crucible fitting into the chamber to be partially immersed in the molten metal therein, a tube extending downward into the molten metal in the chamber and term-inating at its upper end in an inlet opening in the crucible above its bottom, the crucible having a discharge opening below the inlet opening, a discharge tube communicating with the discharge opening and extending upward therefrom to a level above the normal maximum level of molten metal in the chamber and discharging outside of the chamber, means connected to the top of the crucible to subject the upper part of the crucible to a subatmospheric pressure suflicient to draw molten metal from the minimum level in the chamber through the first named tube and inlet opening into the crucible, control means -responsive to the level of molten metal in the crucible to interrupt the subatmospheric pressure in the crucible and subject the crucible to an intermediate pressure sufiicient to depress the molten metal in the first named tube below the inlet opening, means to supply a high pressure to the crucible to force molten metal out the discharge tube but insufiicient to blow past the molten metal in the first named tube, a vent tube opening into the crucible at a level slightly above the maximum desired level of molten metal therein, and a fusible closure for the lower end of the vent tube to be melted by molten metal if its level exceeds said maximum desired level.

References Cited by the Examier UNITED STATES PATENTS 2,209,882 7/40 Galloway 22-209 X 2,397,512 4/46 Schwartz 22--79 2,846,740 8/58 Edstrand 22-79 2,847,739 8/58 Sylvester 22--69 2,937,789 5/60 Tania 266-38 3,0S0,794 8/62 Holz 22-79 3,123,877 3/64 Sylvester 22--141 MORRIS O. WOLK, Pr'mary Exam'rer.

RAY K. WINDI-IAM, NATHAN MARMELSTEIN,

MARCUS U. LYONS, Exam'ners.