US2122233A - Means for melting metal - Google Patents

Description

June 28', 1938. P. DUNSHEATH 2,122,233

MEANS FOR MELTING METAL: I

Filed May 29, 1936 2 Sheets-Sheet 1 June 28, 1938. P. DUNSHEATH MEANS FOR MELTING METAL Filed May 29, 1936 2 Sheets-Sheet 2 Fig. 2.

37 31 F739. [(coni) 5 Patented June 28, 1938 pairs snares attain MEANS FQR mmmo RETAIL Percy lllunsheath, Kent, England, assignor to Henley Extrusion Machine Company limited, London, England, a British company Application May 29, 1936, Serial No. 82,539 lln Great Britain .llune ll, M35

9 (Claims.

This invention relates to apparatus for melting of metals and particularly to apparatus for melting metal pigs or ingots, that is, bodies of solid metal that are of regular form and dimensions and are generally materially longer in one direction than in the others.

The invention has for an object the production of an improved apparatus for the conversion of ingot metal into molten metal, which is 10 particularly, though not exclusively, suitable for use in conjunction with a metal-working machine demanding a continuous supply of molten metal. A second object of the invention is to provide an apparatus for the production of molten metal in which the volume of metal in the apparatus, a, the period of time during which it remains in?" the molten state, and the possibility of its contamination are reduced to a minimum. A further object of the invention is the provision of apparatus for the continuous production of molten metal from pigs or ingots at a rate which under working conditions is substantially equal to the rate at which molten metal is withdrawn from the apparatus, and also, if required, at a predetermined temperature. Yet another object of the invention is to provide a completely automatic melting apparatus in which ingot metal is automaticallydntroduced into the melting furnace as and when required.

' With these and other objects in view the invention consists in the'lmproved means for melting the ingot metal, for regulating the rate of melting, for controlling the final temperature of the metal, for the preventionof oxidation, for automatically introducing ingots into the melting furnace from a feed chamber and for maintaining'the feed chamber supplied with ingots;

in the various combinations of such means; and

in the various structures, arrangements and com- 40 binations of parts, all as hereinafter described and particularly defined in the appended claims.

The invention will now be described with reference to the accompanying drawings which show, by way of example only, a completely automatic machine, constructed in accordance with the invention, for the continuous production of molten lead from ingot lead at a rate approximately equal to the rate at which molten metal is withdrawn therefrom by the metal-working machine in conjunction with which it is to be used. During the course of the description various modifications that may be made are pointed out and it will be appreciated that these and 5 other changes may be made without departing (Cl. 266-33l from the invention as defined in the app claims. Figure l is an elevation, partly in section, of the complete machine,

Figure 2 is a diagram of the electrical circuit employed in the machine shown in Figure 1,

Figure 3 is a cross section to an enlarged scale of the melting chamber, the cross section being taken on the line m-nl of Figure 1.

Referring now to the drawings, it will be 0b- 10 served that the melting chamber l is of tubular shape and for convenience is formed of two parts 2 and t disposed end to end and making a flanged joint t with each other. The chamber is disposed with its longitudinal ams at an angle of 15 about to the horizontal. Naturally the angle of inclination may be more or less than this and may be as much as 90. The melting chamber is supported at itsupper and lower ends by supporting members 5 and t. The length of the 20 chamber is such that it can accommodate at least two, preferably three, ingots placed end to end and its section approximates to that of an ingot, that is to say, its cross-sectional dimensions do not exceed, say, about twice those of 25 the ingot. It is preferable to make the crosssection of the chamber only of such a size as to permit a pig or ingot to slide along it freely. To this end the chamber may beof circular or rectangular cross-section or of semi-circular 30 cross-section depending on the shape of the ingots to be melted. As shown in Figure 3 of'the drawings the chamber is of semi-circular crosssection with the curved surface uppermost. This arrangement reduces the tendency of the ingots 35 to become wedged. An opening l is provided in the lower end wall of the chamber through which molten metal may be withdrawn. The upperend of the chamber is closed by a door 8, which is opened only to permit a fresh ingot to 40 be fed into the chamber, in order to reduce the access of oxidizing atmospheric gases to the chamber. The chamber is surrounded by two mufi heaters 9 and W. The lower one 9 encloses approximately the lower :third of the chamber,-45 the remaining two thirds of the length of the chamber being surrounded by the upper muff heater I t. These heaters are independent of each other, and each may be either gas or electrically heated. The mufi heaters shown in the drawings are both fitted with similar gas burners Ill and lZ-respectively, each comprising a series of jets to which a mixture of gas and air is supplied. The purpose of the lower heater, is to apply a melting heat to the lowermost ininserted through the door 8.

got l3 and firstly to produce, and then to maintain, a column of molten metal it in the lower end of the chamber 8. The upper of the two mufi heaters serves to pre-heat the ingots it: and id in this part of the chamber. Mufl heater it is heated by gas supplied to the burners 52, through pipe W controlled by a suitable valve 52. As the ingot i3 gradually melts the following ingots slide down the chamber and the lower of these begins to melt. When these have slid down to a sufiicient extent a fresh ingot may be The amount of heat supplied by the lower heater ii is controlled automatically in such a manner that the rate at which ingot metal is melted approximates under working conditions to the rate at which molten metal is withdrawn from the furnace. As shown in the drawings this is done by providing a float chamber H in which works a float it. This float is coupled to a pivoted arm l9 which carries a mercury switch Ell. When the level of molten metal is at or below a predetermined normal, the arm is maintained horizontal and the switch in the open condition. As the level increases, the float rises and tilts the arm thus closing the switch 2E3. This switch closes a circuit 26 extending from a suitable source of electric supply 22 to an electromagnetic relay device 23 which may be a spring controlled solenoid, as shown in Figure 2. The core of the solenoid is mechanically coupled to a regulating valve 2d and actuates this valve in a direction such as to reduce the supply of gas to the burner ii. Preferably the burner ii is supplied through a main feed pipe 25 and an auxiliary feed pipe 25 and the valve on which the float actuated electromagnetic relay operates is inserted in the auxiliary gas feed 26. This aumliary feed is then automatically cut on when the leveloi' the metal is too high and permitted to take place as the level returns to nol. Alternatively the float may be arranged to reduce the supply of:

fuel below the normal value when the level of the metal is above the normal and to increase the supply of fuel above the normal value when the level of the metal is below normal. Similar methods of control can be used where electrical heating is employed.

The second mun heater iii may be dispensed with if rare-heating of the ingots is not required. However this is not recommended as pre-heating has the advantage of reducing the temperature variation of the molten metal in the lower end of the chamber 8.

For some purposes it is extremely desirable to be able to supply molten metal at a definite constant temperature. This is so in the case where the furnace is used to supply molten metal to a continuous extrusion machine oi the screw thread impeller type. In such cases it is preferred to provide a second chamber it below the melting chamber into which molten metal spaced a short distance apart, as shown, and

placed in communication by a connecting tube 3!! ofreduced cums-sectional area as compared with those of the chambers l and 36. This reduces the transfer of heat by conduction from one chamber to the other. As the molten metal amazes flows through the lower chamber 30 it is heated to the desired temperature by a muff heater 32, the heat applied .by which is controlled by the temperature of the metal in the chamber. As shown in the drawings, the. muff is heated by a-gas burner 33, similar to burner it, provided with a. main and an auxiliary supply of gas through main and auxiliary supply . pipes 36 and 35 respectively. The auxiliary supply of gas to the burner is controlled by a thermostatic valve 36 which may be of any well known form, for instance, it may be of the kind in which the expansion of mercury in the thermometer bulb 3? produces a displacement of a diaphragm on which the needle of the valve-is carried. From this lower chamber 30 the metal is fed through the pipe 38 to the machine. The pipe 38 is provided with a drain plug 39 to facilitate the emptying of the furnace when required.

This device, mounted in the upper end of the melting chamber, is a device which comprises a pivoted arm till carrying at its free end a roller ll bearing on the upper surface of the top ingot it. As this ingot slides past the end of the arm fill the arm falls and operates an automatic device for feeding in another ingot. For this purpose the tubular member 3 forming the upper end of the melting chamber 0 is continued be: yond the door 8 to form a feed chamber 63 in which an ingot it may be placed as required,

either manually or automatically as hereinafter described. Normally the door 3 is closed and the ingot i l in the feed chamber rests against' a stop 35. When the arm tit falls it closes a connects a solenoid it to a suitable source of supply dd. This solenoid is mounted on a bracket 553 above the entrance to the melting chammr and the lower end of its core carries a rack 5i which engages a pinion 52 carried by the pivot of the door The extremity of the core is connected to one end of a lever 53 pivoted at 5%. The other end of this lever is pivotally connected to the stop #35. Accordingly when the solenoid is energized, the door 8 is opened and the stop withdrawn. The ingot id is released and slides down into the melting furnace i, whereupon the arm 48 is lifted again and switch l2 re-opened. This tie-energizes the relay iii and cuts oil the supply to the solenoid 68, the core of which falls and recloses the door and returns the stop 55 to its normal projecting position.

It will be seen that with this type of melting chamber, there is only a comparatively small quantity of metal in the molten state at any time and that the area of the exposed surface of the metal is a Under normal working conditions the molten metal is being withdrawn at the same rate as it is being produced so that it remains in the molten state for a very short time. These factors all tend to reduce the opportunities for oxidation of the metal by atmospheric gases. This tendency is further reduced by the provision of the door 8 which is opened only for a period of time sumcient to allow of the introduction of a fresh ingot into the cham-. her. It is preferred however to reduce this tendency still further by the use of an inert gas araaaaa or a vacuum in the upper part of the melting chamber. In this case it is preferable to provide a door 55 at the upper end of the feed chamber #33 to allow it to function as a lock or trap chamber which prevents the interior of the melting chamber from being placed in direct communication with the atmosphere when the door ii is opened. The doors 8 and 55 are suitably timing the opening and closing of the doors.

In general, it will be preferable to make the introduction of ingots into the feed chamber 63 travelled through one cradle pitch. As the arm 30 falls, thereby operating the automatic means, previously described, for transferring an ingot from the lock chamber 53 to the melting chamber i, it closes a second switch which completes a circuit extending from one terminal of the source of supply 22, through the coil of a self-locking relay 62, a switch 63 that is normally closed and back to the other terminal of the source 22. This energizes the relay 6? and pulls over itsarmature M. Movement of the armature Mi closes the switch 65, which locksthe relay,

and tilts a mercury switch 66 which in turn puts the auto starter 6H into action. This starts the motor and sets the elevator 55 in motion. The empty cradle opposite the sliding door 55 rises, engages a projection 68 on the door and lifts the door with it. Meanwhile the next full cradle rises and, as it passes the end of the guide rail ti which holds the ingots in place as they travel upwards, the ingot thereon is released and slides into the lock chamber d3. As soon as this has taken place the cradle which has lifted the door moves away from the door and releases it. As it falls a projection 69' carried by it strikes the switch b3 and momentarily opens it against the spring so. This breaks the locking circuit of the relay 52 which in turn opens the control circuit of the auto starter at and stops the motor 5%.

It will be realized of course that the action of transferring an ingot from the lockchamber to the melting chamber takes place much more rapidly than that of raising the next ingot on the elevator to the level of the lock chamber and that the former operation is completed before the'door 59 is opened.

Where the upper part of the melting chber lb and leaves by the pipe l5 Preferably the top of the container is made closely to approach the surface of the metal so as to reduce to a minimum the depth of the stream of gas passing over the surface of the metal. If this metal is the same as, or is a more-readily oxidizable metal than, that on which the melting apparatus is working, and the temperature in the chamber 82, is kept well above the oxidation. temperature, it can be ensured that very little of the oxygen that is always present in commercial supplies of inert gases, such as nitrogen, is retained in the gas entering the melting chamber l.

Before setting the machine into operation, the cradles on the full side below the charging opening are first filled when this has been done and the burners have been lighted power may be supplied to the. various automatic control circuits, whereupon the elevator would be started and would deliver threeingots in rapid succession into the melting chamber i because as soon as the elevator was stopped by the opening of the switch 63 it would be restarted by the falling of the arm (i8. When the third ingot reached the chamber l the arm it would be raised and the or 8 automatically closed. The elevator would continue running until the next ingot was delivered into the feed chamber and the switch 63 opened by the downward movement of the released door 55. It will be appreciated of course that the switch 63 is not actuated by upward movement-of the door. After the initial rapid succession of four cycles the operation of feeding proceeds, as described earlier in the specification, according to the rate at which molten metal is drawn ofi.

In the apparatus described above the method of heating is by gas but other methods are also applicable. For instance oil fired -or solid fuel furnaces can be used. Alternatively themetal in the melting chamber and in the temperatureadiusting chamber may, be heated electrically,

either by electric resistance heating or by alternating current induction heating.

Although the invention has been described with reference to the melting of lead it will be appreciated that it can be readily applied to the melt- 1 ing of other metals. In many cases no structural alteration will be needed but where the .ant material.

It will be appreciated that the objects of the invention will be achieved to the fullest extent by use of the completely automatic arrangement as described above or a modified form thereof but it will-also be appreciated that the combination of the improved melting chamber with the means for automatically controlling the rate of melting in accordance with the rate of withdrawal and with the means for introducing ingots at a rate automatically controlled by the rate of melting y elds a number of advantages as compared with the usual types of melting apparatus. The use of the additional features described above enables the aforesaid combination to be employed in the most beneficial manner.

, What I claim as my invention is:--

1. Apparatus for the continuous melting of metal ingots, comprising in combination, a closed tubular melting chamber inclined to permit ingotsthere'in to move, downwards by gravity and having a cross-section approximating to/thatiif an ingot, means for melti ng ingotnnfil in said closed chamber at a rate substantially equal to and automatically controllable by the rate at which molten metal is withdrawn from the apparatus, a door for closing a charging aperture in the upper part of said chamber, means for opening said door and feeding an ingot into said chamber, and means automatically controllable by the rate at .which ingots are melted. in said chamber for controlling said door opening and ingot feeding means, whereby to introduce ingot metal into said chamber at a rate substantially equal to the rate at which metal is melted therein.

2. Apparatus for the continuous melting of metal ingots, comprising in combination, a closed tubular melting chamber inclined to permit ingots therein to move downwards by gravity and having a cross-section approximating to that of an ingot, means for heating the lower end of said chamber, means automatically controllable by the level of molten metal in the said chamber for controlling the said heating means whereby to melt metal in said chamber at a rate substantially equal to the rate at which molten metal is withdrawn therefrom, a door for closing a charging aperture in the upper end of said chamber, means for opening said door and feeding an ingot into said chamber, and means automatically controllable by the rate at which ingots are melted in said chamber for controlling said door opening and ingot feeding means, whereby to introduce ingot metal into said closed chamber at a rate substantially equal to the rate at which metal,

is melted therein. I

3. Apparatus for the continuous production of molten metal at a predetermined temperature from ingots, comprising in combination, a closed tubular melting chamber inclined to permit ingots therein to move downwards by gravity and having a cross-section approximating to that of an ingot, means for melting ingot metal in said closed chamber at a rate substantially equal to and automatically controllable by the rate at which molten metal is withdrawn from the apparatus, a door for closing a charging aperture in' the upper part of said chamber, means for opening said door and feeding an ingot into said chamber, means automatically controllable by the rate at which ingots are melted in said chamber for controlling said door opening and. ingot feeding means, whereby to introduce ingot metal into said chamber at a rate substantially equal to therate at which metal is melted therein, a second closed chamber at a lower level than the first said cham-- her and in communication with the lower end of.

the first said chamber, means for heating said second chamber, and means automatically controllable by the temperature of the molten metal in said second chamber for controlling the said heating means, whereby to raise the metal to a predetermined temperature as it flows through said second chamber.

.4. Apparatus for the continuous melting of metal ingots, comprising in combination, a closed tubular chamber which'is inclined to permit ingots therein to move downwards by gravity, has a cross-section approximating to that of an ingot and is capable of holding a plurality of lngots arranged end to end, means-for melting the lowermost ingot in said chamber at a rate substantially equal to and controlled by the rate at which molten metal is withdrawn from the said chamber, a door for closing a charging aperture in the upper part of said chamber, means for opening said door and feeding an additional ingot into said chamber, and means controlled by the araaaas position of an ingot in"the upper part of said melting chamber for controlling said door opening and'ingot feeding means, whereby to introduce ingot metal into said chamber at a rate substantially equal to the rate at which metal is melted therein.

5. Apparatus for the continuous melting of metal ingots, comprising in combination, a closed tubular chamber which is inclined to permit ingots therein to move downwards by gravity, has a cross-section approximating to that of an ingot and is capable of holding a plurality of ingots arranged end to end, means for melting the lowermost ingot in said chamber at a rate substantially equal to and controlled by the rate at which molten metal is'withdrawn from the said chamber, a door for closing a charging aperture in the upper part of said chamber, means for opening said door and feeding an additional ingot into said chamber, an electric circuit, a relay in said circuit for controlling said door opening and ingot feeding means, a switch in said circuit for controlling the operation of said relay, said switch having an actuating arm disposed within the said chamber and normally sustained by the uppermost ingot therein, said arm being releasable by a downward movement of said uppermost ingot to a predetermined extent, whereby to bring about the introduction of additional ingot metal into said chamber at a rate substantially equal to the rate at which metal is melted therein.

' 6. Apparatus for the continuous melting of metal ingots comprising in combination, a closed tubular melting chamber inclined to permit in-' gots therein to move downwards by gravity and having a cross section approximating to that of an ingot, means for melting ingot metal in said chamber at a rate substantially equal to and automatically controlled by the rate which molten metal is withdrawn from the apparatus, a feed chamber at the upper end of said melting chamher, a door separating said melting chamber from said feed chamber, means for temporarily open'- ing said door and for efiecting the transfer 'of an ingot from said feed chamber to said meltingchamber, and means, automatically controllable gots therein to move downwards by. gravity andhaving a cross-section approximating to that of an ingot, means for melting ingot metal in said closed chamber at a rate substantially equal to and automatically controllable by the rate at which molten metal is withdrawn from the apparatus, a feed chamber at the upper end of said melting chamber, a door separating said melting chamber from said feed chamber, means automatically controlled by the rate at which ingots are melted in said chamber for temporarily opening said door and transferring an ingot from said feed chamber to said melting chamber and means comprising an elevator operating at intervals which are also controlled by the rate at which ingots are melted, for inserting an ingot into said feed chamber to replace the ingot transferred to the said melting chamber, whereby to introduce ingot metal into the said melting cham amaaaa a tubular melting chamber, disposed with its ans at an angle tothehorizontal, capable oi accom modatine at least two ingots law A 'end to end v and having a cross-section apprommhna to that of an ingot, means for melting ingot metal contalned in said chamber, means for wlthdra i'le' molten metal from said melting chamber, a few chamber at the upper end of said melting chamber, an elevator for delivering ingots to said iced chamber, means actuated by the downward movement of an ingot in the said melting chamber, for setting said elevator in motion, and means for stopping said elevator automatically when the transfer of an ingot from said elevator to said feed chamber has been completed.

9. Apparatus for the conversion of ingot metal into molten metal, comprising in combination, a tubular melting chamber, u with its axis at an analeto the horizontal, capable of accommodating; at least two ingots placed end to end and having a cross-section approximating to that of an ingot, means for melting ingot metal contained in said melting chamber, means for withdrawing molten metal from said melting chamher, a feed chamber at the upper end of said meltins chamber, a door at the entrance of said feed chamber, an elevator for delivering ingots to said teed chamber, means for retaining each ingot on said elevator until it is opposite the entrance 1- means, actuated by the downward movement of an ingot in said melting chamber, for setting said elevator in motion, means, actuated by movement of said elevator, for opening said door to permit the entry of an ingot intoosaid feed chamber and for releasing said door immediately after the transfer of the ingot from said elevator tosaid feed chamber, and automatic mmns, actuated by the closing movetor.

ment of said door, for stopping said eleva i 1 1:1 1 TH

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