Process and apparatus for charging metal ingots into a melting furnace

Abstract: A process for charging ingots (11) of metal materials into a melting furnace (12) consists in pre-heating one single ingot by positioning it over the melting furnace mouth and plunging it into the fused material bath by a controlled lowering. Also provided is an automatic apparatus (1) for charging ingots (11) of metal materials into the melting furnace (12) which comprises at least one charge manipulator (2) consisting of a fixed support post (3), a transverse arm (4) slidably in engagement with the support post, a slide (7) slidably connected to the transverse arm, and a picking up unit (10) integral with the slide.

Description: The present invention relates to an automatic apparatus for charging ingots of metal materials into a melting furnace. It is known that in melting furnaces for metal materials, in particular in furnaces intended for melting of light alloys and designed to feed presses or other similar pressing devices located downstream of the production process, charging of these materials into the furnace crucibles must be periodically carried out, so as to keep the level of the fused material bath substantially constant. One known technique for executing said charging of the metal material is based on the direct manual intervention of an operator who, with the aid of simple tools, carries out handling of ingots, i.e. blocks of said metal material of even shape, for example in the form of a parallelepiped of a 50 x 100 mm section, which are 700 mm long and the weight of which is about 8-10 kg, so as to put them over the furnace mouth and plunge them into the underlying fused material bath. The above mentioned manual technique however has many limits and drawbacks. First of all the continuous presence of an operator is required, because the absence of said operator causes stopping of the continuous production cycle of the machines fed from the furnace. Substantially, the work autonomy of the machines using the material previously melted in a furnace is closely dependent on the possibility of ensuring the presence of an appropriate amount of this melted material in the furnace itself. By way of example, a 200 ton press carrying out pressing of a piece made of an aluminium alloy of a weight of 250 g and involving a production of 100 pieces per hour, has a consumption of 25 kg of material per hour and therefore requires that about three ingots per hour should be introduced into the furnace, assuming that the unit weight of each ingot is about 8 kg. Independently of the above, even if we suppose that the uninterrupted assistance of an operator to the melting furnace can be ensured, manual charging involves serious risks and inconveniences. In fact, this type of charging generally causes strong sudden temperature changes in the fused material bath due to the rapid admission of a great mass of cold material thereto, since necessarily the operator performs the charging operation by a quick succession of operating steps consisting in moving an ingot over the furnace mouth and immediately lowering it into the underlying bath, possibly releasing it when said ingot has its lower portion already partly immersed or very close to the liquid surface. The melted mass of the metal present in the furnace therefore undergoes important temperature alterations which can cause a great reduction in the quality of the subsequently obtained castings, which poor quality is due to the formation of structural defects therein, such as hard points and pores. The above mentioned temperature changes can be particularly emphasized if the operator alters the ingot charging evenness modifying the interval between two or more chargings and for example introducing an important number of ingots almost simultaneously into the fused material bath. It is also to note that the above mentioned temperature changes necessarily involve the immediate intervention of heating means to bring the melted mass to the operative temperature in a very short lapse of time. Obviously, as a result of this, an important energy absorption and waste takes place which greatly increases the overall managing costs of the process. It should be also noted that the manually charged ingot, at the moment it is plunged into the fused material bath, can have residual humidity traces on its surface which, due to a quick evaporation, can give rise to additional temperature irregularities and further reduce the quality of the final products. It should be added that a manual charging greatly affects the operator's safety as he is obliged to move close to the melting furnace and is therefore exposed to the risk of being hit by possible splashes of melted material and even to the danger that the fused material bath may burst. Not to be neglected are possible risks of damages to the furnace structure due to accidental drops or sudden releases of ingots that by falling into the fused material bath can damage the furnace bottom and even cause perforation of same which, as a result, will bring about escape of the melted metal therefrom and sometimes even short-circuits and fires. Finally it is to note that manual charging is closely connected with the production rate of the machines fed from the furnace and therefore the operator is obliged to follow this production rate in a strictly regular manner. In order to at least partly overcome the above mentioned drawbacks, a second known technique contemplates charging of holding furnaces by the use of ladles containing the metal material already in a melted state and fed by appropriate hoppers from big melting furnaces earlier pre-charged. This second known technique however, in addition to requiring the availability of a wide space for installation, also involves big installation investments and heavy managing costs. Furthermore, the use of this second technique needs transportation of the melted material, which results in risks from an operative point of view and, in addition, a big amount of material is to be maintained to a constant temperature. Under this situation, the technical task underlying the present invention is to devise an automatic apparatus for charging ingots of metal materials into melting furnaces, which process and apparatus are capable of substantially obviating the above drawbacks. It is known from patent application DE 644 079 a device for contuiinuously feeding a melting furnace with metal ingots. This document discloses a device for charging ingots into a melting furnace. This device has self stopping capabilities because it has means for detecting the liquid metal bath level and enabling consequently the immersion of a portion of an ingot should the bath level become too low. The structural arrangement comprises a winch, a drive chain partially rolled on the winch and bearing at one of its ends a lead ingot and a braking system acting on the winch. Furthermore, the device disclosed in this document is designed to achieve continuous feeding of metal in the melt bath as long as one ingot is attached to the device itself. It is also known from JP 06 312255 a machine for continuously feeding a melting furnace. This machine essentially comprises a charging drum for the ingots and an automated feeding system for transferring the ingots from the charging drum to the furnace. The feeding system controlling criterion is based on the detection of the melt metal bath level, and the immersion of a single ingot is performed gradually. within the scope of this technical task it is an important aim of the invention to devise an automatic apparatus enabling the level of the liquid metal to be maintained substantially constant in a melting furnace, without being obliged to resort to the installation of expensive and bulky holding melting furnaces and capable of reducing as much as possible the dependence of the machines fed from the furnace on the presence of an operator assigned to charging, and of substantially operating in a continous cycle without the occurrence of halts due to the furnace being empty for lack of material or to the operator having finished his work shift. Another important aim of the invention is to devise an automatic apparatus for charging ingots of metal materials into a melting furnace which are capable of greatly increasing the quality of the products obtained from said metal materials. A still further aim of the invention is to devise an apparatus enabling the operator's safety to be increased and the risks of damages to the melting furnace to be decreased. The technical task mentioned and the aims specified are substantially achieved by an automatic apparatus for charging ingots of metal materials into a melting furnace as defined in the claims. The description of some preferred but not exclusive embodiments of an automatic apparatus in accordance with the invention is now given by way of non-limiting example. This description will be taken with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a first embodiment of an automatic charging apparatus in accordance with the prior art; Fig. 2 is a second embodiment of the automatic apparatus in accordance with the prior art; Fig. 3 shows a first embodiment of the automatic apparatus in accordance with the invention; Fig. 4 shows a second embodiment of the automatic apparatus in accordance with the invention, capable of directly utilising ingots of metal material loaded on pallets; Fig. 5 is a third embodiment of an automatic apparatus similar to the one shown in Fig. 4; Fig. 6 reproduces a fourth embodiment of the automatic apparatus again similar to the one shown in Fig. 4. With reference to the drawings, a single ingot of metal material is positioned over the melting furnace mouth so as to carry out a first pre-heating of the ingot and is plunged into the fused material bath present in the melting furnace by lowering it in a controlled manner. It is to point out that lowering of the ingot into the bath can be also managed in a continuous manner. At all events, this lowering is conveniently operated by a control system capable of, instant by instant, knowing the bath level or the amount of drawn material per unit time. With reference to the drawings, the automatic apparatus is generally denoted by reference numeral 1. Apparatus 1 comprises handling means 2 to pick up at least one single metal ingot 11 from a picking up position and bring it to a position above a fused material bath of a melting furnace 12 and gradually plunging it thereinto. Apparatus 1 further provides for the use of control means capable of detecting the amount of fused metal present in the melting furnace 12 and correspondently operating said handling means. In more detail, the handling means 2 comprises a charge manipulator formed of a fixed support post 3 extending vertically, a transverse arm 4 in slidable engagement with the support post 3 along a vertical-translation direction 5 by means of vertical guides 6, a slide 7 slidably connected to the transverse arm 4 along a horizontal-translation direction 8 by means of horizontal guides 9, and a grasping unit 10 integral with the slide 7 and arranged to grasp the upper portion of an ingot of metal material 11 preferably disposed in a vertical orientation at a picking up position, to be plunged into a melting furnace 12. Apparatus 1 further comprises an auxiliary unit, denoted by 13 independently of the distinct embodiments hereinafter described, adapted to define an ingot magazine for the charge manipulator 2 and comprising feeding members variously shaped and differently operating depending on the different embodiments, which are adapted to dispose each individual ingot in said picking up position provided for the charge manipulator 2. In one embodiment shown in Fig. 1, the auxiliary unit 13 comprises a rotating storing table 14 extending around the fixed post 3 and provided with a plurality of seatings 15, twelve seatings for example, each adapted to house a vertically directed ingot 11. Clearly, depending on requirements, a rotanting table having a greater number of seatings may be provided. In said first embodiment, the grasping unit 10 comprises a horizontally-directed linear actuator 16 and a gripper 17 driven by the linear actuator 16. The gripper 17, in turn, comprises two jaws 18 disposed at right angles and having end portions 18a directed vertically, that is capable of grasping one ingot 11 from top. In a second embodiment shown in Fig. 2, the auxiliary unit 13 comprises at least one endless conveyor or moving chain 19 such disposed as to rest on the ground and having a plurality of pockets 20 each adapted to hold an ingot 11 in a vertical orientation. The pocket 20 number can vary depending on the conveyor 19 length. For instance, if such a conveyor is 4 metres long, positioning of about 70 aluminium ingots or ingots of other materials can take place. In order to increase the magazine capacity, extension of the conveyor 19 can be envisaged or another auxiliary conveyor can be placed alongside the first one, said additional conveyor acting as a storage unit for the main conveyor. Transferring of ingots from one chain to the other can take place by a pneumatic system, for example. In this second embodiment as well, the grasping unit 10 comprises components similar to those already shown with reference to the first embodiment in Fig. 1. In a third embodiment shown in Fig. 3, the auxiliary unit 13 comprises an endless conveyor of the overhanging or cantilever type 21, that is spaced apart from the ground, and having a plurality of hanging compartments 22 each adapted to hold one ingot disposed vertically. In this embodiment the grasping unit 10, in addition to comprising a horizontally-directed linear actuator 16, is also formed of a gripper 17 having two elongate jaws 23 extending horizontally in the extension of the linear actuator 16, that is capable of laterally grasping one ingot 11. In the fourth, fifth and sixth embodiments shown in Figs. 4, 5 and 6 respectively, the auxiliary unit 13 comprises one rest base 24 of at least one ingot-receiving pallet (only partly shown in the interest of a clear representation of the components of apparatus 1), for reception of 121 ingots disposed horizontally, for example. More particularly, said ingots are normally stacked up in superposed layers on the pallets, each layer being formed of ingots disposed parallelly in side by side relation and transversely of the ingots of the adjacent layers. The feeding members of the auxiliary unit 13 in the last-mentioned three embodiments comprise one picking-up manipulator 25 provided with a grasping device 26 having two elements adapted to grip the end of each ingot resting on the pallet 24, end a device 27 for tilting over to a vertical position the ingot lifted up by the picking-up manipulator 25. In the fourth embodiment (Fig. 4) said rest base of a pallet is defined by a revolving platform 28 rotating about a vertical axis at least through a right angle. The picking-up manipulator 25 comprises a movable portal-shaped frame 29 overhanging the revolving platform 28 and horizontally movable so as to bring the grasping device 26 close to the tilting-over device 26. Slidably connected to the portal-shaped frame 29, in a vertical direction, is a moving support 30 with which the grasping device 26 is integral. In the fifth embodiment (Fig. 5), there is a revolving platform 28 for receiving one pallet whereas the picking-up manipulator 25 comprises a fixed tower-shaped frame 31 overhanging the revolving platform 28 and close to the tilting-over device 27. A first moving carriage 32 is slidably connected to the fixed frame 31 in a vertical direction, whereas a second moving carriage 33 can slide along the first carriage 32 in a horizontal direction. Integral with the second carriage 33 is the grasping device 26. Finally, in the sixth embodiment shown in Fig. 6 said rest base is defined by a fixed structure 34 and the picking-up manipulator 25 comprises a movable post 35 to be horizontally displaced along said fixed structure until the tilting-over device 27, and an articulated support body 36 in turn comprising an attachment portion 36a slidably linked with the movable post 35 in a vertical direction, and an articulated cantilever portion 36b rotating about a vertical axis 37 through at least one right angle relative to the attachment portion 36a. Integral with the cantilever portion 36b is the grasping device 26, said grasping device 26 being then mounted to the cantilever portion 36a so as to be able to carry out a horizontal translation as well, in a direction perpendicular to the post 35, by means of the slidable element 36c. Both the charge manipulator 2 of all depicted embodiments of the apparatus and the picking-up manipulator 25, as well as the other movable members of the apparatus can be moved by operating units of the pneumatic, hydraulic or electric type and their movements can be controlled by sensor means known per se. Operation of the apparatus described above mainly as regards structure is as follows. In the three first embodiments the operator initially must position the ingots into the seatings 15, pockets 20 or compartments 22, whereas in the three last embodiments the ingots keep their position on the pallets by which they have been conveyed. After a push-button for starting a cycle is depressed, the apparatus runs in a completely automatic manner until all ingots have been exhausted. The charge manipulator 2 grasps each single ingot disposed vertically in the intended picking up position by an appropriate combination of movements controlled by the sensor means and involving a vertical translation of the transverse arm 4 and a horizontal translation of the slide 7. Then the ingot is brought to place over the vertical line of the melting furnace 12 where a first pre-heating to dry the ingot occurs, so that possible traces of humidity are eliminated from the surface thereof due to heat mounting from the furnace mouth. Subsequently the charge manipulator 2 causes the gradual introduction of the ingot into the fused material bath by small successive lowering movements to be adjusted by the user depending on the drawing speed of the melted material. The progressive plunging of the ingot into the fused material bath involves a second pre-heating by heat conduction, due to a contact between the fused material and the plunged portion of said ingot: practically, the ingot is introduced into the bath at a temperature much higher than the storage temperature. In the fourth, fifth and six embodiments, the operator only positions one pallet on the revolving platform 28 or the fixed structure 34 and takes the packaging ribbons away; therefore the charging storage unit consists of the pallet itself. The picking up manipulator 25 will then move each individual ingot successively from the pallet and lay it down on the tilting-over device 27 where it is rotated to the vertical position so that it is already conveniently directed for being introduced into the furnace, which operation will be executed by the charge manipulator 2. More particularly, in the fourth embodiment the revolving platform 28, if necessary, suitably orientates each ingot layer, so that the ingots can be terminally grasped by the grasping device 26. Grasping and displacement of each ingot takes place by the combination of horizontal movements and vertical movements carried out by the portal-shaped frame 29 and moving support 30 respectively. In the fifth embodiment, in addition to the rotation of the revolving platform, if necessary, grasping and displacement of each ingot is carried out by suitably combining vertical and horizontal movements of the first and second moving carriages 32 and 33, respectively. Finally, in the sixth embodiment grasping, displacement and deposit of each ingot on the tilting-over device 27 is the result of a combination of movements involving translation of the movable post 35, vertical movement of the attachment portion 36a, rotation through 90°, if necessary, of the cantilever portion 36b and optional horizontal translation of the grasping device. Since the apparatus 1 in the three last-mentioned embodiments enables the simultaneous presence of three ingots, i.e. one ingot being worked, that is which is about to be charged into the melting furnate by the charge manipulator 2, one ingot waiting for charging in the tilting-over device 27, and one ingot clamped by the grasping device 26, a time interval which is three times the time of exhaustion of each individual ingot is made available for changing the pallet; hence practically the melting furnace can be continuously fed. At all events the autonomy of operation, that is the absence of interventions on the part of an operator, results not only (as is obvious) from the hourly consumption of the fused material, but also from the ingot-holding capacity of the auxiliary units 13 and can reach several ten hours, in the case of a pallet loaded with 121 ingots, for example. The invention achieves important advantages. First of all, the charging evenness and automation enables sudden changes of temperature in the fused material bath to be eliminated because the gradual lowering of ingots previously heated both by heat rising along the vertical line of the furnace and by contact with the bath itself, does not involve admission of a great amount of cold material, which on the contrary happens in the known manual technique. Thus, since a substantial temperature evenness is maintained in the fused mass and ingots are pre-heated, the structural quality of the obtained products can be increased, since hard points and pores are therein eliminated, and energy consumptions are greatly reduced. In addition, a gradual, controlled and automatic admission of ingots to the melting furnace eliminates the danger both of splashes and/or bursts of fused material, and of even serious damage to the furnace bottom and avoids handling of slags possibly present in the fused mass. The operator's safety is therefore greatly increased. It is to be added that the time of activity of an operator assigned to charging is greatly reduced and is no longer bound to the production rates, since the charging operations can be also carried out at irregular time intervals, by virtue of the apparatus of the invention performing the function of a storage unit.

Claims: An automatic apparatus for charging ingots of metal materials into a melting furnace comprising handling means (2) for picking up at least one single metal ingot (11) from a picking up position and bring it to a position above a fused material bath of a melting furnace (12) and gradually plunging it thereinto; control means capable of detecting the amount of melted metal present in the melting furnace (12) and correspondently operating said handling means (2) and an auxiliary unit (13) adapted to define an ingot magazine for said charge manipulator (2), said auxiliary unit comprising feeding members adapted to arrange each individual ingot in succession in said picking up position for said charge manipulator, characterized in that said auxiliary unit (13) comprises; a rest base (24) and at least one ingot-receiving pallet on which ingots (11) are disposed in a horizontal direction, and in that said feeding members comprise: a picking-up manipulator (25) having a grasping device (26) adapted to grip the end portion of each individual ingot resting on said pallet; and a tilting-over device (27) for arranging in a vertical position the ingot (11) picked up from said picking-up manipulator (25). An apparatus according to claim 1, characterized in that said handling means (2) comprises at least one charge manipulator having: a fixed support post (3) extending vertically, a transverse arm (4) in slidable engagement with said support post in a vertical translation direction (5), a slide (7) slidably connected to said transverse arm in a horizontal translation direction (8), and a grasping unit (10) integral with said slide and arranged to grip the upper part of said one ingot (11) disposed in a vertical orientation in the picking up position. An apparatus according to claim 2, characterized in directed linear actuator (16) and a gripper (17) controlled by said linear actuator and comprising two jaws (18) disposed at right angles and having their end portions directed vertically. An apparatus according to claim 1, characterized in that said rest base (24) of at least one pallet is defined by a revolving platform (28) moving about a vertical axis through at least one right angle, and in that said picking-up manipulator (25) comprises a portal-shaped movable frame (29) overhanging said revolving platform (28) and movable in a horizontal direction until said tilting-over device (27), and a moving support slidably in engagement with said movable frame (29) in a vertical direction, said grasping device (26) being integral with said moving support (30). An apparatus according to claim 1, characterized in that said rest base (24) of at least one pallet is defined by a revolving platform (28) moving about a vertical axis through at least one right angle, and in that said picking-up manipulator (25) comprises: a fixed tower-shaped frame (31) overhanging said revolving platform (28) and adjacent to said tilting-over device (27), a first moving carriage (32) slidably connected to said fixed frame (31) in a vertical direction, and a second moving carriage (33) slidably connected to said first carriage (32) in a horizontal direction, said grasping device (26) being integral with said second moving carriage (33). An apparatus according to claim 1, characterized in that said rest base (24) of one pallet is defined by a fixed structure (34), and in that said picking-up manipulator (25) comprises: one movable post (35) carrying out a horizontal translation at said fixed structure until said tilting-over device (27), and an articulated support body (36) comprising an attachment portion (36a) slidably linked with said movable post (35) for movement in a vertical direction and an articulated cantilever portion (36b) rotating about a vertical axis (37) through at least one right angle relative to said attachment portion (36a), said grasping device (26) being integral with said cantilever portion (36b). An automatic apparatus for charging ingots of metal materials into a melting furnace comprising handling means (2) for picking up at least one single metal ingot (11) from a picking up position and bring it to a position above a fused material bath of a melting furnace (12) and gradually plunging it thereinto; control means capable of detecting the amount of melted metal present in the melting furnace (12) and correspondently operating said handling means (2) and an auxiliary unit (13) adapted to define an ingot magazine for said charge manipulator (2), said auxiliary unit comprising feading members adapted to arrange each individual ingot in succession in said picking up position for said charge manipulator, characterized in that said auxiliary unit (13) comprises at least one endless conveyor of the cantilever type (21) having a plurality of hanging compartments (22), each adapted to support one ingot (11) disposed vertically. An apparatus according to claim 7, characterized in that said handling means (2) comprises at least one charge manipulator having: a fixed support post (3) extending vertically, a transverse arm (4) in slidable engagement with said support post in a vertical translation direction (5), a slide (7) slidably connected to said transverse arm in a horizontal translation direction (8), and a grasping unit (10) integral with said slide and arranged to grip the upper part of said one ingot (11) disposed in a vertical orientation in the picking up position. An apparatus according to claim 8, characterized in that said grasping unit (10) comprises a horizontally-directed linear actuator (16) and a gripper (17) controlled by said linear actuator and comprising two elongate jaws (23) extending horizontally in the extension of said linear actuator (16).

Inventors: ZANI ACHILLE ROMANO, ZANI, ACHILLE ROMANO
Applicants: LUMPRESS S R L, LUMPRESS S.R.L.
Application year: 1996
Main classification: F27D3
IPC codes: F27D3, F27B3, B22D17