Abstract:
The device, which can be used for filling containers in a lost-foam casting system, includes in a singe operational combination: supporting devices for containers with associated vibration devices to set the containers into vibration; a sand-feeding device, such as a hopper, for feeding dosed quantities of sand into the container; and a positioning device that make it possible to locate foam models into containers and sustaining them both while the sand is being fed into the containers and while the containers are being vibrated, thus avoiding the risks of malpositioning and/or breakage. Preferably, both the sand feeding hopper and model-positioning device on the same equipment capable of moving between a raised position in which the hopper may be loaded with the sand, while the foam models are being transferred by the positioning device, by a robot for example, and a lowered position, in which the models are inserted into the containers, after which the latter can be filled with sand.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to devices for filling containers in lost-foam casting systems. 
     The lost-foam casting technique represents an ever more widely employed foundry technique that is essentially based on the preparation of a model, generally made of polystyrene or some similar material, that exactly reproduces the characteristics of the piece to be cast. This model is inserted in a container (flask) filled with sand, which is then vibrated until the sand is distributed and compacted in such a manner as to adapt itself closely to and reproduce the exact shape of the model. Hot casting material (typically molten metal) is then poured into the space occupied by the model. The casting material dissolves the model and thus occupies the space that was previously occupied by the model in the surrounding sand. The final result is therefore the obtainment of a casting, i.e. a workpiece, that exactly reproduces the shape of the model. 
     SUMMARY OF THE INVENTION 
     The present invention comes to grips, first and foremost, with the problem of optimizing the operations that lead to the model being inserted or drowned in the sand prior to its compaction by vibration. In particular, the present invention avoids breakage or displacement of the model (typically realized in the form of a cluster of smaller individual models). Additionally, the invention also provides a filling device of the intelligent type, capable, in particular, of identifying the individual model and/or the container into which it has been inserted and thus making it possible, for example, to achieve selective specialization of the various processing operations, this to the point of treating each model/casting in accordance with a particular tailor-made process. 
     According to the present invention, this scope is attained by means of a container-filling device for lost-foam casting systems, including in a single operational combination: 
     supporting means for containers with associated vibration means to set the containers into vibration; 
     sand-feeding means capable of selectively feeding dosed quantities of sand into the containers; and 
     positioning means that can selectively be associated with the containers to position foam models into the containers; the positioning means being capable of sustaining the models both while the sand is being fed into the containers by the feeding means and while the containers containing the said models are being vibrated by the vibration means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, though purely by way of example and not to be considered limitative in any way, by reference to the attached drawings, where: 
     FIG. 1 shows a general view in side elevation of a container-filling station in a lost-foam casting system; 
     FIG. 2 shows a larger-scale view of the part of FIG. 1 indicated by the arrow II; 
     FIG. 3 shows another view in side elevation of the device shown in FIG. 2, but this time seen in a direction that is substantially orthogonal with respect to the viewing direction of FIG.  2 . 
     FIG. 4 is a simplified explanatory view based on FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The general view of FIG. 1 represents a station  2  for filling the containers of a lost-foam casting plant or system. The plant in question could consist, for example, of the system described in greater detail in a European patent application filed on the same date by the same applicants. 
     At the station  2  the models S are inserted into the containers C in which the casting operations are to be performed, the said containers being subsequently filled with sand and subjected to vibration, so that the sand will eventually become compacted and be in close contact with the outer surface of the said models S. 
     The movement of the containers C is from left to right, with respect to the viewing direction of FIG. 1 so as to produce a step-by-step forward motion of the containers below a main silo  20  designed for feeding sand by means of free fall to four successive filling substations. The said filling substations are consecutively numbered from 21 to 24 in the direction in which the containers C move forward beneath the silo  20 . For this purpose the containers C are usually placed on platform trolleys  50  that move forward (under the action of movement control means not shown on the drawing) on rotating bodies  51  that could be, for example, rollers or wheels. 
     In particular, the substation  21  can be defined as a prefilling station since a certain quantity of sand F (not shown in FIG. 1) originating from within the silo  20  is fed through a duct  25  and an associated hopper  26  into the bottom part of the container C that at any given moment happens to be in the substation  21 . 
     The next substation, indicated by  22 , has a somewhat more complex structure that will be described in greater detail later. At the substation  22  the polystyrene models S (usually in the form of model clusters, as already noted) are arranged inside the containers that have already had a certain quantity of sand filled into their bottom parts at the substation  21 . The models S are usually taken from a feeder turntable (not shown in the figure) by means of a robot of which only the pick-up arms is shown by means of a dashed line in FIG.  2 . The design and operating details of the robot in question (which could be of any known type, an anthropomorphic robot being a case in point) are not in themselves relevant for a proper understanding of the invention and will not therefore be described in any detail. Here it will be sufficient to recall the fact that the model S normally consists of a model cluster provided with a grip formation T by means of which it can be picked up by the arm R of the robot to be sustained centrally, i.e. in a position that substantially coincides with the barycentre, by a positioning element indicated by the reference number  27  and subsequently described in greater detail. 
     At the substation  22  the container C receives, this time from the hopper  30 , a further quantity of sand intended to cover the model S for a substantial part of its height. 
     At the said substation  22  the container C is also lifted slightly in a vertical direction to detach it from the conveyor structure  50 , while the lifting organs  31   a  (see FIG. 3) that perform the said lifting action are caused to vibrate by means of a vibration device  32   a . In this way the sand inside the container C is subjected to the necessary vibration and compaction action. Both the pick-up (gripping) organs  31   a  and the vibration device  32   a  are well known in the art and need not therefore be described in further detail. 
     The action of filling the container C with sand is completed at the subsequent substations indicated by  23  and  24 . As far as complexity is concerned, these two substations may be said to be intermediate between the complexity of substation  21  and that of substation  22 . In fact, the substations  23  and  24  include respective ducts  33  and  34  for feeding sand from the silo  20  into the hoppers  35  and  36 . In this case, of course, there is no longer present the complex of parts and elements needed for arranging the models S inside the containers C. But what does have to be present at this stage are the lifting organs  31   b  and  31   c  and the vibration devices  32   b  and  32   c , which are substantially similar to the devices  31   a  and  32   a  that have already been described in connection with substation  22 . 
     The choice of carrying out the filling and the vibration of the containers C in successive phases is in keeping with the need for gradual immersion of the model S in the sand, thereby assuring that the sand around it will become fully compacted. This choice is also imposed by the general needs bound up with the timing of the forward movement of the containers C on the conveyor system and assuring the desired productivity levels. 
     FIG. 3 shows in greater detail the structure of the device that constitutes the substation  22 . Referring to the side elevation shown in this figure, an upright  100  is in a position that can be described as being by the side of the line along which the trolleys  50  bearing the containers C are moving forward. 
     Mounted on the said upright  100  in such a way as to enable it to move up and down under the action of an appropriate fluid jack  101  there is a mobile item of equipment  102  having the general structure of a projecting bracket. This bracket-like structure  102  sustains the hopper  30  below the bottom outlet opening  20   a  of the silo  20  and also extends downwards in the form of a cage structure  29  which carries a frame  103  in a position below the hopper  30 . In its turn, the said frame  103  sustains the previously mentioned positioning element  27  in a generically central position. 
     The complex of parts just described, usually realized in the form of structural steelwork, is therefore capable of moving vertically along an axis X c  along which the following elements are arranged: 
     the bottom outlet opening  20   a  of the silo  20 , 
     the hopper  30  with its discharge opening  104 , complete with an appropriate opening and closing system  105  of a known type, 
     the frame  103  with the positioning element  27  that, in its turn, sustains the model S in a central position, and 
     the container C that at that particular moment occupies the substation  22 . 
     The bracket-like structure  102  is in the form of a square metal frame capable of carrying the hopper  30  through the intermediary of appropriate load cells  106  (which may be three in number, for example) on which rest the correspondingly positioned bracket structures  107  projecting radially from the upper edge of the hopper  30 . The load cells  106  therefore provide signals that indicate the quantity of sand present in the hopper  30  and, consequently, the quantity of sand that will eventually be transferred into the container C below the hopper. 
     The frame  103  is suspended from the structure  102  by means of the legs  108 , which do not in any way encumber the space within the frame  103  intended to be occupied by the positioning element  27 . 
     The said element includes a central hub  109  that carries a clamp  110  with a control unit  116 . The hub  109  is sustained by a series of spokes  111  that connect it to an inner frame on which there is mounted at least one other clamp  112  with its own control unit  113 . Preferably, however, there will be three such clamps, distributed in a substantially uniform manner along the circumference of the inner frame. 
     The frame  103  also carries one or more centering formations  114 . 
     The said centering formations preferably include a fork element  114   a , which, when the element  27  comes to be located (as will be described in greater detail later) at the level of the upper rim of the container C, will engage with an appropriate counterpart projecting from that rim and will thus avoid undesired relative rotations. Usually there will also be present a pin  114   b , as well as a corresponding cavity  115  carried in a peripheral position by the inner frame of the frame  103 . 
     The operating units  116  and  113  of the clamps  110  and  112  are in their turn controlled, just like the unit that controls the aperture of the outlet opening.  20   a  of the silo  20 , by the unit  105 . The unit  105  also controls the feeding of the sand from the bottom opening  104  of the hopper  30 , the load cells  106  and the control unit of the jack  101 , by a processor-type control unit K. The control unit K may consist, for example, of a so-called PLC (acronym of Programmable Logic Controller) or some equivalent processing unit that controls (in accordance with criteria that are in themselves known and/or will be rendered obvious by the present description) the operation of these organs in a manner that is fully coordinated with the operation of the other parts of the plant, especially the robot R and the trolleys  50 . 
     The operating unit  113  is preferably configured in such a manner that, with the system at rest, the return elements, springs for example, will keep the clamps  112  in their fully open position. 
     As can be more readily appreciated from the view reproduced in FIG. 2, the positioning element  27  is not fixed to the frame  103 , but rather rests freely and, be it noted, in an exactly centred position on the said frame, and can therefore become disengaged from the frame  103  by performing an upward movement relative to it. 
     The operating cycle of the device constituting the substation  22  can be summarily described in the following terms. 
     The device gets ready to receive a container C (already containing the quantity of sand received at the substation  21  on the upstream side) while the complex of parts sustained by the bracket-like structure  102  is in the position shown by means of full lines in both FIG.  2  and FIG.  3 . In other words, when the substation is ready to receive a new container, the fluid jack  101  keeps the entire structure at the upper end of its travel. 
     Let us suppose that when the container C arrives, as also in the phase that immediately precedes or follows its arrival, the robot R has already picked up a model S and inserted the grip formation T with which it is provided into the clamp  110 . The clamp is first maintained in its open position, which enables it to receive the said grip formation T, and is then closed around it, so that it will carry the model S. After releasing the model S it has just loaded into the substation  22 , the robot arm R returns towards the structure from which the models are picked up (which is typically of the turntable type and is not illustrated) in search of a new model S. 
     In the meantime, the outlet aperture  20   a  of the silo  20  has been opened, so that there has dropped into the hopper  30  a quantity of sand corresponding to the quantity it is subsequently desired to discharge into the container C. 
     At this point the jack  101  is operated in such a way as to cause the entire supporting structure  102  to become gradually lowered towards the container C. This operation ensures that the model S will be lowered into the container C. 
     In the course of this operation the model is lowered from the position shown in FIGS. 2 and 3 by means of full broken lines to the position indicated by means of the chain-dotted lines in the same figures. 
     In the lowered position previously referred to, the model S usually comes to rest on top of the sand F already contained in the container C as a result of the pre-filling operation previously carried out at the substation  21 . In any case, the said downward movement causes the clamps  112  to engage the upper rim of the container C. Activation of the control unit  113  (likewise controlled by the PLC K) ensures that the clamps  112 , originally open, will now tighten and grip the rim of the container C. The series of spokes  111 , and therefore also the hub  109  they carry in a central position, will thus come to constitute what is de facto a single piece with the container C. This applies also as regards the clamps  110  carried by the hub  109  and, consequently, the model S. 
     In the said lowered position, therefore, the operating unit  105  controlling the bottom outlet of the hopper  30  can be activated to open the said outlet, so that the quantity of sand contained in it will now be discharged into the container C and thereby cover the model S. 
     It will readily be appreciated that the said model is kept firmly in a fixed position with respect to the container C by means of the clamp  110  carried by the hub  109 , which in its turn is linked by means of the spokes  111  to the clamps  112  that grip the rim of the container C. 
     The descending sand will not therefore be able to cause any undesired displacements of the model S while the container is being filled. There is no undescribed displacement even when the sand comes down in a rush of considerable intensity and/or when the model has surfaces orientated in such a manner as to exert a certain deflection action on the falling sand F so that the model, by reaction, becomes subject to a certain fluid dynamic thrust. 
     Examination of FIG. 2 also makes it clear that, since the clamps  112  grip the rim of the container C, the positioning element  27 , taken as a whole, will no longer be able to follow the downward movement of the frame  103 . The travel of the jack  101  is in fact regulated (in a manner coordinated with all the other dimensional magnitudes in play) in such a manner as to ensure that when the frame  103  reaches its lowermost position, it will be wholly disengaged from the positioning element  27  and, consequently, also from the model S. 
     In these conditions, the container C, complete with the model S and the further quantity of sand it received at the substation  22 , can be subjected to the vibration operation, which is performed, in a known manner, with the help of the generator  32   a  while the lifting organs  31   a  keep the container C lifted off the trolley  50  used to transport it. 
     Vibratory motion is applied to the body of the container while the model S is kept in a fixed position with respect to the container C by means of the various parts numbered  109  to  112 . This ensures that the said vibratory motion, no matter how great its amplitude or intensity, will not be able either to displace the model S from its correct position or to cause a breakage of its gripping formation T, which in most cases will eventually define the channel through which the casting material will be poured into the container C. 
     On completion of the vibration operation, the lifting organs  31   a  will again lower the container C onto its trolley  50 . At this point the jack  101  can be operated in the direction that will cause the structure  102  to become raised, while both the clamps  110  and the clamps  112  are opened, so that the positioning element  27  becomes disengaged from both the rim of the container C and from the grip formation T of the model S, which has to remain within the container C. 
     The frame  103  will therefore begin to rise and engage with the positioning element  27 . 
     The presence of the centering formations  114  ( 114   a ,  114   b ) and their respective complementary formations ensures that the positioning element  27  will again become engaged with the frame  103  in an accurately defined position, so that the starting conditions indicated by means of the full lines in FIGS. 2 and 3 can eventually become exactly reconstituted. 
     FIG. 4 is view similar to FIGS. 2 and 3 in as much as three containers C are shown with the middle one being located above a vibration device  32   a  to set the middle container C in motion. Supporting means are provided for each container C which is placed on and supported by a trolley  50 . Sand feeding means are comprised of the hopper  30  for feeding sand into the container C. Positioning means  27  as well as the model S which is clamped to the positioning means  27  by means of the clamp  110  is shown in the raised position as well as in the lowered position in which the model is located within the container C. Container gripping means  112  are comprised of three peripheral clamps  112  two of which are shown in FIG.  4 . The one shown on the left is also shown to an enlarged scale is for flipping the container C. The gripping means  112  are in the open position when the positioning means is in the raised condition as shown in FIG.  4 . Vertical movement of the positioning means. 
     Vertical movement of the positioning means  27  is controlled by the fluid jack  101  shown in FIG. 3 which moves a bracket like structure  102  up and down. Suspended to the vertically moveable bracket-like structure  102  by legs  108  is a frame  103  having cavities  115 . The positioning means  27  includes vertical pins  114   b  of the centering formations  114  which engage corresponding cavities  115  which are carried by the frame  103  whereby the positioning means  27  rests on the frame  103  in the raised or resting position as shown in FIG.  4 . Upon lowering the frame  103  the positioning means  27  will engage the upper edge of the container C and the positioning means  27  will become disengaged from the frame  103 . In this position the clamps  112  will automatically clamp onto the container C. Since the positioning means  27  is now clamped to the model S by means of the clamp  110  and simultaneously is clamped to the container by means of the clamps  112 , the model S and the container C will be joined as single piece for vibration as a unit. 
     When the structure  102  and the various elements it carries have eventually returned to their raised position, the container transport line can again be set in motion, so that the container C that has just been processed will be moved forward to substation  23  of FIG. 1, while a new container will be moved from substation  21  to the device that constitutes substation  22 . 
     While this is happening, the robot R has the time it needs to insert a new model S into the clamp of the positioning element  27  and the bottom outlet  20   a  of the silo  20  can be opened again to reconstitute the sand supply needed in the hopper  30  for the next filling. 
     In addition to the previously described advantages in connection with the operations of filling the sand into the container C and vibrating it, the solution according to the invention therefore has the further advantage of permitting the operations of loading the models S and filling the hopper  30  to be carried out while the containers are being moved, thus avoiding possible idle times. 
     As already mentioned in the introductory part of the present description, the substation  22  that has just been described in detail usually forms part of a plant or system that, in addition to the said substation  22  and the container transport system  50 , includes also other stations and substations for carrying out the following technological operations in due succession: 
     sand filling and vibration (other substations  21 ,  23  and  24  as already described) 
     casting (one station) 
     extraction of castings and sand (one station). 
     The last two of these stations are of a known type and have known characteristics and have not therefore been illustrated on the attached drawings. 
     As already mentioned, at the entry side of the system the clusters constituting the models S are loaded with the help of a buffer turntable that presents them to the robot R, which then picks them up from the turntable and automatically feeds them into the sub-station  22 . 
     Given the different types of pieces (and therefore models and castings) that may have to be made, the following may vary: 
     sand filling (speed at which the containers C are filled, as well as the level to which the containers are filled at the various sub-stations  21 - 24 ); 
     vibration (vibration frequency and/or duration); 
     casting (quantity of metal to be cast, casting modalities); 
     extraction of the castings (angle of inclination of the container when it is tipped to permit the castings to be picked up, usually by means of an anthropomorphic robot). 
     These variables and the possible changes associated with them can therefore be configured as a typical recipe for each casting. 
     The solution according to the invention is such that these functions can be completely automated. To this end, matters can be arranged in such way that the robot R, immediately after picking up a model S from the turntable, presents it in front of an identification station consisting, for example, of a television camera P and an appropriate model recognition module of a known type and possibly resident in the control unit K. The identification station recognizes the model S (among a set of possible models) and thereupon informs the system of the particular recipe needed for: this model. This can be done by means of an appropriate type identification signal generated, for example, in the control unit K. 
     Once it has been inserted in the container C at the sand-filling station, the model S is—as it were—paired with the container (which is provided with a plate DP, which could be—for example—of the magnetic or optical reading type, on which the casting data, recipe included, can be memorized). Prior to entry into each technological station, an electronic reader informs the station in question of the contents of the container, thus enabling it to fall into line with the parameters of a particular recipe. 
     Naturally, the realization details and the implementation forms can be widely varied with respect to what has hereby been described and illustrated without in any way altering the principle of the present invention or going beyond its scope as defined by the claims set out below.