Abstract:
In a method of extracting castings ( 1, 2, 3 ) from moulds in a mould-string plant, the downstream-most mould ( 1 ) is gripped by a robot gripper ( 9 ) and made to cooperate with an engagement member ( 14 ), the latter first penetrating into the mould adjacent the casting ( 4 ) and then pulling the latter away from the mould. By proceeding in this manner it is possible to achieve a reliable extraction using relatively simple equipment and procedures. Other types of engagement members could be suctions cups or electromagnets.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method of extracting castings from moulds in the manner set forth in the preamble of claim  1 . 
     BACKGROUND ART 
     Previous methods of the kind referred to above have normally been based upon the mould being smashed in a more or less rough fashion, such as being tumbled in a drum or dropped onto a vibrating conveyor. 
     Especially in the case of aluminium castings, this rough treatment of the mould may damage the castings. Attempts have been made to “save” aluminium castings by manually gripping them before they hit the conveyor, but—as will readily be appreciated by persons skilled in the foundry trade—such manual work is both strenuous and monotonous, as well as unhealthy due to the air in the extraction station being heavily dust-laden. 
     Attempts have also been made by using a robot with gripper arms, making the latter penetrate through the main body of each mould to engage the casting or castings. This method is costly, as a robot with ample “muscle power” is required. Further, this method is not suitable for extracting multiple castings, because the latter will offer a too high resistance to the penetration. Still further, the gripper arms must not be too thick, calling for a compromise between mechanical strength and penetrating ability. 
     DISCLOSURE OF THE INVENTION 
     It is the object of the present invention to provide a method of the kind referred to initially, with which it is possible to extract the castings from the moulds using less costly equipment and with reduced risk of damage to frail castings, and this object is achieved by proceeding in the manner set forth in the characterizing clause of claim  1 . By so doing, the castings may be extracted by moving each mould with the casting or castings so as to bring the latter into engagement with the engagement member or members referred to, and then again moving the mould in a manner causing the engagement member or members to loosen and liberate the casting or castings from the mould. In the simplest manner, this could be achieved by means of a hook or hooks not having to penetrate through more of the mould body than superficial portions adjacent the castings, said hook or hooks then being used to pull the castings out of the part of the casting cavity formed in the downstream face of the mould. Obviously, relatively little force is needed for these steps, for which reason a less costly robot may be used. 
     The present invention also relates to an automated foundry plant for carrying out the method of the invention. This plant is of the kind set forth in the preamble of claim  12 , and according to the invention, it also comprises the features set forth in the characterizing clause of this claim  12 . 
     Further embodiments of the method and the plant, the effects of which—beyond what will be obvious to a skilled person—are explained in the following detailed part of the present description, are set forth in claims  2 - 11  and  13 - 18 , respectively. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following detailed part of the present description, the invention will be explained in more detail with reference to the exemplary embodiment of an automatic foundry plant according to the invention, shown in a highly simplified, diagrammatic manner in the drawings, of which 
     FIG. 1 is a perspective view showing the downstream end of a string of moulds carried and advanced on bars extending in the direction of movement, as well as a robot gripper for handling the moulds one by one, and 
     FIGS. 2-7 show the downstream end of a string of moulds, in which molten metal has previously been poured and then solidified prior to their arrival at said downstream end, showing successive steps during the extraction, using a robot, of a casting from the downstream-most mould. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 2 shows a string of moulds, of which only the “oldest” or downstream-most mould  1  and the next following moulds  2  and  3  are shown, carrying in their casting cavities castings  4 ,  5  and  6  respectively, of which only the downstream-most casting  4  is accessible, due to the preceding mould (not shown) having been removed in a previous step. 
     The string of moulds  1 ,  2 ,  3  etc. rests on a supporting arrangement consisting of a number of parallel bars  7 . The bars  7  may be part of a “walking conveyor” comprising at least two sets of bars alternatively lifting and advancing the string of moulds from a pouring station (not shown), but they may also be a simple “table top”, on which the string of moulds slides, being pushed by suitable means (not shown). 
     The extraction station  8 , here simply the region immediately downstream of the “oldest” mould  1 , comprises a robot gripper  9 , in the exemplary embodiment shown comprising a rectangular frame  10 , adapted to be carried and manipulated by a distal arm (not shown) on a robot (likewise not shown), being connected to the latter through a coupling part (also not shown) comprising the requisite mechanical, fluidic and/or electrical connections. 
     The robot gripper  9  comprises, secured to the frame  10 , two pneumatically operated lateral pressure pads  12  adapted to grip a mould between them by pressing against the lateral faces of the mould, and further, a number of lifting bars  13  so placed and spaced, that they can be inserted longitudinally into the spaces between the bars  7  and then raised, so as to lift a mould free of the bars  7 , after which the mould is moved into the extraction station  8 , cf. the steps shown in FIGS. 2-4. An upper pressure pad  11  serves to press the mould against the lifting bars  13 , so as to increase the force used to pull the downstream-most mould  1  free from the casting  5  in the next mould  2 . 
     A further important feature of the extraction station is an engagement hook  14 , of FIGS. 5 and 6. 
     In the exemplary embodiment shown, there is only one engagement hook (or only one for each casting in the case of a multiple-casting mould), and this hook is stationary, i.e. anchored to some stationary object (not shown). In other embodiments (not shown), the hook or hooks is/are movable, and if there are at least two hooks for each casting, they can also be arranged to cooperate like a pair of tongs or plies, so as to grip the casting firmly and hold it until it is deposited on e.g. a conveyor for transfer to a succeeding work station. 
     Now back to the exemplary embodiment shown in FIGS.  1 - 7 : When, as shown in FIG. 4, the downstream-most mould  1  has been gripped by the robot gripper  9  and moved from the bars  7  into the extraction station  8 , the gripper  9  is moved so as to cause the face of the mould  1 , on which the casting  4  is situated, being carried by the part of the casting cavity formed in this face of the mould, into a position, of FIG. 5, in which the engagement hook  14  penetrates the mould material (normally compacted mould sand) superficially, i.e. only to the extent necessary for the hook to engage an upstream surface on the casting  4 . 
     In the next step, shown in FIG. 6, the mould  1  is again moved away from the hook  14 , which will then pull the casting  4  out of the casting cavity part concerned, after which the casting  4  falls down on a conveyor  15 , on which it is carried to the next station (not shown) for further processing, if necessary. 
     FIG. 7 shows the frame  10  in an inclined position with the pressure pads  11  and  12  disengaged from the mould  1 , immediately before the latter slides down on the lifting bars  13  to fall onto a suitable conveyor (not shown) for recycling. When the frame  10  is free, it will be returned to the position shown in FIG. 2 in readiness for the next operating cycle. 
     Although not clearly evident from FIG. 6, the conveyor  15  may be placed at such a high level, e.g. by making it extend transversely to the plane of the drawing, that the height of fall for the casting  4  will be a minimum. 
     In the above-mentioned embodiment (not shown) having two or more engagement hooks cooperating in the manner of a pair of tongs,it is, of course, possible to arrange for the castings to be placed gently on e.g. a conveyor, so as to eliminate any risk of damage during this step. 
     In the exemplary embodiment shown in the drawing, the engagement member used for extracting the castings  4 ,  5 ,  6  etc. from the moulds  1 ,  2 ,  3  etc. is constituted by a hook  14  capable of engaging an upstream surface just behind the edge of each casting. In another embodiment (not shown), the engagement member is constituted by a more or less straight or smooth “finger” merely jerking or prodding the casting loose from the mould. 
     In a further embodiment (also not shown), the engagement member is constituted by a suction cup of a shape complementary to that of the casting, connectable to a suitable vacuum source, capable of both pulling the casting out of the casting cavity and (if required) holding it until it can be deposited gently on e.g. a conveyor. 
     In a still further embodiment (also not shown), the engagement member is constituted by an electromagnet connectable to a suitable source of electric current. This embodiment will function in the same manner as the embodiment mentioned in the previous paragraph, but its use is—necessarily—limited to castings consisting of ferro-magnetic material having a temperature below the Curie point. In this case, the requisite cooling could be achieved by increasing the length of the part of the mould string extending from the pouring station (not shown) to the extraction station  8 . 
     LIST OF PARTS 
       1  downstream-most mould 
       2  mould 
       3  mould 
       4  casting 
       5  casting 
       6  casting 
       7  bar 
       8  extraction station 
       9  robot gripper 
       10  frame 
       11  upper pressure pad 
       12  lateral pressure pad 
       13  lifting bar 
       14  engagement hook 
       15  conveyor