Abstract:
A tool, especially for producing molding cores. The tool is disposed in a casting apparatus and is provided with first half-shells ( 13, 15 ) and second half-shells ( 14, 16 ). Two parting planes are provided, and two casting units are formed from the first and second half-shells. These parting planes are situated one behind the other in the direction of movement of the two casting units.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of co-pending international application no. PCT/EP99/05322, filed Jul. 26, 1999, designating the United States of America. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a tool, especially for producing cores, which is arranged in a casting system and wherein the tool comprises first casting half shells and second casting half shells. 
     Such tools are used, for example, in the so-called “lost core technique,” in which cores of a low-melting metal alloy are cast in the low-pressure process in a multi-part mold. These cores are then placed in a plastic injection molding machine. The plastic part is produced by injecting synthetic resin material around the core into the injection molding die. After the synthetic resin enclosed core has cooled, the core is melted out by applying appropriate fusion heat. For this purpose the plastic part with its enclosed core is immersed in a heated bath and by inductive support a uniform fusion of the core is achieved. The core is produced in a horizontally arranged casting system. Since the core has a relatively large mass, a long cooling phase is necessary. This means that the cycle times are substantially influenced by the cooling times and under some circumstances they are substantially longer than the subsequent cycle times when thermoplastic synthetic resin is injected around the core. 
     Consequently, until now it has been necessary to have several core casting machines to make it possible to produce a certain number of cores within a certain period of time. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to provide a a tool, especially for the production of cores, which enables shorter cycle times to be achieved. 
     This and other objects have been achieved in accordance with the present invention by providing a tool which comprises first casting half-shells and second casting half-shells, with two planes of separation or parting planes being provided and two casting units having first and second casting half-shells being formed, in which the parting planes are situated one behind the other in the direction of movement of the two casting units. 
     A significant advantage of this invention is that at least two cores can simultaneously be cast in parallel in a single core casting machine, and thus the cycling time can be halved. 
     In one embodiment of the invention it is proposed to couple the casting half shells, which move parallel to one another, together by means of connecting rods. The application of force thus is effected through these connecting rods, and optionally a packet of springs can be provided to compensate for tolerances. 
     In accordance with another embodiment of the invention, each half shell is equipped with one or more ejectors. The core casting machine can be provided with a plurality of casting units arranged side by side. Thus, for example, four or six cores can be produced in a single working cycle. 
     To enable the cores to be removed by a gripper, in another embodiment of the invention the tool is moved after the casting operation such that the cores on both sides are released and can be removed. 
     These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or the drawings, and the individual features each may be implemented in embodiments of the invention either individually or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawings in which: 
     FIG. 1 shows a core casting tool in the closed state; 
     FIG. 2 shows a core casting tool in the open state; 
     FIG. 3 shows a plan view of the core casting tool in the closed state; 
     FIG. 4 shows an engine air intake tube which was produced by the melted core technique; 
     FIG. 5 shows a core composed of several half shells; 
     FIG. 6 shows a cross section through a half-shell core; and 
     FIG. 7 shows a tool for the production of half shells. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The core casting machine  2  of FIG. 1 comprises a support plate  10  which is fastened on a casting machine (not shown here). On this support plate  10  a casting distributor  11  is arranged with a tool carrier  12  fastened thereon. On the tool carrier  12  are the casting half-shells  13 ,  14 ,  15 ,  16 , which are shown here in the closed state. The casting half-shell  13  is coupled to casting half shell  15  by connecting rods  17  and  18 . The casting half-shell  14  is coupled with the casting half shell  16  by the connecting rods  19  and  20 . The casting half-shells are fastened in corresponding tool holders  21 ,  22 ,  23 ,  24 . The tool holders  21  and  24  are in turn arranged on supports  25  and  26 . On these supports is a multiple coupler  27 ,  28 , to carry the hydraulic lines and supply cooling fluid. Ejectors  29 ,  30 ,  31  and  32  are provided in the tool holders  21 ,  22 ,  23 ,  24 . 
     The melt is introduced through the feeders  33  and  34  to the corresponding cavities  35  and  36 . After the cast cores have solidified, the tools are opened. 
     In FIG. 2 the tools are shown in the opened state. Like parts are identified by the same reference numerals. Through movement of the supports  25  and  26  as indicated by the arrows  37  and  38 , both half shells are separated from the cast cores due to the action of the connecting rods  17 ,  18 ,  19  and  20 . After separation of the casting half-shells, the cores  39  and  40  are held on cylindrical projections on a base portion of the tool. The completed cores  39  and  40  then can be removed. 
     FIG. 3 shows a plan view of the tool in the closed state. Here again, like parts are identified by the same reference numerals. The casting half-shells  13 ,  14 ,  15  and  16  are configured so that three cores can be cast simultaneously each time. The core planes are offset from one another and the connecting rods  17 - 20  are connected to the supports  25  and  26  with tolerance-equalizing spring packets  41  and  42  in order to compensate for machine tolerances or tolerances due to temperature fluctuations. In the representation depicted here, only the connecting rods  17  and  20  are shown, but of course the connecting rods  18  and  19  also may have tolerance-equalizing spring packets. 
     FIG. 4 shows an engine air intake manifold  110  for an internal combustion engine which is produced of thermoplastic synthetic resin material. The intake manifold  110  comprises an air collection chamber  111  to which filtered clean air is fed from a filter element, not shown here. From this air collecting chamber  111 , individual intake tubes  112 ,  113 ,  114 ,  115 ,  116  and  117  extend to a connection flange  118 , which interconnects the individual intake tubes. In the connection flange there are openings  119 ,  120 ,  121 ,  122 ,  134 ,  134  for injection nozzles, as well as mounting holes. 
     The first process step in the production of such an intake manifold are the manufacture of the core in a low-pressure process from a tin-bismuth alloy. This core is removed from the casting tool and placed in an injection molding machine. After the thermoplastic synthetic resin material has been injected around the core, the core is melted out and the plastic component is washed out. A core of this type for producing intake manifolds having six individual intake tubes weighs between 40 and 50 kg. This weight, of course, makes them difficult to handle. 
     FIG. 5 shows a core for the intake manifold shown in FIG.  4 . It includes six tubes  125 ,  126 ,  127 ,  128 ,  129  and  130 , which are made by the half-shell technique, together with a collection chamber tube  131 . The tubes  125  to  130  are attached to the collection chamber tube  131  by plug connections. FIG. 5 also shows internal structures  137 ,  138  and  139  for supporting the partial shells. 
     The structure of the cores is shown in FIG.  6 . They are comprised of an upper half-shell  132  and a lower half-shell  133 , which are interlocked or snapped together, for example, enclosing a hollow space  136 . As previously mentioned, the cores have synthetic resin material  135  injected around them. This forms the intake manifold or the individual intake tubes in accordance with FIG.  4 . Depending on their geometry, the half-shells  132  and  133  can be produced in a core casting machine, since the machines can be opened from both sides and a multi-stage tool can be used without additional expense. 
     In particular it is possible to carry out the process of press fitting the half-shells to each other in the core casting tool. For this purpose, as shown schematically in FIG. 7, the center plate  142  of the tool is removed and the two outer halves  143  and  144  are closed so that the half-shells  140 ,  141  can be interfitted together. Thus there is no need for an additional fitting device to join the half shells. 
     A significant advantage of the use of tubes as cores also is that, when the core is melted out, the melted fluid can pass into the core, which leads to a faster heat transfer and a faster melt-out. 
     The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed broadly to include all variations falling within the scope of the appended claims and equivalents thereof.