Metal founding – Means to shape a forming surface – Including means for compacting particulate fluent mold...
Reexamination Certificate
1999-05-04
2002-07-23
Elve, M. Alexandra (Department: 1725)
Metal founding
Means to shape a forming surface
Including means for compacting particulate fluent mold...
Reexamination Certificate
active
06422296
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an apparatus and a method for making ready-to-pour shells or core assemblies with a number core shooting machines corresponding to the number of different cores needed for completing a core assembly and an assembly line, wherein the produced and solidified cores are removed from the core shooting machines and completed on the assembly line to the core assembly.
Basically, the present invention relates to the field of foundry practice. To produce castings of any kind, foundry cores or foundry molds are generally made as separate parts, combined, and joined together to form a casting mold or core assembly. Thereafter, these core assemblies are filled with molten metal for producing, for example, a metallic workpiece. In mass production, these core assemblies that are to be filled with molten metal, pass one after the other through the production line.
Within the scope of conventional production, the core shooting machines producing the required cores are linearly arranged in one line. The produced cores that are removed from the core shooting machine and processed, if need be, are deposited one after the other on an assembly line that rigidly couples the core shooting machines. Finally, the core assembly is completed from core shooting machine to core shooting machine, namely in the strictly predetermined sequence of their arrangement, which must exactly correspond to the sequence in the assembly of the cores.
In such a rigid, conventional production, the downtimes of an individual core shooting machine present a quite significant problem. Such downtimes result from repairs or maintenance. Thus, if one of the core shooting machines is down, the entire assembly line will have to be stopped, since each individual core or type of core is needed for completing the core assembly. If one wanted to continue in such a situation the operation of the assembly line and, thus, the assembly of cores, each core shooting machine would have to be provided with an adequately large inventory of cores to be entered as substitutes into the assembly process. However, such an inventory would be extremely space-intensive and problematic with respect to a safe storage of the cores, inasmuch as cores made of molding sand are highly sensitive parts, whose handling and storage is again problematic. Finally, in practice shells or core assemblies of the kind under discussion are produced by the core shooting machines without an additional inventory of cores, whereby high downtimes on individual core shooting machines cause quite considerable total downtimes of the production plant as a whole.
For example, assuming an annual requirement of 400,000 core assemblies, 48 work weeks per year, and three shifts per day, taking as a basis the linear arrangement of a total of eight core shooting machines with a cycle time per machine of 45 seconds, and 85% guaranteed availability of each machine, and further assuming that necessitated by maintenance (cleaning, repair, and service), a total of six work days per week and 23 work hours per day are available, i.e., a total of 48 weeks×6 days×23 hours=6,624 hours per year, an average total downtime will result in an amount of 7.23 hours per day and 50.7 hours per week. The downtime will then amount to 2.95 hours per day, or 20.7 hours per week with a maintenance duration of 4.28 hours per day and 30 hours per week.
Lastly, with a rigid linear coupling of the core shooting machine without additional core inventory, the conventional production leads to quite considerable downtimes and maintenance times of the entire production plant. Added to this is the further problematic situation that in the case of a downtime of a production plant comprising, for example, eight core shooting machines, several maintenance crews will be needed for simultaneously maintaining all core shooting machines. Had one maintained or repaired or serviced one core shooting machine after the other by a single maintenance crew, the total downtime would increase quite considerably. However, the employment of several maintenance crews is extremely costly with respect to personnel, and increases production costs quite significantly.
With respect to a relevant prior art, reference is made, only by way of example, to DE 31 48 461 C1 that discloses a core and shell shooting machine of the described type. Furthermore, U.S. Pat. No. 5,996,681 discloses an arrangement of the described kind for making ready-to-pour shells and core assemblies. In this arrangement, the core shooting machines producing the required cores as described above are linearly arranged along an assembly line. While the assembly line interconnects the core shooting machines in functional respect, one will have to expect quite considerable total downtimes for lack of individual core inventories at the respective core shooting machines.
It is therefore an object of the present invention to improve and further develop both an apparatus and a method for making ready-to-pour shells or core assemblies of the initially described kind in such a manner that in comparison with conventional production, it is possible to increase production capacity with the least possible expenditure.
SUMMARY OF THE INVENTION
The above and other objects and advantages of the invention are achieved by the provision of an apparatus which comprises a plurality of core shooting machines disposed along a production line, with the number of core shooting machines corresponding to the number of cores required to form a desired core assembly. An assembly line is positioned adjacent the production line so that the produced cores removed from the core shooting machines may be assembled into the desired core assembly, and at least one additional core shooting machine is positioned along or adjacent the assembly line, with the one additional core shooting machine being configured for the selective production of each of the cores required to form the desired core assembly.
In accordance with the invention, one departs from the conventional concept to the extent that no core inventories are provided for bridging downtimes. Instead, in accordance with the invention, the additional core shooting machine, hereafter also referred to as the standby machine, is provided, which can assume as a substitute the operation of each regular core shooting machine and, thus, serves to produce each of the cores required for completing the assembly. Lastly, each core that is produced as a substitute is supplied to the assembly process at the right time and at the right place.
In a particularly advantageous manner, the standby machine is stationarily arranged and thus is not moved as needed to the vicinity of the respectively shut down core shooting machine. Instead, the core produced by the standby machine is supplied to the assembly process at the right time and at the right place. To this end, it would be possible to associate the standby machine directly to the assembly line, for example, arrange it along the assembly line to precede or follow the regular core shooting machines.
Likewise, it would be possible to arrange the standby machine at a second assembly line, an additional line, that communicates with the first assembly line to the extent that a core produced by the standby machine is deposited on the additional line and transported via this additional line, which may extend, for example, parallel to the actual assembly line, to the region of the inoperative core shooting machine. A takeover by the active manipulators for subsequently completing the core assembly can be realized without difficulties.
As previously described, the assembly line could be linearly arranged at least in the broadest sense. In this instance, the additional line could extend substantially parallel to the assembly line, so that the core produced as a substitute by the standby machine can be transported exactly to where it is also actually needed due to a failure of a core shooting machine. By way of a kind of cross assembly, completion of the
Pöhlandt Werner
Seiraffi Mohammed Ali
Alston & Bird LLP
Elve M. Alexandra
Hottinger Maschinenbau GmbH
Kerns Kevin P.
LandOfFree
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