Patent Application
20180155898
The present disclosure relates to manufacturing of an excavator bucket. More specifically, the present disclosure relates to a modular mold assembly for manufacturing the excavator bucket by casting process.
Buckets are generally used as an implement with earth moving machines such as an excavator, a wheel loader etc., and are subjected to extreme loads and wear. Besides withstanding loads and abrasive environment, an excavator bucket must also be strong enough to endure many thousands, or in some cases, millions of cycles. (A cycle is each repetition of penetrating into the material, scooping, and dumping.) If the excavator bucket fails readily, replacement of the excavator bucket may amount to a great expense in parts and labor and downtime. A reliable bucket that lasts through many cycles without breaking can be an important requirement for owners of earth moving machines.
The bucket can be expensive and difficult to manufacture because of its size and weight and other factors. Buckets are typically constructed as weldments of multiple pieces of plate steel. Manipulating these large and heavy pieces to align them to one another, and then correctly performing the welds can be a difficult and expensive task. Further, it has been observed of late that the buckets manufactured by welding metal pieces together are failing well before completing an expected life span. Commonly, the buckets fail at a welding joint, owing to the relatively lower structural strength of the welding joint under various stresses and strains compared to other parts of the bucket.
Another method of manufacturing buckets other than welding metal pieces together can be a casting process. The bucket is produced as a single part through the casting process eliminating any major joints etc. Molten metal is poured in a bucket-shaped cavity of a certain volume in a mold, and the molten metal is solidified and post-processed to produce the bucket. However, as the buckets are produced in various volumetric capacities as per the application area in which they are to be used, it may be expensive to have separate set ups of molds corresponding to all volumetric capacities.
For example, European patent application 2,149,639 (referred to as the '639 application) discloses a wear-resistant, impact-resistant excavator bucket manufactured by casting. The excavator bucket is manufactured by making a wooden or metallic casting pattern having the same shape as that of the bucket. The casting pattern is inserted into a molding box and subjected to sand casting using molding sand so as to form a sprue. The pattern is taken out from the molding box to form a mold cavity. An ingot is heated and poured into the mold cavity. The poured ingot is solidified and the upper mold portion and the molding box are separated from the solidified ingot to produce a sand-cast bucket. However, the manufacturing method of the excavator bucket disclosed in the '639 application does not allow manufacture of varying sizes of the excavator bucket by making use of same set of tooling. In order to manufacture the excavator bucket of a different size, a new casting pattern will be required. It may not be cost efficient to maintain an inventory of casting patterns corresponding to all the sizes of the excavator buckets required.
Thus, an improved casting mold is required to accommodate casting of buckets of varying volumetric capacities.
In an aspect of the present disclosure, a method of manufacturing a bucket by casting is provided. The method includes determining a volumetric capacity of the bucket. The method includes configuring a modular mold assembly to manufacture the bucket. The configuring of the modular mold assembly includes selecting a cope box from a plurality of cope boxes based on the volumetric capacity of the bucket. The configuring of the modular mold assembly includes selecting a drag box from a plurality of drag boxes based on the volumetric capacity of the bucket. The configuring of the modular mold assembly includes selecting a first core from a plurality of first cores based on the volumetric capacity of the bucket. The configuring of the modular mold assembly further includes assembling the cope box, the first core, a second core, and the drag box such that the cope box, the first core, the second core, and the drag box together define a bucket-shaped mold cavity. A volume of the mold cavity depends on the selection of the cope box, the first core, and the drag box. The method further includes pouring a molten material in the mold cavity and removing the cast bucket after solidification of the molten material from the modular mold assembly.
In another aspect of the present disclosure, a pattern assembly for preparing a modular mold assembly is provided. The modular mold assembly produces buckets of varying volumetric capacity. The pattern assembly includes a box having a hollow shape. The box includes a base and four side walls coupled to the base. The pattern assembly includes a first pattern coupled to the base of the box. The pattern assembly further includes a second pattern removably coupled to the first pattern. The second pattern is selected from a plurality of second patterns based on a required volumetric capacity of the bucket.
In yet another aspect of the present disclosure, a modular mold assembly for manufacturing a bucket by casting is provided. The modular mold assembly includes a cope box selected from multiple cope boxes based on a volumetric capacity of the bucket. The modular mold assembly includes a drag box selected from multiple drag boxes based on the volumetric capacity of the bucket. The modular mold assembly includes a first core selected from multiple first cores based on the volumetric capacity of the bucket. The modular mold assembly further includes a second core. The cope box, the first core, the second core, and the drag box together define a bucket-shaped mold cavity, such that the volume of the mold cavity depends on the selection of the cope box, the first core, and the drag box.
Wherever possible, the same reference numbers will be used throughout the drawings to refer to same or like parts.
The bucket 100 is manufactured through a casting process as an integral structure. It should be noted that the first side plate 102, the second side plate 104, the back plate 106, the support plate 108, and the pair of hinge plates 110 are depicted as different parts for illustrative purposes only. The bucket 100 has a symmetrical structure, and the first side plate 102 and the second side plate 104 are structurally mirror images of each other. The first side plate 102 and the second side plate 104 may include means to reinforce structural rigidity of the first side plate 102 and the second side plate 104. In the illustrated embodiment, the first side plate 102 and the second side plate 104 include wear pads 120.
A first section 200 is defined as a portion of the bucket 100 towards right side of the plane A-A′ including the first side plate 102. A second section 202 of the bucket 100 is defined as a portion of the bucket 100 towards left side of the plane B-B′ including the second side plate 104. A third section includes the back plate 106 extending between the planes A-A′ and B-B′ from the first hinge plate 112 to the second hinge plate 114, and a portion of the support plate 108. The first section 200, the second section 202, the back plate 106, and the support plate 108 together complete the shape of the bucket 100. In order to vary volumetric capacity of the bucket 100, dimensions of the back plate 106 are kept constant and dimensions of the first section 200, the second section 202 and the support plate 108 are varied.
The cope box 302, the first core 304, the second core 306, and the drag box 308 shape different parts of the bucket 100. The cope box 302 defines shape of the first section 200 and the drag box 308 defines shape of the second section 202. The first core 304 defines shape of the support plate 108 and the second core 306 defines shape of the back plate 106. An imaginary sectional plane C-C′ divides the modular mold assembly 300 in two parts. The plane C-C′ passes through all the parts of the modular mold assembly 300 including the cope box 302, the first core 304, the second core 306, and the drag box 308.
The cope box 302 is prepared by compacting sand inside a first pattern assembly 700. The sand may be mixed with binders or any other such material which may be suitable to hold the sand together.
An inventory of multiple second patterns 710 may be maintained corresponding to the various volumetric capacities of the buckets 100 being produced. The multiple second patterns 710 are used for producing the multiple cope boxes 500. After the second pattern 710 of an appropriate width is coupled to the first pattern 708 inside the box 702, the first pattern assembly 700 is filled with sand. Sand is compacted inside the first pattern assembly 700 to make sure that the sand is not loose and then the first pattern assembly 700 is inverted to obtain the cope box 302 by removing the box 702, the first pattern 708 and the second pattern 710. As the width of the second pattern 710 is varied, the shape of the cope box 302 varies accordingly. One of the cope boxes 302 is selected from the multiple cope boxes 500 to configure the modular mold assembly 300 as per the required volumetric capacity of the bucket 100.
The drag box 308 is prepared in a similar manner as the cope box 302. The drag box 308 is prepared by compacting sand inside a second pattern assembly 1000. Sand may be mixed with binders or any other such material which may be suitable to hold the sand together.
An inventory of multiple second patterns 1010 may be maintained corresponding to the various volumetric capacities of the buckets 100 being produced. The multiple second patterns 1010 are used for producing the multiple drag boxes 504. After the second pattern 1010 of an appropriate width is coupled to the first pattern 1008 inside the box 1002, the second pattern assembly 1000 is filled with sand. Sand is compacted inside the second pattern assembly 1000 to make sure that the sand is not loose and then the second pattern assembly 1000 is inverted to obtain the drag box 308 by removing the box 1002, the first pattern 1008 and the second pattern 1010. As the width of the second pattern 1010 is varied, the shape of the drag box 308 varies accordingly. One of the drag boxes 308 is selected from the multiple drag boxes 504 to configure the modular mold assembly 300 as per the required volumetric capacity of the bucket 100 being manufactured.
The first core 304 is prepared by compacting sand inside a hollow structure having a shape complementary to the outer surface of the first core 304. The first core 304 may be solid or the first core 304 may be partially solid having a cavity at centre and a particular thickness of sand defining the shape of the first core 304. The multiple first cores 502 may be prepared corresponding to various volumetric capacities of the bucket 100 and an appropriate first core 304 of required shape and size may be selected based on the volumetric capacity of the bucket 100 being manufactured.
After preparing the cope box 302, the first core 304, the second core 306, and the drag box 308, the modular mold assembly 300 is configured according to the volumetric capacity of the bucket 100 being prepared.
The present disclosure provides an improved method 1400 to manufacture the bucket 100 by casting process using the modular mold assembly 300. The method 1400 is explained with a flow chart as shown in
The method 1400 at step 1408 selects the drag box 308 from the multiple drag boxes 504 based on the volumetric capacity of the bucket 100. The multiple drag boxes 504 correspond to various volumetric capacities of the bucket 100 which may be manufactured from the modular mold assembly 300. The drag box 308 of appropriate size is selected as per the required volumetric capacity of the bucket 100. The method 1400 at step 1410 selects the first core 304 from the multiple first cores 502 based on the volumetric capacity of the bucket 100. The multiple first cores 502 correspond to various volumetric capacities of the bucket 100 which may be manufactured from the modular mold assembly 300. The first core 304 of appropriate size is selected as per the required volumetric capacity of the bucket 100.
The method 1400 at step 1412 assembles the cope box 302, the first core 304, the second core 306, and the drag box 308, such that the cope box 302, the first core 304, the second core 306, and the drag box 308 together define the bucket-shaped mold cavity 400. The volume of the mold cavity 400 depends on the selection of the cope box 302, the first core 304, and the drag box 308. The method 1400 at step 1414 pours molten material in the mold cavity 400. The molten material may be a metal, or any other suitable material which may be used to manufacture the bucket 100 by casting process as per the need of the current application. The method 1400 at step 1416 removes the cast bucket 100 after solidification of molten material from the modular mold assembly 300. The bucket 100 may be further post-processed by heating the bucket 100 in an electric furnace. The bucket 100 may be quenched in cold water afterwards to finish the manufacturing process of the bucket 100. Post-processing steps may vary as per the desired structural properties of the bucket 100 being manufactured.
The present disclosure facilitates manufacturing of the bucket 100 of varying volumetric capacities through a single set of tooling for the casting process by selecting appropriate size of the cope box 302, the first core 304, and the drag box 308 from a variety of different sizes as per the required volumetric capacity of the bucket 100 being manufactured. A significant amount of cost savings can be done by using the modular mold assembly 300 and the method 1400 described in the present disclosure to manufacture the bucket 100. Apart from the savings in the cost of the manufacturing set up, since the bucket 100 is being manufactured as an integral part by casting, life of the bucket 100 is considerably increased and longer life cycles are expected. This leads to further increase in productivity of the machine using the bucket 100 as the downtimes due to failure of the bucket 100 are considerably reduced. Further, as the design of the modular mold assembly 300 is very simple, all the parts of the modular mold assembly 300 can be easily accessed for maintenance against any wear over prolonged usage. Any changes in the design of the bucket 100 may also be easily incorporated by making changes in the design of different parts of the modular mold assembly 300.
While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.
