Metal founding – Means to shape a forming surface – Including means for compacting particulate fluent mold...
Reexamination Certificate
2000-04-06
2001-11-20
Nguyen, Nam (Department: 1722)
Metal founding
Means to shape a forming surface
Including means for compacting particulate fluent mold...
C222S502000
Reexamination Certificate
active
06318447
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for use in a foundry operation. More particularly, the present invention relates to an apparatus for controlling the distribution of sand into a mold flask in a casting process, such as a lost foam casting process.
BACKGROUND OF THE INVENTION
In a typical lost foam casting process, a foam mold pattern is placed within a mold flask, wherein the foam pattern includes a foam riser that extends from the foam pattern towards the top of the flask. Sand from a hopper located above the flask is poured into the flask around the foam pattern. As the sand fills the flask, the sand becomes compacted about the foam pattern. After the flask has been adequately filled with sand, which preferably corresponds to a level equal to the top of the riser, molten metal is poured onto the riser to engage the foam pattern, and the molten metal vaporizes the foam riser and pattern. Thus, the molten metal replaces the foam pattern. The metal is cooled until the casting is solidified, at which time the casting and sand are removed from the flask.
A problem that has been encountered in the industry is that if sand is not uniformly distributed about the foam pattern during the sand filling process, the foam pattern is subjected to uneven weight distribution from the sand which can damage or distort the foam pattern, potentially resulting in an inferior or unusable casting. As a result, there have been various improvements in sand distribution assemblies to address this problem, with the solutions having been implemented with varying degrees of success.
One improvement is the use of sand distribution plates to promote uniform distribution of sand in the flask, wherein a first distribution plate (“fixed plate”) having a plurality of apertures therethrough is affixed to the bottom of the hopper and a second distribution plate (“slide plate”) having a plurality of apertures therethrough, corresponding to the apertures through the proximal distribution plate, is slidably mounted subjacent the proximal distribution plate such that the distal distribution plate is movable between a closed position, wherein the apertures in the first and distal distribution plates do not overlap, and an open position, wherein the apertures in the first and distal distribution plates overlap such that multiple streams of sand “rain” into the flask. The apertures through the plates can be fully overlapped for maximum sand flow, or they can be partially overlapped to infinitely variable degrees for reduced sand flow. This is an important feature because when sand is initially poured into the flask, the flow rate should be reduced so that the sand will not damage the foam pattern and so that the sand will have an adequate time to fill any cavities in the foam pattern. As the sand level rises above the top of the foam pattern, the apertures through the distribution plates are preferably fully overlapped for maximum sand flow to quickly fill the remainder of the flask, thereby maximizing production efficiency.
While use of the sand distribution plates, collectively known in the art as a “rain gate” or “sand gate”, has substantially improved uniform sand distribution in the flask, other problems have arisen. First, when the apertures in the distribution plates are partially overlapped, the sand flow therethrough is skewed such that the sand tends to accumulate towards one side of the flask rather than uniformly therein. Additionally, the sand is offset from the center of the apertures through the fixed plate, thereby shifting the predetermined streams of sand such that the sand tends to accumulate towards one side of the flask rather than uniformly therein. The non-uniform sand accumulation results in uneven weight distribution about the foam pattern, which can damage or distort the foam pattern, potentially resulting in an inferior or unusable casting.
Accordingly, what is needed is an improved sand gate design to promote uniform sand distribution in a mold flask that overcomes the problems in the prior art.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus for controlling the distribution of sand into a mold flask in a casting process.
It is another object of the present invention to provide a sand distribution apparatus for controlling the distribution of sand into a mold flask at different rates of sand flow.
It is another object of the present invention to provide a sand distribution apparatus having one fixed distribution plate and one slide distribution plate with a masking plate attached to the slide distribution plate to provide multiple patterns for distributing sand into a mold flask.
It is another object of the present invention to provide a sand distribution apparatus that produces substantially vertical streams of sand at any designated flow rate to promote uniform sand distribution within the mold flask.
It is another object of the present invention to provide a sand distribution apparatus that substantially reduces or eliminates skewing of flowing sand during reduced flow rates to promote uniform sand distribution within the mold flask.
It is another object of the present invention to provide a sand distribution apparatus that substantially eliminates offset of flowing sand from the center of the apertures through the fixed plate during reduced flow rates to promote uniform sand distribution within the mold flask.
These and other objects of the present invention are accomplished through the use of an improved sand gate in a sand distribution apparatus for promoting desired sand distribution into a mold flask in a casting process, such as a lost foam casting process. The sand distribution apparatus comprises a proximal fixed plate mounted subjacent a hopper, wherein the proximal fixed plate has a plurality of uniform primary apertures therethrough through which sand flows from the hopper. The sand distribution apparatus additionally includes a distal distribution plate slidably mounted subjacent the proximal fixed plate, wherein the distal distribution plate has a repeating series of uniform secondary apertures therethrough, with each series of secondary apertures corresponding to one primary aperture. Consequently, the distal distribution plate is movable between a closed position, wherein the primary apertures of the proximal fixed plate and the secondary apertures of the distal distribution plate do not overlap; and a plurality of open positions, wherein the primary apertures through the proximal fixed plate and the distal distribution plate do overlap. Moreover, the sand distribution apparatus includes a set of positive stop locators that ensure the positive location of the distal distribution plate at open positions.
The sand distribution apparatus additionally includes a masking plate assembly that is used in conjunction with the distal distribution plate. The masking plate assembly includes a masking plate and a masking plate holder, with a second embodiment also including a series of ring members. The masking plate assembly is attached subjacent to the distal distribution plate. The masking plate includes a series of masking plate bores that traverse therethrough, with each masking plate bore corresponding to one secondary aperture traversing the distal distribution plate. When the masking plate is connected to the distal distribution plate, each masking plate bore will be positioned in direct alignment with the corresponding secondary aperture. Moreover, each masking plate bore has a principal diameter that extends through the masking plate, with the width of the principal diameter determining the flow rate of sand through the masking plate in this first embodiment.
In a second embodiment, the masking plate bore includes an auxiliary diameter subjacent the top surface of the masking plate. The auxiliary diameter is greater than the principal diameter such that a shoulder is created within the masking plate bore. The ring member of the masking plate assembly has an outer diameter and an inner diameter, with
Burr & Forman LLP
Holland Christopher A.
Lin I.-H.
Nguyen Nam
Veal Robert J.
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