Fluent material handling – with receiver or receiver coacting mea – Processes
Reexamination Certificate
2000-06-14
2001-10-16
Douglas, Steven O. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Processes
C141S095000, C141S198000, C222S064000
Reexamination Certificate
active
06302158
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 toward the top of the flask. Sand from a batch hopper located above the flask is poured into the flask around the foam pattern. As the sand fills the flask, the sand compacts about the foam pattern through the use of vibration. 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.
The distribution of sand into the flask in many prior art embodiments is controlled through monitoring the period of time during which the sand gate is in an open position. Using such a method, the user estimates the length of time that is required to distribute the desired amount of sand around a particular foam pattern according to the complexity of the design of the pattern, and the user opens the sand gate for this proper period of time. As a result, the accurate and desired distribution of sand using this method may not occur due to the varying conditions of the types of sand used and the flowability related thereto. For example, if the sand does not flow well from the batch hopper, then the sand received in the flask will be too low to fill the cavities of the foam pattern. This problem is illustrated in
FIG. 1A
wherein sand
2
does not engage the cavity
6
within the foam pattern
4
. However, if the sand overflows into the flask, there is too much overburden at the entrance of the cavity
6
and the sand will not be fluidized at the entrance of the cavity
6
of the pattern. As a result, the sand will not be able to fully fill the cavities of the pattern. This problem is illustrated in
FIG. 1B
wherein sand
2
substantially overburdens the foam pattern
4
and does not fully fill the cavity
6
. Additionally, if the user desired to deposit multiple different layers of sand from the batch hopper using the timing method, each independent and different layer of sand would be subject to inaccuracies caused by the variations in the flow rates of sand, which will also provide a cumulative effect of providing multiple inaccurate layers within the flask. However, looking at
FIG. 1C
, when the proper depth of sand
2
is distributed into the flask having the desired flow rate, there will be only a slight overburden of the sand
2
on the pattern
4
, which will promote the rapid and complete filling of the cavity of the pattern
4
.
Accordingly, what is needed is a sand level sensing and distribution apparatus to provide an accurate control of the depth and flow rate of the layers of sand that are deposited into the flask such that the sand in the flask will flow to a proper height around the mold positioned in the flask to substantially surround and engage a foam pattern.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus operating to control the depth of the distribution of sand from a batch hopper into a mold flask in a casting process to surround a mold and substantially fill the cavities of the mold with sand.
It is another object of the present invention to provide a sand distribution apparatus to continuously monitor and control the amounts of sand distributed from the batch hopper into the mold flask.
It is a further object of the present invention to provide a sand distribution apparatus having an improved method of controlling the amount of sand distributed from the batch hopper into the mold flask.
It is a further object of the present invention to provide a sand distribution apparatus to disperse varying amounts of sand from a batch hopper to a mold flask according to predetermined sand level requirements according to the mold being cast.
These and other objects of the present invention are accomplished through the use of a sand level sensing and distribution apparatus for promoting desired sand distribution into a mold flask in a casting process, such as a lost foam casting process. The sand level sensing and distribution apparatus comprises a batch hopper substantially filled with sand to be distributed from the batch hopper into a mold flask. The batch hopper includes a window that allows a sensor assembly to monitor the sand contained within the batch hopper. The sensor assembly is proximately positioned close to the side of the batch hopper, with the sensor assembly including a sensor member positioned adjacent the window to monitor the distribution of sand into the flask below. The sensor assembly is attached to a level actuating assembly that is operable to move the sensor assembly vertically such that the sensor member may traverse the length of the window. The level actuating assembly includes a motor that is connected to a central processing unit such that the central processing unit controls the operation of the motor in vertically positioning the sensor assembly. The sensor assembly is additionally connected to the central processing unit, and the central processing unit uses the sensor assembly to receive current information to control the operation of the motor of the level actuating assembly.
In operation, the sensor assembly is first moved to a “start” or “home” position, and then locates the top level of the sand within the batch hopper via the sensor assembly. The sensor assembly provides one signal while measuring sand, and once the sensor reaches the top level of sand, the state of the sensor changes, indicating that the sensor assembly has come to the top level of sand within the batch hopper. The central processing unit, having been programmed with a “recipe” of the desired parameters for distributing the sand into the flask, then controls the downward movement of the sensor assembly. From the top level of the sand within the batch hopper, the sensor assembly is moved downward a distance as desired by the user and programmed into the central processing unit. Once the sensor assembly has reached the desired level, the central processing unit opens the sand gate subjacent the batch hopper such that sand is distributed from the batch hopper into the flask. The sensor assembly provides a continuous monitoring of the distribution of sand into the flask, and once the top level of sand reaches level of the sensor assembly, a signal is provided to the central processing unit to close the sand gate and stop the flow of sand. The sensor assembly, controlled by the central processing unit, is then moved downward again, according to the recipe, to the next desired level. The central processing unit again opens the sand gate, and sand flows until the top level of the sand reaches the sensor assembly. These steps are thereby repeated, as programmed in the recipe, until the sand completely and substantially evenly surrounds the mold in the flask as desired by the user. The flask is then moved to a separate station to allow molten liquid to be poured onto the mold surrounded by sand.
Once the flask is moved to a separate station, the batch hopper is again partially filled with sand, and the sensor assembly is reset to the top sand level within the batch hopper. The sensor assembly is then operable to control the distribution of sand as desired by the user, and repeats the sand distribution steps described above.
These and other objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiment of the invention.
REFERENCES:
patent: 4593739 (1986
Burr & Forman LLP
Douglas Steven O.
Holland Christopher A.
Veal Robert J.
Vulcan Engineering Company, Inc.
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