Patent Application
20150276317
The subject matter disclosed herein relates to a melt furnace and a melt furnace control system and, more particularly, to a melt furnace burner output control system and methods of controlling burners in a melt furnace.
Melt furnaces and control systems for melt furnaces for providing molten material for die casting metal components are well known in the art. Many large-scale operations rely on multiple furnaces to provide enough molten material to maintain a constant production pace. Configuration and physical layout of melt furnaces represent significant capital expenditures for die cast manufacturing operations.
All die cast manufacturing operations produce scrap and require an almost constant supply of molten metal. Scrap material from the production process can build up and present an issue for a manufacturing facility if not dealt with efficiently. One common solution is to feed the scrap material back into the melt furnace to be consumed again along with new raw stock. Maintaining a constant supply of molten metal can be energy intensive and requires active management of the material going into a melt furnace.
A melt furnace and a melt furnace control system configured to maximize consumption of scrap materials from a production process, while minimizing energy consumption of the melting process and maintaining a constant flow of molten material to the production process is desirable.
According to one aspect, a melt furnace includes a first reservoir including a first material level sensor and at least one first reservoir melt burner, a second reservoir including a second material level sensor and at least one second reservoir melt burner, and a holding reservoir including at least one holding reservoir burner, a temperature sensor, and a molten material level sensor assembly. The first reservoir and the second reservoir are in fluid communication with the holding reservoir to flow molten materials to the holding reservoir. A control system includes a controller in signal communication with the first material level sensor, the second material level sensor, the holding reservoir temperature sensor, and the molten material level sensor assembly. The controller is adapted to adjust an output level of at least one of the at the least one first reservoir melt burner and the at least one second reservoir melt burner to one of a plurality of levels based, at least in part, on one or more signals received from at least one of the first material level sensor, the second material level sensor, the holding reservoir temperature sensor, and the molten material level sensor assembly, to control the flow of molten materials from at least one of the first reservoir and the second reservoir to maintain a level of molten material in the holding reservoir.
According to another aspect, a control system for a melt furnace is provided. The melt furnace includes a first reservoir having a first material level sensor and a first reservoir burner, a second reservoir having a second material level sensor and a second reservoir burner, and a holding reservoir having a molten material level sensor assembly, a temperature sensor, and a holding reservoir burner. The holding reservoir is in fluid communication with each of the first reservoir and the second reservoir to receive a first flow of molten material from the first reservoir and a second flow of molten material from the second reservoir. The control system includes a controller in signal communication with each of the first material level sensor, the second material level sensor, the holding reservoir temperature sensor, and the holding reservoir material level sensor assembly. The controller is configured to maintain a level of molten material in the holding reservoir by adjusting at least one of a first output level of the first reservoir burner and a second output level of the second reservoir burner based, at least in part, on one or more signals received from one or more of the first material level sensor, the second material level sensor, the holding reservoir temperature sensor, and the molten material level sensor assembly, to control the first flow of molten material and the second flow of molten material.
According to a further aspect, a method for controlling a melt furnace is provided. The melt furnace includes a first reservoir having a first material level sensor and a first reservoir melt burner, a second reservoir having a second material level sensor and a second reservoir melt burner, and a holding reservoir having a molten material level sensor assembly, a temperature sensor, and a holding reservoir burner. The holding reservoir is in fluid communication with each of the first reservoir and the second reservoir to receive a first flow of molten material from the first reservoir and a second flow of molten material from the second reservoir. The method includes receiving by a controller one or more signals from one or more of the first material level sensor, the second material level sensor, and the molten material level sensor assembly. At least one of a first output level of the first reservoir burner and a second output level of the second reservoir burner is adjusted with the controller to one of a plurality of output levels between and including a high output level and a low output level. A level of molten material in the holding reservoir is maintained with the controller by controlling at least one of a first molten material flow from the first reservoir into the holding reservoir and a second molten material flow from the second reservoir into the holding reservoir based, at least in part, on the one or more signals.
Other aspects and advantages of certain embodiments will become apparent upon consideration of the following detailed description, wherein similar structures have similar reference numerals.
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In one embodiment, all of the burners are gas-burning devices that operate in a similar fashion. Each of the first reservoir melt burner 112, the second reservoir melt burner 118, and the holding reservoir burner 124 are connected to a gas supply 128 through an independent gas valve 130 and each is connected to an air supply 132 through a servo motor controlled air valve 134. In one embodiment, the gas valves 130 are diaphragm valves and the air vales 134 are butterfly valves or any suitable valve that is known to one having skill in the art. The controller 126 is in communication with the servo motors of the servo motor controlled air valves 134. The amount of air that flows through the air valve 134 is directly related to the position of the servo motor and controllable by the controller 126. Air flows from each air valve 134 to the respective burners 112, 118, 124. Air also flows from each air valve 134 to the associated gas valve 130. The amount of gas that flows from each of the gas valves 130 to the respective burners 112, 118, 124 is proportional to the amount of air flowing from the air valves 134. Thus, the controller 126 is configured to control the burners 112, 118, 124 each of which includes an output level depending on the amount of air and gas flowing to it respectively. Each burner 112, 118, 124 may be at a low level burner or a high level burner. In one embodiment, the controller 126 is also capable of positioning the air valves 134 in a plurality of positions between a minimum air flow position corresponding to a low output level for the associated burner and a maximum air flow position corresponding to a high output level for the associated burner. The minimum output level for the first reservoir melt burner 112 and the second reservoir melt burner 118 corresponds to a temperature that is below the melting point of the materials in the respective reservoirs. The maximum output level for the first reservoir melt burner 112 and the second reservoir melt burner 118 corresponds to a temperature that is above the melting point of the materials in the respective reservoirs. All of the burners 112, 118, 124 are at peak gas burning efficiency when at a maximum output level and consume a minimum amount of gas when at a minimum output level.
In one embodiment, the holding reservoir burner 124 is the same or similar to the melt burners 112, 118. In this embodiment, the controller 126 closes the air valve 134 to prevent air from being supplied to the holding reservoir burner 118 allowing the output level of the holding reservoir burner 118 to be at a temperature below the melting point of the materials within the holding reservoir 124. Alternatively, the minimum output level of the holding reservoir burner 124 corresponds to a temperature above the melting temperature of the molten materials within the holding reservoir 124. It is further contemplated that all of the burners 112, 118, 124 in the furnace 100 may be set to an output level by the controller 126 independently of each other. Further still, the low output level of the melt burners 112, 118 is sufficient to maintain the temperature of the materials stored in the first reservoir 102 and the second reservoir 104, respectively, near but below the melting temperature of the materials. Thus, the controller 126 is capable of controlling a first flow of molten material 136 from the first reservoir 102 into the holding reservoir 106 and a second flow of molten material 138 from the second reservoir 104 into the holding reservoir 106 independently to maintain a desired or selected level of molten material in the holding reservoir 106. As the controller 126 increases the output level of the melt burners 112, 118 the volume of the first flow of molten material 136 and the volume of the second flow of molten material 138 increases to a maximum volume at the high output level of the melt burners 112, 118. The controller 126 may be capable of correlating the volume of the first flow of molten material 136 and the volume of the second flow of molten material 138 to the output levels of the respective melt burners 112, 118 in certain embodiments.
In one embodiment, the controller 126 is also in operational control and/or signal communication with a first reservoir charge indicator or sensor 140 and a second reservoir charge indicator or sensor 142. The reservoir charge sensors 140, 142 detect the level/amount of material in the charge areas 144, 146 respectively. For example, the first reservoir charge sensor 140 detects when a first charge area 144 is full and ready to transfer materials to the first reservoir 102 and the second reservoir charge sensor 142 detects when the second charge area 146 is full and ready to transfer materials to the second reservoir 104. In one embodiment, the first reservoir 102 receives ingot material from the first charge area 144 after first reservoir charge sensor 140 indicates a full charge and the second reservoir 104 receives scrap material from the second charge area 146 after the second reservoir charge sensor 142 indicates a full charge. In this embodiment, the controller 126 actively manages the amount and/or type of materials melted by the furnace 100 and maintains the molten material level in the holding reservoir 106 at a desired or selected level based, at least partially, on one or more signals received from one or more of the first reservoir charge sensor 140, the first reservoir material level sensor 110, the second reservoir charge sensor 142, and the second reservoir material level sensor 116. The materials within the first charge area 144 and the second charge area 146 may be manually or automatically loaded into the respective reservoirs 102, 104 in response to signals from the charge sensors 140, 142. The controller 126 will only allow the transfer of materials to the respective reservoirs 102, 104 when the first material level sensor 110 or the second material level sensor 116 indicates that space is available with the respective reservoir 102, 104. The molten material in the holding reservoir 106 may be drawn out or flow to a dispensing area 148 to be consumed by the production process.
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Alternatively, the above-described configuration is reversed when there is a shortage of scrap materials in the second reservoir 104 or the second reservoir charging area 146. If the situation occurs that either the first reservoir 102 or the second reservoir 104 runs out of charging materials, the respective burner output level is lowered by the controller 126 to a low level to limit or prevent the flow of molten material for the respective reservoir into the holding reservoir 106.
In another alternative embodiment, in an operational configuration in which there is a varying supply of scrap material and a constant supply of ingot, the servo motor controlled air valves 134 of the respective melt burners 112, 118 allow for the output of the respective melt burners 112, 118 to be at one of a plurality of levels between a high level and a low level. Thus, the controller 126 is configured to set the second reservoir melt burner 118 output level at a level between the high level and the low level such that the melting of the scrap in the second reservoir 104 is proportional to the amount of scrap being produced by the production process. In this operational configuration, the output levels of the melt burners 112, 118 are adjusted to any one of a plurality of levels between the high level and the low level depending on a ratio of available scrap material to available ingot material. This operational configuration allows for increased flexibility depending on the availability of the materials to be melted.
In all of the operational configurations described above, the controller 126 monitors the molten material level in the holding reservoir 106. The first flow of molten material 136 and the second flow of molten material 138 may be reduced or completely stopped as the level of molten material in the holding reservoir 106 increases. Environmental conditions along with the rate that the production process dispenses molten materials out of the dispensing area 148 may result in the cooling of molten material in the holding reservoir 106. The controller 126 detects the temperature of the molten material in the holding reservoir 106 and adjusts the output level of the holding reservoir burner 124 to one of a plurality of levels between a high output level and a low output level so that the temperature of the molten material in the holding reservoir 106 is always above the melting point.
It is also contemplated that the melt furnace 200 include redundant back-up systems. For example, the controller 126 and all of the sensors (temperature 120, molten metal level sensor assembly 122, material level sensors 110, 116, and charge sensors 140, 142) include primary systems and secondary back-up systems. Thus, in case of a failure of the primary system, the back-up system will continue functioning to prevent an unsafe operating condition.
The foregoing description of embodiments and examples has been presented for purposes of illustration and description. It is not intended to be exhaustive or limiting to the forms described. Numerous modifications are possible in light of the above teachings. Some of those modifications have been discussed and others will be understood by those skilled in the art. The embodiments were chosen and described for illustration of various embodiments. The scope is, of course, not limited to the examples or embodiments set forth herein, but can be employed in any number of applications and equivalent devices by those of ordinary skill in the art. Rather, it is hereby intended the scope be defined by the claims appended hereto. Additionally, the features of various implementing embodiments may be combined to form further embodiments.
