Information
-
Patent Grant
-
6763879
-
Patent Number
6,763,879
-
Date Filed
Monday, July 1, 200222 years ago
-
Date Issued
Tuesday, July 20, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- MacMillan, Sobanski & Todd, LLC
-
CPC
-
US Classifications
Field of Search
US
- 164 458
- 164 348
- 164 1546
- 164 1556
- 164 122
-
International Classifications
-
Abstract
A mold temperature control system comprises a mold section having a cavity, a fluid circuit to distribute a flow of a conditioning fluid, the fluid circuit being positioned spaced apart from the cavity, a temperature sensor positioned in the mold to generate a signal representative of a temperature in the mold, a controllable supply of the conditioning fluid, and a controller for automatically initiating flow of the conditioning fluid through the fluid circuit in response to an initiation temperature and for automatically terminating flow of the conditioning fluid through the fluid circuit in response to a termination temperature.
Description
BACKGROUND OF THE INVENTION
This invention relates in general to controlling mold temperature in a casting system to produce a cast article. Pressure pouring of molten metal from a furnace to fill a mold cavity has been used for several decades. At room temperature, the metal is solid and becomes fluidic when melted with sufficient heat.
It is known to use a low pressure countergravity casting apparatus to cast molten metal into a mold. One example of such an apparatus is described in U.S. Pat. No. 5,215,141. Basically, in a low pressure countergravity casting apparatus, molten metal is supplied to a machine furnace. The machine furnace includes a supply conduit for introducing a gas under pressure into the machine furnace. As the gas is introduced into the machine furnace, the molten metal in the machine furnace is forced through a submerged feed tube, or evacuation conduit, into the mold. The evacuation conduit is commonly referred to as a stalk tube. The mold receives the molten metal through holes in the bottom of the mold.
The molten metal must cool in the mold and harden to produce the cast article. Cooling of the molten metal is generally done by cooling the mold using a cooling fluid flowing through cooling channels in the mold. Conventionally, cooling of the mold has been controlled by a skilled human operator who adjusts the flow of the cooling fluid, which has been rather imprecise. Insufficient cooling times can lead to an improperly formed cast article. Excessive cooling time leads to decreased cycle times and economic inefficiency.
In order to make a solid cast article with the best possible structural properties in the least amount of time, the mold temperature during metal filling and during cooling must be accurately controlled regardless of environmental conditions (e.g., ambient air temperature, humidity, and temperature and pressure of the cooling fluid). During casting, the heat energy of the molten metal (e.g., aluminum) flows into the mold and then into the cooling fluid. Preferably, a temperature profile is achieved such that a directional solidification of the cast article occurs wherein the article solidifies from the outside and then in towards the filling area (i.e., stalk tube). After a solidified article is removed from the mold, it is prepared as quickly as possible for casting another part. This includes ensuring that the mold starts the next cycle at a predetermined temperature. Thus, it is desired to cool a mold as quickly as possible while maintaining acceptable structural properties of the article and providing directional solidification.
SUMMARY OF THE INVENTION
The above advantages as well as other advantages not specifically enumerated are achieved by a mold temperature control system comprising a mold section having a cavity, a fluid circuit to distribute a flow of a conditioning fluid, the fluid circuit being positioned spaced apart from the cavity, a temperature sensor positioned in the mold to generate a signal representative of a temperature in the mold, a controllable supply of the conditioning fluid, and a controller for automatically initiating flow of the conditioning fluid through the fluid circuit in response to an initiation temperature and for automatically terminating flow of the conditioning fluid through the fluid circuit in response to a termination temperature.
Various advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a cross-sectional schematic of a mold temperature control system according to the invention.
FIG. 2
is a plan schematic of a mold temperature control system according to the invention.
FIG. 3
is a plan schematic of a zone temperature control system according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Terms indicating direction may be used in this application. For example, the terms “upper,” “lower,” and “side”, may be used for the purpose of facilitating discussion of the figures under discussion and are not a limitation on the invention or the use or orientation of the invention. Referring now to the figures, a mold temperature control system, indicated generally at
12
, is illustrated in accordance with the present invention. Although this invention will be described and illustrated in conjunction with the particular mold disclosed herein, it will be appreciated that this invention may be used in conjunction with other molds. The general structure and operation of the mold is conventional in the art. Thus, only those portions of the mold which are necessary for a full understanding of this invention will be explained and illustrated in detail. In the illustrated embodiment, the mold temperature control system
12
includes a mold
16
, at least one fluid circuit
20
a-f
, and at least one temperature sensor
24
a-e
.
The illustrated mold
16
includes a first mold section
28
and a second mold section
32
. The mold
16
may include any suitable number of mold sections. For the illustrated mold
16
, the first mold section
28
and the second mold section
32
are positioned to meet at a part line
36
when the mold
16
is in a closed position, as illustrated. The first mold section
28
and the second mold section
32
cooperate to define a cavity
40
. The illustrated cavity
40
is in the general shape of a wheel. The wheel is a cast article
44
. It should be understood that the mold temperature control system
12
may be used to manufacture other types of the cast article
44
in addition to the wheel and is not limited to the manufacture of wheels. The illustrated first mold section
28
includes an upper surface
48
and a lower surface
52
. The illustrated second mold section
32
includes an upper surface
56
and a lower surface
60
. The illustrated first mold section
28
includes side surfaces
64
,
68
,
72
. The illustrated second mold section
32
includes side surfaces
76
,
80
,
84
. It will be appreciated that the side surfaces
64
,
68
,
72
,
76
,
80
,
84
are external surfaces of the mold
16
. Likewise, the surfaces
48
,
52
,
56
and
60
are external surfaces of the mold
16
.
The illustrated mold temperature control system
12
includes six fluid circuits
20
a-f
, although any suitable number of the fluid circuits may be employed. It should be noted that the fluid circuits
20
a-f
may be positioned within the mold temperature control system
12
other than as illustrated. The type, number and positioning of the fluid circuits can vary with a number of factors, including but not limited to the configuration of the mold
16
, the cavity
40
and the cast article
44
to be produced.
FIGS. 1 and 2
illustrate one potential positioning of the fluid circuits. The fluid circuits may be of the bubbler type or of the galley type, for example. Depending upon the needs of a particular application (e.g., temperature profiles desired in a particular mold), the conditioning fluid may be either cooled or heated in order to control the temperature of mold
16
. Different temperature zones within the mold can also be established with different controlled temperatures to assist in directional solidification, and with selective application of heating or cooling fluid within different zones.
It will be appreciated that the fluid circuit
20
a
is positioned for fluid flow between the upper surface
48
of the first mold section
28
and the upper surface
56
of the second mold section
32
, although the fluid circuit
20
a
need not be so positioned. For example, the fluid circuit
20
a
might be positioned for fluid flow between two portions of the upper surface
48
of the first mold section
28
or two portions of the upper surface
56
of the second mold section
32
. It will also be appreciated that the fluid circuit
20
b
is positioned for fluid flow between the lower surface
52
of the first mold section
28
and the lower surface
60
of the second mold section
32
, although the fluid circuit
20
b
need not be so positioned. For example, the fluid circuit
20
b
might be positioned for fluid flow between two portions of the lower surface
52
of the first mold section
28
or two portions of the lower surface
60
of the second mold section
32
.
It will be appreciated that the fluid circuit
20
c
is positioned for fluid flow between the side surface
64
and the side surface
68
of the first mold section
28
. It will also be appreciated that the fluid circuit
20
d
is positioned for fluid flow between the side surface
72
and the side surface
68
of the first mold section
28
. It will be appreciated that the fluid circuit
20
e
is positioned for fluid flow between the side surface
84
and the side surface
80
of the second mold section
32
. It will also be appreciated that the fluid circuit
20
f
is positioned for fluid flow between the side surface
76
and the side surface
80
of the second mold section
32
. The illustrated positioning of the fluid circuits is not intended to be limiting on the invention, but merely illustrative of one possible positioning of the fluid circuits.
The fluid circuits
20
a-f
preferably include first openings
88
a-f
. The fluid circuits
20
a-f
also preferably include second openings
92
a-f
. The first openings
88
a-f
may be fluid inlets or fluid outlets as desired. The second openings
92
a-f
may also be fluid inlets or fluid outlets as desired. The first openings
88
a-f
and the second openings
92
a-f
permit fluid flow. A pump
104
may be employed to distribute a conditioning fluid through the fluid circuits
20
a-f
. The conditioning fluid may be any suitable fluid, such as for example water, oil, liquid or the like. The conditioning fluid may be also be any suitable gas. The conditioning fluid may be also be any suitable solid having fluidic characteristics. The conditioning fluid may move through the fluid circuits
20
a-f
from the first openings
88
a-f
to the second openings
92
a-f
, as indicated by the arrows
96
a-f
. The conditioning fluid may also move through the fluid circuits
20
a-f
from the second openings
92
a-f
to the first openings
88
a-f
, as indicated by the arrows
96
a-f
. Any fluid circuits may be positioned for fluid communication with any other one or more fluid circuits. The fluid circuits distribute a flow of the conditioning fluid. Although the illustrated fluid circuits
20
a-f
are generally arc shaped, they may include one or more straight portions, serpentine portions or may have any other suitable shape.
The mold temperature control system
12
may include any suitable number of the one or more temperature sensors
24
a-e
. The temperature sensor may be a thermocouple, a resistance temperature device (RTDs), a thermistor, an infrared thermometer or the like. The temperature sensor is preferably a K-type thermocouple. In a preferred embodiment, one or more of the temperature sensor generates a signal representative of the temperature at respective locations within the mold
16
. For purposes of clarity, the mold temperature control system
12
will be discussed concerning an embodiment which includes five temperature sensors
24
a-e
. The type, number and positioning of the temperature sensors can vary with a number of factors, including but not limited to the configuration of the mold
16
, the cavity
40
and the cast article
44
to be produced.
FIGS. 1 and 2
illustrate one potential positioning of the temperature sensors
24
a-e
.
Various positions for the temperature sensors are contemplated with the mold temperature control system
12
. It will be noted that the temperature sensors
24
a
,
24
c
,
24
e
may be positioned between an external surface of the mold
16
and one or more fluid circuits
20
a-f
of the mold
16
. It will also be noted that the temperature sensor
24
d
may be positioned between one or more of the external surfaces of the mold
16
and the cavity
40
of the mold
16
. It will likewise be noted that the temperature sensor
24
b
may be positioned between the cavity
40
of the mold
16
and one or more fluid circuits
20
a-f
of the mold
16
. In a preferred embodiment, the temperature sensors are spaced apart from one or more of the external surfaces of the mold
16
by a distance within the range of from about 17 mm to about 21 mm, more preferably a distance of about 19 mm. Likewise, in a preferred embodiment the temperature sensors are spaced apart from the one or more fluid circuits
20
a-f
by a distance within the range of from about 17 mm to about 21 mm, more preferably a distance of about 19 mm. Similarly, in a preferred embodiment the temperature sensors are spaced apart from the cavity
40
by a distance within the range of from about 17 mm to about 21 mm, more preferably a distance of about 19 mm.
Due to the spacing of a temperature sensor from a mold surface heated by molten metal and a fluid circuit cooled by the fluid, temperature changes at those surfaces are not sensed until after a time lag of up to about 10 seconds. A highly preferred location for one or more temperature sensors is a location approximately equidistant between the cavity
40
and a fluid circuit
20
, such that the temperature sensor is equally affected by such temperature changes.
The mold temperature control system
12
may include a controller
100
. In a preferred embodiment, the controller
100
is operative to detect when a portion of the mold
16
reaches an initiation temperature and a termination temperature. The initiation temperature and the termination temperature are temperatures that are approximately proportional to the signal representative of the temperature in the mold
16
being generated by one or more of the temperature sensors
24
a-e
. The initiation temperature is a predetermined temperature at which the conditioning fluid preferably begins to flow through at least one of the fluid circuits
20
a-f
. It should be noted that each of the fluid circuits
20
a-f
may be positioned to coincide with the same or a different initiation temperature. The termination temperature is a predetermined temperature at which the conditioning fluid preferably ceases to flow through at least one of the fluid circuits
20
a-f
. It should be noted that each of the fluid circuits
20
a-f
may be positioned to coincide with the same or a different termination temperature.
It should be noted that each of the temperature sensors
24
a-e
may be positioned to coincide with the same or a different initiation temperature. Likewise, it should be noted that each of the temperature sensors
24
a-e
may be positioned to coincide with the same or a different termination temperature. It will be appreciated that at least one of the temperature sensors
24
a-e
preferably generates a signal representative of the initiation temperature. Likewise, it will be appreciated that at least one of the temperature sensors
24
a-e
preferably generates a signal representative of the termination temperature.
The temperature sensor is operative to cooperate with the fluid circuits to provide cooling of the mold
16
. Likewise, the temperature sensor is operative to cooperate with the fluid circuits to control directional solidification of the cast article
44
. Further, the temperature sensor is operative to cooperate with the fluid circuits to bring the mold
16
to an acceptable temperature for the addition of the molten metal to the cavity
40
.
The controller
100
is preferably operatively connected to a pump
104
and a motor
108
. The pump
104
and the motor
108
are operative to provide the conditioning fluid to the fluid circuits
20
a-f
in the mold
16
. One or more automatically-controlled valves may also be provided that can be adjusted by controller
100
in order to direct fluid flow to individual fluid circuits. In operation of a preferred embodiment, the signal representative of a temperature in the mold
16
controls the flow of the conditioning fluid in one or more of the fluid circuits
20
a-f
. Thus, when the initiation temperature is achieved, the conditioning fluid begins to flows through one or more of the fluid circuits
20
a-f
in the mold
16
. Likewise, when the termination temperature is achieved, the conditioning fluid ceases to flow through one or more of the fluid circuits
20
a-f
in the mold
16
. The controller
100
may also be employed to synchronize the flow of the conditioning fluid through the one or more of fluid circuits
20
a-f
.
FIG. 3
shows an embodiment of the invention wherein automatically-controlled valves
110
selectively direct conditioning fluid to respective temperature zones established within the mold. Each zone
112
,
114
,
116
,
118
, and
120
has a respective fluid circuit and a respective thermocouple. Each zone has a respective initiation and termination temperature used by controller
100
to maintain each temperature zone within a desired temperature range. Controller
100
separately controls each individual cooling/heating circuit by individually adjusting (e.g., turning on and off) each respective valve
110
. The temperature ranges in each zone may change at different times within a manufacturing cycle (e.g., one temperature range used during article solidification and another temperature range used during mold preparation for molten metal pouring). Furthermore, different zones may be controlled at different temperatures simultaneously to provide a desired temperature profile. During solidification of a cast article in cavity
40
, for example, the preferred directional solidification takes place so that solidification at portions within cavity
40
that are the most remote from stalk tube
41
occurs first. Thus, zones
112
and
116
are controlled to a lower temperature than zone
114
, for example. The configuration of cooling/heating zones can be adapted to each specific mold design and can achieve substantially any desired directional solidification pattern. Since a respective temperature sensor is used to control each respective zone created in the mold by the respective fluid circuits, a controlled temperature environment is provided so that consistently high quality cast articles can be produced with optimum cycle times.
The principle and mode of operation of this invention have been described in its preferred embodiments. However, it should be noted that this invention may be practiced otherwise than as specifically illustrated and described without departing from its scope.
Claims
- 1. A mold temperature control system for controlling mold temperature in a countergravity casting system to assist in directional solidification in producing a cast article comprising:a mold section having a cavity and a stalk tube; a plurality of individual selectively controllable temperature zones established within the mold section, each of the plurality of individual selectively controllable temperature zones having a respective fluid circuit to distribute a flow of a conditioning fluid therethrough and a respective initiation and termination temperature, each respective fluid circuit being positioned spaced apart from the cavity; at least one temperature sensor positioned in the mold in each of the plurality of individual selectively controllable temperature zones for generating a respective signal representative of a temperature in each of the plurality of individual selectively controllable temperature zones; a controllable supply of the conditioning fluid to each of the respective fluid circuits of each of the plurality of individual selectively controllable temperature zones, the conditioning fluid can be either cooled or heated in order to control the temperature in each of the plurality of individual selectively controllable temperature zones; and a controller for automatically initiating flow of the conditioning fluid through each of the respective fluid circuits in response to an initiation temperature and for automatically terminating flow of the conditioning fluid through each of the respective fluid circuits in response to a termination temperature to thereby maintain each of the plurality of individual selectively controllable temperature zones within a desired temperature range to thereby assist in the directional solidification of the cast article; wherein during the solidification of the cast article in the cavity the directional solidification takes place first at the respective plurality of individual selectively controllable temperature zones in the mold section that are the most remote from the stalk tube.
- 2. The mold temperature control system of claim 1 wherein the temperature sensor is a thermocouple.
- 3. The mold temperature control system of claim 1 further comprising an external surface of the mold wherein the at least one temperature sensor is positioned between an external surface of the mold and the respective fluid circuit of the mold in each of the plurality of individual selectively controllable temperature zones.
- 4. The mold temperature control system of claim 1 further comprising an external surface of the mold wherein the at least one temperature sensor is positioned between an external surface of the mold and the cavity of the mold in each of the plurality of individual selectively controllable temperature zones.
- 5. The mold temperature control system of claim 1 wherein the at least one temperature sensor is positioned between the cavity of the mold and each of the respective fluid circuits of each of the plurality of individual selectively controllable temperature zones.
- 6. The mold temperature control system of claim 5 wherein the al least one temperature sensor is located substantially equidistant from the cavity of the mold and each of the respective fluid circuits of each of the plurality of individual selectively controllable temperature zones.
- 7. The mold temperature control system of claim 5 wherein the at least one temperature sensor is spaced apart from the cavity by a distance within the range of from about 17 mm to about 21 mm.
- 8. The mold temperature control system of claim 5 wherein the at least one temperature sensor is spaced apart from each of the respective fluid circuits by a distance within the range of from about 17 mm to about 21 mm.
- 9. A method for casting an article using a mold temperature control system for controlling mold temperature in a countergravity casting system to assist in directional solidification in producing the cast article, the method comprising the steps of:(a) providing a mold section having a cavity and a stalk tube; (b) providing a plurality of individual selectively controllable temperature zones established within the mold section each having a respective fluid circuit to distribute a flow of a conditioning fluid therethrough and a respective initiation and termination temperature, each respective fluid circuit being positioned spaced apart from the cavity; (c) providing at least one temperature sensor positioned in the mold in each of the plurality of individual selectively controllable temperature zones for generating a respective signal representative of a temperature in each of the plurality of individual selectively controllable temperature zones; (d) providing a controllable supply of the conditioning fluid to each of the respective fluid circuits of each of the plurality of individual selectively controllable temperature zones, the conditioning fluid can be either cooled or heated in order to control the temperature in each of the plurality of individual selectively controllable temperature zones; and (e) providing a controller for automatically initiating flow of the conditioning fluid through each of the respective fluid circuits in response to an initiation temperature and for automatically terminating flow of the conditioning fluid through each of the respective fluid circuits in response to a termination temperature to thereby maintain each of the plurality of individual selectively controllable temperature zones within a desired temperature range to thereby assist in the directional solidification of the cast article; wherein during the solidification of the cast article in the cavity the directional solidification takes place first at the respective plurality of individual selectively controllable temperature zones in the mold section that are the most remote from the stalk tube.
US Referenced Citations (8)