Abstract:
A method for producing a sand core includes the following steps: (a) providing a casting mold having a mold cavity, the casting mold including at least one first conduit and at least one second conduit; (b) providing a sand core disposed in the mold cavity; (c) providing a supply of conditioning gas to the casting mold, the conditioning gas being supplied to the casting mold through at least one of the first and second conduits; (d) providing a controller connected to the first conduit and the second conduit to selectively control the supply of conditioning gas; (e) providing a gas exhaust unit operatively connected to the casting mold; (f) operating the gas exhaust unit to cause the conditioning gas to be moved through the sand core; and (g) removing the sand core from the casting mold.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates in general to sand cores and in particular to an improved method for producing such a sand core. 
     A sand core is well known in the foundry art for forming and shaping internal cavities and openings in finished castings. The internal cavities and openings offer the advantage of allowing for a lower weight and more reliable finished casting. Oftentimes, these cavities and openings cannot be made using permanent, reusable molds and the like. Another way to produce these openings is to mold the casting around a one-time-only core which complements the configuration of the intended cavities and openings. After making the casting, the core can be destroyed or disintegrated, thereby leaving the cavities and openings in the casting available for their intended purpose. 
     The above one-time-only cores are commonly used in the foundry and casting industries. Manufacturers that desire a lower weight, strong finished casting typically employ sand cores in their production methods. For example, the automotive industry employs sand cores to make lower weight, fuel efficient automobile cast component parts. 
     Suitable materials are needed to produce the cores. The cores are typically made of materials which allow the cores to be formed into complex shapes or configurations so as to complement the cavities and openings to be created in the finished molded product. The materials must also be stable or strong enough to withstand the molding process for the application they are intended, yet weak enough so as to be easily disintegrated and removed upon completion of the molding process. 
     Foundry cores made of sand are produced from a variety of known methods, some of which include hot box, warm box, shell, oil sand, cement, and cold box methods. Foundry sand binders that are used for making the cores can be classified in one of two main chemical classes: organic and inorganic. Organic sand cores can employ compounds that are environmentally unfriendly. With an increased amount of concern being given to preserving the environment, the relatively environmentally friendly inorganic cores, such as those which are sand-based, grow in popularity. 
     A conventional inorganic sand core is formed by adding a binder to the sand to form a binder/sand mix before placing the binder/sand mix into a mold. In the mold, the binder/sand mix is shaped into a sand core having a desired shape. U.S. Pat. No. 5,711,792 to Miller discloses a foundry binder which can be used in producing inorganic sand cores. A discussed in the Miller patent, the flowability of the binder/sand mix or the ability of the binder/sand mix to properly fill the mold is an important characteristic for a properly shaped and stable sand core. The flowability of the binder/sand mix is also important to fill the molds efficiently, which promotes an acceptable production rate. 
     While the use of the binder provides the benefit of additional strength, it can reduce the user&#39;s ability to handle the sand and to form intricate and complex shaped cores. Also, the temperature and humidity conditions at which the core is produced and stored can cause the core to soften and possibly lose its shape over time. Thus, it would thus be desirable to be able to produce a non-organic sand core which is durable, can be of an intricate and complex shape, yet is economical and relatively easy to produce. 
     SUMMARY OF THE INVENTION 
     This invention relates to a method for producing a core and includes the steps of: (a) providing a casting mold having a mold cavity, the casting mold including at least one first conduit and at least one second conduit; (b) providing a sand core disposed in the mold cavity; (c) providing a supply of conditioning gas to the casting mold, the conditioning gas being supplied to the casting mold through at least one of the first and second conduits; (d) providing a gas exhaust unit operatively connected to the casting mold; (e) operating the gas exhaust unit to cause the conditioning gas to be moved through the sand core; and (f) removing the sand core from the casting mold. 
     Other 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 DRAWING 
     FIG. 1 is a schematic diagram of a core producing system for producing an inorganic sand core in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, there is illustrated a schematic diagram of a core producing system, indicated generally at  5 , for producing an inorganic sand core in accordance with the present invention. As shown therein, the core producing system  5  includes a conditioning gas dryer  20  which supplies a source of dried conditioning gas to a heater  30 . The heater  30  heats the dried conditioning gas and supplies the heated conditioning gas to a casting mold  74 . The core producing system  5  further includes a vacuum unit  120  which is operative to assist in processing the conditioning gas used in the core producing system  5  as described below in detail. 
     In the illustrated core producing system  5 , a compressor  10  delivers a supply of a conditioning gas through a conduit  15  to the conditioning gas dryer  20  through a control valve  17 , as indicated by the arrow  18 . The conditioning gas may be atmospheric air or any other suitable gas or fluid. The conditioning gas supplied by the compressor  10  to the conditioning gas dryer  20  is at a predetermined pressure, preferably at a pressure of about 100 p.s.i. The illustrated conditioning gas dryer  20  includes two desiccant tanks  22 , though any suitable number of desiccant tanks  22  may be used. When two desiccant tanks  22  are employed, one desiccant tank  22  can be employed during operation of the core producing system  5  while the other desiccant tank  22  can be serviced or regenerated, thus minimizing the down-time of the core producing system  5  due to maintenance of the desiccant tanks  22 . A valve  23  is employed to selectively control the flow of the conditioning gas from the desiccant tanks  22  to the atmosphere via an exhaust line  24  or to the heater  30  via a conduit  25 . 
     The conditioning gas dryer  20  of the invention preferably dries or dehumidifies the conditioning gas to a desired dew point of within the range of from about minus 10 degrees Fahrenheit (−10° F.) to about minus 40 degrees Fahrenheit (−40° F.). It should be understood that the conditioning gas may be dried to a different degree and any suitable type of conditioning gas dryer  20  may be used to accomplish this. A suitable conditioning gas dryer  20  that can be used is a MBCI Model h-600 heatless desiccant dryer with NEMA 4 controls and a blue moisture indicator, manufactured by Daniel L. Bowers Co., Inc. of Rochester Hills, Mich. 
     The dried conditioning gas from the conditioning gas dryer  20  is then heated in accordance with this invention to a temperature of within the range of from about 200 degrees Fahrenheit (200° F.) to about 400 degrees Fahrenheit (400° F.). To accomplish this, the core producing system  5  includes the conduit  25  which is operative to supply the dried conditioning gas from the conditioning gas dryer  20  to the heater  30 . Preferably, in the illustrated embodiment, the core producing system  5  includes an air control valve  16  in the path of the conduit which is operative to selectively control the supply of the dried conditioning gas from the conditioning gas dryer  20  to the heater  30 . 
     The illustrated heater  30  includes a heat exchanger  27 , a combustion chamber  50 , and a burner  55 . The heater  30  is preferably a natural gas fired heater; however any suitable heater  30  can be used, including an electrical air heater. 
     The heat exchanger  27  includes one or more heat exchanger tubes (not shown) which are operative to heat the dried conditioning gas supplied to the heater  30  from the conditioning gas dryer  20 . A suitable heat exchanger  27  is available from Thermal Transfer Corporation of Monroeville, Pa. 
     The heat exchanger  27  receives a supply of heated fluid from the combustion chamber  50  through a suitable conduit  40  into the heat exchanger tubes. The dried conditioning gas enters the heat exchanger  27  from the conditioning gas dryer  20 . The dried conditioning gas does not commingle with the heated fluid in the heat exchanger tubes. The dried conditioning gas is heated by the heated fluid in the heat exchanger tubes in the heat exchanger  27 . The supply of the dried conditioning gas passing through the heat exchanger  27  and exiting therefrom is delivered to a supply line or conduit  61 , as indicated by the arrow  43 . 
     It should be understood that any suitable type of combustion chamber  50  can be used. A suitable combustion chamber  50  is a Model 600M-DL2 manufactured by Pyronics, Inc. of Cleveland, Ohio. The combustion chamber  50  preferably includes an insulated jacket (not shown) and a flanged flue gas outlet  31 . In the preferred embodiment, a 1/16 DIN digital temperature control, and a 1/16 DIN high temperature limit control, manufactured by Clos-Vendal, also known as C.V.A. Inc. of Dearborn Heights, Mich. are provided for controlling the combustion in the combustion chamber  50 . In the illustrated embodiment, a blower  35  is provided and used to supply the fluid to be heated in the combustion chamber  50 , which is then supplied to the heat exchanger  27 . The combustion chamber  50  further includes a thermocouple (not shown) to control the heating of the combustion chamber  50  by the burner  55 . 
     The burner  55  supplies heat by a flame to the combustion chamber  50 . It should be understood that any suitable type of burner  55  may be used. A suitable burner  55  which can be used is a spark igniter model TA100, fired excess air, manufactured by Pyronics, Inc. of Cleveland, Ohio. It should be understood that the combustion chamber  50  and burner  55  can be other than illustrated. Also, a plurality of combustion chambers  50  and burners  55  can also be used. 
     A suitable gas supply train  60  can be employed to deliver a supply of natural gas  41  to the burner  55 . In the illustrated embodiment, the gas supply train  60  includes a control valve  42  to facilitate the flow of gas through the gas supply train  60  in the direction of arrow  51 . The preferred controls for the heater  30  include a flame monitor (not shown), the gas supply train  60 , and a temperature control (not shown). A suitable flame monitor is a model RM7890A. manufactured by Honeywell, Inc. of Minneapolis, Minn. Conventional interlocks, shutoff valves, regulators, and proportional control valves are preferably included with the gas supply train  60 . Alternatively, other suitable flame monitors, gas valve trains  60 , temperature controls and thermocouples can be used if desired. 
     The supply line  61  is divided so as to be operative to supply the heated conditioning gas from the heater  30  to a first gas circuit, indicated generally at  62 , and a second gas circuit, indicated generally at  63 . The first gas circuit  62  and the second gas circuit  63  are configured such that the heated conditioning gas from the heater  30  preferably flows through the first gas circuit  62  and the second gas circuit  63 . It should be understood that the heated conditioning gas from the supply line  61  as discussed herein is preferably dried and heated conditioning gas when delivered to the casting mold  74 . 
     The illustrated first gas circuit  62  includes a first control valve  64  to regulate the flow of the conditioning gas through a first common conduit  65  and a second control valve  66  to regulate the flow of the conditioning gas through a second common conduit  67 . The first control valve  64  and the second control valve  66  preferably include an opened position and a closed position. The first control valve  64  and the second control valve  66  may be infinitely variable between the opened position and the closed position. As will be discussed below, the first control valve  64  and the second control valve  66  cooperate when in their opened positions to allow the conditioning gas to flow through the core producing system  5  into the casting mold  74 . 
     The illustrated first gas circuit  62  includes a first manifold  70  on a first side or end  72  of the casting mold  74  and a second manifold  71  on a second opposite side or end  73  of the casting mold  74 . The flow of the conditioning gas through the first gas circuit  62  is from the first side  72  of the casting mold  74  to the second side  73 . The illustrated first gas circuit  62  also includes a conduit  91  which allows for fluid communication between the second valve  66  and the vacuum unit  120 . 
     The illustrated second gas circuit  63  includes a third control valve  68  to regulate the flow of the conditioning gas through the second common conduit  67  and a fourth control valve  69  to regulate the flow of the conditioning gas through the first common conduit  65 . The third control valve  68  and the fourth control valve  69  include an opened position and a closed position. The third control valve  68  and the fourth control valve  69  may be infinitely variable between the opened position and the closed position. As will be discussed below, the third control valve  68  and the fourth control valve  69  cooperate when in their opened positions to allow the conditioning gas to flow through the core producing system  5  illustrated into the casting mold  74 . The flow of the conditioning gas through the second gas circuit  63  illustrated is from the second side  73  of the casting mold  74  to the first side  72 . The illustrated second gas circuit  63  also includes a conduit  92  which allows for fluid communication between the fourth control valve  69  and the vacuum unit  120 . 
     The flow of the conditioning gas through the first gas circuit  62  occurs when the first control valve  64  and the second control valve  66  are substantially in their opened positions, and the third control valve  68  and the fourth control valve  69  are substantially in their closed positions. The flow of the conditioning gas through the second gas circuit  63  occurs when the third control valve  68  and the fourth control valve  69  are substantially in their opened positions, and the first control valve  64  and the second control valve  66  are substantially in their closed positions. 
     The core producing system  5  preferably includes a controller  132  which is operative to control the operation of the first control valve  64 , the second control valve  66 , the third control valve  68 , and the fourth control valve  69 . The controller  132  regulates the flow of the conditioning gas from the supply line  61  to the first gas circuit  62  and the second gas circuit  63 . The controller  132  may be any suitable type of controller, mechanical or electrical controller and/or automatic or manual. 
     The illustrated casting mold  74  is a core box. The casting mold  74  includes a first mold half or cope  75  which is operatively joined to a second mold half or drag  80  along a parting line  85  and which defines a mold cavity  90 . A core  95  is disposed in the mold cavity  90 . The core  95  is preferably a foundry core made of sand. It should be understood that the term “sand” as used herein includes binders or other chemicals mixed with or applied to the sand. It should be understood that the core  95  is approximately the same shape and contour as that of the mold cavity  90 . 
     In the illustrated embodiment, the casting mold  74  includes a first wall  100  having a plurality of first feed gates  105  formed therein which establish fluid communication between the mold cavity  90  and the first wall  100  of the casting mold  74 . For the sake of clarity, only three of such first feed gates  105  are shown; however, any suitable number of the first feed gates  105  may be employed. The casting mold  74  further includes a second wall  110  having a plurality of second feed gates  115  formed therein which establish fluid communication between the mold cavity  90  and the second wall  110  of the casting mold  74 . For the sake of clarity, only nine of such second feed gates  115  are shown; however, any suitable number of the second feed gates  115  may be employed. The first feed gates  105  and the second feed gates  115  are preferably generally round and may have any suitable diameter, but need not have the same diameter. 
     The casting mold  74  is constructed from conventional foundry mold materials and according to conventional practices known in the art. Metal dies may also be used. As conditioning gas flows through the casting mold  74 , the conditioning gas flows through the associated core  95  disposed therewithin. The vacuum unit  120  is preferably provided to facilitate the removal of the gas from the core  95 . The vacuum unit  120  receives conditioning gas from the first gas circuit  62  and the second gas circuit  63 . The illustrated vacuum unit  120  is a turbine unit vacuum and includes a turbine  124  with a motor  128 . An exhaust  130  is provided to facilitate the removal of the moisture from the core producing system  5 . Alternatively, the vacuum unit  120  can be replaced with other suitable exhaust means for exhausting the gas from the casting mold  74  if so desired. 
     It should be understood that the compressor  10  and the vacuum unit  120  are each a means for moving the dried heated conditioning gas through the core  95 . Alternatively, other means for moving the dried heated conditioning gas through the core  95  may be employed. 
     Without wishing to be bound by theory, it is believed that the casting mold  74  and the core  95  contain excess moisture before the application of the conditioning gas. Thus, in accordance with the present invention, a more desirable core  95  is produced by optimally reducing moisture in the core  95  according to the method described above. 
     The present invention can be practiced in a number of environments, including but not limited to warm/hot box, warm box/warm air, and no bake environments. To practice the invention in the warm/hot box environment, the box temperature is preferably employed at a temperature range of from about 300 degrees Fahrenheit to about 450 degrees Fahrenheit. To practice the invention in the warm box/warm air environment, the box temperature is preferably employed at a temperature range of from about 180 degrees Fahrenheit to about 400 degrees Fahrenheit and the temperature of the conditioning gas, including the purged conditioning gas, is preferably at a temperature range of from about 200 degrees Fahrenheit to about 350 degrees Fahrenheit. To practice the invention in the no bake environment, typical organic ester catalysts are employed. While the description above is directed to the production of inorganic cores, the invention may be used in conjunction with the production of organic cores where suitable. 
     The conditioning gas to be used to treat the shaped sand core  95  is preferably conditioned in the core producing system  5  in one or more ways before it is applied to the shaped sand core  95 . The conditioning gas is preferably compressed, dried, and heated as discussed below. It should be understood that not all three ways of treating the conditioning gas need be employed. Likewise, the ways of treating the conditioning gas need not be employed in the way or order discussed herein. 
     In accordance with the provisions of the patents statues, the principle and mode of operation of this invention have been described and illustrated in its preferred embodiments. However, it must be understood that the invention may be practiced otherwise than as specifically explained and illustrated without departing from the scope or spirit of the attached claims.