Abstract:
A mold has mold walls defining a cavity and a plurality of heated fluid inlets communicating with the cavity. An enclosed frame for storing a heated fluid is positioned about the mold. Valves are positioned completely within the enclosed frame and each of the valves is coupled to one of the heated fluid mold inlets.

Description:
FIELD OF THE INVENTION 
     This invention relates to a method of forming patterns, and will have special but not limited application to a method of molding smooth patterns from expandable plastics. 
     BACKGROUND OF THE INVENTION 
     Current procedures for casting metal articles involve the creation of master patterns which are used to form impressions in a sand mold prior to pouring in the molten metal. Cores (often formed of sand) are inserted into the sand to form the internal holes into the cast product. These procedures require that a binder intermixed with the sand in the mold to allow the sand to retain its shape during casting operations. The currently available binders are formed from chemicals which are toxic and extreme care must be experienced in disposal operations. Also, new cores must be formed for each use of the mold, a time consuming and expensive procedure. 
     SUMMARY OF THE INVENTION 
     This invention involves a process for producing master patterns out of an expandable plastic material. These patterns may be placed in a sand mold which is free of any binders or cores. As the molten metal is poured into the mold, its heat vaporizes the pattern and allows the molten metal to occupy the space in the mold previously taken up by the pattern. When the metal has solidified and cooled, the casting is removed and another pattern is placed in the sand mold as before. No cores are required since the mold sand prohibits intrusion of molten metal into intended casting openings and no binding is required to hold the sand in place. 
     The process involves blowing a quantity of expandable particles into a heated mold. Live steam is injected through pinholes in the mold, and is controlled by a series of valves, to insure proper fusion of the expanded particles. Due to the absence of vent holes in the mold, a smooth, accurate pattern may be formed. 
     Accordingly, it is an object of this invention to provide for a novel method of forming patterns from expandable plastics. 
     Another object of this invention is to provide for a method of forming molded patterns which are smooth and accurate in dimensions and shape. 
     Another object of this invention is to provide for a method of forming molded patterns which is efficient and economical. 
     Other objects of this invention will become apparent upon a reading of the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Two preferred embodiments of an apparatus for performing the method have been depicted as illustrative of the process wherein: 
     FIG. 1 is a sectional view of one embodiment of an apparatus used to produce patterns according to a method of this invention. 
     FIG. 2 is a sectional view of a modified apparatus used to produce the patterns. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred machines herein disclosed are intended to assist in illustrating the principles of the claimed method. They are not to be considered exhaustive or to limit the method to the precise forms disclosed. The preferred method is described to explain the principles thereof, so as to allow others skilled in the art to practice the method. 
     The preferred method of this invention may be best understood by the following description of the apparatus generally designated by the numeral 10 in FIG. 1 or the modified apparatus 10&#39; in FIG. 2. With regard to FIG. 1, apparatus 10 includes two steam chests 12 and 14. Steam chest 12 includes an outer frame plate 16 and an inner frame 18 which may be shaped as shown in FIG. 1 to form a closed steam reservoir 20. The surfaces 22, 24 and 26 of steam chest 12 are formed so as to accurately resemble the exterior shape of the article to be molded. Steam chest 12 also includes a steam inlet 28 and a steam outlet 30. The innermost inner frame part 32 has a plurality of small pin holes 34 (approximately 0.01-0.001 inches in diameter) formed therein which extends from surface 25 to surface 26 completely through the frame part. A valve network 36 is positioned within steam chest reservoir 20 and includes individual valves 37, 38, 39 communicating with each pin hole 34. Valves 37-39 are interconnected by conduit 40 which also connects the valves to a central control member 42 positioned along outer wall 15 of steam chest 12. Each valve 37-39 is threadably secured to frame part 32 and has a bore 45 which communicates with reservoir 20. Steam chest 14 includes an outer frame plate 44 and an inner frame 46 which form an enclosed steam reservoir 48 as is shown in FIG. 1. The surfaces 50, 52, and 54 are formed so as to accurately resemble the interior of the article to be molded. Steam chest 14 also includes steam inlet port 56 and outlet port 58. As is shown in FIG. 1 with surfaces 60 and 62 of steam chest 14 abutting surfaces 64 and 67 of steam chest 12 a mold cavity is formed between surfaces 26 and 50 of steam chests 12 and 14. 
     Steam chest 14 is then brought in contact with the steam chest 12 until surfaces 60 and 62 of steam chest 14 abut surfaces 64 and 67 of chest 12. In use, a quantity of expandable polystyrene beads 66 is delivered by injection or other conventional process within the cavity formed by surfaces 22, 24, and 26 of steam chest 12. Steam chests 12 and 14 are then purged with a quantity of steam until surfaces 50 and 26 obtain a predetermined temperature at which time outlets 30 and 58 are closed to retain steam within reservoirs 48 and 20. To expand beads 66 into a homogenized mass a quantity of steam is admitted into the mold cavity by supplying air pressure through control valve 42 at approximately 80 PSI to conduit 40. Valves 37-39 are normally closed and open upon being pressurized and thereby allow steam to pass from steam reservoir 20 through bore 45 and pin holes 34 to the mold cavity. Steam entering the mold cavity causes polystyrene beads 66 to expand and form a homogenized mass which conforms to the inner mold surfaces 50 and 26. Upon a sufficient amount of steam entering the mold chamber, pressure is removed from control valve 42 which causes valves 37 through 39 to close. After sufficient expansion of the polystyrene beads, outlets 58 and 30 are reopened to allow steam trapped within reservoirs 20 and 48 to escape thereby allowing steam chests 12 and 14 to cool. Upon sufficient cooling, steam chests 12 and 14 may be separated and the homogenized mass of polystyrene may be removed from the mold halves. 
     It is to be understood that while the figures show steam valves 37-39 as being positioned on the lower steam chest 12 it is obvious to one skilled in the art that they may be placed in both steam chests if the mold so requires. 
     FIG. 2 illustrates a modified valve sysem 36&#39; which includes entry tubes 70, 72 and 74 communicating through pin holes 34 with the mold cavity. Entry tubes 70, 72 and 74 also communicate with a steam manifold 76 which communicates with an air operated pinch valve 78. Pinch valve 78 communicates with an air control unit 42&#39; as shown in FIG. 2 through conduit 80. All other parts of apparatus 10&#39; are identical with those of apparatus 10. 
     In operation, when it is desired to deliver steam to the mold cavity, the flow of air through control unit 42&#39; is stopped, allowing pinch valve 78 to open and admit steam from chest 12 into manifold 76 and to the mold cavity through entry tubes 70, 72 and 74. When desired, control unit 42&#39; is actuated and delivers air (80 PSI) to pinch valve 78 to close the valve and cut off steam flow to the mold cavity. All other operations are identical to those discussed above. 
     It is also to be understood that the invention is not limited to the scope of the above given details, but may be modified within the scope of the appended claims.