MOLD BOX WITH MEANS TO SUPPORT HEATER WIRES FOR MAKING CERAMIC DIES

Abstract: A Mold Box (2) for molding a ceramic die having spaced heating wires embedded therein. Removable rod supports (18) support rods (16) which extend into close relationship to the mold surface in the mold box (2). Rods (16) support heater rods (6) in space relation to the mold surface. Removable tapered plugs (12) hold heater wires (6) in the end walls (8, 10) of mold box (2). Rods (16) are withdrawn after heating wires (6) have been covered with ceramic material. Additional ceramic material is added to give the desired die thickness.

Description: MOLD BOX WITH MEANS TO SUPPORT HEATER WIRES FOR MAKING CERAMIC DIES Method and Apparatus for Supporting Die Heater Wires Technical Field A method and apparatus for supporting the die heater wires in position while embedding them in ceram¬ ic to form the body of the die. The die is used in hot forming sheet metal parts. Background Art To assure " uniform heating of the forming surfaces of cooperating dies it is essential that the heating wires usually nichrome be uniformly spaced apart and uniformly spaced from the operative guide surfaces. This becomes a major problem when the die surfaces are irregular as needed in forming irregularly curved work- piece con igurations. The wires must be securely fixed while the ceramic is being positioned in the mold in which the die is formed but the wires mtist be readily releasable from the supporting structure in order to remove this structure from the ceramic of the die. The wires must be securely held in position since the posi¬ tioning of the ceramic in the mold generally includes a vibration of the mold. Disclosure of the Invention A feature of this invention is an arrangement of a number of supporting rods for each of the heating wires with the wires releasably held on the ends of the rods during the positioning of the ceramic in the mold. Another feature is the use of a releasable device for the wires that will not affect the mold in any detrimental way. Another feature is the arrangement for removing the supporting rods when the ceramic has been placed in the mold and is hard enough to hold the wires -in position. According to the invention the device includes a plurality of rod supports removably attached to the mold with each support carrying a plurality of wire sup¬ port rods extending into the mold cavity with the ends of the rods uniformly spaced from the surface of the mold on which the ceramic is to be formed. Each rod has a slot in the end to receive a heater wire and a flexible element such as string extends around the heater wire and is brought up on the opposite, sides of the rod to secure at the outer end of the rod to hold the heater wire in place. The rods are generally uni¬ formly spaced in the rod support so as to hold the heater wires in uniformly spaced relation to each other. Upon release of the retention devices the rod can be withdrawn from the ceramic leaving the heater wires e - bedded therein.in the desired position. The heater wires are individually held in the end walls of the mold by releasable tapered plugs. The foregoing and other objects, features and ad¬ vantages of the present invention will become more ap- parent in the light of the following detailed descrip- . tion of preferred embodiments thereof as shown in the accompanying drawing. Brief Description Of The Drawing Fig. 1 is a perspective view of the mold box with parts broken away. Fig. 2 is a sectional view along line 2-2 of Fig. 1. Fig. 3 is a sectional view at right angle to Fig. CI-ΪPI ,. w VV jirl o' 2 on the line 3-3 of Fig . 2 . Fig. 4 is a detail of the heater wire end of the support rod. Fig. 5 is a detail of the other end of the support rod. Fig. 6 is a detail of the plug for the ends of the heater wire. Best Mode For Carrying. Out The Invention The ceramic die is formed in a mold box 2 having in the bottom thereof a surface 4, Fig. 2 , contoured to the shape of the die to be formed. It will be under¬ stood that two mating dies are made between which the sheet metal is positioned and heated to conform to the contour of the mating dies. The heater wires 6 extend- ing in parallel relation to one another and in uniform¬ ly spaced relation to the surface 4 are held in the end walls 8 and 10 of the mold box by tapered plugs 12. The heater wires are generally nichrome wire and are enclosed in a tube 14 the latter being generally plastic and this plastic is burned out during curing of the ceramic. The heater wires in the tubes are held in position while the ceramic is placed in the mold by rows of rods 16, each row extending down from a rod support 18 in the form of a bar removably held as by screws 20 at op¬ posite ends engaging the side walls of the mold. These supports extend at right angles to the heater wires and thus the several rods in each support rod are uniformly spaced so that one rod engages each wire to hold the wires in the desired spaced relation. With the plural¬ ity of spaced rod supports each heater wire is support¬ ed at spaced points along its length so that it is se¬ curely held in position although the individual wires are bent to conform to the contour of the mold surface. Obviously the number of rod supports may vary depending upon the irregularity of the mold surface and the stiffness of the heater wire. As will be apparent the bottom ends of all the rods are uniformly spaced from the mold surface. Each rod has a notch 22 at the bottom to receive the heater wire and is held therein by a string 24 hav¬ ing a loop 26 to engage a wire the string then extend- ing upward along opposite sides of the rod to be held at the top end of each rod as by a fastener 28. This fastener may be a plug 30 engaging the string and clamping it in a recess 32 in the end of the rod.. The ceramic material of the die is placed in the mold and surrounds the heater wires and the ends of the rods. The mold is generally vibrated to assure that the ceramic material fills the mold completely and fully encloses the wires. Obviously the ceramic must form an unbroken surface where it engages the mold surface in order to assure a suitable forming surface when the dies are in use. After the ceramic is in position and has hardened enough to hold the heater wires in place the strings on all the rods are released at the upper ends of the rods and the rods may then be withdrawn from the ceramic leaving the wires in position. The mold is then filled further to the desired die thick¬ ness with some of this mold material filling the rod holes. The strings may remain in the ceramic as they present no stress areas and will burn out while curing the ceramic. In removing the mole box from the ceramic die the tapered plugs are released from the end walls of the box so that the ends of the heater wires are free to be withdrawn from these end walls. To make the device above described adaptable to more general use the in¬ dividual rods may be held in the rod support by set screws 34 in the supports. This will then permit adjustment of any of the rods individually in adapting the mold to the production of the die having a dif¬ ferent die forming surface. Although the rods are described as rods it may be understood that for pur¬ pose of weight reduction the rods may be tubes and the tubes will function in the same manner as would the solid rods. In the above description the heater wire has been described just as a heater wire but it is normally provided as above stated with a plastic covering. It will be understood that when the mold is cured the plastic tube that surrounds the wire will burn out leaving the heater wire a loose fit within the space provided by the tube. Although the invention has been shown and described with respect to the preferred embodiment thereof,, it should be understood by those skilled in the art that various changes and omissions in the form and detail thereof may be made therein without departing from the spirit and scope of the invention. OMPI Λ, W IiF-rO

Claims: * ¥»Q *Λ Claims 1. A mold box* for making a ceramic die said box hav¬ ing: .a bottom mold surface to form the operative sur- face of the die; side walls and end walls on said box; support bars releasably secured to said side walls at points above the mold surface; a plurality of parallel rods carried by said bars and extending downwardly into spaced relation to said mold surface, said bars being notched at their lower ends; heater wires extending across said mold surface in spaced relation thereto said wires engaging in the notches in the rods; and means for holding the wires releasably. in the notches in the rods. 2. A mold box as in claim 1 in which each heater wire has a surrounding plastic tube. 3. A mold box as in claim 1 in which said wire hold¬ ing means -are releasable at the upper ends of the rods.. 4. A mold box as in claim 1 in which each said wire holding means is a loop of string engaging the wire and extending upwardly along the rod to be secured at the top thereof. 5. A mold box as in claim 1 in which the support bars are on the side walls and the heater wires extend be¬ tween the end walls being positioned at right angles to the support rods. 6. A mold box as in claim 5 in which one rod on each support is provided for e ' ngagement with each individual heater wire. 7. A mold box as in claim 1 in which the rods are ad¬ justable in the support bars. 0 _ - _ . -siy

Inventors: DILLNER JAMES R, STONE JR HILTON F, DILLNER, JAMES, R., STONE, JR., HILTON, F.
Applicants: UNITED TECHNOLOGIES CORP, UNITED TECHNOLOGIES CORPORATION
Application year: 1981
Main classification: B29C1
IPC codes: B21D37, B23P15, B28B7, B28B23