A dewaxing device includes a dewaxing system which includes a rinsing device and a storage device connected with the rinsing device via a circulation pipe, and a recycling system which includes a containing trough connected with the storage device and a recycling trough connected between the containing trough and the storage device. The recycling system further includes a rotating device, a condensing unit and a heating unit which cooperate to treat mixed solution with wax into pure chemical solvent in the containing trough. The rotating device is rotatably mounted above the containing trough with the bottom half thereof being dived into the mixed solution. The condensing unit and the heating unit are disposed at two opposite sides of the top half of the rotating device. The rotating device is rotated towards the condensing unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a dewaxing device, and more particularly to a chemical dewaxing device used in dewaxing process of the metal injection molding.

2. The Related Art

Metal injection molding is a metalworking process where finely-powdered metal is mixed with a measured amount of binder and wetting agent to comprise a feedstock capable of being handled by plastic processing equipment through a process known as injection mold forming. Subsequent conditioning operations are performed on the molded shape, where the wetting agent and the binder are removed from a green part of product and metal particles are coalesced into the desired state for the metal alloy. In detail, the wetting agent is removed by chemical solvent or sintering furnace to form pores in dewaxing process of the metal injection molding, and the binder is thermal-cracked into binder gas to go out through the pores in sintering process of the metal injection molding.

In order to effectively achieve the dewaxing process, it is a common way that the wetting agent is removed by the chemical solvent. In detail, the wetting agent can be removed by repeatedly rinsing the green part of product with the chemical solvent or keeping soaking the green part of product in the chemical solvent so as to dissolve the wetting agent out of the green part of product, wherein the chemical solvent can be n-hexane, n-butane, bromopropane, cleaning naphtha and so on. Because of increased awareness of environmental protection, the chemical solvent has gradually tended to use the bromopropane solvent which has recyclable characteristics.

In the dewaxing process, when the bromopropane solvent reaches saturation state, a recycling process is done. In detail, in the recycling process, the saturated solution needs to be heated to boiling to separate into bromopropane steam and high concentration of non-volatile liquid waste wax. Then utilize a condensing unit to condense the bromopropane steam into liquid so as to obtain pure bromopropane solvent again. The high concentration of non-volatile liquid waste wax is removed out. However, in the recycling process, the saturated solution needs to be heated to boiling and then be cooled so that will have a strong impact on use life of the bromopropane solvent. So, a dewaxing device having an improved recycling system for doing the recycling process is required.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a dewaxing device of utilizing chemical solvent to dewax a green part of product formed by metal injection molding. The dewaxing device includes a dewaxing system for dewaxing the green part of product and a recycling system. The dewaxing system includes a rinsing device where the green part of product is placed and a storage device where the chemical solvent is stored. The storage device is connected with the rinsing device via a circulation pipe for utilizing the chemical solvent to soak and rinse the green part of product. The recycling system includes a containing trough which is connected with the storage device for containing mixed solution with wax from the storage device, and a recycling trough which is connected between the containing trough and the storage device for containing and conveying pure chemical solvent from the containing trough back into the storage device to be reused. The recycling system further includes a rotating device, a condensing unit and a heating unit which cooperate to treat the mixed solution with wax into the pure chemical solvent in the containing trough. The rotating device is rotatably mounted above the containing trough with the bottom half thereof being dived into the mixed solution. The condensing unit and the heating unit are disposed at two opposite sides of the top half of the rotating device. The rotating device is rotated towards the condensing unit.

As described above, according to the technical principle that the soluble wax quantity of the chemical solvent does change with temperature, the dewaxing device in this invention utilizes the cooperation design of the rotating device and the condensing and the heating units to effectively remove the wax in the mixed solution and obtain pure chemical solvent in the recycling process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference toFIG. 1andFIG. 2, a dewaxing device according to an embodiment of the present invention is used in dewaxing process of metal injection molding for removing wax of a green part of product by virtue of utilizing chemical solvent to soak and repeatedly rinse the green part of product. In this embodiment, the chemical solvent is bromopropane solvent. The dewaxing device includes a dewaxing system10and a recycling system20.

The dewaxing system10is used to dewax the green part of product. In detail, the dewaxing system10includes a rinsing device11where the green part of product is placed for being soaked and rinsed with the bromopropane solvent, and a storage device12where the bromopropane solvent is stored. The storage device12is connected with the rinsing device11via a circulation pipe so that the bromopropane solvent can circulation flow through the rinsing device11to repeatedly rinse the green part of product so as to dissolve the wax out of the green part of product as thorough as possible. The storage device12is equipped with a heating equipment13which is used to heat the bromopropane solvent so as to improve dewaxing efficiency. A condensing equipment14is connected between the rinsing device11and the storage device12via another pipe. Because bromopropane is highly volatile, the condensing equipment14is used to condense volatilized bromopropane steam in the dewaxing process into liquid bromopropane solvent and further make the condensed bromopropane solvent flow back into the storage device12.

The recycling system20is connected with the storage device12of the dewaxing system10for treating mixed solution with wax into pure chemical solvent. In detail, the recycling system20includes a containing trough21connected with the storage device12via a pipe, and a recycling trough22connected between the containing trough21and the storage device12via another pipe. The containing trough21is used to contain mixed bromopropane solution with wax from the storage device12. The recycling trough22is used to contain pure bromopropane solvent from the containing trough21and further convey the pure bromopropane solvent back into the storage device12to be reused.

The recycling system20further includes a rotating device23, a condensing unit24and a heating unit25which cooperate to treat the mixed bromopropane solution into the pure bromopropane solvent in the containing trough21. In detail, the rotating device23is rotatably mounted above the containing trough21. The condensing unit24and the heating unit25are disposed at two opposite sides of the rotating device23. The rotating device23rotates towards the condensing unit24. The rotating device23includes a shaft231and a plurality of blades232radially extending outward around outer periphery of the shaft231and arranged at regular intervals on generatrices of the shaft231. The condensing unit24and the heating unit25are mounted at two sides of the top half of the rotating device23at the shaft231boundaries. Free ends of the blades232could be further provided with columnar or block metal slices233for increasing contact area of the blades232with the mixed solution contained in the containing trough21. The shaft231is hollow for gathering liquid waste wax removed out from the mixed solution.

In use, the dewaxing system10is firstly used to dewax the green part of product. When the bromopropane solvent in the storage device12is monitored to reach saturation state, the saturated solution with wax is conveyed into the containing trough21. The bottom half of the rotating device23at the shaft231boundaries is dived into the saturated solution with wax. Then, the rotating device23is driven to rotate towards the condensing unit24so as to utilize the condensing unit24to rapidly cool the blades232close to the condensing unit24. With the rotation of the rotating device23, the cooled blades232are further rotated into the saturated solution to cool the saturated solution contacting with the cooled blades232. As a result, the solubility of the cooled saturated solution is decreased to precipitate wax out of the cooled saturated solution, and the precipitated wax is adhered on the blades232and the metal slices233. Last, the blades232and the metal slices233together with the precipitated wax are rotated out of the mixed solution to close the heating unit25and be rapidly heated by the heating unit25so as to melt the precipitated wax into liquid. Then with the upward rotation of the rotating device23, the liquid wax flows into the shaft231along the blades232by virtue of its own gravity. So the wax dissolved in the mixed solution can be gradually removed and gathered by the foregoing recycling process to make the saturated solution with wax become pure bromopropane solvent. Then the pure bromopropane solvent flows into the recycling trough22and further is conveyed back into the storage device12to be reused.

The technical principle used in the recycling process of the dewaxing device in this invention is that the soluble wax quantity of the bromopropane solvent does change with temperature. As shown inFIG. 3, the soluble wax quantity of the bromopropane solvent can reach a maximum value of 16% at 45 degrees Celsius, but once back to the room temperature, the soluble wax quantity of the bromopropane solvent will plummet to about 3%; when the temperature of the bromopropane solvent is 0 degrees Celsius, the soluble wax quantity has fallen to 0.1%; if the temperature of the bromopropane solvent continues to be cooled to −30 degrees Celsius, the soluble wax quantity is about 0.01% and the bromopropane solvent is almost pure.

As described above, according to the technical principle that the soluble wax quantity of the bromopropane solvent does change with temperature, the dewaxing device in this invention utilizes the cooperation design of the rotating device23and the condensing and the heating units24,25to effectively remove the wax in the saturated solution and obtain pure bromopropane solvent in the recycling process.