Method and apparatus for forming compact bodies from conductive and non-conductive powders

The method of forming a compact body of powdered material comprising the steps of at least partially filling the die cavity with powdered material retained in a protective inert atmosphere, locating the die cavity including the powdered material, within a vacuum chamber, forming a vacuum in said chamber to remove essentially all free gases from within said powdered material, slowly heating the die cavity and powdered material to less than the melting temperature of the powdered material, to a sintering temperature, and alternately increasing and decreasing the pressure in the die cavity to create a pulsating pressure application to said powdered material, while maintaining said vacuum and said sintering temperature, thereby to form said compact body.

The method of forming a multiple component compact body including the steps of;

• providing a die cavity including a tubular body with opposed plungers forming the ends of the cavity, thoroughly mixing the individual powders in an inert atmosphere to form a powder mixture, removing one plunger within said inert atmosphere, introducing said powder mixture into said die cavity while maintaining said inert atmosphere, locating said die cavity in a vacuum, replacing the said one plunger to capture the powder mixture in said die cavity, moving at least one of said plungers inwardly and outwardly of said die cavity without complete removal thereof, thereby to increase and decrease, respectively, the pressure in said die cavity with increasing pressure levels for short periods to progressively compress the powder mixture, slowly heating the die cavity and powder mixture to less than the melting point of the powder component having the lowest melting point and establishing the final forming pressure and maintaining said pressure for a predetermined period substantially greater than the alternate pressure and release periods.

The method of forming a multiple component compact body for use as a high current electrical arcing contact suitable for use in a vacuum interrupter, plasma device or the like comprising;

• thoroughly mixing a plurality of individual powders, each of said individual powders being suitable for use as a component of said contact, while retaining said powders in a protective inert atmosphere, placing the thoroughly mixed powders in a die cavity while maintaining said mix powders and the die cavity in said protective inert atmosphere, partially closing the die cavity to prevent free fluid movement of the mixed powders, locating the filled die cavity including the powdered material, within a vacuum chamber, forming a predetermined vacuum in said chamber without significantly closing the die cavity, said vacuum being sufficently high to remove gases from said mixed powders, slowly heating the die cavity and mixed powders to a temperature less than the melting temperature of the individual powders having the lowest melting temperature of the plurality of the mixed powders and at least to the sintering temperature of said mixed powders and closing the die cavity to incrementally compress the mixed powders, thereby to form said compact body.

The method of forming a multiple layered conducting member including a graphite portion having a surface defining a plurality of surface pores and a conductive portion formed of particles, comprising the steps of providing a die cavity having an opening and plunger means receivable and movable in said opening, partially filling the die cavity with a first layer of said particles and a second layer of graphite powder, locating said plunger means in said opening adjacent the graphite powder, thereby to partially close the die cavity, locating the die cavity in a vacuum chamber, forming a vacuum in said chamber, heating the die cavity, particles and graphite powder to less than the melting temperature of said graphite powder and to a sintering temperature, incrementally moving said plunger means into said opening to incrementally compress said particles and graphite powder in the presence of the vacuum and sintering temperature.

Apparatus for vacuum hot pressing metallic powder to form a compact body usable as an electrical contact comprising a die assembly having a cavity for containing a predetermined quantity of loose powder reaching a predetermined level therein and at least one movable die closure means movable into and out of said cavity for compressing said powder, said die assembly having outgassing opening means communicating with said cavity and placed inwardly of the movable die closure means and outwardly of the level of said powder, a chamber including means to create a vacuum therein, said chamber including heating means, means for mounting said die assembly in heating relation with heating means in said chamber for heating said powder to a predetermined temperature in said cavity, and pressure applying means mounted incrementally for moving said die closure means into said cavity incrementally for compacting said powder, said heated and compacted powder forming said compact body.