Method of producing a hollow poppet valve and an apparatus therefor

Abstract

A method of producing a hollow valve comprises the step for forming material having a blind hole along its axis, the step for extruding the material in a shaping hole in a die downward and the step for lowering a lower part of a pin to an upper part of a smaller-diameter portion of the shaping hole to allow the material to plastically flow downward through a gap between the lower part of a pin and the smaller-diameter portion of the shaping hole thereby molding a primary intermediate of the hollow valve having a stem and a head at the upper end of the stem through which a hole is formed.

1 . A method of producing a hollow poppet valve, the method comprising:
 forming material that has a blind hole which is open at an upper end;   pressing the material in a shaping hole in a die strongly to allow the material to pass through a downward-tapered squeezing portion of the shaping hole to extrude the material into a smaller-diameter portion of the shaping hole; and   moving a pin down to allow the lower end of the pin to invade into an upper end of the smaller portion of the shaping hole to allow the material to plastically flow through an annular gap between an outer circumferential surface of a lower end of the pin and an inner circumferential surface of the smaller-diameter portion of the shaping hole thereby molding a primary intermediate of the valve, the primary intermediate comprising a stem and a larger-diameter head at an upper end of the stem, the primary intermediate having a cavity that has an opening at an upper end of the head.   
     
     
         2 . The method of  claim 1  wherein the lower end of the pin is moved down to a lower end of the blind hole of the material before the material is strongly pressed by the punch. 
     
     
         3 . The method of  claim 1  wherein the pin is elevated after the primary intermediate is molded while the upper end of the primary intermediate is pressed by the punch. 
     
     
         4 . The method of  claim 1 , further comprising forging the head of the primary intermediate to mold a secondary intermediate which comprises a stem, a head and a cavity; and closing the opening of the head with a closure. 
     
     
         5 . The method of  claim 4  wherein metallic sodium is inserted into the cavity in the stem through the opening of the head, before the opening of the head is closed with the closure. 
     
     
         6 . The method of  claim 4  wherein the hole in the head of the secondary intermediate gradually increases in diameter upward. 
     
     
         7 . A method of producing a hollow poppet valve, the method comprising:
 pressing a cylindrical material disposed in a shaping hole in a die, with a pin strongly to deform the material plastically to move a lower end of the pin into the material to form a blind hole having an opening at a top along an axis of the material;   pressing the material strongly to allow the material to pass through a squeezing hole which tapers downward of the shaping hole to exclude the material toward a smaller-diameter portion of the shaping hole; and   allowing the material to plastically flow downward through an annular gap between an outer circumferential surface of a lower end of the pin and an inner circumferential surface of the smaller-diameter portion of the shaping hole to mold a primary intermediate which comprises a stem and a larger-diameter head at an upper end of the stem, the primary intermediate having a cavity that has an opening at an upper end.   
     
     
         8 . The method of  claim 7  wherein the pin is elevated after the primary intermediate is molded while the upper end of the primary intermediate is pressed by the punch. 
     
     
         9 . The method of  claim 7 , further comprising forging the head of the primary intermediate to mold a secondary intermediate which comprises a stem, a head and a cavity; and closing the opening of the head with a closure. 
     
     
         10 . The method of  claim 9  wherein metallic sodium is inserted into the cavity in the stem through the opening of the head, before the opening of the head is closed with the closure. 
     
     
         11 . The method of  claim 7  wherein the hole in the head of the secondary intermediate gradually increases in diameter upward. 
     
     
         12 . An apparatus for producing a hollow poppet valve, the apparatus comprising a first press that comprises:
 a die having a shaping hole that comprises a larger-diameter portion into which material can be inserted, a squeezing portion which communicates with the larger-diameter portion and tapers downward, and a smaller-diameter portion which communicates with the squeezing portion to form a stem of the poppet valve;   a ram that rises and lowers above the die;   a punch attached to the ram, a lower end of the punch being capable of moving into the larger-diameter portion of the shaping hole in the die; and   a pin disposed to move up and down in a vertical guide hole along an axis of the punch and connected to the ram, a smallest portion at a lower end projecting from the punch downward to put into the smaller-diameter portion of the shaping hole.   
     
     
         13 . The apparatus of  claim 12 , further comprising pressing means for forcing the punch downward to press the primary intermediate downward until the pin moves up. 
     
     
         14 . The apparatus of  claim 13  wherein the pressing means comprise a compression spring. 
     
     
         15 . The apparatus of  claim 12 , further comprising a second press disposed near the first press, the second press comprising:
 a die holder;   a ram above the die holder to rise and lower;   a die in a recess in the die holder having a shaping hole; and   a punch in a recess in the ram and having a projection at a lower end, the head of the primary intermediate being forged and molded between the projection of the punch and the shaping hole of the die by the second press to form a head of the secondary intermediate of the hollow poppet valve.