Conveying jig, method of manufacturing conveying jig, and method of heat-treating metal rings using conveying jig

A feed jig for feeding a metal ring having an elastic recovering capability, comprising:

• a base plate;
• and
• at least three holder shafts vertically mounted on the base plate and extending parallel to each other,
• wherein each of the holder shafts comprises a hollow body pressed by a die from an inner wall thereof to have a plurality of ridges on a side wall thereof and a plurality of recesses between the ridges, for holding the metal ring.

A method of heat-treating a metal ring having an elastic recovering capability, comprising the steps of:

• holding the metal ring with recesses defined in side walls of at least three holder shafts of a feed jig, the holder shafts comprising hollow bodies, respectively;
• introducing the feed jig, which holds the metal ring, into a heat treatment furnace;
• and
• heat-treating the metal ring in the heat treatment furnace while an atmospheric gas flows through the holder shafts,
• wherein the metal rings are heat-treated, while the holder shafts have respective interiors held in fluid communication with the heat treatment furnace, and wherein inlets for introducing the atmospheric gas into the holder shafts are oriented upstream with respect to a direction along which the atmospheric gas flows.

A feed jig for holding a plurality of metal rings having an elastic recovering capability in a row within three or more metal ring holder members that extend parallel to each other, wherein:

• each of the metal ring holder members comprises a columnar member having a polygonal cross-sectional shape as viewed in a longitudinal direction, and a side surface facing the metal rings;
• each of the metal ring holder members has teeth for holding the metal rings, the teeth being disposed only on an end face thereof that faces toward the metal rings;
• and
• the metal rings have outer circumferential edges gripped between adjacent ones of the teeth.