Heat treatment material handling unit

A material handling unit for sequentially processing each of a plurality of parts through a heat treatment cell for a predetermined period of time, comprising

• a vertical guide for holding a plurality of parts in a vertical stack,
• means for sequentially interchanging parts at the top and bottom of the stack at a predetermined rate, including
• means for lifting the stack to a raised position and lowering the stack to a lowered position,
• means for selectively maintaining the stack in raised position,
• means for withdrawing a part from the bottom of the stack when the stack is in raised position, and
• means for inserting a part into the top of the stack, and
• control means for selectively varying said predetermined period of time and said predetermined rate,
• whereby the number of parts in the stack equals the predetermined time period multiplied by the predetermined rate.

A method for sequentially processing a plurality of parts individually through a heat treatment process at a predetermined rate, whereby each part is heat treated for a predetermined time so that all parts are heat treated equally, comprising the steps of

• arranging a plurality of parts in a vertical stack in a heat treatment furnace,
• arranging a plurality of stacks of parts in said furnace,
• providing a parts transfer station in said furnace for moving parts into and out of said furnace,
• moving said stacks of parts sequentially to said transfer station, and
• sequentially removing and inserting parts at both ends of a stack at predetermined intervals when the stack is at the transfer station so that each part progresses from one end of the stack to the other and is heat treated equally.