Method of making a sand mold with a back draft

Claim 1

A method of making a sand mold having an internal back draft portion in its cavity, said mold being of the cured type, comprising; forming a composite pattern of metal portion and flexible portion, said flexible portion joined to said portion complementing the shape of the said back draft portion of such cavity in said mold; placing curable sand mixture around said pattern; curing said sand mixture to thereby cure and harden said sand and form a cavity having a back draft portion; and separating said mold from said composite pattern in a substantially straight line of movement so that the shape of the mold causes said flexible portion to temporarily deform sufficiently to permit it to egress from said back draft portion without damage to said mold or flexible material.

Claim 2

A method of making a sand mold having an internal back draft portion in its cavity, said mold being of the cured type, comprising; forming a composite pattern of metal portion and flexible portion, said flexible portion joined to said portion complementing the shape of the said back draft portion of such cavity in said mold; placing curable sand mixture around said pattern; curing said sand mixture to thereby cure and harden said sand and form a cavity having a back draft portion; and separating said mold from said composite pattern in a substantially straight line of movement so that the shape of the mold causes said flexible portion to temporarily deform sufficiently to permit it to egress from said back draft portion without damage to said mold or flexible material.

Claim 3

A method of making a sand mold having an internal back draft portion in its cavity, said mold being of the heat-cured type, comprising; forming a composite pattern of metal portion and silicone rubber portion, said silicone rubber portion joined to said metal portion complementing the shape of the said back draft portion of such cavity of said mold; placing heat-curable sand mixture around said composite pattern; heating said composite pattern and said mixture to cure and harden said sand mixture and form a cavity the resulting cured mold having a back draft portion; and separating said mold from said composite pattern in a substantially straight line of movement so that the shape of the mold causes said silicone rubber to temporarily deform sufficiently to permit said composite mold to be withdrawn from said back draft portion without damage to said mold or silicone rubber.

Claim 4

A method of making a sand mold having an internal back draft portion in its cavity, said mold being of the heat-cured type, comprising; forming a composite pattern of metal portion and silicone rubber portion, said silicone rubber portion joined to said metal portion complementing the shape of the said back draft portion of such cavity of said mold; placing heat-curable sand mixture around said composite pattern; heating said composite pattern and said mixture to cure and harden said sand mixture and form a cavity the resulting cured mold having a back draft portion; and separating said mold from said composite pattern in a substantially straight line of movement so that the shape of the mold causes said silicone rubber to temporarily deform sufficiently to permit said composite mold to be withdrawn from said back draft portion without damage to said mold or silicone rubber.

Claim 6

A method of making a sand mold having an internal back draft portion in its cavity, said mold being of the heat-cured type, comprising; providing a composite pattern formed of a metal portion and silicone rubber portion, the silicone rubber portion complementing the shape of the said back draft area of said mold; placing resin-bonded and heat-curable sand mixture around said pattern; heating said pattern and sand mixture to at least approximately 400* F. to thereby cure and harden said sand and form a mold having an internal back draft portion in its cavity; and separating said mold by shifting it bodily in a substantially straight line from said composite causing said silicone rubber portion to temporarily deform sufficiently to permit it to be withdrawn from said back draft portion without damage to the resulting cured sand mold.

Claim 7

A method of making a sand mold having an internal back draft portion in its cavity, said mold being of the heat-cured type, comprising; providing a composite pattern formed of a metal portion and silicone rubber portion, the silicone rubber portion complementing the shape of the said back draft area of said mold; placing resin-bonded and heat-curable sand mixture around said pattern; heating said pattern and sand mixture to at least approximately 400* F. to thereby cure and harden said sand and form a mold having an internal back draft portion in its cavity; and separating said mold by shifting it bodily in a substantially straight line from said composite causing said silicone rubber portion to temporarily deform sufficiently to permit it to be withdrawn from said back draft portion without damage to the resulting cured sand mold.

Claim 8

A method of making a sand mold having an internal back draft portion in its cavity, said mold being of the cured type, comprising; forming a composite pattern formed of a metal portion and flexible portion, said metal portion having a generally cylindrical and axially extending central opening and also having an external surface inclined to the longitudinal axis of said pattern and forming a large end and a small end of said metal portion, the flexible portion complementing the shape of the said back draft portion of said mold; said flexible portion forming a generally radially extending flange extending from said small end, said flexible portion having a rounded internal corner at the junction of said central opening; placing curable sand mixture around said composite pattern; heating said composite pattern and sand mixture to cure and harden said sand mixture and form a resulting cured sand mold having a back draft portion in its cavity and then separating said cured mold by shifting it bodily in a subsTantially straight line from said composite pattern to cause said flexible portion to temporarily deform sufficiently to permit it to be withdrawn from said back draft portion without damage to said cured mold.

Claim 9

A method of making a sand mold having an internal back draft portion in its cavity, said mold being of the cured type, comprising; forming a composite pattern formed of a metal portion and flexible portion, said metal portion having a generally cylindrical and axially extending central opening and also having an external surface inclined to the longitudinal axis of said pattern and forming a large end and a small end of said metal portion, the flexible portion complementing the shape of the said back draft portion of said mold; said flexible portion forming a generally radially extending flange extending from said small end, said flexible portion having a rounded internal corner at the junction of said central opening; placing curable sand mixture around said composite pattern; heating said composite pattern and sand mixture to cure and harden said sand mixture and form a resulting cured sand mold having a back draft portion in its cavity and then separating said cured mold by shifting it bodily in a subsTantially straight line from said composite pattern to cause said flexible portion to temporarily deform sufficiently to permit it to be withdrawn from said back draft portion without damage to said cured mold.

Claim 10

A method of making a one-piece sand mold for castings having back draft portions which prevent the withdrawal of a rigid pattern from such a one-piece mold comprising: forming a composite pattern of a metal portion and a silicone rubber portion, said silicone rubber portion complementing the shape of any back draft portion of said pattern which would prevent removal of said pattern from a one-piece mold; placing said composite pattern on a surface having curing means for a sand mold mixture; enveloping said composite mold so placed with a curable sand mold mixture; curing said curable sand mixture with said curing means to form a one-piece cured mold; and separating said one-piece cured mold in said composite pattern by withdrawing the metal portion thereof in a direction avoiding disruption of said one-piece sand mold during which withdrawal said silicone rubber portion attached thereto recedes from any said back draft area by deflecting without damage to said one-piece cured mold.

Claim 11

A method of making a one-piece sand mold for castings having back draft portions which prevent the withdrawal of a rigid pattern from such a one-piece mold comprising: forming a composite pattern of a metal portion and a silicone rubber portion, said silicone rubber portion complementing the shape of any back draft portion of said pattern which would prevent removal of said pattern from a one-piece mold; placing said composite pattern on a surface having curing means for a sand mold mixture; enveloping said composite mold so placed with a curable sand mold mixture; curing said curable sand mixture with said curing means to form a one-piece cured mold; and separating said one-piece cured mold in said composite pattern by withdrawing the metal portion thereof in a direction avoiding disruption of said one-piece sand mold during which withdrawal said silicone rubber portion attached thereto recedes from any said back draft area by deflecting without damage to said one-piece cured mold.