Process for forming thin walled plastic articles

Claim 1

The method for producing elongated relatively thin walled hollow thermoplastic articles with controlled wall thicknesses in an injection-blow molding arrangement, wherein the male injection mold part is retained at one end against axial movement within and relative to the female injection mold part to define a mold cavity and wherein the other end of said male injection mold part is capable of being deflected in a radial direction and wherein the injection molded preform is susceptible to shifting on said male mold part in blowing said article in a female blow mold having the shape of said article comprising the steps of: directing a stream of a molten thermoplastic material into the injection mold cavity through the female injection mold part toward said other end of said male injection mold part and along the axis from which the male injection mold part is deflectable, thereafter directing said stream consecutively through restricted circumferentially continuous concentric annular areas encircling the entrance of said stream of molten thermoplastic material into said cavity and maintaining said axially fixed relation of said male injection mold part while continuing the foregoing flow of molten thermoplastic material through said concentric annular areas to fill said cavity to form the injection molded preform with circumferentially continuous concentric annular portions at said other end, moving said male injection mold part with said preform thereon into a female blow mold with said other end of said male injection mold part spaced from and sufficiently adjacent to one interior surface of said female blow mold to mechanically lock said circumferentially continous concentric annular portion of said preform on said male injection mold part during initial blowing, applying blowing air through the sides and said other end of said male mold part to blow the sides of said preform against the interior surface of said female blow mold during initial blowing and to thereafter blow said other end of said injection molded preform into the shape of said article

Claim 2

The method for producing elongated relatively thin walled hollow thermoplastic articles with controlled wall thicknesses in an injection-blow molding arrangement, wherein the male injection mold part is retained at one end against axial movement within and relative to the female injection mold part to define a mold cavity and wherein the other end of said male injection mold part is capable of being deflected in a radial direction and wherein the injection molded preform is susceptible to shifting on said male mold part in blowing said article in a female blow mold having the shape of said article comprising the steps of: directing a stream of a molten thermoplastic material into the injection mold cavity through the female injection mold part toward said other end of said male injection mold part and along the axis from which the male injection mold part is deflectable, thereafter directing said stream consecutively through restricted circumferentially continuous concentric annular areas encircling the entrance of said stream of molten thermoplastic material into said cavity and maintaining said axially fixed relation of said male injection mold part while continuing the foregoing flow of molten thermoplastic material through said concentric annular areas to fill said cavity to form the injection molded preform with circumferentially continuous concentric annular portions at said other end, moving said male injection mold part with said preform thereon into a female blow mold with said other end of said male injection mold part spaced from and sufficiently adjacent to one interior surface of said female blow mold to mechanically lock said circumferentially continous concentric annular portion of said preform on said male injection mold part during initial blowing, applying blowing air through the sides and said other end of said male mold part to blow the sides of said preform against the interior surface of said female blow mold during initial blowing and to thereafter blow said other end of said injection molded preform into the shape of said article

Claim 4

The method for producing relatively thin walled hollow thermoplastic articles with controlled wall thicknesses in a blow molding arrangement using a molded preform which is susceptible to shifting on the male mandrel in blowing said preform in a female blow mold having the shape of said article comprising the steps of: forming said preform with a central wall portion indented inwardly to form a projection extending from one interior wall of said preform which is substantially less in diameter than the remaining wall portions of said preform, providing said mandrel with the shape of the interior of said preform and including a recess in the mandrel having a shape complementary to the shape of said projection and further providing air blowing passageways through the mandrel to the outer surface thereof and including the surface of said recess, applying said preform onto said mandrel with said projection of said preform disposed within said recess in said mandrel, heating said preform to a suitable condition for blowing, inserting said mandrel with said preform thereon into a female blow mold with the wall of said preform having said projection spaced from and sufficiently adjacent to one interior surface of said female blow mOld to mechanically lock said continuous annular portion of said preform within said continuous annular recess in said mandrel during initial blowing, and applying blowing air through said passageways to blow said remaining wall portions of said preform against the interior surface of said female blow mold during initial blowing and to thereafter blow said projection of said preform against the interior surface of said female blow mold.

Claim 5

The method for producing relatively thin walled hollow thermoplastic articles with controlled wall thicknesses in a blow molding arrangement using a molded preform which is susceptible to shifting on the male mandrel in blowing said preform in a female blow mold having the shape of said article comprising the steps of: forming said preform with a central wall portion indented inwardly to form a projection extending from one interior wall of said preform which is substantially less in diameter than the remaining wall portions of said preform, providing said mandrel with the shape of the interior of said preform and including a recess in the mandrel having a shape complementary to the shape of said projection and further providing air blowing passageways through the mandrel to the outer surface thereof and including the surface of said recess, applying said preform onto said mandrel with said projection of said preform disposed within said recess in said mandrel, heating said preform to a suitable condition for blowing, inserting said mandrel with said preform thereon into a female blow mold with the wall of said preform having said projection spaced from and sufficiently adjacent to one interior surface of said female blow mOld to mechanically lock said continuous annular portion of said preform within said continuous annular recess in said mandrel during initial blowing, and applying blowing air through said passageways to blow said remaining wall portions of said preform against the interior surface of said female blow mold during initial blowing and to thereafter blow said projection of said preform against the interior surface of said female blow mold.