Balloon blown plastic molding

Claim 2

An injection blow molding apparatus including an injection mold, a core rod that extends into the injection mold, a support for the core rod at one end thereof, an elastic balloon permanently connected at one end to the core rod and that covers and hugs the core rod, means for injecting molten material into the injection mold to apply a parison over the balloon, a blowing mold enclosing a cavity, means for moving the support to transfer the core rod, balloon and parison from the injection mold to the blowing mold, and for locating the core rod in a position extending into the blowing mold and supporting the parison therein, the parison being smaller than the blowing mold cavity, and the core rod having a passage through which fluid is supplied to expand the balloon and by the pressure on the fluid from the core rod, transmitted through the balloon to the parison, to expand the parison into contact with the surface of the mold cavity as the balloon is blown up by said fluid from the core rod.

Claim 3

The blow molding apparatus described in claim 1 characterized by the balloon being made of elastic material capable of repeatedly expanding successive parisons and then contracting back to its original shape after each expanding operation at the temperature of the material injected into the injection mold.

Claim 4

The blow molding apparatus described in claim 1 characterized by the balloon having an open end that fits over the core rod at a location beyond the mold cavity and adjacent said support, and means permanently securing the balloon to the core rod near the open end of the balloon.

Claim 5

The blow molding apparatus described in claim 3 characterized by the means permanently securing the balloon to the core rod being a clamping ring, the core rod completely filling the open end of the balloon and having a circumferential groove into which the balloon is clamped by said ring, a shoulder on the core rod beyond the groove, and a clearance between the core rod and balloon near said shoulder and into which the balloon can collapse to move the balloon away from the inside surface of a blown parison to admit air into the parison as the balloon collapses after each blowing operation.

Claim 6

The blow molding apparatus described in claim 1 characterized by means for circulating fluid simultaneously into and out of the balloon to cool the parison from the inside while building up pressure in the balloon to expand the balloon and the parison.

Claim 7

The blow molding apparatus described in claim 5 characterized by the means for circulating fluid including a pump, a source of liquid at a substantially lower temperature than the parison for cooling the balloon and cooling the parison from the inside by conduction of heat through the wall of the balloon from the inside surface of the parison in contact with the balloon, the blowing mold having cooling chambers therein around the cavity for cooling the mold and cooling the parison by contact with the outside surface of the parison with the surface of the cavity.

Claim 8

The blow molding apparatus described in claim 6 characterized by a closed circuit in which the blowing liquid for the core rod flows, a partition in the core rod for controlling the flow, means adjustable to control the rate of exhaust of liquid from the core rod independently of the rate of supply of liquid for building up pressure in the balloon, and means for cooling the liquid as it travels from the core rod exhaust back to the source of liquid.

Claim 9

The blow molding apparatus described in claim 1 characterized by means for supplying fluid to the core rod to expand the balloon and to expand the parison into contact with the wall of the mold cavity, the fluid supply means being capable of delivering fluid at a pressure that expands the balloon and the parison when the plastic of the parison is at a temperature at which crystallization of the plastic begins.

Claim 10

The blow molding apparatus described in claim 1 characterized by the balloon having side walls of different degrees of elasticity at different regions of the ballon so that regions of greater elasticity expand ahead of those of lesser elasticity to obtain a selective sequence of expansion of the parison.

Claim 11

Blow molding apparatus including a blowing mold enclosing a cavity, a core rod that extends into a parison that is smaller than the blowing mold cavity and through which fluid is supplied to expand the parison into contact with the surface of the mold cavity, and an elastic balloon on the core rod and permanently connected at one end to the core rod and within the parison and through which pressure of the fluid from the core rod is transmitted to the parison to expand the parison into contact with the surface of the mold cavity as the balloon is blown up by said fluid from the core rod, characterized by the apparatus being an injection molding machine with an injection Chamber in which the core rod is originally located for receiving a coating of plastic on the outside surface of the balloon, means for effecting transfer of the core rod and balloon from the injection mold to the blowing mold cavity, means for obtaining the orientation temperature for the parison prior to the blowing operation, the balloon being of shorter length and less cross section than the blowing mold cavity whereby the plastic deposited on the balloon in the injection mold is stretched both circumferentially and axially during expansion of the balloon in the mold cavity to effect biaxial orientation of the molecules of the plastic material.

Claim 12

Blow molding apparatus including a blowing mold enclosing a cavity, a core rod that extends into a parison that is smaller than the blowing mold cavity and through which fluid is supplied to expand the parison into contact with the surface of the mold cavity, and an elastic balloon on the core rod and permanently connected at one end to the core rod and within the parison and through which pressure of the fluid from the core rod is transmitted to the parison to expand the parison into contact with the surface of the mold cavity as the balloon is blown up by said fluid from the core rod, characterized by the apparatus being an injection molding machine with an injection Chamber in which the core rod is originally located for receiving a coating of plastic on the outside surface of the balloon, means for effecting transfer of the core rod and balloon from the injection mold to the blowing mold cavity, means for obtaining the orientation temperature for the parison prior to the blowing operation, the balloon being of shorter length and less cross section than the blowing mold cavity whereby the plastic deposited on the balloon in the injection mold is stretched both circumferentially and axially during expansion of the balloon in the mold cavity to effect biaxial orientation of the molecules of the plastic material.

Claim 13

The blow molding apparatus described in claim 10 characterized by the injection chamber being in a mold at an injection station of the machine, a turret to which the core rod is secured and by which the core rod is moved from one station to another, a conditioning station to which the coated balloon is transferred after leaving the injection station, a blowing station at which the blow mold cavity is located and to which the core pin and balloon are transferred after leaving the conditioning station, and a stripping station beyond the blow molding station and to which the core pin and blow parison are transferred by the turret after blowing at the blowing station.

Claim 14

The injection blow molding apparatus described in claim 1 characterized by the core rod having openings therein for the discharge of blowing fluid from the core rod at different locations along the length thereof to expand the balloon, the material of the balloon, when contracted into contact hugging the core rod being sufficiently stiff to prevent material of the balloon from being extruded through said openings and into the core rod by the pressure in the injection mold when applying a molten parison to the outside of the balloon in the injection mold.

Claim 15

The injection blow molding apparatus described in claim 1 characterized by the balloon hugging the core rod for substantially the full length of the portion of the core rod that extends into the blowing mold cavity, and the balloon having a closed end beyond the end of the core rod that is remote from said core rod support.