Apparatus for injection molding of parts from foam plastics material and/or from solid plastics material

An apparatus for continuously extruding plastics material in either a homogeneous or foam condition and intermittently molding a plastic part in a mold assembly comprising:

• an elongated tubular barrel member having an elongated main passageway therein;
• said main passageway having a melt zone and/or a melt and gas mixing zone;
• an elongated screw member located in and extending along said main passageway;
• means for introducing plastics material into said barrel member at one end thereof;
• means for rotating said screw member in said barrel member for heating and plasticating the plastics material while simultaneously causing the plastics material to advance through said passageway from said one end towards the discharge port at the other end thereof;
• first injection means including a plastics injection chamber provided with an injection discharge nozzle;
• second injection means including a temporary plastics storage chamber;
• first conduit means connected on opposite ends thereof to said plastics injection chamber and to said temporary plastics storage chamber;
• second conduit means connecting the discharge port of said screw and barrel members to said first conduit means;
• a first multi-position flow control valve in said first conduit means for directing the molten plastics material to either said plastics injection chamber or to said temporary plastics storage chamber;
• means for changing the flow directional positions of said first flow control valve upon the filling of either chamber with the molten plastics material and the discharging of the molten plastics material from the other chamber;
• said rotating means for energizing said screw member directing the molten plastics material through said multi-position flow control valve to either of said plastics chambers depending on the position of said multi-position flow control valve;
• fluid operated means for energizing said first injection means for discharging the plastics material from said plastics injection chamber through said injection discharge nozzle into the mold for making plastic parts;
• said screw member, while said first injection means is injecting the plastics material through said discharge nozzle into the mold, continuing to advance the molten plastics material along the barrel member from where it is directed by said first multi-position flow control valve to said first conduit means and into said temporary plastics storage chamber;
• said fluid operated means, after the molten plastics material has been discharged from said plastics injection chamber and after other plastics material has been stored in said other chamber, being energized to direct the stored plastics material from said temporary plastics storage chamber across said first multi-position valve and said first conduit means towards said plastics injection chamber;
• said rotating means continuously advancing the molten plastics material along said screw member during the operation of either of said first and second injection means whereby the molten plastics material is directed to one or the other of the injection and storage chambers depending on the position of said first multi-position flow control valve;
• and a plastic flow control valve located adjacent the injection discharge nozzle of said plastic injection chamber;
• said plastic flow control valve when in one position permitting the plastics material to enter the plastics injection chamber and blocking flow through said discharge nozzle;
• and said plastic flow control valve when in another position permitting said first injection means to inject the plastics material therein through said discharge nozzle while blocking flow in said first conduit means.

An apparatus for extruding foam plastics material comprising:

• an elongated tubular barrel member having an elongated main passageway therein;
• an elongated screw member located in and extending along said main passageway;
• means for introducing plastics material into said barrel member at one end thereof;
• means for rotating said screw member in said barrel member for heating and plasticating the plastics material while simultaneously causing the plastics material to advance through said passageway from said one end towards the discharge port at the other end thereof;
• means for introducing an inert gas into the melt zone of said main passageway, said last mentioned means including;
• an elongated passage extending from said one end of said screw member to the other end thereof where it communicates with said main passageway;
• a pump;
• a source of gas inert to said plastics material connected to the suction side of said pump;
• means connecting the discharge side of said pump to the entrance to said screw passage at said one end of said screw member whereby the inert gas is directed by said pump through said elongated screw passage where it exits therefrom into said barrel member and from where it mixes with the molten plastics material as a result of the rotation of said screw member to form foam plastics material which is discharged from said barrel member through said discharge port;
• said screw member including one or more radially extending gas discharge passages which communicate on the inner ends thereof with the longitudinally extending screw passage;
• a pair of check valves in each radially extending gas discharge screw passage which are opened when the gas is delivered by said pump to said main passageway and are closed when said pump is de-energized, one check valve of each radially extending gas discharge passage preventing the molten plastics material from the main passageway from entering the radial and longitudinal screw passages, and the other check valve of each radially extending gas discharge passage being spring biased for preventing the gas in said radial and longitudinal screw passages from entering said main passageway.