Electromechanical drive assembly for an accumulator head

Abstract

An accumulator head for a blow molding machine uses an electromechanical drive assembly for the purging and programming functions. The purging actuator of the drive assembly includes a ball screw and nut assembly in which the ball screw is rotated by an electric motor to move the ball nut assembly vertically and operate the plunger of the accumulator. A second ball screw and nut assembly is included in the programming actuator of the drive assembly for moving the mandrel vertically, thereby controlling the size of the die outlet opening of the accumulator. Preferably, the ball screws of the programming and purging actuators are axially aligned with the nut assemblies each carried by a yoke that travels on guide rods. Four support rods are provided to maintain alignment and provide stationary mounting for the respective motors. The structure has sufficient rigidity to supply the force required for the purging operation, but uses no hydraulic actuators.

What is claimed is: 
     
       1. In an extrusion blow molding machine that includes an extruder to supply plasticized material to an accumulator head having a plunger to eject plasticized material collected within a chamber in the accumulator head through an annular die outlet to form a tubular parison, the annular die outlet being defined by diverging or converging tooling that includes a die outer ring and an inner mandrel, wherein the inner mandrel is movable to alter the size of the annular die outlet, and an electromechanical drive assembly for the accumulator head comprising: (a) a programming actuator including a first ball screw driven by an electric motor and a first ball nut assembly that is connected to the mandrel of the accumulator head, wherein the first ball nut assembly and mandrel are linearly driven when the first ball screw is rotated to move the mandrel and alter the size of the die outlet;   (b) a purging actuator including a second ball screw driven by an electric motor and a second ball nut assembly that is connected to the plunger of the accumulator head, wherein the second ball nut assembly and plunger are linearly driven when the second ball screw is rotated to move the plunger and eject the plasticized material collected within the chamber;   (c) a frame for supporting the programming actuator and purging actuator such that the axes of the first ball screw and the second ball screw are parallel, the frame including a plurality of guide rods positioned parallel to the axes of the ball screws; and   (d) a yoke configured to engage the guide rods included in each of the first and second ball nut assemblies, the yoke of the first ball nut assembly connecting to the mandrel, and the yoke of the second ball nut assembly connecting to the plunger.   
     
     
       2. The extrusion blow molding machine as set forth in claim 1 wherein the first ball screw and the second ball screw are positioned in axial alignment and the plunger and mandrel of the accumulator head are in axial alignment with the first and second ball screws. 
     
     
       3. In an extrusion blow molding machine that includes an extruder to supply plasticized material to an accumulator head having a plunger to eject plasticized material collected within a chamber in the accumulator head through an annular die outlet to form a tubular parison, the annular die outlet being defined by diverging or converging tooling that includes a die outer ring and an inner mandrel, wherein the inner mandrel is movable to alter the size of the annular die outlet, and an electromechanical drive assembly for the accumulator head comprising: (a) a programming actuator including a first ball screw driven by an electric motor and a first ball nut assembly that is connected to the mandrel of the accumulator head, wherein the first ball nut assembly and mandrel are linearly driven when the first ball screw is rotated to move the mandrel and alter the size of the die outlet;   (b) a purging actuator including a second ball screw driven by an electric motor and a second ball nut assembly that is connected to the plunger of the accumulator head, wherein the second ball nut assembly and plunger are linearly driven when the second ball screw is rotated to move the plunger and eject the plasticized material collected within the chamber;   (c) a frame for supporting the programming actuator and purging actuator such that the axes of the first ball screw and the second ball screw are parallel, the frame including a plurality of support rods positioned parallel to the axes of the ball screws and connecting to a base plate, an intermediate plate and an upper plate; the upper plate serving to support the programming actuator, the intermediate plate serving to support the purging actuator, and the base plate serving to support the electromechanical drive assembly and connect it with the accumulator head.   
     
     
       4. The extrusion blow molding machine as set forth in claim 3 wherein the electric motor of the programming actuator is suspended from the upper plate and is drivingly connected to the first ball screw by means of pulleys and a belt, and the electric motor of the purging actuator is suspended from the intermediate plate and is drivingly connected to the second ball screw by means of pulleys and a belt. 
     
     
       5. In an extrusion blow molding machine that includes an extruder to supply plasticized material to an accumulator head having a plunger to eject plasticized material collected within a chamber in the accumulator head through an annular die outlet to form a tubular parison, the annular die outlet being defined by diverging or converging tooling that includes a die outer ring and an inner mandrel, wherein the inner mandrel is movable to alter the size of the annular die outlet, and an electromechanical drive assembly for the accumulator head comprising: (a) a programming actuator including a first ball screw driven by an electric motor and a first ball nut assembly that is connected to the mandrel of the accumulator head such that the mandrel is axially aligned with the first ball screw, wherein the first ball nut assembly and mandrel are linearly driven when the first ball screw is rotated to move the mandrel and alter the size of the die outlet;   (b) a purging actuator including a second ball screw driven by an electric motor and a second ball nut assembly that is connected to the plunger of the accumulator head such that the plunger is axially aligned with the second ball screw, wherein the second ball nut assembly and plunger are linearly driven when the second ball screw is rotated to move the plunger and eject the plasticized material collected within the chamber; and   (c) a frame for supporting the programming actuator and purging actuator such that the first ball screw and the second ball screw are positioned in axial alignment, the frame including (i) a plurality of guide rods positioned parallel to the axes of the first and second ball screws for constraining the first and second ball nut assemblies when linearly driven by the associated ball screw, and   (ii) a plurality of support rods positioned parallel to the axes of the ball screws and connecting to a base plate, an intermediate plate and an upper plate; the upper plate serving to support the programming actuator, the intermediate plate serving to support the purging actuator, and the base plate serving to support the electromechanical drive assembly and connect it with the accumulator head. .Iadd.     
     
     
       6.  In an extrusion blow molding machine that includes an extruder to supply plasticized material to an accumulator head having a plunger to eject plasticized material collected within a chamber in the accumulator head through an annular die outlet to form a tubular parison, the annular die outlet being defined by diverging or converging tooling that includes a die outer ring and an inner mandrel, wherein the inner mandrel is movable to alter the size of the annular die outlet, and an electromechanical drive assembly for the accumulator head comprising: (a) a programming actuator including a first screw driven by an electric motor and a first nut assembly that is connected to the mandrel of the accumulator head, wherein the first nut assembly and mandrel are linearly driven when the first screw is rotated to move the mandrel and alter the size of the die outlet;   (b) a purging actuator including a second screw driven by an electric motor and a second nut assembly that is connected to the plunger of the accumulator head, wherein the second nut assembly and plunger are linearly driven when the second screw is rotated to move the plunger and eject the plasticized material collected within the chamber;   (c) a frame for supporting the programming actuator and purging actuator such that the axes of the first screw and the second screw are parallel, the frame including a plurality of guide rods positioned parallel to the axes of the screws; and   (d) a yoke configured to engage the guide rods included in each of the first and second nut assemblies, the yoke of the first nut assembly connecting to the mandrel, and the yoke of the second nut assembly connecting to the plunger. .Iaddend..Iadd.7. The extrusion blow molding machine as set forth in claim 6 wherein the first screw and the second screw are positioned in axial alignment and the plunger and mandrel of the accumulator head are in axial alignment with the first and second screws. .Iaddend..Iadd.8. In an extrusion blow molding machine that includes an extruder to supply plasticized material to an accumulator head having a plunger to eject plasticized material collected within a accumulator head through an annular die outlet to form a tubular parison, the annular die outlet being defined by diverging or converging tooling that includes a die outer ring and an inner mandrel, wherein the inner mandrel is movable to alter the size of the annular die outlet, and an electromechanical drive assembly for the accumulator head comprising:   (a) a programming actuator including a first screw driven by an electric motor and a first nut assembly that is connected to the mandrel of the accumulator head, wherein the first nut assembly and mandrel are linearly driven when the first screw is rotated to move the mandrel and alter the size of the die outlet;   (b) a purging actuator including a second screw driven by an electric motor and a second nut assembly that is connected to the plunger of the accumulator head, wherein the second nut assembly and the plunger are linearly driven when the second screw is rotated to move the plunger and eject the plasticized material collected within the chamber,   (c) a frame for supporting the programming actuator and purging actuator such that the axes of the first screw and the second screw are parallel, the frame including a plurality of support rods positioned parallel to the axes of the screws and connecting to a base plate, an intermediate plate and an upper plate; the upper plate serving to support the programming actuator, the intermediate plate serving to support the purging actuator, and the base plate serving to support the electromechanical drive assembly and connect it with the accumulator head. .Iaddend..Iadd.9. The extrusion blow molding machine as set forth in claim 8 wherein the electric motor of the programming actuator is suspended from the upper plate and is drivingly connected to the first screw by means of pulleys and a belt, and the electric motor of the purging actuator is suspended from the intermediate plate and is drivingly connected to the second screw by means of pulleys and a belt. .Iaddend..Iadd.10. In an extrusion blow molding machine that includes an extruder to supply plasticized material to an accumulator head having a plunger to eject plasticized material collected within a chamber in the accumulator head through an annular die to form a tubular parison, the annular die outlet being defined by diverging or converging tooling that includes a die outer ring and an inner mandrel, wherein the inner mandrel is movable to alter the size of the annular die outlet, and an electromechanical drive assembly for the accumulator head comprising:   (a) a programming actuator including a first screw driven by an electric motor and a first nut assembly that is connected to the mandrel of the accumulator head such that the mandrel is axially aligned with the first screw, wherein the first nut assembly and mandrel are linearly driven when the first screw is rotated to move the mandrel and alter the size of the die outlet;   (b) a purging actuator including a second screw driven by an electric motor and a second nut assembly that is connected to the plunger of the accumulator head such that the plunger is axially aligned with the second screw, wherein the second nut assembly and plunger are linearly driven when the second screw is rotated to move the plunger and eject the plasticized material collected within the chamber; and   (c) a frame for supporting the programming actuator and purging actuator such that the first screw and the second screw are positioned in axial alignment, the frame including (i) a plurality of guide rods positioned parallel to the axes of the first and second screws for constraining the first and second nut assemblies when linearly driven by the associated screws; and   (ii) a plurality of support rods positioned parallel to the axes of the screws and connecting to a base plate, an intermediate plate and an upper plate; the upper plate serving to support the programming actuator, the intermediate plate serving to support the purging actuator, and the base plate serving to support the electromechanical drive assembly and connect it with the accumulator head. .Iaddend.