PLASTICATING AND INJECTION MOLDING SYSTEM

Abstract

An injection molding apparatus that employs a stationary plasticating screw relative to feed port, non-reciprocal helical plasticating screw housed within an inner barrel that is coupled to a plunger head assembly, drive housing, motor and injection cylinders that is housed within an outer barrel/pressure vessel that conveys, melts, homogenizes and pumps polymeric plastic material precisely and efficiently along One axis. The helical plasticating screw is fixed in relative position within the inner barrel so that the material feed opening of the inner barrel and helical plasticating screw are aligned to accept pellets, powder or liquid of polymetric substance. The inner barrel is fixed to a plunger head assembly on the distal end that is housed within a pressure vessel with close proximity between the outside diameter of the plunger head and the inside diameter of said pressure vessel that upon screw rotation transfers polymetric material through the center passageway of said plunger head opening a normally closed one-way shut-off mechanism into said pressure vessel precisely for future displacement of polymeric mass into a mold or other. The apparatus and process of feeding, melting and injecting Polymeric material all occurs on one axis.

Claims

1. An injection process comprises, a fixed position non-reciprocating helical plasticating screw within an inner barrel, a feed port to accept polymeric material, liquid or powder material that is fixed to said inner barrel in a position complimentary to said non-reciprocating helical plasticating screw feed port a plunger head assembly in end communication on said inner barrel, a drive housing, a drive motor and injection cylinders forming an integral reciprocating injection assembly with said helical plasticating screw, inner barrel and a plunger head, a fixed cylindrical pressure vessel registerably receiving said plunger head, inner barrel, and integral reciprocating injection assembly selectively there within, means for closing said cylindrical pressure vessel downstream of said plunger head, means for transferring heat from heater bands placed on outer diameter of said cylindrical pressure vessel into said inner barrel, said helical plasticating screw and said polymeric material that are housed entirely within said pressure vessel, processible plastic material received within said helical plasticating screw in said injection assembly for processing, transferring processed plastic material in fluid form from said helical plasticating screw through said plunger head into said cylindrical pressure vessel forcing said injector assembly to move upstream to a preset position determined by polymeric material mass displacement to fill an injection mold in communication with a nozzle on said pressure vessel from an injector forward position, means for energizing injector cylinders on said injector assembly and direct drive means for said helical plasticating screw.

2. The injector process and apparatus of claim 1 wherein said plunger head is movable from a first closed position to a second open position under processed plastic material flow from said helical plasticating screw by a poppet valve within said material flow path, whereas said plunger head is of a known outside diameter to that of said pressure vessel to form a seal therewith for displacement of liquid processed plastic material from said pressure vessel through said nozzle to said injection mold.

3. The injector process and apparatus of claim 1 wherein said plunger head is mechanically operated using kinetic energy of a spring to operate in the normally closed position, said plunger head requiring flow from the polymeric fluid to open before allowing said polymeric fluid to pass between said poppet and a seat to advance downstream.

4. The injector process and apparatus of claim 1 wherein said processible plastic material is received into said reciprocal injector assembly via said feed port that is independent of injector assembly reciprocal positions.

5. The injector process and apparatus set forth in claim 1 wherein the said reciprocating injector assembly with mechanisms for feeding melting and injecting molten polymeric material all occurs along One axis.

6. The injector process and apparatus set forth in claim 1 wherein said helical screw, inner barrel and plunger head of said injector assembly is housed entirely within a pressure vessel that serves as support for alignment and for heat transfer from said external heater bands that are used for conductive heat to melt said polymeric material.

7. The injector process and apparatus set forth in claim 6 wherein said pressure vessel is in close proximity to said inner barrel so as to be able to support the inner barrel for alignment and conductive heat transfer from said heater bands to the polymeric material within the helical plasticating screw.

Description

DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a top plan view of the injection molding device of the invention.

[0018] FIG. 2 is an enlarged partial top plan sectional view thereof.

[0019] FIG. 3 is a side elevational view of the injection molding device of the invention.

[0020] FIG. 4 is a partial side elevation view of the helical plasticating screw, inner barrel, screw drive motor, feed opening and plunger head of the invention.

[0021] FIG. 5 is an enlarged side elevational view of the plunger head.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Referring to FIGS. 1 and 3 of the drawings, a plasticating injection device 10 of the invention can be seen for an injection molding machine.

[0023] The plasticating device 10 includes a stationary non-reciprocal helical screw 11 that is housed within an inner barrel 12 whose purpose is to convey, melt, homogenize and pump polymeric material (PM) through a plunger head 13 that is mounted to an inner barrel 12 within a pressure vessel 14 displacing volume which thereby forces the helical screw 11, inner barrel 12, plunger head 13 and a drive housing 15 with motor 16 to retract in the upstream direction to a set stop position. The drive housing 15 rides on a linear rail system 17 or the like keeping the injection assembly defined by these elements on the same linear axis.

[0024] As best seen in FIG. 4 of the drawings, the stationary non-reciprocating helical plasticating screw 11 within the inner barrel 12 can be seen with a plunger head 13 of the invention.

[0025] Referring now to FIG. 4-5 of the drawings, the plunger head 13 is illustrated in an open position depicting a seat 19 that forms a seal with a poppet valve 20 that is in normally closed position until the liquified polymer flow discharged from the helical screw 11 forces the poppet valve 20 off of its seat 19 creating a product flow opening and thereby urging springs 21 positioned within to deform while the liquid polymer, not shown, flows through the inside diameter of the springs 22 and through a now defined passageway orifice 23.

[0026] In operation, it will be seen that the plasticating injector device 10 of the invention utilizes the axially stationary non-reciprocating helical plasticating screw 11, feed opening 27, inner barrel 12, plunger head assembly 13, pressure vessel 14 and a nozzle body 25 with drive housing 15, motor 16, linear rail 17 guide, and external heater bands 29 that transfers heat into polymeric material that sits within the helical screw channel 11B which defines the injector assembly that will reciprocate as a unit to prepare molten/liquid polymetric material PM for subsequent injection through into an injection mold, not shown.

[0027] The helical screw 11 within the inner barrel 12 is coupled directly to the drive housing 15. The shank of the screw 11A has an attachment and is directly coupled to a screw drive motor 16 that provides the power to turn the screw 11 that conveys, melts, homogenizes and pumps molten liquid polymeric material PM forward and downstream along a flight channel 11B through the plunger head 13 and into the pressure vessel chamber 26, as noted. The plunger head 13 is directly coupled to the inner barrel 12 so as to become integral and by its nature opens and allows molten polymeric liquid material to flow downstream in one direction only and whose outside diameter is closely proximate with the inside diameter of a pressure vessel 14 forming a seal there between, as noted above. The helical plasticating screw 11 feed section extends beneath and forward from a material feed opening 27 where the polymeric material is to be processed and introduced and to be carried forward along the screw flight channel 11B inside the inner barrel 12 absorbing heat from said external heater bands 29.

[0028] The polymeric material is then worked and heated in the transition section so that melting of the polymer occurs as the material is moved forward along said screw flight channel 11B towards the passageway orifice Using an alternate liquid material, it is conveyed along the axis of the screw but is not heated. The polymer is passed through the transition section to reduce the root depth of the helical passageway to reflect the volume reduction due to the melting of the feed. The reduction of depth in the transition section also compresses the solid bed of pellets, liquid or powder. The transition section leads to a metering section, which has a shallow root depth helical passageway. The preferred geometry moving from the deep feed section to the shallow metering section takes the form of an involute taper geometry. The metering section has as its function the exertion of a constant flow rate pumping action on the molten polymer. In addition, any un-melted solids should be melted in the metering section as well as to mix the melted polymer homogenously. The molten/liquid polymeric material is forced into a center opening of the plunger head 13 that is mated to the inner barrel 12, through the plunger head and into a pressure vessel chamber 26 that is closed off, forcing the injection assembly to move backwards in the upstream direction, indicated by broken line arrow, along an alignment system while filling the pressure vessel 14 with molten/liquid polymeric material in the downstream direction. This process continues until the unitary injection assembly reaches a set axial stop position that in theory equals the mass necessary to fill the injection mold. However, since polymeric material is a compressible fluid there is no guarantee that the volume of material in the pressure vessel is enough to fill the mold so the injection device 10 may utilize a process with a change in programing whereas it will keep the injection assembly in a locked axial position and continue to rotate the screw 11 to build additional pressure until the proper volumetric mass density is reached, a feature that cannot be performed accurately with the reciprocating screw design. The measurement of the proper mass density may be determined by a direct exchange from sensors that are not shown, that detects melt density, then the screw 11 rotate phase will be stopped for preparation for the next injection forward phase of the cycle, the injection assembly is moved forward/downstream under power from hydraulic or electric or other mechanical source of the injection cylinder(s) 30, displacing the molten polymeric material through the nozzle body 25 and into a waiting vacant injection mold, not shown. The unitary movement of the injection assembly, improved homogenous melt preparation of the non-reciprocation stationary helical plasticating screw 11, precise, independent and instantaneous shutoff of the inside mechanism of the plunger head 13, determination of the mass of the compressible polymeric material with the addition of a mass density sensor which is not shown, exposed to the melt stream, precise seal between the plunger head 13 and pressure vessel 14 and a polymer that moves along one axis from feeding to injection into a mold makes up the improved injection molding process of this invention. Therefore, I claim: