Method for Molding Plastic Materials

Abstract

A method for material handling and mold filling is provided which directs the flow of molten plastic material from an extruder and allocates the molten material to a plurality of nozzles through the use of independently operated, variable valves. The method therefore provides independent streams of molten plastic material having variable temperatures and flow rates or volumes to particular sections or regions of the mold. This independent temperature or flow of molten plastic material facilitates the complete, rapid and accurate filling of the molds, reducing turbulence and other temperature or flow-related imperfections in the finished components. A method of using a multiphase material handling system is also disclosed for expeditious sequential and simultaneous filling and pressing of the mold and extracting the completed component from the system.

Claims

1. A method for sequentially forming of a plurality of molded components from molten plastic material, comprising: positioning at least one first mold component and an affixed receiving table in a first filling position, said at least one first mold component occupying a filling station and said receiving table occupying a pressing station; introducing molten plastic material to a manifold to permit a preselected flow of said molten plastic therefrom; distributing said molten plastic material from said manifold to said at least one first mold component; translating said at least one first mold component and said affixed receiving table from said first filling position to a second extraction position, said at least one first mold component occupying said pressing station and said receiving table occupying an extraction station; pressing said molten plastic material in said first mold component with at least one corresponding second mold component, said at least one second mold component forming a top of said first mold component, said at least one first and at least one second mold components forming a completed molded plastic component; removing said completed molded plastic component from said at least one first mold component with said at least one corresponding second mold component; and translating said at least one first mold component and said affixed receiving table from said second extraction position to said first filling position.

2. A method as described in claim 1, further comprising the step of removing said completed molded plastic component from said receiving table when said receiving table is in said extraction position.

3. A method as described in claim 1, further comprising the step of detecting the condition of said molten plastic material.

4. A method as described in claim 1, further comprising the step of detecting the position of said at least one first mold component and said receiving table.

5. A method as described in claim 4, wherein said translation of said at least one first mold component and said receiving table is electronically controlled based upon said detection of said position of said at least one first mold component and said receiving table in accordance with preselected electronic instruction signals.

6. A method as described in claim 4, wherein the introduction of said molten plastic material is electronically controlled based upon said detection of said position of said at least one first mold component and said receiving table in accordance with preselected electronic instruction signals.

Description

DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a diagrammatic view of the molding control system.

[0024] FIG. 2 is a schematic view of the molten material flow system and molding apparatus.

[0025] FIG. 2a is a diagrammatic side view of the filling operation of a mold.

[0026] FIG. 3a is a side view, partially in section, of a flow controller.

[0027] FIG. 3b is a bottom plan view of a flow controller.

[0028] FIG. 4 is a diagrammatic view of the molding control system including a material handling sequence.

DETAILED DESCRIPTION

[0029] Referring now to FIGS. 1 and 2, the system 10 is controlled by central controller 15. Central controller 15 is comprised of a computing device of a known type, having processor, memory and I/O capabilities. Central controller 15, in addition to human input devices for the purpose of programming and monitoring, has inputs from various sensors throughout system 10. These include temperature sensors 20, extruder flow sensors 25 and, optionally, mold position sensors 30. It is to be specifically noted that system 10 may be adapted for single mold use, in which a single mold is manually positioned for filling and no conveyor or other transport system is necessary. Extruder flow sensors 25 may additionally be positioned in conjunction with an optional accumulator 78 for downstream flow information.

[0030] Central controller 15 includes a variety of outputs, m addition to those intended for human monitoring, programming and control. Heat control circuit 35 is utilized to maintain adequate temperatures in the various components of system 10, as will be more fully described below. Heat control circuit 35 is designed to operate in conjunction with temperature sensors 20 to create a feedback loop for the maintenance of preselected temperatures within system 10. Extruder control circuit 40 is utilized to monitor the operating parameters of the extruder 70. Accumulator control circuit 43 is utilized to monitor the operating parameters of the accumulator 78. Accumulator control circuit 43 and extruder control circuit 40 are designed to operate in conjunction with extruder flow sensors 25. Material handling control circuit 45 is utilized to interface with any mold transport or conveyor 115 and operates in conjunction with mold position sensors 30. Output flow control circuit 50 is utilized to interface and control the flow control system for the molten plastic material as will be described more fully below. Press control circuit 55 is optionally provided to the extent that system 10 is utilized to control the pressing phase of the molding process.

[0031] Material input feed 60 is provided for the introduction of the raw, typically pelletized, plastic materials to the extruder. Typically, material input feed will include some type of hopper system which will permit the bulk loading and storage of the raw materials. While in most cases the frictional operation of the extruder is sufficient to form the molten plastic web of material from the raw pellets, an optional heater circuit 65 is provided. Heater circuit 65 is operated in conjunction with temperature sensors 20, heat control circuit 35 and controller 15. Extruder 70 receives the raw plastic material from material input feed 60 and converts it into the molten web of plastic material. Typically, extruder 70 utilizes an auger within a confined environment to frictionally engage the raw plastic, with or without additional heat, in order to form a web of preselected characteristics, including temperature, viscosity and curing. Extruder flow sensors 75 are provided to monitor the gross flow of the plastic web, as well as any particular characteristics of the plastic material necessary to ensure performance.

[0032] Accumulator 78 provides a variable volume repository for molten plastic material output from extruder 70. Extruder 70 provides a relatively constant flow of such molten plastic material which is temporarily stored in accumulator 78 under controlled temperature and pressure as dictated by accumulator control circuit 43. Accumulator control circuit 43 utilizes extruder flow sensors 25 and temperature sensors 20 at various points within the system 10 as input, regulating flowability and delivery of molten plastic material to the manifold 85. Accumulator 78 may be of any known design, so long as it is adapted to receive the molten plastic material and facilitate its delivery to the manifold 85.

[0033] Central to the operation of system 10 is flow controller 80 and manifold 85. While flow controller 80 and manifold 85 are described and illustrated as particular combinations of components, it is to be specifically understood that each component thereof may be assembled and operated separately. Flow controller 80 receives the molten plastic material from extruder 70 and allocates the molten material to a plurality of nozzles 90 through the use of valves 95. Each nozzle 90 is associated with an independently controlled valve 95 on a one to one basis. Valves 95 are in electronic communication with controller 15 through output flow control circuit 50. Valves 95 are solenoid controlled gate valves which have variable operating parameters, allowing full operational control of the flow there through from 0-100%. Heating components may be optionally added to valves 95 to ensure flowability of the molten plastic material or otherwise independently alter the temperature of the molten plastic material independently flowing through each of valves 95.

[0034] Referring now to FIGS. 2, 2a, 3a, 3b and 4, flow controller 80 and manifold 85 cooperatively provide the flow of molten plastic material having variable flow rates to mold 100. Flow controller 80 receives signals from controller 15 through output flow control circuit 50. Controller 15 is programmed or manually operated to cause valves 95 to open, close or be positioned at an intermediate stage on an individual basis. This permits the independent flow of molten plastic material 105 from each nozzle 90 in varying amounts and/or rates, as diagrammatically illustrated in FIG. 2a, through the use of varying width arrows A. This independent flow of molten plastic material 105 facilitates the complete, rapid and accurate filling of mold 100. Mold 100 is provided with a number of surface features 110, which are diagrammatically represented in a simple manner in FIG. 2a. It is well within the ambit of one skilled in the art to apply the principles identified herein to a mold of higher complexity. In any mold 100 having surface features 110a-d, a varying amount of molten plastic material 105 is preferentially added to mold 100 during the filling phase. Surface features, such as exemplified by surface feature 110c, which will result in a protruding section of the finished component, require a higher volume of molten plastic material 105 in the same filling period as a relatively flat portion of the finished component, exemplified by surface feature 110a. Flow controller 80 is directed to permit higher and lower flow volumes of molten plastic material 105 based upon the mapping of the relevant nozzles 90 and such surface features 110. This rapid and variable volume filling of mold 100 reduces filling time and turbulence within mold 100. Additionally, the uniform filling of mold 100 reduces setting while mold 100 is only partially filled.

[0035] As a matter of practicality, manifold 85 is sized and positioned above mold 100 and manifold face 87, containing the nozzles 90, extends peripherally in all directions to a size at least equal to mold 100, if not larger. A plurality of nozzles 90 are positioned above mold 100, with a density selected based upon the degree of control necessary to fill mold 100. It is to be specifically noted that the number and spacing of nozzles 90 are a design choice and manifold 85 may be designed to correspond with a particular mold 100 or a plurality of molds of varying types and designs. Nozzles 90 are sized and positioned, in conjunction with the flow capacity of valves 95, to provide rapid and even filling of mold 100, reducing the need for lateral flow of molten plastic material 105 from high surface features 110a to low surface features 110b, c. This reduces turbulence and other flow-related imperfections in the finished components.

[0036] Mold 100 may be manually or mechanically positioned below manifold 85 with manifold face 87 facing mold 100. It is to be specifically noted that mold 100, or a plurality of molds 100 may be sequentially located beneath manifold 85, but that one by one manufacturing of finished components is also contemplated. Mold 100 is statically positioned beneath manifold 85 during the filling operation, and there is no need or desire for any motion of the mold 100 during filling. To the extent desired, molds 100 may be positioned beneath manifold 85 by a conveyor 115 or other material handing device, controlled by controller 15 through material handling control circuit 45. In this manner, controller 15 can detect the position of mold 100 by receiving signals from mold position sensors 30. A feedback loop then permits controller 15 to position mold 100 at the correct location with respect to manifold 85 for filling, and move mold 100 to a press or other location subsequent to the filling operation as will be described below with particular reference to FIG. 4.

[0037] In operation, raw plastic material is added to material input feed 60, which then signals controller 15 through material handling control circuit 45 that the system 10 is ready for operation. The controller 15 will also receive signals from extruder 70 through extruder flow sensors 40 that the molten plastic material is flowing properly therethrough. Temperature sensors 20 permit controller 15 to monitor the condition of the flow and apply heat as necessary with heater 65 through heater control circuit 35. Controller 15 is programmed with a flow profile corresponding the appropriate mold 100, which is positioned for filling by system 10. Mold position sensors 30 may also be adapted to detect the type or design of the mold and signal the same to controller 15, identifying the appropriate flow profile for use with mold 100. Controller 15 applies the appropriate flow profile to flow controller 80 through output flow control circuit 50. Flow controller 80 directs respective valves 95 to open to a position corresponding with the appropriate volume and/or rate of flow of molten plastic material 105 and directs molten plastic material 105 into mold 100, positioned below manifold 85. Mold 100 is then directed, manually or automatically, away from manifold 85 and the next mold 100 is positioned for filling.

[0038] Referring now to FIG. 4, extruder 70 generates a flow of molten plastic material which is temporarily stored in and dispensed from accumulator 78 as monitored by controller 15 through extruder control circuit 40. Accumulator 78 accepts the molten plastic material and maintains it in accordance with preselected temperature and pressure parameters. Controller 15, in accordance with a preselected flow profile, signals accumulator 78, through accumulator control circuit 43, to release a volume of molten plastic material to manifold 85. Manifold 85, also in conjunction with said preselected flow profile, directs the molten plastic material 105 into mold 100, positioned below in filling station I. Mold 100 and extraction table 125 are mechanically affixed together to move as a single unit. Therefore, when mold 100 is positioned in filling station I, extraction table 125 is positioned in pressing station II. When mold 100 is positioned in pressing station II, extraction table 125 is positioned in extraction station III. At the time of filling, the mold 100/extraction table 125 unit is positioned in accordance with the diagram A portion of FIG. 4, a first filling position.

[0039] The volume of molten plastic material 105 is distributed within mold 100 and upon completion, mold 100 is moved to pressing station II, in accordance with the diagram B portion of FIG. 4, or from a first filling position to a second extraction position. Mold 100, being filled with molten plastic material 105 is moved to pressing station II, as detected by mold position sensors 30. Press 120 is constructed of any known type, and is typically a hydraulic or mechanical press. Operation of press 120 is controlled by controller 15 through press control circuit 55. Upon detection of mold 100 in pressing station I through mold position sensors 30, press 120 is operated to engage upper mold 100 with mold 100, encasing molten plastic material 105 therein. Mold 100 and/or upper mold 100 may be equipped with cooling or other temperature control means to reduce the temperature of mold 100, or mold 100 may be allowed to return to a set temperature by uncontrolled means. In either event mold 100 is equipped with appropriate temperature sensors which may be manually observed or interfaced with controller 15 through heat control circuit 35. Upon reaching a preselected target temperature, press 120 disengages upper mold 100 from mold 100. While the completed component may be permitted to rest within mold 100 for extraction, in the preferred embodiment, the completed component 105 is retained by upper mold 100 and raised out of mold 100.

[0040] At the point that completed component 105 is removed from mold 100, mold 100 is returned to filling station I from pressing station II through the action of conveyor 115 through material handling control circuit 45, and diagrammatically from diagram B to diagram A in FIG. 4, or from the second extraction position to the first filling position. Upon detection by mold position sensors 30 that mold 100 has returned to filling station I and that affixed extraction table 125 has returned to pressing station II, system 10 will initiate another filling sequence for mold 100 as described above. Simultaneously, press 120 will release completed component 105, which will either drop or be lowered in accordance with arrow C to extraction table 125. After the initial loading sequence, while conveyor 115 is the position indicated by diagram B of FIG. 4, extraction table 125 is positioned in extraction station III with completed component 105 loaded thereon. Completed component 105 may be removed from extraction table 125 by any appropriate manual or automatic material handling procedure. It is to be specifically noted that while an automated material handling system is disclosed, all of the steps associated with FIG. 4 may be performed manually.

[0041] The terms and expressions which have been employed herein are used as terms of description and not as limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that vanous modifications are possible within the scope of the invention claimed. Although particular embodiments of the present invention have been illustrated in the foregoing detailed description, it is to be further understood that the present invention is not to be limited to just the embodiments disclosed, but that they are capable of numerous rearrangements, modifications and substitutions.