WO2002036323A1

WO2002036323A1 - Co-injection valve-gate bushing with separate material flow paths

Info

Publication number: WO2002036323A1
Application number: PCT/US2001/046230
Authority: WO
Inventors: Eric J. Seres, Jr.; Scott R. Greb
Original assignee: Incoe Corp
Current assignee: Incoe Corp
Priority date: 2000-10-31
Filing date: 2001-10-23
Publication date: 2002-05-10
Anticipated expiration: 2003-04-30
Also published as: WO2002036323B1; AU2002228761A1; WO2002036323A9

Abstract

Apparatus and methods for co-injection of plastic materials. Two plastic materials are injected through separate passageways (44, 48) in a bushing member (12) into the mold cavity (26). A pin member (60) positioned in a third passageway (46) in the mold bushing controls the introduction of the two plastic materials through an orifice (42) and into the cavity. An actuator mechanism (71) with pressure actuated piston members (70, 72) controls the movement of the pin member.

Description

CO-INJECTION VALVE-GATE BUSHING WITH SEPARATE MATERIAL FLOW PATHS

Technical Field

The present invention relates to pin-type valve-gate bushing devices for use with co-injection molding systems.

Background ofthe Invention

There are many processes and techniques today for co-injection molding. Such systems are shown, for example, in U.S. Patent Nos...5, 650, 178, 5,891,381, and^" 6,062,840. Co-injection systems are often also caliefl co-extrusion systems. In general, co-injection or ^" - ^~ extrusion systems inject two different materials, typically an inner core material and an outer skin material, into a single or multiple-cavity mold. The outer skin material typically enters the cavity first and the core material is injected into the center of the skin layer forcing- the skin material against the walls of the cavity. Co-injection systems enable the use of less expensive materials as the core material, and thus can significantly lower the cost of molded products .

Summary ofthe Invention

It is an object of the present invention to provide an improved apparatus and system for the co- injection of plastic materials. It is also an object of the present invention to provide a co-injection system which utilizes a valve-gate bushing.

It is another object of the present invention to provide an improved co-injection molding system which has less waste and improved efficiency relative to the use of plastic materials.

These objects are met with the present invention which, in general, provides a co-injection process utilizing a valve-gate bushing with separate material flow paths into the mold cavity. A valve-gate bushing is provided with a pin-type material shutoff mechanism. The bushing has two separate passageways^ for flow of the core and skin materials into the mold cavity, as well as a separate passageway for the v kve . pin. The pin-type valve-gate device easily and effectively opens and closes the flow of the two plastic materials into the mold cavity as desired.

In particular, the bushing has an actuation mechanism which operates a pin member to selectively open and close the bushing orifice, as well as the two plastic material passageways. The movable elongated pin member is movable between at least three positions. A piston-type actuation mechanism, which is operated either hydraulically, electrically, pneumatically, or the like, selectively moves the pin member longitudinally to open and close the bushing orifice and the two plastic material passageways. The end of the pin member mates with the orifice in the end of the bushing or nozzle member creating a valve or "gate" for entry of the plastic materials into the mold cavity. The pin member can also be moved longitudinally away from the orifice in order to allow selective passage of the two plastic materials forming the skin and core of the molded part .

In a preferred embodiment, a pair of movable piston members are positioned in the actuation (control) mechanism. The- elongated pin member is adjustably attached to one of the piston members. The two piston members are moved together or independently, thus resulting in the desired movement of the pin member relative to the orifice and the two plastic material passageways.

These and other objects, features, and- benefits of the invention will become apparent from the following description of the invention, when taken. together in view of the accompanying drawings and appended claims.

BriefDescription OfThe Drawings

FIGURE 1 schematically illustrates a preferred embodiment of the present invention; FIGURES 2 and 3 are plan and side views, respectively, of the embodiment shown in Figure 1; and FIGURES 4-6 illustrate the three main positions of the piston and pin members, and also depict the operation of the preferred embodiment of the invention.

Best Modes For Carrying Out The Invention

Figures 1-3 illustrate a preferred embodiment of the present invention, while Figures 4-6 illustrate its use in a co-injection plastic molding process. The inventive system is referred to generally by the reference numeral 10 in the drawings.

The system 10 includes a bushing member 12, a manifold 14, and a cylinder or block member 16. The mold bushing 12, which is sometimes referred to as a "nozzle," is mounted in a cavity 18 in a mold 20. The mold 20 can be of any conventional type and has a first plate member 22 in which the bushing 12 is at least partially positioned, as well as a second plate member 24 which has a mold cavity 26 therein. The mold cavity 26 is formed or machined in the size and shape of the final part to be produced, as is well known in the art- Also, it is understood that the bushing and cavity ca be positioned in one plate. ..-_.- _. The sprue bushing or nozzle 12 has a metal body or shank member 30, an external heater member 32, and a screw on tip member 34. The tip member 34 has a forward end 36 which is adapted to fit within the end of the recess 18. The end of the recess 18 forms an orifice or "gate" 42 through which the plastic material flows into the mold cavity 26.

The body member 30 has three elongated passageways 44, 46, and 48 formed therein. Passageway 44 is for injection of the core material 50 into the cavity, while passageway 48 is for injection of the plastic skin material 52 into the mold cavity. Passageway 46 is centrally located in the body member 30 and is provided for pin member 60, which is positioned in it. The pin member 60 has an upper end 62 and a lower end_. 64 and is positioned in the passageway 46. The pin member 60 is movably positioned inside the elongated passageway 46 in the body 30 of the bushing 12. The upper end 62 of the pin member 60 is secured to piston member 70 in the actuator mechanism 71 positioned in the block member 16. The actuator mechanism 71 includes a pair of piston members, 70 and 72, which are slidably positioned in a cylindrical cavity 74. The upper end 62 of the pin member 60 is threadedly attached to a threaded internal bore 76. The open end 78 of the bore 76 allows adjustment of the position of the pin member 60 relative to the piston member 70 by use of an appropriate tool, such as a- screwdriver. If desired, a cap or plug member 80 can be provided to cover the openings in the block and. protect the open end 78 from dust, oil and other undesirable matters.

The cavity 74 is enclosed by a cover or cap member 82. The cap member 82 is fastened to the block member 16 by a plurality of bolts, screws, or other fasteners 84, only one of which is shown in the drawings .

Appropriate seals are provided in the actuator mechanism 71 in order to allow accurate movement of the piston members 70 and 72 in the chamber 74 without leakage of pressurized fluid. A plurality of seal members are provided. The seal members are generally designated by the letter "S" in Figure 1 and can be of any conventional type used with pressurized and/or hydraulic systems known today. The piston members 70 and 72 are slidably positioned in the chamber cavity 74 and used to operate the movement of the pin member 60 in the bushing member 12. A pressurized fluid, such as a liquid or gas, is introduced into portions or areas of the chamber cavity 74 by channels 86, 88, and 90, as desired, and provide movement of the pistons 70 and 72. The precise movement of the piston members and resulting movement of the pin member 60 are described in more detail below.

The bushing member 12 is attached to or secured to the manifold 14 in any conventional manner. Typically, the manifold 14, together with the mold plates 22 and 96 are tightly clamped together. The manifold 14 has passageway 100 for passage of the- plastic core material from an injection molding machine. "I -B" into the bushing 12 and, in turn, into the moi . cavity 26. The manifold 14 also has passageway 102 for passage of the skin material from an injection molding machine "I -A" and into the bushing 12 and mold cavity 26. The passageways 100 and 102 are aligned with passageways 44 and 48, respectively, in the bushing member 12. Appropriate seals are provided in grooves

104 at the interface between the body member 30 of the bushing 12 and the lower surface of the manifold member 14.

The heater member 32 can be of any conventional type and is used to maintain the plastic material in the passageways 44 and 48 in the bushing 12 in a molten condition. The heater member 32 is typically a resistance-type heating member or element and is energized through lead or connector member 33. The tip member 34 is preferably threadedly secured to the lower end of the body member 30 of the bushing member 12. An insert member 36, secured by tip member 34 has connecting passageways 44A and 48A, which are aligned with the passageways 44 and 48 in the body member 30. The lower end 44B of passageway 44A connects with and opens into the passageway 46 in which the pin member 60 is positioned. Similarly, the lower end 48B of passageway 48A connects to and opens into the passageway 46. The ends 44B and 48B open into the central passageway 46 at positions which are spaced longitudinally or axially relative to one another. This allows entry of the skin and core material into the central passageway 46 and thus through the orifice- 42 and into the mold cavity 26 separately as desired during the molding process. ••-;_--_. The entry of the plastic material into the mold cavity is controlled by movement of the pin member 60. In this regard, as shown in Figures 4, 5, and 6., the piston members 70 and 72 in the actuator mechanism 71 are operated to longitudinally move the lower end 64 of the pin member 60 in at least three positions. Hydraulic or pneumatic fluid or gas is supplied to the passageways 86, 88, and 90 from one or more conventional hydraulic or pneumatic power sources (not shown) . If desired, the passageways can all be connected to the same pressure source and selectively utilized by an appropriate valving and control system.

Passageways 86, 88.. and 90 are machined or provided in the cylinder^' block 16 and cover member 82 in the positions shown in Figures 1 and 4-6, although it is understood that they can be provided in other locations within the skill of persons in the art. The lower end 64 of pin member 60 is adapted to mate with the opening 42 (orifice) of the bushing 12 and form a valve-gate mechanism. When the system 10 is used, the valve or gate into the mold cavity is initially its closed position, as closed in Figure 4. In this condition, plastic material present in the manifold 14 and bushing 12 is prevented from entering into the mold cavity. In order to arrive at the closed position, pressurized fluid is introduced into cavity 74 through passageway 88. This causes the piston member 70 to be- moved toward the lower end 74A of the cavity 74, thereby causing the lower end 64 at the pin member 60r- to enter into and close the orifice 42. -. »

Thereafter, the plastic material which ---is - used to form the skin of the molded product is allowed to enter the mold cavity. This is shown in Figure 5 in which the lower end 64 of the pin member 60 is longitudinally moved in order to allow plastic material in passageways 48, 48A and 48B to enter the central cavity 46 and pass into the mold cavity 26. In order to move the pin member 60 into this position, pressurized fluid is introduced through passageway 86 forcing the piston member 70 in a longitudinally upward direction. In this regard, in order to prevent the piston member from moving further in the chamber 74, pressurized fluid is introduced at the same time through passageway 90 forcing and holding the piston member 72 against surface or shoulder member 73 in the chamber 74. Also at the same time, the pressurized fluid in cavity 74 earlier introduced through passageway 88 is relieved or exhausted in order to allow ease of movement of the piston member 70.

In the next step of the co-injection or co- extrusion process, the pin member 60 is raised an additional amount in the central passageway 46 in order to allow passage of the plastic core material into the mold cavity. This is shown in Figure 6. In this position, the end 64 of the pin member 60 is raised sufficiently to allow injection of plastic material in passageways 44, 44A and 44B into the central passageway 46 and into the mold cavity. In order to conduct this step in the molding process, pressurized fluid is- continued to be introduced through passageway 86. At the same time, pressurized fluid in chamber 74 which. had been provided through passageway 90 is relieved or exhausted through passageway 90. In this manner, pistons 70 and 72 are both moved longitudinally upwardly as viewed in Figure 6 which, in turn, pulls the pin member 60 in an upward direction, opening passageway 44B.

As shown in Figure 1, the molded part in accordance with the present process, has an outer skin layer 52 and an inner core layer 50. After the molding process is complete, the molded part is allowed to cool in the mold until it becomes solid and hard. Thereafter, the mold is opened and the formed part is ejected. Thereafter, the cycle is repeated and additional co-extruded molded parts are formed.

The specific pressures utilized and process steps . for the co-injection molding process are well- known in the art and any conventional times, temperatures, and plastic materials can be utilized.

Upon entering the mold cavity, the skin material will develop a flow front through the cavity toward the end walls thereof. As the skin material contacts the cold walls of the mold, it begins to solidify, developing a solid outer layer. Before skin material reaches the end of the cavity, however, the core material is injected into the part to form the core. The core material develops a second flow front and pushes the skin material ahead of it. The core material expands and pushes the skin material outwardly- until the entire mold cavity is filled. . »

An advantage of co-injection molding is t-Jie . use of a core material having a different material than the skin material which appears visible on the molded part. Co-injection enables the use of less expensive materials as the core material, and can lower part cost substantially. In accordance with standard injection molding techniques, after the requisite amounts of plastic material are introduced into the mold, the pressures are maintained to compensate for any volumetric shrinkage of the plastic . as it cools and solidifies. Also, for cooling, the mold members 12 and 24 are typically cooled by circulation of a coolant through appropriate channels or passageways (not shown) which assist in solidifying the plastic.

Virtually all the members of the system 10, with the exception of the seals, are made from a metal material, such as steel. Of course, any other conventional materials used in injection molding systems can be utilized so long as they meet the requirements of the present invention.

As shown in Figures 1-3, the plastic materials are introduced into the manifold 12 from two different injection molding machines, IM-A and I -B. As indicated, any conventional injection molding machine can be utilized for this system. Injection molding machine IM-A is used to inject the skin material into the manifold 14 for formation of the molded part in the mold cavity 26. For this purpose, adapter member 110 is used to orient injection molding- machine IM-A relative to the plate member 96. Also,_.- a. nozzle bushing 112 is utilized to permit passageway. of, the plastic material from the injection molding machine into the passageway 102 in the manifold member 14. In this regard, if the nozzle seat has a significant length, it is preferable to use a heater member, such as the coil heater member 114, in order to maintain the plastic material in a molten condition in the passageway 116 in the nozzle seat 112. The heater member 114 is typically a resistance-type heating member or element and is energized by a connector or lead 118. The injection molding machine IM-B is similarly attached to and arranged with the system 10. As shown in Figures 2 and 3, the injection molding machine IM-B is connected to mold plate 93 through adapter member 120 and nozzle seat 122. The nozzle seat 122 has a heater member 124 thereon. Plastic injected through injection molding machine IM-B is injected through passageway 126 in the nozzle seat 122 and into the passageway 100 in the manifold 14. From there, the material is passed through bushing member 12 and into the mold cavity. In this regard, in the system shown in Figures 1-3, a two-cavity molding system is utilized. Thus, the materials entering the passageways 100 and 102 are split or divided and travel in two directions into two identical bushing members 12 (only one of which is shown in Figure 1) . While the invention has been described in connection with one or more embodiments, it is to be understood that the specific mechanisms and techniques- which have been described are merely illustrative of_ the principles of the invention. Numerous modifications may be made to the methods and apparatus described without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

What Is Claimed Is:

1. A valve-gate mechanism for use in a co- injection molding process, said mechanism comprising: a bushing member having a first end and a second end, said bushing member having a first longitudinally extending passageway extending from said first end to said second end, a second longitudinally extending passageway extending from said first end and in communication with said first passageway adjacent said second end, and a third longitudinally extending passageway extending from said first end and in communication with said first" passageway adjacent said second end and at an axial spaced location from the communication of said second passageway with said first passageway; a pin member positioned in said first passageway and having an upper end and a lower end; and an actuating mechanism for controlling the longitudinal movement of said pin member in said first passageway, said upper end of said pin member being connected to said actuating mechanism; said actuating mechanism being operable to move said pin member into at least three positions including a first position wherein only plastic material in said second passageway is allowed to enter said first passageway, a second position wherein plastic material from both said first and second passageways are allowed to enter said first passageway, and a third position wherein no plastic material from either the second or third passageway is allowed to enter said first passageway.

2. The valve-gate mechanism as set forth in claim 1 wherein said actuating mechanism comprises a first pressure actuated piston member and a .second pressure actuated piston member, and wherein said pin member is connected to said first piston member.

3. The vaive-gate mechanism as set forth in claim 2 further comprising means for pressure actuating said first and second piston members.

4. The valve-gate mechanism as set forth .in. claim 2 further comprising a block member having- A . cavity chamber and wherein said first and second piston members are movably positioned in said cavity chamber.

5. The valve-gate mechanism as set forth in claim 2 wherein said pin member is adjustably connected to said first piston member.

6. A system for co-injection molding, said system comprising: a mold having a mold cavity; a first . source of a first molten plastic material for being supplied into said mold cavity; a second source for a second molten plastic material for being supplied into said mold cavity; a bushing member positioned in said mold and having a first passageway and a first valve member for supplying the first and second molten plastic materials into said mold cavity; an actuating mechanism having a fluid cavity therein and a plurality of passageways in fluid communication with said fluid cavity; a second passageway in said bushing member for entry and passage of a first molten plastic material through said bushing, into said first passageway, and into said mold cavity; a third passageway in said bushing member for entry and passage of a second molten plastic material through said bushing, into said first passageway, and into said mold cavity; a pin member movably positioned in said first- passageway and having a second valve member for mating with said first valve member to form a first valv.e . means; and a first piston member connected to said pin member and movably positioned in said cavity in said actuating mechanism; wherein said actuating mechanism is adapted to control the movement of said pin member in order to regulate the flow of plastic materials in said second and third passageways and into said mold cavity.

7. The system of claim 6 further comprising a manifold member positioned between said bushing member and said actuating mechanism, said manifold member having fourth and fifth passageways for introduction of the first- and second plastic materials into said bushing member.

8. The system of claim 6 further comprising sealing members for sealingly positioning said piston member in said fluid cavity.

9. The system of claim 6 further comprising a second piston member in said cavity.

10. A method for injecting two plastic materials into a mold cavity, said method comprising the steps of: introducing a first plastic material into a first passageway in a bushing member; introducing a second plastic material into a^" second passageway in said bushing member; introducing said first plastic material into said mold cavity from said bushing member; introducing said second plastic material into said mold cavity from said bushing member; and selectively preventing the introduction of said first and second plastic materials into said mold cavity by a movable pin member positioned in a third passageway in said bushing member.