SKORCH THOMAS (US)
SMITH MICHAEL B (US)
SKORCH THOMAS (US)
| DE4041799A1 | 1992-07-02 | |||
| US4805991A | 1989-02-21 |
| 1. | A manifold for an injection molding system comprising: a cold runner for delivering material into a cavity of a mold; a first valve gate coupled to said cold runner for delivering a first injection of material into said cold runner and creating a first flow of said first injection of material through said cold runner ; a second valve gate coupled to said cold runner for delivering a second injection of material into a center region of said cold runner to combine with said first flow of said first injection of material to form a combined melt comprising an outer core melt of said first injection of material and an inner core melt of said second injection of material prior to injection into said cavity of said mold. |
| 2. | A manifold as set forth in claim 1 wherein said cold runner includes at least two inlets each for passing material between one of said first and second valve gates and said cold runner. |
| 3. | A manifold as set forth in claim 2 including at least two hot runners each for delivering molten material through one of said first and second valve gates to one of said inlets in said cold runner. |
| 4. | A manifold as set forth in claim 3 wherein each of said hot runners includes an inlet for receiving preheated material therethrough and an outlet coupled to one of said first and second valve gates for selectively controlling the delivery of said first and second injections of material through said respective inlets into said cold runner. |
| 5. | A manifold as set forth in claim 4 wherein each of said first and second valve gates includes a drop operatively coupled to said respective inlet in said cold runner for passing said first and second injections of material through said drop into said cold runner. |
| 6. | A manifold as set forth in claim 5 wherein said drops in said first and second valve gates each include a pin movable between a closed position seated within said drop to prevent delivery of said first and second injections of material, respectively, into said cold runner and an open position to allow delivery of said first and second injections of material into said cold runner. |
| 7. | A manifold as set forth in claim 6 wherein said pin in said second valve gate, while in said closed position, extends into said central region of said cold runner, so that upon retraction of said pin to said open position, said second injection of material is delivered into said central region of said cold runner and into an inner region of said first flow of said first injection of material to form said combined melt. |
| 8. | A manifold as set forth in claim 7 wherein said inner core includes a different composition of material than said outer core. |
| 9. | A manifold as set forth in claim 8 wherein said inner core includes reinforcing materials for reinforcing a molded component formed in said cavity of said mold. |
| 10. | A manifold for a coinjection molding system comprising: a mold having a mold cavity and at least one cold runner, said at least one cold runner having a first inlet at an upstream end, an outlet at a downstream end and a second inlet intermediate said upstream and downstream ends, said outlet communicating with the mold cavity, at least two injection units for delivering a first and second plasticized melt, and a manifold for communicating between said injection units and said mold cavity, said manifold comprising at least two hot runners each having an inlet at an upstream end, and an outlet at a downstream end, one of said hot runner inlets communicating with one of said injection units for receiving the first plasticized melt, a first hot runner outlet having a first valve gate for opening and closing a flow of said first plasticized melt through said hot runner, said first hot runner outlet communicating with said first inlet of said at least one cold runner, the other of said hot runner inlets communicating with the other of said injection units for receiving the second plasticized melt, a second hot runner outlet having an extended valve gate for opening and closing a flow of said second plasticized melt through said other hot runner, said second hot runner outlet communicating with said second inlet of said at least one cold runner, said extended valve gate having a pin extending into said cold runner whereby upon retraction of said extended valve gate pin to open said flow of said second plasticized melt, said second plasticized melt is introduced in an inner region of said flow of said first plasticized melt. |
Background of Invention WO 01/62488 discloses a method of making a co-injected molded vehicle component such as a fascia. The method provides for the injection of two plastic materials during the same molding process. A first material is injected into the mold through a first gate and then a second material is injected at a second gate.
As disclosed in WO 01/62488, the two plastic materials are mixed in a hot runner manifold as described in United States Patent No. 6,062, 840. This arrangement leads to a problem of consistency and contamination of each of the plastic materials on subsequent shots.
The nozzle of the hot runner must be cleaned out with the skin material after the core material is injected to ensure a clean nozzle for the next shot. This cleaning requires more material to eliminate contaminated materials, restricting the amount of re-ground material or lower cost core that can be re-used in subsequent shots which results in a lower cost savings.
It remains desirable to provide a dual drop co-injection manifold that allows injection of two plastic materials through separate respective hot runners and gates into a single cold runner to form a combined melt prior to injection into a cavity of a mold to minimize or eliminate cleaning of the hot runner between shots, as required in conventional dual injection manifold designs.
SUMMARY OF INVENTION According to one aspect of the invention, a manifold for an injection molding system is provided. The manifold includes a cold runner for delivering material into a cavity in a mold. A first valve gate is coupled to the cold runner for delivering a first injection of material into'the cold runner and creating a first flow of the first injection of material through the cold runner. A second valve gate is coupled to the cold runner for delivering a second injection of material into the center of the cold runner to combine with the first flow of the first injection of material to form a combined melt having an outer core melt of the first injection of material and an inner core melt of the second injection of material prior to injection into the cavity of the mold.
DESCRIPTION OF THE DRAWINGS In drawings which illustrate preferred embodiments of the present invention, Figure 1 is a schematic plan view of the manifold arrangement of the present invention; Figure 2 is a schematic elevational view of a dual manifold arrangement similar to the manifold arrangement of Figure 1; and Figures 3-5 are schematic views of the sequence of co-injection of the present invention.
DESCRIPTION OF THE INVENTION Referring to Figure 1, there is schematically illustrated a manifold 12 and a mold 14. The manifold 12 includes at least two cold runners 16, each having two inlets 18,20 and an outlet 22.
The mold 14 includes at least two mold portions that cooperate together to define a mold cavity 24, as known by those of ordinary skill in the art. The mold cavity 24 has a predetermined shape to define the part to be molded. The cavity 24 has at least two inlets 26 that communicate with the cold runners 16 of the manifold 12.
The schematic drawing of Figure 1 illustrates two cold runners 16. It is apparent to those skilled in the art that more than two cold runners 16 may be incorporated, depending upon the design of the part to be molded. Further, sequential valve gating techniques as taught by United States patent No. 5,762, 855 may also be employed and are incorporated herein by reference.
Referring to Figure 2, a manifold 12 for a dual injection is illustrated. The manifold 12 has a body 50 having at least two hot runners 52,54. Each hot runner 52,54 has an inlet 56,58 for receiving an injection end of an injection unit (not illustrated). Each hot runner 52,54 has an outlet 60,62. Each outlet 60,62 has an independent heated manifold drop 28,30 that communicates with the inlets 18,20, respectively, of the cold runners 16. The drop 30 is provided with an extended valve gate pin 32 that extends into the cold runner 16 when in a closed condition and is movable to an open position to allow flow of molten material through the drop 30. Drop 28 has a drop pin 34 of conventional length. Each drop pin 32,34 is operatively controlled by a driver, as is conventional in the art.
In operation, the valve gate pin 34 of the first drop 28 will be opened delivering a first plasticized melt 36 into the cold runner 16. The front 38 of the plasticized melt 36 will flow by and around the extended valve gate pin 32 of the second drop 30. Once the flow front 38 of the first plasticized melt 36 has traveled downstream of the extended valve gate pin 32, the valve gate pin 32 of the drop 30 is retracted to the open position to allow flow of a second plasticized melt 40 from the drop 30 to a central region of the cold runner 16, wherein the second plasticized melt 40 displaces the first plasticized melt in an inner or core region of the flow of first plasticized melt 36. The two plasticized melts 36,40 are co-injected into the mold cavity 24.
The combined melts 36,40 will comprise an inner core melt 40 and an outer melt 36.
Once the mold cavity 24 has been filled, the drop pins 28,32 are moved back to the closed condition terminating the flow of plasticized melt. The mold 14 can be opened and the molded part removed, together with the solidified melt in the cold runners 16. The excess material is removed from the molded part and can be re-ground and re-introduced into one of the extruders. Preferably, the inner core melt 40 will comprise material from both a virgin source and a re-ground source and the outer melt 36 will comprise material from only a virgin source.
Optionally, reinforcing materials such as glass fibers, nano-particles and the like can be added to the inner core melt 40 to improve strength and flex modulus.
The above-described embodiment of the invention is intended to be an example of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention as defined by the attached claims.