초록 ▼

The invention relates to an injection mechanism for molding plastics, comprising at least one injection bushing, at least one lower needle valve, which is supplied by the injection bushing with molten plastics and opened by the pressure of the molten plastics during injection, further comprising hea

The invention relates to an injection mechanism for molding plastics, comprising at least one injection bushing, at least one lower needle valve, which is supplied by the injection bushing with molten plastics and opened by the pressure of the molten plastics during injection, further comprising heating means and cooling means adjacent to the flow path of the plastics, control means for maintaining the plastics at an adjusted temperature, further control means for injecting the molten plastics into at least one mold cavity via a corresponding injection aperture, and for the closing off the mold cavity after finishing the injection, wherein for improving this mechanism, especially for facilitating very small distances between injection openings, only one plunger within a heated distributor block is provided, which actuates several needle valves, situated at different locations within the distributor block, for supplying the molten plastics to the mold cavity via one single injection bushing, an injection nozzle and several lower injection openings.

대표청구항 ▼

1. A mechanism for injecting plastics from an injection molding machine into one or more mold cavities via one or more gates in said one or more mold cavities, said mechanism comprising: an injection bushing for receiving molten plastic from said injection molding machine; more than one injectio

1. A mechanism for injecting plastics from an injection molding machine into one or more mold cavities via one or more gates in said one or more mold cavities, said mechanism comprising: an injection bushing for receiving molten plastic from said injection molding machine; more than one injection nozzle for injecting molten plastic into said one or more mold cavities, each of said nozzles having one or more nozzle conduits therethrough for passage of molten plastic, each said nozzle conduit terminating in a nozzle aperture positioned immediately opposite one of said mold cavity gates; a distributor block for providing flow paths for the molten plastic between said receiving bushing and said injection nozzles, said distributor block including distributor channel means communicating with said nozzle conduits, said injection nozzles being connected to said distributor block; means for maintaining the molten plastic at an adjusted temperature; means for injecting the molten plastic from said injection bushing through said distributor channel means and said nozzle conduits into said mold cavity gates; a needle valve positioned in each of said nozzle conduits for closing each respective mold cavity gate when moved longitudinally outwardly from said nozzle aperture; a guide bushing slideably mounted for longitudinal movement in said distributor block opposite each said nozzle conduit, each said guide bushing having the end of one of said needle valves remote from said nozzle aperture fixedly mounted therein, each said guide bushing also having a surface area exposed to the molten plastic being injected through said distributor block whereby the pressure of the molten plastic when being injected by said injection means tends to move said guide bushing away from said nozzle aperture thereby moving said needle valve longitudinally and opening said mold cavity gate; a chamber in said distributor block; and, one plunger slideably mounted in said distributor block chamber and connected to several of said guide bushings and thereby to their respective needle valves for moving said needle valves longitudinally outwardly to close their respective mold cavity gates, said plunger being actuated by fluid pressure and being adapted for longitudinal movement in the same direction as said needle valve to which said plunger is connected. 2. The mechanism of claim 1 and including means within each said guide bushing and said plunger for adjusting the fixed longitudinal position with respect to said guide bushing of said needle valve mounted in said guide bushing. 3. The mechanism of claim 2 wherein said adjusting means comprises adjustable screws and lock screws. 4. The mechanism of claim 1 wherein said distributor block includes a removable cover for providing access to said distributor block chamber and said plunger contained therein. 5. The mechanism of claim 1 wherein each of said guide bushing includes means about the sides thereof for collecting leakage of molten plastic from said distributor channel means. 6. The mechanism of claim 5 wherein: said plunger and said distributor block chamber define a first space within said chamber above said plunger and a second space below said plunger, said fluid pressure for actuating said plunger being applied in said first space; a drainage channel in said distributor block connected to each said leakage collecting means of each said guide bushing for draining molten plastic leakage from said guide bushing; and, an exhaust channel in said distributor block connected to said second space of said chamber and said drainage channel whereby fluid expelled from said second space causes a partial vacuum in said drainage channel thereby assisting in drainage. 7. The mechanism of claim 1 wherein: each said guide bushing includes a collar about the periphery thereof, said collar being located at the end of each said guide bushing exposed to the molten plastic whereby the surface area of each said guide bushing exposed to the pressure of the molten plastic is increased, the wall of said distributor block at which each said guide bushing is mounted including an annular recess for said collar, each said collar and annular recess cooperating to provide a positive stop against said needle valve of each respective guide bushing from opening too far. 8. The mechanism of claim 1 wherein said plunger is actuated pneumatically. 9. The mechanism of claim 1 wherein said plunger is actuated hydraulically. 10. The mechanism of claim 1 wherein said plunger includes about the periphery thereof a gasket for providing a seal between said plunger and the wall of said distributor block chamber. 11. The mechanism of claim 10 wherein: said plunger includes a shoulder in the peripheral wall thereof; the wall of said distributor block chamber includes a seat adapted to receive said plunger shoulder; said plunger shoulder being adapted to contact said seat after being actuated by said fluid pressure such that the fluid cannot pass said plunger shoulder and said seat in the event of leakage around said plunger gasket; and, the peripheral wall of said plunger and the wall of said distributor block chamber having a close fit thereby providing a third barrier against fluid leakage. 12. The mechanism of claim 4 wherein said plunger is composed of two parts forming an integral unit which can be removed and installed in said distributor block chamber through said removable cover. 13. The mechanism of claim 7 wherein each said guide bushing has a large ratio of length to diameter and a close fit with the wall of the distributor block at which said guide bushing is mounted thereby tending to prevent leakage of molten plastics. 14. The mechanism of claim 1 wherein said plunger and each said guide bushing have been provided with corresponding flat spots so that the guide bushing can be prevented from turning during assembly and disassembly. 15. The mechanism of claim 1 wherein said injection nozzles are each provided with a heating element having a thermocouple, the part of each said nozzle containing said one or more nozzle conduits being made from highly conductive material. 16. The mechanism of claim 1 wherein said distributor channel means are coated with a protective surface layer for processing corrosive plastics. 17. The mechanism of claim 1 and including adjustable fixed needles in one or more of said nozzle conduits of one or more of said injection nozzles, each fixed needle having a point positioned in its respective mold cavity gate for preventing a molded product from receiving an injection spot. 18. The mechanism of claim 1 wherein each said nozzle includes means for properly aligning said nozzle with respect to said one or more mold cavity gates and for insulating said nozzle with respect to said one or more mold cavities. 19. The mechanism of claim 1 wherein each said nozzle conduit includes therein at said nozzle aperture projecting points for engaging said needle valve in said nozzle conduit for assisting in centering said needle valve in said nozzle aperture. 20. The mechanism of claim 1 wherein at least one injection nozzle includes more than one nozzle conduit, each of said nozzle conduits having individual locating and centering means for properly aligning each said nozzle conduit with respect to its respective mold cavity gate and for forming a closure between said nozzle conduit and its respective mold cavity gate to prevent leakage of plastic, said injection nozzle also including an overall locating and centering means for said nozzle enclosing all said individual locating and centering means for properly aligning said nozzle with respect to said one or more mold cavity gates and for insulating said nozzle with respect to said one or more mold cavities.