Basic valve gate hot runner injection molding systems typically include a resin distribution system, plates that enclose the distribution system, nozzles that direct the outflowing resin to cavities for molding, and actuation hardware that opens and closes the resin flow path of a given nozzle into its respective cavity. A valve pin provides the resin flow path gating function. The valve pins are typically connected and secured to a piston in a way that does not permit the valve pin to move laterally or independently of the lateral position of the piston. The piston rides within a cylinder chamber contained in a backing plate, as shown in
Since the manifold is a heated component, feature axial positions change due to thermal expansion as the manifold temperature increases from room temperature to its operating temperature required to melt resin. As the system components expand due to the increased operating temperatures, the components can become misaligned. The misalignment is problematic in hot runner systems because as the valve pin becomes misaligned, due to the thermal expansion and movement of the manifold, the valve pin experiences increased side loading and lateral stress. The increased loading and increased stress may damage the valve pin resulting in undue weepage or loss of melted resin from the distribution system. The thermal expansion creates an unresolved conflict: to best seal resin from escaping the runner system, the stem must be aligned to the manifold bushing while to best seal the actuation system, the stem and piston must be aligned to the cylinder. In a standard arrangement, these two conditions cannot be met simultaneously.
It is an object of the injection molding systems and methods disclosed herein to provide a novel solution to the problems associated with cooling the actuating system and cooling the manifold bushing of injection molding systems. The injection molding systems disclosed herein include a newly designed drop plate that defines walls of a cylinder within which a piston reciprocates. The injection molding systems may have multiple drop plates, with each drop plate independent of the other drop plates, and each drop plate dedicated to a single nozzle assembly. The novel drop plate includes cooling circuits in close proximity to the actuating system and manifold bushing, resulting in more effective management of the exit temperatures of the manifold bushing, which in turn, reduces the amount of melted resin escaping the system during use. An additional benefit of the novel drop plate design is that it provides improved access to the system for maintenance and repair.
It also an object of the unique injection molding systems and methods disclosed herein to eliminate damage to the system caused by misalignment of the system components due to thermal expansion. The injection molding system disclosed herein includes a valve pin coupling system configured to permit movement of the valve pin in a lateral direction independent from a lateral position of the piston. This design minimizes the axial misalignment of the valve pin due to thermal expansion and extends the life of the valve pin.
It also an object of the unique injection molding systems and methods disclosed herein to reduce the overall shut-height and weight of the injection molding system. By employing the novel drop plate that defines the walls of the cylinder in which the piston reciprocates, and eliminating the need for a back plate used in conventional systems, the overall shut-height of the system is reduced. The unique valve pin coupling system disclosed herein further results in a reduction in the overall shut-height of the system. The injection molding systems disclosed herein also include a unique nozzle locator that engages the manifold plate at multiple points minimizing axial misalignment due to thermal expansion and further reduces the system shut-height. In addition, the stack valve gate hot runner arrangement disclosed herein eliminates the center plate requirement of conventional systems, which further reduces system shut-height and overall system weight.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. The Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
Injection molding systems have various features that are described herein. In some embodiments, a hot runner system is disclosed that may include a plurality of nozzles, a plurality of corresponding drop plates wherein each drop plate may be independent of the other drop plates and may be dedicated to a single nozzle. In some examples, each drop plate may define a cylinder that a piston can ride or reciprocate within, and a valve pin associated with each drop plate and each nozzle. In certain examples, the valve pin may be configured to extend from the piston through at least a portion of the nozzle melt channel such that a forward end of the valve pin may be seatable within the mold gate. In still other examples, the drop plates may be bolted to separate manifold plates, and each drop plate may be associated with a separate manifold, and each drop plate may be configured to seal melted resin within a manifold cavity in the manifold. In another example, the hot runner drop plates may further include a rod seal, and the drop plates may be configured to seal air in the cylinder. In yet another example, the hot runner system may also include an insulator board configured to cover the plurality of drop plates and plurality of nozzles to reduce system contaminants. In one example, each drop plate may further include a cooling circuit. In certain examples, each drop plate may also include a first and a second air circuit.
In other embodiments, an injection molding system is disclosed herein that may include a manifold having a manifold melt channel for receiving melted resin, a nozzle having a nozzle melt channel for receiving the melted resin from the manifold melt channel and delivering the melted resin to a mold cavity via a mold gate, an actuating system that may include a cylinder that a piston rides within, a valve pin configured to extend from the piston through at least a portion of the manifold melt channel and the nozzle melt channel such that a forward end of the valve pin is seatable within the mold gate, and a valve pin connecting assembly that may be configured to connect the valve pin to the piston, and configured to permit the valve pin to move in a lateral direction independent from a lateral position of the piston. In another example, the valve pin connecting assembly may include a stem holder, a slider, and a retaining ring. In certain examples, a stem head of the valve pin may be seated between the stem holder and a bottom portion of the piston. In some examples, the retaining ring may retain the slider to the piston, and the stem holder may be configured to be in sliding engagement with the slider and the bottom portion of the piston to permit the valve pin to move in a lateral direction independent from a lateral position of the piston. In yet other examples, the injection molding system disclosed herein may also include a drop plate that may define a cylinder that the piston may be configured to ride within. In still other examples, the injection molding system drop plate may further include a cooling circuit or line, and a plurality of air circuits or lines to drive the piston between an open position to a closed position.
In another example disclosed herein, an injection molding system may include a plurality of nozzles, a plurality of corresponding drop plates in which each drop plate may be independent of the other drop plates and may be dedicated to a single nozzle. In some examples, each drop plate may define a cylinder wall that a piston may ride within, and a valve pin may be associated with each drop plate and may be configured to engage the piston. In other examples, valve pin connection assembly may be configured to connect the valve pin to the piston, and the valve pin connection assembly may be configured to permit axial movement of the valve pin relative to the piston. In still other examples, the injection molding system valve pin connection assembly may include a stem holder, slider, and a retaining ring. In certain examples, a stem head of the valve pin may be seated between the stem holder and a bottom portion of the piston. In some examples, the retaining ring may retain the slider to the piston, and the stem holder may be configured to be in sliding engagement with the slider and the bottom portion of the piston to permit the valve pin to move in a lateral direction independent from a lateral position of the piston. In still other example injection molding systems disclosed herein, the drop plate may further include a cooling circuit. In various examples, the drop plate may also include a circuit for pressurized air or fluid to drive the piston between an open position and a closed position.
In still other embodiments disclosed herein, an injection molding system may comprise a melted resin distribution system comprising a first manifold and a second manifold, a first drop plate configured to connect to a first manifold plate. In certain examples, the first drop plate may define a cylinder that a first piston may ride within. In some examples, a second drop plate may be configured to abut the first drop plate and configured to connect to a second manifold plate, the second drop plate defining a first cylinder that a first piston rides within. In some example a first valve pin may be configured to engage the first piston and may extend from the first piston through at least a portion of a melt channel in the first manifold and a first nozzle melt channel such that a forward end of the first valve pin is seatable within a first mold gate. In another example, a second valve pin may be configured to engage the second piston and may extend from the second piston through at least a portion of a melt channel in the second manifold and a second nozzle melt channel such that a forward end of the second valve pin is seatable within a second mold gate. In other examples, the first drop plate and second drop plate may be located between the first manifold plate and the second manifold plate.
In still other example injection molding system disclosed herein, each drop plate may contain a valve pin connection assembly configured to connect the valve pin to the piston, and the valve pin connection assembly may be configured to permit axial movement of the valve pin relative to the piston. In other examples, the valve pin connection assembly may comprise a stem holder, slider, and a retaining ring. In certain examples, a stem head of the valve pin may be seated between the stem holder and a bottom portion of the piston. In another example, the retaining ring may secure the slider to the piston, and the stem holder may be configured to be in sliding engagement with the slider and the bottom portion of the piston to permit the valve pin to move in a lateral direction independent from a lateral position of the piston. In yet another example, each of the first and second drop plates may further include a cooling circuit and a pressured circuit for driving each of the pistons between an open position and a closed position.
In still other embodiments disclosed herein, an injection molding system may comprise a melted resin distribution system comprising a manifold, a nozzle assembly, a valve pin configured to extend through at least a portion of a nozzle melt channel in the nozzle assembly such that a forward end of the valve pin may be seatable within a mold gate. In some examples, a nozzle locator may be configured to engage the manifold plate and the outside surface of the nozzle assembly. In other examples, the nozzle locator may engage a first manifold plate shelf In another example, the drop plate may also include a cooling circuit and a plurality of air circuits to drive the piston between an open position and a closed position.
These and various other features will be described more fully herein.
The present invention is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements and in which:
Further, it is to be understood that the drawings may represent the scale of different components of one single embodiment; however, the disclosed embodiments are not limited to that particular scale.
Aspects of this disclosure relate to injection molding systems. Injection molding systems generally include an injection molding unit and a hot runner system, wherein the hot runner system has one or more manifolds and one or more nozzles in fluid communication with each other. The hot runner manifolds receive a resin melt stream of moldable material from the injection molding unit and transfer the resin melt stream to one or more mold cavities via a respective hot runner nozzle.
Control of the resin melt stream is achieved by raising (i.e., opening) and lowering (i.e., closing) the valve pin 130 via the actuating system. Retracting the valve pin 130 from the mold gate permits the resin melt stream to flow into the mold cavity while re-seating the downstream end of the valve pin 130 within the mold gate prevents further flow of the resin melt stream into the mold cavity. Although only one actuating system and nozzle assembly 111 is shown in
While the piston 110 may be driven by pressurized air or fluid, the backing plate 106 shown in
It is known in the art that dimensional variations in the components of existing hot runner systems, especially the hot runner manifold, occur as a result of heat expansion and cooling during operation. The thermal expansion and contraction may misalign the system components and may cause damage to the components. For example, under operating conditions, the thermal expansion of the manifold 102 can shift and misalign the manifold 102 relative to backing plate 106. When the misalignment exceeds system tolerances, elongated valve pin 103 may be subjected to side loading and excessive bending forces due to mechanical interference. The misalignment or deflection leads to bending and subsequent damage of the valve pins and then damage to the mold gates. The damage to the valve pin 130 and mold gates leads to a loss of control of the flow of the resin melt stream due to improper or inadequate seating of the valve pin 130 in the mold gates due to the inadequate seating of the tip of the valve pins 130 in the mold gates and/or changes in timing of closing of the mold gates. In addition to excessive wear on the elongated valve pin 130, the actuation mechanism is placed under considerable load, decreasing system efficiency, and increasing the likelihood of pin seizure and/or actuator system malfunction.
The drop plate 208 of the system 200 defines an interior cylinder chamber/wall 209. Piston 210 reciprocates within the cylinder 209 formed in the drop plate 208. The system 200 further includes nozzle assembly 211, nozzle locator 224, valve pin 230 extending from and coupled to the piston 210, backup pad 220, and rod seal 212. The valve pin 230 may include a valve head 226 and a valve stem 232. Valve pin 230 passes through the manifold bushing 205 and extends into and through a melt channel 203 of the nozzle assembly 211 to have a downstream end seatable within a mold gate of a mold cavity (not shown). Like conventional systems, control of the resin melt stream is achieved by raising (i.e., opening) and lowering (i.e., closing) the valve pin 230. Retracting the valve pin 230 from the mold gate permits the resin melt stream to flow into the mold cavity while re-seating the downstream end of the valve pin 230 within the mold gate prevents further flow of the resin melt stream into the mold cavity.
While the piston 210 may be driven by pressurized air or fluid, the embodiment in
Drop plate 208 further includes a cooling circuit 214 in close proximity to the actuating system for direct cooling of the cylinder 209. The cooling circuit 214 also has the benefit of controlled proximity to the manifold bushing 205. The unique drop plate 206 that permits placement of the cooling circuit 214 in close proximity to both the cylinder 209 and manifold bushing 205 is an improvement over existing systems where the placement and arrangement of the cooling lines are dictated and limited by the features of the backing plate 106. The ;unique drop plate 206 that permits the cooling circuit 214 in close proximity to both the cylinder 209 and manifold bushing 205 increases the life of seals in the actuating system and reduces the variation of and improves the control of drop to drop manifold bushing exit temperature, which, in turn, results in better management of resin weepage out of the manifold bushing 205
Although only one drop plate 208 and nozzle assembly 211 is shown in
A valve pin connection assembly is provided to disassociate the valve pin’s axial position from the piston’s axial position thereby eliminating the effects of side loading and lateral displacement forces. As shown in
The nozzle locator 224, as shown in
The present disclosure is disclosed above and in the accompanying drawings with reference to a variety of examples. The purpose served by the disclosure, however, is to provide examples of the various features and concepts related to the disclosure, not to limit the scope of the invention. One skilled in the relevant art will recognize that numerous variations and modifications may be made to the examples described above without departing from the scope of the present disclosure.
Filing Document | Filing Date | Country | Kind |
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PCT/US2021/016346 | 2/3/2021 | WO |
Number | Date | Country | |
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62969904 | Feb 2020 | US |