Patent Application
20100044896
1. Field of the Invention
This invention relates to an injection molding apparatus, and more particularly, an injection molding apparatus having a valve pin.
2. Related Art
Injection molding apparatuses, such as hot halves and hot runners, commonly use valve pins to control flow of molding material.
When a cavity, valve pin, heater, mold gate, or other related component wears or fails, the molded product may have defects and the injection molding apparatus may have to be shut down for maintenance or repair. Such downtime eats into production time, which is nearly always sought to be maximized.
An injection molding apparatus, such as a hot half or hot runner, includes an actuated valve pin plate, a manifold defining a manifold channel, a plurality of nozzles defining nozzle channels in communication with the manifold, each nozzle associated with a mold gate, and a plurality of valve pins releasably coupled to the actuated valve pin plate. Each valve pin extends through the one of the nozzles for controlling flow of molding material in the nozzle channel. The actuated valve pin plate is operable to move the plurality of valve pins between open and closed positions of the mold gates. At least one nozzle includes a nozzle tip component having a tapered interior surface that circumferentially surrounds and grips the associated valve pin to lock the valve pin in the closed position and prevent flow of molding material.
Embodiments of the present invention will now be described more fully with reference to the accompanying drawings, where like reference numbers indicate similar structure.
a and 5b are cross-sectional views of one of the magnetic couplings of
The injection molding apparatus includes an actuator plate 102, actuators 104, an actuated valve pin plate 106, a back plate 108, a manifold 110, nozzles 112, a mold plate 114, a cavity plate 116, cores 118, valve pins 120, valve pin bushings 122, and magnetic couplings 124. The injection molding apparatus 100 can include any number of manifolds and nozzles, in any configuration. In this embodiment, one manifold is shown for simplicity. The injection molding apparatus 100 can include additional components, such as mold plates, alignment dowels, mold gate inserts, and cooling channels, among others.
The actuator plate 102 has openings for accommodating the actuators 104. If the actuators 104 depend on a working fluid for operation (i.e., pneumatic or hydraulic types), fluid conduits can be provided in the actuator plate 102. Should the actuators 104 be electric or magnetic or of some other design, electrical conduits can be provided.
The actuators 104 are disposed in the actuator plate 102 and can be pneumatic, hydraulic, electric, magnetic, or of some other design. The actuators 104 can translate the valve pin plate 106 by linear motion (e.g., a pneumatic piston) or rotary motion (e.g., an electric screw drive). To accomplish this, each actuator 104 has a stationary part (e.g., a housing or cylinder) connected to the actuator plate 102 and has a movable part 125 (e.g., a piston) connected to the valve pin plate 106. The number of actuators is a design choice, and in other embodiments more or fewer actuators can be used. Any style of actuator is suitable, provided that it can move the valve pin plate 106.
The valve pin plate 106 is connected to the movable part 125 of each actuator 104. The valve pin plate 106 has a plurality of threaded openings for receiving the magnetic couplings 124. The valve pin plate 106 can move up and down in response to the actuation of the actuators 104. The valve pin plate 106 need not be a plate as such, but can be any rigid member capable of connecting one or more actuators to a plurality of magnetic couplings. In other embodiments, the valve pin plate 106 is an assembly of stacked plates.
The back plate 108 is disposed between the valve pin plate 106 and the valve pin bushings 122 and serves to secure the valve pin bushings 122 in the manifold 110. The back plate 108 has several bores through which the valve pins 120 extend.
The manifold 110 defines a manifold channel 126 and includes a manifold heater 127. The manifold channel 126 receives molding material (e.g., plastic melt) from an inlet component (not shown) or an upstream manifold (not shown). The manifold heater 127 can be of any design, such as the insulated resistance wire illustrated. It should also be mentioned that, because of the plate interconnections (not shown), the manifold 110 is stationary relative to the stationary parts of the actuators 104.
The nozzles 112 are connected to the manifold 110 and each nozzle 112 defines one of a plurality of nozzle channels 128 in communication with the manifold channel 126. In this embodiment, each nozzle 112 includes a nozzle body, a nozzle flange, a nozzle heater embedded in the nozzle body, a thermocouple, a terminal end for connecting the heater to a power source, a nozzle tip, and a tip retainer. The nozzles 112 in combination with the manifold 110 define a hot runner.
The mold plate 114 has wells to accommodate and support the nozzles 112. The wells are sized to thermally insulate the nozzles 112 from the surrounding material.
The cavity plate 116 and the cores 118 define cavities 130, and the cavity plate 116 defines mold gates leading to the cavities 130. The cavity plate 116 and cores 118 are separable from the mold plate 114 along a parting line to allow ejection of molded products from the cavities 130. In other embodiments, a single cavity can be fed molding material by several nozzles 112.
Each of the valve pins 120 extends from one of the magnetic couplings 124 to one of the nozzles 112 for controlling flow of molding material through the mold gates and into the cavities 130.
Each valve pin bushing 122 is held to the manifold 110 by the back plate 108. Each valve pin bushing 122 includes a disc-shaped main body and a cylindrical bushing portion connected to and extending from the main body and into the manifold 110. Each valve pin bushing 122 has a valve pin bore, which creates a seal with the valve pin 120 while still allowing the valve pin 120 to slide.
Each magnetic coupling 124 couples a respective valve pin 120 to the valve pin plate 106. Each magnetic coupling 124 directly transmits actuator closing force to the respective valve pin 120 when the valve pins 120 are being closed (i.e., moved down). Each magnetic coupling 124 also applies a magnetic force to move the respective valve pin 120 when the valve pins 120 are being opened (i.e., moved up). During normal operation, the magnetic force is sufficient to keep the valve pins 120 coupled to the valve pin plate 106 when the valve pins 120 are opened and closed. If one of the valve pins becomes immovable, the respective magnetic force is overcome by an actuator opening force so that the valve pin plate 106 and remaining valve pins 120 move (i.e., up) with respect to the immovable valve pin. It should be noted that the directions indicated above are reversed if the valve pins 120 are designed to open flow of molding material when moved down and to close flow when moved up. The magnetic couplings 124 are described in more detail below. Further, the magnetic couplings 124 are described in more detail in U.S. patent application Ser. No. 11/876,706, filed Oct. 22, 2007, which is herein incorporated by reference in its entirety.
The housing 202 connects the first magnetic part 204 to the valve pin plate 106. The housing 202 is threaded into a threaded bore of the valve pin plate 106. A bore 208, which can also be threaded, is provided through the back end of the housing 202.
The first magnetic part 204 is connected to the valve pin plate 106 via the housing 202 and thus moves with the valve pin plate 106. The first magnetic part is 204 is inserted into the housing 202 and fixed to the housing 202 by way of magnetic attraction when the housing 202 is made of a magnetically responsive material such as steel. If the housing 202 is not made of a magnetically responsive material or if additional fixing force is required, an adhesive or a tight friction fit can be used, for example. A tool can be inserted into the bore 208 of the housing 202 to push the first magnetic part 204 free from the housing 202.
The second magnetic part 206 is positioned below the first magnetic part 204 and close enough to establish a magnetic force with the first magnetic part 204. In this embodiment, the second magnetic part 206 is attractively aligned with the first magnetic part 204 and the resulting the magnetic force is an attractive magnetic force. The second magnetic part 206 is slidable in the housing 202 and is thus moveable with respect to the first magnetic part 204. The second magnetic part 206 has a T-shaped slot for receiving the head of the valve pin 120, so that the second magnetic part 206 and the valve pin 120 are connected and can move together. By way of its location, the first magnetic part 204 defines a stopped position of the second magnetic part 206 relative to the first magnetic part 204 (and thus to the valve pin plate 106), and the attractive magnetic force tends to force the second magnetic part 206 into the stopped position. When the second magnetic part 206 is pulled away from the first magnetic part 204, the attractive magnetic force tends to pull the second magnetic part 206 back towards the first magnetic part 204 and into the stopped position.
In one embodiment, the first magnetic part 204 is a permanent magnet, such as a neodymium magnet or a samarium-cobalt magnet, and the second magnetic part 206 includes magnetically responsive material, such as steel, iron, or similar. The choice between a neodymium magnet, a samarium-cobalt magnet, and a magnet of some other material should be made addressing concerns such as temperature exposure and impact during operation. Magnetically responsive material can be ferromagnetic, ferrous material, or any other kind of material that experiences a significant force in the presence of a magnetic field. In this embodiment, the second magnetic part 206 is made of steel. In other embodiments, the first magnetic part 204 can be of a magnetically responsive material and the second magnetic part 206 can be a permanent magnet, or both parts 204, 206 can be some combination of permanent magnets and electromagnets. It should be noted that embodiments of the valve pin plate injection molding apparatuses described herein may include alternate designs than magnetic couplings 124 for coupling a respective valve pin 120 to the valve pin plate 106. For example, the injection molding apparatus may include spring couplings such as those described in U.S. Pat. No. 7,210,922, herein incorporated by reference, rather than magnetic couplings 124.
In
As described in U.S. patent application Ser. No. 11/876,706, filed Oct. 22, 2007, solidified molding material may be utilized to hold a valve pin associated with an out-of-service nozzle in a closed position. More particularly, the nozzle heater may be shut down such that solidified or cooled molding material immobilizes the valve pin. That is, when a nozzle is to be taken out of service because of a worn valve pin or leaking cavity, the nozzle's heater can be shut down to stop molding material from flowing. Solidified molding material can also occur if a nozzle heater fails. The magnetic couplings 124 are designed to have a magnetic force less than the expected immobilizing force, such that the magnetic couplings 124 will allow for continued operation of valve pins when one or more nozzles are taken out of service. Shutting down the nozzle's heater also helps to prevent drooling in the out-of-service nozzle.
However, in some applications, the solidified melt around the valve pin may not be sufficient to completely immobilize the out-of-service valve pin such that it is prevented from moving up and down with the other valve pins because the magnetic force of the magnetic couplings 124 (or other attractive force if magnetic couplings 124 are not present) is greater than the immobilizing force. In some instances, heat elsewhere in the apparatus may prevent the melt from sufficiently solidifying. Further, taking the valve pin out of service by solidified melt causes a small force on the valve pin plate 106 as the immobilizing force of the melt overcomes the magnetic force between the plate and the valve pins. If several valve pins are out-of-service, this small force is multiplied and may damage the magnets of the magnetic couplings.
Thus, in addition to turning off the nozzle heater in order to immobilize the out-of-service valve pin, the present invention is directed to embodiments of a nozzle tip component that may be installed for taking a nozzle of an injection molding apparatus out of service. Embodiments of the present invention include a retainer and/or a locking liner at the nozzle tip area that grips a valve pin associated with the nozzle selected to be taken out of service in order to maintain the valve pin in a closed position. The retainer can also have a seal portion to prevent leakage past the nozzle tip area and into the well.
Turning now to
A selected nozzle 112 can be taken out of service by closing the valve pins 120, removing the nozzle tip that is utilized when the nozzle is in-service, and installing nozzle tip component 431. That is, when a nozzle is to be taken out of service, a nozzle tip component 431 may be installed in order to maintain the valve pin in a closed position. The nozzle tip component 431 creates a definite out-of-service position that prevents unwanted travel of the valve pin in an out-of-service nozzle, because such unwanted travel may damage the magnets in the magnetic couplings 124. More particularly, if space permits, the valve pin may be pulled closer to the mold cavity than usual when installing the nozzle tip component 431 to completely disengage the magnet of the magnetic coupling to further reduce the possibility of damaging the magnet contact surfaces. Once the selected valve pin 120 is immobilized, the magnetic couplings 124 allow the valve pin plate 106 to still actuate the remaining in-service valve pins 120. The injection molding apparatus 100 can be restarted as usual, and the selected valve pin 120 of the immobilized nozzle will remain stationary.
a and 5b show a magnetic coupling 124 associated with an immobilized valve pin 120.
In another embodiment, the exterior tapered surface of the locking liner may include one or more threads. As shown in
In another embodiment, the locking liner may have a collet-type configuration with a split front.
In another embodiment illustrated in
In other embodiments, a nozzle tip component is used to grip and lock a valve pin in the closed position, when the valve pin is not used in conjunction with an actuated valve pin plate. For example, a group of valve pins can be individually controlled by actuators that are fed by a common fluid source (e.g., a common air line). In such case, the valve pins will operate together (much like when connected to an actuated plate) and it may be problematic to turn off the specific actuator controlling the valve pin to be taken out of service without turning off all the actuators. Any of the nozzle tip components described herein can be used in this situation to lock the valve pin in the closed position.
In embodiments described herein, supplementary components have been omitted for clarity. For example, a designer may choose to provide many of the threaded components described with lock nuts or another mechanism to stop the threads from working free over time.
In addition, the valve pins described are down-closed and up-open. Reverse gating (up-closed, down-open) and lateral gating (e.g., edge gating) are also possible.
Lastly, the terms fixed, connected, coupled, etc used herein do not exclude indirect connections between parts. For example, a part can be fixed to another part with any number of parts in between or none at all (i.e., directly fixed). In addition, parts described as fixed, connected, coupled, etc can also be integral, if the resulting functionality is not changed.
Although many embodiments of the present invention have been described, those of skill in the art will appreciate that other variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims. All patents and publications discussed herein are incorporated in their entirety by reference thereto.
