Patent Description:
Injection molding is a technology commonly used for high-volume manufacturing of parts constructed from thermoplastic materials. During repetitive injection molding processes, a thermoplastic resin, typically in the form of small pellets or beads, is introduced into an injection molding machine which melts the pellets under heat and pressure. The molten material is then forcefully injected into a mold cavity having a particular desired cavity shape. The injected plastic is held under pressure in the mold cavity and subsequently is cooled and removed as a solidified part having a shape closely resembling the cavity shape of the mold. A single mold may have any number of individual cavities which can be connected to a flow channel by a gate that directs the flow of the molten resin into the cavity.

Additional materials, other than the injected plastic, may be required during an injection molding process to generate specific devices. For example, structural foam materials may be introduced into an injection molding process to produce products that use less material to create, that have increased strength and/or stiffness due to the internal cell structure, and with high strength to weight ratios among other features. Expanding crosslinking polymers (e.g., ethylene-vinyl acetate or "EVA") are one class of polymers that are commonly injection molded as a structural foam. A typical injection molding process of expanding crosslinking polymers generally includes four basic operations: First, the plastic is placed in the hopper and heated in the injection molding machine to allow the plastic to flow under pressure. When injection molding expanding crosslinking polymers, at this step, the polymer is heated to a temperature that is below an activation temperature of the polymer, or the temperature at which expansion and crosslinking within the polymer begins to occur.

Next, the melted plastic is injected into a mold cavity or cavities defined between two mold halves that have been closed. The mold or cavity temperature is set to a value that is high enough to activate a chemical reaction or reactions that cause the polymer to begin expansion and crosslinking. At a third step, the plastic is held under pressure to allow adequate crosslinking and expansion (or blowing) to occur in the cavity or cavities. Last, the mold halves are opened, and the molded article is removed or ejected from the mold, thereby allowing the plastic to expand to a final shape and configuration that is larger than the internal volume of the mold cavity.

In conventional systems, a fixed, predetermined volume of plastic is injected into the mold cavity. This volume only partially fills the cavity. The mold cavity is then heated to cause a chemical reaction, upon which the plastic is then left to expand to fill the mold cavity and crosslink for a specified hold time, which is typically determined via a "gate freeze study" where the part weight is measured over a period of time. In this gate freeze study, part weights are periodically measured during the injection molding process until the weight begins to level off. The point at which the part weight levels off is identified as generally being the optimum time to eject the part. This gate freeze study is typically performed during a process validation stage, and is oftentimes used for the entirety of subsequent injection molding cycles.

After the part is ejected, it is quickly removed from the mold to a stabilization tunnel where curing occurs. By quickly removing the part from the mold, the part can fully expand, and will not be deformed due to the material being constrained from expanding at areas where the part is still captured in the mold. During the curing phase, the part is allowed to slowly cool to a temperature near room temperature. Excess internal gases will slowly escape from the part.

Typically, additional injected materials, other than the injected plastic, are injected along with the injected plastic through a nozzle of an injection molding machine. The nozzle is typically upstream of the mold cavity, causing the addition material to travel with the injected plastic flow front into the mold cavity reducing the control over the final location and concentration of the additional material in the mold cavity. For example, the additional material may migrate to a surface of the mold cavity causing surface defects for parts where the additional material is intended to be in the center of a part surrounded by the injected plastic. Additionally, the additional material may be a foaming agent which, if at the surface of a mold cavity, causes open cell surfaces on parts. At least in some applications, such as personal hygiene products, the presence of open cell surfaces can be susceptible to bacterial ingress and growth, resulting in the use of foaming agents for the surfaces of such products being banned by the FDA. Material and machine variances can also result in varying internal peak cavity pressures, which can cause inconsistencies in crosslinking and expansion of a material in the mold cavity further exacerbated by the effects of an incorrect location of an injected additional material. Additionally, inconsistencies in additive material location and density may cause expansion and crosslinking to occur at varying rates when the part is ejected from the mold and in a curing state where the molded parts continue to expand and crosslink until reaching a final form, thus resulting in inconsistently sized parts. Further, the parts may be deformed, have unsightly blemishes, and other undesirable flaws.

Inconsistencies in the location and density of additional materials can also cause structural and physical instabilities for parts. The size and density of cells in foaming agents depends on internal pressures, the location, and the density of the additional foam material in the mold cavity. Therefore, the cell structure of a molded part may be non-uniform, meaning free radical molecules may not be aligned. When these molecules are uniformly distributed, the resulting part has more consistent and stable dimensions and physical properties. For example, errors in the location and density of additional materials in the mold cavity may cause parts to be incorrectly dimensioned (i.e., parts may be either too large or too small) and may potentially be too soft or too resilient due to insufficient crosslinking or quantities of foam. As a result, the molded part may fail any number of objective test such as in abrasion test, a comprehension test, and/or dynamic elasticity test where energy loss is measured over a number of closely times impacts with a controlled load.

Further, conventional systems typically do not provide uniform heat distribution throughout the plastic during the molding process due to varying mold thicknesses. By unevenly heating the plastic, inconsistent regions of plastic and additional material within the mold cavity can expand at undesirable rates, which can result in inconsistent parts having wide tolerances.

<CIT> describes a method for introducing an additive into a flowing stream of media pulsing discrete quantities of the additive into the stream at a pressure higher than the pressure of the stream and at set time periods to cause the pulses to penetrate into the stream. Use is made of a nozzle that can introduce the additive in flow and counterflow to the stream of media.

<CIT> describes an injection moulded product, an expanded foam product, a method of injection moulding a plastisol an expandable plastic embryo during which the foaming of the plastic embryo is suppressed throughout the moulding operation. The invention further relates to a mould and an injection moulding device.

<CIT> describes injection molding systems and methods useful for making microcellular foamed materials and microcellular articles. Pressure drop rate and shear rate are important features in some embodiments, and the invention provides systems for controlling these parameters in an injection molding system. Another aspect involves an injection molding system including a nucleator that is upstream of a pressurized mold.

<CIT> describes continuous polymeric extrusion nucleation systems and methods useful for making polymeric microcellular foamed materials, including crystalline and semi-crystalline polymeric microcellular materials. The document provides systems for controlling these and other parameters. One aspect involves a multiple-pathway nucleator that is separated from a shaping die by a residence chamber.

<CIT> describes a plasticizing screw, a foaming agent supply apparatus, a stirring screw and an injection nozzle.

<CIT> describes a gas assisted molding apparatus having gas introduced into the plastic charge as the charge is flowing into the mold cavity. The gas and plastic are simultaneously injected into the mold cavity and the gas can be introduced at the nozzle end or barrel of the injection molding machine. Optionally, the gas may be injected into a hot runner manifold or into the cavity itself simultaneously with the plastic.

It is an object of the present invention to overcome problems anticipated in and improve technologies of the prior art.

In this description the non-standard unit psi has been used. It can be converted into metric units in the following way: <MAT>.

While the invention is defined in the independent claims, further aspects of the invention are set forth in the dependent claims, the drawings and the following description.

An additive injection device for an injection molding system of the present disclosure includes an additive injection unit with one or more additive tanks, each having a supply of an additive fluid. The additive fluid may be an expanding polymer or another additive material to be injected into a molten flow or mold cavity. One or more additive injectors in fluid communication with the one or more additive tanks receive the additive fluid and may inject the additive fluid material into an injection molding machine. One or more additive pumps may provide a pressure to the additive fluid in the tanks, manifold, and/or additive injectors and pump the additive fluid through additive injector nozzles. The additive fluid may be injected directly into a mold cavity, or upstream of a mold cavity such as in a manifold connecting each of the additive tanks with the additive injectors.

Typical injection molding systems that employ the addition of an additive material introduce the additive materials prior to injection of the molten resin into a manifold or mold cavity, which allows for variations in the location of the additive material in the mold cavity due to differences in molten resin flow and resin and mold cavity temperature among other factors. The injection of additive material directly into a mold cavity, or upstream of a mold cavity, near the mold cavity, may allow for more consistent fabrication of molded pieces across multiple fabrication sessions, and for better control over the location of additive materials or additive fluids in a mold cavity during a fabrication session.

An additive injection system of the present disclosure includes an additive injection device for use in an injection molding machine having an additive injection unit. A controller may control additive injectors and/or pumps of the additive injection unit to pump additive fluid in a pulsed or continuous manner. The additive fluid can also be pumped at low pressures for implementation in non-naturally balanced feed systems. Sensors, coupled to the controller, can provide feedback to the controller to allow for the controller to monitor variables such as flow temperature, cavity temperature, flow location, cavity pressure, and other factors during a fabrication session. The controller may also provide closer-loop control of the additive injection system during a fabrication session to allow for more accurate execution of an additive injection fabrication profile.

The systems and methods herein may provide better mixing of an additional material in a molten plastic material, provide better formation of cells or voids in an injection molded part, a better yield of a foaming agent, and a higher accuracy of the location of an additive fluid in a mold during an injection molding fabrication session therefore improving injection molding systems that employ the injection of additive fluids and materials.

The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals which:.

An injection molding process for the injection of additive materials into mold gating systems and cavities is herein described. <FIG> is a simplified drawing illustrating an exemplary injection molding machine <NUM> and an additive injection device <NUM>. <FIG> is offered as an example of geometries in an injection molding machine and an additive injection device that may generate parts that have additive materials. It should be understood that any injection molding machine and additive injection device may be employed with the disclosed system, including simpler or more complex devices.

The injection molding machine <NUM> includes an injection unit <NUM> and a clamping system <NUM>. The approaches described herein may be suitable for vertical press injection molding machines and any other known types of injection molding machines. The injection unit <NUM> includes a hopper <NUM> adapted to accept plastic or polymer injection materials in the form of pellets <NUM> or any other suitable form. In many examples, the pellets <NUM> include any number of thermoplastic materials including polyethylene, polypropylene, and nylon among others.

The hopper <NUM> feeds the pellets <NUM> into a heated barrel <NUM> of the injection unit <NUM>. Upon being fed into the heated barrel <NUM>, the pellets <NUM> may be driven to the end of the heated barrel <NUM> by a reciprocating screw <NUM>. The heating of the heated barrel <NUM> and compression of the pellets <NUM> by the reciprocating screw <NUM> causes the pellets <NUM> to melt, thereby forming a molten plastic material <NUM>. The molten plastic material <NUM> is typically processed at a temperature selected within a range of about <NUM>° C and about <NUM> ° C.

The reciprocating screw <NUM> advances forward and forces the molten plastic material <NUM> toward a nozzle <NUM> to form a shot of plastic material <NUM> which will ultimately by injected into a mold cavity <NUM> of a mold <NUM> via one or more gates <NUM> which direct the flow of the molten plastic material <NUM> to the mold cavity <NUM>. In other embodiments, the nozzle <NUM> may be separated from the one or more gates <NUM> by a feed system (not illustrated). The mold cavity <NUM> is formed between a first mold side <NUM> and a second mold side <NUM> of the mold <NUM> and the first and second mold sides <NUM> and <NUM> are held together under pressure via a press or clamping unit <NUM>. The mold <NUM> may include any number of mold cavities <NUM> to increase overall production rates. The shapes and/or designs of the cavities may be identical, similar, and/or different from each other.

The press or clamping unit <NUM> applies a predetermined clamping force during the molding process which is greater than the force exerted by the injection pressure acting to separate the first and second mold sides <NUM> and <NUM>, thereby holding together the first and second mold sides <NUM> and <NUM> while the molten plastic material <NUM> is injected into the mold cavity <NUM>. To support the clamping forces, the clamping unit <NUM> may include a mold frame and a mold base, in addition to any other number of components.

The reciprocating screw <NUM> continues forward movement, causing the shot of molten plastic material <NUM> to be injected into the mold cavity <NUM>. Once the shot of molten plastic material <NUM> is injected into the mold cavity <NUM>, the reciprocating screw <NUM> stops traveling forward. The molten plastic material <NUM> takes the form of the cavity <NUM> and the molten plastic material <NUM> cools inside the mold <NUM> until the molten plastic material <NUM> solidifies. Once the plastic material <NUM> has solidified, the clamping unit <NUM> releases the first and second mold sides <NUM> and <NUM>, the first and second mold sides <NUM> and <NUM> are separated from one another, and the finished part may be ejected from the mold <NUM>.

The additive injection system <NUM> may also inject materials into the mold cavity <NUM>. The additive injection system <NUM> includes a source of additive material that may be in the form of an additive tank <NUM> that contains a supply of an additive material <NUM> and additive injectors <NUM> each of which receives additive material <NUM> from the additive tank <NUM> and injects the additive material <NUM> into the mold cavity <NUM>. The additive injectors <NUM> may be connected to the additive tank <NUM> by a common manifold <NUM>, or additive feed channel, that provides a channel for the additive material <NUM> to travel from the additive tank <NUM> to the additive injectors <NUM>. An additive pump <NUM> is connected to the additive tank <NUM> and/or the common manifold <NUM> and may pump the additive material <NUM> from the additive tank <NUM> and/or the common manifold <NUM> to the additive injectors <NUM>.

The additive injection system <NUM> also includes a controller <NUM> that is communicatively coupled with the additive injection system <NUM> via one or more connections <NUM>, and is generally used to control operation of the additive injection system <NUM>. The one or more connections <NUM> may be any type of wired and/or wireless communications protocol adapted to transmit and/or receive electronic signals. In these examples, the controller <NUM> is in signal communication with at least one sensor, such as a sensor <NUM> located in the nozzle <NUM> and/or a sensor <NUM> located proximate to an additive injector <NUM>. The sensor <NUM> may be located at any position within or near the mold cavity <NUM>. In addition, the controller <NUM> may be in signal communication with one or more of the additive injectors <NUM>. Feedback information from the additive injectors <NUM> may also be sent to the controller <NUM>. It is understood that any number of additional sensors capable of sensing any number of characteristics of the mold <NUM> and/or the machine <NUM> may be placed at desired locations of the machine <NUM> and/or the additive injection device <NUM>.

The controller <NUM> can be disposed in a number of positions with respect to the injection molding machine <NUM> and the additive injection device <NUM>. As examples, the controller <NUM> can be integral with the additive injection device <NUM>, contained in an enclosure that is mounted on the additive injection device <NUM>, contained in a separate enclosure that is positioned adjacent or proximate to the additive injection device <NUM>, or can be positioned remote from the additive injection device <NUM>. In some embodiments, the controller <NUM> can partially or fully control functions of the additive injection device <NUM> via wired and/or wired signal communications as known and/or commonly used in the art.

The sensors <NUM> and <NUM> may be any type of sensor adapted to measure (either directly or indirectly) one or more characteristics of the molten plastic material <NUM>. The sensors <NUM> and <NUM> may measure any characteristics of the molten plastic material <NUM> and/or additive material <NUM> that is known in the art, such as pressure or temperature, or any one or more of any number of additional characteristics which are indicative of these. The sensors <NUM> and <NUM> may or may not be in direct contact with the molten plastic material <NUM> and/or the additive material <NUM>. In some examples, the sensors <NUM> and <NUM> may be adapted to measure any number of characteristics of the injection molding machine <NUM> and/or the additive injection system <NUM> and not just those characteristics pertaining to the molten plastic material <NUM> and/or the additive material <NUM>.

The sensors <NUM> and <NUM> generate signals that are transmitted to an input <NUM> of the controller <NUM>. If the sensor <NUM> is not located within the nozzle <NUM>, the controller <NUM> can be set, configured, and/or programmed with logic, commands, and/or executable program instructions to provide appropriate correction factors to estimate or calculate values for the measured characteristic in the nozzle <NUM>.

Similarly, the sensor <NUM> may be any type of sensor adapted to measure (either directly or indirectly) one or more characteristics of the molten plastic material <NUM> and/or the additive material <NUM> to detect its presence and/or condition in the mold cavity <NUM>. In various embodiments, the sensor <NUM> may be located at or near an end-of-fill position in the mold cavity <NUM> or near an additive injector <NUM>. The sensor <NUM> may measure any number of characteristics of the molten plastic material <NUM> and/or the additive material <NUM> in the mold cavity <NUM> that is known in the art, such as pressure or temperature, or any one or more of any number of additional characteristics which are indicative of these. The sensor <NUM> may or may not be in direct contact with the molten plastic material <NUM> and/or the additive material <NUM>.

The sensor <NUM> generates a signal that is transmitted to the input <NUM> of the controller <NUM>. If the sensor <NUM> is not located at the end-of-fill position in the mold cavity <NUM> or near an additive injector <NUM>, the controller <NUM> can be set, configured, and/or programmed with logic, commands, and/or executable program instructions to provide appropriate correction factors to estimate or calculate values for the measured characteristic at the end-of-fill position or near the additive injectors <NUM>. It is understood that any number of additional sensors may be used to sense and/or measure operating parameters. For example, <CIT> and published as <CIT>, describes a sensor positioned prior to the end-of-fill to predict the end-of-fill.

The controller <NUM> is also in signal communication with the additive pump <NUM>. In some embodiments, the controller <NUM> generates a signal that is transmitted from an output <NUM> of the controller <NUM> to the additive pump <NUM>. The controller <NUM> can control any number of characteristics of the additive injection device <NUM>, such as injection pressures (by controlling the additive pump <NUM> and the additive injectors <NUM> at a rate which maintains a desired additive injection pressure of the additive material <NUM>), additive injection speeds, inject forward time, injection pulse rates, and injection times among other characteristics.

The controller <NUM> may control the additive pump <NUM> and the additive injectors <NUM> to inject additive material <NUM> in a pulsed manner. In embodiments, the additive injectors <NUM> may be instructed by the controller <NUM> to inject additive material <NUM> into the cavity mold <NUM> at different pulse rates during a single injection cycle. For example, the additive injectors <NUM> may be instructed by the controller <NUM> to inject additive material <NUM> at a rate ranging from as few as <NUM>,<NUM> injections per minute during a first amount of time in an injection cycle, to as many as <NUM>,<NUM> injections per minute during a second amount of time in an injection cycle, the first and second amounts of times being part of an additive injection profile. The additive injection profile may include injection of additive material <NUM> from various additive injectors <NUM> simultaneously or independently, at various times during an injection mold cycle, and at various injection pulse rates among other characteristics.

In some embodiments, the controller <NUM> may control the additive pump <NUM> and the additive injectors <NUM> to inject additive material <NUM> at lower pressure (e.g., less than <NUM>,<NUM> psi) which may improve the dispersion of the additive material <NUM>. Additionally, low pressure injection of additive materials may allow for the use of molds formed of easily machineable materials that are less costly and faster to manufacture than typical injection molds. In some embodiments, the additive pump <NUM> may pump the additive material <NUM> in a manner that provides a constant pressure to the additive injectors <NUM>. A valve at an inlet of each of the additive injectors <NUM> may then be selectively openable to pressurize, and thereby pump, the additive material <NUM> through the associated additive injector <NUM>. The controller <NUM> may control the additive pump <NUM> and the valves to pump additive material <NUM> according to an additive injection profile.

The signal or signals from the controller <NUM> may generally be used to control operation of the additive injection device <NUM> such that variations in material viscosity, activation temperatures, and other variations influencing the injection location and density of additive material <NUM> are taken into account by the controller <NUM>. Adjustments may be made by the controller <NUM> in real time or in near-real time (that is, with a minimal delay between sensors <NUM> and <NUM> sensing values and changes being made to the process), or corrections can be made in subsequent cycles. Furthermore, several signals derived from any number of individual cycles may be used as a basis for making adjustments to the additive injection process or additive injection profile. The controller <NUM> may be connected to the sensors <NUM> and <NUM>, the additive pump <NUM>, the additive injectors <NUM>, and/or any other components in the additive injection device <NUM> via any type of signal communication known in the art or hereafter developed.

The controller <NUM> includes software <NUM> adapted to control its operation, any number of hardware elements <NUM> (such as a memory module and/or processors), any number of inputs <NUM>, any number of outputs <NUM>, and any number of connections <NUM>. The software <NUM> may be loaded directly onto a memory module of the controller <NUM> in the form of a non-transitory computer readable medium, or may alternatively be located remotely from the controller <NUM> and be in communication with the controller <NUM> via any number of controlling approaches. The software <NUM> includes logic, commands, and/or executable program instructions that may contain logic and/or commands for controlling the additive injection device <NUM> according to an additive injection profile for a mold cycle. The software <NUM> may or may not include one or more of an operating system, an operating environment, an application environment, or a user interface.

The hardware <NUM> uses the inputs <NUM> to receive signals, data, and information from the injection molding machine and the additive injection device <NUM> being controlled by the controller <NUM>. The hardware <NUM> uses the outputs <NUM> to send signals, data, and/or other information to the additive injection device <NUM>. The connection <NUM> represents a pathway through which signals, data, and information can be transmitted between the controller <NUM> and its additive injection device <NUM>. In various embodiments this pathway may be a physical connection or a non-physical communication link that works analogous to a physical connection, direct or indirect, configured in any way described herein or known in the art. In various embodiments, the controller <NUM> can be configured in any additional or alternate way known in the art.

As previously stated, during an injection molding cycle, the sensors <NUM> and <NUM>, in addition to transmitting feedback from the additive injectors <NUM>, provide signal data indicative of at least one variable related to operation of the additive injection device <NUM>. During operation, the controller <NUM> commences an additive injection profile that may be stored in the software <NUM>. The additive injection profile is commenced upon the measured variable reaching a threshold value. The variable or characteristic is one other than time (e.g., a cycle, step, or any other time), thus time may not be directly measured and used to determine the initiation or length of the additive injection profile, and accordingly, time is not directly measured and used to determine when the additive injection profile has completed. Rather, the variable or characteristic relies on another value or indicator as a determining factor for completion of the additive injection profile. The use of one or more non-time dependent variables is advantageous because, during successive runs, even with the same supply of pellets <NUM>, variations in pellet quality, amount of additive material <NUM>, catalyst stability, ambient conditions, or other factors may influence the accuracy of the location and density of additive material <NUM> in the mold cavity <NUM>. While a time-dependent process may provide satisfactory parts most of the time, a system that determines the progress of the additive injection profile in an injection cycle based on one or more non-time dependent variables is preferable, as this provides a more accurate assessment of additive material readiness for each individual cycle of the molding system <NUM> and the additive injection device <NUM>.

<FIG> is an embodiment of an additive injector <NUM> with an electromagnetic valve <NUM>, an injector holder <NUM>, and a nozzle <NUM>. Additive material may pass through the electromagnetic valve <NUM>, through the injector holder <NUM>, into the nozzle <NUM>, and out of the nozzle <NUM> into a mold cavity such as the mold cavity <NUM> of <FIG>. The electromagnetic valve <NUM> may be electrically connected to a controller, such as the controller <NUM> of <FIG>, and be controlled by the controller <NUM> in a manner that causes the electromagnetic valve <NUM> to open, to close, to partially open, to partially close, or to open and close in pulses at a given frequency or at various frequencies according to an additive injection profile.

Feedback information from the additive injector <NUM> may provide real-time information about the progress of the additive injection profile. One example of potential feedback information is the pressure of additive material inside of the injector holder <NUM>. Monitoring of the pressure in the injector holder <NUM> may allow for the detection of the presence of molten plastic material at the location of the additive injector nozzle <NUM> in the mold cavity <NUM> that may provide information to the controller <NUM> causing the controller <NUM> to commence, end, modify, or advance an additive injection profile. The feedback information may also be used by a controller <NUM> to determine the amount of additive material or density of the additive material being injected into the mold cavity <NUM> over a period of time, which contributes to the temperature and pressure of the material inside of the mold cavity <NUM>. Other factors may also be measured and used as feedback from the additive injector <NUM> to the controller <NUM> such as temperature of the additive injector <NUM>, flow rate of additive material through the electromagnetic valve <NUM>, through the injector holder <NUM>, and/or through the nozzle <NUM> among other measurable factors.

<FIG> is an enlarged view of the nozzle <NUM> on the additive injector <NUM> in <FIG>, disposed inside of a wall of a mold <NUM>. The mold <NUM> has an injector seat <NUM> and one or more orifices <NUM>. The orifices <NUM> provide a channel for additive fluid to be injected by the additive injector <NUM> directly into a mold cavity. The additive injector <NUM> may inject the additive material into the mold cavity while the cavity is substantially filled (i.e., greater than <NUM>%) to introduce additive material at a time near the end of an injection cycle, which may be useful for introducing additive materials onto surfaces of a molded part. In some embodiments, the additive injector <NUM> may be disposed upstream of a mold cavity in a gate that directs the flow of molten plastic material <NUM> into the cavity. Injection of additive materials upstream of a mold cavity, as close to the mold cavity as possible, may provide more accurate final positioning of the additive material in a mold cavity, and allow for more consistent part fabrication across multiple fabrication sessions. In embodiments with an expanding crosslinking polymer as the additive material, injection of additive materials close to the mold cavity may allow for better control of the chemical reactions occurring in the expanding crosslinking polymers. In some embodiments, the additive injector <NUM> may be implemented in naturally or non-naturally balanced feed systems. Artificially (or non-naturally) balanced feed systems are described in <CIT> "NON-NATURALLY BALANCED FEED SYSTEM FOR AN INJECTION MOLDING APPARATUS".

Additive injectors <NUM> in gates may inject additive material into a flow of molten plastic material <NUM>. In some embodiments, the orifice <NUM> may guide injected additional material into the gate in an upstream manner, i.e., against the direction of the flow of molten plastic material <NUM>. Injecting additional material into molten plastic material <NUM> in an upstream manner may induce additional shear providing better mixing of an additional material in the molten plastic material <NUM>. Alternatively, in other embodiments, the orifice <NUM> may guide injected additional material into the gate in a downstream manner, i.e., the same direction as the flow of molten plastic material <NUM> providing better formation of cells or voids in an injection molded part and potentially a better yield of a foaming agent. In embodiments, such as the embodiment of the additive injector <NUM> of <FIG>, there may be multiple orifices <NUM> that guide additional material into the flow of molten plastic material <NUM> at multiple locations and with multiple angles relative to the direction of the flow of molten plastic material <NUM>. In other embodiments, the orifice may guide injected addition material into the gate perpendicularly to the flow of molten plastic material <NUM>, or any combination of orifices <NUM> that may inject additional material into the flow of molten plastic material <NUM> at various angles relative to the flow of molten plastic material <NUM>. In embodiments, the nozzles of additive injectors and orifices of molds may be strategically placed near or at a pinch-off points to reduce potential part defects.

Some additive materials may not require further mixing or dispersion into a molten flow other than mixing and dispersion due to injection by additive injectors as described herein. Depending on the material properties or the additive material, some additive materials may require further mixing or dispersion into a molten flow. In such embodiments that require further mixing of the additive material, a mixer element may assist with mixing of the additive material into the molten flow. The mixer element may be disposed in a gate or manifold upstream or downstream of the additive injector to induce movement in the polymer molten flow to mix the additive material into the polymer in a more homogeneous dispersion throughout the polymer molten flow. Additionally, the mixing element may be disposed anywhere in an injection molding system where the molten polymer flows. The mixing element may be a single protrusion from a side wall of the gate, a grid pattern which the molten polymer flows through, a rotating structure such as a rotating blade or multiple fan blades, or any other structure that enables the mixing of the additive material into the molten polymer.

In some embodiments, the additive material may be a foaming agent, crosslinking agent, or the like. A class of polymers commonly used as a foaming agent in injection molding are expanding crosslinking polymers. Expanding crosslinking polymers have an activation temperature at which expansion and crosslinking within the polymer begins to occur. Examples of expanding crosslinking polymer is ethylene-vinyl acetate or "EVA", which, when polymerized, include any number of blowing agents and any number of crosslinking agents with are activated by a specified activation temperature. For example, the blowing agents and crosslinking agents may be activated at temperatures between approximately <NUM>° C and approximately <NUM>° C, or preferably, at temperatures between approximately <NUM>° C and approximately <NUM>° C, and more preferably, at temperatures between approximately <NUM>° C and approximately <NUM>° C, which may provide an optimal range for blowing and crosslinking to occur. Other examples of suitable temperature ranges are possible.

Referring now back to <FIG>, in embodiments that employ expanding crosslinking polymers as the additive material, the additional material <NUM> may be injected into the mold cavity <NUM> while the mold cavity <NUM> is at a temperature below the activation temperature, for example between <NUM>° C and <NUM>° C. As the mold cavity <NUM> continues to fill with molten plastic material <NUM> and additional material <NUM>, the mold cavity <NUM> is heated to a temperature that is higher than the activation temperature of the additional material <NUM>. For example, the mold cavity <NUM> may be heated to a temperature between approximately <NUM>° C and approximately <NUM>° C, and preferably, to a temperature between approximately <NUM>° C and <NUM>° C. As such, a chemical reaction begins to occur within the additional material <NUM>. It is understood that walls of the mold cavity <NUM> may be preheated prior to injection the molten plastic material <NUM> and/or the additional material <NUM>, or alternatively, may be rapidly heated to a suitable temperature as the molten plastic material <NUM> and/or the additional material <NUM> enters the mold cavity <NUM>. Examples of heating techniques that may be used to heat surfaces of the mold that define the mold cavity are: resistive heating (or joule heating), conduction, convection, use of heated fluids (e.g., superheated steam or oil in a manifold or jacket, also heat exchangers), radiative heating (such as through the use of infrared radiation from filaments or other emitters), RF heating (or dielectric heating), electromagnetic inductive heating (also referred to herein as induction heating), use of thermoelectric effect (also called the Peltier-Seebeck effect), vibratory heating, acoustic heating, and the use of heat pumps, heat pipes, cartridge heaters, or electrical resistance wires, whether or not their use is considered within the scope of any of the above-listed types of heating.

Foaming agents may be used to reduce the weight or density of a final product or to introduce break points in a part. For example, <FIG> is an illustration of a molded part <NUM> in a mold cavity filled with molten plastic material <NUM> and additive material creating additive material cells <NUM>. In embodiments, a single additive injector 306A may inject additive material into the molten plastic material <NUM>. In <FIG> the additive material may be a foaming agent, fluid, or a gas creating additive material cells <NUM>. The additive injector 306A may be controlled by a controller, such as the controller <NUM> of <FIG>, to inject additive material according to an additive injection profile. <FIG> illustrates one example of an additive injection profile that may be implemented to generate additive material cells <NUM> of different sizes and densities, such as the cells <NUM> illustrated in <FIG>. Referring now simultaneously to <FIG>, the additive injector 306A may inject additive material into the molten plastic material <NUM> at a slow repetition rate, Rs, during a first time period, t<NUM>, of an injection mold production cycle generating additive material cells <NUM>. The additive injector 306A may stop injecting additive material into the molten plastic material <NUM> for a second period of time, t<NUM>, to create a solid plastic region in the part being molded. The additive injector 306A may inject additive material into the molten plastic material <NUM> at a faster repetition rate, Rf, for a third time period, t<NUM>, resulting in larger, higher density additive material cells <NUM>. In addition to changing the pulse rate, the open-to-close duty cycle of the nozzle of the additive injector 306A may be increased or decreased to generate larger or smaller additive material cells <NUM> accordingly. Higher density, larger cells, such as those injected during the time t<NUM>, may be generated by increasing the repetition rate of injections as well as increasing the open-to-close duty cycle of the nozzle. Further, the additive injector 306A may reduce the injection repetition rate back to the slower rate Rs for a time period t<NUM> resulting in smaller, less dense additional material cells <NUM> in a corresponding region of the molded part <NUM>. As illustrated in <FIG> the molded part <NUM> then has a region of large, high density additional material cells which may result in a region where the part is structurally weaker than other regions. The weakness introduced by the large higher density additional material cells <NUM> may allow for the part to have a break point in the region containing the large, higher density additional material cells <NUM> intended to be broken off, such as a plastic tab or a twist off breakable tab for a plastic drink container.

In some embodiments, multiple additive injectors 306A, 306B, and 306C may be implemented to achieve the three regions of additive injection cells illustrated in <FIG>. The additive injectors 306A, 306B, and 306C inject additive material into a molten material <NUM> at respective fast and slow rates to achieve the desired size and density of additional material cells in each of the additive injector's 306A, 306B, and 306C corresponding regions of the mold cavity. Each of the additive injectors is independently controlled by a controller, such as the controller <NUM> of <FIG>, to inject additive material according to additive injection profiles that depend on the location, density, and size of desired additive material cells <NUM> in each additive injector's 306A, 306B, and 306C corresponding regions of the mold cavity. The example illustrated in <FIG> illustrates that a single additive injector 306A may be used to generate varied cell sizes and densities in a molded part implementing a dynamic additive injection profile, and that more additive injectors 306B and 306C may be used to generate the same part using multiple independent generally static additive injection profiles. Although <FIG> illustrates three additive injectors 306A, 306B, and 306C, any number of additive injectors may be used to inject additive material into a mold cavity. Additionally, any number of dynamic injection profiles, static injection profiles, or combination thereof, may be implemented to achieve the desired location, concentration, and amount of additional material and/or size of additional material cells in a mold cavity.

In some embodiments, the additive material may be a non-foaming material. Additive material cells, such as the cells <NUM> of <FIG> may be created by injection a non-foaming material into a mold cavity in a pulsed manner. The cell sizes and locations can be controlled with high precision by injecting the additive material directly into a gate or directly into the mold cavity, instead of injecting the additive material further upstream. In some embodiments, air or another light-weight fluid may be implemented as the additive material which may allow for the generation of lighter, less heavy, parts, for reducing the cost of generating a part, and/or reducing the amount of molten plastic material required for a part.

In other embodiments, the additive material may be a colorant. It may be desirable to inject colorants into a flow of molten plastic material to create a colored core for a molded part, or a colored surface of a part. The amount of colorant and location of the colorant may be precisely controlled by injecting a colorant into the gate or directly into the mold cavity of an injection molding machine, which may allow for higher resolution physical features and color designs in a part and on the surface of a molded part. In addition, the additive injectors and methods described herein provide more control over the density of an injected colorant which may allow for a wider range or gradient of colors for parts, and/or reduce color defects and inconsistencies of molded parts.

In embodiments the additive material may be a catalyst or a surfactant for controlling the surface tension of an injected plastic or molten material. In embodiments the additive material may be a thermoplastic material such as ABS, polypropylene, polyoxmethylene, polycarbonate, PVC, nylon, acrylic, styrene, polyether imide, or blends of the aforementioned material. In embodiments the additive material may be a supercritical fluid which may be used for localized dyeing, dissolving of a polymer, and potentially for accelerating the diffusion of a polymer. In yet other embodiments the additive material may be a powder introduced with solution assist. For example, in a metal injection molding system the additive material may be a metal powder to fabricate a part molded as a mix of between <NUM> to <NUM>% of the atomized metal powder and <NUM> to <NUM>% of a polymer wax.

The location and amount of the additive material <NUM> injected into the mold cavity <NUM> can be finely controlled, reducing the number of defects in molded parts. In addition, the methods and devices described herein enable high pressure, high speed material atomization during an injection mold cycle leading to possibilities for direct polymerization processes. The method and devices described herein enable increased control of device properties creating ranges for a parts weight, cost, durability, and color among other properties.

<FIG> is a flowchart illustrating an embodiment of a method <NUM> for injecting additive material into an injection molding machine, such as the machine <NUM> in <FIG>, downstream of the nozzle <NUM> of the injection molding machine <NUM>. At a block <NUM>, a physical injection molding machine (such as the injection molding machine <NUM> of <FIG>) and a physical additive injection device (such as the additive injection device <NUM> of <FIG>) are provided. A controller controls the additive injection device and receives information from sensors and/or additive injectors. At <NUM>, an additive injection profile including pressure, volume, and temperature curves and/or other information is provided to a controller for a desired injection rate or pulsed injection pattern of additive material.

At <NUM>, an initiating condition, which may be included in the additive injection profile, may be detected causing, at <NUM>, the initiation of injecting additive material according to the additive injection profile. The initiating condition may be a limit or initiating value such as an initiating temperature value, initiating pressure value, detected location of injected molten material in a gate or mold cavity, a detected flow rate of molten material, or any other measurable factor or value. In some embodiments the initiating condition may be time dependent such as a time delay after the initiation of an injection molding cycle. At <NUM>, sensors may sense or monitor the pressure, volume, temperature or other property of the additive material, additive injectors, molten material, or other parts of the injection molding machine and/or additive injection system. If, during an additive injection during an injection molding cycle, the sensed pressure, volume, temperature, and/or other properties do not match the corresponding curves or desired values in the additive injection profile, the injection of the additive material may be adjusted (at <NUM>).

In some embodiments, the controller controlling the additive injection system may send a signal to another controller controlling the injection molding machine to alter the injection of molten material to assist with achieving injection of additive material according to the additive injection profile. In other embodiments, the controller controlling the additive injection system may also control, or communicate directly with the injection molding machine allowing a single controller to make adjustments to the injection of both the molten plastic material, and the additive injection material. The controller may also be connected to other devices or send signals to other devices to make corrections or alterations to the pressure, temperature, volume, or other characteristics of the molten material, additive injection material, injection molding machine, and/or the additive injection system (e.g., controlling active heating of the mold cavity through means of heating lines, resistive heating elements, or other devices).

If during an additive injection cycle, the measured conditions or properties match the additive injection profile, additive material injection continues (at <NUM>) and the additive injection is monitored to see if the additive injection profile has been completed (at <NUM>). If the additive injection profile has not been completed, the additive injection continues (at <NUM>), and may be further monitored by the sensors and controller (at <NUM>) to ensure the additive injection is performed according to the additive injection profile. If it is determined that the additive injection profile has completed (at <NUM>) the additive injection ends (at <NUM>).

The device and method of implementing additive injectors to inject additional material into an injection molding system may be used in an injection molding process, which is the primary process discussed herein. However, the method of injection additive material may alternately be used in other molding processes, such as a substantially constant pressure injection molding process, an injection-blow molding process, a blow molding process, a metal injection molding (MIM) process, a reaction injection molding (RIM) process, a liquid injection molding (LIM) process, a structural foam molding process, a liquid crystal polymer (LCP) molding process, and an injection-stretch blow molding process.

In some embodiments, a controller, such as the controller <NUM> of <FIG>, may interface with or control the injection molding machine <NUM> in addition to controlling the additive injection device <NUM>. The controller <NUM> may control the injection of the molten plastic material <NUM> and the additive material <NUM>, and may monitor any properties including the pressure, volume, temperature, flow rate, or any other characteristic of the molten plastic material <NUM>, additive material <NUM>, the injection molding machine <NUM> and/or the additive injection device <NUM>. Controlling both the injection of the injection molding machine <NUM> and the additive injection device <NUM> with the same controller may allow for more accurate control of the injection of additive materials during an injection molding cycle due to the ability to monitor and control the characteristics and injection of the plastic molten material.

The device and method of implementing additive injectors to inject additional material into an injection molding system may be used in micro-molding, 3D printing processes, wire electrical discharge machining (EDM), additive manufacturing processes, material deposition, and similar technologies. <FIG> is an illustration of a system <NUM> that integrates an apparatus for producing, processing, depositing, and fusing polymer droplets, flakes, and/or particles onto a part to achieve high resolution printing of polymer or metal parts and structures. An additive injection device <NUM> with additive injectors <NUM> may inject additive materials onto a photoreceptive tape <NUM> to assist in ink and laser printing onto a polymer structure or part <NUM>. A recharging drum <NUM> may apply an AC or DC bias to the photoreceptive tape <NUM> to remove any residual charges on the photoreceptive tape <NUM> and to ensure a uniform negative potential on the photoreceptive tape <NUM>. The additive injection device <NUM> may have one or more additive injectors <NUM> that deposit additive material onto the photoreceptive tape <NUM> at rates up to <NUM>,<NUM> injections per minute to generate high resolution depositions of the additive material. A precharge station <NUM> may provide a positive charge or remove areas of negative charge on the photoreceptive tape <NUM>. A charging station <NUM> may further provide positive charge or remove negative charge from the photoreceptive tape <NUM>. A solutions assist deposition station <NUM> may deposit negatively charged particles or material onto the photoreceptive tape <NUM>. The negatively charged particles or material only adhere to the photoreceptive tape <NUM> at locations where the negative charge has been removed from the photoreceptive tape <NUM> due to the fact that negatively charged particles repel each other. A fusion station <NUM> may then heat the materials on the photoreceptive tape <NUM> causing the materials to fuse to a part <NUM> at the corresponding locations of the materials on the photoreceptive tape <NUM>. A cooling drum <NUM> may provide thermal cooling to the photoreceptive tape to allow for the tape to be recharged, and reused for another iteration of the described deposition process. The system <NUM> may be implemented in high temperature (<NUM>) fusion processes to achieve molding and deposition capabilities for metals. While the description of the system <NUM> herein pertains to deposition of materials onto a part <NUM> in a fusion system, similar implementations of a system <NUM> with an additive injection device <NUM> may be implemented for ink and laser printing systems, wire electrical discharge machining, and fusion systems in electron microscopy.

To the extent that the term "includes" or "including" is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term "comprising" as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term "or" is employed (e.g., A or B) it is intended to mean "A or B or both. " When the applicants intend to indicate "only A or B but not both" then the term "only A or B but not both" will be employed. Thus, use of the term "or" herein is the inclusive, and not the exclusive use. See, Bryan A. Gamer, A Dictionary of Modem Legal Usage <NUM> (2d. Also, to the extent that the terms "in" or "into" are used in the specification or the claims, it is intended to additionally mean "on" or "onto. " Furthermore, to the extent the term "connect" is used in the specification or claims, it is intended to mean not only "directly connected to," but also "indirectly connected to" such as connected through another component or components.

Claim 1:
An additive injection device for an injection molding system comprising:
an additive injection unit including
one or more additive tanks (<NUM>), each having a supply of an additive fluid (<NUM>;
one or more additive injectors (<NUM>) in fluid communication with the one or more additive tanks (<NUM>), each of which receives and injects an additive fluid material into an injection molding machine (<NUM>);
a common manifold (<NUM>) connecting each of the one or more additive tanks (<NUM>) and the one or more additive injectors (<NUM>);
and one or more additive pumps (<NUM>) that pump the additive fluid through the one or more additive injectors;
a controller (<NUM>) adapted to control operation of the additive injection device; and
one or more sensors (<NUM>, <NUM>) coupled to the additive injection device and the controller (<NUM>);
wherein at least one of the one or more sensors (<NUM>, <NUM>) is adapted to measure at least one non-time dependent variable during an injection mold cycle;
wherein
the controller (<NUM>) is adapted to commence an additive injection profile upon the at least one non-time dependent variable reaching a threshold value.