WO2014089305A1

WO2014089305A1 - Injection molding apparatus

Info

Publication number: WO2014089305A1
Application number: PCT/US2013/073337
Authority: WO
Inventors: Tomasz Uracz; Darrin Albert Macleod; William Steven Keir; Berend Doane
Original assignee: Husky Injection Molding Systems Ltd; Husky Injection Molding Systems SA
Current assignee: Husky Injection Molding Systems Ltd; Husky Injection Molding Systems SA
Priority date: 2012-12-05
Filing date: 2013-12-05
Publication date: 2014-06-12
Anticipated expiration: 2015-06-05

Abstract

An injection molding apparatus including a body and a self-regulating heating element. The self-regulating heating element is thermally connected to the body. The self-regulating heating element is configured to regulate, in use, a temperature of the body.

Description

INJECTION MOLDING APPARATUS

RELATED APPLICATIONS This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Serial No. 61/733,444, entitled "INJECTION MOLDING APPARATUS" filed on December 5, 2012, which is herein incorporated by reference in its entirety.

TECHNICAL FIELD

Non-limiting embodiments disclosed herein generally relate to an injection molding apparatus. More particularly, non-limiting embodiments disclosed herein generally relate to an injection molding apparatus including a self-regulating heating element. BACKGROUND

Molding is a process by virtue of which a molded article can be formed from molding material by using a molding system. Various molded articles can be formed by using a molding process, such as an injection molding process. One example of a molded article that can be formed, for example, from polyethylene terephthalate (PET material) is a preform suitable for subsequent blow molding into a final shaped container.

A typical molding system includes inter alia an injection unit, a clamp assembly and a mold assembly. One example of an injection unit is a reciprocating screw type injection unit. Within the reciprocating screw type injection unit, molding material (such as PET or the like) is fed through a hopper, which in turn feeds an inlet end of the injection unit. A screw is encapsulated in a barrel, which is heated by a barrel heater. Helical flights of the screw convey the molding material along an operational axis thereof. Typically, a root diameter of the screw is progressively increased along the operational axis thereof, in a direction away from the inlet end.

As the molding material is conveyed along the screw, it is sheared between the flights of the screw, the screw root, and the inner surface of the barrel. The molding material is also subjected to some heat emitted by the barrel heater and conducted through the barrel. When a desired amount of the molding material is accumulated in a space at a discharge end of the screw (which is an opposite extreme of the screw vis-a-vis an inlet end), the screw stops its rotation. The screw is then forced forward (in a direction away from the inlet end thereof), forcing the desired amount of the molding material into one or more molding cavities. The screw may perform two functions in the screw type injection unit, namely plasticizing of molding material and injecting the molding material into a mold cavity. The molding material may enter the mold cavity through a gate via a molding material distribution device, e.g. a hot runner. A molding material distribution device is typically comprised of several components, including a sprue to receive molding material from the injection unit, a manifold assembly to distribute the molding material to several ports, and a plurality of nozzles to transfer the molding material from the ports to the receiving mold cavity defined by the mold assembly. Usually, molding material distribution devices and mold assemblies are treated as tools that may be sold separately (or together) from molding systems.

SUMMARY In accordance with an aspect disclosed herein, there is provided an injection molding apparatus. The injection molding apparatus includes a body. The injection molding apparatus further includes a self- regulating heating element. The self-regulating heating element is thermally connected to the body. The self-regulating heating element is configured to regulate, in use, a temperature of the body. According to another aspect disclosed herein, an injection molding apparatus to pass melt into a mold cavity includes a body and a self -regulating heating element thermally connected to the body. The self-regulating heating element includes a conductive-polymer matrix. The self-regulating heating element is configured to regulate a temperature of the body. According to yet another aspect disclosed herein, an injection molding apparatus for passing melt into a mold cavity includes a body and at least one self-regulating heating element disposed on the body. The self-regulating heating element has at least two heating wires arranged in parallel. The wires have a sufficient effective temperature coefficient of resistivity to regulate a temperature of the body. These and other aspects and features of non-limiting embodiments will now become apparent to those skilled in the art upon review of the following description of specific non-limiting embodiments in conjunction with the accompanying drawings. DETAILED DESCRIPTION OF THE DRAWINGS

The non-limiting embodiments will be more fully appreciated by reference to the accompanying drawings, in which:

FIG. 1 depicts a schematic representation of an injection molding apparatus including a manifold assembly according to one embodiment;

FIG. 2A depicts a plan view of a manifold assembly according to one embodiment;

FIG. 2B depicts a perspective representation of a manifold assembly according to the embodiment depicted in FIG. 1 ;

FIG. 3 depicts a perspective representation of a nozzle according to one embodiment;

FIG. 4 depicts a perspective representation of an injection molding apparatus including a manifold plate according to one embodiment;

FIG. 5 depicts a perspective representation of a sprue bushing according to one embodiment; FIG. 6 depicts a perspective representation of a transition bushing according to one embodiment; FIG. 7 depicts a perspective representation of a sprue bar according to one embodiment; FIG. 8A depicts a perspective representation of a nozzle according to one embodiment; FIG. 8B depicts a perspective representation of a nozzle according to another embodiment; FIG. 9A depicts a perspective representation of a nozzle according to one embodiment; FIG. 9B depicts a perspective representation of a nozzle according to another embodiment; FIG. 10 depicts a schematic representation of a manifold according to another embodiment; and FIG. 11 depicts a schematic representation of an injection molding apparatus according to another embodiment.

The drawings are not necessarily to scale and may be illustrated by phantom lines, diagrammatic representations and fragmentary views. In certain instances, details that are not necessary for an understanding of the embodiments or that render other details difficult to perceive may have been omitted.

DETAILED DESCRIPTION OF THE NON-LIMITING EMBODIMENT(S)

Reference will now be made in detail to various non-limiting embodiment(s) of injection molding apparatus. It should be understood that other non-limiting embodiment(s), modifications and equivalents will be evident to one of ordinary skill in the art in view of the non-limiting embodiment(s) disclosed herein and that these variants should be considered to be within scope of the appended claims.

Furthermore, it will be recognized by one of ordinary skill in the art that certain structural and operational details of the non-limiting embodiment(s) discussed hereafter may be modified or omitted (i.e. non-essential) altogether. In other instances, well known methods, procedures, and components have not been described in detail.

FIG. 1 is a schematic representation of an injection molding system 900 in accordance with one embodiment. Generally, the injection molding system 900 includes (and is not limited to): (i) an injection unit 902, (ii) mold assembly 904, (iii) a clamp assembly (not separately numbered), and (iv) a melt distribution device 906. The injection unit 902 includes: (i) a barrel 908, (ii) a hopper 910, and (iii) a screw 912. The mold assembly 904 includes: (i) a movable mold portion 914, and (ii) a stationary mold portion 916. The movable mold portion 914 and the stationary mold portion 916 cooperate to define at least one mold cavity 918. The melt distribution device 906 includes: (i) a manifold assembly 920, and (ii) a plate framework 922. The manifold assembly 920 defines a flow channel 924. The plate framework 922 includes: (i) a manifold plate 926 and (ii) a backing plate 928.

FIG. 1 also depicts an injection molding apparatus including a body 100 and self-regulating heating element 120, according to one embodiment. The body 100 includes a manifold assembly 920. Self- regulating heating element 120 is thermally connected to the body 100. FIG. 1 further depicts an injection molding apparatus including a body 200 and self-regulating heating element 120, according to another embodiment. The body 200 includes a barrel 908. Self- regulating heating element 120 is in thermal communication with the body 200. As depicted, the self-regulating heating element 120 is attached to an outer surface of the body 100, 200. Self-regulating heating element 120 may be attached to the body 100, 200, by any suitable means. For example, the self-regulating heating element 120 may be attached to the body 100, 200 via a fastener (e.g. a screw, a bolt, a rivet, etc.). The self-regulating heating element 120 may also be attached to the body 100, 200 via an adhesive, or secured in any other manner (e.g. a combination of an adhesive and a fastener, etc.), as the present disclosure is not limited in this respect. In some embodiments, the self -regulating heating element 120 is embedded in the body.

The self -regulating heating element 120 has a conductive-polymer heating matrix (not separately numbered) extruded between two parallel bus conductors (not separately numbered). The two parallel conductors are configured, in use, to carry an electric current. The conductive-polymer heating matrix may be extruded between two parallel bus conductors such that the two parallel conductors are encased together within the conductive-polymer heating matrix. Heat is generated in the conductive polymer matrix when the two parallel bus conductors are energized. The two parallel bus conductors provide uniform voltage across the conductive-polymer heating matrix by providing current down the entire length of the self-regulating heating element 120. The conductive-polymer heating matrix generally includes a semi-conductive polymer having a high positive temperature coefficient. The conductive-polymer heating matrix behaves as an infinite number of parallel resistors, which permits the self -regulating heating element 120 to be cut to any length without creating cold sections.

As depicted in FIG. 1, the self -regulating heating element 120 is configured as an elongate conductive-polymer web. However, the configuration of the conductive-polymer heating matrix is not limited to a specific configuration. The conductive-polymer heating matrix may be configured as, for example, a cable, a tape, a mat, etc. An optional metallic braid (not depicted) covering the self- regulating heating element 120 may be provided for additional mechanical or electrical protection, or for use in hazardous areas.

In operation, heat output varies along the length of the self -regulating heating element 120 depending upon the temperature of the conductive-polymer heating matrix. Once the two parallel bus conductors are energized, the temperature of the self-regulating heating element 120 starts to increase proportionally to the amount of current flowing. As the temperature increases, the electrical paths in the conductive-polymer heating matrix become longer. As the electrical paths in the conductive- polymer heating matrix become longer, overall the resistance of the self-regulating heating element 120 increases. This causes the amount of current flowing to decrease, thereby decreasing the heat output of the self -regulating heating element 120 and producing a self-regulating effect. As will become apparent below, the self -regulating heating element may be coupled to any suitable injection molding component, as aspects disclosed herein are not limited to any particular component to which the self -regulating heating element is attached.

FIG. 2A is a perspective representation of an injection molding apparatus according to one embodiment. As depicted, the body 300 includes a manifold assembly 920. The self-regulating heating element 120 is attached to an outer top surface of the manifold assembly 920. The self- regulating heating element 120 at least partially surrounds an outer circumference of the outer top surface of the manifold assembly 920. In one embodiment, the self-regulating heating element 120 is configured as a web.

FIG. 2B is a perspective representation of the injection molding apparatus according to the embodiment depicted in FIG. 1. As depicted, the body 100 includes a manifold assembly 920. The self-regulating heating element 120 is attached to an outer side surface of the manifold assembly 920. In one embodiment, the self -regulating heating element 120 is configured as a web.

FIG. 3 is a perspective representation of an injection molding apparatus according to another embodiment. As depicted, the body 400 includes a nozzle 930. The self-regulating heating element 120 is attached to and surrounds an outer surface of the nozzle 930. In one embodiment, the self- regulating heating element 120 is configured as a web.

FIG. 4 is a perspective representation of an injection molding apparatus according to an embodiment. As depicted, the body 500 includes a manifold plate 926. A plurality of self-regulating heating elements 120 is attached to a surface of the manifold plate 926. In the embodiment shown, each of the plurality of self-regulating heating elements 120 is configured as a web.

FIG. 5 is a perspective representation of an injection molding apparatus according to another embodiment. As depicted, the body 600 includes a sprue bushing 940. The self-regulating heating element 120 is attached to and surrounds an outer surface of the sprue bushing 940. In one embodiment, the self-regulating heating element 120 is configured as a web. FIG. 6 is a perspective representation of an injection molding apparatus according to one embodiment. As depicted, the body 700 includes a transition bushing 950. The self -regulating heating element 120 is attached to and surrounds an outer surface of the transition bushing 950. In one embodiment, the self-regulating heating element 120 is configured as a web.

FIG. 7 is a perspective representation of an injection molding apparatus according to another embodiment. As depicted, the body 800 includes a sprue bar 960. The self -regulating heating element 120 is attached to an outer surface the sprue bar 960. In one embodiment, the self-regulating heating element 120 is configured as a web.

Although the self-regulating heating element has been shown and described as having a conductive- polymer heating matrix, a person having skill in the art should appreciate that the self-regulating heating element may have other suitable configurations and comprise other suitable materials, as the present disclosure is not limited in this respect.

In some embodiments, for example, the self-regulating heating element includes a resistive material. The resistive material may include a resistive metal alloy. The resistive material also may include a conductive alloy. In some embodiments the resistive material has a high temperature coefficient of resistivity (TCR). The resistive material also may have a high positive temperature coefficient. In some embodiments, although the physical mechanisms may differ, the high TCR wire may be used interchangeably with the conductive polymer matrix.

Without wishing to be bound by theory, conductors may experience a rise in electrical resistance with a rise in temperature. For materials having a high TCR, the increase in resistance can be determined by:

R_x = Ro ( 1 + TCR x ΔΤ)

where R_x is a resistance of the conductor at a reference temperature, Ro is the resistance of the conductor at a known or starting temperature, TCR is the temperature coefficient of resistivity of the selected material of the conductor, and ΔΤ is the change in temperature between the reference temperature Τχ and the starting temperature To.

In some embodiments, the resistive material (or materials) is selected based on the material's TCR to allow the heating element to passively limit power. Without wishing to be bound by theory, as the temperature increases, resulting in an increased resistance, the current flow, and thus the heat production, drops proportionally across the resistive material. For a high TCR resistive material, there is a threshold temperature TTCR at which heat the production equals the heat loss such that the temperature remains constant, or substantially constant. In some embodiments, the TCR, and thus the material, can be selected such that the threshold temperature TTCR is well above the desired operating temperature but remains below the melting temperature of the resistive material. This, in turn, may prevent the heater from overheating, melting or failing.

As illustrated in FIG. 8 A, which is a perspective view of a nozzle body 800 used in an injection molding apparatus according to one embodiment, the self-regulating heating element 802 may include a resistive wire 804 that is thermally connected to an exterior surface 806 of the nozzle 800. The self -regulating heating element 802 may be attached to the exterior surface 806 of the nozzle by any suitable means. For example, the heating element 802 may be attached via a fastener (e.g. a screw, a bolt, a rivet, etc.), via an adhesive, or secured in any other manner (e.g. a combination of an adhesive and a fastener, etc.), as the present disclosure is not limited in this respect. In some embodiments, the wire 804 is attached directly to the surface of the nozzle, while in other embodiments the wire may be placed in a ceramic tube that is attached to the surface 806 of the nozzle 800. The wire 804 also may be wrapped around the surface 806 of the nozzle 800. In some embodiments, the self-regulating heating element 802 is embedded in the nozzle 800. The wire also may be placed onto a dielectric layer that is first deposited onto or otherwise disposed over the surface 806 of the nozzle 800. In some embodiments the wire 804 may be permanently attached to the nozzle, although in other embodiments the wire may be removably attached. The heating element 802 also may be covered with a protective layer (not shown).

The resistive wire 804 of the heating element 802 may include a single resistive material in some embodiments, while in other embodiments, the resistive wire may include more than one resistive materials. For example, in one embodiment, the resistive wire includes Nichrome A, a resistive material with a TCR of 0.0001 /°C. In other embodiments, the resistive wire includes a nickel - cobalt - iron alloy with a TCR of 0.0033 /°C. Although two examples of resistive materials are provided above, this aspect of the disclosure is not limited in this regard. Other suitable resistive materials, and combinations of materials, may be used in to form the resistive wire 804. Although only one wire is shown in the heating element 802 of FIG. 8A, the self-regulating heating element 802 may include more than one wire in other embodiments. For example, as shown in FIG. 8B, the heating element 802 may include first and second wires 804a, 804b having first and second TCR, TCR1 and TCR2, respectively. In some embodiments, the wires 804a, 804b are arranged in parallel. Without wishing to be bound by theory, in embodiments having first and second wires 804a, 804b in parallel, the heating element has an effective TCR equal to the average of the TCR of the first and second wires 804a, 804b, namely the average of TCR1 and TCR2. As with the heating element 802 having only one wire 804, the effective TCR for embodiments having two high TCR wires 804a, 804b in parallel also may be chosen to passively limit power.

In embodiments having two wires, the first wire 804a and second wire 804b may include the same material. The first and second wires 804a, 804b also may include different materials. Additionally, while in some embodiments the first and second TCR (i.e., TCR1 and TCR2) may be the same, or substantially the same, in other embodiments, the first and second TCR (i.e., TCR1 and TCR2) may be different. Without wishing to be bound by theory, the first and second TCR may be the same, or substantially the same, in embodiments in which the first and second wires 804a, 804b include different materials. As with the embodiments including a single wire, the first and second wires 804a, 804b each may include Nichrome A or a nickel - cobalt - iron alloy. Other resistive materials having a high TCR also may be used for the first and second wires as this aspect of the disclosure is not limited in this regard. As shown in FIGS. 8 A and 8B, the wire (or wires) may be arranged on the surface 806 of the nozzle 800 in a pattern. Without wishing to be bound by theory, the pattern of the wire(s) may be chosen to effectuate a desired temperature profile for the plastic material or melt being passed through the nozzle during injection molding. As illustrated in FIGS. 8A and 8B, the wire (or wires) may be wrapped helically around the exterior surface 806 of the nozzle. A person having ordinary skill in the art should appreciate that the pitch of the wire(s) may be varied to adjust the desired temperature profile of the nozzle. A skilled artisan should further appreciate that the pattern of the wire(s) may be varied in other embodiments as this aspect of the disclosure is not limited in this regard.

Without wishing to be bound by theory, the conduction path of the heating element 802 is along the wire (or wires). In some embodiments, the conduction path of the wire (or wires) is oriented such that heat is generated perpendicular to the natural temperature gradient of the heated nozzle. As is shown in FIGS. 8A and 8B, the wires 804, 804a, 804b are arranged around the circumference of heating element 802 on a plane perpendicular to an axis A of the nozzle. In some embodiments, the heating element 802 provides its own temperature feedback. As seen in FIGS. 8 A and 8B, the heating element 802 may be connected to a controller 808. In some embodiments, the heating element 802 is connected to the controller via two wires 810a, 810b, although heating element 802 may be connected to the controller 808 via only one wire. Without wishing to be bound by theory, the controller 808 may be configured to calculate the temperature of the heating element 802 from the current and/or voltage across the heating element 802. In some embodiments, this is determined by measuring the difference in current and/or voltage across the first and second wires 810a, 810b. In some embodiments, the temperature of the heating element 802 represents the temperature of the entire heating element 802, or the bulk temperature. The temperature also may be indicative of the heat production. In some embodiments, the temperature is calculated by taking the average of the temperature of the entire heating element 802.

In embodiments in which the heating element 802 serves as the temperature sensor, fewer wires may be used to connect the nozzle 800 to the controller 808. In some embodiments, the injection molding apparatus uses half the number of wires than would otherwise be used. In some embodiments, as is shown in FIG. 9A, the self-regulating heating element 802 includes a resistive wire 804 extending between first and second parallel bus conductors 812a, 812b and around the circumference of exterior surface 806 of the nozzle 800. As shown in FIGS. 9A, although the heating element 802 has seven (7) wires 804 connected between the first and second bus conductors 812a, 812b, the heating element 802 may include more or less wires 804 in other embodiments. As with other embodiments, the wires 804 may be arranged around the circumference of heating element 802 on a plane perpendicular to an axis A of the nozzle. The wires 804 also may include the same or different resistive material as this aspect of the disclosure is not limited in this regard. A skilled artisan should further appreciate that the pattern and/or pitch of the wires 804 may be varied in other embodiments to effectuate a desired temperature profile for the nozzle 800.

As illustrated in FIG. 9B, in some embodiments, the heating element 802 includes first and second parallel wires 804a, 804b extending between the first and second bus conductors 812a, 812b. Although seven (7) sets of first and second 804a, 804b wires are shown in this embodiment, a person having skill in the art should appreciate that more of less sets of first and second wires 804a, 804b may be used as this aspect of the disclosure is not limited in this regard.

As is shown in Figure 9 A and 9B, the bus conductors 812a, 812b may be arranged parallel to the axis A of the nozzle 800. The bus conductors 812a, 812b, may be positioned on any suitable portion of the nozzle 800, although they are shown on a front portion of the nozzle 800 in these figures. In some embodiments, as is shown, the bus conductors 812a, 812b are separated from one another by a distance. Without wishing to be bound by theory, any suitable distance for insulating the first bus conductor 812a from the second bus conductor 812b may be used as this aspect of the disclosure is not limited in this regard. In the embodiments shown in FIGS. 9 A and 9B, the nozzle 800 includes a separate temperature sensor 816. The temperature sensor 816 may include a thermocouple, an RTD, or another suitable sensing device, as this aspect of the disclosure is not limited in this regard. In some embodiments, the nozzle 800 includes a thermocouple for measuring the temperature at a point of contact between the thermocouple and the nozzle 800. As is shown in FIGS. 9A and 9B, the temperature sensor 816 is connected to the controller 808 via a wire 818. A person having skill in the art should appreaciate that more than one wire may be used to connect the temperature sensor 816 to the controller 808 in other embodiments. In operation, the temperature sensor 816 may provide temperature feedback to the controller 806.

As shown in FIGS. 9 A and 9B, the first and second bus conductors 812a, 812b are connected to the controller 808 via first and second wires 814a, 814b. As with other embodiments, in operation, once the bus conductors 812a, 812b are energized, a uniform voltage is provided to each of the resistive wires 804, 804a, 804b. In some embodiments, the temperature of the self-regulating heating element 802 starts to increase proportionally to the amount of current flowing through the resistive material. Without wishing to be bound by theory, when a high TCR resistive material is used, localities with relatively high heat losses and correspondingly lower temperatures may receive more heat, while localities with relatively low heat loss and correspondingly high temperatures may receive less heat. This, in turn, may result in a self-adjusting heat delivery system that may deliver heat where it is needed most, irrespective of the changes in heat loss over time. As with other embodiments, the resistive wires used in these embodiments may be selected such that the TCR (or effective TCR) of the wire(s) allows the wire(s) to passively limit power.

Although the self-regulating heating element 802 is shown and described as being attached to the nozzle 800 in the embodiments shown in FIGS. 8 and 9, a skilled artisan should appreciate that the heating element 802 may be used with any part of the injection molding apparatus. For example, the heating element 802 may be attached to the manifold assembly, to the barrel, to the manifold plate, to the sprue bushing, to the transition bushing, or to another suitable part of the molding apparatus. The heating element 802 also may be affixed to any suitable portion of the nozzle 800, or to any a suitable portion of another part of the apparatus. Additionally, while only one heating element 802 is shown on the nozzle 800 in FIGS. 8 and 9, a skilled artisan should appreciate that the nozzle (or other suitable part of the injection molding apparatus) may have more than one heating element 802.

As shown in FIG. 10, a perspective view of a manifold 1000 according to another embodiment, the manifold 1000 may include more than one high TCR heating element 1002. In some embodiments, the heating elements 1002 are arranged in parallel. In some embodiments, each heating element 1002 is connected to an individual, corresponding controller 1004. As with previous examples, the heating element 1002 may be connected to the controller via two wires (as is shown), although the heating element also may be connected to the controller via only one wire. Each controller, in turn, may be connected to a central controller or control system 1006. In some embodiments, the heating elements 1002 are not connected to individual controllers 1004 but are instead all directly connected to the central controller 1006.

Although the heating elements are shown as having a helical pattern in FIG. 10, a person having ordinary skill should appreciate that other suitable patterns may be used. A skilled artisan also should appreciate that although eight heating elements 1002 are shown in this figure, the manifold may have more or less heating elements. Additionally, while each of the heating elements 1002 is shown having two wires arranged in parallel, each heating element also may include only one wire as this aspect of the disclosure is not limited in this regard. Further, as discussed above with respect to the nozzle, more than two wires in a parallel configuration may be employed.

In some embodiments, the average temperature of the manifold 1000 shown in FIG. 10 is calculated from the resistance of all the heating elements 1002 in parallel and the overall current. In other embodiments, the temperature may be measured with a temperature sensor such as a RTD, a thermocouple, or another suitable sensing device. Without wishing to be bound by theory, in some embodiments, the controller 1004, 1006 may be used to maintain the average temperature of the manifold 1000. For each of the individual heating element 1002, the individual heating element temperature may be used to determine individual or local current flow and the rate of local heat delivery. Without wishing to be bound by theory, localities with relatively high heat losses, and correspondingly lower temperatures may receive more heat, while localities with relatively low heat loss and correspondingly high temperatures may receive less heat. This, in turn, may result in a self- adjusting heat delivery system that may deliver heat where it is needed most, irrespective of the changes in heat loss over time.

Although the self-regulating heat delivery systems in FIGS. 8-10 are described as having one heating element, or, for FIG. 10, more than one heating element, in a single part, a skilled artisan should appreciate that the injection molding system may have at least one heating element in more than one part. For example, as shown in FIG. 11, the apparatus 1100 may have a heating element in each of the nozzle 1102, the manifold 1104, and the bushing 1106. Although only one heating elements is shown in each of the three parts in this embodiment, a person having ordinary skill in the art should appreciate that there may be more or less heating elements in each part. A skilled artisan also should appreciate that the apparatus may include heating element(s) in only two of the shown parts. As with other embodiments, the heating elements in the apparatus may be wired in parallel. In some embodiments, each of the heating elements are connected to individual, corresponding controllers (not shown). In other embodiments all the heating elements are connected to a central controller 1108. As with the system described in FIG. 10, the average temperature of the apparatus may be calculated or monitored to maintain the average temperature of the apparatus. Additionally, as discussed above, the local temperature of one of the heating elements may determine the local current flow and thus the rate of local heat delivery. In some embodiment, parts with relatively high heat losses and correspondingly lower temperatures may receive more heat while parts having relatively low heat losses and correspondingly high temperatures may receive less heat.

It is noted that the foregoing has outlined some of the more pertinent non-limiting embodiments. It will be clear to those skilled in the art that modifications to the disclosed non-embodiment(s) can be effected without departing from the spirit and scope thereof. As such, the described non-limiting embodiment(s) ought to be considered to be merely illustrative of some of the more prominent features and applications. Other beneficial results can be realized by applying the non-limiting embodiments in a different manner or modifying them in ways known to those familiar with the art. This includes the mixing and matching of features, elements and/or functions between various non- limiting embodiment(s) is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as appropriate, unless described otherwise, above. Although the description is made for particular arrangements and methods, the intent and concept thereof may be suitable and applicable to other arrangements and applications.

Claims

WHAT IS CLAIMED IS:

1. An injection molding apparatus to pass melt into a mold cavity, the apparatus comprising:

a body; and

a self -regulating heating element thermally connected to the body, the self-regulating heating comprising a conductive-polymer matrix;

wherein the self -regulating heating element is configured to regulate a temperature of the body.

2. The injection molding apparatus of claim 1, wherein the conductive-polymer heating matrix is extruded between two parallel conductors.

3. The injection molding apparatus of claim 2, wherein the conductive-polymer heating matrix is configured as a web.

4. The injection molding apparatus of claim 1, wherein the self-regulating heating element is attached to an outer surface of the body.

5. The injection molding apparatus of claim 1 , wherein the body includes one of a manifold assembly, a barrel, a nozzle, a manifold plate, a sprue bushing, a transition bushing, and a sprue bar.

6. The injection molding apparatus of claim 2, wherein the parallel conductors are configured to carry an electric current.

7. The injection molding apparatus of claim 2, wherein the parallel conductors are encased together within the conductive-polymer heating matrix.

8. The injection molding apparatus of claim 1, wherein the conductive-polymer heating matrix is configured to be one of a cable, a tape, and a mat.

9. An injection molding apparatus for passing melt into a mold cavity, the apparatus comprising; a body;

at least one self -regulating heating element disposed on the body, the self -regulating heating element having at least two heating wires arranged in parallel;

wherein the wires have a sufficient effective temperature coefficient of resistivity to regulate a temperature of the body.

10. The injection molding apparatus of claim 9, further comprising a first controller, the at least one self-regulating heating element being connected to the first controller.

11. The injection molding apparatus of claim 9, wherein the at least two heating wires comprise a resistive material.

12. The injection molding apparatus of claim 11, wherein the at least two heating wires comprise a resistive alloy.

13. The injection molding apparatus of claim 9, wherein the at least two heating wires comprise the same material.

14. The injection molding apparatus of claim 9, wherein the at least two heating wires comprise different materials.

15. The injection molding apparatus of claim 9, wherein the effective temperature coefficient of resistivity is sufficient to allow the temperature of the body to at least meet a desired operating temperature while also remaining below a failing temperature of the at least one self-regulating heating element.

16. The injection molding apparatus of claim 15, wherein the failing temperature is a melting temperature of the at least two heating wires.

17. The injection molding apparatus of claim 10, further comprising a second controller, the second controller being connected to one of the at least one self -regulating heating element and the first controller.

18. The injection molding apparatus of claim 11, wherein the injection molding apparatus includes at least two self -regulating heating elements, the at least two self-regulating heating elements being arranged in parallel.

19. The injection molding apparatus of claim 9, wherein the body comprises at least one of a manifold assembly, a barrel, a nozzle, a manifold plate, a sprue bushing, a transition bushing, and a sprue bar.