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Controller for a heater and an associated method of useRelated Patent Categories: Electric Heating, Heating Devices, With Power Supply And Voltage Or Current Regulation Or Current Control Means, Automatic Regulating Or Control MeansController for a heater and an associated method of use description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070215598, Controller for a heater and an associated method of use. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD OF THE INVENTION [0001] The present invention relates to control of a heater, and particularly an improved controller utilizing a digital signal processor with feedback for fast and accurate control of a heater that can be utilized in an injection molding system. BACKGROUND OF THE INVENTION [0002] In a typical injection molding system, molten resin is loaded into a tubular passage called a runner. The molten resin flows from the runner through a gate valve and into the cavity of the mold. The resin in the mold is then cooled and hardens into an article. The mold is opened and the article is ejected. [0003] In a cool runner injection molding system, resin inside the runner and the cavity of the mold is cooled and ejected. In contrast, in a hot runner injection system, resin in the hot runner is kept molten and injected into the cavity during the next molding cycle. In order to keep the resin in the runner molten, the runner is heated. In addition, the resin at the gate valve is cooled to prevent molten resin from dripping out when the mold is opened. This process requires precise and fast temperature control to effectuate changes. In addition, in the hot runner injection molding system, a heater can be utilized with a number of components, including, but not limited to a barrel, a distributor, and a nozzle. [0004] There are a number of different ways to heat the runner. These include: electric resistance heating; induction heating; and a combination of both types of heating. Induction heating consists of winding insulated, conductive wires around the area surrounding the runner near the gate. When the windings are supplied with high frequency power, the area around the runner is heated by electromagnetic induction. [0005] U.S. Pat. No. 4,726,751 to Shibata et al. discloses a temperature control system for a hot runner plastic injection molding system where the voltage frequency is varied that is applied to the heater windings. However, Shibata et al. only adjusts the power to the heaters in discrete, automatic steps with parallel resistors and/or capacitors rather than utilizing seamless frequency variations based on a sensed temperature. Furthermore, Shibata et al. is limited to only varying voltage frequency and not voltage amplitude. U.S. Pat. No. 4,726,751 to Shibata et al. is incorporated herein by reference in its entirety. [0006] U.S. Pat. No. 4,788,485 to Kawagishi et al., U.S. Pat. No. 5,136,494 to Akagi et al., U.S. Pat. No. 5,177,677 to Nakata et al., U.S. Pat. No. 5,504,667 to Tanaka et al., and U.S. Pat. No. 5,663,627 to Ogawa disclose utilizing pulse width modulation to convert AC power to DC power and are directed solely to motor control and not heating systems. U.S. Pat. No. 4,851,982 to Tanahashi discloses a system that uses pulse width modulation, conversion of AC power to DC power and then back to AC power, and then varying the voltage and the frequency for use with elevator motors. [0007] U.S. Pat. No. 5,285,029 to Araki, U.S. Pat. No. 4,545,464 to Nomura, U.S. Pat. No. 4,879,639 to Tsukahara, U.S. Pat. No. 4,894,763 to Ngo, U.S. Pat. No. 5,465,202 to Ibori et al., and U.S. Pat. No. 5,694,307 to Murugan disclose converting AC power to DC power and then back to AC power but does not involve the field of temperature control. U.S. Pat. No. 6,603,672 to Deng discloses conversion of DC current to AC current which is then converted from AC current to DC current and then controlling the output frequency. However, Deng does not disclose applying these methods to temperature control in the field of heaters. U.S. Pat. No. 6,009,003 to Yeo and U.S. Pat. No. 4,816,985 to Tanahashi disclose current/voltage control for an elevator system. [0008] U.S. Pat. No. 3,881,091 to Day discloses a control for heating currents in a multiple cavity injection molding machine using a solid state, bidirectional conducting device for controlling current load, a phase shifting capacitor connected to the conducting device, a variable resistor connected in parallel to the conducting device and a switch to short out the variable resistor to maximize the flow of current. However, Day does not disclose utilizing a digital signal processor for controlling voltage frequency or amplitude. U.S. Pat. No. 3,881,091 to Day is incorporated herein by reference in its entirety. [0009] U.S. Patent Application No. 2005/0184689 to Maslov et al. discloses a microprocessor controller that alters the power supply based on current feedback. U.S. Pat. No. 6,090,318 to Bader et al. discloses taking a mean of measured temperatures in individual hot runners and raising and lowering the measured melt temperatures together. This Reference also appears to teach away from the present invention by stating: "To prevent continuous fluctuation in the hot-runner temperatures, however, the new temperature set points for the various cavities are first compared with the measured actual temperatures and the old set points, and only after this comparison in stage 33 of the computer is it decided whether a command should be given to the hot-runner controller 17 to alter the set point for a cavity." (Column 5, Lines 38-45). Therefore, there is not a fast and efficient control of the heater but an analysis of a number of set points and then an alteration of the current set point. [0010] Existing temperature controllers are not capable of fast and precise control of temperature. This lack of control allows temperature swings in the heater windings which causes heater failure creating a major problem. As shown in FIG. 1, a large temperature excursion is shown in the graph indicated by numeral 10. The temperature excursion ("dT") is 300.degree. Celsius with duty cycle of 14 seconds on and 114 seconds off. The results for a first temperature sensor are indicated by numeral 76, the results for a second temperature sensor are indicated by numeral 86 and the results for a third temperature sensor are indicated by numeral 96. The heaters, measured by all three (3) temperature sensors 76, 86 and 96, failed prior to 8,000 cycles. In addition, existing control systems utilize either zero switching or phase firing for control of the voltage supplied to the windings of the heaters. Phase firing introduces the problem of electrical noise into the system which also makes it difficult to have a fast and precise control of temperature. [0011] The present invention is directed to overcoming one or more of the problems set forth above. SUMMARY OF INVENTION [0012] In one aspect of this invention, a digital signal processor ("DSP") that can utilize software algorithms, feedback signals, and output signals to provide temperature control is disclosed. The DSP has the ability to digitally control temperature with both accuracy and speed. [0013] In another aspect of this invention, a digital signal processor that can utilize both zero switching and phase firing control methods for control of voltage for heating is disclosed. These control methods reduce heater temperature oscillations around a set point in order to extend the life of a heater as well as reduce noise generation. Maximum voltage and frequency will be applied to the windings of a heater for maximum heat generation without affecting the reliability of the heaters. The digital signal processor will use temperature feedback, set point control and monitoring, and open loop percentage control that will give a significant advantage in processing polymers with an injection molding system where direct temperature control at the hot nozzle tip is not always possible. [0014] In still another aspect of this invention, a controller for at least one heater is disclosed. The controller includes a regulated voltage supply that is electrically connected to the at least one heater, at least one temperature sensor located distal proximate to the at least one heater, and at least one digital signal processor that is operatively connected to the at least one heater, the regulated voltage supply and the at least one temperature sensor for regulating temperature of the at least one heater based on feedback from the at least one temperature sensor, a voltage sensor, a current sensor or combination of sensors to achieve better heater control. [0015] In still another aspect of this invention, a controller for at least one heater is disclosed. The controller includes a regulated voltage supply that is electrically connected to the at least one heater, at least one first sensor associated with the at least one heater from the group consisting of a temperature sensor located distal proximate to the at least one heater, a current sensor and a voltage sensor, at least one.second sensor associated with at least one heater from the group consisting of a material state change sensor, a pressure sensor, a resistance shift sensor, a capacitance sensor, an inductance sensor, a material phase change sensor, a permeability sensor, a density sensor, a viscosity sensor, a shear feedback sensor, a material flow sensor, a polymerization response sensor, a strain sensor, a stress sensor and a transformation function sensor, and at least one digital signal processor that is operatively connected to the at least one heater, the regulated voltage supply, the at least one first sensor associated with the at least one heater and the at least one second sensor associated with the at least one heater. [0016] In still yet another aspect of the invention, a controller for at least one heater is disclosed. The controller includes a regulated voltage supply that is electrically connected to the at least one heater, at least one first sensor from the group associated with the at least one heater consisting of a temperature sensor located distal proximate to the at least one heater, a current sensor and a voltage sensor, at least one second sensor associated with the at least one heater from the group consisting of a material state change sensor, a pressure sensor, a resistance shift sensor, a capacitance sensor, an inductance sensor, a material phase change sensor, a permeability sensor, a density sensor, a viscosity sensor, a shear feedback sensor, a material flow sensor, a polymerization response sensor, a strain sensor, a stress sensor and a transformation function sensor, at least one digital signal processor that is operatively connected to the at least one heater, the regulated voltage supply, the at least one first sensor and the at least one second sensor, at least one output switching module electrically connected to the at least one heater and the regulated voltage supply, wherein the at least one output switching module varies at least one of voltage and frequency to the at least one heater through at least one of pulse width modulation and zero crossing detection, at least one trigger control module that transmits command signals to the output switching module and the at least one trigger control module is electrically connected to the at least one digital signal processor and the regulated voltage supply, and at least one controller interface that is electrically connected to the at least one digital signal processor. [0017] In an aspect of the invention, a method for controlling temperature of at least one heater is disclosed. The method includes receiving an input voltage with a regulated voltage supply that is electrically connected to the at least one heater, obtaining at least one temperature value from at least one temperature sensor located distal proximate to the at least one heater, and regulating temperature of the at least one heater with at least one digital signal processor that is operatively connected to the at least one heater, the regulated voltage supply and the at least one temperature sensor. [0018] In yet another aspect of the invention, a method for controlling temperature of at least one heater is disclosed. The method includes receiving an input voltage with a regulated voltage supply that is electrically connected to the at least one heater, obtaining at least one first input value from at least one first sensor associated with the at least one heater selected from the group consisting of a temperature sensor located distal proximate to the at least one heater, a current sensor and a voltage sensor, obtaining at least one second input value from a second sensor associated with the at least one heater selected from the group consisting of a material state change sensor, a pressure sensor, a resistance shift sensor, a capacitance sensor, an inductance sensor, a material phase change sensor, a permeability sensor, a density sensor, a viscosity sensor, a shear feedback sensor, a material flow sensor, a polymerization response sensor, a strain sensor, a stress sensor and a transformation function sensor, and regulating the at least one heater with at least one digital signal processor that is operatively connected to the at least one heater, the regulated voltage supply, the at least one first sensor and the at least one second sensor. [0019] These are merely some of the innumerable aspects of the present invention and should not be deemed an all-inclusive listing of the innumerable aspects associated with the present invention. These and other aspects will become apparent to those skilled in the art in light of the following disclosure and accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS [0020] For a better understanding of the present invention, reference may be made to the accompanying drawings in which: Continue reading about Controller for a heater and an associated method of use... Full patent description for Controller for a heater and an associated method of use Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Controller for a heater and an associated method of use patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. 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