Wire temperature controller

• US 4,506,146 A
• Filed: 02/21/1984
• Issued: 03/19/1985
• Est. Priority Date: 08/21/1981
• Status: Expired due to Term

• Current Assignee: Reynolds Metals Company (Howmet Aerospace, Inc.)
• Original Assignee: Reynolds Metals Company (Howmet Aerospace, Inc.)
• Inventors: Rice, Richard M., Henderson, Drew R., Watling, Robert E.
• Primary Examiner(s): Paschall, M. H.
• Application Number:
  US06/581,603
• Time in Patent Office: 392 Days
• Field of Search: 219/497, 219/494, 219/499, 219/501, 219/507-510, 219/483, 219/486, 219/505, 307/39-41, 323/235, 323/236
• US Class Current: 219/499
• CPC Class Codes: B29C 65/222 comprising at least a single heated wire
• CPC Class Codes: B29C 65/223 comprising several heated wires
• CPC Class Codes: B29C 65/30 Electrical means B29C65/38 takes precedence
• CPC Class Codes: B29C 66/43 Joining a relatively small portion of the surface of said articles B29C66/45 takes precedence
• CPC Class Codes: B29C 66/91213 and measuring the electrical resistance of a resistive element belonging to said welding jaws, said element being, e.g. a thermistor
• CPC Class Codes: B29C 66/91231 of the joining tool
• CPC Class Codes: B29C 66/91313 by measuring the voltage, i.e. the electric potential difference or electric tension
• CPC Class Codes: B29C 66/91317 by measuring the electrical resistance
• CPC Class Codes: B29C 66/91421 of the joining tools
• CPC Class Codes: B29C 66/91431 the temperature being kept constant over time
• CPC Class Codes: B29C 66/91651 by controlling or regulating the heat generated by Joule heating or induction heating
• CPC Class Codes: B29C 66/91653 by controlling or regulating the voltage, i.e. the electric potential difference or electric tension
• CPC Class Codes: B29C 66/91655 by controlling or regulating the current intensity
• CPC Class Codes: B29C 66/9192 in explicit relation to another variable, e.g. temperature diagrams
• CPC Class Codes: B29C 66/91951 in explicit relation to time, e.g. temperature-time diagrams
• CPC Class Codes: B29C 66/94 by measuring or controlling the time
• CPC Class Codes: B29C 66/949 characterised by specific time values or ranges
• CPC Class Codes: B29C 66/9592 in explicit relation to another variable, e.g. X-Y diagrams
• CPC Class Codes: B29C 66/961 involving a feedback loop mechanism, e.g. comparison with a desired value
• CPC Class Codes: G05D 23/2401 using a heating element as a sensing element

Abstract

A method and apparatus are described for controlling the temperature of a heated wire, such as on a wire sealer for plastic film. Temperature control is based upon measurements of changes in the resistance of the wire as it is heated, through bridge circuit and microprocessor techniques.

Claims

1. An apparatus for controlling the temperature of an electrically heated wire comprising an alternating current voltage power supply in a circuit with said wire, said circuit comprising a zero crossing detector for determining each zero crossing of said alternating current voltage power supply, a bridge circuit containing said wire, means for electrically exciting said bridge circuit in response to each zero crossing of said alternating current voltage power supply, said means for electrically exciting comprising a voltage supply for a high impedance side of said bridge circuit and a current supply of opposite polarity to said voltage supply for a low impedance side of said bridge circuit, means for measuring the voltage at a pair of detector corners of said bridge circuit comprising a summing junction, a thyristor and a firing circuit for said thyristor for electrically connecting said wire and said alternating current voltage power supply in response to the summed voltage of said detector corners of said bridge circuit and a microprocessor for controlling said means for exciting in response to each zero crossing of said alternating current voltage supply and for controlling said firing circuit and said thyristor in response to the summed voltage of said detector corners of said bridge circuit.

2. The apparatus of claim 1 wherein said means for measuring the voltage at said pair of detector corners further comprises an amplifier.

3. The apparatus of claim 1 further comprising a heating cycle controller for maintaining a set point temperature for a preselected number of alternating current half cycles after reaching said set point temperature.

4. The apparatus of claim 3 further comprising a cooling cycle controller for preventing power supply to said wire for a predetermined number of alternating current half cycles after said heating cycle controller has deactivated.

5. The apparatus of claim 1 further comprising a second electrically heated wire, a second alternating current voltage power supply, a second bridge circuit containing said second wire, means for electrically exciting said second bridge circuit in response to each zero crossing of said alternating current voltage power supply, said means for electrically exciting said second bridge circuit comprising a second voltage supply for a high impedance side of said second bridge circuit and a second current supply of opposite polarity to said second voltage supply for a low impedance side of said second bridge circuit, means for measuring the voltage at a second pair of detector corners of said bridge circuit comprising a second summing junction and a second thyristor and a second firing circuit for said second thyristor for electrically connecting said second wire and said second alternating current voltage power supply in response to the summed voltage of said second detector corners of said second bridge circuit, said microprocessor controlling said second means for electrically exciting in response to each zero crossing of said alternating current voltage power supply and controlling said second firing circuit and said second thyristor in response to the summed voltage of said second detector corners of said second bridge circuit.

6. The apparatus of claim 5 wherein said voltage supply and said second voltage supply are a common voltage supply source.

7. The apparatus of claim 5 wherein said means for measuring the voltage at said pair of detector corners and said means for measuring the voltage at said second pair of detector corners further comprises a multiplexor and an amplifier.