Induction heating system

• US 6,359,267 B1
• Filed: 07/26/2000
• Issued: 03/19/2002
• Est. Priority Date: 05/31/2000
• Status: Expired due to Fees

• Current Assignee: Ambrell Corporation (inTEST Corporation)
• Original Assignee: Ameritherm, Inc. (inTEST Corporation)
• Inventors: Wilcox, Dale, Dahake, Girish
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US09/625,835
• Time in Patent Office: 601 Days
• Field of Search: 219/603, 219/608, 219/615, 219/633, 219/635, 219/647, 219/650, 219/651, 219/656, 219/653, 219/655, 219/665, 219/667, 219/662, 228/102, 228/221, 228/218, 228/219
• US Class Current: 219/615
• CPC Class Codes: B23K 1/002 Soldering by means of induction heating

Abstract

An induction heating system that can be used to braze metals and that overcomes many of the disadvantages of conventional brazing systems. The induction heating system improves quality and lowers production cost for many brazing requirements. The system is designed to quickly, accurately and cost effectively heat individual parts, and to replace flame brazing procedures and batch vacuum furnaces. Because the system can braze parts in an inert atmosphere or in no atmosphere (e.g., in a vacuum), no flux or acid cleaning bath is necessary and oxidation on the part is eliminated. Further, by including a gas quenching feature, the system prevents the annealing of parts and produces high quality brazed parts that meet desired hardness specifications. In one embodiment, the induction heating system includes a vacuum chamber; a support surface located within the chamber for providing a surface onto which a part to be heated is placed; moving means connected to the support surface for moving the support surface within the chamber; a vacuum system connected to the chamber for exhausting gases from the chamber; an electrically conductive coil located inside of the chamber or located adjacent to the chamber; an induction heating unit, coupled to the coil, for providing an alternating current to the coil; a temperature sensing means for sensing the temperature of the part; an operator interface for displaying a user interface comprising one or more selectable push button icons and for receiving input from an operator; and a controller interfaced to the operator interface, the vacuum system, the induction heating unit, the moving means, and the temperature sensing means.

Claims

1. An induction heating system, comprising:

a vacuum chamber;

a support surface located within the chamber for providing a surface onto which a part to be heated is placed;

moving means connected to the support surface for moving the support surface within the chamber;

a vacuum system connected to the chamber for exhausting gases from the chamber;

an electrically conductive coil located inside of the chamber or located adjacent to the chamber;

a power supply for providing an alternating current to the coil;

a temperature sensing means for sensing the temperature of the part;

an operator interface for displaying a user interface comprising one or more selectable push button icons and for receiving input from an operator; and

a control system interfaced to the operator interface, the vacuum system, the power supply, the moving means, and the temperature sensing means, wherein the controller is programmed to perform a procedure in response to an operator selecting one of the selectable push button icons, the procedure comprising the steps of;

sending a signal to the moving means to cause the moving means to move the support surface so that the part is appropriately located with respect to the coil;

sending a signal to the vacuum system to cause the vacuum system to exhaust gases from the chamber;

monitoring the pressure within the chamber;

after the pressure within the chamber reaches a predetermined threshold, sending a signal to the power supply to cause the power supply to provide to the coil an alternating current having sufficient power to heat the part to a predetermined temperature;

waiting for a predetermined amount of time; and

after the predetermined amount of time has elapsed, sending a signal to the power supply causing the power supply to stop providing the alternating current to the coil.

2. The induction heating system of claim 1, further comprising a parallel resonant tank circuit connected between the power supply and the coil.

3. An induction heating system, comprising:

two or more vacuum chambers;

a valve system;

a single vacuum system for exhausting gases from the chambers, the single vacuum system being connected to each of the two or more vacuum chambers through the valve system;

two or more electrically conductive coils, wherein each one of the coils is either located inside of or adjacent to one of the two or more chambers;

a single power supply coupled to each of the two or more coils, wherein the power supply is for providing an alternating current to the coils;

an operator interface for displaying a user interface and for receiving input from an operator; and

a control system, interfaced to the operator interface, the vacuum system, and the power supply, for receiving signals from the operator interface after the operator interface receives an input from the operator and for sending control signals to the power supply, the vacuum system, and the valve system.

4. A method for joining two or more parts, comprising the steps of:

placing the parts into a vacuum chamber;

positioning the parts so that the parts are placed in a predetermined location with respect to an induction heating coil;

sealing the vacuum chamber;

activating a vacuum system to exhaust gases from the vacuum chamber, thereby lowering the pressure within the chamber;

providing to the coil a first alternating current for the purpose of inductively heating at least a portion of one of the parts to a first predetermined temperature, wherein the first alternating current is provided to the coil after the pressure within the chamber reaches a first predetermined pressure level;

providing a second alternating current to the coil to inductively heat the portion of the part to a second predetermined temperature after the pressure within the chamber reaches a second predetermined pressure level, wherein the second predetermined pressure level is less than the first predetermined pressure level; and

maintaining the temperature of the portion of the part at the second predetermined temperature for a predetermined amount of time.

5. The method of claim 4, wherein the second predetermined pressure level is about an order of magnitude less than the first predetermined pressure level.

6. The method of claim 5, wherein the first predetermined pressure level is about 5×

10<sup>−

5</sup> torr and the second predetermined pressure level is about 1×

10<sup>−

6</sup> torr.

7. The method of claim 4, wherein the first predetermined temperature is less than the second predetermined temperature.

8. The method of claim 7, wherein the first predetermined temperature is between about 400 and 800 degrees Fahrenheit and the second predetermined temperature is between about 1000 and 3000 degrees Fahrenheit.

9. The method of claim 8, wherein the first predetermined temperature is about 700 degrees Fahrenheit and the second predetermined temperature is about 2100 degrees Fahrenheit.

10. An induction heating system, comprising:

a vacuum chamber;

a support located within the chamber for supporting a part to be heated;

moving means connected to the support for moving the support within the chamber;

a vacuum system connected to the chamber for exhausting gases from the chamber;

an atmospheric control system means, connected to the chamber, for showering the part with a flow of a gas for the purpose of cooling the part;

an electrically conductive coil located inside of the chamber or located adjacent to the chamber;

a power supply for providing an alternating current to the coil;

a temperature sensing means for sensing the temperature of the part;

an operator interface for displaying a user interface and for receiving input from an operator; and

a control system, interfaced to the operator interface, the temperature sensing means, the power supply, the vacuum system, the atmospheric control system means, and the moving means, for receiving input from the operator interface and for sending control signals to the power supply, the vacuum system, the atmospheric control system means, and the moving means.

11. The induction heating system of claim 10, wherein the gas is an inert gas.

12. An induction heating system for use in brazing applications, comprising:

a chamber;

a vacuum system coupled to the chamber, wherein the vacuum system is configured to exhaust gases from the chamber;

a support located inside of the chamber that supports one or more parts to be heated;

an electrically conductive element located inside of the chamber or located adjacent to the chamber;

an induction heating unit that is electrically coupled to the element and that uses the element to inductively heat the one or more parts;

a temperature sensing means for sensing the temperature of the one or more parts located within the chamber;

a pressure sensor for sensing the pressure within the chamber;

an operator interface that displays a user interface and that receives input from an operator; and

a control system interfaced to the operator interface, the vacuum system, the induction heating unit, and the temperature sensing means, wherein the control system is programmed to perform a procedure, the procedure comprising the steps of;

sending a control signal to the vacuum system to cause the vacuum system to lower the pressure within the chamber;

reading an output of the pressure sensor to monitor the pressure within the chamber;

comparing the pressure within the chamber to a predetermined pressure threshold; and

after the pressure within the chamber reaches or falls below the predetermined pressure threshold, sending one or more control signals to the induction heating unit, the one or more control signal causing the induction heating unit to inductively heat the one or more parts to a predetermined temperature using the conductive element.

13. The induction heating system of claim 12, wherein the procedure further comprises the step of monitoring the temperature of at least a portion of one of the one or more parts being heated.

14. The induction heating system of claim 13, wherein the procedure further comprises the step of sending one or more control signals to the induction heating unit so as to maintain the temperature of the portion being monitored at or about a predetermined temperature for at least a predetermined amount of time.

15. The induction heating system of claim 12, wherein the procedure further comprises the steps of:

activating a timer to expire after a predetermined interval of time has passed; and

sending a second control signal to the induction heating unit after the timer expires, wherein the second control signal causes the induction heating unit to cease heating the one or more parts.

16. The induction heating system of claim 12, further comprising a motor, coupled to the support, for moving the support so that the one or more parts within the chamber can be moved, and wherein the procedure further comprises the steps of sending a control signal to the motor, wherein the control signal sent to the motor causes the motor to move the support so that the one or more parts are appropriately positioned with respect to the element.

17. The induction heating system of claim 12, further comprising an atmospheric control system means for quenching the one or more parts after the one or more parts have been heated.

18. The induction heating system of claim 12, wherein the procedure further comprises the step of:

comparing the pressure within the chamber to a second predetermined pressure threshold after the pressure within the chamber reaches or falls below the first predetermined pressure threshold; and

sending a second control signal to the induction heating unit after the pressure within the chamber reaches or falls below the second predetermined pressure threshold, wherein the second control signal causes the induction heating unit to inductively heat the one or more parts to a second predetermined temperature, wherein the second predetermined temperature is greater than the first predetermined temperature.

19. The induction heating system of claim 18, wherein the procedure further comprises the steps of:

activating a timer to expire after a predetermined interval of time has passed; and

sending a third control signal to the induction heating unit after the timer expires, wherein the third control signal causes the induction heating unit to cease heating the one or more parts.

20. An induction heating system for use in brazing applications, comprising:

a chamber;

a vacuum system coupled to the chamber, wherein the vacuum system is configured to exhaust gases from the chamber;

a source of inert gas coupled to the chamber through a valve;

an electrically conductive element located inside of the chamber or located adjacent to the chamber;

an induction heating unit that is electrically coupled to the element and that uses the element to inductively heat a part located in the chamber;

a temperature sensing means for sensing the temperature of at least a portion of the part;

a pressure sensor for sensing the pressure within the chamber;

an operator interface that displays a user interface and that receives input from an operator; and

a control system interfaced to the operator interface, the vacuum system, the induction heating unit, the temperature sensing means, and the valve, wherein the control system is programmed to perform a procedure, the procedure comprising the steps of;

sending a control signal to the vacuum system to cause the vacuum system to lower the pressure within the chamber;

opening the valve to allow the inert gas to flow into the chamber and produce a partial pressure within the chamber;

sending one or more control signals to the induction heating unit to cause the induction heating unit to inductively heat said portion of the part to a predetermined temperature using the conductive element.

21. The induction heating system of claim 20, wherein after said portion of the part reaches the predetermined temperature, the procedure further comprises the step of sending one or more control signals to the induction heating unit to maintain the temperature of said portion of the part at the predetermined temperature for at least about a predetermined amount of time.

22. The induction heating system of claim 21, wherein, after the temperature of said portion of the part has been maintained at the predetermined temperature for about at least the predetermined amount of time, the procedure further comprises the steps of:

sending a control signal to the induction heating unit that causes the induction heating unit to cease inductively generating currents in the part; and

opening the valve further to increase the flow of inert gas into the chamber to cool the part.

23. The induction heating system of claim 20, wherein, after said portion of the part reaches the predetermined temperature, the procedure further comprises the step of sending one or more control signals to the induction heating unit to maintain the temperature of said portion of the part at the predetermined temperature for not more than about a predetermined amount of time.

24. The induction heating system of claim 23, wherein, after the temperature of said portion of the part has been maintained at the predetermined temperature for not more than about the predetermined amount of time, the procedure further comprises the steps of:

sending a control signal to the induction heating unit that causes the induction heating unit to cease inductively generating currents in the part; and

opening the valve further to increase the flow of inert gas into the chamber to cool the part.

25. A method for inductively heating a part, comprising the steps of:

placing the part into a chamber;

positioning the part near an induction heating element;

sealing the chamber;

exhausting gases from the chamber, thereby lowering the pressure within the chamber;

comparing the pressure within the chamber to a first predetermined pressure level;

using the induction heating element to inductively heat at least a portion of the part to a first predetermined temperature after the pressure within the chamber reaches or falls below the first predetermined pressure level;

comparing the pressure within the chamber to a second predetermined pressure level after the pressure within the chamber reaches or falls below the first predetermined pressure level; and

using the induction heating element to inductively heat the portion of the part to a second predetermined temperature after the pressure within the chamber reaches or falls below the second predetermined pressure level.

26. The method of claim 25, wherein the second predetermined temperature is greater than the first predetermined temperature.

27. The method of claim 26, wherein the first predetermined pressure level is greater than the second predetermined pressure level.

28. The method of claim 27, further comprising the step of maintaining the temperature of the portion of the part at the second predetermined temperature for at least about a predetermined amount of time.

29. The method of claim 28, further comprising the step of introducing a flow of quenching gas into the chamber to cool the part after maintaining the temperature of the portion of the part at the second predetermined temperature for at least about the predetermined amount of time.

30. The method of claim 27, further comprising the step of maintaining the temperature of the portion of the part at the second predetermined temperature for not more than about a predetermined amount of time.

31. The method of claim 30, further comprising the step of introducing a flow of quenching gas into the chamber to cool the part after maintaining the temperature of the portion of the part at the second predetermined temperature for not more than about the predetermined amount of time.