Induction coil design for portable induction heating tool and method for its use

1. A coil head for an induction heating apparatus, said coil head comprising:

(a) an outer member;

(b) an inner member, said inner member having an inner side wall and an outer side wall, said inner side wall forming an opening fbr receiving a workpiece; and

(c) an induction coil disposed between said inner and outer members, said induction coil comprising an electrical winding that runs substantially along said outer side wall of said inner member, wherein said induction coil is a primary source of thermal energy for heating said workpiece;

further comprising: at least one external heat pipe that runs into said coil head at a location different than at said opening for the workpiece, wherein said heat pipe tends to transfer thermal energy away from said inner side wall of said inner member, and away from said opening; and

wherein said heat pipe is not the primary source of thermal energy for heating the workpiece.

2. The coil head as recited in claim 1 , wherein said induction coil has a length dimension that extends substantially along the electrical winding run along said outer side wall of the inner member, and exhibits one of the following shapes:

(a) substantially a U-shape when viewed from a direction that is substantially perpendicular to said length dimension of the induction coil; and

(b) substantially a semi-circular shape when viewed from a direction that is substantially perpendicular to said length dimension of the induction coil.

3. The coil head as recited in claim 2 , wherein:

(a) said induction coil has a width dimension that runs substantially perpendicular to said length dimension, and

(b) wherein said induction coil comprises at least one individual turn having an outer dimension that is less than or equal to said width dimension in a direction that is substantially perpendicular to said length dimension.

4. The coil head as recited in claim 1 , wherein:

(a) said induction coil has a first thickness dimension that represents a distance between said outer side wall of the inner member and an inner side wall of said outer member,

(b) said induction coil comprises at least one individual turn that is disposed within said first thickness dimension between the inner and outer members; and

(c) said at least one heat pipe also is disposed between said inner and outer members.

5. The coil head as recited in claim 4 , wherein a location of said at least one heat pipe is disposed in at least one of:

(a) between a surface of said outer side wall of the inner member and a surface of said inner side wall of said outer member,

(b) within a slot in said inner member; and

(c) within a slot in said outer member.

6. The coil head as recited in claim 4 , wherein a location of said at least one heat pipe is selected so as to relatively minimize an effect of a magnetic field emitted by said induction coil upon an electrically conductive portion of said at least one heat pipe.

7. The coil head as recited in claim 1 , wherein said at least one heat pipe is interspersed with at least one turn of the electrical winding of said induction coil.

8. The coil head as recited in claim 1 , wherein said induction coil is formed substantially in a racetrack configuration.

9. The coil head as recited in claim 8 , wherein said outer member at least partially covers said induction coil.

10. The coil head as recited in claim 9 , wherein said inner member is made of a temperature-resistant material that allows it to come into direct contact with said workpiece while said workpiece is being heated.

11. The coil head as recited in claim 1 , further comprising a heat sink; wherein said heat pipe comprises a tubular structure that is hermetically sealed, and has a first end proximal to said coil bead and a second, opposite end proximal to said heat sink, said heat pipe containing a liquid that substantially vaporizes at said first end as it is heated by said coil head, said liquid then transferring heat toward said second end, where said liquid substantially condenses.

12. The coil head as recited in claim 11 , wherein said heat pipe includes a wick material within said hermetically sealed tubular structure, and said condensed liquid flows, from said second end toward said first end, by way of a capillary action through said wick material.

13. A coil head for an induction heating apparatus, said coil head comprising:

(a) an outer member;

(b) an inner member, said inner member having an inner side wall and an outer side wall, said inner side wall forming an opening for receiving a workpiece; and

(c) an induction coil disposed between said inner and outer members, said induction coil comprising an electrical winding that runs substantially along said outer side wall of said inner member;

Her comprising: at least one external heat pipe that runs into said coil head, wherein said heat pipe tends to transfer thermal energy away from said inner side wall of said inner member, and away from said opening;

wherein:

(d) said induction coil has a width dimension that runs substantially perpendicular to said length dimension;

(e) said induction coil comprises at least one individual turn having an outer dimension that is less than or equal to said width dimension in a direction that is substantially perpendicular to said length dimension;

(f) said induction coil has a length dimension that extends substantially along the electrical winding run along said outer side wall of the inner member, and exhibits one of the following shapes:

(i) substantially a U-shape when viewed from a direction that is substantially perpendicular to said length dimension of the induction coil; and

(ii) substantially a semi-circular shape when viewed from a direction that is substantially perpendicular to said length dimension of the induction coil;

(g) said induction coil has a width dimension that runs substantially perpendicular to said length dimension, and said induction coil comprises at least one individual tarn having an outer dimension that is less than or equal to said width dimension in a direction that is substantially perpendicular to said length dimension;

(h) said induction coil has a first thickness dimension that represents a distance between said outer side wall of the inner member and an inner side wall of said outer member; and

(i) said induction coil comprises a plurality of individual turns that are arranged in at least one of the following configurations:

(i) the individual turns are layered within said first thickness dimension between the inner and outer members, such that said first thickness dimension is greater than a second thickness dimension representing a thickness an electrical conductor of a single of said individual turns; and

(ii) the individual turns are wound such that they lie alongside one another within said first thickness dimension between the inner and outer members, and the first thickness dimension is substantially the same as said second thickness dimension representing a thickness an electrical conductor of a single of said individual turns.

14. A method for heating a workpiece, using an induction heating apparatus, said method comprising:

(a) providing a coil head having:

(i) an outer member,

(ii) an inner member, said inner member having an inner side wall and an outer side wall, said inner side wall forming an opening for receiving a workpiece;

(iii) an induction coil disposed between said inner and outer members, said induction coil comprising an electrical winding that runs substantially along said outer side wall of said inner member, wherein said induction coil is a primary source of thermal energy for heating said workpiece;

(b) providing at least one external heat pipe that runs into said coil head at a location different than at said opening for the workpiece;

(c) placing said inner side wall proximal to said workpiece;

(d) energizing said induction coil to generate a magnetic field that induces eddy currents in an electrically conductive portion of said workpiece, and thereby raising a temperature of said workpiece; and

(e) transferring, by use of said heat pipe, thermal energy away from said inner side wall of said inner member, and away from said opening, wherein said heat pipe is not the primary source of thermal energy for heating the workpiece.

15. The method as recited in claim 14 , wherein said heat pipe comprises a tubular structure that is hermetically sealed, and has a first end proximal to said coil head and a second, opposite end proximal to a heat sink, said heat pipe containing a liquid that substantially vaporizes at said first end as it is heated by said coil head, said liquid then transferring heat toward said second end, where said liquid substantially condenses.

16. The method as recited in claim 15 , wherein said heat pipe includes a wick material within said hermetically sealed tabular structure, and said condensed liquid flows, from said second end toward said first end, by way of a capillary action through said wick material.

17. The method as recited in claim 14 , wherein:

said workpiece is substantially cylindrical in shape, and said cylindrical workpiece exhibits a longitudinal axis;

said induction coil has a length dimension that extends substantially along the electrical winding along said outer side wall of the inner member,

said induction coil has a width dimension that runs substantially perpendicular to said length dimension, and

further comprising the step of: (e) heating a longitudinal portion of said cylindrical workpiece to an extent along said longitudinal axis that is substantially equal to said width dimension of the induction coil.

18. A method for heating a workpiece, using an induction heating apparatus, said method comprising:

(a) providing a coil head having:

(i) an outer member;

(ii) an inner member, said inner member having an inner side wall and an outer side wall, said inner side wall forming an opening for receiving a workpiece;

(iii) an induction coil disposed between said inner and outer members, said induction coil comprising an electrical winding that runs substantially along said outer side wall of said inner member;

(b) providing at least one external heat pipe that runs into said coil head;

(c) placing said inner side wall proximal to said workpiece;

(d) energizing said induction coil to generate a magnetic field that induces eddy currents in an electrically conductive portion of said workpiece, and thereby raising a temperature of said workpiece; and

(e) transferring, by use of said heat pipe, thermal energy away from said inner side wall of said inner member, and away from said opening;

wherein:

said workpiece is substantially cylindrical in shape, and said cylindrical workpiece exhibits a longitudinal axis;

said induction coil has a length dimension that extends substantially along the electrical winding run along said outer side wall of the inner member,

said induction coil has a width dimension that runs substantially perpendicular to said length dimension, and

further comprising the step of: (f) heating a longitudinal portion of said cylindrical workpiece to an extent along said longitudinal axis that is substantially equal to said width dimension of the induction coil;

and wherein said cylindrical workpiece comprises:

a cylindrical coupler of a first outer diameter and a first inner diameter, and a first longitudinal length; a first cylindrical pipe section of a second outer diameter; a second cylindrical pipe section of a third outer diameter, which is substantially equal to said second outer diameter; wherein said first inner diameter of the coupler is at least as large as said second and third outer diameters of the first and second pipe sections; and

and further comprising the steps of:

(g) substantially abutting said first and second pipes sections together such that their longitudinal axes are substantially co-linear,

(h) placing said coupler over both said first and second pipe sections;

(i) introducing a bonding compound between said coupler and at least one of the first and second pipe sections;

(j) placing said coil head at a position proximal to said coupler, and

(k) energizing said induction coil to heat said coupler and said bonding compound, thereby forming a bond between said coupler and said at least one of the first and second pipe sections.

19. The method as recited in claim 18 , wherein said induction coil width dimension is greater than or equal to said first longitudinal length of the coupler, thereby allowing said induction coil to simultaneously heat the entire coupler.

20. The method as recited in claim 19 , wherein said induction coil has a thickness dimension that represents a distance between said outer side wall of the inner member and an inner side wall of said outer member; and said coil thickness dimension is substantially equal to a radius of said workpiece along its outer diameter.