Abstract:
A portable induction heater with a rotating head portion which can be used to rapidly, detachably connect a work coil. The portable induction heater is also provided with various other advantages detailed here.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to portable handheld induction heaters. Such induction heaters have a variety of uses, such as in the automotive aftermarket for vehicle repair and maintenance, i.e., selectively heating automotive metallic and adjacent components, and removing components bonded or attached to metallic surfaces (e.g., fasteners), or removing structure attached by means of adhesive (e.g., glass). Other uses for such induction heaters include similar, maritime uses, industrial uses such as heating rods to bend them in a fabrication process, annealing ammunition cartridges, etc. 
         [0002]    Portable handheld induction heaters useful in the automotive aftermarket are known. See for example, Applicant&#39;s U.S. Pat. Nos. 6,563,096 and 6,670,590, titled “Eddy Current/Hysteretic Heater Apparatus And Method Of Use” and “Eddy Current/Hysteretic Heater Apparatus,” respectively, each of which is incorporated by reference in its entirety. Applicant&#39;s pending U.S. Ser. No. 14/065,844, filed Oct. 29, 2013, titled “Portable Induction Heater,” and Ser. No. 14/330,429 filed Jul. 14, 2014, titled “Induction Heater Coil Accessory,” disclosing, e.g., handheld induction heaters which can run on power supplied at 12-24 volts, as well as 110-240 volts, and disclosing alternative forms of work coils, respectively, are each hereby incorporated by reference in their entirety. 
         [0003]    Induction heaters may be air-cooled or water-cooled. The present invention concerns air-cooled induction heaters. Three main components of a modern induction heater include the power unit (power inverter), optional output/isolation transformer and the coil (inductor). Induction heating is a non-contact method of heating a conductive body by utilizing a strong magnetic field. Induction heaters may incorporate a coil directly fed from the electricity supply. The power unit/inverter is used to take the supply/mains frequency and increase it to a higher frequency, typically anywhere between 1-400 kHz. Typical power output of a unit system may be about 1-500 kW. The work head/transformer may include a combination of capacitors and transformers used to mate the power unit to the work coil. The work coil/inductor is used to transfer the energy from the power unit and work head to the work piece. Inductors of the type of the present invention consist of a simple wound solenoid with a number of turns of copper tube wound around a mandrel. 
         [0004]    To work properly, the coil must be placed in close proximity to the work piece (e.g., a nut to be loosened). This can be difficult in tight or difficult to access areas and/or where there are closely adjacent surfaces to the work piece, which the operator does not wish to heat or damage, 
         [0005]    A conventional coil configuration used for handheld induction heaters utilizes round conductor wire (e.g., copper), which may be bent into various coil shapes, and which typically have two lead wires or “legs”  32  which may be detachably connected to the induction heater. Work coils typically have circular cross-sections. However, the round wire of work coils may be flattened to provide work coils with semi-circular and rectangular cross-sectional geometries, as has been recently disclosed (see Applicant&#39;s U.S. Ser. No. 14/330,429, referenced above). 
         [0006]    In the past, the ends or legs of work coils have been attached to the head of a portable induction heater using thumb screws. Thumb screws take a relatively long time to change the work coil, i.e., the user must loosen the two thumb screws, remove the coil legs, insert the coil legs of a different work coil (such as one of a different size and/or shape), and re-tighten the two thumb screws. Thumb screws can loosen over time, as the induction heater is used. The user may not be aware that loosening has occurred, until various conditions occurs, such as: (a) excessive heat develops in the heat dissipating terminal (“HDT”), which can melt the thumb screw cap; or (b) a loose coil creates sparks, which can damage electronics in the induction heater. 
         [0007]    Accordingly, it would be advantageous to provide a faster, more reliable method for attaching and detaching the work coil legs to an induction heater. It would also be advantageous to provide a secure attachment device and method which works with work coil legs of different cross-sectional geometries, including circular, semi-circular and rectangular geometries. 
       DEFINITION OF CLAIM TERMS 
       [0008]    The following terms are used in the claims of the patent as filed and are intended to have their broadest meaning consistent with the requirements of law. Where alternative meanings are possible, the broadest meaning is intended. All words used in the claims are intended to be used in the normal, customary usage of grammar and the English language. 
         [0009]    “Automotive applications” means applications for selectively heating automotive metallic and adjacent components, and removing components bonded or attached to metallic surfaces (e.g., fasteners), or for removing structure attached by means of adhesive (e.g., glass, parts, components). 
         [0010]    “Coil” or “work coil” means the portion of the induction heater used to heat a work piece. This typically is either an open or closed loop permanently attached to and/or integrally formed with the legs; however, a connection, such as an extension cable or a pair of legs attachable to and removable from the induction heater body, may be provided between the coil and the induction heater. Each work coil can be replaced with another work coil, either because of durability concerns or because a differently shaped or sized work coil is desired to be used for a certain application, 
         [0011]    “Rapidly” means the substantial time-savings enabled by the present invention, in comparison to the time required to attach and detach the legs of a work coil to a portable induction heater using conventional thumb screws, 
       SUMMARY OF THE INVENTION 
       [0012]    The objects mentioned above, as well as other objects, are solved by the present invention, which overcomes disadvantages of prior portable induction heaters, while providing new advantages not previously obtainable with such heaters. 
         [0013]    In a preferred embodiment, a portable induction heater is provided which may be detachably connected to different work coils. Each work coil includes a coil portion and two legs. The induction heater includes a head with a portion capable of limited rotation, and a body which may be held by a hand of a user during use of the induction heater. Upon insertion of the legs of the work coil into apertures on the head, and rotation of the head portion, the legs are thereby locked to the head. The head may include a heat dissipating terminal, and the head portion may include a collar capable of limited rotation about the heat dissipating terminal. Two copper contactors may be provided, each of which is attached to the heat dissipating terminal. 
         [0014]    One or more inner surfaces of the collar may be permitted to contact and bend each of the two copper contactors during rotation of the collar, causing each of the two legs of the work coil to be locked in place against each of the two corresponding copper contactors within the head, and providing positive feedback to the user that the legs are locked in place. 
         [0015]    In a particularly preferred embodiment, upon limited rotation of the collar, each of the two legs of the work coil may be locked in place between opposing, adjacent surfaces of a corresponding one of each of the two copper contactors. 
         [0016]    Preferably, the induction heater is an air-cooled induction heater. The heat dissipating terminal may be made of extruded aluminum. 
         [0017]    Non-circular grooves, such as generally V-shaped grooves, on the induction heater may be used to accept the legs of the work coil. The heat dissipating terminal may have fins with serrations, and the non-circular grooves may not have serrations. 
         [0018]    The portable induction heater of the invention may be used for automotive, industrial, maritime or other applications. 
         [0019]    The portable induction heater may also be provided with an isolation transformer with two legs. Each leg of the isolation transformer may be connected to one of the two copper contactors. The heat dissipating terminal may include two separate portions, which may be separated by a heat sink insulator; each of the two copper contactors may be directly connected to one of the two portions of the heat dissipating terminal. 
         [0020]    A method for rapidly, detachably connecting legs of a work coil to a portable induction heater also forms part of the present invention. The induction heater is provided with a head which has a portion capable of limited rotation, and a body which may be held by a hand of a user during use of the induction heater. The legs of the work coil may he inserted into apertures on the head. Next, the head portion may be rotated to thereby lock the legs of the work coil to the head. Now, the head portion may again be rotated, in a rotational direction opposite to the locking rotation, enabling the legs to be removed from the head. The output voltage of the work coil may be monitored and, upon detection of a. fault condition, the induction heater may be shut down for a predetermined time period. Additionally, the amount of current drawn from the induction heater may be monitored, and upon detection of a fault condition, the induction heater may be shut down for a predetermined time period; the fault condition may now be rechecked and if the fault condition is corrected, the induction heater may be permitted to operate. 
         [0021]    The present invention permits the work coil to be rapidly tightened to the portable induction heater, providing a time-savings of at least 50%, and preferably at least about 75%, as compared to the time taken to tighten a work coil using a conventional portable induction heater with thumb screws. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The novel features which are characteristic of the invention are set forth in the appended claims. The invention itself, however, together with further objects and attendant advantages thereof, will be best understood by reference to the following description taken in connection with the accompanying drawings, in which: 
           [0023]      FIG. 1  is a perspective view of a preferred embodiment of a portable induction heater of the present invention, shown engaged to a work coil, for heating a fastener; 
           [0024]      FIG. 1A  is a schematic view of the fastener adjacent the work coil, and the magnetic field created by the induction heater; 
           [0025]      FIG. 2  is a perspective, exploded view of a preferred portable induction heater of the present invention; 
           [0026]      FIGS. 3-6  are sectional views taken along reference lines  3 - 3 ,  4 - 4 ,  5 - 5  and  6 - 6 , respectively, of  FIG. 2 ; 
           [0027]      FIG. 7  is a perspective view of an EDT similar to the one shown in  FIG. 2 , utilizing an alternative contactor embodiment; 
           [0028]      FIGS. 8-11  are sectional views taken along reference lines  8 - 8 ,  9 - 9 ,  10 - 10  and  11 - 11 , respectively, of  FIG. 7 ; 
           [0029]      FIG. 12  is a perspective view of an alternative embodiment of a portable induction heater of the present invention; 
           [0030]      FIG. 13  is an exploded view of the portable induction heater shown in  FIG. 12 ; 
           [0031]      FIG. 14  is a perspective view of the interior of a preferred portable induction heater, which is a slightly different embodiment than that shown in  FIG. 13  (e.g., the transformer is canted slightly differently); and 
           [0032]      FIG. 15  is a schematic diagram of one preferred fault detection scheme which may be used with a portable induction heater of the present invention. 
       
    
    
       [0033]    The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. In the drawings, like reference numerals designate corresponding parts throughout the several views. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    Set forth below is a description of what are currently believed to be the preferred embodiments and/or best examples of the invention claimed. Future and present alternatives and modifications to this preferred embodiment are contemplated. Any alternatives or modifications which make insubstantial changes in function, in purpose, in structure, or in result are intended to be covered by the claims of this patent. 
         [0035]    Referring first to  FIG. 1 , in a particularly preferred embodiment of the present invention, an air-cooled., portable induction heater  10  is shown, for use with a work coil  30  having legs  32 . Using induction heater  10  connected to work coil  30 , a magnetic field  90  may be generated in the vicinity of work coil  30  to quickly heat material, such as fastener  80 , as discussed in U.S. Pat. Nos. 6,563,096 and 6,670,590, and as well known in the art. Coil  30  may be made of round copper wire or another suitable round conductive wire, which may but need not be flattened as described in Applicant&#39;s U.S. Ser. No. 14/330,429, referenced above, such that legs  32  may have circular, semi-circular, square or rectangular cross-sections. 
         [0036]    Referring now to  FIG. 2 , induction heater  10  may include a hand-held base or body  12 , a top interior portion  14  covered by rotatable panels  13   a,    13   b,  and a top nose portion  22 . Top interior portion  14  may include a heat dissipating terminal (HDT)  15 , with left and right portions  15   a,    15   b,  respectively. HDT  1 . 5  may be extruded out of aluminum, for example. A flexible conductive contactor  20  with a depressible portion  20   a,  which may contact base  21 , may be made from a highly conductive metal such as copper, and may be attached to an outer portion of each side of HDT portions  15   a,    15   b  using fasteners  20   a.  An upper base portion  17  may be made out of hard plastic, for example, to encase the HDT and the isolation transformer  92  ( FIGS. 13-14 ) behind it. Connecting wire (not shown) from an output location on the isolation transformer may be crimped and attached at copper wire holder  94  on the HDT ( FIG. 7 ), by tightening using fastener  94   a.  Power cord  90  including electrical prongs  90   a  may be attached at a rear end of the unit  10  ( FIGS. 1, 14 ). PCB components  121  and fan  140  may be provided as shown in FIG.  14 . Switch cover  88   a  ( FIG. 13 ) may be provided adjacent LED  88  ( FIG. 15 , not shown on  FIG. 13 ). 
         [0037]    Referring again to  FIG. 2 , to secure nose portion  22  to upper base portion  17 , fasteners (not shown) may be inserted into nose apertures  22   b  and corresponding apertures  17   a  and  37   a  on upper base portion  17 . Nose  22  may provide venting for the unit  10 , and also function to hold LED  87  (not shown in  FIG. 2 , but shown in  FIGS. 3-5 ) in place (for this purpose, a central aperture (not shown) may be provided in nose  22 , to allow LED  87  to be visible). Hemispherical outer panels  13   a,    13   b  may be attached to the upper body of unit  10  using fasteners (not shown) attached through apertures  13   a′  and  13   b′.    
         [0038]    Referring to  FIGS. 2-5 , heat sink insulator  37  may act: as an insulator between the two HDT portions  15   a,    15   b;  serve as a conduit for the LED wires (not shown); and also aid in securing isolation transformer  92 . 
         [0039]    Work coil  30  may be connected and disconnected from portable heater  10  as now discussed. Referring to  FIG. 2 , legs  32  of work coil  30  may be inserted into first nose apertures  22   a  and then HDT apertures  16 . 
         [0040]    Referring to  FIGS. 2, 7, 13 and 14 , each of two legs (not shown) of isolation transformer  92  is connected to one of the (left and right side) copper contactors  20 ; each of the copper contactors  20  is, in turn, connected to a side ( 15   a,    15   b ) of HDT  15 . Finally, to complete the connections and actuate the induction heater, each leg  32  of work coil  30  must be connected to one of the copper contactors  20 , in operation, and now referring to  FIG. 1 , with work coil  30  properly seated and tightened to portable induction heater  10 , coil  30  is directly fed from an electric power supply (not shown) within heater  10 , with electricity provided by power cord  70 . Isolation transformer  92  ( FIGS. 13-14 ) is used to take the supply/mains frequency and increase it to a higher frequency, such as about 1-400 kHz, providing power output of about 1-500 kW. A magnetic field is generated in the vicinity closely adjacent the work coil, inducing induction heat within a work piece (e.g., a fastener) adjacent the work coil. 
         [0041]    The grip area of induction heater  10 , including lower outside body surface  12  and upper body panels  13   a,    13   b,  may be made of a variety of high-strength materials which can withstand high temperatures, including: nylon; PBT(polybutylene terephthalate); polysulfone; PPS(polyphenylene sulfide); polyetherimide; PEEK(polyetheretherketone); or PVDF (polyvinylidene difluoride). 
         [0042]    Referring now to  FIGS. 2-7 , a novel aspect of the present invention concerning engaging and disengaging work coil  30  is now discussed. Outer panels  13  may be provided with the ability to rotate relative to upper body  17  and HDT  15 . Collar support  27  ( FIG. 2 ) is shaped and spaced so that when panels  13   a,    13   b  are rotated, collar support  27  will exert pressure on depressible portion  20   a  of conductive copper contactor  20 , both tightening legs  32  between copper portion  20   a  and copper base  21 , and also placing legs  32  of work coil  30  in electrical conductivity, via the copper contactor, with HDT  15  and isolation transformer  92 . (Collar support  27  also exists on the inside surface of panel  13   a,  although hidden on  FIG. 2 .) Apertures  16  preferably have V-shaped grooves in at least a portion of their length (see  FIGS. 4 and 8-10 ) as it has been found that this shape is particularly effective at holding legs of different cross-sectional geometries, including round, square and rectangular. 
         [0043]    Panels  13  may be designed so that they have unlimited rotation. Alternatively, it may be preferred to provide panels  13  with limited rotation (by appropriately locating and sizing collar supports  27  in relation to copper contactor  20 ), so that for example a 20°-30° turn of the panels will cause legs  32  to be tightened or loosened, providing a user with tactile feedback relatively rapidly. In practice, panels  13  may be rotated  20 ° , for example, legs  32  may be inserted within nose apertures  22   a  and HDT apertures  16 , and panels may now be rotated  20 ° in the opposite direction, to tighten the legs within copper contactor  20 . 
         [0044]    As suggested in  FIG. 2 , portable induction heater  10  may be linear in shape. Alternatively, as shown in  FIGS. 1, 12 and 13 , heater  10  may be angled, such as shown in these drawings. The angled design may be preferred by users working in tight, difficult-to-access areas, or may be preferred simply from an aesthetic standpoint. Note that trigger  130  may be actuated using a torsion spring  131  located between trigger  130  and trigger stop  132 ; trigger  130  pivots about pivot point  130   a  ( FIG. 13 ). 
         [0045]    Referring now to  FIGS. 7 and 13 , a new method is also provided of securing isolation transformer  92  to work coil  30 . In the past, the isolation transformer has been connected to the work coil by connecting the transformer, via a set screw, to the aluminum HDT. There is a resultant heat loss moving from copper to aluminum and back to copper. The new method of the present invention secures isolation transformer  92  directly to copper contactor  20  (by wire, using copper crimping support  94 , per  FIG. 7 , as discussed above); as work coil legs  32  are also connected directly to copper contactor  20 , this provides a copper-to-copper-to-copper connection, limiting heat loss. 
         [0046]    A way is also provided to detect issues with the work coil such as open coil, no coil present, or a shorted work coil. Currently, users of portable induction heaters used for the automotive aftermarket, for example, rely on the use a good working coil, and properly securing the work coil to the induction heater. If a work coil with breached insulation is used, or a coil is not secured properly (“fault conditions”), this can cause a transient voltage spike across the IGBTs (insulated-gate bipolar resistors) of the unit. A preferred embodiment of the present invention monitors the output voltage and will shut down the output of the induction heater if either of these fault conditions are detected, turning on a fault indicator. The unit may remain in shut-down condition for a period of time so that the condition can be corrected by the user, avoiding damage to the tool. The unit may also enter a fault mode when it detects that a work coil is not present in the tool. 
         [0047]    Conventional portable induction heaters used for the automotive aftermarket, for example, also will use as much current as needed to try and heat the load. If too much current is drawn from the unit, this can damage the unit. In a preferred embodiment of the present invention, the induction heater also includes an over-current detector and shut-down feature. The amount of current being used is monitored, and if the unit draws too much current, it will enter into a fault mode. The allowed amount of current can be set to different levels, allowing the induction heater to he customized for various needs. 
         [0048]    In a preferred embodiment schematically shown in  FIG. 1 , a fault-indicator, multi-color (e.g., red, green) LED  88  (preferably different and in addition to LED  87 ), may be used for both fault indication and normal operation. (Referring to  FIGS. 13-14 , light pipe  89  may be used to transmit light from fault-indicating LED  88  (shown in  FIG. 15  and not shown in  FIG. 14 , and which may be located on PCB  121 ) to the outer portion of the housing visible to the user. Referring to  FIG. 14 , work illumination switch  141  allows the user to keep LED  87  illuminated during heating, or to turn the LED off, at the user&#39;s discretion.) In an exemplary operation, the red LED may illuminate under any one of the following fault conditions: 1) if there is not a work coil attached to the tool when the trigger ( 130 ) is operated ( 112 ); or 2) if an over-current is detected as a result of using the tool for an excessive load ( 114 ); 3) if an arc is detected due to a loose connection to the work coil or coil open under use ( 116 ); or 4) if the tool heats to the point where the thermal switch opens ( 118 ). The green LED may illuminate while the trigger is active and the tool is heating properly, 
         [0049]    With this exemplary operation, any event that causes the red LED to illuminate may start a 3-second ( 120 ) lock-out of the tool ( 122 ). LED  88  may dim as the time elapses. Holding the trigger  130  active during a fault may cause the tool to restart after the delay cycling until the fault is corrected or the trigger is released. 
         [0050]    Fan  140  may be permitted to continue to run after trigger  130  is released to aid in thermal cycle time reduction, for up to two minutes ( 145 ). Fan  140  may be controlled so that it slows down with time, consuming less current, which becomes advantageous if operating on battery-power. Preferably, fan  140  may stay powered when the thermal switch opens ( 118 ) to aid in cooling the tool. Fan  140  may be permitted to run for up to two minutes after the thermal switch resets. (Over temp.  118  and delay (e.g., 2 min.) may meet at junction point  157 .) 
         [0051]    A separate white LED  87  ( FIGS. 8-10 ) may be used, and may be controlled exclusively by a separate switch  141  ( FIG. 13 ), providing the user with the ability to power on or off the work illumination LED  87 , which may be a separate LED from the fault-indicator LED  88 . As long as the tool is powered and its internal power supply is operating, white LED $ 7  may remain illuminated when the switch is on. 
         [0052]    If the fuse (not shown) is open, then no power is being provided to the unit, and no LEDs will be permitted to illuminate. 
         [0053]    The present invention allows a work coil to be rapidly tightened to a portable induction heater, as compared to a conventional tightening using thumb screws, providing a time saving of at least 50% or more. “Quick timing” comparison tests were performed. Using both hands to tighten thumbscrews, it took an average of about 8.5 seconds to tighten a work coil to a conventional portable induction heater, Using the present “twist-lock” invention, this was accomplished in about 2 seconds, providing a time savings of about 75%. If only one hand is used to tighten both thumbscrews, tightening a work coil took an average of about 13.30 seconds, while one hand using the “twist-lock” feature could accomplish this in about 2 seconds, yielding a time savings of about 85%. 
         [0054]    The above description is not intended to limit the meaning of the words used in the following claims that define the invention. For example, while various preferred and less preferred embodiments have been described above, persons of ordinary skill in the art will understand that a variety of other designs still falling within the scope of the following claims may be envisioned and used, it is contemplated that future modifications in structure, function or result will exist that are not substantial changes and that all such insubstantial changes in what is claimed are intended to be covered by the claims.