Abstract:
A soldering iron is configured to heat its tip and emit inert gas near the tip. This is accomplished by providing a heater cartridge having a heater pipe with a tip portion and a base portion. The heater pipe has a first hole in the tip portion and a second hole at the base portion. The heater pipe has a passage between the first and second holes so that gas can enter through the second hole and exit through the first hole. The heater cartridge has a grip handle between the tip and base portions of the heater pipe. The soldering iron has a handle base with a cavity adapted to receive the base portion of the heater pipe and at least a portion of the grip handle. The handle base is adapted to provide power and gas to the base portion of the heater pipe. The heater pipe transfers the power and gas from the base portion to the tip portion to heat the tip and emit gas near the tip. The cavity of the handle base is configured to substantially seal gaps between the grip handle and the handle base so that gas does not leak between the handle base and the grip handle.

Description:
RELATED APPPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 10/686,439, filed on Oct. 14, 2003, which claims priority to two Japanese patent applications, (1) 2003-101427, filed Apr. 4, 2003; and (2) 2003-118048, which was filed Apr. 23, 2003, which are all hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to a cartridge-type soldering iron capable of performing soldering operations and emitting inert gas, and more particularly, to a cartridge-type soldering iron capable of soldering operations in a constricted space.  
         [0004]     2. General Background and State of the Art  
         [0005]     As printed circuit boards are discarded, lead (Pb) embedded in the circuit board can release into the environment. The release of lead into the environment can lead to environmental hazards. To remedy this problem, some have developed soldering compounds that are free of lead. One of the drawbacks with lead free solder, however, is that the melting point of lead-free solder is 30° C. to 50° C. higher than the melting level of 210° C. to 232° C. of lead solder. This means that a soldering tip temperature of 350° C. or higher must be maintained in order to perform soldering operations with lead free solder. With such a high soldering tip temperature, flux in the solder can deteriorate, which can cause rapid oxidation in the soldering tip. As such, when lead free solder is used, the life of the soldering tip is shortened.  
         [0006]     Various solutions to the above problems have been proposed, including the methods described in Japanese Utility Model Application Laid-Open No. H6-70962 and U.S. Pat. No. 6,247,631. The preferred method described in No. H6-70962 relates to a cartridge-type soldering iron where threaded solder is supplied automatically. This is accomplished by providing a soldering iron having a heating element with a bent top end, and a handle that intersects with the body of the heater and forcing the thread solder into the bent top end of the heating element. As such, the soldering iron disclosed in the &#39;962 application cannot be applied to a cartridge-type soldering iron where the soldering tip and the handle are arranged in a straight line. In addition, to form a flow path for the inert gas, a cylindrical pipe attached to the heating element projects at an angle from the handle. This cylindrical pipe obstructs precise soldering operations, and it is difficult to precisely position the cylindrical pipe in order to maintain a uniform flow path for the inert gas. The supplied thread solder also hinders the soldering operation, so that it is generally not used in a printed circuit board with a high degree of concentration.  
         [0007]     The &#39;631 patent attempts to solve the shortcomings of the &#39;962 application with a cartridge-type soldering iron where the soldering tip and the handle are arranged in a linear configuration. Projections are provided on an outer periphery of the heating element and the inner periphery of the pipe, and the heating element and the pipe are precisely positioned to provide a uniform flow path for the inert gas. However, the plurality of projections on the outer periphery of the heating element and the inner periphery of the pipe in the &#39;631 patent are inherently inefficient. Accordingly, a more easily produced cartridge-type soldering iron is desirable. A cartridge-type Pb-free soldering iron with readily interchangeable soldering tips that can be replaced by the user without special tools is also highly desirable.  
       INVENTION SUMMARY  
       [0008]     This invention provides a soldering iron that heats the tip and emits inert gas near the tip. This is accomplished by providing a heater cartridge having a top or tip end and a base end with a soldering tip at the top end, an input opening closer to the base end and an output opening closer to the top end. The soldering iron also includes a gas injector having a gas chamber adapted to receive the heater cartridge such that the input opening of the heater cartridge is within the gas chamber so that gas is injected into the input opening. At least a portion of the top end and the output opening of the heater cartridge is enclosed with an exhaust pipe to form a gas passage between the outer surface of the heater cartridge and the exhaust pipe. As such, gas injected through the input opening passes through the opening within the heater cartridge and exit through the output opening, then pass through the gas passage and emit through an outlet defined by the space between the top end and the exhaust pipe to provide inert gas near the tip.  
         [0009]     The soldering iron described above works efficiently and conveniently even at high temperatures, while preventing oxidation of the soldering tip. Further, according to the invention, in its assembled state, a uniform gas flow path can be formed around the heating element of the cartridge-type soldering iron without creating obstacles to the use of the soldering iron in constricted spaces. The invention also makes possible a much more compact cartridge-type soldering iron, further aiding in the performance of precise soldering operations, and can perform soldering operations while emitting inert gas.  
         [0010]     Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within the description, be within the scope of the invention, and be protected by the accompanying claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The invention can be better understood with reference to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.  
         [0012]      FIG. 1  is a perspective view showing the cartridge-type soldering iron in a disassembled state.  
         [0013]      FIG. 2  is a perspective view showing the disassembled elements of a cartridge-type soldering iron according to an embodiment.  
         [0014]      FIG. 3  is a cross-sectional view of the front end of the cartridge-type soldering iron shown in  FIG. 1 .  
         [0015]      FIG. 4 ( a ) is a cross-sectional view of a gas injecting device of  FIG. 2 .  
         [0016]      FIG. 4 ( b ) is a front view of the gas injecting device of  FIG. 4 ( a ).  
         [0017]      FIG. 4 ( c ) is a rear view of the gas injecting device of  FIG. 4 ( a ).  
         [0018]     FIGS.  5 ( a ) through  5 (C) are side view of a handle portion of the soldering iron.  
         [0019]      FIG. 6 ( a ) is a perspective view of the conductive part embedded in the handle portion.  
         [0020]      FIG. 6 ( b ) is a front view of the conductive part shown in  FIG. 6 ( a ).  
         [0021]      FIG. 6 ( c ) is a cross-sectional view taken along a line A-A in  FIG. 6 ( a ).  
         [0022]      FIG. 7 ( a ) is a cross-sectional view of the conductive part shown in  FIG. 6 ( a ) taken along a line C-C.  
         [0023]      FIG. 7 ( b ) is a cross-sectional view along the line B-B of the conductive part in  FIG. 6 ( a ).  
         [0024]      FIG. 7  ( c ) is a close up view of the base end of the heater cartridge.  
         [0025]      FIG. 7 ( d ) is a close up view of the terminal plate.  
         [0026]      FIG. 7 ( e ) is a close up view of the base end of the terminal body.  
         [0027]      FIG. 8  is an exploded view of a soldering iron according to a second embodiment;  
         [0028]      FIG. 9  is an enlarged view of a portion of  FIG. 8 ;  
         [0029]      FIG. 10 ( a ) is an enlarged view of a handle base, a connection and a gas injector in their assembled state;  
         [0030]      FIG. 10 ( b ) is a partial cross-sectional view showing the handle base, the connection and the gas injector in their separated state; and  
         [0031]      FIG. 10 ( c ) is a front view showing the handle base, the connection and the gas injector in their separated state. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]      FIG. 1  illustrates a cartridge-type soldering iron (soldering iron)  1  including an exchange member  100  and a connector member  102  adapted to receive the exchange member  100 .  FIG. 2  is a perspective view illustrating the disassembled elements of the soldering iron  1 . The exchange member  100  includes a heater cartridge  2 , a gas-exhaust pipe  3  capable of coupling to a top or tip end of the heater cartridge  2 , and a grip handle  4  configured to receive the heater cartridge  2 . The grip handle  4  couples to the heater cartridge  2  along a central portion of the heater cartridge  2 . The connector member  102  includes a handle base  5  with an inner configuration adapted to receive the base end of the heater cartridge  2  and the outer surface configured so that the top end of the handle base  5  is enclosed within a gas injector  6 . The connector member  102  further includes the gas injector  6  coupled to the handle base  5  for injecting inert gas into the heater cartridge  2 , and an electric connector  8  positioned on a terminal end of cable  7  that extends from the handle base  5 .  
         [0033]     An inert gas supply tube (not shown) is coupled to the gas injector  6 . As such, when the soldering operation is to be changed, the operation can be carried out continuously only by exchanging the exchanging member  100 . The gas exhaust pipe  3  is coupled to the heater cartridge  2  from the front, and a grip handle  4  is coupled to the heater cartridge  2  from the behind. As a result, the gas exhaust pipe  3 , the heater cartridge  2 , and the grip handle  4  are assembled as an integral unit.  
         [0034]     When the assembly comprising the gas exhaust pipe  3 , the heater cartridge  2 , and the grip handle  4  is inserted into the handle base  5 , the cartridge-type soldering iron  1  is fully assembled. In this case, the base end of the grip handle  4  is abut against the top end of the gas injector  6 , thereby preventing the excessive insertion of the heater cartridge  2 . In this configuration, minimal stress if any may be applied to the base end of the heater cartridge  2 . The gas exhaust pipe  3 , the heater cartridge  2 , and the grip handle  4  is integrally formed and this formation may be prepared as an exchange member  100 . Alternatively, the heater cartridge  2  to which the gas exhaust pipe  3  is coupled may be prepared as the exchange member  100 .  
         [0035]     Once the connection member  102  is assembled, the base end of the grip handle  4  is in contact with the gas injector  6 , and the contact point between the grip handle  4  and the gas injector  6  is closer to the top end than the center point of the entire length of the cartridge-type soldering iron  1 . The diameter of the grip handle  4  is the proper size to be gripped comfortably by three fingers (thumb, index and middle finger) and the grip handle  4  is manufactured of material of appropriate elasticity. Therefore, intricate soldering operations may be performed on highly integrated printed circuit boards.  
         [0036]     As shown in  FIGS. 2 and 3 , the heater cartridge  2  includes a cylindrical, conductive hollow pipe  9 , a soldering tip  10  coupled to the top or tip end of the hollow pipe  9 , a mounting part  11  coupled to an outer periphery of the hollow pipe  9 , and a heater part  12  inserted into a mounting hole  10   a  of the soldering tip  10 . The heater part  12  is provided with a temperature sensor  13  at its top end. The heater part  12  and the temperature sensor  13  are held in position by a ceramic coat material  14  filled in the mounting hole  10   a . The ceramic coat material  14  may be solidified water solution including binder and alumina, or any other insulatory material known to one skilled in the art.  
         [0037]      FIG. 3  illustrates that two conductors  15   a  and  15   b  extend from the heater part  12  passing through the hollow pipe  9 . The two conductors  15   a  and  15   b  are electrically connected to annular terminals  16   a  and  16   b  on the base end side of the hollow pipe  9 . The base end of the heater cartridge  2  is substantially closed with an insulation material  17   a  (as shown in  FIG. 2 ). The base end of the heater cartridge  2  is hermetically sealed in the handle base  5  when the soldering iron  1  is in use, so that inert gas injected into the hollow pipe  9  does not leak from the handle base  5 . As explained below, the base end side of the handle base  5  is substantially closed, and the top end side thereof is hermetically sealed by the hollow pipe  9  and the elastic body  27   b.    
         [0038]     In the base end of the hollow pipe  9 , insulation materials  17   b  and  17   c  are respectively disposed between the annular terminal  16   a  and the annular terminal  16   b , and between the annular terminal  16   b  and the pipe body  16   c , such that the three members  16   a ,  16   b  and  16   c  are electrically insulated from one another. The pipe body  16   c  of the hollow pipe  2  is electrically connected to the soldering tip  10 .  
         [0039]      FIGS. 2 and 3  illustrate that the pipe body  16   c  is formed with a plurality of (e.g., four) first holes  18  located near the top side of the mounting part  11 , and is formed with a plurality of (e.g., two) second holes  19  at locations corresponding to the gas injector  6 . Inert gas is injected into the hollow pipe  2  through second holes  19 , and discharged through first holes  18 . The second holes  19  are separated from each other along the same circumference of the pipe body  16   c . The first holes  18  are separated away from one another in an axial direction and in a circumferential direction of the pipe body  16   c . Two projections  50  and  51  are provided between the rear end and the mounting part  11  of the pipe body  16   c . The outer peripheral diameters of the projections  50  and  51  are substantially the same as an inner peripheral diameter of the grip handle  4  so that the outer periphery of the projection  50  is substantially fit within an inner periphery of the grip handle  4 . As a result, deflection between the grip handle  4  and the heater cartridge  2  along the radial direction is substantially prevented.  
         [0040]     The projection  51  engages with a step (not shown) formed in the inner periphery of the grip handle  4  when the grip handle  4  is inserted from the rear end of the heater cartridge  2  so that the projection  51  positions the grip handle  4  in a predetermined position along the axial direction. That is, before the top end of the grip handle  4  comes into contact with the mounting part  11 , the projection  51  prevents the grip handle  4  from being further inserted.  
         [0041]      FIG. 3  illustrates that the gas exhaust pipe  3  includes a plurality of portions: an inner portion  20 ; an outer portion  21 ; and a box nut  22 . The inner portion or pipe  20  is slightly larger in diameter than the hollow pipe  9 . The outer portion or pipe  21  is tightly fitted around the outside of the top end of the inner pipe  20 . The cylindrical box nut  22  is movably fitted into an outer periphery of the inner pipe  20 . The top end of the outer pipe  21  is tapered to conform to the shape of the soldering tip  10 . The inner pipe  20  is formed at its base end with a flange part  20   a  which has a large diameter formed into an annular shape diametrically outward. To accommodate a plurality of differently shaped soldering tips designed to accomplish various different soldering operations, a plurality of differently shaped outer pipe  21  to fit different soldering tip  10  may be provided.  
         [0042]     As shown in  FIG. 3 , the box nut  22  is divided into the top end  22   a  and the base end  22   b , which have different inner peripheral diameters. An inner peripheral surface of the base end  22   b  is formed with a threaded groove corresponding to the mounting part  11 . The inner peripheral diameter of the top end  22   a  is greater than an outer diameter of the inner pipe  20 . The inner peripheral diameter of the top end  22   a  is smaller than the outer diameter of the flange part  20   a  of the inner pipe  20  and the outer diameter of a base end of the outer pipe  21 . As such, the box nut  22  is not detached from the inner pipe  20  either in its forward or backward direction.  
         [0043]     The inner peripheral diameter of the base end  22   b  of the box nut  22  is substantially the same as the outer peripheral diameter (r) of the flange part  20   a . Contact surfaces between the top end  22   a  of the box nut  22  and the mounting part  11  which abut against the front and rear surfaces of the flange part  20   a  intersect with an axial direction of the hollow pipe  9  at right angles in correspondence with the flange part  20   a . As such, if the box nut  22  is screwed onto the mounting part  11  and the flange part  20   a  is pushed against the contact surface of the mounting part  11 , the inner pipe  20  is positioned correctly with respect to the box nut  22  as shown in  FIG. 3 . Once the box nut  22  is screwed, the box nut  22 , the mounting part  11  and the inner pipe  20  are integrally coupled so that the inner pipe  20  is positioned correctly with respect to the hollow pipe  9 , thereby forming a uniform gap between the inner pipe  20  and the hollow pipe  9 , to provide a gas passage.  
         [0044]     With the soldering iron described above, unlike U.S. Pat. No. 6,247,631, it is unnecessary to provide a positioning projection on the inner peripheral surface of the inner pipe  20  or the outer peripheral surface of the hollow pipe  9 , to provide a uniform gas passage.  FIG. 3  illustrates that inert gas introduced from the first holes  18  passes through the gas passage formed between the hollow pipe  9  and the inner pipe  20  toward the top end, reaches a gas passage formed between the outer pipe  21  and the soldering tip  10 , and is emitted toward an operation surface. Since the inert gas is emitted as described above, the oxidation of the soldering tip is minimized. The base end of the gas passage is closed by tight contact between the flange part  20   a  and the mounting part  11 .  
         [0045]     As shown in  FIG. 2 , the grip handle  4  is comprised of a plastic inner cylindrical body  23  and an elastic polymer outer cylindrical body  24  enclosing the plastic inner cylindrical body  23 . In this embodiment, PVC (polyvinyl chloride) is used as the elastic polymer, but other elastomers, including rubber, may be used. The inner cylindrical body  23  and outer cylindrical body  24  are made of material having low thermal conductivity so that the outer cylindrical body  24  can be comfortably grasped by the user. Different colors of elastic polymer of the outer cylindrical body  24  may be used to distinguish a plurality of different outer cylindrical bodies.  
         [0046]     The inner cylindrical body  23  is provided with a flange part  23   a  which receives the insertion of the outer cylindrical body  24 . The rear end of inner cylindrical body  23  is axially notched by a plurality (in one embodiment, four) of notched grooves  23   b  in the axial direction. The elastic body rings  25   a  and  25   b  are fitted around the notched grooves  23   b . The elastic body rings  25   a  and  25   b  reduce the diameter of the end of the inner cylindrical body  23 , which are then inserted into outer cylindrical body  24 . In this manner, cylindrical body  23 , and cylindrical body  24  are combined to form the grip handle  4 . When inner cylindrical body  23  is inserted into outer cylindrical body  24  they are integrally coupled, then this assembly may receive the hollow pipe  9 . Outer cylindrical body  24  has an appropriate elasticity, and its outer diameter is of a size to be comfortably grasped by three fingers (the thumb, index and middle fingers).  
         [0047]     While the diameter of hollow pipe  9  may be small in accordance with degree of integration of IC mounted on a printed circuit board, the diameter of outer cylindrical body  24  is adapted to fingers of an operator. Further, the contact point between outer cylindrical body  24  and the gas injector  6  is slightly closer to the tip than the central point of the soldering iron  1 . As a result, the soldering iron  1  is more comfortable to use in soldering operations.  
         [0048]      FIG. 4  illustrates that the gas injector  6  includes a sealing screw  30 . The top end and base end of the charging body  26  are hermetically sealed by O-rings  27   a  and  27   b . O-ring  27   a  is held by a pushing plate  28 ( FIG. 2 ), and the O-ring  27   b  is held in place by the top end surface of handle base  5 . The base end of charging body  26  is cylindrical in order to receive handle base  5 , and the handle base  5  is fixed in place by holding screws  31 . The charging body  26  has a mounting opening  33  into which an introducing member  32  is inserted. Inert gas introduced through the introducing member  32  moves inward and then reaches a central gas chamber  34 .  
         [0049]     The inert gas used with the soldering iron  1  may be nitrogen gas. The inert gas is supplied through a tube (not shown) coupled to the introducing member  32 . The tube is disposed along the axial direction of the soldering iron to not obstruct with soldering operations. The supply of inert gas through the tube member mounted to introducing member  32  is controlled by an ON/OFF toggle switch (not shown).  
         [0050]     The diameter of gas chamber  34  is slightly greater than that of hollow pipe  9 . When hollow pipe  9  is inserted into gas chamber  34 , the ends of gas chamber  34  are sealed by O-rings  27   a  and  27   b . When hollow pipe  9  is inserted into handle base  5 , the second holes  19  of hollow pipe  9  are located at the gas chamber  34 . As such, the inert gas in gas chamber  34  passes through the second holes  19  into hollow pipe  9 . With the top end and the base end of hollow pipe  9  being sealed as discussed above, the inert gas is discharged from the holes  18 .  
         [0051]     FIGS.  5 ( a ) through  5 ( c ) illustrate a cylindrical first part  35  opened at both axial ends, and a cap-shaped second part  36  is screwed onto the linkage part  43 , providing a handle base  5 . The first part  35  includes an electrical connector assembly  37 . When the top end  35   a  is inserted into the base end of the body  26  of a gas injector part  6 , the top end  35   a  makes contact with elastic body  27   b . Therefore, when the heater cartridge  2  is inserted into the handle base  5 , a secure seal is formed by the outer periphery of the hollow pipe  9  and the elastic body  27   b.    
         [0052]      FIG. 5 ( a ) illustrates that the handle base  5  is separated into first part  35  and second part  36 . The base end of second part  36  is closed by cable  7  inserted into this base end and leads  44 ,  45 ,  46  are derived from cable  7  as shown in  FIG. 5 ( b ). In order to close the base end of second part  36  securely, a sealing member may be adhered to the outer periphery of the cable  7  and forcibly inserted into the base end of second part  36 .  
         [0053]     The linkage part  43  includes a body  43   a  having screw grooves in axial opposite ends and attachment plates  43   b ,  43   c  projecting frontward and rearward in an axial direction from the body  43   a . The body  43   a  has three penetration holes passing three leads  44 ,  45  and  46 . The attachment plate  43   c  couples to the top end of the cable  7  from the second part  36 , and the attachment plate  43   b  couples the linkage part  43  with the electrical connector assembly  37 .  
         [0054]      FIG. 6 ( a ) illustrates that the electrical connector assembly  37  is formed with a ground terminal plate  40 , a first terminal plate  41 , and a second terminal plate  42  built into a plastic terminal body  39  of the electrical connector assembly  37 . Although not shown, the ground terminal plate  40 , the first terminal plate  41 , and the second terminal plate  42 , are respectively connected with the leads  44 ,  45 ,  46  derived from the cable  7  and passing through body  43   a.    
         [0055]      FIG. 7 ( e ) illustrates that the terminal body  39  is cylindrical, and an installation hole  46  corresponding to the terminal plate  40 , an installation hole  47  corresponding to the terminal plate  41 , and an installation hole  48  corresponding to the terminal plate  42  are formed in the base end side of the terminal body  39 . Each installation hole  46 ,  47  and  48  is respectively divided into installation groove  46   a ,  47   a  and  48   a , with a breadth of L 1 , and installation openings  46   b ,  47   b  and  48   b , with a breadth of L 2 . The first terminal plate  41  is inserted from the installation hole  47  at the base end of terminal body  39  toward the top end, and the second terminal plate  42  is inserted from the installation holes  48  toward the top end. The first and second terminal plates  41  and  42  are thus fixed to the terminal body  39 .  
         [0056]      FIG. 7 ( a ) illustrates that the first rectangular windows  51   a  and  51   b  and the second rectangular windows  52   a  and  52   b  are formed in the terminal body  39  in a radially symmetric direction. The third rectangular window  53   b  is 90 degrees apart from windows  51   b  and  52   b  as shown in  FIG. 7 ( b ). The first rectangular windows  51   a  and  51   b  correspond to the first terminal plate  41 , the second rectangular windows  52   a  and  52   b  correspond to second terminal plate  42 , and the third rectangular window  53   b  corresponds to ground terminal plate  40 .  
         [0057]     As shown in FIGS.  7 ( a ) and  7 ( c ), the inner diameter φ′ of terminal body  39  is the same as or slightly greater than the outer diameter φ of hollow pipe  9 . The axial length of terminal body  39  is sufficient to contain two annular terminals  16   a ,  16   b  and the base end of handle body  16   c.    
         [0058]     The ground terminal plate  40  shown in  FIG. 7 ( b ) extends to the top end side of the terminal body  39  and couples with the annular electrical conductor  38 . In  FIG. 6 ( a ), the annular electrical conductor  38  is made of an elastic material and a notch  38 a is formed throughout an axial direction in a part of its circumference. Therefore, annular electrical conductor  38  becomes radially telescopic. When contracted, the annular electrical conductor  38  is inserted into terminal body  39 , and spreading more or less in a radial direction, the annular electrical conductor  38  is securely inserted into the terminal body  39 .  
         [0059]     As shown in  FIG. 7 ( a ), in the axial center of the annular electrical conductor  38 , a small diameter projection  38   b  projects inward radially around the entire circumference. The inner diameter of small diameter projection  38   b  is slightly smaller than the outer diameter φ of hollow pipe  9 . Therefore, when heater cartridge  2  is inserted- into handle base  5 , the small diameter projection  38   b  extends slightly in an axial direction or outward in a radial direction by the hollow pipe  9 . Thus, small diameter projection  38   b  contacts and holds the hollow pipe  9  securely.  
         [0060]     FIGS.  7 ( a ) and  7 ( c ) illustrate that the projection  38   b  is formed in a position of contact with the pipe body  16   c . As such, the electrically secure ground terminal  40  is connected with the pipe body  16   c  through the small diameter projection  38   b  when the heater cartridge  2  is inserted into handle base  5 . Further, the ground terminal  40  is inserted from the top end of the terminal body  39  (see the left side of  FIG. 7 ) into the base end and a projecting cut piece  40   b  of ground terminal plate  40  is engaged with the third small window  53   b  of the terminal body  39 . Thus, the insertion is completed as shown in  FIG. 7 ( b ).  
         [0061]     The first terminal plate  41  is smaller than the second terminal plate  42 , and both plates are made of an elastic material. In  FIG. 7 ( d ), the first and second terminal plates  41  and  42  comprise bodies, top ends and base ends. The width of terminal plates  41  and  42  is almost the same as the width L 1  of installation holes  47   a ,  48   a . The width of the top ends of terminal plates  41  and  42  is slightly smaller than the width L 2  of installation openings  47   b  and  48   b . The base ends of the terminal plates  41  and  42  provide stoppers ST to prevent excessive insertion. As shown in  FIG. 7 ( d ), projecting cut piece  41   b  is formed in the body of first terminal plate  41 , and the stopper ST and an opening  41   c  connected with the lead  45  are formed in the base end of first terminal plate  41 . Likewise, the projecting cut piece  42   b  is formed in the body of the second terminal plate  42  and the stopper ST and an opening  42   c  are formed in the base end of second terminal plate  42 , as shown in  FIG. 7 ( a ).  
         [0062]     When the first terminal plate  41  and the second terminal plate  42  are inserted into the installation holes  47  and  48 , the plates  41  and  42  slide into installation grooves  47   a  and  48   a  respectively, and the stoppers ST come into contact with terminal body  39 . In this state of contact, projecting cut pieces  41   b  and  42   b  are engaged with rectangular windows  51   b  and  52   b  of terminal body  39 , respectively, to securely hold terminal plates  41  and  42 .  
         [0063]      FIG. 7 ( a ) illustrates that the tops of terminal plates  41  and  42  are bent radially inward. In a free state, the bent parts  41   a ,  42   a  are located inside the outer diameter of the hollow pipe  9 . In  FIG. 7 ( c ), with hollow pipe  9  inserted, bent part  41   a  of the first terminal plate  41  makes contact with annular terminal  16   a  and bent part  42   a  of the second terminal plate  42  makes contact with the annular terminal  16   b.    
         [0064]     The first terminal plate  41  makes an electrically secure connection with annular terminal  16   a  and the second terminal plate  42  makes an electrically secure connection with annular terminal  16   b . In this manner, when terminal plates  41  and  42  are supported, bent parts  41   a  and  42   a  of the top end only swing and terminal plates  41  and  42  of this embodiment receive no pressure from the hollow pipe  9 . Therefore, the stress due to the insertion of the hollow pipe is substantially minimized.  
         [0065]     The electrical connection is made by bringing the two terminal plates  41 ,  42  of different lengths into contact with the two annular terminals  16   a ,  16   b  respectively. No rotational orientation is necessary when the heater cartridge  2  is inserted. With this invention, the complexity of inserting the heater cartridge  2  into the electrical connector assembly  37  may be minimized. Moreover, in a state in which the hollow pipe  9  is inserted, the ground terminal  40  is securely connected making an electrical contact with the pipe body  16   c  as explained above.  
         [0066]     The outer diameter of the hollow pipe  9  is almost the same as the inner diameter of terminal body  39 , such that the hollow pipe  9  is held loosely within terminal body  39 . On the other hand, the pipe body  16   c  spaced properly from the base of the pipe is held securely over its entire length by annular electrical conductor  38 . As such, when hollow pipe  9  is inserted into the electrical connector assembly  37 , the hollow pipe  9  is held securely by electrical connector assembly  37 . That is, with the length of the terminal plate  41  being different from that of the terminal plate  42 , the distance from the base end of the electrical connector assembly  37  to small diameter projection  38   b  inevitably becomes long, so that hollow pipe  9  can be more securely held.  
         [0067]     As shown in  FIG. 1  the grip handle  4  and handle base  5  are separated. When hollow pipe  9  is inserted into the grip handle  4 , heater cartridge  2 , gas exhaust pipe  3 , and the grip handle  4  are combined as a single unit. As such, the soldering iron  1  is used for a variety of operations by replacing the exchange member  100  comprised of heater cartridge  2 , gas exhaust pipe  3  and grip handle  4 . That is, when a soldering tip  10  is to be changed, the assembly comprising a heater cartridge  2 , gas exhaust pipe  3  and grip handle  4  may be pulled out integrally. And an exchange member  100  comprising another soldering tip  10 , may be inserted into gas injector  26  and handle base  5 . In addition, to expedite the selection of an appropriate soldering tip, the cylindrical body  24  of grip handle  4  of each exchange member  100  may be made of a different color material.  
         [0068]     In addition to the exchange member  100  described above, another exchange member may be constructed with the gas exhaust pipe  3  and the heater cartridge  2 , both integrally coupled. Such exchange member, the heater cartridge  2  of the exchange member is inserted into grip handle  4  which has been used heretofore and grip handle  4  is used as it is.  
         [0069]     The grip handle  4  is detachably fitted over the heater cartridge  2 , so that it is possible to produce a grip handle having the shape, size, color and material desired by a user. Further, since each user may have a personal grip handle, sanitation level is high, and when the grip handle becomes worn it may be replaced without having to replace the entire cartridge-type soldering iron, thereby reducing costs.  
         [0070]     It is understood by those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope thereof. For example, although the cartridge-type soldering iron in which the grip handle  4  and the handle base  5  can be separated from each other, the present invention can also be applied to a cartridge-type soldering iron in which the grip handle  4  and the handle base  5  are integrally coupled with each other, and then the heater cartridge  2  is inserted into the integral grip handle  4  and handle base  5 .  
         [0071]      FIG. 8  is an exploded view showing the entire structure of a soldering iron  1 A according to another embodiment.  FIG. 8  corresponds to  FIG. 2 .  FIG. 8  shows a gas-exhaust pipe  3 , a heater cartridge  2 , a grip handle  4 , a handle base  5 , a gas injector  6  and an electric connector  8 .  FIG. 9  is an enlarged view of a portion of  FIG. 8 , and shows the heater cartridge  2 , the gas-exhaust pipe  3  and the grip handle  4 . The heater cartridge  2  and the gas-exhaust pipe  3  are exchange members  100  which are exchanged if necessary. The heater cartridge  2  and the gas-exhaust pipe  3  are exchanged for new exchange members  100 ′. The heater cartridge  2  and the gas-exhaust pipe  3  are integrally formed with the grip handle  4 . When the heater cartridge  2  and the gas-exhaust pipe  3  are exchanged for new exchange members  100 ′, the heater cartridge  2  and the gas-exhaust pipe  3  may be separated from the grip handle  4  or the heater cartridge  2  and the gas-exhaust pipe  3  may be left as an integral piece together with the grip handle  4 .  
         [0072]     In this soldering iron  1 A, the handle base  5  is divided into a first part  35  and a second part  36 , and the first part  35  receives a top end  36   a  of the second part  36 . The first part  35  of the handle base  5  is made of an elastic polymer, as well as an outer cylindrical body  24  of the grip handle  4 . Thus, if the heater cartridge  2  is inserted into a handle base  5  when the heater cartridge  2  is to be exchanged, a base end (right side in  FIG. 8 ) of the cylindrical body  24  enters into the first part  35  of the handle base  5 , and the soldering iron  1 A is air-tightly integrally assembled.  
         [0073]     In the soldering iron  1  shown in  FIG. 2 , the first part  35  of the handle base  5  is provided at its tip end  35   a  with the gas injector  6 . In the soldering iron  1 A shown in  FIG. 8 , the second part  36  of the handle base  5  is provided at its base end  36   b  with the gas injector  6 . Second holes  19  of the heater cartridge  2  are formed in the vicinity of annular terminals  16   a  and  16   b  formed on the side of the base end of the pipe body  16   c  at positions corresponding to the gas injector  6  (see  FIG. 9 ). First holes  18  are formed at the same positions as those shown in  FIG. 2 , and the first holes  18  are formed at positions slightly closer to the tip end than the mounting part  11 .  
         [0074]     FIGS.  10 ( b ) and ( c ) show the second part  36  of the handle base  5 , a connection  43  and the gas injector  6  in their separated state. As shown in the drawings, the gas injector  6  has a plastic charging body  26  which is of substantially cylindrical shape as a whole. The charging body  26  is formed with a mounting opening  33 , an introducing member  32  is threadedly inserted into the mounting opening  33 , and a tube member  60  through which inert gas is supplied is connected to the introducing member  32 . A guide hole which is perpendicular to the mounting opening  33  is closed with a sealing screw  30 .  
         [0075]     The charging body  26  is provided at its inner periphery with a tip end  26   a  having a screw groove, a base end  26   b  receiving a rubber bushing  7 A fitted over the cable  7 , and an annular small-diameter part  26   c . An inner diameter of the annular small-diameter part  26   c  is substantially the same as an outer diameter of the cable  7 . Therefore, if the cable  7  is inserted into the gas injector  6 , the outer periphery of the cable  7  is fitted into the inner periphery of the annular small-diameter part  26   c . Since the bushing  7 A is tightly pushed into the base end  26   b , in the assembled state of the soldering iron  1 A, the air-tightness is established. Thus, inert gas introduced from the tube member  60  is preventing from flowing rearward by the annular small-diameter part  26   c  and the bushing  7 A, and the inert gas flows only forward (leftward in  FIG. 10 ).  
         [0076]     As shown in  FIGS. 8 and 10 ( c ), the gas injector  6  and the handle base  5  are connected to each other through a translucent plastic connection  43 . An electric connector assembly  37  shown in  FIG. 6  is incorporated in the second part  36  of the handle base  5  ( FIG. 10 ( a )). The structure of the connection  43  is the same as that shown in  FIG. 5 ( b ), and the connection  43  comprises a body  43   a  and mounting plates  43   b  and  43   c  ( FIG. 10 ( c )). The body  43   a  is provided at its axially opposite ends with screw grooves. The mounting plates  43   b  and  43   c  project from the body  43   a  forward and backward in the axial direction. The cable  7  is fixed to the mounting plate  43   c , and the electric connector assembly  37  shown in  FIG. 7  is fixed to the mounting plate  43   b.    
         [0077]     The plastic body,  43   a  is formed with a through hole in the axial direction. Three conductive wires pulled out from the cable  7  are inserted through the through hole. The body  43   a  is also formed therein with a columnar lateral hole, a light-emitting diode  61  is inserted into the lateral hole, and the light-emitting diode  61  is connected, in parallel, to the heater  12  which extends by way of the annular terminals  16   a  and  16   b . Therefore, the light-emitting diode  61  is lit at the same time as the electricity is fed to the heater  12 , and a user can check the lightening state through the translucent body  43   a.    
         [0078]     The base end  36   b  of the second part  36  of the handle base  5  is formed at its inner periphery with a screw groove, and a tip portion of the body  43   a  is threadedly inserted into the base end  36   b . A screw groove is formed also in a tip end  26   a  of the gas injector  6 , and the base portion of the body  43   a  is threadedly inserted into the tip end  26   a.    
         [0079]     In the assembled state, the annular terminals  16   a  and  16   b  of the heater cartridge  2  come into contact with the electric connector assembly  37 , and electricity is supplied to the soldering tip  10 . Inert gas introduced from the gas injector  6  flows through the through hole formed in the body  43   a  of the connection  43  and then, the inert gas is introduced into the opening  19  of the heater cartridge  2  through the gap formed in the electric connector assembly  37 . According to this soldering iron  1 A, the through hole formed in the body  43   a  serves as a passage of the three conductive wires pulled out from the cable  7 , and also serves as a passage of the inert gas. In the assembled state, the outer cylindrical bodies  24  and the handle base  5  are integrally assembled and the tip end  35   a  of the first part  35  of the handle base  5  is closed with the outer cylindrical body  24  and thus, the inert gas is prevented from leaking.  
         [0080]     When the handle base  5 , the connection  43  and the gas injector  6  are to be assembled, the second part  36  of the handle base  5  is allowed to rotate, and its base end  35   b  is threadedly fitted with the connection  43 . The bushing  7 A is retracted toward the base end (rightward in the drawing) and in this state, the gas injector  6  is turned, and the tip end  26   a  of the gas injector  6  is threadedly fitted with the connection  43 . Then, if the bushing  7 A is moved forward and is pushed into the base end  26   b  of the gas injector  6 , the entire soldering iron is integrally assembled.  
         [0081]     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of this invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.