Abstract:
A simple and inexpensive gas nozzle for arc welding capable of reducing adhesion of sputter and enhancing welding quality and welding workability. A gas nozzle ( 5 ) so fixed removably to the torch head ( 2 ) of a welding torch ( 1 ) as to surround a contact chip ( 4 ) for feeding a welding wire (W) is formed of a material, e.g., a pasteboard a part of which is carbonized through adhesion of sputter (S) and comes off together with the sputter (S). When the sputter (S) adheres to the gas nozzle ( 5 ) during welding, the adhering part is carbonized because of the heat of the sputter (S) and comes off together with the sputter (S). Consequently, adhesion and deposition of the sputter (S) onto the gas nozzle ( 5 ) can be reduced infallibly.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a gas nozzle attached to, for example, a welding torch of a consumable electrode mode arc welder. 
       BACKGROUND OF INVENTION 
       [0002]    As consumable electrode mode arc welding such as MIG welding, a welding torch  21  as shown in a schematic section view of  FIG. 6  is used. In the welding torch  21 , a contact tip  24  made of metal for feeding a welding wire  23  as a consumable electrode is removably screwed to the tip portion  22   a  of an insulating torch head  22 , and simultaneously a base portion  25   a  of a gas nozzle  25  made of metal is removably screwed to the tip portion  22   a  of the insulating torch head  22  so as to surround the contact tip  24 . Moreover, the welding wire  23  is used as plus-side electrode and a workpiece W of material to be welded is used as minus-side electrode, and arc is generated between the welding wire  23  and the workpiece W while inert gas such as argon gas as shield gas is fed to the inside of the gas nozzle  25 , and then the heat by the arc melts the welding wire  23  to weld the two workpieces W. 
         [0003]    In the arc welding using the welding torch  21 , the operation of welding brings about dispersal of a great amount of spatters S consisting of small particles of molten metal, and a part of the spatters S adheres to and deposits on a tip portion  25   b  corresponding to gas discharge side of the gas nozzle  25  and an inner surface  25   c  of the nozzle. The spatters S deposited on the gas nozzle  25  inhibit flow of the shield gas to reduce the shield property on the welding, whereby porosities such as blowholes or pits are apt to occur on the welded portions to bring about reduction of welding quality. 
         [0004]    Further, the spatters S also adhere to and deposit on a surface of the contact tip  24 , and connect with the spatters S deposited on the gas nozzle  25 , and hence the contact tip  24  and the gas nozzle  25  electrically connect with each other. Thus, when the tip portion  25   b  of nozzle of the gas nozzle  25  is brought about into contact with the workpiece W, short and spark by the contact occurs, whereby there is possibility of burning of the welding torch  21  or damage of the workpiece W. 
         [0005]    In order to reduce deposited amount of the spatters S on the welding torch  21 , for example, Patent Document 1 proposes a gas nozzle made of ceramic, Patent Document 2 proposes formation of a ceramic covering layer on a surface of a contact tip  24 , or Patent Document 3 proposes formation of a metal layer having high melting point (m.p. 2,500° C.) on a surface of a contact tip  24 . 
         [0006]    Furthermore, to prevent short between a gas nozzle  25  and a workpiece W, for example, Patent Document 4 proposes that an insulating resin is covered on a surface of a contact (electrode) tip  24  and/or an inner surface of a gas nozzle  25 . 
         [0007]    List of Patent Documents: 
         [0008]    Patent Document 1: JP61-111783A 
         [0009]    Patent Document 2: JP61-296969A 
         [0010]    Patent Document 3: JP63-66577U 
         [0011]    Patent Document 4: JP05-5272U 
       SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
       [0012]    However, in case a gas nozzle  25  made of ceramic is adopted as described the patent Document 1, the gas nozzle has a tendency to increase cost. Further, in case a gas nozzle  25  having a ceramic covering layer or a high melting point metal layer formed on a surface of a contact tip  24  is adopted as described the patent Document 2 or 3, a process for formation of the layer is required for the preparation of the contact tip to bring about increase of cost. 
         [0013]    In case a gas nozzle  25  having an insulating resin covered on a surface of a contact tip  24  and/or an inner surface of the gas nozzle is adopted as described in Patent Document 2, electric connection (short) between the contact tip  24  and gas nozzle  25  via spatters S can be prevented but it is difficult to prevent the adhesion and deposition of the spatters S to the contact tip  24  and the gas nozzle  25 . Therefore the deposition of the spatters S inhibits a flow of a shield gas whereby porosity occurs on a welded portion to lower welding quality. Further, in order to prevent lowering of the welding quality, it is required to remove the deposited spatters S by frequent cleaning of the gas nozzle  25  to reduce welding workability. 
         [0014]    Thus, in view of the above-mentioned circumstances, the object of the present invention is to provide a gas nozzle for arc welding that can be simply and cheaply obtained, reduced in deposition of spatters, and improved in welding quality and welding workability. 
       Means of Solving Problem 
       [0015]    The present invention (first aspect) attained to the above object is provided by a gas nozzle removably attached to a tip portion of a torch head of a welding torch so as to surround a contact tip for feeding welding wire, 
         [0016]    a tip portion on at least a gas discharge side of the gas nozzle comprising material that is capable of carbonizing due to weld spatters adhered to the material and allowing the carbonized material together with the spatters to fall from the tip portion of the gas nozzle. 
         [0017]    In the gas nozzle as defined above, it is preferred that whole of the gas nozzle is formed from the material (second aspect). 
         [0018]    In the gas nozzle as defined above, it is preferred that the material is paper board (third aspect). 
         [0019]    In the gas nozzle as defined above, it is preferred that the material has been impregnated with oil (forth aspect). 
         [0020]    In the gas nozzle as defined above, it is preferred that the gas nozzle comprises a base side nozzle made of metal and a tip side nozzle made of the material, a base portion of the base side nozzle being removably attached to the tip portion of a torch head and a base portion of the tip side nozzle being removably attached to the tip portion of the base side nozzle (fifth aspect). 
       EFFECT OF THE INVENTION 
       [0021]    According to the invention of the first aspect, when spatters shattered during a welding operation are adhered to and deposited on at least a tip portion of a nozzle of a gas nozzle, the spatters-deposited portion carbonizes due to heat of the spatters and the carbonized portion exfoliates and falls together with the spatters from the tip, whereby the amount of spatters deposited on the gas nozzle can be reliably reduced. Hence, the gas nozzle is free from the defect that the deposition of the spatters inhibits a flow of a shield gas, and therefore shield effect by the shield gas can be ensured, which brings about no occurrence of porosity on the welded portion to enhance welding quality. Further, material capable of carbonizing owing to weld spatters adhered to the material and allowing the carbonized material together with the spatters to fall can be formed from, for example, paper-like material, such as paper board which can be used in cardboard, woodfiber, nonwoven, or synthetic paper, and therefore can be simply and cheaply obtained, and simultaneously when the carbonized portion of the material comes to increase owing to the deposition of weld spatters, the material have only to be changed with new one, and therefore it is possible to dispense with cleaning operation of the gas nozzle to greatly improve welding workability. 
         [0022]    According to the invention of the second aspect, the whole of gas nozzle is made of the material capable of carbonizing owing to weld spatters adhered to the material and allowing the carbonized material together with the spatters to fall, and hence the amount of spatters deposited on whole of the gas nozzle is reduced to enable improvement of welding quality and workability. 
         [0023]    According to the invention of the third aspect, the use of paper board as the material renders the preparation of a gas nozzle simple and cheap. 
         [0024]    According to the invention of the forth aspect, the use of the material impregnated with oil effectively reduces the deposited and carbonized amounts of spatters to bring about longer operating life of the gas nozzle. 
         [0025]    According to the invention of the fifth aspect, only a tip side nozzle, which forms a tip portion of a gas discharge side of a gas nozzle to which spatters are apt to adhere, is formed from of the material capable of carbonizing owing to weld spatters adhered to the material and allowing the carbonized material together with the spatters to fall, whereby the deposited amount of the spatters can be effectively reduced and simultaneously the tip side nozzle can be changed with new one to enable the gas nozzle to prepare more simply and cheaply. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a schematic section view showing a welding torch provided with a gas nozzle according to a first embodiment of the invention. 
           [0027]      FIG. 2  is a schematic section view showing a welding torch provided with a gas nozzle according to a second embodiment of the invention. 
           [0028]      FIG. 3  is a schematic section view showing a welding torch provided with a gas nozzle according to a third embodiment of the invention. 
           [0029]      FIG. 4  is a schematic section view showing a welding torch provided with a gas nozzle according to a forth embodiment of the invention. 
           [0030]      FIG. 5  is a view for explaining an example of usage pattern of a welding torch provided with a gas nozzle according to a fifth embodiment of the invention. 
           [0031]      FIG. 6  is a schematic section view showing a conventional welding torch. 
       
    
    
     DESCRIPTION OF THE REFERENCE NUMBERS 
       [0000]    
       
         
           
               1 : welding torch 
               2 : torch head 
               3 : welding wire 
               4 : contact chip 
               5 : gas nozzle 
               5   b : tip portion of nozzle 
               6 : base side nozzle 
               6   a : base portion 
               6   b : tip portion 
               7 : tip side nozzle 
               7   a : base portion 
               7   b : tip portion of nozzle 
               8 : band 
               11 : vessel 
               12 : oil 
             W: workpiece 
             S: spatters 
           
         
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0049]    The embodiments of the gas nozzle for arc welding according to the present invention are explained by reference to drawings below. 
       First Embodiment 
       [0050]      FIG. 1  is a schematic section view showing a welding torch provided with a gas nozzle according to a first embodiment of the invention. 
         [0051]    In this welding torch  1 , a contact tip  4  made of metal for feeding welding wire  3  as consumable electrode is removably screwed with a tip portion  2   a  of a torch head  2  of the welding torch, and simultaneously a gas nozzle  5 , which is prepared so as to surround the contact tip  4  and so as to form cylinder shape over the range of from a base portion  5   a  of the nozzle  5  to a tip portion  5   b  of the nozzle  5  corresponding to a gas discharge side, is removably screwed with the tip portion  2   a  of the torch head  2 . 
         [0052]    Further, the welding wire  3  is used as a plus-side electrode, and a workpiece W as material to be welded is used as a minus-side electrode. Under such conditions, while an inert gas such as argon gas or CO 2  gas is fed as a shield gas to the torch, arc is generated between the welding wire  3  and the workpiece W and heat by the arc melts the wire  3  to weld the workpieces W and W. 
         [0053]    In the first embodiment, whole of the gas nozzle  5  is formed from paper board as material that is capable of carbonizing owing to weld spatters adhered to the material and allowing the carbonized material together with the spatters to exfoliate and fall. 
         [0054]    By using the gas nozzle  5  wholly formed from the paper board as above, when the spatters S are adhered to the nozzle tip portion  5   b  or the inner periphery surface  5   c  of the gas nozzle, the spatters-adhered portion carbonizes by heat of the spatters S and the carbonized portion exfoliates and falls together with the spatters, whereby the amount of the spatters deposited on whole of the gas nozzle can be reliably reduced. 
         [0055]    Hence, it is possible to avoid adhesion and deposition of the spatters S to the tip portion  5   b  and the inner periphery surface  5   c  of the gas nozzle  5 , whereby inhibition of flow of shield gas owing to the spatters S is solved. Thus, shielding by the shield gas is ensured to avoid occurrence of porosities such as blowholes, pinholes or pits, which enables improvement of welding quality. 
         [0056]    Further, since whole of the gas nozzle  5  is formed from paper board, the gas nozzle can be easily and cheaply prepared and simultaneously when proportion of carbonized area of the nozzle owing to adhesion of the spatters S is increased, the paper board only has to be replaced with new one and therefore it is possible to dispense with cleaning operation of the gas nozzle to greatly improve welding workability 
         [0057]    For example, a welding torch  1  provided with the gas nozzle  5  of the first embodiment was used and separately a welding torch  21  provided with conventional gas nozzle  25  shown in  FIG. 6  was used, and then in each case two workpieces W and W having thickness of 2.0 to 2.3 mm were welded under the conditions of shield gas of CO 2 , welding wire  3 ,  23  having diameter of 1.2 m, welding electric current of 190 A and welding voltage of 22V. As a result, the use of the welding torch  21  provided with conventional gas nozzle  25  needs cleaning of the gas nozzle  25  at welding length of 9.4 m, whereas the use of the welding torch  1  provided with the gas nozzle  5  of the first embodiment enables welding of length of 18.8 m, which is twice as long as the former, without cleaning of the gas nozzle  5 . 
       Second Embodiment 
       [0058]      FIG. 2  is a schematic section view showing a welding torch provided with a gas nozzle according to a second embodiment of the invention. 
         [0059]    In the first embodiment, a gas nozzle  5  is structured as below. The gas nozzle  5  is composed of a cylinder-shaped base side nozzle  6  made of metal removably screwing the base portion  6   a  with the tip portion  2   a  of the torch head  2  by the tip portion  2   a , and a tip side nozzle  7 , which is adhered to an edge side  6   c  of a tip portion  6   b  of the base side nozzle  6  such that a base portion  7   a  can be removed, which comprises paper board as material that is capable of carbonizing owing to weld spatters adhered to the material and allowing the carbonized material together with the spatters to fall, and which is formed in the cylinder shape over the range of a base portion  7   a  of the nozzle to a tip portion  7   b  of the nozzle corresponding to a gas discharge side. The constitution of the welding torch  1  other than the features mentioned above is the same as that of  FIG. 1 , and therefore the same reference numbers as those of  FIG. 1  are given to the same constituent elements to omit their explanation. Length L in an axis direction of the tip side nozzle  7  is set to, for example, approx. 30 mm. 
         [0060]    As described above, only tip side nozzle  7 , which forms the nozzle tip portion  7   b  corresponding to the gas discharge side where the spatters S are easily adhered in the gas nozzle  5 , is formed from paper board as the material that is capable of carbonizing owing to weld spatters adhered to the material and allowing the carbonized material together with the spatters to exfoliate and fall, whereby the deposited amount of the spatters S can be effectively reduced to ensure good shield property by shield gas which enables improvement of welding quality and workability, in the same manner as the first embodiment. Further, in case the carbonated amount is too increased by adhesion of the spatters S, the tip side nozzle only has to be changed with new one without changing the base side nozzle  6  made of metal, which is simple and cheap operation. 
       Third Embodiment 
       [0061]      FIG. 3  is a schematic section view showing a welding torch provided with a gas nozzle according to a third embodiment of the invention. 
         [0062]    In the second embodiment, a tip side nozzle  7  is structured as below. The base portion  7   a  of the tip side nozzle  7  is designed to be removably adhered to the inner periphery surface  6   d  of the tip portion  6   b  of the base side nozzle  6 . The constitution of the welding torch  1  other than the features mentioned above is the same as that of  FIG. 2 , and therefore the same reference numbers as those of  FIG. 2  are given to the same constituent elements to omit their explanation. 
         [0063]    The third embodiment shows the same effects as in the second embodiment and further the insertion of the tip side nozzle  7  can be easily carried out compared with the structure obtained by adhering the tip side nozzle  7  to the edge side  6   c  of the base side nozzle  6  according toe the second embodiment, whereby the tip side nozzle  7  can be smoothly changed to other one to bring about simple maintenance. 
       Forth Embodiment 
       [0064]      FIG. 4  is a schematic section view showing a welding torch provided with a gas nozzle according to a forth embodiment of the invention. 
         [0065]    In the second embodiment, a base side nozzle  6  is structured as below. The base portion  7   a  of the tip side nozzle  7  is designed to be removably inserted to the outer periphery surface  6   e  of the tip portion  6   b  of the base side nozzle  6 , and the outer periphery of tip side nozzle  7  is tightened and fixed by a band  8 . The constitution of the welding torch  1  other than the features mentioned above is the same as that of  FIG. 2 , and therefore the same reference numbers as those of  FIG. 2  are given to the same constituent elements to omit their explanation. 
         [0066]    The forth embodiment shows the same effects as in the second embodiment and further the tip side nozzle  7  is tightened and fixed on the outer periphery surface  6   e  of the tip portion  6   b  of the base side nozzle  6 , and therefore the tip side nozzle  7  can be reliably and smoothly changed to other one compared with in the third embodiment. 
         [0067]    While the presently preferred embodiments of the present invention have been shown and described, it is to be understood that the invention is not limited to the embodiments and that various changes and modification may be made without departing from the scope of the invention as set forth in the appended claims. For example, in the first embodiment, the gas nozzle  5  formed from paper board can be impregnated with oil in a whole area or at least nozzle tip portion  5   b  of the gas nozzle  5 . Further, at least nozzle tip portion  5   b  of the gas nozzle  5  can be impregnated at fixed intervals, for example one time per three welding operations, with oil  12 , which is charged in a vessel  11  as shown in  FIG. 5 . Otherwise, at least nozzle tip portion  5   b  of the gas nozzle  5  can be impregnated with oil by spraying mists containing oil. Such impregnation of oil enables the reduction of the adhesion of spatters and the carbonization by the adhesion owing to the oil, which brings about longer operating life of the gas nozzle  5 . Though the welding torch illustrated in  FIG. 1  is shown in  FIG. 5 , the welding torch illustrated in  FIG. 2 ,  3  or  4  is also used in  FIG. 5  in the same manner. 
         [0068]    Further Examples of the material that is capable of carbonizing owing to weld spatters adhered to the material and allowing the carbonized material together with the spatters to exfoliate and fall include, in addition to paper board, woodfiber, nonwoven, and synthetic paper. 
         [0069]    Furthermore, the gas nozzle of the invention has the nozzle tip portion on as at least gas discharge side consisting of the material that is capable of carbonizing owing to weld spatters adhered to the material and allowing the carbonized material together with the spatters to exfoliate and fall, and the nozzle tip portion shows insulation property. Hence the use of the gas nozzle has an advantage that the torch head supporting the contact tip and gas nozzle can be formed from desired material such as insulating or conducting material.