Abstract:
A device for grinding welding electrodes comprises a driving motor, a shaft driven by said driving motor and a grinding wheel driven by said driving motor through said shaft, said grinding wheel having a first and a second grinding surface. A first guiding block is provided having at least one first opening, said first opening defining a position relative to said first grinding surface and said opening being adapted to guide a welding electrode for grinding into said defined position relative to said first grinding surface, and a second guiding block having at least one second opening, said second opening defining a position relative to said second grinding surface and said second opening being adapted to guide a welding electrode for grinding into said defined position relative to said second grinding surface.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Welding electrodes consist of a very hard material such as tungsten with high stability even at high temperatures. There are welding electrodes with different cross sections. The welding electrodes have a tip or an edge at its end. The form of the welding electrodes depends on their respective application. Such tips suffer from wear during operation. 
         [0002]    Welding electrodes can be bought with pre-manufactured tips. The tip is worn after its use. The welding electrodes are then discarded. This is expensive because high-quality material is expensive. 
         [0003]    It is known to regrind used welding electrodes. This is usually carried out manually on open grinding- or cutting-off wheels. This method is inaccurate and dangerous. Furthermore devices are known with an open grinding wheel wherein the welding electrodes are guided at a certain angle with respect to the grinding wheel by a guiding sleeve. Such devices are also expensive. It is especially expensive to adapt the device to match the various types of welding electrodes or the various shapes of the tips or cutting edges. This requires the exchange of the guiding sleeves. 
         [0004]    A device for producing electrodes with a plurality (for example 6) of different electrode cross sections with a plurality of different tip angles (for example 4) and a plurality of lengths is a useful and cost-saving means. 
         [0005]    From the DE 100 10 520 A1 a device for processing welding electrodes with a grinding wheel is known. The grinding wheel rotates within a grinding wheel housing. The device also has a housing cap fixed to the grinding wheel housing and having at least one lateral opening for guiding a welding electrode for processing into a defined position relative to the grinding wheel. The plane of the grinding wheel is essentially the separating plane between the grinding wheel housing and the cap. The cap can have a plurality of different lateral openings spaced apart for receiving different types of welding electrodes. The cap can also have a plurality of lateral openings spaced apart with axes crossing the plane of the grinding wheel at different angles. A radial slit can be formed in the grinding wheel housing extending over the front surface of the housing. A welding electrode can be guided through the slit for cutting at the lateral surface of the grinding wheel. In the disclosed device the grinding wheel is fixed to a grinding wheel seat which is connected to the shaft of the driving motor. The entire device is a portable unit. 
         [0006]    The device known from the prior art allows the grinding of thick electrodes as well as thin electrodes. It is, however, a disadvantage that the grinding wheel which is required to achieve a fine grinding result has only a small grinding rate. This is particularly disadvantageous with thick electrodes. Therefore, each time, when a high grinding rate is necessary the fine grinding wheel has to be replaced by a rougher grinding wheel. This is time consuming. 
         [0007]    US 2004/0127149 A1 to the applicant discloses an assembly, where two parallel grinding wheels with different graining are used. A first grinding wheel runs in a cavity between the motor flange and a first housing. The second grinding wheel runs in a second hollow space between the first housing and a second housing. The housings are provided with openings for guiding the welding electrodes. The known assembly allows the use of different grinding wheels without dismounting and re-assembling. 
         [0008]    Thus, one object of the invention is to provide a less expensive assembly of the above mentioned kind with smaller diameters. 
       SUMMARY OF THE INVENTION 
       [0009]    The invention relates to a device for grinding welding electrodes comprising a driving motor, a shaft driven by the driving motor, a grinding wheel driven by the driving motor through the shaft, the grinding wheel having a grinding surface, and a guiding block having at least one opening, the opening defining a position relative to the grinding surface and being adapted to guide a welding electrode for grinding into the defined position relative to the grinding surface. 
         [0010]    According to one aspect of the invention device is provided for grinding welding electrodes comprising a driving motor; a shaft driven by said driving motor; a grinding wheel driven by said driving motor through said shaft, said grinding wheel having a first and a second grinding surface; a first guiding block having at least one first opening, said first opening defining a position relative to said first grinding surface and said opening being adapted to guide a welding electrode for grinding into said defined position relative to said first grinding surface, and a second guiding block having at least one second opening, said second opening defining a position relative to said second grinding surface and said second opening being adapted to guide a welding electrode for grinding into said defined position relative to said second grinding surface. 
         [0011]    The assembly differs from known assemblies in so far as both grinding surfaces run in the same space. Therefore the entire assembly can be produced for less money, it is shorter and easier to handle. 
         [0012]    It is understood, that the grinding wheel may comprise several layers. While a grinding wheel with two grinding surfaces is preferable, the grinding wheel may also comprise two grinding wheel portions each having one grinding surface. The grinding wheel portions may then be assembled with the grinding surfaces directed in opposite directions. 
         [0013]    Only one grinding wheel assembly is used, which is, however, used from two sides. The openings extend in the direction of the top surface of the grinding wheel as well as in the direction of the bottom surface of the grinding wheel. The direction of the openings for guiding the welding electrodes in the direction of the bottom surface of the grinding wheel enables the use of the motor flange for the openings. The motor flange thereby constitutes a guiding block. As less additional guiding blocks are used the entire length of the driving shaft for the grinding wheel assembly is shorter. Less connecting elements are necessary also. 
         [0014]    Preferably the grinding surfaces of the first and the second grinding surfaces have a different graining. If the first grinding surface is provided on a first grinding wheel and the second grinding surface is provided on a second grinding wheel a particularly cheap production is possible. The grinding wheels do not need to be provided with different grainings on the top surface and the bottom surface. Conventional grinding wheels with uniform graining may be used. The grinding wheels are disposed in the cavity in such a way, that the grinding surfaces are directed in opposite directions. 
         [0015]    In a modification of the invention a wheel with a larger diameter is provided between the grinding wheels for lateral cutting of electrodes. In this case the electrodes may not only be grinded or re-grinded but also cut. 
         [0016]    In another aspect of the invention a device for grinding welding electrodes is provided comprising a driving motor; a shaft driven by said driving motor; a grinding wheel driven by said driving motor through said shaft, said grinding wheel having a grinding surface; a guiding block having at least one opening, said opening defining a position relative to said grinding surface and said opening being adapted to guide a welding electrode for grinding into said defined position relative to said grinding surface, wherein said opening is provided in a portion of said guiding block directly engaging said motor housing, said portion having a first side directed towards said driving motor and a second side opposite to said first side, and wherein said grinding wheel is disposed on said second side of said portion of said guiding block. In other words: the motor flange is used as a guiding block. It is, therefore, provided with a plurality of openings 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention will be described herein below in greater detail with reference to the accompanying drawings in which: 
           [0018]      FIG. 1  is an exploded view of a device for processing welding electrodes with several connected grinding wheels with a view from the upper end on the housing components according to a first embodiment of the invention; 
           [0019]      FIG. 2  is an exploded view of the device of  FIG. 1  with a view from the lower end of the housing components; 
           [0020]      FIG. 3  is a detailed perspective view of the driving shaft of the embodiment of  FIG. 1 ; 
           [0021]      FIG. 4  is a detailed perspective view of the motor flange with openings for guiding welding electrodes according to the first embodiment of the invention; 
           [0022]      FIG. 5  is a detailed perspective view of the housing according to the first embodiment of the invention; 
           [0023]      FIG. 6  shows the motor flange with the shaft and the housing of the first embodiment of the invention in an assembled state; 
           [0024]      FIG. 7  shows the grinding wheel assembly in detail; 
           [0025]      FIG. 8  shows the connecting nut in detail; 
           [0026]      FIG. 9  shows the first grinding wheel of the grinding wheel assembly; 
           [0027]      FIG. 10  shows the second grinding wheel of the grinding wheel assembly; 
           [0028]      FIG. 11  shows the exploded grinding wheel assembly; 
           [0029]      FIG. 12  shows an exploded view of a device according to a second embodiment of the invention; 
           [0030]      FIG. 13  is a perspective view of the motor flange according to a second embodiment of the invention; 
           [0031]      FIG. 14  is a cross sectional view of the device of  FIG. 12 ; 
           [0032]      FIG. 15  is an exploded view of a device for processing welding electrodes with several connected grinding wheels with a view from the lower end on the components according to a third embodiment of the invention; 
           [0033]      FIG. 16  is a perspective view of a motor flange according to the fourth embodiment of the invention; 
           [0034]      FIG. 17  is an exploded view of the device of  FIG. 16 ; and 
           [0035]      FIG. 18  is a perspective view of a fifth embodiment of the invention with an integrated guiding block. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    Referring now to the drawings, wherein numeral  10  in the drawings generally denotes a device for grinding tungsten welding electrodes. The device  10  comprises a motor (not shown) in a motor housing  12 , a motor flange  14  screwed to the motor housing  12  and a cylindrical housing part  16  arranged on the motor flange  14 . The motor flange  14  and the housing part  16  constitute guiding blocks for guiding electrodes. The housing part  16  is connected to the motor and the motor flange in a way which is described below in greater detail. A grinding wheel assembly  18  with grinding wheels  20  and  22  having different graining rotates in the plane between the motor flange  14  and the housing part  16 . 
         [0037]    In  FIG. 4  the motor flange  14  is separately shown. The flange  14  is provided with bore holes  24 . The flange is screwed to the motor through these bore holes as shown in  FIG. 1 . A plate like depression  26  is provided on the end of the motor flange  14  which is remote to the motor. This depression serves as a receiving unit for the grinding wheel assembly  18 . This is shown in the exploded view of  FIGS. 1 and 2 . A connecting shaft  30  is screwed above the grinding wheel assembly  18 . The connecting shaft  30  is separately shown in  FIG. 3 . The shaft  30  has an upper portion  28 . Furthermore the shaft  30  has an internally threaded bore hole  32 . The bore hole  32  is provided with a collar  34  projecting outwardly in an axial direction. The grinding wheel assembly  18  is set on this collar acting as a centering means. 
         [0038]    The grinding wheels of the grinding wheel assembly  18  are provided with a central bore hole  38  and an off-axis bore hole  40 . The central bore hole  38  is positioned and centered on the collar  34 . The rotation is effected about the axis of the bore hole  38 , a pin  36  engaging the bore hole  40  and transmitting the driving power to the grinding wheel assembly  18 . The grinding wheel assembly  18  is fixed with the screw  37  in the inner thread of the shaft  30 . 
         [0039]      FIG. 11  shows the exploded grinding wheel assembly  18  with a cutting wheel  42  in the middle and grinding wheels  20  and  22  on both sides thereof, the grinding wheels having either the same, a different or a partial graining. 
         [0040]    The grinding wheel assembly  18  comprises a rough grained grinding wheel  20  ( FIG. 9 ) and a fine grained grinding wheel  22  which otherwise has the same constitution. A further middle wheel  42  is disposed between the two grinding wheels  20  and  22  of the grinding wheel assembly the middle wheel  42  having a particularly thin edge. This edge serves for cutting the electrodes with improved cutting behaviour. Additionally to the central bore hole  38  and the off-axis bore hole  40  for a fixed connection of the wheels  20 ,  22  and  42  further off-axis bore holes  64  and  56  are provided in the middle wheel  42  ( FIG. 10 ). Projections  68  provided on the wheel  20  extend through each of the holes into the corresponding recess in the wheel  22  and a projection on the wheel  22  extending into the corresponding recess  70  in the wheel  20 . 
         [0041]    If the grinding wheel assembly  18  is mounted with the shaft the essentially cylindrical housing portion  16  is coaxially arranged on the motor flange  14 . 
         [0042]    The housing portion  16  is shown in detail in  FIG. 5 . The housing part  16  has a center bore hole  44 . The center bore hole  44  is aligned with the bore holes  38  of the grinding wheel assembly  18  and the rotational axis of the shaft  30 . A depression  50  is provided around the bore hole at the plane surface  46  of the housing (see  FIG. 2 ). This depression  50  has about the same dimensions as the depression  26  in the motor flange  14 . The depressions  26  and  50  together form a cavity when the assembly is assembled ( FIG. 6 ). The cavity serves to receive the grinding wheel assembly  18 . The housing  16  has a depression  52  on its plane surface  51  on the upper end serving for receiving means for the removal of grinding leftovers such as dust and other leftovers. Furthermore the housing  16  has a slit  54  in a radial direction extending along the entire width of the housing. The slit  54  is wide enough to insert electrodes. When the grinding wheel assembly  18  rotates the electrode can be shortened at the middle wheel  42  by cutting off the worn end of the electrode. As in the housing  16  a slit  52  is provided in the motor flange  14 . The slits  52  and  54  in the motor flange and in the housing  16  are aligned as it is shown in  FIG. 6 . 
         [0043]    A bore hole  60  is provided in the housing  16 . The bore hole  60  extends over the entire length of the housing. A screw  62  ( FIG. 1 ) engages through the bore hole  60  for screwing the housing  16  to the motor flange  14 . The screw  62  is screwed into a nut  72  which is provided in a recess  74  in the motor flange  14 . The motor flange has a pin  66  whereon the housing  16  can be inserted with a bore hole  58  ( FIG. 2 ). In such a way the housing  16  is tightly fixed to the motor flange  14  by only one screw ( 62 ). This enables a particularly simple and quick disassembling and assembling if a grinding wheel must be exchanged. Contrary to known assemblies with two grinding wheels a shaft  30  with a particularly short neck may be used in the present assembly. 
         [0044]    The housing  16  and the motor flange  14  have groups  76  and  78  of lateral openings. These groups of lateral openings extend along the circumference of the housing and the motor flange, respectively, in the direction of the grinding wheel next to the housing or motor flange, respectively, on the plane end  48 . Each group comprises six lateral openings  82  of different diameter which is indicated by an engraving  80  over the lateral opening. The angle under which an electrode is inserted in a lateral opening  82  contacts a grinding wheel is the same within each group of lateral openings. It can be seen from the drawing, that the lateral opening  82  has a diameter of 1.6 mm and a grinding angle of 22.5 degrees. The angle for each group is indicated by a further engraving  84  above the first engraving. In the present embodiment there are four different angles possible for grinding the electrode tips. Also, electrodes with as many as up to six different diameters can be used. The electrode is so well guided by the lateral opening  82  that reproducible results can be achieved without any expense or danger. 
         [0045]    More grinding angles, further electrode diameters or the use of a grinding surface with different graining are considered by providing similar lateral openings  90  in the motor flange  14 . An electrode can be, for example, roughly pre-grinded by guiding it through the opening  82  in the housing  16 . The grinding wheel  22  having a grinding surface which is upwardly directed has a rough graining. For the fine grinding the opening  90  in the motor flange  14  is used. The corresponding grinding wheel  20  having a grinding surface which is downwardly directed has a fine graining. 
         [0046]    Furthermore, the housing  16  has a group of openings vertically extending from the upper end to the lower end of the housing  16 . The openings of this group also have different diameters corresponding to the diameters of the previously mentioned groups. The openings of the group  92  enable the perpendicular grinding of the electrode tips. 
         [0047]    The entire assembly is screwed on a hand-held unit. The grinding wheel assembly is positioned directly in front of the ball bearing of the motor shaft. This prevents lurching at high angular rates. 
         [0048]    The assembly is much shorter than comparable assemblies having two grinding wheels. It is, therefore, much easier to handle. It requires less components and it is thereby cheaper in transport, keeping and production. 
         [0049]    An alternative embodiment is shown in  FIGS. 12-14 . A grinding wheel assembly  118  is provided, which is the same as the grinding wheel assembly  18  of  FIG. 1 . The grinding wheel assembly  118  is driven by a motor through a shaft. The grinding wheel assembly  118  is disposed between a motor flange  114  and a guiding block  116 . 
         [0050]    In  FIG. 13  the motor flange  114  is separately shown. The flange  114  is provided with bore holes  124 . The flange is screwed to the motor through these bore holes as shown in  FIG. 12 . The motor flange  114  constitutes a solid guiding block. The grinding wheel assembly  18  is disposed between the guiding block  116  and the motor flange  114 . This is shown in the exploded view of  FIG. 12  and the cross sectional view in  FIG. 14 . 
         [0051]    In this embodiment, the housing portion  116  does not need a center bore hole or a depression. The housing  116  has a slit  154  in a radial direction extending along the entire width of the guiding block. The slit  154  is wide enough to insert electrodes. When the grinding wheel assembly  118  rotates the electrode can be shortened by cutting off the worn end of the electrode. As in the guiding block  116  a slit  152  is provided in the motor flange  114 . The slits  152  and  154  in the motor flange and in the housing  16  are aligned as it is shown in  FIG. 12 . 
         [0052]    Two bore holes  160  and  161  are provided in the guiding block  116 . The bore holes  160  and  161  extend over the entire length of the guiding block. Screws  162  engage through the bore holes  160  and  161  for screwing the housing  116  to the motor flange  114 . Two nuts  172  and  173  are provided to maintain a distance between the motor flange  114  and the guiding block  116 . The grinding wheel assembly  118  rotates in the space between the motor flange  114  and the guiding block  116 . The screw  162  extends through the nut  172  into a bore hole  174  in the motor flange  114 . 
         [0053]    The guiding block  116  and the motor flange  114  have groups of lateral openings as it is the case with the housing of the first embodiment. 
         [0054]    In an alternate embodiment only one screw  262  can be utilized. This enables a quicker assembling and disassembling if, for example, the grinding wheel  218  is exchanged. This screw  262  extends through a bore hole  242 , as it is shown in  FIG. 15 . 
         [0055]    A further alternative embodiment is shown in  FIG. 16  and  FIG. 17 . A grinding wheel assembly  318  is provided, which is the same as the grinding wheel assembly  118  of  FIG. 12 . Contrary to the second embodiment the guiding block  316  does not have lateral openings. It is, therefore, much flatter than the guiding blocks or housings of the previous embodiments. As in the third embodiment, the guiding block  316  is fixed to a motor flange  314  by means of only one screw  362  and a nut  372 . The guiding block  316  constitutes a lid for protection of the grinding wheel assembly  318 . It also serves to grind electrodes flat without tip. 
         [0056]      FIG. 18  shows an embodiment which is similar to the embodiment of  FIGS. 16 ,  17 . However, instead of a screw  362  and a nut  372  the guiding block  416  forms an integral part of the motor flange  414 . The entire part is screwed to the motor housing. The grinding wheel assembly (not shown) rotates therebetween. 
         [0057]    In all embodiments, the grinding wheel assembly has a first grinding surface which is directed into a direction towards the motor. Thereby, the motor flange can be used as a guiding block.