Abstract:
Connection between a plasma torch wearing part and a plasma torch wearing part holder, plasma torch wearing part and plasma torch wearing part holder.

Description:
BACKGROUND 
       [0001]    The present invention relates to a connection between a plasma torch wearing part and a plasma torch wearing part holder, a plasma torch wearing part and a plasma torch wearing part holder. 
         [0002]    Plasma torches are known, which comprise a plasma torch shaft and a plasma torch head, which can be interconnected by a quick-change closure. The plasma torch head contains the plasma torch parts which, during operation, rapidly wear and must frequently be replaced. These are in particular the electrode, nozzle, nozzle protection cap and gas guidance part, particularly the plasma gas guidance part. However, when there are changes in the uses of the plasma method, e.g. between the cutting of structural steel and the cutting of high grade steel or when changing the use from cutting to welding or vice versa, the replacement of one electrode, nozzle, nozzle protection cap, gas guidance part, etc. for another may be necessary. In order to rapidly implement this, a quick-change possibility is appropriate. 
         [0003]    To avoid damage or e.g. for producing correct supply connections, the quick-change possibility must provide a clear, radial positioning or a positioning along the circumference of the wearing parts. 
       SUMMARY 
       [0004]    The invention provides such a quick-change possibility for the wearing parts of a plasma torch. According to the invention, a connection between a plasma torch wearing part and a plasma torch wearing part holder is characterized in that either the plasma torch wearing part holder or the plasma torch wearing part has on its connecting side a first cylinder wall with an outer surface and a circular ring surface, as well as an external diameter D 41   a  and the other from among the plasma torch wearing part holder and the plasma torch wearing part has on its connecting side a second cylinder wall with an inner surface and an internal diameter D 52 , where D 51 &gt;D 41   a  and n pro  radial projections and n dep  radial depressions run around the inner surface, in which n pro , n dep ≧0 and n pro +n dep =≧5. On the outer surface is provided an equal number of in particular corresponding depressions or projections engaging therewith. In the case of n=5, the sum of two adjacent midpoint angles by which the projections or depressions or a projection and a depression are displaced relative to one another is not ≧180° and the five midpoint angles differ. In the case of n&gt;5 the sum of two adjacent midpoint angles by which the projections or depressions or a projection and a depression are displaced relative to one another is not ≧180° and the n&gt;5 midpoint angles differ or at least two of the n&gt;5 midpoint angles are of the same magnitude and then in each case the sum of the twice occurring midpoint angles and the midpoint angles adjacent thereto on either side is &lt;180°. 
         [0005]    The plasma torch wearing part is characterized in that on its connecting side it has a cylinder wall with an outer surface and a circular ring surface, n dep  radial depressions and n pro  radial projections passing round the outer surface, where n dep , n pro ≧0 and n dep +n pro ≧5. In the case of n=5, the sum of two adjacent midpoint angles by which the projections or depressions or a projection and a depression are displaced relative to one another is not ≧180° and the five midpoint angles differ. In the case of n≧5, the sum of two adjacent midpoint angles by which the projections or depression or a projection and a depression are displaced relative to one another is not ≧180° and the n≧5 midpoint angles differ or at least two of the n&gt;5 midpoint angles are of the same magnitude and then in each case the sum of the twice occurring midpoint angles and the midpoint angles adjacent thereto on either side is &lt;180°. 
         [0006]    This plasma torch wearing part holder is characterized in that on its connecting side it has a cylinder wall with an inner surface, n pro  radial projections and n dcp  radial depressions passing round the inner surface, n pro , n dep ≧0 and n pro +n dep ≧5. In the case of n=5, the sum of two adjacent midpoint angles by which the projections or depressions or a projection and a depression are displaced relative to one another is not ≧180° and the five midpoint angles differ. In the case of n&gt;5, the sum of two adjacent midpoint angles by which the projections or depressions or a projection and a depression are displaced relative to one another is not ≧180° and the n&gt;5 midpoint angles differ or at least two of the n&gt;5 midpoint angles are of the same magnitude and then in each case the sum of the twice occurring midpoint angles and the midpoint angles adjacent thereto on either side is &lt;180°. 
         [0007]    In the case of the connection, the sum of two adjacent midpoint angles (α and β or β and γ or γ and δ or δ and ε or ε and α) can be ≦170°. 
         [0008]    According to a special embodiment of the invention, n=5 and the sum of two adjacent midpoint angles (α and β or β and γ or γ and δ or δ and ε or ε and α) is not repeated. 
         [0009]    In some embodiments, the plasma torch wearing part to have the first cylinder wall and the plasma torch wearing part holder the second cylinder wall. 
         [0010]    In some embodiments, the ratio of the surfaces of a projection and an associated depression can be in the range 1:1 and 1:4. In the case of an e.g. rectangular slot and nose, as shown in  FIGS. 6 and 7 , the surface results from the product of B and T of the slot and nose. 
         [0011]    In some embodiments, the ratio of the surfaces of the n pro  projections and/or the n dep  depressions can be in the range 1:1 to 1:4. 
         [0012]    In some embodiments, there can be n pro  equal radial projections and n dep  equal radial depressions. 
         [0013]    Advantageously, the depressions can be rectangular slots. However, they can also have a different configuration, such as e.g. triangular, arcuate, etc. 
         [0014]    Advantageously, on the inner surface of the second cylinder wall in the connection direction and upstream of the projections and/or depressions there can be a circumferential, radially outwardly extending chamfer, which facilities the introduction of the first cylinder wall into the second cylinder wall. 
         [0015]    In some embodiments of the invention n pro ≧5. It is alternatively possible for n dep ≧5 within the contemplated invention scope. 
         [0016]    Advantageously, there is a holding together device for holding together the plasma torch wearing part and plasma torch wearing part holder. It can e.g. comprise a clamp collar. 
         [0017]    The plasma torch wearing part can be a nozzle, an electrode, a nozzle protection cap or a gas guidance part, particularly a plasma gas guidance part. 
         [0018]    In some embodiments of the invention, the plasma torch wearing part holder is an integral part of the plasma torch. 
         [0019]    In some embodiments of the invention, a plasma torch wearing part holder is detachably connected to a plasma torch. 
         [0020]    In some embodiments of the invention, the plasma torch is a plasma cutting torch, or alternatively, it can be a plasma welding torch. 
         [0021]    In accordance with the invention, as a result of the specific number and arrangements of projections and corresponding depressions, it is possible to obtain a simple, rapid joining together of plasma torch wearing part and plasma torch wearing part holder without tilting occurring. For engagement purposes, the circular ring surface has to be simply engaged with the projections, i.e. brought into a joining position, and then turned relative to the projections until the joining position is reached, where in the case of an axially acting force, the projections and depressions engage with one another. This is particularly advantageous in situations where the plasma torch wearing part and/or plasma torch wearing part holder are not visually accessible. The quick-change can so-to-speak take place blindly. 
         [0022]    The invention also provides a connection between plasma torch wearing part and plasma torch wearing part holder with twisting protection, a limited tolerance between the axes of the plasma torch wearing part and plasma torch wearing part holder and high centricity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    Further features and advantages of the invention can be gathered from the claims and the following description of two embodiments relative to the attached diagrammatic drawings, which show: 
           [0024]    FIG.  1 —A sectional view of a front part of a plasma torch head according to a special embodiment of the invention. 
           [0025]    FIG.  2 —A perspective view of a nozzle and a nozzle holder according to a special embodiment of the invention prior to the connection thereof. 
           [0026]    FIG.  3 —A similar view to  FIG. 2 , where also water supply and return ducts are shown 
           [0027]    FIG.  4 —Two perspective views of an electrode and an electrode holder prior to the connection thereof. 
           [0028]    FIG.  5 —A similar view to  FIG. 4 , also showing water supply and return ducts. 
           [0029]    FIG.  6 —A sectional view of the nozzle and nozzle holder of  FIG. 2  in the joining position. 
           [0030]    FIG.  7 —A sectional view of the electrode and electrode holder of  FIG. 4  in the joining position. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]      FIG. 1  shows a plasma torch head  1  with a nozzle cap  2 , a plasma gas guidance part  3 , a nozzle  4 , a nozzle holder  5 , an electrode holder  6 , an electrode  7 , a nozzle protection cap holder  8 , an insulating part  8   a  and a nozzle protection cap  9 . 
         [0032]    Each of  FIGS. 2 and 3  show a nozzle  4  for a plasma cutting torch and a nozzle holder  5  for the nozzle. Nozzle  4  has a cylinder wall  41  with an outer surface  41   a  and a circular ring surface  42 , the latter also fuliflling the surface of a (second) bearing surface, Nozzle holder  5  has a cylinder wall  51  with an inner surface  51   a  and a bearing surface  546 . The internal diameter D 52  of cylinder wall  51  is larger than the external diameter D 41   a  of cylinder wall  41 . Five identical rectangular slots pass round the outer surface  41   a , but only two of these are visible and carry the reference numerals  431  and  435 . 
         [0033]    Five identical, corresponding noses are located around the inner surface  51   a , but only three are visible and carry reference numerals  532 ,  533  and  534 . 
         [0034]    In the direction of nozzle  4  and upstream of noses  532  to  534 , the nozzle holder  5  has an outwardly extending chamfer  52  facilitating the introduction of nozzle  4 . Internal diameter D 52  corresponds to the diameter on the upper edge of chamfer  52  and provides a clearance S=(D 52 -D 41   a )/2. After passing chamfer  42 , it tapers to internal diameter D 51   a  in order to reduce the clearance S=(D 51   a -D 41   a )/2 to almost zero. This brings about a simplification of positioning while ensuring high centricity. 
         [0035]    Compared with  FIG. 2 ,  FIG. 3  additionally shows a water supply  53  and water return  54 , as well as a water supply duct  43  and water return duct  44 , said embodiment corresponding to  FIG. 1 . 
         [0036]    The water supply duct  43  and water return duct  44  are worked into nozzle  4  in order to improve the water cooling thereof. Therefore, the cooling water enters an annular groove  45  which brings about a particularly good cooling of the thermally maximum stressed part of the nozzle  4 , namely nozzle duct  46 . As opposed to  FIG. 2 , the cooling water is directly supplied to this area. In the embodiment according to  FIG. 2 , a tributary can form and part of the cooling water flows through it and is then unavailable for cooling nozzle  46 . Through the design of nozzle  4  and the nozzle protection cap  9 , it is possible to fix the ratio of the proportions of cooling water which, via annular groove  45 , cool nozzle duct  46  and conical outer surface  47 . 
         [0037]    The improvement to the nozzle duct cooling while at the same time maintaining cooling for the entire nozzle surface results from the worked in water supply  43  and water return ducts  44  as well as a widening, i.e. an enlargement of the conical areas thereof, combined with an e.g. standard nozzle cap. It is ensured that there is always a closed, moving water film on the conical nozzle portion, whereas most of the cooling medium flows through the annular groove around the nozzle duct. The ratio of the surface areas can be in the range 3:1 to 20:1 (cooling duct: conical outer surface). 
         [0038]    The clear positioning of nozzle  4  relative to nozzle holder  5  through the noses and slots leads to an improvement in the cooling of nozzle  4 . The noses and slots also facilitate the assembly, while at the same time bring about high centricity in the final joining position. 
         [0039]      FIG. 4  shows the corresponding situation for an electrode  7  and electrode holder  6 . Electrode  7  has a cylinder wall  71  with an outer surface  71   a , a circular ring surface  72  and a bearing surface  746 . Electrode holder  6  has a cylinder wall  61  with an inner surface  61   a  and a bearing surface  646 . The internal diameter D 61   a  of cylinder wall  61  is larger than the external diameter D 71   a  of cylinder wall  71 . Five identical slots run round the outer surface  71   a , but only two of these are visible and carry reference numerals  731  and  735 . 
         [0040]    Five identical, corresponding noses run round the inner surface, but only three are visible and carry reference numerals  632 ,  633  and  634 . 
         [0041]    In the direction of electrode  7  and upstream of noses  632  to  634 , the electrode holder  6  has an outwardly extending chamfer or circular ring surface  62  facilitating the introduction of electrode  7 . Internal diameter D 62  corresponds to the diameter on the upper edge of chamfer or circular ring surface  62  and gives a clearance S  1  (D 62 -D 71   a )/2. After passing chamfer or circular ring surface  62 , it tapers to internal diameter D 52  in order to reduce the clearance almost to zero. 
         [0042]    To improve the cooling of electrode  7 , in the connection end there is a subdivision into a water supply duct  73  and water return duct  74  by means of a partition  75  and in electrode holder  6  is provided a partition  65  for the subdivision into a water supply duct  63  and a water return duct  64  (cf.  FIG. 5 ). 
         [0043]      FIG. 6  shows slots  431  to  435  of nozzle  4  in engagement with the noses  531  to  535  of nozzle holder  5  in the joining position. As the sum of two adjacent midpoint angles of angles (α, β, γ, δ, ε) under which slots  431  to  435  are arranged, is not ≧180° and the five midpoint angles differ, only in this joining position can all noses be brought into engagement with all the slots. In all other radial positions, known as joining positions, the circular ring surface  42  rests on at least three noses. 
         [0044]      FIG. 7  shows the corresponding joining position and corresponding conditions for the joining position of electrode  7  and electrode holder  6 . 
         [0045]    In the embodiments shown hereinbefore, the depressions and projections or noses and slots are so positioned and dimensioned that it is no longer possible for there to be any twisting of the nozzle and nozzle holder or electrode and electrode holder after reaching the joining position. 
         [0046]    The features of the invention disclosed in the present description, drawings and claims can be essential both individually and in random combinations to the implementation of the different embodiments of the invention.