Abstract:
The catching nozzle according to the invention for a powder conveying device has a tubular powder flow duct and a shoulder, with which the position of the catching nozzle is predetermined in the powder conveying device and that is arranged between a upstream catching nozzle section and a downstream catching nozzle section. The shoulder has a duct for dosage air, wherein the duct connects the upstream catching nozzle section to the downstream catching nozzle section. The downstream catching nozzle section is developed such that it forms, with a hose socket that can be pushed over the downstream catching nozzle section, another duct for dosage air in order to lead the dosage air up to the downstream end of the catching nozzle.

Description:
CLAIM FOR PRIORITY UNDER 35 USC §119  
       [0001]     This application claims priority under 35 USC §119 to German Patent Application No. 20 2004 019 438.4, filed Dec. 16, 2004, the entire contents of which are incorporated herein by reference.  
       TECHNICAL FIELD  
       [0002]     The invention relates to a device for conveying powder and a catching nozzle, which can be used in the powder conveying device.  
         [0003]     In order to coat objects or work pieces with powder, the powder is conveyed from a powder storage reservoir to a powder spray gun with the help of a powder conveying device and there it is applied on to the work piece with the powder spray gun. The powder conveying device, which is also called powder injector in the following, conveys the powder with the help of conveying air from the storage reservoir. Here the mixture from conveying air and powder flows into the inside of the powder injector through a powder duct of a catching nozzle, wherein additional dosage air is mixed with the powder conveying air mixture with the help of the catching nozzle in order to achieve a defined total air flow.  
       DESCRIPTION OF THE RELATED ART  
       [0004]     A powder conveying equipment with a catching nozzle is known from the state of the art DE 43 19 726, wherein the catching nozzle has several inclined boreholes leading from outside towards the powder duct, in order to lead the dosage air into the powder duct. However, this embodiment of the catching nozzle has the disadvantage that the manufacturing of the diagonally running boreholes is quite laborious. Basically, boreholes, which are running crosswise to the longitudinal axis of the catching nozzle, can be produced only with additional expenditure.  
       SUMMARY OF THE INVENTION  
       [0005]     An object of the invention is therefore to indicate a catching nozzle for a powder conveying device, which can be easily produced. In particular, boreholes, which are running crosswise to the longitudinal axis of the catching nozzle, should be avoided.  
         [0006]     Advantageously the catching nozzle can be easily replaced anytime and is developed in such a way that it can be precisely arranged in the powder conveying device. Especially, the lateral and axial play as well as the angle error should be as low as possible.  
         [0007]     Moreover, the grip of the catching nozzle should be ensured. This is especially important when taking out the catching nozzle from the powder conveying device.  
         [0008]     Another object is to configure the catching nozzle in such a way that the powder conveying device, after the replacement of the catching nozzle, has the same qualities during the powder conveying as before the replacement. This means that the qualities of the powder conveying device should not change merely due to the replacement of the catching nozzle.  
         [0009]     Furthermore, an object of the invention is to indicate a powder conveying device suitable to the catching nozzle.  
         [0010]     The object is solved by a catching nozzle for a powder conveying device with the characteristics according to claim  1 .  
         [0011]     The catching nozzle according to the invention for a powder conveying device has a tubular powder flow duct and a shoulder, with which the position of the catching nozzle in the powder conveying device is predetermined and that is arranged between a upstream catching nozzle section and a downstream catching nozzle section. The shoulder itself has a duct for the dosage air, wherein the duct connects the upstream catching nozzle section to the downstream catching nozzle section. The downstream catching nozzle section is developed in such a way that it forms, with a hose socket that can be pushed over the downstream catching nozzle section, another duct for dosage air in order to lead the dosage air until the downstream end of the catching nozzle.  
         [0012]     In addition, the object is solved by a powder conveying device with a catching nozzle with the characteristics according to claim  11 .  
         [0013]     For this purpose the powder conveying device according to the invention includes the just described catching nozzle, which is arranged in a housing of the powder conveying device. Moreover, the powder conveying device has a hose socket, which surrounds the downstream catching nozzle section of the catching nozzle.  
         [0014]     Advantageous further developments of the invention result from the characteristics stated in the dependent claims.  
         [0015]     In a first further development of the catching nozzle according to the invention for a power conveying device, the downstream catching nozzle section has at least one recess.  
         [0016]     In a second further development of the catching nozzle according to the invention, a screw-shaped rib runs on the external side of the downstream catching nozzle section.  
         [0017]     In a third further development of the catching nozzle according to the invention, the external side of the downstream catching nozzle section is cross-knurled or knurled in the longitudinal direction.  
         [0018]     In addition, in the case of the catching nozzle according to invention, the external diameter of the downstream catching nozzle section is developed smaller than the internal diameter of the hose socket and that for the creation of the further duct for the dosage air. This has the advantage that the dosage air arrives without further ado up to the downstream end of the catching nozzle and from there it can be added to the power—conveying air mixture.  
         [0019]     Moreover, in the case of the catching nozzle according to the invention, the duct in the shoulder can be developed as groove or as borehole.  
         [0020]     In order to be able to place the catching nozzle precisely in the housing of the powder conveying device, an embodiment of the catching nozzle according to the invention has a first cylindrical guide surface and a second cylindrical guide surface at a distance from it and the shoulder has a conical side, wherein the guide surfaces and the side are provided for predetermining the position of the catching nozzle in the power conveying device. The shoulder can be clamped in the powder conveying device.  
         [0021]     In addition, in the case of the catching nozzle according to the invention, the shoulder can also have another conical side.  
         [0022]     It is further recommended, in order to solve the object, that the catching nozzle according to the invention has an annular groove for retaining an O-ring, wherein the annular groove is arranged in the area of the catching nozzle inlet. As a result, if the catching nozzle is mounted in the powder conveying device, the dosage air duct can be sealed upstream compared to the powder duct of the powder conveying device.  
         [0023]     In another embodiment of the catching nozzle according to the invention, the diameter of the first cylindrical guide surface is smaller than the diameter of the second cylindrical guide surface. This has particularly the advantage that the catching nozzle equipped with the O-ring can be mounted more easily and that it can also again be removed more easily from the housing of the powder conveying device.  
         [0024]     In a further development of the powder conveying device according to the invention a borehole is provided in the housing of the powder conveying device and the upstream catching nozzle section of the catching nozzle is arranged in such borehole, whereas the downstream catching nozzle section protrudes from the housing. The housing forms the stopper for the shoulder.  
         [0025]     In an additional further development of the powder conveying device a union nut is provided, with which the catching nozzle and the hose socket can be fixed on the housing.  
         [0026]     Finally, in the powder conveying device according to the invention a hose can be provided, which is pushed over the hose socket. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     These and other aspects of the invention are apparent from and will be elucidated in details with reference to the five embodiments described hereinafter.  
         [0028]      FIG. 1  shows the catching nozzle according to the invention in the side view.  
         [0029]      FIG. 2  shows a possible embodiment of the powder conveying device in a cross-section.  
         [0030]      FIG. 3  shows a second possible embodiment of the catching nozzle in a three-dimensional view.  
         [0031]      FIG. 4  shows a third possible embodiment of the catching nozzle in a three-dimensional view.  
         [0032]      FIG. 5  shows a fourth possible embodiment of the catching nozzle in a three-dimensional view. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]     A possible embodiment of the catching nozzle  1  according to the invention is shown in  FIG. 1  in the side view. The catching nozzle  1  has inside a duct  22 , through which, if the powder conveying device is in use, the mixture of powder and conveying air FL flows. The duct  22  is also called powder flow duct in the following. The longitudinal axis of the catching nozzle  1  is marked with the reference symbol  21  and the direction of flow is marked by the arrow  7 . The mixture enters at the funnel-shaped nozzle inlet  16  into the catching nozzle  1  and is again discharged at the nozzle outlet  18  from the catching nozzle  1 . In the area of the nozzle inlet  16 , the catching nozzle  1  is developed cylindrically on the outside, which is used as cylindrical first guide surface  2 . 1 .  
         [0034]     In the embodiment shown in  FIG. 1 a  shoulder  5  is located approximately in the center of the catching nozzle  1 , to which a second cylindrically developed guide surface  2 . 2  is connected on the upstream side. Both the sides  5 . 1  and  5 . 2  of the shoulder  5  are developed as double cone. The position of the catching nozzle  1  in the powder conveying device is provided above the first guide surface  2 . 1 , the second guide surface  2 . 2  and the conical side  5 . 1  of the shoulders  5 .  
         [0035]     The catching nozzle  1  is essentially divided into two catching nozzle sections  17 . 1  and  17 . 2 , wherein the upstream arranged catching nozzle section  17 . 1  is separated by the downstream arranged catching nozzle section  17 . 2  through the shoulder  5 . However, in order that the dosage air DL, which is also call auxiliary air, arrives from the upstream catching nozzle section  17 . 1  to the downstream catching nozzle section  17 . 2 , one or more grooves  3  are provided in the shoulders  5 . Instead of the groove  3  shown in  FIG. 1 a  through borehole can be provided in the shoulders  5  for connecting both the catching nozzle sections  17 . 1  and  17 . 2 . Two screw-shaped ribs  4 . 1  and  4 . 2  are arranged on the downstream catching nozzle section  17 . 2 , as shown in  FIG. 1 . The functioning of the individual components of the catching nozzle  1  is described in details later on.  
         [0036]     A possible embodiment of a powder conveying device is shown in a cross-section in  FIG. 2 . The conveying air FL flows through the conveying air inlet  13  into the powder conveying device and ensures in the inside that the powder is suctioned through the powder inlet  15  into the powder conveying device. The powder air mixture formed from the conveying air FL and the powder is now led through the catching nozzle  1  arranged in the downstream end of the powder conveying device. The catching nozzle  1  is arranged in such a way in the powder conveying device that its upstream catching nozzle section  17 . 1  is located in a borehole  19  of the powder conveying device and the downstream catching nozzle section  17 . 2  of the catching nozzle  1  protrudes from the housing  9  of the powder conveying device. A hose socket  11  is put over the downstream catching nozzle section  17 . 2  of the catching nozzle  1  and such hose socket  11  is fixed, together with the catching nozzle  1 , on the housing  9  of the powder conveying device by means of a union nut  10 . The powder conveying device also has a dosage air inlet  14 , through which the dosage air DL can be added to the powder air mixture. The dosage air DL flows for this purpose first through the dosage air inlet  14  into a first dosage air duct  20 . 1 , which is formed by the upstream catching nozzle section  17 . 1  and the borehole  19 , and from there, through the groove  3 , in a second dosage air duct  20 . 2 , which is formed by the downstream catching nozzle section  17 . 2 , the ribs  4 . 1  and  4 . 2  and the hose socket  11 . However, the ribs  4 . 1  and  4 . 2  are not compulsorily required for the dosage air duct  20 . 2 . After that the dosage air DL has left the second dosage air duct  20 . 2 , it is added to the mixture made from conveying air FL and powder.  
         [0037]     Both screw-shaped ribs  4 . 1  and  4 . 2  ensure that the dosage air DL gets a twist. The arrow  8  in  FIG. 1  indicates the direction of flow of the dosage air DL. The twist enables that the dosage air does not generate a suction effect while exiting from the downstream dosage air duct  20 . 2 . Both ribs  4 . 1  and  4 . 2  also have the advantage that they increase the grip of the catching nozzle  1 . After the union nut  10  was unscrewed, the catching nozzle  1  can be pulled out manually without further ado from the powder conveying device. The number of the required ribs on the downstream catching nozzle section  17 . 2  depends on the technical general conditions. The same applies correspondingly to the number of the grooves  3  and/or the through boreholes through the shoulder  5 .  
         [0038]     The hose socket  11 , as described in the German registered utility model DE 202 04 116, can consist of an electric non-conductive material and can be surrounded, on the outside, by a layer or a sleeve made from electrically conductive material. The sleeve surrounding the hose socket  11  can for example consist of metal or of an electrically conductive synthetic material. For the case that the hose socket  11  is surrounded by such a sleeve, the sleeve can be fixed electrically by means of the union nut  10 , which also has an electrically conductive material, on the earthed injector housing  9 . For this purpose the sleeve can be provided with an annular flange, which is kept pressed by the union nut against a collar on the housing  9  of the powder conveying device. For more information, particularly regarding the electrical and mechanical design of the hose socket  11 , refer to the description in the document DE 202 04 116, wherein the form of the hose socket  11  should be adapted to the specific properties of the catching nozzle  1  according to the invention. It is envisaged that the hose socket  11  and the union nut  10  remain on the hose. Hence if the hose is, together with the union nut  10 , separated from the injector housing  9 , so the union nut  10  and the hose socket  11  remain on the hose, whereas the catching nozzle  1  remains in the injector housing  9 .  
         [0039]     The ribs  4 . 1  and  4 . 2  can be designed such that they ensure that the hose socket  11  is kept at a defined distance to the catching nozzle  1 , so that the already mentioned dosage air duct  20 . 2  is formed between the outside of the catching nozzle  1  and the inside of the hose socket  11 .  
         [0040]      FIG. 3  shows a second possible embodiment of the catching nozzle in a three-dimensional view. It is essentially differentiated from the embodiment shown in  FIG. 1  due to the fact that the downstream catching nozzle section  17 . 2  has several recesses  23 . In addition two narrow annular elevations  24 . 1  and  24 . 2  and a wide annular elevation  24 . 3  are provided in the downstream catching nozzle section  17 . 2 . The annular elevations  24 . 1 ,  24 . 2  and  24 . 3  in connexion with the recesses  23  improve, among others, the grip of the catching nozzle, what is of advantage while inserting and taking out the catching nozzle from the housing  9  of the powder conveying device.  
         [0041]     The  FIGS. 4 and 5  show a third and a fourth embodiment of the catching nozzle  1  in a three-dimensional view. The catching nozzles shown there are essentially differentiated from the embodiment shown in  FIG. 1  due to the fact that the downstream catching nozzle section  17 . 2  has several recesses  23  running in longitudinal direction. These can be produced, for example, with a knurling machine.  
         [0042]     Alternatively to the shown embodiments, the downstream outside of the catching nozzle  1  can also be cross-knurled.  
         [0043]     The embodiment shown in  FIG. 4  is also differentiated from the embodiment shown in  FIG. 1  due to the fact that several boreholes  3 . 1  and  3 . 2  as dosage air ducts are provided in the shoulder  5  instead of in the groove  3 .  
         [0044]     With the help of the O-ring  12  placed in the groove  6  it is ensured that the dosage air duct  20 . 1  is airtight sealed upstream compared to the powder duct of the injector. This ensures that the dosage air DL cannot arrive upstream into the powder suction duct.  
         [0045]     The preceding description of the embodiments according to the present invention is used only for illustrative purposes and not for the purpose of restricting the invention. Different alterations and modifications are possible within the scope of the invention without abandoning the scope of the invention and its equivalents.  
       REFERENCE SYMBOLS LIST  
       [0000]    
       
           1  catching nozzle  
           2 . 1  first cylindrical guide  
           2 . 2  second cylindrical guide  
           3  groove  
           3 . 1  borehole  
           3 . 2  borehole  
           4 . 1  rip  
           4 . 2  additional rip  
           5  shoulder  
           5 . 1  side, which is conical  
           5 . 2  side, which is conical  
           6  annular groove  
           7  direction of flow of the powder  
           8  direction of flow of the dosage air  
           9  injector housing  
           10  union nut  
           11  hose socket  
           12  O-ring  
           13  conveying air inlet  
           14  dosage air inlet  
           15  powder inlet  
           16  catching nozzle inlet  
           17 . 1  upstream catching nozzle section  
           17 . 2  downstream catching nozzle section  
           18  catching nozzle outlet  
           19  borehole  
           20 . 1  upstream dosage air duct  
           20 . 2  downstream dosage air duct  
           21  longitudinal axis  
           22  powder duct  
           23  recess  
           24 . 1  narrow ring  
           24 . 2  narrow ring  
           24 . 3  wide ring  
          FL conveying air  
          DL dosage air