Abstract:
The invention relates to a paint-spraying apparatus for generating a shaped paint jet, including a paint nozzle positioned in an annular gap, wherein the paint nozzle comprises a needle with a needle head and also comprises a paint outlet opening, wherein the needle head is displaceable with respect to the paint outlet opening over a longitudinal axis of the needle in order to control a needle valve formed from the paint outlet opening and the needle head, and wherein the needle head, in a closed position of the paint nozzle, plugs in a form-fitting manner with respect to the longitudinal axis in the paint outlet opening, wherein the paint outlet opening is rotatable together with the needle head about the longitudinal axis in order to rotate the orientation of the shaped paint jet with respect to the longitudinal axis.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/EP2012/001914 filed May 4, 2012, which designated the United States, and claims the benefit under 35 USC §119(a)-(d) of German Application No. 10 2011 100 806.7 filed May 6, 2011, the entireties of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a paint-spraying apparatus for producing a shaped paint jet, and to a needle for a needle valve for a paint-spraying apparatus. 
       BACKGROUND OF THE INVENTION 
       [0003]    In accordance with the invention, the paint-spraying apparatus can also be used for other air-driven application methods which make use of the function according to the invention of the rotatable production of a shaped paint jet of the paint-spraying apparatus. 
         [0004]    In the field of spraying application methods, for example in the case of paint spraying or lacquer spraying, there are a large number of basic technical principles. Besides what are known as airless methods, which atomize paint at high pressure and apply it to a surface, there are a large number of methods operated on the basis of compressed air. Here, a paint jet exiting from a nozzle is nebulized by means of air masses (primary atomization air) flowing past and is thus transported in the form of a paint jet mist in the direction of a working plane. The working plane arranged at a suitable working distance for a coating procedure is contacted in this way by the paint jet, and the paint is thus applied thereto. In this case, apparatuses operated on the basis of compressor compressed air and also what are known as HVLP (high volume low pressure) apparatuses inter alia are known from the prior art and differ in terms of some operating parameters, for example the nozzle air pressure, from the conventional high-pressure apparatuses. 
         [0005]    The type of apparatus from the prior art is suitable for providing a flat paint jet, which provides advantages when applying a paint to a surface. Compared to a radially symmetrical round paint jet, a flat jet provides increased homogeneity as the paint is applied, similarly to application by means of brush or application by means of roller, whereby the result of the paint coating is considerably improved. 
         [0006]    Paint-spraying devices, in which a radially symmetrical round paint jet, which exits from a paint nozzle, is deformed by air deflection means which are arranged to the side of the paint nozzle and are designed in the form of what are known as air horns, such that a produced flat paint jet appears in the region of a working plane, are known from the prior art, for example from EP 0 596 939 B1. 
         [0007]    Furthermore, a spray head for producing a flat paint jet on a paint-spraying apparatus is known from DE 10 2009 053 449 A1, with which wall paint or viscous paint can also be processed well. Depending on the design of the spray head, the flat jet that can be produced has a vertical or horizontal alignment, such that it is either suitable for applying the paint optimally to vertical or horizontal wall faces. A flat paint jet in horizontal and vertical direction is used above all to allow the user to coat the surfaces vertically and horizontally in the two primary working directions (=gun movement). This is important in particular in order to carry out what is known as cross-coating, in which a surface is coated successively once in a vertical working direction and once in a horizontal working direction in order to avoid structural shadowing. 
       SUMMARY OF THE INVENTION 
       [0008]    The object of the invention is to further develop a paint-spraying apparatus for producing a shaped paint jet, wherein the paint-spraying apparatus is suitable for dispensing the shaped paint jet (with unchanged alignment of the paint-spraying apparatus in space) in a different orientation. 
         [0009]    The invention relates to a paint-spraying apparatus in which the paint outlet opening is rotatable together with the needle head about the longitudinal axis of the needle in order to rotate the orientation of the shaped paint jet with respect to the longitudinal axis. It is thus possible to rotate the shaped paint jet (with unchanged alignment of the paint-spraying apparatus) about its own axis. For example, a shaped paint jet initially formed as a horizontally arranged bar can thus be used in order to then spray a vertically aligned wall face by means of a shaped paint jet formed as a vertically running bar whilst avoiding spraying an area to be kept free from paint. A rotational adjustability of this type of the shaped paint jet allows the user, in particular when working in edge regions, to maintain a relaxed position or to become accustomed to comfortable motion sequences. Furthermore, the user does not have to apply any torsional force in order to rotate about the longitudinal axis the paint-spraying apparatus, which is formed as a paint-spraying gun or paint-spraying or paint-atomizing lance and has an eccentric weight distribution, in particular caused by a paint container and/or feed lines. 
         [0010]    The core of the invention is therefore a division into two of the paint-spraying apparatus into a main unit grasped by the user by one or both hands and a dispensing unit coupled rotatably to the main body, wherein the dispensing unit is rotatable with respect to the main unit, such that a continuous spraying process is ensured. 
         [0011]    The embodiment, which is considered to be completely novel and previously unconventional compared to the prior art, of forming components of the paint-carrying portions of a paint-spraying apparatus so as to be rotatable about a longitudinal axis and, in doing so, of providing an ensured function without clogging with paint or restriction of the functional scope will be described in greater detail in the following exemplary embodiments. Here, the exemplary embodiments describe individual features of the invention, of the dependent claims, or groups thereof. The dependent claims however are not to be considered as being linked in accordance with the exemplary embodiment. Rather, they form individual building blocks having individual expedient features, which are implemented and presented fully or at least partly in the exemplary embodiment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a more detailed explanation, the following are shown in the figures: 
           [0013]      FIG. 1  a first exploded illustration of a paint-spraying apparatus according to the invention; 
           [0014]      FIG. 2  an assembled paint-spraying head; 
           [0015]      FIG. 3  a second exploded illustration of a paint-spraying head with needle; 
           [0016]      FIG. 4  a cross section through an assembled paint-spraying apparatus; and 
           [0017]      FIG. 5  a needle according to the invention for the paint-spraying apparatus. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    More specifically,  FIG. 1  shows an exploded illustration of a paint-spraying apparatus  1 . The paint-spraying apparatus is formed in the base by a body  2 , at the lower end of which a receptacle  3  for a paint container is provided. An alternative embodiment (not illustrated) is conceivable, in which the receptacle  3  for the paint container is omitted and a paint feed line feeds the paint to the body  2  from a remote container. This is described for example in German patent application DE 10 2009 048 022 A1, in the name of the applicant. 
         [0019]    The body  2  has a trigger  4 , which is fixed in an oscillating manner to the body  2  on an upper side and entrains a coupling pin (illustrated in  FIG. 4 ) via a blind hole arranged laterally in the trigger lever  5  or a bore (covered here by the covering cap  6 ). This coupling pin is used, as is known in general from the prior art, to press a needle  7  back against a spring weight or the like in order to operate a needle valve for controlling an outlet of paint. 
         [0020]    The paint-spraying apparatus  1  according to the invention, besides the body  2  and the needle  7 , comprises an air link  8 , a control disk  9 , an air cap  10 , a cap nut  11  and a rotary actuator  12  with drivers  13  arranged thereon and, where necessary, a further driver  14  arranged thereon. The mentioned component parts are arranged in the direction of air flow, starting from the body  2 , in the manner illustrated in  FIG. 1 . 
         [0021]    The air cap  10 , the control disk  9 , the air link  8  and the needle  7  here form a structural unit  15 , which provides the technical preconditions for the paint atomizing process. Here, the needle  7  with its needle head  16  engages in a paint outlet opening  17 , which is arranged centrally in the air link  8 . The wedge shape of the needle head  16  is adapted here to the shape of the paint outlet opening  17  in such a way that it closes the opening in a paint-tight manner as a result of engagement in the fully inserted position. The technical principles of a needle valve, which provides an opening gap in a paint outlet opening  17  by pulling back the needle, wherein paint can then exit through the opening gap in a metered manner, are known a number of times from the prior art for rotationally symmetrical needles and paint outlet openings. 
         [0022]      FIG. 2  shows an assembled embodiment of a spray head  20  of a paint-spraying apparatus according to the invention. The spray head  20  is formed here by the air link  8 , the control disk  9  arranged thereon, the air cap  10  covering the control disk, the cap nut  11  arranged thereover and also the rotary actuator  12  clipped thereonto and the further driver  14 . The needle  7  starting from the body  2  is not illustrated in the present case. 
         [0023]    A paint nozzle  21  is formed on the paint outlet side of the spray head  20  by the paint outlet opening  17  and the needle  7  (not illustrated). The paint nozzle  21 , which is slot-shaped in the present case, is arranged inside an atomizer air opening  22  in the air cap  10 . The edge of the atomizer air opening  22  and also the edge of the paint outlet opening  17  define the annular gap  23  which surrounds the paint nozzle  21  and through which the atomizer air for atomizing the paint exiting from the paint outlet opening  17  flows. A paint mist is thus produced by known atomizing principles. 
         [0024]    In the continuation of the longitudinal axis of the slot-shaped paint outlet opening  17 , air horns  24  are arranged in such a way that they direct a directed shaping air jet onto the paint mist exiting from the paint outlet opening  17  and the annular gap  23  and thus further intensify the formation of a flat jet. This principle is likewise known from the prior art in the name of the applicant mentioned in the introduction. 
         [0025]    The rotary actuator  12  is clipped via lateral clamping wings  25  onto the cap nut  11  and, as a result of the form fit  26 , engaging from behind, of the clamping wings  25 , is thus arranged rotatably on the cap nut  11  along a longitudinal axis  27 . The rotary actuator  12  comprises drivers  13 , which are arranged in accordance with the air horns  24  and which, by wrapping around the air horns in a form-fitting manner, ensure that the air horns are also driven as the rotary actuator  12  is rotated. Furthermore, the rotary actuator  12  has a saddle guide  30  in which the further driver  14  is guided, wherein the further driver  14  is in turn secured to the rotary actuator  12  via a clamping wing  28  and a form-fitting engagement from behind  29 , in such a way that it is displaceable along the saddle guide  27  over a circular path about the longitudinal axis  27 . The further driver  14  here operates a pin  31 , which is arranged on the control disk  9 . The control disk  9 , arranged behind the air cap  10 , can thus be rotated by the further driver  14 . 
         [0026]    In  FIG. 3 , the exploded illustration illustrated in accordance with  FIG. 1  is shown, wherein the gun body  2  is not illustrated and the arrangement of the individual component parts has been rotated through 90° in a clockwise direction as considered in the air flow. 
         [0027]    The needle  7  on its side facing away in the needle head  16  has a seal arrangement. The seal arrangement comprises a contact surface  40 , in front of which at least one seal  41  (in the present case two seals are provided) is arranged. The seal or the seals  41  is/are held by a thread  42  arranged on the needle  7  via a clamping nut  43  screwed thereonto and can be adjusted in terms of their sealing effect by corresponding pre-stressing of the clamping nut  43 . 
         [0028]    In the rearward direction, the needle  7  then follows a seal arrangement of the passage  44  for the coupling pin (illustrated in  FIG. 4 ), which comprises the pressure surfaces  45  for the force transmission for pulling back the needle  7 . 
         [0029]    The passage  44  is formed as a substantially quadrangle-shaped passage  44 , wherein this passage  44  is likewise provided symmetrically about the longitudinal axis  27  on the other side of the needle (not illustrated here). Due to the substantially quadrangle-shaped design of the passage  44 , it is made possible for the needle to be rotatable through an angle of approximately 90° in accordance with the passage opening  44  without resulting in any torsion effects on the needle  7  by the coupling pin passing through the needle. 
         [0030]    Besides the arrangement of the pressure surface  45  and the seal, which will be described in greater detail in subsequent  FIG. 5 ,  FIG. 3  shows the arrangement of the passage openings for the individual air guides. Besides the passage opening for the atomizer air  51 , which subsequently passes through the annular gap  23  described in  FIG. 2 , the air link  8  comprises openings for the horn air  50  and also openings for the compensating air  52 . The control disk  9  comprises two control openings  53  and  54 , which, as the control disk  9  is rotated about the longitudinal axis  27 , can be brought into line either with the openings for the horn air  50  or the openings for the compensating air  52 . Corresponding air channels for the horn air and the compensating air are also provided in the air cap  10 . 
         [0031]    The control disk  9  is slightly smaller in diameter compared to the diameter of the air link  8 . The air link  8  on its surface facing the control disk  9  has springs  60  and  61 , between which the control disk  9  is inserted and is guided in the event of rotation about the longitudinal axis  27 . At least one of the springs  60 ,  61  still protrudes here in the assembled state beyond the control disk  9 , such that, for defined arrangement and rotational positional fixing of the air cap  10 , it engages in a groove  62  arranged in the air cap  10  on the contact side to the air link  8  and the control disk  9 . 
         [0032]    The technical function of the described air paths, which can be changed over, between an air passage through the horns  24  and an air passage through the compensating bores  65  lies in the avoidance of a rise of the internal air pressure in the paint-spraying apparatus. Since, in the apparatuses, fans are usually used to provide the working air and use a specific volume flow rate for their own cooling, it is disadvantageous to reduce the volume flow rate that can pass through a spray head. As soon as the air horns  24  forming the spray jet are therefore switched off by moving the control disk  9  via the pin  31  in order to influence the dispensed spray jet, a reduced total air volume flow rate would be produced without the compensating bores  65 . The fan should be able to cope with this. If the fan is dependent on the volume flow rate for cooling, the corresponding volume has to be discharged through the compensating bores in order to avoid an increased backup and to further cool the fan sufficiently. This technique is described for another type of spray guns in the prior art document EP 0 596 939 B1. 
         [0033]      FIG. 4  shows a cross section through a paint-spraying apparatus  1  according to the invention. The individual component parts are denoted in accordance with the above-described reference signs. 
         [0034]    Proceeding from a paint-conveying tube (not illustrated) in a paint container screwed onto the receptacle  3 , paint is transported through a riser pipe  70  via the paint chamber  71  to the paint nozzle  21 . The paint chamber  71  is formed here substantially as a sleeve receiving the needle  7  completely and having an opening for the coupling pin  72  and also having the access of the riser pipe  70 . During operation, only the front part of the paint chamber  71  is filled with paint. 
         [0035]    Inside the paint chamber, the needle  7  is arranged displaceably along the longitudinal axis  27  relative to the opening of the paint outlet opening  17 . The needle can be provided as a two-part design, for example if a front portion  75  with the needle head  16  is to be produced from a material different from that of a rear portion  76 . This is to be provided for example for the formation of the needle head as a closure part, which is to be replaced more frequently compared to the rest of the arrangement. In principle, it is also possible to form a simple rotary joint by means of the parts of the front and rear portion  75 ,  76  pushed one inside the other in order to mount the needle head  16  rotatably with the paint outlet opening  17 . In this case, the above-described semi-circular passage could be omitted. A problem with this rather deteriorated embodiment could be a sticking of the component parts as a result of paint. 
         [0036]    In  FIG. 5 , a needle  7  according to the invention is illustrated in detail. In contrast to conventional feedthroughs known from the prior art of the needle through a seal assembly which is arranged fixedly in the housing and which is costly and of complex design, the seal arrangement in the present case is fixed on the needle  7 . Whether the needle is formed here as a two-part embodiment, as presented in the present case, or is present in the form of a one-part needle is insignificant for the seal arrangement and the functionality described hereinafter. 
         [0037]    Specifically in the field of professional tools, seal assemblies of which the tension can be adjusted are often of great advantage. The adjustment or readjustment of a seal tension makes it possible to access the optimum trigger pressure point, which is determined by the sliding friction of the needle  7  in the seal, or in the present case by that of the seal  41  in the paint chamber  71 . 
         [0038]    The adjustability is provided in the present case by the tension that is exerted by means of the clamping nut  43  onto the seal assembly consisting of the two ring seals  41 . The clamping nut  43  is to this end screwed on the thread  42  against the seals  41  and presses these against the contact surface  40 . Depending on the contact pressure, a sealing bead is produced radially outwardly from the longitudinal axis  27  and brings about the sealing effect with respect to the wall of the paint chamber  71 . 
         [0039]    Alternatively, it is also possible for a coupling means of the needle trigger  4 ,  5  to bear against a radial widening or radial constriction of the needle  7  with respect to the longitudinal axis  27  and to thus move this in the manner of a plate driver. 
         [0040]    The invention therefore also comprises a paint-spraying apparatus for producing a paint jet with a needle  7  received displaceably in a channel, wherein a paint-carrying portion of the channel is sealed by a seal sheathing the needle, and the seal is fixed in the axial direction relative to the needle. 
         [0041]    Here, the seal is fixed between a first stop and a second stop, wherein at least one stop on the needle is preferably adjustable in the axial direction. 
         [0042]    For improved guidance of the seal, this is fixed in the peripheral direction relative to the needle, for example by a form-fitting tongue-and-groove rotary fixing or a rough structure on the contact surface  40 , for example a toothed lock washer structure. 
         [0043]    If the needle  7  is provided in two parts or a number of parts, the front needle portion  75  and the rear needle portion  76  can be rotatable relative to one another about a common longitudinal axis  27 . Here, the first material of the front portion  75  is advantageously a plastic material (for example POM material), and the second material of the rear portion  76  is advantageously a metal material (for example a zinc casting). The front portion  75  can be connected here to the rear portion  76  during the production process by insert molding of the rear portion. 
         [0044]    It is additionally advantageous for the paint outlet opening  17  to be formed from a third material, which is harder than the material of the front needle portion  75 , and for the third material to be in particular ceramic and in particular sintered ceramic. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           1  paint-spraying apparatus 
           2  body 
           3  receptacle 
           4  trigger 
           5  trigger lever 
           6  cover cap 
           7  needle 
           8  air link 
           9  control disk 
           10  air cap 
           11  cap nut 
           12  rotary actuator 
           13  driver 
           14  further driver 
           15  structural unit 
           16  needle head 
           17  paint outlet opening 
           20  spray head 
           21  paint nozzle 
           22  atomizer air opening 
           23  annular gap 
           24  air horn 
           25  clamping wing 
           26  form fit 
           27  longitudinal axis 
           28  clamping wing 
           29  form-fitting engagement from behind 
           30  saddle guide 
           40  contact surface 
           41  seal 
           42  thread 
           43  clamping nut 
           44  passage 
           45  pressure surface 
           50  opening for the horn air 
           51  opening for the atomizer air 
           52  opening for the compensating air 
           53  control opening 
           54  control opening 
           60  spring 
           61  spring 
           62  groove 
           65  compensating bore 
           70  riser pipe 
           71  paint chamber 
           72  coupling pin 
           75  front portion 
           76  rear portion