Abstract:
In a spray gun ( 1 ) for spraying paint with a gun housing ( 2 ) provided with a handle ( 3 ) with a union nut ( 10 ) screwed onto it that holds an air cap ( 11 ) provided with offset outlet openings ( 14, 15 ) for compressed air, the union nut ( 10 ) is positively connected to the air cap ( 11 ) in a circumferential direction. This embodiment makes it possible for the spray jet to be set in a brief time and without difficulties without having to put up with getting dirty. It is merely necessary to turn the union nut ( 10 ) accordingly in order to control the air supply to the outlet openings ( 14, 15 ) of the air cap ( 11 ) and therefore to influence the formation of the spray jet.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a spray gun for spraying paints and similar viscous media that can be propelled pneumatically or electrically, comprising a gun housing for accommodating the propulsion mechanism, components of the spray gun that effect mixture and/or metering, a handle projecting from the gun housing, and a reservoir tank removably attached to the gun housing for holding the medium to be processed, as well as a union nut placed on the gun housing or an intermediate piece connected to the gun housing or an extension pipe, and an air cap surrounded by the union nut provided with mutually offset outlet openings for compressed air by means of which various spray jets can be formed and with an atomiser nozzle assigned to it that is held in an oriented position and can be opened by means of a nozzle needle. 
   2. Description of the Prior Art 
   Spray guns of this type have been offered for sale for many years by J. Wagner GmbH, Markdorf under the name W 850 E and have proven their effectiveness in practice. By turning the air cap through 90° in this case, it is possible to set three jet shapes for performing different jobs, namely a horizontally oriented flat jet, a round jet and a vertically oriented flat jet. 
   In order to set one of these spray shapes with this spray gun of the prior art, it is necessary to unscrew the union nut and turn the air cap to the corresponding position by hand with the union nut loosened. Then the union nut needs to be tightened again. However, the air cap has to be held in place when doing this in order to prevent it turning inadvertently. Also, the air cap can only be aligned precisely by visual contact, particularly when setting a round jet in order to cover the air supply to the outlet openings. Quite apart from the significant amount of time required in order to make these adjustments and settings, it is also necessary for the operator who is using the spray gun to use both hands in order to perform this task. Since it is necessary to use one hand to grip the air cap that has paint residue on it, the unavoidable consequence of changing the spray shape is that the operator will get his or her hands dirty. In many cases, therefore, the operator prefers not to change the spray shape in order to avoid getting paint on his or her hands. 
   The purpose of the present invention is therefore to create a spray gun of the aforementioned type that enables the shape of the spray jet to be changed within a short time without the need to grip the air cap and therefore without the need to put up with getting dirty hands. Rather, it should be possible to change the spray shape merely by turning the union nut or an equivalent holding element. The constructional complexity required in order to achieve this should be kept at a low level whilst nevertheless always allowing a reliable setting to be achieved quickly and in a straightforward procedure. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, this is achieved in a spray gun of the aforementioned type in that the union nut or a holding element equivalent to it is positively connected with the air cap in the circumferential direction. 
   In this case, the air cap can be inserted into the union nut or the holding element and firmly connected to it, for example by welding. However, it is also possible for the air cap and the union nut or holding element to be manufactured from one piece and configured as an injection-moulded component. 
   According to a different embodiment, however, it is also possible for the air cap to be positively connected to the union nut or holding element by one or more radial cams, preferably projecting from the outer jacket surface of the air cap and distributed evenly around its circumference, with the cams engaging in slots worked into the union nut or holding element, with the further possibility of the air cap to be inserted into a ring and firmly connected to the ring, with cams projecting radially from the ring engaging in slots in the union nut or the holding element. 
   In accordance with a preferred embodiment, it should be possible to lock the holding element in the angular positions corresponding to the spray jets to be formed in an oriented position in relation to the component carrying it, for example the gun housing. 
   This can be accomplished in that the component carrying the holding element, for example the gun housing, that is used for setting and holding the air cap in an oriented position, or the holding element is provided with one or more, and preferably two, diametrically opposed control cams that are open at one end and run in the circumferential direction and the holding element or the component carrying the holding element is provided with guide elements protruding inwards or outwards that engage in the control cams. 
   In this case, the guide elements can be configured as guide pins and the control cams in which they engage can be provided with axially offset recesses for accommodating the guide pins in the operating positions corresponding to the air cap, whilst it is also possible for the guide elements to be configured as radially sprung tabs and for the control cams holding them to be provided with detent cams distributed in the circumferential direction, preferably with even spacing, between which the tabs can be locked in the operating positions corresponding to the air cap. 
   Also, the air cap on its end facing the housing of the spray gun should be sealed against the component supporting it by means of a labyrinth seal, this ensures that the atomiser nozzle is in a precisely coaxial alignment in relation to the air cap. 
   Also, the air cap on its end facing the housing of the spray gun should be sealed against the component supporting it by means of a labyrinth seal, furthermore this ensures that the atomiser nozzle is in a precisely coaxial alignment in relation to the air cap. 
   If a spray gun is configured in accordance with the present invention, it is possible for the spray jet to be set within a short time and without difficulties and without the need to put up with getting dirty hands. The air cap is positively connected to the union nut or holding element in the circumferential direction and this means it is merely necessary to turn the union nut or holding element accordingly in order to control the air supply from the atomiser nozzle installed in its fixed position to the outlet openings of the air cap and therefore to influence the formation of the spray jet. Also, different detent positions are assigned to the holding element, therefore it is assured that different formations of the spray jet are provided merely by turning, for example through 45°. 
   The constructional complexity by means of which this is made possible is extremely low because only a positive connection between the air cap and the union nut or holding element is provided in the turning direction and this connection can be configured in different ways. Also, the adjustment is very easy and can be performed with only one hand, which means that adaptations of the spray jet in accordance with the work to be performed can be undertaken with practically no interruption in the job. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings shows some sample embodiments of the spray gun configured in accordance with the present invention which are explained in detail below. In the drawings, 
       FIG. 1  shows a perspective view of the spray gun with the air cap unscrewed, 
       FIG. 2  shows a magnified view of part of the housing of the spray gun in accordance with  FIG. 1  with the air cap unscrewed, 
       FIGS. 3 to 5  show sample embodiments of the positive connection between the air cap and the union nut in defined detent positions as exploded views, 
       FIG. 6  shows a developed view of the control cams provided in the embodiments in accordance with  FIGS. 3 to 5 , 
       FIGS. 7 to 9  show further embodiments of the positive connection between the air cap and a holding element, also in defined detent positions and in exploded views, 
       FIG. 10  shows the control cams provided in the embodiments in accordance with  FIGS. 7 to 9 , 
       FIG. 11  shows a sectional view of the air cap inserted in the holding element and 
       FIGS. 12   a ,  12   b  and  12   c  show the spray jets created by the spray gun in accordance with  FIG. 1  and the corresponding embodiments. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The spray gun shown in  FIG. 1  and identified with  1  is used for spraying paints or varnishes and principally comprises a gun housing  2  for accommodating the propulsion mechanism, the components that effect mixture and/or metering, a handle  3  projecting from the gun housing  2  and a reservoir tank  4  for holding the medium to be processed. The medium sucked up from the reservoir tank  4  is atomised by compressed air that is supplied via a line  7  of an atomiser nozzle  5  through the housing  2 . In the sample embodiment shown, the atomiser nozzle  5  is held by a union nut  10  that can be screwed onto a thread  9  worked into the gun housing  2 . A nozzle needle  16  reaching into the atomiser nozzle  5  can be actuated by a handle  6 , and additionally the quantity of paint can be controlled using a set screw  8 . 
   The spray gun  1  is equipped with an air cap  11  by means of which, as is shown in  FIGS. 12   a ,  12   b  and  12   c , it is possible to twist the air cap  11  to create three different spray jets I, II and III, namely a horizontally oriented flat jet I, a round jet II and a vertically oriented flat jet III. 
   In order to achieve this, the atomiser nozzle  5  is installed in an oriented position in the gun housing  2  and is provided with penetrations  19  for the compressed air, and the air cap  11  possesses two diametrically opposed horns  12  and  13  with air outlet openings  14  or  15  worked into them. The compressed air flowing out of outlet openings  14  and  15  has an effect on the continuous jet of paint ejected from the atomiser nozzle  5  during the operation of the spray gun  1  such that the jet is turned into spray jets I and III. In the position of the atomiser nozzle  5  shown in  FIG. 12   b , the supply of compressed air to the outlet openings  14  and  15  is shut off and compressed air only continues to flow out of a ring duct  18  that is formed by the atomiser nozzle  5  reaching into a hole  17  arranged centrally in the air cap  11 . 
   In order to allow the air cap  11  to be adjusted quickly and easily, it is positively connected with the union nut  10  in a circumferential direction, with the effect that it is only necessary to twist the union nut through 45° or 90° in order to set the spray gun  1  from the position corresponding to spray jet I to the positions for spray jet II or spray jet III. There is no need to grip the air cap  11  in order to do this, therefore there is practically no risk of getting dirty. It is merely necessary to move the union nut  10  screwed onto the gun housing  2  by means of an internal thread  20  through either 45° or 90° into the positions shown in  FIG. 12   b  or  12   c.    
   The positive connection between the air cap  11  and the union nut  10  in the turning direction can be achieved in different ways. In accordance with  FIGS. 1 and 2 , the air cap  11  is directly formed into the union nut  10  with the effect that they are configured in one piece and can be manufactured as an injection-moulded component. 
   In accordance with  FIG. 3 , the air cap  11  is provided with a ring  21  firmly connected to it and with radially projecting cams  22  attached to the ring  21 . The union nut  10  furthermore possesses lengthways grooves  23  into which the cams  22  engage. The air cap  11  is therefore driven by the union nut  10  when it is turned, and is moved accordingly. 
   In the embodiments shown in  FIGS. 4 to 10 , a holding element  31  with an equivalent effect to the union nut  10  is once again positively connected to an air cap  32  in the turning direction and can additionally be locked in the operating positions corresponding spray jets I, II, III. This is achieved in each case by means of a control cam  35 ,  35 ′,  35 ″ or  35 ′″ into which guide elements  36 ,  36 ′,  36 ″ or  36 ′″ engage. Also, radially projecting cams  33  serve to connect the air cap  32  to the holding element  31  in a torsionally rigid arrangement and these cams  33  engage in slots  34  worked into the union nut  31 . 
   In the embodiment shown in  FIG. 4 , two control cams  35  arranged opposite to one another are worked into the gun housing  2  and guidance elements  36  are provided in the form of two pins  37  projecting radially inwards from the holding element  31 . In accordance with  FIG. 5 , however, the guide elements  36 ′ are attached to the gun housing  2  and the control cams  35 ′ are provided in the holding element  31 . 
     FIG. 6  shows the manner in which the control cams  35  and  35 ′ in the embodiments in  FIGS. 4 and 5  are configured. In this case, the control cams  35  or  35 ′ are open at one end and are equipped with three detent positions a, b and c into which the pins  37  can be engaged in the operating positions corresponding to spray jets I, II and III. 
   In accordance with  FIGS. 7 ,  8  and  9 , each of the guide elements  36 ″ and  36 ′″ is formed by radially sprung tabs  38  or  38 ′ provided with humps, with the tabs being formed by U-shaped slots  40  worked into the holding element  31  or the housing  2  of the spray gun  1 . In turn, the control cams  35 ″ and  35 ′″ that are open at one end possess, as is shown in the embodiments in  FIG. 10 , detent cams  39  in the form of elevations between which the tabs  38  or  38 ′ in the air cap  32  can be locked in the three corresponding operating positions. 
   In accordance with  FIG. 7 , the air cap  32  is provided with radially projecting cams  33  that engage in the holding element  31  in the area of the tabs  38 . In accordance with  FIGS. 8 and 9 , however, the air cap  32  is firmly connected to the holding element  31  in that they are made as one piece. 
   A corrugated spring washer  41  is inserted between the holding element  31  and the air cap  32  in the embodiments shown in  FIGS. 4 and 5  so as to guarantee good contact between the air cap  32  and the gun housing  2 , or the atomiser nozzle  5 , at all times, with the spring washer  41  pressing the air cap  32  against the gun housing  2  or the atomiser nozzle  5 . Furthermore, as shown in  FIG. 11 , a labyrinth seal  42  can be provided between the atomiser nozzle  5  and the air cap  32 , with a circumferential web  44  axially projecting from the air cap  32  engaging in a groove  43  worked into the atomiser nozzle  5 . This measure prevents the compressed air flowing out radially, whilst in addition the atomiser nozzle  5  is coaxially aligned in this way. Furthermore, in order to counteract a pressure increase in the gun housing  2  when the outlet openings  14  and  15  are closed, several openings  24  can be provided in the air cap  11  or  32  by means of which the compressed air can flow out of the housing  2  into the atmosphere. 
   It goes without saying that the spray jets I, II and III can be set by turning the union nut  10  or the holding element  31  in all the illustrated embodiments.