Abstract:
A selective venting spray assembly is disclosed which includes a sprayer for dispersing a spray of liquid and a spray shaping air flow. An aircap is attached to the sprayer for atomizing and directing the spray. The aircap includes one or more spray shaping passages for receiving the airflow and directing it against the spray to alter the shape of the spray. A flow channel assembly is provided to fluidly connect the aircap to the sprayer. The flow channel assembly includes a flow passage selectively switchable between a first position where airflow is admitted from the sprayer to the spray shaping passage, and a second position where the airflow is diverted to a vent, to produce a non-shaped spray without creating damaging back pressure within the sprayer.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to the field of sprayer systems, particularly those of the type used to produce more than one spray pattern, e.g. high volume, low pressure (HVLP) paint sprayers that use air jets to deform a circular spray pattern into a flat &#34;fan&#34; spray pattern. 
     A typical paint sprayer includes a sprayer nozzle that disperses a diverging conical spray envelope of paint for producing a circular pattern. Typical sprayers also include an aircap for alternately admitting the conical spray or deforming it into a fan pattern. The aircap includes spray shaping passages formed in wings of the aircap, on either side of the conical spray. These passages direct pressurized air from within the sprayer toward the conical spray, altering the shape of the conical spray to flatten it into a fan pattern. 
     The round pattern is selectively restored by shutting off the spray shaping passages. This is commonly accomplished by providing a rotatable aircap which is movable between two positions. In the first position, the spray shaping passages are in registration with corresponding openings in the sprayer, to admit pressurized air to the aircap shaping passages. The aircap can then be rotated to a second position where the spray shaping passages are blocked, thereby discontinuing airflow. However, this shut-off condition restricts the flow of air through the sprayer system, thus creating an increase in back pressure and motor speed (i.e. RPMs). This increases heat in the motor, resulting in additional wear and tear and thereby reducing the expected service life of the motor, and increases heat in the air hose, thus reducing its structural integrity. 
     SUMMARY OF THE INVENTION 
     In view of the difficulties and drawbacks encountered with previous systems, there is therefore a need for a selective sprayer system in which the air motor observes equalized flow and pressure in both fan and circular positions. 
     There is also a need for a selective sprayer having an air motor with reduced operational wear and increased motor life and hose life. 
     These needs and others are satisfied by the present selective venting spray assembly which includes a sprayer for dispersing a spray of liquid and a spray shaping air flow. An aircap is attached to the sprayer for atomizing the fluid and directing the spray. The aircap includes one or more spray shaping passages for receiving the air flow and directing it against the spray to alter the shape of the spray. A flow channel assembly is provided to fluidly connect the aircap to the sprayer. The flow channel assembly includes a variable flow passage selectively switchable between a first position that admits air flow from the sprayer to the spray shaping passage, and a second position that diverts the air flow to a vent, to produce a non-shaped spray without creating back pressure within the sprayer. 
     As will be appreciated, the invention is capable of other and different embodiments, and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view illustrating the general aircap assembly as according to the present invention. 
     FIG. 2 is an exploded view detailing the aircap plate and sprayer plate of the present invention. 
     FIGS. 3A, B and C are respective exploded, side sectional, and oblique sectional views depicting the assembly and operation of the present sprayer in a first operative position. 
     FIGS. 4A, B and C are respective exploded, side sectional, and oblique sectional views depicting the assembly and operation of the present sprayer in a second operative position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The figures will now be discussed where it is understood that like reference numerals correspond to like elements, wherein a selective venting sprayer system is shown that operates with continuous air flow and pressure while functioning, in circular pattern and fan pattern modes. FIG. 1 shows a sprayer 10 which cooperates with an aircap 12 and is attached with a retaining ring 14, all of which are assembled along a central axis 16. The retaining ring 14 can be a typical threaded ring as shown, received by mating threads on the sprayer 10. The retaining ring 14 can optionally employ a biasing spring to apply a biasing force during rotational indexing. Alternatively, the retaining ring can include an integral spring such as shown in U.S. application Ser. No. 09/240,808, filed Feb. 1, 1999, and entitled &#34;INDEXING AIRCAP RETAINING RING&#34;, also to the present inventor, the disclosure of which is hereby incorporated by reference. 
     An HVLP spray gun atomizes fluids with low pressure air (10 psi or less). Fluid is discharged from the fluid nozzle 20 and atomization takes place at the aircap 12 in an area directly in front of the nozzle 20. Air from the sprayer 20 passes over the nozzle 20 and through a central hole 22 in the aircap 12, producing a diverging conical spray of atomized fluid, e.g. paint. This conical spray can selectively be reshaped into a flat fan spray pattern using spray shaping passages 24, formed with wings of the aircap 12, and displaced from the central axis 16. These passages 24 receive air from the sprayer 10, which can be selectively directed to the conical spray. The spray shaping passages 24 are inclined at an angle toward the central axis 16, preferably about 45 degrees, to produce the desired shaping. 
     The aircap 12 is selectively indexed between a circular pattern position and a fan pattern position by rotating the aircap 12 about the axis 16, in order to respectively block and unblock the spray shaping passages 24. In order to prevent creating damaging back pressure within the sprayer 10, the present invention includes a flow channel assembly, external to the aircap 12, for fluidly connecting the aircap 12 to the sprayer 10. This flow channel assembly defines a flow passage, switchable with the selective indexing of the aircap 12 between a first position that admits air flow from the sprayer to the spray shaping passages 24 and a second position that diverts the air flow to a vent when the spray shaping passages 24 are blocked. 
     In the preferred embodiment, as illustrated, the flow channel assembly is defined by first and second blocking members, in the form of an aircap plate 30, affixed to the aircap 12, and a sprayer plate 32, affixed to the sprayer 10. The aircap and sprayer plates 30, 32 are substantially abutting when assembled, but are rotationally movable with respect to each other, following the rotation of the aircap 12. The aircap plate 30 includes two apertures, opened to the spray shaping passages 24. The sprayer plate 32 as shown includes four apertures 36, equally spaced and centered about the axis 16. However, the sprayer plate 32 can include two apertures, or any other respective numbers of corresponding apertures without departing from the invention. The sprayer plate apertures 36 are open to an air flow passage within the sprayer 10. Flow passages to the spray shaping passages 24 are established when the spray plate apertures 34 are in registration with a respective pair of sprayer plate apertures 36. In the illustrated embodiment, the apertures 34 are in registration with apertures 36, when the aircap 12 is in either a horizontal or vertical orientation. 
     As shown in FIG. 2, the aircap plate 30 and the sprayer plate 32 each include a substantially flat surface plane. The sprayer plate 32 preferably includes a plurality of restriction wings 40 in the form of arcuate relieved portions extending outwardly from the plane of the sprayer plate 32, and spaced in between the sprayer plate apertures 36. The restriction wings 40 are dimensioned in order to be received within corresponding arcuate recessed portions 42, formed inwardly from the plane of the aircap plate 30. The wings 40 and recessed portions 42 are formed to be mating surfaces, and cooperate with the respective surface planes to form a transverse flow passage, as will be shown below. It should be understood that the wings 40 and recessed portions 42 could be formed on the respective other plates 30, 32, or both, all without departing from the invention. The aircap plate 30 and the sprayer plate 32 are each generally annular, and include respective central passages. The recessed portions 42 meet the edge of the aircap plate annular passage to permit fluid communication there between. The central passage of the sprayer plate 32 is smaller, sized to be secured behind the nozzle 20. A number of arcuate apertures 44 are formed radially outward from the sprayer plate central passage, adjoining the restriction wings 40, for admitting atomizing air into the central hole of the aircap 12. 
     FIGS. 3A, 3B and 3C show the present sprayer in the first position. The apertures 34, 36 are in registration, and the flow passage 50 fluidly connects the spray shaping passage 24 to the air supply. The restriction wings 40 are received within the respective recessed portions 42, so that the respective surface planes substantially abut, thereby sealing the transverse passage between the plates 30, 32 against airflow. 
     FIGS. 4A, 4B and 4C show the present sprayer in the second position. In the illustrated embodiment, the aircap 12 is rotated to a 45 degree position between vertical and horizontal. The aircap plate apertures 34 are moved to a position where they are blocked by the restriction wings 40, thereby closing off air flow to the spray shaping passages 24. The mating structures 40, 42 are thus offset from each other so that the restriction wings 40 abut the surface plane of the aircap plate 30. Thus, a transverse passage opens up, defining the flow passage 50 as an open vent 52 between the recessed portions 42 and the surface plane of the sprayer plate 32. The airflow is thereby diverted to the vent 52, extending to an edge region defined by the plates 30, 32. In this way, air pressure is relieved within the sprayer 10, and damaging pressure buildup is avoided. From the vent 52, the airflow discharges through the interstices of the retaining ring 14. 
     As an additional feature of the invention, the wings 40 and recessed portions 42 can be formed to include respective secondary relieved and recessed portions. For example, the wings 40 can include a relieved circular dot 60, and the recessed portion 42 can include a circular dimple 62, which has a corresponding shape for receiving the dot 60. The dots 60 are shaped to contain to the aircap plate apertures 34, and thereby provide additional sealing and securement in the second position, as well as the first position. Of course, the dots 60 and dimples 62 can be of any corresponding shape and be placed on any respective surface feature without departing from the invention. 
     The dimensions of the various elements formed on the plates 30, 32 can be sized to produce a desired match of flow and pressure between the circular spray and fan spray positions. These dimensions can also be selected to provide higher or lower pressures and/or flow, depending on the specific requirements. This design can be implemented without creating additional components or manufacturing processes, thereby not adding to the cost of manufacture. 
     As described hereinabove, the present invention solves many problems associated with previous systems, and presents many improvements in efficiency and operability. However, it will be appreciated that various changes in the details, materials and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principle and scope of the invention as expressed by the appended claims.