Abstract:
An improved paint spray gun, including high volume and low pressure air paint spray guns, siphon-type paint spray guns, and gravity-fed-type spray guns, having a built-in gas pressure gauge.

Description:
RELATED APPLICATIONS 
       [0001]    There are no related applications. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0003]    None. 
       FIELD OF THE INVENTION 
       [0004]    The invention relates to improved paint spray guns, including spray guns using low pressure and high volume air for atomizing the paint. The apparatus includes a built-in gas pressure gauge and adjustable controls for modulating the spray characteristics of the paint, stain or similar liquid being ejected therefrom. 
       BACKGROUND OF THE INVENTION 
       [0005]    Spray guns, especially those used with spray painting apparatuses, atomize the liquid paint by means of compressed air, generally provided via an air compressor, which enters a nozzle area via a chamber surrounding a fluid nozzle. This atomizing air is then impinged at the end of the chamber and exits via a central aperture located at the end of the chamber. Utilizing the physical phenomenon of the Venturi effect, paint is drawn from a reservoir and atomized by the pressure gradient created by the pressurized air as it exits the spray gun nozzle via the aperture. 
         [0006]    Numerous factors affect the volume of liquid being ejected from conventional spray gun nozzles and the pattern at which it sprays, including the viscosity of the liquid, the cubic feet per minute (c.f.m.) of air being supplied by the compressor, the pressure at which that air is being regulated, regulation of the air by control valves in the spray gun itself, the length and diameter of the air hose connecting the compressor and spray gun, and modulation of the spray gun trigger by the user. Hence, while effective for quickly and efficiently covering a surface with paint, varnish, shellac, or similar liquid, the spray pattern of these devices can be difficult to control. Each parameter is independently adjustable with the result that adjusting the spray pattern is a complex, time consuming, and multi-handed procedure, entailing repeated trial and error. 
         [0007]    Modern paints require precise control of air pressure in order to coat uniformly and hence the air pressure provided by the compressor and the consistency of same are particularly important. Accordingly, compressors generally include pressure regulators and pressure gauges so that the pressure at the junction of the compressor outlet and hose inlet may be monitored. However, because the length and diameter of the hose connecting the compressor affect the pressure actually delivered at the spray gun air inlet, the pressure reading indicated at the compressor regulator can differ significantly from that actually being delivered at the spray gun. Elaborate charts and diagrams are available which take into account variables such as the air hose length and diameter thereby allowing a user to estimate the delivery pressure. Additionally, accessory pressure gauges have been developed for installation between the air hose outlet and the inlet of the spray gun. However, the aforementioned charts are only able to provide estimates of the actual pressure being delivered and inline pressure gauges do not indicate the pressure actually being delivered at the spray gun nozzle. What is needed therefore is an indication of the air pressure actually being supplied at the spray gun nozzle. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is an improvement with regard to pneumatic paint sprayers, in particular including those utilizing high volume low pressure air sources, and including gravity fed as well as siphon type apparatuses. The improvement includes a gas pressure gauge built into the paint sprayer in communication with the paint sprayer gas passages. The user is thereby able to monitor and control the air pressure as close to the nozzle of the paint sprayer as possible and optimizing the delivery of the material being sprayed. 
         [0009]    It is an object of the invention to provide a spray gun having a built-in pressure gauge; 
         [0010]    It is another object of the invention to provide a pneumatic spray gun with a pressure gauge that accurately indicates the pressure at which material is being sprayed; 
         [0011]    It is yet another object of the invention to provide a pneumatic spray that facilitates monitoring of fluctuations in air pressure; and, 
         [0012]    It is finally an object of the invention to provide a pneumatic spray gun that facilitates optimal delivery of the material being sprayed. 
         [0013]    The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a preferred embodiment of the invention; 
           [0015]      FIG. 2  is a perspective view of a second embodiment of the invention; and, 
           [0016]      FIG. 3  is a cutaway view of the first preferred embodiment shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    The preferred embodiments and best modes of the invention are shown in  FIGS. 1 through 3 . While the invention is described in connection with certain preferred embodiments, it is not intended that the present invention be so limited. On the contrary, it is intended to cover all alternatives, modifications, and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the appended claims. 
         [0018]    This invention may be constructed from any suitable material including but not limited to appropriate metals, plastics and other polymers, ceramics, and combinations thereof. 
         [0019]    In  FIGS. 1 and 2 , a first preferred embodiment  10  and second preferred embodiment  20  are shown. Both function identically with regard to the present invention and differ essentially only in the mechanism by which the liquid to be sprayed is delivered to the spraying assembly  15 ,  15 ′.  FIG. 1  depicts the invention  10  configured as a siphon-style spray gun, including a reservoir  30  mounted generally below the spraying assembly  15  with the liquid being sprayed is drawn into the spraying assembly  15  via a siphon tube  31  (see  FIG. 3 ) operated via the vacuum created by operation of the spraying assembly  15 .  FIG. 2  depicts the invention  20  configured as a gravity-fed-style spray gun, including a hopper  30 ′ mounted generally above the spraying assembly  15 ′. Instead of the siphon mechanism used with regard to the siphon-style device  10  of  FIG. 1 , an aperture (not shown) in the hopper  30 ′ allows the to-be-sprayed material to essentially drip into the spraying assembly  15 ′. Absent the improvements of the present invention  10 ,  20 , both apparatuses operate in a conventional manner understood by those skilled in the art. 
         [0020]    As shown in  FIG. 3 , the apparatus of the present invention and first preferred embodiment  10  is shown in a cutaway view. Included is a reservoir  30  and siphon tube  31  used in a conventional manner to supply paint, varnish, or similar liquid to the spraying assembly  15  of the instant invention  10 . The spraying assembly  15  operates in a generally conventional manner that will be understood by those skilled in the art and includes a fluid nozzle  52  in communication with the reservoir  30  and siphon tube  31 . An air nozzle  50  generally surrounds the fluid nozzle  52  such that a vacuum created by air entering the nozzle and thereafter being expelled from the spray aperture  56  tends to draw liquid up from the reservoir  30  via the siphon tube  31 . The liquid drawn through the siphon tube  31  subsequently mixes with and is atomized by the air from the air nozzle  50  with the result that the atomized paint, varnish, shellac, stain or similar liquid is ejected from the spray aperture  56  of the spraying assembly  15 . The amount of liquid being supplied to the spraying assembly  15  is controlled by a needle valve screw assembly  80  which is screwed into the pistol grip  17 . 
         [0021]    The pistol grip  17  of the inventive apparatus  10  generally holds the assembly for introduction of the compressed air or similar gas used for operation of the apparatus  10 . An air inlet  40  is formed at the base of the pistol grip  17  allowing an air supply hose (not shown) to be attached in a conventional manner, for example using ¼ inch or ⅜ inch NPT (National Pipe Thread) fittings known to those skilled in the art. Gross adjustment of air pressure is regulated by an air adjustment screw  42  in communication with the air inlet  40  via an air channel  43  defined within the pistol grip  17 . Additionally, a secondary air adjustment screw  54  is provided in the upper portion of the pistol grip  17 . A plunger valve  44  impinging on the air channel  43  facilitates infinitely adjustable control of the air supplied to the apparatus  10  whereby fore and all manipulation by the operator of the trigger  46  rotating about its trigger pivot  48  and bearing on the plunger valve  44  causes air to enter the spraying assembly  15  as described above with the result that atomized liquid is ejected from the spraying assembly  15 . 
         [0022]    A gas pressure gauge  86  is mounted in the upper portion of the pistol grip  17 . In a preferred embodiment, the gas pressure gauge  86  is a digital gas pressure gauge  86  and includes a battery  87  in electrical communication therewith. The battery  87  is housed in a chamber defined in the spray gun housing. One skilled in the art will understand, however, that pressure gauges are well known and include force collector type sensors, for example, piezoresistive strain gauge, capacitive, electromagnetic, piezoelectric, optical, and potentiometric sensors, as well as electronic pressure sensors utilizing other phenomena, for example, resonant, thermal, ionization sensors, and the like. All are contemplated herein. The gas pressure gauge  86  is in gaseous communication with air channel  43  such that gas pressure is sampled essentially adjacent the air nozzle  50  of the spraying assembly  15 . In a preferred embodiment the gas pressure gauge  86  further includes a digital display  90 ,  90 ′ (see  FIGS. 1 and 2 ). It is contemplated, however, that any suitable display may be included, including but not limited to an analog display. 
         [0023]    In a preferred embodiment, the gas pressure gauge  86  and digital display  90 ,  90 ′ are able to accommodate pressure readings up to and including 2 bar (approximately 29 lbs/in 2  (i.e., p.s.i.)). Larger and smaller maximum pressure readings are also contemplated. 
         [0024]    In use, the proximity of the gas pressure gauge  86  of the apparatus of the present invention ensures accurate and convenient monitoring and control of the actual gas pressure at the point at which material is being ejected from a pneumatic paint and/or liquid sprayer. 
         [0025]    The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. However, the invention should not be construed as limited to the particular embodiments which have been described above. Instead, the embodiments described here should be regarded as illustrative rather than restrictive. Variations and changes may be made by others without departing from the scope of the present invention as defined by the following claims: