CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims the benefit of U.S. Provisional Patent Application No. 60/786,890, filed Mar. 29, 2006. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to spray guns, and more particularly to hand held and operated spray guns for spraying high pressure liquid flow streams. 
       BACKGROUND OF THE INVENTION 
       [0003]    Hand held spray guns commonly are used for directing high pressure liquid flow streams, up to 5,000 psi, such as in car washes and in conjunction with use of household and commercial pressure washer systems. Such hand held spray guns often are manufactured by what is referred to in the industry as a “disposable product.” Such disposable spray guns are designed and manufactured for long-term reliable usage without the manufacturer inventorying or supplying replacement parts. In the event of a part failure after normal life of the spray gun, it is customary for the product to be replaced rather than repaired. 
         [0004]    While such disposable hand held spray guns are designed for long-term maintenance free usage, they nevertheless have been subject to problems that can impede reliable usage or substantially shortened their intended useful life. Such disposable hand held spray guns, for example, typically are controlled by a trigger actuated ball valve mechanism. Actuation of the spray gun trigger causes a valve stem to move a ball valve away from its valve seat against the biasing force of a coil spring aligned coaxially with the valve seat. The valve seat, in turn, is maintained in a sealed seated position by a separate concentrically-mounted valve-seat retaining coil spring. 
         [0005]    High pressure liquid entering the valve chamber of the mechanism upon actuation of the trigger can forcefully move the valve ball out of axial alignment with the valve seat such that upon release of the trigger the ball return spring tends to urge the valve ball laterally to a side, rather than axially into a seated valve closing position. This can either prevent or at least impede reliable closure of the valve. Moreover, the high pressure liquid entering the valve chamber can physically force the valve ball into lodged engagement between coils of the concentrically mounted valve seat retaining coil spring, which can prevent the ball valve from returning to a closed position upon release of the trigger. This not only prevents control of the spray gun, but can create a potentially dangerous condition, if the operator without knowledge of the malfunction, is unable to turn off the spray gun. 
         [0006]    To facilitate manufacture and assembly of the valve mechanism into a valve chamber from a rear access opening in the valve body, it is customary following assembly to close the rear access opening by a threaded bolt or stud that is screwed into the access opening, which further retains biasing springs of the mechanism. In order to seal the valve chamber, an o-ring is provided in a retaining groove about a terminal end of the threaded stud, which sealingly engages an internal wall of the spray gun housing adjacent the valve chamber. During assembly, however, it is possible for the o-ring to be scratched or abrased by the sharp internal threads of the access opening as the stud is positioned into the opening for threaded engagement with the housing. Even slight abrasions of the o-ring, which initially can go unnoticed, can cause early failure of the o-ring, and hence, premature failure of the spray gun. 
         [0007]    In such high pressure hand held spray guns, it also is customary to have a trigger lock that prevents accidental and potentially dangerous unattended discharge of high pressure/liquid from the spray gun. Such a trigger lock typically is pivotably mounted on the spray gun handle for movement between an extended locking position that prevents actuating movement of the trigger and a retracted or unlocking position that permits trigger actuation. A problem with such trigger locks is that they can be cumbersome to manipulate and locate in a locking position, and hence, simply often are not used by an operator between operating sequences of the spray gun. 
       OBJECTS AND SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to provide a disposable hand held spray gun that is adapted for more reliable long term usage in the spraying of high pressure liquids. 
         [0009]    Another object is to provide a hand held spray gun as characterized above that has a liquid control ball valve mechanism adapted for more stable and reliable operation when spraying high pressure liquids. 
         [0010]    A further object is to provide a hand held spray gun of the above kind in which the ball valve is maintained in substantial axial alignment with the valve seat notwithstanding the sudden introduction of high pressure liquid into the valve chamber upon actuation of the spray gun. 
         [0011]    Another object is to provide such a hand held spray gun with a ball valve mechanism adapted for preventing forceful engagement of the valve ball between windings of a concentrically mounted valve seat retaining spring as an incident to the introduction of high pressure liquid into the valve chamber. 
         [0012]    Yet a further object is to provide a high pressure hand held spray gun of the foregoing type in which the valve chamber of the spray gun has an improved sealing member in which a closure and retaining screw has an annular sealing arrangement that is less susceptible to abrasion or damage during assembly and manufacture of the spray gun. 
         [0013]    Another object is to provide a hand held high pressure spray gun of such type which has locking trigger which is adapted for easier and reliable usage by an operator. A related object is to provide such a spray gun trigger lock which tends to encourage locking of the spray gun trigger following usage. 
         [0014]    Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a perspective of an illustrative spray gun in accordance with the present invention; 
           [0016]      FIG. 2  is a vertical section of the spray gun shown in  FIG. 1  taken in the plane of line  2 - 2 ; 
           [0017]      FIG. 3  is an enlarged fragmentary section of the trigger operated flow control valve of the illustrated spray gun; 
           [0018]      FIG. 4  is an enlarged fragmentary section of the trigger lock of the illustrated spray gun; 
           [0019]      FIG. 5  is a plan view of the trigger lock taken in the plane of line  5 - 5  in  FIG. 4 ; 
           [0020]      FIG. 6  is an enlarged fragmentary view of the mounting hub of the illustrated trigger lock, taken in the plane of line  6 - 6  in  FIG. 5 ; 
           [0021]      FIG. 7  is a fragmentary side elevational view of the trigger of the illustrated spray gun with the trigger lock in an inactive position; and 
           [0022]      FIG. 8  is an enlarged view of an end of the trigger lock, taken in the plane of line  8 - 8  in  FIG. 7 . 
       
    
    
       [0023]    While the invention is susceptible of various modifications and alternative constructions, a certain illustrative embodiment thereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary,, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]    Referring now more particularly to the drawings, there is shown an illustrated hand held spray gun  10  in accordance with the invention adapted for directing high pressure liquid fluid streams, up to about 5,000 psi. The illustrated spray gun  10  has a pistol configured body or housing  11  having a barrel portion  12  and a depending handle portion  14  disposed at an obtuse angle to the barrel portion  12 . The housing  11  in this case is formed by right and left hand housing sections which are secured together by a plurality of fastening screws  15 . A liquid supply line  16  is connected to an adapter fitting  18  at a lower or heel end of the handle portion  14  for supplying pressurized liquid to the spray gun  10 , such as from a pressure washer or other high liquid pressure supply source. 
         [0025]    For controlling the flow of pressurized liquid to and through the spray gun  10 , a trigger actuated valve assembly  20  ( FIGS. 2-3 ) is captively supported within the housing sections. The valve assembly  20  includes a valve body  21  having a depending portion  22  formed with an internally-threaded inlet port  24  for threadably receiving a liquid supply pipe  25  connected to and communicating with the inlet adapter  18 . An inlet port  26  of the body  21  communicates with a valve chamber  28  which in turn communicates with an outlet port  29 . The outlet port  29  communicates with an elongated liquid discharge passageway  30  in the valve body, the outlet end of which threadably receives an appropriate spray nozzle  31  from which a discharging flow spray is emitted. The valve assembly  20  includes a valve seat  32  and a valve member  34 . The valve seat  32  in this instance is in the form of an angular insert that is maintained in a sealed mounted condition with a downstream end of the valve chamber  28  by a valve seat retaining spring  35  axially biased within the valve chamber  28 . An o-ring seal  36  is interposed between a downstream side of the valve seat  32  and the end of the valve chamber  28 . 
         [0026]    The valve member  34  in this instance has a two-part construction comprising a valve ball  40  and a separate forwardly extending valve stem  41  projecting through an axial bore of the valve seat  32 . The valve stem  41  has a terminal end projecting outwardly of the valve body  21 , with an o-ring and back up ring pair  44  mounted in a counter bore  45  of the valve body  21  for effecting a sliding seal about the valve stem  41 . The valve member  34  is biased toward a valve closing position with the ball  40  seated against the seat  32  by a ball spring  46  interposed between the valve ball  40  and a counter bore in a retaining screw  47  secured within an internally threaded bore  48  leading to the valve chamber  28 . 
         [0027]    In order to move the valve member  34  between its closed position in a seated engagement with the valve seat  32  and an open position ( FIG. 3 ) that permits communication of high pressure liquid through the inlet port  26 , valve chamber  28  an outlet port  29 , a trigger  50  is pivotably mounted at  50 a on an underside of the forwardly extending portion of the valve body  21  and has a downwardly extending gripping end that is pivotable by the hand of the user while gripping the handle portion  14  of the gun. The trigger  50  in this case carries a striker pin  51  for engagement by the protruding end of the valve stem  41 . Upon release of the trigger  50  during operation of the gun, the ball spring  46  and the pressure acting against the valve ball  40  will urge the valve ball toward and into engagement with the valve seat  32  with the valve stem  41  moving the trigger  50  to the right, as viewed in  FIG. 2 . 
         [0028]    As indicated above, heretofore, the introduction of high pressure liquid into the valve chamber upon actuation of the trigger can cause the valve ball to be forced laterally in the valve chamber and become jammed between coils of the valve seat retaining spring, which can prevent or impede return movement of the valve member to a closing position upon release of the trigger. Moreover, with the valve ball offset in the valve chamber as a result of such lateral movement or jamming, the ball spring can tend to engage a side of the valve of the ball, and further urge the valve ball in a jammed condition, rather than axially move the valve ball to its seated position. 
         [0029]    In accordance with the invention, the valve ball has a relatively large diameter in relation to the internal diameter of the valve seat retaining spring such that upon actuation of the spray gun and the introduction of high pressure liquid fluid transversly into the chamber the valve ball is retained by the valve seat retaining spring in substantial axial alignment with the valve seat so that upon release of the actuating trigger the ball spring will reliably return the valve ball to a shut off position. To this end, the valve ball  40  is sized relative to an internal diameter “d1” of the valve seat retaining spring  35  such that even if the high pressure liquid stream should laterally displace the ball  40 , the center  40   a  of the ball is maintained within an internal diameter “d2” of the ball spring  46 . As a result, upon release of the trigger  50 , the ball spring  46  will still exert a substantially axial force on the valve ball  40  for reliable return and shut off in the valve seat  32 , without laterally urging the ball in a direction in which it might jam or stick between coils of the concentrically mounted and surrounding valve seat retaining spring  35 . Preferably, the ball  40  has a diameter “d” that is at least ¾ the inner diameter “d1” of the valve seat retaining spring  35 . 
         [0030]    In carrying out the invention, coils of the valve seat retaining spring  35  have a pitch set such that the spacing between coils of the spring, when installed in the spring gun, are sufficiently small as to prevent the ball  40  from being lodged between the coils by high pressure liquid entering the valve chamber  28 . Preferably, the coils of the valve seat retaining spring  35 , when installed have a spacing of less than  1 / 8  the diameter of the ball  40 . 
         [0031]    In an operative embodiment of the invention, reliable performance consistent with the invention has been achieved with a valve assembly having a valve ball  40  that is 0.3125″ in diameter, a valve seat retaining spring  35  having the following specifications:
       Outer Dia.=0.480 in   Inner Dia.=0.378 in   Wire Dia.=0.051 in   Free Length=0.750 in   Installed Length=0.450 in   No of active coils=3.4   No of total coils=5.4
 
and a the ball spring  46  having the following specifications;
   Outer Dia.=0.300 in   Inner Dia.=0.198 in   Wire Dia.=0.051 in   Free Length=0.875 in   Installed Length=0.775 in   No of active coils=8.1   No of total coils=10.1       
 
         [0046]    In keeping with a further aspect of the invention, the valve mechanism retaining screw  47  has an improved sealing arrangement which is protectively contained from damage during manufacturer and assembly of the spray gun. To this end, an o-ring sealing member  55  is disposed about an upstream end of the threaded shank  56  of the retaining screw adjacent a head  58  of the screw for engaging a tapered sealing surface  59  of the valve body  21  adjacent the outwardly opening end of the threaded access opening  48  of the valve body. It will be appreciated by one skilled in the art by locating the o-ring  55  about the retaining screw in such manner prior to threadedly engaging the retaining screw  47  into the threaded access opening  48  of the valve body, the o-ring sealing member  55  is not moved or positioned over the threads of the opening  48  of the valve body during assembly, and hence is not subjected to possible abrasions that can result from rubbing contact with the threads of the body access opening that can cause premature failure and substantial shortening of the life of the spray gun. Instead, the o-ring  55  can be more easily and assuredly positioned over the threaded shank  56  of the screw prior to assembly with the spray gun without damaging contact with the screw threads. 
         [0047]    In carrying out a further aspect of the invention, the spray gun has a trigger lock  60  that is adapted for easy and reliable operation, which encourages usage for preventing unintended potentially dangerous discharge from the spray gun. The trigger lock  60  in this case is in the form of an elongated finger pivotably mounted from a lower end of the trigger  50 . For pivotably supporting the trigger lock  60 , the trigger lock  60  has a pair of axially-spaced lugs  61  with axial mounting pins  62  for positioning in mounting apertures  63  in the trigger  50 . The mounting hubs  61  of the trigger lock  60  have generally cylindrical configurations disposed within a semi-circular recess  64  in the trigger  50 , as depicted in  FIG. 4 and 6 . 
         [0048]    In carrying out the invention, the trigger lock mounting hubs  61  each has a locating nib  65  that is positionable against a peripheral locating corner  66  of the trigger recess  64  for locating and orienting the trigger lock  60 , for engagement with a locking recess or aperture  68  ( FIG. 2 ) in the spray gun housing. The locating nibs  65  further defines a detent which can be forcefully past over the locating corner  66  of the trigger recess  64  upon further clockwise pivotable movement of the trigger lock  60 , as viewed in  FIG. 4 , into an inactive position adjacent the back side of the trigger as viewed in  FIG. 1 . For releasably retaining the trigger in such an inactive position, detent nibs  69  are provided on a flange  50   b  ( FIGS. 7 and 8 ) of the trigger  50  for positively retaining the trigger lock  60  in such position. It will be understood by a person skilled in the art that the trigger lock  60  can be easily moved to and retained in an inactive position during usage of the spray gun and also be easily located in position with the assistance of the locating nib  65  for locking the trigger during periods of non-use of the spray gun for preventing accidental dangerous high pressure discharge from the spray gun. 
         [0049]    From the foregoing, it can be seen that the hand held spray gun of the present invention can be manufactured as a disposable product with long term reliable usage in spraying high pressure liquids. The spray gun has a liquid control valve mechanism that is adapted for more stable and reliable operation without jamming as an incident to controlling the flow of high pressure liquids to the valve mechanism. The spray gun further has an improved valve mechanism sealing arrangement and a trigger lock design that encourages safe usage of the spray gun.
A hand-held trigger operated spray gun for dispersing high pressure liquids. The spray gun includes a control valve assembly which has a first annular coil spring for maintaining a valve seat in position and a second annular coil spring for biasing a valve ball into closing engagement with the valve seat. The valve ball is sized such that the valve seat retaining spring retains it in centered relation to the ball biasing spring even when subjected to high liquid pressure fluctuations. The spray gun further has an improved sealing and trigger lock features.