Abstract:
An improved supply/shut-off valve for use in a multiple-user gas system wherein the valve is located in the gas supply line of each user, for the purpose of preventing pressure increases and decreases in the gas supply to each of the users when any of the other users is either added to or deleted from the multiple-user gas system.

Description:
FIELD OF THE INVENTION 
     The invention relates to an improved supply/shut-off valve, and more particularly relates to an improved supply/shut-off valve for use in a multiple-user gas system of the type having a plurality of users. 
     BACKGROUND OF THE INVENTION 
     In multiple-user gas systems of the type having a plurality of users each of which is operating a separate although usually identical gas using apparatus, problems can occur when any one of those independent users either suddenly discontinues use, or if such a user was not previously using gas suddenly begins use. More specifically, an example of a multiple-user gas system would be a multiple station air operated spray painting system. In such a system each of a plurality of spray paint operators has a hand held air atomized spray gun, each gun of which is connected to a central or common air source. The problem occurs when any one of those operators either discontinues use or begins use of a gun that was not previously in use. The conventional supply/shut-off device provided at each of the air operated paint spray guns in a multiple-user system simply turns-on or turns-off the air supply without any consideration of the other operators. In a compressible gas system the volume of gas maintained in the lines to each of the multiple users from the common source will suffer either a pressure increase spike when use is discontinued or a sudden pressure decrease at the moment when use of a previously unused nozzle is commenced. This pressure increase or decrease is only a momentary occurence since the system is a flow system and each of the guns in use will quickly bleed off the excess pressure or the central air supply unit will make up the defficiency in pressure thereby overcoming the spike or dip, depending upon what has occurred. However, during that momentary pressure increase or decrease, the delicate balance between air usage and paint usage is interrupted. If there is a pressure increase the paint spray guns remaining in use will over-atomize the paint thereby causing &#34;over-spray&#34;, which will result in an improper paint job or if a momentary pressure decrease occurs there will be under-atomization for a short period of time on the remaining nozzles resulting in paint globules of too large a size. Either of these conditions results in an improper paint job and heretofore there has been no practical method of solving such a problem, manufacturers and spray paint operators simply having learned to live with the problem. 
     Therefore, there is a need for an improved supply/shut-off device specifically for use in a multiple-user gas system of the previously described type that will allow for any one of the multiple gas users to either discontinue or to re-commence use of his gas using machine. 
     SUMMARY OF THE INVENTION 
     The present invention is a method of preventing gas pressure variations in a multiple-user gas system of the type previously described. At each of the independent gas users (machines) an improved supply/shut-off valve is installed in the gas supply line. The improved supply/shut-off valve is a valve having a valve body with inlet and outlet ports. The valve is completed with a valve internal that is mounted within the valve body. Additionally, means, as for example a handle, are provided for rotating the valve internal within the valve body between its various positions. The valve internal has an aperture which is configured in one position to the inlet and outlet ports of the valve body so that when the valve is in its supply position, gas will freely flow from the gas supply source through to the gas user machine. The valve internal additionally has a second position in which in the internal is positioned such that when the aperture of the rotatably mounted internal is not aligned with the inlet and outlet ports of the valve body, a diverting port is in communication with the inlet port and the exterior of the valve body. The diverting port is specifically sized to have the gas capacity and gas pressure drop of the gas user, machine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The best mode contemplated in carrying out this invention is illustrated in the accompanying drawings in which: 
     FIG. 1 is a schematic representation of a multiple-user gas system utilizing the supply/shut-off valve according to the present invention. 
     FIG. 2 is a perspective view of the supply/shut-off valve according to the present invention. 
     FIG. 3 is a cross section of the valve of FIG. 2 in the supply position taken along line 3--3 of FIG. 2. 
     FIG. 4 is a cross section of the valve of FIG. 2 in the diverting position, the cross section taken along line 3--3 of FIG. 2. 
     FIG. 5 is a cross section of the valve of FIG. 3 taken along line 5--5 of FIG. 3 with valve internal rotated to the position shown in FIG. 4. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings, FIG. 1 depicts a multiple-user system in which six, an arbitrary number, air atomized paint spray guns 10 are connected to a common compressed air source line 12. Each paint spray gun 10 has a supply/shut-off valve 14 in the compressed air line to the gun. When any operator operating his individual paint spray gun 10 desires to discontinue spray painting he will turn his supply/shut-off valve 14 to the off position. Additionally when such an operator returns to his paint spray gun 10, as for example, at the beginning of the work shift or after having discontinued use, he desires to commence or re-commence spray painting operations he will turn his supply/shut-off valve 14 to it on position. The supply/shut-off valve may be located at the spray gun 10 or at the manifold, both positions are shown in FIG. 1. 
     With reference to FIG. 2 which is a perspective view of the supply/shut-off valve 14 according to the present invention, which is a stem type valve in which the valve interal 16 is preferably a stem, rotatably mounted within valve body 18. The valve body 18 has inlet port 20 and outlet port 22 located 180° apart upon the valve body. Additionally in the embodiment shown in FIG. 2, a means 24 for rotating the valve internal 16 within valve body 18 is preferably a knob which in this case is simply an extension of the stem. 
     It will be appreciated that the rotatable valve internal may also be a ball and that a valve body configured to receive a bal type rotating valve internal would be equivalently effective. 
     The function of the supply/shut-off valve is more clearly understood by reference to FIGS. 3 and 4. Referring initially to FIG. 3, valve internal 16 can be seen mounted within valve body 18 and additionally the disposition of inlet port 20 and outlet port 22 relative to the valve internal and valve body is more clearly perceived. Valve internal 16 is rotatably maintained within valve body 18 by O-ring 26 and the end of the valve internal is maintained lockably within the valve body by retaining means 28. In the position of the valve internal within valve body 18 as shown in FIG. 3, compressed gas passing from the common compressed air source 12 travels to inlet port 20 through the aperture 30 which is bored through valve internal 16 and exiting the valve body via outlet port 22. It will be appreciated that aperture 30 is preferably a full-ported aperture relative to the inlet and outlet ports of the valve body 18 so that the pressure drop through the supply/shut-off valve to the paint spray gun 10 is minimized. The positioning of the valve shown in FIG. 3 is that position in which the operator would maintain the supply/shut-off valve 14 in order to operate his paint spray gun 10. 
     Turning now to FIG. 4 which represents the configuration of supply/shut-off valve 14 when the valve is in the shut-off position. In the cross sectional view represented in FIG. 4 again the positioning of the valve internal 16 relative to the valve body 18 and also relative to the orientation of inlet port 20 and outlet port 22 shows that flow through aperture 30 cannot occur. However, flow is achieved from inlet port 20 through diverting port 32 which in the configuration shown in FIG. 4 diverts the inlet air or gas to the atmosphere. The sizing of diverting port 32 is very critical indeed. Diverting port 32 is specifically sized and designed to have the same gas or air capacity as the paint spray gun 10 and additionally to have the same pressure drop as the paint spray gun 10 thereby simulating the existence of the paint spray gun 10 even when the air supply to that gun has been interrupted by the supply/shut-off valve 14. 
     In operation in a multiple-user system such as that shown in FIG. 1, supply/shut-off valve 14 functions to prevent a pressure increase when the supply of air to a particular paint spray gun has been interrupted by the operator or alternatively, the air pressure decrease that would normally be experienced by the initiation of air supply to a paint spray gun. It can be seen that by the operation of the supply/shut-off valve 14 according to the present invention, that no such pressure peak or dip will occur because of its operation. Therefore, there will be no noticeable change in the air pressure and supply characteristics to the other operating paint spray guns in the multiple-user system. 
     It will be appreciated that the diverting port 32 could also vent to some other place than to the atmosphere through a vent port in the valve body 18, not shown in this configuration. 
     Referring now to FIG. 5, the specific location of diverting port 32 relative to aperture 30 within the valve internal 16 of a supply/shut-off valve is of critical importance since it is necessary for the diverting port 32 to come into play by diverting inlet air through valve 14 to the atmosphere prior to the complete elimination of air flow through the valve and out of outlet port 22. An electrical analogy to such an operation is that the diverting port must be &#34;made&#34; before the aperture flow is &#34;broken&#34;; a make-before-break concept. Therefore, FIG. 5 indicates that diverting port 32 is encountered by inlet port 20 at an angular location of less than 90° from the axis of aperture 30. It is necessary to have the make before break location of diverting port 32 in order to assure a smooth transition between flow through aperture 30 and air flow through the pressure drop device diverting port 32. 
     It will be apparent from the above that the present invention provides a means for smoothly adding or removing a gas user to a multiple-user gas system so as to prevent pressure increases or decreases to the other users during the transition of adding or removing a user.