Abstract:
This invention relates generally to systems for depositing a material onto a surface, and more particularly, to control systems for metering the amount of material being dispensed. The present invention provides an active compensation metering system that automatically compensates for material changes due to changes in material pressure, material temperature, and material viscosity.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to systems for depositing a material onto a surface, and more particularly, to control systems for metering the amount of material being dispensed. 
     BACKGROUND OF THE INVENTION 
     Materials are often applied over surfaces using a fluid dispensing system. Generally, the fluid dispensing system includes a reservoir, a material delivery system, an application apparatus, and a control system. The reservoir stores the material. The material may include a wide variety of materials such as paints, ultraviolet (UV) acrylic gels, moisture and thermal cure silicones, and the like. The material delivery system delivers the material from the reservoir to the application apparatus. The material delivery system may include conduits for carrying the material and a control valve to control the flow of material. The application apparatus may include a spraying and/or dispensing device, and a positioning apparatus, such as a multi-degree of freedom robotic positioning apparatus. The spraying or dispensing devices are commonly attached to the positioning apparatus, which provides accurate positional displacement relative to an article in which the material is being applied. 
     There are two basic methods of applying materials to surfaces. These include beads of material applied to specific locations on the article, and substantially uniform thickness coatings applied over large sections of the article. For most articles, the materials are typically applied using devices such as spray guns, spray nozzles, or dispensing nozzles. For spraying, such devices generally include a pressurized liquid material that is atomized by compressed gas and is then directed toward the surface to be coated. For dispensing, such devices generally include a pressurized liquid material that is dispensed through a nozzle tip in close proximity to the surface being coated. 
     Generally, the liquid material is applied during a fixed period of time. Unfortunately, changes in the viscosity of the liquid material may cause a change in the amount of liquid material that is applied to the surface during the fixed period of time. Temperature changes of the liquid material may produce a change in the liquid material viscosity. Commonly, ambient temperature changes occur in a production area, causing the viscosity of the liquid material to change. Also, changes in the pressure of the liquid material may result in a change in the amount of liquid material delivered during the fixed period of time. Additionally, some materials will change viscosity when subject to flow. Furthermore, a time-consuming manual adjustment of a control valve mounted on each spraying or dispensing apparatus is often necessary when these changes occur. 
     SUMMARY OF THE INVENTION 
     In order to overcome the above deficiencies, the present invention provides an active compensation metering system. The active compensation metering system automatically compensates for material changes due to changes in material pressure, material temperature, and material viscosity. A computerized controller included in the active compensation metering system can turn a plurality of spraying or dispensing valves on or off. Additionally, the active compensation metering system eliminates the necessity for an operator to manually adjust a control valve on the spraying or dispensing valve during a production cycle. 
     The present invention generally provides an apparatus comprising: 
     a reservoir containing a material; 
     an application apparatus for applying the material onto a surface; 
     a material control valve apparatus for regulating a volume of the material flowing from the reservoir to the application apparatus; 
     a flow measuring device for measuring the volume of the material flowing from the reservoir to the application apparatus; and 
     a controller coupled to the flow measuring device for calculating a volume flow rate during a first interval of time, and for adjusting the material control valve to obtain a predetermined volume flow rate during a second interval of time. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention will best be understood from a detailed description of the invention and a preferred embodiment thereof selected for the purposes of illustration and shown in the accompanying drawings in which: 
     FIG. 1 illustrates a schematic drawing of an active compensation metering system in accordance with a preferred embodiment of the present invention; 
     FIG. 2 illustrates a side view of a material control valve apparatus; and 
     FIG. 3 illustrates a front view of the material control valve apparatus. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although certain preferred embodiments of the present invention will be shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of the appended claims. The scope of the present invention will in no way be limited to the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc., and are disclosed simply as an example of the preferred embodiment. The features and advantages of the present invention are illustrated in detail in the accompanying drawings, wherein like reference numerals refer to like elements throughout the drawings. Although the drawings are intended to illustrate the present invention, the drawings are not necessarily drawn to scale. 
     FIG. 1 illustrates a schematic view of an active compensation metering system  10  in accordance with a preferred embodiment of the present invention. The active compensation metering system  10  includes a reservoir  12 , a material  14  contained within the reservoir  12 , a material control valve apparatus  16 , a flow measuring device  18 , an application apparatus  20 , and a computerized controller  22 . The reservoir  12  includes a pressurized vessel  24  containing the material  14 . The material  14  may comprise, e.g., paints, ultraviolet (UV) acrylic gels, moisture and thermal cure silicones, etc. A regulated gas supply system  26  is connected to the pressurized vessel  24  and supplies gas pressure or force to the material  14  contained in the pressurized vessel  24 . An outlet connector  28  is attached to the pressurized vessel  24 . A conduit  30  connects the outlet connector  28  with an inlet port  32  of a metering valve  34 . Material  14  flows from the pressurized vessel  24 , through the outlet connector  28 , through the conduit  30 , and into the inlet port  32  of the metering valve  34 . A conduit  36  connects an outlet port  38  of the metering valve  34  with an inlet port  40  of the flow measuring device  18 . Material  14  flows from the outlet port  38  of the metering valve  34 , through the conduit  36 , and into the inlet port  40  of the flow measuring device  18 . A conduit  44  connects the outlet port  39  of the flow measuring device  18  with an inlet port  46  of a manifold  48 . Material  14  flows from the outlet port  39  of the flow measuring device  18 , through the conduit  44 , and into the inlet port  46  of the manifold  48 . 
     The application apparatus  20  includes at least one applicator valve  50  (two are shown as  50 A,  50 B in FIG.  1 ). The applicator valves  50 A,  50 B may comprise a dispensing and/or spraying valve. For example, the applicator valve  50 A can be a dispensing valve that applies a bead of material onto a surface  52 A. Additionally, the applicator valve  50 B can be a spraying valve that applies a substantially uniform thickness coating over a section of the surface  52 B. 
     A conduit  54 A connects the outlet port  56 A of the manifold  48  with the applicator valve  50 A. Material  14  flows from the manifold  48  thorough the conduit  54 A and into the applicator valve  50 A. A conduit  54 B connects the outlet port  56 B of the manifold  48  with the applicator valve  50 B. Material  14  flows from the manifold  48  through the conduit  54 B and into the applicator valve  50 B. A fluid control element  58 A and a fluid control element  58 B are provided to turn on or shut off the flow of material  14  passing through the applicator valves  50 A and  50 B, respectively. The applicator valves  50 A and  50 B include flow adjusters  112 A and  112 B, respectively. The flow adjusters  112 A and  112 B are manually rotated by an operator to adjust the amount of material  14  flowing past the fluid control elements  58 A and  58 B, respectively. The material  14  leaving each applicator valve  50 A and  50 B is applied onto the surfaces  52 A and  52 B. The applicator valves  50 A and  50 B are attached to a multi-degree of freedom positioning apparatus  60  through members  62 A and  62 B, respectively. The multi-degree of freedom positioning apparatus  60 , e.g., a positional robotic apparatus, can position the applicator valves  50 A and  50 B in a desired location over the surfaces  52 A and  52 B, respectively. 
     FIG. 2 illustrates a side view of the material control valve apparatus  16 , and FIG. 3 illustrates a front view of the material control valve apparatus  16 . The material control valve apparatus  16  includes a valve position encoder  64 , a motor  66 , a coupling apparatus  68 , the metering valve  34 , a limit sensor  70  and a support housing  72 . Preferably, in the present invention, the motor  66  is a servo or stepper driven motor. The motor  66  includes an output shaft  74 . 
     The coupling apparatus  68  connects the output shaft  74  of the motor  66  with the metering valve  34 . The coupling apparatus  66  may include any suitable means to connect the output shaft  74  with the metering valve  34 . In the present invention, the coupling apparatus  66  may be a magnetic coupling apparatus  76 . The magnetic coupling apparatus  76  includes a first member  78  attached to the output shaft  74  of the motor  66 , and a second member  80  attached to a shaft  82  of the metering valve  34 . The first member  78  and the second member  80  do not physically contact each other, however, they are magnetically coupled so that rotation of the first member  78  causes rotation of the second member  80 . Rotation of the shaft  82  of the metering valve  34  causes the threaded portion (not shown) of the shaft  82  to move in an axial direction as indicated by the directional arrow  89  in FIG.  3 . This axial-movement of the shaft  82  is accomplished by the free axial movement allowed between the first member  78  and the second member  80  of the magnetic coupling apparatus  76 . Thus, rotation of the output shaft  74  of the motor  66  rotates the first member  78 , the second member  80 , and the shaft  82  of the metering valve  34 . The metering valve  34  is opened or closed by the rotation of the motor in a clockwise or counter-clockwise direction. 
     In another embodiment of the present invention, the coupling apparatus  66  may comprise a splined coupling (not shown) that allows free axial movement between the output shaft  74  of the motor  66  and the shaft  82  of the metering valve  34 . 
     The valve position encoder  64  provides rotational positional information of the metering valve  34  (e.g., digital counts) to the computerized controller  22  through a cable  84 . 
     The support housing  72  includes a motor support plate  86 , a metering valve support plate  88 , a plurality of struts  92 A,  92 B, and a mounting plate  90 . The motor  66  is attached to the motor support plate  86 , and the metering valve  34  is attached to the metering valve support plate  88 . Struts  92 A and  92 B are attached to the motor support plate  86  and the metering valve support plate  88 . The motor support plate  86  and the metering valve  34  are attached to the mounting plate  90 . The mounting plate  90  is attached to a support structure (not shown). 
     As illustrated in FIG. 1, the flow measuring device  18  includes a flow meter  94  and a flow volume encoder  96 . The flow meter  94  measures the volume of material  14  flowing through the flow measuring device  18  to the application apparatus  20 . The flow volume encoder  96  sends the information corresponding to the volume of material  14  flowing to the application apparatus  20  to the computerized controller  22  through the cable  98 . Preferably, in the present invention, the flow volume encoder  96  sends digital information such as counts per cubic centimeter, or counts per gallon. 
     As illustrated in FIG. 1, the computerized controller  22  receives information from the flow measuring device  18 , from the material control apparatus  16 , from the limit sensor  70 , and from a low level sensor  100 . The flow volume encoder  96  sends the information corresponding to the volume of material  14  flowing to the application apparatus  20  from the flow measuring device  18  to the computerized controller through the cable  84 . The valve position encoder  64  sends rotational position information of the metering valve  34  to the computerized controller  22  through the cable  98 . The limit sensor  70  sends positional limit information from the metering valve  34  to the computerized controller  22  through a cable  102 . The positional limit information is used by the computerized controller  22  to ensure that the metering valve  34  is kept within a specified operating range. The low level sensor  100  sends information to the computerized controller  22  through a cable  104 . The low level sensor  100  indicates when the material  14  level falls below a desired level in the reservoir  12 . When this low level occurs, the computerized controller  22  alerts the operator to increase the material level in the reservoir  12 . The computerized controller  22  can sound an alarm such a loud noise or a flashing light to alert the operator. Additionally, the computerized controller  22  may stop the application process when the low level occurs. 
     The computerized controller  22  operates the motor  66  of the material control valve apparatus  16  through a cable  106 . The motor  66  is rotationally operated to open or close the metering valve  34 . The valve position encoder  64  provides actual rotational positional information of the metering valve  34  so that the computerized controller  22  can operate the motor  66  to obtain a specific desired metering valve  34  opening. 
     The computerized controller  22  controls the fluid control elements  58 A,  58 B through cables  108 ,  110 , respectively. The fluid control elements  58 A,  58 B are activated to turn on or shut off the flow of material  14  through the applicator valves  50 A and  50 B, respectively. 
     In operation, the computerized controller  22  activates the fluid control elements  58 A,  58 B to turn on the flow of material  14  flowing through the applicator valves  50 A and  50 B onto the surfaces  52 A and  52 B. The computerized controller  22  determines a first volume of material  14  that passes through the flow measuring device  18  during a first interval of time. The computerized controller  22  turns off the material  14  flowing through the applicator valves  50 A and  50 B at the end of the first interval of time. During this first interval of time, the computerized controller  22  acquires the first volume of material  14  measurement from the flow volume encoder  96  during the time from the start of the first interval of time to the end of the first interval of time. 
     Additionally, during the first interval of time the computerized controller  22  accumulates a first total length of time during which any applicator valve  50 A and  50 B is open. Next, the computerized controller  22  calculates a first volume material  14  flow rate by dividing the first volume of material  14  by the first total length of time during which any applicator valve  50 A or  50 B is open. 
     Next, the computerized controller  22  compares the first volume of material  14  flow rate to a predetermined volume flow rate. The predetermined volume flow rate indicates the desired amount of material  14  to be applied onto the surfaces  52 A and  52 B by all of the applicator valves (e.g.,  50 A and  50 B), respectively. 
     If the first volume of material  14  flow rate is less than the predetermined volume flow rate, the computerized controller  22  adjusts the metering valve  34  to a further open position by sending a command to the motor  66  of the material control valve apparatus  16 . The valve position encoder  64  verifies the opening of the metering valve  34 . If the first volume flow rate is greater than the predetermined volume flow rate, the computerized controller  22  adjusts the metering valve  34  to a further closed position by sending a command to the motor  66  of the material control valve apparatus  16 . 
     The computerized controller  22  determines a second volume of material  14  that passes through the flow measuring device  18  during a second interval of time. The computerized controller activates the fluid control elements  58 A,  58 B to turn on the flow of material  14  through the applicator valves  50 A and  50 B onto the surfaces  52 A and  52 B. During this second interval of time, the computerized controller  22  acquires the second volume of material  14  measurement from the flow volume encoder  96  during the time from the start of the second interval of time to the end of the second internal of time. The computerized controller than deactivates the fluid control elements  58 A,  58 B to turn off the flow of material  14  through the applicator valves  50 A and  50 B onto the surfaces  52 A and  52 B. Next, the computerized controller  22  calculates a second volume of material  14  flow rate by dividing the second volume of material  14  by the second interval of time. Next, the computerized controller  22  compares the second volume flow rate to the predetermined volume flow rate. If further adjustment is necessary the computerized controller  22  further opens or closes the metering valve  34  and repeats the above process, until the desired predetermined volume flow rate is achieved. 
     Thus, as the viscosity or pressure of the material  14  varies, the active compensation metering system is able to adjust the metering valve  34  to maintain a desired standard material flow rate that results in a desired material  14  application thickness and coverage by the plurality of applicator valves  50 A and  50 B onto the surfaces  52 A and  52 B. Also, if the applicator valves  50 A and  50 B speed of movement over the surfaces  52 A and  52 B should change, the active compensation metering system is able to adjust the metering valve  34  to maintain the desired standard material flow rate that results in a desired material  14  application thickness and coverage by the plurality of applicator valves  50 A and  50 B onto the surfaces  52 A and  52 B. 
     Initial manual adjustment of the flow adjuster  112 A and  112 B is generally required prior to turning on the active compensation metering system  10 . Further, manual adjustment of the flow adjuster  112 A and  112 B is not required after the active compensation metering system  10  is activated, since the computerized controller  22  can automatically adjust the metering valve  34  to provide the predetermined flow rate. 
     The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teaching. For example, a plurality of material  14  application devices (e.g., spray guns, spray nozzles, dispensing devices, etc.) can be simultaneously connected to the active compensation metering system  10 . The application devices may apply material  14  onto a wide variety of surfaces (e.g., metal, circuit boards, plastic, etc.). Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.