Abstract:
A flow system includes a proportional valve constructed of chemically inert materials (PTFE) to produce variable fluid flow rates of liquids including inert, and high purity, and even highly corrosive liquids. Gases of many varieties can also be flow controlled. The valve may be precisely set, either manually, or by use of an actuating motor, remotely or electronically, for various flow rates for the required fluid. The valve allows for specific proportional flow parameters to be programmed into valve structure and configuration to provide precise and repeatable highest resolution flow control for a wide variety of complex flow conditions (pressure, temperature and viscosity).

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to flow measurement and control systems and proportional valves for providing variable programmed flow rates in fluids in such systems. 
   2. Description of the Related Art 
   So far as is known, existing liquid flow control valve devices for proportional flow control applications have certain shortcomings or inadequacies. Proportional solenoid operated valves or a diaphragm valves have rapid operating speed. However, there are problems in programming solenoid and diaphragm valves inexpensively for accurate flow control under widely varying flow conditions. 
   Rotatable control valves typically have good flow control resolution and can hold flow set points. However, rotatable control valves are slow to respond. Further, rotatable control valves have problems with achieving high resolution over a wide range of flow rates in a relatively small valve size. In addition, programming for accurate flow control over a wide variety of flow conditions is often a problem. 
   Valve designs other than rotatable control valves have included diaphragm actuation for flow control and generally used more expensive diaphragm structure. These other types of valves do not have, so far as known, programmable actuating features. These other types of valve designs did not have programmable flow characteristics over widely varying flow conditions; higher resolution; and inexpensive programming characteristics. 
   A particular problem has been present when the fluid was in the form of a slurry, such as a polishing slurry of the type used in the semiconductor industry. These types of slurries often contained abrasive materials. Over a service life, it was necessary to adjust the valve flow control settings to compensate for component wear because of the effect of the abrasive materials in the slurries. 
   SUMMARY OF THE INVENTION 
   Briefly, the present invention provides a new and improved flow system for a fluid. The flow system includes a new and improved flow controller and may be a flow measuring system or a flow control system. The flow measuring device of the present invention includes a housing body having a flow receiving chamber in it, and a flow inlet and flow outlet for fluid supply to the flow receiving chamber. 
   An adjustable diaphragm member is formed along a portion of the flow receiving chamber of the flow measuring device and an actuator is provided to control the position of the adjustable diaphragm member to regulate the flow of fluid through the housing body. The actuator takes the form of a motor driving a cam and connected by a linkage to the adjustable diaphragm member to control the position of the diaphragm member to regulate the flow of fluid. 
   The flow system of the present invention may take the form of a flow measuring system with a flow controller of the present invention operating in conjunction with a flow sensing device. The flow system of the present invention may also take the form of a flow control system with a flow controller of the present invention operating in conjunction with a flow sensing device and a control device such as a computer or processor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation view, taken in cross-section, of a proportional valve and flow measuring system according to the present invention. 
       FIG. 2  is an enlarged view of a portion of the proportional valve of  FIG. 1  encircled and having reference numeral  2  designating same. 
       FIG. 3  is a view taken along the lines  3 — 3  of  FIG. 2 . 
       FIG. 4  is a view taken along the lines  4 — 4  of  FIG. 3 . 
       FIG. 5  is a side elevation view, taken in cross-section, of the proportional valve and flow measuring system of the present invention with fluid flow in a different direction from that of  FIG. 1 . 
       FIG. 6  is a schematic diagram of a flow control system according to the present invention based on the flow measuring system of  FIG. 1  and a control computer. 
       FIG. 7  is an enlarged view of a portion of the structure of proportional valve of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the drawings, the letter F ( FIG. 6 ) designates generally a flow control system for controlling the flow of a fluid to desired flow parameters according to the present invention. The flow control system F includes a flow control valve V ( FIGS. 1 and 2 ) in the form of a proportional valve, a flow measuring device or apparatus M ( FIGS. 1 and 2 ) to measure the flow of the fluid, and a flow control device or computer C ( FIG. 6 ).  FIG. 5  of the drawings shows the flow control system F of the present invention of like structure to  FIG. 1  but arranged to receive fluid flow in a reverse direction from that of  FIG. 1 . The flow control system F is suitable for fluids including liquids and gasses. The liquids may be inert or high purity, or even highly corrosive liquids, or slurries containing any of the foregoing types of liquids. The flow control system F of the present invention is also suitable for use with a wide variety of gasses to control the flow of the gas to desired flow parameters. 
   Considering first the proportional flow control valve V, a housing body  10  is preferably formed of an organic polymer, such as polytetrafluorethylene (PTFE), which is corrosion resistant so that the valve V may be used with both corrosive fluids and non-corrosive fluids. A flow inlet  12  is formed in the housing body  10  and communicates through a passage or conduit  14  to a flow receiving chamber  16 . The flow-receiving chamber  16  is formed by removing a portion of a front wall  11  adjacent a surface  11   a  of the housing body  10 . The flow-receiving chamber  16  is located between an annular flat surface  17  on a seal-receiving groove or slot  19 . The annular flat surface  17  is located in a common plane with the front wall  11  and is adapted to be contacted by an adjustable diaphragm member  22 . One or more, in the embodiment disclosed three, flow passages  18  are formed in the front wall  11  of the housing body  10 . The number and size of flow passages  18  are based on flow requirements to conduct fluid from the flow receiving chamber  16  to a flow manifold or outlet  20  formed in a lower surface  21  of the housing body  10 . 
   The adjustable diaphragm member  22  ( FIGS. 1 and 4 ) of the flow control valve V, along with a surface portion  11   a  of the front wall  11  of the housing body  10 , form the walls of the flow receiving chamber  16 . The adjustable diaphragm member  22  is also preferably formed from PTFE so that corrosive fluids may flow through the flow control system F. The adjustable diaphragm member  22  is movable selectively inwardly and outwardly in response to an actuator assembly A to adjust the flow of fluid through the flow receiving chamber  16  and consequently through the flow housing body  10 . As will be set forth, the adjustable diaphragm member  22  may move from a fully open position for maximum flow through the chamber  16  and the valve V to a fully closed position blocking flow of fluid through the valve V. 
   The flow measuring device M is mounted with the flow control valve V in fluid communication with the flow receiving chamber  16  through fluid outlet  20 . As has been mentioned above, the system of  FIG. 5  illustrates a flow control system like that of  FIG. 1 , but adapted to measure fluid flow. The flow measuring device M may be any of several types, depending on the type of fluid being measured, the operating conditions and the desired flow parameters, for example. The flow measuring device may be, by way of example, a turbine flow wheel flow measuring transducer of the types described in the U.S. Pat. Nos. 5,542,302; 5,728,949 or 4,467,660, each owned by the assignee of the present application. The subject matter of each of these patents is specifically incorporated herein by reference. For turbine flow wheel flow measuring transducers, the arrangement and mounting of the flow measuring transducers may be adjusted depending on the flow of fluid through the measuring system. 
   It should be understood, however, that the other types of flow rate sensors or measuring transducers may also be used with the present invention in place of the turbine wheel types discussed above. Examples of flow rate sensors based on other types of designs or technologies which could be used in connection with the present invention include the following types: impeller or Pelton wheel flow sensors; differential pressure sensing flow rate sensors; ultrasonic flow rate sensors; thermal detection flow rate sensors; Coriolis effect flow rate sensors; vortex shedding flow rate sensors; and other types as well. 
   The flow measuring device or transducer M includes a transducer body  28  which is mounted to the housing body  10  of the flow control valve V through a connector or middle body  30  with dowel pins or other suitable connecting mechanisms. An annular fluid flow passage  34  is formed between the housing body  10  and the transducer body  28  to permit fluid flow from the fluid outlet  20  to a fluid inlet passage  36  of the flow measuring device M. The flow measuring transducer, such as a turbine wheel  38  in the flow measuring device M senses and measures the flow of fluid through the flow control system F. A transducer fluid outlet passage  40  allows fluid to flow from the measurement transducer  38  to an exit port or passage  42  in an outlet plug or tap  44  mounted with or integrally formed with the transducer body  28 . As is shown in  FIG. 1  and  FIG. 5 , the transducer M is adapted for fluid flow measurement in either direction of fluid flow. The structure of  FIGS. 1 and 5  is the same except for the arrangement of the flow measuring transducer  38  which is determined by the direction of flow of the fluid to be measured. For this reason like reference numerals are used in  FIGS. 1 and 5 . 
   The measurements from the flow measurement transducer M are provided as information signals to the flow control device or computer C ( FIG. 6 ) and there compared with a specified or established flow parameter. Variations in the flow parameters indicated as a result of comparisons in the computer C are sensed and used to form correction signals which are furnished to the actuator assembly A by the computer C to adjust the flow through the valve V and achieve the specified or established flow parameters in the flow control system F. 
   Considering now the structure of the flow control valve V, the flow passage  12  is connected to an inlet passage  50  in a flow inlet plug or housing tap  52  mounted with or integrally formed with the housing body  10 . The flow passage  50  is of like diameter to the flow passage  12 , which is connected to the flow passage  14  at a transition point  54 . Fluid enters the flow receiving chamber  16  where flow control occurs in response to relative movement of the adjustable diaphragm  22  by the actuator A either by control signals from the computer C or by appropriate other input such as manual input entered as controls to the actuator A from an equipment operator. The outlet flow passage  18  leads from the flow receiving chamber  16  to an elbow  18   a  and an extension  18   b  and thence to flow outlet  20 . 
   The housing body  10  is mounted with a top support plate  60  by a suitable number of appropriately spaced mounting nuts  62  and washers  64  such as Belleville washers. A bearing block  70  is mounted by connecting screws  72  to the rear wall or surface  26  of the housing body  10  beneath the top support plate  60 . The flow receiving chamber  16  is formed by the adjustable diaphragm  22  in an inner central portion of the space between the bearing block  70  and the housing body  10 . The adjustable diaphragm member  22  is mounted as one wall of the flow receiving chamber  16  and is engaged around outer surface portions  22   a  by an O-ring  76  or other suitable seal mounted in a seal receiving groove  78  formed on the rear surface  26  of the housing body  10 . 
   The adjustable diaphragm member  22  of the proportional valve V is formed from a sheet  80  ( FIGS. 2 and 4 ) of corrosion resistant synthetic resin, preferably PTFE, and is generally rectangular in form and of suitable thickness based on fluid flow conditions, valve responsiveness and accuracy, and other considerations. In one embodiment, the PTFE sheet  80  is about 0.015″ thick. Openings  81  are formed in the sheet  80  for passage of connectors or screws  79  to mount the diaphragm member  22  with the housing body  10 . The connectors are received in sockets  11   b  formed in the front wall  11  of housing body  10 . 
   A circular indentation or rim  82  ( FIGS. 2 and 4 ) is formed in a central portion  84  of the adjustable diaphragm member  22  extending away from a front surface  86  of the PTFE sheet  80 , facing inwardly towards the flow receiving chamber  16  of the housing body  10 . A typical diameter of the circular rim  82  is 0.625″. The depth of the indentation is such that an inner surface  88  of the adjustable diaphragm member  22  extends about one-third of its thickness, or 0.005″, inwardly as indicated by arrows  89  ( FIGS. 2 and 7 ) in the area of the circular indentation  82 . A flexed inwardly extending central hub area  90  is formed in the adjustable diaphragm member  22  within the circular indentation  82  extending at its inner surface  88  towards the flow receiving chamber  16 . 
   The adjustable diaphragm member  22  is flexible and the central hub area  90  is movable inwardly and outwardly with respect to the flow receiving chamber  16  in response to the actuator A to selectively vary the flow through the proportional valve V according to the expected fluid flow rate and control condition. A typical range of such movement of the central hub area  90  is about that of the thickness of the sheet  80 , or 0.028″ in the embodiment shown in the drawings, based on the dimensions of a cam  100  in the actuator A to be described below. Adequate movement is provided so that an innermost portion  90   a  of the hub area  90  at its innermost position sealingly engages the annular flat surface  17  between the flow receiving chamber  16  and the port at the innermost inward travel position in order to seal and block flow of fluid through the proportional valve V. 
   A seal device in the form of an O-ring seal  91  is formed in the seal-receiving slot or groove  19  in the housing body  10 . The O-ring seal  91  may be made from any suitable sealing material according to the fluid in the valve V, and is provided to seal the surface between diaphragm  22  and the housing body  10 . A backup washer pad or gasket  93  is provided between the diaphragm member  22  and a pusher rod assembly  92  of the actuator assembly A. The washer  93  is formed of a suitable material such as fluoroelastomer sold under the trademark Viton® from DuPont Dow Elastomers. The backup washer  93  provides a resilient, compliant material between the piston rod  92  and the diaphragm  22 . The resilient fluoroelastomer washer  93  functions as a spring, and also provides protective wear prevention and overtravel protection. 
   A pusher rod  92  of the actuator assembly A has an inner end  92   a  contacting a rear surface  90   b  of the hub area  90  of the adjustable diaphragm member  22  to cause relative movement of the adjustable diaphragm member  22 . The pusher rod  92  is received within a bushing member  94  for relative inward and outward movement. The bushing member  94  is mounted within the bearing block  70  and moves reciprocally to vary the relative position of the adjustable diaphragm member  22  and vary the volume of the flow receiving chamber  16 . 
   The pusher rod  92  has an arcuate curved rear surface  92   b  at an opposite end from the adjustable diaphragm member  22  to engage and respond to a cylindrical outer surface  96 a of a rotatable cylindrical bearing  96 . The cylindrical bearing  96  is rotatably mounted on a bearing roller shaft  98  within the proportional valve V, and the cylindrical bearing  96  and roller shaft  98  are adapted for relative movement within the proportional valve V in response to a cam member  100  of the actuator assembly A. 
   The cam member  100  is preferably a vertically reciprocating cam which has a tapered contact surface  102 . The cam member  100  is shown in a full open position in  FIGS. 1 and 2  at its uppermost position. The cam member  100  is adapted to move upwardly and downwardly in response to an electric motor  104  which incrementally moves an extendable shaft  105  in response to control signals from the computer C or other input control signals from an operator or other input source. A suitable motor  104  in the preferred embodiment of the present invention is of the commercially available type known as a linear stepper motor. 
   The surfaces of the cam member  100  ( FIG. 7 ) are ground and polished, both along the contact surface  102  and an oppositely facing rear portion  103 . The contact surface  102  has an initial lower flat portion  102   a  ( FIG. 7 ) extending vertically upwardly a suitable distance as indicated at D, such as 0.100″, and the rearwardly tapering or sloped upper portion  102   b . In the disclosed embodiment, the taper of surface  102   b  is at an angle  102   c  of 1.124° or an amount of 0.028″ rearwardly from the vertical flat surface  102   a . Depending upon the particular flow control application, and requirements, the slope of surface  102   b  can be differently configured or selected. The contact surface  102  of the cam member  100  thus has a shape and dimension conformed to calculations defining the requisite movement of the pusher rod  92  and the adjustable diaphragm member  22 . As noted, the slope of surface  102   b  is chosen according to the desired parameters of flow through the proportional valve V and based on varying conditions of flow of fluid through the proportional valve V. 
   The cam member  100  is mounted, such as by a set screw  106 , with shaft  105  of the motor  104 . The shaft  105  extends from a motor shaft housing  108  of motor  104  and is advanced or withdrawn on activation of the motor  104 . The motor  104  of valve V also preferably has a static characteristic of holding the presently established position (and thus the flow set point of the cam  100  of actuator A) without power or forces being applied to the shaft  105 . The actuator A thus holds its last position without user intervention—unlike a spring loaded electromagnetic valve which loses position at power off mode. This is particularly helpful for processes that have steps which need fastest return to a previous flow setting, after a major process disruption occurs. 
   The motor  104  is mounted with a motor support plate  110  spaced from a motor mounting housing or plate  112  by spacer or mounting screws  114 . The motor mounting housing or plate  112  is mounted to a lower plate or base member  116  of the valve V by mounting or spacer screws  118 . The relative position of the motor plate  112  is initially adjusted to set the shut-off position of the valve V and also to locate the motor  104  and its shaft  105  on an axis perpendicular to the axis of movement of the pusher rod  92 . The lower plate  116  and top support plate  60  are connected by a set of spacer or mounting screws  121  or other suitable structure such as a rear wall, if desired. 
   The bearing  96  which contacts the pusher rod  92  and a rear or back up bearing  120  of the actuator assembly A are mounted with a bearing holder plate  122  beneath the top support plate  60 . The bearing holder plate  122  is connected by a shoulder bolt  124  with associated Belleville washer  126  to the top support plate  60 . An adjustment block  130  is mounted to the top support plate  60  by an adjustment screw  132  and to the bearing holder plate  122  by an adjustment screw  134 . 
   The adjustment structure of the valve V is used for initial set-up and calibration. Initially, the cam member  100  is moved to its fully upwardly extended position so that the flat surface  102   a  engages the rear of actuator rod  92 . The diaphragm  22  is in a flow blocking position in contact with the annular flat surface  17  on the housing body  10 . The position of adjustment screw  134  in the adjustment block  130  is moved to cause the backup bearing  120  to engage and support the cam member  100 . 
   It can thus be seen that the valve V includes the external actuating pusher rod or shaft  92  that is mechanically moved by a customized profile cam contact surface  102 . The actuating rod  92  presses against the adjustable diaphragm member  22  which is a flexible synthetic resin (typically PTFE). The cam contact surface  102  is configured so that it can be moved to position causing the diaphragm member  20  to close/open a PTFE flow path in chamber  16  between the diaphragm  22  and the PTFE housing body  10 . The fluid flows toward the diaphragm  22  from passageway  14 . The flow rate is controlled by the relative position of diaphragm  22  as established by the actuator A. Return flow from the chamber  16  is through an exit flow path beginning at outlet flow passage  18 . 
   The relative size and position of the inlet passage  14  and outlet passage  18  in housing body  10  are customizable to match specific flow parameters. As the actuator rod  92  is pressed against the diaphragm  22 , the flow through chamber  16  is gradually restricted. At the innermost end of the stroke of the actuator rod  92 , fluid passage through chamber  16  is closed to stop flow of the fluid through the valve V. 
   As the actuator rod  92  is moved away from the diaphragm  22 , the flow gradually increases, up to a maximum flow rate which is obtained through the valve V with the diaphragm  22  fully retracted. During the movement of the actuator rod  92 , the flow rate is changing according to pre-programmed features in the profiled cam surface  102  based on the specific flow parameters for the exact fluid, pressures, temperature and viscosity. 
   The proportional valve V also permits adjustment of movement of diaphragm  22  by actuator A by setting the travel range of actuating cam  100 . This adjustment provides a capability to compensate for any wear of the diaphragm  22  or its mating surface  26  in the housing body  10  in the flow control region of the valve. Over time, and especially when using polishing slurries, some component surface wear may occur. If no adjustment is provided, the fully closed flow position of the valve would eventually permit some amount of flow as wear occurs. Also, without adjustment component wear would compromise the accuracy of movement of cam  100  to precisely provide for proportional flow control over the specified possible flow range. 
   The valve V according to the present invention thus has programmable flow characteristics, allowing it to produce more accurate flow control over widely varying conditions or the fluid flow parameters, and is suitable for proportional flow control of most fluids, including highly corrosive liquids. Flow rates can be controlled with a great degree of resolution from a few mL/min up to several L/min with a relatively small size valve. 
   Flow characteristics can be programmed easily and inexpensively into the valve in a manufacturing/production environment, providing a low-cost solution. The flow system F of the present invention can be used with polishing slurries, with its adjustment for wear during extended use, as described above. This is advantageous, since certain industrial processes such as semiconductor processes often use these slurries which contain abrasive materials. As noted above, other uses for the flow system F include: gas or vapor flow control, steam flow control, or for flow control of mixtures of gas and liquid. 
   The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, and components, as well as in the details of the illustrated construction may be made without departing from the spirit of the invention.