Flow system with high resolution proportional valve with customizable performance

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).

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.

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. 5of the drawings shows the flow control system F of the present invention of like structure toFIG. 1but arranged to receive fluid flow in a reverse direction from that ofFIG. 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 body10is 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 inlet12is formed in the housing body10and communicates through a passage or conduit14to a flow receiving chamber16. The flow-receiving chamber16is formed by removing a portion of a front wall11adjacent a surface11aof the housing body10. The flow-receiving chamber16is located between an annular flat surface17on a seal-receiving groove or slot19. The annular flat surface17is located in a common plane with the front wall11and is adapted to be contacted by an adjustable diaphragm member22. One or more, in the embodiment disclosed three, flow passages18are formed in the front wall11of the housing body10. The number and size of flow passages18are based on flow requirements to conduct fluid from the flow receiving chamber16to a flow manifold or outlet20formed in a lower surface21of the housing body10.

The adjustable diaphragm member22(FIGS. 1 and 4) of the flow control valve V, along with a surface portion11aof the front wall11of the housing body10, form the walls of the flow receiving chamber16. The adjustable diaphragm member22is also preferably formed from PTFE so that corrosive fluids may flow through the flow control system F. The adjustable diaphragm member22is movable selectively inwardly and outwardly in response to an actuator assembly A to adjust the flow of fluid through the flow receiving chamber16and consequently through the flow housing body10. As will be set forth, the adjustable diaphragm member22may move from a fully open position for maximum flow through the chamber16and 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 chamber16through fluid outlet20. As has been mentioned above, the system ofFIG. 5illustrates a flow control system like that ofFIG. 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 body28which is mounted to the housing body10of the flow control valve V through a connector or middle body30with dowel pins or other suitable connecting mechanisms. An annular fluid flow passage34is formed between the housing body10and the transducer body28to permit fluid flow from the fluid outlet20to a fluid inlet passage36of the flow measuring device M. The flow measuring transducer, such as a turbine wheel38in the flow measuring device M senses and measures the flow of fluid through the flow control system F. A transducer fluid outlet passage40allows fluid to flow from the measurement transducer38to an exit port or passage42in an outlet plug or tap44mounted with or integrally formed with the transducer body28. As is shown inFIG. 1andFIG. 5, the transducer M is adapted for fluid flow measurement in either direction of fluid flow. The structure ofFIGS. 1 and 5is the same except for the arrangement of the flow measuring transducer38which is determined by the direction of flow of the fluid to be measured. For this reason like reference numerals are used inFIGS. 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 passage12is connected to an inlet passage50in a flow inlet plug or housing tap52mounted with or integrally formed with the housing body10. The flow passage50is of like diameter to the flow passage12, which is connected to the flow passage14at a transition point54. Fluid enters the flow receiving chamber16where flow control occurs in response to relative movement of the adjustable diaphragm22by 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 passage18leads from the flow receiving chamber16to an elbow18aand an extension18band thence to flow outlet20.

The housing body10is mounted with a top support plate60by a suitable number of appropriately spaced mounting nuts62and washers64such as Belleville washers. A bearing block70is mounted by connecting screws72to the rear wall or surface26of the housing body10beneath the top support plate60. The flow receiving chamber16is formed by the adjustable diaphragm22in an inner central portion of the space between the bearing block70and the housing body10. The adjustable diaphragm member22is mounted as one wall of the flow receiving chamber16and is engaged around outer surface portions22aby an O-ring76or other suitable seal mounted in a seal receiving groove78formed on the rear surface26of the housing body10.

The adjustable diaphragm member22of the proportional valve V is formed from a sheet80(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 sheet80is about 0.015″ thick. Openings81are formed in the sheet80for passage of connectors or screws79to mount the diaphragm member22with the housing body10. The connectors are received in sockets11bformed in the front wall11of housing body10.

A circular indentation or rim82(FIGS. 2 and 4) is formed in a central portion84of the adjustable diaphragm member22extending away from a front surface86of the PTFE sheet80, facing inwardly towards the flow receiving chamber16of the housing body10. A typical diameter of the circular rim82is 0.625″. The depth of the indentation is such that an inner surface88of the adjustable diaphragm member22extends about one-third of its thickness, or 0.005″, inwardly as indicated by arrows89(FIGS. 2 and 7) in the area of the circular indentation82. A flexed inwardly extending central hub area90is formed in the adjustable diaphragm member22within the circular indentation82extending at its inner surface88towards the flow receiving chamber16.

The adjustable diaphragm member22is flexible and the central hub area90is movable inwardly and outwardly with respect to the flow receiving chamber16in 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 area90is about that of the thickness of the sheet80, or 0.028″ in the embodiment shown in the drawings, based on the dimensions of a cam100in the actuator A to be described below. Adequate movement is provided so that an innermost portion90aof the hub area90at its innermost position sealingly engages the annular flat surface17between the flow receiving chamber16and 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 seal91is formed in the seal-receiving slot or groove19in the housing body10. The O-ring seal91may be made from any suitable sealing material according to the fluid in the valve V, and is provided to seal the surface between diaphragm22and the housing body10. A backup washer pad or gasket93is provided between the diaphragm member22and a pusher rod assembly92of the actuator assembly A. The washer93is formed of a suitable material such as fluoroelastomer sold under the trademark Viton® from DuPont Dow Elastomers. The backup washer93provides a resilient, compliant material between the piston rod92and the diaphragm22. The resilient fluoroelastomer washer93functions as a spring, and also provides protective wear prevention and overtravel protection.

A pusher rod92of the actuator assembly A has an inner end92acontacting a rear surface90bof the hub area90of the adjustable diaphragm member22to cause relative movement of the adjustable diaphragm member22. The pusher rod92is received within a bushing member94for relative inward and outward movement. The bushing member94is mounted within the bearing block70and moves reciprocally to vary the relative position of the adjustable diaphragm member22and vary the volume of the flow receiving chamber16.

The pusher rod92has an arcuate curved rear surface92bat an opposite end from the adjustable diaphragm member22to engage and respond to a cylindrical outer surface96a of a rotatable cylindrical bearing96. The cylindrical bearing96is rotatably mounted on a bearing roller shaft98within the proportional valve V, and the cylindrical bearing96and roller shaft98are adapted for relative movement within the proportional valve V in response to a cam member100of the actuator assembly A.

The cam member100is preferably a vertically reciprocating cam which has a tapered contact surface102. The cam member100is shown in a full open position inFIGS. 1 and 2at its uppermost position. The cam member100is adapted to move upwardly and downwardly in response to an electric motor104which incrementally moves an extendable shaft105in response to control signals from the computer C or other input control signals from an operator or other input source. A suitable motor104in the preferred embodiment of the present invention is of the commercially available type known as a linear stepper motor.

The surfaces of the cam member100(FIG. 7) are ground and polished, both along the contact surface102and an oppositely facing rear portion103. The contact surface102has an initial lower flat portion102a(FIG. 7) extending vertically upwardly a suitable distance as indicated at D, such as 0.100″, and the rearwardly tapering or sloped upper portion102b. In the disclosed embodiment, the taper of surface102bis at an angle102cof 1.124° or an amount of 0.028″ rearwardly from the vertical flat surface102a. Depending upon the particular flow control application, and requirements, the slope of surface102bcan be differently configured or selected. The contact surface102of the cam member100thus has a shape and dimension conformed to calculations defining the requisite movement of the pusher rod92and the adjustable diaphragm member22. As noted, the slope of surface102bis 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 member100is mounted, such as by a set screw106, with shaft105of the motor104. The shaft105extends from a motor shaft housing108of motor104and is advanced or withdrawn on activation of the motor104. The motor104of valve V also preferably has a static characteristic of holding the presently established position (and thus the flow set point of the cam100of actuator A) without power or forces being applied to the shaft105. 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 motor104is mounted with a motor support plate110spaced from a motor mounting housing or plate112by spacer or mounting screws114. The motor mounting housing or plate112is mounted to a lower plate or base member116of the valve V by mounting or spacer screws118. The relative position of the motor plate112is initially adjusted to set the shut-off position of the valve V and also to locate the motor104and its shaft105on an axis perpendicular to the axis of movement of the pusher rod92. The lower plate116and top support plate60are connected by a set of spacer or mounting screws121or other suitable structure such as a rear wall, if desired.

The bearing96which contacts the pusher rod92and a rear or back up bearing120of the actuator assembly A are mounted with a bearing holder plate122beneath the top support plate60. The bearing holder plate122is connected by a shoulder bolt124with associated Belleville washer126to the top support plate60. An adjustment block130is mounted to the top support plate60by an adjustment screw132and to the bearing holder plate122by an adjustment screw134.

The adjustment structure of the valve V is used for initial set-up and calibration. Initially, the cam member100is moved to its fully upwardly extended position so that the flat surface102aengages the rear of actuator rod92. The diaphragm22is in a flow blocking position in contact with the annular flat surface17on the housing body10. The position of adjustment screw134in the adjustment block130is moved to cause the backup bearing120to engage and support the cam member100.

It can thus be seen that the valve V includes the external actuating pusher rod or shaft92that is mechanically moved by a customized profile cam contact surface102. The actuating rod92presses against the adjustable diaphragm member22which is a flexible synthetic resin (typically PTFE). The cam contact surface102is configured so that it can be moved to position causing the diaphragm member20to close/open a PTFE flow path in chamber16between the diaphragm22and the PTFE housing body10. The fluid flows toward the diaphragm22from passageway14. The flow rate is controlled by the relative position of diaphragm22as established by the actuator A. Return flow from the chamber16is through an exit flow path beginning at outlet flow passage18.

The relative size and position of the inlet passage14and outlet passage18in housing body10are customizable to match specific flow parameters. As the actuator rod92is pressed against the diaphragm22, the flow through chamber16is gradually restricted. At the innermost end of the stroke of the actuator rod92, fluid passage through chamber16is closed to stop flow of the fluid through the valve V.

As the actuator rod92is moved away from the diaphragm22, the flow gradually increases, up to a maximum flow rate which is obtained through the valve V with the diaphragm22fully retracted. During the movement of the actuator rod92, the flow rate is changing according to pre-programmed features in the profiled cam surface102based on the specific flow parameters for the exact fluid, pressures, temperature and viscosity.

The proportional valve V also permits adjustment of movement of diaphragm22by actuator A by setting the travel range of actuating cam100. This adjustment provides a capability to compensate for any wear of the diaphragm22or its mating surface26in the housing body10in 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 cam100to 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.