Dynamic orifice valve apparatus and method

In a fluid transmission line, a valve comprising a housing that establishes a lumen for transmission of a fluid through said valve; a drive mechanism and a drive gear mounted in said housing to be selectively driven in a first or second rotational direction by said drive mechanism. The drive gear has a central throughhole and a plurality of pins around the central throughhole. A plurality of leaves are pivotally mounted on the pins, and oriented to extend radially inward into said central throughhole. A fixed extension has an annular aspect disposed in the drive gear, and has a plurality of engagement members disposed to operatively engage one of said leaves. The engagement members bias the leaves to close an orifice when said drive gear rotates in said first direction and to open the orifice when said drive gear rotates in said second direction. Each of the leaves maintains a substantially sealing engagement with each adjacent leaf throughout a range of motion of the leaves.

CROSS-REFERENCE TO RELATED APPLICATIONS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of this invention is in valves for fluid and gas flow, particularly natural gas.

2. Related Art

The flow of the fluids and gases being piped through lines is typically controlled with valves. The valves of course control flow through a pipe by obstructing the pipe in one form or another. In the prior art, the form of obstruction is asymmetrical. For example if a simple screw or needle type valve mechanically advances a gate or needle into a cylinder from one side. Even well-known butterfly valves are symmetrical in one direction, but asymmetrical in another, in that half of the butterfly disk advances towards the source of flow while the other half recedes away from it.

The effect on the flow of the fluid gases that is created by the simple mechanical devices is also asymmetrical, irregular and unpredictable. Generally, it is desirable to have more symmetrical fluid flow throughout the range of constriction that a valve is designed to achieve. This promotes a more rapid return to laminar flow, reduces friction, avoids obstruction from contaminants, reduces back pressure and enables more accurate flow rate and pressure control. More particularly, in some applications, particularly pressurized applications for gas, there is a desirability and need for a symmetrical and therefore more precise constriction of gas flow in order to promote predictably and accuracy of use of the gas thereby making its use more economical across all ranges of pressure and volume to be executed by the valve.

Most particularly, some applications of natural gas use, for example, heat treatment of production material, most especially heat treatment of ferrous metals, requires an optimally precise control of gas flow. More particularly still, a gas flow is combined with gas or air in order to achieve a precise control of how lean or rich will be the output of the gas line for combustion in the heat treating chamber. Precise control of how lean or rich the gas output into the heating chamber is important because the chemical and rheological properties of the metal being treated are sensitive to the chemical atmosphere in the chamber which in turn is dependent upon the gas/air mixture received from the gas line.

FIG. 1, depicting a prior art natural gas burner assembly (10) shows the natural gas line (12) in combination with an air or oxygen line (14). The air line (14) is controlled by a butterfly valve (16). Downstream of the butterfly valve, a flow sensor control (18) controls an impulse valve (20) in the gas line (10). If any fine adjustment is needed, a needle valve (22) is fitted downstream of gas line (10). This is an example of an unintegrated assembly created from separate components. A disadvantage of such an assembly is that the final output does not vary proportionally with adjustment of controls. In prior art valves, such as valve16inFIG. 1, the amount of flow allowed to pass varies with opening in an unpredictable fashion that is not continuously proportional to the progressive opening or closing of the valve. The volume, pressure and turbulence of flow are not mathematically predictable or precisely controllable. Accordingly, in the prior art application illustrated, the mixture of the gas/air combination is also unpredictable and poorly controlled. The volume of flow as a function of the percentage of opening of a valve is complex, difficult to model, variable over time and sometimes discontinuous.

There is a need in the art for a valve that opens and closes in a manner that will increase or decrease flow of the fluid or gas to the valve in a mathematically predictable, controlled fashion that is proportionate to the percentage of the opening or closing of the valve. There is a continuing need in the art for durability, efficiency, integration of components, type of sealing to prevent leaks, economy and durability.

SUMMARY OF THE INVENTION

In a fluid transmission line, a valve comprises a housing that establishes a lumen having an axial length for transmission of a fluid through said valve; a drive mechanism; a drive gear being mounted in said housing to be selectively driven in a first or second rotational direction by said drive mechanism, said drive gear having a central throughhole coaxial with an axis of said valve; a plurality of pins circumferentially spaced around said central throughhole of said drive gear; a plurality of leaves, each being pivotally mounted on one of said plurality of pins, and oriented to extend radially inward into said central throughhole; a fixed extension having an annular aspect disposed in close cooperation with said drive gear, and said fixed extension having a plurality of engagement members disposed to operatively engage one of said leaves at a position intermediate to said pivotal pin mount of each of said leaves and to said axis of said valve; said engagement members biasing said leaves to close an orifice when said drive gear rotates in said first direction and to open said orifice when said drive gear rotates in said second direction; and each of said leaves maintaining a substantially sealing engagement with each adjacent leaf throughout a range of motion of said plurality of leaves.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 2A and 2Bdepict a housing comprised of a housing top52and bottom54portion which house the valve of present invention. Housing top52includes a seat56for a drive motor. Housing top52and bottom54include through holes58and60, respectively, for mounting a pipe or line through which a fluid or gas may be directed. The line may be a natural gas line. In the depicted embodiment, a recess62is shown in the housing bottom54for containing the hereinafter described components. The valve housing consists of two plates. Each plate has a hexagonal pipe-fitting boss on one side, and is threaded with a standard NPT thread. The opposite side of each housing contains features for the alignment and mounting of the internal valve components, namely the iris assembly, the drivetrain gears, and the sealing mechanisms. There are features on the inside of one of the housing plates which allow mechanical fastening of a motor/electrical control interface. The two housing plates mechanically fasten together.

A motor (not shown) housed in recess62will drive a drivetrain, which in the depicted embodiment is a drive gear64which in turn is drivingly engaged with a main gear66. Assembled coaxially with main gear66and through holes58and60, is a bushing68having an annular extension. In the depicted embodiment, the bushing has a seal70, an O-ring is depicted, for sealing against a flush face of housing top52. In the embodiment depicted inFIG. 2, main gear66has a sufficient number of teeth to correspond with the full range of motion for the valve leaves, described below. The opposite face of the gear has a protruding boss. The gear has a throughhole through the center. The boss is positioned within a counterbore in the housing, which allows the gear to freely rotate.

FIGS. 3A and 3Bare close-ups of the main or iris gear66. In the embodiment depicted inFIGS. 3A and 3B, the entire circumference of main gear66is toothed.FIG. 3Adepicts an upstream facing surface of main gear66. This surface includes a boss72dimensioned to seat in sealing fluid communication with through hole60in housing bottom54. Also depicted in3A are pin holes74.

As seen inFIGS. 3A and 3Ba valve orifice80is defined by a plurality of leaves. An individual leaf82is depicted inFIG. 5. In the depicted embodiment there are 16 leaves. Each of the depicted leaves82has a substantially flat, curvilinear portion. A first end of the leaf82has a through hole86for receiving a pin for mounting the leaf82under the main gear66in a pivoting manner. The second end of leaf82terminates in a fin or flange88(FIG. 5). In the depicted embodiment, the fin88is substantially perpendicular to the plane of the curvilinear portion84. It is within the scope of the present invention that the flange88may be at an angle to the curvilinear portion84of the leaf within a range of substantially about 90° to substantially about 135°. Those of skill in the art will appreciate that the use of a flange allows for overlapping leaves, including multiple overlaps, that is, more than two leaves overlapping one another relative to the longitudinal axis of the valve. This feature, independently or in combination with the integral fabrication of the gear66, allows the design to be used in high pressure applications as well as other more abusive environmental conditions, such as high temperature or corrosive fluid flow, and promotes tighter sealing. Portions of the leaves, such as curvilinear portion84, may be flared, twisted, torqued or otherwise non-planar to further promote a sealing engagement with neighboring leaves.

The leaves may be made from two different materials, and arranged so that each leaf is a different material than the adjacent leaf. Physical forces, such as magnetism, or an integral torsion in each leaf, bond the leaves together while allowing them to slide relative to each other.

FIG. 4is a cutaway side view of main gear66including a through hole96which is centered on valve axis95and define a part of a lumen through which a fluid material would flow. Also depicted are pin holes74and pins92installed therein. The pins are long enough in axial direction to also anchor leaves82in their engagement with pin holes86. At least a portion of a lower surface98of each leaf abuts an upper surface100of a recess94in main gear66. This abutment is sufficient to maintain a seal. The seal is in turn sufficient to maintain itself against the anticipated use of the installed device. Fixation of leaf82to main gear66with pin92may be adjusted for an appropriate tractive force to be applied against leaf82by pin92in order to maintain sealing abutment.

In assembly, each leaf82is pinned to main gear66. Each leaf thereafter has fin88projecting axially, downstream in the depicted embodiment. Thereafter, a bushing or extension68is installed on top of the plurality of leaves82such that each axially projecting fin88is received into each of a plurality of slots90in bushing68. The flanges of the leaves are guided within slots in the bushing or extension68. This guide extension68fixedly locks into the housing to prevent rotation. A protruding ring has the thin slots cut for the leaf flanges to engage. Another ring may provide a sealing surface.

In the depicted embodiment, when assembled, each pin is substantially equidistant radially to the center axis95of the through hole96and orifice80of the valve. Correspondingly, slots90are also substantially equidistant radially, and substantially equally spaced circumferentially in the depicted embodiment. Each fin is also substantially linear in the depicted embodiment. The assembled components of leaves82, bushings68and main gear66are thereafter further installed with O-ring70into recess62of housing bottom54. The main gear66engages with drive gear64. Bushing68is fixedly attached to housing top52by means of a key and slot, boss and detent, snap fit, screws or otherwise. The motor and housing top52assembly is thereafter installed over housing bottom54thereby encapsulating the components.

The drive mechanism may consist of an electric gear motor, either electrically powered, capable of being driven in both the forward and reverse directions. The motor has two output shafts. The primary output shaft penetrates one of the housing plates to drive the iris diaphragm through the drivetrain. The secondary output shaft is used for valve position sensing. The valve may also be manually adjustable, through the use of a lever, worm screw, etc.

In operation, a drive motor turns drive gear64in response to either automatic control or user selection. Drive gear64through its meshing engagement with main gear66turns main gear66. Bushing68does not rotate. As drive gear66rotates, the second inner end of each leaf82is held fixed against circumferential displacement by engagement of the fin88with its corresponding slot90of fixed bushing68. As the main gear66rotates, it circumferentially turns the outer end of each leaf82. Each leaf82rotates around its pin hole86. Accordingly, traction on each leaf82through pin92by main gear66causes each leaf to advance radially inward. As main gear66is driven in a first direction, each of the plurality of leaves moves inward. That is to say, an inside edge102each leaf advances in a manner reducing the distance between the inner edge102of the leaf and a center axis of orifice80. Accordingly, orifice80closes.

To open the orifice80and allow a larger volume of fluid or gas to pass therethrough, main gear66is driven in an opposite direction. Each leaf is thereby driven by its pin hole86against the slot90. Engagement of each fin88against slot90causes the leaf to move radially outward from the center axis of the orifice80, thereby opening it. Accordingly, a dual polarity motor may provide driving force in each of two directions in order to selectively open and close the orifice80through which fluid or gas flows.

In the depicted embodiment, the16leaves form an orifice that is substantially circular. The iris type configuration depicted provides for the orifice to remain symmetrical, and as depicted substantially centered on the valve axis throughout variations in its size or variations in the flow volume through it. As such, the valve provides a mathematically predictable proportion between orifice size and flow volume. Because the orifice is centered on the lumen defined by the housing and geometrically symmetrical, the flow of fluid or gas through it is much more directly proportional to the opening or closing of the orifice80than prior art valves. Accordingly, a more precise control of flow may be achieved. Laminar flow of fluid is re-established immediately after the orifice and may be established within the lumen of the valve itself, minimizing turbulence as the fluid exits the valve.

FIG. 6depicts an alternate embodiment of the present invention. It includes a housing156supporting a drive gear164driven by a motor in the housing156, which is obscured from view in the partially disassembledFIG. 6. As above, a main iris gear166has a plurality of leaves182mounted thereon. Gear166has an annular recess dimensioned to receive a bushing or extension (not shown inFIG. 6) having guide members such as slots for biasing the leaves182towards constriction or expansion in response to rotation of iris gear166. In the embodiment depicted inFIG. 6, the driving force is transferred from drive gear164to iris gear166through transfer gear165.

FIG. 7is a top, partially disassembled, cutaway view of the iris gear166, depicting the deployment of sixteen leaves182.

The sealing system is best seen inFIG. 8. The sealing system consists of several resilient gaskets, such as O-rings. The primary housing seal100is of a contoured shape, and rests within a groove in one of the housing plates. This seal engages the opposite housing plate when assembled. The fluid channel seal consists of two O-rings. One seal102(optionally,102A) rests in a groove in the housing plate and engages the surface of the main iris gear166near the protruding boss. The other seal104rests in a groove in the other housing plate and engages the surface of the diaphragm guiding extension or bushing168. There is also a seal106within the iris gear166, which seals between the iris gear and the guide extension168. The shaft sealing system consists of two O-rings that engage the drive motor shaft. One of these O-rings108rests in a groove inside of one of the housing plates. The other O-ring rests in a groove on the outside of one of the housing plates. All sealing system components are compressed when the mechanism is fully assembled.

Each housing plate156may also contain passages120,122through which the differential pressure across the iris can be measured, either internally within the valve or through an external device. The valve may also contain an electronic differential pressure transducer which provides actual flow characteristic feedback. Also shown inFIG. 8is a cam110for engaging limit switches as an optional control modality.

FIG. 9depicts an alternative embodiment of the present invention. In the depicted embodiment a bi-metal torsion spring drives the drive gear. Differential expansion and contraction of the two metals comprising the spring in response to temperature changes causes the metal strip to expand and contract rotationally, imparting drive when mounted as depicted. The center shaft202of drive gear264is fixed to the housing and remains stationary. The drive gear264is mounted to rotate around it. The internal end of bi-metal torsion spring204is fixedly attached to center shaft202. Anchor shaft206is fixedly attached to or integrally formed with drive gear264at or near its outer edge. Bi-metal torsion spring204is attached at its outermost end to anchor shaft206. Accordingly, expansion of bi-metal torsion spring204biases anchor shaft206and drive gear264in a first direction and contraction of bi-metal torsion spring204biases anchor shaft206in order to turn drive gear264in an opposing direction. As described hereinabove, rotation of drive gear264imparts counter rotation to the main or iris gear266. Rotation of iris gear266opens and closes orifice280.

FIGS. 10 and 11depict an alternate embodiment of the present invention. The drive gear266is driven through engagement of its teeth with the drive gear as described hereinabove. The iris leaves282are attached as before to pins283, which are pivotally mounted in drive gear266in throughholes274. In the embodiment depicted inFIGS. 10 and 11, the leaf282does not have a flange, vane or fin at its inner terminal end as in the previous embodiments (although it may be flared, twisted or otherwise non-planar in order to promote a sealing engagement with its neighboring leaves). Instead, the fixed valve mount includes an annular extension or bushing272that has a smaller diameter than the center hole of the drive gear266and extends axially into it. This annular extension272also has leaf engagement members that are pin holes289circumferentially spaced around its perimeter, which serve as mounts for pintels287which are pivotally engaged in the holes289and also through the leaves282. Since the annular extension272is fixed, when the drive gear266rotates in either direction, the pivotal attachment of each leaf284to its drive gear pin283will cause the leaf282to be rotated in one direction or the other around inner pintel287. Accordingly, the orifice extension288of each leaf will be rotated such that the orifice280will be opened or closed.

In the depicted embodiment, sufficiently wide tolerances are allowed in the pin283—throughhole274and/or pin hole289—pintels287relationships to allow opening and closing of orifice280despite the fixed coaxial relationship of iris gear266and extension274.

The electrical control interface consists of multiple functional components. In one embodiment the main control interface consists of a sealed multi-pin plug. This plug may be wired to a printed circuit board. The PCB contains two DPDT relays which allow for switching of the polarity of the input drive signal. The primary PCB101also contains limit switches that indicate the valve position sensed from a mechanical positioning device attached to the secondary output shaft. The primary PCB may also contain limit switches which detect (as by cam110) and control the travel limits of the drive system which can be positioned by a user. In one embodiment, a secondary PCB is wired to the primary PCB. The secondary PCB contains electronic control architecture which allows the reception, interpretation, and use of one of several standard control signals, such as 4-20 mA, 0-10 Vdc, etc. for valve position. The entire electronic control package may be physically contained within a protective cover116, which is physically attached to one of the housing plates. There is a seal between the protective cover and the housing plate. There may also be indicators, which may be mechanical or electrical, on the housing which relay status of the valve position. There may also be a rotary position sensor118which provides valve position feedback to a supervisory control system.

The present invention provides for a mathematically predictable flow according to the equation:

flow=K⁢⁢A⁢hg,
in which K is a constant particular to the valve design. A is the area of the orifice, h is the pressure drop across the orifice, and g is the specific gravity of the fluid or gas flowing through it.

FIG. 12depicts the novel feedback circuitry of the present invention. A pressure transducer300(see124inFIG. 8) is operatively engaged with pressure sensor port120. The pressure transducer300signals a pressure gain stage302to yield a direct pressure reading output304. Alternatively, a pressure differential output can be generated by incorporating a second pressure transducer operatively engaged to the second pressure sensor port122on the opposite of the valve orifice.

In order that the present invention may be incorporated into devices using an alternate control regimen, the feedback circuits also include a position encoder306operatively engaged with the drive train, usually at the motor shaft (see125,FIG. 8). It too feeds into a position gain stage308in order to yield a position output310. Such a position output310may be used with the equation

flow=K⁢⁢A⁢hg,
in order to yield a cubic feet per hour corresponding to a percent that the valve orifice is open.

Thus, the present inventive mechanisms and controls provide greater precision for all gas or fluid control systems, including but not limited to trim gas flow in combination with protective atmospheric gas such as endothermic gas.