Abstract:
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.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     None 
     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 valve  16  in  FIG. 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. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic side view of a prior art valve system. 
         FIG. 2A  is an interior view of one side of a housing. 
         FIG. 2B  is an exterior view of another side of a housing. 
         FIG. 3A  is an isometric view of the main gear of the valve. 
         FIG. 3B  is an opposing isometric view of the main gear of the valve. 
         FIG. 4  is a cutaway side view of the main gear and iris of the valve. 
         FIG. 5  is an isometric view of a single leaf of the iris. 
         FIG. 6  is a partially disassembled isometric view of an alternate embodiment. 
         FIG. 7  is a partially disassembled cutaway top view of an alternate embodiment. 
         FIG. 8  is a cutaway side view of an alternate embodiment. 
         FIG. 9  is an isometric view of a second alternate embodiment. 
         FIG. 10  is a first isometric view of a third alternate embodiment. 
         FIG. 11  is an opposing isometric view of the third alternate embodiment. 
         FIG. 12  is a circuit diagram of a novel feedback circuit for the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
       FIGS. 2A and 2B  depict a housing comprised of a housing top  52  and bottom  54  portion which house the valve of present invention. Housing top  52  includes a seat  56  for a drive motor. Housing top  52  and bottom  54  include through holes  58  and  60 , 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 recess  62  is shown in the housing bottom  54  for 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 recess  62  will drive a drivetrain, which in the depicted embodiment is a drive gear  64  which in turn is drivingly engaged with a main gear  66 . Assembled coaxially with main gear  66  and through holes  58  and  60 , is a bushing  68  having an annular extension. In the depicted embodiment, the bushing has a seal  70 , an O-ring is depicted, for sealing against a flush face of housing top  52 . In the embodiment depicted in  FIG. 2 , main gear  66  has 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 3B  are close-ups of the main or iris gear  66 . In the embodiment depicted in  FIGS. 3A and 3B , the entire circumference of main gear  66  is toothed.  FIG. 3A  depicts an upstream facing surface of main gear  66 . This surface includes a boss  72  dimensioned to seat in sealing fluid communication with through hole  60  in housing bottom  54 . Also depicted in  3 A are pin holes  74 . 
     As seen in  FIGS. 3A and 3B  a valve orifice  80  is defined by a plurality of leaves. An individual leaf  82  is depicted in  FIG. 5 . In the depicted embodiment there are 16 leaves. Each of the depicted leaves  82  has a substantially flat, curvilinear portion. A first end of the leaf  82  has a through hole  86  for receiving a pin for mounting the leaf  82  under the main gear  66  in a pivoting manner. The second end of leaf  82  terminates in a fin or flange  88  ( FIG. 5 ). In the depicted embodiment, the fin  88  is substantially perpendicular to the plane of the curvilinear portion  84 . It is within the scope of the present invention that the flange  88  may be at an angle to the curvilinear portion  84  of 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 gear  66 , 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 portion  84 , 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. 4  is a cutaway side view of main gear  66  including a through hole  96  which is centered on valve axis  95  and define a part of a lumen through which a fluid material would flow. Also depicted are pin holes  74  and pins  92  installed therein. The pins are long enough in axial direction to also anchor leaves  82  in their engagement with pin holes  86 . At least a portion of a lower surface  98  of each leaf abuts an upper surface  100  of a recess  94  in main gear  66 . 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 leaf  82  to main gear  66  with pin  92  may be adjusted for an appropriate tractive force to be applied against leaf  82  by pin  92  in order to maintain sealing abutment. 
     In assembly, each leaf  82  is pinned to main gear  66 . Each leaf thereafter has fin  88  projecting axially, downstream in the depicted embodiment. Thereafter, a bushing or extension  68  is installed on top of the plurality of leaves  82  such that each axially projecting fin  88  is received into each of a plurality of slots  90  in bushing  68 . The flanges of the leaves are guided within slots in the bushing or extension  68 . This guide extension  68  fixedly 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 axis  95  of the through hole  96  and orifice  80  of the valve. Correspondingly, slots  90  are 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 leaves  82 , bushings  68  and main gear  66  are thereafter further installed with O-ring  70  into recess  62  of housing bottom  54 . The main gear  66  engages with drive gear  64 . Bushing  68  is fixedly attached to housing top  52  by means of a key and slot, boss and detent, snap fit, screws or otherwise. The motor and housing top  52  assembly is thereafter installed over housing bottom  54  thereby 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 gear  64  in response to either automatic control or user selection. Drive gear  64  through its meshing engagement with main gear  66  turns main gear  66 . Bushing  68  does not rotate. As drive gear  66  rotates, the second inner end of each leaf  82  is held fixed against circumferential displacement by engagement of the fin  88  with its corresponding slot  90  of fixed bushing  68 . As the main gear  66  rotates, it circumferentially turns the outer end of each leaf  82 . Each leaf  82  rotates around its pin hole  86 . Accordingly, traction on each leaf  82  through pin  92  by main gear  66  causes each leaf to advance radially inward. As main gear  66  is driven in a first direction, each of the plurality of leaves moves inward. That is to say, an inside edge  102  each leaf advances in a manner reducing the distance between the inner edge  102  of the leaf and a center axis of orifice  80 . Accordingly, orifice  80  closes. 
     To open the orifice  80  and allow a larger volume of fluid or gas to pass therethrough, main gear  66  is driven in an opposite direction. Each leaf is thereby driven by its pin hole  86  against the slot  90 . Engagement of each fin  88  against slot  90  causes the leaf to move radially outward from the center axis of the orifice  80 , 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 orifice  80  through which fluid or gas flows. 
     In the depicted embodiment, the  16  leaves 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 orifice  80  than 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. 6  depicts an alternate embodiment of the present invention. It includes a housing  156  supporting a drive gear  164  driven by a motor in the housing  156 , which is obscured from view in the partially disassembled  FIG. 6 . As above, a main iris gear  166  has a plurality of leaves  182  mounted thereon. Gear  166  has an annular recess dimensioned to receive a bushing or extension (not shown in  FIG. 6 ) having guide members such as slots for biasing the leaves  182  towards constriction or expansion in response to rotation of iris gear  166 . In the embodiment depicted in  FIG. 6 , the driving force is transferred from drive gear  164  to iris gear  166  through transfer gear  165 . 
       FIG. 7  is a top, partially disassembled, cutaway view of the iris gear  166 , depicting the deployment of sixteen leaves  182 . 
     The sealing system is best seen in  FIG. 8 . The sealing system consists of several resilient gaskets, such as O-rings. The primary housing seal  100  is 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 seal  102  (optionally,  102 A) rests in a groove in the housing plate and engages the surface of the main iris gear  166  near the protruding boss. The other seal  104  rests in a groove in the other housing plate and engages the surface of the diaphragm guiding extension or bushing  168 . There is also a seal  106  within the iris gear  166 , which seals between the iris gear and the guide extension  168 . The shaft sealing system consists of two O-rings that engage the drive motor shaft. One of these O-rings  108  rests 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 plate  156  may also contain passages  120 ,  122  through 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 in  FIG. 8  is a cam  110  for engaging limit switches as an optional control modality. 
       FIG. 9  depicts 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 shaft  202  of drive gear  264  is fixed to the housing and remains stationary. The drive gear  264  is mounted to rotate around it. The internal end of bi-metal torsion spring  204  is fixedly attached to center shaft  202 . Anchor shaft  206  is fixedly attached to or integrally formed with drive gear  264  at or near its outer edge. Bi-metal torsion spring  204  is attached at its outermost end to anchor shaft  206 . Accordingly, expansion of bi-metal torsion spring  204  biases anchor shaft  206  and drive gear  264  in a first direction and contraction of bi-metal torsion spring  204  biases anchor shaft  206  in order to turn drive gear  264  in an opposing direction. As described hereinabove, rotation of drive gear  264  imparts counter rotation to the main or iris gear  266 . Rotation of iris gear  266  opens and closes orifice  280 . 
       FIGS. 10 and 11  depict an alternate embodiment of the present invention. The drive gear  266  is driven through engagement of its teeth with the drive gear as described hereinabove. The iris leaves  282  are attached as before to pins  283 , which are pivotally mounted in drive gear  266  in throughholes  274 . In the embodiment depicted in  FIGS. 10 and 11 , the leaf  282  does 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 bushing  272  that has a smaller diameter than the center hole of the drive gear  266  and extends axially into it. This annular extension  272  also has leaf engagement members that are pin holes  289  circumferentially spaced around its perimeter, which serve as mounts for pintels  287  which are pivotally engaged in the holes  289  and also through the leaves  282 . Since the annular extension  272  is fixed, when the drive gear  266  rotates in either direction, the pivotal attachment of each leaf  284  to its drive gear pin  283  will cause the leaf  282  to be rotated in one direction or the other around inner pintel  287 . Accordingly, the orifice extension  288  of each leaf will be rotated such that the orifice  280  will be opened or closed. 
     In the depicted embodiment, sufficiently wide tolerances are allowed in the pin  283 —throughhole  274  and/or pin hole  289 —pintels  287  relationships to allow opening and closing of orifice  280  despite the fixed coaxial relationship of iris gear  266  and extension  274 . 
     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 PCB  101  also 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 cam  110 ) 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 cover  116 , 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 sensor  118  which 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   ⁢       h   g           ,         
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. 12  depicts the novel feedback circuitry of the present invention. A pressure transducer  300  (see  124  in  FIG. 8 ) is operatively engaged with pressure sensor port  120 . The pressure transducer  300  signals a pressure gain stage  302  to yield a direct pressure reading output  304 . Alternatively, a pressure differential output can be generated by incorporating a second pressure transducer operatively engaged to the second pressure sensor port  122  on 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 encoder  306  operatively engaged with the drive train, usually at the motor shaft (see  125 ,  FIG. 8 ). It too feeds into a position gain stage  308  in order to yield a position output  310 . Such a position output  310  may be used with the equation 
               flow   =     K   ⁢           ⁢   A   ⁢       h   g           ,         
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. 
     As various modifications could be made to the exemplary embodiments, as described above with reference to the corresponding illustrations, without departing from the scope of the invention, it is intended that all matter contained in the foregoing description and shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.