Abstract:
Valves, particularly useful for controlling flow of heat transfer fluids in various heating, air conditioning and ventilation systems, are provided. The valves are of the curtain valve type and operate at very low torque and provide easy assembly and repair. The valve or actuator has an adjustment for the flow coefficient. A disclosed valve comprises a valve body having an inside surface, an inlet port comprised of an opening through the inside surface and enabling fluid flow into the valve body, an outlet port comprised of an opening through the inside surface and enabling fluid flow from the valve body, and a curtain valve closure. The closure adjustably controls fluid flow through the outlet port and is of a modular design including a flexible diaphragm held in an insert positioned at least partially within the outlet port. The insert has at least one dimension larger than a mating surface on the internal surface of the valve body. In this manner the insert is secured without fasteners and properly oriented within the outlet port, facilitates easy assembly and enables the use of low-torque actuators. The valve can employ a radially- and axially-moveable shoe to assure tight close off.

Description:
“This application claims the benefit of U.S. Provisional Application 60/311,902 filed on Aug. 13, 2001, and U.S. Provisional Application 60/306,280 filed on Jul. 18, 2001.” 

   BACKGROUND OF THE INVENTION 
   The invention concerns valves, especially those designed for use in controlling flow of heating and cooling fluids in various heating, air conditioning and ventilation systems. The invention provides inexpensive valves of the curtain valve type that can operate at very low torque and have the ability to be adjusted to a range of flow coefficients. Thus, fewer valves must be maintained in inventory to meet demand for a full range of valve sizes. The valves can have a variety of utilities in a wide range of sizes, but are especially useful as zone valves, enabling operation by a simple and inexpensive actuator. In the preferred forms, the valves exhibit a long life span and can be easily replaced or repaired as needed. 
   There are currently a variety of on-off zone control valves that have the advantage of being relatively inexpensive, making them useful for commercial as well as residential applications. Unfortunately, these valves as presently available suffer from a number of limitations due to their structures which affect the ability to open, close off or perform other control functions at high flow coefficients and differential pressures. As generally available, these valves are not capable of operating with a constant, low close-off torque independent of flow coefficient. Moreover, they each have a predetermined fixed flow coefficient (degrees of opening), which cannot be easily adjusted. 
   Exemplary of the type of valves and associated actuators in wide use and in need of lower cost alternatives, are those shown in U.S. Pat. No. 6,073,907, and the prior art cited therein. As commonly available, on-off zone control valves control flow of hot or chilled water to terminals and are usually in the sizes of ½″, ¾″, 1″ and 1 ¼″. Each size is made in a variety of flow coefficients (Cv). They are available as two-way or three-way valves and are typically operated by on-off thermostats. Power-to-close and power-to-open valves exist. Currently, large inventories are required to meet the full range of flow rates. 
   A zone control valve of the type shown in U.S. Pat. No. 6,073,907, typically has an essentially cylindrical cavity with circular cross section and two openings for fluid flow in and out of the cavity. In this regard, reference can be made to FIG. 4 of U.S. Pat. No. 6,073,907. The valves have an arm with a closure, e.g., a disk or flapper, mounted on one end. The arm and closure pivot on a shaft rotatable about an axis so that the closure can be moved to cover and uncover an opening by moving over and away from the opening, thereby permitting or stopping the flow. The direction of the flow is from an inlet opening into the cavity and out of the cavity past the closure through an outlet opening. The torque required is first to compress the disk enough for close-off, and then to provide a force sufficient to overcome the force produced by the differential pressure working over the area of the opening. Operating in this manner, fluid pressure strives to open the valve. 
   A drive mechanism, typically including a cogwheel segment located outside the valve body, rotates the shaft about the axis. The drive can be spring loaded to bias the closure in one way or the other, depending upon if it is a power-to-open or power-to-close valve. The valve, or actuator, is typically capable of operating at pressures of from about 10 psi up to a maximum of about 60 psi. The lower number is valid for high flow coefficients. 
   The cogwheel segment is driven by a small gear, which in turn is connected to a gearbox and a small AC motor. In a power-to-close valve, the motor runs in one direction only when power is applied and stalls when the mechanism has closed the valve. When power is not applied, the biasing spring causes the motor and gearbox to run backward and open the valve. 
   One drawback of this prior art design is that low close-off pressures are not satisfactory for the larger flow coefficients. Another, is that the drive mechanism has a limited life span due especially to wear of the cogwheel segment and gear. 
   Valves having flexible curtain closure members for providing adjustable flow control are available for large-scale installations, but have not been thought suitable for low-cost, HVAC applications. Curtain valves tend to leak at low pressures and tend to be large and to require costly hand assembly in a manner making them unsuitable for use in HVAC and related systems. 
   It remains that valves currently available for use in HVAC applications have a number of failings in terms of effective operation, high cost, and the need to inventory a large number of sizes. And, as currently available, curtain valves cannot be made economically for HVAC or other systems requiring relatively small sizes. 
   SUMMARY OF THE INVENTION 
   There is a need for an inexpensive valve that can be operated to provide an adjustable flow coefficient by application of a very low torque, enabling operation by a simple and inexpensive actuator. There is a further need for a valve of this type that will exhibit a long life span and can be easily replaced or repaired as needed. It would be desirable to provide improvements to curtain valves, to enable their use as very low torque valves available at a low cost to permit their use in HVAC and related systems to facilitate control over a range of flow coefficients. 
   Accordingly, it is an object of the invention to provide a valve capable of providing adjustable flow control while requiring only low-cost parts. 
   It is another object of the invention to provide a valve capable of easy assembly. 
   It is another object of the invention to provide a valve that enables the use of low-torque actuators. 
   It is another object of the invention to provide a valve which requires low torque for closing at high pressure differentials yet provides for positive closure at low pressure differentials. 
   It is another object of the invention to provide an adjustable valve which permits a number of flow coefficients for a given valve size. 
   It is another object of the invention to provide a valve which enables reducing the number of valves necessary to be kept in inventory. 
   It is another object of the invention to adapt curtain valves for use in HVAC systems. 
   It is another and more specific object of the invention to provide improvements in curtain valves for providing adjustable flow control suitable for low-cost, HVAC applications. 
   It is another specific object of the invention to improve curtain valves to assure positive close-off at low pressure differentials. 
   It is yet another object of the invention to provide a curtain valve with a detachable modular assembly of moveable parts that can be readily inserted into a valve body. 
   It is yet another object of the invention to provide a curtain valve with a modular assembly of moveable parts that can be readily inserted into a valve body to facilitate economical assembly of curtain valves of sizes suitably small to permit use in HVAC systems. 
   It is another and more specific object of the invention to provide an inexpensive curtain valve to control fluid flow to enable low-torque actuation for operation by a very simple and inexpensive actuator. 
   It is another specific object of the invention to provide a curtain valve to control fluid flow in an HVAC system to enable low-torque actuation and provide a longer life span for the actuator. 
   It is another object of the invention to provide valves particularly adapted to HVAC applications wherein valves are required to operate with fluid flow having large flow coefficients and can yet close off against high pressures. 
   It is another object of the invention to provide valves particularly adapted to HVAC applications wherein valves are required to close-off at very high pressure while requiring a control actuation essentially independent of the flow coefficient. 
   It is another object of the invention to provide valves particularly adapted to HVAC applications wherein the flow coefficient can be adjusted to suit the application. 
   These and other objects are accomplished by the present invention, which provides a curtain valve comprising a valve body having an inside surface, an inlet port comprised of an opening through said inside surface of said valve body and enabling fluid flow into the valve body, an outlet port comprised of an opening through said inside surface of said valve body and enabling fluid flow from the valve body, and a curtain valve closure for controlling fluid flow through said outlet port and comprised of a flexible diaphragm extended between two locations, one of said two locations being a pivotally-moveable support and the other being a fixed support, wherein said curtain valve closure further comprises: 
   an insert holding said diaphragm, said insert positioned at least partially within said outlet port and having at least one dimension larger than a mating surface on said valve body to thereby secure and orient said insert within said outlet port. 
   The invention provides a valve having an adjustable flow coefficient, operable at very low torque and particularly useful for controlling flow of heat transfer fluids in heating, air conditioning and ventilation systems, which comprises a valve body having an inside surface, an inlet port comprised of an opening through the inside surface and enabling fluid flow into the valve body, an outlet port comprised of an opening through the inside surface and enabling fluid flow from the valve body, and a curtain valve closure, 
   wherein the closure is adjustable to different flow coefficients to control fluid flow through the outlet port and is of a modular design including a flexible diaphragm connected to an insert positioned at least partially within the outlet port, and the insert has at least one dimension larger than a mating surface on the internal surface of the valve body to thereby secure the insert to the valve body without fasteners and to properly orient it within the outlet port. 
   In one preferred form of the above and other embodiments, the insert comprises a curtain valve support extending over an opening which aligns with the outlet port when positioned in the valve body, comprising at least one support member suspended over the opening, preferably a plurality of support members extending over the opening and dividing it into at least two passages. 
   In another preferred form of the above and other embodiments, the insert comprises one or more spring biased hooks at its outlet end and said valve body comprises a recess to mate the hook or hooks, whereby positioning of the hook or hooks within said recess secures the insert into the valve body in position in the outlet port. 
   In another preferred form of the above and other embodiments, a shoe is provided which is adapted to press against the curtain and insert when the valve is closed. In some embodiments means are provided for achieving eccentric shoe movement. 
   In another preferred form of the above and other embodiments, the insert comprises a seal on said portion of said insert which extends though said outlet port. In preferred forms, the seal can be an O-ring or an integrally molded section of said insert. 
   Many other preferred aspects and variations of the invention as set forth above are shown in the drawings and described in detail below. 

   
     DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and its advantages will become more apparent from the following written description, especially when read in light of the accompanying drawings wherein: 
       FIG. 1  is an exploded perspective view showing a two-way valve according to the invention. 
       FIG. 2  is a perspective view, partially cut away, of a valve as shown in  FIG. 1 . 
       FIG. 3A  is a top plan view of a valve as shown in  FIG. 1  with the cover removed and the curtain closure in closed position. 
       FIG. 3B  is a top plan view of a valve as shown in  FIG. 1  with the cover removed and the curtain closure in open position. 
       FIG. 3C  is a schematic top plan enlarged view of a the camming mechanism for a valve as shown in  FIG. 1 , showing the camming mechanism in movement from open to closed position. 
       FIG. 3D  is a view similar to that of  FIG. 3D  showing the camming mechanism in closed and unlocked position. 
       FIG. 3E  is a view similar to that of  FIG. 3C  showing the camming mechanism moving into closed and locked position. 
       FIG. 4  is an exploded perspective view showing a three-way valve according to the invention. 
       FIG. 5  is a perspective view, partially cut away, of a valve as shown in  FIG. 4 , with the cover removed and the inlet and a portion of the right outlet port removed. 
       FIG. 6A  is a top plan view of a valve as shown in  FIG. 5  with the cover removed and the curtain closure directing flow out of the left outlet port. 
       FIG. 6B  is a top plan view of a valve as shown in  FIG. 5  with the cover removed and the curtain closure directing flow out of the right outlet port. 
       FIG. 7A  is a side elevation of an alternative two-way valve according to the invention. 
       FIG. 7B  is a top plan view of a valve as shown in  FIG. 7A . 
       FIG. 7C  is a cross section taken along line  7 C— 7 C in  FIG. 7A . 
       FIG. 7D  is a cross section taken along line  7 D— 7 D in  FIG. 7B . 
       FIG. 7E  is a top plan view of a two-way valve of the type shown in  FIGS. 7A–7D , with the cover removed. 
       FIG. 7F  is a top view of a valve insert for a valve of the type shown in the views of  FIGS. 7A–7D . 
       FIG. 7G  a front elevation a valve insert for a valve of the type shown in the views of  FIGS. 7A–7D . 
       FIG. 8A  is a top plan view of a two-way valve of the invention with the cover removed to show an axially and radially moveable shoe to position and press the curtain valve closure into closed position. 
       FIG. 8B  is a top plan view showing some detail of a shoe for a valve of  FIG. 8A . 
       FIG. 8C  is a schematic view showing an axial position of a shoe of the type in  FIG. 8A  in an open position. 
       FIG. 8D  is a schematic view showing an axial position of a shoe of the type in  FIG. 8A  in a closed, but not yet axially extended, position. 
       FIG. 8E  is a schematic view showing an axial position of a shoe of the type in  FIG. 8A  in a closed and fully axially extended position. 
       FIG. 8F  is a schematic view showing the detail of a cam arrangement holding the shoe and closure curtain in the position shown in  FIG. 8D . 
       FIG. 8G  is a schematic view showing the detail of a cam arrangement holding the shoe and closure curtain in the position shown in  FIG. 8E . 
       FIG. 8H  is a top plan view of the valve shown in  FIG. 8D , shown with the cover removed. 
       FIG. 8I  is a top plan view of the valve shown in  FIG. 8E , shown with the cover removed. 
       FIG. 8J  is a cross section of the valve shown in  FIG. 8A , taken on a line  8 J— 8 J in  FIG. 8H . 
       FIG. 8K  is a cross section of the valve shown in  FIG. 8A , taken on a line  8 K— 8 K in  FIG. 8I . 
       FIG. 8L  is a front elevation a valve insert for a valve of the type shown in the views of  FIGS. 8A–8K . 
       FIG. 8M  is a curtain closure element for a valve of the type shown in the views of  FIGS. 8A–8K . 
       FIG. 8N  is an actuator shaft for a valve of the type shown in the views of  FIGS. 8A–8K . 
       FIG. 9A  is a top plan view of another two-way valve according to the invention with an alternative shoe and cam structure. 
       FIG. 9B  is a cross sectional view taken along line  9 B— 9 B in  FIG. 9A . 
       FIG. 9C  is a view similar to  FIG. 9A , but with the cover removed. 
       FIG. 10A  is a top plan view of another two-way valve according to the invention with the cover removed to reveal an alternative shoe and cam structure. 
       FIG. 10B  is a cross sectional view taken along line  10 B— 10 B in  FIG. 10A . 
       FIG. 10C  is a cut-away schematic of the valve shown in  FIG. 10A , showing the shoe and curtain in closed, but not extended position. 
       FIG. 10D  is a cut-away schematic of the valve shown in  FIG. 10A , showing the shoe and curtain in closed, fully extended position. 
       FIG. 10E  is a top plan view of the valve shown in  FIG. 10A , showing the shoe and curtain in open position. 
       FIG. 10F  is a top plan view of the valve shown in  FIG. 10A , showing the shoe and curtain in closed, but not extended position. 
       FIG. 10G  is a top plan view of the valve shown in  FIG. 10A , showing the shoe and curtain in closed and extended position. 
       FIG. 11A  is a top plan view of another two-way valve according to the invention with the cover removed to reveal an alternative shoe and cam structure and showing the closure in the open position. 
       FIG. 11B  is a top plan view of the valve shown in  FIG. 11A  showing the closure in the closed position. 
       FIG. 11C  is an enlarged top plan view of the camming structure locked by a spring mechanism in the open position as in  FIG. 11A . 
       FIG. 11D  is an enlarged top plan view of the camming structure unlocked in the closed position as in  FIG. 11B . 
       FIG. 12A  is a top plan view, with the cover removed, of a three-way version of a valve of the type shown in the views of  FIGS. 7A–7D . 
       FIG. 12B  is a cross sectional view taken along line  12 B— 12 B in  FIG. 12A . 
       FIG. 13A  is a front elevation showing detail of a shoe face having a sealing rim extending above the surface. 
       FIG. 13B  is a top plan showing the shoe and sealing rim illustrated in  FIG. 13A . 
       FIGS. 14A–14F  are front elevations followed by side views for three variations of curtain closures suitable for use in the valves of the invention. 
       FIG. 15A  is a side elevation view of a valve of the invention in operable configuration with a valve actuator with a side removed to show the interior. 
       FIG. 15B  is a top plan view of an actuator of the type shown in  FIG. 15A . 
       FIG. 16  is a top plan view of another form of valve of the invention wherein the closure is arranged to close off either of two outlet ports. 
   

   DETAILED DESCRIPTION 
   The following description illustrates two-way and three-way, power-to-open valves as exemplary of the invention and will be referenced unless another structure is specifically referred to. In all cases, the invention will be described in a preferred form wherein a curtain valve employs an insert, which can be installed by pushing the insert in place in an outlet port of the valve. A primary advantage the invention is that it takes a very small torque to operate this two-way or three-way valve. 
   The various views described below show valves of this preferred type, each being described as comprising a valve body, an inlet port to the valve body, an outlet port to the valve body, and a curtain valve closure comprised of a flexible diaphragm held between two locations, one of the two locations being moveable, e.g., at a pivot arm, and the other being stationary, e.g., at a support means adapted to hold said flexible diaphragm. An insert is preferably provided and is preferably held in operable position in the outlet without fasteners. In several embodiments, a pressure element, referred to herein as a shoe, can provide an added degree of sealing, which enhances operation at low pressure differentials. The various embodiments will be explained in relation to the drawings wherein the elements in  FIGS. 1–3E  will be identified with two digit numbers. Parts in other embodiments which correspond to these numbered parts will be given three digit numbers ending with the two digit numbers assigned for  FIGS. 1–3B , but having a first digit corresponding to other parts in that embodiment. 
   Reference is first made to the embodiment of one preferred form of the invention illustrated in  FIGS. 1 through 3E , wherein  FIG. 1  is shows an exploded view of a curtain valve  20  according to the invention. The valve  20  has a body  22  with an inlet  23  and an inlet connector  24  and at least one outlet  25  and one associated outlet connector  26 . Both connectors are adapted to be connected to pipes or other conduits (not shown). The inner surface  27  of the valve body  22  extends between the inlet  23  and outlet  25  to define a flow passage. The flow passage includes a valve cavity  28 . The cavity  28  can have any shape, but in most of the illustrations it is shown as cylindrical. The cavity  28  is shown in  FIG. 1  as having a single inlet  23  and one outlet  25 , but could have multiple inlets and/or outlets as the needs dictate. 
     FIG. 2  shows in a partially broken away section of the valve  20  of  FIG. 1 , showing how the parts shown in the exploded view of  FIG. 1  are assembled. The curtain valve  20  is illustrated as including a closure insert  30  comprised of a flexible diaphragm  40  supported between two locations, one of said two locations  52  being at a rotatable pivot arm  50  and the other  62  on outlet closure support  60  (on shaft  70 ). The flexible diaphragm  40 , also referred to as a curtain closure, has first and second gripping sections  42  and  44 , respectively, which are shown as enlarged end rib areas but can be formed in any manner effective for the purpose of securing them between two support locations. Reference can be made to  FIGS. 14A–14F  for a number of alternative structures for the flexible diaphragm  40 . In  FIGS. 1–3B , the two support locations  52  and  62  are illustrated as comprising grooves which permit the enlarged gripping sections of the diaphragm to slide into secure supporting connections. Any suitable means for securing the diaphragm  40  in place can be employed, e.g., screws, snaps, hooks and eyes, rivets, stitching, wire, adhesive, or the like. The body can be made of plastic or metal. The construction of the diaphragm will be discussed below. 
   The flexible diaphragm  40 , pivot arm  50 , outlet closure support  60 , shaft  70  supporting the pivot arm and first support location  52  are all shown as comprised in the insert  30 , which is preferably held in operable position in the outlet without fasteners. A cover  80  is affixed to the valve body  22  by suitable means such as fasteners  82  which can be threaded or snap-fit fasteners (e.g., 2–6 screws) suitable for the purpose. In some cases it will be useful to permanently attach the cover by means of adhesive or welding. An O-ring  84  is preferably provided to form a fluid tight seal between the cover  80  and the shaft  70 . The cover  80  can be located at any one or more of the wall sections of body  22 . 
     FIGS. 1 and 2  show detail of the shaft  70 . The shaft  70  is shown to include a central drive shaft  72  and an enlarged cam section  74 . The cam section has a substantially rounded surface  76  extending the major portion of the circumference and a flattened area  78  on one side (seen also in  FIGS. 3C–3E ). Rotatable pivot arm  50 , preferably made of a durable structural plastic, such as nylon or Delrin, for curtain closure  40  is supported on and rotates with shaft  70 , which runs through the cover  80  and the cavity  28 . The part of section  72  of the shaft  70  that extends through the lid  80  and outside the valve body  22  can be turned by an actuator (not shown here, but see  FIGS. 15A and 15B ). The opposite end  73  of shaft  70  is supported at the bottom interior surface of valve cavity  28 , preferably in a recess (not shown here, but see recess  229  in  FIG. 7D ). It is an advantage of the invention that valve operation requires less torque and the actuator required to turn the shaft  70  can be smaller and less expensive than actuators necessary for current HVAC control valves of the type described above. 
     FIG. 2  shows insert  30  positioned at the outlet  25 . The closure support  60  is shown in nested relation in the outlet  25  and has a convex outer surface  63  contacting the inner surface  27  of the valve body  22 . The closure support  60  has an outlet opening  61  with a plurality of diaphragm support members  64  positioned across it. The number of diaphragm support members is optional, typically from 1 to 10, and their extent across the opening  61  and shape and pattern are optional. At least one diaphragm support member  64  should be provided and should extend at least partially across the opening  61 . Preferably, a plurality of support members  64  extend across the opening  61  and divide it into several passageways  65  for fluid to flow out of cavity  28 . The closure support  60  is shown with the support members  64  forming a curved internal face  66  (see corresponding to part  166  in  FIG. 4 ) that extends into the cavity  28  beyond the internal surface  27 . The face  66  can have a slight slant, be flat, concave (shown), convex or of compound shape as predetermined for proper variation of Cv and pressure differential during closing. 
   Rotatable pivot arm  50  is comprised of a number of component parts which enable the arm to hold a moveable end  42  of the flexible diaphragm  40  and move it between closed position shown in  FIG. 3A  and open position shown in  FIG. 3B . Rotatable pivot arm  50  is also operable to move radially and exert closing force holding diaphragm  40  against support  60  to assure a tight seal independent of fluid pressure.  FIGS. 3C through 3E  are schematic enlarged top plan views of a portion of a camming mechanism for a valve as shown in  FIG. 1 , showing how radial movement of the shaft  70  enables the pivot arm  50  to move first rotationally and then radially, thereby moving the pivot arm  50  from an open position toward a closed and locked position. 
   In  FIG. 3C , the flat side  76  of the enlarged section  74  of shaft  70  is seen pressed against a cam following front edge surface  54  of opening  53  of the pivot arm  50 . Reference to  FIG. 2  shows an integral spring  56  providing a radial biasing pressure. In this position, as the shaft  70  rotates, the arm  50  will rotate with it and move diaphragm toward closed position as shown in  FIG. 3A . It is also possible to use a curtain that is mounted on a free rolling roller (not shown), and that the arm is spring loaded, so it can follow the face of the insert. In  FIG. 3D , the shaft  70  has been fully rotated counter clockwise to the closed position shown. In this position, leading edge  57  of arm  50  comes into contact with stopping surface  66   a  of outlet closure support  60 . As the shaft  70  rotates counterclockwise, the effective radius of the shaft  70  increases and pushes against the cam following surface  54  and moves the whole arm  50  radially outward. The shaft will continue its rotation while the pivot arm rotation is stopped until the rounded camming surface  78  contacts cam following front edge surface  53  to, complete the outward radial extension.  FIG. 3D  is a view similar to that of  FIG. 3C  showing the camming mechanism in closed and unlocked position.  FIG. 3E  is a view similar to that of  FIG. 3C  showing the camming mechanism in closed and locked position. 
   As can be seen by reference to  FIGS. 3A and 3B  front surface  51  of the pivot arm  50  is shaped to conform to the inner surface  66  of the closure support  60  so that when flexible closure  40  is moved to closed position as illustrated in  FIG. 3A , the surfaces mate and a good seal can be achieved. This is a distinct advantage of the invention, which is especially useful at low operating pressures where sealing might be a problem for some operations. It can be seen that shaft  70  extends lengthwise through partially squared opening  53  of rotatable pivot arm  50 . As shaft  70  is rotated counter clockwise from the valve open position as shown  FIG. 3B  to the closed position shown in  FIG. 3B , flat surface  78  on enlarged cam section  74  is forward to engage the front edge  54  of opening  53  of rotatable pivot arm  50 . 
   In the arrangement just described, counter clockwise movement of the shaft will move the rotatable pivot arm  50  and bring with it the moveable end  42  of flexible closure diaphragm  40  and extend it across the opening  61  of the closure support  60 . In some embodiments, this motion alone will be sufficient for sealing and no camming is required, but for the preferred operation, especially under low-pressure conditions, rotation of shaft  70  will continue as the pivot arm  50  is stopped and ceases rotary movement, by either being held against a stop (as shown) or by the resistance of the fully-extended diaphragm closure  40 . The continued motion will cause the substantially rounded surface  78  of the camming section  74  of shaft  70  to push against the front edge  54  of squared opening  53  and, thereby, radially move the closure support  60  so that the front surface  51  is pressed against the flexible diaphragm  40  and it into tightly-sealed relation with the curved internal face  66  of the closure support  60 . In this embodiment, the camming arrangement of the shaft  70  and the closure support  50  function to move the front surface  51  both axially to position it and then radially to provide closing pressure. Rotation of the shaft  70  in the opposite direction likewise causes radial and axial movement, but this time in reverse, to open the valve to the position shown in  FIG. 3B . Because this axial movement of the front edge  51  of pivot arm  50  can be likened to the movement of a brake shoe, a the moveable front edge  51  having the capability for axial and radial movement can be referred to as a shoe. 
   Forward nipple  67  on closure support  60  is shown to include flexible snap-fit prongs  68  and positioned within and preferably locked in the outlet  25 . Forward nipple  67  extends into the outlet opening  25  and is preferably sealed within the opening by suitable seal means  69 , such as an O-ring as illustrated or similar separate or integrally molded seal, to prevent by-pass leakage and/or to fasten the insert. The flexible snap-fit prongs  68  be provided with a single or plurality of locking means, e.g., raised ends  68   a  shown shaped to function as hook means, preferably spring biased by virtue of the material of construction, which can be either metal or plastic. One special advantage of the hook means  68   a  is that they hold closure support  60  in place even in the case of a misapplied valve, e.g., attached to the system in the reverse of the correct flow direction. The closure support  60  is preferably made of a plastic selected from the group consisting of Tefzel polymer, Delrin polymer, Teflon polymer or a combination of any of these, Tefzel polymer being the most preferred. The hook means  68   a  can be configured to cooperate with a recess, such as a groove  27   a , or the like, in the valve body. 
   The closure support  60  holding the curtain closure diaphragm  40  is shown to be positioned at least partially within said outlet port  25  and having at least one dimension larger than the dimension of mating outlet port  25  at the inner surface  27  of valve body  22  to thereby secure and orient said insert within said outlet port. The mating surface can be within a recess, such as  227   a  as shown in  FIG. 7C , or it can be against the inner surface  27 of the valve body  22  as in  FIGS. 1–3B . The mating surfaces of the closure support  60  and the valve body  22  and/or its inner surface can be shaped to be complementary in such a way as to cause positive seating of the closure support  60  and make it resistant to displacement during operation or installation. 
   The maximum differential pressure the valve  20  can handle is increased by providing the support members  64  as described. The provision of closure support  60  according to the invention with support members  64  designed specifically for the desired flow conditions, the operating pressures and the material of construction of the flexible closure diaphragm  40 , enables various pressures and flow conditions to be accommodated in a convenient and practical manner. Normally, there would be a risk that the flexible closure diaphragm  40  could be pushed through the outlet  25  by the differential pressure on the fluid between the cavity  28  and the outlet  25 . This is avoided according to the invention by the closure support  60  support members  64 , which in the form illustrated, divide the outlet  61  into a number of smaller openings or passages of suitable shape, for example slots  65 . The slots  65  can also be helpful in reducing cavitation, especially a problem in some valves during high flow rate operation. 
   The ability of the invention to enable practical variation of the thickness of the flexible closure diaphragm  40  and its composition can also be important considerations. The flexible closure diaphragm  40  will preferably be made of a material that comprises a member selected from the group consisting of rubber, such as natural, and synthetic rubbers including silicone rubber, and flexible plastic. It can be reinforced by a suitable material, such as a textile, metal wire mesh or plastic or metal structural materials of the type used for flexible bands, ribbons and belts. 
   The valve is shown in  FIG. 3A  as being closed with flexible closure diaphragm  40  covering the channels  65 . By turning the shaft  70  clockwise, the flexible closure diaphragm  40  will roll off the inner face  66  of outlet closure support  60  and uncover the channels  65  and open the valve ( FIG. 3B ). The support ribs  64  support the flexible closure diaphragm  40  when it is closed and prevents the differential pressure from pressing the flexible closure diaphragm  40  out through the channels  65 . The supporting ribs  64  are shown as straight dividers, but can have any shape as long as they can give support to the flexible closure diaphragm  40 . 
   In order to prevent fluid to flow from by-passing the support  60  in the outlet port  25 , the support  60  is provided with a suitable seal  69 , such as an O-ring as shown. Alternatively, the seal  69  can be formed integrally with the insert  44 , which is preferably made of plastic, for example molded in a Delrin® polymer, Teflon® polymer or a combination of these. The O-ring seal  69  can also provide some resistance against pushing out into the cavity  22 , if the valve is piped backwards by mistake. This function can be made more effective, by providing the support  60  with one or more hook means  68   a , which can employ spring action and can interlock with a groove, rim or recess in the outlet port  25 . Preferably, more than one hook or other clipping means is provided. 
   The installation of the different parts is simple and is an advantage of the invention. The insert  30  is comprised of flexible diaphragm  40 , pivot arm  50 , support  60  and shaft  70 . These parts can be assembled as a unit outside of the valve body  22  and inserted as a unit or they can be installed in any convenient sequence. For example a completed assembly of flexible diaphragm  40 , pivot arm  50 , support  60  and shaft  70  can be inserted at once or the support  60  can be inserted first, followed by the flexible diaphragm  40 , pivot arm  50  and shaft  70 . Other sequences can be employed as practical. The support  60  is preferably installed by inserting it into the opening  25  and snapping it into place. The diaphragm  40  is preferably attached to the pivot arm prior to insertion into the opening  28  and attached to the support, if not yet achieved. The shaft  70  can be moved to its proper position at the bearing point and the lid  80  mounted. The invention enables assembly in a manner particularly efficient for small units and can be modified as desired when space within the valve body permits. 
   The valve as illustrated can close off against low and high pressure providing a good valve for both of these applications. Advantageously, this is true against even very low pressure due to the provision of means for enabling axial movement of the rotatable pivot arm  50  to assure a positive seal. This is important because the differential pressure is sometimes insufficient to force the flexible closure diaphragm  40  into good contact with the support members  64  and/or inner face  66  the closure support  60 . The illustrated arrangement enables the valve to close without any leakage regardless of the pressure. 
   In order to reduce the pushing force requirement while still assuring a positive seal, the surface  51  of the pivot arm or shoe  60  which is facing the curtain, can have a raised rim slightly larger than the outlet opening  25 , such as  156  as illustrated in  FIGS. 13A and 13B . When the shoe  150  is applied to the back of a closure diaphragm  40 , the rim  156  enhances the closing pressure on the diaphragm  40 . Alternatively, the rim can be located on the inner surface  66  of the support  60 . 
     FIG. 4  is an exploded perspective view showing a three-way valve according to the invention and similar in many regards to the two-way valve of  FIGS. 1 through 3E , just described.  FIG. 5  is a perspective view, partially cut away, of a valve as shown in  FIG. 4 , with the cover removed and the inlet and a portion of the right outlet port removed. The operation of this valve is illustrated by  FIG. 6A , which is a top plan view of the valve with the cover removed and the curtain closure directing flow out of the left outlet port.  FIG. 6B  is a similar view with the curtain closure directing flow out of the right outlet port. Parts in this embodiment which correspond to numbered parts in the embodiment of  FIGS. 1–3E  will be given three digit numbers starting with  1  and ending with the two digit numbers assigned for  FIGS. 1–3E . Thus, for example the valve body  122  in  FIG. 4  corresponds to valve body  22  in  FIG. 1 , and so on. Accordingly, this description, for conciseness, need only refer to differences not readily apparent and structure associated with them. The primary difference between this embodiment and that of  FIG. 1  is obviously the provision of an additional out port  125 ′ and the elements necessary for operation of the closure between the two outlets. 
     FIG. 7A  is a side elevation of an alternative two-way valve according to the invention.  FIG. 7B  is a top plan view of a valve as shown in  FIG. 7A .  FIG. 7C  is a cross section taken along line  7 C— 7 C in  FIG. 7A . It can be seen from  FIG. 7C  that the pivot arm  250  is of a different cross section than that of the other embodiments. Here, the pivot arm  250  is a half toroidal section having one end of curtain  240  attached at point  252  and the other end attached at point  262  on the outlet closure support  260 . The shaft  270  is shown as a straight shaft without a camming function. In this embodiment, the pivot arm does not have a shoe function and is not adapted for radial movement. However, this feature could be accomplished in the preferred or an alternate form. 
     FIG. 7D  is a cross section taken along line  7 D— 7 D in  FIG. 7B .  FIG. 7E  is a top plan view of a two-way valve of the type shown in  FIGS. 7A–7D , with the cover removed. It can be seen from this figure that the first diaphragm support  252  is comprise of two threaded screws.  FIG. 7F  is a top view of a valve insert for a valve of the type shown in the views of  FIGS. 7A–7D . The insert  230  is comprised of flexible diaphragm  240 , pivot arm  250 , support  260  and shaft  270  a front elevation a valve insert for a valve of this type is shown  FIG. 7G . 
     FIG. 8A  is a top plan view of an alternate form of two-way valve  320  of the invention with the cover removed to show an axially and radially moveable shoe  350  to position and press the curtain valve closure  340  into closed position over valve outlet  325 . The first support  352  for the diaphragm  340  moves with the shoe  350  and comprises a set of screws and washers.  FIG. 8B  is a top plan view showing some detail of a shoe  350  for a valve of  FIG. 8A . The shoe  350  includes a frame  357  connecting front surface  351  with a rear portion  358  having an opening with front edge  354 . The frame  357  includes vertically oriented posts  357  for holding resilient bands  356 , preferably O-rings or otherwise of rubber or spring material. For an elevation of the shoe  350 , including the posts  356  and the bands, see  FIG. 8J  which is a cross section of the valve shown in  FIG. 8A , taken on a line  8 J— 8 J in  FIG. 8H . 
   Operation of this embodiment will become more clear from the simplified sketches of  FIGS. 8C through 8G .  FIG. 8C  is a schematic view showing an axial position of a shoe of the type in  FIG. 8A  in an open position. Here, shaft  370  can be seen moving the shoe  350  axially counterclockwise toward the closed position.  FIG. 8D  is a schematic view showing an axial position of a shoe  350  in a closed, but not yet axially extended, position. And,  FIG. 8E  is a schematic view showing an axial position of a shoe  350  in a closed and fully axially extended position. In this position, the front surface  351  of the shoe  350  is pressing against the diaphragm  340  to provide closing pressure against the opening  325 . The shaft  370  has rotated past the stop position of  FIG. 8D  and caused the shoe  350  to advance axially as indicated by the arrow.  FIG. 8F  is a schematic view showing the detail of a cam arrangement holding the shoe  350  in the position shown in  FIG. 8D . A distance a is indicated as substantially zero showing the distance between the center of shaft  370  and the front surface  354  of the opening in frame  357 .  FIG. 8G  is a schematic view similar to  FIG. 8G , but shown holding the shoe  350  in the position shown in  FIG. 8E . Here, the distance between the center of shaft  370  and the front surface  354  is a finite distance b sufficient to cause radial motion of the shoe to press diaphragm  340  against opening  325  as shown in  FIG. 8E . Resilient bands  356  are biased toward the open position and positive force on the shaft  370  is required in this embodiment to maintain the shown radial extension. When actuator force is removed, the shoe  350  will resume the position shown in  FIG. 8F . 
   The interrelationship of the structure of this alternative form of valve can be best seen in  FIGS. 8H through 8K . Not all parts are shown numbered to avoid clutter, but have the numbers seen in the other views of this embodiment.  FIG. 8H  is a top plan view of the valve shown in  FIG. 8D , shown with the cover removed. The shoe  350  is shown in closed but not locked position.  FIG. 8I  is a top plan view of the valve shown in  FIG. 8E , shown with the cover removed and the shoe  350  is closed and radially-extended locked position.  FIG. 8K  is a cross section of the valve shown in  FIG. 8A , taken on a line  8 K— 8 K in  FIG. 8I .  FIGS. 8J and 8K  show diaphragm support members  364  and flow passageways  365  as they are open in  FIG. 8J  and closed in  FIG. 8K . 
     FIG. 8L  is a front elevation a valve insert for a valve of the type shown in the views of  FIGS. 8A–8K .  FIG. 8M  is a curtain closure element  340  for a valve of the type shown in the views of  FIGS. 8A–8K . Moveable end  342  has openings to secure it to the shoe  350  at locations  352  and the other end is a fixed end to be secured to a stationary member  362  as previously described.  FIG. 8N  is an actuator shaft  370  for a valve of the type shown in the views of  FIGS. 8A–8K . The actuator shaft  370  includes a central drive shaft  372 , an enlarged cam section  374  having a substantially rounded surface  376 , a flattened area  378  and grooves  379  for holding resilient bands  356 . 
     FIGS. 9A through 9C  show another alternative structure with an axial and radially moveable shoe  450 , but with a distinct camming arrangement to begin the radial movement when axial movement of the shoe  450  has been brought to a closed, but not locked position as in  FIG. 9C .  FIG. 9A  is a top plan view of this two-way valve according to the invention with an alternative shoe and cam structure.  FIG. 9B  is a cross sectional view taken along line  9 B— 9 B in  FIG. 9A  and illustrates the diaphragm  440  positioned over openings  465  at outlet  425  due to rotation of shaft  470  while held in cover  480  and central body recess  429 .  FIG. 9C  is a view similar to  FIG. 9A , but with the cover removed to show an elongated V-shaped groove  475  on shaft  470  to press against follower  358 , biased by spring  359 , on shoe  350 . With the exception of the camming structure, the valve can have the structure and operation as in any of the other embodiments. 
     FIGS. 10A and 10G  are views of another two-way valve according to the invention. Again, with the exception of a camming structure, the valve can have the structure and operation as in any of the other embodiments.  FIG. 10A  is a top plan view with the cover removed to reveal an alternative shoe  550  and cam structure  574 .  FIG. 10B  is a cross sectional view taken along line  10 B— 10 B in  FIG. 10A .  FIG. 10C  is a cut-away schematic of the valve shown in  FIG. 10A , showing the shoe and curtain in closed, but not extended position. In this view, the shaft  570  is seen to include a spring holder  578  and an eccentrically-positioned crank arm  575  which perform the functions provided in the previous embodiment by a camming structure. The eccentrically-positioned crank arm  575  causes radial outward closing movement of shoe  550  against biasing spring  579  when the shoe is in position to seal the opening  525  by pressing the diaphragm  540  into it as accomplished in the other embodiments.  FIG. 10D  is a cut-away schematic of the valve shown in  FIG. 10A , showing the shoe and curtain in closed, fully extended position. Again, counter clockwise movement of the shaft  570  has caused the shoe  550  to be extended radially. For a more complete view of the movement,  FIGS. 10E through 10G  are provided.  FIG. 10E  is a top plan view of the valve shown in  FIG. 10A , showing the shoe and curtain in open position.  FIG. 10F  is a top plan view of the valve shown in  FIG. 10A , showing the shoe and curtain in closed, but not extended position. Finally,  FIG. 10G  is a top plan view of the valve shown in  FIG. 10A , showing the shoe and curtain in closed and extended position. 
     FIGS. 11A and 10D  are views of another two-way valve according to the invention. Here also, with the exception of a camming structure, the valve can have the structure and operation as in any of the other embodiments.  FIG. 11A  is a top plan view of a two-way valve with the cover removed to reveal an alternative shoe  650  and crank arm structure and showing the closure in the open position. In this view, the shaft  670  is seen to include a spring  578  and an eccentrically-positioned crank arm  675  which perform the functions provided in the previous embodiment by a camming structure. The eccentrically-positioned crank arm  675  causes radial outward closing movement of shoe  650  against biasing spring  679  when the shoe is in position to seal the opening  625  by pressing the diaphragm  640  into it as accomplished in the other embodiments. A locked position is reached when spring  679  snaps into recess  679 ′ on shaft  670 .  FIG. 11B  is a top plan view of the valve shown in  FIG. 11A  showing the closure in the closed position.  FIG. 11C  is an enlarged top plan view of the camming structure locked by a spring mechanism in the open position as in  FIG. 11A .  FIG. 11D  is an enlarged top plan view of the camming structure unlocked in the closed position as in  FIG. 11B . 
     FIG. 12A  is a top plan view, with the cover removed, of a three-way version of a valve of the type shown in the views of  FIGS. 7A–7D .  FIG. 12B  is a cross sectional view taken along line  12 B— 12 B in  FIG. 12A . Notable here are the cylindrical shoe  750  and the diaphragm  740  attached at two fixed locations to permit either of outlets  725  or  725 ′ to be covered. With the exception of this structure, the valve can have the structure and operation as in any of the other embodiments. 
     FIG. 13A  is a front elevation showing detail of a shoe face  151  having a sealing rim  156  extending above the surface.  FIG. 13B  is a top plan showing the shoe  150  and sealing rim illustrated in  FIG. 13A . 
     FIGS. 14A–14F  are front elevations followed by side views for three variations of curtain closures suitable for use in the valves of the invention. 
     FIG. 15A  is a side elevation view of a valve of the invention in operable configuration with a valve actuator with a side removed to show the interior.  FIG. 15B  is a top plan view of an actuator  900  of the type shown in  FIG. 15A . The advantage this whole design is that it takes a very small torque to operate this two-way or three-way valve. Because a very small torque is needed a very small motor ( 998 ) and return spring can be used. The gear train need only a modest reduction, which reduces cost and makes a stronger gear train possible. If there is no power to the motor, a spiral (torsion) return spring  997  acts upon the shaft and strives to turn it to the clockwise position and close the valve. The return spring will overcome the friction in the motor, gear train and the small torque needed to operate the valve. When electric power is connected to the motor, it runs and will overcome the torque required to operate the valve. Stop pin  999  limits movement of shaft  970  and can be moved to any of various points (e.g., holes  995 ) to adjust the flow coefficient of the valve. The motor runs until it reaches the counter clockwise position where it stalls and the valve is open. The final gear can be a cogwheel or cogwheel segment, but a wheel with an O-ring driven by a smaller wheel is also a possibility. The low torque requirement makes it a possibility which eliminates the wear an tear of the cogwheel segment. The actuator can be of ON/OFF type or proportional. 
   In order to provide a multiple flow coefficients of a valve, an adjustable stop for the curtain of the valve can be utilized, so it opens to a different degree. This can be done by furnishing either the valve or actuator with an adjustable stop. The range of adjustment of the flow coefficient is rather wide. This is due to the design of the valve, with a rather wide turning of the shaft to operate the valve. Thereby adjustment can be done in rather large increments. A conventional valve would require a very fine adjustment of the arm with the disk. Because of the very small torque requirement to operate the valve many other types of actuators than the above described can be used. Such as, electromagnetic, heated bimetal and heated wax elements with rack and pinion. 
     FIG. 16  is a top plan view of another form of valve of the invention wherein the closure is arranged to close off either port, enabling use of either as the inlet or the outlet. 
   The above description is intended to enable the person skilled in the art to practice the invention. It is not intended to detail all of the possible modifications and variations which will become apparent to the skilled worker upon reading the description. It is intended, however, that all such modifications and variations be included within the scope of the invention which is seen in the above description and otherwise defined by the following claims. The claims are meant to cover the indicated elements and steps in any arrangement or sequence which is effective to meet the objectives intended for the invention, unless the context specifically indicates the contrary.