Abstract:
A mixing valve receives water through a first inlet. The water is rotated by vanes in a first direction to produce a vortex. The water exits though an open end of a slidable tube, where it flows radially outward because of its rotational motion. The tube is axially movable by an actuator located near the open end of the tube, and the tube therefore acts as a steam shut off valve. Steam enters through a second inlet adjacent the open end of the tube, and is directed by vanes in an oppositely rotating vortex and radially inward by a conical surface just beyond the end of the tube. The steam and water mix at a location just beyond the end of the tube, and heated water exits through an axial opening which surrounds the actuator. The temperature of the water is regulated by the actuator.

Description:
SUMMARY OF THE INVENTION 
     This invention relates generally to static mixing of fluids, and more particularly to an apparatus for mixing streams of water and steam and delivering a stream of heated water. 
     In many industrial operations, especially in chemical processes, plant steam provides a convenient source of heat, and can be mixed with water, to provide instant hot water. Conventional steam-water mixing devices, however, are subject to several problems. 
     One problem with conventional steam-water mixing devices is due to the rapid collapse of steam bubbles as the steam condenses upon contact with the water. The rapid collapse of steam bubbles sets up vibrations in the mixing device and in associated plumbing, producing a large amount of noise. 
     Another problem is that failure of the water supply to a conventional mixing device can cause it to deliver steam at its outlet unless elaborate precautions are taken to make the mixing device fail-safe. 
     The principal object of this invention is to provide a simple and reliable steam-water mixing device that is much quieter in operation that previously available steam-water mixers. Still another object of the invention is to provide a simple steam-water mixing device that reliably avoids dangerous maloperation in the event of a water supply failure. 
     Briefly, the invention addresses the noise problem by guiding the incoming water and steam into coaxial vortices inside and outside of a tube, respectively. The vortices come together just beyond an open end of the tube, and mix to produce a stream of heated water. Regulation and fail-safe operation are achieved by using the tube itself as a component of a valve. The tube is moved axially by a temperature-responsive mechanical actuator, and cooperates with a deflecting shoulder in a housing to regulate the flow of steam. The movement of the tube relative to the actuator not only regulates the temperature of the water, but also shuts off the flow of steam in the event of a failure of the water supply. 
     The steam and water mixing apparatus in accordance with the invention has, as one of its components, a tube extending along an axis and having an axial opening at one end. Water is directed, preferably by a first set of vanes, into the interior of the tube, to establish a first vortex of water circulating about the axis, both within the tube and beyond the axial opening. Steam is directed, preferably by a second set of vanes, in a second vortex surrounding the tube, circulating about the axis and extending beyond the end of the tube. The vortices are directed into contact with each other, preferably by a deflecting surface which reduces the radius of the steam vortex, and by an expansion space causing the water to be directed outward, so that the water and steam mix together to produce a stream of heated water. 
     Several other features are present in a preferred embodiment of the invention. One such feature is that the water and steam are directed into counter-rotating vortices. Other preferred features include the following. 
     The flow of steam is regulated in response to the temperature of the exiting heated water stream to maintain the heated water at a substantially constant temperature, and the temperature-responsive regulating mechanism also shuts off the flow of steam when the rate of flow of water falls below a predetermined minimum level. The tube and the deflecting surface are relatively movable in the direction of the axis to vary the cross-section of the steam flow passage, so that the tube and surface together serve as a steam valve. The flow of steam is controlled by a temperature-responsive actuator for effecting relative axial movement of the tube and the deflector surface in a direction to reduce the cross section of the flow passage as the temperature of the heated water increases. 
     The actuator is preferably a mechanical actuator comprising a body and a stem which projects from the body as the temperature of the heated water increases. The actuator body is connected to the tube through a sleeve which extends along the axis into the tube through the axial opening. The stem of the actuator bears against a rod which extends, along the axis, through the sleeve and in turn bears against a surface which is held in fixed relationship to the tubular enclosure. Thus, the actuator moves the tube axially relative to the deflector in a direction to decrease the cross-sectional area of the annular opening as the temperature of said heated water in the exiting stream increases. An adjusting screw, threaded into the tubular enclosure and extending along the axis, has an end providing the surface against which said rod bears. 
    
    
     Other objects, details and advantages of the invention will be apparent from the following detailed description when read in conjunction with the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an axial cross-section of a steam-water mixing apparatus in accordance with the invention; 
     FIG. 2 is an axial cross-section of the same mixing apparatus, showing the tube extending past the steam deflector to shut off the flow of steam; 
     FIG. 3 is a radial section taken on plane  3 — 3  in FIG. 1, showing the water vanes; 
     FIG. 4 is a radial section taken on plane  4 — 4  in FIG. 1, showing the steam vanes; 
     FIG. 5 is a radial section taken on plane  5 — 5  in FIG. 1, showing the water openings in the tube. 
    
    
     DETAILED DESCRIPTION 
     The steam-water mixing apparatus of the invention can be housed in a conventional valve body  10 , having first, second and third ports  12 ,  14  and  16 , and a neck  18 . The valve body is cast with an internal wall  20 , having a circular opening  22 , which, in normal usage, would provide a mounting for a valve seat. However, in this case, the opening  22  is formed with a cylindrical inner face having a groove receiving an O-ring  24 . Port  12  serves as a water inlet port, port  14  serves as a steam inlet port, and port  16  serves as a heated water outlet port. 
     The steam-water mixing apparatus  26  comprises a tubular enclosure  28  threaded into neck  18 , and sealed in neck  18  by an O-ring  30 . The apparatus  26  extends through O-ring  24  and into port  16 , with a reduced end portion  32  of the apparatus closely fitting the wall of the upper part of port  16 . 
     Within enclosure  28  is a tube  34  having an opening  36  at its lower end. The upper end of the tube  34  has a flange  38 , and a coil spring  40 , surrounding the tube  34 , is in compression between flange  38  and a retaining ring  42 , which is held in place within enclosure  28  by a snap ring  43 . 
     The tube  34  has a closure  44  in its upper part, and a sleeve  46  is threaded into the closure and locked in place by a set screw  48 . The sleeve receives a rod  50 , the upper end of which engages an adjusting screw assembly including a screw  52  threaded into a neck  54  formed at the upper end of the enclosure  28 , and locked in place by a locking nut  56 . The adjusting screw and locking nut are protected by a cover  58 , which is threaded onto the exterior of the neck. The adjusting screw assembly includes a rod-receiving element  59 , which is engaged by the upper end of the rod  50 , and which has a groove with an O-ring as a seal to prevent water leakage to the vicinity of the adjusting screw. 
     An actuator  60 , comprising an actuator body  62  and a piston  64 , is connected to the lower end of the sleeve  46  by a connector  66 . The actuator body  62  is threaded into the sleeve, and its piston  64  bears against the lower end of rod  50 . The actuator is preferably a thermally responsive mechanical actuator of the kind described in my U.S. Pat. No. 5,816,493, dated Oct. 6, 1998, incorporating a thermally expansible material comprising an elastomer and a thermostatic wax. The disclosure of U.S. Pat. No. 5,816,493 is incorporated by reference. 
     The body of the actuator, which contains the thermally expansible material, is located outside the tube  34  and aligned with opening  36 . It is positioned so that it is responsive to the temperature of the stream of heated water flowing through port  16 . In operation, if the temperature of the exiting water rises, the thermally responsive material will expand, causing piston  64  to extend. The force of the piston against the end of rod  50  produces a reaction by which the actuator body pulls downwardly, on sleeve  46 , causing the tube  34  to move downward, as shown in FIG.  2 . The downward movement of the tube  34  compresses coil spring  40 . 
     Water inlet port  12  communicates with the interior of the enclosure  28  through an annular vaned opening  68 , having vanes  70  (FIG. 3) which are disposed to induce a clockwise vortex (looking down) in the inflowing water. The tube  34  has a set of three openings  72  (FIGS.  1  and  5 ), which are separated from one another by narrow partitions that do not materially affect the vortex flow of water through the openings  72 . The openings are sufficiently large to allow the vortex induced by vanes  70  to continue within the tube  34  and past the opening  36  at the lower end of the tube. Openings  72  are preferably axially longer than vaned opening  68 , and are positioned so that they at least partially overlap vaned opening  68  both when the tube is in its uppermost position as shown in FIG. 1, and in its lowermost position, as shown in FIG.  2 . In normal operation, the tube will be in an intermediate position between the positions shown in FIGS. 1 and 2, with the lower edges of openings  72  either approximately aligned with, or below, the lower edge of vaned opening  68 . 
     The lower part of enclosure  28 , just above its end  32 , and the inner wall of outlet port  16 , define an expansion space that is radially larger than the opening  36  of tube  34 . This expansion space allows the rotating water vortex exiting from the tube through opening  36  to expand radially, so that the water vortex is directed outward in the space below opening  36 . 
     The tube  34  extends through a sealing ring  74  fitted in a groove in an annular barrier  76  formed on the inner wall of the enclosure  28 . This barrier prevents steam and water from coming into contact with each other in the space between the tube and the inner wall of enclosure  28 . 
     Below the location of the barrier, the enclosure  28  has another annular, vaned opening  78  in communication with the steam inlet port  14 . This opening is provided with vanes  80  (FIG. 4) which induce a counterclockwise flow of steam (looking down) in the annular space surrounding the lower portion of tube  34 . 
     A frusto-conical deflecting surface  82  is formed in the inner wall of the enclosure  28  adjacent its lower end. Below the deflecting surface, the inner wall of the enclosure has a diameter slightly larger than the outer diameter of the tube  34 , and has a groove with an O-ring  84  for contacting the lower portion of tube  34  when the tube  34  moves downward. 
     As shown in FIG. 1, when the tube  34  is in its uppermost position, and also during normal operation, there is an annular gap  86  between the lower end of the tube and the frusto-conical deflecting surface for the flow of steam downward and inward toward the water flowing out of the lower end of tube  34 . The clockwise rotation in the water vortex forces the water outward, while the deflecting surface  82  deflects the counterclockwise rotating steam vortex inward, so that the steam and water meet just below the opening  36  at the lower end of the tube  34 . The counter-rotating vortices of steam and water mix in the space just below the lower end of the tube and above the actuator body  62 , producing a stream of heated water, which flows downward through port  16 . 
     In operation of the mixer, the actuator, responding to the temperature of the exiting water stream, regulates the position of the tube  34  to control the size of gap  86  and thereby control the flow of steam through the steam port  14  and through the vaned opening  78 . This holds the temperature of the exiting water stream at a constant level determined by the thermal characteristics of the actuator. 
     Setting screw  52  controls the initial position of tube  34 , and is used to adjust the starting size of gap  86 . 
     Although I do not intend to be bound by any particular theory of operation, I have found that the high noise reduction achieved by the invention is apparently the result of the collision of the steam and water streams by virtue of the inward deflection of the rotating stream of steam by surface  82  and the tendency of the rotating stream of water to move radially outward is it passes beyond the opening of tube  34 . If water is passed into the device through port  14  and steam is passed into the device through port  12 , no similar noise reduction performance occurs. The collision of the steam and water streams eliminates the noise that occurs as the result of collapsing steam bubbles in conventional mixers in which steam is injected into cold water. In the preferred embodiment, the inwardly directed steam vortex collides with an outwardly moving water vortex in the space below the opening  36  of tube  34 . However, it is also possible to achieve noise reduction in an embodiment in which the steam vortex is deflected inward while the water vortex is confined so that it does not expand radially, and in an embodiment in which the water vortex is permitted to expand radially and the steam vortex is not deflected inward. The terminology “means for directing the vortices into contact with each other,” as used herein, should therefore be understood as encompassing the steam deflection surface  82 , or the expansion space below opening  36  of tube  34 , or both, or any equivalent directing means capable of causing inward radial movement of the steam vortex, outward radial movement of the water vortex, or both, whether specifically mentioned herein or within the level of ordinary skill in the art. 
     As mentioned previously, the steam and water vortices preferably counter-rotate. Counter-rotation makes relatively little difference at high flow rates, and it is possible to achieve good noise reduction with the steam and water streams rotating in the same direction. However, at lower flow rates noise reduction is considerably better with counter-rotating steam and water vortices. 
     In the event of a failure of the water supply, the presence of steam in the vicinity of the actuator body will raise the temperature of the actuator to a level such that it moves the tube  34  to the closed position depicted in FIG. 2, rapidly shutting off the flow of steam. In general, the hot water delivery piping connected to outlet port  16  will be sufficiently long that any steam that flows through gap  86  before it is closed by tube  34  will have condensed within the piping. 
     With the flow of steam shut off, the actuator causes the valve to operate as a trap. That is, as the actuator  60  cools, it causes the gap  86  to open slightly, slowly discharging condensate, which accumulates in the steam supply side of the device. The warm condensate, in turn, contacts the actuator body  62 , causing a modulating action, keeping the gap nearly closed. Any steam which escapes through the gap once again causes the gap to close fully until the actuator cools and the modulating action resumes. The gap will not open fully until the water supply is restored. 
     Various modifications can be made to the apparatus described. For example, the thermally responsive actuator can be any of a wide variety of devices, for example a thermostat actuator utilizing a wax pellet, or a positioning motor controlled by an external, temperature-responsive controller such as a PID (proportional integral derivative) controller or PLC (programmed logic controller). 
     Various departures can be taken from the specific structure shown in the drawings. For example, the water vortex can be generated by vanes mounted in tube  34  instead of by vanes mounted in passage  68  of enclosure  28 . Likewise, the steam vortex can be produced by vanes mounted on the exterior of the tube instead of by vanes mounted in opening  78 . The steam and water vortices can also be produced by any of a wide variety of known alternative vortex-producing devices such as deflectors, tangential flow nozzles, spiral inserts, rotating impellers and the like. Thus, the terminology “means for directing water into the interior of the tube and for establishing a first vortex of water” should be understood as encompassing not only a vaned passage external to the tube  34 , but also alternatives such as a simple water conduit external to the tube together with a vortex producing device, such as a spiral insert, within, on or external to, the tube. 
     The configuration of parts at the location of the open end of tube  34  can also be modified. For example, the lower end of tube  34  can be externally tapered, and can cooperate with a horizontal shoulder rather than with frusto-conical deflecting surface  82 . 
     The setting screw  52  can be replaced by an external positioning motor that is modulated by a PID or PLC temperature controller. The controller can be set for any temperature by a thermocouple or a downstream sensor. The actuator  62  can then act as a safety device, setting an upper limit on the discharge temperature. 
     Still other modifications may be made to the apparatus and method described above without departing from the scope of the invention as defined in the following claims.