Abstract:
The method is for treating a liquid or slurry with an ultrasonic energy. A first rotatable member being permeable to a medium and a first vibrating device are provided. The first vibrating device and the first member have a first gap formed therebetween so that the first gap represents a first distance. A guide member aligned with the first member exerts a pressure on the medium. The guide member breaks up fiber flocculation close to the upper surface of the medium. The medium is fed between the first member and the guide member. The first vibrating device generates pulses through the first member to form imploding bubbles in the medium. The bubbles have a critical diameter prior to implosion that is greater than the first distance to prevent the bubbles from growing in the first gap to a size greater than the first distance.

Description:
PRIOR APPLICATION 
     This is a continuation-in-part application of U.S. patent application Ser. No. 10/451,962, filed 27 Jun. 2003, now U.S. Pat. No. 7,147,755, that claims priority from PCT application no. PCT/SE02/02195 filed 28 Nov. 2002 that claims priority from U.S. provisional patent application Ser. No. 60/339,380, filed 11 Dec. 2001. 
    
    
     TECHNICAL FIELD 
     The present invention is an ultrasonic transducer system with a guiding device in operative engagement therewith. More particularly, the transducer system may be used on moving endless members that are permeable to liquid and the guiding device is in contact with the medium on the moving endless members. 
     BACKGROUND AND SUMMARY OF INVENTION 
     Ultrasonic energy has been applied to liquids in the past. Sufficiently intense ultrasonic energy applied to a liquid, such as water, produces cavitation that can induce changes in the physiochemical characteristics of the liquid. The subject of sonochemistry, which deals with phenomena of that sort, has grown very much during recent years. 
     Most of the published material in sonochemistry and related subjects pertains to batch processes, that is, the liquid solution or dispersion to be treated is placed in a container. The liquid in the container is then stirred or otherwise agitated, and ultrasound is applied thereto. It is then necessary to wait until the desired result, physical or chemical change in the liquid, is achieved, or until no improvement in the yield is observed. Then the ultrasound is turned off and the liquid extracted. In this way liquid does not return to its initial state prior to the treatment with ultrasonic energy. In this respect, the ultrasound treatment is regarded as irreversible or only very slowly reversible. 
     Far from all industrial processes using liquids are appropriately carried out in batches, as described above. In fact, almost all large-scale processes are based upon continuous processing. The reasons for treating liquids in continuous processes are many. For example, the fact that a given process may not be irreversible, or only slowly reversible, and requires that the liquid be immediately treated further before it can revert to its previous state. 
     Shock waves external to collapsing bubbles driven onto violent oscillation by ultrasound are necessary for most if not all physiochemical work in liquid solutions. The under-pressure pulses form the bubbles and the pressure pulses compress the bubbles and consequently reduce the bubble diameter. After sufficient number of cycles, the bubble diameter is increased up to the point where the bubble has reached its critical diameter whereupon the bubble is driven to a violent oscillation and collapses whereby a pressure and temperature pulse is generated. A very strong ultrasound field is forming more bubbles, and drives them into violent oscillation and collapse much quicker. 
     A bubble that is generated within a liquid in motion occupies a volume within said liquid, and will follow the speed of flow within said liquid. The weaker ultrasound field it is exposed to, the more pulses it will have to be exposed to in order to come to a violent implosion. This means that the greater the speed of flow is, the stronger the ultrasound field will have to be in order to bring the bubbles to violent implosion and collapse. Otherwise, the bubbles will leave the ultrasound field before they are brought to implosion. A strong ultrasound field requires the field to be generated by very powerful ultrasound transducers, and that the energy these transducers generate is transmitted into the liquid to be treated. Based upon this requirement, Bo Nilsson and Hakan Dahlberg started a development of new types of piezoelectric transducer that could be driven at voltages up to 13 kV, and therefore capable of generating very strong ultrasonic fields. 
     A very strong ultrasonic source will cause a cushion of bubbles near the emitting surface. The ultrasound cannot penetrate through this cushion, and consequently no ultrasound can penetrate into the medium to be treated. The traditional way to overcome this problem is to reduce the power in terms of watts per unit area of emitting surface applied to the ultrasonic transducers. As indicated above, the flow speed of the medium to be treated will require a stronger ultrasound field and therefore an increased power applied to the ultrasonic transducers. The higher the power input is, the quicker the cushion is formed, and the thicker the formed cushion will be. A thick cushion will completely stop all ultrasound penetration into a liquid located on the other side of this cushion. All the cavitation bubbles in this cushion will then stay in the cushion and cause severe cavitation damage to the ultrasound transducer assembly area leading to a necessary exchange of that part of the ultrasound system. This means that little or no useful ultrasound effect is achieved within the substrate to be treated, and that the ultrasound equipment may be severely damaged. There is a need to solve the problems outline above. The transducer systems of the present invention provide a solution to the problems. 
     More particularly, the method is for treating a liquid or slurry with an ultrasonic energy. A first rotatable member being permeable to a medium and a first vibrating device are provided. The first vibrating device and the first member have a first gap formed therebetween so that the first gap represents a first distance. A guide member aligned with the first member exerts a pressure on the medium. The guide member breaks up fiber flocculation close to the upper surface of the medium. The medium is fed between the first member and the guide member. The first vibrating device generates pulses through the first member to form imploding bubbles in the medium. The bubbles have a critical diameter prior to implosion that is large enough to prevent the bubbles from growing in the first gap to a size greater than the first distance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of the formation of a reactor of a prior art system; 
         FIG. 2  is a graphical illustration of the correlation between iodine yield and acoustic power; 
         FIG. 3  is a perspective view of the transducer system of the present invention disposed below a movable endless member; 
         FIG. 4  is a cross-sectional view along line  4 — 4  in  FIG. 3 ; 
         FIG. 5  is an enlarged view of a central segment of the movable endless permeable member, the elongate foil and the slurry; 
         FIG. 5A  is an enlarged view of the cavitation bubbles dispersed in slurry disposed above the movable endless medium, indicated with dashed lines as  5 A in  FIG. 5 ; 
         FIG. 5B  is an enlarged view of a portion of the movable endless permeable member and the elongate foil; 
         FIG. 6  is a cross-sectional view of a second embodiment of the transducer system of the present invention; 
         FIG. 7  is a cross-sectional view of a plurality of transducers disposed below a movable endless medium. 
         FIG. 8  is a schematic cross-sectional side view of transducer system and guiding member of the present invention; 
         FIG. 9  is a schematic cross-sectional side view of transducer system and guiding member including a retardation zone of the present invention; 
         FIG. 10  is a schematic cross-sectional side view of transducer system and guiding member including a load member of the present invention; 
         FIG. 11  is a schematic cross-sectional side view of an outer edge of transducer system and guiding member including a load member of the present invention; 
         FIG. 12  is a schematic cross-sectional side view of a transducer system of the present invention with the transducer above the endless member; 
         FIG. 13  is a schematic cross-sectional side view of the transducer system with a guide member integrated with the transducer system of the present invention; 
         FIG. 14  is a schematic cross-sectional side view of a double-sided transducer system of the present invention; 
         FIG. 15  is a schematic cross-sectional side view of the double-sided transducer system associated with a wire arrangement and suction boxes of the present invention; 
         FIG. 16  is a schematic cross-sectional side view of the double-sided transducer system in a plane wire arrangement of the present invention; 
         FIG. 17  is a schematic cross-sectional side view of the double-side transducer systems associated with a double wire arrangement of the present invention; 
         FIG. 18  is a schematic cross-sectional side view of a wire arrangement of the present invention for high consistency forming of low weight paper direct on the wire; 
         FIG. 19  is a schematic cross-sectional side view of a wire arrangement of the present invention for high consistency forming of high weight paper direct on the wire; and 
         FIG. 20  is a schematic cross-sectional side view of the present invention with three transducers placed at integer multiple wavelength distances from each other. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a side view of a prior art transducer system  10  that has a container  11 , such as a stainless reactor, with a wall  12  for containing a liquid  13 . A transducer  14  is attached to an outside  16  of the wall  12 . When the transducer  14  is activated, a pillow  18  of cavitation bubbles  20  are formed on an inside  22  of the wall  12  due to the fracture zone in the liquid  13  that may be a result of fracture impressions on the inside  22  of the wall  12 . The bubbles may be held to the inside wall due to the surface tension of the liquid  13 . The bubbles  20  are good insulators and prevent the effective transmission of the ultrasonic energy into the liquid  13 . The under-pressure pulses of the ultrasonic energy transmitted by the transducer  14  create the cavitation bubbles. In this way, the pressure inside the bubbles is very low. 
       FIG. 2  is a graphical illustration that shows the iodine yield is affected by increased acoustic power on the system  10 . The more power is applied, the thicker the formation of the bubbles  20 , as shown in  FIG. 1 , and the yield increase is reduced and drops sharply at power ratings over 100 Watts in this case. In this way, the cavitation bubbles severely limit the usefulness of increasing the acoustic power to improve the iodine yield. 
       FIG. 3  is a perspective view of the transducer system  100  of the present invention. The system has a movable endless permeable member  102 , such as a woven material, paper machine plastic wire or any other bendable medium permeable to liquids, that is rotatable about rollers  104  that guide the member  102  in an endless path. As explained below, it is important that the member is permeable to a liquid that may carry ultrasonic energy to the liquid disposed above the member  102  so as to effectively create the cavitation bubbles in the liquid or slurry to be treated. The ultrasonic energy may be used to reduce flocculation  163 , best shown in  FIG. 5A , of fibers in the liquid to be treated because the bubbles implode or collapse to generate pressure pulses to the fiber flocculation  163  so that the fibers are separated from one another to evenly distribute or disperse the fibers in the liquid. The pressure pulses may be about 500 bars so the pulses are more forceful than the forces that keep the fiber flocculation together. In general, the longer the fibers or the higher the fiber consistency is the higher the tendency of flocculation. 
     The member may have a speed up to 2000 meters per minute in the machine direction (MD) as shown by an arrow (F). An elongate foil  106 , made of, for example, steel or titanium is disposed below the permeable member  102  and extends across a width (W) of the member  102 . A plurality of transducers  108 , such as magneto-strictive, piezoelectric or any other suitable type of transducers, is in operative engagement with the foil  106  such as by being integrated therewith or attached thereto. All transducers mentioned below are preferably ultrasound transducers although that is often not mentioned. 
       FIG. 4  is a detailed view of one of the transducers  108  attached to a mid-portion  118  of the hydrodynamic foil  106 . More particularly, the foil  106  has a rear portion  110  and a front portion  112 . The rear portion  110  has a rectangular extension  114  that extends away from a top surface  116  of the foil  106 . The mid-portion  118  of the foil  106  has a threaded outside  120  of a connecting member  122  also extending away from the top surface  116  so that a cavity  124  is formed between the extension  114  and the connecting member  122 . 
     The front portion  112  has an extension  126  that extends away from the top surface  116  and has a back wall  128  that is perpendicular to a bottom surface  130  of the foil  106  so that a cavity  132  is formed between the back wall  128  and the member  122 . The extension  126  has a front wall  134  that forms an acute angle alpha with the top surface  116 . The cavities  124  and  132  provide resonance to the ultrasound transmitted by the transducers  108  to reinforce the amplitude of the vibrations of the ultrasound. The front wall  134  forms an acute angle alpha with a top surface  116  of the foil  106  to minimize the pressure pulse when the water layer under the member is split by the front wall  134  so a larger part of the water is going down and only a minor part is going between the top side of the foil  116  and the member  102 . When the member  102  is moving over the foil surface  116  a speed dependant under-pressure is created that will force down the member  102  against the foil surface  116 . When the member is leaving the foil  106  there is room to urge the liquid  156  through the member  102 . 
     In other words, the design of the extension  126  is particularly suitable for paper manufacturing that has slurry of water and fibers. The water layer split at the front wall  134  creates an under-pressure pulse so that the water on top of the moving medium flows through the member  102  and into a container there below. The design of the extension  126  may also be designed for other applications than paper making that is only used as an illustrative example. 
     The transducer  108  has a top cavity  136  with a threaded inside wall  138  for threadedly receiving the member  122 . The transducer  108  may be attached to the foil  106  in other ways. For example adhesion or mechanical fasteners may attach the transducer and the present invention is not limited to the threaded connection described above. 
     Below the top cavity  136 , a second housing cavity  140  is defined therein. The cavity  140  has a central segment  141  to hold a bottom cooling spacer  142 , a lower piezoelectric element  144 , a middle cooling spacer  146 , an upper piezoelectric element  148  and a top cooling spacer  150  that bears against a bottom surface  152  of the connecting member  122 . The spacers  142 ,  146 ,  150  are used to lead away the frictional heat that is created by the elements  144 ,  148 . 
     By using three spacers, all the surfaces of the elements  144 ,  148  may be cooled. As the piezoelectric elements  144 ,  148  are activated, the thickness of the elements is changed in a pulsating manner and ultrasonic energy is transmitted to the member  122 . For example, by using a power unit with alternating voltage of a level and frequency selected to suit the application at hand, the elements  144 ,  148  start to vibrate radially. In this way, if the AC frequency is 20 kHz then a sound at the same 20 kHz is transmitted. It is to be understood that any suitable transducer may be used to generate the ultrasonic energy and the invention is not limited to piezoelectric transducers. 
       FIG. 5  is an enlarged view of a central segment  154  so that the permeable member  102  bears or is pressed against the top surface  116  of the member  122  of the foil  106  so there is not sufficient space therebetween to capture cavitation bubbles. In other words, an important feature of the present invention is that a gap  155  defined between the foil  106  and the member  102  has is less than one half critical bubble diameter so that no bubbles of critical size can be captured therebetween. The gap  155  between the member  102  and the foil  106  is defined by the tension in the member  102 , the in-going angle between the member  102  and the foil  106 , the pressure pulse induced by the water layer split at the front of the foil  106 , the geometry of the foil  106 , the under-pressure pulse when the member  102  leave the foil  106  and the out-going angle of the member  102 . The bubbles  158  have a diameter d 1  that is at least twice as long as the distance d 2  of the gap  155  between the top surface  116  of the foil  106  and the bottom surface  161  of the permeable member  102 . In this way, the cavitation bubbles  158  are forced through the permeable member  102  to disperse into the liquid substance  156  that is subject to the ultrasonic treatment and disposed above the member  102 . The liquid substance  156  has a top surface  160  so that the bubbles  158  are free to move between the top surface  160  of the substance  156  and a top surface  162  of the member  102 . In general, the effect of the ultrasonic energy is reduced by the square of the distance because the liquid absorbs the energy. In this way, there are likely to be more cavitation bubbles formed close to the member  102  compared to the amount of bubbles formed at the surface  160 . An important feature is that because the member  102  is moving and there is not enough room between the foil  106  and the member  102 , no cavitation bubbles are captured therebetween or along the top surface  162  of the movable member  102 . 
     The second embodiment of a transducer system  173  shown in  FIG. 6  is virtually identical to the embodiment shown in  FIG. 4  except that the transducer system  173  has a first channel  164  and a second channel  166  defined therein that are in fluid communication with an inlet  168  defined in a foil member  169 . The channels  164 ,  166  extend perpendicularly to a top surface  170  of a connecting member  172 . The channels  164 ,  166  may extend along the foil  169  and may be used to inject water, containing chemicals, therethrough. For example, in papermaking, the chemicals may be bleaching or softening agents. Other substances such as foaming agents, surfactant or any other substance may be used depending upon the application at hand. The ultrasonic energy may be used to provide a high pressure and temperature that may be required to create a chemical reaction between the chemicals added and the medium. The channels  164 ,  166  may also be used to add regular water, when the slurry above the moving medium is too dry, so as to improve the transmission of the ultrasonic energy into the slurry. The chemicals or other liquids mentioned above may also be added via channels in the front part of the transducer assembly bar  106 . If the liquid content of the medium to be treated is very low, the liquid may simply be applied by means of spray nozzles under the web. Also in those cases may the applied liquid be forced into the web by the ultrasonic energy and afterwards be exposed to sufficient ultrasound energy to cause the desired reaction to take place between the chemicals and the medium to be treated. 
       FIG. 7  is an overall side view showing an endless bendable permeable medium  174  that are supported by rollers  176   a–e . Below the medium  174  is a plurality of transducer systems  178   a–e  for increased output by adding more ultrasonic energy to the system. By using a plurality of transducers, different chemicals may be added to the slurry  179 , as required. The slurry  179  contains fibers or other solids, to be treated with ultrasonic energy, is pumped by a pump  180  in a conduit  181  via a distributor  182  onto the medium  174  that moves along an arrow (G). The treated fibers may fall into a container  184 . 
     The transducer system of the present invention is very flexible because there is no formation of cavitation bubble pillows in the path of the ultrasonic energy. By using a plurality of transducers, it is possible to substantially increase the ultrasonic energy without running into the problem of excessive cavitation bubbles to block the ultrasound transmission. The plurality of transducers also makes it possible to add chemicals to the reactor in different places along the moving medium, as required. 
       FIG. 8  is a cross-sectional view of a transducer system  200  that has a movable endless permeable member  202  that may be identical to the member  102  above and may be made of a woven material, paper machine plastic wire or any other bendable medium permeable to liquids, that is rotatable about rollers that guide the medium in an endless path. As explained in detail above, it is important that the member is permeable to a liquid or other medium that may carry ultrasonic energy to a liquid or other medium  204  disposed above the member or wire  202  so as to effectively create the cavitation bubbles in the liquid or medium  204  to be treated. The ultrasonic energy may be used to reduce flocculation of fibers in the medium liquid to be treated because the bubbles implode or collapse to generate pressure pulses to the fiber flocculation so that the fibers are separated from one another to evenly distribute or disperse the fibers in the medium  204 . 
     A guide member  206  is disposed above the medium  204  and exerts a downward pressure F 1  on the stock medium  204  so that a distance d 6  is formed between a bottom surface  208  at an outer end  210  of the guide member  206  and an upper surface  212  of the member  202 . It is also possible for the guide member  206  to merely gently rest on the stock medium  204 . Preferably, the distance d 6  is less than a thickness d 7  of the incoming medium  204  upstream of the position of the guide member  206 . A transducer  203  is disposed below the member  202  to provide the ultrasonic energy that is described in detail above. An important feature of the guide member  206  is that it breaks up larger fiber flocculation  207  that may be disposed closer to the upper surface  209  of the stock medium  204 . It is particularly useful for breaking up such flocculation that cannot be reached by the ultrasound generated by the transducer  203  that is located below the wire  202  and thus more affects fiber flocculation closer to the wire  202  than fiber flocculation that may be close to the surface  209 . The use of the transducer improves the fiber formation with up to about 18% compared to using no transducer. The addition of the guide member  206  improves the fiber formation with up to about 28% compared to using no transducer or guide member when all values are measured as according to the Kajaani formation index. It is not possible to merely increase the power of the transducer  203  to reduce fiber flocculation close to the surface  209  because that could destroy the initial fiber network that already has been formed on the wire  202 . 
     As best shown in  FIG. 9 , the pressure F 1  on the medium creates a retardation zone  214  right behind the guide member  206  and an acceleration zone  216  below the guide member  206  since the thickness d 7  of the medium  204  is reduced to the thickness d 6 . The retardation zone  214  may include an area of turbulence of the stock medium and has a thickness d 8  that is greater than both the thickness d 6  and d 7 . This means the medium  204  flows at a higher velocity in the zone  216  compared to the zone  214 . The medium  204  is first exposed to acceleration in the zone  216  and then to retardation to the normal velocity in a normal zone  218  at or downstream of the outer end  210  of the guide member  206 . The thickness of the medium  204  is returned to near the thickness d 7  in the normal zone  218  since some liquid may have been drained through the member  202  during the passage of the transducer system  200 . As explained below, there may also be another retardation zone downstream of the guide member. This increase and then slowdown in velocity exposes fiber flocculation to shear forces that break them up. Also, because the thickness d 6  is less than the thickness d 7 , the fibers are closer to the transducer  203  in the acceleration zone  216  and are therefor exposed to higher ultrasonic energy to better break up flocculation without destroying the fiber network of the medium  204 . By effectively breaking up fiber flocculation without destroying any previously formed fiber network, the fibers are more efficiently distributed for improved strength. 
       FIG. 10  shows the system  200  with a weight  220  such as a liquid bag placed on the outer end  210  of the guide member  206  to increase the downward force to a force F 2  that is greater than the force F 1  and the thickness in the acceleration zone  216  is reduced from the thickness d 6  to a smaller thickness d 9 . A retardation zone  222  with a thickness d 10  may be formed downstream of the outer end  210  before the stock medium  204  returns to a normal thickness d 7  or near d 7 . Because the thickness d 9  is so thin the retardation zone  214  upstream of the guide member  206  is also greater. 
       FIG. 11  shows the system  200  with a large weight  224  that is placed on the outer side ends of the width of the moving member  202  so that the guide member  206  rests on the member  202  and nearly no medium may pass therebetween so that the medium is forced to pass on the inside of the weight  224  and below the guide member  206 . In other words, the medium  204  may be forced to flow inwardly around the weight  224 . This prevents any undesirable cross-flow or transverse flow of the medium out from the member  202 . The weight  224  exerts a pressure F 3  that is greater than the pressures F 2  and F 1 . 
       FIG. 12  is a cross-sectional side view of a system  450  that has an endless wire or member  452  carrying a stock medium  454 . An upstream transducer  456  with a foil  458  is disposed below the wire  452  and a second downstream transducer  460  with a foil  462  is positioned above the wire  452 . A guide member  464  is connected to the foil  462  and a reflector  466  is aligned with the foil  462 . The reflector  466  is preferably positioned immediately below and bears against the wire  452 . In this way, the free fibers in the upper part of the stock medium  454  are substantially affected by the vibrations from the transducer  460  and the foil  462  without destroying the fiber network that has previously been formed on the wire  452 . The reflector  466  prevents fillers and fine fibers from being washed out as a result of the downwardly directed ultrasound from the transducer  460  and the foil  462  associated therewith. The reflector  466  prevents some or most the water from flowing downwardly and some of the ultrasound is reflected off the transducer  460 . One advantage of using a transducer that is placed above the stock medium is that the initial fiber structure that has been formed close to the wire is less likely to be destroyed by the ultrasound that comes in a downward direction from the surface of the stock medium. 
       FIG. 13  is a cross-sectional side view of a system  230  with a transducer unit  232  that is associated with a transverse foil element  234  that has an integrated guide member  236  with a curved or sloping bottom surface  238 . The surface  238  bears against the stock medium  240  disposed on the endless member  242 . A retardation zone  244  is formed behind the surface  238  and an acceleration zone  246  below the bottom surface  248 , as described in detail above. Below the member or wire  242  is a lower foil  250  disposed that bears against a bottom surface  252  of the member  242 . The foil  250  prevents the washing out of fine fiber fractions and fillers. The flexible member  254  prevents too much turbulence from occurring in the top part of the stock medium  240  when it leaves the acceleration zone  246 . 
       FIG. 14  shows a double-sided transducer system  260  that has an upper transducer  262  and foil  263  associated with an upstream guide member  264 . A lower transducer  266  and foil  267  are disposed below the endless member or wire  242  and are preferably aligned with the upper transducer  262 . The system  260  provide such strong ultrasound that it completely fluidizes the stock medium and may destroy any previously formed fiber structure that may exist so that new fiber structures may be formed on the wire downstream of the system  260 . Because most of the forming is done on the wire  242 , the head-box may be reduced to function merely as a transverse and lengthwise manifold to distribute the stock medium  261 . The flexible member  254  prevents too much turbulence from occurring in the top part of the stock medium  261 . 
       FIG. 15  shows an example of the double-sided transducer system  260  used in a papermaking system  270  that includes a breast roll  272  below a head-box  274  and next to a forming board  276  that is upstream of the transducer system  260 . A wet suction box  278  and a dry suction box  280  may be disposed downstream of the transducer system  260 . Over the box  280  it is usually possible to see a dry line that indicates that air is sucked through the medium on the wire. 
       FIG. 16  shows a plane wire system  290  that is suitable for high concentration stock medium  292  that may have a fiber concentration as high as 3–4% or higher. This means the amount of water required is reduced to 1/16 compared to the amount of water required when the concentration is 0.25%. This creates substantial savings in pumping energy. The stock medium  292  is pumped into a manifold  298  and further through a defusor  300  and out on a member or wire  242 . The system  290  has a breast roll  272  for the member or wire  242 . An upstream sealing frame  296  is disposed behind and at each side of the defusor  300 . The system  290  has the upper transducer  262 , the lower transducer  266  and a second lower transducer  294 . A plastic foil  302  is disposed upstream of the transducer  262 . The upper and lower transducers  262 ,  266  together with the transducer  294  may be used to completely fluidize the stock medium although the medium has a very high concentration such as 3–4%. 
       FIG. 17  is a double wire system  310  that has suction boxes  312 ,  314  on the outside of endless members or wires  316 ,  318 , respectively. The system also has a plastic foil  320 , a manifold  322 , a sealing frame  324  and a defusor  326 . A transducer  328  is positioned on the other side of the wires. A breast roll  332  carries the wire  316  and another breast roll  334  carries the wire  318 . 
       FIG. 18  is a side view of a system  350  for forming with high stock concentrations. The system  350  is particularly suitable for paper with a low grammage. The stock medium  352  comes from a manifold  384  through a defusor  386  and out on an endless wire or meter  354 . Transducer units  356 ,  358  connected to a foil are disposed below the wire  354 . The manifold with the defusor  386  is in operative engagement with a sealing frame  388  that is immediately adjacent the wire  354 . A plastic member  368  is connected to the defusor  386 . 
       FIG. 19  is a side view of a system  370  for forming with high stock concentrations. The system  370  is particularly suitable for paper with a high grammage. The stock medium  374  comes from a manifold  384  through a defusor  386  and out on an endless wire or member  372 . The system has transducer units  376 ,  378 ,  380  below the wire and a foil  382 . The system further has a sealing frame  388 . Transducer units  390 ,  392  with a foil  394  may be disposed above the wire  372 . The flexible member  254  will prevent too much turbulence to occur in the top part of the stock medium  374  when it leaves the foil  394 . 
       FIG. 20  is a cross-sectional side view of a system  500  that has an endless wire or member  502  carrying a stock medium  504 . An upstream transducer  506  with a foil  508  is disposed below the wire  502 . A second downstream transducer  510  with a foil  512  is positioned above the wire  502 . A guide member  514  is connected to the foil  512  and a reflector  516  is aligned with the foil  512 . A third downstream transducer  518  with a foil  520  is positioned above the wire  502 . A guide member  522  is connected to the foil  520  and a reflector  524  is aligned with the foil  520 . When more than one transducer is used, as in this set up, it is possible to synchronize the transducers and place them at a distance from one another that is an integer multiple, A or B, of the wave length, W, of sound in water, which may be about 75 millimeters with a speed of sound in water of about 1500 meters per second at an ultrasound frequency of 20 kHz, to control the amplification of the ultrasound fields. By placing the transducers at the correct distance from one another, one transducer may enforce the ultrasound energy produced by another transducer. 
     While the present invention has been described in accordance with preferred compositions and embodiments, it is to be understood that certain substitutions and alterations may be made thereto without departing from the spirit and scope of the following claims.