Abstract:
A compact interaction chamber is used to cause high shear, impact forces, and cavitation to reduce particle size and mix fluids while reducing waste and holdup volume. A first housing made of stainless steel holds an inlet mixing chamber element and an outlet mixing chamber element in a female bore using thermal expansion. The inlet and outlet mixing chamber elements are manufactured so that the diameter of the cooled female bore is slightly smaller than the diameter of the mixing chamber elements. The first housing is heated, expanding the diameter of the female bore enough to allow the inlet and outlet mixing chamber elements to be inserted. After the mixing chamber elements are inserted and aligned within the female bore, the first housing is allowed to cool. Once cooled, the female bore contracts and applies sufficient hoop stress to securely hold the mixing chamber elements during high shear force mixing.

Description:
COPYRIGHT NOTICE 
       [0001]    A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the photocopy reproduction of the patent document or the patent disclosure in exactly the form it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
       BACKGROUND OF THE INVENTION 
       [0002]    For certain pharmaceutical applications, manufacturers need to process and mix expensive liquid drugs for testing and production using the lowest possible volume of fluid to save money. Current mixing devices operate by pumping the fluid to be mixed under high pressure through an assembly that includes two mixing chamber elements secured within a housing. The fluid mixes between the two mixing chamber elements under high pressure, resulting in high energy dissipation. The two mixing chamber elements must be held secure enough to withstand the high pressures and energy resulting from this mixing. In current mixing chambers, the two mixing chamber elements are secured with a tube held under high tension such that the tube stretches slightly, and the necking down effect holds the mixing chamber elements secure. To hold the mixing chamber elements in this way, the tube must be relatively long, and current devices are large and require many component parts. The relatively large and complex construction of current mixing devices also implies a large holdup volume of the fluid being mixed, which results in excess waste of expensive mixing product. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0003]      FIG. 1  is a cross-sectional view of a prior art mixing device. 
           [0004]      FIG. 2  is a cross-sectional view of an example assembled compact interaction chamber taken along line X-X of  FIG. 3 , according to one example embodiment of the present invention. 
           [0005]      FIG. 3  is a top view of the assembled example compact interaction chamber according to one example embodiment of the present invention. 
           [0006]      FIG. 4  is a cross-sectional view of the first housing of the example compact interaction chamber taken along line X-X of  FIG. 3  according to one example embodiment of the present invention. 
           [0007]      FIG. 5  is a cross-sectional view of the second housing of the example compact interaction chamber taken along line X-X of  FIG. 3  according to one example embodiment of the present invention. 
           [0008]      FIG. 6  is a cross-sectional view of the retaining element of the example compact interaction chamber taken along line X-X of  FIG. 3  according to one example embodiment of the present invention. 
           [0009]      FIG. 7  is a perspective cross-sectional view of the inlet mixing chamber element of the example compact interaction chamber according to one example embodiment of the present invention. 
           [0010]      FIG. 8  is a perspective cross-sectional view of the outlet mixing chamber element of the example compact interaction chamber according to one example embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The present disclosure is generally directed to a compact interaction chamber that secures mixing chamber elements using internal forces of the components of the assembly rather than applied torque to put the assembly in tension and cause a necking down effect. The compact interaction chamber results in the requirement of fewer components and a smaller size. By decreasing the size and complexity of compact interaction chamber, the flow paths are also shortened, thereby decreasing the holdup volume and saving the manufacturer using the system valuable resources without sacrificing quality and consistency of the mixing. 
         [0012]    Specifically, the compact interaction chamber of the present disclosure includes, among other components: a first housing; a second housing; an inlet retaining member; an outlet retaining member; an inlet mixing chamber element; and an outlet mixing chamber element. When assembled, the inlet retaining member and the outlet retaining member are situated facing one another within a first opening of the first housing. The inlet and outlet mixing chamber elements reside adjacent one another and between the inlet and outlet retaining members within the first opening. The second housing is fastened to the first housing such that a male protrusion on the second housing is inserted into the first opening making contact with the second retaining member. When the first and second housings are fastened together, the first retaining member and second retaining member are forced toward one another, thereby compressing the inlet and outlet retaining members and properly aligning the inlet and outlet mixing chamber elements together. The mixing chamber elements are further secured for high pressure mixing by the hoop stress exerted on the inlet and outlet mixing chamber elements by the inner wall of the first opening, as will be explained in further detail below. 
         [0013]    Referring now to  FIG. 1 , a prior art mixing assembly is illustrated. The mixing assembly  200  includes an inlet cap  202  and an outlet cap  204 . The inlet cap  202  includes threads that are configured to engage complimentary threads on the outlet cap  204 . The mixing assembly  200  also includes an inlet flow coupler  220 , an outlet flow coupler  222 , an aligning tube  221 , an inlet retainer  224 , an outlet retainer  226 , an inlet mixing chamber element  228  and an outlet mixing chamber element  230 . 
         [0014]    The inlet flow coupler  220  is arranged within the inlet cap  202 , and the outlet flow coupler  222  is arranged within the outlet flow cap  204 . When assembled, the tube  221  stays aligned with both the inlet flow coupler  220  and the outlet flow coupler  222  with the use of a plurality of pins  229 . The inlet retainer  224  and the outlet retainer  226  are arranged within the tube  221 , and serve to align and retain the inlet mixing chamber element  228  and the outlet mixing chamber element  230 . The inlet and outlet retainers  224  and  226  make contact with the inlet flow coupler  220  and the outlet flow coupler  222  respectively. 
         [0015]    When the device is fully assembled, a flow path is formed between the inlet flow coupler  220 , the inlet retainer  224 , the inlet mixing chamber element  228 , the outlet mixing chamber element  230 , the outlet retainer  226  and the outlet flow coupler  222 . The unmixed fluid enters the inlet flow coupler  220  and travels through the inlet retainer  224  and to the inlet mixing chamber element  228 . Under high pressure and as a result of the high energy reaction, the unmixed fluid is mixed between the inlet mixing chamber element  228  and the outlet mixing chamber element  230 . The mixed fluid then travels through the outlet retainer  226  and the outlet flow coupler  222 . 
         [0016]    To ensure that the mixing chamber elements are held with sufficient security to withstand the high pressure and high energy of the mixing, the inlet cap  202  threadingly engages the outlet cap  204 . As torque is increased on the inlet cap  202  and outlet cap  204 , the inlet flow coupler  220  and outlet flow coupler  222  are forced toward one another, and the tube  221  is put under tension. As the tension increases, the tube stretches slightly, undergoing a necking down effect, and thereby reducing in diameter. The fluid being mixed between the inlet mixing chamber element  228  and the outlet mixing chamber element  230  is under very high pressure, and therefore the inlet cap  202  and outlet cap  204  must be capable of imparting high amounts of force on the flow couplers, retainers and mixing chamber elements. Additionally, the inlet cap  202  and the outlet cap  204  must be capable of forcing the tube  221  to stretch and thereby slightly decrease in diameter to clamp down radially on the inlet mixing chamber element  228  and the outlet mixing chamber element  230 . As the force increases, the inlet flow coupler  220  pushes on the inlet retainer  224  and the outlet flow coupler  222  pushes on the outlet retainer  226 , which in turn sealingly compresses the inlet mixing chamber element  228  and the outlet mixing chamber element  230 . To achieve the levels of torque required to ensure a fluid tight seal at high pressure, and to stretch the tube  221  with sufficient tensile force to hold the inlet mixing chamber element  228  and the outlet mixing chamber element  230 , the tube must be relatively long, and therefore flow couplers, the inlet cap and outlet cap must accordingly be large enough to accommodate the longer tube. As a result of the longer tube, and larger flow couplers and caps, the flow path from the inlet flow coupler to the outlet flow coupler is longer than necessary, and therefore the holdup volume and amount of wasted fluid is higher than in smaller devices that provide comparable mixing results. 
         [0017]    As discussed below, in the compact interaction chamber of the present disclosure, the mixing chamber elements are secured using both compression from the torque of fastening two housings together as well as hoop stress of the inner walls of the first housing directed radially inwardly on the mixing chamber elements. However, rather than using a tube member that would need to be stretched to hold the mixing chamber elements radially, the first housing is heated prior to insertion of the mixing chamber elements, and allowed to cool and contract once the mixing chamber elements are inserted and aligned. By securing the mixing chamber elements with the hoop stress of the first housing applied as a result of thermal expansion and contraction, the torque required to compress the mixing chamber elements together is significantly reduced. Therefore, the compact interaction chamber can be reduced in size, number of components, and complexity that results in a significant reduction in holdup volume. 
         [0018]    Referring now to  FIGS. 2 to 8 , one example embodiment of the compact interaction chamber is illustrated.  FIG. 2  illustrates a cross-sectional view of the assembled interaction chamber assembly  100  taken along the line X-X of the top view shown in  FIG. 3 .  FIG. 4  illustrates the first housing  102  in detail,  FIG. 5  illustrates the second housing  104  in detail and  FIG. 6  illustrates the inlet/outlet retainer  108 / 110  in detail.  FIG. 7  illustrates the inlet mixing chamber element  112  in detail and  FIG. 8  illustrates the outlet mixing chamber element  114  in detail. 
         [0019]    As seen in  FIG. 2 , the assembled compact interaction chamber  100  may include a generally cylindrically shaped first housing  102  and a generally cylindrically shaped second housing  104 . The first housing  102  is configured to be operably fastened to the second housing  104  using any sufficient fastening technology. In the illustrated example embodiment, the first housing  102  is fastened to the second housing  104  with a plurality of bolts  106  arranged in a circular array around a central axis A. It should be appreciated that the generally cylindrically shaped first housing  102  and the generally cylindrically shaped second housing  104  share central axis A when assembled. 
         [0020]    Between the first housing  102  and the second housing  104  resides an inlet retainer  108 , an outlet retainer  110 , an inlet mixing chamber element  112  and outlet mixing chamber element  114 . The inlet retainer  108  is arranged adjacent to the inlet mixing chamber element  112 . The inlet mixing chamber element  112  is arranged adjacent to the outlet mixing chamber element  114 , which is arranged adjacent to the outlet retainer  110 . When the compact interaction chamber  100  is assembled, bolts  106  clamp the first housing  102  to the second housing  104 , thereby compressing the inlet mixing chamber element  112  and outlet mixing chamber element  114  between the inlet retainer  108  and the outlet retainer  110 . 
         [0021]    After assembly, an unmixed fluid flow is directed into inlet  116  of the first housing  102 , and through an opening  118  in inlet retainer  108 . As discussed in more detail below, the unmixed fluid flow is then directed though a plurality of small pathways in the inlet mixing chamber element  102  in the direction of the fluid path. The fluid then flows in a direction parallel to the face of the inlet mixing chamber element  112  and the face of the adjacent outlet mixing chamber element  114  through a plurality of micro channels formed between the inlet mixing chamber element  102  and the outlet mixing chamber element  104 . The fluid is mixed when the plurality of micro channels converge. The mixed fluid is directed through a plurality of small pathways in the outlet mixing chamber element  104 , through an opening  120  in outlet retainer  110 , and through outlet  122  of the second housing  104 . 
         [0022]    It should be appreciated that the plurality of bolts  106  used to fasten the first housing  102  to the second housing  104  provide a clamping force sufficient to compress the inlet mixing chamber element  112  and the outlet mixing chamber element  114  so that the microchannels formed between the two faces are fluid tight. However, due to the high pressure and the high energy dissipation resulting from the mixing taking place between the inlet mixing chamber element  112  and the outlet mixing chamber element  114 , the compression force applied by the torqued bolts  106  alone may not be sufficient to hold the mixing chamber elements static within the first opening of the first housing  102  during mixing. Thus, in addition to the compressive force applied by the bolts  106 , the mixing chamber elements  112 ,  114  are held circumferentially by the inner wall  117  of the first opening  115  of the first housing  102 , which applies a large amount of hoop stress directed radially inwardly on the mixing chamber elements, as will be further discussed below. This secondary point of retention and security reduces the required amount of compressive force to hold the mixing chamber elements in place during high pressure and high energy mixing. 
         [0023]    For example, due to the hoop stress applied to the mixing chamber elements, each of six bolts  106  in one embodiment need only a torque force of 100 inch-pounds to hold the mixing chamber elements together to create a seal. Prior art devices that use primarily compression to secure the mixing chamber elements as discussed above, however, tend to require significantly higher amounts of torque force to hold the mixing chamber elements together to create a seal (about 130 foot-pounds of torque). Because the prior art devices use a tube member that must be stretched to decrease its diameter and clamp down on the mixing chamber elements, the prior art devices require larger housings, more components and therefore, a higher hold-up volume of approximately 0.5 ml. In one embodiment of the present disclosure, the mixing chamber elements are secured within the first opening of the first housing and achieve the high hoop stress imparted from the inner wall of the first housing onto the outer circumference of the mixing chamber elements, the present disclosure takes advantage of precision fit components and the properties of thermal expansion. The hold-up volume of the compact interaction chamber of the present disclosure is around 0.05 ml. 
         [0024]    An example procedure for assembling one embodiment of the compact interaction chamber of the present disclosure are now described with reference to the assembled compact interaction chamber in  FIG. 2  and each individual component illustrated in  FIGS. 4 to 8 . 
         [0025]    First, the inlet retaining member  108 , as shown in  FIG. 6 , may be inserted into the first opening of the first housing, as shown in  FIG. 4 . The inlet retaining member  108  has a substantially cylindrical shape, and fits concentrically within the first opening of the first housing. When inserted, the inlet retaining member  108  includes a chamfered surface  130  that is configured contact a complimentary chamfered interior surface  119  of the first housing  102 . This chamfered mating between the first housing  102  and the inlet retaining member  108  ensures that the inlet retaining member  108  self-centers within the first opening and lines up properly and squarely to the inner wall  117  of the first opening  115 . It should be appreciated that the inlet retaining member  108  includes a concentric passageway  132  which allows fluid to flow through the inlet retaining member  108 . The passageway  132  lines up with flow path  116  of the first housing  102 , through which the unmixed fluid is pumped from a separate component in the mixing system. 
         [0026]    Second, the first housing  102  may be heated to at least a predetermined temperature, at which point the first opening  115  expands from a first opening diameter to at least a first opening expanded diameter. In some example embodiments, the first housing is made of stainless steel, and the first housing is heated using a hot plate or any other suitable method of heating stainless steel. In one such embodiment, the predetermined temperature at which the first housing is heated is between 100° C. and 130° C. It should be appreciated that, when the first opening  115  is at the first diameter, the mixing chamber elements  112 ,  114  are unable to fit within the first opening  115 . However, the mixing chamber components  112 ,  114  are manufactured and toleranced such that, after the first housing  102  is heated and the first diameter expands to the first expanded diameter, the mixing chamber elements  112 ,  114  are able to fit within the first opening  115 . In one embodiment, the first expanded diameter is between 0.0001 and 0.0002 inches larger than the first diameter. 
         [0027]    Third, the inlet mixing chamber element  112  is inserted into the first opening  115  of the heated first housing  102 . The top surface  304  of the inlet mixing chamber element  112  is configured to be in contact with the bottom surface  132  of inlet retaining member  108 . Because the inlet retaining member  108  is self-aligned with the chamfered mating surfaces of  119  and  130 , the inlet mixing chamber element  112  is also properly aligned when surface  304  makes complete contact with surface  132  of inlet retaining member  108 . 
         [0028]    Fourth, the outlet mixing chamber element  114  is inserted into the first opening  115  of the heated first housing  102 . The top surface  310  of the outlet mixing chamber element  114  is configured to be in contact with the bottom surface  306  of the inlet mixing chamber element  112 . It should be appreciated that in some embodiments, the surface  306  and surface  310  include complimentary features that ensure the inlet mixing chamber element  112  is properly oriented and aligned with the outlet mixing chamber element  114 . For example, in one embodiment, the inlet mixing chamber element  112  includes one or more protrusions that fit one or more complimentary recesses in the outlet mixing chamber element  114  so as to ensure proper rotational alignment of the two mixing chamber elements. 
         [0029]    Fifth, once the mixing chamber elements  112 ,  114  are arranged within the first opening  115  of the heated first housing  102 , the outlet retaining member  110  may be inserted into the first opening  115 . The outlet retaining member  110  is substantially similar in structure to the inlet retaining member  108 . Similar to the inlet retaining member  108 , surface  132  of the outlet retaining member  110  is configured to make contact with surface  312  of the outlet mixing chamber element  114 . 
         [0030]    Sixth, the second housing  104  is aligned with the first housing  102  and the assembled first and second housings are operatively fastened together. As seen in  FIG. 4 , the second housing  104  includes protrusion  125  extending from top surface  126 . When the first housing  102  is aligned with the second housing  104 , protrusion  125  fits into the first opening  115 . Similar to the opposite end of the first opening  115 , the protrusion  125  includes a complimentary chamfered surface  123 , which is configured to contact the chamfered surface  130  of the outlet retaining member  110 . Also similar to the first housing&#39;s contact with the inlet retaining member  108 , the chamfered surface  123  of protrusion  125  ensures that the outlet retaining member  110  is square to the inner surface  117  of opening  115 . When both the inlet retaining member  108  and the outlet retaining member  110  are properly aligned by the first housing  102  and the protrusion  125  of the second housing  104  respectively, the inlet mixing chamber element  112  and the outlet mixing chamber element  114  are correctly aligned within the first opening  115 . If the mixing chamber elements  112 ,  114  are even slightly misaligned, the elements may be damaged due to incorrect holding forces and the high pressure of the mixing. Additionally, the mixing results will be less consistent and reliable if the mixing chamber elements are not perfectly aligned by the retaining members and the first and second housings. 
         [0031]    Seventh, the first housing may be operatively fastened to the second housing so that the inlet retainer, the inlet mixing chamber element, the outlet mixing chamber element, the outlet retainer, and the male member of the second housing are in compression. In the illustrated embodiment, six bolts  106  may be used to fasten the first housing  102  to the second housing  104 . To ensure equal clamping force between the first housing  102  and the second housing  104 , the bolts  106  are spaced sixty degrees apart and equidistant from central axis A. As discussed above, the fastening of six bolts  106  provides sufficient clamping force to seal surface  306  of the inlet mixing chamber element with surface  310  of the outlet mixing chamber element. It will be appreciated that any appropriate fastening arrangement or numbers of bolts may be used. 
         [0032]    Eighth, the first housing is allowed to cool down from its heated state. In various embodiments, the first housing is cooled down by allowing it to return to room temperature or actively causing it to cool with an appropriate cooling agent. When the first housing is cooled, the material of the first housing contracts back, and the first housing expanded diameter is urged to contract back to the first housing diameter. Because the mixing chamber elements are already arranged and aligned inside of the first opening of the first housing, the contracting diameter of the first opening exerts a high amount of force directed radially inwardly on the mixing chamber elements. This force, in combination with the compressive force applied from the six bolts  106 , is sufficient to hold the mixing chamber elements in place for the high pressure mixing. It should be appreciated that the mixing chamber elements can be made of any suitable material to withstand the radially inward stress of 30,000 pounds per square inch applied when the first opening diameter contracts. In one embodiment, the mixing chamber elements are constructed with 99.8% alumina. In another embodiment, the mixing chamber elements are constructed with polycrystalline diamond. 
         [0033]    Referring now more specifically to  FIGS. 7 and 8 , a more detailed explanation of the mixing process of one example is discussed and illustrated. In  FIG. 7 , the inlet mixing chamber element  112  is illustrated. Top surface  304  is configured to contact the inlet retaining element  108  when inserted into the first opening  115  of the first housing  102 . The inlet mixing chamber element  112  includes a plurality of ports  300 ,  302  extending from surface  304  toward bottom surface  306 . Ports  300 ,  302  are small, and it should be appreciated that  FIGS. 7 and 8  have been drawn out of scale for illustrative and explanatory purposes. On bottom surface  306  of the inlet mixing chamber element  112 , a plurality of microchannels  308  are etched. The ports  300 ,  302  are in fluid communication with microchannels  308 . 
         [0034]    In  FIG. 8 , the outlet mixing chamber element  114  is illustrated. Outlet mixing chamber element  114  includes a plurality of microchannels  318  that are etched into top surface  310 . Microchannels  318  on surface  310  of the outlet mixing chamber element  114  are configured to line up with microchannels  308  on surface  306  of the inlet mixing chamber element  112  of  FIG. 7  when the two mixing chamber elements are aligned and sealingly abutted against one another. When in sealing contact with one another, the microchannels  308 ,  318  on each of the inlet mixing chamber element  112  and the outlet mixing chamber element  314  respectively create fluid-tight micro flow paths. The outlet mixing chamber element  114  also contains a plurality of outlet ports  314 ,  316 , which are in fluid communication with microchannels  318 , and the bottom surface  312  of outlet mixing chamber element  114 . 
         [0035]    In operation, when the inlet mixing chamber element  112  and the outlet mixing chamber element  114  are secured and held in the first housing between the inlet and outlet retaining members, surface  306  makes a fluid-tight seal with surface  310 . The unmixed fluid is pumped through flow path  116  of the first housing  102 , and through inlet retainer  108  to inlet mixing chamber element  112 . At inlet mixing chamber element  112 , the fluid is pumped at high pressure into ports  300  and  302 , and then into the plurality of microchannels  308 . Due to the decrease in fluid port size from flow path  116  to ports  300 ,  302  to microchannels  308 , the pressure and shear forces on the unmixed fluid becomes very high by the time it reaches the microchannels  308 . As discussed above, and because of the secure holding between the inlet and outlet mixing chamber elements, microchannels  308  and  318  combine to form micro flow paths, through which the unmixed fluid travels. When the micro flow paths converge on one another, the high pressure fluid experiences a powerful reaction, and the constituent parts of the fluid are mixed as a result. After the fluid has mixed in the micro flow paths, the mixed fluid travels through outlet ports  314 ,  316  of outlet mixing chamber element  114 . 
         [0036]    It will be understood that the compact interaction chamber assembly of the present disclosure succeeds in reducing the number and size of the components making the mixing assembly, resulting in cheaper manufacture and lower holdup volumes leading to less waste. In addition to saving cost and resources, the present disclosure performs consistently and reliably, and can advantageously be configured to operate with current machines needing no modification. 
         [0037]    In one example embodiment of the present disclosure, the compact interaction chamber assembly includes a first housing with a first central axis, a second housing with a second central axis, a first mixing chamber element, a second mixing chamber element, and at least one retaining member. 
         [0038]    The first housing has a first opening at a bottom face of the first housing, the first opening having a generally cylindrical shape with a first opening diameter and sharing the first central axis. The first housing also includes a first inlet protrusion extending from a top face of the first housing. The first inlet protrusion includes a first flow path that extends from the first opening through the first inlet protrusion and shares the first central axis. 
         [0039]    The second housing includes a second outlet opening at a bottom face of the second housing, the second outlet opening sharing the second central axis. The second housing also includes a second protrusion of a second diameter extending from a top face of the second hosing. The second protrusion includes a second flow path that extends from the second outlet opening through the second protrusion and shares the second central axis. The second housing is configured to be fastened to the first housing so that the second central axis is collinear with the first central axis and the second protrusion is configured to extend into the first opening when the first and second housings are fastened to one another. 
         [0040]    The first and second mixing chamber elements are configured to reside within the first opening of the first housing. As a result of the first and second housings being fastened to one another, a bottom face of the first mixing chamber element makes a fluid tight contact with a top face of the second mixing chamber element. After the first and second mixing chamber elements are arranged within the first opening, an outer edge of each of the first and second mixing chamber elements contacts the inner surface of the first opening such that the first and second mixing chamber elements are stressed radially inwardly to cause a fluid tight seal between the outer edge of each of the first and second mixing chamber elements and the inner surface of the first opening. The at least one retaining member is configured to reside within the first opening of the first housing and contacts the mixing chamber elements. When fully assembled, the hold-up volume of the compact interaction chamber is 0.05 ml, compared to the hold-up volumes of prior art devices that are on the order of about 0.5 ml. 
         [0041]    It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.