Patent Abstract:
An ultra-lean dilution apparatus is provided for proportioning minute quantities of a first fluid, such as a concentrated cleaning solution, for mixing into a second fluid, such as tap water, which provides improved performance and which can be manufactured by assembling several molded components with little or no machining. The dilution apparatus ( 20 ) provides a selective pressure drop in a conduit ( 22 ) by including a plurality of dilution disks ( 50   a-   50   f ), each dilution disk ( 50   a-   50   f ) having a tortuous path ( 52   a-   52   f ) of sufficient cross-sectional area to be resistant to clogging and having a sufficient number of sharp turns to create a desired pressure drop. While each disk ( 50   a-   50   f ) produces a predetermined drop, the serial configuration of the tortuous paths of the plurality of dilution disks is additive to produce a range of dilution suitable for the chemicals used. Advantageously, the tortuous path of a first of the plurality of dilution disks ( 50   a ) is recessed into a front face so that bringing the front face ( 54   a ) of the first dilution disk ( 50   a ) in contact with a back face ( 55   b ) of a second dilution disk ( 50   b ) completes the tortuous path ( 52   a ).

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to devices for dispensing and mixing liquids, and more particularly to such devices that dispense and mix chemicals, and even more particularly to devices that dispense and mix cleaning chemicals. 
     2. Prior Art 
     It is common practice to purchase concentrated cleaning chemicals and to mix them with other liquids such as water to achieve the desired usage concentration for cleaning. A variety of proportioning dispensers have been developed to achieve this. The dispensers often employ venturi-type devices sometimes called eductors to draw the concentrated liquid chemical and mix it with the water stream. Examples of such eductors include the Sand U.S. Pat. Nos. 5,522,419, 5,253,677 5,159,958, and 5,862,829 all of which are assigned to the Assignee of the present invention and are expressly incorporated herein. Water traveling through the central, constricted portion of the venturi creates suction which draws the concentrated liquid chemical into the water stream. 
     The structure of such eductors is generally fixed, and thus, for a given water stream flow rate, the amount of concentrated liquid chemical drawn is a function of the fluid resistance in the flow path of the concentrated liquid chemical. Adjusting the amount of chemical educted is generally controlled by a metering orifice interposed into the flow path of the concentrated liquid chemical. Such orifices may be fixed or adjustable to vary the proportionate flow. Achieving the proper proportion of chemical merely with selection of a metering orifice is complicated by factors which vary per the application, such as the desired usage concentration, the viscosity of the concentrated liquid chemical, and the pressures at which the liquids are provided. Using metering orifices to control dilution means that very small metering orifice sizes are required, as shown in Table 1. 
     
       
         
               
             
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Approximate Dilutions at 40 psi for Water-Thin Products (1.0 cp) 
               
             
          
           
               
                   
                 Ratio (per Eductor Flow) 
               
             
          
           
               
                 Orifice Size (inch) 
                 Standard Drill Number 
                 1 G.P.M. 
                 3.5 G.P.M. 
               
               
                   
               
               
                 0.187 
                 (3/16) 
                  3:1 
                 3.5:1   
               
               
                 0.128 
                 (30) 
                  3:1 
                 4:1 
               
               
                 0.098 
                 (40) 
                  3:1 
                 4:1 
               
               
                 0.070 
                 (50) 
                  4:1 
                 8:1 
               
               
                 0.052 
                 (55) 
                  5:1 
                 14:1  
               
               
                 0.043 
                 (57) 
                  7:1 
                 20:1  
               
               
                 0.040 
                 (60) 
                  8:1 
                 24:1  
               
               
                 0.035 
                 (65) 
                 10:1 
                 30:1  
               
               
                 0.028 
                 (70) 
                 16:1 
                 45:1  
               
               
                 0.025 
                 (72) 
                 20:1 
                 56:1  
               
               
                 0.023 
                 (74) 
                 24:1 
                 64:1  
               
               
                 0.020 
                 (76) 
                 32:1 
                 90:1  
               
               
                 0.018 
                 (77) 
                 38:1 
                 128:1  
               
               
                 0.014 
                 (79) 
                 64:1 
                 180:1  
               
               
                 0.010 
                 (87) 
                 128:1  
                 350:1  
               
               
                   
               
             
          
         
       
     
     Metering orifices generally achieve dilution ratios of 2:1 to 300:1. More dilute mixtures are constrained by the volume rate of water available and by the smallest practical size of the metering orifices. Very small orifices are susceptible to clogging such as from contaminant particles or artifacts in the concentrated chemicals. In addition, the viscosity of the chemical imposes a size limitation. Introducing a fixed pressure drop to the overall dimensioning of the chemical feed line, or supply conduit, to achieve more dilute concentrations would preclude applications requiring less dilute concentrations. 
     Active devices which could monitor the relative amount of liquids being mixed and control dispensing are impractical as being uneconomical, increasing the cost of producing the dispenser. Moreover, providing such active devices with a power supply such as batteries or an electrical outlet is generally uneconomical or inconvenient. Moreover, dispensing devices often dispense conductive or corrosive materials that would further complicate protection of electronic components of an active system. Consequently, passive dispensing devices are generally used, even though this constrains the range of achievable usage concentrations. 
     Consequently, appropriate chemicals for dispensing are not concentrated as much as would be desirable, imposing additional costs of shipment. Dispensing devices for such less-concentrated liquid chemicals are thus required to have provisions for larger storage of chemicals and/or more frequent refills. In addition, at the more dilute end of the generally achievable range of operation, the metering orifice is susceptible to clogging, allowing defective mixtures to be generated. Moreover, certain types of chemicals that tend to have suspended solids are precluded from being dispensed at all by such devices. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an ultra-lean dilution apparatus for proportioning minute quantities of a first fluid, such as a concentrated cleaning solution, for mixing into a second fluid, such as tap water, which provides improved performance and which can be manufactured by assembling several molded components with little or no machining. 
     According to the principles of the present invention and in accordance with the described embodiments, the present invention provides a dilution apparatus for providing a selective pressure drop in a conduit by including a plurality of dilution disks, each dilution disk acting as a channel carrier by including a tortuous path of sufficient cross-sectional area to be resistant to clogging and having a sufficient number of sharp turns to create a desired pressure drop. 
     For ultra-lean dilutions of 350:1 to 1500:1, using metering orifices would require openings smaller than 0.010 inches in diameter. Yet in this range many particles or artifacts in chemicals may clog them. Thus, such metering orifices are generally not used. On the other hand, the disk channel formed herein from a plurality of tortuous paths would be several time larger than 0.010, as shown in three illustrative examples in Table 2. Thus, the channel is of a size to pass such particles or artifacts which would otherwise clog orifices in at least part of the noted range yet still produce the pressure drop necessary to produce the ultra-lean proportion. 
     
       
         
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 oz per minute 
                 Ratio at 1 GPM 
                 Ratio at 4 GPM 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Black (Large passage: 0.033″ × 0.033″ cross-section) full path length 
               
             
          
           
               
                 5 discs 
                 0.486 
                 263 
                 1053 
               
               
                 4 discs 
                 0.551 
                 232 
                 929 
               
               
                 3 discs 
                 0.647 
                 197 
                 791 
               
               
                 2 discs 
                 0.876 
                 146 
                 584 
               
               
                 1 disc 
                 1.299 
                 98 
                 394 
               
             
          
           
               
                 Red (Medium passage: 0.028″ × 0.028″ cross-section) full path length 
               
             
          
           
               
                 5 discs 
                 0.331 
                 386 
                 1547 
               
               
                 4 discs 
                 0.375 
                 341 
                 1365 
               
               
                 3 discs 
                 0.462 
                 277 
                 1108 
               
               
                 2 discs 
                 0.607 
                 210 
                 843 
               
               
                 1 disc 
                 0.936 
                 136 
                 547 
               
             
          
           
               
                 Green (Small passage: 0.025″ × 0.025″ cross-section) full path length 
               
             
          
           
               
                 5 discs 
                 0.231 
                 554 
                 2216 
               
               
                 4 discs 
                 0.291 
                 440 
                 1759 
               
               
                 3 discs 
                 0.382 
                 335 
                 1340 
               
               
                 2 discs 
                 0.502 
                 255 
                 1020 
               
               
                 1 disc 
               
             
          
           
               
                 Green (Small passage: 0.025″ × 0.025″ cross-section) half path length 
               
             
          
           
               
                 5 discs 
                 0.601 
                 213 
                 852 
               
               
                 4 discs 
                 0.792 
                 162 
                 646 
               
               
                 3 discs 
                 0.914 
                 140 
                 560 
               
               
                 2 discs 
                 1.237 
                 103 
                 414 
               
               
                 1 disc 
                 1.77 
                 72 
                 289 
               
               
                   
               
             
          
         
       
     
     While each disk produces a predetermined drop, the serial configuration of the tortuous paths of the plurality of dilution disks is additive to produce a range of dilution suitable for the chemicals used. In other words, disks are selectively inserted or withdrawn from the circuit to vary the pressure drop between the concentrated chemical and the carrier fluid and so vary the proportion of the mix. 
     In one embodiment of the invention, the tortuous path of a first of the plurality of dilution disks is recessed into a front face so that bringing the front face of the first dilution disk in contact with a back face of a second dilution disk completes the tortuous path. Furthermore, a blind intake of the tortuous path of the second dilution disk selectively communicates with an output port of another tortuous path on a front face of the first dilution disk. 
     In a further aspect of the invention, the desired pressure drop across the dilution apparatus is selectable by adding additional dilution disks and/or by varying the length and multiplicity of turns included in the tortuous path. 
     For example, given a predetermined number of dilution disks with a given tortuous path characteristic, a user selectable dilution control is provided by including a bypass for one or more pairs of dilution disks. More particularly, an output port and a blind intake are provided on each dilution disk, such that in an engaged position the output port and the blind intake of one dilution disk aligns respectively to a downstream blind intake and an upstream output port, placing the tortuous path in series. Furthermore, the dilution disk has a bypass position such that the upstream output port communicates via the intervening output port of the interposed dilution disk with the downstream blind intake without going through the tortuous path. 
     In yet a further aspect of the invention, a stack of dilution disks molded from economical elastomeric material are compressed together within an engagable housing including a window access for selectively positioning or rotating each disk into or out of the fluid circuit and to verify the setting of each disk, wherein, once engaged, the housing locks the disks into position. Advantageously provided are a positioning tab and an alignment tab, both peripherally located on each disk. The positioning tab allows for rotatably positioning, and verifying the position, of each disk within the window of the housing. The alignment tab cooperates with an alignment groove within the housing to constrain the range of rotation of each disk such that the two rotation extremes allowed correspond to an engaged and a bypass position for the disk. 
     In an additional aspect of the invention, a dilution reference is provided to indicate the relative dilution ratio based on the position of the positioning tabs. 
     In yet another aspect of the invention, a rotatable dilution disk is separated from another rotatable dilution disk by a fixed dilution disk, wherein the respective alignment tab is substantially constrained by the alignment groove of the housing. Movement of a rotatable dilution disk is thus prevented from inadvertently moving other rotatable dilution disks. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention. 
     FIG. 1 is an illustration of a dispensing system incorporating an ultra-lean dilution apparatus for proportioning a first fluid, such as a concentrated cleaning solution. 
     FIG. 2 is an exploded view of a plurality of three dilution disks, components of the ultra-lean dilution apparatus of FIG. 1, illustrating a flow path serially through a plurality of tortuous paths forming a channel. 
     FIG. 3 is an exploded view of the plurality of three dilution disks of FIG. 2 illustrating how the flow path serially through a plurality of tortuous paths may be selectively shortened by rotating a dilution disk from an engaged position to a bypass position. 
     FIG. 4 a disassembled perspective view of a dilution apparatus including a stack of six dilution disks and a housing assembly. 
     FIG. 5 is a perspective view of the inlet body, including a hose barb, of the housing assembly shown in FIG. 4, illustrating flow path communication from a dilution disk to the exterior of the housing assembly. 
     FIG. 6 is a perspective view of an assembled ultra-lean dilution apparatus of FIG. 1 and 4, showing a window through which a user can verify the locking status of the dilution apparatus and position of the stack of dilution disks. 
     FIG. 7 is a cross-sectional view of the dilution apparatus of FIGS. 4 and 6 illustrating serial flow through the housing assembly and the stack of dilution disks. 
     FIG. 8 is a perspective cross-sectional view of a second embodiment of alternating fixed and rotatable dilution disk shown with the stack encompassed within a housing assembly, with a cross-section chosen to expose a rotatable dilution disk outmost. 
     FIG. 9 is a perspective cross-sectional view of the second embodiment of FIG. 8 shown with the stack encompassed within the housing assembly, with a cross-section chosen to expose a rotatable dilution disk outmost. 
     FIG. 10 is a side view of the second embodiment of FIGS. 8 and 9 showing a dilution reference chart added to the outer housing. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a dispensing system  10 , also referred to as a proportioner unit, is shown incorporating an ultra-lean dilution apparatus  20  for proportioning a first fluid, a concentrated liquid chemical such as a cleaning solution. The dilution apparatus  20  meters the flow of concentrated liquid chemical from a concentrated liquid reservoir  24  into a carrier stream such as water by selectively controlling the pressure drop in a supply conduit  22 . Flow from the concentrated liquid reservoir  24  passes through a foot valve  28 , which minimizes back flow, through tubing  30  to the dilution apparatus  20 . After the flow is metered by the dilution apparatus  20 , flow continues through eductor tubing  32  to an air gap eductor  34 , such as described in the aforementioned U.S. Pat. Nos. 5,522,419, 5,253,677 5,159,958, and 5,862,829. Thus, conduit  22  is shown as including the foot valve  28 , tubing  30 , dilution apparatus  20 , and eductor tubing  32 . 
     The eductor  34  provides a venturi function for mixing a second fluid, such as tap water, with the concentrated liquid chemical. Thus, a pressurized liquid carrier source is provided, such as the depicted water hose  38  operatively coupled with a tap water supply (not shown), typically at 40 psi. A valve  40  controls the flow through the dispensing system  10 . The flow from the valve  40  passes through the eductor  34 . Within the eductor  34 , a constriction (not shown) produces a venturi effect, such that for 40 psi dynamic pressure the eductor creates about 28 in-hg vacuum. This vacuum draws a relatively small amount of concentrated liquid chemical into the flow at the constriction. Thereafter, the usage concentration flow, formed by mixing the regulated flow with the concentrated liquid chemical, passes through a discharge tube  42  to a bottle  44 . The dispensing system  10  includes a button  46  to enable flow through the dispensing system  10  when a user chooses to fill the bottle  44 . 
     Referring to FIG. 2, a plurality of dilution disks  50   a-   50   c  are shown in an exploded view to illustrate a serial flow  48  through the plurality of dilution disks  50   a-   50   c . Each dilution disk  50   a-   50   c  includes a respective tortuous path  52   a-   52   c  on a respective upstream, front face  54   a-   54   c , each tortuous path  52   a-   52   c  including a multiplicity of sharp turns to create a pressure drop in the serial flow  48  while maintaining a sufficient cross-sectional area of serial flow  48  to reduce clogging. Each tortuous path  52   a-   52   c  is closed when brought into contact with another surface, such as the upstream, back face  55   a - 55   c  of another dilution disk  50   a-   50   c.    
     Each tortuous path  52   a-   52   c  includes an output port  56   a - 56   c  passing through the respective dilution disk  50   a-   50   c  to communicate with the downstream portion of the dilution apparatus  20 . Each tortuous path  52   a-   52   c  begins in a blind intake  58   a - 58   c , respectively, each positioned to align with an upstream portion of the dilution apparatus  20 , such as blind intake  58   b  communicating with output port  56   a . Achieving this alignment is provided by mirror image tortuous paths. Thus, dilution disk  50   a  has blind intake  58   a  counterclockwise from output port  56   a  with serial flow  48  generally clockwise through tortuous path  52   a . Then, the adjacent, mirror-image dilution disk  50   b  has output port  56   b  clockwise from blind intake  58   b  with serial flow  48  generally counterclockwise through tortuous path  52   b . Then, the adjacent dilution disk  50   c  is shown as the same as dilution disk  50   a.    
     Positioning the plurality of dilution disks  50   a-   50   c  is advantageously assisted with positioning tabs  60   a-   60   c  and alignment tabs  61   a - 61   c,  shown extending peripherally respectively from each dilution disk  50   a-   50   c , which will be discussed in more detail below. 
     The dilution disks  50   a-   50   c  are advantageously molded from an elastomeric material such as polyethylene or other preferably chemically resistant material, providing economical manufacture as well as providing flexibility to sealably conform to adjacent dilution disks  50   a-   50   c  when assembled. 
     Referring to FIG. 3, a disassembled perspective view of the plurality of three dilution disks of FIG. 2 are shown oriented such that dilution disks  50   a  and  50   b  are bypassed, selectively shortening the length of the serial flow  48  and reducing the number of sharp turns encountered. The bypass position is achieved by rotating dilution disk  50   b  about its center, such as by positioning tab  60   b  counterclockwise until output port  56   b  aligns with the two adjacent output ports  56   a ,  56   c . Thus, tortuous paths  52   a  and  52   b  are not utilized by the serial flow  48 . 
     Referring to FIG. 4, an exploded view of a dilution apparatus  20  is shown including a stack of six dilution disks  50   a - 50   f  and a housing assembly  70 . When assembled, the dilution disks  50   a-   50   f  are radially encompassed by an open ended, generally cylindrical inner housing  72  which includes a discharge path  74  communicating between dilution disk  50   f  and discharge connector  76 . 
     Inner housing  72  includes departures from a cylindrical shape, including an alignment groove  78  which cooperates with alignment tabs  61   a - 61   f  peripherally located respectively on each dilution disk  50   a-   50   f  to constrain the range of rotation available to the dilution disks  50   a-   50   f . Thus, a dilution disk  50   a-   50   f  is placed in a bypass position, such as shown in FIG. 3, when a respective alignment tab  61   a - 61   f  reaches the extreme counterclockwise position allowed by alignment groove  78 . Similarly, proper alignment to an engaged position is achieved when at the extreme clockwise position. Inner housing  72  also includes a cutaway  84  which allows exposing positioning tabs  60   a-   60   f  on each dilution disk  50   a-   50   f  respectively to verify and/or manipulate the position of each dilution disk  50   a-   50   f . Moreover, the combination of cutaway  84  and alignment groove  78  on inner housing  72  with positioning tabs  60   a-   60   f  and alignment tabs  61   a - 61   f  advantageously ensures that dilution disks  50   a-   50   f  are not assembled backwards. 
     The inner housing  72  also includes a locking portion  88  which rotationally engages within a locking detent  90  within a cylindrical opening  92  of an outer housing  94  of the housing assembly  70 . The outer housing  94  also includes a window  96  to expose the cutaway  84 , and hence the positioning tabs  60   a-   60   f . The window  96  advantageously also exposes locking portion  88  to visually confirm whether engaging the locking detent or not, as shown in more detail in FIG.  6 . 
     The housing assembly  70  also includes features to assist in assembly, especially when tools are required to sufficiently compress the dilution disks  50   a-   50   f , such as apertures  98  on the base of the outer housing  94  and wrench engaging surfaces  100  on the inner housing  72 . 
     Referring to FIGS. 4 and 5, an inlet body  102  provides for flow communication between an intake portion  104  of the dilution device  20 , through a centerline discharge path  106  within a cylindrical portion  108 , along channel spokes  110  to internal radial groove  112 , and finally to the output port  56   a  of dilution disk  50   a . Inlet body  102  advantageously includes a hose barb  114  to interference fit tubing  30 . 
     Referring to FIG. 6, the dilution apparatus  20  of FIG. 4 is shown assembled, with locking portion  88  being rotatably engaged to locking detent  90 . Positioning tabs  60   a-   60   f  are shown aligned, with all dilution disks  50   a-   50   f  thus in the engaged position rather than bypassed. Moreover, placing positioning tabs  60   a-   60   f  against counterclockwise limit of the cutaway  84  ensures that serial flow  48  is not interrupted by a dilution disk  50   a-   50   f  being in an intermediate position with its output port  56   a - 56 f out of communication with the preceding dilution disk  50   a-   50   f.    
     Referring to FIG. 7, a cross-sectional view of the dilution apparatus  20  of FIGS. 4 and 6 is shown illustrating serial flow  48  through the housing assembly  70  and the stack of dilution disks  50   a-   50   f.    
     Referring to FIGS. 8-10, a second embodiment ultra-lean dilution apparatus  120  is shown of a five-disk stack of alternating rotatable and fixed dilution disks  150   a-   150   e.  Having fixed dilution disks advantageously prevents inadvertent rotation of adjacent dilution disks. Referring to FIG. 8, the apparatus  120  is shown with a cross-section chosen to expose the rotatable dilution disk  150   a  outmost with positioning tab  160   a  rotated clockwise. Alignment tab  161   a  in alignment groove  178  of the inner housing  172  constrains the rotation of disk  150   a  between an engaged (counterclockwise as shown) and a bypass position. Dilution disk  150   a  is shown having a tortuous path  152   a  similar to that shown for FIGS. 1-7. 
     Behind disk  150   a  is a fixed dilution disk  150   b , shown in more detail in a cross-sectional view of FIG. 9, similar to FIG. 8 except exposing a different disk. Disk  150   b  is shown with a mirror image tortuous path  152   b  to previously discussed tortuous path  152   a  to provide for serial flow as discussed above. Alignment tab  161   b  is substantially constrained by alignment groove  178 , preventing rotation of disk  150   b.    
     Similarly, behind fixed dilution disk  150   b  are rotatable dilution disk  150   c  with positioning tab  160   c  rotated clockwise, fixed dilution disk  150   d,  and rotatable dilution disk  150   e  with positioning tab  160   e  rotated counterclockwise. Cutaway  184  of inner housing  172  exposes positioning tabs  160   a ,  160   c ,  160   e,  but only positioning tab  160   e  in the counterclockwise engaged position is exposed through window  196  of the outer housing  194 , as also further shown in FIG.  10 . 
     Referring to FIG. 10, a side view is shown of the second embodiment ultra-lean dilution apparatus  120 . Window  196  in outer housing  194  is accompanied by a dilution reference  222  which would indicate the relative dilution depending on which position tabs  160   a ,  160   c ,  160   e  are visible. Reference  222  contemplates a stack of dilution disks  150   a-   150   e  such that range of dilutions are achieved from rich (less dilute) to lean (more dilute) by five combinations of rotatable dilution disks  150   a,    150   c,    150   e  in the engaged position as follows: (1) Combination  1 : Disks  1  ( 150   a ); (2) Combination  2 : Disk  5 ; (3) Combination  3 : Disks  1  and  3 ; (4) Combination  4 : Disks  3  and  5 ; and (5) Combination  5 : Disks  1 ,  3  and  5 . Various combinations would be possible depending upon the number of dilution disks and the characteristic of the tortuous path  150   a-   150   e  of each. For example, dilutions disks chosen from the illustrative four tortuous paths shown in Table 2 above would provide a range of dilutions, such as shown in FIG.  10 . As shown in Table 2, the positioning tabs and reference  222  may advantageously be color coded to further aid in rapidly identifying the configuration. 
     By virtue of the foregoing, there is thus provided a dilution apparatus  20  for proportioning minute quantities of a first fluid, such as concentrated cleaning solution, for mixing with a second fluid, such as tap water, the dilution apparatus  20  adapted to impose a pressure drop between a first fluid supply and a second fluid supply. Those skilled in the art will appreciate that the implementation of the present invention herein can be varied, and that the invention is described in an illustrative embodiment. Accordingly, additions and modifications can be made, and details of various embodiments can be interchanged, without departing from the principles and intentions of the invention. 
     For example, although the dilution disks  50   a-   50   f  have been described as being made of elastomeric material, many other materials and methods of manufacture may be used, including rigid materials and/or those requiring machining. Such alternatives may be especially appropriate if chemicals to be passed through the tortuous path  52   a-   52   f  have specific reactive characteristics or are of a high temperature or pressure. 
     As a further example, the tortuous path  52   a-   52   f  described herein is formed on a downstream, front face  54   a-   54   f  of the dilution disks  50   a-   50   f . However, similar tortuous paths  52   a-   52   f  could be incorporated internal to each dilution disk  50   a-   50   f , on the upstream, back face  55   a - 55 f, or on both faces  54   a-   54   f,    55   a - 55   f.    
     As another example, the embodiment shown in FIGS. 4 and 6 had the plurality of dilution disks  50   a-   50   f  in the engaged position with their positioning tabs  60   a-   60   f  at the counterclockwise limit of the cutaway  84 . Consequently, dilution disks  50   b ,  50   d  and  50   f  cannot be rotated counterclockwise to their bypass positions and thus only dilution disks  50   a ,  50   c  or  50   f  can be rotated clockwise to accomplish bypass. Consequently, positioning tabs  60   b ,  60   d  and  60   f  could be deleted to prevent inadvertent positioning of the corresponding dilution disks  50   b ,  50   d  or  50   f  to a clockwise position that would interrupt serial flow  48 . In addition, alignment tabs  61   b,    61   d  and  61   f  may be enlarged to substantially encompass alignment groove  78  to prevent rotation of dilution disks  50   b ,  50   d  or  50   f.    
     Alternatively, the engaged position of dilution disks  50   a-   50   f  could be achieved with the positioning tabs  60   a-   60   f  centered within the cutaway  84 . The variation in the positioning tabs would indicate the direction of travel to place the disk in bypass. The radial position of the respective alignment tabs  61   a,    61   c  and  61   e  would advantageously allow rotation from the centered position to the clockwise bypass position, but not counterclockwise to the interrupted position for dilution disks  50   a ,  50   c  and  50   e . Similarly, alignment tabs  61   b,    61   d  and  61   f  would advantageously allow rotation from the centered position to the counterclockwise bypass position but not clockwise to the interrupted position for dilution disks  50   b ,  50   d  and  50   f.    
     In addition, the tortuous path  52   a-   52   f  may be varied in pattern and amount of surface area utilized of a dilution disk. Moreover, tortuous paths  52   a-   52   f  of varied length, number of sharp turns and/or cross-section flow area may be provided so that a broad range of flow characteristics may be achieved. Also, although the housing assembly  70  shown was configured to use six dilution disks  50   a-   50   f , other housing assemblies would be appropriate to vary the number of disks. Furthermore, although the stack of dilution disks  50   a-   50   f  are shown advantageously held together under compression, the dilution disks  50   a-   50   f  may be fastened or otherwise joined together in a more permanent fashion, as is generally understood. In addition, the dilution disks  50   a-   50   f  need not be generally circular, but other shapes such as square. Similarly, positioning the dilution disks  50   a-   50   f  may alternatively be by linearly translating rather than rotating. 
     Also, the ability to vary the length of the channel formed by the series alignment of a plurality of tortuous paths  52   a-   52   f  is shown as being discrete increments, that is entire tortuous paths  52   a-   52   f  of certain dilution disks  50   a-   50   f  are bypassed. As would be appreciated, the length of the channel may be varied in a more continuous fashion, such as having the output port  56   a - 56 f positionable along a number of points along the preceding tortuous path  52   a-   52   f  rather than only at a blind intake  58   a - 58 f. 
     These and other advantages and modifications will become readily apparent to those of ordinary skill in the art without departing from the scope of this invention. The applicant intends to be bound only by the scope of the claims which follow and equivalents thereof.

Technology Classification (CPC): 1