Patent Publication Number: US-2005126646-A1

Title: Flow rate adjusting device

Description:
The invention relates to a flow control device, in particular for liquids.  
      The object of the invention is to design a flow control device in such a way that the flow path and also the flow rates can be adjusted.  
      According to the invention, this object is achieved by the features in claim  1 . By virtue of the fact that the recesses extending laterally from the through-bores in the adjacent side faces of the disks, which can rotate relative to one another, are able to overlap to different extents, it is possible, for example, starting from a maximum flow rate with the through-bores flush, to adjust to very low flow rates as a result of the terminal points of the tapering recesses overlapping slightly. In this way, flow rates can be adjusted steplessly to the range of microliters to nanoliters. 
    
    
      Illustrative embodiments of the invention are explained in more detail below with reference to the drawing, in which:  
       FIG. 1  shows a perspective view of a flow control device with control unit,  
       FIG. 2  shows a diagrammatic longitudinal section through an embodiment of the flow control device with a plurality of control disks,  
       FIG. 3  shows a perspective view of a stationary control disk,  
       FIG. 4  shows a perspective view of a rotatable control disk,  
       FIG. 5  shows the securing of a rotatable control disk on a wormwheel,  
       FIG. 6  shows a sectional view through a drive means of the wormwheel, and  
       FIG. 7  shows a modified embodiment of a control disk. 
    
    
      In  FIG. 1 , reference number  1  indicates the flow control device through which a liquid flows in the axial direction, indicated by the arrows X and Y. Arranged on the housing  2  of the flow control device, via an attachment  2 ′, there is a coupling and sealing adapter  3  on which a motor housing  4  is secured, in which for example a direct-current motor or a linear motor is arranged. A control unit  5  with electronic control means is arranged on the motor housing  4 .  
       FIG. 2  shows diagrammatically a longitudinal section through the flow control device  1 . A screw-on sleeve  6  with a threaded portion  6 ′ is screwed onto the tubular section  2 ″ of the housing  2 , which screw-on sleeve  6 , together with a separately formed threaded portion  6 ″, holds a housing part  7  bearing on the tubular housing section  2 ″. Reference number  8  indicates a seal, for example an O-ring between the two housing parts  2  and  7 . The threaded portion  6 ′ is for example designed as a right-hand thread, while the threaded portion  6 ″ is designed as a left-hand thread. In this way, the two housing parts  2  and  7  can be fixed by the screw-on sleeve  6  so as to bear tightly on one another.  
      Inserted into a central bore of the housing part  7  there is a fixed plug-in shaft  9  which, on the circumference, has a serrated profile or a toothing which engages with a corresponding serrated profile in the housing bore. In the illustrative embodiment shown, nine control disks  10  to  18  are arranged on this plug-in shaft  9 . The first control disk  10  and the control disk  18  at the opposite end are fixed in a stationary position on the plug-in shaft  9  via the serrated profile, and likewise the control disks  12 ,  14  and  16 , whereas the intermediate control disks  11 ,  13 ,  15  and  17  are rotatable on the plug-in shaft  9  as a result of a greater diameter of the bore. The control disks  10  to  18  are held lying tightly against one another by means of the pretensioning of a cup spring  19  which is arranged in a recess of the housing  2 . The control disks  10  to  18  are surrounded by a sleeve-shaped wormwheel  21  which can be set in rotation by a worm shaft  22  which, as is shown in  FIG. 6 , is rotated by the drive motor arranged in the motor housing  4 . The rotatable control disks  11 ,  13 ,  15  and  17  are each connected to the wormwheel  21 , whereas the stationary control disks  10 ,  12 ,  14 ,  16  and  18  can slide on the inner circumference of the sleeve-shaped wormwheel  21  or can also have an external diameter smaller than the internal diameter of the sleeve-shaped wormwheel  21 . In the illustrative embodiment shown, the rotatable control disks are connected to the wormwheel  21  free from play via a centering grub screw  23 , as is shown in  FIG. 5 . Here, for example, four wedge-shaped carrier grooves  24  are formed on the outer circumference of a rotatable control disk ( FIG. 4 ), into which grooves  24  the wedge-shaped point of the centering grub screw  23  engages. These centering grub screws are provided with a hexagon socket, as is indicated in  FIG. 5 .  
      In the area of the control disk  17 , the sleeve-shaped wormwheel  21  has, on the outer circumference, a worm thread  20  which engages with the thread of a worm shaft  22 . The sleeve-shaped wormwheel  21  is mounted rotatably in both housing parts  2  and  7  via slide bearings  26  at the opposite ends.  
      A seal  27  is provided in each case on the end faces of the two housing parts  2  and  7  and bears on the side faces of the stationary disks  10  and  18 . Both housing parts  2  and  7  are each provided with an attachment piece  28  with external thread and a flanged cone  29  for flanged screwing-on of an attachment hose  52 . The hose  52  or a bundle-tube is connected in a sealed manner to the attachment piece  28  via a rivet nut  51 .  
      The control disks  10  to  18  are each provided with a through-bore  30  which is arranged eccentrically on the individual control disks in the axial direction, as  FIGS. 3 and 4  show. Arranged on the stationary control disk  10 , on one side face  32  of the control disk, there is a recess  31  which, starting from the through-bore  30 , arranged at a distance r from the axis, tapers off in width and depth and extends in an arc of a circle about the axis at the distance r from said axis. In the illustrative embodiment shown in  FIG. 3 , this tapering recess  31  extends almost in a semicircle about the axis on the side face  32 . The opposite side face of the control disk  10  is smooth and is provided only with the through-bore  30 .  
       FIG. 4  shows a rotatable control disk, for example the control disk  11 . Formed on the side face  33  of the rotatable control disk  11  lying opposite the side face  32  of the stationary control disk  10 , there is a recess  31   a  which tapers off starting from the through-bore  30  almost about a semicircle and is identical in design to the recess  31  on the control disk  10 , but extends in the opposite direction. While the recess  31  on the control disk  10  extends in the clockwise direction starting from the through-bore  30 , the recess  31   a  on the opposite side face  33  of the control disk  11  extends in the opposite direction so that, upon alignment of the through-bores  30 , the one recess  31   a  extends in the clockwise direction and the recess  31  on the opposite control disk extends in the anticlockwise direction about the axis. By rotating the control disk  11  relative to the control disk  10 , the passage cross section can be decreased continuously along the recesses  31  and  31   a  until only the terminal points of the two recesses  31  and  31   a  overlap slightly, so that only a minimal passage cross section remains.  
      On the side face opposite from the side  33 , the rotatable control disk  11  has a corresponding recess  31   b  which starts from the through-bore  30 , as shown by broken lines in  FIG. 4 . The recess  31   b  extends in the opposite direction to that on the side face  33  and in the same direction as the recess  31  on the control disk  10 .  
      Correspondingly, the stationary control disk  12  is designed with a recess  31   a  and  31   b  tapering along an arc of a circle on both side faces. In terms of the arrangement and design of the recesses  31   a  and  31   b , the control disks  11  to  17  are of identical design, the respective recesses tapering off continuously in width and depth along the arc of a circle. The stationary control disk  18  at the opposite end has a mirror-inverted design in relation to the control disk  10 , with a recess  31  on only one side face.  
      In  FIG. 2 , the through-bores  30  of all the control disks  10  to  18  are represented in a flush position, so that there is a through-channel with a minimal diameter corresponding to that of the bores  30 . A passage channel  35  starting from the attachment piece  28  extends in a curved configuration through the housing parts  2  and  7  in such a way that it is flush with the eccentric through-bore  30  of the control disks  10  and  18 . In one illustrative embodiment, the internal diameter of the passage channel  35  and the internal diameter of the through-bores  30  can be 5 mm, for example, the recesses  31  tapering off continuously in width and depth to zero starting from the through-bores  30 .  
      The rotatable control disks  11 ,  13 ,  15  and  17  are rotated in synchrony relative to the stationary control disks  10 ,  12 ,  14 ,  16  and  18  by the wormwheel  21 , so that, between the side faces of the individual control disks lying against one another, the same passage cross section corresponding to the overlapping of the recesses  31 ,  31   a ,  31   b  etc. occurs.  
      By means of this succession of reduced passage cross sections corresponding to throttle positions, a high pressure of the liquid entering at the inlet side at X can be reduced in steps at the individual throttle positions as far as the outlet at Y. By means of the throttle positions arranged one behind the other, differential pressures of 2 to 300 bar can be reduced in steps, and very low flow rates in the range of microliters and nanoliters are also possible.  
      When the control disks are rotated relative to one another from the view in  FIG. 2 , so that throttle positions are formed by cross-sectional reduction at the overlapping recesses  31 ,  31   a ,  31   b , etc., channel portions of enlarged cross section form between the individual throttle positions because the liquid leaving one throttle position flows through the full cross section of a through-bore  30  before it comes to the next throttle position. In this way, a staged throttle is obtained, with expansion between the throttle positions, for pressure reduction.  
      Such a flow control device can be used in biotechnology, in fine chemistry and in various fields of application.  
      Instead of the nine control disks provided in the illustrative embodiment shown, a smaller number of control disks or a larger number can also be provided. For example, it is also possible to provide just one rotatable control disk between the stationary control disks  10  and  18 .  
      The control disks can be made of ceramic material or else of a synthetic such as Teflon, the side faces which lie against one another being made smooth so that they lie tightly against one another under the pretensioning of the cup spring  19 . Moreover, pressure compensation channels (not shown) can be provided on the individual control disks in order to compensate for the pressure acting in the axial direction of the flow control device.  
      The central bore  34  on the rotatable control disks  11 ,  13 ,  15  and  17  has a diameter which is equal to or slightly greater than the external diameter of the toothing on the plug-in shaft  9 , so that these rotatable control disks can be easily rotated on the plug-in shaft. By means of the wedge-shaped carrier grooves  24 , a clearance-free adjustment of the rotatable control disks is possible with the wormwheel  21  via the centering grub screws  23 .  
      In the orientation of the through-bores  30  corresponding to the representation in  FIG. 2 , that is with a continuously full cross section, a washing liquid can flow through the device, it being also possible for a ball to be passed through the flow control device in order to clean the passage channels.  
       FIG. 6  shows diagrammatically an example of a means for driving the wormwheel  21  via the worm  22 , which is mounted rotatably in the attachment  2 ′ of the housing. In the illustrative embodiment shown, a wobble rod  40  is arranged between the worm  22  and a shaft  41  mounted in the housing attachment  2 ′, and is guided through a stiff membrane  42  which on the one hand forms an articulation point for the wobble rod  40  and on the other hand seals the housing off from the drive unit.  
      Reference number  43  indicates a radial slide bearing for the worm  22  which at the opposite end bears on an axial bearing  44  and is additionally mounted in the housing via a radial bearing  45 . Reference number  46  indicates a spacer ring between the axial bearing  44  and a ring  47  which holds the membrane  42  and, on the outer circumference, is sealed off from the housing by a seal, for example an O-ring  48 .  
      A sealing shim (not shown) and a corresponding bearing can be provided on the shaft  41 .  
      As  FIG. 1  shows, viewing windows  50  can be provided on the coupling and sealing adapter  3 , through which windows  50  the sealing of the flow control device in relation to the drive unit can be monitored.  
      The flow control device described forms a micro-dosing fixture by means of which it is also possible to control very low flow rates.  
      According to a further embodiment of the invention, the lateral recesses  31  can, depending on the field of application of the flow control device, also have a shape other than that shown in which the width and depth of the recess  31  taper to zero starting from the through-bore  30 . Thus, for example, in the overlapping state, the recesses can form a flow cross section which corresponds to that of the through-bores  30 , so that by rotating the control disks relative to one another, starting from a position in which the through-bores  30  are flush with one another and form the shortest flow distance through the device, the flow path through the device can be lengthened by means of a channel which extends in the circumferential direction being formed between successive through-bores  30 .  FIG. 7  shows, corresponding to  FIG. 3 , a control disk with a recess  31 ′ which, with the opposite recess, forms a channel whose cross section corresponds to that of the though-bores  30  and which extends over an angle range of about 45°. However, this recess  31 ′ can also extend over a greater angle range.  
      Moreover, in an embodiment of the control disks according to  FIG. 7 , throttle positions can be formed by means of the opposite recesses  31 ′ overlapping only at the ends. For this purpose, instead of having the rounded configuration, the ends can also taper to a point. In such an embodiment, the volume between the throttle positions is increased by the extension of the recesses in the circumferential direction toward the through-bore  30 .  
      As has already been stated, this channel extending through the overlapping recesses  31 ′ in the circumferential direction can have a flow cross section corresponding to that of the through-bores  30 , for example for highly viscous fluids such as adhesives and the like. However, it is also possible for these recesses  31 ′ to be designed tapering over a shorter circumferential section than that shown, so that, when the recesses  31 ′ overlap, a connection channel tapering in the flow cross section is obtained between the through-bores  30 . In such a design, for example, the recess  31  shown in  FIG. 3  extends over about a quarter of a circle instead of a semicircle.  
      In addition, the flow cross section formed by the recesses  31  can also be changed by means of the shape of the recess  31  changing about the circumference, for example by means of the recesses  31  which extend in the circumferential direction having indents, or bulges projecting into the recess, presenting obstacles or cross-sectional changes in the channel formed through the overlapping recesses  31 , so that a certain mixing action in the fluid flowing through the device is also produced.  
      In the flow control device described, the diameter of the through-bores  30  is, for example, 5 mm. However, larger flow cross sections can also be provided in such a flow control device.