Patent Publication Number: US-2010127022-A1

Title: Dispensing valve

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to dispensing apparatus, and more particularly to a valve for dispensing small quantities of solid material in powder or granular form. 
     BACKGROUND OF THE INVENTION 
     In various industries, such as the chemical and the pharmaceutical industry, the handling of non-liquid materials in particulate form (e.g., powder or granules) is used for preparing mixtures, drugs, tests, in-process products or final products. Several dispensers for handling powdery materials are known in the prior art, and it is inherent to those devices that in general they are not suitable to precisely dispense different amounts of material, especially when the amount of material to be dispensed is small (e.g., in the range of milligrams). Further, these devices are not suitable to dispense powdery materials if the starting amount is very limited, such as for example 30 mg or less. However, in the chemical and the pharmaceutical industry, for research, development and production, it is important to be able to precisely dose small and very small amounts of powders and solids, with different flow characteristics and independent of the starting amount. 
     Prior art generally relevant to the present invention is described in International Publication No. WO 2007/054135, published May 18, 2007, owned by Symyx Technologies, Inc., the entirety of which is incorporated by reference. 
     SUMMARY OF THE INVENTION 
     This invention is directed to a valve for dispensing small quantities of solid material in powder or granular form. In one embodiment, the valve comprises a valve housing defining a generally vertical flow passage through the housing. The flow passage has an inlet and an outlet. The valve also includes a valve member comprising a valve body rotatable in the valve housing about a generally horizontal axis of rotation between an open position for permitting flow through down through the flow passage and a closed position blocking the flow. A slot is provided in the valve body. The valve body and slot are configured such that the slot communicates with both the inlet and the outlet when the valve member is in its open position, and such that the slot communicates with the inlet but not the outlet when the valve member is in its closed position. 
     In another embodiment, the valve comprises a valve housing defining a generally vertical flow passage through the housing. A horizontal valve opening extends completely through the housing, the valve opening thus having first and second opposite and open ends. The valve also includes a valve member comprising a generally cylindrical valve body configured so that it may be pushed into the valve opening through the first open end of the valve opening. The valve member is rotatable in the valve opening about a generally horizontal axis of rotation between an open position for permitting flow down through the flow passage and a closed position blocking the flow. A retainer is adapted to be positioned at the second open end of the valve opening for securing the valve member in the valve housing. The retainer is releasable for allowing the valve member to be removed from the valve housing through the first open end of the valve housing. 
     In a third embodiment, the valve comprises a valve housing defining a generally vertical flow passage through the housing, the flow passage having an inlet and an outlet. A horizontal valve opening extends completely through the housing so that the valve opening has opposite open ends. The valve includes a valve member comprising a valve body rotatable in the valve opening about a generally horizontal axis of rotation between an open position for permitting flow through down through the flow passage and a closed position blocking the flow. A slot is provided in the valve body. The valve body and slot are configured such that the slot communicates with both the inlet and the outlet when the valve member is in its open position, and such that the slot communicates with the inlet but not the outlet when the valve member is in its closed position. A retainer is adapted for securing the valve member in the valve housing. The retainer is releasable for allowing the valve member to be removed from the valve housing through an open end of the valve housing. 
     Other objects and features will be in part apparent and in part pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing one embodiment of a valve of this invention attached to a source vessel containing a particulate solid material to be dispensed; 
         FIG. 2  is a perspective of the valve of  FIG. 1 ; 
         FIG. 3  is an exploded perspective of the valve showing a valve member removed from a valve housing, and a retainer for retaining the valve member in the housing; 
         FIG. 4  is an enlarged section taken along lines  4 - 4  of  FIG. 3  showing a valve body of the valve member; 
         FIG. 5  is an enlarged section taken along lines  5 - 5  of  FIG. 3  showing the valve housing; 
         FIG. 6  is a vertical section through the valve taken in a plane generally perpendicular to the axis of rotation of the valve member, the valve member being shown in an open position; 
         FIG. 7  is a view similar to  FIG. 6  but showing the valve member in a closed position; 
         FIG. 8  is vertical section through the valve taken in a plane generally parallel to the axis of rotation of the valve member, the valve member being shown in an open position; 
         FIG. 9  is a view similar to  FIG. 8  but showing the valve member in a closed position; 
         FIG. 10  is a side elevation of the valve member; 
         FIG. 11  is a view similar to  FIG. 10  but showing the valve member rotated 90 degrees; and 
         FIGS. 12-14  are sectional views illustrating stops on the valve member engageable with the valve housing for stopping rotation of the valve member at locations corresponding to open ( FIG. 12 ) and closed ( FIG. 14 ) positions of the valve member. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the drawings. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to  FIGS. 1-3  of the drawings, a dispensing valve in accordance with one embodiment of this invention is designated in its entirety by the reference number  1 . The valve  1  is adapted for dispensing small but accurate quantities of solid material in particulate form (e.g., powder or granules) from a source vessel  5 . By way of example but not limitation, the valve  1  is especially suited for dispensing quantities less than about 50 mg, even more desirably less than about 30 mg, even more desirably less than about 10 mg, and even more desirably in the range of about 0.1 to 3 mg. In general, the valve  1  comprises a valve housing  7  and a valve member  11  mounted in the valve housing for rotation between an open position for dispensing a metered quantity of material from the source vessel and a closed position. The material is dispensed into a suitable destination vessel. The components of the valve are described in more detail below. 
     Referring to  FIGS. 1 ,  3 ,  5  and  6 , the valve housing  7  comprises an upper inlet section  15 , a middle valve section  19  and a lower outlet section  21  which combine to define a generally vertical flow passage  25  through the housing for flow of powder from an inlet  31  at the upper end of the housing to an outlet  33  at the lower end of the housing. In this particular embodiment, the flow passage  25  is generally co-axial with the longitudinal central vertical axis  35  of the valve housing. Other configurations are contemplated. 
     The upper inlet section  15  of the valve housing  7  surrounds an upper segment  25   a  of the vertical flow passage  25  and includes an upwardly opening cylindrical wall  37  having internal threads  41  which engage external threads  43  on the source vessel  5  containing material to be dispensed. The valve housing  7  may be connected to the source vessel  5  in other ways. A circumferential flange  45  projects horizontally outward from the wall  37  and includes wrench flats  47  for turning the valve housing  7  on its vertical axis to make the connection with the stated source of powder. The upper inlet section  15  also includes a generally horizontal internal shoulder  51  (see  FIG. 5 ) for supporting a seal or otherwise sealing the connection. The flow passage tapers downward from the shoulder a short distance, as indicated at  55 . A lower horizontal beam structure  61  ( FIG. 2 ) extends below the cylindrical wall  37  for reasons that will become apparent later. 
     The middle valve section  19  of the valve housing  7  comprises a generally part-cylindrical wall or sleeve  65  which defines a valve opening  69  extending completely through the housing from one side of the housing to the other side of the housing (see  FIG. 5 ). The valve opening  69  has a horizontal longitudinal axis  71  extending generally at right angles to the vertical axis of the housing. The valve opening  69  defined by the sleeve  65  has first and second opposite and open ends  75 ,  77 , and the sleeve has a part-cylindrical internal surface  79  which defines a valve seat. An opening  81  in the valve seat communicates with the outlet  33  of the housing  7 . 
     The lower outlet section  21  of the valve housing  7  comprises an upper generally cylindrical portion  91  and a lower funnel-shaped portion  93  for more precisely directing material into destination receptacles of various sizes, including relatively narrow receptacles. The lower segment  25   b  of the flow passage defined by the funnel-shaped portion  91  of the housing tapers toward the outlet  33  of the housing. 
     The valve member  11  is mounted in the valve opening  69  in the middle section  19  of the housing  7  for rotation about a horizontal axis which is generally co-axial with the longitudinal axis  71  of the sleeve  65  and generally transverse to the vertical flow passage  25  through the housing. Referring to  FIGS. 3 ,  10  and  11 , the valve member  11  comprises a generally cylindrical valve body  101  and a slot  105  in the valve body having opposing sides  109 , a closed bottom  111  and an open top  113 . The valve body  101  has first and second end portions  117  with interior faces defining the opposing sides  109  of the slot and a bridging portion  125  having an interior face defining the bottom  111  of the slot. The slot  105  substantially reduces the amount of contact area with the valve seat  79 , resulting in lower friction. 
     The end portions  117  of the valve body on opposite sides of the slot have curved generally cylindrical exterior faces  131  configured for sealing contact with corresponding curved generally cylindrical portions of the valve seat  79 . As illustrated in the drawings, the end portions  117  are shaped like disks having curved exterior faces curving over arcs of 360 degrees. However, it will be understood that the end portions  117  could have exterior faces curved over less than 360 degrees. Desirably, the curved exterior faces should extend over at least 180 degrees to maintain the valve member  11  centered in the valve opening  69  as it is rotated. To prevent the loss (leakage) of particulate material, the curved exterior faces  131  of the end portions  117  have a close conforming contact fit with the valve seat  79 . Desirably, any clearance between these exterior faces  131  and the valve seat  79  should is smaller than the size of the particles being handled. 
     The bridging portion  125  of the valve body  101  has a curved exterior surface  137  configured for sealing contact with a corresponding surface of the valve seat  79  (see  FIGS. 4 and 6 ). The exterior surface  137  is desirably curved over an arc  139  in the range of about 45 to 135 degrees, and desirably at least about 90 degrees. To further reduce friction between the valve body  101  and the valve seat  79 , the exterior surface  137  of the bridging portion is recessed to decrease the amount of surface area of the valve body in frictional contact with the valve seat. One such recess is indicated at  141  in  FIGS. 4 and 10 . Any number of recesses may be used to minimize the amount of surface area in contact with the valve seat to reduce friction. The recess(es) should be surrounded by surface areas of the valve body  101  in sealing contact with the valve seat  79  to prevent powder from becoming captured in the recess(es). 
     The end portions  117  of the valve body  101  are connected by a generally horizontal brace  151  which spans the slot at a location above the bottom  111  of the slot  105  to stabilize (rigidify) the valve body. Desirably, the brace  151  is generally co-axial with the horizontal axis  71  of rotation of the valve body. The brace  151  has an exterior surface which is configured to shed powder. In  FIG. 4 , the exterior surface of the brace  151  has a cylindrical shape, but other shapes capable of deflecting material when the valve  11  is open are suitable. 
     The valve body  101  and slot  105  are configured such that the slot communicates with both the inlet  31  and the outlet  33  of the valve when the valve member  11  is in its open position ( FIGS. 6 and 8 ), and such that the slot communicates with the inlet but not the outlet when the valve member is in its closed position ( FIGS. 7 and 9 ). In particular, the arrangement is such that when the valve member  11  is in its open position the bottom  111  and sides  109  of the slot  105  combine with the valve seat  79  closing the top of the slot to define an enclosed flow path corresponding to a middle segment  25   c  of the vertical flow passage  25  through the housing  7  for allowing flow of powder along the flow passage from the inlet  31  to the outlet  33  of the valve housing. On the other hand, when the valve member  11  is moved to its closed position, the valve seat opening  81  is closed by the bridging portion  125  of the valve body  101 . Desirably, however, the slot  105  remains in communication with the inlet  31  and thus the contents of the source vessel  5 . This is desirable for many reasons, one being that that the vessel  5  and valve  1  may be inverted to empty the entire contents of the valve back into the vessel prior to removal of the valve from the vessel. The material in the slot  105  is not lost because it is not isolated from the vessel when the valve is closed. 
     The slot  105  is dimensioned and configured to permit a free flow of material from the upper segment  25   a  of the flow passage  25  to the lower segment  25   b  of the flow passage. Referring to  FIGS. 10 and 11 , the slot  105  has a length L 1  from one end of the slot to the opposite end of the slot, a width W from one side wall  109  of the slot to the opposite side wall  109  of the slot, and a depth D from the top  113  of the slot to the bottom  111  of the slot. The depth D of the slot is such that the top and bottom of the slot are spaced from the axis of rotation  71  of the valve body on diametrically opposite sides of the axis of rotation. Desirably, the width W of the slot  105  is about the same as the diameter of the valve seat opening  81 . The slot  105  shown in the drawings is generally U-shaped with generally parallel sides  109  and a concave bottom  111  to provide a smooth continuous uninterrupted surface free of sharp corners or other discontinuities which might otherwise interfere with the free flow of material through the slot. The slot may have other shapes. 
     As shown in  FIGS. 10 and 11 , the valve member  11  further comprises a shaft  161  integrally connected to one end portion  117  of the valve body  101 , and a drive mechanism  165  on the shaft for rotating the shaft to move the valve body  101  to positions corresponding to open and closed positions of the valve member  11 . Desirably, the valve body  101 , shaft  161  and drive mechanism  165  are integrally formed (e.g., injection molded) as a one-piece valve member. To reduce cost and weight, the shaft  161  is hollow. 
     Referring to  FIGS. 8-11 , it will observed that the shaft  161  has a first inward-facing shoulder  171  at its inner end for contact with a corresponding outward-facing shoulder  175  on the valve housing  7 . The contact of these shoulders  171 ,  175  with one another properly and accurately positions the valve member  11  with respect to the valve seat  79 . The valve member is held in this position by a retainer  181  configured for releasable engagement with a projection  185  protruding from the end portion  117  of the valve body opposite the shaft  161  for securing the valve member  11  in the valve opening  69 . In the illustrated embodiment, the retainer  181  comprises a resilient clip in the form of a snap ring which snaps into a groove  191  in the projection. The outside diameter of the ring  181  is greater than the valve opening  69  so that the ring contacts an exterior surface of the housing  7  to hold the valve member captive in the valve opening. The retainer  181  is releasable from the groove  191  to allow the valve member  11  to be readily removed from the valve opening  69  in the valve housing. Other mechanisms may be used for retaining the valve member in the valve housing. 
     Desirably, the generally cylindrical valve body  101  configured so that it may be pushed into the valve opening  69  through the first open end  75  of the valve opening. The fit of the valve body  101  in the opening  69  is tight to prevent leakage of material from the valve. The brace  151  spanning the slot  105  provides rigidity to the valve which enables it to be pushed into place without unwanted deformation or damage to the valve. The valve body  101  is pushed to a position in which the shoulders  171 ,  175  on the valve body and the valve housing  7  abut. The retaining clip  181  is then snapped into place on the projection  185  at the opposite (second) end  77  of the valve opening  69  to hold the valve member in proper position in the valve opening. As explained above, the clip  181  is releasable for allowing the valve member  11  to be quickly and easily removed from the valve housing  7  through the first open end  75  of the housing. 
     Stops are provided on the shaft  161  and on the valve housing  7  for stopping rotation of the shaft at positions corresponding to the open and closed positions of the valve member  11 . In one embodiment ( FIGS. 12-14 ), these stops comprise a first flat  201  on the shaft  161  adapted for contact with a first flat  205  on the valve housing  7  to limit rotation of the shaft in a first direction to a position corresponding to the open position of the valve member ( FIG. 12 ), and a second flat  207  on the shaft  161  adapted for contact with a second flat  209  on the valve housing  7  to limit rotation of the shaft in a second direction opposite the first direction to a position corresponding to the closed position of the valve member ( FIG. 13 ). The flats  203 ,  207  on the shaft  161  are located on a curved surface of the shaft outboard of the inner shoulder  171  on the shaft. The flats  205 ,  209  on the valve housing  7  are located on a lower surface of the beam structure  61  on the valve housing. Other stops or mechanisms may be used to stop the rotation of the valve member  11  at its open and closed positions. In the embodiment shown, the rotation of the valve member is limited to about 90 degrees, but it will be understood that this number can vary depending on the configuration of the valve. 
     The drive mechanism  165  comprises a gear having teeth  215  for driving engagement with a suitable drive, e.g., a drive gear on the robot carrying the source vessel  5 . In the embodiment shown in the drawings, the gear is a gear segment having a configuration corresponding to the desired range of rotation of the shaft and valve member (e.g., 90 degrees). The teeth  215  are configured to a very fine tolerance so that movement of the valve member can be closely controlled. In this regard, the valve member  11  is movable from a closed position in which the valve seat opening  81  is 100% closed (i.e., completely blocked) to an open position in which the valve seat opening is either partially open (i.e., less than 100% open) or fully open (i.e., 100% open) to allow flow of material through the vertical flow passage  25  in the valve. Desirably, the fine tolerance of the drive gear  165  permits the size of the opening available for flow to be precisely adjusted so that the rate of flow through the flow passage  25  can be closely controlled. If needed, vibration can also be applied to the source vessel  5  to initiate flow and/or to vary the flow rate. Further, the amplitude and/or frequency of any such vibration can be varied to achieve the desired results. In any event, fine tuning of the flow rate through the valve allows accurate amounts of material to be dispensed in an efficient manner. It is contemplated that drive mechanisms other than a gear can be used for rotating the valve member  11  between its open and closed positions. 
     The overall dimensions of the valve housing  7  and valve member  11  are relatively small in a typical application. In one embodiment, for example, the overall length L 2  of the valve member  11  is desirably about 17.5 mm ( FIG. 10 ), the overall height of the valve housing  7  is about 29 mm ( FIG. 3 ), and the slot has length L 1 , width W and depth D of about 9 mm, 5 mm and 7 mm, respectively ( FIGS. 9 and 10 ). These dimensions may vary. Further, it is contemplated that the size of the valve may be scaled up or down to suit virtually any application. 
     In the illustrated embodiment, the entire valve member  11 , including the valve body  101 , shaft  161  and drive mechanism  165  are integrally formed in one piece. Desirably, the configuration is such that the valve member can be injection molded as a single part. Similarly, the valve housing  7  is desirably formed as one piece, as by injection molding. As a result, the cost of making the valve can be reduced to a point where the valve is disposable after use. 
     In use, the valve  1  is assembled by pushing the valve member  11 , valve body  101  first, into the valve opening  69  through the first open end  25  of the valve opening until the shoulder  171  on the valve member abuts the shoulder  175  on the housing  7 . The retaining clip  181  is then snapped into place on the projection  185  of the valve member  11  at the opposite (second) end  77  of the valve opening  69 . After the valve is assembled, the upper inlet end of the valve housing  7  is threaded onto the lower outlet end of a suitable source vessel  5  containing a particulate material to be dispensed. In many applications, including high-throughput applications, a robot is used to dispense material from the source vessel  5 . The vessel is transported by the robot to the desired location. A suitable drive on the robot in driving engagement with the drive mechanism  165  on the valve member  11  is then operated to move the valve member from its closed position to an open position corresponding to the desired flow rate to be achieved. Material is dispensed from the vessel  5  and through the open flow passage  25  of the valve into a destination vessel which is typically supported by a weighing device. In one application, the weighing device provides real-time feedback to a controller programmed with suitable software to operate the robot according to a desired protocol. After a target weight of material has been dispensed into the receptacle, the controller operates the robot to close the valve. If desired, the vessel is moved to one or more different locations by the robot and the cycle is repeated at each location to deposit material into a destination vessel. After the desired number of deposits are made, the source vessel  5  and valve  1  may be removed from robot and inverted (turned upside down) to empty any material remaining in the valve (now in its closed position) into the vessel. The valve  1  can then be removed from the vessel  5  without any significant amount of material remaining in the valve. Alternatively, the valve can be left on the vessel to function as a cap or closure for the vessel while it is stored or otherwise used. Any material still remaining in the valve is subject to the same storage conditions as the material in the vessel, since the open top of the slot  105  in the valve member is in communication with the interior of the vessel. 
     It will be observed from the foregoing that a valve of this invention has one or more of the following advantages over prior valves used to dispense particulate solid materials such as powder or granules: the valve can be attached directly to a source vessel for dispensing directly from the vessel; the amount of material isolated from the source vessel when the valve is closed is minimized; the number of surfaces on the movable valve member in contact with the material flowing through valve is minimized to reduce the amount of material retained in the valve when the valve is closed; the material contained in the valve when the valve is closed can be emptied into the source vessel simply by inverting the vessel; the amount of contact area between the movable valve member and the valve seat is reduced, resulting in less friction; the valve member is easy to install in the housing and easy to remove from the valve housing  7  by using the releasable retainer  181 ; the tight fit of the valve body  101  in the valve opening  69  minimizes the amount of material lost during use of the valve; and the construction of the valve is such that the parts (valve housing  7 , valve member  11  and retainer  181 ) are easy to make by an injection molding process for reduced cost. 
     Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. 
     When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. 
     As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.