Abstract:
The material handling apparatus is in the form of apparatus for controlling the discharge of flowable material from a store thereof and comprises a hollow support member, a through-flow device slidable within the hollow support member, a closure operating member movable upwardly together with the through-flow device for opening a closure device to allow material to flow from the store into the through-flow device and actuator means between the hollow support member and the through-flow device for moving the through-flow device and the closure operating member relative to the hollow support member.

Description:
This invention relates to material handling apparatus and more particularly to apparatus for controlling the discharge of flowable material from a store thereof, such as a silo or an intermediate bulk container. 
     GB-A-2084969 discloses apparatus for controlling the discharge of flowable material from a store having a discharge opening near a lower end thereof. The apparatus comprises a closure device in the form of a cone valve mounted internally of the discharge opening, a pneumatic actuator in the form of a bellows device for moving the closure device vertically between a position in which the opening is fully closed and a position in which the opening is open for flow of material therethrough, and a vibrator adjacent to the closure device for vibrating the closure device to assist flow of material through the discharge opening. The apparatus also includes guide rods for guiding the closure device and adjustable and lockable bushes on the guide rods to limit the height of the lift to suit different powder characteristics and required flow rates. This type of apparatus is now in common use for controlling the discharge of flowable material such as powder or other particulate material. 
     It has become increasingly important in all processing industries that powders or other particulate materials used are contained within storage and processing vessels without contamination of the material, the outside environment or personnel and without cross contamination with other material or products. This is difficult to achieve with the aforementioned apparatus as all the working parts are within the process vessel and it has to be assembled with extreme care to ensure that nooks and crannies are minimised and there is no leakage through joints. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention there is provided apparatus for controlling the discharge of flowable material from a store thereof, comprising a hollow support member, a through-flow device slidable within the hollow support member, a closure operating member movable upwardly together with the through-flow device for opening a closure device to allow material to flow from the store into the through-flow device and actuator means between the hollow support member and the through-flow device for moving the through-flow device and the closure operating member relative to the hollow support member. 
     With such apparatus it is possible to avoid the use of mechanisms within the flow path of the material and it is, therefore, far easier to avoid contamination of the flowable material, the environment and personnel. 
     According to a second aspect of the invention there is provided apparatus for controlling the discharge of flowable material from a store thereof, comprising a closure device, means defining a discharge opening closable by the closure device, pneumatic actuator means for moving the closure device relative to the discharge opening defining means, means for operating the actuator means so as to move the closure device to a required position relative to the discharge opening defining means and means for pulsing the actuator means so as to oscillate the closure device about said set position. 
    
    
     The invention will now be more particularly described with reference to the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of one embodiment of apparatus according to the invention, fitted to a silo, 
     FIG. 2 is a sectional view of a similar embodiment of apparatus according to the invention in combination with an intermediate bulk container, with an actuator deflated, 
     FIG. 3 is a view similar to FIG. 2, but showing the actuator fully inflated, 
     FIG. 4 is a view similar to FIG. 2, but with the actuator partially inflated, 
     FIG. 5 is a sectional view of another embodiment of apparatus according to the invention, 
     FIG. 6 is an exploded view of part of the apparatus shown in FIG. 5, 
     FIG. 7 is a section taken along line A—A of FIG. 6, 
     FIG. 8 is a sectional view of a further embodiment of apparatus according to the invention, 
     FIG. 9 is a sectional view of an alternative closure device, 
     FIG. 10 is a sectional view of yet another closure device in a closed condition, 
     FIG. 11 is a sectional view of the closure device shown in FIG. 10 in an open condition, and 
     FIG. 12 is a sectional view of yet another embodiment of apparatus according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows one embodiment of apparatus for controlling a discharge of flowable material from a container  10  in a form of a silo having a valve  12  at a lower end thereof. 
     FIGS. 2 to  4  show apparatus similar to that shown in FIG. 1 but at a fixed discharge station  11  for receiving an intermediate bulk container (IBC)  10  having a valve  12  at a lower end thereof. 
     The apparatus comprises a hollow tubular support member  13  having an annular inwardly extending flange  14  at a lower end of the support member  13 , a through-flow device  15 , a closure operating member  16  and a pneumatic actuator  17  in a form of a flexible torroidal member similar to an inner tube of a vehicle tire. 
     The valve  12  comprises a discharge opening defining means in a form of a hopper  18  and a closure device  19 . In the case of the silo shown in FIG. 1, the hollow support member  13  is attached to the hopper  18  by a band clamp  20 . 
     The through-flow device  15  comprises an upper frusto-conical portion  21  and a lower cylindrical portion  22  which extends through an opening defined by the inner edge of the flange  14  and into a pipe  23 . The upper edge of the frusto-conical portion  21  is a close sliding fit within the hollow tubular support member  13 . 
     The closure operating member  16  is in a form of an upstanding probe secured to the frusto-conical portion  21  of the through-flow device  15  by angled rods  24 ′ (as shown in FIG.  7 ). 
     The hopper  18  includes a first cylindrical portion  24  near to an upper end of the hopper  18 , a second downwardly tapered frusto-conical portion  25  at a lower end of the hopper  18  and a third downwardly tapered frusto-conical portion  26  between the first and second portions  24  and  25 . The frusto-conical portion  26  defines a greater angle with the vertical than the frusto-conical portion  25 . 
     The closure device  19  is of double skinned, hollow construction. It is typically of plastics material or flexible steel. This will allow sufficient deformation of the closure device  19  to obtain good sealing contact with the hopper  18  thereby avoiding the need for a separate seal. The closure device  19  has a recess  27  in a lower surface thereof. The recess  27  has a frusto-conical wall  28  for receiving a frusto-conical portion  29  of the probe  16  as a tight fit. This ensures that the closure device  19  cannot tilt when the probe  16  is engaged with the closure device  19 . It also forms a seal so that an underside of the closure device  19  and an upperside of the probe  16  remain dust free. 
     The closure device  19  has a conical upper surface  30 , a cylindrical portion  31  depending from the outer edge of the upper surface  30 , a frusto-conical portion  32  at a lower end of the closure device  19  and a substantially horizontal portion  33  between a lower end of the cylindrical portion  31  and an upper end of the frusto-conical portion  32 . When the closure device  19  fully closes the discharge opening defined by the hopper  18 , the frusto-conical portion  32  of the closure device  19  engages the frusto-conical portion  25  of the hopper  18  and the cylindrical portion  31  of the closure device  19  is disposed within the cylindrical portion  24  of the hopper  18  with a very small annular gap therebetween. As the closure device  19  moves from an open to a closed condition, the cylindrical portion  31  of the closure device  19  will co-operate with the cylindrical portion  24  of the hopper  18  (as shown in FIG. 4) to substantially close the discharge opening before the frusto-conical portions  25  and  32  come into engagement. This will allow material within the hopper  18  and below the horizontal portion  33  of the closure device  19  to fall away so that material is not trapped between the frusto-conical portions  32  and  25  when the closure device reaches a fully closed position. Material flowing through the discharge opening, when the closure device  19  is in an open condition, will pass through the through-flow device  15  and into the pipe  23 . 
     The respective geometries of the hopper  18  and the closure device  19  created by the first and second portions  24  and  25  of the hopper  18  and the portions  31  and  32  of the closure device  19  also prevent the closure device  19  from tilting with respect to the hopper  18  when the closure device  19  closes the opening in the hopper  18 . This is particularly advantageous when used as parts of intermediate bulk containers (IBCs) as it will prevent tilting when the IBCs are away from a fixed discharge station. 
     The actuator  17  being disposed between the through-flow device  15  and the hollow tubular support member  13  is not within the flow path of the material. 
     A pneumatic circuit is provided to inflate and deflate the torroidal actuator  17  in order to vary a position of the closure device  19  and thereby a size of the discharge opening between the closure device  19  and the hopper  18 . The pneumatic circuit is also designed to pulse the torroidal actuator  17  so as to cause the closure device  19  to oscillate about a set position. This helps to break up consolidated powders and bridges within powders and separates the flowing powder out around the closure device  19  and through the annular discharge opening. 
     A frequency and amplitude of the oscillations can be varied according to a type of powder or other particulate material being discharged. 
     A load cell (not shown) could be used to sense a weight of material in a container to which material is discharged by the apparatus described above. A signal representative of the sensed weight could then be used to control a rate of discharge of the material. 
     Any one or more of the closure device  19 , the hopper  18 , the hollow tubular support member  13 , the through-flow device  15  and the probe  16  can be molded in plastics material thereby making them hygienic, maintenance free and easy to clean. 
     As shown in FIGS. 5 and 6, a flexible tubular seal  34  of elastomeric material can be provided between a top of the hollow tubular support member  13  and a bottom of the pipe  23 . In this case, the probe  16  is separate from the through-flow device  15  and the probe  16  includes its own frusto-conical portion  35  which sits in the frusto-conical portion  21  of the through-flow device  15 . The seal  34  extends around an outer surface of the hopper  18  and passes between the frusto-conical portion  35  of the probe  16  and the frusto conical portion  21  of the through-flow device  15 , through the through-flow device  15  and is trapped between a flange  36  at the bottom of the pipe  23  and a customer&#39;s process inlet flange  37 . This ensures a completely smooth unbroken barrier between an interior and an exterior of the apparatus. 
     Alternatively, there could be separate seals between the top of the tubular support member  13  and the probe  16  or the hopper  18  and between the bottom of the tubular support member  13  and the pipe  23 . 
     The apparatus can also be provided with one or more position sensors  38  (see FIG.  8 ). The position sensor or sensors  38  can be mounted on a rodless pneumatic cylinder  39  depending from the bottom of the hollow tubular support member  13  for sensing a bottom edge of the through-flow device  15 . The position of the sensor(s)  38  can be varied by extending or retracting the cylinder  39 . The closure device  19  can be oscillated about a required position either by the actuator  17  being exhausted and then quickly re-inflated as the sensor  38  senses the bottom edge of the through-flow device  15  or by the use of two sensors  38  at slightly different heights to create sequential exhaustion and re-flation of the actuator  17 . The use of two sensors  38  would enable the closure device  19  to be oscillated between two fixed points at a fixed amplitude but at a variable frequency. 
     FIG. 9 shows another embodiment of a closure device  19 ′ which, in this case is in a form of a single skinned device. 
     FIGS. 10 and 11 show another embodiment of a closure device  19 ″. In this embodiment, the closure device  19 ″ is formed in two parts  19   a  and  19   b  secured together by a screw  40 . An annular flexible seal  41  of elastomeric material is trapped between the two parts  19   a  and  19   b  and disposed between the portions  31  and  32 . The annular flexible seal  41  is arranged to engage the frusto-conical portion  26  of the hopper  18  as the closure device  19 ″ reaches a closed position. Use of this seal  41  is particularly useful when discharging extremely free flowing powders or liquids and/or sensitive and easily damaged materials. 
     FIG. 12 shows another embodiment of apparatus for controlling the discharge of flowable material from a container, particularly an intermediate bulk container, and differs from the embodiment shown in FIGS. 5 to  7  in the following respects. Closure device  19 ′″  has an upper conical portion  30 ′, a cylindrical portion  31 ′ depending from an outer edge of the upper portion  30 ′ and an inner tubular portion  45  which is coaxial with the conical upper portion  30 ′. The inner tubular portion  45  has a frusto-conical portion  46  at its lower end which seats against frusto-conical portion  25 ′ of hopper  18 ′ when the discharge opening is closed. An annular gasket may be provided at the upper end of the cylindrical portion  24 ′ of the hopper  18 ′ to provide a wiping seal with the closure device  19 ′″. 
     Probe  16 ′ has an annular recess  47  adjacent to a lower end thereof. The recess  47  is defined by a convergent upper wall  48 , a slightly divergent base  49  and a more steeply divergent lower wall  50 . 
     A pneumatic actuator in a form of a flexible torroidal member  51  is provided in the recess  47 . This member  51  is a tight fit around the probe  16 ′ when deflated and, therefore, when deflated, the actuator  51  is housed wholly within the recess  47  to allow the closure device  19 ′″ to locate and lower onto, and off the probe  16 ′ when the container is lowered onto and lifted off the discharge station. When the closure device  19 ′″ is in position on the probe  16 ′, a lower end of the tubular portion  45  seats and seals against wall  50  of the probe  16 ′. The actuator  51  can be inflated to clamp the closure device  19 ′″ to the probe  16 ′. The actuator  51  is deflated by a quick release exhaust valve (not shown) which exhausts into a space between the probe  16 ′ and the tubular portion  45  of the closure device  19 ′″ to ensure that no product/dust is drawn up to contaminate the closure device  19 ′″ in the short time before seal  34 ′ seals against the outside of the probe  16 ′ when the container  10  and closure device  19 ′″ are lifted off. 
     The inner tubular portion  45  of the closure device  19 ′″ has an inwardly directed circumferentially extending lip  52  which engages a seat portion  53  at an upper end of the probe  16 ′ to prevent the closure device  19 ′″ from tilting with respect to the probe  16 ′. 
     As also shown in FIG. 12, the hollow tubular support member  13  has a downwardly extending extension tube  54  at its lower end. This extension tube  54  surrounds lower cylindrical portion  22 ′ of through-flow device  15 ′. A further flexible inflatable torroidal member  55  is provided in an annular space between the lower cylindrical portion  22 ′ of the through-flow device  15 ′ and the extension tube  54 . A split ring  56  is supported in a circumferentially extending groove  57  at the lower end of the inner tubular portion  45  of the through-flow device  15 ′ and, when inflated, the member  55  bears against this ring  56  to urge the through-flow device  15 ′, together with the probe  16 ′, downwards. This member  55  serves as an air spring to urge the through-flow device  15 ′, together with the probe  16 ′, downwards whenever actuator  17 ′ is deflated. The member  55  will thus clamp the closure device  19 ′″ into the container  10 , when the actuator  17 ′ is not inflated, to ensure a good seal. It will also ensure that the probe  16 ′ is not lifted up together with the container  10 . Also, when the actuator  17 ′ is pulsed so as to cause the closure device  19 ′″ to oscillate about a set position, the member  55  can be used to pull the closure device  19 ′″ downwards in a positive manner to provide better control and promote better flow of material from the container  10 . 
     One or more position sensors (not shown) similar to those described with reference to FIG. 8 can be used in conjunction with a pneumatic control system to control movement and oscillation of the closure device  19 ′″. 
     The embodiments described above are given by way of example only and various modifications will be apparent to persons skilled in the art without departing from the scope of the invention as defined by the appended claims. For example, many parts are described above as being of conical or frusto-conical shape. They could alternatively be of pyramidical or truncated pyramidical shape. By providing air tight seals between the hollow tubular support member  13  and the through flow device  15 , it is envisaged that it may be possible to do away with the torroidal member  17  so that the pneumatic actuator is defined by the chamber between the hollow tubular support member  13  and the through flow device  15 . Also, as described above, the closure device and probe are separate parts so that a transportable container can be removed complete with closure device leaving the probe in position at the station. This also makes it possible in a fixed silo application to remove the whole of the lower mechanism leaving just the closure device in place for ease of maintenance. However, the closure device could be an integral part of the probe particularly on small static silos.