Abstract:
A device for transferring a dusty, powdery, grain-like or granular conveyed material out of a storage receptacle and into a working or transfer receptacle or a similar accommodating space. The device comprises a working chamber, which is connected to a supply line for the conveyed material, and comprises a discharge cross-section. At least one feed line for a flow medium leads into the working chamber, and a filter device is located between the flow medium and the conveyed material. The supply line for the conveyed material leads into a tubular filter space, and a filter insert, which is also tubular and delimits said filter space, is placed inside the working chamber connected to an air line and/or to a gas line.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to an apparatus for conveying a particulate material into a receiving space and also relates to a conveying method. 
   One known apparatus of this type has a receiving container with a conical bottom area at the discharge cross section—which can be closed by means of a flap. Opposite said discharge cross section, there is an air feed in the container head, a series of filter bags being mounted upstream of said air feed in the direction of the container space. 
   Such pneumatic conveying devices are currently used primarily in the chemical and pharmaceutical industry, in the foodstuffs industry and other sectors of industry in which powder-like materials have to be conveyed. The great advantage of this conveying system is that it makes it possible to convey these substances in a controlled atmosphere. The known systems and devices for conveying powder-like materials and bulk materials are in most cases matched in terms of the design to the product that is to be conveyed, which is why these systems are often produced on a one-off basis; as a result, the costs of such systems—which operate relatively slowly and can only be cleaned with difficulty—are relatively high. 
   A further—very significant—problem with known systems is the clogging of the filter after a relatively short operating time, as a result of which disruptions often occur in the production of the powder-like materials and these disruptions lead to greater costs on account of stoppages in production. 
   BE 658 419 discloses a precipitation apparatus for precipitating solid material from the air stream of a pneumatic suction conveying system. A perforated piece of tube is used as filter device for the precipitation of the solid material. The air suction may be interrupted by a flap so that the granules adhering to the piece of tube can automatically fall down. The perforated piece of tube has relatively large pores and is rigid per se. 
   DE 196 54 648 A1 discloses a precipitation apparatus for the precipitation of powder-like materials having a small particle size from a stream of air. The solids/air mixture is passed into a separating chamber through a side entry opening. At the upper end of the longitudinal separating chamber there is a round filter which in terms of its particle size is suitable for retaining the solids. On the underside of the separating chamber there is a discharge opening. 
   It is the object of the present invention to eliminate the problems that occur with the systems and apparatuses described above, and to provide a conveying system which is suitable for different conveyed materials. 
   SUMMARY OF THE INVENTION 
   The foregoing object is achieved by providing an apparatus comprising a working chamber connected to a supply line for the conveyed material and having a discharge cross section, where at least one feed line for a flow medium opens into the working chamber and a filter device is arranged between said feed line and the conveyed material, wherein the supply line for the conveyed material opens into a filter space and a filter insert that delimits the latter is arranged in the working chamber, said working chamber being connected to an air line and/or a gas line. 
   According to the invention, the supply line for the conveyed material opens into a tubular space, and a filter insert that delimits the latter and is also tubular is arranged in the working chamber which is connected to an air line and/or a gas line. 
   In this case, the working chamber for receiving the filter insert comprises a perforated inner tube, which inner tube delimits a gap with a housing that surrounds said working chamber; the longitudinal axis of the housing of the working chamber should in addition determine the axial position of the filter insert and/or of the inner tube. It has been found that by virtue of the concept of a filter tube in the working chamber it is possible to considerably improve both the conveying operation and the cleaning works to be carried out on the apparatus. 
   Advantageously, the inner tube is spanned by a top cover of the filter insert, where this top cover is connected to a top plate of the surrounding housing by at least one fixing device; top cover and top plate delimit a head space which adjoins the gap between housing and filter insert, which head space is separated from the filter space of the filter insert by the top plate. 
   In one preferred refinement, the top cover bears the filter insert, which remains tensible on account of this suspension; according to the invention, in this refinement at least the height of the head space is variable. In addition, the top cover and the top plate should be connected by the supply line passing through them, in particular by a socket piece. According to the invention, this axial socket piece passes through the top plate—in a manner such that it can slide therein—and is connected to the supply line; preferably, the socket piece runs as a section of the supply line in the head space and is provided with an inlet valve which stops the pressure against the inlet direction. 
   It has additionally been found to be favorable to design the working space such that it can be connected to a vacuum source, preferably to the abovementioned head space. In one refinement, the vacuum source and a gas source, with the intermediate connection of a valve, should have a common outlet pipe for the working chamber, which may optionally be subjected to the action thereof. The vacuum serves to suck in the conveyed material and the selected flow medium—that is to say air or gas—in the working chamber washes round the filter insert located therein, penetrates into the interior thereof and conveys away the conveyed material located therein. For this purpose, an inlet valve should be arranged upstream of said valve in a gas line of the gas source. 
   In a further configuration, it has been found to be favorable to provide the vacuum source with a valve and to connect the latter by a line to the inlet valve of a gas source; this line should be designed as a T-piece having an outlet pipe associated with the working chamber, which outlet pipe is connected to the head space of the working chamber. 
   Vibration members which project from the housing in the direction of the axis are particularly important, said vibration members being connected to the inner tube and/or the filter insert and preferably operating at a frequency of between 20 and 150 Hz. By virtue of these vibrators—which in one preferred refinement are connected to the fixing device for the filter insert—an improvement is obtained both in the conveying operation and in the cleaning of the filter. 
   According to another feature of the invention, the filter space is designed at its lower outlet end such that it can be closed—by means of a closure member; this outlet end is conventionally provided at the base of the filter space but in the case of a horizontal arrangement of the filter space may also in turn be horizontal. This closure member may be a flap valve, a butterfly valve, a slide valve or a ball valve, where appropriate also a multichamber sluice. In any case, this closure member may be used to determine the filling level of the filter space and to initiate the conveying-away operation. 
   A filter space having at its lower end a bottom opening of the housing surrounding the working chamber is preferred; this bottom opening is designed such that it can be closed by means of the abovementioned closure member. 
   In one embodiment, the bottom opening may be provided in the cover plate of a container that is associated with the housing. According to a further feature of the invention, a motor-driven sluice device may also be provided on the lower side of the filter space for the step-by-step transfer of the conveyed material into a closed receiving container, which motor-driven sluice device can optionally be rotated and is provided with a number of metering chambers, one of which in each case can be placed in front of the discharge cross section of the filter space. 
   Within the context of the invention there is additionally an apparatus the filter space of which on the discharge side opens into a vibration channel which at the other end is provided with a closure member. A container provided with a weighing element is preferably arranged downstream of the latter. 
   According to the invention, the filter insert is of round, triangular or polygonal cross-sectional shape. The same also applies in respect of the inner tube, where the cross sections of the two components do not have to coincide. Nevertheless, it has proven to be favorable to allow the cross-sectional shape of the filter insert to correspond to the cross-sectional shape of the inner tube that surrounds it. It is also advantageous if the surface of the filter insert corresponds to at least two thirds of the cross-sectional area of the inner tube. A further feature of the invention specifies that the perforated inner tube has round, triangular and/or polygonal holes or is made of a wire netting. 
   The following measures are specified in particular according to the invention: a diameter of the filter tube of between 5 mm and 1000 mm, preferably between 200 mm and 900 mm, 100 mm and 600 mm or between 10 mm and 150 mm, and a length of the filter tube of between 25 mm and 5000 mm, advantageously between 1000 mm and 4500 mm or between 500 mm and 3000 mm or between 50 mm and 600 mm. 
   Within the context of the invention there is also a method for transferring a dust-like, powder-like, grain-like or granule-like conveyed material, in which the conveyed material is sucked up by a vacuum and/or the filter tube is cleaned by overpressure. 
   Overall, this results in an efficient solution to the problems mentioned in the introduction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages, features and details of the invention emerge from the following description of preferred examples of embodiments and with reference to the drawing, in which: 
       FIGS. 1 to 3  show in each case a longitudinal section through an apparatus according to the invention; 
       FIG. 4  shows a perforated tube with inserted tubular filter in longitudinal section as a detail of the apparatus; 
       FIGS. 5 to 7  schematically show cross-sectional shapes on line V-VII of  FIG. 4  for a filter tube; 
       FIGS. 8 ,  9  show in each case a schematic side view of a particular arrangement of the filter tube. 
   

   DETAILED DESCRIPTION 
   An apparatus  10  according to the invention for transferring dust-like, powder-like, grain-like or granule-like substances as conveyed material according to  FIG. 1  has, on a cover plate  12  of a receiving container  14  that forms a base, a tubular housing  16  of a working chamber  18 , which is spanned toward the top by a top plate  19 . Said top plate is in the tube axis A passed through by a short socket piece  22  which may comprise an inlet valve  23  and which is gripped by a collar  20  of the top plate  19 —with the intermediate connection of a sealing ring  21 . At the socket piece  22 , a conveying line indicated at  24 —for conveyed material flowing in the arrow direction x—is connected to a perforated inner tube that is fitted in the working chamber  18 ; this inner tube delimits a gap  29  with said housing  16 . 
   The socket piece  22  opens at a top cover  28  of a tubular filter insert  30  which runs coaxially in the interior  27  of the inner tube  26 . The top cover  28  is suspended in the working chamber  18  by a fixing device  34  that extends between it and the top plate  19 , and the working chamber ends on the cover plate  12  of the receiving container  14 , which cover plate bears both the inner tube  26  and the housing  16  of the working chamber  18 . Toward the interior  15  of the receiving container, the cover plate  12  is provided with a bottom opening  32  as a discharge opening, which is surrounded by the tubular filter insert  30  and the inner tube  26 . 
   A flap valve  40  which is articulated in a pivotable manner at the bearing point  36  is associated with the bottom opening  32 , which flap valve is moved by means of a piston/cylinder unit  38  from a rest position shown at  40   a  into its closed position in which it covers the bottom opening  32  from below. A closure piston  42  which supplies the necessary closing pressure in the closed position in this case passes through the cover plate  12  toward the flap valve  40 . 
   Vibrators  44  (three of which can be seen in  FIG. 1 ) are fitted in the housing  16 , which vibrators act in a vibrating manner on the inner tube  26  and the filter insert  30 . It is not shown that the vibrators  44  by way of example may also act on the abovementioned fixing device  34  for the filter insert ( 30 ). 
   The head section  18   f  of the working chamber  18 , which is delimited by the top plate  19  and the top cover  28  and can be adjusted to a limited extent in terms of its height h, is connected by a radial connection piece  46  to a valve  48 , which is arranged between a vacuum line  52 —coming from a vacuum pump  50 - and a gas line  54 ; the latter comprises an inlet valve  56  which for its part is connected to a control member  58  for the purpose of controlling the gas pressure. 
   On account of the negative pressure generated by the vacuum pump  48 , the conveyed material is sucked up via the supply line  24  and introduced into the working chamber  18 . During this operation—or during emptying—the filter tube  30  inserted into the perforated inner tube  26  is made to oscillate by means of the vibrators  44 , which operate at a frequency of from 20 to 150 Hz, and thus adhesion of the powder-like material is avoided. The vibrators  44  are primarily used to clean the filter tube  30  or to keep the latter clean. 
   Thereafter, air is introduced into the working chamber  18  via the valve  48  and the conveyed material is discharged via the flap valve  40 . Depending on the product that is to be conveyed, the latter may be replaced by a butterfly valve, slide valve, ball valve or a multichamber sluice or the like. The filter tube  30  is cleaned by the air entering through the valve  48  or by compressed air or gas. During the cleaning operation, the filter insert or the filter tube  30  is kept in oscillation via the vibrators  44 . 
   The apparatus  10   a  of  FIG. 2  differs from the abovementioned apparatus  10  firstly by the position of the closing piston  42  for the flap valve  40 ; this is arranged in the interior  27  of the perforated inner tube  26 . Secondly, the cleaning of the filter tube  30  in this case takes place by vibration or air; the valve  48  is not connected to the gas line  52 . 
   Above the bottom opening  32 , the apparatus  10   b  of  FIG. 3  corresponds to the apparatus  10  of  FIG. 1 . Below the bottom opening  32 , there is a base  60  which is funnel-shaped in cross section and which merges into a sluice device  62  with motor-driven sluice wheel  64 ; the latter has eight metering chambers  66 . There is a discharge  68  below this sluice wheel  64 . 
     FIG. 4  mainly shows the perforation of the inner tube  26 ; the latter is provided with round, rectangular or polygonal wall holes  25 . However, it may also be composed of a wire netting (not shown). 
     FIGS. 5 to 7  show cross-sectional variations of the filter tube  30 ,  30   a ,  30   b , namely a cylindrical cross section, a triangular cross section and a hexagonal or polygonal cross section. 
   In  FIG. 8 , a filter tube  30  having a diameter d of 80 mm and a length a of 800 mm is used on an apparatus  10   e  in a horizontal position between a socket piece  22   a  and a flap valve  40   a . The radial connection piece  46   a  which in this case points upward from the housing  16 , as part of a T-piece  47 , connects the filter tube  30  on the one hand to the inlet valve  56  on the control member  58  and on the other hand to the valve  48  in front of the vacuum pump  50 . The use of this arrangement is explained in more detail in Example 6 below. 
   The filter tube  30  of  FIG. 9  projects in the housing  16  of a diameter t vertically from a vibration channel  70  of the apparatus  10   d , which at the other end is connected to a flap valve  40   a  and on the underside is provided with an electrically driven vibrator  44 . Below this flap valve  40 , a container  74  is arranged on a balance  72 , the function of which container can be seen from Example 7 below; a number of application examples are described below. 
   EXAMPLE 1 
   Under hermetically sealed conditions, the very fine residuary powder was to be transferred from the receiving container of an electrostatic spraying system into transport containers (big bags) in order to be transported away. The mean particle size was 1 μm and the bulk density was 300 g/lt. 
   The filter tube  30  of the system had a diameter d of 250 mm and a length a of 1000 mm. Using this system, 800 kg were transferred in 20 min. 
   EXAMPLE 2 
   A pharmaceutical powder having a mean particle size of 25 μm and a bulk density of 600 g/lt was to be transferred from a hopper into a mixer. 
   The hopper, having a capacity of 200 l, from which the powder was taken and transferred into the mixer, was arranged at a distance of 10 m. The apparatus according to the invention for conveying the powder was fitted on the input flange of the mixer having a diameter of 150 mm. 
   A system according to the invention, with a filter tube  30  having a diameter d of 100 mm and a length a of 400 mm, was used for the transfer. 
   The amount conveyed to the mixer was 40 kg in 4 min. 
   EXAMPLE 3 
   In a mill, the air (200 m 3 /h) was very highly enriched with very fine powder having a particle size of 0.5 to 1.5 μm. 
   A system with a filter tube  30  having a diameter d of 250 mm and a length a of 500 mm was used to clean the air. The powder-enriched air was let into the filter tube  30  via the line  24 , which was fitted with a turbofan having a capacity of 200 l which generated the negative pressure. 
   The air could thus be kept dust-free. 
   EXAMPLE 4 
   A silo for 100 t of flour was to be filled at a conveying rate of 25 t/h. The filling level was 12 m. 
   Using a system which had a filter tube  30  having a diameter d of 1.2 m and a length a of 2 m and which was provided to suck using a turbocompressor at a rate of 2000 N/m 3 /h, the necessary conveying rate was readily achieved. 
   EXAMPLE 5 
   A powder-like material was to be transferred from a transport container (big bag) having a capacity of 1 t to a metering device which for the purpose of metering into the inlet hopper was equipped with a level control device, metering worm and a weighing system and was arranged at a distance of 12 m. In order to avoid disruptions for the weighing device, the inlet hopper was filled when the weighing system was in the switched-off state. 
   The apparatus according to the invention which was used for the transfer had a filter tube  30  having a diameter d of 100 mm and a length a of 500 mm. 
   The amount of powder transferred was 500 kg/h. 
   EXAMPLE 6 
   A relatively large amount of calcium carbonate (1 t/h) was to be transported from a silo over a distance of 100 mm to the place of use. In order to convey this amount, the horizontally running filter tube  30  of  FIG. 8  was used. The mode of operation for the sucking up of the powder corresponded to that described below with reference to Example 7, where the powder was discharged over the extent by means of pressure supplied via the inlet valve  56 . 
   EXAMPLE 7 
   In order to convey and meter a powder-like material for the pharmaceutical industry, a filter tube  30  with a filter insert having a diameter d of 60 mm and a length a of 600 mm was fitted in the working chamber  16  as shown in  FIG. 9 . The amounts to be metered were between 500 g and 5000 g with an accuracy of ±1 g. 
   The position of the essential elements at the start of the metering process was as follows: 
   socket piece  22  open; 
   outlet valve  40  closed; 
   valve  48  open; 
   inlet valve  56  closed. 
   By opening the valve  48  to the vacuum pump  50 , in this case the powder that was to be metered was sucked up via the socket piece  22  and the tubular chamber  29   a  was filled. The inlet valve  56  was then opened, the tubular chamber  29   a  was ventilated and the powder that was to be metered was discharged via the vibration channel  70  through the vibrator  44  and the outlet valve  40  into the container  74  arranged on the balance  72 . The outlet valve  40  was controlled via the balance  72 . Thereafter the valves  40   a ,  48 ,  56  were automatically returned to their initial position.