Feeder unit, feeder module comprising feeder units, and method for discharging a constant mass flow of one or more powders into a receiving container

Abstract

A method for processing pharmaceutical powders, which comprises providing a feeder module including a plurality of feeder units each with a storage hopper, a weighing cell, a conveyer, and a discharge end, connecting the storage hopper to a refilling system with a refilling valve, connecting the refilling valve to a level or weight indicator disposed above the refilling valve, connecting the discharge end to a common receiving container, refilling the storage hopper with a powder intermittently 40 to 80 times per hour, storing data during refilling, transporting powder from the storage hopper with the respective conveyer, and discharging powder from each feeder unit into the common receiving container. During each refilling of the storage hopper, the refilling valve dispenses powder into the storage hopper and, during the step of transporting the powder from the storage hopper, the conveyer is operated according to the data collected during previous refills.

Claims

1. A feeder module, comprising: a plurality of feeder units arranged in a spokes-like configuration in a single level, the plurality of feeder units being two to eight in number, each feeder unit comprising a storage hopper, a weighing cell, a conveyer, and a discharge end; and a common receiving container connected to the discharge end of each feeder unit, each feeder unit extending radially outwards from an imaginary inner circle defined by the discharge ends of the plurality of feeder units in the common receiving container to an imaginary outer circle defined by radially opposite ends of the plurality of feeder units, the plurality of feeder units being positioned substantially on radii extending from the imaginary inner circle, wherein: one or more conveyers of the plurality of feeder units is a twin screw conveyor, at least one of the screws of the twin screw conveyor has: a length underneath the storage hopper; and at least one of: a variable pitch along the length underneath the storage hopper; and a variable diameter along the length underneath the storage hopper.

2. The feeder module according to claim 1, wherein the plurality of feeder units are five to eight in number.

3. The feeder module according to claim 1, wherein each feeder unit further comprises: a refilling system including a refilling valve; and at least one of a level indicator and a weight indicator located above the refilling valve, the refilling system being connected to the storage hopper of each of the plurality of feeder units.

4. The feeder module according to claim 1, wherein the storage hopper, the conveyer, and the discharge end of each of the plurality of feeder units are releasably connected to the weighing cell.

5. The feeder module according to claim 1, wherein the at least one of the screws of the twin screw conveyor has the variable pitch along the length underneath the storage hopper.

6. The feeder module according to claim 1, wherein the at least one of the screws of the twin screw conveyor has the variable diameter along the length underneath the storage hopper.

7. The feeder module according to claim 1, wherein the at least one of the screws of the twin screw conveyor has: the variable pitch along the length underneath the storage hopper; and the variable diameter along the length underneath the storage hopper.

8. The feeder module according to claim 1, further comprising a controller configured to process weight signals and to compensate external forces.

9. The feeder module according to claim 1, further comprising a sensor configured to sense material variations.

10. The feeder module according to claim 1, wherein the storage hopper, the conveyer, and the discharge end of the feeder unit are contained and isolated from the weighing cell.

11. The feeder module according to claim 1, further comprising at least one lay flat tube, the discharge end of each of the plurality of feeder units being connected to the common receiving container by the lay flat tube.

12. The feeder module according to claim 11, wherein: each of the plurality of feeder units comprises a pre-feeder element; and the lay flat tube is a plurality of lay flat tubes each between the storage hopper and the pre-feeder element of a respective one of the plurality of feeder units.

13. The feeder module according to claim 12, further comprising a casing disposed around the storage hopper, the conveyer, and the discharge end of each of the plurality of feeder units.

14. The feeder module according to claim 1, wherein: the common receiving container has a diameter; and the diameter of the imaginary inner circle is smaller than the diameter of the common receiving container.

15. The feeder module according to claim 1, further comprising an integrated active vibration compensation scale.

16. The feeder module according to claim 1, wherein the storage hopper comprises a stirrer device.

17. The feeder module according to claim 1, wherein a smallest possible dimension of the imaginary inner circle and, therefore, of the common receiving container, is dependent upon a number of the plurality of feeder units and upon physical dimensions of individual ones of the plurality of feeder units.

18. The feeder module according to claim 17, wherein: the number of the plurality of feeder units is five feeder units distributed substantially evenly about the imaginary inner circle; and a diameter of the imaginary inner circle is between approximately 42 mm and approximately 100 mm.

19. The feeder module according to claim 1, wherein: the number of the plurality of feeder units is six feeder units distributed substantially evenly about the imaginary inner circle; and a diameter of the imaginary inner circle is between approximately 50 mm and approximately 120 mm.

20. The feeder module according to claim 1, wherein: the number of the plurality of feeder units is seven feeder units distributed substantially evenly about the imaginary inner circle; and a diameter of the imaginary inner circle is between approximately 57 and approximately 140 mm.

21. The feeder module according to claim 1, wherein: the number of the plurality of feeder units is eight feeder units distributed substantially evenly about the imaginary inner circle; and a diameter of the imaginary inner circle is between approximately 65 mm and approximately 150 mm.

22. The feeder module according to claim 21, wherein the diameter of the imaginary inner circle is approximately 107 mm.

23. The feeder module according to claim 1, wherein a lateral clearance between parts of neighbouring feeder units is between approximately 1 mm and approximately 10 mm.

24. The feeder module according to claim 23, wherein: one or more conveyers of the plurality of feeder units is a twin screw conveyor; the feeder units associated with the one or more conveyers have twin screw discharge tubes; and the lateral clearance in between two of the twin screw discharge tubes is between approximately 1 mm to approximately 10 mm.

25. The feeder module according to claim 24, wherein: the common receiving container has a diameter; and a discharge tube end of the plurality of feeder units with the imaginary inner circle is smaller than the diameter of the receiving container.

26. A method for providing a mixture of one or more powders in a common receiving container using the feeder module of claim 1, which comprises: providing each of a plurality of feeder units with a storage hopper, a weighing cell, a conveyer, and a discharge end; providing a common receiving container; configuring the plurality of feeder units with the respective discharge ends facing the common receiving container in a single level; connecting the discharge end of the plurality of feeder units to the common receiving container; refilling the storage hopper of a respective one of the plurality of feeder units with a powder; and feeding the powder from the respective storage hopper to the common receiving container to provide the mixture.

27. The method according to claim 26, wherein the common receiving container has inner walls and a throat and, which further comprises, allowing the discharged powder to fall straight into the throat of the receiving container and thereby substantially prevent the falling powder to stick to the inner walls of the common receiving container.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, which are not true to scale, and which, together with the detailed description below, are incorporated in and form part of the specification, serve to illustrate further various embodiments and to explain various principles and advantages all in accordance with the systems, apparatuses, and methods. Advantages of embodiments of the systems, apparatuses, and methods will be apparent from the following detailed description of the exemplary embodiments thereof, which description should be considered in conjunction with the accompanying drawings in which:

(2) FIG. 1 shows a perspective view of an embodiment of a feeder module of the invention;

(3) FIG. 2 shows a top plan view of the feeder module of FIG. 1;

(4) FIG. 2a shows a fragmentary, schematic overview corresponding to FIG. 2, in an embodiment comprising eight feeder units;

(5) FIG. 2b shows a fragmentary, schematic overview corresponding to FIG. 2a, of another embodiment comprising seven feeder units;

(6) FIG. 2c shows a fragmentary, schematic overview corresponding to FIG. 2a, of further embodiment comprising six feeder units;

(7) FIG. 2d shows a fragmentary, schematic overview corresponding to FIG. 2a, of further embodiment comprising five feeder units;

(8) FIG. 3 shows a cross-sectional view of the feeder module of FIG. 1;

(9) FIG. 4 shows a fragmentary, detail cross-sectional view of and exemplary embodiment of a receiving hopper or receiving container of the feeder module of FIG. 1;

(10) FIGS. 5 and 6 show a perspective view from above a feeder module of another embodiment in two different conditions;

(11) FIG. 7 shows a partially transparent, perspective view of a detail of an embodiment of a feeder module and containment of powder contacting powder pump;

(12) FIGS. 8a-c show fragmentary, side views of a detail of a pre-feeder element of a feeder module;

(13) FIG. 9a shows a vertical cross-sectional view of an embodiment of a feeder module;

(14) FIG. 9b shows a top plan view of a feeder unit;

(15) FIG. 9c shows a vertical cross-sectional view of a feeder module; and

(16) FIGS. 10 and 11 show fragmentary, partially transparent plan views of a detail of two different embodiments of a feeder module.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(17) Referring now to the Figures, a feeder module generally designated 1 is shown. In the embodiment shown, the feeder module 1 comprises a plurality of feeder units 2. Each feeder unit 2 comprises a feeder part 20 and a weighing cell. A pre-feeder element 40 is attached to the feeder part 20. In the embodiment shown in FIGS. 1 to 3, there are eight such feeder units 2. The feeder unit 2 according to the invention may also be used independently, as a single unit.

(18) In one development of the preferred embodiment, the feeder module comprises five feeder units 2 and the diameter of the imaginary inner circle is 42-100 mm for a twin screw discharge tube (WDis) of 24 to 45 mm and a lateral clearance (CL) in between two twin screw discharge tubes of 1 to 10 mm, see FIG. 2d.

(19) Alternatively, the feeder module may comprise six feeder units and the diameter of the imaginary inner circle is 50-120 mm for a twin screw discharge tube of 24 to 45 mm and a lateral clearance (CL) in between two twin screw discharge tubes of 1 to 10 mm. See FIG. 2c.

(20) The feeder module comprises seven feeder units and the diameter of the imaginary inner circle is 57-140 mm for a twin screw discharge tube of 24 to 45 mm and a lateral clearance (CL) in between two twin screw discharge tubes of 1 to 10 mm, see FIG. 2b.

(21) As a further and preferred development, the feeder module comprises eight feeder units and the diameter of the imaginary inner circle is 65-150 mm for a twin screw discharge tube of 24 to 45 mm and a lateral clearance in between two twin screw discharge tubes of 1 to 10 mm, see FIG. 2a.

(22) With particular reference to FIGS. 3 and 4, each feeder unit 2 includes a storage hopper 21 to contain material to be processed, a conveyer 22, a discharge end 23, and a weighing cell 24. The conveyer 22 has the function of transporting the material from the storage hopper 21 to discharge the material into a receiving container in a manner to be described in further detail below. Furthermore, it emerges from these Figures that the feeder units 2 are arranged in a single level to discharge into a common receiving container 3.

(23) In the embodiment shown in FIGS. 1 to 4, the feeder units 2 are distributed substantially evenly over 360° in the same level, i.e. on substantially the same horizontal plane. Thus, the feeder units 2 are arranged in a spokes-like configuration, each feeder unit 2 extending radially outwards from an imaginary inner circle 31 defined at the discharge end 23 facing the common receiving container 3 to an imaginary outer circle defined by radially opposite end of each feeder unit. The feeder units 2 are positioned substantially on radii extending from the imaginary inner circle.

(24) The smallest possible dimension of the imaginary inner circle 31, and hence of the receiving container 3, depends on the number of feeder units 2 and of the physical dimensions of the individual feeder units 2. Typical values in embodiments comprising five feeder units, possibly distributed substantially evenly, are a diameter of the imaginary inner circle of 42-100 mm. In an embodiment comprising six feeder units, possibly distributed substantially evenly, the diameter of the imaginary inner circle is typically 50-120 mm. 7 feeders 57-140 mm. In the embodiment shown in FIGS. 1 to 4, where eight feeder units 2 are adapted to be distributed substantially evenly, the diameter of the imaginary inner circle is typically 65 to 150 mm, in the specific embodiment approximately 107 mm. These values are dependent also on the desired clearance of 1-10 mm between parts of neighboring feeder units and the dimensions of the individual parts. In the embodiment shown, the approximate width 26 of the discharge tube of each feeder unit 2 is 40 mm.

(25) The dimensioning of the feeder units 2 of the feeder module 1 depends on the field of application. Sizing may for instance be available as a range, such that each feeder unit 2 in a module 1 is of a different size. In the embodiment shown and described, the dead weight of each feeder unit 2 is below 5 kg, and the capacity of the storage hopper of each feeder unit is less than 2 liters.

(26) Correspondingly, the net weight of the powder to be filled into the storage hop-per 21 of the individual feeder units 2 depend on the volume but also on the kind of pow-der applied. Typically, the maximum volume of powder in the storage hopper lies in the interval 1.6 to 2 liters. The maximum mass flow rate is approximately 50 kg/h.

(27) The ratio of powder weight and the maximum mass flow provide a maximum run time to empty a feeder or a maximum refilling interval pr. hour. Preferably, the arithmetic product of the maximum refilling interval [h] and the dead weight [kg] of each feeder unit 2 is below 0.1 kgh. If the powder density is taken out of the equation and replaced by volume the maximum refilling interval is also the ratio of the hopper volume [L] and the feed rate [L/h]. E.g the capacity of the storage hopper of each feeder unit is less than 1.6 liters. The maximum flow rate is 100 L/h. The maximum refill interval is then 0.016 h. The dead weight of each feeder unit 2 is typically 5 kg.

(28) In the embodiment described, the arithmetic product of the dead weight 5 kg and the maximum refill interval 0.016 h is 0.08 kgh. The arithmetic product is typically below 0.2, preferably below 0.1, most preferably below 0.05 kgh.

(29) Cleaning of at least some parts of the feeder module is advantageously carried out on a regular basis. In order to allow cleaning of in particular the parts in contact with the powder to be processed, the storage hopper, the conveyer and the discharge end of each feeder unit are releasably connected to the weighing cell.

(30) FIG. 4 shows a detail cross section of the receiving hopper or receiving container 3. The discharge tube end 23 of the feeder units 2 with the imaginary circle 31 is smaller than the diameter of the receiving container 3. The discharged powder falls straight into the throat of the receiving container 3 and is substantially not sticking to the inner walls of the receiving container 3.

(31) In the embodiment of FIGS. 5 and 6, the configuration of the feeder units 2 of the feeder module is slightly different from that of FIGS. 1 to 4. Here, there are also eight feeder units 2, but they are distributed over only a part of the circle circumscribing the discharge ends 23 and the receiving container, viz. approximately 270°. Detachment of one feeder unit 2, for instance for cleaning purposes, is carried out by detaching the feeder unit 2 from the receiving container 3. This may take place in a contained manner, for instance by other tightening or sealing devices, such as by Layflat tubing (LFT).

(32) Following detachment of one feeder unit 2, the engagement of the storage hopper, the conveyer and the discharge end 23 with the weighing cell 24 is released to attain the position shown in FIG. 7.

(33) Relative to some prior art devices, it is noted that there is no bellow between the discharge end 23 and the receiving container. Such a bellow has shown to influence the weighing signal due to its stiffness. A casing 250 is provided around the storage hopper, the conveyer 22 and the discharge end 23 of each feeder. The openings in the casing 250 are detached from the weighing cell. The receiving container, which is also detached from the weighing cell, and the feeder part 20 are isolated in a contained way by means of a lay flat tube 260. Lay flat tubes 260 are preferably made of a lightweight material having a very low stiffness, such that the weighing signal is left almost completely unaffected. A lay flat tube 260 may also be provided between the storage hopper 21 and a pre-feeder element (see FIG. 1).

(34) Refilling of the storage hoppers of the feeding units 2 may take place at different points in time, if expedient according to a predefined schedule. The refilling takes place by means of a valve with air compensation, cf. FIGS. 8a-c and part 230 in FIG. 3. Suitable valves are represented by plug valves, rotary dosing valves 41, butterfly valves 42 and slide valves 43. Above the valve a level sensor 44 is provided for use when the weight is fluctuating during refill of the feeder unit 2. The refilling takes place in a contained manner so as to at least assure that no dust enters the surrounding environment by the use of an appropriate seal or tube.

(35) During refilling, special precautions may be taken, such as for instance the use of an algorithm to control dosing during the short refilling time where weighing is paused, this is to compensate for the compacting effect that arises during filling. In the algorithm, a weight is simulated to predict the correct feed factor, and once the seal is released, the weight of the powder in the storage hopper is corrected. Particular details of the refilling procedure will be described in further detail below.

(36) Referring in particular to FIGS. 9a-c, the storage hopper 21 may be supplemented by a stirrer device 211 to break any bridges formed in the powder and to ensure that the conveyer 22 is fed properly. The conveyer 22 is in the embodiment shown a twin screw conveyor. Compared to FIG. 9a, the feeder unit 2 is additionally provided with lay flat tubing 260 and the receiving opening of the storage hopper 21 and at the discharge end 23.

(37) In the embodiment shown in FIG. 10, both of the concave screws 221 and 222 of the twin screw conveyor 22 have a variable pitch along its length, a first pitch p1 and a second pitch p2, being different from the first pitch P1. The conveyer 22 is driven by a motor M. In this embodiment the diameter of each screw is constant. In the embodiment of FIG. 11, the pitch of each screw is constant, whereas the diameter of the screws is variable along the length shown as diameter d1 and diameter d2. It is also possible to have one or more screws with both a variable pitch and a variable diameter.

(38) For both FIGS. 10 and 11 the material to be conveyed moved in the direction of the arrow away from the motor M and into the imaginary circle 31.

(39) Furthermore, although not shown in the drawings, the feeder module may comprise a number of additional features, such as analysis and control systems, loading and discharging stations etc.

(40) As the feeder unit of the feeder module according to the invention has a storage hopper of a limited volume, a rapid or high frequency refilling system is provided.

(41) Typically, feeders of a larger volume are refilled 4 to 8 times per hour. During refilling, the powder which is dropping into the storage hopper causes disturbances on the weight signal (due to the impact forces of the powder) over a period which is equal to the sum of the powder drop time and scale stabilization time. Together with the time of rolling average filters this usually takes 30 s up to 60 s to get a stable weighing signal after a refill or top-up. During this time the feeder is running in a volumetric mode. The screw speed is defined by the Feed Factor curve, the feed factor being defined as the equivalent of the weight per screw revolution, and the accuracy depending on how good the curve is fitting to the reality.

(42) Typical values of the refilling frequency of the feeder module according to the invention are one time per minute at a feed rate of 50 kg/h, i.e. mass flow 5 kg/h refill after 10 min. Due to its reduced weight and dynamic properties, the feeder module stabilizes in 2 to 4 seconds at a feed rate of 50 kg/h.

(43) In general, the summarized refill time of both systems is similar, but the accuracy on the mass flow during refilling volumetric mode (RMS error) is much better compared to conventional top-up systems.

(44) The principle underlying the refilling system of the feeder module according to the invention is different from others as it is based on refilling each time the same amount of power under the same conditions. The refill system has either a weighing scale or a level sensor integrated combined with a volumetric dosing valve. The system itself acts as a (pre)feeder and stores the number of impeller turns together with a level or a weight.

(45) Such a refill or top-up system can also be used for material determination using the feeder data. Furthermore, it can be set to sense material variations. As the powder dosing valve always discharges in the center of the top-up tube, the shape of the powder stack is constant in the same area. During the powder drop, the powder at the bottom of the hopper is more compacted than the powder at the top of the hopper. However, the powder volume in the discharge tube is still not compacted. The screw speed remains unchanged until the fresh (i.e. more compacted) material is coming to the discharge opening. Each refill is reproducible and the system learns and converges to the optimal speed of the screws. Furthermore, analysis of feeder data with fast Fourier Transform (FFT) may be applied to determine the material and differentiate between different types of material (eg. batch to batch variation). Eventually, the feeder data may be used to calculate theoretical compositions and confirm BU and Assay over specified time periods.

(46) During operation, the feeder module is subjected to a number of external and internal disturbances. The disturbances normally include mechanical vibrations, wind load, bellow deformation forces etc. falling into one of two main types, viz. deterministic disturbances, which can be filtered, and non-deterministic disturbances, the effect of which must be reduced in other ways. In order to reduce the external cyclic disturbances, an Active Vibration Compensation (AVC) scale is integrated in the feeder module and compensates in real time the weighing signal. This improves the accuracy on the mass flow even further. In order to reduce the effect of the internal cyclic disturbances, due to gears, agitator in hopper etc., special algorithms are used for real time noise cancelling, according to the “anti-sound” principle, to dampen noise from screws, gearbox etc. without time delay.

(47) Due to the low dead weight of the feeder unit, and the small hopper volume thus limiting the weight of the powder present in the hopper, and the dynamic EMFR weighing scale, the feeder module according to the invention is dynamically more precise and faster responding compared to others. For instance, the recovery from non-cyclic external disturbances will only take about 2 to 4 seconds.

(48) As further features, in order to increase the accuracy even further, a controller adapted to store a conveying parameter together with a level or a weight may be provided, and the feeder unit may further comprise a sensor for sensing material variations.

(49) Operation of the feeding unit may take place by the method according to the invention to be described in the following:

(50) The method is intended for discharging a constant mass flow of one or more powders into a receiving container. Primarily, the method forms part of a process for processing pharmaceutical products, but may also be applied in other fields. The method is suitable for being operated in a feeder unit 2 as described in the above and comprises the steps of:

(51) providing a feeder unit 2 with a storage hopper 21, a weighing cell 24, a convey-er 22, and a discharge end 23,

(52) connecting the storage hopper 21 to a refilling system with a refilling valve 41, 42, 43,

(53) connecting the refilling valve to a level or weight indicator 44, the level or weight indicator 44 being above the refilling valve 41, 42, 43,

(54) connecting the discharge end 23 to a receiving container 3,

(55) refilling the storage hopper 21 intermittently at predefined intervals,

(56) storing data during refilling,

(57) wherein during refilling, the refilling valve 41, 42, 43 dispenses the same amount of powder into the storage hopper 21, and

(58) the conveyer 22 is operated according to the data collected during previous re-fills.

(59) Typically, the storage hopper 21 is refilled 40 to 80 times per hour, preferably 50 to 70 times per hour. The stabilizing time after each refill is in the range 2 to 4 seconds.

(60) A working space is defined by the value resulting from the formula: The arithmetic product of the dead weight [kg] of each feeder unit and the refilling interval [h] is below 0.2 or even below 0.1. Due to the low powder mass in the hopper a very sensitive scale can be used which leads to a very high accuracy. The low powder mass makes a more frequent refilling necessary.

(61) Other aspects of the configuration of the feeder module are the subject of Applicant's co-pending application filed on the same day as the priority application of the present application, which co-pending application was assigned International Application No. PCT/IB2012/052804 and was published under International Publication WO 2013/182870 A1, and the contents of which are incorporated by reference.

(62) According to need (i.e. an indication of a storage hopper being empty) or as a result of a pre-programmed schedule, the storage hoppers of the respective feeder units are refilled intermittently as described in the above.

(63) In order to clean the parts of the feeder module in contact with the powder(s), the method may include the further steps of detaching the storage hopper, the conveyer and the discharge end of each feeder unit from the weighing cell, and cleaning the storage hopper, the conveyer and the discharge end of each feeder unit in a contained manner.

(64) The invention should not be regarded as being limited to the embodiments shown and described in the above. Several modifications and combinations are conceivable within the scope of the appended claims.