DK201270298A - Feeder module and method for providing a mixture of on or more powders to a receing container - Google Patents

Abstract

The feeder module comprises a number, for instance five to eight, feeder units. Each feeder unit inciudes a storage hopper, a weighing cell, a conveyer, and a discharge end. The feeder units may be arranged in a single level and in a spokes-like configuration, in which each feeder unit extends radially outwards from an imaginary inner circle defined at the discharge end adapted to face the common receiving container to an imaginary outer circle defined by radially opposite end of each feeder unit, the feeder units being positioned substantially on radii extending from the inner circle. The feeder module makes it possible to provide a very accurately dosed mixture of one or more powders to a receiving container.

Description

Feeder module and method for providing a mixture of one or more powders to a receiving container

Field of the invention

The present invention relates to a feeder module comprising a number of storage hoppers adapted to contain material to be processed, weighing means, conveying means for transporting the material from the storage hoppers to at least one receiving container, the feeder module comprising a plurality of feeder units. The invention furthermore relates to a method for providing a very accurately dosed mixture of one or more powders to a receiving container.

Background of the invention

Within the pharmaceutical industry there is an increasing interest in providing products of a higher quality, and a number of guidelines and regulations have been formulated during recent years to establish proper quality measurement, analysis and control.

In addition to improving the processing efficiency and quality there is a general interest in providing processes that are both environmentally safer and also pose a reduced risk to an operator of the process. In particular, in a process to produce for instance tablets from active pharmaceutical ingredients (API) and various excipients in a powdery form, the operator may need to wear a protective breathing apparatus, or otherwise personal protective equipment, such as gloves or coverall, to prevent excessive exposure to the API and also the excipients. Reduction of the risk of contamination of the surrounding environment as well as exposure of the operator to a pharmaceutical product in a tabletting process was addressed in W003 / 020499 (Courtoy), where a rotary tablet press was described. However, W003 / 020499 does not fully take into account the interest in providing better process control.

Typical manufacturing processes hitherto employed within the pharmaceutical field are of a batch nature. Batch manufacturing processes have a number of advantages and provide satisfactory results within many areas. However, due to the increasingly widespread application of regulated criteria for monitoring and controlling in particular pharmaceutical manufacturing processes, and to the general increase in demands for quality by design, the level of quality of monitoring and control attainable by a batch process is often not sufficient , I a due to the fact that settings are fixed. Furthermore, a relatively large buffer volume is required, entailing undesired back-mixing of the material stream. As a consequence, manufacturers 'and customers' focus of interest has shifted to continuous processes, in which settings may be varied and allowed to change within a design space. An order to achieve more production output with a batch process, bigger equipment and larger buffer volumes, with different process settings to maintain the same output, would be required. This is known as the scale-up problem. More output with a continuous process just requires longer running, with the ability to maintain the same settings. Furthermore, there is an increased interest in more robust processing equipment and the ability to control more incoming variation while maintaining tablet quality. Special precautions have to be taken in order to ensure traceability in a continuous process, just as the requirements for accuracy and control within the framework of for instance the PAT (Process Analytical Technology) devised by the United States Food and Drug Administration (FDA).

Some examples of continuous processes have been devised in the prior art, for example in EP 0 275 834 A1, in which two or more ingredients are fed into the process line at various feed or inlet points, and the ingredients are mixed, dried and subsequently compacted in a conventional tabletting machine. The process line includes a first mixing unit, a drying unit, a sizing unit and a second mixing unit.

Ideally, the output corresponds to the aggregated input of ingredients at the feed or inlet points, i.e. all of the material is fed to the manufacturing machine in a continuous flow and at a constant rate. Due to a variety of fac tors, this is not feasible in practice. First, under any circumstances it is almost impossible to adjust the output of the mixing and drying units to provide a just-in-time supply of material to the tabletting machine. Second, the continuous production of tablets of a desired high level of quality requires careful monitoring, control and adjustment of process parameters in order to avoid a large rejection number from the tablet machine. This may lead to accumulation of material along the process line awaiting adjustment of certain process parameters. In turn, this inevitably necessitates the use of intermediate buffer vessels in order to store material upstream of the tablet press.

In a more recent document, WO 2010/128359 (GEA Pharma Systems), a contained module being able to operate through a fully continuous process for the production of tablets is devised. By this design of the tablet production module, all units of the tablet process may be contained, thus reducing the risk of operator exposure and facilitating operation of the tablet press, as all preparations of the material stream fed to the tablet press are carried out in and contained and controlled less. The term "contained" is defined by its level of containment according to suitable measurements, and is defined as at least dust-tight.

Common to the above modules and processes is that one or more mixing units are utilized. The term "mixing unit" should in this context be understood in its broadest terms. Thus, the mixing unit refers to a unit operation generally capable of mixing or otherwise processing one, two or more components into a desired form. The mixing unit may thus also be capable of modifying the physical form of dry component (s) processed in the mixing unit, e.g. a feed stream of powder (s) may be converted to a granulate comprising the component (s). The mixing unit may be a granulator for making a granulate from dry powders, such as a granulator to which a granulating liquid is added, or a roller compactor. Further examples include a twin screw blender and a twin screw granulator. Furthermore, the mixing unit may include such equipment as a dryer, a dry blender, a continuous dry blender or the like.

Dispensing or dosing the component (s) to the mixing unit, or to a receiving container upstream of the mixing unit, most often takes place from storage hoppers connected to feeders which in turn supply the mixing unit or receiving container with the desired amount of powder (s) or other components). Feeding of powders is carried out by means of screw conveyors according to one of two main solutions: volumetric feeding or gravimetric feeding. In volumetric feeding, material held in a hopper is fed into a process at a constant volume per unit of time, whereas in gravimetric feeding, material is fed into a process at a constant weight per unit of time. The weight is measured by a weighing cell. Gravimetric feeders may operate on the loss-inweight principle, which provides for more accurate dosing than feeders operating on other principles.

Particularly in the processing of pharmaceutical products, accurate dispensing or dosing of the powders involved is vital, and loss-in-weight feeders are traditionally utilized.

One example of prior art concerned with achieving increased accuracy when feeding powders is EP 290 999 B1, in which powders are fed from storage hoppers to a weighing hopper and further to a mixing or preparation container.

Many existing loss-in-weight feeders thus function well but are often relatively voluminous and heavy, and require certain conditions with respect to the installation conditions in the production area.

Even with all the above mentioned provisions, there is still a need for increasing the quality and operating conditions.

Summary of the invention

Against this background, it is an object of the present invention to provide a feeder module by which the accuracy is improved while simultaneously fulfilling the requirements for flexibility and the overall operational conditions as regards a reduced risk of exposure of the operator.

In a first aspect, this and further objects are met by a feeder module of the child mentioned in the introduction which is furthermore characterized in that each feeder unit includes a storage hopper, a weighing cell, a conveyer, and a discharge end, and that said plurality of feeder units comprises more than four feeder units arranged in a single level to discharge into a common receiving container.

By this design of the feeder module, each feeder unit of the feeder module is able to dispense a very accurately measured amount of material into one common receiving container. Relative to configurations comprising feeder units at different locations and levels, for instance vertically above each other, the configuration of the feeder units in a single level, i.e. on the same horizontal plane, entails a number of advantages. First, the risk of powder from upper levels causing problems with the lower level feeder units is eliminated. Thus, as there is no risk that powder from upper levels falls on the feeder units, the accuracy and quality are improved, as the weighing signal and thereby the mass flow of the feeder units are not affected. Second, as all feeder units feed into one common receiving container, a very precise dispensing is achieved. The invention is i.a. based on the recognition that increased accuracy and thereby quality is achieved when the materials involved are not only dispensed into one and the same receiving container but also at a specific point in time and space.

In a preferred embodiment, five to eight feeder units are arranged in a spokes-like configuration, each feeder unit extending radially outwards from an imaginary inner circle defined at the discharge end adapted to face the common receiving container to an imaginary outer circle defined by radially opposite end of each feeder unit, the feeder units being positioned substantially on radii extending from the imaginary inner circle. This provides for very precise charging of the powder or powders from the individual feeder units, as the discharge point may be formed within a limited area. The footprint at the discharge end is thus limited and constitutes a relatively small area, enabling the use of small dimensions of the parts involved. Thus, the risk of hanging up powders on the side walls of the hopper is reduced, while also reducing the height of the stack up in the hopper.

In one development of the preferred embodiment, the feeder module comprises five feeder units and the diameter of the imaginary inner circle is 42 - 100 mm. Alternatively, the feeder module may comprise six feeder units and the diameter of the imaginary inner circle is 50-1120 mm. 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.lt turns out that the accuracy of the feeder module is highly dependent on the dead weight on the scale of the feeder unit, and in particular the ratio between the dead weight of each feeder unit and the net weight of the powder received in the storage hopper. Furthermore, the response time depends on this ratio as well. The ratio of powder weight and maximum mass flow provides the maximum run time to empty a feeder or the maximum refill interval in hours. Preferably, the arithmetic product of the maximum refilling interval [h] and dead weight [kg] of each feeder unit is below 0.1 kgh. If the powder density is taken out of the equation the maximum refilling interval is also the ratio of hopper volume [L] and feed rate [L / h], For instance, the capacity of storage hopper of each feeder unit may be less than 1.6 liters. The maximum flow rate may for instance be 100 L / h. The maximum refilling interval is then 0.016 h. The dead weight is typically 5 kg.

In one embodiment, the arithmetic product of the dead weight and the maximum refilling interval 0.016 h is 0.087 kgh. The arithmetic product may be below 0.2, preferably below 0.1, most preferred below 0.05 kgh. The very sensitive scale takes a limited amount of powder but is more accurate.

In order to allow detachment of parts of each feeding unit relative to other parts, it is advantageous that the storage hopper, conveyor and discharge end of each feeder unit are releasably connected to the weighing cell.

The powder may in principle be transported or pumped from the storage hopper to the receiving container in any suitable manner. In a preferred embodiment, the conveyor is a twin screw conveyor.

In one development of this preferred embodiment, at least one, preferably both, of the screws of the twin screw conveyor has a variable pitch along its length below the storage hopper.

In a further development, at least one, preferably both, of the screws has a variable diameter along its length below the storage hopper. The variable diameter assures that the entire length of at least one screw, or of both screws, under the hopper is evenly loaded and thereby creates an even transport volume across the section of the hopper.

In another aspect, a method for providing a mixture of one or more powders in a receiving container is provided, said method comprising the steps of: providing a plurality of more than four feeder units with each a storage hopper, a weighing cell, a conveyer , and a discharge end, providing one receiving container, arranging the plurality of feeder units with the respective discharge ends facing the receiving container in a single level, such that all discharge ends are in one horizontal plane. providing a communication between each feeder unit of said plurality of feeder units and the receiving container at the discharge end, filling the storage hopper of the respective feeder unit with a powder, and feeding the powder from the respective storage hopper to the receiving container the mixture of the one or more powders.

The kind of material to be filled into the storage hoppers of the individual feeder units is typically powder. Typically, two or more different types of powder are filled into the individual feeder units. Most often, each powder is a single component powder, rather than a pre-blended powder containing two or more components, as laughter has a tendency to segregate. For instance, any two feeder units may be filled with the same powder such as in the case of 6 feeder units in the feeding module, three different powders may be charged into the receiving container and further processing in the process line. Refilling of the storage hoppers may take place intermittently and possibly such that one feeder unit is filled when there is still powder in the other one of a pair. However, as a further field of application of the feeding module, powder of one kind may only be filled into all of the feeder units. This makes it possible to feed very accurately dispensed amounts of powder at a predefined rate.

Further details and advantages appear from the dependent claims, and from the detailed description of preferred embodiments and examples for carrying out the method set forth below.

Brief description of the drawings

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

FIG. 2 shows a plan view of the feeder module of Fig. 1;

FIG. 2a shows a schematic overview corresponding to Figs. 2, in an embodiment comprising eight feeder units;

FIG. 2b shows a schematic overview corresponding to Figs. 2a, or another embodiment comprising seven feeder units;

FIG. 2c shows a schematic overview corresponding to Figs. 2a, or further embodiment comprising six feeder units;

FIG. 2d shows a schematic overview corresponding to Figs. 2a, or further embodiment comprising five feeder units;

FIG. 3 shows a sectional view of the feeder module of Fig. 1;

FIG. 4 shows a detail cross section of the receiving hopper or receiving container;

Figs 5 and 6 show a plan view of a feeder module of another embodiment in two different conditions;

FIG. 7 shows a perspective view of a detail of an embodiment of a feeder module and containment of powder contacting powder pump according to the invention;

Figs. 8a-c show a side view of a detail of a pre-feeder element of a feeder module according to the invention;

Figs. 9a-9c show a perspective view of an embodiment of a feeder module, a view from above of a feeder unit and a more detailed perspective view of an embodiment of a feeder module according to the invention; spirit

Figs 10 and 11 show plan views of a detail of two different embodiments of a feeder module according to the invention.

Detailed description of the invention and of preferred embodiments

Referring now to the Figures, a feeder module generally designated 1 is 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.

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.

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.

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

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 24 to 45 mm twin screw discharge tube and a lateral clearance in between two twin screw discharge tubes of 1 to 10 mm, see Figs. 2a.

With particular reference to Figs 3 and 4, each feeder unit 2 includes a storage hopper 21 to contain material to be processed, a conveyor 22, a discharge end 23, and a weighing cell 24. The conveyor 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.

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 spokeslike 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.

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 on 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 also depend 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.

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.

Correspondingly, the net weight of the powder to be filled into the storage hopper 21 of the individual feeder units 2 depends on the volume but also on the kind of powder applied. Typically, the maximum volume of powder in the storage hopper lies in the range 1.6 to 2 liters. The maximum mass flow rate is approximately 50 kg / h.

The ratio of powder weight and 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 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 federal [L / h], Eg 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 0.016h. The dead weight of each feeder unit 2 is typically 5 kg.

In the embodiment described, the arithmetic product of the dead weight 5 kg and the maximum refill interval 0.016h is 0.087kgh. The arithmetic product is typically below 0.2, preferably below 0.1, most preferably below 0.05 kgh.

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.

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 hooked up to the inner walls of the receiving container 3.

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).

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. 7th

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 been 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).

Refilling 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. part 25 shown in Figs 8a-c. 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 contained less so as to at least ensure that no dust enters the surrounding environment by using an appropriate seal or tube.

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.

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 conveyor 22 is fed properly. The conveyer 22 is shown in the embodiment 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.

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 the axle 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.

For both Figs. 10 and 11, the material to be conveyed is moved in the direction of the arrow away from the motor M and into the imaginary circle 31.

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.

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

Typically, feeders of a larger volume are refilled 4 to 8 times per hour. During refilling, the powder which is dropped 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. Along 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.

Typical values of the refilling frequency of the feeder module according to the invention are one hour 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 at a feed rate of 50 kg / h for 2 to 4 seconds.

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

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.

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 into 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 arrives at the discharge opening. Each refill is reproducible and the system learns and converges to the optimum 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). Optionally, the feeder data may be used to calculate theoretical compositions and confirm BU and Assay over specified time periods.

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 the weighing signal in real time. This improves the accuracy of the mass flow even further. In order to reduce the effect of internal cyclic disturbances, due to gears, agitator in hopper etc., special algorithms are used for real time noise canceling, according to the "anti-sound" principle, to dampen noise from screws, gearbox etc. without time delay.

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.

Operation of the feeding module may take place by the method according to the invention to be described in the following:

The method is intended to provide a mixture of one or more powders in a receiving container as described above. Primarily, the method forms part of a process for processing pharmaceutical products, but may also be applied in other fields.

In a first step, the desired plurality of feeder units is defined. In the embodiments shown in the above, there are eight such feeder units with each a storage hopper, a weighing cell, a conveyer, and a discharge end. Less than eight, for instance five or six, or more than eight, for instance 10 feeder units are conceivable. A receiving container is provided and is for instance connected to a granulator or to a tablet press. In that case, the method may comprise the additional step of tabletting the mixture of the one or more powders.

The feeder units are arranged with the respective discharge ends facing the receiving container, and are connected thereto, in a single level.

The storage hopper of the respective feeder unit with a powder is filled with a suitable powder, and the powder from the respective storage hopper is fed to the receiving container to provide the mixture of the one or more powders. 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 0.1. 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. Other aspects of the accuracy of the feeder module are the subject of Applicant's co-pending application filed on the same day as the present application and the contents of which are incorporated by reference.

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.

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.

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.

Claims (21)

1. A feeder module (1) comprising a number of storage hoppers (21) adapted to contain material to be processed, weighing means, conveying means for transporting the material from the storage hoppers (21) to at least one receiving container (3), the feeder module (1) comprising a plurality of feeder units (2), characterized in that each feeder unit (2) includes a storage hopper (21), a weighing cell (24), a conveyer (22), and a discharge end (23), and that said plurality of feeder units (2) comprises more than four feeder units (2) arranged in a single level to discharge into a common receiving container (3).

2. A feeder module according to claim 1, wherein five to eight feeder units 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) adapted to face the common receiving container (3) to an imaginary outer circle defined by radially opposite end of each feeder unit (2), the feeder units (2) being positioned substantially on radii extending from the imaginary inner circle (31).

3. A feeder module (1) according to claim 2, wherein the feeder module (1) comprises five feeder units (2) and the diameter of the imaginary inner circle (31) is 42-100 mm.

4. A feeder module (1) according to claim 2, wherein the feeder module (1) comprises six feeder units (2) and the diameter of the imaginary inner circle (31) is 50-120 mm.

5. A feeder module (1) according to claim 2, wherein the feeder module (1) comprises eight feeder units (2) and the diameter of the imaginary inner circle (31) is 65-150 mm.

6. A feeder module (1) according to any one of the preceding claims, wherein the dead weight of each feeder unit (2) is below 5 kg.

7. A feeder module (1) according to any one of the preceding claims, wherein the capacity of the storage hopper (21) of each feeder unit (2) is less than 2 liters.

8. A feeder module (1) according to claim 6 or 7, wherein the maxi- mum net weight of powder in the storage hopper (21) lies in the interval 50 g to 5000 g, the arithmetic product of the dead weight and the maximum refilling interval is below 0.2 kgh, preferably below 0.1 kgh, most preferred below 0.05 kgh.

9. A feeder module (1) according to any one of the preceding claims, wherein the storage hopper (21), the conveyer (22) and the discharge end (23) of each feeder unit (2) are releasably connected to the weighing cell (24).

10. A feeder module (1) according to any one of the preceding claims, wherein one or more conveyers (22) are twin screw conveyors (221, 222).

11. A feeder module according to claim 10, wherein at least one, preferably both, of the screws of the twin screw conveyor (221, 222) has a variable pitch (P1, P2) along its length underneath the storage hopper (21).

12. A feeder module according to claim 10 or 11, wherein at least one, preferably both, of the screws has a variable diameter (d 1, d2) along its length underneath the storage hopper (21).

13. A method for providing a mixture of one or more powders in a receiving container (3), comprising the steps of: providing more than four feeder units with each a storage hopper (21), a weighing cell (24), a conveyer (22), and a discharge end (23), providing a receiving container (3), arranging the plurality of feeder units (2) with the respective discharge ends (23) facing the receiving container (3) in a single level, providing a communication between each feeder unit (2) of said plurality of feeder units (2) and the receiving container (3) at the discharge end (23), filling the storage hopper (21) of the respective feeder unit (2) with a powder, and feeding the powder from the respective storage hopper (21) to the receiving container (3) to provide the mixture of the one or more powders.

14. The method of claim 13, wherein at least some 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 (2), the feeder units (2) being positioned substantially on radii extending from the imaginary inner circle (31), the discharge ends (23) of the feeder units (2) facing each other.

15. The method of claim 14, wherein five to eight feeder units (2) are arranged around the imaginary inner circle (31), the imaginary inner circle (31) having preferably a diameter of 42-100 mm with five feeder units, 50-120 mm, with six feeder units (2), and 65-150 mm with eight feeder units (2).

16. The method of any one of claims 13 to 15, wherein a working space (ws) is defined by the value resulting from the formula: the arithmetic product of the dead weight of each feeder unit and the refilling interval (ri) is below 0.1.

17. The method of any one of claims 13 to 16, wherein the storage hoppers (21) of the respective feeder units (21) are refilled intermittently.

18. The method of any one of claims 13 to 17, wherein the receiving container (3) is connected to a granulator and further comprises the step of granulating the mixture of the one or more powders.

19. The method of any one of claims 13 to 17, wherein the receiving container (3) is connected to a tablet press and further comprises the step of tabletting the mixture of the one or more powders.

20. The method of any one of claims 13 to 19, wherein the method forms part of a process for processing pharmaceutical products.

21. The method of any one of claims 13 to 20, wherein the method comprises the further steps of: detaching the storage hopper (21), the conveyer (22) and the discharge end (23) of each feeder unit (2) from the weighing cell (2) in a contained manner, and cleaning the storage hopper (21), the conveyer (22) and the discharge end (23) of each feeder unit (2).