Feeder Unit, a Feeder Module Comprising a plurality of Feeder Units, and Method for Discharging a Constant Mass Flow of One or More Powders Into a Receiving Container
A feeder unit comprises a storage hopper, a weighing cell, a conveyer, and a discharge end. The storage hopper is to be connected to a refilling system and the discharge end to a receiving container. A working space is defined by the arithmetic product of the dead weight of the feeder unit and the refilling interval, such that the working space is below 0.2 kgh. Furthermore a method for discharging a constant mass flow of one or more powders into a receiving container is defined.
1 . A feeder unit comprising;
a storage hopper shaped to connect to a refilling system;
a weighing cell;
a conveyer; and
a discharge end shaped to connect to a receiving container;
a working space being defined by an arithmetic product of a dead weight of the feeder unit and a refilling interval, the working space being below 0.2 kgh.
2 . A feeder unit according to claim 1 , wherein the working space is below 0.1 kgh.
3 . A feeder unit according to claim 1 , wherein the dead weight of the feeder unit lies in a range of one of:
1 to 8 kg;
1 to 6 kg; and
1 to 3 kg.
4 . A feeder unit according to claim 1 , wherein the storage hopper has a predefined volume to define a capacity of the storage hopper one of:
below 10 liters,
below 5 liters; and
below 3 liters.
5 . A feeder unit according to claim 4 , wherein:
a maximum net weight of powder in the storage hopper lies in the interval 50 g to 5000 g; and
the working space is one of:
below 0.2 kgh;
below 0.1 kgh; and
below 0.05 kgh.
6 . A feeder unit according to claim 1 , further comprising:
a refilling valve connected to the storage hopper; and
a level or weight indicator above the refilling valve controlling predosing of a refill amount.
7 . A feeder unit according to claim 1 , further comprising a controller storing a conveying parameter together with one of a level or a weight.
8 . A feeder unit according to claim 1 , wherein the weighing cell is an Electro Magnetic Force Restoration (EMFR) weighing cell.
9 . A feeder unit according to claim 1 , wherein the storage hopper, the conveyer and the discharge end are releasably connected to the weighing cell.
10 . A feeder unit according to claim 1 , wherein the conveyor comprises a twin screw conveyor.
11 . A feeder unit ( 2 ) according to claim 10 , wherein:
the twin screw conveyor has screws underneath the storage hopper; and
at least one of:
at least one of the screws of the twin screw conveyor has a variable pitch along its length; and
at least one of the screws has a variable diameter along its length.
12 . A feeder unit according to claim 1 , which further comprises a controller processing weight signals and compensating for external forces.
13 . A feeder unit ( 2 ) according to claim 1 , which further comprises a sensor associated with the storage hopper and sensing material variations during refill.
14 . A feeder unit ( 2 ) according to claim 1 , wherein the storage hopper, the conveyer, and the discharge end are contained and isolated from the weighing cell.
15 . A feeder module, comprising:
five to eight feeder units according to claim 1 disposed in a spokes-like configuration, each feeder unit extending radially outwards from an imaginary inner circle defined at the discharge end adapted to face a common receiving container to an imaginary outer circle defined by a radially opposite end of each feeder unit, the feeder units being positioned substantially on radii extending from the imaginary inner circle.
16 . A feeder module according to claim 15 , wherein one of:
the feeder module comprises 5 feeder units and the diameter of the imaginary inner circle is 42-100 mm;
the feeder module comprises six feeder units and the diameter of the imaginary inner circle is 50-120 mm; and
the feeder module comprises eight feeder units and the diameter of the imaginary inner circle is 65-150 mm.
17 . A method for discharging a constant mass flow of one or more powders into a receiving container, said method being suitable for operation in a feeder unit according to claim 1 , said method comprising the steps of:
providing the feeder unit ( 2 ) with the storage hopper ( 21 ), the weighing cell, the conveyer, and the discharge end;
connecting the storage hopper to a refilling system with a refilling valve;
connecting the refilling valve to a level or weight indicator, the level or weight indicator being above the refilling valve;
connecting the discharge end to the receiving container;
refilling the storage hopper intermittently at predefined intervals;
storing data during refilling;
wherein during refilling, the refilling valve dispenses the same amount of powder into the storage hopper; and
the conveyer is operated according to the data collected during previous refills.
18 . The method of claim 17 , wherein a working space is defined by a ratio between dead weight of the feeder unit and the refilling interval, and wherein the working space is below 0.2 kgh.
19 . The method of claim 18 , wherein the working space is below 0.1 kgh.
20 . The method of claim 17 , wherein the storage hopper is refilled one of:
40 to 80 times per hour; and
50 to 70 times per hour.
21 . The method of claim 17 , wherein a stabilizing time after each refill is in the range 2 to 4 seconds.
22 . The method of claim 17 , wherein the method comprises the further steps of:
detaching the storage hopper, the conveyer and the discharge end of each feeder unit from the weighing cell in a contained manner; and
cleaning the storage hopper, the conveyer and the discharge end of each feeder unit.
23 . The method of claim 17 , wherein the receiving container is connected to a granulator and further comprises the step of granulating the mixture of the one or more powders.
24 . The method of claim 17 , wherein the receiving container is connected to a tablet press and further comprises the step of tabletting the mixture of the one or more powders.
25 . The method of claim 17 , wherein the method forms part of a process for processing pharmaceutical products.