Volumetric filling of powders

Abstract

The invention discloses a method and a tool for exact metering and volumetric filling of finely divided dry powder medicament doses into preformed containers, whereby the doses and containers are adapted for administration by inhalation using a dry powder inhaler (DPI). A filling tool illustrating the invention includes at least one receptacle ( 10 ). The shape and size of a receptacle may vary depending on the size and mass of the powder load to be metered. A stretched woven filter ( 106 ) is positioned between the second opening of the receptacle ( 10 ) and a suction nozzle ( 13 ), using flexible seals at joints to stop air and powder leakage. The shape may be circular or elliptical, the wideness and depth, i.e. the volume, is adapted to the intended load and the method of filling and unloading.

1 . A volumetric method of consistent metering and filling of doses of dry powder medicaments into dose containers, the method comprising the steps of:
 providing a filling tool comprising at least one powder receptacle having a first opening and a second opening, and having a volume corresponding to a chosen load mass of a selected medicament powder, the load mass representing at least a part-dose and preferably representing a dose, a stretched woven filter is arranged between the second opening of the receptacle and a nozzle, using flexible seals at joints to stop air and powder leakage, whereby distortion and variation of the receptacle volume is prevented during a filling operation and where the woven filter eliminates a risk of loose filter fibers getting mixed with the powder load;   filling the at least one powder receptacle with the selected medicament powder from a storage chamber using suction power through the woven filter, whereby the chosen load mass is formed by the assistance of the woven filter;   moving the filling tool to a new position such that the at least one powder receptacle, now filled with the load mass, is brought in a general downward facing, emptying position;   applying air pressure to the second opening of the at least one powder receptacle through the filter such that the load mass is ejected and directed towards a dose container positioned beneath the receptacle, whereby at least a part-dose or preferably the dose is formed in the dose container; and   repeating the steps of filling the at least one powder receptacle, moving the filling tool and applying air pressure, whereby doses are produced in a multitude of dose containers, the doses having a relative dose-to-dose standard deviation below 10% and preferably below 5%.   
   
   
       2 . The method according to  claim 1 , further comprising the step of:
 using a woven filter with a supporting wire netting arranged at one or optionally both sides of the woven filter to re-enforce the mechanical strength of the woven filter.   
   
   
       3 . The method according to  claim 1 , wherein surfaces of said at least one powder receptacle have a hard-wearing, low-friction coating to reduce the dynamic friction and powder retention susceptibility of the surfaces and facilitating cleaning. 
   
   
       4 . The method according to  claim 1 , further comprising the step of:
 applying a spring force to keep contact pressure substantially constant between the nozzle, the filter and the second opening of the at least one powder receptacle, such that elastic seals sealing the nozzle, the filter and the at least one powder receptacle will stop leakage of air and powder into and out of the receptacle.   
   
   
       5 . The method according to  claim 1 , further comprising the step of:
 using at least one receptacle having a shape of an elliptic form in order to adapt the physical form of the load mass to fit a pre-defined elongated form of the dose container, which will receive the load mass upon unloading from the at least one powder receptacle.   
   
   
       6 . The method according to  claim 1 , further comprising the step of:
 neutralizing electrically charged particles in ejected load masses while being transferred through the air by arranging a source of electric charges, preferably an ion source, in an air gap between the filling tool and the dose container.   
   
   
       7 . The method according to  claim 1 , further comprising the step of:
 arranging sources of electric charges, preferably ion sources, at a working distance to the filling tool and optionally at a working distance to the powder in the storage chamber in order to substantially neutralize electrostatic charges on the tool and associated equipment and powder particles in the storage chamber such that the filling process is not adversely affected.   
   
   
       8 . The method according to  claim 1 , further comprising the step of:
 reducing the height of a deposited load mass in the dose container by subjecting the load mass, or the dose container and load mass, to an energy source, which may be ultrasonic, vibrating, shocking or electrical in nature, such that the load mass is spread out inside the dose container and cannot interfere with a cover, preferably a sealing foil, in an ensuing sealing procedure.   
   
   
       9 . The method according to  claim 1 , further comprising the step of:
 reducing the height of a deposited load mass in the dose container by subjecting the load mass, or the dose container and load mass, to a doctor blade such that the load mass is spread out inside the container and cannot interfere with a cover, preferably a sealing foil, in an ensuing sealing procedure.   
   
   
       10 . The method according to  claim 1 , wherein the load mass of the selected medicament powder is in a range 100 μg-50 mg and preferably in a range 100 μg-10 mg and most preferably in a range 100 μg-5 mg. 
   
   
       11 . A volumetric method of consistent metering and filling of doses of dry powder medicaments into dose containers, the method comprising the steps of
 providing a filling tool comprising at least one powder receptacle in a shape of an elliptical truncated cone, the at least one powder receptacle having a first opening and a second opening and having a volume corresponding to a chosen load mass of a selected medicament powder, the load thus formed representing a metered dose, said load having a shape fitting a selected dose container when said load is ejected from the at least one powder receptacle into the dose container, a woven or non-woven filter being provided between the second opening of the at least one powder receptacle and a nozzle, using flexible seals at joints to stop air and powder leakage, whereby distortion and variation of the receptacle volume is prevented during a filling operation;   filling the at least one powder receptacle with the selected medicament powder from a storage chamber using suction power through the woven or non-woven filter, whereby a chosen load mass is formed in the at least one powder receptacle by the assistance of the woven filter;   moving the filling tool to a new position such that the at least one powder receptacle, now filled with the load mass, is brought in a generally downward facing, emptying position;   applying air pressure to the second opening of the at least one powder receptacle through the woven or non-woven filter such that the load mass is ejected and directed towards the dose container positioned beneath the at least one powder receptacle, whereby the load mass is deposited in the dose container; and   repeating the steps of filling the at least one powder receptacle, moving the filling tool and applying air pressure, whereby doses are produced in a multitude of dose containers, the doses having a relative dose-to-dose standard deviation below 10% and preferably below 5%.   
   
   
       12 . The method according to  claim 11 , further comprising the step of
 using at least one powder receptacle in a shape of a circular truncated cone.   
   
   
       13 . The method according to  claim 11 , further comprising the step of
 using at least one powder receptacle in a shape of an elliptical truncated cone having a height of not less than 0.3 mm and not more than 2.0 mm.   
   
   
       14 . A filling tool device for consistent, precise, repeatable metering and filling of doses of dry powder medicaments into dose containers, said filling tool device comprises:
 at least one powder receptacle having a first and a second opening, and having a volume corresponding to a chosen load mass of a selected medicament powder, the load mass representing at least a part-dose or preferably representing a dose;   a stretched, form-stable, woven filter arranged between the second opening of the at least one powder receptacle and an external nozzle, and flexible seals are arranged at joints to stop air and powder leakage, the woven filter preventing distortion and variation of the receptacle volume during a filling operation and eliminating a risk of loose filter fibers getting mixed with the load mass;   the at least one powder receptacle is adapted for being filled with the selected powder from a storage chamber by suction power through the woven filter, whereby a consistent powder load mass is formed by the assistance of the form-stable, woven filter; and   the filling tool is arranged for being movable to an emptying position where air pressure of sufficient power is applied to the second opening of the at least one powder receptacle through the filter such that the load mass may be ejected in a direction towards the dose container generally positioned beneath the at least one powder receptacle, whereby the at least part-dose and preferably the dose is deposited into the dose container.   
   
   
       15 . The filling tool device according to  claim 14 , wherein the operation of the dose filling tool device during the steps of filling the at least one powder receptacle, moving the filling tool and applying air pressure allows for deposition of doses in a multitude of dose containers, where the doses having a relative dose-to-dose standard deviation below 10% and preferably below 5%. 
   
   
       16 . The filling tool device according to  claim 14 , wherein the mechanical strength of the woven filter is re-enforced by arranging a supporting wire netting at one or optionally both sides of the woven filter. 
   
   
       17 . The filling tool device according to  claim 12 , wherein the material of the filling tool has appropriate properties regarding stability of form, machining, resistance to abrasion and low friction and is selected from a group of materials consisting of stainless steel, metals, alloys and glass. 
   
   
       18 . The filling tool device according to  claim 14 , wherein a hard-wearing, low-friction coating is applied to at least surfaces of the at least one powder receptacles in the filling tool, optionally to other surfaces of the same, thereby reducing the dynamic friction and powder retention susceptibility of exposed surfaces and making cleaning easier. 
   
   
       19 . The filling tool device according to  claim 14 , wherein a spring force is applied to keep contact pressure substantially constant between the nozzle, the filter and the second opening of the at least one receptacle, such that elastic seals sealing the nozzle, the filter and the at least one receptacle will stop leakage of air and powder into and out of the at least one receptacle. 
   
   
       20 . The filling tool device according to  claim 14 , wherein the shape of the at least one powder receptacle of the filling tool has elliptic form in order to adapt the physical form of the powder load mass to fit a pre-defined elongated form of the dose container, which will receive the load mass upon unloading from the at least one powder receptacle. 
   
   
       21 . The filling tool device according to  claim 14 , wherein a source of electric charges, preferably an ion source, is arranged in an air gap between the filling tool and the container(s) such that electrically charged particles in ejected powder loads become electrically neutralized while being transferred through the air. 
   
   
       22 . The filling tool device according to  claim 14 , wherein sources of electric charges, preferably ion sources, are arranged at a working distance to the filling tool and optionally at a working distance to the powder in a storage chamber in order to accomplish that electrostatic charges on the tool and associated equipment and powder particles in the storage become electrically neutralized such that the filling process is not adversely affected. 
   
   
       23 . The filling tool device according to  claim 14 , wherein the height of a deposited powder load in a destination container is reduced by subjecting the load, or the container and load, to an energy source, which may be ultrasonic, vibrating, shocking or electrical in nature, such that the load is spread out inside the container and cannot interfere with a cover, preferably a sealing foil, in an ensuing sealing procedure. 
   
   
       24 . The filling tool device according to  claim 14 , wherein the height of a deposited powder load in a destination container is reduced by subjecting the load, or the container and load, to a doctor blade such that the load is spread out inside the container and cannot interfere with a cover, preferably a sealing foil, in an ensuing sealing procedure. 
   
   
       25 . The filling tool device according to  claim 14 , wherein the load mass of the selected medicament powder is in a range 100 μg-50 mg and preferably in a range 100 μg-10 mg and most preferably in a range 100 μg-5 mg. 
   
   
       26 . A filling tool device for consistent, precise, repeatable metering and filling of doses of dry powder medicaments into dose containers, said filling tool device comprises:
 at least one powder receptacle in a shape of an elliptical truncated cone having a first opening and a second opening, and having a volume corresponding to a chosen powder mass representing a metered dose of a selected medicament powder;   a form-stable, woven or non-woven filter arranged between the second opening of the at least one powder receptacle and an external nozzle, and flexible seals are arranged at joints to stop air and powder leakage, the woven or non-woven filter preventing distortion and variation of the receptacle volume during a filling operation and eliminating a risk of loose filter fibers getting mixed with the powder load;   an air suction power device arranged for applying air suction power to the external nozzle to fill the at least one powder receptacle with powder through the woven or non-woven filter, whereby a consistent powder load mass is formed by the assistance of the form-stable, woven filter; and   an air pressure power device arranged for applying air pressure power to the second opening of the at least one powder receptacle through the woven or non-woven filter for ejecting the powder load into a selected dose container when suitably positioned relative the at least one powder receptacle, said powder load having a shape fitting the dose container, said shape being defined by the at least one powder receptacle, whereby the powder load does not collapse in the following production stages.   
   
   
       27 . The filling tool device according to  claim 26 , wherein the powder load mass of the selected medicament powder is in a range 100 μg-50 mg and preferably in a range 100 μg-10 mg and most preferably in a range 100 μg-5 mg. 
   
   
       28 . The filling tool device according to  claim 26 , wherein the selected dose container is adapted for insertion into a dry powder inhaler and the dose in the dose container is adapted for delivery by inhalation. 
   
   
       29 . The filling tool device according to  claim 26 , wherein the at least one powder receptacle has a shape of a circular truncated cone. 
   
   
       30 . The filling tool device according to  claim 26 , wherein the truncated cone of the at least one powder receptacle has a height of not less than 0.3 mm and not more than 2.0 mm.