Method and apparatus for the application of powder material to substrates

A method for electrostatically charging powder material and supplying it to an applicator for electrostatically applying the powder material to solid dosage forms, the method comprising the steps of:

• mixing a sump of the powder material to electrostatically charge the powder material, the step of mixing comprising rotating two substantially parallel elongate mixing shafts in opposite directions, the mixing shafts having oppositely angled mixing paddles;
• removing the electrostatically charged powder from the sump;
• and
• supplying the electrostatically charged powder material to the applicator.

A method for electrostatically applying powder material to solid dosage forms, the apparatus comprising the steps of:

• mixing a sump of the powder material combined with a magnetized carrier material to electrostatically charge the powder material, the step of mixing comprising rotating two substantially parallel elongate mixing shafts in opposite directions, the mixing shafts having oppositely angled mixing paddles;
• removing the mixture of electrostatically charged powder material and magnetized carrier material from the sump;
• supplying the mixture of electrostatically charged powder material and magnetized carrier material to a sleeve;
• rotating the mixture around the sleeve by applying a rotating magnetic field to the sleeve;
• passing solid dosage forms alongside the sleeve;
• and
• applying an electric potential to the sleeve, thereby driving the electrostatically charged powder material onto the solid dosage forms.

A method for electrostatically applying powder material to substrates, the method comprising the steps of:

• mixing a sump of the powder material combined with a magnetized carrier material to electrostatically charge the powder material, the mixing comprising rotating three substantially parallel elongate mixing shafts, the first mixing shaft and the second mixing shaft having oppositely angled mixing paddles, the third mixing shaft being positioned between the first and second mixing shafts and having mixing paddles thereon, the paddles on the three mixing shafts meshing as the mixing shafts rotate;
• removing the mixture of electrostatically charged powder material and magnetized carrier material from the sump;
• supplying the mixture of electrostatically charged powder material and magnetized carrier material to a sleeve;
• rotating the mixture around the sleeve by applying a rotating magnetic field to the sleeve;
• passing substrates alongside the sleeve;
• and
• applying an electric potential to the sleeve, thereby driving the electrostatically charged powder material onto the substrates.

A method for electrostatically applying powder material to substrates, the method comprising the steps of:

• mixing a sump of the powder material combined with a magnetized carrier material to electrostatically charge the powder material, the step of mixing comprising rotating two substantially parallel elongate mixing shafts in opposite directions, the mixing shafts having oppositely angled mixing paddles;
• removing the mixture of electrostatically charged powder material and magnetized carrier material from the sump;
• supplying the mixture of electrostatically charged powder material and magnetized carrier material to two sleeves;
• rotating the mixture around the sleeves in opposite directions by applying a rotating magnetic field to each sleeve;
• passing substrates alongside the sleeves;
• applying an electric potential to each sleeve, thereby driving the electrostatically charged powder material onto the substrates.

Apparatus for electrostatically applying powder material to substrates, the apparatus comprising:

• a mixer for mixing a sump of the powder material combined with a magnetized carrier material to electrostatically charge the powder material, the mixer comprising three substantially parallel elongate mixing shafts, the first mixing shaft and the second mixing shaft having oppositely angled mixing paddles thereon and being arranged to rotate in opposite directions, the third mixing shaft being positioned between the first and second mixing shafts, having mixing paddles thereon and being arranged to rotate in either direction, the paddles on the three mixing shafts being arranged to mesh as the mixing shafts rotate;
• a feeder for removing the mixture of electrostatically charged powder material and magnetized carrier material from the sump and supplying it to an applicator;
• an applicator comprising two sleeves for receiving a mixture of electrostatically charged powder material combined with a magnetic carrier material, the sleeves being arranged to have electric potentials applied thereto to drive the electrostatically charged powder material onto substrates passing alongside the sleeves, the sleeves being arranged to have rotating magnetic fields applied thereto for rotating the mixture around the sleeves, the magnetic fields applied to the two sleeves being arranged to rotate in opposite directions.

A method for electrostatically applying powder material to substrates, the method comprising the steps of:

• mixing a sump of the powder material combined with a magnetized carrier material to electrostatically charge the powder material, the mixing comprising rotating three substantially parallel elongate mixing shafts, the first mixing shaft and the second mixing shaft having oppositely angled mixing paddles, the third mixing shaft being positioned between the first and second mixing shafts and having mixing paddles thereon, the paddles on the three mixing shafts meshing as the mixing shafts rotate;
• removing the mixture of electrostatically charged powder material and magnetized carrier material from the sump;
• supplying the mixture of electrostatically charged powder material and magnetized carrier material to two sleeves;
• rotating the mixture around the sleeves in opposite directions by applying a rotating magnetic field to each sleeve;
• passing substrates alongside the sleeves;
• applying an electric potential to each sleeve, thereby driving the electrostatically charged powder material onto the substrates.