Dispensing small quantities of particles

1. A method of dispensing small quantities of particles, the method comprising the steps of: disposing in a hopper provided with a sieve at a bottom portion thereof a powder to be dispensed therefrom through the sieve; supporting the hopper by holding a portion of the hopper with a support so that the hopper is held above a container into which the dispensed powder is to be received, providing an element which is adapted to permit controlled vertical movement of the hopper relative to the support, wherein the element comprises a clamp for clamping the hopper to the support, the clamp being configured to permit the hopper to move vertically in the clamped configuration over a particular distance; and delivering impact energy to the hopper by at least one actuator thereby to cause powder to be dispensed through the sieve when the hopper receives the impact energy and to permit controlled vertical movement of the hopper relative to the support.

2. A method according to claim 1 wherein the clamp comprises a biasing device for biasing the hopper to a first position of the clamped configuration, the hopper being movable towards a second position of the clamped configuration against the bias of the biasing device.

3. A method according to claim 2 wherein the biasing device comprises a compression spring.

4. A method according to claim 3 wherein the compression spring urges the hopper downwardly.

5. A method according to claim 1 wherein the clamp comprises a stop member, spaced above a holder for the hopper, to define a height by which the holder can move vertically.

6. A method according to claim 5 wherein the height of the stop member is adjustable.

7. A method according to claim 1 wherein the element is adapted to permit controlled rotational movement of the hopper relative to the support.

8. A method according to claim 7 wherein the support comprises an annular portion having an aperture within which the hopper is received, the upper surface of the annular portion has a stepped ratchet configuration adapted to permit rotational movement of the hopper, and a holder for the hopper rests on the stepped ratchet configuration.

9. A method according to claim 8 wherein the stepped ratchet configuration comprises a succession of abutting inclined step portions extending peripherally around the upper surface of the annular portion.

10. A method according to claim 9 wherein the step portions are separated by radially directed edges.

11. A method according to any one of claims 6 to 10 wherein the holder is provided with a plurality of downwardly depending members which rest on the ratchet surface.

12. A method according to claim 11 wherein rotational movement of the hopper causes a change in the at least one of the angle and direction of tilt of the hopper.

13. An apparatus for dispensing small quantities of particles, the apparatus comprising a hopper provided with a sieve at a bottom portion thereof, the hopper defining a powder-containing zone above the sieve which in use contains powder to be dispensed therefrom through the sieve, a support for the hopper, the support holding a portion of the hopper so that the hopper can in use be held above a container into which the dispensed powder is to be received, at least one actuator for delivering impact energy to the hopper for causing powder to be dispensed through the sieve when the hopper receives the impact energy, and an element which is adapted to permit controlled vertical movement of the hopper relative to the support, wherein the element comprises a clamp for clamping the hopper to the support, the clamp being configured to permit the hopper to move vertically in the clamped configuration over a particular distance.

14. An apparatus according to claim 13 further comprising a biasing device for biasing the hopper to a first position of the clamped configuration, the hopper being movable towards a second position of the clamped configuration against the bias of the biasing device.

15. An apparatus according to claim 14 wherein the biasing device comprises a compression spring.

16. An apparatus according to claim 15 wherein the compression spring is disposed between two parts of the clamp and urges the hopper downwardly.

17. An apparatus according to claim 13 wherein the clamp comprises a stop member, spaced above a holder for the hopper, to define a height by which the holder can move vertically.

18. An apparatus according to claim 17 further comprising a height adjustment mechanism for adjusting the height of the stop member.

19. An apparatus according to any one of claims 13 to 16 wherein the support comprises an annular portion having an aperture within which the hopper is received, the upper surface of the annular portion has a stepped ratchet configuration adapted additionally to permit rotational movement of the hopper, and a holder for the hopper rests on the stepped ratchet configuration.

20. An apparatus according to claim 19 wherein the stepped ratchet configuration comprises a succession of abutting inclined step portions extending peripherally around the upper surface of the annular portion.

21. An apparatus according to claim 20 wherein the step portions are separated by radially directed edges.

22. An apparatus according to claim 21 wherein the holder is provided with a plurality of downwardly depending members which rest on the ratchet surface.