Conveyors: fluid current – Intake to fluid current conveyor – Load receptacle type
Reexamination Certificate
1998-08-13
2001-02-06
Ellis, Christopher P. (Department: 3651)
Conveyors: fluid current
Intake to fluid current conveyor
Load receptacle type
C406S052000, C406S075000, C406S086000, C406S092000, C406S135000, C406S176000, C222S637000
Reexamination Certificate
active
06183169
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the accurate dispensing of very small quantities of ultra-fine particles in a reproducible manner.
2. Description of the Prior Art
In the pharmaceutical industries (and also other industries), it is often necessary to accurately dispense very small quantities (order of 1 mg or less) of ultra-fine (<10 mm) pharmaceutical (and other) particles on a dry basis in a reproducible manner. For example, very fine particles are administered to patients by means of inhalation. Higher potency of these new drug compounds requires much smaller doses than in previous dispensing applications. The existing equipment available commercially can only dispense an amount of the order of 5±0.5 mg. It would be desirable to be able to dispense quantities of 1 mg or less with a spread of ±0.1 mg or less.
There is no available technology to dispense such small quantities of ultra-fine particles on a dry basis. For quantities larger than 5 mg, several types of solids feeding systems have been developed over the years. Among them are feeders designed to deliver particles at flowrates of the order of 1 kg/h for laboratory and pilot scale gas-solid reactions (e.g. combustion, gasification, catalytic reactions and metallurgical processes). The most common kind of solids feeder is the mechanical feeder such as a belt or screw conveyor. However, mechanical feeders are generally inefficient and unreliable in feeding very fine particles due to the cohesive properties of the powder which prevent free-motion of solids and lead to difficulty in transporting the powder.
A fluidized bed feeder as a non-mechanical solids feeder would have the potential to dispense smaller quantities with suitable reproducibility. While there are several types of conventional fluidized bed feeders developed, none of them is suitable for the required small quantities and ultra-fine particles. None of the reported feeders can dispense the very small quantity of fine particles of interest here.
Processing of fine particles (including nanometer particles) have been identified by governments and industries as one of the key development areas for the 21st century.
To accurately dispense ultra-fine particles, all mechanical methods would fail due to the cohesive nature of the ultra-fine particles. The existing conventional solids feeders cannot handle the small quantities of particles for drug doses of the order of 1 mg or less.
SUMMARY OF THE INVENTION
It is an object of the invention to accurately dispense very small quantities of ultra-fine particles, such as pharmaceuticals, on a dry basis in a reproducible manner.
In the invention, there is provided a two-stage fluidization via the use of a pressure difference between the two stages.
According to the invention there is provided an apparatus for dispensing particles on a dry basis comprising: a first gas-solids suspension chamber having particle fluidization means adapted thereto; at least one conduit adapted to said first gas-solids chamber and a second gas-solids chamber for communicating via at least one particle opening adapted thereto particles between said chambers; means for providing a pressure difference between said first gas-solids suspension chamber and said second gas-solids suspension chamber, whereby said pressure difference means creates a low pressure zone within said at least one conduit thereby drawing in particles from said first gas-solids suspension chamber into said at least one conduit; and, means for withdrawing particles from said second diluted gas-solids suspension chamber into a collection area.
One application of this new fluidized dispensing system is in the pharmaceutical industry to dispense very small doses for drug administration. This technology can also find applications in many other industries when the metering of small quantities of particles is required.
One advantage of this invention is that accurate dispensing of small quantities of fine particles using cost-effective pneumatic rather than mechanical means is achieved.
Although the invention is well suited for ultra-fine particles and for small quantities, the invention can handle larger particles and quantities of larger than 1 mg, up to the point where other more conventional methods begin to work more effectively—for example in the 100-200 mg range. However, the smaller the particles the more difficult it is to dispense them using conventional methods. The application of the invention is, therefore, not to be construed as one that is strictly limited to only dispense very small quantities of the order of 1 mg or less, and ultra-fine particles.
Further features of the invention will be described or will become apparent in the course of the following detailed description.
REFERENCES:
patent: 2715551 (1955-08-01), Kiernan
patent: 4367685 (1983-01-01), Frame et al.
patent: 4545704 (1985-10-01), Heinemann
patent: 4824295 (1989-04-01), Sharpless
Grace John R.
Pourkavoos Nazaneen
Zhu Jingxu
Armstrong R. Craig
Dillon, Jr. Joe
Ellis Christopher P.
The University of Western Ontario
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