Agitating – With specified discharge means – Valve or gate
Reexamination Certificate
2001-10-09
2003-12-16
Cooley, Charles E. (Department: 1723)
Agitating
With specified discharge means
Valve or gate
C366S273000, C366S286000, C366S194000, C366S195000
Reexamination Certificate
active
06663276
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to the stirring of a substance in a container and the metering of quantities of such substance from the container. More specifically, the present invention relates to the design of the stirring element or agitator used to stir substances in containers.
BACKGROUND ART
Liquid metering systems are used in a wide variety of applications in the pharmaceutical industry, such as for injecting metered doses of viscous or concentrated suspensions or slurries onto or into substrates and other drug containment media.
FIG. 1
illustrates an example of a recently developed liquid metering device in the form of a liquid metering gun generally designated
10
. Metering gun
10
is generally supported by a mounting bracket
12
. Included with this particular system are a solenoid
14
, a syringe-type liquid cylinder
16
, a needle valve assembly generally designated
20
, and a magnetically-driven stirring assembly generally designated
50
. Liquid cylinder
16
is secured and sealed to solenoid
14
with a TEFLON® cap
31
. Cap
31
is attached to solenoid
14
by means of four machine screws
32
(only two of which are shown in FIG.
1
). An O-ring
33
is fit into a groove of cap
31
located at the end of cap
31
most distal to solenoid
14
. O-ring
33
seals cylinder
16
and maintains the dispensing pressure differential.
Needle valve assembly
20
includes an elongate pin or needle
22
, a needle seat
24
and a needle seat holder
26
. An outer gun casing
35
is coaxially disposed around liquid cylinder
16
, and includes a lower cap
37
in which needle seat holder
26
and a nozzle
39
are disposed. A conical element
22
A (also shown in perspective view in
FIG. 3
) is slid onto needle
22
such that it rests on the top surface of a suspension contained in cylinder
16
. Conical element
22
A prevents upward splashing of the suspension during agitation thereof, and also prevents evaporation of volatile media during agitation.
Stirring assembly
50
includes an external magnetic drive member or stirring ring
52
mounted coaxially around gun casing
35
. Magnetic drive member
52
includes two diametrically opposed external magnets
54
A and
54
B, and is operatively connected to a pneumatic stirrer motor
56
through a coupling
58
. Coupling
58
operates to transfer rotational force developed by stirrer motor
56
to rotational motion effected by stirring ring
52
, such that external magnets
54
A and
54
B can rotate about the central longitudinal axis of metering gun
10
. For example, coupling
58
could be a toothed gear which engages teeth on stirring ring
52
. The position of motor
56
is determined by a mounting bracket
59
. Stirring assembly
50
also includes a stirring element in the form of a magnetic stir bar
60
, which has a dominant length along an axis transverse to the central longitudinal axis of metering gun
10
. Magnetic stir bar
60
has a bore drilled therethrough, such that needle
22
extends through the center of magnetic stir bar
60
and the magnet therein. Importantly, magnetic stir bar
60
is by necessity supported by an O-ring
62
.
In operation, cylinder
16
is filled with a suspension and secured to solenoid
14
. Magnetic drive assembly
50
is activated such that external magnets
54
A and
54
B rotate around cylinder
16
and induce a magnetic coupling with magnetic stir bar
60
. This in turn causes magnetic stir bar
60
to rotate about needle
22
to thereby agitate the suspension contained in cylinder
16
and prevent the suspension from separating in cylinder
16
, such as by sedimentation or creaming. Needle
22
is used to meter suspension from cylinder
16
. When needle
22
is seated in needle seat
24
, metering gun
10
is closed. At predetermined intervals, however, solenoid
14
of metering gun
10
causes needle
22
to lift upwardly out of needle seat
24
to create a passage from cylinder
16
to nozzle
39
, and a metered dose of the suspension can be dispensed through nozzle
39
under the influence of a pressure differential.
Some problems have been observed in the use of metering systems such as that described hereinabove. The configuration of stirring assembly
50
is such that O-ring
62
is needed to support the vertical position of magnetic stir bar
60
within cylinder
16
and needle
22
is needed to maintain a proper axis of rotation for magnetic stir bar
60
. With repeated use of metering gun
10
, O-ring
62
begins to loosen from its fixed position on needle
22
and slip downwardly towards the bottom of cylinder
16
. This causes magnetic stir bar
60
to jam or seize against the inside surface of cylinder
16
, thereby defeating the function of stirring assembly
50
. On other occasions, either the weight of magnetic stir bar
60
on O-ring
62
, the mass of magnetic stir bar
60
, or the contact made between magnetic stir bar
60
and needle
22
causes downward and/or lateral forces on needle
22
. Consequently, needle
22
is often deflected laterally and hence fails to seat properly onto needle seat
24
at the intended points of time, thereby causing a “constantly open” malfunction. Alternatively, the forces imparted on needle
22
can cause needle
22
to become jammed in needle seat
24
such that the valve becomes clogged. These failure events have been observed to occur both sporadically and completely, and are believed to be due at least in part to the rocking of magnetic stir bar
60
back and forth at an angle to needle
22
. In addition, the rapid vertical oscillation of needle
22
during high-frequency metering operations imparts a hammering effect on magnetic stir bar
60
, causing stir bar
60
to move O-ring
62
downwardly.
An additional problem stems from the fact that a bore is drilled through magnetic stir bar
60
to enable needle
22
to pass therethrough. The drilling of the bore can produce residual ferromagnetic particles which, due to magnetic attraction, are difficult to identify and eliminate from the bore prior to installation of magnetic stir bar
60
in cylinder
16
. These particles can contaminate the suspension, and additionally can cause seizing of stir bar
60
on needle
22
.
The configuration of magnetic stir bar
60
is also believed to engender a further problem observed wherein portions of the suspension splash upwardly to regions of cylinder
16
from which the suspension cannot easily be extracted, especially when the height of the suspension falls down to or below the level at which stir bar
60
is operating.
It is also believed that the configuration of the stirring element could be improved over the current stir bar design in order to improve the ability to stir suspensions having broader concentration, viscosity and thickness ranges.
The present invention is provided to solve these and other problems associated with the operations of liquid metering systems.
DISCLOSURE OF THE INVENTION
According to one embodiment of the present invention, an agitator assembly for agitating a substance in a container comprises a container, a magnetic drive device, and an agitator element. The container has a central longitudinal axis and includes a lateral wall defining an inside wall surface and an outside wall surface. The magnetic drive device is disposed adjacent to the outside wall surface of the lateral wall. The agitator element is disposed in the container and is magnetically coupled with the magnetic drive device for self-supported rotation about the central longitudinal axis. The agitator element includes an agitator body, a first magnet mounted at the agitator body, and a second magnet mounted at the agitator body and circumferentially spaced from the first magnet. The agitator element substantially centered about the central longitudinal axis and supported at a substantially constant axial position within the container by the magnetic drive device.
According to another embodiment of the present invention, a fluid metering device comprises a container, an elongate valve member, and an agitator assembly
Cooley Charles E.
Riek James P.
SmithKline Beecham Corporation
Sorkin David
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