U.S. patent application number 11/795425 was filed with the patent office on 2008-06-12 for liquid dispensing system.
This patent application is currently assigned to Norgren Limited. Invention is credited to Mark Caswell, Richard Nighy.
Application Number | 20080135583 11/795425 |
Document ID | / |
Family ID | 33515969 |
Filed Date | 2008-06-12 |
United States Patent
Application |
20080135583 |
Kind Code |
A1 |
Caswell; Mark ; et
al. |
June 12, 2008 |
Liquid Dispensing System
Abstract
A liquid dispensing system comprises a cartridge (2) in which
liquid to be dispensed is retained and at least one solenoid
assembly. The solenoid assembly comprises a coil (15) and an
armature (3), the armature (3) being movably mounted within the
cartridge (2) and the coil (15) being separate from the cartridge
(2). Movement of the armature (3) acts to expel liquid from the
cartridge (2).
Inventors: |
Caswell; Mark;
(Warwickshire, GB) ; Nighy; Richard;
(Stratford-on-Avon, GB) |
Correspondence
Address: |
THE OLLILA LAW GROUP LLC
2060 BROADWAY, SUITE 300
BOULDER
CO
80302
US
|
Assignee: |
Norgren Limited
Lichfield
GB
|
Family ID: |
33515969 |
Appl. No.: |
11/795425 |
Filed: |
November 3, 2005 |
PCT Filed: |
November 3, 2005 |
PCT NO: |
PCT/GB05/04239 |
371 Date: |
July 13, 2007 |
Current U.S.
Class: |
222/333 ;
222/494 |
Current CPC
Class: |
B01L 3/0265 20130101;
B01L 2400/0666 20130101; G01F 11/021 20130101; B01L 2200/0605
20130101; B01L 2400/0487 20130101; G01N 35/1002 20130101 |
Class at
Publication: |
222/333 ;
222/494 |
International
Class: |
B65D 88/54 20060101
B65D088/54; B65D 35/38 20060101 B65D035/38 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 3, 2004 |
GB |
0424313.5 |
Claims
1. A liquid dispensing system comprising a cartridge (2) in which
liquid to be dispensed is retained and at least one solenoid
assembly, the solenoid assembly comprising a coil (15) and an
armature (3), the armature (3) being movably mounted within the
cartridge (2) and the coil (15) being separate from the cartridge
(2), movement of the armature (3) acting to expel liquid from the
cartridge (2).
2. A liquid dispensing system according to claim 1, in which the
cartridge (2) is disposable.
3. A liquid dispensing system according to claim 1, in which the
cartridge (2), when assembled, comprises a cartridge body (5), the
armature (3), a return spring (14) for the armature (3) and a
nozzle assembly (4).
4. A liquid dispensing system according to claim 3, in which the
armature (3) is biased by the return spring (14) towards a first
position, and towards a second position by activation of the coil
(15).
5. A liquid dispensing system according to claim 1, in which the
armature (3) slides within the cartridge (2).
6. A liquid dispensing system according to claim 4, in which in the
first position the armature (3) closes off flow through the nozzle
assembly (4).
7. A liquid dispensing system according to claim 6, in which
activation of the coil (15) moves the armature (3) to allow flow
through the nozzle assembly (4), and movement of the armature in
response to the return spring (14) dispenses the liquid.
8. A liquid dispensing system according to claim 3, in which the
return spring (14) is a separate component from the cartridge (2),
armature (3) and nozzle assembly (4).
9. A liquid dispensing system according to claim 4, in which in the
first position the armature (3) allows flow through the nozzle
assembly (4).
10. A liquid dispensing system according to claim 9, in which
activation of the coil (15) moves the armature (3) to dispense the
liquid.
11. A liquid dispensing system according to claim 3, in which the
return spring (14) is formed integrally with the nozzle assembly
(4).
12. A liquid dispensing system according to claim 1, in which the
armature (3) comprises iron or other magnetic material.
13. A liquid dispensing system according to claim 1, in which the
cartridge (2) is disposed within the coil (15) when the cartridge
(2) is mounted in the dispensing system (1).
14. A liquid dispensing system according to claim 1, in which the
cartridge (2) has two chambers, of which the first chamber (6) is a
reservoir for the liquid and the second chamber (7) retains the
armature (3).
15. A liquid dispensing system according to claim 14, in which the
second chamber (7) is disposed within the coil (15) when the
cartridge (2) is mounted in the dispensing system (1).
16. A liquid dispensing system according to claim 14, in which the
armature (3) defines a dispensing chamber (32) in the second
chamber (7) in which the liquid to be dispensed collects.
17. A liquid dispensing system according to claim 16, in which the
armature (3) has a fluid flow path (26) for transferring fluid from
the reservoir (6) to the dispensing chamber (32).
18. A liquid dispensing system according to claim 17, in which the
fluid flow path (26) comprises a bore through the armature (3).
19. A liquid dispensing system according to claim 17, in which the
fluid flow path (26) comprises an annular groove in the outer
surface of the armature (3).
20. A liquid dispensing system according to claim 16, in which
axial movement of the armature (3) in one direction dispenses the
liquid and in the other direction, pumps liquid from the reservoir
(6) into dispensing chamber (32).
21. A liquid dispensing system according to claim 3, in which the
nozzle assembly (4) includes a one-way valve.
22. A liquid dispensing system according to claim 21, in which the
one-way valve is a "duck-bill" valve (33).
23. A liquid dispensing system according to claim 1, in which the
dispensing system (1) includes one solenoid coil (15).
24. A liquid dispensing system according to claim 1, in which the
dispensing system (1) includes two solenoid coils (15, 58).
25. A liquid dispensing system according to claim 24, in which the
cartridge (2) contains two armatures (3, 61) and two dispensing
chambers (32, 64).
26. A liquid dispensing system according to claim 14, in which
reservoir (6) has a pressure/vacuum source (30) attached
thereto.
27. A liquid dispensing system according to claim 1, in which the
cartridge (2) includes a lid (24) having a moulded hinge.
28. A liquid dispensing system according to claim 3, in which the
nozzle assembly (4) is mounted with the cartridge (2) by
interference fit.
29. A liquid dispensing system according to claim 3, in which the
nozzle assembly (4) is mounted with the cartridge (2) with
adhesive.
30. A liquid dispensing system according to claim 3, in which the
nozzle assembly (4) is integrally moulded with the cartridge
(2).
31. A liquid dispensing system according to claim 3, in which the
nozzle assembly (4) has a nozzle (12) and a shroud (13).
32. A liquid dispensing system according to claim 31, in which the
nozzle (12) has a hydrophobic coating to aid complete expulsion of
liquid therefrom.
33. A liquid dispensing system according to claim 16, in which
dispensing chamber (32) has a hydrophobic coating to aid complete
expulsion of liquid therefrom.
34. A liquid dispensing system according to claim 1, adapted to
dispense quantities of liquid in the order of microlitres.
Description
[0001] This invention relates to a liquid dispensing system for
dispensing sub-millilitre volumes of liquid. Such small volumes are
used in laboratory experiments and tests such as in vitro diagnosis
of conditions from samples such as blood serum, urine and the like.
This invention could also be applied in the field of drink
dispensing.
[0002] In vitro diagnosis requires the use of between two and five
reagents (most commonly three) stored in a machine and added
successively to a prepared sample. The reagents are generally
expensive, so that it is advantageous to use as little as possible
for each test, particularly in view of the fact that medical staff
require an increasing number of tests to be done in order to
confirm diagnoses. It is important that the volumes of reagent used
are measured accurately, so that the test results are accurate and
repeatable. Currently, the amount of reagent used is in the range
of 200 to 1000 microlitres, as it is difficult and expensive to
make a diagnostic machine which can dispense lesser volumes from a
reservoir sufficiently accurately. The liquid is usually dispensed
via pipettes or syringes, using systems involving valves and seals,
which suffer from hysteresis and so affect accuracy.
[0003] A further problem with dispensing liquids is
cross-contamination, which occurs when the reagent touches samples,
other reagents or non-sterile surfaces. Drops of liquid tend to be
left on the dispenser, and these may be difficult to remove without
touching. Obviously, cross-contamination needs to be avoided if the
tests are to be accurate and repeatable.
[0004] A further problem with dispensing small volumes of liquid is
that, in order to maintain accuracy, it must be ensured that all of
the liquid intended to be dispensed is actually expelled from the
dispensing device.
[0005] The aim of the invention is to increase the accuracy of
dispensing small volumes of liquid (from 2 to 80 microlitres) from
a machine, while avoiding cross-contamination, and providing ease
of replenishment of the liquids in the machine, such as by the use
of disposable cartridges.
[0006] According to a first aspect of the invention, we provide a
liquid dispensing system comprising a cartridge in which liquid to
be dispensed is retained and at least one solenoid assembly, the
solenoid assembly comprising a coil and an armature, the armature
being movably mounted within the cartridge and the coil being
separate from the cartridge, movement of the armature acting to
expel liquid from the cartridge.
[0007] This is advantageous as the coil can be made part of the
dispensing apparatus and the cartridge, which contains the
armature, can be mounted within the coil. Once the liquid has all
been dispensed by movement of the armature, the cartridge can be
replaced. Thus, preferably the cartridge is disposable. This
reduces the chance of contamination and the cartridge can be
constructed in a factory to dispense accurate and consistent
volumes of liquid, such as a reagent. The use of the armature
movement to actively expel the liquid assists in accurate
dispensing.
[0008] Preferably the cartridge, when assembled, comprises the
cartridge body, the armature, a return spring for the armature, and
a nozzle assembly. The liquid is expelled through the nozzle
assembly.
[0009] The armature is biased by the return spring towards a first
position, and towards a second position by activation of the coil.
Thus, the armature is moved in one direction by activation of the
coil, and in the opposite direction by the return spring. The
armature conveniently moves axially within the cartridge.
[0010] The arrangement may be such that in the first position the
armature closes off flow through the nozzle assembly. This means
that the normal position of the armature (that is, with the coil
inactive or when the cartridge is not installed in the dispensing
system) is to prevent flow from the cartridge. This has the
advantage that liquid will not escape in the normal position, so
that the cartridge can be filled with liquid, sealed and delivered
to the point of use without fear of loss of liquid. It also means
that the nozzle assembly is closed off, when the cartridge is
installed in the dispensing system, but no liquid is being
dispensed.
[0011] Activation of the coil then moves the armature to allow flow
through the nozzle assembly, and movement of the armature in
response to the return spring actually dispenses the liquid.
[0012] With this arrangement, the spring is normally separate from
the cartridge, armature and nozzle assembly.
[0013] Alternatively, the arrangement may be such that in the first
position the armature allows flow through the nozzle assembly.
Activation of the coil then moves the armature to dispense the
liquid, while the return spring simply returns the armature to the
first position.
[0014] With this arrangement the return spring may be integrally
formed with the nozzle assembly. This is advantageous from a
manufacturing point of view, as it reduces the number of
components.
[0015] Preferably the armature comprises iron or other magnetic
material. The armature can be constructed relatively inexpensively
and is thus disposable as the solenoid coil is separate from it.
Preferably, the armature slides within the cartridge.
[0016] The cartridge may be disposed within the coil when the
cartridge is mounted in the dispensing system.
[0017] Preferably the cartridge has two chambers, of which the
first chamber is a reservoir for the liquid and the second chamber
retains the armature. Thus, preferably the second chamber is
disposed within the coil when the cartridge is mounted in the
dispensing system.
[0018] The armature may define a dispensing chamber in the second
chamber in which the liquid to be dispensed collects. This is
advantageous as a measured quantity of liquid can be transferred to
the dispensing chamber from the reservoir before dispensing.
[0019] Preferably the armature has a fluid flow path for
transferring fluid from the reservoir to the dispensing chamber.
The fluid flow path may comprise a bore through the armature.
Alternatively it may comprise an annular groove in its outer
surface.
[0020] Preferably axial movement of the armature in one direction
dispenses the liquid and in the other direction, pumps liquid from
the reservoir into the dispensing chamber.
[0021] The nozzle assembly may also include a one-way valve, such
as a "duck-bill" valve. This is advantageous, especially where
liquid is dispensed by movement of the armature due to activation
of the coil, as no air is also drawn into the dispensing chamber
when the armature pumps liquid from the reservoir.
[0022] Preferably the dispensing system includes one solenoid coil.
However alternatively it may comprise two solenoid coils. Thus, the
cartridge may contain two armatures and two dispensing
chambers.
[0023] The reservoir may have a pressure/vacuum source attached
thereto. The pressure/vacuum source can be used to control more
carefully the amount of fluid dispensed, and, if a vacuum is
applied to the reservoir, the hydrostatic pressure of a large head
of liquid in the reservoir can be supported.
[0024] Preferably the cartridge includes a lid having a moulded
hinge. This allows the liquid in the reservoir to be agitated or
refilled as necessary.
[0025] Preferably the nozzle assembly is mounted with the cartridge
by interference fit or with adhesive or it may be integrally
moulded therewith.
[0026] Preferably the nozzle assembly has a nozzle and a shroud to
protect the nozzle from damage or contamination. Further the nozzle
or dispensing chamber may have a hydrophobic coating to aid
complete expulsion of liquid therefrom. Preferably, they both have
a hydrophobic coating.
[0027] Preferably the liquid dispensing system of the invention is
adapted to dispense microlitres of liquid.
[0028] There now follows by way of example only a detailed
description of the present invention with reference to the
accompanying drawings in which;
[0029] FIG. 1 shows an exploded view of the cartridge and solenoid
coil according to the invention;
[0030] FIG. 2 shows a modification to the nozzle assembly shown in
FIG. 1;
[0031] FIGS. 3a and 3b show a first embodiment of the
invention;
[0032] FIG. 4 shows a modification to the nozzle of the dispensing
system shown in FIGS. 3a and 3b;
[0033] FIG. 5 shows a second embodiment of the invention;
[0034] FIGS. 6a, 6b and 6c show a third embodiment of the
invention;
[0035] FIGS. 7a, 7b and 7c show a fourth embodiment of the
invention;
[0036] FIGS. 8a, 8b and 8c show a fifth embodiment of the invention
that incorporates a collar section on the armature;
[0037] FIG. 9 is a perspective view of the armature and the collar
section of the fifth embodiment; and
[0038] FIGS. 10a, 10b and 10c show a sixth embodiment of the
invention that incorporates two solenoid assemblies.
[0039] The liquid dispensing system 1 of FIG. 1 comprises a
cartridge 2, an armature 3 and a nozzle assembly 4. The cartridge 2
comprises a hollow body 5, which is divided into a first chamber 6
and a second chamber 7 by a valve seat 8. The first chamber 6 forms
a reservoir which, in use, retains liquid to be dispensed by the
system. The second chamber 7 defines an axial armature bore within
which the armature 3 can move. The nozzle assembly 4 retains the
armature 3 in the bore 7. The liquid dispensing system 1 also
includes a solenoid coil 15 of conventional construction having a
bore 16 therethrough. Thus, the solenoid coil 15 and the armature 3
together form a solenoid assembly. The second chamber 7 of the
cartridge 2 is, in use, adapted to be mounted within the bore 16,
thereby enabling the magnetic field generated by the coil 15 to
move the armature 3. Movement of the armature 3 causes liquid from
the reservoir 6 to be expelled through the nozzle assembly 4.
[0040] The nozzle assembly 4 comprises a body 11 of a diameter to
closely fit within the bore 7, an elongate nozzle 12, a shroud 13
and an integrally formed spring member 14. The elongate nozzle 12
comprises a tapering cylindrical member extending from the body 11,
which has a dispensing bore 17 therethrough. The dispensing bore 17
also extends through the nozzle assembly body 11. The spring member
14 is helical and is moulded integrally with the body 11. When the
nozzle assembly 4 is mounted within bore 16, the spring member 14
abuts a shoulder 18 on the armature 3 to bias the armature 3 into a
first position in which it is adjacent the reservoir 6. The shroud
13 is annular and extends from the body 11 concentrically with the
nozzle 12. The annular shroud 13 also extends radially outwards
adjacent its junction with the body 11 to define a shoulder 19. The
shoulder 19 is adapted to abut the free end of the second chamber 7
to ensure that the nozzle assembly 4 is appropriately mounted
therein. The shroud 13 protects the nozzle 12 from damage. Further,
the nozzle 12 may comprise or be coated with a hydrophobic material
to aid the expulsion of liquid therefrom.
[0041] A modification to the nozzle assembly 4 is shown in FIG. 2
in which the shroud 13 comprises two arcuate sections 20, 20'
defining two diametrically opposed slots 21, 21'. This allows the
shroud 13 to provide protection for the nozzle 12 and is also
easier and cheaper to manufacture, as the nozzle assembly can be
moulded across the slots 21, 21'. FIG. 2 also shows a modification
to the spring member 14. In this modification the spring member 14
comprises two spring sections 22, 22'. The spring sections 22, 22'
first extend in a longitudinal direction from diametrically opposed
edges of body 11 and then extend circumferentially. The inwardly
facing sides 23 of the spring sections 22, 22' are arcuate and
define a gap to receive the armature 3, with the spring sections
22, 22' in abutment with the armature shoulder 18. As can be
appreciated, this modification to the spring member 14 results in
less linear travel but is easier and cheaper to manufacture.
[0042] The cartridge 2 has a hinged lid 24 that provides access to
the reservoir 6. The lid 24 allows the reservoir 6 of the cartridge
2 to be filled with liquid, such as a reagent for diagnostic
testing, and for the liquid to be agitated as necessary. The
cartridge 2 also has clips 25 projecting from the body 5 which
allow the cartridge 2 to be mounted within dispensing apparatus
(not shown), or the like, so that the cartridge 2 can be
appropriately positioned with the coil 15.
[0043] The cartridge 2 may be of plastics and formed integrally
with the hinged lid 24 by injection moulding or any other
appropriate method. It will be appreciated that the material used
for the cartridge will depend upon the liquid that is to be
dispensed, to ensure that the cartridge material does not react or
degrade in the presence of the liquid. The nozzle assembly 4 may
also be formed by injection moulding. The armature 3 or a
proportion thereof may be of iron or other magnetic material.
Further, the armature 3 may be coated to ensure it does not react
or degrade in the presence of the liquid. Advantageously the
cartridge 2, armature 3 and nozzle assembly 3 are simple and
inexpensive to manufacture and thus can be disposable.
[0044] FIGS. 3a and 3b show, in section, a first embodiment of the
liquid dispensing system 1 assembled and mounted in the bore 16 of
the solenoid coil 15. Corresponding reference numerals have been
applied to corresponding parts. In this embodiment the armature 3
has a fluid flow path 26 that extends axially part way through the
armature and then radially. Thus, aperture 27, formed in the base
of the armature 3, adjacent the nozzle assembly 4, is connected via
the flow path 26 to aperture 28 formed in a circumferential side of
the armature 3, adjacent the reservoir 6. The armature ledge 18 is
located around the periphery of aperture 27 and thus the spring
member 14 has a smaller diameter. Further, the reservoir 6 has a
port 30 formed in its side wall for applying pressure or a vacuum
to the reservoir 6. The solenoid coil 15 has terminals 10 for
connecting it to a control system of the dispensing apparatus (not
shown).
[0045] In use, the reservoir 6 is filled with liquid 31 and is
sealed by the lid 24. In FIG. 3a the coil 15 is not activated and
thus the spring member 14 urges the armature 3 into the first
position. In the first position the nozzle assembly 4 and the
armature 3 define therebetween a dispensing chamber 32 in the
second chamber 7. Further, in the first position the armature 3 is
adapted such that it projects into the reservoir 6 such that
aperture 28 is open to the liquid 31. Thus, the liquid 31 from the
reservoir enters aperture 28, travels through the fluid flow path
26 and out of aperture 27, and collects in the dispensing chamber
32. The liquid is prevented from draining from the nozzle 12 due to
the surface tension formed at the free end of the dispensing bore
17. It will be appreciated that the form, and in particular the
diameter, of the nozzle 12 is chosen to ensure that the particular
liquid 31 being dispensed is able to exhibit sufficient surface
tension to be retained in the dispensing chamber 32. The pressure
port 30 may apply a vacuum to the reservoir 6 to allow a larger
"head" of liquid in the reservoir 6 to be supported by the surface
tension at the dispensing nozzle 12. Further, the exact location of
the armature 3 in the first position and the diameter of the
dispensing chamber 32 is chosen so that a precise measured volume
of liquid collects in the dispensing chamber 32, to ensure accurate
and repeatable dispensing.
[0046] In FIG. 3b, electrical power has been applied to the coil 15
by the dispensing apparatus resulting in a magnetic field, which
has drawn the armature 3 into a second position in which it abuts
the nozzle assembly 4. In moving from the first position to the
second position the aperture 28 is closed off from the reservoir 6
by the wall of the second chamber 7. Further, as the armature 3
moves to the second position the volume of the dispensing chamber
32 is reduced which forces a measured quantity of liquid from the
dispensing chamber 32 out of the dispensing bore 17. Thus, movement
of the armature from the first position to the second position is
an active dispensing stroke in which liquid is actively expelled
thereby improving accuracy.
[0047] Once the liquid has been dispensed the electrical power to
the solenoid coil 15 is removed and the armature 3 will be urged to
return to the first position by the spring member 14. In moving
from the second position to the first position, the volume of the
dispensing chamber 32 increases, which leads to a decrease in
pressure within chamber 32. This decrease in pressure effectively
pumps liquid 31 from the reservoir 6 into the dispensing chamber
32, once the aperture 28 is open to the reservoir 6. This ensures
that the dispensing chamber 32 is reliably filled with liquid after
each dispensing stroke and operation of the dispensing system does
not have to rely solely on gravity to fill the dispensing chamber,
which improves reliability. Thus, movement of the armature 3 from
the second position to the first position is a pumping stroke.
However, it will be appreciated that during the pumping stroke, air
will also be drawn in through the dispensing bore 17 and therefore
the system will still rely on gravity to an extent to ensure the
dispensing chamber 32 is completely filled.
[0048] In a modification (not shown) the pressure/vacuum port 30 is
omitted. Instead, the dispensing bore 17 is elongated with a length
of capillary tubing, and the spring 14 is constructed so that the
force acting on the armature returns it relatively slowly to the
first position. The return force needs to be chosen so that the
velocity of the armature creates sufficient force to draw in liquid
from the reservoir 6 to the dispensing chamber 32, but not enough
to overcome the surface tension at the capillary end of the bore
17, so that air is not drawn in. The spring force can be altered
for different liquids according to their viscosity to achieve this
result. Activation of the coil, however, will cause a more rapid
movement of the armature, so that the pressure created in the
dispensing chamber 32 is sufficient to overcome the surface tension
and dispense the liquid.
[0049] FIG. 4 shows a modification to the nozzle assembly 4 of the
embodiment shown in FIGS. 3a and 3b, which also addresses this
problem. In FIG. 4, the pressure/vacuum port 30 is absent and the
nozzle 12 incorporates a one-way "duck-bill" style valve 33. The
valve 33 only permits flow out of the dispensing bore 17. As the
dispensing bore 17 is not open to atmosphere, the dispensing system
1 does not rely on surface tension to retain a measured volume in
the dispensing chamber 32. This obviates the need for the
pressure/vacuum port 30. Further, during the pumping stroke, the
valve 33 prevents air entering the dispensing chamber 32 through
the dispensing bore 17 and therefore the reduction in pressure in
the dispensing chamber 32 will solely cause liquid 31 from the
reservoir 6 to be drawn into chamber 32. This improves the accuracy
and the repeatability of the dispensing device. In the embodiment
of FIGS. 1 to 4 it will be noted that when the coil 15 has no
electrical power (i.e., it is inactive) the nozzle 12 is open, so
that it may be possible for liquid to leak out. In a further
modification (not shown) the armature 3 and spring 14 are arranged
so that the spring force biases the armature 3 to the position
where it closes off the dispensing bore 17, and activation of the
coil 15 moves the armature 3 away from the bore 17. The spring 14
is then provided on the opposite end of the armature 3, as a
separate component.
[0050] In operation, activation of the coil 15 moves the armature 3
away from the bore 17 to allow liquid to flow into the dispensing
chamber 32 from the reservoir 6. When the coil 15 is de-activated
the armature 3 returns under the force of the spring 14 to dispense
the liquid.
[0051] This has the advantage that, as well as preventing leakage
when the cartridge is installed in the system, leakage is also
prevented before the cartridge is installed. This means that the
cartridge can be manufactured, filled with liquid, sealed and
delivered to the point of use without fear of loss of liquid.
[0052] FIG. 5 shows a second embodiment of the invention having a
modified armature 3. The remainder of the liquid dispensing system
1 is the same as the first embodiment and corresponding reference
numerals have been applied to corresponding parts. The armature 3
of FIG. 5 does not have a machined fluid flow path 26 through the
body of the armature 3. Instead, it is of a lesser diameter than
the second chamber 7 such that a flow path is formed between the
armature 3 and the walls of the second chamber 7. As the armature 3
is not machined, this makes it simpler and cheaper to
manufacture.
[0053] In use, the liquid dispensing system 1 of this embodiment
operates in a similar manner to the previous embodiment in that
liquid 31 collects in the dispensing chamber 32 when the armature 3
is in the first position. Similarly, the surface tension of the
liquid 31 at the free end of the dispensing bore 17 retains the
liquid 31 in the chamber 32. Upon activation of the solenoid coil
15, the armature 3 is driven into the second position by the
magnetic force, against the force of the spring member 14. This
dispensing stroke forces the fluid 31 in the dispensing chamber 32
out of the nozzle 12. It will be appreciated that a certain amount
of liquid will also be forced back into the reservoir 6 through
flow path 26. However, the area of the flow path 26 and the size of
the dispensing chamber 32 when the armature 3 is in the first
position can be chosen so that a precise and repeatable quantity of
liquid is expelled from the nozzle 12 during each dispensing
stroke. During the pumping stroke, both liquid from the reservoir 6
and atmospheric air through the dispensing bore 17 will be drawn
into the dispensing chamber 32. The chamber 32 is then completely
filled with liquid 31 by it flowing under gravity from the
reservoir 6, through the fluid flow path 26.
[0054] FIGS. 6a, 6b and 6c show a third embodiment that includes a
modified armature 3 and second chamber 7. The armature 3 comprises
a cylindrical body having a circumferential groove 34 therein, such
that when the armature 3 is in the first position (see FIG. 6a),
the groove 34 is open to the reservoir 6. The second chamber 7 also
has a groove in its inner wall that forms an intermediate chamber
35. The intermediate chamber 35 is positioned such that when the
armature 3 is in the second position the groove 34 aligns with the
chamber 35. In the second position, liquid 31 is prevented from
flowing freely from the reservoir 6 to the intermediate chamber 35
by a radial flange 36 of the armature 3.
[0055] Upon first use, liquid 31 from the reservoir 6 collects
within the groove 34 when the armature 3 is in the first position.
Activation of the solenoid coil 15 draws the armature 3 downwards
into the second position against the force of the spring member 14.
The liquid that has collected with the groove 34 is drawn downwards
with the armature 3. In the second position, the groove 34 is
aligned with the intermediate chamber 35. Thus, the liquid in the
groove 34 flows freely into the intermediate chamber 35 (as shown
in FIG. 6b). Thus, in this embodiment the pumping stroke, in which
liquid 31 is urged from the reservoir 6, occurs when the armature
moves from the first position to the second position. When the
solenoid coil 15 is deactivated, the armature returns to the first
position under the force of spring member 14. The liquid 31
transferred to the intermediate chamber 35 is then able to flow
from the chamber 35 into the dispensing chamber 32. As shown in
FIG. 6c, the majority of the liquid collects in the dispensing bore
17 and the majority of the dispensing chamber 32 is filled with
air. The liquid is held in the dispensing bore 17 by surface
tension. The liquid is dispensed when the solenoid coil 15 is
activated once again and the armature 3 moves to the second
position. The resulting pressure from reduction in volume of the
dispensing chamber 32 overcomes the surface tension and forces the
liquid from the dispensing bore 17. The air in the dispensing
chamber 32 is also forced out of the bore 17, which helps to ensure
that all of the liquid is actively expelled from the dispensing
chamber 32 and bore 17. Thus, movement of the armature 3 from the
first position to the second position is also an active dispensing
stroke. Although, the first dispense from this embodiment requires
two cycles of the armature 3 (i.e. the solenoid coil 15 is
activated and deactivated twice), it will be appreciated that
liquid is dispensed on every cycle thereafter.
[0056] A fourth embodiment of the invention is shown in FIGS. 7a,
7b and 7c, in which there are modifications to the armature 3, the
second chamber 7 and nozzle assembly 4. Firstly, the armature 3
comprises a body 37 of smaller diameter than the second chamber 7
and has an annular peripheral flange 38 that extends radially
outward to a diameter that approaches the internal diameter of the
second chamber 7. The armature 3 also carries seals 40, 41 in its
top and bottom faces respectively. The second chamber 7 includes an
annular elastomeric inlet seal 42 mounted within the second chamber
7, adjacent the junction with the reservoir 6. The inlet seal 42
prevents flow between itself and the wall of the second chamber 7
and has an aperture 43. The seal 42 is comparable to the valve seat
8 shown in FIG. 1. The nozzle assembly 4 also has an annular
elastomeric outlet seal 44 in the nozzle body 11, which surrounds
the proximal end of the dispensing bore 17. The spring member 14
has been omitted from these Figures for clarity, but would extend
from the nozzle assembly body 11 and abut flange 38 of the armature
3.
[0057] In FIG. 7a the armature 3 is shown in the first position,
wherein the dispensing chamber 32 is sealed from the reservoir 6 by
seal 40 on the armature 3 abutting the inlet seal 42. On activation
of the solenoid coil 15, the armature 3 moves to the second
position. The seal 40 moves away from the inlet seal 40 and into
sealing contact with the outlet seal 44 on the nozzle assembly 4.
This movement of the armature 3 acts as a pumping stroke, drawing
liquid 31 from the reservoir 6, past the flange 38 into the
dispensing chamber 32 (as shown in FIG. 7b). Deactivation of the
solenoid coil 15 causes the armature 3 to return to the first
position under the force of the spring member (not shown). Thus,
seals 41 and 44 are separated, which allows a proportion of the
liquid in the dispensing chamber 32 to flow into the dispensing
bore 17. The liquid 31 is retained in the dispensing bore 17 by
surface tension (see FIG. 7c). When the solenoid coil 15 is
activated again and thus the armature 3 moves to the second
position, a proportion of the liquid in the dispensing chamber is
expelled from the nozzle 12. As with the previous embodiment, after
the first cycle as described above, liquid is dispensed and pumped
from the reservoir 6 on the same stroke of the armature 3 from the
first to the second position.
[0058] A fifth embodiment is shown in FIGS. 8a, 8b and 8c. In this
embodiment the nozzle assembly 4 comprises an elongate nozzle 12
that first extends radially from an aperture 48 in the second
chamber 7 and then axially, adjacent the coil 15 (when the second
chamber 7 is mounted within the solenoid coil aperture 16). The
second chamber 7 includes an extension portion 45 that extends into
the reservoir 6 and has an open end 47 and an inlet aperture 46 in
its side wall. The second chamber 7 also includes a hollow guide
member 50 having a cylindrical open bore 51. The armature 3
comprises a head portion 52 having a support section 53 and a guide
section 54, separated by a shoulder 55, depending axially
therefrom. The guide section 54 is received in the bore 51 of the
guide member 50 and can axially slide therein. An annular slider
member 56 is slidably mounted on the support section 53 of armature
3. Thus, the slider member 56 can slide between the head portion 52
and shoulder 55. The slider member 56 has a series of
circumferentially spaced axial channels 57 (see FIG. 9) that allows
liquid to flow through the member 56.
[0059] FIG. 8a shows the armature 3 biased into the first position
by the spring member (not shown) in which the head 52 extends into
the extension portion 45, adjacent the reservoir 6. The slider
member 56 abuts the shoulder 55 and as such, seals the inlet
aperture 46. Liquid 31 from previous cycles is shown in the
dispensing chamber 32 and the dispensing bore 17. Upon activation
of the coil 15 the armature 3 is drawn into the second position
where, in this embodiment, the slider member 56 abuts the guide
member 50. This downward movement of the armature 3 is the active
dispensing stroke, which reduces the volume of the dispensing
chamber 32 and therefore causes liquid 31 to be expelled from the
dispensing chamber 32 and bore 17. As the slider member 56 seals
the inlet aperture 46, movement of the armature 3 can only force
liquid out of the dispensing chamber 32 and bore 17 and therefore a
precise and reliable volume is dispensed. Before the active
dispensing stroke is complete (as shown in FIG. 8b) the head 52
abuts the slider member 56 and draws it downward with the armature
3. In the second position the slider member 56 seals the outlet
aperture 48 (as shown in FIG. 8c). Thus, when the coil 15 is
deactivated and the armature 3 is urged by the spring member (not
shown) to return to the first position (the pumping stroke), no air
can be drawn in through the dispensing bore 17 and therefore only
liquid 31 from reservoir 6 is drawn into the dispensing chamber 32
through aperture 46. Before the pumping stroke is complete the
slider member 56 abuts the shoulder 55 and is drawn upwards with
the armature 3 and returns to the position shown in FIG. 8a for
further cycles.
[0060] A sixth embodiment is shown in FIGS. 10a, 10b and 10c. The
construction of the liquid dispensing system 1 in this embodiment
is similar to the first embodiment except that the cartridge 2
includes third section 59 which extends within an aperture of a
second coil 58 and has a second nozzle 60 and second armature 61
mounted within. The second coil has terminals 62 for connecting it
to the control system of the dispensing apparatus (not shown). The
second armature 61 has a bore therethrough in which is mounted a
one-way valve 63. The third section 59 defines a second dispensing
chamber 64 having a second dispensing bore 65. Operation of the
first armature 3 is the same as described for the first embodiment,
except that downward movement of the armature 3 performs a dosing
stroke, in which a measured amount of liquid is transferred through
the one-way valve 63 of the second armature 61, into the second
dispensing chamber 64 (as shown in FIG. 10b). Then, the second coil
58 can be activated to move the second armature 61 through an
active dispensing stroke from a first position in which it is
adjacent the nozzle 4, downward to a second position where it abuts
the second nozzle 60. During the active dispensing stroke, the
liquid in the second dispensing chamber 64 is expelled from the
second dispensing bore 65 (as shown in FIG. 10c). The solenoid
coils 15 and 58 can then be deactivated so that the first armature
3 returns to the first position under the force of spring member 14
and the second armature returns to its first position under the
force of a return spring (not shown). As a measured quantity of
liquid 31 is transferred between dispensing chambers 32, 64 it is
isolated from the effect of the hydrostatic pressure in the
reservoir 6. This is advantageous as the volume of liquid to be
dispensed is unaffected by the change in hydrostatic pressure as
the quantity of fluid in the reservoir decreases. The use of two
armatures 3, 61 and two dispense chambers 32, 64 also erasures a
consistent dispense volume irrespective of the viscosity of the
liquid as at no stage does movement of the armature force liquid
back into the reservoir 6. By appropriately sequencing the
activation of the solenoid coils 15, 58 a fast and reliable
dispense rate can be achieved.
[0061] It will be appreciated that the pressure/vacuum source may
be incorporated in any of the embodiments shown or equally omitted,
depending upon the application of the liquid dispensing system and
the type of liquid being dispensed. The pressure/vacuum source can
be used to allow greater control of the amount of liquid being
dispensed. For example, a vacuum can be applied to reduce the
pressure in the reservoir 6, thereby impeding the flow of liquid
from the reservoir 6. Alternatively, pressure could be applied to
urge liquid from the reservoir 6, to promote rapid and complete
filling of the dispense chamber 32, for example. The "duck-bill"
valve 33 or any other suitable one-way valve may also be included
in any of the embodiments. The armature or nozzle assembly may be
coated in or comprise a material suitable for use with the liquid
being dispensed which, in particular, may be a hydrophobic material
to promote full expulsion from the dispensing chamber 32 and bore
17 on the active dispensing stroke. In all the embodiments, the
spring member 14 may be omitted and the armature 3 may be returned
to its first position by a reversal of the magnetic field generated
by coil 15.
[0062] It will also be appreciated that the modifications described
in relation to FIGS. 3 and 4, (the choice of the spring force
dependent on the viscosity of the liquid to ensure filling of the
dispensing chamber without drawing in air, and the reversal of the
normal position of the armature) could equally be applied to the
embodiments of FIGS. 5 to 10.
* * * * *