CONTINUOUS POSITIVE DISPLACEMENT METERING VALVE

VALVE DOSEUSE A DEPLACEMENT POSITIF EN CONTINU

English Abstract

A continuous operation metering valve, based on true volumetric positive
displacement technology, uses an innovative dual rack and drive pinion design
that enables the valve (34) to dispense from one meter chamber (32) while the
other meter chamber (32) is filling. This provides greater dispense cycle
rates because it does not require a fill or reload period. With an optional
encoder-controlled motor (42), the inventive metering valve is capable of
almost unlimited precision dispensing with "on-the-fly" adjustment capability.
The metering valve is easily disassembled and cleaned, using stainless steel
wetted path components and Teflon seals for the widest range of chemical
compatibility. An integral electronic board, mounted to the side of the valve,
may be utilized to control the 4-way directional valve and motor direction
(when not using a rotary encoder control).

French Abstract

La présente invention concerne une valve doseuse à fonctionnement continu, fondée sur une technologie de déplacement volumétrique positif réel, qui utilise un double râteau innovant et une conception de pignon d'entraînement permettant à cette valve (34) de distribuer à partir d'une chambre (32) de mesure tandis qu'on remplit l'autre chambre (32) de mesure. Ce processus permet d'obtenir des vitesses de cycle de distribution plus élevées car la durée de remplissage ou de recharge n'est pas nécessaire. Avec un moteur (42) optionnel commandé par un encodeur, cette valve doseuse est capable d'effectuer une distribution de précision presque illimitée avec une capacité de réglage <= en mode de fonctionnement>=. Cette valve doseuse peut être facilement démontée et nettoyée, et elle utilise des composants de trajet mouillé en acier inoxydable et des joints en Téflon de façon à disposer d'une compatibilité chimique la plus large. On peut utiliser une carte électronique intégrale, montée sur le côté de la valve, pour commander la valve directionnelle à quatre positions et la direction du moteur (lorsqu'on n'utilise pas de commande d'encodeur rotatif).

Claims

THE EMBODIMENTS OF THE INVENTION FOR WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A positive displacement dispensing system for dispensing an adhesive onto a
work surface, comprising:
a metering block defining first and second bores;
a valve block coupled to said metering block and defining a first metering
chamber and a second metering chamber, said first metering chamber
communicating
with and having a smaller cross-section than said first bore and said second
metering
chamber communicating with and having a smaller cross-section than said second
bore;
first and second metering rods disposed within said bores for reciprocation
therein, said first metering rod having a first metering tip at one end and a
first rack
toward an opposing end, and said second metering rod having a second metering
tip at
one end and a second rack toward an opposing end;
a motor in meshing engagement with said first rack and said second rack, such
that angular displacement of said motor causes a linear displacement of said
first and
second metering rods in simultaneous opposing dispensing and reloading
directions;
a motor controller configured to precisely control the angular displacement of
said
motor; and
wherein the system is configured to dispense adhesive through a fluid outlet.
2. The positive displacement dispensing system of claim 1, further comprising
a
source of adhesive, wherein said adhesive is selected from the group
consisting of
epoxies, potting compounds, SMT adhesives, two-part adhesives, or solder
pastes.
3. The positive displacement dispensing system according to claim 1 or 2,
further
comprising a directional valve for selectively allowing communication between
the first
and second metering chambers and said fluid outlet.
4. The positive displacement dispensing system of any one of claims 1 to 3,
further
comprising fastening hardware for removably securing said meter block, motor
block,
and valve block to one another, such that said meter block, motor block, and
valve block
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are readily separable from one another by manipulating said fastening hardware
for the
purpose of cleaning said first and second metering chambers and said
directional valve.
5. The positive displacement dispensing system of claim 4, wherein said
fastening
hardware comprises screws.
6. The positive displacement dispensing system of any one of claims 1 to 5,
wherein
said valve block is formed from either stainless steel or plastic.
7. The positive displacement dispensing system of any one of claims 1 to 6,
wherein
said meter block is formed from either stainless steel, plastic, or tool
steel.
8. The positive displacement dispensing system of any one of claims 1 to 7,
further
comprising gears disposed within said motor block for engaging said racks on
each of
said first and second metering rods and further engaging said motor.
9. The positive displacement dispensing system of any one of claims 1 to 8,
wherein
said motor controller is configured to accurately control said motor to result
in desired
dispensing volumes.
10. The positive displacement dispensing system of any one of claims 1 to 9,
wherein
said motor controller is configured to precisely control said motor to result
in a desired
dispensing flow rate.
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Description

CA 02463721 2008-01-29
A-1638PCT
CONTINUOUS POSITIVE DISPLACEMENT METERING VALVE
BACKGROUND OF THE INVENTION
This invention relates to continuous positive displacement metering valves,
and
more particularly to an improved linear metering valve having an innovative
dual rack
and pinion design that enables a valve to dispense from one meter chamber
while another
meter chamber is filling.
Microvalves are known in the prior art for dispensing fluid materials such as
adhesives, epoxies, potting compounds, SMT adhesives, two part adhesives, and
solder
pastes (with solids dispersed therein), and the like, in a repeatable and
accurate manner.
Typically, these dispensers for fluid material are usd in a wide variety of
industries, such
as electronic assembly and repair, form in place gasketing, component assembly
and
sealing, mold making, casting, tool and machine and equipment fabrication and
assembly, SMT repair, and a variety of other uses.
Existing positive displacement dispensing systems of this type are of a rotary
construction, such as the valve disclosed in U.S. Patent No. 5,931,355,
commonly assigned with the present application. Thus, they
are not based on true volumetric positive displacement technology. It would be
advantageous for at least some dispensing applications to utilized metering
valves based
on true volumetric positive displacement technology, which enable the valve to
dispense
from a first meter chamber while the second meter chamber is filling, and vice-
versa.
The result would be continuous operating cycle, with greater dispense cycle
rates
because of the lack of need for a fill or reload period.
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SUMMARY OF THE INVENTION
The present invention comprises continuous operation metering valve based on
true volumetric positive displacement technology. Unlike conventional metering
valves,
the inventive valve uses an innovative dual rack and drive pinion design that
enables the
valve to dispense from one meter chamber while the other meter chamber is
filling. This
provides greater dispense cycle rates because it does not require a fill or
reload period.
With an optional encoder-controlled motor, the inventive metering valve is
capable of
almost unlimited precision dispensing with "on-the-fly" adjustment capability.
The metering valve is easily disassembled and cleaned, using stainless steel
wetted path
components and Teflon seals for the widest range of cheinical compatibility.
An integral electronic board, mounted to the side of the valve, may be
utilized to control
the unique 4-way directional valve and motor direction (when not using a
rotary encoder
control).
The invention, together with additional features and advantages thereof, may
best
be understood by reference to the following description taken in conjunction
with the
accompanying illustrative drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a cross-sectional frontal view of a metering valve constructed in
accordance with the principles of the present invention;
Fig. 2 is a partial cross-sectional view similar to Fig. 1;
Fig. 3 is a partial cross-sectional side view of the metering valve
illustrated in
Figs. 1 and 2;
Fig. 4 is a plan view, in isolation, of a meter rod which forms a part of the
present
invention;
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Fig. 5 is an end view of the meter rod shown in Fig. 4;
Fig. 6 is a back view of a valve block which forms a part of the present
invention;
Fig. 7 is a side view of the valve block illustrated in Fig. 6;
Fig. 8 is an front view of the metering block shown in Figs. 6 and 7;
Fig. 9 is a cross-sectional view of the valve block illustrated in Figs. 6-8,
taken
along lines 9-9 of Fig. 8;
Fig. 10 is a cross-sectional view of the valve block illustrated in Figs. 6-9,
taken
along lines 10-10 of Fig. 8;
Fig. 11 is a schematic plan view of a directional valve which forms a part of
the
present invention;
Fig. 12 is an end view of the directional valve shown in Fig. 11; and
Fig. 13 is a cross-sectional view taken along lines 13-13 of Fig. 11.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now more particularly to the drawings, there is shown in Figs. 1-3 a
continuous metering valve 10 constructed in accordance with the principles of
the
present invention. The valve 10 is advantageously constructed in a modular
fashion, to
include a valve block 12, a meter block 14, and a motor block 16. The valve
block may
be constructed of stainless steel or other suitable material, and comprises in
a preferred
embodiment a tapered bore 18 for receiving therein a tapered directional valve
20. The
valve 20 preferably comprises a 4-way tapered seat valve, of a known
construction, and
is secured within the bore 18 using a nut and washer assembly 22 (Fig. 3).
However,
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alternatively, for example, a 4-way cylindrical seat valve and corresponding
cylindrical
bore could be utilized, and the employment of other known directional valve
configurations is within the scope of the invention as well.
The directional valve 20 is actuated, in the illustrated embodiment, using a
pivot
arm 24 (Fig. 3), which in turn is responsive to a pivot plate 26. An air
cylinder 28 may
be utilized to drive the pivot plate 26, responsive to the actuation of a
solenoid valve (not
shown), driven in turn by commands from a control circuit/switch 30, or other
suitable
means.
The meter block 14 may be constructed, as well, of stainless steel or other
suitable material. A pair of bores 32 in the meter block 14 are adapted to
accommodate
corresponding ones of a pair of meter rods 34. The meter rods 34 each include
a
respective meter tip 36, which is particularly adapted to apply displacement
pressure
against fluid contained in the bore 32 and metering chamber 37 corresponding
thereto.
Such fluid is a fluid to be dispensed, as discussed supra in the background
portion of this
application, and may include, for example, adhesives, epoxies, potting
compounds, SMT
adhesives, two part adhesives, and solder pastes (with solids dispersed
therein), and the
like, or any other desired fluid. The fluid is introduced into the valve 10
via a fluid inlet
port 38 which preferably comprises a female Luer Lock or 10-32 inlet. A
syringe mount
bracket 40 may be employed, to accommodate industrial syringes containing the
fluid to
be dispensed, and to be introduced into the valve through the inlet port 38.
Typically,
such syringes have a fluid capacity of up to 35 cc.
With reference now to the motor block 16, this housing element may be
constructed of tool steel, for example, plated with a hard chrome finish to
provide
improved wear resistance. To the motor block 16 is attached a motor 42, which
may
comprise a 6 watt, 24 VDC gear motor, in one preferred embodiment. The motor
drives
a drive gear 44 in the motor housing 16, which housing also contains a
spur/idler gear 46
and a thrust washer 48.
The upper ends of the meter rods 34, better seen in Fig. 4, are configured as
racks
in a rack and pinion system. In other words, the outer perimeters of the meter
rods 34 in
this region coinprise gear teeth 50 which are adapted to engage corresponding
teeth on
the outer perimeter of the drive gear 44, so that, as in a rack and pinion
system, rotation
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of the drive gear 44 by the motor 42 causes linear actuation of the meter rods
34 in both
an upward and a downward direction. Advantageously, rotation of the motor in a
first
direction will cause the respective meter rods 34a and 34b to move linearly in
opposing
directions, with one moving upwardly and the other downwardly. Then, when an
upper
end of the upwardly moving meter rod 34a, 34b contacts a switch plate 52
disposed at an
upper end of the motor block 16, a limit switch is actuated, which in turn
reverses the
direction of the motor 42. Now, the meter rod 34a, which was moving upwardly,
moves
downwardly, and the meter rod 34b moves upwardly.
In operation, a controlled signal to the drive motor 42 rotates the drive gear
44,
which in turn pushes one of the two racks or meter rods 34 in the dispense
direction
(downwardly) and the other rack or meter rod 34 in the fill direction
(upwardly). The
meter rods 34 are assembled with cup seals to provide a chemically compatible,
positive
fluid seal. This linear rack movement results in positive volumetric fluid
displacement.
Low voltage signals to the motor result in a low dispense rate. Small voltage
signals
result in small shot sizes.
Each side of the dual meter chamber valve preferably holds 1 cc of fluid
volume,
although smaller or larger capacity metering valves may be appropriate for
certain
applications. When one metering chamber 37 and bore 34 empties, the limit
switch on
the switch plate 52 reverses the motor polarity and begins dispensing from the
opposing
metering chamber. Simultaneously with the reverse in motor polarity, the valve
20 is
actuated to an alternate position, so that the other metering chamber is
established in
fluid contact with a fluid outlet 54, which preferably comprises a male Luer
Lock.
A rotary encoder on the motor 42 can provide a closed loop signal that rotates
the
motor in controlled discrete angular movements that result in precise linear
displacement.
A particular advantage of the present invention is the ability to easily
disassemble
the system components for easy maintenance and cleaning. Only three screws
need be
removed to complete the disassembly. Once disassembled, the bores may simply
be
brushed out to clean them.
In alternative embodiments, a disposable path version of the inventive
metering
valve may be employed, wherein the meter block and valve block assemblies may
be
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provided in low cost injection molded plastic for applications where two part
materials
may set up or where clean up is not safe, as with hazardous materials, or not
cost
effective. A stepper motor could be utilized, if desired. Additionally, a
microshot
version can be utilized, using a specialized coupling design, where smaller
meter rod tips
are attached to the standard meter racks.
Accordingly, although an exemplary embodiment of the invention has beenshown
and described, many changes, modifications, and substitutions may be made by
one having ordinary skill in the art without departing from the spirit and
scope of the
invention.
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Representative Drawing