Syringe pump abstract
The invention generally provides the apparatus for liquid delivery
comprising a syringe pump for reactant delivery and a syringe pump
for liquid chase material delivery.
Syringe pump claims
1. A method of liquid delivery comprising delivering reactant material
into a pipe, delivering chase material into said pipe to chase said
reactant material into a reaction vessel wherein a constant combined
volumetric flow rate of reactant and chase material is provided
by acceleration of a syringe pump containing said chase material
at the same time a reactant syringe pump is decelerated and a valve
in said pipe is switched from said reactant material to said chase
2. The method of claim 1 wherein said reactant comprises silver
nitrate solution or alkali metal halide solution and said chase
material comprises water.
3. The method of claim 2 wherein said silver nitrate and metal
halide solution are delivered by separate pairs of reactant and
chase syringe pumps.
4. The method of claim 1 wherein said chase material is sufficient
to push all of said reactant material into said reaction vessel.
5. The method of claim 1 wherein liquid delivery is complete in
less than 30 seconds.
6. The apparatus for liquid delivery comprising a syringe pump
for reactant delivery into a pipe leading to a reactor vessel, a
syringe pump for liquid chase material delivery into said pipe,
and a valve in said pipe adapted to switch from said syringe pump
for reactant delivery to said syringe pump for chase material delivery,
wherein constant combined volumetric flow rate of reactant and
chase material is provided by acceleration of the liquid chase syringe
pump as the reactant syringe pump decelerates and said valve is
switched to said chase syringe pump, and wherein the reactant in
the delivery pipe is chased into the reaction vessel by the chase
liquid from the syringe pump for chase material after said valve
7. The apparatus of claim 6 wherein said syringe pumps are driven
by a linear actuator with DC servo feedback motor and multiaxis
linear motion controller.
8. The apparatus of claim 6 wherein said syringe pump is remote
from the point of addition into the reactor.
9. The apparatus of claim 6 wherein the apparatus comprises four
syringe pumps, two for reactant delivery and two for liquid chase
10. The apparatus of claim 6 wherein the apparatus can complete
reactant delivery in less than 30 seconds.
11. The apparatus of claim 6 wherein the apparatus can deliver
a partial syringe of material.
12. The apparatus of claim 6 further comprising a means for gas
13. The apparatus of claim 6 further comprising a means to blow
the apparatus dry with air or other inert gas.
14. The apparatus of claim 6 further comprising a means for leak
15. The apparatus of claim 6 further comprising a means for temperature
compensation of the reactant delivery.
16. The apparatus of claim 6 further comprising means for controlling
reactant delivery with consideration of reactant density.
17. The apparatus for formation of a silver halide emulsion comprising
a syringe pump for silver ion delivery, a pipe for silver ion delivery,
a syringe pump for water chase material for said silver ion, a syringe
pump for halide ion delivery, a pipe for halide ion delivery, and
a syringe pump for delivery of water chase material for said halide
ion wherein silver ion in said silver pipe for silver halide delivery
is chased into the reaction vessel by water chase material and halide
ion in the halide ion delivery pipe is chased into said reaction
vessel by said water chase material for said halide ion.
18. The apparatus of claim 17 wherein said silver ion comprises
19. The apparatus of claim 17 wherein sid halide ion material comprises
at least one chloride, bromide, or iodide salt.
Syringe pump description
FIELD OF THE INVENTION
This invention relates to precision pumping. It particularly relates
to the delivery of reactants for formation of silver halide emulsions.
BACKGROUND OF THE INVENTION
In the formation of silver halide grains for use in photographic
elements, the reactant materials comprising a silver salt and a
halide salt are brought together with agitation to form the grains.
The formation of silver halide grain requires very careful control.
During nucleation, the reactant materials must be added in such
a manner that uniform nuclei are formed. These reactant materials
must be added in accurate and precise quantities, and at accurate
and precise rates in order that grains with the desired properties
are formed. These grains must subsequently be grown without renucleation
in order to produce uniform emulsions suitable for photographic
Present reactant delivery systems use recirculating pumps, typically
either speed controlled gear/lobe pumps or constant speed centrifugal
pumps with control valves. The flow is monitored by either a mass
flow meter or volumetric flow meter, and flowrate is controlled
by varying the speed and/or control valve position in response to
a control algorithm which compares the measured flowrate with a
setpoint. Flow is typically diverted from the recirculation mode
to the reaction vessel by means of ball valves, plug valves, or
other suitable valves. In such a typical system, fluid which is
at rest in the piping to the reaction vessel must be accelerated
when the flow is diverted from the recirculation mode to the reaction
There are several deficiencies with the present system for delivering
reactants for the nucleation of silver halide grains. One disadvantage
of such a system is that pressure transients are formed as valves
are switched. These transients are caused by changes in the effective
discharge coefficient of the valves as they turn, the momentum change
as the fluid at rest is accelerated, and differences in flow resistance
between the recirculation piping and the piping to the reaction
vessel. These pressure changes directly affect the flowrate of the
recirculating pump, and the feedback control system can't react
quickly enough to maintain a precise, uniform flowrate. Another
disadvantage of the present system is that timing variability exists,
caused by imprecise valve switching and inherent time lags in many
digitally controlled systems. As a result, the instantaneous flowrate
relationship of the two reacting streams may vary considerably,
and the total delivery amount will vary, especially for deliveries
of short duration. Lesser concerns include the inaccuracies of flowrate
measurement, the presence of pump pulsations, and the difficulties
associated with flow control loop tuning.
New precipitation techniques require delivery of reactant materials
to the reaction vessel during nucleation periods whose duration
is less than 30 seconds, sometimes as little as 4 seconds or even
less. While the disadvantages of the present reactant delivery system
may be of marginal significance for nucleation periods of one minute
or more in most current silver halide emulsions, these disadvantages
become severe limitations as nucleation periods of 4 seconds or
shorter are explored in these new precipitation techniques.
In U.S. Pat. No. 5194887 Farling et al discloses a system wherein
syringe pumps are utilized for the delivery of the constituents
of an emulsion (note column 5 and FIG. 2). In U.S. Patent No. 4921133
Roeser discloses a system wherein syringes are utilized for the
delivery of chemical reactants. However, the above systems, and
most others, are small in size and achieve accurate total delivery
by injecting the precharged reactants into the reaction vessel at
very close proximity.
PROBLEM TO BE SOLVED BY THE INVENTION
There is continuing need for a system for the delivery of reactants
for silver halide grain formation that will generate accurate and
precise delivery (both total delivery and flowrate) of reactants
over a very short duration from a remote location. Further, there
is a need for the system that is insensitive to pressure transients
and momentum changes during reactant delivery to the reaction vessel.
There is a need for a system capable of delivering a preset quantity
of reactants precisely and accurately from a remote location.
SUMMARY OF THE INVENTION
An object of the invention is to overcome disadvantages of the
prior system for delivering reactants for silver halide grain formation.
Another object of the invention is to provide accurate and precise
chasing of the reactants remaining in the process piping between
the remotely located syringe pump and the addition point(s) in the
Another object of the invention is to provide better control of
the emulsion precipitation process by providing accurate and precise
delivery of reactants into the reaction vessel, particularly during
nucleations of short duration.
These and other objects of the invention generally are accomplished
by providing apparatus for liquid delivery comprising a syringe
pump for reactant delivery and a syringe pump for liquid chase material
ADVANTAGEOUS EFFECT OF THE INVENTION
The invention allows the rapid, accurate, and precise delivery
of reactant materials from a remote location into a reactor.
BRIEF DESCRIPTION OF DRAWINGS
FIGS. 1-11 are schematic views of the apparatus of the invention
performing a delivery cycle for reactants.
FIG. 12 is a graph which shows that the combined delivery flowrate
for reactant and water chase is constant.
DETAILED DESCRIPTION OF THE INVENTION
The invention has numerous advantages over the prior art. The invention
allows nucleation of silver halide emulsion batches with short duration
of delivery, such as four seconds or even less. The use of a water
chase to follow the reactant material into the emulsion making reaction
vessel ensures that the entire amount of reactant delivered by the
pump is delivered into the reaction vessel. The uniform and precise
delivery of the reactants to the reaction vessel for silver halide
grain formation produces more uniform grains, thereby allowing more
uniform photographic products. The grain morphology is more repeatable
and, therefore, grain properties are more uniform. In addition to
allowing short duration delivery for nucleation, the method of the
invention allows uniform delivery during growth of silver halide
grains, also contributing to the formation of uniform grains. The
invention utilizes the water chase to ensure delivery of all reactant
and allows the location of the syringe pump for the reactants to
be distant from the reaction vessel where silver halide is formed.
This allows more convenient location of the syringe pump cylinders,
pistons, and drives for manufacturing and maintenance. The system
of the invention utilizes four syringe pumps for delivering two
reactive components, as two syringe pumps are required for each
reactant. However, the system requires low maintenance, as each
reactant syringe pump requires only one seal. The system of the
invention makes practical the construction of large syringe pump
systems for emulsion formation (such as 300 to 600 gallon reaction
vessels) with accurate delivery using a low maintenance system.
Further, the delivery is uniform and ensures that all intended reactants
are delivered to the reaction vessel. These and other advantages
will become apparent from the detailed description below.
In the present application, as in many manufacturing applications,
equipment is large and cannot be located in close proximity to the
mixing region within the reaction vessel. Considerations, such as
the large volume of reactant to be delivered, the high flowrates
of the delivery, and the high pressure that is developed during
delivery, force the syringe cylinder/piston to be located remotely
from the reaction vessel. In this application, a remote location
of the syringe pump relative to the reaction vessel is defined as:
the syringe pump cylinder/piston being located beyond the confines
of the reaction vessel itself, and having piping connecting the
syringe pump outlet to the reactant addition point(s) within the
reaction vessel. The above-referenced U.S. patents for syringe delivery
systems produce very accurate and precise total delivery. In contrast,
the present invention makes possible both accurate and precise total
delivery and accurate and precise delivery flowrate. The present
invention also sets forth a system capable of operating over a wide
range of flowrates, total delivery volumes, and system pressures.
This invention describes a device and the control of the operation
of that device for the metering of reactants into an emulsion precipitation
reactor. The unit preferably consists of two sets of two syringe
pumps and their associated piping, valving, reactant supply vessels,
and various monitoring and control devices. The syringe pumps consist
of precision honed cylinders, each with a piston which is driven
by a high precision linear actuator. Each of the reactants to be
delivered to the reactor requires two syringes; one syringe pushes
a reactant into a pipeline to the reaction vessel, and the second
syringe follows the first, pushing water (liquid chase material)
at the same volumetric flowrate as the reactant in order to push
the reactant into the reaction kettle. A four axis, linear motion
controller accurately controls the absolute and relative motion
of all of the syringes. By using this device, a small amount of
two different reactants can be delivered from a remote location
very accurately and precisely.
The operation of the apparatus of the invention will become clear
from the description of FIGS. 1-11. As shown in FIG. 1 the apparatus
is being filled with water entering from pipe 12 where it passes
into pipes 14 and 16 passing through the water syringe 18 and reactant
syringe 20. The water entering from 12 then is utilized to fill
vessel 22 with water. Valve 24 is then closed.
The process continues at FIG. 2 with filling of water syringe 18.
With valves 26 and 28 closed, piston 32 of water syringe 18 is withdrawn
to fill the water syringe 18 with water 34. The water is withdrawn
from vessel 22.
The process of apparatus use continues in FIG. 3 with extraction
of excess water from vessel 22 by withdrawal of the piston 36 of
reactant pump 20 to remove water from vessel 22 after which valve
38 is closed. In FIG. 4 it is shown that piston 36 is moved into
the reactant syringe 20 to eject the water through valves 28 and
40 into drain line 42. Ideally, valve 28 is located in close proximity
to reactant syringe 20
As shown in FIG. 5 valve 44 is now open, allowing air to purge
reactant syringe 20 and line 16 to drain line 42. Also in FIG. 5
reactant 46 has been added to vessel 22 either from a supply tank
through valve 45 by manual addition.
In FIG. 6 is illustrated the filling of reactant syringe 20 by
withdrawing piston 36 after opening valve 38 and closing of valve
44. Reactant 46 thereby fills reactant syringe 20.
In FIG. 7 piston 36 of reactant syringe 20 is brought forward
after valves 28 40 and 42 have been opened to expel sufficient
reactant to fill line 16 with reactant. Then valves 28 and 40 are
closed. FIG. 8 illustrates the apparatus of the invention ready
to deliver reactants to reactor 52. Reactant is in pipe 54 while
water is in pipes 56 58 and 62.
FIG. 9 illustrates reactant delivery wherein piston 36 is brought
forward in syringe pump 20 after valve 64 has been opened, and valve
66 has been poitioned for delivery to reactor 52.
FIG. 10 illustrates that immediately after reactant syringe 20
has completed ejection of reactant by moving of piston 30 piston
32 in water syringe 18 is moved forward to eject water to chase
reactant from pipes 58 and 62. Valve 65 is opened to allow the water
to enter into pipe 58.
FIG. 11 illustrates the system after delivery. It is apparent from
the system illustrated that reactant material of the quantity ejected
by piston 36 of reactant syringe 20 was delivered to the reaction
vessel in a rapid, precise, and accurate manner. It is noted that
valves 65 and 64 are located in very close proximity to pipe 58
insuring that all reactant injected into pipe 58 by syringe pump
20 is pushed by the water from syringe pump 18 into reactor 52.
With reference to FIG. 12 it is shown that the combined volumetric
flowrate of the reactant and water chase remains constant, as the
controls are set to accelerate the water piston at the same time
that the reactant piston starts to decelerate. This produces a constant
volumetric flowrate of delivery. This crossover profile requires
that both valves 64 and 65 be open simultaneously during the crossover
FIGS. 1-11 depict the basic steps in the operation of the syringe
pump system. FIGS. 2 6 9 and 10 show the most important steps.
For clarity only half of the total system is shown; the other half
is identical. One half delivers silver nitrate solution, and the
other half delivers alkali metal halide solution, the basic reactants
for making a photographic emulsion. FIGS. 2 and 6 show how the water
and reactant are drawn into their respective syringes; as can be
seen, both water and reactant use the same holding vessel, although
separate vessels could be used by varying the piping configuration.
Water is added to the jar 22 through appropriate valving from a
piped high purity water source; reactant is added to the vessel
manually or through valve 45 from a supply vessel (not shown). The
water syringe draws in an amount of water equal to approximately
2 1/2 times the piping volume to be chased to the reaction vessel
(FIG. 2); the reactant syringe draws in an amount of reactant equal
to the amount to be delivered to the reaction vessel plus an amount
in excess of the volume of the piping between the reactant syringe
20 and the vessel 22 (FIG. 6). Prior to delivery all air is displaced
out of the system. The system is now ready for delivery of reactants
when it is called for by the process control computer (FIG. 8).
When delivery is initiated, the silver nitrate and alkali metal
halide solution syringes start simultaneously and accelerate to
full speed in a short, precise time period, such as 1/10 second,
whereupon they are pushed at a constant formula flowrate into the
reaction vessel (FIG. 9); when the formula amount has been delivered,
the reactant syringes then decelerate to zero velocity in 1/10 second.
As the reactant syringes begin to decelerate, the water chase syringes
accelerate in 1/10 second to the same formula flowrate and push
the reactants remaining in the piping totally into the remote reaction
kettle (FIG. 10). The precisely controlled crossover of reactant
to water syringes results in a cumulative constant flow of reactants
(FIG. 12). If FIG. 8 is compared to FIG. 11 it can be seen that
the only difference is the amount that the syringe pistons have
moved; this amount is exactly the amount called for by the formula,
and all of this reactant amount has been pushed at a precisely controlled
rate in the reaction vessel. There may be other steps in the overall
operation which have not been illustrated; these other steps may
include flushing, draining, air removal, air testing, leak testing,
and temperature compensation.
The apparatus of the invention may be utilized in formation of
any silver halide grains. Further, the utilization of this system
for delivery of the silver and halide reactants does not exclude
the use of other systems for addition of photographically useful
materials such as other silver or halide salt solutions, dopants,
or pH adjusters to the emulsion forming reaction vessel. As discussed
above, two generally matching systems will generally be utilized,
one for delivery of halide and the other for silver. However, the
system may also be utilized in a single jet system where one of
the reactants is already in the reaction vessel, and the other one
is delivered by the apparatus of this invention.
The apparatus of the invention is believed to be suitable for any
silver halide emulsion grains. Typical of such grains are those
disclosed in Section I of Research Disclosure 36544 of September
While this invention has been described specifically with respect
to the formation of emulsions, it is useful for other reactant delivery
processes. It is particularly desirable for those processes where
precise control of reactant delivery must be maintained. While it
is illustated with water as the liquid chase material to purge the
piping of reactants, it is clear that in other reactant processes,
other materials serving as a medium for reaction could be utilized
as the chase liquid. The liquid chase material is any lqiuid that
serves as a reaction medium for the reactants. Other processes where
the apparatus could be used would consist of any other chemical
reactions where the final product is dependent on accurate and precise
delivery of reactants.
The system of the invention utilizes linear actuators as a means
to push the pistons in the syringe pumps. Linear actuators convert
rotary motion to linear motion through the interaction of a rotating
wall screw and a recirculating ball carrier. The carrier is attached
to the linear actuator shaft which becomes the piston rod. The linear
actuator is driven by a DC servo feed back motor. A resolver on
the motor generates thousands of pulses for every revolution of
the motor. The multi-axis linear motion controller reacts to the
generation of the rate and quantity of these pulses to provide accurate
and precise motion control. Since this is a multi-axis controller,
each of the systems syringes can be controlled accurately and precisely
relative to each other, as well as in absolute terms.
The means for the detection of the presence of air in the system
utilizes the difference in compressibility of gases and liquids.
The test for air in the system is done after the syringe pumps and
piping are filled with liquid. After closing all system valves,
the piston is moved forward a small set amount; if there is no air,
a specific pressure will be recorded. If there is even a very small
quantity of entrained air, the presssure will be much lower. An
alternative means is to record pressure as the piston is moved.
If there is no air, the pressure level will increase linearly with
position. It will be non-linear if any air is present.
The means for determination of leaks is similar to the air test
except that the pressure developed after a specific piston movement
is completed is evaluated after a hold period. If the developed
pressure holds constant, there are no leaks; if it falls, there
are leaks in the system.
Temperature and/or density compensation is accomplished automatically
by measuring the reactant temperature just prior to delivery using
an RTD. The actual temperature is used to adjust the volumetric
flowrate and total delivery amount, in order to assure the correct
molar addition rate and amount. In order to accomplish this on-line
correction, the syringe must be over prepped, and the delivery completed
with a portion of the over prep remaining in the syringe pump.
The invention has been described in detail with particular reference
to preferred embodiments thereof, but it will be understood that
variations and modifications can be effected within the spirit and
scope of the invention.