 |
Description  |
|
|
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to a method and apparatus for
mixing chemicals and, more particularly, to a small, preferably portable,
system for mixing non-reactive chemicals.
Description of the Related Art
Many industries worldwide use chemicals to perform a wide variety of tasks.
In fact, chemical consumers range from a typical homekeeper who purchases
basic cleaning supplies to multi-national energy producers who require
customized chemicals for the various stages of energy production.
Historically, these larger chemical users have purchased chemicals in
bulk. Thus, the chemical companies that supply these industries with
chemicals have made the various chemical blends in large batches.
These larger chemical users often desire thousands of different blended
chemicals. For example, oil refineries use custom-blended corrosion
inhibitors in their processing plants to provide maximum corrosion
protection for prolonging the life of the processing plants. Therefore, a
chemical company may be required to stock hundreds of different
intermediate chemicals, concentrates, or solvents, in order to produce
these blended chemicals.
A typical device for blending chemicals includes a large vat capable of
holding in excess of ten thousand pounds of chemicals. Large agitators are
placed inside the vat to mix the chemicals that are added to the vat. A
plurality of lines feed chemicals into the vat. One end of a line is
coupled to the vat, and the other end of the line is coupled to a
container holding a chemical to be added to the mix. Pumps, coupled to the
lines, draw the chemicals through the lines from the containers to the
vat. The amount of chemicals added to the vat is controlled by mass flow
meters, which are connected to the lines, or by determining the weight of
the chemicals added to the vat.
Once the large batch of chemicals has been thoroughly mixed in the vat, a
sample is removed and taken to a laboratory for testing. The testing may
vary depending on the type of blended chemical desired. However, typical
testing may include measuring the density of the blended chemical or
taking the FTIR fingerprint of the chemical. If the blended chemical
passes the test, it is packaged into appropriate containers and shipped to
the customer. If not, the blended chemical must be further tested to
determine the percentages of the individual chemicals which comprise the
blended chemical. Then, it must be determined how the blended chemical can
be reworked in order to produce the desired blend. Finally, the proper
amounts of additional chemicals must be added to the blend to achieve the
desired blend. Once reworked, the blended chemical may be packaged and
shipped to the customer.
After a particular chemical blend has been packaged, i.e., removed from the
mixing vat, the entire mixing device must be cleaned out. The clean out
procedure typically includes flushing the lines and rinsing the vat. Next,
the device must be set up in order to mix a different blend. This set up
procedure may include connecting different lines to the vat, connecting
the appropriate measuring devices to the lines or the vat, and connecting
the lines to the appropriate chemical containers. After set up, the device
charges chemicals into the mixing vat one at a time. Typically, the
charging is performed manually with operators viewing the measuring
devices and controlling the flow of chemicals through manually-operated
valves. After the charging has been completed, the agitators mix the
chemicals in the vat, and the inspection process is repeated, as set forth
above.
The method and device set forth above suffer from many problems. First, the
vat and agitators used to make large batches cannot make small batches. A
small batch will not immerse the agitators, and, thus, the agitators are
rendered ineffective. Second, the mass flow meters used to monitor the
amount of chemical being charged through the line are expensive.
Furthermore, since the chemicals being charged may exhibit widely varying
densities or viscosities, the flow meters tend to provide inaccurate
information or to require frequent recalibration. Third, operators follow
a written procedure to mix each batch. Thus, human error poses a
continuous problem. Fourth, the required quality testing may add ten
percent or more to the final cost of the blended chemical. Providing a
laboratory and a staff of chemists requires significant overhead.
Furthermore, the process often requires rework to prevent waste. Rework is
not only expensive, but time consuming. Fifth, the fact that operators
manually control the charging process inherently introduces undesirable
inaccuracies. Although a skilled operator may minimize these inaccuracies,
the use of human judgment and manual operation remains a problem. Finally,
the cleaning of the device wastes chemicals. Moreover, the chemicals
removed from the device during its cleaning require disposal. This
disposal is already quite expensive, and is becoming even more expensive
with the increasing amount of government regulation.
The present invention is directed to overcoming, or at least reducing the
effects of, one or more of the problems set forth above.
SUMMARY OF THE INVENTION
The method and apparatus disclosed herein offer one or more of the
following advantages over the prior art. The invention decreases
manufacturing costs and eliminates operator error. Since the blended
chemicals produced by the invention are statistically proven, little
inspection is necessary. Furthermore, there are fewer incorrectly blended
chemicals, so most rework is eliminated. Since the hydraulic pumps
reverse, chemicals in the lines are returned to their respective
containers, thus eliminating waste and the costs and hazards associated
with the disposal of chemical waste.
The invention also decreases distribution costs. Since the agitator is
adapted for mixing chemicals in a typical shipping vat, once the agitator
is removed, the vat need only be sealed prior to shipping. The apparatus
is small, and preferably portable, so that it may be located at various
sites at relatively little expense in order to save freight costs.
Moreover, since the invention is capable of mixing an average blend in
less than an hour, typically using widely available intermediate
chemicals, concentrates and solvents, warehouse, handling, and inventory
management costs are greatly reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other advantages of the invention will become apparent
upon reading the following detailed description and upon reference to the
drawings in which:
FIG. 1 illustrates an apparatus for blending chemicals, in a non-blending
position, in accordance with the present invention;
FIG. 2 illustrates the device of FIG. 1 in a blending position;
FIG. 3 illustrates a side view of a truck on which the apparatus
illustrated in FIG. 1 may be carried in accordance with the present
invention;
FIG. 4 illustrates a side view of a skid platform in accordance with the
present invention;
FIG. 5 illustrates an end view of the skid platform illustrated in FIG. 4;
FIG. 6 is a schematic diagram of a manually operated chemical blending
apparatus in accordance with the present invention;
FIG. 7 is a schematic diagram of a computer-controlled apparatus for
blending chemicals in accordance with the present invention;
FIG. 8 is a block diagram illustrating the computer controlled device for
controlling the apparatus illustrated in FIG. 7;
FIG. 9 is a schematic diagram illustrating the key pad and digital input of
the device illustrated in FIG. 8;
FIG. 10 is a schematic diagram illustrating the digital output of the
device illustrated in FIG. 8;
FIG. 11 is a schematic diagram illustrating a load cell coupled to the
analog input of the device illustrated in FIG. 8;
FIG. 12 illustrates the power supply for the computer-controlled apparatus;
FIGS. 13A and B illustrate display screens in accordance with the present
invention;
FIG. 14 illustrates a first portion of a flowchart describing the operation
of the blending system;
FIG. 17A illustrates a second portion of the flowchart describing the
operation of the blending system;
FIG. 17B illustrates a third portion of the flowchart describing the
operation of the blending system;
FIG. 18 illustrates a fourth portion of the flowchart describing the
operation of the blending system;
FIG. 19 illustrates a fifth portion of the flowchart describing the
operation of the blending system;
FIG. 20 illustrates a sixth portion of the flowchart describing the
operation of the blending system;
FIG. 15 is a truth table that links the flowchart with the apparatus
illustrated in FIG. 7; and
FIG. 16 is a table that re-defines elements of FIG. 7 for the truth table
of FIG. 15.
While the invention is susceptible to various modifications and alternative
forms, specific embodiments have been shown by way of example in the
drawings and will be described in detail herein. However, it should be
understood that the invention is not intended to be limited to the
particular forms disclosed. Rather, the invention is to cover all
modifications, equivalents and alternatives following within the spirit
and scope of the invention as defined by the appended claims.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to the drawings and referring initially to FIGS. 1 and 2, an
apparatus for blending chemicals is illustrated and generally designated
by the reference numeral 10. The apparatus 10 may be directly mounted onto
a vehicle, such as the truck 14 illustrated in FIG. 3. So mounted, the
apparatus 10 may serve as a mobile chemical blending unit. However, the
apparatus 10 is preferably mounted on a skid 12 to facilitate
transportation of the apparatus 10, since the apparatus 10 and the skid 12
may be mounted onto the truck 14. While this too could serve as a mobile
blending unit, the fact that the apparatus 10 is mounted on the skid 12
facilitates the removal of the apparatus 10 and skid 12 for placement in a
desired plant location.
The apparatus 10 includes a blending auger 16 that is coupled to a moveable
mast 18. The mast 18 is hydraulically controlled and moveable between an
upper, non-blending position, as illustrated in FIG. 1, and a lower,
blending position, as illustrated in FIG. 2. In addition to the auger 16,
the mast 18 also carries two hoses 20 and 22. The hoses 20 and 22 are
connected to respective charge pumps 24 and 26. Preferably, the hose 20
and the charge pump 24 are dedicated to water-based chemicals, and the
hose 22 and charge pump 26 are dedicated to oil-based chemicals. In
addition, another hose 25 and another pump 27 (shown in FIGS. 6 and 7) may
be added as a spare or to be used with another class of chemicals, such as
paraffin-based chemicals.
The hoses 28 and 30, connected to the other end of the charge pumps 24 and
26, respectively, deliver chemicals to the apparatus 10 from appropriate
containers 32, 34, 36, and 38. It should be understood that the apparatus
10 is quite versatile in regard to its chemical supply. While the hoses 28
and 30 may be coupled to the large containers 32-38 in a warehouse or
outdoor facility, the ends of the hoses 28 and 30 may also be immersed in
smaller, portable containers 40, 42, 44, 46, or 48, which may be mounted
on the truck 14 with the apparatus 10 or which may be otherwise available.
Regardless of where and how the chemicals to be mixed are stored, the
charge pumps 24 and 26 draw them through the respective hoses 28 and 30
and deliver them into a vat 50 through the hoses 20 and 22, respectively.
Preferably, the apparatus 10 uses two mixing vats 50 and 52, the vat 50
being used to mix water-based chemicals, and the vat 52 being used to mix
oil-based chemicals. Although, as illustrated, the vats 50 and 52 sitting
side by side are approximately the same width as the apparatus 10, an
additional mixing vat (not shown) may be added for other types of
chemicals, such as paraffin-based chemicals. In this situation, however,
it may be preferable to use smaller mixing vats in order to limit the
overall width of the apparatus 10. While this may not be a significant
concern in warehouse operations, it is often desirable to limit the size
of the apparatus 10 when it is mounted onto the vehicle 14.
The mast 18 that carries the blending auger 16 is preferably moveable
between the vats 50 and 52. Therefore, the mast 18 not only moves the
auger 16 in the vertical direction, but also horizontally. Of course, it
may be desirable to operate the apparatus 10 in an assembly line. In this
situation, the mixing vats would be serially fed through the apparatus 10.
For instance, the vats may be placed on a conveyor that sequentially
delivers an empty vat under the auger 16. After chemicals have been
charged into the vat and blended, the auger 16 is raised so that the
conveyor may move the vat of blended chemicals from beneath the auger 16
and replace it with another empty vat. In such an operation, the mast 18
would only be required to move the auger 16 vertically, not horizontally.
Preferably, the apparatus 10 operates under computer control. As
illustrated in FIGS. 1 and 2, the apparatus 10 includes a computer 54,
which is shown as being encased for protection, and an operator interface
56. Moreover, since the apparatus 10 is preferably adapted for use in
either a warehouse or a portable environment, the apparatus 10 preferably
includes a dual voltage system. As will be explained subsequently, the
electrical components of the apparatus 10 preferably operate on 12 volt DC
so that the battery on the truck 14 will power them. However, the
apparatus 10 preferably includes a 240 volt AC to 12 volt DC converter 58
for warehouse applications.
As previously stated, the apparatus 10 is preferably skid-mounted to
facilitate warehouse or portable applications. The preferred embodiment of
the skid 12 is illustrated in FIGS. 4 and 5. The skid 12 includes a base
60 that is adapted to support the apparatus 10 in the warehouse or
portable environments. Extending upward from and perpendicular to the base
60 is a mast support 62. At the upper end of the mast support 62 is a
horizontally extending arm 64 which supports the auger 16. The mast
support 62 also supports two pipes 66 and 68. The pipes 66 and 68 are
coupled between the hoses 20 and 22, respectively, and the charge pumps 24
and 26, respectively. The skid is preferably 12 feet long, 5 1/2 feet
wide, and 8 feet high (with the mast 18 in its lowered position).
Since hydraulics preferably operate the auger 16 and the mast 18, the base
60 also supports a hydraulic oil tank 70. The schematic diagrams
illustrated in FIGS. 6 and 7 show how the tank 70 is coupled to the
hydraulic system. A hydraulic motor support 72 and a pump support 74 are
also carried by the base 60. The hydraulic motor support 72 couples the
motor (98 or 170) associated with the tank 70 to the skid 12. The pump
support 74 couples the charge pumps 24, 26, and 27 and the discharge pump
150 (see FIGS. 6 and 7) to the skid 12.
The apparatus 10 may be either manually operated or computer-controlled.
Each offers advantages over the other. For instance, the manually operated
apparatus 10, as schematically illustrated in FIG. 6, costs far less than
the computer-controlled apparatus 10, illustrated schematically in FIG. 7.
However, the computer-controlled apparatus 10 is still the most preferable
embodiment due to the statistically high repeatability of its operation
and of the blends produced. However, since both offer distinct advantages
over the prior art, both of the embodiments of the apparatus 10 will be
described herein.
FIG. 6 illustrates the manually operable embodiment of the apparatus 10.
Hydraulic fluid is supplied to the apparatus 10 via the hydraulic oil tank
70. A motor 98 and pump 102 pump fluid from the tank 70 through a line 104
into a pressure relief valve 94. Preferably, the motor 98 is a 5
horsepower, 240 VAC, three-phase, electric motor that produces an
operating pressure for the apparatus 10 of about 600 psi. If the pressure
becomes too high, such as above about 1000 psi, fluid flows through a line
106 to a flow divider 108. The fluid then flows in return line 110,
through a filter 111, back to the tank 70. Fluid flows to the rest of the
apparatus 10 through the valve 94 on the line 112. The line 112 is coupled
to a pump control valve 80, which preferably has two fluid outlets, which
are connected to lines 115 and 117. Fluid flows through the line 115 into
a manual control valve 114. Fluid exits the valve 114 on the line 116 and
enters the hydraulic cylinder 118 of the mast 18. The fluid pressure
causes the hydraulic cylinder 118 to extend and, thus, raise the mast 18.
The fluid returns through the line 120 to a divider valve 122 and, then,
returns to the divider valve 108 through the line 124. The valve 114
allows the fluid on line 116 to be manually controlled. Fluid not diverted
into line 116 is diverted back to the divider 122. Thus, the mast may be
raised or lowered using the manual control valve 114.
Initially, the mast 18 is raised so that the auger 16 rests above the vat
50 when chemicals are being charged into the vat 50. To charge chemicals
from a first container (not shown) that is coupled to line 28, an operator
actuates a control lever 82 on the pump control valve 80. The control
lever 82 controls the hydraulic fluid flowing through a control valve 126
which is coupled to the charge pump 24. Fluid flows into and out of the
valve 126 through lines 128 and 130, respectively. The chemicals are
pumped by the charge pump 24 through the line 20 and into the vat 50.
The vat 50 rests on a load cell 132, such as a commercially available load
cell produced by Pennsylvania Scale Co. The load cell 132 includes a
display 134, which is preferably calibrated to display the weight of the
chemicals in the vat 50. In other words, the display is calibrated so that
the weight of the vat 50 is subtracted from the total weight on the load
cell 132. Preferably, the load cell 132 is calibrated by placing a known
weight on the cell and determining whether the display 134 accurately
displays the proper weight. Preferably, the load cell 132 is designed to
display weights up to 5000 pounds. However, the apparatus 10 is designed
to operate where the total weight on the load cell 132 never exceeds 2500
pounds. It has been found that testing the low end of this range using a
50 pound known weight will properly calibrate the load cell 132. In other
words, if the load cell 132 is accurate in its lower range, it is accurate
in its upper range also.
The signals from the load cell 132 are preferably filtered so that the
weight displayed on the display 134 does not fluctuate wildly. It will be
appreciated that the display 134 could not otherwise display the accurate
weight of the chemicals in the vat 50, because the chemicals falling into
the vat 50 and splashing around tends to obscure the determination of the
actual weight. The filter, therefore, filters out fluctuations produced as
the chemicals fall into the vat 50, so that the signal displayed on the
display 134 provides a more accurate indication of the actual weight of
chemicals in the vat 50. One particular filter suited for this purpose is
the HI2151/20 weight controller with "Waversaver" filtering available from
Hardy Instruments of 9440 Carol Park Drive, San Diego, California.
The operator views the display 134 and controls the chemicals being charged
into the vat 50 by carefully actuating the control lever 82. Precise
operator control is particularly important when the amount of the chemical
being charged into the vat 50 approaches the desired amount. Once the
desired amount of chemical has been charged into the vat 50, the operator
actuates the control lever 82 to reverse the charge pump 24. The charge
pump 24 pumps the chemicals back through the line 20 and back into the
container through the line 28. Thus, the line 20 is automatically cleaned
out, without any waste of chemicals, so that the line 28 can be attached
to another container of chemicals to be charged into the vat 50.
As previously mentioned, each charge pump 24, 26, and 27 is preferably
dedicated to a particular type of chemical. Thus, if the second chemical
to be charged into the vat 50 is incompatible with the particular type of
chemical dedicated to the charge pump 24, the charge pump 26 or 27 is
used. The operation of these charge pumps 26 and 27 is virtually identical
to the operation of the charge pump 24 as just described. The control
lever 84 controls the hydraulic fluid flow to valve 136 via lines 138 and
140. The valve 136 controls the speed and direction of charge pump 26.
Therefore, the line 30 can be connected to a container (not shown), and
charge pump 26 will pump chemicals from the container, through line 30,
through line 22, and into the vat 50. Once the charging is complete, the
operator may actuate control lever 84 to reverse the charge pump 26 so
that chemicals in the line 22 will be pumped back through line 30 and into
the container. Similarly, the control lever 86 controls the fluid flow
through the valve 142 via lines 144 and 146. The line 31 is connected to a
container (not shown), and the charge pump 27 pumps chemicals from the
container through line 31, through line 25 and into the vat 50. Like the
charge pumps 24 and 26, the pump 27 may be reversed using the control
lever 86, so that chemicals in the line 25 are pumped back through line 31
and into the container.
It should also be noticed that the lines 20, 22, and 25, which deliver
chemicals to the vat 50, are grounded via lines 160, 162, and 164,
respectively. The chemicals pumped through the lines 20, 22, and 25 may
carry electrostatic charges. Therefore, it is desirable to provide a
ground path or each of the lines 20, 22, or 25 to dissipate these charges.
As will be subsequently described, the apparatus 10 may be automatically
shut off if one of the ground lines 160, 162 or 164 fails.
Once the necessary chemicals have been charged into the vat 50, the control
levers 82, 84, 86 and 88 are returned to their neutral positions, and the
mast 18 is lowered to place the auger 16 in the vat 50. Fluid may now flow
through the outlet line 117 to the manual control valve 119. Fluid exits
the valve 119 on the line 163 and enters the mixer motor 161. The fluid
pressure causes the mixer motor 161 to rotate the auger 16. The fluid
returns through the line 165 to a divider valve 90 and, then, returns to
the divider valve 108 through the line 124. The valve 119 allows the fluid
on line 163 to be manually controlled. Fluid not diverted into line 163 is
diverted back to the divider 90. Thus, the auger 16 may be controlled
using the manual control valve 119.
Finally, the control lever 88 controls fluid flow through a valve 148 that
is coupled to a discharge pump 150. Fluid is delivered to and received
from the valve 148 via lines 152 and 154, respectively. As illustrated, a
line 156 couples the discharge pump 150 to a lower portion of the vat 50.
Thus, after the chemicals in the vat 50 have been mixed, the operator may
actuate the discharge pump 150 to remove chemicals from the vat, and
deliver the chemical, via line 158, to an appropriate container.
Alternatively, if the vat 50 is the shipping container for the blended
chemical, it is removed, sealed, and shipped. Then, another empty vat 50
is placed under the auger 16.
It is important to note that the control of the entire apparatus 10 is
centered about the pump control valve 80. When any of the pumps are in
use, the outlet lines 115 and 117 receive virtually no fluid pressure.
Therefore, the mast 18 and the auger 16 are effectively disabled while
chemicals are being charged into the vat 50.
FIG. 7 illustrates the computer-controlled embodiment of the apparatus 10.
Similar elements will usually be numbered using the same reference
numerals found in the previously discussed figures. Unlike the manually
operable embodiment illustrated in FIG. 6, the computer-controlled
embodiment illustrated in FIG. 7 requires very little operator
interaction. However, before discussing the computer control, the
hydraulic circuit and chemical delivery circuit used with the computer
control will be discussed with reference to FIG. 7.
Hydraulic fluid is supplied to the apparatus 10 via the hydraulic oil tank
70. A motor 170 drives a pump 172, which is coupled to the tank 70 via
line 174. The pump 172 delivers fluid to the apparatus 10 via line 176. A
return line 178, which includes a pressure relief valve 180, returns fluid
to the tank 70.
An on-off solenoid dump valve 182 delivers hydraulic fluid to the rest of
the circuit via lines 184 or 186. As illustrated, in its de-energized
state, the solenoid dump valve 182 delivers fluid to the mast control
valve 188 via line 186. To raise the mast 18, the control lever 190 of the
mast control valve 188 is actuated to produce hydraulic fluid flow through
line 186 to the hydraulic cylinder 118. Fluid returns to the valve 188
through line 192 and to the tank 70 through a filter 194. To lower the
mast 18, the control lever 190 is actuated to provide a cross flow between
lines 186 and 192. This reverses the flow of hydraulic fluid in the lines
186 and 192, thus lowering the mast 18 by retracting the hydraulic
cylinder 118.
When the solenoid dump valve 182 is energized, hydraulic fluid is diverted
away from the mast control valve 182 and delivered to a two-speed circuit
196. The two speed circuit 196 delivers hydraulic fluid via line 210 to
the charge pumps 24, 26, and 27 and to the discharge pump 150. The two
speed circuit 196 adjusts the flow of hydraulic fluid to these pumps so
that the pumps may operate at a high speed when a large quantity of
chemical is left to be charged or discharged, and at a slow speed when the
amount of chemical to be charged or discharged approaches the desired
amount.
The two-speed circuit 196 includes an on-off solenoid valve 198 connected
in parallel with a flow control solenoid valve 200. A pressure release
pilot valve 202 is connected in series with the on-off solenoid valve 198.
A metering valve 206 and a check valve 208 are also connected in parallel
with the flow control valve 200. When the pilot valve 202 is energized,
the two-speed circuit 196 operates the selected pump in its "fast" mode.
Fluid flows through the flow control valve 200 on the line 210 to the
pumps. Any excess fluid is diverted through the line 211 to the energized
pilot valve 202, which diverts the fluid to the return line 204. When the
pilot valve 202 is de-energized and the on-off valve 198 and the flow
control valve 200 are energized, the two-speed circuit 196 operates the
selected pump in its "slow" mode. Fluid flows through the on-off valve
198, through line 211, to the flow control valve 200. Fluid flows through
the flow control valve 200 on the line 210 and through the metering valve
206 on the return line 213. Due to the metering valve 206, a portion of
the fluid, rather than being delivered to the pumps, returns to the tank
70. This reduced flow slows the rate at which the pumps turn, and, thus,
slows the rate at which the pumps pump chemicals to or from the vat 50.
The valve 206 is preferably a metering valve so that an operator or
engineer can manually calibrate the flow of hydraulic fluid delivered on
line 210 when the two-speed circuit 196 is in the "slow" mode. Preferably,
the pumps operate at about 50 gallons/minute in the "fast" mode, and at a
preselected percentage (or ratio) of that rate in the "slow" mode. In the
preferred embodiment, the ratio is about 3:1, so the pumps operate at
about 16.7 gallons/minute in the "slow" mode. However, this ratio can be
altered using the metering valve 206 from 1:1, by turning the valve 206
off, to almost any reasonable desired ratio.
The charge pumps 24, 26, and 27 and the discharge pump 150 operate
essentially as described in FIG. 6. However, instead of being controlled
by manually-operated valves, the pumps 24, 26, 27, and 150 are controlled
by respective three-position solenoid valves 212, 214, 216, and 218. As
illustrated, the valves 212, 214, 216, and 218 are normally closed when
de-energized to prevent fluid flow to the respective pumps. To operate one
of the charge pumps 24, 26, or 27 in a "forward" direction to pump
chemicals from a respective line 28, 30, or 31 through a respective line
20, 22, or 25 and into the vat 50, the appropriate solenoid valve 212,
214, or 216 is actuated into its "down" position to provide a normal flow
path through the respective charge pump 24, 26, or 27. The fluid flow from
the line 210 to the actuated charge pump 24, 26, or 27 determines the rate
of pumping, as previously described. At the appropriate time, as will be
discussed later, the energized valve 212, 214, or 216 is de-energized into
its "off" position to complete the charging cycle. Once the charging is
complete, the valve 212, 214, or 216 is energized into its "up" position
to provide a cross flow through its respective charge pump 24, 26, or 27.
This cross flow causes the pump to operate in reverse and pump the
chemical back through the respective line 20, 22, or 25, through the line
28, 30, or 31, and into the container from which it came.
Once all of the desired chemicals have been charged into the vat 50, an
operator actuates the control lever 190 of the mast control valve 188 to
lower the auger 16 into the vat 50. Then, an on-off solenoid valve 220 is
energized to provide fluid flow to the mixer motor 161 via lines 222 and
224. When the mixing is complete, the on-off solenoid valve 220 is
de-energized to stop the mixer motor 161. Then, an operator may actuate
the control lever 190 to raise the auger 16 from the vat, so that the
chemicals may be discharged using the discharge pump 150, or so that the
vat 50 can be removed and replaced with another vat.
The discharge pump 150 and its associated solenoid valve 218 operate in
much the same way as the charge pumps and their associated valves,
described above. However, although valve 218 is illustrated as a
three-position solenoid valve, an on-off solenoid valve is typically all
that is needed. When the solenoid valve 218 is energized into its "on," or
"down", position, the discharge pump 150 operates to pump mixed chemicals
from the vat 150, through line 156, and out to a container via line 158.
Because there is typically no reason to operate the discharge pump 150 in
reverse to add chemicals to the vat 50 throuqh line 156, the valve 218 is
rarely energized into its "up" position to provide a cross flow that would
reverse pump 150.
FIG. 8 illustrates the computer-based device, generally illustrated by the
reference numeral 250, that controls the apparatus 10 illustrated in FIG.
7. It should be understood that the device 250 is only a preferred
embodiment and that many other computer-based devices could control a
blending apparatus such as that illustrated in FIG. 7. The device 250
includes a computer 252, which is preferably a 386-based personal
computer. The compute | | |
