U.S. patent number 3,826,904 [Application Number 05/295,060] was granted by the patent office on 1974-07-30 for method and apparatus for the optimum blending of lubricating base oils and an additive.
This patent grant is currently assigned to Texaco Inc.. Invention is credited to John M. Leonard, John S. Lewis, Jr..
United States Patent |
3,826,904 |
Leonard , et al. |
July 30, 1974 |
METHOD AND APPARATUS FOR THE OPTIMUM BLENDING OF LUBRICATING BASE
OILS AND AN ADDITIVE
Abstract
A method and apparatus for enabling the computation of a minimum
cost blend of lubricating oil base stocks, wherein a viscosity
index improver additive is included. System includes measurement of
viscosity and related data at two separate concentrations of the
additive where such concentrations are in the range from about 1
percent to about 10 percent of the additive with a given base oil.
Data obtained are used in non-linear formulae to provide bases for
calculating optimum blends to obtain particular specifications with
minimum cost.
Inventors: |
Leonard; John M. (Houston,
TX), Lewis, Jr.; John S. (Huntsville, AL) |
Assignee: |
Texaco Inc. (New York,
NY)
|
Family
ID: |
26782061 |
Appl.
No.: |
05/295,060 |
Filed: |
October 4, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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90244 |
Nov 17, 1970 |
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Current U.S.
Class: |
705/413; 700/265;
700/36; 208/DIG.1 |
Current CPC
Class: |
G06Q
50/06 (20130101); G01N 33/2888 (20130101); Y10S
208/01 (20130101) |
Current International
Class: |
G01N
33/26 (20060101); G01N 33/28 (20060101); G01n
025/46 (); F23m 005/00 (); G06p 015/46 () |
Field of
Search: |
;235/151.1,151.12 ;444/1
;252/59,65R ;208/DIG.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Morrison; Malcolm A.
Assistant Examiner: Wise; Edward J.
Attorney, Agent or Firm: Whaley; Thomas H. Ries; C. G.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation as to all subject matter common
to U.S. application, Ser. No. 90,244, now abandoned, filed Nov. 17,
1970 by John M. Leonard et al., and assigned to Texaco Inc.,
assignee of the present invention, and a continuation-in-part for
all additional subject matter.
Claims
What is claimed is:
1. A system for controlling the blending of base oils and an
additive, to achieve a desired blend having predetermined
characteristics, being provided to blending means, comprising means
for controlling the quantities of base oils and additive being
provided to the blending means to be blended in accordance with
control signals, means for providing signals corresponding to the
predetermined characteristics for a desired blend of base oils and
the additive, means for providing signals corresponding to the
economic values of the base oils, memory means for storing values
of different combinations of the base oils and the additive
quantities, means connected to the value signal means, to the
memory means and to the characteristic signal means for selecting a
desired combination of base oil and additive quantities in
accordance with the economic value signals and the characteristic
signals and providing signals corresponding thereto to the control
means as control signals so as to achieve the desired blend of base
oils and the additive.
2. A system as described in claim 1 in which the selecting means
includes means connected to the memory means for controlling the
memory means to provide signals corresponding to quantities of base
oils & additive for different combination thereof comprising
different blends in an iterative manner, means connected to the
memory means and to the value signal means for providing a signal
corresponding to the cost of a combination of the quantities
represented by the signals provided by the memory means in
accordance with the economic value signals and the following
equation: ##SPC8##
where c.sub.i is the cost of a particular base oil, x.sub.i is the
percent volume of the particular base oil and x.sub.1 is the
percent volume of the additive, means connected to the
characteristic signal means for determining those combinations of
base oil quantities that meet the predetermined characteristics in
accordance with the characteristic signals and providing a signal
corresponding thereto, and output means connected to the cost
signal means, to the determining means, to the memory means and to
the control means for providing the quantity signals from the
memory means, corresponding to the combination of quantities of the
base oils and the additive having a minimum cost that meet the
predetermine characteristics as the control signals in accordance
with the determination signal and the cost signal.
3. A system as described in claim 2 in which the predetermined
characteristics are the H value, the pour blend value PBV, and ASTM
color blend value, the flash point blend value BV and the aniline
point blend value and the determining means includes means
receiving direct current voltages corresponding to terms h, a and b
for the different base oils and l, associated with the following
equations, and connected to the memory means for providing a signal
corresponding to H for a present combination of base oils
quantities in accordance with the following equation: ##SPC9##
where h.sub.i is the H value for a base oil.sub.i ; a.sub.i and
b.sub.i are constants associated with the base oil i, and e is a
constant; means receiving direct current voltages corresponding to
pvb, c, d, and l and connected to the memory means for providing a
signal corresponding to the pour blend value PBV of the present
combination of base oils quantities in accordance with the
following equation: ##SPC10##
where pvb.sub.i is the pour blend value of the base oil i and
c.sub.l and d.sub.i are constants associated with the base oil i,
means receiving direct current voltages corresponding to blend
values bv for the ASTM color, flash point and aniline point of the
different base oils and l and connected to the memory means for
providing signals corresponding to blend values BV of the ASTM
color, the flash point value and aniline point of the present
combination of base oils quantities in accordance with the
following equation: ##SPC11##
where BV is the blend value of a particular characteristic such as
the ASTM color, the flash point and the aniline point for the
present combination of base oil quantities and bv.sub.i is the
blend value of a particular characteristic for the base oil i; and
means connected to the H signal means, to the PBV signal means, to
the BV signal means and to the output means and receiving direct
current voltages corresponding to limits for the H value, the pour
blend value PBV, the ASTM color blend value BV, the flash point
blend value BV and the aniline point blend value BV for providing a
signal to the output means as the determination signal having one
amplitude when the H factor, the pour blend value PBV, the ASTM
color blend value BV, the flash point blend value BV and the
aniline point blend value BV are within their respective limits and
another amplitude when at least one of the determined
characteristics is not within its corresponding limits.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns lubricating oil blending in general. More
particularly, it relates to an improved method of blending
lubricating oils where the blend includes a viscosity index
improver additive.
2. Description of the Prior Art
Heretofore, in the blending of lubricating oil base stocks, to
obtain desired specifications there was no particular difficulty
because the blend viscosities were proportional to the percentage
amounts of the base stocks by making use of the so-called "H-value"
used in determining the viscosity index. However, it was found that
where such blends included therein one of more viscosity index
improvement-type additives, the resulting blend was not
predictable. Thus, it was found that additives of the sort
mentioned could not be blended on the basis of a predetermined
viscosity index for the additive, since the "H-value" would vary in
a non-linear manner with the amount of additive and the particular
base oil with which it was blended. Pour points also varied
non-linearly with the amount of additive and the base oil used.
Consequently, it is an object of this invention to provide a method
and system for predetermining a particular blend of base oils with
a viscosity index improver additive, so as to provide predetermined
characteristics for the resulting blend.
SUMMARY OF THE INVENTION
A system controls the blending of base oils and an additive to
achieve a desired blend oil having predetermined characteristics at
minimum cost. The system includes apparatus which controls the
quantities of base oils and additive being provided to a blending
tank in accordance with control signals. A circuit provides signals
corresponding to the predetermined characteristics to a network.
The network provides the control signals to the apparatus in
accordance with the characteristic signals.
The objects and advantages of the invention will appear hereinafter
from a consideration of the detailed description which follows,
taken together with the accompanying drawings wherein two
embodiments of the invention are illustrated by way of example. It
is to be expressly understood, however, that the drawings are for
illustration purposes only and are not to be construed as defining
the limits of the invention.
DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a simplified block diagram of a control system,
constructed in accordance with the present invention, controlling
apparatus shown in schematic form, for the blending of base oils
with an additive.
FIGS. 2, 3, 4 and 7 are detailed block diagrams of the programmer,
the x.sub.i signal means, the constraint control means and the
blending control means, respectively, shown in FIG. 1.
FIGS. 5 and 6 are detailed block diagrams of the H.sub.i network
and the BV.sub.i network, respectively.
FIG. 8 shows another embodiment of the present invention in which a
general purpose digital computer is used to control the blending of
base oils with an additive.
FIG. 9 is a non-linear graph illustrating the non-linear
relationship of a base oil mixture and the percentage of additive
in the mixture.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Lubricating oils are often blended in order to meet predetermined
specifications, e.g., those called for to meet a customer's
desires. Heretofore, that could be accomplished in a
straightforward manner since the characteristics of the blend
varied in proportion with the volume-fraction of the base oils of
the blend. However, it was found that the addition of a viscosity
index improver additive created conditions such that the linear
blending of the base stocks of lubricating oils could no longer be
carried out with an expectation of providing a predetermined blend
viscosity or viscosity index. It was found that the viscosity index
improver additive did not act as a lubricating oil in that its own
viscosity H-value was not a constant but varied according to the
base oil or oils in the blend. It was also discovered that the pour
point depressant effects of the VI improver additive varied
according to the base oil or oils in the blend. Thus, a
relationship between the viscosity and pour point of a blend of
base oils and the viscosity and pour point of that blend with a
viscosity index improver additive could not be defined.
It may be noted that the above-mentioned "H-value" is an element in
the formula for calculating the viscosity index of any given oil.
The formula is given and explained in the "Standard Method for
Calculating Viscosity Index from Kinematic Viscosity" of the
American Society for Testing and Materials under the fixed
designation D2270. Such Standard is published by the Society with
an annual issue.
Another approach to the problem was to assume a constant H-value
for a particular additive over a limited range of viscosity of a
base oil blend. However, this was found not to work since it
appeared that the effect of the additive on the viscosity of
several different base oil blends, each of which blends had the
same viscosity, indicated that the assumed or pseudo H-values were
not usable.
It was discovered that if the viscosities of a particular
lubricating oil base stock at standard temperatures, e.g.,
100.degree.F and 210.degree.F, were measured under two separate
percentage mixtures with the additive, a predetermined relationship
could be expressed for each base oil. Such relationship follows a
curve of the general form as illustrated in FIG. 9. This could be
represented by the following equation:
(.DELTA.H).sub.i = H.sub.i - h.sub.i = a.sub.i (1 - e .sup..sup.-b
.sup.x ) (1)
wherein H.sub.i is the viscosity "H-value" of a given base
oil-additive combination; and h.sub.i is the viscosity H-value of
the base oil aone; a.sub.i and b.sub.i are constants; and x.sub.l
is the volume-fraction of the additive; and e is the natural log
base.
Since the h.sub.i is known or can be readily determined for each
base oil, the H-value of a base oil i with any volume-fraction
x.sub.l of a given additive, from 0.0 to somewhat above 0.06, could
be predicted by the following equation:
H.sub.i = h.sub.i + a.sub.i (1 - e .sup..sup.-b .sup.x ) (2)
These base oil-additive combinations can then be treated as
separate components in a blend, each with H-value H.sub.i. The
viscosity H-value of a blend of n base oils with a given
concentration x.sub.l of an additive is thus calculated by
##SPC1##
where x.sub.i (i = 2, 3, . . . ., n) is the volume-fraction of base
oil i in the blend. The blend H-values at 100.degree.F and
210.degree.F may then be used in the Standard formula noted above
to calculate a predetermined blend viscosity and viscosity
index.
It will be understood that throughout this disclosure the
abbreviation "VI" stands for viscosity index.
It was also discovered that the pour point of each base oil mixed
with the additive would have a predetermined relationship which
follows the general form similar to that for the H-value, as
illustrated in FIG. 9, except that the pour point decreases with
increasing additive dosage. Consequently, if the pour points of the
base oil-additive mixtures using two separate percentages, e.g.,
with 3 and 6 percent of the additive, was also measured, such data
could be converted to form a blending equation comparable to the
H-value equation for viscosity.
Thus, using calculations similar to those made for viscosity, the
pour blending value (PBV) of any blend of base oils with
volume-fraction x.sub.l of the additive could be found by using the
following equation: ##SPC2##
where PBV is the pour blending value of a blend with
volume-fraction x.sub.l of additive; (pbv).sub.i is the pour
blending value of base oil i; and where c.sub.i and d.sub.i are
constants calculated for base oil i.
With respect to other characteristics of a blend of base oils with
a VI improver additive included, such as flash point, aniline
point, and ASTM color, there was found to be no significant change
because of the additive. Consequently, linear blending values
previously developed for such property of each base oil could be
used to predetermine these characteristics of blends. The
characteristic blending value of a blend containing volume-fraction
x.sub.i of base oil i (i = 2, 3, . . . ., n) could thus be found by
the equation: ##SPC3##
where BV is the characteristic blending value of a blend;
(BV).sub.i is the corresponding property blending value for base
oil i; and x.sub.l is the volume-fraction of the additive in the
blend, as above.
The resulting expressions, e.g., (3), (4) and (5) above, allow
prediction of the viscosities at 100.degree.F and 210.degree.F (and
hence VI), plus pour point, flash point, aniline point, and ASTM
color of any blend of base oils with a VI improver. It is to be
noted that the entire relationship of the constituents of a blend
with an additive may be derived from data taken at only two
additive levels for each base oil. It will be appreciated that
conventional and/or stardard equipment (not shown) may be employed
in carrying out the measurements of the properties. As pointed out
above, the measurements are made using each of two different
percentage amounts of an additive in therange from about 1 to about
10 percent mixed with each base oil individually. Actual percentage
amounts of an additive that were used in carrying out the invention
were 3 and 6 percent.
The entire lube oil blending procedure and system lends itself to
use with a computer in order to find the minimum-cost blend which
meets a given set of characteristic specifications. Using a digital
computer, a skilled programmer could write a program using
non-linear constraints so as to minimize the cost function which
would be expressed in the form: ##SPC4##
subject to contraints (i.e. specifications) expressed in forms such
as the following:
The viscosity constraints H.sub.L and H.sub.U would be:
##SPC5##
The pour constraints PBV.sub.L and PBV.sub.U would be: ##SPC6##
and each additional specification would have constraints BV.sub.L
and BV.sub.U of the form ##SPC7##
where C is the total cost of a blend; C.sub.i is the cost of a
constituent base oil i; and x.sub.i is the volume-fraction of base
oil i in the blend, as in previous expressions; and where H, PBV
and BV are characteristics; and the other terms used in the
expressions (7), (8) and (9) are all the same as in previous
expressions. Some typical specification characteristics are
gravity, flash point, etc.
Referring to FIG. 1, base oils A, B and C from storage facilities
(not shown) are provided to a blending tank 1 through lines 2, 3
and 4. For convenience, the following example disclosing the
present invention will show the use of three base oils, although
there is no restriction on the number of base oils that may be
blended in tank 1 to provide a blend oil. The flow rate of a base
oil is directly related to the quantity of that base oil in the
final blend oil. The flow rate of the base oil A in line 2 is
controlled by a valve 6 receiving a signal from a flow recorder
controller 8. Flow recorder controller 8 receives a signal
corresponding to the flow rate of base oil A in line 2 from a flow
rate sensor 10. The set point of flow rate controller 8 is
positioned to a desired flow rate, as hereinafter described, which
will provide the desired portion of base oil A for a desired blend
oil in blending tank 1. Flow recorder controller 8 provides the
signal to valve 6 in accordance with the difference between the
flow rate signal from sensor 10 and the position of its set point
so that the flow rate in line 2 assumes the desired flow rate.
Similarly the flow rate of base oil B in line 3 is controlled by
the cooperation of a valve 6A, a flow rate sensor 10A and a flow
recorder controller 8A. The quantity of base oil C entering tank 1
is also controlled in a similar manner by a valve 6B and flow
recorder controller 8B and a flow rate sensor 10B. Elements having
a number and a suffix are connected and operate in a similar manner
to those elements having the identical number without a suffix.
A viscosity improver additive is also provided to tank 1 through a
line 11. A valve 6C, a flow recorder controller 8C and a sensor 10C
cooperate to control the flow rate of the additive in line 11. A
direct current voltage V.sub.A sets the set point in controller 10C
to a position corresponding to the predetermined flow rate.
Although, for purposes of illustration, the flow rate of the
additive and base oils are shown as being controlled by flow
recorder controller cooperating valves and flow sensors, it would
be obvious to one skilled in the art that the flow rates can be
controlled using meters, valves, differential control counters and
digital-to-analog converters. Such a control method is discussed in
an article by Mr. J. J. Jiskoot in the Oct., 1968 issue of the
Chemical and Process Engineering at page 87.
The set points of flow recorder controllers 8, 8A and 8B are
controlled in accordance with equations 6, 7, 8 and 10. In this
regard, a programmer 12, which is shown in detail in FIG. 2,
provides control pulses E.sub.A through E.sub.E to X.sub.i signal
means 14 through 14C, respectively. X.sub.i signal means 14 through
14C cooperate to provide signals E.sub.2 through E.sub.2C,
respectively, which correspond to the quantities of base oils A, B
and C, and the additive, respectively, for a particular blend oil.
The providing of signals E.sub.2 through E.sub.2C may also be done
by various types of memory means, in which various combinations of
base oils A, B and C have been stored, that would replace
programmer 12 and X.sub.i signal means 14 through 14C.
Referring now to FIGS. 1, 2 and 3, signals E.sub.2 through E.sub.2C
are developed as follows. An operator activates a switch 20 in
programmer 12 receiving a direct circuit voltage V.sub.1. Switch 20
may be a conventional type "momentary on" type of switch. Voltage
V.sub.1 passed by switch 20 triggers a flip-flop 24 to a set state.
A flip-flop provides a high level direct current output when in a
set state and a low level direct current output when in a clear
state. The high level output from flip-flop 24 causes an AND gate
26 to pass timing pulses from a clock 27 to a counter 30. Counter
30 counts the timing pulses and its content is decoded by a logic
decoder 31 to provide a plurality of outputs to a corresponding
plurality of one shot multivibrators 35. One shot multivibrators 35
provide a plurality of control pulses E.sub.A through E.sub.E and a
reset pulse E.sub.1. Reset pulse E.sub.1 occurs when counter 30 is
full. Reset pulse E.sub.1 resets flip-flop 24 to a clear state
thereby disabling AND gate 26. When disabled AND gate 26 blocks the
timing pulses from clock 27 to prevent further counting by counter
30. Reset pulse E.sub.1 also resets counter 30 to a zero count.
Programmer 12 provides reset pulse E.sub.1 to other portions of the
control system as hereinafter disclosed.
Each pulse passed by AND gate 26 triggers a time delay one shot
multivibrator 36 to provide a time delay pulse. The time delay
pulse allows calculating networks to complete the calculation
before triggering another one shot multivibrator 37 to provide a
pulse. The pulse from multivibrator 37 is inverted by an inverter
38 to provide an inhibiting pulse E.sub.6.
FIG. 3 shows in detail X.sub.i signal means 14 which includes a
plurality of conventional type electronic switches 40 through 40D.
The number of switches correspond to the number of combinations of
base oils A, B and C and additive that is expected to be utilized.
For example, if more base oils than base oils A, B and C were
desired for blending, then more switches are needed because there
would be more possible blend combinations of the various base
oils.
Direct current voltages i.e., B through V.sub.F, provided by a
conventional type direct current voltage source not shown,
correspond to predetermined quantities of base oil A for different
blend oils. For a count of one, electronic switch 40 receiving
voltage V.sub.B is activated by pulse E.sub.A from programmer 14,
to provide voltage V.sub.B as signal E.sub.2. Similarly, pulse
E.sub.A causes signal means 14A, 14B, 14C to provide other direct
current voltages corresponding to the quantities of base oils B
& C standard the additive necessary for that particular blend
oil to be provided as signals E.sub.2A, E.sub.2B and E.sub.2C.
Similarly, pulses E.sub.B, E.sub.C, E.sub.D the range and E.sub.E
will render switches 40A, 40C and 40D, respectively, conductive in
turn to provide direct current voltages V.sub.C through V.sub.F
respectively as base oil A quantity signal E.sub.2. In a similar
manner signal means 14A, 14B, 14C are also controlled to provide
corresponding direct current voltages so that at any one time
signals E.sub.2 through E.sub.2C correspond to quantities of base
oil A, B and C and the additive required to make a particular blend
oil. In essence, signal means 14, 14A, 14B, and 14C, along with the
voltage source, comprise memory means storing signals corresponding
to quantities of base oils A, B and C and the additive for
different blend oils.
Although a particular blend oil has been defined by signals
E.sub.2, E.sub.2A and E.sub.2B it does not necessarily follow that
the particular blend oil is acceptable or that the particular blend
oil, if acceptable, is the most economical blend oil
obtainable.
Referring to FIGS. 1, 4 and 5, control means 42 determines if a
particular blend oil, as defined by signals E.sub.2, E.sub.2A,
E.sub.2B and E 2.sub.C meets the various constraints imposed on a
blend oil and more particularly the characteristics defined by
equations 3, 4 and 5. Constraint control means 42 includes an H
constraint circuit 44, a pour constraint circuit 45, a flash point
constraint circuit 46, an aniline constraint circuit 47 and an ASTM
color constraint circuit 48. Constraint circuits 44 through 48
provide a plurality of direct current outputs to an AND gate 50.
Each constraint circuit will provide a high level output when a
parameter, being monitored by the constraint circuit, is within
upper and lower constraint limits and a low level output when the
monitored parameter is not within the constraint limits. When all
parameters are within their constraint limits, AND gate 50 provides
an output E.sub.3 at a high level output as signal E.sub.3 and a
low level output as signal E.sub.3 when any or all of the
constraint circuits outputs are at a low level.
Signals E.sub.2, E.sub.2A, E.sub.2B, E.sub.2C are applied to
H.sub.i networks 55, 55A and 55B, respectively, providing signals
E.sub.4, E.sub.4A and E.sub.4B, respectively, corresponding to the
H values for blend oils A, B and C, respectively. In network 55, a
multiplier 56 multiplies direct current voltage V.sub.3
corresponding to the term b.sub.2, with signal E.sub.2C from signal
means 14.sub.C to provide a signal corresponding to the term
b.sub.2 X.sub.l. The signal from multiplier 56 is applied to a
unity gain inverting amplifier 57. A logarithmic amplifier 58
provides an output corresponding to the logarithm of a direct
current voltage V.sub.4 which corresponds to the term e in equation
3. A multiplier 63 multiplies the output from amplifiers 57, 58 to
provide a signal corresponding to the term -b.sub.2 X.sub.l log e
to an antilog circuit comprising an operational amplifier 64 having
a function generator 65 as a feedback network. Function generator
65 may be of the type manufactuered by Electronic Associates under
their Part Number PC12. Thus, the output from amplifier 64
corresponds to the term e.sup..sup.-b .sup.X .
The output from amplifier 64 is subtracted from a direct current
voltage V.sub.5, corresponding to the term 1 in equation 3, by
subtracting means 70. A multiplier 71 multiplies the output from
subtracting means 70 with a direct current voltage V.sub.6,
corresponding to the term a.sub.2. Summing means 72 sums the output
from multiplier 71 with a direct current voltage V.sub.7,
corresponding to the term h.sub.2 in equation 3, to provide a
signal to another multiplier 73. A divider 74 divides signal
E.sub.2 with a signal from subtracting means 75 corresponding to
the term l - X.sub.l, to provide an output to multiplier 73.
Subtracting means 75 subtracts signal E.sub.2C from voltage
V.sub.5. Multiplier 73 multiplies the output from summing means 72
and divider 74 to provide signal E.sub.4.
Similarly networks 55A and 55B operate on signals E.sub.2A,
E.sub.2B, E.sub.2C, respectively, to provide signals E.sub.4A and
E.sub.4B.
In circuit 44, summing means 80 sums signals E.sub.4, E.sub.4A and
E.sub.4B to provide a signal E.sub.5 corresponding to the H value
for base oil A with direct current voltages V.sub.9 and V.sub.10
corresponding to predetermined upper and lower constraint limits,
respectively. Comparator 81 provides a high level output when
voltage V.sub.9 is more positive than signal E.sub.5 and a low
level output when V.sub.9 is not more positive than signal E.sub.5.
Comparator 81A provides a high level output when signal E.sub.5 is
more positive than voltage V.sub.10 and a low level output when
signal E.sub.5 is not more positive than voltage V.sub.10 so that
when H is within the constraint limits, comparators 81, 81A provide
high level outputs which cause an AND gate 82 to provide a high
level output to AND gate 50. When the H value exceeds the upper
constraint limit, signal E.sub.5 is more positive than voltage
V.sub.9 causing comparator 81 to provide a low level output which
disables AND gate 82 causing it to provide a low level output to
AND gate 50. Similarly, when the H value is less than the lower
constraint limit signal E.sub.5 is not more positive than voltage
V.sub.10 which causes comparator 81A to provide a low level output
which has the same effect as when comparator 81 provided a low
level output.
Pour constraint circuit 45 is similar to constraint circuit 44.
Pour constraint circuit 45 utilizes PBV.sub.i networks in place of
the H.sub.i networks 55 through 55D in constraint circuit 45. The
PBV.sub.i circuits are similar to the H.sub.i networks with the
difference being that the direct current voltages received
correspond to the constants c and d instead of a and b and the
PBV.sub.i network has summing means instead of having subtracting
means 70 which sums the output from the operational amplifier with
a direct current voltage corresponding to PBV.sub.i.
Constraint circuits 46, 47 and 48 are identical with each other and
are similar to constraint circuit 44. The difference between
constraint circuits 46, 47 and 48 are constraint circuit 44 is that
constraint circuit 44 uses H.sub.i networks 55 through 55B while
constraint circuits 46, 47, 48 use PV.sub.i networks in lieu of
networks 55 through 55B. Referring to FIG. 6, there is shown a
BV.sub.i network. A divider 88 divides signal E.sub.2 with a signal
from subtracting means 90. Means 90 subtracts signal E.sub.2 from
voltage V.sub.5. A multiplier 89 multiplies the signal from divider
88 with a direct current voltage V.sub.10 which corresponds to the
blend value of a particular characteristic, which by way of example
may be the ASTM color, for base oil A to provide a signal
corresponding to a particular BV.sub.i value.
Referring now to FIGS. 1 and 7, programmer 12 provides reset pulse
E.sub.1 to blending control means 90 which also receives signals
E.sub.2, E.sub.2A and E.sub.2B from X.sub.i signal means 14, 14A
and 14B, respectively, and signal E.sub.3 from constraint control
means 42. Blending control means 90 provides signals E.sub.10,
E.sub.10A and E.sub.10B corresponding to desired set point
positions for flow recorder controllers 8, 8A and 8B, respectively,
to set their set points to control the blending of base oils A, B
and C with the additive in tank 1. Multipliers 93, 93A and 93C in
blending control means 90 provides signals corresponding to the
cost for the different component portions of a particular blend
oil. Multiplier 93 multiplies direct current voltages V.sub.11 and
V.sub.12 corresponding to X.sub.l and C.sub.l, the cost of the
additive, to provide a cost signal. Similarly, direct current
voltages V.sub.13, V.sub.14 and V.sub.15 corresponding to economic
values of base oils A, B and C, respectively, are multiplied with
signals E.sub.2, E.sub.2A and E.sub.2B, respectively, by
multipliers 93A, 93B and 93C, respectively, to provide cost
signals. Summing means 94 sums the cost signals from multipliers 93
through 93C to provide a blend oil cost signal E.sub.12
corresponding to C in equation 6.
Signal E.sub.12 is applied to a conventional type analog-to-digital
converter 98 which provides digital signals, corresponding to
signal E.sub.12, to a plurality of AND gate 99. Signal E.sub.3 is
also provided to AND gates 99 to partially enable those gates. When
AND gates 99 receive a transfer pulse as hereinafter explained, the
digital signals from converter 98 are transferred to a storage
register 100.
Storage register 100 effectively stores the minimum cost signal.
This is accomplished by applying outputs from storage register 100
to a conventional type digital-to-analog converter 101 which
provides an analog signal E.sub.14 corresponding to the content of
register 100. Signal E.sub.14 is applied to an electronic switch
107 and to a comparator 108. Electronic switch 107 is in effect a
single pole double throw switch receiving a direct current voltage
V.sub.16. Voltage V.sub.16 has an amplitude larger than the
amplitude of a typical cost signal E.sub.12. Comparator 108
receives voltage V.sub.17 which substantially corresponds to a zero
value so that when the content of storage 100 is zero comparator
108 provides a high level signal to electronic switch 107.
Electronic switch 107 passes voltage V.sub.16 to a comparator 112
when comparator 108 provides a high level signal and signal
E.sub.14 when comparator 108 provides a low level signal.
The use of switch 107, comparator 108 and voltages V.sub.16 and
V.sub.17 is necessitated by the initial condition of storage
register 100. Since the object of register 100 is to store the
minimum cost signal, when register 100 initially has a zero content
it is impossible to enter any cost signal into register 100 but for
the operation of switch 107 and comparator 108.
An AND gate 113 controls an electronic switch 114 receiving signal
E.sub.12 from converter 98 and direct current voltage V.sub.16 in
accordance with signal E.sub.3 and inhibiting pulse E.sub.6. Switch
114 passes signal E.sub.12 and blocks voltage V.sub.16 when signal
E.sub.3 is at a high level and inhibiting pulse E.sub.6 is absent.
Switch 114 blocks signal E.sub.12 and passes voltage V.sub.16 when
signal E.sub.3 is at a low level or inhibiting pulse E.sub.6 is
present.
During the initial phase of the operation, comparator 112 goes to a
low level in response to voltage V.sub.16 being greater than a
passed signal E.sub.12 from switch 114.
A one shot multivibrator 118 is triggered by the change to a low
level in the output from comparator 112 to provide a reset pulse to
an AND gate 121 which is controlled by signal E.sub.3. When switch
114 blocks signal E.sub.12, comparator 112 output would go to a low
level causing one shot multivibrator 118 to provide a reset pulse
which would erroneously reset register 100 and other registers if
AND gate 121 was not there. However, AND gate 121 is disabled by
the low level of signal E.sub.3 and blocks such an erroneous
pulse.
The pulse provided by one shot multivibrator 118 passes through AND
gate 121 and is applied to another one shot multivibrator 119 and
to register 100 through an OR gate 120. Register 100 is reset by
the pulse while one shot multivibrator 119 is triggered by the
trailing edge of the pulse to provide a transfer pulse to AND gates
99. AND gates 99 in response to the transfer pulse and a high level
signal E.sub.3 enters the digital signals from converter 98 into
register 100.
Now signal E.sub.14 from converter 101 is greater than voltage
V.sub.17 causing the output from comparator 108 to go to a low
level. The low level output from comparator 108 causes switch 107
to pass signal E.sub.14 to comparator 112 and to block voltage
V.sub.16. Comparator 112 now effectively compares the present blend
oil cost, as represented by signal E.sub.12, with the previous
minimum blend oil cost as represented by signal E.sub.14. When the
present cost is less than the previous minimum cost, comparator 112
output goes to a low level causing the previous minimum cost stored
in register 100 to be replaced by the present cost.
At this time, it would be appropriate to explain the effect of
inhibiting pulse E.sub.6. Without AND gate 113, voltage V.sub.16
and inhibiting pulse E.sub.6 and with signal E.sub.3 controlling
switch 114 directly, a condition in which successive lower blend
oil costs occurred would cause all but the first lower cost to be
lost. Under that condition, the output of comparator 112, already
providing a low level output due to the first lower cost condition,
cannot change to a lower level and therefore cannot trigger one
shot multivibrator 118. However, as previously stated, the presence
of inhibiting pulse E.sub.6 causes switch 114 to provide voltage
V.sub.16 to comparator 112. Since voltage V.sub.16 is greater than
signal E.sub.14, comparator 112 output goes to a high level. Now,
when the next successive cost is lower than the next preceding
cost, comparator 112 output will change from a high level to a low
level triggering one shot multivibrator 118.
Where the present cost is greater than the minimum cost, comparator
112 output remains at a high level and does not trigger one shot
multivibrator 118. Since one shot multivibrator 118 is not
triggered, the minimum cost remains stored in register 100. When
all the costs for different blend oils have been computed, storage
register 100 will contain the minimum cost.
Concurrent wth storing of the minimum cost in register 100, it is
necessary that the quantities of base oils A, B & C and the
additive comprising the blend oil having the minimum cost be stored
in registers. The pulse from one shot multivibrator 118, passed by
AND gate 121 resets a storage register 128 in set point signal
means 130. Signal E.sub.2 is applied to a conventional type
analog-to-digital converter 131 which provides corresponding
digital signals to a plurality of transfer AND gates 135. AND gates
135 are fully enabled by the pulse provided by one shot
multivibrator 119 so that when a particular cost signal is
transferred to storage register 100, signal E.sub.2 corresponding
to the quantity of base oil A contributing to that particular cost
is also transferred to storage register 128. Thus, at any time the
content in register 128 corresponds to the quantity of base oil A
in the blend oil that has the minimum cost.
Register 128 provides a plurality of outputs to transfer AND gates
140, wich are connected to storage register 141. Reset pulse
E.sub.1 from programmer 12 resets registers 100 and register 141.
Pulse E.sub.1 also triggers a one shot multivibrator 142 causing it
to provide an enabling pulse to AND gates 140 causing them to
transfer the content of registers 128 to 141. Register 141 holds
the content corresponding to the quantity of base oil A in the
minimum cost blend oil until the operation is repeated.
The signals stored in register 141 correspond to a quantity and
must be converted to a flow rate control signal. A conventional
digital-to-analog converter 150 converts the outputs from register
141 to an analog signal. A multiplier 151 multiplies the signal
from converter 150 with a conversion signal E.sub.60 to provide
signal E.sub.60. Summing means 152 sums x.sub.1 through x.sub.4
signals from signal means 130-130C, respectively, to provide a sum
signal to a divider 153. Divider 153 divides a direct current
voltage V.sub.59 with the sum signal to provide signal
E.sub.60.
Set point signal means 130A, 130B, 130C provides signal E.sub.10
and E.sub.10A, respectively, in a similar manner to that of the set
point signal means 130 so that valves 6 through 6C are controlled
to allow the proper rates of the base oils & additive to
achieve a minimum cost blend oil.
Although an analog computer has been used to describe the present
invention, it would be obvious to one skilled in the art to use a
general purpose digital computer so that the present invention is
not restricted to an analog computer but also encompasses digital
computer control as well as hybrid digital and analog control
systems. Referring to FIG. 8, a general purpose digital computer
140 provides digital outputs to digital-to-analog converters
141-141C which converts the digital outputs to signals E.sub.10
through E.sub.10C, respectively. Computer 140 is programmed in a
conventional manner to provide the digital outputs as follows:
1. Store in the computer memory values for different quantities of
base oils A, B and C & the additive.
2. Store in the computer memory, equations 3 through 6.
3. Store in the computer memory, predetermined values for a, b, c,
d, h, phv, ASTM color bv, flash point bv and aniline point bv for
each base oil.
4. Store predetermined limits for H, PBV, ASTM color BV, flash
point BV and aniline point BV.
5. Store the costs c.sub.1, c.sub.2 and c.sub.3 of base oils A, B
and C, respectively, in the memory.
6. Select a first combination of base oil and additive
quantities.
7. Calculate H using equation 3, PBV using equation 4 and the ASTM
color BV, flash point BV and aniline point BV using equation 6 in
accordance with the selected base oils quantities values and the
stored values of a, b, c, d, h, pbv, AST, color bv, flash point bv
and aniline point bv.
8. Compare the calculated values of H, PBV, ASTM color BV, last
point BV and aniline BV with their respective limits stored in the
memory.
9. If any of the calculated values are not within the limits,
repeat steps 6 through 8 and 9 or 10, whichever is applicable, for
the next blend combination of base oil quantities.
10. If all of the calculated values are within the limits,
calculate the cost of the blend combination.
11. If there is no minimum cost, store the present cost and blend
combination quantities values and select a next combination of
blend oil quantities values and repeat steps 7 through 11.
12. If there is a stored minimum cost, compare the present cost
with the stored cost.
13. If the stored cost is less than the present cost, select a next
combination of base oils quantities values and repeat steps 7
through 12.
14. If the stored cost is not less than the present cost, store the
present cost and the blend combination quantities values associated
with the present cost.
15. Select a next combination of blend oils quantities values and
repeat steps 6 through 14 until all of the different combination of
quantities values have been processed, at that time the digital
signals corresponding to the stored values of quantities of base
oils and additive are provided as the digital outputs.
The apparatus of the present invention as heretofore described
controls the blending of base oils with an additive to achieve a
blend oil meeting predetermined characteristics. The apparatus also
computes the cost for difference blend oils and effectively
controls the blending of the base oils and additives to achieve the
blend oil meeting the predetermined specifications but also having
a minimum cost. The apparatus may be an analog computer
specifically arranged to solve the equations heretofore described
or it may be a general purpose digital computer program to solve
the equations and to provide outputs controlling the blending of
the base oils and additives.
* * * * *