U.S. patent application number 14/864625 was filed with the patent office on 2016-03-31 for system and method for reducing viscosity variations in roofing asphalt.
The applicant listed for this patent is TAMKO Building Products, Inc.. Invention is credited to David C. Humphreys.
Application Number | 20160090512 14/864625 |
Document ID | / |
Family ID | 55539919 |
Filed Date | 2016-03-31 |
United States Patent
Application |
20160090512 |
Kind Code |
A1 |
Humphreys; David C. |
March 31, 2016 |
SYSTEM AND METHOD FOR REDUCING VISCOSITY VARIATIONS IN ROOFING
ASPHALT
Abstract
An asphalt shingle coating system that includes a coater, a
mixer, a viscosity gauge, a wax supply, a wax pump and a control
system. The coater applies a layer of a coating asphalt mixture on
an asphalt shingle substrate. The mixer mixes the coating asphalt
mixture and is positioned upstream of the coater. The viscosity
gauge may be positioned between the coater and the mixer, and it
measures the viscosity of said coating asphalt mixture before it is
delivered to the coater. The wax supply is in fluid communication
with the mixer and a wax pump may deliver a volume of wax from the
wax supply to the mixer, and the control system may selectively
adjust the operation of the wax pump to substantially maintain a
desired viscosity of said coating asphalt mixture.
Inventors: |
Humphreys; David C.;
(Joplin, MO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TAMKO Building Products, Inc. |
Joplin |
MO |
US |
|
|
Family ID: |
55539919 |
Appl. No.: |
14/864625 |
Filed: |
September 24, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62055465 |
Sep 25, 2014 |
|
|
|
Current U.S.
Class: |
118/698 ;
106/270 |
Current CPC
Class: |
C08L 95/00 20130101;
C09D 195/00 20130101; B01F 3/10 20130101; C08L 2555/10 20130101;
B01F 15/0408 20130101; B01F 3/088 20130101; B01F 15/00246 20130101;
B01F 5/106 20130101 |
International
Class: |
C09D 195/00 20060101
C09D195/00; B01F 15/00 20060101 B01F015/00; B01F 5/06 20060101
B01F005/06; B01F 15/02 20060101 B01F015/02; C08L 95/00 20060101
C08L095/00; E04D 1/26 20060101 E04D001/26 |
Claims
1. An asphalt shingle coating system comprising: a coater for
coating an asphalt shingle substrate with a coating asphalt
mixture; a mixer for mixing said coating asphalt mixture, said
mixer in fluid communication and upstream of said coater; a
viscosity gauge for measuring the viscosity of said coating asphalt
mixture delivered to said coater, said viscosity gauge disposed
between said coater and said mixture; a wax supply in fluid
communication with the mixer; a wax pump for delivering a volume of
wax from the wax supply to the mixer; and a control system in
electronic communication with said viscosity gauge and said wax
pump, said control system operable to selectively adjust the
operation of said wax pump to substantially maintain a desired
viscosity of said coating asphalt mixture.
2. The asphalt shingle coating system of claim 1 further comprising
a supply return valve and a supply return line for directing and
conveying the asphalt coating back to the mixer if the asphalt
coating is out of specification.
3. The asphalt shingle coating system of claim 1 wherein the mixer
includes two or more level sensors used to determine the amount of
wax to be added to result in the desired proportions and material
properties.
4. An asphalt shingle coating system comprising: a coater for
coating an asphalt shingle substrate with a coating asphalt
mixture; a mixer for mixing said coating asphalt mixture, said
mixer upstream of said coater; a supply conduit connecting said
coater and said mixer for placing said mixer in fluid communication
with said coater; a static mixer tube disposed in said supply
conduit; a viscosity gauge for measuring the viscosity of said
coating asphalt mixture delivered to said coater, said viscosity
gauge disposed between said coater and said mixture and downstream
of said static mixer; a wax supply in fluid communication with the
supply conduit, the wax supply having an inlet into said supply
conduit upstream of the static mixer; a wax pump for delivering a
volume of wax from the wax supply to the static mixer; and a
control system in electronic communication with said viscosity
gauge and said wax pump, said control system operable to
selectively adjust the operation of said wax pump to substantially
maintain a desired viscosity of said coating asphalt mixture.
5. A method for substantially maintaining the viscosity of a
coating asphalt mixture delivered to a coater during the
manufacture of a roofing shingle, the method comprising the steps
of: measuring the viscosity of the coating asphalt mixture prior to
the asphalt mixture being delivered to the coater; comparing the
measured viscosity to a desired viscosity; and adjusting the amount
of wax in the coating asphalt mixture if the measured viscosity
varies from said desired viscosity.
6. The method of claim 5 further comprising adding wax to the
coating asphalt mixture if the measured viscosity is higher than
said desired viscosity range.
7. The method of claim 5 further comprising reducing the amount of
wax added to the coating asphalt mixture if the measured viscosity
is lower than said desired viscosity range.
8. The method of claim 5 further comprising mixing the coating
asphalt mixture until the mixture is at least substantially
homogeneous.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 62/055,465 filed Sep. 25, 2014, the entire
disclosure of which is hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] This present invention relates to a system and method of
reducing the variations in the viscosity of a coating asphalt
mixture during the manufacturing of roofing shingles.
BACKGROUND OF THE INVENTION
[0003] The costs of asphaltic material and other petroleum based
products have steadily risen over time. Optimizing the use of
coating asphalt is a continual goal in the art. An inefficiency
that has remained relatively unaddressed in the manufacture of
asphalt roofing shingles is the inherent variations in the
viscosity of the coating asphalt mixture and its effect on material
inefficiencies and/or product quality.
[0004] Base asphalt used in roofing mixtures often includes a
number of material variations due to nature or the refining
process. Thus, even slight variations in the viscosity of the
coating asphalt mixture can result in applying a thicker or thinner
layer of asphalt coating to the shingle substrate. If the applied
coating layer is too thick, then material inefficiencies are
experienced. If the applied coating layer is too thin, then product
performance issues may arise. In any event, variations in asphalt
coating mixture viscosity results in losses due to material
application inefficiencies and/or variations and uncertainty in
product performance.
[0005] Thus there is a need in the art to supply a coater used in
the manufacture of asphalt shingles with a coating asphalt mixture
which provides the asphalt coating at a consistent viscosity to
provide and apply a coating layer of consistent thickness on the
substrate in order to optimize material efficiency and provide
consistent product performance.
SUMMARY OF INVENTION
[0006] The present invention is directed toward an asphalt shingle
coating system comprising a coater, a mixer, a wax supply and a wax
pump, a viscosity gauge, and a control system. The coater coats an
asphalt shingle substrate with a coating asphalt mixture. The mixer
mixes the coating asphalt mixture and is in fluid communication and
upstream of the coater. The wax supply provides a wax that can be
used to control (usually decrease) the viscosity of the coating
asphalt mix, and the wax pump is used to supply the system a volume
of wax from the wax supply to the mixer when or if it is needed.
The viscosity gauge measures the viscosity of the coating asphalt
mixture delivered to the coater and is disposed between the coater
and the mixer. The control system is in electronic communication
with the viscosity gauge and the wax pump, and is operable to
selectively adjust the operation of the wax pump to substantially
maintain a desired viscosity of the coating asphalt mixture.
[0007] In one embodiment, the present asphalt shingle coating
system may further comprise a supply return valve and a supply
return line for directing and conveying the asphalt coating back to
the mixer if the asphalt coating is out of specification. Another
embodiment may further include the mixer having two or more level
sensors used to determine the amount of wax to be added to result
in a coating asphalt mixture exhibiting the desired component
proportions and material properties.
[0008] Another embodiment further includes a supply conduit that
places the coater in fluid communication with the mixer, and a
static mixer tube disposed in the supply conduit. In this
embodiment, the viscosity gauge is disposed downstream of the
static mixer, and the wax supply is in fluid communication with the
supply conduit rather than or in addition to the mixer. The wax
supply has an inlet into the supply conduit that is located
upstream of the static mixer.
[0009] The present asphalt shingle coating system may be used
according to the following method for substantially maintaining the
viscosity of a coating asphalt mixture delivered to a coater during
the manufacture of a roofing shingle. The present method includes
the steps of measuring the viscosity of the coating asphalt mixture
prior to the asphalt mixture being delivered to the coater,
comparing the measured viscosity to a desired viscosity, and
adjusting the amount of wax in the coating asphalt mixture if the
measured viscosity varies from the desired viscosity.
[0010] In addition, the method for coating shingles herein may also
include one or more of the steps of adding wax to the coating
asphalt mixture if the measured viscosity is higher than the
desired viscosity range, reducing the amount of wax added to the
coating asphalt mixture if the measured viscosity is lower than the
desired viscosity range, and mixing the coating asphalt mixture
until the mixture is at least substantially homogeneous.
[0011] Other aspects and advantages of the present invention will
be apparent from the following detailed description of the
preferred embodiments and the accompanying drawing figures.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0012] The accompanying drawings form a part of the specification
and are to be read in conjunction therewith, in which like
reference numerals are employed to indicate like or similar parts
in the various views.
[0013] FIG. 1 is a schematic view of one embodiment of an asphalt
coating system in accordance with the teachings of the present
disclosure;
[0014] FIG. 2 is a schematic view of another embodiment of an
asphalt coating system in accordance with the teachings of the
present disclosure; and
[0015] FIG. 3 is a schematic view of the flow chart for a control
algorithm that may be used in one embodiment of an asphalt coating
system in accordance with the teachings of the present
disclosure.
[0016] While the disclosure is susceptible to various modifications
and alternative forms, a specific embodiment thereof is shown by
way of example in the drawing and will herein be described in
detail. It should be understood, however, that the drawings and
detailed description presented herein are not intended to limit the
disclosure to the particular embodiment disclosed, but to the
contrary, the intention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the present
disclosure as defined by the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The following detailed description of the present invention
references the accompanying drawing figures that illustrate
specific embodiments in which the invention can be practiced. The
embodiments are intended to describe aspects of the present
invention in sufficient detail to enable those skilled in the art
to practice the invention. Other embodiments can be utilized and
changes can be made without departing from the spirit and scope of
the present invention. The present invention is defined by the
appended claims and, therefore, the description is not to be taken
in a limiting sense and shall not limit the scope of equivalents to
which such claims are entitled.
[0018] The present invention relates to a system and method for
adding varying amounts of wax to a roofing asphalt mixture based
upon the measured viscosity of the coating asphalt mixture
proximate the point of application to a roofing substrate. The
present invention allows for the regulation of the viscosity of the
asphalt through the insertion of a known quantity of wax material
into the asphalt mixture, wherein the amount can vary to maintain a
consistent viscosity. FIG. 1 illustrates an schematic of an
embodiment of an asphalt shingle coating system 10 including an
asphalt supply line-in 12 for feeding a base roofing asphalt
mixture, and an aggregate/filler inlet 14 which provides aggregate
or filler from an aggregate/filler supply hopper 16 into a
horizontal mixer 18. The horizontal mixer 18 includes a mixer motor
20 that drives the mixing components to mix the asphalt mixture and
the filler into a filled coating asphalt mixture to apply on the
shingle substrate.
[0019] The filled coating exits the horizontal mixer 18 at a
horizontal mixer output 22 into a filled coating supply line 24,
wherein the filled coating is fed into a vertical mixer 26 driven
by a vertical motor 28. The filled coating enters vertical mixer 26
from supply line 24 through a filled coating inlet 30. Wax may be
selectively mixed into the coating asphalt mixture and may enter
vertical mixer 26 through a wax inlet 32 after traveling through a
wax supply line 34 from a wax supply tank 36. Wax supply tank 36
may be a heated storage tank to maintain the wax in a liquid state.
Wax supply tank 36 may be an electric trace tank with insulation or
the wax may be a low temperature heated fluid. Wax supply tank 36
may be supported on one or more load cells 37, which monitor the
weight of the volume of wax contained in wax supply tank 36 and can
be used to monitor the volume of wax that is dispersed from wax
supply tank 36 at any given time. Load cell 37 may also be used to
monitor the wax supply so as to indicate when the supply needs to
be replenished. Other embodiments may measure the volume of wax
being added into the mixture using flow meters or a pump estimation
technique which estimates the volume of wax delivered using the
known volume that the pump delivers per unit of time. The flow of
wax into vertical mixer 26 and the mixture rate may be selectively
and variably controlled using a wax valve 38, and/or a wax supply
pump 40 driven by a wax supply pump motor 42. Wax valve 38 may be
an "on or off" valve, a variable flow valve, or a check valve. Pump
40 may be any type of pump known in the art, including a
centrifugal or positive displacement valve. Wax supply tank 36 may
also include a temperature gauge 39 to measure the temperature of
the wax additive.
[0020] Any type of wax that is now known or may be used in the
future, which can be added to an asphalt composition is within the
scope of the present invention. As will be recognized by a person
of skill in the art, some waxes may be more preferable than others
for particular circumstances. Waxes now known in the industry
include: tailing wax, paraffin wax, microcrystalline wax (both high
and low melting point), ethylene bis-stearamide wax (EBS),
Fischer-Tropsch wax (FT), oxidized Fischer-Tropsch wax (FTO),
polyolefin waxes, polyethylene wax (PE), oxidized polyethylene wax
(PEO), polypropylene wax, polypropylene/polyethylene wax, alcohol
wax, silicone wax, chlorinated wax or paraffin, amide waxes, ester
waxes, carboxylic acid waxes, candelilla wax, carnauba wax, rice
wax, Japan wax, jojoba oil, beeswax, lanolin, and whale wax, montan
wax, ozokerite, and ceresin. In addition, other viscosity modifiers
may be used in place of wax, including tall oil pitch, soybean
by-products, naphthenic oils, or recycled oils.
[0021] Vertical mixer 26 is of a type that is generally known in
the art and may be jacketed with hot oil heating fluid or other
heating method to maintain an operational temperature of the
coating asphalt in the mixer between three-hundred-fifty (350)
degrees and four-hundred-fifty (450) degrees. Vertical mixer 26 may
include one or more contents level probes 41. The content level
probes 41 may be used to manage batch insertion and delivery
processes within the vertical mixer to manage a real-time
concentration problem between the low and high level probe set
points in order to achieve and maintain a homogenous mixture of
limestone, coating asphalt, and a desired quantity of wax material
based on the required or desired physical properties of the
delivered coating asphalt mixture.
[0022] The final formulation of the coating asphalt mixture then
exits vertical mixer 26 through a vertical mixer outlet valve 44
and travels through a coater supply line 46 to a coater 48. A
coater asphalt pump 50 driven by a motor 52 pumps the coating
asphalt to coater 48. The flow of the coating asphalt may be
monitored by any number of instruments and/or monitors including at
least a density gauge 54, and a viscosity gauge 56. Other gauges
are within the scope of the present invention, including a
temperature gauge, flow velocity gauge, or any other gauge or
monitor for measuring a physical or operational property of the
flowing coating asphalt. Supply return valve 68 and all valves
utilized in the present coating system may be an "on or off" valve,
a variable flow valve, or a check valve. Any of the holding tanks,
mixers or supply lines of the present invention may include one or
more monitors or gauges for temperature, weight, density, pressure,
or to measure any other desired operational or processing
property.
[0023] Viscosity as used herein is defined as the resistance of
fluid to both shear and flow. As such, the present invention may
utilize both kinematic viscosity and/or dynamic viscosity
measurements. The viscosity gauge 56 may provide a proportional
control signal to a controller in the form of a prescribed voltage
or a 4-20 milliamp signal to indicate the viscosity measurement of
the coating asphalt flowing through the coater supply line 46.
[0024] In delivering the coating asphalt mixture to the coater, a
back coating line 58 may branch off of coater supply line 46 to
deliver coating asphalt for coating the back side of a shingle
substrate. The flow of the coating asphalt to the coater for back
coating may be controlled using a back coating line valve 60.
Similarly, a front coating line 62 may branch off of coater supply
line 46 to deliver coating asphalt for coating the front side of a
shingle substrate. The flow of the coating asphalt to the coater
through the front coating line 62 may be controlled using a back
coating line valve 64.
[0025] Coater supply line 46 may become a coater supply return line
66 around a supply return valve 68 which allows the coating asphalt
to cycle back to the vertical mixer 26. Supply return valve 68 may
be selectively operated to direct all or part of the asphalt
coating flow to coaters 48. Alternatively, valve 68, valves 60 and
64 may be coordinated so all the coating asphalt in coating supply
line 46 returns to vertical mixer 26, for example, if the asphalt
coating is out of specification. In addition, any coating asphalt
that does not adhere to the shingle substrate at coater 48 may be
collected and fed back to vertical mixer 26 through a coating
return line 70. The flow of un-adhered coating asphalt collected at
coater 48 may be controlled using at least one of a first coating
return valve 72, a coating return pump 74, a coating return pump
motor 76, and a coating return second valve 78.
[0026] The operation of all or a part of the present asphalt
shingle coating system 10 may be controlled using a controller 80.
Controller 80 may be in electronic communication with any of the
pumps, valves, motors, and measurement devices of the present
asphalt shingle coating system 10. Particularly in the embodiment
shown in FIG. 1, controller 80 is in electronic communication with
at least wax supply tank 36, load cell 37, wax valve 38, wax supply
pump motor 42, and the viscosity gauge 56.
[0027] Controller 80 may include one of or all of the following
control and optimization methods: proportional control, integral
control, and derivative control. Proportional control is the
control step that calculates the difference between the target
viscosity and the actual viscosity measured by viscosity gauge 56
in coater supply line 46. A proportional value is applied against
the resulting error factor, which results in a quantity of wax that
should be added to or withheld from the overall mixture to adjust
the viscosity. Controller 80 then controls, operates and/or
monitors one of pump motor 42, wax valve 38, and load cell 37 or
other volume measurement method to deliver the required quantity of
wax to result in the desired viscosity.
[0028] Integral control involves evaluating the effect of
successive portion control sequences as sequential batches are
completed. If over time the proportional adjustments are not
achieving the target viscosity, then the integral control function
will increase the calculated volume of wax during a proportional
calculation to drive toward the target in increasingly aggressive
steps. If an over-compensation condition occurs, the integral
control function may result in a reduction of the amount of wax
introduced into the mixture.
[0029] Derivative control involves using successive proportional
control and integral control iterations to evaluate the rate of
change between batches and, thus, make an initial shock adjustment
to the overall control algorithm. This may allow a reduction in the
amount of time it takes for the proportional control and integral
control iterations to reach target values of viscosity. This may
become a slope calculation and a resultant prediction over time
from the current measured value of viscosity. The integral and
derivative control methods provide for increased overall efficiency
and optimization of the control system.
[0030] In one embodiment, controller 80 may be a standard PID
control system such as that described in SIEMENS Standard PID
Control Manual, Edition 3/2003, found at
http://cache.automation.siemens.com/dnl/DQ/DQ1MzA5AAAA.sub.--1137084_HB/S-
tdpid_e.pdf. In addition, controller may utilize a control
algorithm in optimizing the viscosity of the coating asphalt. One
embodiment of such a control algorithm which may be used in the
present invention is shown in FIG. 3.
[0031] FIG. 2 illustrates an alternative embodiment wherein the wax
is introduced in coater supply line 46 upstream of a static mixer
tube 82 disposed in the supply line 46 at an inlet 84. The static
mixer tube 82 is preferably upstream of viscosity gauge 56. If the
inlet of the wax supply 84, the static mixer tube 82 and viscosity
gauge 56 are in close proximity, then this configuration may
provide a faster response time and reduce the duration of time that
the viscosity may be out of a desired range, but a person of skill
in the art would appreciate that care must be taken to ensure
homogeneity of the coating asphalt mixture when using the static
mixer tube 82.
[0032] The present asphalt shingle coating system 10 is used to
provide coater 48 with a supply of coating asphalt which has a
relatively constant viscosity. This provides numerous benefits
including increasing product uniformity, ensuring a consistent
product quality, increasing material-use efficiency, and benefiting
the proper operation of the coating machinery. In particular, the
present asphalt shingle coating system 10 includes a variable and
controlled introduction of wax into the coating asphalt mixture in
response to the measured or actual viscosity of the coating asphalt
in the coater supply line 46 measured by viscosity gauge 56.
[0033] Raw asphalt and the granular filler are introduced into
horizontal mixer 18 where they are mixed together. The filled
coating is then piped through filled coating supply line 24 to a
vertical mixer 26. The operation of the vertical mixer 26 may allow
for the homogenous mixing of the coating asphalt, which includes
the base asphalt, aggregate filler (limestone), and other additives
desired in the coating mixture. In one embodiment, wax may be
selectively delivered into vertical mixer 26 to affect the
viscosity of the coating asphalt mixture to the coater 48. Vertical
mixer 26 may also be used to mix the wax homogenously with the
other ingredients of the coating asphalt.
[0034] The coating asphalt mixture flows out of the vertical mixer
26 through the coater supply line 46 to coater 48. Coater asphalt
pump 50 and motor 52 ensure that the coating asphalt mixture is
delivered to the coater 48 in the desired quantity and rate. One or
more gauges or sensors may be disposed in coater supply line 46 to
measure various physical properties of the coating asphalt mixture
for quality control or operational purposes. In particular,
viscosity gauge 56 may measure the kinematic viscosity and/or
dynamic viscosity of the coating asphalt mixture. Viscosity gauge
56 is in electronic communication with controller 80 wherein
controller 80 receives a signal from viscosity gauge 56
corresponding to the desired viscosity measurements.
[0035] Controller 80 compares the measured or actual viscosity to a
desired or target viscosity to determine whether the viscosity of
the coating asphalt mixture is within the desired range. If the
viscosity is higher than the desired range, controller 80 estimates
the amount of wax that needs to be added to the filled coating
mixture and signals to wax supply motor 42 of wax pump 40 to
increase the flow of wax and/or adjust wax valve 38 to add the
desired volume of additional wax into the formulation. The
additional wax may be added directly to the vertical mixer 26 or
may be added into the coater supply line 46 and incorporated into
the mixture using a static mixing tube 82. Controller 80 may record
and analyze the cycles of individual adding of wax to optimize and
learn how much wax needs to be added at various occurrences of the
viscosity of the coating asphalt mixture being higher than the
desired range.
[0036] In the event the viscosity measured by viscosity gauge 56 is
lower than the desired range, then controller 80 may similarly act
to reduce the volume of wax being added to the filled coating
mixture in either vertical mixer 26 or the coater supply line 46.
Thus, controller 80 actively monitors the viscosity of the coating
asphalt mixture and reacts in substantially real-time to increase
or decrease the amount of wax added to the coating asphalt mixture
based upon the measured viscosity.
[0037] The present asphalt shingle coating system 10 may be used
when the base coating asphalt mixture formulation to be used does
not include wax and then exclusively adds wax as determined to
decrease the viscosity. Alternatively, if the base coating asphalt
mixture formulation already includes wax, the present system may be
used to vary the proportionate quantity of wax in the mixture to
create and maintain the desired viscosity. There are many factors
which will be considered by a person of skill in the art with
respect to the base formulations such as the initial quality of the
base asphalt, the volume of filler, whether the base asphalt is
blown, or whether additional admixtures are added to the asphalt
mixture. Thus, once a base coating asphalt mixture is specified,
the present asphalt shingle coating system 10 may be adapted as
necessary and used to maintain the desired application viscosity
using the addition of wax as described herein.
[0038] As shown in FIG. 3, one embodiment of a control algorithm
which may be carried out by control system/controller 80 includes
step 100 of inputting a step or ramp function as an input signal in
controller 80. In step 102, controller 80 seeks to determine
whether there is an error between the viscosity measured at the
sensor and a target viscosity. Step 104 involves controller 80
determining if the measured viscosity is above the target
viscosity. If the measured viscosity is below the target viscosity,
controller 80 initiates step 106, which includes applying a
negative proportional control constant "P" to reduce the wax pump's
flow rate. In step 108, controller 80 then determines if the
resample time interval has elapsed. If not, then controller 80
continues performing step 106. If the resample time interval has
elapsed, then controller 80 moves to step 114 to again measure
and/or determine if the viscosity is at target.
[0039] If in step 104, it is determined that the measured viscosity
is above the target viscosity, then controller 80 initiates step
110, which comprises applying a positive proportional control
constant "P" to increase the wax pump's flow rate to decrease the
viscosity. In step 112, controller 80 then determines if the
resample time interval has elapsed. If not, then controller 80
continues performing step 110. If the resample time interval has
elapsed, then controller 80 moves to step 114 to determine if the
viscosity is at target.
[0040] If controller 80 determines in step 114 that the system is
not at target, then controller again performs step 104 and adjusts
the operation of the wax pump based on whether the measured
viscosity is above or below the target. If, in step 114, controller
80 determines the system is at the target viscosity, then
controller 80 moves to step 116 and maintains the wax pump flow
rate. In step 118, controller 80 then determines whether the
resample interval has elapsed. If not, it keeps performing step 116
of maintaining the wax pump flow rate. If the resample interval has
elapsed, controller 80 again performs step 114 to determine whether
the system is operating to deliver a coating asphalt that is at
target viscosity.
[0041] The resample interval may be set to best optimize
performance. In one embodiment, the interval is less than a second
(in the milliseconds), and in another embodiment, the interval may
be multiple minutes. This variable may be left to the discretion of
the operator; however, it will be appreciated that the closer the
interval, the less likelihood of the coating asphalt will be
delivered to the coater outside of the target viscosity.
[0042] As is evident from the foregoing description, certain
aspects of the present invention are not limited to the particular
details of the examples illustrated herein. It is therefore
contemplated that other modifications and applications using other
similar or related features or techniques will occur to those
skilled in the art. It is accordingly intended that all such
modifications, variations, and other uses and applications which do
not depart from the spirit and scope of the present invention are
deemed to be covered by the present invention.
[0043] Other aspects, objects, and advantages of the present
invention can be obtained from a study of the drawings, the
disclosures, and the appended claims.
* * * * *
References