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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to paving materials and more particularly
to an apparatus and method for mixing asphalt and rubber to form an
asphalt-rubber pavement surfacing and repairing composition.
2. Description of the Prior Art
The increased volume of traffic along with general aging has caused severe
problems on many roadways, streets, and other paved surfaces in this
country. A particular problem results from elastic type failures in
pavements which causes cracking patterns of the type sometimes referred to
as an "alligator" cracking pattern. This type of elastic failure is caused
by fatigue of the pavement surface resulting from repeated deflections.
Other problems of concern are random cracking of paved surfaces due
primarily from expansion and contraction, and the general aging of the
sealing materials in expansion joints. All of these types of pavement
failures must be repaired to prevent water and/or uncompressible materials
from entering into the cracks or joints. If water enters into such cracks
or joints it can either wash out the base materials, or cause a general
breaking up of the pavement due to freezing. If uncompressible materials,
such as sand, enter into the cracks or joints it will severely restrict
expansion of the pavement and again result in a general breaking up of the
pavement surface.
Considerable experimentation has been conducted in recent times to provide
relatively low cost repair techniques, and of particular interest is an
asphalt-rubber composition which has proven to be a very satisfactory
material for use as a seal coating, for filling and sealing random cracks,
as a replacement for deteriorated materials in expansion joints, and the
like.
Briefly, the asphalt-rubber composition is a reaction product which is
neither asphalt nor rubber in nature but is an elastomeric sealing
compound. The asphalt-rubber composition includes a mixture of paving
grade asphalt and granulated crumb rubber of the non-oil resistant
asphalt-soluble type, which are prepared and mixed in conformity to a
specific method and mixture proportions. The asphalt is heated to a range
of between 350.degree. F. to 500.degree. F. and the granulated rubber is
added thereto, and mixed together. Although the mix proportions may vary
somewhat, it has been found that mix proportions of between 2 to 3 parts
of asphalt and one part of rubber are satisfactory and that a mix
proportion of 75% plus or minus 2% of asphalt by weight and 25% plus or
minus 2% of rubber provides the ideal composition which possesses an ideal
balance between the sealing characteristics of the asphalt and the
elasticity of the rubber. This particular asphalt-rubber composition is
fully disclosed in U.S. Pat. No. 3,891,585 issued on June 24, 1975 to
Charles H. McDonald.
Although the asphalt-rubber composition is an excellent material, its more
widespread usage has been held back by problems with handling and mixing
of the asphalt and rubber materials.
The asphalt material is normally delivered in bulk form, such as in tank
cars, to the mixing site and other than some occassional and relatively
minor contamination, will not pose any problems in addition to the well
known and expected difficulties associated with the handling of such
material.
The rubber generally used for this purpose is obtained from a supplier who
grinds up old automobile tires and packages the granulated crumb rubber in
bags of predetermined weight for shipment to the mixing site. The rubber
supplier is responsible for removing all metal and other contaminants from
the rubber, and for the most part does a pretty good job. However, some
metal, primarily from ground up steel belted radial tires, will be found
in the granulated rubber, and when this occurs, the useful life of pumps
and other equipment used in the handling and application of the
asphalt-rubber composition will be severely shortened.
Although the above described contamination of the asphalt and rubber
materials can be detrimental to the finished product and the handling
equipment, the inherent characteristics of those materials pose the
biggest problem, in that it is very difficult to mix those materials and
produce a consistently blended mixture of the proper proportions. The
granulated rubber is a somewhat cohesive material and as such will often
form clods that block supply conduits, applicator devices and the like. In
addition, the rubber has a tendency to float and avoid mixing with the
asphalt.
In general, the prior art practice for mixing the asphalt and rubber
materials includes pumping the molten asphalt (350.degree. F.-500.degree.
F.) through a suitable flow meter into a mixing tank and manually adding
an appropriate number of bags of granulated rubber. The flow meter is used
to control the amount of asphalt that is pumped into the mixing tank, and
the amount of rubber is controlled by counting the number of pre-weighed
bags of rubber that are added to the tank. Although this method of
determining the mix proportions is rather crude, if carefully done, the
results can be quite satisfactory. However, the packaging, handling,
weighing, and particularly shipping of the individual bags of granulated
rubber is very costly and time consuming, but is indispensable as far as
the prior art technique of mixing is concerned, in that the individual
bags of predetermined weight are relied upon for controlling the mix
proportions.
The prior art mixing tanks, although varying somewhat in configuration, are
all basically the same. Briefly, the mixing tanks are elongated
horizontally disposed structures with some sort of an agitation device
such as an auger arrangement which extends longitudinally through the
bottom of the tank. The asphalt and rubber materials are introduced into
the mixing tank through suitable ports and conduits located at the top
thereof, and the mixed asphalt-rubber composition exits the tank by means
of a pump and conduit arrangement located at the bottom of the tank. A
typical prior art mixing structure of the above described type is fully
shown and described in U.S. Pat. No. 3,610,588 issued on Oct. 5, 1971 to
G. W. Diefenbach.
The above described prior art practice and mixing mechanisms have proven
less than satisfactory for several reasons. First, the prior art makes no
provisions for ridding the asphalt and granulated rubber of contaminants.
Secondly, the manual introduction of the granulated rubber into the mixing
tank is of course, subject to human error and improper formulation of the
asphalt-rubber composition can occur. Thirdly, the prior art mixing
apparatus will not always break up the lumps or clods of granulated rubber
and this can cause plugging of the conduits and applicator devices. The
fourth, and most troublesome problem with the prior art method and the
apparatus, is that the produced asphalt-rubber composition is not always a
consistently blended mixture of the proper mix proportions.
As previously mentioned, the granulated rubber has a tendency to float and
avoid mixing with the molten asphalt, and therefore, the upper portion of
the materials within the tank will have a somewhat larger concentration of
rubber than the materials in the lower part of the tanks. During draining
the mixture having a lower rubber concentration will be pumped out faster
and easier than that having a high concentration of rubber. Since the
asphalt-rubber composition is pumped out of the bottom of the mixing tank,
the floating rubber will coat the interior of the tank, and the residual
composition remaining in the tank after draining, will have a high rubber
concentration. It is very rare for a mixing tank to be used for mixing a
single batch of the asphalt-rubber composition in that production and/or
job requirements most often require very large quantities of the
composition.
The above described coating of the tank and residual concentrations will
have a cumulative effect and it has been estimated that rubber
concentrations will reach between 30% and 35% near the end of a day's
continuous mixing tank usage, and this, of course, can cause serious
problems with the integrity of the asphalt-rubber composition.
Therefore, a need exists for a new and improved method and apparatus for
mixing an asphalt-rubber composition which overcomes some of the problems
and shortcomings of the prior art.
SUMMARY OF THE INVENTION
In accordance with the present invention, a new and improved apparatus and
method for mixing an asphalt-rubber composition is disclosed.
The apparatus includes an asphalt input system for supplying molten asphalt
at a known and variable rate, a granulated rubber input system for
supplying the rubber at a consistent and known rate, and a two-stage
mixing system for complete and consistent blending of the asphalt-rubber
composition.
The molten asphalt input system includes strainer means for removing
contaminants from the asphalt, a variable speed positive displacement pump
and asphalt flow sensing means for supplying the asphalt at a known and
variable rate, and an input spray manifold which extends longitudinally
across the top of a first mixing means for even distribution of the
supplied asphalt to all areas of the first mixing means.
A first embodiment of the granulated rubber input system is designed to
handle the bags of granulated rubber, and includes an input hopper located
at the lower end of an upwardly inclined variable speed conveyor. The
conveyor delivers the granulated rubber to an accumulation hopper which
feeds the rubber to a positive displacement feeding means that delivers
the rubber at a constant rate into the top of the first mixing means. A
magnetic separator is interposed between the feeding means and the first
mixing means to remove metal fragments from the granulated rubber.
A second embodiment of the granulated rubber input means is designed for
supplying the rubber from a bulk source, such as a tank car, to the first
mixing means, and includes a materials feeding centrifugal blower which
directs the materials from the supply to a cyclone. The output of the
cyclone has a magnetic separator for the above described purpose, and the
rubber passes therethrough into an input hopper located at the bottom of
an upwardly inclined variable speed conveyor. The rubber delivered to the
upper end of the conveyor is deposited into an accumulation hopper which
is provided with a positive displacement feeding means as described above.
Alternately, the rubber from the conveyor may be delivered to an endless
electronic conveyor scale which senses the weight and the speed of the
rubber being delivered into the first mixing means and is adapted to
appropriately adjust the speed of the endless electronic conveyor scale
and the speed of the variable speed conveyor to arrive at and maintain the
desired constant feed rate of the rubber.
The first mixing means of the two-stage mixing system, which is optionally
equipped with a heating means, includes a tank having a pair of rotatably
driven augers which extend across the bottom of the tank. A float
mechanism is provided in the tank which maintains the materials therein at
a predetermined level and does so by controlling the operation of a
variable speed positive displacement asphalt output pump located in the
output conduit leading from the bottom of the first mixing means. The
materials moving through the output conduit are passed under pressure
through a second mixing means in the form of a motionless mixer which is
the second stage of the two stage mixing system. The motionless mixer
completes mixing of the asphalt and rubber materials to produce a
completely and consistently blended product which is delivered from the
output end of the motionless mixer to a point of use.
Accordingly, it is an object of the present invention to provide a new and
improved apparatus and method for mixing molten asphalt and granulated
rubber.
Another object of the present invention is to provide a new and improved
apparatus for mixing molten asphalt and granulated rubber which may
include means for removing contaminants from the asphalt and rubber
materials.
Another object of the present invention is to provide a new and improved
apparatus for mixing molten asphalt and granulated rubber which includes
means for controlling the input feed rate and the amount of molten asphalt
delivered thereto.
Another object of the present invention is to provide a new and improved
apparatus for mixing molten asphalt and granulated rubber which includes
means for controlling the input feed rate and the amount of granulated
rubber delivered thereto.
Another object of the present invention is to provide a new and improved
apparatus for mixing molten asphalt and granulated rubber which includes a
granulated rubber input system that is configured to receive and handle
rubber that is manually supplied thereto from pre-weighed bags.
Another object of the present invention is to provide a new and improved
apparatus for mixing molten asphalt and granulated rubber which includes a
granulated rubber input system that may be configured to receive and
handle rubber from a bulk supply thereof.
Another object of the present invention is to provide a new and improved
apparatus of the above described character which includes a two-stage
mixing means for mixing and blending the molten asphalt and granulated
rubber to produce a completely and consistently blended composition.
Still another object of the present invention is to provide a new and
improved apparatus of the above described character in which the two-stage
mixing system includes a mixing tank and a motionless mixer.
The foregoing and other objects of the present invention, as well as the
invention itself, may be more fully understood from the following
description when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a first embodiment of the asphalt-rubber
mixing apparatus of the present invention illustrating the various
features thereof.
FIG. 2 is a fragmentary perspective view of the asphalt input system and
the first mixing means of the apparatus of the present invention with
portions thereof broken away to show the various features.
FIG. 3 is a fragmentary elevational view of the positive displacement
rubber feeding means which forms part of the granulated rubber input
system of the present invention, with portions broken away to show the
various features thereof.
FIG. 4 is an end view of the first mixing means of the apparatus of the
present invention with portions broken away to show the various features
thereof.
FIG. 5 is a fragmentary perspective view of the first mixing means with
portions thereof broken away and illustrating a modification thereof.
FIG. 6 is a perspective view of the second mixing means in the form of a
motionless mixer which forms the second stage of the two-stage mixing
system of the apparatus of the present invention, with portions of the
motionless mixer broken away to illustrate the various features thereof.
FIG. 7 is a diagrammatic illustration of the first embodiment of the
apparatus of the present invention showing the various systems thereof in
schematic form.
FIG. 8 is a perspective view of a second embodiment of the apparatus of the
present invention.
FIG. 9 is a diagrammatic view of the second embodiment of the apparatus of
the present invention showing the various systems thereof in schematic
form.
FIG. 10 is a diagrammatic illustration showing a modification of the
asphalt input system of the apparatus of the present invention.
FIG. 11 is an enlarged sectional view taken on the line 11--11 of FIG. 10.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring more particularly to the drawings, FIG. 1 shows a first
embodiment of the asphalt-rubber mixing apparatus of the present
invention, with the apparatus being indicated in its entirety by the
reference numeral 15.
The apparatus 15 is shown as being supported on a suitable frame 16 which
is preferably in the form of a trailer device having the usual wheels 17.
It is to be understood that the trailer configuration shown is not to be
construed as a limitation of the present invention in that the frame 16
could be suitably configured for a fixed installation, or could be a
self-propelled automotive vehicle as dictated by the intended usage.
In any event, the apparatus 15 includes various systems and subsystems
which cooperate in the mixing of an aspalt-rubber compound, and as will
hereinafter be described in detail, the main systems include an asphalt
input system, a granulated rubber input system, a two-stage mixing system,
and a control system.
As best seen in FIG. 2, the asphalt input system includes an asphalt input
pipe 20 for receiving molten asphalt from a remote heating mechanism (not
shown). The asphalt input pipe 20 is one branch of a Y-shaped conduit 22
the other branch of which is closed with a removable cover 23 which
provides access to a first strainer means in the form of a relatively
large mesh strainer basket 24 which is removably mounted in the trunk 25
of the conduit 22. The conduit 22 is suitably mounted on the inlet port 26
of a positive displacement asphalt input pump 28 which is driven by a
variable speed motor 30. The output from the pump 28 is coupled by means
of a conduit 31 to a second comparatively fine mesh strainer means 33
which is removably carried in a T-shaped conduit 34 that has a capped
branch 35 which allows the strainer basket 33 to be removed and replaced
for cleaning purposes. The other branch 37 of the T-shaped conduit 34 is
coupled to the inlet of an asphalt flow sensing means 40 which is in the
form of a flow meter having an indicator device 41 which displays the
gallons per minute of the asphalt flowing therethrough. The flow meter and
display device are well known commercially available mechanisms such as
that available from the Liquid Controls Corporation of North Chicago,
Ill., and identified as model number M-15-H. The output from the flow
meter 40 is supplied through a conduit 43 to the asphalt inlet port 44 of
a first mixing means 46 which forms the first stage of the two-stage
mixing system of the present invention. The molten asphalt input system
further includes a spray manifold 48 which is mounted in the upper portion
of the first, or premixing, means 46 so as to extend substantially the
full length thereof. The manifold is connected on its inlet end to the
inlet port 44 of the first mixing means 46 and has its other end closed as
at 49. The manifold 48 is provided with a plurality of spray nozzles 50
that are spacedly arranged along the length thereof.
From the above, it will be seen that the molten asphalt input system
includes means for removing contaminants from the supplied asphalt in the
form of the first and second strainer means 24 and 33, respectively, means
for indicating the asphalt flow rate in the form of the flow sensing means
40 and indicator 41, means for adjustably varying the asphalt flow rate in
the form of the variable speed motor 30, and means for dispensing the
asphalt evenly across the top of the first, or premixing means 46 in the
form of the spray manifold 48.
The granulated rubber input system, as best seen in FIGS. 1 and 3, includes
an input hopper 54 having a relatively large input opening 55 at the upper
end thereof with a pair of opposed converging sidewalls which terminate at
a relatively small outlet opening 56 located at the bottom of the hopper.
The input hopper 54 has a plurality of bars 58 spacedly arranged in the
inlet opening 55 thereof which form a grate that is designed to allow the
granulated rubber to freely fall into the hopper and to catch fragments of
the bags (not shown) in which the rubber is supplied. An upstanding
wedge-shaped spike 60 is provided on one of the bars 58 by which the bags
of granulated rubber may be torn open so that the contents of the bags
will empty into the hopper. The input hopper 54 is suitably supported on
the lowermost end of an angularly upwardly extending conveyor 62 which
includes the usual endless conveyor belt 63 having spacedly arranged
transverse ribs 64 thereon. The conveyor belt is driven by a variable
speed motor 66 which is connected to drive the belt moving roller 67
located at the lowermost end of the conveyor.
The upper end of the conveyor 62 is connected to an accumulation hopper 70
so that the granulated rubber transported by the conveyor 62 will be
deposited into the open input opening 71 of the hopper 70. The purpose of
the accumulation hopper 70 is to maintain a stockpile of the granulated
rubber during operation of the apparatus 15 so that the operation of the
rubber feeding means, which will hereinafter be described in detail, will
not be interrupted or otherwise effected by any deviations in the rate at
which the bags of rubber are emptied into the input hopper 54. The
accumulation hopper 70 is a downwardly converging structure having a
relatively small outlet opening 72, and the hopper is supported atop the
rubber feeding means 74.
The rubber feeding means 74 includes a horizontally disposed cylindrical
housing 75 having an upwardly opening radially extending inlet port 76
formed at one end thereof, with that port being in communication with the
outlet opening 72 of the accumulation hopper 70 and a downwardly opening
radially extending outlet port 77 at its opposite end. An auger 78 is
axially disposed in the bore 79 of the cylindrical housing 75 and is
rotatably journaled on its opposite ends in suitable bearing means 80. The
auger 78 is sized to be a close tolerance fit in the bore 79 of the
housing so as to be a positive displacement feeding mechanism, and the
auger is driven by a variable speed motor 82 which is mounted on one end
of the housing 75 and is suitably coupled to the shaft of the auger.
The radial outlet port 77 of the positive displacement rubber feeding means
74 is coupled to the inlet of a suitable electromagnetic separator means
84 which is intended to remove ferromagnetic particles which may be in the
granulated rubber. Electromagnetic separators of the type suitable for
this purpose are well known in the art and a detailed discussion thereof
is not felt to be necessary. A suitable electromagnetic separator is
available from the S. G. Frantz Company, Inc., P.O. Box 1138, Trenton,
N.J. 08606, and is identified as Model No. 68V-HP.
From the above discussion, it will be seen that the granulated rubber input
system includes means for receiving the rubber in the form of the input
hopper 54, means for transporting the rubber at a variable speed in the
form of the conveyor 62 with its variable speed drive motor 66, means for
stockpiling the rubber in the form of the accumulation hopper 70, means
for delivering the rubber at a controllable constant feed rate to the
first mixing means 46 in the form of the positive displacement rubber
feeding means 74 with its variable speed drive motor 82, and means for
removing ferromagnetic contaminants from the granulated rubber in the form
of the separator means 84.
As hereinbefore mentioned, a first, or pre-mixing means 46 is the first
stage of the two-stage mixing system of the present invention, and
receives molten asphalt from the spray manifold 48 in variably
controllable amounts from the hereinbefore described asphalt input system,
and receives rubber in a variably controllable constant feed rate through
the rubber inlet port 86 thereof from the separator means 84 of the
hereinbefore described granulated rubber input system, and accomplishes a
preliminary mixing of the received materials to produce the asphalt-rubber
composition 88.
As seen in FIGS. 1, 2, 4 and 5, the first, or pre-mixing, means 46 includes
an elongated horizontally disposed tank 90 having the hereinbefore
described asphalt inlet port 44, spray manifold 48, and rubber inlet port
86 located in the upper portion thereof. Agitation means in the preferred
form of a spaced apart pair of augers 92 and 94 are rotatably journaled in
the bottom portion of the tank 90 and are disposed to extend the full
length thereof. As seen in FIG. 1, the axial shafts 95 and 96 of the
augers 92 and 94, respectively, extend through one end of the tank 90 and
have sprockets 97 and 98 mounted fast thereon. The sprockets 97 and 98 are
coupled by suitable chains to a variable speed drive motor 100.
The tank 90 has an asphalt-rubber composition outlet port 102 (FIG. 4) in
the bottom thereof which is coupled by means of a conduit 104 to the inlet
port 105 of a positive displacement asphalt output pump 106 which is
driven by a variable speed motor 108, as seen best in FIG. 2.
The tank 90 has a materials level sensing means in the form of a float
mechanism 110 mounted therein to automatically maintain the asphalt-rubber
composition 88 at a predetermined level. The float mechanism 110 includes
a float body 111 which has its opposite ends supported by a pair of swing
arms 112, with the opposite ends of the arms 112 being attached to a shaft
113 which is journaled for rotation, as at 114, in the end walls of the
tank 90. One end of the rotatable shaft 113 extends through the end wall
of the tank 90 as shown in FIG. 5, and has a level indicator 116 mounted
fast thereon, with the indicator being in the form of a pointer which, in
conjunction with a suitable scale 117, provided on the exterior of the
tank 90, provides a visual indication of the level of the asphalt-rubber
composition 88 in the tank 90. The extending end of the shaft 113 also has
a linkage assembly 118 connected thereto and the purpose of this linkage
assembly will hereinafter be described in detail.
Although the asphalt-rubber mixing apparatus 15 of the present invention is
primarily intended to operate with substantially constant input feed rates
of the molten asphalt and the granulated rubber, and a substantially
constant asphalt-rubber composition output rate, instances may occur where
the asphalt-rubber composition must be held in the first mixing means 46
for undetermined periods of time. For example, when the asphalt-rubber
composition is being mixed for supplying spreader vehicles (not shown),
unusually long periods of time may occur between successive vehicles; in
this and other situations, the molten state of the asphalt-rubber
composition must be maintained to prevent cooling and the resulting
solidification thereof. Therefore, the first mixing means 46 may include a
heating means for maintaining the molten state of the asphalt-rubber
composition 88 when needed.
To accommodate the above mentioned heater means, the tank 90 as seen best
in FIGS. 2 and 4, is formed with a substantially cylindrical outer shell
124 with a cylindrical hot tank 126 mounted therein. A heating jacket 128
having a heating oil 129 or other heatable liquid, therein is positioned
below the hot tank 126 in coextensive contiguous engagement with
approximately one half of the curved peripheral surface thereof. The hot
tank 126 and the heating jacket 128 have a suitable insulative blanket 130
wrapped therearound to retard heat loss. A heating oil drain line 131
depends from the bottom of the heating jacket 128 and extends exteriorly
from the outer shell 124. A fill line 132 extends upwardly from the
heating jacket and is capped with a dip stick assembly 133, and a vent
line 134 similarly extends from the heating jacket.
A flammable gas supplied from a suitable source, either from tanks (not
shown) mounted on the frame 16, or from a remote location, is supplied
through a suitable control box 136, mounted on the first mixing means 46,
to a pair of burners 137 and 138. The burners are disposed within
different ones of a spaced pair of heater flues 139 and 140 which extend
through the end wall of the outer shell 124 into the heating jacket 128.
The flues 139 and 140 are formed into looped configurations as at 142, so
as to return through the same end wall of the outer shell 124 and extend
upwardly therefrom to provide exhaust stacks 143 and 144.
One end of a conduit 146 (FIG. 2) is connected to the outlet port 148 of
the asphalt-rubber composition output pump 106, with the other end of the
conduit 146 being connected to the inlet port of a second mixing means in
the form of a static, or motionless mixer 150 (FIGS. 1 and 6) which is the
second stage of the two-stage mixing system of the apparatus of the
present invention.
As seen in FIG. 6, and as is well known in the art, the motionless mixer
150 includes a cylindrical housing 152 having a series of alternating
right hand and left hand helical elements 154 fixedly mounted in the bore
155 thereof. The asphalt-rubber composition 88 pumped through the
motionless mixer 150 is subjected to dividing and rotational forces due to
the helical elements 154, with the degree of mixing being considerably
greater than anything possible with an agitation type of mixing device
such as the hereinbefore described first mixing means 46. A motionless
mixer suitable for this purpose is available from The Luwa Corporation of
P.O. Box 16348, Charlotte, N.C. 28216.
After passing through the motionless mixer 150, the thoroughly blended
asphalt-rubber composition enters into a conduit 157 for delivery to a
point of use.
Referring once again to FIG. 1 wherein an engine 160 is shown for driving a
hydraulic pump assembly 162, which will hereinafter be described in
detail. Also shown is a fuel tank 164 for operation of the engine 160, and
a hydraulic oil reservoir tank 166.
The control system of the apparatus 15 of the present invention, along with
the operation of the apparatus itself will now be explained in detail with
particular reference being made to FIG. 7.
The engine 160 is coupled to a suitable pump drive means 168 which drives a
plurality of hydraulic pumps 170, 172, 174, 176 and 178, with those pumps
operating the various systems and subsystems of the apparatus 15.
Hydraulic oil from the reservoir tank 166 is supplied through line 180 to
the inlet of the hydraulic pump 170 which is a split pump in that the oil
is simultaneously directed into two separate segments of the pump with
each of those segments delivering a different outlet pressure to their
respective outlet ports 181 and 182. The hydraulic oil from the outlet
port 181 is directed into a supply manifold 184 which supplies that oil
under pressure to the hydraulic pumps 172, 174, 176 and 178 as will
hereinafter be described. The hydraulic oil from the outlet port 182 is
directed by a line 185 to a tee 186 into a line 187 which is connected to
the variable speed hydraulic motor 108 which drives the asphalt-rubber
composition output pump 106, and this oil which drives the motor 108 is
directed through a return line 188 to a suitable collection manifold 190
which returns the oil to the reservoir tank 166. A bypass line 192 is
connected between the tee 186 and the collection manifold 190 with a flow
control valve 194 in the bypass line 192. The flow control valve 194 is an
adjustable mechanism which allows more or less oil under pressure to be
fed directly into the collection manifold 190 and will thus cause more or
less oil under pressure to be directed through the line 187 to the motor
108. Therefore, the speed of the motor 108 and thus the output pump 106 is
variable in accordance with the adjustment of the flow control valve 194.
As hereinbefore mentioned, the float mechanism 110 in the tank 90 of the
first mixing means 46 has a linkage assembly 118 connected thereto. This
linkage assembly 118 as shown in dashed lines in FIG. 7, is connected to
the flow control valve 194, which may be housed in the control panel 195
as seen in FIGS. 1 and 5, and will adjust the valve in accordance with the
level of the asphalt-rubber composition 88 in the first mixing means 46.
Hydraulic oil under pressure is supplied to the inlet port of the hydraulic
pump 172 from the supply manifold 184 and passes through the pump 172 into
a line 196 which is connected to a tee 197. A line 198 from the tee 197
supplies the hydraulic oil under pressure to the variable speed hydraulic
motor 82 which drives the positive displacement rubber feeding means 74.
After driving the motor 82, the hydraulic oil is directed through a return
line 199 to the collection manifold 190 which in turn directs the oil back
to the reservoir tank 166. A bypass line 200 is connected between the tee
197 and the collection manifold 190 and a flow control valve 202 is
located in that bypass line. The flow control valve 202 is a manually
adjustable device for allowing more or less oil under pressure to be fed
directly into the collection manifold 190 and thus will cause more or less
oil under pressure to be directed through the supply line 198 to the motor
82. Therefore, the speed of the motor 82, and thus the feed rate of the
positive displacement rubber feeding means 74, is variable in accordance
with the adjustment of the flow control valve 202. As shown in FIG. 7, the
motor 82 is equipped with a suitable tachometer 204 which indicates the
speed of the motor 82 and thus the RPM of the positive displacement
feeding means 74. Therefore, an operator can adjust the RPM of the
positive displacement feeding means 74 by manually adjusting the flow
control valve 202.
Hydraulic oil from the supply manifold 184 passes through the pump 174 into
a line 206 which is connected between that pump and a tee 207. Line 208
supplies the hydraulic oil under pressure from the tee 207 to the variable
speed motor 100 which drives the mixing augers 92 and 94 that are mounted
in the mixing tank 90. After driving the motor 100, the hydraulic oil is
directed through a return line 210 to the collection manifold 190 and is
thus returned to the reservoir tank 166. A bypass line 212 is connected
between the tee 207 and the collection manifold 190 and a flow control
valve 213 is located in that line. The flow control valve 213 is a
manually adjustable device which allows more or less hydraulic oil to be
fed directly into the collection manifold and thus allows more or less oil
to be directed to the auger motor 100 for driving thereof in accordance
with the adjustments made by an operator.
The supply manifold 184 also supplies hydraulic oil to the pump 176 which
passes therethrough into a line 215 having a tee 216 therein. A line 217
supplies the hydraulic oil under pressure to the variable speed motor 30
which drives the molten asphalt input pump 28 of the asphalt input system.
Oil from the motor 30 is directed through a return line 218 to the
collection manifold 190 and is thus returned to the reservoir tank 166. A
bypass line 219 is connected between the tee 216 and the collection
manifold 190 and a flow control valve 220 is positioned in that line. The
flow control valve 220 is a manually adjustable device for directing more
or less hydraulic oil through the bypass line 219 and thus allowing more
or less oil to be directed to the motor 30 for variable speed driving of
the asphalt input pump 28 in accordance with adjustments made by an
operator.
Hydraulic oil from the supply manifold 184 passes through the pump 178 into
the line 222 which is connected between the pump and a tee 223. A line 224
supplies the hydraulic oil under pressure from the tee 223 to the variable
speed motor 66 which drives the conveyor 62 of the granulated rubber input
system. Oil from the motor 66 is directed through a return line 225 to the
collection manifold 190 and is thus returned to the reservoir tank 166. A
bypass line 226 is connected between the tee 223 and the collection
manifold 190 and a flow control valve 228 is located in the bypass line
226. The flow control valve 228 is a manually adjustable mechanism for
directing more or less hydraulic oil through the bypass line 226 and thus
allowing more or less oil to be directed to the motor 66 for variable
speed driving thereof in accordance with adjustments made by an operator.
It will be understood, particularly by those skilled in the hydraulic arts,
that the above described control system is but one way that the desired
control functions can be achieved. To illustrate this point, each of the
previously described pumps 170, 172, 174, 176 and 178 and their
respectively associated flow control valves 194, 202, 213, 220 and 228
could be replaced with a variable volume axial piston pump (not shown). As
is well known, a variable volume axial piston pump is a device which
includes a built-in control device commonly referred to as a swash plate,
and by suitably positioning the swash plate the output volume of such a
pump can be infinitely varied. This is simply a hardware modification in
that the control system function and operation will remain the same.
Further hardware modifications can be made with the resulting control
system being functionally unaffected. For example, the hydraulic control
system hereinbefore disclosed could be completely electric, completely
pneumatic, or could be hybrid combinations thereof.
Modification of the basic control system function and operation are also
possible without effecting the over all operation of the apparatus 15. In
the above described control system, both the asphalt input system and the
granulated rubber input system are fully and independently adjustable.
Since the granulated rubber feeding means 74 is a positive displacement
feeding device, due to the close tolerance fit of the auger 78 in the
housing 75, it will deliver a given amount of rubber for each revolution
of the auger. Thus, fixed nonadjustable driving of the rubber feeding
means 74 at a predetermined RPM will deliver a fixed constant quantity of
the rubber in a given length of time, and the asphalt input system can be
appropriately adjusted to deliver the proper amount of asphalt to match
the known amount of rubber, and thus arrive at the desired mixture
proportions.
Referring now in particular to FIGS. 8 and 9 wherein a second embodiment of
the asphalt-rubber mixing apparatus of the present invention is shown and
is indicated generally by the reference numeral 15a. As will be seen as
this description progresses, some of the systems and subsystems of the
apparatus 15a are identical to those of the hereinbefore described
apparatus 15, and in such instances those systems and subsystems will be
identified by the previously mentioned reference numerals are the detailed
descriptions thereof will not be repeated.
The asphalt-rubber mixing apparatus 15a is provided with a granulated
rubber input system that is designed to extract and otherwise handle the
rubber from a bulk supply of such material, as for example, from a tank
car (not shown) or any other bulk material transport and/or storage
apparatus.
Therefore, the granulated rubber input system of the apparatus 15a includes
a materials feeding blower means 240 which is driven by a variable speed
motor 242. The axial inlet port 243 of the blower means 240 has a suction
line, or hose, 244 connected thereto with the suction line being intended
to reach into the previously mentioned bulk granulated rubber supply (not
shown) and extract the rubber therefrom due to the negative static
pressure created by operation of the blower means. The granulated rubber
is fed by the blower means 240 under pressure through its outlet port 246
into a conduit 248 to the top of a suitable cyclone 250 which is supported
by a superstructure 252 mounted on the frame 16. The cyclone 250 separates
the air from the granulated rubber passing therethrough in accordance with
the well known operating principles of cyclones and the granulated rubber
will pass through the electromagnetic separator means 84 which separates
ferromagnetic particles from the rubber in the manner hereinbefore
described.
The granulated rubber falling from the cyclone 250 and the separator means
84 enters into an accumulation hopper 254 which contains a predetermined
amount of the granulated rubber at all times during operation of the
apparatus 15a to insure an interrupted and steady feeding of the rubber as
will become apparent as this description progresses.
The accumulation hopper 254 is supportingly carried on the lowermost end of
the conveyor 62 which, as hereinbefore described, is driven by the
variable speed | | |
