Note: Descriptions are shown in the official language in which they were submitted.
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This application is divided out of copending Canadian application
No. 285,295, filed October 13, 1977.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a new and improved apparatus and
method for making molds and encompasses both conventional or green sand mold-
ing processes and the newer process known as no-baké wherein the binder is a
catalyzed plastic resin material rather than the conventional natural material
binders commonly used in green molding.
One of the most common and economical metal forming techniques in-
volves the pouring of molten metal into a preformed cavity called a mold
wherein the metal then solidifies. After solidification, the mold is opened
and the casting is removed or knocked out of the mold for further processing
and the mold is destroyed in the process. Just as the characteristics of the
liquid or molten poured into the mold cavity may vary dependent on the design
of the particular casting, the molding material utilized in making the mold
cavity may also vary widely. At the present time, the most commonly used
molding material is silica sand and the silica sand grains are bound together
to provide sufficient mold strength by many types of binding materials. In
green sand molding, which is by far the most wi.dely used method in molding
metal castings, the binding material comprises a mixture of clay, water and
bentonite and the silica sand and binder are treated in various types of
equipment until a more or less homogeneous mold forming mixture of sand and
binder is achieved. A mold cavity is then formed with this mixture by depos-
iting the mixture over a pattern which is removed to form the cavity.
The sand and binder mixture should have a number of characteristics
to be successfully used for high quality castings. The mold forming material
must be flowable in order to readily fill the cavities and contours of the
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pattern needed. The material must haye sufficient green strength to retainthe cavity shapc while the pattern is remo~ed until the molten metal is intro-
duced. The material must also have sufficient hot strength to contain the
high temperature molten metal within the mold cavity and provide the needed
dimensional accuracy while allowing for the escape of gases which develop as
the molten metal flows into the mold cavity and cools. After cooling of the
casting, the material must be readily destructable so that the finished cast-
ings can be removed or "knocked-out". The spent molding material, for econ-
omical reasons, must also be reworkable or reclaimable for re-use in succes-
sive mold forming operations with a minimum of refinement and treatment beingrequired.
It should be noted that some of the characteristics required are
conflicting, for example, the needed hot strength of a mold to provide for
good dimensional accuracy makes the mold much tougher to destroy and the
"knock-out" process is difficult after the casting process has been completed
and the casting has cooled. In addition, the greater amount of binder added
for producing hot strength make reclamation of the molding materials more
difficult and more expensive. Because of these types of conflicts, a com-
promise in characteristics of the molding material is usually made becatlse
all of the desired characteristics are not achievable. These same problems
are present with the more modern method of "no-bake" molding wherein a cata-
lyzed plastic resinous material is used for binder with silica sand. In "no-
bake" processes high mold strength is achieved but the process is considerab-
ly more expensive because of the relatively high cost of the plastic resin
binders. Also, the "knock-out" process is much more difficult and the mat-
erial is not generally re-usable on an economical basis~ Moreover, sometimes
"no-bake" process molds do not readily permit the hot gases formed during the
molding process to readily escape and thus, gas pockets develop in the cast-
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ings. In addition, the dispensing apparatus used in the "no-bake" molding
process is subject to clogging and other problems because the mixture sets up
or hardens very quickly after the catalyst is added to the sand-resin mixture.
Description of the Prior Art
In prior art green sand molding systems the sand and binder are
mixed in batches or continuously in a constant ratio to provide the necessary
compromise characteristics needed for the mold. After mixing is completed,
the material is deposited into a mold flask around a pattern and subsequently,
the pattern is then separated from the mold. Usually a pair of mold flasks,
called a cope and a drag, are coupled together to form the completed mold
cavity. The characteristics of the molding sand mixture is usually constant
for a given operation and hence certain parts of the mold may have more binder
than is actually needed. This, of course, results in increased difficulty in
the knock-out operation and in the reclamation process to re-use the same
molding sand again after the castings are knocked-out and removed. Because
of the complexity of making different or varying mixes of sand and binder for
different portions of a mold to provide the different strength characteristics
as required in the prior art system a uniform mixture was usually established
and used throughout. Because of this, many of the foregoing problems in green
sand casting occurred.
In no-baké molding systems, only relatively small batches of sand
and binder are mixed at one time because of the relatively short working time
available before setting of the resin takes place. Once the resin is catal-
yzed, the batch of material has to be placed in the molds very quickly in
order that the material does not set up before the mold is completed. Usual-
ly, the whole surface of the mold pattern is covered with the molding sand
and catalyzed resin mix having a relatively uniform ratio of sand and resin-
ous material and accordingly in areas where the mold strength required is not
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high, excess resin is wasted with the attendant economic loss and knock-out
problems. Also, since a large amount of resinous material is present through-
out the mold, the organic material in the binder cannot all be oxidized during
the casting operation with the result that heavy vapor and fumes are produced
during the casting operation which is obnoxious to the operators and from an
air pollution standpoint.
It is therefore an important object of the present invention to pro-
vide a new and improved method and apparatus for making customized molds.
More particularly, it is an object to provide a new and improved
method and apparatus of the character described which eliminates or reduces
one or more of the foregoing mentioned difficulties of prior art systems.
Yet another object of the present invention is to provide a new and
improved program controlled customized method and apparatus for making molds
wherein a layer of molding material comprising a mixture of sand and binder
is dispensed over a mold forming pattern by relative movement between the
pattern and the dispenser with the ratio of sand and binder automatically
and selectively controlled and varied as needed in accordance with the rel-
ative position of the dispenser and the pattern. Thus, in areas on the
pattern where high stress occurs in the mold, more binder or resin is mixed
with the sand and in other areas where the mold strength requirement is
~educed, lesser amounts of binder or resin are utilized. This results in
economic savings all the way down the line in producing finished castings.
Yet another object of the present invention is to provide a new and
improved program controlled, customized method and apparatus for making molds
of the character described wherein the thickness of the layer of mold forming
material deposited on the surface of the pattern is automatically controlled
and can be varied at different positions over the mold forming pattern in
accordance with the strength required at a particular point on the pattern
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surface.
Still another object of the invention is to provide a new and im-
proved method and apparatus of the character described wherein the ratio of
molding sand and binder is selectively controlled and variable in response
to the point of application of the molding mixture onto the surface of the
pattern used for forming the mold cavity.
Still another object of the present invention is to provide a new
and improved method and apparatus of the character described wherein a pro-
grammed control system of the tape or drum controlled type is provided for
selectively and variably controlling relative movement between a molding
material dispenser and a mold forming pattern as well as the ratio of sand
and binder being deposited at any particular location.
Still another object of the present invention is to provide a new
and improved method and apparatus of the character described wherein the
relative position of a molding material dispensing device and a mold forming
pattern surface are automatically controlled in a plural axis coordinate
system and the thickness of the deposited layer of molding material is also
automatically controlled.
Another object of the present invention is to provide a new and im-
ZO proved apparatus and method of the character described wherein either a mold-
ing material dispensing device is movable relative to a fixed mold forming
pattern surface or vice versa.
Another object of the invention is to provide a new and improved
mold having an inner layer formed of molding material including a wetting
agent for improving the surface of the material being cast and reducing the
amount of mold material tending to stick to the casting after the knock-out
process and having succeeding layers around the inner layer without said
wetting agent.
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Yet another object o~ the invention is to pro~ide a new and improv-
ed mold havillg an inner first layer forming a mold cavity comprising a mix-
ture of sand and organic binder of a thickness such that substantially all of
the binder is oxidized by the heat received from the molten material cast in
the cavity and having successive layers around said inner layer comprising a
mixture of sand and inorganic binder.
Yet another object of the invention is to provide a new and im-
proved continuous mixer for molding material including a first portion for
mixing sand and uncured resin binder and a second portion for mixing catalyst
with said sand and uncured binder.
Yet another object of the invention is to provide a new and im-
proved continuous mixer as in the preceding object including a controllable
metering plate for controlling the flow between said first and second
portions of said mixer.
A further object of the present invention is to provide a new and
improved method and apparatus of the character described wherein the suc-
cessive layers of molding material which are automatically deposited on the
pattern may have different organic or inorganic binders so as to facilitate
knock-out and reclaiming of the mixture and to minimize smoke and fumes
during the casting process.
Still another object of the present invention is to provide a new and
improved method and apparatus of making molds of the character described
wherein program controlled apparatus is provided for forming molds in a
highly accurate and repeatable manner.
SUMMARY OP THE INVENTION
The foregoing and other objects and advantages of the present in-
vention are accomplished by providing a dispenser for mixing and discharging
successive layers of molding material onto the surface of a mold forming
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pattern mounted in a mold flask. An automatic control system is pro~ided for
producing controlled relative movement between the dispenser and the pattern
and including facilities for varying the ratio of sand and binder being de-
posited onto the pattern from the dispenser in accordance with the mold
strength needed for the mold cavity at any particular position on the casting
surface. This automatic control system may be of the type shown in Forrester
et al. Patent No. 3,069,608 wherein digital representations are provided on a
control tape in which successive blocks of information correspond to desired
increments of movement in a plural axis coordinate system. Briefly stated,
in such a control system a clock oscillator is employed to develop a series
of pulses which are then supplied to a linear interpolator which in response
to numerical commands read from the tape produces separate streams of pulses
for each controlled axis which are uniformly spaced in time and quantitative-
; ly represent the desired increment of movement in that axis. These separate
pulse streams are then utilized to control movement in each axis so that a
desired path in space is achieved. If a curved path is desired it is achiev-
ed by programming a series of closely spaced straight line segments which
approximate the desired curve to a predetermined degree of accuracy.
The mixing and dispensing apparatus of the present invention is
particularly suited for use in the no-bake type of process and includes
facilities for separately supplying controllable amounts of resin and catalyst
to the mixing chamber. To this end, the volume of sand supplied to the mixing
chamber is continuously measured and this measurement is employed in con-
junction with a ratio number obtained from the system control tape or drum
to control the amount of resin supplied to the mixing chamber at any particu-
lar instant. A similar arrangement is employed to controL the amount of cat-
alyst supplied to the mixing chamber at any particular instant. The dispens-
ing apparatus also includes facilities for mixing the sand, resin and catalyst
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in a vertically arranged self-draining mixing chamber and means are provided
for shutting off the supply of sand and resin mixture ahead of the point
where the catalyst is introduced so that the mixing apparatus can be shut
down without clogging due to setting of the sand-resin-catalyst mixture. The
control system also provides for automatically controlling the thickness of
each layer of molding mixture deposited on the pattern by the dispenser.
Control of layer thickness may be obtained by means of a feed rate number ob-
tained from the system control tape or drum in which case layer thickness may
be varied at different locations on the pattern by varying the velocity of
movement of the mixing head in these areas. In the alternative the velocity
of the mixing head may be controlled at the start of each pass over the
pattern by manually adjusting the frequency of the clock which supplies con-
trol pulses to the linear interpolator portion of the automatic control sys-
tem.
BRIEF DESCRIPTION OF THE DRA~INGS
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For better understanding of the invention, reference should be had
to the following detailed description taken in conjunction with the drawings
in which:
Figure 1 is a schematic perspective view of a new and improved ap-
Z0 paratus for the customized making of molds constructed in accordance with thefeatures of the present invention;
Figure 2 is an enlarged, vertical cross-sectional view of a mixing
head dispenser of the apparatus depicted in Figure l;
Figure 2A is a horizontal, cross-sectional view take~ substantially
along lines 2A-2A of Figure 2;
Figure 2B is a horizontal, cross-sectional view taken substantially
along lines 2B-2B of Figure 2;
Pigure 2C is a horizontal, cross-sectional view taken substantially
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along lines 2C-2C of Figure 2;
Figure 3 is a block diagram of the process control system portion
of the automatic control system of the present invention, including components
of the control system for controlling the mixing head dispenser;
Figure 4 is a top plan view of the apparatus of Figure l;
Figure 5 is a vertical elevational view with portions in section of
the apparatus of Figure l;
Figure 6 is a schematic perspective view similar to Figure 1 of
another embodiment of the apparatus constructed in accordance with the fea-
tures of the present invention;
Figures 7A and 7B comprise a block diagram of the tape controlledautomatic control system of the present invention with the process control
portion thereof shown in more detail than in Figure 3; and
Figure 8 is a diagrammatic representation of a control tape for the
automatic control system of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now more particularly to Figures 1-5 of the drawings,
therein is illustrated a new and improved program controlled apparatus for
making customized molds constructed in accordance with the featwres of the
present invention and referred to generally by the reference numeral 10. As
viewed somewhat schematically in Pigure l, the mold making apparatus 10 in-
cludes a movable mixing head dispenser 12 which is adapted to discharge a
downwardly directed stream of molding material of predetermined cross-section
into a mold flask 14 mounted on a fixed or movable platen 16. A mold cavity
forming pattern 18 of the shape of the casting is mounted in the mold flask
to form the shape of the mold cavity in the moulding material 20 dispensed
into the flask in successive layers of moulding material 20a, 20b, 20c of
selectively controlled, variable characteristics and thickness which are
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deposited on the surface of the pattern until the mold flask is filled to the
desired level. Relative movement between the dispenser head 12 and the pat-
tern 18 is provided by the automatic control system of the present invention
described in more detail hereinafter~ so that the flask is filled by de-
position of successive layers of material on the surface of the pattern by
movement of the dispensing head in a precision controlled manner measured on
a coordinate system relative to horizontal axes "X" and "Y" and a vertical
axis "Z" all at right angles to each other. In this connection, the dis-
pensing head 12 may be moved over the mold flask 14 in any desired manner
such that a layer of desired thickness is deposited over the pattern. For
example, the dispensing head 12 may be moved back and forth across the flask
14 in parallel paths which are spaced apart by an amount determined by the
width of the stream of molding material issuing from the head 12 so that a
layer of uniform thickness is applied to the pattern. In addition, the dis-
penser head is controllable to move up and down as measured along the verti-
cal axis "Z" so that the distance of travel from the lower outlet end of the
dispenser to the surface of the mold pattern 18 may be variably selected and
controlled. Also, the velocity of movement of the dispenser head along one
of the paths may be selectively varied, as will be described in more detail
hereinafter.
Referring now to Figures 2, 2A, 2B and 2C, the dispenser head 12
includes a generally cylindrical mixing chamber 22 having a frustroconical
upper end portion 24 and an enlarged lower end portion 26 with an open lower
end orming a discharge outlet 28 for dispensing the molding material over
the pattern 18. The mixing head is provided with a vertical rotor shaft 30
supported in a plurality of bearings 32 and is driven with a V-belt drive 34
at the upper end of the mixing head powered by an electrical motor 36.
Silica sand for the molding material is delivered into a hopper
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section 38 in communication with an inlet openin~ 40 in the frustroconical
upper end port~on 24 of the dispenser as best shown in Figure 2 and the sand
is supplied by means of an endless belt conveyor generally indicated by the
reference numeral 42. The belt conveyor is powered by an electrical motor 44
through a V-belt drive 46 and the motor is of a type having an electronic
speed control so that the flow rate of sand to the mixing head may be select-
ively controlled and varied. Similarly, the motor 36 on the dispenser head is
of the type including an electronic speed control so that the speed of the
rotor shaft 30 in the mixing head may be selectively controlled and varied as
desired, and integrated with the speed or rate of flow of silica sand deliver- `
ed into the mixing chamber by the belt conveyor 42.
In the intermediate level of the mixing chamber 22, the rotor shaft
30 is provided with a plurality of radial mixing elements 48 (Figure 2A) of
different lengths and at several levels, and these mixing elements retard the
downward flow of sand within the chamber so that the sand remains suspended
for an interval for thorough mixing of the sand with a plastic resin binder.
An uncured plastic resin binder such as a furfuralcohol resin is introduced
into the mixing chamber at an upper level therein through one or more resin
injection nozzles 50 and the nozzles spray the resin in small droplets for
intimate intermixing with the downwardly flowing sand in the chamber which is
moved in a rotary swirling pattern by the mixing elements 48. After the resin
and sand are intermixed thoroughly, the mixture flows into a lower portion of
the chamber where a catalyst is introduced for curing the resin. The catalyst
is introduced through one or more spray nozzles 54 at a level just above the
enlarged area section 26 and when the catalyst is mixed with the resin and
sand mixture, the resin starts to cure, and fast intimate mixing is desired.
For this purpose, the enlarged lower chamber section 26 is provided with a
fan-like mixing element 56 carried on the rotor shaft just below the level of
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catalyst injection nozzle 54. The fan-like mixing element 56 includes a
plurality of impellers separately hinged and attached to a collar on tne ro-
tating shaft 30. And these impellers force the sand resin mixture outwardly
towards the wall of the enlarged section 26 of the mixing chamber and act as
spatulas to spread the catalyst thoroughly in the sand-resin mixture. The
downward movement of the mixture is accelerated by the sloped surface of the
impellers and the completed mixture of catalyzed resin and sand is then dis-
charged downwardly in a flowing stream onto the surface of the mold pattern
18 mounted in the mold flask 14 therebelow. If desired, an additional sand
slinging blade 58 may be mounted adjacent the lower end of the rotor shaft 30
to more forcefully expel the sand and catalyzed resin mixture outwardly
through the discharge opening 28 to more uniformly cover a predetermined path
on the surface of the pattern 18 in the flask.
In order to contain the sand-binder mixture within the upper
portion of the mixing chamber 22 so that proper mixing action may be obtained
and a predetermined flow of material maintained, a slotted disc 51 is positi-
oned across the mixing chamber 22 and is provided with a clearance opening
53 at the center thereof for the shaft 30. A cooperating slotted metering
plate or disc 52 is positioned above the disc 51 and is rotatable with res-
pect to the fixed disc Sl so that the cooperating openings therein may beclosed or opened more widely by rotation of the metering plate 52. To this
end an arm 52a on the plate 52 extends through a slot 55 in the wall of the
chamber 22 and is provided with a gear segment 57 which is arranged to be
driven by the pinion gear 59 so as to rotate the plate 52 relative to the
disc 51.
The details of the arrangement for controlling movement of the
disc 52 will be described in more detail hereinafter. However, it should be
noted that the metering plate 52 is positioned above the injection nozzle
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54, i.e. the point at which a catalys-t is introduced into the sand-binder mix-
ture. Accordingly, the plate 52 may be closed off so as to prevent the sand
and binder mixture from flowing downwardly into the area where the catalyst is
introduced when it is desired to shut down the apparatus. The sand-binder
mixture which does contain catalyst below the slotted plate 52 simply falls
out of the lower portion 26 of the head 12 so that no catalyzed sand-binder
mixture remains in the mixing chamber which could harden and clog up the mix-
ing chamber 22 once the apparatus has been shut down.
In order to provide controlled relative movement between the dispen-
sing head 12 and the mold orming pattern 18 contained in the mold flask 14,
the dispensing head is supported on a frame 72 mounted for rolling movement
along the X-X axis on a pair of parallel guide rails 60. The guide rails are
mounted on a rectangular frame or carriage 62 which is movable in a trans-
verse direction on a horizontal Y-Y axis at right angles to the horizontal
X-X axis. The carriage 62 is provided with pairs of rolls 64 carried on axles
66, as best shown in Figure 5 and the rolls ride on a pair of elongated paral-
lel tracks 68 which are mounted on spaced apart trunnion bases 70 disposed on
opposite sides of the platen 16 on which the mold flask and pattern are sup-
ported. The dispenser head 12 is supported or vertical movement along the
Z-Z axis on frame 72 and is selectively adjustable thereon to provide for the
desired clearance or spacing between the lower outlet 28 and the upper surface
of mold forming pattern 18. The frame 72 is provided with a plurality of
rolls 74 carried on axles 76 and the rolls ride on the rails 60 of the
carriage 62.
In order to control the relative position of the dispenser head 12,
~;~ on the carriage 62 with respect to the horizontal axis X-X, at least one of
the roll axles 76 is powered with an X-axis servomotor 78 connected with the
axle by a suitable drive train 80. Similarly, positioning of the dispenser
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head relative to the pattern 18 in the Y axis is selecti~ely and variably con-
trollable ~y means of a servomotor 82 interconnected to one or more of the
drive axles 66 through a suitable drive train 84. The servomotor 82 moves the
carriage 62 back and forth along the rails 68 parallel to ~he Y-Y axis while
the servomotor 78 moves the frame 72 along the rails 60 of the carriage paral-
lel to the X-X axis. The mixing head 12 is movable in a vertical direction
with respect to the Z-Z axis by means of a servomotor 86 drivingly intercon-
necting the mixing chamber 22 and frame 72 by means of threaded screw 88 and a
bracket 90 as shown in Pigure 5. From the foregoing it will be seen that the
servomotors 78, 82 and 86 provide precision driving power for moving the mix-
ing head 12 over the mold forming pattern 18 to precise positions and at sel-
ectively controllable rates of movement.
Silica sand for the molding material is supplied to the belt convey-
or 42 from a hopper 92 having a lower outlet discharging sand directly onto
the belt which underlies the hopper. The hopper is supported on uprights 94
for movement with the carriage 62. The liquid resin is supplied to one of the
resin inlet nozzles 50 through a flexible resin line 96 (Figure 3) connected
to the output side of a variable volume resin pump 98. Resin is supplied to
the pump from a resin storage tank 100 through a tank supply line 102. Simi-
larly, the catalyst is supplied to one of the catalyst injection nozzles 54via a flexible catalyst supply line 104 connected to the output side of a
variable volume catalyst pump 106. The catalyst pump is in turn supplied from
a storage reservoir 10~ via a supply line 110 as shown in Figure 3. The resin
and catalyst storage tanks may be mounted for movement with the carriage 62
or may be stationed at a fixed location adjacent the apparatus 10. All of the
resin and catalyst lines 96, 102, 104 and 110 are flexible lines to provide
for the relative movement of the mixing head 12.
In accordance with the present invention, movement of the mixing
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head dispenser 12 relative to the mold forming pattern 18 is controlled by a
numerical control system which may be of the type as shown and described in
Forrester et al. United States Patent No. 3,069~608 and this nurnerical control
system is coordinated with control of the resin pump 98 and catalyst pump 108
and the flow of molding material through the mixing chamber 22 to deposit the
above-described layers of molding material into the flask 14. More particular-
ly, this automatic control system includes a tape reader 112 ~Figure 7) which
is arranged to read successive blocks of information derived from a suitable
control medium such as the punched tape shown in Figure 8. The output from
the tape reader 112 is supplied to a buffer storage register 114 and as the
next block of information is read from the tape 113, the information stored in
the buffer register 114 is advanced and stored in an active storage register
116.
Each block of information on the tape 113 includes a series of num-
erical representations corresponding to a desired increment of movement in the
X, Y and Z axes as well as a numerical representation of the desired direction
of movement in each axis. In addition, each block of information includes
numerical representations corresponding to the desired volume or flow of
resin to the mixing chamber during the period while the mixing head is being
moved over the prescribed distance, as well as numerical representations
corresponding to a desired volume or flow of catalyst to the mixing chamber
22.
In addition, the tape 113 may include a numerical representation
corresponding to a desired velocity of the dispensing head 12 in each of the
X, Y and Z axes. The punched tape 113 may also include further information
relating to the supply of molding material to the head 12, as will be des-
cribed in more detail hereinafter.
The numerical representations which are stored in the active stor-
,, . . :
age register 116, which are usually in binary coded decimal form, are suppliedto a linear interpolator 118 which is arranged to receive a series of clock
pulses from a clock oscillator 120. The linear interpolator responds to the
numerical values supplied to it from the active storage register 116 by devel-
oping separate streams of command pulses on the output lines 122? 124 and 126
thereof corresponding to the X, Y and Z axes respectively. More particularly,
the linear interpolator provides a stream of command pulses on the output line
122, each of which corresponds to a predetermined increment of movement in the
X axis, these command pulses being equally spaced apart in time and quantita-
tively representing the distance to be moved in the X axis. In a similar
manner, separate streams of pulses on the lines 124 and 126 correspond to the
distance to be moved in the Y and Z axes.
The command pulses on the lines 122, 124 and 126 are supplied to
pulse-code-to-analog servomechanisms 128, 130 and 132 for the X, Y and Z axes,
respectively. As described in more detail in Fcrrester et al. Patent No.
3,069,608, each pulse-code-to-analog mechanism includes a reversible binary
counter ~identified as the summing register 140 in said Forrester et al.
United States Patent) to one input of which the command pulses are supplied,
a decoder for converting the coded error output signal of the summing register
into an analog signal, an amplifier and servomotor for driving an output
synchro, a position encoder mechanically connected to the synchro shaft, and
a position code converter for converting movement of the position encoder
into a series of response pulses which are fed back to the summing register
to subtract from the count produced therein by the command pulses. The syn-
chro output of the pulse-code-to-analog servomechanism is then employed to
control the drive servomotor for each of the respective controlled axes.
Thus, the pulse-code-to-analog mechanism 128 is employed to control the move-
ment of the X axis servomotor 78. The pulse-code-to-analog servomechanism
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130 is employed to control movement of the Y axis servomotor 82, and the pulse-
code-to-analog servomechanism 132 is employed to control movement of the Z
axis servomotor 86.
It is pointed out that the command pulses may be employed to control
movement of the mixing chamber 22 in the respective axes with other types of
arrangements. For example, an open loop type of system wherein stepping
motors for each of the X, Y and Z axes are controlled directly from their
respective command pulses through suitable buffer amplifiers and the like may
be employed to control movement of the dispensing head 12, as will be readily
10 understood by those skilled in the art.
Considering now the manner in which numerical information is includ-
ed on the punched tape 113 to control movement of the dispenser head 12 and
variations in the sand-binder ratio of the molding sand mixture developed by
the dispensing head 12, it is pointed out that each block of information on
the tape 113 includes a series of transverse rows of information which are
successively read by the tape reader 112 and stored in the buffer storage
register 114. In the illustrated embodiment in Figure 8, each row of inform-
ation comprises three binary digits to the right of the sprocket holes 134 and
five binary digits to the left of these sprocket holes.
The quantity represented by each transverse row of binary inform-
ation on the tape 113 is shown immediately adjacent the righthand edge of the
tape and it will be seen that the first rows of information in each block on
the tape 113 consist of a series of binary coded distances and directions to
be moved in the X, Y and Z axes. In this connection it will be understood
that representation of a desired increment of movement in the X, Y and Z axes
may be provided in any other suitable manner on either a magnetic tape or a
punched paper tape, as will be understood by those skilled in the art.
Following the X, Y and Z axes information, a series of transverse
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rows of in~ormation, indicated collectiyely as the sub=block 136 in ~igure 8,
are provided on the tape 113. The first rows of information in the sub-block
136 identifies the succeeding rows as relating to a desired volume of resin
flow during the period of movement represented by the X, Y and Z information
and the succeeding rows in the sub-block 136 constitute a desired numerical
command or set point signal which is employed to control resin flow in a
manner to be described in more detail hereinafter. Immediately following the
resin flow block 136 a second block of transverse rows indicated at 138 is
provided on the tape 113 and identifies a block of information as catalyst
volume flow, the last three rows in this group providing a numerical command
or set point valve corresponding to a desired catalyst flow.
~ ollowing the catalyst volume information, a third sub-block 140 is
provided on the tape 113 which includes a transverse row identifying the in-
formation as relating to a desired maximum velocity or feed rate in the X, Y
and Z axes, the succeeding three rows of information in the sub-block 140 pro-
viding a numerical velocity number which is employed to control movement of
the dispensing head 12.
Following the sub-block 140 a single row of information provides on-
off information for the addition of iron oxide to the sand-binder mixture, as
will be described hereinafter in more detail. The last row of information on
the tape 113 is an end of block signal which controls the tape reader 112 to
stop reading information until the dispenser head 12 has been moved the desig-
nated distance in the X, Y and Z axes.
The linear interpolator 118 consists of a series of divider stages
which are controlled spirally one after the other from the clock pulses which
are supplied by the clock oscillator 120. When the last divider stage in the
linear interpolator 118 is reset, a control signal is supplied over the line
142 to the tape reader 112 so as to enable the tape reader 112 to read the
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5.~
next block of information from the tape 113. Since each block of information
is automatically stored in the bu~fer storage re~is-ter 114 while the informa-
tion stored in the active register 116 is being utilized by the linear inter-
plator 118 to produce command pulses, continuous motion of the dispenser head
12 is achieved despite the discontinuous mode of reading information from the
tape 113, as described in detail in said Forrester et al. Patent No. 3,069,608.
Considering now the manner in which the numerical information on the
tape 113 relating to resin and catalyst flow, etc. is employed to control the
operation of the mixing chamber 22, it is first pointed out that this numeri-
cal information is supplied to a control system which is similar to a conven-
tional process control system and is employed to control the flow of resin and
catalyst to the dispensing head 12 and adjustment of the metering plate 52.
More particularly, the numerical information which is stored in the active
storage register 116 is supplied to a multi-channel digital-to-analog con-
verter indicated generally at 144. Each channel of the converter 144 pro-
vides a suitable analog control signal or set point signal corresponding to
the numerical information in one of the sub-blocks on the tape 113. Thus, an
analog organic resin volume control signal is developed on the output con-
ductor 136 of the converter 144, an organic catalyst flow analog control
signal is developed on the output conductor 148 thereof and an analog vel-
ocity signal is supplied on the output conductor 150.
Since the flow of sand from the hopper 92 is not necessarily uniform,
it is necessary first to develop an electrical signal corresponding to volume -`
of sand which is supplied to the hopper portion 38 of the dispenser head 12 at
any given instant. To this end, a sand density detector indicated generally
at 152 is provided continuously to measure the density of sand supplied to the
conveyor 42 from the hopper 92. The density detector 152 may, for example,
comprise a suitable source of gamma rays 154 which is located above the upper
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.. . . . . .
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run of the conveyor 42 and a gamma ray detector 156 located below the conveyor
belt in such manner that the number of gamma rays received by the detector 156
per unit of time is a measure of the density of the intervening sand on the
conveyor belt. In the alternative, any other suitable arrangement may be em-
ployed for determining the density of the sand on the conveyor belt 42.
The velocity of the conveyor belt 42 is also determined by means of
a tachometer 158 which develops an electrical output signal corresponding to
the velocity of the conveyor 42, as will be readily understood by those skil-
led in the art.
The output signals from the sand density detector and the conveyor
tachometer 158 are supplied to a multiplier 160 which may be in the form of an
electronic module such as used in conventional process control system equip-
ment and the output signal 162 of the multiplier 160 comprising an analog
electrical signal equal to the product of the two analog input signals. This
product represents the volume of sand supplied to the dispenser head 12 per
unit of time.
The output 162 from the multiplier 160 is supplied as one input to
a divider module 164 to the other input of which is supplied the organic resin
set point signal developed by the digital-to-analog converter 144 on the line
146. The coded resin volume number in sub-block 136 on the tape 113 is in
the form of a fraction representing the desired percentage of resin which is
to be added to the sand at a particular location within the flask 14 to pro~
vide a desired strength of the mold at that particular location. In this
connection, it will be understood that the resin volume number, i.e. the sub-
block 136 on the tape 113, may vary with successive blocks of information so
that the resin flow from the nozzle 50 is varied at different locations with-
in the mold flask thereby providing different ratios of sand-to-binder at
different desired locations in the mold.
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-
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The divider module 164 deyelops an analog output signal on the out-
put conducto~ 166 thereof which is proportional to the resin set point signal
developed on the conductor 146. For e~ample, if the sand volu~e signal ap-
pearing on the conductor 162 is five volts and two percent of organic resin is
to be added in the mixing chamber 22, the output signal from the divider
module 164 on the conductor 166 will be 0.10 volts. This 0.10 volt signal is
supplied to a resin flow controller 168, the output of which is employed to
control the setting of the variable volume resin pump g8. In order to provide
feedback information for the resin flow controller 168, a resin flow meter 170
is provided in the output line of the pump 98 and develops an electrical feed-
back signal which is supplied over the conductor 172 to the input of the resin
flow controller 168. Accordingly, the volume of resin pumped by the pump 98
per unit of time varies in response to the resin volume number on the tape 113.
In this connection, it will be understood that the resin and catalyst numbers
on the tape may be in terms of a percentage of the weight of the sand per unit
of time rather than a percentage of the sand volume.
Since the amount of catalyst needed is dependent upon the amount of
resin being used at any particular instant, it is necessary to control the
flow of catalyst in accordance with the control signal supplied to the resin
flow controller 168. To this end, the output signal from the divider module
164 is supplied as one input to a divider module 174 to the other input of
whlch is supplied the catalyst set point or control signal developed by the
converter 144. If, for example, it is desired to use a volume of catalyst
flow equal to thirty percent of the resin flow the output from the divider
module 174 will provide a 0.033 volt signal on the output conductor 176 there-
of (assuming an output signal of 0.10 volts from the divider 164 as in the
above example).
The output of the divider module 174 is supplied to an organic cat-
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.
2~
alyst flo~ controller 178 which cont~ols the catalyst pump 106. A catalyst
flow meter 180 Is provided in the output line of the pump 106 and produces a
feedback signal which is supplied ove~ the conductor 182 to the other input
of the catalyst flow controller 178. Accordingly, the pump 106 is adjusted
to provide a flow thirty percent as large as the volume of the resin flow and
this amount of catalyst is supplied through the flexible hose 104 to the cat-
alyst nozzle 54.
In the field of no-bake binders a number of resin-catalyst combin-
ations have come into use with good results and these are especially well
suited for the process and apparatus of the present invention. Organic bind-
ers may include f.urfuralcohol resins, alkyd resins, phenolic resins and
others and inorganic binders may include solium silicate or water glass among
others.
Furfuralcohol resins may be modified with urea and a typical
example of this resin system would be as follows. For each 100 lb. quantity
of silica sand (washed and containing 98% SiO2, sieved #50-60 American Foundry
Society screen size), the resin would normally be added in a ratio in the
range of 1.1% to 2.0%, based on the weight of sand. A catalyst for the resin,
such as phosporic acid would be added in a ratio in the range of 30% to 45%,
based on the weight of resin. Another catalyst such as sulphoric acid could
be used in a ratio in the range of 20% to 35%, based on the weight of resin.
Sulphoric acid (called T.S.A.), although somewhat more expensive, can be used
in 10sser percentages than phosphoric acid and has the advantage that this
catalyst burns out of the mold more completely leaving little, if any resid-
ual catalyst. The ratio of catalyst to resin effects the curing time and as
more catalyst is used, curing is speeded up. For example, with a 33% catalyst
to resin ratio (phosphoric acid~ in a typical mix, the average working time
may be 30 minutes. By reducing the catalyst 5%, the working time is increased
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'
to 40 minutes or by increasing the catalyst 10%, the working time is shortened
to 20 minutes. With the sand--resin-catalyst example as set forth, the pattern
18 and other working surface coming into contact with the mixture should be
precoa~ed with a suitable releasing agent. Before the application of the mold-
ing mixture onto the surface of the pattern, the mixing head of the pattern is
coated with a release agent so that the pattern can be readily removed from
the mold 20. One such releasing agent is marketed under the registered trade-
mark ZIP-SLIP, LP-15 by Ashland Chemical Company of Cleveland, Ohio. With the
resin system described, a stripping time of about 60 minutes results when the
sand is at ambient temperature of about 75F. The Ashland Chemical Company
Technical Bulletin Nos. 5401-1 and 5415 describe in greater detail, the char-
acteristics of the furfuralcohol resins and various catalysts.
Another resin system suitable for the present invention includes an
alkyd resin with drier included and a catalyst of isocyanate. For each 100
lbs of 50-60 A.F.S. washed silica sand of the Illinois type, resin is added
in the ratio range of 1.2% to 2.1% based on the weight of sand. With this
resin, a drier such as a lead or cobalt napthanate in the range of 0% to 10%
based on the weight of resin is premixed. The resin and drier combination are
introduced into the mixing head 12 through the upper nozzle 50 and a catalyst
of isocyanate is used in the ratio range of 18% to 20%, based on the weight
of the resin. Technical Data Bulletins 5408-2 and 5411-2 of Ashland Chemical
Company describe other characteristics of this resin system.
A suitable inorganic no-baké binder system employs sodium silicate
in the ratio o~ about 3% based on sand and the catalyst used is glycerol ace
tate in the ratio range of 10% to 15% based on the weight of binder. This
material provides a heavier more dense molding mixture when mixed with 50-60
A~F.S. washed silica sand. Again, the working and stripping times required
may be adjusted by varying the ratio of catalyst to binder.
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~ hile the above descr~ed numerical control system may be programmed
in accordance with conventional parts, programming techniques so that succes-
sive blocks of information in the tape 113 are effective to move the dispenser
head 12 over a path which conforms generally to the contour o~ the pattern 18
during successive passes within the flask 14, in many instances it is desir-
able also to control the velocity with which the dispenser head 12 is moved
along the programmed path defined by the X, Y and Z axes information on the
tape 113. Thus, if it is assumed that an essentially constant volume of mix-
ture is dispensed from the dispenser head 12, it may be desirable to move the
dispenser head over its predetermined path at increased velocity so that the
thickness of the layer deposited over the pattern is reduced for a particular
pass over the entire flask or in a particular area of the pattern. In the
alternative~ it may be desirable to slow down movement of the dispenser head
12 in a particular area of the pattern so that with a constant sand-binder
ratio the deposited layer will be built up in thickness in a particular area
of the pattern to provide additional strength in this area.
In accordance with a further aspect of the present invention, numer-
ical information is provided on the tape 113 to control the velocity of move-
ment of the dispenser head over the predetermined path defined by the X, Y
and Z axis information which is also provided on the tape. More particularly,
the velocity number defined by the sub-block of information 140 is stored in
the active storage register 116 and is converted to an analog signal by the
converter 144 and is supplied as one input to a divider module 184. The other
input to the divider 184 is the output signal 162 from the multiplier 160,
which represents the volume of sand supplied to the dispenser head 12. The
divider 184 develops an output signal in accordance with the ratio determined
by the path velocity set point signal on the conductor 150 so that a signal
which is a programmed percentage of the sand volume signal is developed on the
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output conductor 186 of the divider 184. The output signal 186 is supplied to
a clock frequency control circuit 188, the output of which is supplied over
the conductor 190, to the clock 120. Accordingly, the frequency of the pulses
supplied to the linear interpolator 118 may be varied in accordance with the
velocity number on tape 113.
This means that the rate at which the command pulses for all three
axes are produced in response to a given numerical command on the tape 113 may
be varied in accordance with the velocity number on the tape 113. The velo-
city with which the dispenser head 12 may be moved in a given area or for a
complete pass over the flask 14 may thus be varied as desired by choosing the
appropriate velocity code on the tape 113 in that particular area.
In many instances, it is desirable to add a predetermined percentage
of wetting agent such as iron oxide to the initial layer deposited over the
pattern so as to reduce sticking and also to provide a smoother surface on the
metal casting which is produced during the casting process. In accordance
with the present invention, such a wetting agent as iron oxide may be select-
ively added to the mixture during one or more passes over the flask 14 in a
fully automatic manner. Different wetting agents can be used depending on the
type of material being cast in the mold cavity. ~ore particularly, an iron
oxide storage hopper 192 is provided above the conveyor 42 at a point beyond
the detector 152 and is provided with an on-off control 194 which is effective
either to produce a predetermined flow of iron oxide onto the conveyor belt
42 or to be completely shut off. The tape 113 is also provided with a control
number, which may be a single binary bit in the row following the sub-block
140, which is detected by one of the channels of the converter 144 and is em-
ployed to supply an on-off signal over the conductor 196 to the on-off control
194.
When a binary iron oxide on signal is provided on the tape 113, in-
. , ., , ~,., ' '
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- . ' ~ ' '
dicating that iron oxide is to be added to the sand-binder mixture, the on-
off control 194 responds thereto by opening the hopper 192 a fixed, predeter-
mined amount to add a predetermined percentage of iron oxide to the sand.
Thus, if during the first pass over the pattern, it is desired to include iron
oxide, the iron oxide on signal is provided in each block of information on
the tape 113. In the alternative, a single control number could be provided
on the tape 113 at the start of the first pass and the on-off control 194
could be set to the on position when this control number is detected by the
tape reader 112. At the end of the first pass, or whenever it is desired to
shut off the hopper 192, another control number could be provided at the
appropriate point on the tape 113 and the on-off control would respond to this
second number by closing the hopper 192. Such an arrangement avoids program-
ming an iron oxide number on the tape for each block of informationr
In accordance with an important aspect of the present invention,
the automatic control system is arranged automatically to shift over from an
organic binder and catalyst to an inorganic binder and catalyst at any desired
point in the mold forming process. Such an arrangement has the advantage that
an initial thin layer of organic binder and catalyst may be initially deposi-
ted over the pattern 18 and then subsequent layers may be deposited over the
initial layer using an inorganic binder and catalyst. When a mold is formed
in this manner, the relatively thin layer containing an organic binder, which
is next to the molten metal during the casting process, is completely oxidized
and burned up and produces relatively little smoke and fumes in the process.
The inorganic binder which constitutes the remaining portion of the mold does
not oxidize and hence, the overall casting process produces much less noxious
gases and fumes and is therefore much more desirable from an air pollution
standpoint.
To accomplish this objective, an inorganic binder storage tank 200
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- ' ' ' '' ' ~ ' : '
;i2~
is proyided and supplies an inorganic binder such as sodium silicate (water
glass~ to a ~ariable volume pump 202. An inorganic catalyst storage tank 204
is also provided which supplies a diluted inorganic acid which acts as an in-
organic catalyst, to a variable volume pump 206. The output of the pump 202
is supplied to an inorganic binder injection nozzle 208 through a suitable
check valve, the nozzle 208 corresponding to the injection nozzle 50, which is
used to introduce an organic binder, but is positioned at a different location
around the periphery of the mixing chamber 22. The output of the variable
volume pump 206 is supplied to a suitable inorganic catalyst injection nozzle
210 which is positioned diametrically opposite the organic catalyst injection
nozzle 54. Suitable flow meters 212 and 214, which correspond to the flow
meters 170 and 180, are employed to provide feedback signals for the flow
controllers associated with the variable volume pumps 202 and 206.
In order to automatically control the changeover from an organic
binder and catalyst flow to the inorganic binder and catalyst, suitable in-
formation is provided on the tape 113 to control this changeover. For example,
the binary number corresponding to the row identified as "a" in sub-block 136
may have a first designation "a-l" when an organic binder is to be used and a
second representation "a-2" when an inorganic binder is to be used. The
remaining three rows of information in the sub-block 136 will then provide
the numerical value of the set point for either the organic binder or the in-
organic binder.
A similar designation can be made by means of the row of holes
identified as "b" in sub-block 138 to identify either an organic catalyst
(b-l) or an inorganic catalyst (b-2). The remaining three rows of informa-
tion in sub-block 138 will then provide the set point value with either the
organic catalyst or the inorganic catalyst.
The digital-to-analog converter 144 is provided with separate
- 27 -
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channels for the diferent a-l, a-2, b~l, and b-2 values as shown in Figure 7.
The inorganic binder and inorganic catalyst set point values are supplied
respectively- to the dividers 216 and 218 to which the sand velocity signal on
the conductor 162 is also supplied as a second input.
The output of the divider 216 is supplied to an inorganic binder
flow controller 220 which controls the inorganic binder pump 202, and the out-
put of the divider 218 is supplied to an inorganic catalyst flow controller
222 which controls the pump 206. The inorganic binder and catalyst con-
trollers 220 and 222 function in a manner described heretofore in connection
with resin flow controller 168 and catalyst flow controller 178 and hence a
detailed description need not be included herein.
In operation, if an organic resin and catalyst are to be used, the
a-l and b-l lines of the converter 144 will supply set point information to
the dividers 164 and 174 while the lines a-2 and b-2 provide disabling inputs
to the dividers 216 and 218 so that the pumps 202 and 206 are closed. Accord-
ingly,during the first initial pass oYer the pattern 18 the organic binder
and catalyst are mixed with the sand and deposited on the pattern. If it is
desired to use an inorganic binder and catalyst for the remaining passes over
the pattern, the a and b rows of information in the sub-blocks 136 and 138
will contain the a-2 ~md b-2 codes respectively, so that the converter 144
supplies set point information to the dividers 216 and 218 while disabling
inputs are supplied to the dividers 164 and 174. The inorganic binder and
catalyst from the tanks 200 and 204 are then mixed with the sand for the re-
maining passes during the mold forming operation. It is also pointed out
that regardless of whether an organic or an inorganic binder is being used,
the ratio of binder to sand may be varied at predetermined locations over
the pattern by appropriate variation in the set point value on the tape 113
at these locations.
. ,: . -.' : . -'- .
If it is desired to maintain a constant ratio of binder and catal-
yst to sand for either the organic binder or the inorganic binder it will be
appreciated that a single sub-block of information corresponding to the sub-
blocks 136 and 138 can be employed at the start of a particular pass during
which it is desired to use either an organic binder or an inorganic binder,
thus eliminating the necessity for including the sub-blocks 136 and 138 with
each block of information on the tape 113. However, when only one initial
sub-block of information is employed to control the selection of organic or
inorganic binder and to fix the sand-binder ratio for the remainder of the -
pass, it will be necessary to hold the organic or inorganic set point value
in the active storage register 116 for the duration of the pass during which
this set point value is to control the mixing operation. This can be done by
providing suitable flip-flops in the channels in the active storage register
116 corresponding to the sub-blocks 136 and 138 as will be readily under-
stood by those skilled in the art.
When the mixing operation is initially started, it is necessary to
first provide a sufficient volume of sand in the mixing chamber 22 to obtain
good mixlng action. To this end, the metering plate 52 is arranged to be in-
itially closed off. As sand pours into the mixing chamber 22 from the con-
veyor 42, the driving motor 36 will have an increased load on it as it movesan increasing volume of sand within the chamber 22. As the load on the motor
36 increases, the current drawn from the power source will also increase and
can be used as a feedback signal to control movement of the metering plate
52 to an average open position.
More particularly, a current sensor 230 is connected in one of the
three phase power lines to the driving motor 36 and produces an output sig-
nal proportional to the current drawn by the motor 36 and hence, the amount
of sand and binder combination rotated by this motor in the mixing chamber
- 29 -
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~252~
22.
A load set point potentiometer 232 (Figure 7) is employed to estab-
lish a fixed set point signal corresponding to a desired load condition with-
in the mixing chamber 22, this set point signal being supplied to a mixing
head load controller 234.
The output of the controller 234 is supplied to a metering plate
driving motor 236 (Figure 3) which functions through a suitable gear reduc-
tion mechanism to drive the pinion gear 59 ~Figure 2B) and hence, produce
rotation of the metering plate 52. The output of the current sensor 230 is
also supplied to the load controller 234 as the input variable.
When there is no load on the mixing head motor 36 and the current
sensor 230 produced a relatively low output signal the controller 234 is
arranged to control the motor 236 so that the metering plate 52 is closed.
However, as sand builds up in the mixing chamber 22 and the load on the
mixing head motor 36 increases, the signal developed by the current sensor
230 will approach the set point signal determined by the setting of the
potentiometer 232 so that the metering plate 52 will be moved to an open or
mid-position.
Small variations in the flow of sand into the chamber will then be
compensated by the controller 234 since these small variations in load will
produce corresponding changes in the output of the current sensor 230 with
respect to the set point established by the potentiometer 232. The controller
234 thus operates to maintain an essentially constant flow of sand, binder
and catalyst mixture rom the dispensing head 12. However, it should be
pointed out that major changes in the flow of sand into the mixing chamber 22,
which may be due to changes in the speed of the conveyor, may necessitate re-
adjustment of the potentiometer 232 to give an appropriate mid-point value
about which the controller 234 can operate.
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In accordance with the invention, a mold 20 ha~ing plural lay-ers
20a, 20b, 20c etc., may be automatically produced with the inner layer 20a
having an organic type binder dimensioned with a thickness and having a sand-
binder ratio such that substantially all of the binder in the layer 20a is
completely oxidized or burned out by the heat from the molten material in the
mold cavity. The layers 20b, 20c, etc., may be formed with an inorganic
binder and accordingly, the molding process contributes little if any to
common pollution problems wherein an organic binder residue remains in the
mold or wherein an organic binder is not completely but only partially oxi-
dized or burned out in the casting process. In addition, sand reclamation ofthe molds 20 is much more economical than heretofore possible with no-bake
binders because of the fact that a substantially complete burn out of the
organic binder occurs with little or no residual binder and the remaining in-
organic binder of the outer layers 20b, 20c, 20d, etc. can be subjected to
economical reclamation processes.
Moreover, mold of the type just described, can be economically pro-
duced and in addition, a wetting agent such as iron oxide (per gray iron cast-
ings) can be intermixed and applied only with the inner layer 20a to provide
a better surface on the casting and ]ittle, if any, sticking betw0cn the mold
and the casting produced. In prior systems, it was practically impossible or
at least very difficult to use two different binder systems in a single mold
with any control and similarly, if a wetting agent was used, it was usually a
practical necessity to simply add the iron oxide to the entire batch of mold-
ing sand used in the mold even though the iron oxide was only needed at the
wall surface of the cavity coming into direct contact with the molten metal.
Referring to Figure 5, in order to provide for more rapid mold pro-
duction rates, the mold supporting platten 16 may be provided with pairs of
rolling wheels 248 mounted on axles 250 to roll along parallel rails 252
- 31 -
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provided in the adjacent foundry floor so that an orderly procession of molds
may be continuously maintained. The automatic molding system as described,
may be utilized for customized mold making for castings ranging in size from
several cubic inches of metal to large castings having a volume of many cubic
feet. With the larger size castings, such as engine blocks or railway wheel
truck units, it is desirable to maintain the heavy mold pattern and flask in
a fixed position while the mixing head 12 is moved to make the mold. However,
with smaller castings it may be desirable to retain the mixing head in a fix-
ed position and move the mold forming pattern 18 relative thereto, but with
the same type of selectable control over the ratio of sand to binder and con-
trol over volume flow rate of material into the mold flask. In some in-
stances, it may be desirable to have accurate positioning control and movable
drive means for both the mixing head 12 and the platen 16 supporting the
mold flask 14 and pattern 18 therein.
Referring now to Figure 6, therein is illustrated another embodiment
of the present invention wherein the platen 16 is movable along X, Y and Z
axes relative to the mixing head 12 which may also be movable along these
axes as described hereinbefore. The movable platen 16 of Figure 6 is sim-
ilar to the work table of a machine tool, for example, of the type shown in
the aforementioned Forester et al. Patent No. 3,069,608 as illustrated, the
platen 16 may be supported on a pair of guide rails 254 extending transver-
sely across a rectangular frame or base having a side rail 256. Movement of
the platen 16 along the X axis is controlled by means of a threaded lead
screw 258 powered by a syncro-type motor 260 which is controlled from the
integrating logic system as previously described. The frame 256 is movable
in the direction of the Y axis and is supported on rolls 262 which ride on
side rails 264 of a lower rectangular frame 266. Movement of the platen 16
in the direction of the Y axis is controlled by another threaded drive screw
. , -
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52~
268 which is powered by a Y axis drive motor 270. ~ertical of Z axis movement
of the platen 16 may also be provided by means of a plurality of vertical
drive screws 272 which are powered by a plurality of syncro-type drive motors
274. From the foregoing it will be seen that the mold forming pattern 18 may
be selectively moved along the respective X, Y and Z axes relative to the
mixing head 12 which may either be fixed in position or movable as desired.
Precision control movement of the platen 16 is provided by the integrating
logic system of the programmable control unit as in the manner heretofore
described.
33 -
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