US3249970A - Apparatus and method for controlled addition of one ingredient to a mixture of foundry sand ingredients - Google Patents

Description

May 10, 1966 N. HARTLEY 3,249,970

APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENT TO A MIXTURE OF FOUNDRY SAND INGREDIENTS Filed Dec. 13, 1961 10 Sheets-Sheet 1 INVENTOR- N54 50 HF7TLEY l l l 1 I I 1 l i l WEDMIW N. HARTLEY May 10, 1966 APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENT TO A MIXTURE OF FOUNDRY SAND INGREDIENTS 13, 1961 10 Sheets-Sheet 2 Filed Dec.

IN VEN TOR. 4 54 50 Amen-Ev BY [041%, W! W ArroeMsv May 10, 1966 N. HARTLEY 3,249,970

APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENT TO A MIXTURE OF FOUNDRY SAND INGREDIENTS Filed Dec. 13, 1961 10 Sheets-Sheet 5 I N V EN TOR. M5450 flmensv y 1966 N. HARTLEY 3,249,970

APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENT TO A MIXTURE OF FOUNDRY SAND INGREDIENTS l0 Sheets-Sheet 4 Filed Dec. 13, 1961 k l izz do I l a M i I 17/3 .16

INVENTOR. N54 50M H/ZQ r Y A Tree/vs v5 N. HARTLEY May 10, 1966 APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENT TO A MIXTURE OF FOUND Filed Dec. 13. 1961 RY SAND INGREDIENTS l0 Sheets-Sheet 5 m m. J

May 10, 1966 Filed Dec. 13, 1961 O O O O O 9 O O N. HARTLEY APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENT TO A MIXTURE OF FOUNDRY SAND INGREDIENTS l0 Sheets-Sheet 6 Monsrma 70.0.

TEMP 70.0

INVENTOR. N54 50M Hear-45v May 10, 1966 N. HARTLEY 3,249,970

APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENT TO A MIXTURE OF FOUNDRY SAND INGREDIENTS Filed Dec. 15, 1961 10 Sheets-Sheet 7 Z52. Zd Z 59 I NVENTOR.

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APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENT TO A MIXTURE OF FOUNDRY SAND INGREDIENTS Filed Dec. 13, 1961 10 Sheets-Sheet 8 INVENTOR. M5450 HHETLEV m,mvm

May 10, 1966 HARTLEY 3,249,970

APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENT To A MIXTURE OF FOUNDRY SAND INGREDIENTS l0 Sheets-Sheet 9 Filed Dec. 13, 1961 CURRENT m! WATEK TANK (Ion- DEPTH OF WATEE IN TANK INVENTOR.

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. APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENTTO A MIXTUREOF FOUNDRY SAND INGREDIENTS Filed Dec. 13, 196], l0 Sheets-Sheet 10 "Egg Q30 INVENTOR. A/Eua/v HHETAEY HTTOEA/EYS United States Patent 3 249,970 APPARATUS AND METHOD FOR CONTROLLED ADDITION OF ONE INGREDIENT TO A MIX- TURE 0F FOUNDRY SAND INGREDIENTS Nelson Hartley, Baltimore, Md., assignor to Hartley Controls Corporation, Neenah, Wis., a corporation of Wisconsin Filed Dec. 13, 1961, Ser. No. 159,183 36 Claims. (CI. 22-89) The present application is a continuation-in-part of my co-pending application Serial No. 656,592, filed May 2, 1957, now abandoned and is a companion to pending applications filed by me, Serial No. 373,229, filed August 10, 1953, now Patent No. 3,172,175, issued March 9, 1965; Serial No. 448,201, filed August 6, 1954, now abandoned; Serial No. 610,820, filed September 19, 1956, now Patent No. 2,989,349, issued June 20, 1961, and Serial No. 739,251, now abandoned, to which reference will be made hereinafter.

This invention relates-to the controlled addition of one ingredient to a mixture of ingredients in accordance with the measured deficiency in said mixture of the ingredient to be added. In one important aspect, this invention relates to control of moisture in finely divided materials such as foundry sand. The control may also be used to regulate the moisture in sand used in the making of cement; sand or clay used in the ceramic industries, as well as other manufacturing processes of which the foregoing constitute examples. In another important aspect, this invention relates to the controlled automatic addition of bond to foundry sand in accordance with the actual requirements of the sand for bond.

According to one embodiment of the means and method hereinafter disclosed in more detail, the invention comprises a novel integrating device wherein a sensitive relay biased toward one position has its contact controlled by an armature subject to the attraction of opposed windings. For the purposes of temperature and moisture control herein contemplated, I connect one winding to an instrument for measuring the moisture content of such material and another instrument responsive to its temperature in a manner to compensate for temperature-induced inaccuracies in the moisture measurement. Thereby it is possible to cause the relay to respond accurately to an integrated function of heat and moisture to determine the amount of moisture which must be added to the solids to yield proper consistency. The arrangement is such that the amount of moisture added will increase with the temperature, but will be decreased by the amount of moisture already present.

In one embodiment herein disclosed, alternating current is used to measure the moisture present in the solid material. It has generally been supposed that this would be impossible of accomplishment. In fact, it gives greatly improved results with increased accuracy :and no electrolytic corrosion. However, it is found desirable, particularly when A.C. current is used, that one of the poles of the armature bars of the opposed relay coils have a tapered end. According to the degree of taper and the location of the taper on the one pole or the other, a differential response of the armature is secured which enhances the accuracy of control.

The organization is such that three different increments of water may be introduced into the mixer. The first increment is introduced immediately prior to the introduction of the solids, and it serves to flush or wash the mixer walls to prevent accumulation thereon. The circuit is such that if the solids are already very wet, neither this increment nor the subsequent increments will be intro duced into the mixer at all. Another safety factor is provided by a relay which automatically tests all of the circuits at the commencement of each cycle and shuts off the apparatus if the circuits are not in proper operating condition.

Another very important feature of the invention is a special probe exposed to the sand in the mixer for determining the amount of primary water and the increment of secondary water, if any, which are to be introduced. This probe not only is part of the circuit which measures the amount of water in the solids as a function of the resistance, but it, is also a part of the circuit which measures the temperature of the solids. It has been found that in previously known devices for this purpose, any

substantial change in the temperature of the solids will also affect the moisture reading, as the resistance of the sand is not only a function of its moisture content, but also a function of its temperature. As the heat increases, the resistance decreases.

By incorporating in that portion of the probe which is exposed to sand temperature a thermistor of the type disclosed in United States Patent 2,676,305 so chosen :as to have approximately the same fluctuation of resistance at different temperatures as does the sand or other solid itself, a compensating factor is introduced which substantially eliminates the effect of sand temperature from the moisture measuring circuit.

In practice, the probe is so mounted as to be constantly subject to the substantially uniform pressure of sand or other solids in the mixer. The choice of location is important since the solids in the mixer are constantly being stirred, and if the probe were not associated with some paddle or baffle against which the sand accumulates during mixing, the probe might somtimes be engaged with the material and might at other times lie in a void. Another feature of the probe is an arrangement whereby the operative current conducting and heat responsive terminal portion thereof is replaceable as a unit without changing a wire. Also, in order that the probe may remain subject to uniform pressure of solids during rotation of the mixing paddle with which it is associated (assuming that it is used in that type of mixer), the probe current supply desirably has a swivel permitting the probe to rotate with the paddle and providing reliable brush contacts accommodating such rotation and protected from dust and moisture.

Since the thermistor will only give fully accurate response for a particular type of solids, facilities are made for adjustment when the solids handled in the mixer are different. Once the apparatus has been calibrated, it is possible, by changing the resistance in a shunt circuit across one of the relays, to make the response of the instrument vary with reasonable accuracy in accordance with any type of solids within the capacity of the device. In other words, the shunt balances out the variation resulting from the use of solids other than those which correspond accurately with the characteristics of the selected thermistor.

In another embodiment of the invention, all readings for determination of base water addition are made in the batch hopper and a quantity of water is accumulated in a tank as determined by these readings for discharge into the mixer simultaneously with discharge into the mixer of material in the batch hopper. During the mixing cycle, readings are made in the mixer for the addition of any such quantity of trim water as is necessary to exactly balance the moisture requirements of the material. In

' practice, about ninety-five percent of the water which is ultimately required is accumulated in the tank and is denominated herein as the base water, the remaining five percent being measured and added during the mixing cycle and denominated herein as trim water.

The foregoing sequence'has several important advantages, particularly when dealing with foundry sand. By early addition to the material of almost all of the required amount of water, there will be a relatively long time exposure of the water to the material. Inasmuch as return foundry sand is ordinarily quite hot because of its previous exposure to molten metal in the castings, the early exposure of the sand to the water will tend to cool the sand by evaporation or steaming off of some of the water during the mixer operation. This will require additional water in the trim cycle to replace the quantity of water which has been evaporated from the sand and the resultant addition of more Water to the sand than would have been added if the water had been added steadily during the mixing operation, as in the previously described embodiment.

Inasmuch as the sand temperature is thus reduced considerably, there will be less subsequent evaporation of water from the sand between the time the sand is mixed and is actually utilized by the molder. Accordingly, the temper or moisture balance of the sand at the time of sand mixing will tend to be closer to its ultimate temper at time of use.

The earlier addition of water also appears to condition the sand for more complete aeration and penetration of the water into the sand and results in a sand having better molding characteristics.

In my United States Patent No. 2,709,843, a water accumulating tank is disclosed. The level of the water in this tank is sensed by a float. According to the present invention, a similar tank is used for accumulation of base water, but the level of the water in the tank is sensed electrically.

The electric signal based on tank water level is integrated with signals based on initial temperature and initial moisture content in a novel relay having three coils. One of the coils is subject to a signal responsive to the level of water in'the tank, another coil is subject to a signal responsive to the initial temperature of the material in the batch hopper, and the third coil is subject to a signal responsive to the initial moisture content of the material in the batch hopper.

When the level of water in the tank has risen to a piont which will exactly balance the moisture deficiencies of the material, as reflected in the signals integrated in the relay, the armature of the relay will move in response to the integrated signal from the three coils and a valve which adds water to the tank will be closed.

Wholly apart from its adaptability for use in a moisture tempering circuit of the type herein disclosed, the multiple coil relay has a wide range of use in connection with adjustable level control for liquids in a tank. Heretofore it has been very diificult to sense electrically liquid level in a tank. Attempts to measure the electric resistance of the liquid, as measured between a probe in the tank to the tank wall through the liquid, have not heretofore proven satisfactory. This is attributed to the fact that after a certain level of liquid has been admitted into the tank, the resistance from the probe to the tank wall will change very little as additional water is added. A curve plotting resistance as against water level will flatten out after a certain level is reached so that the electric resistance of the liquid as thus measured is not a sensitive indicator of liquid level.

According to the present invention, however, the resistance of the liquid is a useful measure of the level of water in the tank, because the voltage applied to the tank probe circuit is made variable and can be adjusted to change the shape of the curve derived by plotting current through the liquid against water level. In this way, the relay can be made more sensitive to resistance changes and useful readings and measurements obtained. Moreover, by the use of multiple coils in the relay and the interaction of these coilsupon the armature, it is possible to change the sensitivity of the relay by increasing or decreasing the current flowing through one of the other coils of the relay.

In a still further embodiment of the invention, the deficiency of moisture in the material is used as an index of the deficiency of other ingredients in the material, which may then be added to the material in accordance with such index. While this embodiment of the invention is also suitable for use in various environments,

it will be described specifically in connection with foundry sand in which the ingredient to be added is bond. Foundry sand bond ordinarily comprises such finely divided solid materials as Wood flour, sea coal, bentonite, etc., which is added to the sand for proper molding consistency thereof. These foundry sand additives or bond which lie in close proximity to.the molten metal poured into the mold to form the casting are carbonized or burned and are removed from the sand in the form of dust by the ventilating system of the foundry. Accordingly, the foundryman must constantly add bond to replace that part of the bond which has been lost in the carbonizing process.

Heretofore there has been no commercially practical apparatus for automatically adding bond in any precise amount related to the rate of loss thereof. Conventionally, bond is added periodically in fixed amounts. These fixed amounts are predetermined in accordance with reports received from the molders, the appearance of the finish on the castings, and the results observed at the shakeout apparatus. Moreover, laboratory tests of the green strength of the sand will be taken at periodic intervals and bond added Where it is determined that the sand is deficient in green strength.

In accordance with this invention, it has been determined that need for addition of bond is related to that proportion of the total quantity of sand in a mold which is exposed to the molten metal of the casting. This depends on the size of the casting, the size of the mold in which the casting is poured, and the amount of sand in the mold which is not directly exposed to the molten metal so that its bond content is not materially altered in the casting process.

For example, assume the mixerman to be adding a predetermined amount of bond to each mixer batch when the foundry is fabricating small castings. If the Scheduling Department of the foundry changes the patterns to larger castings in the same size mold, there will be a material increasein carbonization of bond and loss thereof and unless there is a corresponding increase in the addition of bond, the green strength of the sand will drop. Heretofore there has been no commercially practical way to automatically match the addition of bond to the need therefor.

It has been determined in accordance with the present invention that there is a very close relationship between the loss of moisture in the sand and the loss of bond in the sand. According to one aspect of the present invention, bond will automatically be added to the mixer in substantially the same proportion as-water is added. Accordingly, bond will be added in relatively precise amounts directly related to the deficiency in bond of the return sand and the amounts added will be highly sensitive to changes in the character of the return sand.

Bond deficiency in foundry sand is closely related to moisture deficiency because the moisture is-steamed off in the mold in direct relationship to its proximity to the molten metal of the casting, this being also characteristic of the loss of bond.

In this embodiment of the invention, a triple coil relay is also used for controlling the addition of bond. The upper and lower coils of the relay respond respectively to moisture content and temperature of the sand. Accordingly, the electromagnetic field about these coils and which acts upon the armature will vary in strength and direction in accordance with the deficiency of the sand in moisture and temperature. These characteristics of the sand are related to the bond deficiency of the sand in substantially the same way as to its moisture deficiency. The middle coil of the relay is connected in a timing circuit which is coordinated with the amount of bond or like material which is accumulated in a holding hopper. As the accumulated quantity of bond increases, the current flowing through the middle coil will increase correspondingly. The electromagnetic field about the center coil is thus integrated in the relay armature with the electromagnetic fields about the other two coils. When the amount of bond which has been accumulated exactly equals the bond deficiency of the material, the'relay will be actuated to terminate the accumulation of bond. Subsequent addition of the accumulated bond will then exactly satisfy the bond needs of the material. This aspect of the invention is not limited to the addition of bond to foundry sand. Apparatus embodying the invention can be used to control the addition of one ingredient to others in a dry mix, in accordance to the measured deficiency of said ingredient in said mix.

In the drawings:

FIG. 1 is a diagrammatic view of apparatus embodying the invention, the water tank, batch hopper and mixer being shown on a reduced scale and the various circuits and relays and timers being shown diagrammatically.

FIG. 2 is a greatly enlarged detail view in vertical axial section through a probe used in the mixer embodying the invention.

FIG. 3 is a view taken in section on line 3-3 of FIG. 2.

FIG. 4 is a view taken in section on line 44 of FIG. 2.

FIG. 5 is a view taken in section on line 55 of FIG. 2.

FIG. 6 is a view taken in section on line 66 of FIG. 2.

FIG. 7 is a detail view in perspective of the thermistor used in the probe of FIG. 2.

FIG. 8 is a plan view of a conventional mixer showing the preferred installation therein of the probe illustrated in FIGS. 2 to 6.

FIG. 9 is a view taken in section on line l -Si of FIG. 8.

FIG. 10 is a plan view of a different well-known type of mixer showing the prefrred probe location therein.

FIG. 11 is a view in side elevation of an integrating relay made in accordance with the invention, the case being shown in section.

FIG. 12 is a view taken in section on line 1212 of FIG. 11.

FIG. 13 is a view taken in section on line 1313 of FIG. 11.

FIG. 14 is a view taken in section on line 1414 of FIG. 11.

FIG. 15 is a view taken in section on line 1515 of FIG. 11.

FIG. 16 is a fragmentary circuit diagram illustrating the I operating principle of the relay shown in FIGS. 11 to 15.

FIG. 17 shows a modified form of relay shown in section on the line 1717 of FIG. 18.

FIG. 18 is a view of the modified embodiment of relay taken in section on line 18-18 of FIG. 17.

FIG. 19 is a view in side elevation of a modified embodiment of armature and moving contactor unit usable in a relay such as that shown in FIGS. 17 and 18.

FIG. ZO-Iragmentarily shows a further modified embodiment of such a unit.

FIG. 21 shows a further modified unit.

FIG. 22 is a fragmentary detail view in perspective of one of the solenoid armatures used in the units of FIGS. 17 to FIG. 23 is an enlarged detail View taken in cross section on line 2323 of FIG. 22.

FIG. 24 is a fragmentary modification of the circuit shown in FIG. 1 to illustrate the connections employed when'A.C. current, rather than DC. current, is used in the relays exemplified in FIGS. 17 to 20.

FIGURES 25a, 25b, 25c and 25d are diagrammatic views of a modified embodiment of apparatus and an electric circuit diagram embodying the invention, the water tank, batch hopper, and certain other physical apparatus being shown on a reduced scale and the various circuits, relays, timers, etc., being shown diagrammatically. These figures appear on separate sheets of the drawing and can be combined to assemble the complete diagram. Each component part of the figure is separately described, as follows:

FIG. 25a shows the batch hopper, mixer, water tank, etc. The terminal strip at the left of the figure matches with the terminal strip at the right of FIG. 250.

FIG. 25b shows the base water circuit and also in diagrammatic form the cam shaft and timers, etc. The disconnected circuit lines at the right of this figure match with the disconnected circuit lines at the left of FIG. 250.

FIG. 250 shows the trim water circuit. The disconnected circuit lines at the left of this figure match with those at the right of FIG. 2512, the terminal strip at the right match with that at the left of FIG. 25a, and the dis-' connected circuit lines at the top match with those at the bottom of FIG. 25d.

FIG. 25d shows the control panel mounted components. The disconnected circuit lines at the bottom match with those at the top of FIG. 25c.

FIG. 26 (no figure identified by number 26 the drawings in this application).

FIG. 27 is a simplified plot showing a family of curves relating the current flowing in the water tank coil of the relay to the depth of water in the tank, for various applied voltages which change the slope of the curve.

FIG. 28 is a simplified schematic diagram of the triple coil relay used in the base water circuit of this embodiment.

FIG. 29 is a cross section taken through a triple coil relay embodying the invention.

FIG. 30 is a schematic circuit diagram of the embodiment of the invention in which the triple coil relay is used to control the addition of bond or other material to a mixture which is deficient therein.

In the embodiment shown in the diagram of FIG. 1, the mixer is shown at 25. The hopper from which solids are supplied to the mixer is designated by reference character 26, and the tank from which liquids are supplied to the mixer is shown at 27. For foundry sand purposes, bond material and the like may also be supplied to the mixer from a source (not shown) through pipe 28 as disclosed, for example, in copending application Serial No. 610,820.

The normally filled tank 27 receives its liquid (herein referred to as water, by way of exemplification) from the supply pipe 30 subject to the control of a solenoid valve 31. The tank is grounded. An insulated probe 32 projects into the tank at the desired water level and when the water reaches the probe, the relay 3 3 controlled by the probe is energized to shut oh the valve 31, thereby determining the depth of water in the tank.

. To make the discharge from tank 27 independent of gravity, air pressure may be supplied to the tank from pipe 34 subject to the control of solenoid valve 35 and a pilot valve 36 which vents the tank during the water filling operation.

A separate water supply line 37 is controlled by solenoid valve 3 8 for the introduction of trim water into the mixer 25, this being that amount of water smaller than appears in the batch originally dumped into the mixer to reach with exactitude the precise amount of moisture required.

The moisture of the solid material is initially determined in batch hopper 26 by the resistance of the material as measured by the flow of current between the wall of the batch hopper and a probe 40. This current flow controls a relay to preclude introduction of flush or base water into the batch hopper if the sand is already sufficiently wet. The relay will be identified later when the circuit is described. A mercury switch 4 1 is mounted on a paddle 42 which is displaced When the batch hopper is full. It controls motor 106 of the timer to prevent the timer from initiating the cycle unless there is adequate sand in the hopper.

Final determination'of liquid requirements on the basis of temperature and moisture is made in the mixer 25. Two well-known types of mixers are shown in FIGS. 8 and 10, by way of example. The mixer in FIGS. 8 and -9 comprises a stationary wall internally provided with a rotatable head 46 from which the mulling rollers 47 are carried. Also mounted on the head for rotation therewith are the plows 48, 49 which, as the head rotates counterclockwise as viewed in FIG. 8, plow the contents of the tank 45 into the path of the mulling rolls 47.

In such a device, the special probe designated by reference character 50 is desirably located where the sand will almost invariably pile up against the thermally conductive plate 51 at the lower end of the probe. In the case of the mixer 250, shown in FIG. 10, the tank 450 is rotatable and the mulling rolls 470 are carried on a shaft 53 which does ont partake of hopper movement. The plow 490 has a function similar to the plow 49 of FIG. 8. The rotary disk plow 480 is likewise similar in function when positioned as shown at full lines in FIG. 10. However, this rotatably mounted disc has its axle shaft 54 pivotally movable on the upright pintle 55 to move the plow to the position shown in dotted lines, whereupon the sand is discharged by being thrown over the top of the rotating receptacle 450.

There is a rotary mixer at 57' which is fixed against translation on the supporting bracket 58 and is rotatable by the action of the sand itself. I have found that the probe 50 may conveniently be mounted on an arm 59 attached to bracket 58, and in this position the sand piles up against it so that it is subject to substantially uniform pressure and exposure.

In all cases, the probe desirably comprises a tube 60 (FIG. 2) which supports the plate 51. The tube 60 is sealed at its upper end by an annular plug 65. It has a flange 64 anchored by screws 66 to the flange 67 of a conductive tube 68 insulated by the non-conductive sleeve 69 from the pipe 70 which has the non-conductive shell 61 surrounding it externally, and held thereto by clamps 71. The pipe 70 is anchored by setscrews 72 to a mounting bracket 73 attached to any suitable portion of the apparatus as shown, for example, in FIGS. 9 and 10.

Within the tube 60 is a compression spring 75 seating at its upper end upon an insulating washer 76 on spring contact 80. This contact is guided in the bushing 81 in plug 65. Connected to the yieldable contact within the spring is an insulated conductor 82 attached at its lower end to a flanged contactor 83 which carries an insulated spring seat 84 upon which the lower end of spring 75 is seated. Confined between the contactor 83 and the closed lower end of the tube 60 is the thermistor 85. This thermistor is separately illustrated in FIG. 7. It comprises a ring of compressed ceramic material, the resistance of which varies inversely as its temperature. These thermistors are standard articles of commerce and available with different characteristics. For foundry purposes, the thermistor has electrically conductive characteristics corresponding as closely as possible to those of the sand engaged by the plate 51 and the outside of,

the tube 60. Thus, as the temperature of the sand atfects its conductivity, so any corresponding fluctuations in the temperature of the thermistor 85 will affect its conductivity.

As will be shown hereinafter, there are two electrical circuits completed through the probe. Both are supplied through the wire 87. The return side of one of the circuits is completed through the thermistor 85 and Wire 82, contact 80 and wire 89, as clearly shown in FIG. 2. The other circuit is completed through the sand with which plate 51 is engaged to an electrode which here comprises the grounded wall of the mixer 25. The first circuit responds substantially solely to the temperature of the sand as conducted through plate 51 and tube 60 to the thermistor S5. The second cirtent of the sand as reflected :in its conductivity to the tent of the said as reflected in its conductivity to the wall of the mixer housing, the efiect of temperature being practically eliminated by the fact that any temperature-induced variations in sand resistance are com-- pensated by corresponding variations in conductivity of the thermistor.

In the circuit hereinafter described, there is means for making adjustments to take care of minor discrepancies between the conductivity of the thermistor and the conductivity of the sand at varying temperatures. However, should it become necessary to replace the thermistor for this or any other reason, it is possible to do so simply by unscrewing the retaining screws 66 and substituting a different responsive unit. The tube 60 and its contents, including the thermistor, together with the heat exchange and sand contact plate 51, are then replaced by a substitute unit.

Upon replacement, the yieldable contact 80 engages the insulated contact 86 within tube 68, to which the conductor 89 is connected.

Assuming that the probe is mounted rotatively as in p the mixer shown in FIGS. 8 and 9, swiveled electrical connections to it are provided- The sheath 90 for the conductors 87 and 89 passes from the cap 91 at the upper end of pipe 70 through a flexible hose or the like at 92 which is sleeved onto the tubular spindle 93 which is rotatable in bearings 94 provided in a closed housing 95 on the cover of the mixer. At the top of spindle 93 is a commutator 96 provided with inner and outer contacts 97, 98 (FIGS. 2 and 4). Fixed in housing 95 is an insulating brush carrier 99 provided with brushes 100 and 101 respectively registering with the contact rings 97 and 98 (FIGS. 2 and 3). From the brushes, conductors lead outwardly through the fixed conduit 102. The circuit shown in FIG. 1 will be described with reference to the functioning of the system as-a whole.

With the mixer in normal and substantially continuous use, the water tank 27 will be full of water and the hopper 26 full of sand. The mixer 25 will just have emptied,

its discharge gate 104 being operated pneumatically subject to the control of valve 105, cam operated from motor 106 subject to the control of a timer 107 as disclosed in my companion application Serial No. 373,229, filed August 10, 1953.

As soon as the cam closes valve 105, the cam 116 on cam shaft 109 Will close switch 117 to close a circuit through the relay 1'20 (first row) to admit to the mixer 25 a portion of the water stored in tank 27 through the discharge solenoid valve 114 and pipe 114. Air will concurrently be admitted to the tank by means of solenoid valve 35 to effect flow regardless of relative elevation of the tank and the mixer. The duration of flow of the flushing water can be controlled by the setting of the cam 108. It will tend to wash down the sides of the tank so that sand will not accumulate thereon. The safety relay 111 will not close unless the moisture measuring circuits are in proper functioning condition.

The circuits which control the flushing water as completed through relay 120" (first row) are controlled by current flowing between the probe 40 and the wall of sand hopper 26. If the flow of current indicates that the sand in the hopper is already adequately moist,

. relay 120 will open and no discharge of flushing water erate valve 122 which, through pneumatic connections not shown, will open the charging gate 123 in the hopper 26 for the delievery of sand into the mixer.

The functioning of relay 120 as aforesaid has transferred the control from relay 111 (second row) to relay 115 (third row). This is a highly specialized type of relay which performs an integrating function, and utility of which is not limited to this particular use. Various embodiments of this relay are shown in FIGS. 11 to 23 of the drawings and it will now be described.

As illustrated in FIG. 1, the relay is a DC. relay, the various circuits being powered by rectifiers .116. A DC. relay is shown in FIGS. 11 to 16. Its armature 120 is subject to the opposing action of electromagnetic influencing coils at 121 and 122. It is desirably biased toward the poles of one of these coils, as by the tension spring 123 which, in the illustrated device, favors movement of the armature toward coil 122. As the device is shown, the movable contactor 125 connected with the armature is thereby maintained normally disengaged from the fixed contact 1126 of the relay.

A moisture control is effected by varying the voltage on coil 122 by adjusting the variable transformer 117. Whereas the output of the similar transformer is adjusted to a fixed value of about 14 volts, the transformers 117 and 119 are set to yield ten to sixty volts (or an average of twenty to thirty-five volts) on the associated mete- rs 124 and 124. The percentage of moisture added to the sand will be varied accordingly in the operation of the integrating relays 115 and 115'.

A circuit through the thermistor 85 in the probe 50 in the mixer is connected through coil 122. This circuit is independent of the sand in the mixer and hence is afiected only by changes of temperature and not by changes of moisture. The other circuit through the probe, which includes the sand of the mixer, and which is therefore responsive to sand moisture independent of temperature, is connected to the magnet coil 121. Thus, the current flowing through the coil 122 supplements the action of the biasing spring 123 intending to maintain contacts 125 and 126 disengaged, while current tfiowing through the coil 121 tends to attract the armature 120 and to move it in a direction to engage such contacts.

The circuit controlled by contacts [125 and 126 can close only when the moisture of the sand reaches a value such that the current in the coil 121 can overcome the fixed bias of spring 123 and the magnetic strength of coil 122 as influenced by sand temperature and by the voltage imposed on the circuit by the variable transformer 117. The hotter the sand, the lower its resistance and the more current will fiow through coil .121. That compensate for this fluctuation in resistance, the thermistor will pass increased current to coil 122 at high sand temperatures. Similarly increased current will flow in coil 1-22, requiring more water in the sand to lower its resistance until the current in coil 121 is sufficient to trip the relay. Thus, the closing of the circuit controlled by contacts 125 and 12-6 is not only controllable as to water requirements, but is an integrated function of both heat and moisture, being directly responsive to moisture and inversely affected by heat.

FIG. 24 shows a very slight modification which is made in each of rows 2, 3 and 4 of the relays shown in FIG. 1 to convert the system for alternating current by omission of the rectifiers and associated condensers illustrated in FIG. 1. As shown in FIG. 24, the secondary winding of transformer 127 connects directly to magnet 1220. This magnet corresponds to magnet 122 in the D.C. device, but, in order to make the integrating relay. function satisfactorily, it is desired that the magnets 1210 and 1220 constitute solenoids as best shown in FIG. 17.-

The member 1200, instead of being acted upon directly, carries armature bars 1201 and 1202 which are pivoted to it to hang within the solenoid coils 1210 and 1220. Each of these bars is desirably provided externally with two slightly spaced semi-tubular facings of copper as indicated at 1203 and 1204 in FIGS. 22 and 23. Moreover, it has been found desirable that a differential factor be introduced by finishing differently the ends of the respective armature bars. It will be noted that the bar 1201 in FIG. 17 has its end portion flat whereas bar 1202 has a slight conical taper 130, the surface of which may vary anywhere from a minimum of 5 to 10 to a maximum of 60 or 70 from the flat end of bar 1201 in the other coil.

For the particular purposes of the present device, I have found it desirable to taper the end of armature 1202 in the coil 1220 whose current is proportionate to moisture and the angle used is about respecting the axis of the armature bar. For other integrating purposes, I may taper the end of armature bar 1205 as in FIG. 19, or I may produce a more pronounced taper as indicated at and 136 either on the armature bar 1206 of FIG. 21 or the armature bar 1207 of FIG. 20. The angularity of the conical points indicated in FIGS. 20 and 21 happens to be an angle of 30 from the axis in each instance, but the figures given are purely by way of exemplificat-ion.

In either case, the conical beveling of the end of one of the armature bars, or the differential beveling of one with respect to the other, makes it possible to increase the accuracy of response. Using constant 14 volts in the thermistor circuit, the AC. current in the righthand coil 1220 varies from 15 to 100 milliamperes directly as the temperature of the sand in the mixer while the typical voltage of 20 to 30 volts AG. in the probe circuit through the sand varies from 25 to 100 milliamperes in coil 1210. Again the figures are given by way of exemplification and not by way of limitation, since the actual current flow and the voltage used may vary quite widely according to the type of material which is being handled.

Merely as a guide to the proper settings, it may be stated that in the average typical installation, the armature lever will trip to close the circuit through the relay at 25 to 30 milliamperes of current in the moisture controlled circuit in coil 1210 with approximately 15 milliamperes of current in the temperature control holding coil 1220.

The above presupposes an average operating sand temperature of about 140. The thermistor used has 410 ohms of resistance at 75. This will quite closely balance a particular sand at the operating temperature indicated, but some change would have to be made to permit the thermistor to balance increases in sand dryness with increases in temperature if a different type of sand were in use.

Minor differences between the characteristics of the sand and the thermistor can be compensated by adjusting the rheostat in the shunt circuit across the relays. For major dilferences, a different thermistor may be required. The shunt rheostats used are variable between 500 ohm minimum and 2500 ohm maximum, and they are ordinarily used at a value of between 1000 and 1500 ohms. Once the shunt is adjusted to the correct value by test-ing the moisture actually resulting from the operation of the circuit, the operator can get that particular moisture value at all sand temperatures through the automatic functioning of the device.

The use of alternating current in the relay has been found greatly preferable to the use of direct current. In the first place, the contacts are no longer subject to corrosion by electrolysis. In the second place, the regulation is much more sensitively accurate. This is believed to be possibly attributable to the fact that the circuit functions in reliance upon changes in conduc tivity of sand, and the sand is made up of numerous particles which are not always in intimate contact. Apparently the fluctuations of the alternating current may have something like the effect of a vibrator in promoting a more uniformly equalized contact between the discrete particles of moist sand. Whatever the reason may be, very superior results are noted through the use of the A.C. circuit.

As above indicated, the initial control through relay 120 according to the moisture of the sand in the hopper 26 was shifted to the balancing relay 115 (or. 1150) by the locking relay 112 which also maintains the circuit perative to the end of the cycle and causes flow of water to continue subject to the control of solenoid valve 114 and air valve 35 until the integrating relay 115 or 1150 trips to indicate that the water supplied to the mixer is nearly adequate. As an example, I have used a circuit in which the armature trips with 80 milliamperes in the moisture affected winding and 40 milliamperes in the holding coil. At the point when the integrated relay 115 trips, the water is desirably less than that ultimately desired by no more than /2 of 1 percent.

The tripping of integrating relay 115 shuts off the water. Control then passes to the timer 107. When timer contacts 143 close at the conclusion of the mulling cycle, relays 141 and 161 are energized to transfer the moisture control circuits to relay 115 (or 1150) in the fourth row in FIG. 1. Continued determination by the probe of the moisture requirements is now effective to determine the amount of trim water required to leave the sand at exactly the right degree of moistness. Locking relay 140 in the third row holds the trim water circuit effective until the close of the cycle.

The resulting circuit is such that assuming some small additional amount of water is still required, the valve 38 rather than valve 114 will now be open to deliver water directly from the line 30 into the mixer through a spray head 144 at the lower end of the trim water pipe 145.

The integrating control is the same as before and this time, when the flow of current in the moisture responsive coil overcomes the flow of current in the heat responsive coil to trip the integrating relay 115', the supply of water is cut ot'I' completely and the circuit to the timer is reestablished. The mulling operation continues only until the discharge cam of cam shaft 109 functions to open the discharge gate 104 from the mixer. At that time switch 110 opens and all the relays are cleared for the next cycle.

After the device has been shut down for a period, the circuit will not operate exactly as above described because of the incorporation in the circuit of an electronic tube 150 which requires about one minute for the warming up of its filament before it is ready to function. The thermistor very quickly reaches the temperature of the sand it the thermistor is not, at the outset, too far below the normal temperature of returning sand. This only happens after shut down. The purpose of the delay factor introduced by tube 150 is to allow the thermistor to come up to sand temperature under those circumstances.

The base water, or principal water supply, is controlled by the'diiferential relay 115 and the trim water by relay 115', it being understood that the A.C. relay 1150 may be substituted. To insure that the holding coils of the respective relays will dominate to prevent any differential respectively. Within this brief period the current through the thermistor and the holding coil will reach full value. Normally the current through the holding coil does reach full value in any event, even without the time delay relays,

but occasionally the current through the sand will build up the current in the coil 121 before the current in coil 122 reaches full value. The'delay relays take care of this unusual situation.-

Should the operator desire to add water for any special condition, he may do so by closing the manually operable switch 151.

For the convenience of the operator, pilot lights, volt meters and milliammeters are provided. The pilot light 152 above the main control switch 153 indicates that the device is energized for operation. The pilot light 154 above the switch 151 which controls the addition of water will light only when the probe circuit is functioning satisfactorily. The pilot light 155 will be lit only when base water is flowing into the mixer. The pilot light 156 will be illuminated only when trim water is flowing into the mixer.

From the foregoing, it will be apparent that the checking of the sand starts in the batch hopper 26 with the flow of current from the probe 40 to the wall of the hopper. If the sand is wet enough so as not to require the addition of moisture, the normally closed relay 120 will open and not even flushing water will be added to the mixer.

Assuming that the sand in the batch hopper is dry enough to require moisture, a portion of the requisite water will be discharged into the mixer to flush the walls before or at the time of introduction of sand to the batch hopper. The control will then be transferred to relay 111 in the second row. If the probe circuit is in operating condition, relay 111 will immediately energize relay 112 to close the normally open contacts of relay 112 and to energize thereby the interlock which will keep this relay closed to the end of the cycle. At the same time, the current needed to energize the solenoid air valve and to start the base water into the mixer will be supplied, regulated by the thermistor circuit to integrating relay 115 (third row).

When the supply of base water closely approaches the amount required by the sand, the flow of current through the sand and coil 121 will balance the flow through the thermistor S5 and coil 122, exclusively of the sand, to trip thearmature of the integrating relay 115. This will then close the normally open locking circuit 140 which will remain closed for the rest of the cycle.

When the mulling cycle times out, control of the moisture supply will be transferred to the relays of the fourth row subject to the closing of the contacts of relays 141 and 161 between the third and fourth rows. These relays are energized only by the cam actuated closing of switch contacts 143 controlled by the timing motor at the conclusion of the mulling cycle. will final control he transferred to the integrating relay 115'.

When relays 141 and 161 are energized, relay 163 starts the water flowing through the spray head 144 into the mixer and energizes the heater in the thermostatic time delay relay 164 to close the normally open contacts in this relay.

When sufficient current is flowing through the sand to energize coil 121 of relay 115' to trip the armature against the counter-attraction of coil 122, the relay 163 will be energized to close the solenoid water valve 38 and stop the flow of trim water into the mixer. The trim water circuit, is, of course, controlled by the delay tube 150 so that water cannot enter the mixer through the trim water circuit after a shutdown of the apparatus untilone full minute after the beginning of the cycle.

Relay 165 is energized only when the trim water valve is open. This relay interrupts the operation of the timing motor 106 until the requirements in the way of trim water have been satisfied. This prevents'the sand from being discharged through gate 104 prematurely. Upon satisfying of the trim water demand, relay 165 recloses, motor 106 resumes operation, and the discharge switch is cam actuated to discharge the sand and, at the same time, to release all of the locking'relays to reinstate the circuits for a new cycle of operation. This operation recommences when the discharge gate 104 closes.

Only at this time The embodiment of the invention shown schematically in FIGURE 25 includes a batch hopper 200, a mixer 201 and a water accumulating tank 202. There is a cam shaft 253 operated by motor 254 to actuate switches disposed along the shaft 253, as in the FIGURE 1 embodiment.

A combined temperature and moisture sensing probe 203, similar to the probe shown in FIGURE 2, is mount-- ed in the batch hopper to sense initial moisture content and temperature of the material in the batch hopper in the course of determining the amount of base water which should be added to the mixer 201.

Signals from the probe 203 and from a probe 204 in the water tank 202 are integrated in a triple coil relay 205, which is also shown in FIGURE 29 and schematically in FIGURE 28. This relay has an elongated armature 206, about which are wound the temperature signal responsive coil 207, the moisture signal responsive coil 208, and a coil 209 which is responsive to the signal from the probe 204 in the water tank 202.

Armature 206 is connected to the contactor plate 212. The armature is biased by gravity to draw the contactor plate 212 away from closing the contactor 213, which energizes the circuit to the solenoid 240, which controls the valve 216, which supplies water to the tank 202.

As is indicated in FIGURE 28, the coil 209 is polarized to assert upward thrust in the direction of arrow 217 on the armature 206. Moisture signal responsive coil 208 is also polarized to assert upward thrust in the direction of arrow 218 on the armature 206 and temperature signal responsive coil 207 is oppositely polarized to assert downward thrust on armature 206 in the direction of arrow 219.

As noted in the symbols in FIGURE 28, in a practical embodiment of the invention, coil 209 has a resistance of three ohms and coils 207, 208 each have a resistance of seventy ohms. This is to approximately match the resistance of the respective coils in the relay to the resistance offered to the respective probe elements which energize the respective coils. The thermistor in the temperature probe will have a resistance value for temperatures normally encountered in return foundry sand, which will range in the neighborhood of seventy ohms. The moisture probe circuit from the moisture probe plate 51 to the side of the batch hopper will range in the neighbor- 'hood of seventy ohms, depending, of course, on the moisture content of the return sand. Accordingly, each coil of the triple coil relay is matched approximately to the resistance offered to the probe from which it gets its signal.

After the granular material from the batch hopper 200 and the base water from tank 202 are deposited in the mixer 201, a dual coil relay 222, of the type hereinbefore described or as described in copending application Serial No. 739,251 aforesaid and which is in circuit with the probe 223 in mixer 201, is effective to control the addition of trim water to the mixer through the water line 224 under control of the valve 272, the solenoid 271 of which is energized to open and close the valve under control of the dual coil relay 222, as hereinafter explained.

FIGURE 27 diagrammatically shows the family of curves for various applied voltages derived from the variable transformer 262. These curves show the relationship of the current flowing in water tank coil 209 of the relay 205 as against the quantity of water in the tank as measured in inches of depth therein. It is clear from an inspection of this figure that the slope of the curve increases with voltage. This makes it possible to adjust the relay for greater sensitivity at the depth of the base water in the tank which will ordinarily be required for any particular kind of material in the batch hopper 200.

The adjustment of voltage is usually made on the assumption that the material is bone dry and at room temperature.

It is thus possible by adjusting the voltage derived from the variable transformer 262 to cause the flow of any predetermined value of current through coil 209 for any predetermined quantity of water in the tank. This adjustment can be made on installation of the equipment for any particular type of material to be handled and no further adjustment is ordinarily required. The adjustment is made so that the relay will be sensitive at anticipated base water levels.

In the initial setup of the controller, there are three initial control settings which will ordinarily be made and which will ordinarily not require any substantial change thereafter. The voltage delivered by the variable trans former 262 will be set to give an appropriate current in the water tank coil 209 for a predetermined amount of water that will automatically be repeated for each batch of material. This predetermined amount of water will be based on dry material at room temperature. If the material is neither dry nor at room temperature, the actual amount of water which will be accumulated will vary in accordance with the degree of energization of the two coils 207, 208 of the relay, but this is automatic and does not require the setting of any dial.

The next setting will be to adjust the variable transformer 264 to establish a predetermined rate of increase in the water added to the tank for increases in temperature. Any variation in the voltage applied to temperature signal responsive coil 207 of relay 205 will be reflected in the ultimate actuation of the armature and will change the requirement for current flow through coil 209 at the point where the'relay will trip.

Where the material in the batch hopper is moist, the amount of water added to the tank 202 will be decreased proportionately, according to the energization of the moisture signal responsive coil 208. The rate of decrease in the amount of water added in the tank is controlled by the setting of the variable transformer 263 which impresses its voltage across the coil 208 in the moisture probe circuit.

When all three variable transformers aforesaid have been properly set, the amount of water accumulated in the tank 202 will automatically increase or decrease, according to the moisture and temperature of the incoming material, and this amount of water will be held in the tank for discharge into the mixer concurrently with the discharging of the granular material from the batch hopper 200 into the mixer. As aforestated, this accumulated water is the base water which will ordinarily amount to about percent of the total water requirements of the material. adding the material and water to the mixer will energize a timer 265 which will control the mixing cycle and will place the dual coil relay 222 in circuit with the trim water probe 223 into circuit operation to add trim water in accordance with the final moistutre requirements of the material.

If desired, the trim water circuit can be inactivated and the base water circuit adjusted so that all of the water requirements of the material are supplied under control of the probe 203 in the batch hopper 200. The converse is true in that the base water circuit can be inactivated and the entire water requirements of the material satisfied under control of the trim water probe 223.

A more detailed explanation of the circuit of FIGURE 25 is as follows:

If there is insufficient sand in the batch hopper 200 to make up a complete batch, the paddle switch 229 in the batch hopper 200 will remain open and interlock relay 230 against actuation, thus to prevent any water from being put into the water tank. When there is sufficient material in the batch hopper for a complete batch, paddle switch 229 will close and energize relay 232 and hence energize relay 230 through a circuit including the normally closed contact of relay 231 and the now closed nor- As will hereinafter be described, the step of mally open contacts of relay 232. Relay 230 will remain energized until the cycle is completed.

When relay 230 is energized, it will energize relay 233 through the normally closed contact of relay 234. When the contacts in relay 233 close, it will energize relay 235 and close the control circuit to the triple coil relay 205. Relay 233 will also energize relay 236 and this will energize the water tank solenoids 239, 240, allowing the water to flow in the tank. Solenoid 239 operates valve 214, which will bleed air out of tank 202 and solenoid 240 operates valve 216, which admits water to the tank.

If the material in batch hopper 200 is entirely dry, i

enough water will have to flow into the tank 202to allow enough current to flow through the water from the water tank probe 204 to the shell of the tank to sufficiently energize the center coil 209 of the triple coil relay 205, so that this coil can close the contacts 212, 213 of the relay 205 and energize relay number 234. If there is moisture present in the material in the batch hopper, there will also be a flow of current through the top coil 208 of the triple coil relay 205 and the amount of current flowing through coil 208 will reduce in direct proportion the amount of current needed through the water tank probe coil 209 for lifting armature 206 and closing the contacts of this relay.

If there is heat present in the material in the batch hopper, the bottom coil 207 of the triple coil relay 205 will be energized in direct relation to the temperature of the material. Because coil 207 is polarized against coil 209, more current than would otherwise be required must flow through coil 209 in order to trip the relay.

Accordingly, coils 208 and 209 aid one another in lifting the armature 206 and coil 207 opposes coils 208, 209..

In effect, the magnetomotive forces about the three coils 207, 208, 209 are integrated in the armature 206, the net thrust on the armature being the sum of the magnetomotive forces aforesaid.

As soon as the contacts 212, 213 on the triple coil relay close, relay 234 will be energized and locked in energized position. When relay 234 is energized, it will de-energize relays 236, 235 and 233. Accordingly, water tank solenoids 239 and 240 will be de-energized to close valves 214 and 216 and shut off the flow of water into the tank 202. De-energization of relay 235 will open the control circuit to the coils 208, 209 of the triple coil relay 205.

Energization of relay 234 will also energize relays 241 and 242. When relay 242 is energized, it will energize the transformer 244 that supplies relay 243. When relays 241 and 243 are both energized, a circuit will be complete, except for relay 245, to the solenoid 246 for delivering the water from the water tank 202 to the mixer 201 through valve 249.

Energization of relay 234 will also result in energization of solenoid 250 and supply controlled air pressure to'the water tank 202 through valve 251 for subsequent delivery of the water to the mixer.

Switch 252 on the cam shaft 253 of the timer-controlled motor 254 is set so that it will close as soon as the discharge door (not shown) of the mixer 201 closes. When switch 252 closes, it will energize relay 245, which, through relays 241 and 245, will energize solenoid 246 for valve 249, thus allowing the water that has been stored in the water tank to be delivered to the mixer.

As soon as the level of the water in the water tank 202 falls below the bottom of the probe 204, relay 243 will become deenergized and in turn deenergize solenoid 246 for valve 249 and shut off the water flowing from the tank to the mixer.

Relay 261 will remain open and prevent the water tank from recycling until the circuit to probe 223 in the mixer has been satisfied for addition of trim water. Thereafter relay 261 will be energized and this will energize relay 231 and deenergize the entire water tank control circuit and condition it for the start of the next cycle.

The amount of base water admitted into the water tank 202 will be controlled by the setting of the variable transformer 262, which adjusts the voltage applied to the circuit including probe 204 and the center coil 209 of the triple coil relay 205. As indicated in FIGURE 27, an increase in voltage will decrease the quantity of water added to the tank before the current in coil 209 is sufiicient to close the relay, and vice versa.

The rate of decrease in accumulated water to compensate for moisture in the incoming material is controlled by the voltage setting of the variable transformer 263 in the circuit to the top or moisture responsive coil 208 of the triple coil relay 205, The higher this voltage, the greater is the rate of decrease in the amount of water admitted into the tank. The lower this voltage, the lower is the rate of decrease in the amount of water admitted into the tank.

The rate of increase or decrease in the amount of water to be added to the tank in relation to the temperature of the material is controlled by the setting of the variable transformer 262 in the circuit to the lower or temperature responsive coil 207 of the triple coil relay 205. The higher this voltage, the greater is the amount of increase in the water as the temperature increases in the material. The lower the voltage in this circuit, the lower is the rate of increase in the amount of water to be added to the tank.

When the main switch 255 for the base water circuit is closed, relay 232 will become energized and remain energized continuously as long as switch 255 is closed. Relay 232 is used for transferring the operation of the paddle switch 229 in the batch hopper, as between the base water circuit and the trim water circuit. When the water tank base water circuit is in use, the batch hopper switch 229 will energize relay 230 to start the water tank base water cycle. If the water tank base water cycle is not to be used, in favor of complete control in the trim water circuit, relay 232 will be deenergized by opening switch 255 and the circuit of switch 229 in the batch hopper will be transferred through the normally closed contacts-of relay 241 and 232 to the switch 256 on the control panel door for starting the mixer timer 273 through the cycle without the use of the water tank.

The trim water control circuit as shown in FIGURE 25 will now be described.

There is a separate switch 257 for controlling the trim water circuit. When this switch is turned on, it will complete a circuit through the supply line to switch 258 on the cam shaft 253 of the motor 254. As soon as shaft 253 starts to turn, cam switch 259 will close and close the discharge door of the mixer. As soon as the discharge door is closed, cam switches 260 and 252 will close. Switch 252 controls the circuit to add water from tank 202 to the mixer and switch 260 controls the circuit to the motor 210, which opens batch hopper door'211 to admit the sand or like material into the mixer. Closure of switch 258 energizes the trim water timer 265., This timer is adjustable from zero to five minutes and will be set to allow enough time for the water from the water tank to be blended thoroughly with the material added to the mixer before any trim water is added. When this timer 265 times out, it will energize relays 266 and 267. When relay 267 is energized, it will energize relay 268 through the normally closed contact of relay 269. As soon as the contact in relay 268 closes, relay 270 will be energized. This will energize solenoid 271 for valve 272 and start the trim water flowing into the mixer. It will also close the circuits from the probe 223 in the mixer to the coils of the dual coil relay 222 iiithe trim water circuit. These coils integrate moisture and temperature signals as hereinbefore described.

Water will continue to flow into the mixer through valve 272 until the water requirements of the material are exactly satisfied, when the coils of relay 222 coact to close the contact of relay 222, whereupon to energize relay 269. This will deenergize relay 270 to close valve 272 and stop I 17 the trim water flowing into the mixer. When the contacts in relay 268 open, relay 270 will become deenergized and open the control circuit to the dual coilrelay 222.

The trim water is added to the mixer during the mixing cycle, while the timer 273 is controlling the mixing cycle and is in its timing position. If the trim water is satisfied by the time the mixing cycle timer 273 times out, the mixer will go from there into discharge as soon as the timer motor starts. If, however, the trim water circuit is not satisfied when the mixing cycle timer times out, relay 275 will be energized through the right hand contacts 274 of the mixing cycle timer 273. As long as relay 275 remains energized, it will be impossible for the timer motorto start. As soon as the trim water circuit has been satisfied, relay 275 will be deenergized allowing the mixer to go into its discharge position.

Relay 266 functions as a safety device in the circuit to probe 223 in the mixer, If the probe circuit to the mixer is open, relay 266 will not be energized and this will prevent relay 267 from being energized Accordingly, no water will flow into the mixer through valve 272.

The final moisture percentage of the material to be mixed will be determined by the setting of variable trans former 276 in the trim. water circuit. This varies the voltage on the moisture sensing coil of the dual coil relay 222. The voltage on the temperature sensing coil of relay 222 is fixed.

The circuit shown in FIGURE 30 relates to an embodiment of the invention to automatically add to the mixer 281 a quantity of dry material (typically toundry sand bond) from the holding hopper 280 which is related to the deficiency of such material in the material in the batch hopper 282. For example, foundry sand bond may be furnished to the holding hopper 280 from a pneumatic teeder 285, as shown in my United States Patent No. 2,989,349. The valve 286, which meters bond from the feeder pipe 287, is controlled by the solenoid 288. The quantity of bond accumulated in the hopper 280 will be directly related to the time duration during and the amount of travel required of the rheostat sweep arm for actuating the relay will determine the total time during which valve 286 will remain open and, accordingly, the amount of bond which will be accumulated in the receiving hopper 289.

The speed of motor 292 will be adjusted initially in accordance with the composition of the foundry sand (for example) in the batch hopper 282 to produce a certain base amount of bond for each batch. Departures from such requirements as thus established and as are indicated by the degree of energization of the tempera ture responsive coil 292 and the moisture responsive coil 293 of relay 290 will result either in earlier or later actuation of the relay, with a corresponding time change in the sequence of actuation of the valve 286, thus to accumulate an amount of bond in hopper 280 which is accurately related to bond deficiency.

The motor-operated timer rheostat 291 aforesaid functions in somewhat the same manner as similar timer rheostats disclosed in my Canadian Patents 550,962 and 550,963. For example, if the temperature of return sand is high so that there is an increased current flow in the temperature coil 292, more current will have to flow in the rheostat supplied coil 289 of relay 290 in order to trip the relay. This will require that the sweep arm 295 of the rheostat 291 be turned farther to achieve By adjusting the speed of motor 292, the amount of 9 material added for any given sweep of arm 295 of rheostat 291 can be increased or decreased, 'thus to match the equipment to the requirements of any kind of material in the batch hopper.

As shown in FIGURE 30, the temperature-coil 292 and moisture coil 293 of the relay 290 are connected to a probe 294 in the batch hopper 282. This probe can be of the same construction heretofore described and shown in FIGURE 2. The probe may be separate and independent from the probe shown in FIGURE 25. If desired, the

same probe can be used to signal both to the circuitry of FIGURE 25 and to the circuitry of FIGURE 30.

The controller of FIGURE 30 is equipped with a master switch 276 and three pilot lights 277, 278, 279 on the control panel door. Pilot light 277 shows if the master switch 276 is turned on, pilot light 278 indicates when the material is being metered into the receiving hopper 280, and pilot light 279 indicates when the hopper 280 is being charged into the mixer 281.

There is also a toggle switch 297 that will start the metering operation when thrown to one position and will discharge the material from hopper 280 into the mixer 281 when thrown to its opposite position.

As long as the master switch 276 is closed, a constant voltage transformer 298 will be energized and all of the control circuits for the triple coil relay 290 are supplied thereby.

There are three variable transformers 299, 380, 301 for adjusting the voltage on the secondary transformers 302, 383 and 304 for the probe circuits. This arrangement makes it possible to satisfy the requirements of the triple coil relay 2% according to the size of the batch beingmixed. When these variable transformers have been set for any given operation, it is not necessary to readjust them.

A common line 307 from transformers 302, 303, 304

is connected to the probe 294 in the batch hopper 282.

The probe is sensitive to the temperature of the sand and also the moisture content. of the sand in the batch hopper as aforestated. Common line 307 is also connected to one side of the motor driven rheostat 291. There are also milliammeters 308, 309, 310 respectively in series with the coils in the triple coil relay. These indicate the fiow of current through each one of the three coil'circuits.

When the toggle switch 297 is turned to metering, it will energize relay 311 through the normally closed contacts of relay 312. When relay 311 becomes energized,

- it will energize solenoid 288 to open valve 286 and start When relay 290 is actuated, it will actuate relay 312,

which, in turn, will deenergize relay 311. This will deenergize solenoid 288 to close valve 286 and terminate fiow of material into hopper 280. This will also transfer the control circuit through the normally closed contacts of relay 313 to the normally closed contact of relay 311.

When relay 312 is energized, it will reverse motor 292 and return the sweep arm 295 of rheostat 291 to its starting position. When the rheostat sweep arm 295 reaches its starting position, it will close limit switch 314. Switch 314 will energize relay 313 and open the circuit to motor 292.

To deliver the accumulated material in hopper 280 to the mixer 281, switch 297 on the control panel is turned to discharge to mixer. This will energize solenoid 317 to open gate valve 318 and charge the material in the receiving hopper into the mixer. It will also deenergize the control circuit used for metering the material in the receiving hopper.

When the batch hopper has been refilled, the control switch 297 can be turned to metering and the triple coil relay 290 will control the accumulation of dry mix in hopper'280 according to the temperature and moisture of the material in the next batch in hopper 282. Switch 297 can be controlled automatically in timed relation to the overall operation of the circuit of FIGURE 25 to make manual manipulation of switch 297 unnecessary, where both circuits are used in the same installation.

There is desirably a paddle switch 319 in the hopper 282 in a circuit that will prevent the control mechanism from delivering any material to the receiving hopper 280 until the batch hopper has been filled,

I claim:

1. A device for controlling the addition of moisture to finely divided material in relation to its temperature, said device including a temperature circuit and a moisture circuit, each having an electromagnetic coil, means for establishing current flow in the temperature circuit and its coil generally related to the temperature of the material, means for establishing current flow in the moisture circuit and its coil generally related to the moisture of the material, integrating armature means associated with said coils and responsive to the current flow in the respective circuits and coils and control means subject to said armature means, the actuation of which control means is a function of moisture in relation to temperature, and means for supplying water to said material subject to said control means for determining the amount of water supplied.

2. In a device for the control of moisture in relation to temperature in finely divided materials, the combination with electrically controlled means for supplying water, of a relay switch controlling said means and comprising armature means in operative connection with the switch and having a plurality of electromagnetic windings, disposed to act oppositely upon the armature means, an electric circuit including a source of energy'and one of said windings and having a probe and an electrode spaced in said material for determining the moisture thereof, and another electrical circuit connected to another of said windings and including a resistance variable inversely in accordance with the temperature of such material and exposed to the material, whereby the warmer the material, the higher will be the current flowing in the last mentioned winding and the greater the amount of current 'which will have to flow through the material and the first mentioned winding to eifect movement of said armature.

3. In a device for determining moisture to be supplied to a finely divided material in relation to its temperature, the combination with a probe exposed to the material, a thermistor within the probe comprising a resistor ofiering resistance inversely variable in proportion to temperature, said probe having an external surface connected to one side of the thermistor and having an insulated conductor leading to the other side of the thermistor, electrode means spaced from the probe and exposed to the material, the flow of current between the probe surface and electrode means being proportional to the moisture in the material,

a first circuit including the probe surface and the electrode means and a first relay coil, a second circuit including the probe surface, the thermistor and a second relay coil, ar-

mature means upon which said coils act electromagnet ically in opposition, means for supplying water to the said material, and means for cutting oif the supply of water to said material from said water supply means and including a switch connected with the armature means and operable thereby when the attraction of the second coil for said armature means exceeds the opposed force to which the armature means is subject including the attraction of the first coil.

4. The device of claim 3 in which the armature means is subject to a bias supplementing the attraction of the first coil therefor.

5. The device of claim 3 in which the said circuits are provided with means for supplying alternating current thereto.

6. The device of claim 5 in which the armature means comprises a lever having armature bars extending into the coils.

7. The device of claim 6 in which one of said bars has a cross section varying axially and differentiating it from the other bar.

8. In a device for supplying water to a finely divided solid material having resistance variable inversely as to its temperature and its moisture, the combination with means for passing a first current directly through such material in direct proportion to its dampness and temperature, means for developing a second current inversely proportional to the temperature only of the said material, means for supplying water, and water supply controlling means including an electrically responsive means subject to opposing action of the first and second currents, whereby the effect of temperature is cancelled out and water is supplied in an amount inversely related to dampness.

9. In a device for determining the moisture requirements in relation to temperature of a finely divided material, the combination with a container for such material, a probe exposed to the material within the container, variable resistance means within the probe and subject to temperature communicated thereto from the material through the thermally conductive portion of the probe, said variable resistance means having the capacity to vary its resistance according to the temperature to which it is subject, and an external instrument and a source of current connected in series through the said resistance means for response according to the temperature of the material in the container, said container being further provided with electrode means spaced from said probe, and an electrical circuit including a source of current supply connected in series with said electrode means and the resistance means within the probe, the said resistance means fluctuating in its resistance in approximately the same manner as the resistance of the material between the electrode means and the probe, a second instrument connected in series in said circuit and responsive to the conductivity of the material between the probe and the electrode in proportion to the moisture content of such material and independently of the temperature of such material, and means for integrating the response of said instruments.

10. The combination with a probe having an electrically and thermally conductive wall portion, a thermistor resistance within the probe in electrical contact with and

Claims (2)

1. A DEVICE FOR CONTROLLING THE ADDITION OF MOISTURE TO FINELY DIVIDED MATERIAL IN RELATION TO ITS TEMPERATURE, SAID DEVICE INCLUDING A TEMPERATURE CIRCUIT AND A MOISTURE CIRCUIT, EACH HAVING AN ELECTROMAGNETIC COIL, MEANS FOR ESTABLISHING CURRENT FLOW IN THE TEMPERATURE CIRCUIT AND ITS COIL GENERALLY RELATED TO THE TEMPERATURE OF THE MATERIAL, MEANS FOR ESTABLISHING CURRENT FLOW IN THE MOISTURE CIRCUIT AND ITS COIL GENERALLY RELATED TO THE MOISTURE OF THE MATERIAL, INTEGRATING ARMATURE MEANS ASSOCIATED WITH SAID COILS AND RESPONSIVE TO THE CURRENT FLOW IN THE RESPECTIVE CIRCUITS AND COILS AND CONTROL MEANS SUBJECT TO SAID ARMATURE MEANS, THE ACTUATION OF WHICH CONTROL MEANS IS A FUNCTION OF MOISTURE IN RELATION TO TEMPERATURE, AND MEANS FOR SUPPLYING WATER TO SAID MATERIAL SUBJECT TO SAID CONTROL MEANS FOR DETERMINING THE AMOUNT OF WATER SUPPLIED.

29. APPARATUS FOR CONTROL OF THE LEVEL OF LIQUID IN A TANK HAVING A SOURCE OF LIQUID, A VALVE THEREFOR AND VALVE CONTROL MEANS, SAID APPARATUS COMPRISING AN ARMATURE, THE POSITION OF WHICH WILL DETERMINE THE OPERATION OF SAID VALVE CONTROL MEANS, A COIL ACTING ON SAID ARMATURE, A PROBE IN SAID TANK, A SOURCE OF VOLTAGE, AND AN ELECTRIC CIRCUIT INTERCONNECTING SAID SOURCE, COIL AND PROBE WHEREBY CURRENT FLOW THROUGH SAID COIL WILL ACTUATE SAID ARMATURE ACCORDING TO THE LEVEL OF LIQUID IN THE TANK AS MEASURED BY THE PROBE, AND MEANS FOR VARYING THE VOLTAGE OF SAID SOURCE TO CHANGE THE VALUE OF CURRENT AT WHICH THE COIL WILL ACTUATE THE ARMATURE TO DETERMINE THE LIQUID LEVEL AT WHICH THE SAID VALVE CONTROL MEANS WILL BE ACTUATED, A SECOND COIL ACTING ON SAID ARMATURE AND A SECOND SOURCE OF VARIABLE VOLTAGE FOR SAID SECOND COIL, THE LEVEL OF WHICH WILL ALSO CHANGE THE VALUE OF CURRENT AT WHICH THE COIL FIRST MENTIONED WILL ACTUATE THE ARMATURE.

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