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Publication numberUS3601373 A
Publication typeGrant
Publication dateAug 24, 1971
Filing dateSep 19, 1969
Priority dateSep 19, 1969
Publication numberUS 3601373 A, US 3601373A, US-A-3601373, US3601373 A, US3601373A
InventorsHartley Nelson
Original AssigneeHartley Controls Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Moisture controller
US 3601373 A
Images(5)
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Description  (OCR text may contain errors)

United States Patent Primary ExaminerRobert W. Jenkins Anorney-Wheeler, Wheeler, House and Clemency ABSTRACT: This disclosure relates to apparatus for electrically controlling the addition or removal of water with respect to material undergoing mixing. Moisture and heat sensors are exposed to the material. These sensors signal an electric circuit which energizes a reversible electric motor connected to a valve in a fluid line. When removal of water is desired, the motor can be connected to a control valve for a heater, such as a dryer In some embodiments the motor periodically is energized to move in opposite directions. When the motor moves in one direction, it tends to close the valve. In this movement the motor functions independently of the electric sensing circuit. When the motor moves in the opposite direction, it tends to open the valve. ln this movement the motor functions subject to the electric sensing circuit. The motor is also coupled to a balance element in the electric circuit to cause the motor and the relay which energizes it to hunt in a narrow range when the moisture requirement of the material is substantially satisfied. In other embodiments the motor does not hunt.

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ATTOINIV MOISTURE CONTROLLER CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of my copending U.S. patent application Ser. No. 648,060, filed June 22, 1967, now abandoned, and of my copending U.S. patent application Ser, No. 725,117, filed Apr. 29, 1968, now abandoned.

BACKGROUND OF THE INVENTION This invention involves a further development of the moisture controller shown in my US. Pat. No. 3,250,287 in which a similar reversible electric motor is utilized to actuate a valve supplying water to a continuous mixer. The apparatus of the present invention is characterized by greater reliability in operation and fewer mechanical parts.

This invention also involves a further development of the moisture controller shown in my US. Pat. No. 3,249,970 which shows control of addition of water to a batch mixer and in which readings of moisture deficiency are taken in both the batch hopper and the batch mixer. Water to supply the base water deficiency is accumulated in a tank.

SUMMARY OF THE INVENTION As compared to the moisture controller of my prior US. Pat. No. 3,250,287, greater reliability of operation is achieved in the moisture controller of the present invention by eliminating mechanical parts and utilizing components which are primarily electrical. The instant moisture controller has no photocells or exposed electrical contacts subject to fouling by dirt. In some embodiments where the mix moves past the probe, a sensitive relay which energizes the motor in response to the sensor circuit is required to hunt'in a narrow range, thus to narrow the range through which the relay must be sensitive and to require repeated operation of the relay and preclude sticking of its contacts.

The signals responsive to moisture and temperature conditions of the material are electrically integrated in a relay actuating circuit in which coils are connected in series. This eliminates physical movement of an armature, as is required in the devices shown in my prior patents aforesaid.

As compared to the moisture controller of my prior US. Pat. No. 3,249,970, the moisture controller of the present invention utilizes many of the principles of operation of the continuous mixer controller in control of moisture for batch mixers. The principle of adding water in two stages, namely, base water addition and trim water addition, is retained. In ac cordance with this aspect of the invention, control of the water valve regulating mechanism includes a batch hopper probe which controls the addition of the base water addition and a batch mixer probe which controls the addition of the trim water addition.

In preferred embodiments of the present invention, the valve which controls addition of base water is coupled to a reversible motor which moves the valve respectively toward open and closed positions, thus to modulate or change the rate of fluid flow through the valve. In some embodiments, the duration of motor 'energization in one of its directions of movement is controlled in accordance with signals received from the sensors exposed to the material, and the duration of motor energization in its opposite direction of movement is independent ofsuch signals.

In such embodiments, the motor turns in a direction to reduce the rate of fluid flow for a short cycle and turns in the opposite direction in which the rate of fluid flow is increased in a longer cycle. The sensors control the motor energizing circuit only in the longer cycle. The motor is coupled to a balance coil in the series aforesaid to require the motor and its actuating relay to hunt in a narrow range whenmoisture requirements are balanced. When moisture requirements are unbalanced, the motor will have a net movement in a direction to correct the unbalance. This may be referred to as a stepping movement.

In other embodiments, the motor will not have the stepping movement, but will move steadily in a direction to correct the unbalance.

In some batch mixer embodiments, the control for the trim water circuit is based on taking both moisture and temperature readings in the mixer. In other embodiments the temperature reading is taken in the batch hopper and is memorized" for that batch while it is in the mixer.

In some batch mixer embodiments, the same electric components are used to control the valve regulator, and these components are switched between a batch hopper sensor and a mixer sensor, depending on the location of the material. In other embodiments each sensor has its own responsive electric components, and there are separate valve controlling regulators independently actuated thereby.

Other objects, features, and advantages of the invention will appear from the disclosure hereof.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a panel on which are mounted mechanical components of the apparatus embodying the present invention.

FIG. 2- is an electric circuit diagram showing the electrical components embodying the invention, as applied to a continu ous mixer.

FIG. 3 is an electric circuit diagram of a modified embodiment of the invention as applied to a continuous mixer, certain mechanical components being also shown in this figure.

FIG. 4 is a diagrammatic view illustrating the relationship between the constant speed motor, cam, and cam actuated switch.

FIG. 5 is a composite electric circuit diagram and schematic diagram of a modified embodiment of the invention in which the moisture added to a batch mixer is controlled.

FIG. 6 is a composite electric circuit diagram and schematic diagram of a further modified embodiment of the invention in which the moisture added to a batch mixer is controlled.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto.

Like parts are indicated by the same reference characters in the several views.

The basic principles disclosed herein are applicable both to continuous mixing and to batch mixing. Embodiments of the invention utilized to control moisture of material in a continuous mixer (FIGS. l4) will be described first. Thereafter, embodiments utilized to control moisture in a batch mixer (FIGS. 5, 6) will be described.

CONTINUOUS MIXER EMBODIMENTS 3,249,970 in which the probe will generate one signal voltage responsive to the degree of moisture in the sand and will generate another signal voltage responsive to sand temperature. The moisture signal is imposed on the primary coil 20a of moisture transformer 20 through line 10. The source of this voltage is coupling transformer 4 connected to probe 8 by line 9. The temperature signal is imposed on the primary coil 22a of temperature transformer 22 through line 11. The source of this voltage is coupling transformer 6. Transformer 21 is associated with the transformers 20, 22 and has a primary coil 21a energized by coupling transformer 5.

The respective coupling transformers 4, 5, and 6 for transformers 20, 21, 22 are energized by variable transformers 23, 24, and 25 which are connected in parallel to the output of line transformer 27. Transformers 23 and 25 are used to calibrate the circuit at the time of its initial setup. Rheostats 40 and 41 are also used for calibration purposes. This calibration takes into account the volume of material processed through the mixer, the constituents of the material, etc.

The respective transformers 20, 21, and 22 have output coils b, 21b, and 22b which are connected in series to the input of a full wave bridge rectifier 35. The DC output of the bridge rectifier 35 is imposed across a capacitor 37 and across the energizing coil of a sensitive DC relay 14. The coils of the transformers 20, 21, and 22 are desirably spool coils coaxial about armatures which keep the spools in alignment. This facilitates replacement of the coils.

While the invention is not limited to controlling the addition of moisture to foundry sand, the specific circuit disclosed herein is for that purpose. The invention can also be adapted to control a fluid valve for gas, oil, or steam, or the like, thus to adapt the same unit for removing moisture from granular material which it is desired to dry. Accordingly, the fluid controlled by valve 51 can be any of,those above mentioned, although in the specific example disclosed herein it is water.

As in the apparatus shown in my prior U.S. Pat. No. 3,250,287, and in the disclosed embodiment, water is supplied from a water source 50 through a water valve 51 to the foundry sand in the mixer 7. Valve 51 may be under control of a pneumatic actuator 52. Air under variable pressure is supplied to the valve actuator 52 from a pneumatic regulator 53 which controls the pressure of air supplied from a source of compressed air 54.

Regulator 53 is similar to the one shown in FIG. 18 of my prior U.S. Pat. No. 3,250,287. Regulator 53 is under control of a reversible electric motor 29 which rotates the screw shaft 57 of regulator 53 through a gear train including the bevel gears 38 and a gear box 58. When motor 29 rotates in one direction (forward), it will turn shaft 57 to reduce the pressure of the air furnished by regulator 53 to the valve actuator 52. This tends to close the valve 51 and reduces the rate of flow of water to the mixer 7.

When the motor 29 rotates in the opposite direction (reverse), it will turn the screw shaft 57 in the opposite direction to increase the air pressure on valve actuator 52 and tend to turn the valve 51 in the opposite direction to increase the flow of water to the mixer. Motor 29 is connected in the electric circuit shown in FIG. 2. When energized from AC source 70 and master switch 71 through line 59, it will turn in its forward direction to decrease water flow. When energized through line 60, it will reverse to turn in the direction to increase water flow.

The motor 29 is also connected by a shaft 61 (through worm gears 63) to the sweep arm 62 on the variable transformer 24, thus to variably energize the primary coil 21a of the balance transformer 21.

The direction of motor rotation is controlled by relays 11,

12, and 13 and by a range finder or hunting" switch 32 which is cyclically actuated by the cam 65 mounted on the shaft of motor 33.

The range finder" switch 32 and motor 33 are utilized primarily in mixing environments in which the material is moving past the probe. Thus constantly varying signals may emanate from the probe, depending on the conditions of the material increment in contact with the probe.

If a wet" spot is against the probe, for example, because of receipt of a charge of water from pipe 50 and insufficient time to distribute the water throughout the mixer, the probe may temporarily emit false signals with respect to both the temperature and moisture content of the material of the mixer. After the wet spot passes the probe a dry" spot may be against the probe, temporarily resulting in oppositely oriented false signals. As the material is blended, the signals will be more uniform. However, regardless of the tendency of the probe to emit false signals, the range finder switch 32 and motor 33 will slow the response-of the motor 29 to the sensor signals. Accordingly, if the signals are temporarily false, the

motor 29 will not have moved excessively from its more typical position and can quickly be brought back to a more typical position. Thus, the range" through which motor 29 moves in response to probe signals is limited.

Motor 33 is continuously energized. In a typical installation, motor 33 will rotate once every 8 seconds. The cam 65 has a high lobe 66 and a low lobe 67. The low lobe 67 will engage the follower roller 68 of switch 32 for three seconds of the 8 second cycle. The high lobe 66 will engage the cam follower roller 68 for five seconds of the 8 second cycle.

The speed of rotation of the motor 33 can be varied and the configuration of the cam 65 can also be varied according to circumstances and for purposes of matching the moisture controller to specific controlled material. In any event, switch 32 will open and close in a complete cycle in which it is closed for a short period and opened for a longer period.

When switch 32 is closed, both relays l1 and 12 will be energized. Switch contact blade 69 in relay 12 will then move to its broken line position shown in FIG. 2 to complete a forward circuit to motor 29 through line 59 from the alternating current source 70. Motor 29 will rotate in a forward" direction for the 3 second interval aforesaid. During this cycle, valve 51 will be slowly moved toward closed position, thus to reduce slightly the rate of flow of water into the mixer 7. At the same time, relay 11 is actuated to move its switch contact blades 72, 73 to their dotted line positions. This opens the circuit to relay 14. Contact blade 74 of relay 14 moves to full line position to open the circuit to relay 13. This sequence isolates motor 29 from the electric circuitry which energizes rectifier 35 so that motor 29 turns forward for the full 3 second interval that cam roller 28 rides on cam lobe 67 of cam 65.

During this cycle motor 29 is turning its shaft 61 to rotate the sweep arm 62 of variable transformer 24 in a direction to reduce the voltage on the primary coil 21a of the balance transformer 21.

When the cam switch 32 is open during its 5 second cycle when roller 68 rides on high lobe 66 of cam 65, both relays l1 and we will be deenergized. Switch contact blades 69, 72, and 73 will return to their normal full line position shown in FIG. 2. Accordingly, line 59 to motor 29 will open to discontinue forward energization of motor 29.

Moreover, as soon as switch contact blade 69 in relay 12 moves to its full line position, it will close a reversing circuit to motor 29, through reverse line 60 and through the normally closed switch contact blade 75 of relay 13 which is shown in its normally closed position in full lines in FIG. 2. Motor 29 will now reverse direction for the full 5 seconds during which switch 32 is open, unless the reversing circuit is interrupted at the beginning or at any time during this period.

While motor 29 is turning in reverse direction, it will also reverse the direction of rotation of shaft 61 for reverse rotation of the sweep arm 62 of variable transformer 24, thus to increase the voltage on primary coil 21a of balance transformer 21.

As motor 29 reverses, it will move valve 51 toward its open position to slightly increase the rate of water flow to the mixer 7. If the rate of water flow is sufficient to satisfy the water requirements of the material in the mixer 7, either at the comtnencement of the reversing cycle of motor 29 or during the cycle, relay 13 will be energized by relay 14 in response to the signal from transformers 20, 21, and 22 and switch blade 75 of relay 13 will open to deenergize the reversing cycle of motor 29 and hold the water flow rate steady.

The closure ofswitch blade 72 in relay II (at the beginning of the 5 second cycle of switch 32) will condition sensitive relay 14 for energization front the DC signal emanating from rectifier 35, if the output from rectifier 35 is sufficient to pull in the relay [4. This will occur if the moisture content of the sand is balanced. The addition of voltages induced in the series connected secondary coils 20b, 21b, and 22b will then be sufficient to produce a DC output of rectifier 35 sufficient to energize relay 14. Switch contact blade 74 of relay 14 will then be pulled to its dotted'line position shown in FIG. 2 to close a circuit through switch blade 73 in relay 11 to the relay 13, thus to energize relay 13 and move its switch contact blade 75 to its dotted line position in FIG. 2 and interrupt the reverse of movement of the motor 29 and hold the water flow rate steady.

Accordingly, it is clear that in the specific circuit of FIG. 2 the motor 29 will periodically and invariably run in its forward direction for a short cycle (3 seconds) in which valve 51 tends to close to reduce the rate of water flow. Motor 29 will also periodically be conditioned for a longer cycle (5 seconds) to rotate in the opposite direction and increase the flow of water. During this longer cycle the motor is subject to deenergization in the reverse direction if there is sufficient output from rectifier 35 to energize the sensitive relay 14.

If the material in the mixer 7 needs water, the motor 29 will reverse for the full long cycle. Thus where there is a moisture deficiency on each complete cycle of the motor 29, the increase in the rate of water flow (for 5 seconds) will exceed the decrease in the rate of water flow (for 3 seconds) for a net increase in the flow rate for each complete cycle. If the moisture requirement of material has already been satisfied and is in exact balance, themotor 29 will reverse during the long cycle for the same amount of time as it turns forwardly in the short cycle (3 seconds in the stated example) so that there will be no net change in the rate at the end of each complete cycle. If the material has moisture excess, the relay 14 will not be energized at all during the reverse cycle (or will be energized for a period less than 3 seconds) so that there will be a net decrease in the rate of water flow in each complete cycle.

Accordingly, as the demand for water changes, the rate of water flow will adjust to meet this demand. In every 8 second complete cycle the motor 29 will hunt through a narrow range, returning to initial positions if the moisture requirements of the material are in balance. If there is more or less moisture in the material than should be present therein, the motor will step the valve 51 toward a position that will compensate for the unbalance.

Note from FIG. 2 that the series connected secondary coil b of the moisture transformer and secondary coil-22b of the temperature transformer are polarized in opposite directions. Thus as the temperature increases in the mixer the induced voltage in'coil 22!; will call for more water, whereas an increase in moisture in the mixer will call for less water. The demands for water based on existing moisture and temperature are thus integrated in the series connected coils 20b and 22b and a signal imposed on the rectifier 25 which is an integral thereof.

The secondary coil 21b of balance transformer 21 is polarized in the same direction as coil 20b of moisture transformer 21. Accordingly, as motor 29 turns forward to reduce the rate of flow of water through valve 51 it will also reduce the voltage on balance coil 21a in transformer 21 below what it was at the beginning of a complete cycle to artificially unbalance the control circuit. This will require motor 29 to turn reversely in the next cycle at least far enough to restore the voltage on coil 21a to what it was at the beginning of the complete cycle, even if there is no actual change in the demand for water in the sand during the cycle.

Accordingly, by reason of the balance transformer 21 and its energization by variable transformer 24 coupled to motor 29, the motor will constantly hunt in a narrow range even when there is no change in demand. This means that the contact blade 74 in relay 14 will be actuated repeatedly to insure against sticking and to maintain the relay at full sensitivity.

The only time the motor 29 will run longer in one direction than the other. thus to change the rate of water flow, is when the demand for water varies either in accord with the signal to the moisture transformer 20 or to the temperature transformer 22. Then there will be a net difference in forward and reverse running time of the motor in each complete cycle,

until the valve has been turned through a wider range and reaches a new range in which it will hunt narrowly at a new level of fiow rate appropriate for the changed condition of the material.

FIG. 3 shows a modification where an additional volume, transformer is associated with transformers 20, 21, and 22, thus to make the circuit which actuates sensitive relay 14 also responsive to the volume of material supplied to continuous mixer 7 on a belt 81. Transformer 80 provides continuous recalibration of the circuit to accommodate for change in volume. This makes it unnecessary to adjust the transformers 4 and 6, as would be the case in the circuit of FIG. 2, if volume is changed.

The primary coil 80a of transformer 80 is energized by variable transformer 82 and coupling transformer 83. Secondary coil 80b of transformer 80 is in series connection with secondary coils 20b, 21b, and 2212 as in the previously described circuit. Coil 80b is polarized in the same direction as temperature coil 22b.

Coils 80a and 8011 are relatively slidable on armature 84 and will slide toward and away from each other in accordance with the position of roller 85 which rides on the sand conveyed by belt 81 toward mixer 7. Roller 85 swings on arm 86 pivotally mounted on bracket 87 which carries a platform 88 to which coil 80!; is fast. Coils 80a and 80b will vary directly as the volume of sand on the belt 81.

Accordingly, as volume increases, the spacing between coils 80a and 80b will correspondingly increase to reduce the voltage induced in coil 80b and increase the net voltage imposed on rectifier 35 to pull relay 14 closed earlier in the cycle and increase the rate of water flow to the mixer to accommodate the increase in volume.

The calibration achieved by adjustment of transformer 82 is such that when the roller rests on belt 81 (no material is conveyed to the mixer) the increased voltage induced in coil 80b is so large as to override the signals from coils 20b and 21b and drive the motor 29 to shut off valve 51 regardless of the signals from probe 8.

BATCH MIXER EMBODIMENT One batch mixer embodiment of the invention is shown in FIG. 5. Another batch mixer embodiment is shown in FIG. 6.

.Both such embodiments incorporate the basic principle of operation previously described in connection with the continuous mixer embodiment. Any granular material may be treated. In the illustrated embodiment the granular material is foundry sand, typically foundry sand return from the shakeout apparatus.

In this embodiment a batch mixer is successively supplied with batches of foundry sand from a batch hopper 101. Hopper 101 has a discharge gate 102 through which sand is discharged into the mixer 100. Water is added to the mixer, and the sand and water is blended therein. Mixer 100 has a discharge gate 103 by which properly moisture tempered foundry sand is discharged to the sand distribution mechanism in the foundry.

Water in a sufficient amount to balance the moisture requirements of the sand is supplied to the mixer 100 through water line 50, as controlled by means of valve 51 which has an air operated modulator 52 under control of the air regulator 53 in the air line 54, as previously described in connection with the continuous mixer embodiment. In the batch mixer embodiment of FIG. 5, however, there is a shutoff valve 104 in the air line 54, between the pressure regulator 53 and valve modulator 52. Valve 104 is controlled by a solenoid actuator 105. Accordingly, valve 104 can override the pressure regulator 53 to shutoff valve means 51, regardless of the setting of pressure regulator 53.

The batch mixer embodiment of the present invention is adapted to add water to the mixer 100 in two increments, fun- 'damcntally in the same manner as two increments of water are added to the batch mixer of my prior US. Pat. No. 3,249,970, aforesaid. The first increment is denominated a base water increment. This quantity of water will be measured in accordance with the readings taken by a sensor probe 106 in the batch hopper 101. The second increment is denominated a trim water increment.

In the embodiment of FIG. 5, this quantity of water will be measured entirely in accordance with readings taken by a sensor probe 107 in the mixer 100. While these increments could be added by separate water lines, in the embodiment of FIG. both the base water increment and the trim water increment are added through the same water line 50, under control of the air modulated valve 51. The air pressure on the modulator 52 is controlled by the valves 53, 104.

In the embodiment of FIG. 6, the trim water increment is based on a temperature reading taken in the batch hopper and memorized, and a moisture reading taken in the mixer.

' In the continuous mixer embodiment shown in FIG. 2, the probe 8 in the continuous mixer 7 continuously senses moisture and temperature conditions of the moisture in the mixer. The water is added more or less continuously to the mixer 7 in accordance with signals from the probe 8 to the control transformers 20 and 22. Accordingly, the mechanism shown in FIG. 1 and the control circuitry therefor shown in FIG. 2 is constantly active and range finder motor 33 is constantly energized.

In the batch mixer embodiment of FIG. 5, the control mechanism is inactive during that part of the total cycle when the control function is undergoing transfer from the batch hopper to the mixer and until the base water addition has been completed. After the trim water addition has been completed the circuit is again inactive.

In the continuous controller embodiment of FIG. 2, the control mechanism is constantly subject to sensing signals derived from the probe 8. In the batch mixer embodiment of FIG. 5, the control mechanism is alternatively subject to sensing signals derived from the batch hopper probe 106 and from the batch mixer probe 107. The respective probes 106, 107 are transferred into and out of the control circuit, depending upon the cycle stage and the physical location (hopper or mixer) of the sand batch which is being measured. When the sand batch is in the hopper 101, its temperature and moisture will be measured by the probe 106 to determine the amount of base water to be added to this batch after it is dumped into the mixer 100. After the batch has been transferred to the mixer 101 and the base water addition completed, probe 107 will measure the moisture and temperature of the mixing batch to determine the amount of additional or trim water that must be added to bring the batch into exact moisture balance. Typically about 90 percent of the total water requirement is added in response to measurements in the hopper 101. The trim water added in response to measurements in mixer 100 amounts to the remaining percent of the total.

Many of the control elements are the same for the embodiment of FIG. 5 as for the embodiment of FIG. 2 and are given the same reference characters. The apparatus shown in FIGS. 1 and 4 is identical. The components shown in the upper righthand portion of FIG. 5 are substantially the same as those shown in the upper right hand portion of FIG. 2. The main power line 70 is connected to the motor 29 and the range finder motor 33 through a master control switch 71 in the same manner as hereinbefore described. The only difference in this portion of the circuit is that the power line to motors 29, 33 is subject to be opened by a total cycle switch 108 which is connected in series into the main power line through the leads 109. Switch 108 is responsive to a total cycle cam 110 on a cam shaft 111 which is turned by a time motor 114. Shaft 111 also turns cams 115, 117, and 119 and other cams not shown. Cam 115 actuates timer switch 116. Cam 117 actuates switch 118. Cam 119 actuates switch 120.

The functions of the cam actuated switches 108, 116, 118, 120 will be described later on in this specification. Generally speaking, these components are present in the circuit because the embodiment of FIG. 5 is dealing with a batch mixing operation, and it is necessary to periodically transfer control from the hopper probe 106 to the mixer probe 107, etc.

In the embodiment of FIG. 2, there are three control transformers 20, 21, and 22. The circuit of FIG. 5 utilizes similar transformers which are similarly located on the drawing, but

are turned on their sides to simplify circuit illustration. Transformer 123 is the temperature transformer and corresponds to transformer 22 of FIG. 2. It has a primary coil 1230 subject to the temperature" signal from one or the other of probes 106, 107, depending on whether relay 148 is in" or out.

There is a balance transformer 124 (corresponding to balance transformer 21 of FIG. 2) having a primary coil 124a which is variably energized by the variable balance transformer 24.

There is a moisture transformer 125 which has a primary coil 125a subject to the moisture signal from one or the other of hopper probe 106 and mixer probe 107, depending on whether relay 148 is in" or "out".

In addition to the three control transformers 123, 124, 125, the embodiment of FIG. 5 has an adjustably fixed balance transformer 122, the function of which will be described later on in this specification. Fixed balance transformer 122 has a primary coil 122a which is energized from a variable transformer 127 coupled to the coil 122a through a coupling transformer 128.

The primary coil 123a of temperature transformer 123 is variably energized from the variable transformer 131 and coupling transformer 132. A control rheostat 133 is also included in the circuit to the primary coil 123a.

As hereinbefore indicated, the balance transformer 124 has its primary coil 124a variably energized by the variable balance transformer 24 through a coupling transformer 134. The variable transformer 24 is the same as the corresponding transformer shown in FIGS. 1 and 2 and has a sweep arm 62 coupled to the drive shaft 61 of motor 29.

The primary coil 12511 of moisture transformer 125 is selectively energized from one or the other of variable transformer 135 and variable transformer 136. One or the other of transformers 135, 136 is selectively coupled to primary coil 1250 through the coupling transformer 137, and one or the other of control rheostats 138, 139 in accordance with the position of control relay 140. Control relay 140 is pulled in and out when the control circuit is transferred between probes 106, 107. Accordingly, when coil 125a is subject to the signal from probe 106, it is energized from transformer 136, and when subject to the signal from probe 107 it is energized from transformer 135.

As in the embodiment of FIG. 2, the control rheostats (133, 138, 139 of FIG. 5 and 40, 41 of FIG. 2) are in parallel with the appropriate probe and in series with the appropriate primary coil of the appropriate control transformer. Accordingly, as the resistance of the probe changes, current flow through the primary coil will change. Calibrating adjustment is made by adjusting the rheostat.

The rectifier 35 which supplies actuating current for the sensitive relay 14 (in the same manner as in the circuit of FIG. 2) is connected in series with various secondary coils on the temperature transformer 123, the balance transformer 124, and the moisture transformer 125. These secondary coils are identified as coils 1231) and 1230 of temperature transformer 123; secondary coils 124b and 1240 of balance transformer 124; and secondary coils 125b and 1250 of moisture transformer 125. The secondary coils 122k and 1220 of adjustably fixed balance transformer 122 are not included in the circuit to rectifier 35.

This circuitry is substantially identical to that shown in FIG. 2 except that there are two series connected, spool type secondary coils for each of the transformers 123, 124, 125, instead of the single secondary coils 20b, 21b and 22b of the circuit of FIG. 2. Two series connected secondary coils are utilized for each of the transformers 123, 124, 125 in the circuit to rectifier 35 to facilitate matching coil characteristics to the action of the transformer. This is not critical, however, as a single secondary coil on each transformer 123, 124, 125 in the circuit to rectifier 35 could be substituted for the two coils connected in series.

Temperature transformer 123 and moisture transformer 125 are each provided with another secondary coil, namely,

123d and 125d. These secondary coils, in series with the two series connected secondary coils 122b and 122C on the adjustably fixed balance transformer 122, are in an energizing circuit to another rectifier 143. No secondary coil on balance transformer 124 is in this circuit. Rectifier 143 is the source of energizing current for another sensitive relay 144 which functions to control the energization of a control relay 145 and a control relay 146 only when the moisture controller is controlled from the mixer probe 107, as hereinafter explained.

To transfer control of the primary coils of transformers 123, 125 from the hopper probe 106 to the mixer probe 107, and vice versa, the circuit includes transfer relays 148 and 149. The actuation of these relays occurs under control of the cam actuated switches 118, 120 in time with the transfer of the sand batch from the hopper 101 to the mixer 100.

As will be hereinafter explained in more detail, the batch mixer embodiment of FIG. 6 utilizes separate sets of transformers for each probe. Accordingly, there is no need to transfer control in that embodiment.

The operation of the circuit of FIG. will now be described. This description will assume the beginning of a control cycle to commence at a point in time when the batch hopper 101 is about to discharge a batch of sand into the mixer 100. The moisture and temperature of this batch has been measured just previously by the hopper sensor probe 106 and the pressure regulator valve 53 has been positioned by motor 29 in accordance with this reading. Switch 108 is opened by timer cam 110 on shaft 111 of timer motor 114, thus to deenergize motors 29, 33 and hold the pressure regulator 53 at the setting previously established by probe 106. Accordingly, the air pressure which is available to be imposed on the diaphragm valve modulator 52 is at an appropriate level so that when solenoid actuated valve 104 is opened for a fixed period of time, the modulation of valve 51 will be such that a sufficient quantity of base water will flow into the mixer 100 through the amount of water in a flush cycle just before the hopper gate 102 opens to discharge the batch of sand into the mixer 100. It is advantageous to start the flush or base water into the mixer just ahead of the batch of sand, thus to flush the sides of the mixer 100 and militate against encrustation of the mixer walls. Valve 104 is opened under control of the solenoid 105 which is energized by closure of the time cam actuated switch 118. The cam 117 is shaped to keep the switch 118 closed for the 10 second period aforesaid.

This circuit to the solenoid 105 is completed through the normally closed switch contactor arm 152 of relay 146 where the normally closed position of the contactor arm 152 is shown in full lines. Opening of the valve 104 exposes the diaphragm 52 of valve 51 to the air pressure established by the pressure regulator valve 53, thus to open the valve 51 to such an extent that the flow of base water therethrough for a 10 second period will add the amount of water previously determined by mixer probe 106 to meet approximately 90 percent of the water requirements of the batch.

Another time actuated switch (not shown) on cam shaft 111 will then actuate mechanism (not shown) to open hopper gate 102 to dump the sand from the hopper 101 into the mixer 100 shortly after the flush water has started into the mixer 100.

After the base water is added, timer cam 117 opens switch 118 to deenergize solenoid 105 and close valve 104. This closes valve 51 and stops water flow. After a short time lapse during which there is an initial blend of the base water with the sand, cam 110 will close switch 108 to reenergize the circuit to motors 29, 33, and cam 119 on shaft 111 will close switch 120. Closure of switch 120 completes a circuit to relay 146 to pull its contactor 152 to dotted line position in FIG. 5. Closure of switch 120 will also transfer the signalling connections for primaries 123a and 125a of transformers 123 and 125 from hopper probe 106 to the mixer probe 107. This transfer is cffectuated because closing'of switch will close a circuit to the transfer relays 140, 148, 149 through the normally closed contactor 153 of relay 145. Energization of transfer relays 148 and 149 will pull their contactors 154, 155, 156 from the normal] y closed full line positions shown in FIG. 5 to their dotted line positions shown in FIG. 5. This disconnects hopper probe 106 from the primary coil 123a of temperature transformer 123 and primary coil a of moisture transformer 125 and transfers these primary coils to the mixer probe 107.

Concurrent energization of relay 140 will concurrently transfer primary coil 125a of moisture transformer 125 from energization by variable transformer 136 to energization by variable transformer 135. This is because the contactors 157 and 158 of relay 140 will be pulled from their normally closed full line positions to their dotted line positions shown in FIG. 5. In a typical embodiment of the invention, variable transformer 136 will be set to supply 20 volts to the circuit of primary coil 125a, and variable transformer will be set to deliver 30 volts thereto. Accordingly, when control of the moisture transformer 125 is switched from the hopper probe 106 to the mixer probe 107, the voltage on primary coil 125a will be sharply increased. The purpose of this change in voltage is to better relate control of the air pressure in pressure regulator valve 53 to the moisture conditions existing in the mixer.

The previous measurement of moisture in the hopper 101, by hopper probe 106, typically involved the measurement of dry, hot sand. However, when the probe 107 measures the mixture of the mixer, its moisture will have been materially increased by the addition of the base or flush water through the line 50, Accordingly, the voltage on the primary coil 125a is changed to accommodate for this changed condition. In effect, the increase of the imposed voltage on primary coil 125a will so energize rectifier 35 that motor 29 will repeatedly step pressure regulator 53 toward a level that will reduce flow of water through line 50. At the same time, balance transformer 24 will be stepped to reduce the voltage on primary coil 124a of balance transformer 124 to a level where a new balance will obtain between the primary voltages on transformers 124, 125, whereupon the motor 29 will hunt at the new level of adjustment of the pressure regulator 53,

During this transition, motor 29 will move forward during all of the short 3 second cycles of the cam 67 of range finder motor 33 and will stop entirely during the longer 5 second cycle of the cam 66. Accordingly, motor 29 will step repeatedly in its forward direction to quickly reduce the air pressure on pressure regulator valve 53. Motor 29 will also step the balance transformer 24 repeatedly in a direction to decrease the voltage on primary coil 124a of balance transformer 124 and hence reduce the current in the secondary coils 124!) of balance transformer 124, until the current flow through the rectifier 35 is reduced to a point when the relay 14 will open. By this time the pressure on valve 53 will have dropped to a proper level to modulate the diaphragm valve 52 at an opening appropriate for addition of trim water. Thereafter, the circuit will respond to signals from probe 107 in a hunting range of motor 29 about this new level of air pressure on valve 53.

At a point in time after which the pressure regulator valve 53 has been modulated to a pressure appropriate for trim water addition, cam 115 on shaft 111 closes timer switch 116 which closes the circuit through switch contactor 152 of relay 146 (now in dotted line position) to the solenoid 105 for air line valve 104 to permit pressure of the modulated air in line 54 to open valve 51 to an extent determined by the new setting of the pressure regulator valve 53 and permit trim water to start flowing into the mixer through the line 50. The primary coils of temperature transformer 123 and moisture transformer 125 are now subject to the signal from the mixer probe 107. The stepping motor 29 will respond to the signals from probe 107 to change the modulation of the pressure regulator valve 53 in accordance with these readings. As the water content of the material in the mixer increases with the addition of trim water, the pressure on valve 53 will be reduced to slowly throttle the flow of water through pipe 50.

Moreover, the secondary coil 123d of temperature transformer 123 and secondary coil 125d of moisture transformer 125 will generate voltages responsive to the signal from mixer probe 107. These voltages will influence the flow of current through the rectifier 143. The series-connected secondary coils 1221: and 122a of adjustably fixed balance transformer 122 are also in the circuit to the input of rectifier 143. In this secondary circuit, the major part of the voltage comes from transformer 122. Its adjustment is fixed at the time of installation and is not normally changed thereafter.

As soon as a balance is reached between the voltages generated in the temperature transformer 123 and moisture transformer 125, sufficient current will be flowing through the rectifier 143 to energize the sensitive relay 144. This will close relay contactor 159 which will then assume its dotted line position in FIG. and will close a circuit to the energizing coil of relay 145. This will pull in the two contactors 153 and 162 of relay 145. When contactor 162 moves to its dotted line position, it will open the circuit through timer switch 116, thus to open the circuit to the solenoid actuated valve 104, shutting off the air to the air control modulator 52 and closing water valve 51, thus discontinuing flow of trim water into the mixer 100.

When contactor 153 of relay 145 is pulled into its dotted line position, this will open the circuits to the relays 140, 148 and 149 so that the respective contactors of these relays will move to their normally closed, full line positions, thus to transfer control of the transformers 123, 124, 125 from the mixer probe 107 back to the hopper probe 106. It also transfers the source ofenergy for the primary coil 125a of moisture transformer 125 from variable transformer 135 back to variable transformer 136.

The sequencejust described restores control ofthe stepping motor 29 to the batch hopper probe 106 at the low voltage in primary coil 125a of moisture transformer 125 derived from variable transformer 136. This will reduce the current flow through rectifier 35 to immediately open relay 14 and require the motor 29 to step in its reverse direction to increase the air pressure on pressure regulator 53 to a level appropriate for addition of base water, and also restore the variable transformer 24 to its position in which a higher voltage is imposed on the primary coil 124a of the balance transformer 124.

The mixer continues to mull the material in the mixer for a period of time established by its timer. During this period of time the air pressure on pressure regulator valve 53 will come up to its correct value appropriate for admitting flush water based upon the signals from probe 106 exposed to the next batch in the hopper 101. This batch is already in the hopper and is being measured by the hopper probe 106. The combined signals from probe 106 and the feedback from the stepping motor 29 through the balance transformer 124 will remodulate the pressure on pressure regulator valve 53 to a point which is appropriate for the addition of the correct quantity of the base water addition.

This measurement and modulation is completed by the time the mixer times out on the previous batch. The total cycle switch 108 is then opened by cam 110 on the shaft 111 of timer motor 114. When switch 108 opens, stepping motor 29 and range finder motor 33 will deenergize, thus to hold the pressure in the pressure regulator valve 53 at the point measured from the hopper probe 106.

A new cycle will now start after the door 103 in the mixer 100 has released all of the blended material in the mixer. Door 103 closes and at this point cam 117 closes switch 118 to energize solenoid 105 of valve 104 through the normally closed contact 152 of relay 146. Thus the water valve 51 is opened at a degree of opening established by the modulated air pressure of pressure regulator valve 53, at the level existing therein when motor 29 stopped.

As aforestated, the flush water will flow through line 50 for a period of time determined by the timer cam 117. As soon as the mixer is charged with the new batch, relays 140, 148, 149 are energized by closure of switch 120 to transfer the circuit to the control of the mixer probe 107.

MODIFIED BATCH MIXER EMBODIMENT FIG. 6 shows a further modification for moisture control in a batch mixer. This embodiment incorporates variations from the apparatus shown in FIG. 5. In FIG. 5 a single set of transformers 122, 123, 124, 125 is utilized to control the operation of the motor 29 which, in turn, controls the pressure regulator 53. In FIG. 5, this set of transformers is selectively energized from probe 106 in the batch hopper 101 and from probe 107 in the mixer 100. Switching relays 148, 149 accomplish this transfer. However, in the circuitry shown in FIG. 6, separate sets of transformers are provided, one set for control of the addition of base water and another set for the control of the addition of trim water. Each set is continuously energized, and there is no need for switching the respective probes from one transformer to another.

The circuitry of FIG. 6 also improves on the circuit of FIG. 5 in that the temperature reading utilized for control of the addition of trim water to the batch in the mixer is not taken from the mixer, but is taken from the batch hopper while the batch is still in the batch hopper. This temperature reading, as integrated with the moisture signal, is memorized in a circuit which applies a corresponding signal to the trim circuit control after the batch has been dumped into the mixer and during the trim cycle.

The probe in the batch hopper is much lighter and has less mass than the probe in the mixer. Hence the batch hopper probe is more sensitive to temperature changes than is the mixer probe, which takes considerable time to heat up and cool off. The mixer probe must be made strong and heavy because it is subject to abrasion and pressure of moving material. The probe in the batch hopper is not subject to these forces, and can be made lighter and hence more sensitive. Accordingly, a more accurate and responsive temperature reading can be made in the batch hopper than in the mixer. Inasmuch as the same batch of material is involved, a temperature reading in the batch hopper can be utilized for controlling the addition of trim water to the same batch after it has been emptied into the mixer.

Another significant difference between the circuitry of FIG.

- 5 and FIG. 6 is the elimination in FIG. 6 of the range finder switch 32 and range finder motor 33 which are in FIG. 5. These components have the primary function of limiting the range through which the motor 29 operates in environments (such as the trim probe in the mixer of FIG. 5) where the material being measured is in motion with respect to the probe. This motion exposes to the probe successive increments of material of widely varying temperature and moisture characteristics. In FIG. 6 the temperature readings are taken in the batch hopper where the material is stationary. Accordingly, the probe is not subject to varying conditions, and it is unnecessary to limit the range.

In FIG. 6 there are two sets of transformers. The first set which controls the addition of base or flush water to the mixer is near the left-hand side of the drawing. The transformers are numbered respectively 181, 182, 183. Transformer 181 is responsive to the moisture content in the batch hopper. Transformer 182 is the balance transformer (similar to balance transformer 124 of FIG. 5). Transformer 183 is responsive to the temperature in the batch hopper.

The four transformers near the right-hand side of FIG. 6 control the addition to the mixer of trim water. Transformer 184 is responsive to the moisture in the mixer. Transformer 185 is a balance transformer, the energization of which is normally preset. Transformer 186 is responsive to the temperature previously sensed in the same batch of material when it was in the batch hopper 101. Transformer 186 is energized in accordance with signals transmitted to it by a memory motor balance transformer 187, in a manner hereinafter described.

Motor 29 is connected through coupling 190 to a pressure regulator 53 which is in one branch 191 of an air line supplying the air line 54 for the pneumatic control valve 52. In this embodiment of the invention there is a parallel air line 192 in which there is another pressure regulator 193 which functions during the operation of the trim circuit and which is normally preset to furnish a constant pressure on air line 54 during the trim cycle. Hence, pressure regulator 53 functions during the base cycle, under control of motor 29, and pressure regulator 193 functions during the trim cycle, at a preset pressure.

Motor 29 is also connected through coupling 61 to variable transformer 24 which controls the primary coil 182a on the balance transformer 182, as described in connection with balance transformer 124 of FIG. 5.

Probe 106 in the batch hopper 101 will respond to both the moisture content and temperature of the material in the hopper and will signal those readings respectively to the moisture transformer 181 and temperature transformer 183. Moisture transformer has a primary coil 181a responsive to the moisture content in the hopper 101. Temperature transformer 183 has a primary coil 183a responsive to the temperature of the material in the batch hopper 101.

Moisture transformer 181 has a secondary coil 181b and temperature transformer 183 has a secondary coil 183b, these being connected in series with the input of the bridge rectifier 35 which controls the relays 11, 12, 13, 14, which correspond generally to similarly numbered relays described in connection with the circuitry of FIG. 5. Balance transformer 183 has secondary coils 182b and 1820 which are also connected in series with the secondary coils 18lb and 18%.

Accordingly, the motor 29 will be run in either forward or reverse direction in accordance with the signals from the probe 106 in the batch hopper 101. Thus the pressure regulator 53 will increase or decrease the air pressure imposed upon the operator 52 of valve 51, thus to increase or decrease the amount of water supplied through pipr- 50 during the flush or base water cycle of the controller. Unlike the embodiment of HG. 5, motor 29 of FIG. 6 runs steadily in one direction or the other until a balance is reached. It does not step, as in the embodiment of FIG. 5. 7

While the readings are being made of both temperature and moisture in the hopper 101, a memory circuit in the trim water control apparatus is concurrently being signalled to memorize the moisture and temperature conditions in the batchhopper. For this purpose batch hopper moisture transformer 181 is provided with a secondary coil 1810 and batch hopper temperature transformer 183 is provided with a secondary coil 1830. These secondary coils are connected in series with the secondary coil 187a of the memory motor balance transformer 187 and with the input to bridge rectifier 194 in the trim circuit. Secondary transformer coils 18711 and 1870 of transformer 187 are connected in series with rheostat 195, the shaft of which is coupled to the shaft of memory circuit balance motor 196. The shaft of motor 196 also turns another rheostat 197. Rheostat 197 is in series with the primary coil 186a of temperature transformer 186 in the trim circuit.

Memory motor 196 will be positioned in accordance with the signals impressed on the rectifier 194 from the secondary coils 181a and 183C in the transformers 181, 183 in the base circuit. The output of the rectifier 194 is impressed on a sensitive relay 198 and thence upon the relays 201 and 202 which energize and control motor 196. Relay 202 is also subject to the cam switch 203 which is operated by cam 204 on the shaft 111 of the timer motor 114. When cam switch 203 closes, it energizes relay 202, thus energizing motor 196 to turn the rheostats 195, 197 toward their zero positions.

When cam switch 203 opens, relay 202 is deenergized, thus energizing memory motor 196 to turn in the opposite direction through the normally closed contacts of relay 201. Motor 196 will turn rheostat 195 (and also rheostat 197) until sufficient current is flowing through the primary coils 187b and 187c of the memory balance transformer 187 to energize sensitive relay 198. When relay 198 is energized, it energizes relay 201, thus to lock relay 201 and hold the motor 196 in its position which memorizes the readings taken from the base water circuit and which will be utilized as the temperature readings in the trim circuit by reason of the concurrent positioning of the rheostat 197. Accordingly, when the trim circuit subsequently functions, the voltage induced in the secondary coil 186b of the temperature transformer 186 will be determined by the position of the rheostat 197.

Secondary coil 181c on the batch hopper moisture transformer 181 is adjustable on the extended armature 205 of transfonner 181. The purpose of adjusting coil 1810 is to reduce the inductive relationship between the primary coil 181a and the secondary coil 1810, thus to get a proper reading on the secondary coil. The amount of base water required will vary in relation to the size of the batch. Accordingly, when batch sizes change, it is necessary to raise or lower the secondary coil 181c with respect to primary coil 181a in order to get proper signals from a secondary coil 181a memory circuit.

The trim circuit moisture transformer 184 has a primary coil 184a which responds directly to the moisture signals emanating from the probe 107 in the mixer 100. The secondary coil 184b in transformer 184 is connected in series with the secondary coil 186b of the temperature transformer 186. As before indicated, transformer 186 is controlled by rheostat 197 and has no direct response to the conditions in the mixer 100.

Also connected in series with the secondary coil 184b are the secondary coils l85b and 1850 of the trim circuit balance transformer 185 which has its primary coil 185a energized from a variable transformer 206. This balance transformer 206 is ordinarily preset and is utilized only for supplying a base amount of current in the trim circuit which controls the bridge rectifier 103. The output of rectifier 103 is impressed upon the sensitive relay 144 which is in the circuit to the solenoid 105 of air valve 104 during the trim cycle. When water has been added to the mixer 100 through pipe 50 during the trim cycle in an amount sufficient to bring the moisture into balance with the requirements of the material, relay 144 will be energized from rectifier 103 to actuate solenoid 105 and close the water valve 51, thus to terminate addition of water.

In the circuitry of FIG. 6 as just described, relay 144 is controlled by the integration of temperature readings previously taken in the batch hopper and moisture readings concurrently taken in the mixer. As before indicated, the temperature readings from the batch hopper are taken more accurately than from the mixer. The memory circuit aforedescribed will result in a more accurate control of the quantity of trim water added to the mixer than has been heretofore achieved.

A brief summary of the sequence will now be described, starting with the supposition that the batch hopper is full and timer motor 46 started. When cam switch 207 (subject to cam 208 on shaft 111 of motor 114) closes, it will energize solenoid 105 to open air valve 104 and permit imposition on air controller 52 of whatever pressure is established by regulator 53. During this part of the cycle, cam switch 209 (actuated by cam 210 on shaft 111 of motor 114) will also be open. Thus coil 213 of valve 214 will function to supply air to line 191. Cam switch 211 (actuated by cam 212 on shaft 111 of timer motor 114) opens to deenergize relay 11 and energize motor 29 through the normally closed contacts of relay 12. Pressure regulator 53 will function and will be subject to motor 29. Base or flush water will be furnished through the pipe 50 through a preset time on cam switch 207, thus allowing base water to enter the mixer in an amount controlled by the motor driven regulator 53. When cam switch 207 opens, solenoid 105 will be deenergized thus shutting off the air supply to air controller 52 of valve 51 which is normally closed.

When cam switch 207 opens, cam switch 209 will close, thus energizing solenoid 213 in valve 214 to shut off the air supply to air line 191 and pressurize air line 192 to the pressure regulator 193 which is preset at a fixed value for addition of trim water.

When cam switch 215 (subject to cam 216 in shaft 111 of motor 114) closes, it will energize solenoid 105 through the normally closed contacts of relay 145. Inasmuch as regulator 193 is preset, the trim water will flow at a uniform rate which is only as fast as the mixer 100 can blend the water with the material. This avoids wet spots caused by the addition of too much water during the early part of the trim cycle, in those rare instances where an insufficient quantity of base water was added during the base cycle. When the moisture requirements of the material are exactly balanced in the mixture, the current flow through the primary coils of transformers 184, 185, 186 will energize relay 144, thus energizing relay 145 and deenergizing solenoid 105, thus shutting ofi the air to air operator 52 and permitting valve 51 to move to its normally closed position.

When relay 145 is thus energized, it also forms an interlock that will prevent the trim water from coming on until the next trim cycle.

At the time of calibration of the device, the control rheostats 217, 218, 219 are locked into position. Transformers 222, 223, 206, 224 and 225 are also locked into position. Transformer 226 for the trim circuit moisture transformer 184 is left subject to change to facilitate adjustment of the amount of final moisture addition to the mixer.

lCLAlM:

1. Apparatus for controlling moisture in granular material, said apparatus comprising a source offluid,

a valve controlling the rate of flow of said fluid,

valve regulating mechanism including a reversible motor and mechanism driven by the motor to move the valve toward open and closed positions respectively in accordance with the direction of motor operation,

means for energizing the motor to move alternately in successive forward and reverse cycles,

a moisture sensor exposed to the granular material,

and control means responsive to said sensor for controlling the duration of motor energization in one of said cycles.

2. The apparatus of claim 1 in which one cycle is longer than the other, the valve being moved toward closed position in the short cycle and being moved toward open position in the long cycle.

3. The apparatus of claim 1 in which one cycle is longer than the other, and means for disconnecting said control means from the motor during the short cycle and for connecting said control means to the motor during the long cycle.

4. The apparatus of claim 1 in which the control means comprises a motor reversing circuit having a switch, the actuation of said switch being required for reversing the motor, a switch actuator relay and a relay energizing circuit including coils in series, said sensor comprising means for variably energizing one ofsaid coils.

5. The apparatus of claim 4 in which said reversible motor is coupled to a source of variable energy for another of said coils in series whereby said other coil is variably energized in accordance with the movement ofsaid motor.

6. The apparatus of claim 4 in which there is balancing coil in said series, said balancing coil being variably energized in accordance with motor movement.

7. The apparatus of claim 4 in which there is a volume coil in said series, and a sensor responsive to the volume of material for variably energizing said volume coil.

8. The apparatus of claim 1 in which the means for energizing the motor comprises a constant speed motor, a cam and a switch, said cam having a short lobe for actuating said switch in said short cycle and a long lobe for actuating said switch in said long cycle.

9. The apparatus of claim 1 in which the granular material is in a continuous mixer supplied with fluid from said source.

10. The apparatus of claim 1 in which the granular material is transferred from a batch hopper to a batch mixer supplied with fluid from said source, said moisture sensor comprising a hopper probe and a mixer probe, said control means being responsive to the batch hopper probe to regulate the addition to the mixer of a base fluid, and being responsive to the mixer probe to regulate the addition to the mixer of a trim fluid.

11. The apparatus of claim 10 in combination with transfer means for transferring response of said control means from the hopper probe to the mixer probe in time with the transfer of material from the batch hopper to the batch mixer.

12. The apparatus of claim 11 in which the control means comprises a motor reversing circuit having a switch, the actuation of said switch being required for reversing the motor, a switch actuator relay and a relay energizing circuit including coils in series, one of said coils being selectively variably energized by the hopper probe and by the mixer probe in accordance with whichever one of said probes is in the circuit with the control means.

13. The apparatus of claim 12 in which said coils in series constitute secondary coils of transformers having primary coils, and switching means for selectively connecting said hopper probe and mixer probe to a primary coil 14. Apparatus for controlling moisture in granular material, said apparatus comprising a source of fluid,

a valve controlling the rate of flow of said fluid,

valve regulating mechanism including a reversible motor and mechanism driven by the motor to move the valve toward open and closed position respectively in accordance with the direction of motor operation,

an electric circuit for controlling motor energization and including a switch in the circuit to the motor and a switch actuation circuit including coils in series,

a moisture sensor exposed to the granular material and comprising means to generate in one of said coils a voltage related to moisture present in said material and to generate in another of said coils a voltage related to the temperature of said material, the sum of said voltage being impressed on said switch actuation circuit.

15. The apparatus of claim 14 in combination with means to energize another one of said coils in response to motor movement.

16. The apparatus of claim 14 in further combination with means independent of said switch actuation electric circuit for periodically running the motor in one direction in short cycles and for periodically subjecting the motor to said switch actuation electric circuit in long cycles.

17. The apparatus of claim 14 in combination with means to variably energize another one of said coils in response to the volume of material undergoing treatment.

18. The apparatus of claim 14 in combination with hunting means to require the motor to periodically reverse even when no change in flow rate is required.

19. The apparatus of claim 18 in which said hunting means comprises one of said coils in series being a balance coil and means variably energizing said balance coil in response to motor movement.

20. Apparatus for controlling moisture in a batch of granular material and in which the batch is transferred from a batch hopper to a mixer, said apparatus comprising a source of water for the mixer,

valve means controlling the rate of flow of said water,

valve regulating mechanism including a reversible motor and mechanism driven by the motor to move the valve means toward open and closed positions in accordance with the direction of motor operation,

a hopper probe,

a mixer probe,

an electric control circuit for controlling said reversible motor,

transfer means for connecting said electric circuit to the hopper probe when the batch is in the hopper to measure a quantity of base water and to connect said electric circuit to the mixer probe to measure a quantity of trim water when the batch is in the mixer.

21. The apparatus of claim 20 in which said electric control circuit comprises a motor reversing circuit having a switch, the actuation of said switch being required for reversing the motor, a switch actuator relay and a relay energizing circuit including coils in series, said probes comprising means for variably energizing one of said coils.

22. The apparatus of claim 21 in which said coils are secondary coils of transformers, said transformers having primary coils, the primary coil associated with said one coil being selectively connected to said hopper probe and said mixer probe by said transfer means.

23. The apparatus of claim 22 in which said transfer means comprises switching relays actuated in timed relation to the transfer of the batch from the hopper to the mixer.

24. The apparatus of claim 20 in which said valve regulating means further includes a shutoff valve which can override the mechanism driven by said reversible motor, another electric control circuit for controlling said shutoff valve, said transfer means further comprising means for connecting the mixer probe to said other electric circuit when the batch is in the mixer.

25. Apparatus for controlling moisture in a batch of granular material and in which the batch is transferred from a batch hopper to a mixer, said apparatus comprising:

a source of base water for the mixer,

valve means controlling the flow of said base water,

valve regulating mechanism including a reversible motor and mechanism responding to the motor to move the valve means toward open and closed positions in accordance with the direction of motor operation,

a hopper probe,

an electric base water control circuit for controlling said reversible motor from the hopper probe when the material is in the hopper to measure a quantity of base water, a source of trim water for the mixer,

valve means controlling flow of water from said source of trim water into the mixer,

a mixer probe,

and an electric trim water control circuit for controlling said valve means from the mixer probe when the material is in the mixer to measure a quantity of trim water.

26. The apparatus of claim 25 in which the electric trim water control circuit comprises memory means responsive to the temperature of the material while it is in the batch hopper and which memorizes said response and applies said response to the measurement of the quantity of trim water.

27. The apparatus of claim 26 in which said electric trim water control circuit comprises a relay and a relay energizing circuit including coils in series, one of said coils being sensitive to changes in the moisture content of the material in the mixer and being variably energized in response to the mixer probe, said memory means comprising means to variably energize another of said coils in response to the temperature of the material while it is in the batch hopper.

28. The apparatus of claim 27 in which the last mentioned means comprises a transformer on which said other coil is wound as a secondary coil, a primary coil on said transformer, a variably resistance in circuit with said primary coil, and means for adjusting said variable resistance in response to the temperature of the material while it is in the batch hopper.

29. The apparatus of claim 28 in which the means for adjusting said variable resistance comprises an electric motor, and means to turn said motor in response to the temperature of the material while it is in the batch hopper.

Patent Citations
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US3110421 *May 24, 1961Nov 12, 1963Matthias Karl HeinrichSupervising apparatus for maintaining predetermined mixture proportions in the dry constituents of a mixture more particularly for road construction
US3161927 *Oct 12, 1959Dec 22, 1964Dietert Co Harry WMethod and apparatus for taking a measurement of compensated moisture content of granular material
US3249970 *Dec 13, 1961May 10, 1966Hartley Controls CorpApparatus and method for controlled addition of one ingredient to a mixture of foundry sand ingredients
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4027859 *May 25, 1976Jun 7, 1977Pettibone CorporationAutomatic control of liquid addition to a mixture by power sensing
US4245915 *Feb 22, 1979Jan 20, 1981Bracegirdle P EApparatus for making asphalt concrete
US4378162 *Nov 12, 1980Mar 29, 1983Bracegirdle P EProcess for making asphalt concrete
US7856737 *Aug 28, 2007Dec 28, 2010Mathews CompanyApparatus and method for reducing a moisture content of an agricultural product
USRE32206 *Mar 27, 1985Jul 15, 1986 Process for making asphalt concrete
WO1980001816A1 *Feb 15, 1980Sep 4, 1980P BracegirdleProcess and apparatus for making asphalt concrete
Classifications
U.S. Classification366/17, 137/88
International ClassificationB28C7/00, G05D11/10, G05D11/00, B01F15/04, G05D11/13, B28C7/02
Cooperative ClassificationB28C7/024
European ClassificationB28C7/02B2