US2673463A - Consistency determination - Google Patents

Description

c. N. KIMBALL ET AL CONSISTENCY DETERMINATION March 30, 1954 5 Sheets-Sheet 2 Filed Oct. 28, 1948 m AR ' INVENTOR. Charles N. Kimball BY William F. Lewis A TTORNE YS March 30, 1954 c. N. KIMBALL ET AL 2,673,463

CONSISTENCY DETERMINATION Filed Oct. 28, 1948 3 Sheets-Sheet 3 v mi - INVENTOR. Charles Kimball BY William R Lewis 17 A TT OE EYS a w @w @W Mum" w Patented Mar. 30, 1954 CONSISTENCY DETERMINATION Charles N. Kimball, Detroit, Mich., and William R. Lewis, Kansas City, Mo., assignors to C. J. Patterson Company, a corporation of Missouri Application October 28, 1948, Serial No. 57,066

3 Claims. 1

This invention is directed to the determination of the consistency of materials. In particular, the invention is directed to ascertaining both the relative consistency of a material and the change in consistency of the material while the material is being stirred or mixed. The invention enables the study of the rheological properties of materials.

In many arts the consistency of materials is of considerable importance. Consistency may be defined as the degree of firmness, density, viscosity or resistance to movement or separation of constituent particles, and is dependent upon many factors such as time of stirring, temperature, both of the material and surroundings, absorptive quality and the quantity and nature of additives to the material. Tests for consistency ranging from visual inspection and manual feel of the material to charts indicating the power required to stir the material have not been fully satisfactory as they do not provide a uniform standard by means of which a proper determination of the characteristics of the material to provide for a desired consistency can be'made.

Accordingly an object of the invention is to produce a new apparatus for measuring the consistency of materials. Another object of this invention is to produce a means by which the consistency of a. material, or a mixture of materials can be graphically indicated in a simple interpretative form. Other objects of the invention are to produce a means by which a consistency of a predetermined character can be achieved in the mixture of materials; to produce a means for exploring the rheological properties of materials; to produce a means for indicating human errors in the mixing of materials; to achieve a given consistency; to produce a means by which the change in consistency can be observed; and to produce a consistency determining instrument which can be used with conventional mixing equipment without modifying the same.

Generally these and other objects of the invention are realized from the discovery that a relationship exists between certain proportionate parts of the energy required to stir or mix a material and the consistency of the material. Consequently, whereas a measurement of the power required to stir a material will produce upon a recording, such as a recording watt meter, a serrated curve incapable of ready and accurate analyzation, a substantially smooth curve is obtained by plotting the values intermediate the envelopes of the serrated power curve, and a curve so formed not only gives aread'y indication of the consistency of the material, but also is remarkably sensitive to variations in the factors which affect consistency. The values indicated by the curve are simply a characterization of consistency which is arbitrarily entitled relative consistency.

The means by which the objects of the invention are obtained are more fully described with reference to the accompanying drawings in which:

Fig. 1 is a graph of a curve such as obtained by the measurement of the power consumed by a stirring device;

Fig. 1a; is an exaggerated form of the curve of Fig. l for purposes of illustrating how values are obtained therefrom;

Fig. 2 is a graph illustrating the form of curves obtained by the instant invention;

Fig. 3 is a diagram of the electrical circuit used to obtain the curves of Fig. 2; and

Fig. 4 is a diagram of a modified electrical circuit used to obtain curves similar to those of Fig. 2.

While the invention is applicable to the determination of viscosity characteristics of a single material or a mixture of materials, whether in the laboratory or in connection with commercial size mixing vats, for convenience the invention is described with reference to the mixing of dough. It is the usual practice of commercial bakeries to first make a sample dough, which often is done on a laboratory scale, and kneading it until an adequate consistency is reached. The record kept of time, temperature and ingredients used in this sample mix theoretically should enable th making up of subsequent doughs of the same consistency. However, the hygroscopic properties .of flour may vary from sack to sack, weighing equipment may not be calibrated, temperature control not effective, and human errors in the adding and handling of materials not compensated for, so that the rule has heretofore been that batches of dough of non-uniform consistency are to be expected, rather than otherwise. Efforts to measure in some way the consistency of the dough batches have been limited to the laboratory samples. One common practice is to obtain a graphical representation of the power used to operate the mixer.

Such a power graph is illustrated in Fig. 1, which reads from right to left. The serrate form of curve a indicates that there are surges of power required during the mixing operation and these-surges of power become greater in extent a's the time of mix progresses. The difiiculty with this curve lies in that it is not easily interpreted, as variations in the factors affecting consistency are not readily apparent in the form of the curve. Even the average of the curve appears as a substantially horizontal wavy line b and does not show clearly the efiect of variance in these factors.

It is a discovery of this invention that if a curve is plotted from measurements taken between the upper and lower envelopes of the curve of Fig. 1 on the same time scale, a smooth curve will result which is very sensitive to variations in consistency factors. Thus, as seen from Fig. 1a, the distance is plotted in Fig. 2 as an arbitrary numerical value at one instant of time, and successive points similarly plotted as the measurements at d and e, a smooth curve being drawn through these points. Curves f, g, h and in Fig. 2 are representative of the curves thus obtained.

Curve 1 is characteristic of a dough which has all the ingredients in proper proportion, and which after being mixed for eleven minutes has reached a desired consistency. As shown the curve has reached a relative consistency value of 7 on the chart at which point the mixing was stopped and the curve dropping to zero. Had the mixing continued for a longer time, the curve would have levelled off or dropped slightly, thus indicating that the optimum consistency has been passed. Curve f, in dough making, may be determined by experiment and subsequently used as a standard or control curve for subsequent batches.

The sensitivity of this manner of determining relative consistency is illustrated by curves 9, h and Curve 9 is characteristic of a dough mix in every respect similar to that used for curve I with the exception that the shortening lard is omitted. For the first six minutes of mixing time curve 9' deviates but little from standard curve I, but then starts to waver and rises above curve f at about eight minutes time, and continues to rise thereafter. Repeated experiments have shown this to be a characteristic curve peculiar to the lack of sufficient lard in the dough being mixed. In practice, as soon as the baker has identified the shape curve g is taking, he will add lard to the dough and extend the time of mix until the dough reaches the relative consistency of seven.

Similarly, curve It illustrates the lack of salt in the dough, this being characterised by a rapid initial rise in the curve followed by an early falling off in about six and one-half minutes time. Salt may be added, and the mixing continued until the relative point seven is reached. Again, curve 51' is obtained when milk (dried powdered) is omitted, this error clearly appearing early in the mixing by being well below the standard curve.

The other factors affecting consistency produce similar characteristic curves, as, for example, a high temperature will produce a lower than standard curve, while a low temperature for the batch will produce a higher than standard curve. Variations in the water absorption qualities of the flour, the proportion of the flour in the mix, the speed of the mixer and other factors will each produce a characteristic variance from the standard curve.

A further feature of this invention lies in the discovery that a more sensitive response to the consistency of a material can be obtained if, in Fig. 1c, the measurements from the power curve are taken from a point on the envelope ofthe curve to some proportional point intermediate the envelopes for the curve. Thus, measurements taken from the upper envelopes to the average, or halfway values, of the curve as at It, will result in the form of curves shown in Fig. 2, but more sensitive to variations of consistency factors. This is believed due to the fact that sudden wide variations in the power curve of Fig. 1, occasioned as, for example, a beater arm in the mixer will miss the batch of dough, are lessened in their effect upon curves produced by measuring from one envelope to a curve proportionately between the upper and lower envelopes.

Thus, the curves of Fig. 2 indicating relative consistency are not power curves, but rather curves representing values taken from power curves. It does not matter therefore whether the curves of Fig. 1 are produced from mechanically achieved power curves as shown in the U. S. patent to Hogarth, No. 474,636, or from electrically produced curves from a recording watt meter. However, a particular means for obtaining the curves of Fig. 2 directly from power measurements of a stirring or mixing mechanism constitutes a part of the invention herewith disclosed.

In Fig, 3 an electrical apparatus is shown by means of which the power requirements of the mixer are translated to the graphic form of Fig. 2. The power lines 29 for mixer motor 22 are tapped for two components to be fed to the electrical system, one component through the induction coil 25 being a function of the amperage in the power lines 20, while the second component through transformer 28 being a function of the voltage in lines 20. In the system to be described the product of these components represents proportionately the power required to operate the mixer.

The component from coil 26 is fed to an electronic wattmeter consisting of resistance 30, tubes 32 and 34 the plates of which are connected by resistances 36, 38 and 40. The com ponent from the transformer 28 is introduced into the wattmeter through resistances 42 and 44 after first passing through a phase adjuster indicated in toto at 46. As the output of the wattmeter, if recorded, would produce the serrated curve of Fig. 1, the envelopes for the curve are produced by a voltage doubling peak rectifier composed of the oppositely disposed tubes 50 and 52 connected to the output of the wattmeter in the manner shown. The output from the peak rectifier is then fed to a differential volt meter circuit including the tubes 54 and 56. The output from this circuit is taken by leads 60 and 62 to a recorder, which may be a conventional recording milliammeter upon which the curves of Fig. 2 are reproduced.

As the power line voltage in feed line 20 may vary considerably, it is necessary to eliminate voltage variations in the above system. This is accomplished by employing a gas tube regulator system well known in the art. This system is indicated by the tubes 10 and 12 in Fig. 3 with their associated circuits, it being noted that the diagrammatically shown filaments 32a, 50a, and 54a represent the filament heating means for tubes 32-34, 50-52, and 54-56, respectively.

A relay I6 is provided in the power supply system in order to activate the chart recording motor at the same time the mixer motor 22 is operating.

As previously stated, a more sensitive response to. t e. cqn is en y 03 ami c be O ned by' analyzing the values existing". between' the outer envelope-of the. curve of Fig. 1 and some proportion of the distance between the upper and lower envelopes forthe curve. The means for accomplishing-this is shown in Fig; 4. Mixer motor I is servedby power line I02. From this line, a potential proportional to the current drawn by the mixer motor is taken through induction coil I04'and fed into an electronic wattmeter indicated by tubes I05 and I06. Likewise, a potential proportional to the voltage in line I02 is taken by transformer I08, put through phase adjuster I I0 and into the wattmeter. The alternating current potential between the plates of tubes I05 and I06 is proportional to the instantaneous power drawn by the motor at any time. The output of the wattmeter is fed to a peak rectifier circuit consisting of tube II2, resistance H4 and condenser II6, the voltage output across resistance IE4 and condenser H6, in parallel, being a potential proportional to the upper envelope of the curve of Fig. 1, thus being proportional to the peak power drawn by the motor mixer.

To obtain a potential representing a proportion of the power drawn by the mixer motor, as the average power, the instantaneous variations in power are filtered out by means of resistors I20, I22 and I24 and condensers I26 and 128, these serving to pass the substantially long time D. C. average component of potential existing across the plates of tubes I04 and I06 and failing to pass rapid fluctuations in potential. A portion of this potential is taken off through the variable resistor I30. The output from resistor I24 now represents a portion of a potential which is related to the average power drawn by the mixer motor.

The potentials representing the peak power from tube I I 2 and a fraction of the average power from resistor I24 are subtraotively combined to obtain values indicated by the distance it in Fig. 2. This is done by passing the two potentials into a difierential D. C. vacuum tube meter circuit composed of the two tubes I 32 and I34. A recording milliammeter I36 is connected between the plates of these tubes, the milliammeter carrying a pen which inscribes a curve on a chart driven by chart motor I38. It is apparent that the output from the tubes I32 and. I34 will be currents as determined by the potentials in respective tubes, and the milliammeter in effect operates as a volt meter to measure the potential dilference between the tubes. Initially,

the plate currents are balanced and the milliammeter set to read zero. Then when the mixer motor is started, and motor I38 moves a chart, the ammeter I36 plots the variations in potential across tubes I 32 and I 34 against time, and thus produces the curves of Fig. 3.

Chart motor I38 is startedby means of relay M0 so that the chart motor operates only upon operation of mixer motor I00. Switch I42 is operated by a cam on motor I38 so that motor I38 continues to operate, after mixer motor I00 stops, until the chart paper moves a suflicient distance to bring a full minute line beneath the recording pen.

A gas tube regulator including gas tube I50 and its adjoined circuit is employed for making constant the D. C. voltage in the system despite fluctuations in voltage in power supply line I02. The current source for this constant voltage regulator also serves, through leads I04a, to heat the filaments of tubes I04 and I06. Similarly gas tuber I 60 serves as I a second: constant-voltage regulator for the. circuit. betweenthe. :wattmeter and the recording milliammeter. Lead 2a serves to supply heating eurrenttothe-filaments of tubes H2, H3, I32, and I34.

Variation in the filament potentials in the'various tubes will have an objectionableinfluence-on the contact potential of the tubes. This latter potential is the voltage which must be applied between the plate-and filament of av diode, or between the plate and gridof a triode, to cause the net plate. current, in the absence of any other signal or potential, to be reduced substantially to zero. As tubes I05 and I06 are in opposition, as are tubes I32 and I 34, contact potential has no appreciable effect. Tube I I2 exists as a single diode and variations in the contact potential would cause the potential at the grid of tube I34 to drift with the power line voltage and thus destroy the precision of the instrument. To oifset such variation, a second diode II 3 is connected in opposition to tube I I2, the filaments of the two tubes being connected in parallel. Thus tube II3 cancels the influence of the variation in filament voltage affecting tube II2.

This instrument has many advantages over heretofore known devices for determining the consistency of materials. It can be connected to the power line for any mixer or stirrer and consequently no modification of existing equipment is necessary. As the consistency of the mix is being graphically illustrated while mixing is taking place, additions can be made to the mix at any time to bring the materials to a desired consistency. Time is saved in mixing operations as the mixing can be stopped as soon as the curve being produced by the instrument has reached an optimum value. In particular, as exemplified in dough making, once a standard curve has been determined for the desired consistency of the dough, successive batches of dough can be brought to the same consistency and thus produce a uniformity of output which has heretofore been very difficult to achieve.

The discovery that a relationship exists between the numerical difierence between the peak power used to stir a material and either the minimum power or some proportionate part of the difierence between the peak and the minimum powers during an increment of time, and the consistency of the material, is considered to be one of the most important features of the invention. It provides a new method of defining a relative consistency from which the character of the actual consistency can be judged. It is applicable to many fields and to all materials whether in a dry or plastic state, as long as there exists a power, mechanical or electrical, to drive a stirrer or beater.

Having now described the means by which the objects of the invention are obtained, we claim:

1. An instrument for measuring the relative consistency of a material as it is being stirred by a power driven blade, comprising means for creating a fluctuating electrical potential proportionate to the instantaneous fluctuation in power consumed in driving the stirring blade, means for rectifying said potential to produce a unidirectional potential having amplitudes proportionate to said fluctuating potential, smoothing filter means connected to the output of said rectifying means, and means for recording the output of said filter means in the form of a smooth curve.

2. An instrument as in claim 1, said filter means further comprising a differential volt meter circuit.

3. An instrument as in claim 1, said rectifying means further comprising means for producing a potential proportionate to the peak power consumed, means for producing a potential proportionate to the average power consumed, and means for subtractively combining the peak power and average power potentials.

CHARLES N. KIMBALL. WILLIAM R. LEWIS.

References Cited in the file 01 this patent UNITED STATES PATENTS Number Name Date Hogarth Nov. 13, 1894 Sutermeister Mar. 27, 1923 Peterson June 1, 1926 Fawkes Jan. 9, 1934 Bjork Feb. 1, 1944 Strobel June 13, 1944 Hathaway Aug. 24, 1948 Clark Oct. 4, 1949

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