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Publication numberUS3609316 A
Publication typeGrant
Publication dateSep 28, 1971
Filing dateMay 23, 1967
Priority dateMay 24, 1966
Also published asDE1648073A1
Publication numberUS 3609316 A, US 3609316A, US-A-3609316, US3609316 A, US3609316A
InventorsNoel M H Brosset, Johan Winther
Original AssigneePedershaab Maskinfabrik As
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Composite mixture batching
US 3609316 A
Images(10)
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Description  (OCR text may contain errors)

United States Patent No'e'l M. H. Brosset [50] Field of [72] inventors Le Vesinet, France; Johan Winther, Bronderslev, Denmark 640,57 1

[2i] Appl. No. [22] Filed [56] References Cited UNITED STATES PATENTS 3,186,596 6/1965 Badgett........................

May 23, 1967 [45] Patented Sept. 28, 1971 [73] Assignee Pedershaab Maskinfabrik A/s Bronderslev, Denmark [32] Priority May 24, 1966 [33] France I [31 62732 [54] COMPOSITE MIXTURE BATCHING 27 Claims, 13 Drawing Figs.

using an analogue computing device for proportioning a plurality of components of a batch mixture in obtaining a composition exhibiting desired physical properties.

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BY @uv 8 7 ATTOR N I 1Y3 COMPOSITE MIXTURE BATCHING In batch blending it is often the case that one physical property of the mixture is determined by the ratio between two of the components, while another physical property is determined by the amount of one of the components.

A typical example of such a mixture is concrete. In addition to the skeleton, concrete comprises cement and water and as well known by those skilled in the art, the ratio between cemerit and water determines the concrete strength while the amount of water determines the slump. v

a In most concrete mixing stations a plurality of precalculated standard mixtures are available for immediate delivery. The calculation of such standard mixtures requires the use of tabulations and formulas known to those skilled in concrete technology.

It happens, however, several times daily in most concrete mixing stations that immediate delivery of a mixture is specified with a proportioning which differs from any of the standard mixtures.

Though the ready-mix operator is a qualified man with practical experience, he is not skilled in calculating the correct blending of a new batch according to individual requirements and even if he was, such a recalculation would not be feasible under practical conditions because it would require much more time than available when a lorry driver pulls in and requests a modified batch to be taken back to a building site.

The mix-operator knows, however, that if the customer wants a mixture with more water than in standard mixture then it is necessary to add more cement to make sure that the mixture keeps its strength, and for that reason mix-operators all over the world are inclined to overproportion the cement in such individually specified mixtures.

Since the cement is the most expensive component in readymixe'd concrete,'the result is that in a mixing station a substantial amount of cement is given away or wasted each year. Furthermore the addition of an arbitrary amount of cement to make up for an extra amount of water also changes the total volume.

This waste could be avoided, provided a method and an apparatus can be found for quickly determining the correct amount of cement to be used in an individually specified concrete mixture to give the required strength of the mixture.

Corresponding conditions prevail in other technical fields and even though the invention will be described hereinafter basically with reference to concrete mixtures, it will be understood that the invention is not limited to concrete but can be used in other technical fields where similar conditions are found, namely that the ratio between two components of a mixture determines one physical property and the amount of one of the two components determines another physical property.

It is an object of the invention to provide a simple method which enables a quick and safe proportioning of the correct amount of the components to ensure the first mentioned physical property with a specified amount of the second of the two components which determines the second physical property.

According to the invention this is achieved by using an analogue computing device which is programmed for reading in the analogue values of two of the components and which is also provided with means for dividing an analogue value which is the sum of an analogue value corresponding to the two components the ratio between which determines the first physical property and means for indicating that ratio. This analogue computing device is used in such a manner that the ratio between said two last mentioned components is first adjusted to the value which determines the first physical property whereafter the amounts of that amount of the one of the two components which determines the other physical property is adjusted until a predetermined analogue value can be read out whereafter the analogue values are used for proportioning the batch.

It has been suggested to use analogue computing devices in various embodiments in connection with batch blending, for example to solve such complicated problems as minimum costs blending, using the method of steepest ascents.

In such cases, however, the analogue computer has'not been preprogrammed and the programming of such a computer is obviously far beyond what can be done by the mix-operator of a ready-mix concrete station. In addition, the problems to be solved by such a specially programmed analogue. computer are entirely different from the problems which are solved according to this invention.

It has also been proposed to store a substantial amount of data relating to a plurality of standard mixtures on punched cards or tape in a general purpose computer to enable the selection of an already calculated mixture of concrete among so many precalculated mixtures that practically all deviations from standard mixtures can be avoided.

This solution is, however, not feasible under practical conditions. First of all a computer of sufficient capacity to meet all practical requirements is a fairly expensive equipment which must be written off and the writing off must be calculated in the price of all the mixtures. In addition, the selection of the correct one of maybe several thousand standard mixtures stored in a computer requires a substantial training of the mix-operator far beyond what he nonnally has and with such a large amount of standard mixtures a mistake is very likely to occur. Thus even if the best standard mixture to meet a customer's specification may be No. I237, the mix-operator may very well supply No. 1252.

The merits of the present invention are that it provides a very simple method and a correspondingly simple preprogrammed analogue computer which can be used by any mixoperator after short training without any knowledge of analogue computers because it is preprogrammed and the operation is limited to the adjustment of a few controls and the reading of a few indicators which even may be calibrated to indicate the desired physical properties directly.

The method is so simple that mistakes can be practically completely avoided.

The solution of the problem by a simple method also provides for construction of a simple analogue computer.

The simplest possible analogue computer according to the invention has the character of a slide rule and provides two rulers which are reciprocal in two directions with an angle of therebetween into engagement with an abutment on an arm which is pivotable about the point of intersection between two sidelines of a hypothetical equilateral triangle in which the sides are perpendicular on the direction of reciprocation of the two rulers and with the position of the abutment relatively to the two sidelines of the triangle being readable on a scale.

8? calibrating this scale to show the ratio between the components and calibrating the readings of the two rulers to show the distance from the abutment to each of the two sides in the hypothetical triangle, the well-known teaching that the sum of the distance from each point inside an equilateral triangle perpendicular to each of its three sides is equal to the height of the triangle enables the correct proportioning of the two of the components by first adjusting the pivotable arm to indicate the desired ratio and thereafter displacing the abutment in the direction of the arm until the reading on one of the rulers indicates the desired amount. By using a third ruler reciprocable perpendicular to the third side of the hypothetical triangle, the reading on the third ruler indicates the analogue value of the third component of the mixture, the total amount of which is the analogue value of the height of the triangle.

By calibrating the first two rulers into amounts correspond ing to cement and water in a concrete mixture and the third ruler corresponding to gravel such a slide rule device can be used as a simple calculation aid for concrete proportioning.

A mechanical-geometrical system based on this principle can obviously be constructed by means of rails and reciprocal rulers and by using the reciprocating of the rulers, if desired, in connection with mechanical amplifiers the reciprocation of the rulers can be used directly or indirectly to control the supply of the components in amounts corresponding to the analogue values readable on the rulers from automatic weighing devices.

It will also be possible to combine the rulers with electrical devices in such a manner that the reciprocation of each of the rulers controls the movement of a variable tapping on a voltage divider so as to thereby produce electrical voltages which represent analogue values of the readable analogue values of the rulers and thereby provide for electrical control of automatic dispensing of the individual components.

An analogue electrical system which enables the same simple method to be used can, however, be constructed by means of voltage dividers which provide an electrical analogue computer which is preprogrammed to use the method. In a mixture with three components it is only necessary to first adjust an analogue value which corresponds to the total amount of the batch, thereafter adjusting the ratio between the two of the components and eventually adjusting the desired analogue value of one of the two components, the ratio between which must be kept constant.

A simple analogue computer for proportioning three components of a batch comprises basically only two voltage dividers, each having an adjustable tapping. The first voltage divider is connected across the voltage source and thereby supplied with an input voltage which corresponds to the analogue value of the total amount of the batch. The other voltage divider is connected between the variable tapping of the first voltage divider and one end thereof. The adjustment of the tapping of the second voltage divider is made readable either by a graduation of a control member or by means of a suitable instrument. Output terminals are connected with each end of the first voltage divider as well as with the two variable tappings. An indicator is provided for reading out the voltage which corresponds to one of the portions into which the second voltage divider divides the potential thereacross so as to readout the analogue value of one of the components.

A simple analogue computer of this kind with two potentiometers can be used for carrying out the method whereby the variable tapping of the second potentiometer first is adjusted to the desired ratio between the two components until the indicator shows the ratio, whereafter the variable tapping of the first potentiometer is regulated until the desired analogue value of one of the two components is indicated between the outlets which are connected with the two variable tappings of the potentiometers.

In the case of concrete the first adjustment determines the ratio between cement and water, while the second adjustment regulates the ratio between gravel and cement plus water. During the last regulation the ratio is kept constant, and the amount of cement and water is readjusted with the ratio therebetween maintained until the desired amount of water can be read out of the computer.

It will often be found in a mixture that a third component of a mixture such as a filler has a content of one of the two other components. In concrete it is nearly always the case that the gravel is wet, Le. a part of water is included in the gravel.

The invention also enables a correction for such a case. Obviously, if there is for example l percent water in the gravel, the amount of water used must be reduced correspondingly because otherwise the adjusted cement/water ratio will not be kept.

By the method according to the invention this can be compensated for by measuring the amount of one component which is contained in the other component and using an analogue computer which comprises an adjustable summator device which is operatively connected with the outputs for the two components. By adjusting the summator device according to the measured contents of one of the components in the other. it will in the case of for example water in the gravel automatically decrease the analogue value which corresponds to the contents of water with an amount corresponding to the water which is included in the gravel.

It will also often be the case that the quality of one of the components differs from one supply thereof to the next. It is well known that the quality of cement differs and it has therefore previously been necessary to dispense sufficient cement to ensure that cement of the poorest quality always will give the desired strength of the concrete. The strength of concrete is governed by the coefficient of variation, variations of the quality of the cement increase the coefficient of variation. The more uniform the cement quality is, the smaller becomes the coefficient of variation.

The invention also provides for automatically readjusting the dispensing of that one of the components of a mixture the quality of which varies from supply to supply in such a manner that in order to keep a substantially uniform physical property of the mixture and savings with respect to the components in question a relatively increased amount of the component is dispensed when the quality is poor, while a relatively smaller amount of the component is dispensed when the quality is better.

According to the invention this is achieved in that the analogue value of the component in question, the quality of which varies, is adjusted as a reference value derived from the physical properties of a reference mixture whereafter a test mixture is produced with a different quality of the component in question and the physical properties of the test mixture are derived whereafter a digital ratio between the two physical properties is calculated and an adjustable multiplication device which is connected with the analogue value of the component in question as adjusted according to the reference mixture is adjusted to the ratio calculated so as to thereby produce a corrected analogue value of the component in question which corresponds substantially to the amount of the component which with different quality will produce substantially the same physical property of the mixture in which the component of different quality is used.

With specific reference to concrete this method can be used in such manner that the reference value of the analogue amount of cement is adjusted according to a reference mixture for which the factor K in Bolomeys formula is calculated whereafter the strength of a test mixture in which a different cement quality is used is determined and the K-factor of the test mixture is calculated, whereafter the multiplication device is adjusted on the ratio between the two K-factors and the analogue value for the amount of cement of different quality is derived from the multiplication device.

Further details with respect to the method and the construction of geometrical mechanical analogue computers as well as equivalent electrical analogue computers will be described in the following with reference to the accompanying drawings in which FIG. I is a diagrammatic illustration of controls, indicators and analogue values illustrating schematically the connections in order to explain the method. and the principle of an analogue computer according to the invention,

FIG. 2 is a perspective illustration of a computing device according to the invention,

FIG. 3 is a schematic illustration of a mechanical geometrical system which provides a part of an analogue computer according to the invention with appertaining electrical equivalence for that part of the computer,

FIG. 4 is an illustration similar to that of FIG. 3 with respect to other parts of the computer,

FIG. 5 is a schematic combination of the systems of FIGS. 2 and 3,

FIG. 6 is a complete mechanical geometrical system constructed according to the principles of FIGS. 3 and 4 and 5,

FIG. 7 is the electrical equivalence of FIG. 6,

FIG. 8 is a schematic illustration of the control of dispensing one component by using the electrical analogue value of the amount of components as reference voltage,

FIG. 9 is a schematic illustration of a further modification of the principle of FIG. 3,

FIG. 10 is a schematic illustration of a simple calculating device based on the mechanical geometrical system,

FIG. 11 is a detail of the calculating device of FIG. 10.

FIG. 12 is a diagrammatic illustration of a part of an analogue computer according to the invention for automatically correcting the analogue value of one of the components, in response to variations of quality of the component, and

FIG. 13 is the circuit arrangement of FIG. 12 illustrating a further automatic correction of a third component in response to the variation of the analogue value of the component the quality of which varies.

FIG. 1 illustrates schematically the principles of an analogue computer for adjusting the desired amounts of seven analogue values L, C, W, G, 8,, S and S corresponding to the amounts of seven components of a composite product. The components will in the following by referred to by the same capital letters as their analogue values. It is supposed that the ratio between the analogue values or components C and W determines one physical property of the composite product and that the absolute analogue value or amount of W determines another physical property.

To begin with only the part of the computer which relates to the three components C, W and G will be considered.

The computing device has a first control member K, which by means of connections f and 1], shown in dotted lines and symbolizing adjustments is connected with analogue outputs for the values C and W so as to adjust the ratio therebetween. The control K, is also connected with a ratio indicator I, operable to indicate the ratio W/C. The computing device furthermore has another control member K, which through one connection f, is connected with the analogue output G and through another connection f is connected with the total analogue output C+W.

The control member K is furthermore connected with an indicator I, which indicates the value of the analogue value W and preferably also with indicators I and I, which indicate the values of C and G respectively.

The method of using this part of the computing device is as follows:

The ratio between the analogue values C and W is first adjusted by means of the control member K, until the desired ratio is readable on the indicator l corresponding to the physical property of the composite product which is determined by the ratio W/C. The indicator I, may within the scope of the invention be an instrument or a graduated scale or any other type of indicator.

Hereafter the ratio (C+W):G is adjusted by means of the control member K Obviously, the ratio W/C as previously adjusted by means of the control member K, will not be influenced by the adjustment of the control member K but the analogue values W and C are changed, still with the same proportion between them. When, during the adjusting of the control member K, the indicator l, shows the desired amount of the component W which is required in the mixture in order to obtain the second physical property, all the three analogue values will be correctly adjusted and the components can be dispensed in accordance with the analogue values to provide a composite mixture in which the physical properties will be as determined by the ratio W/C as well as by the absolute amount of W.

Through the indicators I and 1, are not absolutely necessary we have found it convenient that also the analogue values of C and G can be indicated.

In the following it will be supposed that the mixture is concrete in which the analogue values C, W and G stand for the components, cement, water and gravel.

When the delivery of concrete of a predetermined strength is specified by a customer, the ready-mix operator of a concrete station knows that within practical limits the strength is determined by the ratio between water and cement and that the second physical property, namely the slump, is determined by the contents of water.

The part of the analogue computer briefly described hereinbefore provides for a method which avoids the danger of overdispensing cement and thereby wasting cement when the customer requires an individually composed mixture with a certain absolute amount of water in order to obtain a certain slump.

Obviously the method obtaining an immediate answer to the correct composition of a concrete mixture is that the water/cement ratio is first adjusted to obtain the desired strength by reading the ratio on the indicator I,, whereafter the amount of water is adjusted until the desired amount is readable on the indicator 1 By the last adjustment the analogue value C of cement is readjusted because the water/cement ratio is kept constant so that a mixture is always obtained with the desired strength as determined by the control member K, and there is no risk of overdispensing the cement with waste as a result or of underdispensing with less strength as a result.

In the following the remaining part of the analogue computer device of FIG. 1 will be explained with reference to concrete technology.

In addition to cement/water and gravel, concrete usually contains entrained air L and skeleton composed of different modules aggregate or sizes of stones 5,, S, and S; which in the following will be supposed to be small, medium and large sizes of stones.

The computer device has a control member K with one connection f,, operable to adjust the analogue value of S another connection f, operable to adjust the analogue values S +S and an indicator 1,, for the amount of stones 8,. A further control member K has connections f, and f operable to adjust the ratio between the stones S, and S; as well as a connection to indicators I and I for indicating the values of these analogue values. A further control member K,; is provided with connections j}, and f, to adjust the ratio between the entire amount of stones S,+S,+S and the entire amount of all the components in the mixture as well as an indicator I,, for indicating some of the analogue values S,+S +S in proportion to the sum of all the analogue values.

By initially setting the control member K to read a unit value of the amount S +S +S on the indicator I,, such as for example by volume and determining that for example the ratio between 5,, S and 8; should be 50:30:20 it is possible to obtain the adjustment in the following manner:

The control member K is operated until the indicator S, shows 50 whereafter the control member K,, is operated until the indicators S and 8;, show 30 and 20 respectively.

When thereafter the control member K is operated and the analogue value of the total batch amount also is a unit value. for example 1,000, and it is desired to have for example 40 percent skeleton in the mixture, this can be adjusted directly by means of the member K,;, by calibrating the indicator l,, to show percent. Thereby the exact analogue values of the three amounts 8,, S and 8;, will be readjusted but the initially adjusted ratio will be kept constant.

The analogue value L for entrained air is adjustable relatively to the entire sum of analogue values by means of a member K by means of connections 1",, and f, as indicated, and the contents of entrained air as adjusted thereby can be read out in percent on the indicator I When the four adjustment herein described have been made, the total amount of cement, water and gravel is the difference between the entire batch amount and the sum of contents of air and skeleton.

The final step of determining the composition is thereafter to use the controls K, and K. as hereinbefore described to determine the water/cement ratio according to the desired strength and the amount of water according to the desired slump.

More specifically the strength is determined by the water/cement ratio according to Bolomeys formula cr=K(C/V0.5) in which 0- is the strength and K is a constant which is deter mined by the quality of the cement.

It will be understood that it is possible to calibrate the indicator I, directly in strength according to Bolomeys formula so as thereby to avoid the use of tabulations for determining the water/cement ratio as a function of strength.

Regarding the adjustment of the amount of water which determines the slump, it should be observed that the slump is also governed by the largest size of stones which must be smaller than the narrowest cross section of the mould. Since the stones already have been selected according to previous adjustments, the adjustment of K, is the actual slump determination.

Obviously, if the amount of water is increased, this will cause an increase of the total amount of paste which is the sum of cement and water, and decrease the amount of gravel and alternatively, if the amount of water is decreased the amount of cement will be proportionally decreased and the amount of gravel increased.

It will be appreciated that the method of using the schematically shown computing device of FIG. 1 is extremely simple and provides for quickly obtaining the correct analogue values of an individually specified mixture. We have found that the method is so simple that it is possible with relatively short training to teach the mix-operator of a concrete station to use the method and obtain the correct answer in less than I minute.

A practical design of an analogue computing equipment according to the invention is illustrated in FIG. 1 in which 100 is a control panel on the front side of which the various control members K 8,, are shown in the form of control knobs and in which also the indicators are shown as readable instruments.

It will be understood that the control knob assembly which in FIG. 1 is referred to by KP represents means for adjusting the analogue values and ratios therebetween and once a predetermined batch of a composite product has been calculated and the analogue values adjusted, the computing device can be used to reproduce the same composition by retaining the controls.

In other words it is possible to completing the system of FIG. I with a plurality of preadjusted controls in groups corresponding to the group KP and selecting each one of said preadjusted groups of controls to select a corresponding one of a plurality of precalculated standard mixtures.

This possibility is indicated in FIG. 2 in which Stl, Stll StX indicate each one of ten different groups of controls which by way of trimming are adjustable to respond to each one of ten different standard mixtures and can be selected individually by means of corresponding selector members Sel. Sell SeX of a selector board 102 which is connected with the control panel 100 by means of a cable I04.

The arrangement of FIG. 2 is such that all the indicators are common to each of a selected one of control groups whether it is the group for individual adjustment KP as shown in FIG. I. or any one of the standard mixture groups Stl, Stll The selector board 102 has in addition to the selectors SeI, Sell a selector K, for selecting the group of controls KP for individual batch mixing.

While the adjustment members of the group of selectors KP may be in the form of control knobs or the like which can be individually adjusted, the corresponding control members of the standard mixture controls should be designed in such a manner that they can only be readjusted by means of special tools or the like and only for the purpose of minor readjustments or trimmings. The groups of standard mixture controls however, correspond individually with respect to their connections with the instruments and the analogue value outputs to the control group KP of FIG. 1, and it will be appreciated that initially they have to be adjusted individually precisely in the manner described hereinbefore to correspond to selected standard mixtures.

In a concrete mixing station the selector board I02 may be arranged on the platform where the mix-operator can surbey the delivery and can select either a specified one of the standard mixtures by pushbutton control or the individual control selector group KP of FIG. 1 in the case where a mixture which deviates from 'any of the available standard mixtures is specified.

The control panel of FIG. 2 has in addition to the controls hereinbefore described a pushbutton SW and two other controls K and K the function of which will be described in the following and the selector board 102 has a further control K the function of which also will be described in the following.

It is indicated that the selector board is connected with a cable 106 which is the output cable from the entire computer device and adapted to be connected with the dispensing equipment for automatic dispensing of the individual components according to the adjusted analogue values of each of them.

As will be appreciated from the foregoing the adjustment procedure is the same the whole way through and always starts with adjusting the ratio between two numerical values and -after the first adjustment another adjustment of ratio between two numerical values is effected and so forth, all in accordance with a pattern which is related to the technology of the mixture to be produced.

This simple method provides for a simple construction and preprogramming of an analogue computing device, either in the form of a simple mechanical calculation device or an equivalent electrical computer as will be described in the following.

FIG. 3 illustrates a mechanical geometric system and the corresponding electrical equivalent for determining the analogue values of C, W and G.

The mechanical geometrical system comprises three rulers C,, W, and G, each of which extends perpendicularly to each one of three sidelines a, b, and c of a hypothetical triangle or as a system of guide members constructed as an equilateral triangle with a height M which may be variable.

An arm K, which corresponds to the control member K, of FIG. 1 and therefore is designated by the same reference numeral is pivotally mounted about a top A of the triangle and points on a scale I, which is the equivalent of the indicator l,of FIG. 1.

The interior ends of the rulers C,, W, and G, are adapted to engage or are connected with an abutment K, which corresponds to the control member K of FIG. 1 and which is movable along the geometrical line which coincides with the longitudinal direction of the arm K,. This abutment may either be reciprocally mounted on the arm K,, or the arm may be reciprocally mounted with the abutment firmly secured on the arm.

The geometrical system of FIG. 3 is based on the discovery that the geometry of equilateral triangles and the electrical analogy thereof provide a computing aid for proportioning components of a mixture to fulfil requirements as hereinbefore described.

From the geometry of equilateral triangles it is known that the sum of the distance from any point inside the triangle perpendicular to all the three sides is equal to the height of the triangle. It will therefore be understood that the lengths of the rulers C,, W, and G, inside the triangle which are referred to by C, W and G will be the analogue values of the three components of the mixture, the entire amount of which is equal to the height M of the triangle.

By considering the case where the abutment K is moved down to the bottom c of the triangle corresponding to the analogue values W, and C," of the components W and C the point Q where the arm K, intersects the bottom line c of the triangle will divide the bottom line into two portions the lengths of which are 2: V3 C and 2:\ W

Insofar as the factor 2: 3 is the same this means that for any angular position of the arm K, there will be a predetermined ratio FWtC, and by letting the arm point on the scale I, and calibrating the same the ratio can be made readable.

By designing the system in such a manner that the rulers are reciprocable in their longitudinal direction for pen'nanent cooperation or engagement with the abutment K and simultaneously can be displaced in the direction perpendicular to their longitudinal directions, the geometrical system provides a calculation aid for proportioning a mixture which satisfies the conditions W:C=W f and (W+C):(W-l-C+G)=g corresponding to a concrete mixture with water, cement and gravel as basic components.

The geometrical system is used in the simple manner that the arm K, first is adjusted to read the desired ratio f on the indicator I,. Thereby the ratio W:C is adjusted and this ratio is kept constant during displacement of the abutment I( along the arm K,. By displacing the abutment K until the desired analogue value W can be read on the ruler W, a mixture is calculated with the desired water/cement ratio and the desired amount of water whereby the analogue values of gravel and cement can be read on the rulers C and W,.

The corresponding electrical equivalent of the geometrical system is also included in FIG. 3 and comprises a voltage di vider P, in the form of a potentiometer with a movable tapping K,,. An input voltage corresponding to the height of the triangle M=C+ W+G is applied over the potentiometer P Between the top end of the potentiometer I, and its movable tapping, a further potentiometer P, is provided with a variable tapping K, which is provided with an indicator (not shown) corresponding to the indicator I, in FIG. 1, so that for example the control knob of the potentiometer points on a scale which is graduated corresponding to the scale I, of FIG. 3.

The two variable tappings are connected with output terminals MS and MS and the ends of the potentiometer P, is connected with output terminals OM and OMS.

An indicator I, for the analogue value of water is provided between the two variable tappings of the potentiometers and further indicators L and 1,, corresponding to those of FIG. 1 may be provided between the other output terminals.

As indicated in dash and dotted lines the tapping K, of the potentiometer P,corresponds to the arm K, of the geometrical system and the tapping K of the potentiometer P corresponds to movement of the abutment K along the line of the arm K,.

The electrical system of FIG. 3 is used for proportioning the concrete mixture in such manner that when a predetermined strength is specified, the water/cement ratio is first adjusted by means of the tapping K, until the desired ratio can be read on the indicator. When, thereafter, the tapping K is adjusted until the indicator I,, shows a predetermined amount of water corresponding to the desired slump, the outputs C, W and G between the output terminals are electrical voltages corresponding to the analogue values of each of the three components. I A similar mechanical geometrical system with electrical analogy is shown in FIG. 4 adapted to adjust between the three sizes of stone in the skeleton as well as adjusting the ratio between skeleton and the total amount of the batch.

For the sake of simplification the three rulers are designed by the analogue values 5,, S, and 8:, as readable inside the orbits of the triangle. The three rulers are connected at a point AN where two pivotable arms K and K intersect.

Provided the mixture is going to be calculated with the ratio a b c it will be usual to specify the ratio between the sizes of the stone in percent such as for example a=50 percent, b=30 percent and c== percent.

By adjusting the angular positions of the two pivotable arms K, and K relatively to each other it is possible to adjust the ratio between 8,, S and 8:, as a:b:c.

By, prior to this adjustment, adjusting the height of the triangle according to a unit analogue value, for example 100, the ratio between 8,, S and S will be expressed in percent and can be indicated on correspondingly calibrated scales on the rulers S S and 8,.

By thereafter decreasing the height of the triangle by displacing the horizontal top line until its adjustment member K indicates the desired ratio between the total amount of skeleton and the total mount of the mixture on the scale I, and keeping the arms K and K locked in the adjusted positions, the length of the rulers inside the triangle will be reduced while retaining the adjusted proportions in percent and when the control member K has been adjusted to the desired ratio g according to the last one of the two formulas hereabove the actual analogue values of 8,, S and 8;, can, by correspondingly calibrated scales of the rulers, be read out of the device.

The electrical analogy of FIG. 4 comprises an input potentiometer D which an input potential is applied. By initially adjusting the variable tapping K of the potentiometer D, to the top of the potentiometer as indicated in dotted lines the input potential will be applied across the potentiometer A, which is provided between the variable tapping K and the bottom of the potentiometer D and by means of the variable tapping K of the potentiometer A, and the variable tapping K, of the potentiometer B, which is provided between tapping K and the bottom of the potentiometer A,, the input voltage can be divided in the proportions azbzc with the proportions readable on the indicators I I, and in percent.

When thereafter the variable tapping K of the potentiometer D is adjusted to the desired ratio between the entire amount of skeleton and the entire batch amount as readable in percent on the indicator I the analogue output values between the output terminals OMS, 08,, OS, and CS respectively will be proportionally reduced, while retaining the percentage adjustment between the three components.

As previously mentioned it will frequently be found that a mixture, such as is the case with concrete, is specified to contain a further component L which in concrete stands for entrained air in a certain proportion to the entire amount of the batch whereby the following conditions must be fulfilled S ,+S +S L+C+ W+G+S ,+S +S )=d in which d is the air in percent.

Such a single component can be symbolized by the height of an equilateral triangle.

As apparent from the foregoing the height of the triangle of FIG. 3 which is referred to by M corresponds to the entire amount of mortar which is water plus cement plus gravel and the height of the triangle of FIG. 4 when adjusted to the desired percent of skeleton in the entire mixture corresponds to the skeleton. The triangle of FIG. 3 can therefore be referred to as the M-triangle, and the triangle of FIG. 4 as the S-triangle.

By calculating the entire batch by using the mechanical geometrical systems it is therefore possible to combine the M- triangle and the S-triangle in the manner indicated in FIG. 5 and by spacing these two triangles a distance corresponding to the height of a small triangle L which symbolizes the amount of entrained air the total height of the sum of the three triangles between the points A and A will represent the entire amount of the batch.

Normally the amount of entrained air will be approximately 2 percent when no special measures are taken.

In some cases it is desired, however, to provide more air in the final mixture by means of additives.

Since it is desired in analogue computer to have the analogue value corresponding to the entire batch by way of a unit analogue such as L000 corresponding to, for example l m which is equal to 1,000 litres, it is in FIG. 5 supposed that in such cases where there will be more air than the natural 2 percent in the mixture, the compensation for different air contents is obtained by diminishing the amount of mortar by displacing the bottom line of the M-triangle to read in the percent of air on a correspondingly calibrated scale I corresponding to the indicator I, of FIG. 1.

Obviously it will also be possible to keep the height of the M-triangle constant and reduce the height of the S-triangle in accordance with the amount of air.

While FIG. schematically indicates a combination of the systems of FIGS. 3 and 4, a more specific combination of the geometrical mechanical systems of FIGS. 3 and 4 is illustrated in FIG. 6.

The apparatus comprises a system of rails with stationary rails M.., M, and M M which form the sides in two oppositely directed equilateral triangles with tops A and A the distance between which can be indicated on a scale I, to be adjusted according to a unit analogue value of the entire amount such as for example I rn. equal to 1,000 liter.

The bottom rail M,- of the M-triangle can be displaced by means of an adjustment member K to indicate the distance between the two triangles L corresponding to the contents of entrained air on a scale I, which extends from the horizontal line M of the S-triangle.

In its turn the horizontal line M of the Striangle can be displaced by means of the adjustment member K to indicate the percentage contents of skeleton in the entire batch on the scale I The remaining adjustment members of FIG. 6 are referred to by the same reference numerals as in the previously explained figures.

In the following it is supposed that a concrete mixture is desired proportioned according to the following specification:

l. Skeleton composition 2. Ratio Paste-Skeleton (S,+S,+S;, L+C+ W+G+S,+S +S -,)=d 3. Entrained air in percent of total mix L:(L+C+W+G+S +S,+S)=e 4. Water-Cement ratio W: C=f 5. Mortar composition, i.e. W+C in percent of mortar (W+C):( W+C+G)=g and 6. Total amount of a computing size batch by volume In previous computations of concrete a typical procedure has been substantially as follows:

The water/cement ratio is calculated from a formula to give the desired strength. The volume of air is taken from a table. The approximate quantity of water needed to produce the desired slump is taken from a table whereafter the exact volume of water can be calculated. Thereafter, knowing the water/cement ratio, the exact volume of cement can be calculated. Thereafter the percent of coarse aggregate or skeleton can be taken from a table. The volume of sand can then be calculated. Eventually, by multiplying with the specific gravity, the batch quantities can be calculated. Such calculation based entirely on concrete theory requires an expert and will take him between 1 and 2 hours.

By means of the proportioning aid or computing device according to the invention it is only necessary to read the proportions as specified, i.e. a,'b, c, d, e andfinto the device, i.e. to put the data into the device, which is a simple manual procedure. and by eventually adjusting g until the analogue value of water W indicates the desired amount, all the other values readjust themselves and all the batch quantities can be read out of the device. The whole procedure takes less than 1 minute and the use of the device does not require an expert.

By means of the system of FIG. 6 it is only necessary to read in the proportional values a, b. c, d and e which is a simple manual procedure and thereafter adjusting the value g until the desired analogue value of water W is readable on the scale. Thereby all the other analogue values have readjusted themselves and all the correct analogue values can be read out of the system which thereby provides a calculation aid for quickly and exactly determining the correct analogue values of the individual components of the mixture according to individual specifications without the necessity of using an expert.

The mode of use and operation of the proportioning aid or computing device of FIG. 6 is compared with the calculation procedure hereabove explained as follows with respect to proportioning a batch as hereabove specified.

The adjustment member K is initially set in a position corresponding to a unit amount of total skeleton so as thereby to enable the proportions between S, and S, and S to be read out in percent.

Thereafter the arms K and K are swung relatively to the size of the S-triangle until the desired percent between the stones can be read out of the rulers S 5,, and S, and the arms are locked in the adjusted positions relatively to the sides of the S-triangle.

By means of the member K,;, the line M of the S-triangle is thereafter displaced until the percentage contents of skeleton relative to the entire amount is readable on the scale I,,.

Thereafter the bottom line M of the M-triangle is displaced until indication of the percent of air which is expected--either about 2 percent naturally or more in the case of use of additives-is readable on the scale I,

Thereafter the pivotable arm K, is adjusted to read the ratio f between water and cement on the scale I and eventually the abutment K, is displaced until the desired amount of water W is readable on the appertaining ruler on the M-triangle.

After these adjustments all the analogue values can be read out of the system.

The electrical analogy of the geometrical system of FIG. 6 is shown in FIG. 7 in which the electrical analogies of FIGS. 3 and 4 are combined.

The voltage from a stabilized voltage source VS is adjustable by means of a member OP in such a manner that a stabilized voltage which is supplied between input terminals IT, and IT has an analogue value which represents the value L+C+W +S+S. +S;=l,000 for example corresponding to l m. or 1 ,000 litres.

This analogue value is readable on an indicator I, and corresponds to the geometrical distance between the tops A and A of the triangles of FIG. 6.

As an equivalent to adjusting the distance between the triangles of FIGS. 5 and 6, the potentiometer D of FIG. 5 is connected directly over the input terminals so as to enable the proportion L:(L+C+W+G+S +S +S to be directly adjusted on this potentiometer and the analogue value of the amount L of entrained air can be read between the output terminals 0L and OM on the indicator I,

The potentiometer D is also connected directly across the input terminals I and 1, The variable tapping K of the potentiometer D is connected with the output terminal OMS. I-Iereby the voltage portion between the terminals OMS and 08 corresponds to the entire amount of skeleton and is referred to by S and the output voltage between the output terminals OM and OMS corresponds to the entire amount of mortar and is designated by M.

The skeleton voltage S is divided into three portions by means of the potentiometers A and B, of FIG. 4 and in a similar manner the mortar voltage M is divided into three portions by means of the potentiometers P, and P, of FIG. 3.

The potentiometer arrangement P as indicated in dotted lines will be explained later.

The terminal IT, is connected with the variable tapping K of the potentiometer D through a connection in which a manually operable switch S, is provided so as to enable the input voltage to be applied directly across the input potenita sfsr tsiths ke et voltage v In the e mbodiment illustratedrthe ratio indicator for W:C is a differential coil instrument, the two coils of which at one end are connected with the variable tapping K, and the other ends of each of the coils are connected with the outputs OM and M8 respectively.

The previously described method is, by means of the arrangement of FIG. 7, carried out in the following manner.

A. ADJUSTMENT OF SKELETON COMPOSITION a. The switch S is closed. The adjustable tapping K, of the potentiometer A is adjusted until the indicator I indicates the desired percent of stones of size S,, for example the smallest size.

b. The variable tapping K, of the potentiometer B, is adjusted until the desired percent ratio of stones of size S is readable on the indicator I The latter adjustment also automatically adjusts the analogue output voltage S to the desired percent of the amount of stones of size 8;, so that the three amounts S +S +.S':,----l00 percent.

c. The switch 8,, is opened.

d. The variable tapping K, of the potentiometer D is thereafter adjusted until the indicator 1,, indicates the r desired percent of skeleton in the entire amount.

8. ADJUSTMENT OF AIR IN THE MIXTURE IN PER- CENT ln ready mixed concrete there is always a natural content of air of between I and 2 percent and normally it will be sufficient to set the air adjustment K to 2 percent. By use of additives the amount of air can be increased and if it is specified that additives giving for example 5 percent air are going to be used in the specific mixture, the adjustment K should be set to 5 percent, whereby the output between the terminals L and OM will correspond to the adjusted amount of entrained air in the mixture.

e. The air is accordingly adjusted by setting the variable tapping K Hereby the total batch analogue voltage has been disposed of with respect to the skeleton and the air, and the remaining voltage which is now disposable is between the terminals OM and OMS.

C. ADJUSTMENT OF STRENGTH AND SLUMP.

The remaining adjustment is now to divide the remaining output voltage between the output terminals OM and OMS ac cording to specified strength and slump which is done in the following manner.

' f. The tapping K, is adjusted until the desired water/cement ratio is readable on the indicator I, which may be calibrated directly according to the strength of the concrete.

Finally the tapping K is adjusted until the specified amount of water is readable on the indicator I Hereby the amounts of gravel and cement are automatically readjusted and both amounts can be read out on the instruments I and I, and the output voltages C and G correspond to the adjusted values.

After this procedure which can be completed in less than one minute by a trained person all the analogue output voltages are adjusted to respond to the desired amounts by volume of the components of the mixture of a predetermined total amount, for example 1,000 litres which is the value to which the indicator I, is supposed to have been set initially.

In the foregoing no attention was paid to the potentiometer P shown in dotted lines in FIG. 7 and provided between the variable tappings K and K, of the potentiometers P, and D The variable tapping K of this potentiometer is connected with the input of an operational amplifier DA, the other input of which is connected with the variable tapping K and which operates as a multiplicator. When this arrangement is used the connection between the point x and the output terminal M is disconnected and the output of the amplifier DA is connected directly with the output M This arrangement serves the purpose of correcting the output voltages W and G for a contents of water in the gravel which will be found normally under practical conditions.

Obviously, if there is percent water in the gravel and the water/cement ratio is adjusted according to a predetermined strength, the addition of gravel with 5 percent water will increase the water contents and disturb the adjusted balance of the ratio W2C with the result that the concrete strength will be reduced. In such an event is is therefore necessary to reduce the analogue value W between the terminal M, and M, with a corresponding amount of water which is present in the gravel.

increased by 5 percent and the W-voltage is reduced corresponding to the volume of 5 percent gravel whereby the total volume is kept constant.

Instead of using a manually operable adjustment by means of the potentiometer P it is possible to use an electronic network such as a servomultiplier which is controlled by means of the output voltage of an equipment which measures the contents of water in the gravel so that an automatic correction for the content of water in the gravel is obtained without the necessity of making any manual adjustments.

In smaller mixing stations where the administration of each component is effected under manual control, a remote control instrument panel may be provided with indicators which give precise instructions to the personnel about the amount of each individual component. In such event each instrument should be calibrated to show the exact amount of each component by volume or by weight according to standard practice. In order to avoid mistakes with the use of such a scheme, the instru ments for the commands may be digital instruments giving the amounts by weight or volume in exact figures.

In most concrete mixing stations, however, automatic or semiautomatic administration devices are used with weighing stations for the components to be dispensed by weight and/or fluid meters for components to be dispensed by volume. In

such event the proportioning or computing device according to the invention with output voltage fractions each of which is the analogue value of one componentwhich also may be derived from a triangle system to which electrical output devices are added-lends itself to a substantially complete automatic administration by combining the application of a analogue output voltages as amount control voltages to the corresponding respective administration stations with sequence control operable to select the stations in sequence one after the other in response to the programmed completion of the operation of each station.

In practice the use of the analogue output values from the computing device to control automatic dispensing of the components in a weighing station can be achieved by means of a device in the weighing station which produces an analogue value which increases as the dispensing proceeds, a differential which compares the analogue value produced in the weighing station and control means operable to interrupt the dispensing when the analogue values have become equal.

Preferably a stepwise interruption of the dispensing will be used in such a manner that the rate of dispensing will be decreased at a predetermined stage of the dispensing such as at a predetermined difference between the analogue value supplied by the computer and the corresponding voltage supplied by the weighing stations such as for example corresponding to dispensing of between and percent of the predetermined amount so as to thereby ensure against overdispensing of any of the components.

Such a dispensing arrangement is shown schematically in FIG. 8 and illustrates the arrangement in connection with the dispensing of one of the components, for example the cement.

In FIG. 8, 50 is a silo with a closure member 52 the opening and closing of which can be controlled by a control member 54 and which can be partly closed from the open condition by means of a control member 56.

When the closure member is open the material is guided from the silo 50 along a chute 58 or in any other suitable manner to a weighing device 60 with a scale 62 which indicates the amount of material supplied to the weighing device.

An arrangement operable to produce a potential is connected with the weighing device and comprises a voltage source BW and a potentiometer P with a variable tapping K which is moved by the movable parts of the weighing device as the dispensing proceeds so as to thereby produce an increasing voltage C between the top of the potentiometer P and the variable tapping K Obviously, when the analogue voltage C corresponding to the desired amount of the component in question is supplied across the input terminals i and I of the device, it is possible to use a differential which compares the analogue input voltage and the voltage produced by the weighing device and which interrupts the dispensing when the desired amount is supplied to the weighing device.

The voltage source BW is adjustable and is initially adjusted to a value which by the dispensing of an amount of cement by weight between the tapping K,,,, and the top end of the potentiometer P produces a voltage C,,, which is equal to the analogue input voltage between the terminals I, and I when the cement amount indicator l which is calibrated according to weight indicates the same amount of cement.

For practical purposes, however, it is necessary in the system to include a multiplication amplifier in the form of an operational amplifier 0A with feedback over a potentiometer P by means of which the multiplication factor of the amplifier can be adjusted.

The reason is as follows:

As previously mentioned the analogue computer is constructed to always give an analogue voltage portion corresponding to the values of the individual components corresponding to a total batch volume of for example 1 m.

If a different total amount is specified by the customer it is obviously necessary to provide for a proportional correction of the amount of the individual components. Since the analogue input voltage for the amount C of cement always corresponds to the amount of cement in 1 m.'', it is necessary if for example 3 m. is requested to reduce the voltage produced by the weighing device in the proportion 1:3 which can be obtained by adjusting the potentiometer P of the amplifier 0A to an amplification factor corresponding to multiplication in proportion 1:3.

The output of the amplifier 0A is connected with the input terminal I through a differential device indicated by way of a relay R, with a normally closed contact K which is connected with the control device 54 for closing the closure member 52. The differential member R. is shunted by another .differential member R, which is provided with a bias in such a manner that it will be actuated when the output voltage from the amplifier CA has been increased to a value which is slightly less than the value at which the differential device R. will respond. The relay R has a contact K which is normally closed and which is opened to actuate the control device 56 to partly close the member 52 when the device R is actuated.

In the embodiment shown, the bias for the relay R is ,produced by supplying an alternating voltage across a potentiometer P, between the variable tappings of which and the one end of the primary winding of a transformer T, is connected with a secondary winding in which a rectifier E, is connected. The arrangement of FIG. 8 indicates schematically the arrangement used for one of the components, for example the cement and it will be appreciated that similar arrangements are used for the other components and are adjusted from a central location such as from the selector board 102 of FIG. 2 in which the control member K, is operable to adjustthe amplification factors of the potentiometers as well as the tapping of the potentiometer P, to thereby regulate the bias of the relays R in accordance with the ratio between the total amountto be dispensed and the unit amount corresponding to the analogue values supplied from the computing device.

By means of the ratio of the transformer T, and if necessary by using an unlinear potentiometer P, it is possible to control the part closing of the closure member 52 with substantial uniform difference between actual amounts dispensed and desired amounts without that difference being influenced by the total amount.

The mode of operation of the arrangement of FIG. 8 is substantially as follows:

When a dispensing switch such as indicated by SD of the selector board of FIG. 2 is actuated, the closure member 52 of the silo is opened and the dispensing starts.

As the dispensing proceeds, the tapering K of the potentiometer P is moved and depending on the amplification factor of the amplifier CA as adjusted by means of the proportion selector member l( of the selector board of FIG. 2 the analogue voltage C produced by the weighing device is converted into. an analogue voltage C... which is equal to the unit value of the computing device. As the voltage C, increases the differential device R,, will first be actuated when the voltage supplied from the amplifier 0A is slightly less than the input analogue voltage or reference voltage C.

Hereby the contact K is opened and actuates the control member 56 to partly close the member 52 so as to thereby decrease the rate of dispensing of the component. When thereafter the voltage C' supplied by the amplifier CA has been increased to be equal with the voltage C, the differential device R is actuated and actuates the control member 54 to close the member 52 and thereby interrupt the dispensing.

The other components are dispensed in a similar manner by means of similar control arrangements either simultaneously by means of individual weighing devices or in sequence controlled by a suitable sequence control.

In concrete production it is possible to control the dispensing of gravel and the skeleton components by using a single weighing device to which the components are supplied from different silos by connecting the differential devices R, and R to be actuated in cascade.

In the case of compensation for difference in quality of one of the components such as difference in quality of cement, an arrangement in FIG. 12 can be included in the computing device or added to an existing computing device.

The arrangement of FIG. 12 provides for automatic adjustment of the analogue value of that component of a mixture which varies with respect to quality.

Obviously if a component of a mixture varies in quality from one supply to the next, it is not necessary to use so much of the component in a mixture when the quality is better as when the quality is worse.

The arrangement of FIG. 12 enables a simple method for correcting the dispensing in response to changes in the quality of one component by using in the beginning the calculated analogue value of the component in question as based on a known mixture and adjusting a multiplication device in the analogue computer to the ratio between two digital values which can be calculated from proportions between the physical properties of the known mixture as a master mixture or reference mixture and a test mixture produced with a part of the component from a new supply.

In the following the arrangement of FIG. 12 will be described with reference to concrete mixing.

In the production of ready mixed concrete it is necessary to dispense the cement with a sufiicient supply to ensure that the nominal strength of the concrete is always obtained. The strength of the concrete is governed by the coefficient of variation which is the ratio between the crush strength of the concrete by standard deviations and the middle crush strength. Variations in the strength of the cement which can be quite substantial from supply to supply increase the coefficient of variations substantially but by uniform cement quality the coefficient of variation is reduced whereby the otherwise necessary strength margin can be reduced and result in savings of cement.

The proportion between the strength of a known mixture and a mixture to be produced subsequently can be expressed by the ratio between two digital values.

The crush strength of a concrete mixture after 28 days can be calculated by using Bolomey's formula in which is the crush strength for example in kg/cmfi, K is a constant which primarily depends on the strength of the cement, C, is the cement by weight and W is the water by weight.

For each new mixture it is possible to determine the factor K by means of a test moulding and using an accelerated test method used by those skilled in the art and one of which is referred to as the .Iespersen-method which will give the result in about 2 hours.

By making such a test with cement of one supply and inserting the values in Bolomeys formula it will be found that a K 0 s in which 0, K, and C are strength, K-factor and amount of cement in this mixture which can be used as the reference mixture. I

With the next supply of cement a corresponding test is made with the same amount of cement C,, as in the reference mixture whereby other values of strength and factor K are found, namely Since it is desired to obtain the same physical property, namely the strength, this means that the following conditions must be fulfilled:

If the amount of cement of different quality which is necessary in order to obtain the same strength is called C,,,, and this value is inserted in Bolomeys formula for cr the condition is By solving this equation it is possible to calculate the amount C of cement which must be used in the mixture with cement of quality according to the new supply as As apparent from this formulifthe proportion between the necessary amount of cement of new quality and cement of old quality is basically determined by the proportion between the two factors K and K It is therefore possible to proceed in such manner that after having calculated this proportion which can be referred as the ratio between physical properties of the reference mixture and the new mixture, the analogue value of the amount of cement in the reference mixture can be found by multiplying with this ratio after consideration of the other digital values of the formula in order to produce an analogue value of the amount of cement which is corrected to comply with the cement quality of the new mixture. Hereby the same physical properties will substantially be obtained by means of the new cement quality in the new mixture.

The computing device of FIG. 12 is especially constructed for this method in connection with concrete mixing.

In FIG. 12 AC is an analogue computing device with input terminals I, and I, for reading in the analogue values of the amountC, of cement which is necessary in the reference mixture with the known factor K and with input terminals I, and I, for reading in the analogue amount of water W As indicated in FIG. 12 in dotted lines the ratio between water and cement can be adjusted on a potentiometer P, so that the calculation device of FIG. 12 can be directly connected with a computing device of FIG. 7. The analogue computing device of FIG. 12 may, however, also be used in connection with other kinds of devices which are able to produce analogue values corresponding to the desired amounts of cement and water in a reference mixture.

The arrangement of FIG. 12 is provided with an adjustable control member K which is also shown as an adjustment member in FIG. 2 for adjusting the ratio K zK and output terminals O', and 0",. for reading out analogue value C of the amount of cement which is to be used in the new mixture with quality of the new supply. The arrangement also has output terminals 0' and 0",, for reading out the amount of water W Preferably the amount of water is kept constant in order to secure the same slump of the new mixture as of the reference mixture. I

Between the input terminals I, and I and the outputs O, and 0', an analogue multiplicator is provided which when the ratio K zK is adjusted by means of the member K automatically gives the correct analogue value of cement C If the specific gravity of cement which is 3.15 is inserted in the last of the formulas hereabove, the following expression for the amount of cement C by volume is found as By means of the system of voltage dividers shown in FIG. 12 where the input voltage W,, is divided by means of two resistors R, and R, and the potential between the point a between these two resistors and the input terminal I, is divided by means of two resistors R, and R",, it is possible to obtain such voltage proportions that the potentiometer R can be calibrated in accordance with the ratio K,,:l(,,,.

0A is an operational amplifier which is connected as a multiplicator.

This can be understood in the following manner:

It is required that the potential between the terminals I, and I should be proportional with the expression in parenthesis in the formula, i.e. proportional with C,,,(). l 59'W so as to obtain direct proportionality with adjustment of the potentiometer R between the input on the terminal I, and the output on the terminal O',. The potential which must be added to the expression in parenthesis is 0.159-W and this potential must be applied between the input terminal I and the output terminal O,. This condition can be obtained by the following proportion between the resistors R, and R,

By proportioning the resistors R, and R, in this manner a voltage across the resistor R, is obtained which is equal to 0.159-W and between the point a and the input terminal I a voltage is obtained corresponding to C,,,+0. I 59".

. By using equal values of the resistors R, and R", this voltage will be divided into two equal portions which means that across the resistor R" a voltage is provided which is VAC, -0.l59-W) which multiplied by 2-km/K gives the first part of the expression in the analogue value for C If the potentiometer R, is adjusted to a ratio the voltage across the potentiometer R, is

C m 0. 159 W Ze By calibrating the potentiometer in such a manner that the total voltage between the output terminals 0' and 0",. will be equal to the expression for C because the output voltage is composed by the voltage across the potentiometer R, and the resistor R, of the voltage divider R,, R

When K i.e. when the cement quality is improved, the analogue value C is decreased and a saving is obtained.

When K K,,,, i.e. when the quality is decreased, the amount C is increased to obtain the same quality of the mixture.

As mentioned the analogue output values are calculated by volume. Since the volume of water the analogue of which is the same between the output terminals 0' and 0",, as between the input terminals I and I, and since it is always desired to deliver a volume unit, the system is also adapted to automatically recalculate the analogue value of such a third component of the mixture the amount of which can be allowed to be increased or decreased in response to decreasing or increasing of the amount of cement.

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Classifications
U.S. Classification700/239, 708/800, 700/265, 235/69
International ClassificationB28C7/04, G06G3/00, G05D11/13, G06G7/75
Cooperative ClassificationG05D11/133, G05D11/134, G06G7/75, B28C7/0418, G06G3/00
European ClassificationG06G3/00, G06G7/75, G05D11/13B4B, B28C7/04B4, G05D11/13B4