US 3403546 A
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Description (OCR text may contain errors)
1963 c. c. STRATTON 3,403,546
SLUMP INDICATOR FOR CONCRETE Filed Aug. 18, 1965 INVENTOR. WHA NN 4 M6 MAN/ 5A L A/brneys fbr fi llirab/ by g;
United States Patent 3,403,546 SLUMP INDICATOR FOR CONCRETE Cleo C. Stratton, 1732 Mallory St., San Bernardino, Calif. 92405 Filed Aug. 18, 1965, Ser. No. 480,658 1 Claim. (Cl. 73-54) ABSTRACT OF THE DISCLOSURE A slump indicator for concrete while being mixed in a rotatable mixing barrel driven from a power source by a power transmitting chain trained over a drive sprocket and driven sprocket at the barrel, wherein a single roller is spring urged against the tensioned side of the chain at a point between the sprockets to forcibly deflect the chain from a straight line axis and provide a member movably responsive to variations in the load torque due to variations in the liquid content of the mix, this member being connected to a resistor for varying the energization of an ohmmeter calibrated in terms of slump. In mobile mixers, this meter is mounted in the vehicle cab, and additional resistors are selectively added and removed from the energizing circuit to compensate for variations in the quantity of the mix being worked in the mixing barrel.
The present invention relates generally to means for determining characteristics of concrete mixtures, and is more particularly concerned with means for obtaining accurate and continuous indications of the characteristic commonly referred to as slump.
In the mixing of concrete, the liquid content or amount of water therein is a very important consideration. For example, the amount of water has a material effect upon the strength of the concrete, when it has cured or dried. Smaller amounts of liquids produce greater strength. Therefore, in those situations where strength is the prime factor, the amount of water is therefore held to a minimum. If strength is not a consideration, then the use of more water permits easier pouring and finishing of the concrete.
The above considerations are of primary importance, particularly to producers of ready-mix or transit-mix concrete, these producers being constantly called upon to deliver mixes which may have varying amounts of water. For such mixers, the conventional method of determining the slump is very time consuming and unreliable. In the usual method the slump is determined by means of a slump cone which is approximately 12" high and may vary somewhat as to size. A sample of the mix is placed in the cone with the cone apex uppermost, and after agitating the cone it is then lifted off and the number of inches which the top of the concrete cone settles is noted and taken as the slump in inches. For example, if the top settles 5", it would be called a 5" slump. This procedure manifestly is very time consuming and may indeed be a very critical factor in the delivery of concrete which is being mixed during transit. In case of delays due to unforeseen hazards, breakdowns or the like additional tests become necessary, since the mix will become stiffer as its time in the mixer ice increases, due to the rapid evaporation of the water caused by the heat that is generated from the chemical reaction of the cement and water.
Having the foregoing in mind and the inherent disadvantages of the present method utilized to determine slump, it is one object of the present invention to provide a unique slump indicator which can be used for concrete mixers, and particularly for mobile mixers having power driven barrels, and which will continuously provide an indication of the slump characteristic of the concrete mix.
Another object is to provide apparatus which is susceptible of use in transit or mobile mixers, and which embodies a slump indicator positioned in the operators cab so that it can be read at any time to remotely indicate the slump characteristic of the material which is being mixed in the barrel of the mixer.
It is also an object to provide remote slump indicator means which will be accurate and continually indicate the slump of a concrete mix while the mixing operation is being carried out at a stationary plant, or while in transit in a mobile unit, and which may be readily variably adjusted to compensate for different quantities or amounts of mix.
In its broad concept, the present invention comprises means which are responsive to variations of load-torque of the mixer barrel, due to either (a) variations in the liquid content of the mix, or (b) a change in the quantity or amount of the mix being worked or carried, e.g. one cubic yard, two cubic yards, etc. The load-torque responsive means is used to vary a component such as a resistor in the energizing circuit of an electro-magnetic meter, such as an ohmmeter which is calibrated in terms of slump. Additional compensating resistors are provided for selectively changing the energizing circuit so that the 'meter readings will apply to whatever quantity or amount of the concrete material that is being mixed.
Further objects of the invention will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing the invention without placing limitations thereon.
Referring to the accompanying drawings, which are for illustrative purposes only:
FIG. 1 is an elevational view of a ready-mix or transitmix vehicle of the type utilizing a slump indicator according to the present invention;
FIG. 2 is a view diagrammatically illustrating the torque-load responsive sensing mechanism, and further showing its schematic circuitry interconnection with the remote indicating instrumentalities mounted in the cab of the mobile mixer;
FIG. 3 is an enlarged face view of the slump indicating meter; and
FIG. 4 is a fragmentary view diagrammatically illustrating a sensing mechanism utilizing a mechanically actuated slump indicator.
Referring now generally to the drawings, for illustrative purposes, there is shown in FIG. 1 a mobile concrete mixer 10 which is representative of the type of equipment upon which the present invention has been installed to indicate slump while in transit.
The mobile mixer is of conventional construction and includes a Wheeled frame structure 11 having an operators cab 12 at its forward end, and rearwardly of the cab mounting a rotatable mixing drum or barrel 13 which is supported on end bearing structures 14 and 15 in an inclined position with its charging end elevated at the rear end of the vehicle. The charging end is provided with a conventional hopper 16 and is further provided with the necessary attachments for unloading the cement at point of destination.
Mobile concrete mixers of this type are constructed with various types of power transmitting means for rotating the mixing drum or a barrel during transit. One conventional arrangement embodies a power take-off at the front of the mobile unit in which an engine drive pulley is connected through a plurality of V-belts with a driven pulley carried by a power transmitting shaft to the rear end of the mobile unit where the power delivery shaft 17 carries a drive sprocket 18 which is connected through a driving chain 19 with a large annular driven sprocket 20 surrounding the charging end of the mixing barrel.
Since the power required to drive the mixing barrel will be directly proportional to the water content of the mix, and hence provide a measure of the slump characteristic, provision is made to sense the variations of loadtorque required to actuate the barrel. In other words, a torque sensing device is utilized between the engine delivery point and the power delivery point at the barrel. Such devices may constitute a torsion bar which will react to variations of the barrel load. In its broad concept, the invention envisions the use of any torque responsive device which can be utilized to provide a sensing unit. For illustrative purposes, however, a simple arrangement will hereinafter be described which may be associated either with the V-belt power take-off at the front end of the mobile unit, or with the chain drive at the rear end of the mobile unit. A device associated with the latter will be described.
As shown in FIG. 2, a load-torque responsive unit A is mounted at the rear end of the mobile unit and is connected through conductors 21 and 22 with a remote indicating unit B which may be mounted in the cab of the mobile unit where it may be readily observed by the operator.
As shown in FIG. 2, the load-torque responsive unit includes a pivoted arm 23 that carries a rotatable member 24 such as a pulley or a gear which is urged against the tension side of the chain 19 by means of a suitable spring 25 of predetermined strength so as to deflect the chain in the portion between the drive sprocket 18 and driven sprocket 20 laterally from its straight line position. This spring should be of sufiicient strength to deflect the chain out of line the greatest amount when the barrel is empty, that is, when there is no concrete mix therein. As the sand, rock, raw cement, water and other constituents of the mix are placed in the barrel, the power required to rotate the barrel varies in direct ratio to the amount of water in the mix. Variations of the power required will be reflected by pivotal movement of the arm 23. Thus, as the load increases the chain will become increasingly stressed and swing the arm 23 against the opposing force of spring 25. This movement of the arm 23 is sensed by a variable resistor 26 having a slide contact 27 which is connected to an arm 28 extending in a direction opposite the arm 23. As thus arranged, as the driving power increases, the effective resistance of the variable resistor 26 will increase.
By means of the conductors 21 and 22, the load-torque responsive unit A is remotely connected with the indicating unit B, and a circuit is established through the resistor 26 so that it becomes a part of an energizing circuit by means of which a slump indicating meter 29 is connected with a battery source 30. One side of the battery 30 is connected through a conductor 31 and zero adjusting resistor 32 to one side of the meter 29, while the other side of the battery 30 connects through conductor 21, resistor 2 4 1 26, conductor 22, switch 33, conductor 34, and button switch 35 to the other side of the meter.
The switch 33 is of the single-pole double-throw type having a movable element 36 which can be selectively engaged with switch contacts 37a and 37b. When the movable element of the switch is engaged with the contact 37a, the variable resistor 26 is connected into the energizing circuit. Upon connecting the movable element with contact 37b connection is made with a common con ductor 38 of a resistor network containing a plurality of individually adjustable resistors 39 for connection in each case by a switch 40 so as to be placed in the energizing circuit of the meter 29 in series relation with the variable resistor 26.
Operation of the remote slump indicator as described above will now be explained. In order to calibrate the system, the meter 29, which is a conventional ohmmeter, is initially set at its zero resistance position at the right end of the scale by means of the zero adjusting resistor 32. This adjustment is made when there is no charge in the barrel. Thus, only varying power will be shown on the meter. The resistor 26 is chosen of such value that within its range of adjustment it will indicate on the meter the proper slump reading depending upon the liquid content of the mix. The resistor 26 has a value which would correspond with a particular number of cubic yards which will be mixed in the barrel. For example, the resistor 26 would be used for a charge of nine cubic yards.
It will be appreciated that as the amount of charge is reduced, it will take less power to turn the barrel. As a result, the driving chain 19 will be less tensioned so that the action of the spring 25 will permit movement of the arm 28 in a direction to decrease the effective resistance of the resistor 26 with respect to the energizing circuit of the meter 29. In order to compensate for this change of load when working a smaller charge, the proper resistor 39 is inserted into the energizing circuit in series with resistor 26. Assume for example that the charge being worked is eight cubic yards rather than nine cubic yards. In this case, the resistor 39 as indicated at 8Y would be inserted by closing the switch 40, and moving the element 36 into engagement with contact 37b. The resistor 39 is properly calibrated for the eight cubic yard charge. For lesser charges the other resistors of the network will be inserted.
As shown in FIG. 3, the slump in inches is indicated on the meter scale 41 by numerals in this case which read from zero to nine in increasing opposite direction than that in which the pointer 42 is moved to indicate increasing changes in the resistance of the energizing circuit of the meter. The other compensating resistors for different amounts of charge are designated by the indicia 1Y, and 5Y to 9Y inclusive.
While the remote indicating unit arrangement provides for a most convenient check by the operator as to the slump of the mix, an alternative arrangement is possible wherein mechanical indication of slump may be provided in connection with the load-torque responsive unit A. Referring to FIG. 4, direct indication may be obtained by providing a pointer 43 on the arm 23, this pointer being arranged to traverse a scale bearing member 44 having graduations thereon indicative of the slump for a given number of cubic yards in the mix.
From the foregoing description, it is clearly evident that the invention described provides an accurate and efficient means for indicating the slump of the mix in a concrete mixing barrel or drum, and that the delineated objects will be effectively accomplished.
Various modifications may suggest themselves to those skilled in the art without departing from the spirit of my invention, and, hence, I do not wish to be restricted to the specific form shown or uses mentioned, except to the extent indicated in the appended claim.
1. Slump indicating mechanism for a concrete mixer push having a rotatable mixing barrel driven from a power source, said mechanism comprising:
(a) an electro-magnetic meter having an indicating scale calibrated in terms of slump and an energizing circuit;
(b) load-torque responsive means including a resistor in said energizing circuit variable in accordance with changes of the liquid content in the mix; and
(c) other resistors for selectively modifying the energizing circuit to compensate for variations in the quantity of the mix being worked in the barrel.
References Cited UNITED STATES PATENTS Roesen 73144 Decker 73-144 XR Zanzig 73-136 Cook 7388.5 Moseley 346-32 Hilkemeier 73-54 10 DAVID SCHONBERG, Primary Examiner.