US 3460812 A
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Description (OCR text may contain errors)
Aug. 12, 1969 F N 3,460,812
CONCRETE MIXING CONTROL APPARATUS FOR CONCRETE MIXING TRUCKS Filed March 25, 1968 FIGURE l 24 26 25 K 2? momsumnv CONTACT 22 swn'cu ME DELAY 3| O- DROPOUT 2a RELAY DELAY g OVERLOAD SOLENOID o-n BREAKER 2e 32 THROTTLE FIGURE 2 INVENTOR ROBERT R. KAUFMAN BY W'" w ATTORNEY United States Patent CONCRETE MIXING CONTROL APPARATUS FOR CONCRETE MIXING TRUCKS Robert R. Kaufman, Maitland, Fla.
(45 Wisteria Drive, DeBary, Fla. 32713) Filed Mar. 25, 1968, Ser. No. 715,650 Int. Cl. B28c 7/02 US. Cl. 259-177 6 Claims ABSTRACT OF THE DISCLOSURE A concrete mixing control apparatus comprising a concrete mixing truck having a mixing drum with an engine power source. A solenoid is adapted to pull and hold the throttle of the engine a preset distance upon actuation by a timing relay. The timing relay is actuated by a momentary contact switch and operated for a preset timing cycle during which the solenoid holds the engine throttle. When the cycle is completed the power to the solenoid is cut off, and the throttle is released. The mixing drum is thus capable of being rotated a preset time at a preset speed of rotation to assure quality mixing of the concrete.
BACKGROUND OF THE INVENTION Field of the invention The present invention relates to controlling the mixing of ready-mix concrete, or the like, being mixed in a trucl' mixer. Control of the mixing and supplementary agitatior are of great importance and involve a wide range in con ditions requiring careful attention.
Ready-mixed concrete is mixed and delivered by one of several methods. Central mixed concrete is completely mixed in a stationary mixer and then transported to the work site, while shrink-mixed concrete is partially mixed at a stationary site and completed on a truck mixer. Finally, transit or truck mixed concrete is completely mixed in a truck mixer. The present invention is concerned with truck-mixed and shrink-mixed concrete.
In normal operation, a truck mixer drum is loaded with a concrete batch by the appropriate batching equipment and driven to the work site with the drum rotating at an agitating speed. Either immediately after the truck mixer is loaded or when the work site is reached, the truck mixer drum is rotated at mixing speed for a desired number of rotations prior to discharge. Proper control of the mixing operation will produce concrete that is thoroughly mixed and of uniform consistency throughout a batch as well as from batch to batch. The thoroughness of mixing is determined primarily by the number of revolutions of the mixing drum, together with the peripheral speed of the mixer.
For some jobs, specifications are set as to the number of rotations at agitating and at mixing speeds, and as to the speeds to be used for agitating and for mixing.
Typically, a fully loaded truck mixer will be required to rotate between 60 and 100 revolutions of the mixing drum at mixing speed the exact number being specified. Specifications also will generally require that a total number of revolutions including 'both mixing and agitating not be exceeded. Mixing speed may be from 4 revolutions per minute up to 12. revolutions per minute, while agitating speed may be varied between 2 and 6 revolutions per minute of drum rotations.
It should be noted at this point that the mixing drum or concrete mixing trucks may be powered by a separate motor or more commonly may have a common engine to drive the truck and the mixing drum.
In accordance with my invention, I provide a concrete mixing truck having a mixing drum with a DC. solenoid 3,460,812 Patented Aug. 12, 1969 "ice connected to the throttle of the truck engine used to drive the mixing drum, so that when activated the throttle will he held in a manner to maintain the mixing drum rotating at a predetermined speed. The electrical leads for providing the power to the solenoid are connected to a timing relay adapted to activate the solenoid for a preset period of time upon actuation by a momentary contact switch. A slow blow type overload breaker circuit or relay may also be used, as well as a master switch for disabling the circuit.
Description of the prior art In the past it has been common to provide concrete mixing trucks with revolution counters to count the number of revolutions of mixing the batch. Counters have also been provided to count the total revolutions including the rotations at agitating speed as well as at mixing speed, and to count agitating and mixing revolution separately.
One prior teaching provides for a tachometer to indicate the speed of rotation of the drum and to have a counter incorporated herein. One such counter would indicate total revolution of the drum while a second such counter would provide an easily resettable means whereby it could be reset upon starting the mixing operation to indicate revolutions at mixing speed.
It has also been suggested to provide a drum rotating counter which counts total revolutions and also counts separately only those revolutions above a predetermined speed so that some assurance could be provided that sufficient revolutions are completed at mixing speed. Such counters may also provide for a timer to indicate the time that has elapsed since starting of the rotation of the drum.
One previously used means provides an interlock arrangement to prevent discharge of the cement until completion of a desired number of rotations, and another prior device has provided a recording device to the counters to record on paper the total revolutions or even the total revolutions at mixing speed. This provides the recipient of the ready-mix concrete with a record of the amount of rotations of each batch.
Finally, the prior art teachings for control mixed concrete mixed in stationary mixers provides several types of control apparatus such as a power driven control mechanism operating a complex plurality of cams to initiate and/ or terminate various operations in sequence. Another such apparatus provides a cam in a timing arrangement whereby the cam activates an electrical switch.
BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features, and advantages of this invention will be apparent from a study of the written description and the drawings in which:
FIGURE 1 is a side view of a cement mixing truck as used in the present invention; and
FIGURE 2 is a block diagram of an embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGURE 1, a concrete mixing truck 10 may be seen having wheels 11, a mixing drum 12, water tank 13, drivers compartment or cab 14, and engine compartment 15. The mixing drum 12 of truck 10 is filled with a batch of materials for the mixing of concrete and the drum set to rotate an an agitating speed through a geared arrangement 16 connected with the drive of the truck 10. The truck mixer is shifted into mixing speed and the concrete mixed prior to the truck being driven to a job site with the drum 12 rotating at agitating speed. The engine of the truck located at 15 is speeded up to provide the necessary speed of rotation of the drum 12 for mixing. The mixing is preferably done only before leaving for the work site or after the truck has arrived at the work site since the faster rotation of a drum loaded with a full batch of concrete would make control of the truck difficult and dangerous. After the concrete batch is mixed the desired number of rotations at the desired speed, the drum is discharged upon arrival at the job or agitating may continue for a reasonable time until required to discharge, and the truck may return for another load.
It should be noted that truck could also have the drum 12 rotated by a separate motor rather than connected to the drive of the truck.
Referring to FIGURE 2, there is a block diagram of a preferred control circuit for performance of my invention, having a battery 20, which may be the battery of truck 10, connected to ground 21. Battery is connected to the truck 10 ignition switch 22.
A momentary contact switch 24 may be located in the drivers cab 14 of truck 10 and when actuated provides a momentary surge of direct current to input 25 of time delay on dropout relay 26. Input 25 may connect to a coil (not shown) in relay 26 acting as an electromagnet which coil may also be connected to ground at output 27. The momentary activation of the current through the coil may start the timing circuit of the relay 26 whereby current would begin to flow through a delay overload breaker 28, through time delay on dropout relay 26, at input 29, and output 30. The DC current actuates a DJC. solenoid 31 which is connected to the relay 26 at output 30 and to ground. Solenoid 31 is connected to the throttle of the truck 10 at 32 and upon actuation pulls the throttle a set distance which determines the speed the trucks engine will be maintained. This in turn determines the speed of rotation of mixer drum 12 to truck 10 (FIGURE 1) and maintains a mixing speed until the dropout of relay 26. Relay 26 will remain activated during the timing period or cycle whereupon it will drop out, disconnecting the flow of current between input 29 and output 30, and disengaging solenoid 31, thereby releasing the throttle at 32. The relay 26 can be set for a predetermined time and I have found that with only slight adjustments, I can determine the timing of the relay to correspond with the desired number of rotations needed for a particular mix of concrete. Therefore the number of rotations and the speed of rotation may be set in advance and with the truck driver having only the responsibility of pushing the momentary contact switch 24 and no control over the mixing time of the concrete. A disabling switch may be provided between the solenoid 31 and ground to disable the circuit as desired.
At this point it can be seen that a control apparatus has been provided whereby ready-mix concrete may be accurately mixed in a concrete mixing truck with uniform control of the mix both as to the number of revolutions of rotation and as to the speed of rotation. While the inventor does not wish to be limited to any particular components for the embodiment described, it should be remembered that fairly accurate components are required especially with respect to the timing relay. I have found that solenoid 31 may be a 12-volt D.C. type having 30 pulling amps and .6 holding amp and having a 10-lb. pull rate for a 1-inch stroke. The 30 pulling amps are of course only for the short pulling stroke but may require a delay overload breaker so as to provide protection but without stopping the circuit during the short period of the pulling stroke. It has also been found that a 2422 series-Type 2, time delay on dropout relay manufactured by the Agostat Division of Elastic Stop Nut Corporation of America, Elizabeth, NJ, operates with the required accuracy for measuring the time of the mixing operation. This relay unit has an optional tamper-proof cap to prevent anyone from changing the set timing period on the relay during the trucks trip.
As can readily be seen, the timing unit may be set upon loading a batch of concrete ingredients upon the concrete mixing truck. The driver may then shift the drum drive into mixing position and then push the momentary contact switch 24, which in turn activates relay 26 to provide current for actuation of solenoid 31 which in turn pulls and holds the truck throttle until the relay 26 completes its cycle. The driver may then drive to the work site and discharge the concrete from the mixing drum or continue at agitating speed until discharged.
This invention is not to be construed as limited to the particular forms disclosed herein, since these are to be regarded as illustrative rather than restrictive.
1. A concrete mixing control apparatus for controlling the mixing of ready-mix concrete comprising in combination:
(a) a concrete mixing truck having a mixing drum therein, said mixing drum adapted to be rotated by an engine having a throttle for varying the speed thereof;
(b) a solenoid means connected to said throttle of said engine and adapted to pull and hold said thottle a preset distance upon actuation thereof;
(c) timing relay means connected to said solenoid means, said timing relay means having a preset timing cycle and adapted to actuate said solenoid during said timing cycle; and
(d) momentary contact switch means connected between said timing relay means and a DC. power source adapted to initiate said timing cycle of said timing relay means;
(e) whereby initiation of said momentary switch means maintains said mixing drum at a predetermined speed of rotation for the duration of said timing cycle.
2. The apparatus according to claim 1 in which said timing relay means timing cycle is variable.
3. The apparatus according to claim 2 in which said timing relay means has locking means to lock said timing relay means timing cycle for a preset time period.
4. The apparatus according to claim 2 in which said solenoid means pulling stroke may be varied.
5. The apparatus according to claim 4 but including a delay overload breaker connected parallel to said momentary contact switch means between said timing relay means and said DC. power sources.
6. The apparatus according to claim 5 in which said engine also powers the concrete mixing truck.
References Cited UNITED STATES PATENTS 2,781,186 2/1957 Harbers. 2,968,915 1/1961 Feistel. 3,160,398 12/1964 Green. 3,168,295 2/ 1965 Dorrell. 3,215,411 11/1965 Pitts.
ROBERT W. JENKINS, Primary Examiner