FI124462B

FI124462B - A method for controlling the compaction of concrete in an extruder and an extruder

Info

Publication number: FI124462B
Application number: FI20135117A
Authority: FI
Inventors: Jukka Ahonen
Original assignee: Concore Bv
Priority date: 2013-02-08
Filing date: 2013-02-08
Publication date: 2014-09-15
Also published as: FI20135117A

Description

Method for controlling compaction of concrete in extruder and extruder Technical Field

The present invention concerns manufacturing concrete products by an extruder.

5 Especially the invention concerns a method for improving the control of compaction of the cast concrete during manufacture.

Background

In the building industry, large numbers of various concrete products, which are 10 prefabricated in factories, are used. Examples of such products are slabs, columns, and prefabricated units. Known methods for casting elongated concrete products are the extrusion technique and the slipformer technique. These methods have been in general use since about the end of the 1960s. They are typically used to manufacture floor units and simple beam profiles.

15 In the extrusion technique, concrete is fed to an elongated form base with the aid of screws through nozzles and forming elements. The axes of the screws are parallel to the casting base and thus also to the cast, and comprise shaping elements, with the aid of which cavities, for example, can be formed in the unit. The shaping elements are usually extensions of the screws. Most typically, the products are hollow-core slabs, which in ^ 2 0 practice have become typically standardized as 1200 mm wide and 150 mm - 500 mm c\j ^ thick or even thicker. Widths of600, 100,1500 or 1800 are also commonly used. The o ^ compaction of the concrete takes place mainly with the aid of the feed pressure of the o screws and vibration, or the feed pressure of the screws and mechanical compaction cr movements i.e. shear compaction. In the method, it is typically possible to use dry >- 25 concrete and in it a good concrete compaction and strength are generally achieved. Thanks

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£2 to the dry mass, the cast product remains highly cohesive immediately after casting, which δ ^ is a precondition for the manufacture of hollow-core products.

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The screw’s function in the extruder is to transport the concrete mass into the space delimited by the shaping elements and at the same time to create a pressure, which will be a central factor in promoting and controlling the compaction gradient. The screw also participates in compaction in connection with shear compaction. As the screw moves 5 typically backwards and forwards along with the core, its shape creates an oriented compaction in the space between two screws and between the screw and the other delimiting nozzle components. For reasons of balance, the adjacent screws move in opposite directions and a float is created, in which the mass under increasing pressure is floated and consolidates due to the compaction movement. The elementary units of the 10 mass seek an increasingly compact space.

The compaction rate of a concrete slab or other product made by an extruder should be as even as possible since the compaction greatly affects the properties (strength) of the product. One common way to effect the compaction is adjusting the feed force or rotational speed of the extruder screws. The drawback of this method is variations of the 15 casting speed and juddering of the machine, which leads to variations in compaction. The speed variations are caused by variations in composition and consistency of the concrete mix and partly of variations in travel resistance of the extruder machine. In order to avoid these drawbacks, a brake system has been implemented for stabilizing the running resistance of the machine. The brake can be set manually or adjusted automatically.

2 0 However, the brake system only allows setting of a minimum travel resistance level but not active control of the speed of the machine.

<t Other ideas for controlling the compaction include measuring the power of trowelling or ° shear plates or beams and adjusting the feed force of the screws or other control variables o of the machine accordingly. All these methods involve a control loop based on indirect o 2 5 measurement of the compaction rate as the actual compaction rate of the concrete can’t be g effectively measured during manufacture.

GB 1586181 discloses an extruder wherein the torque forces acting on auger is monitored

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$2 in order to keep the compaction and casting rates constant. Speed of the extruder is not o 00 monitored. FI 83937 discloses a method wherein the speed of the extruder is measured and 3 0 the speed of a strand guide trolley is adjusted to the speed of the extruder. The speed of the 3 extruder is not adjusted, but variations of travel resistance of the strand guide trolley are compensated.

Summary of Invention 5 Present methods and apparatuses are either complicated or insufficient for effectively controlling the compaction of concrete mix during manufacture. This may lead to undesired variations in the quality and properties of the products.

For the above reasons, it would be beneficial to provide an improved method and apparatus for controlling the compaction of cast concrete during manufacture by an 10 extruder. The present invention may have beneficial effects even if applied in a similar manner to a slipformer or other kind of a continuous horizontal casting machine or method.

The invention is based on measuring the speed of the extruder during movement and adjusting the speed by an active speed control device.

15 According to one embodiment, the adjustment of the speed is done by at least one traction wheel driven by drive means that are arranged to propel the extruder on basis of speed measurement so that variations in its travelling speed are reduced.

According to one embodiment, the drive means are at least one electric motor and the rotation speed and torque of the motor is controlled on basis of measured speed of the ^ 2 0 extruder in order to provide an auto-active electric axis for the extruder.

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o According to one embodiment of the invention, at least one auxiliary variable such as o electric power of the drive motor, rate of compaction, variation on the rate of compaction k (variation in the time axis to illustrate the behavior and performance to be used in p— optimation), electric power of the top sealing unit, electric power of any other compacting

Ln 2 5 or sealing element, electric power of the drive mechanism of a feeding screw, is measured co δ and used for controlling the drive means.

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According to one embodiment of the invention, at least variations in the travelling speed of the extruder during casting of a specific concrete mix composition are measured and analyzed in order to find an optimum set speed for said concrete mix composition.

Some of the advantageous effects of the various embodiments of the invention and their 5 combinations are a simple way to implement the invention and minimum changes to the construction of the extruder. In general, the speed control would be easier to implement than previously know methods based on measuring compaction power or other variable relating more directly to compaction. Even the simplest embodiment of the invention, wherein only speed of the extruder is measured for controlling the drive means, provides a 10 way to optimize the casting process and decrease variations in the quality of the products.

If more data is collected and analyzed, further possibilities for controlling the quality of the product are provided. The control system that is based on minimizing or at least decreasing the speed variations is independent from other variations or changes in operation variables. Therefore changes in concrete mix composition such as change in flowability or water 15 content don’t affect the compaction as the correction of travelling speed automatically compensates changes caused. Movements and power of sealing elements, feed screws and core forming sleeves or any other process variable may be compensated by the system.

Other objects and features of the invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be 2 0 understood, however, that the drawings are intended solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims δ

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N- o o Description of Drawings

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cc 25 Fig. 1 is a schematical view of an extruder and one embodiment of the invention, r- ijj Fig. 2 is a block diagram of one embodiment of the invention, co δ

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Description of embodiment 5

The invention is explained as applied to an extruder. It can be applied in a similar manner to a slipformer of other kind of a continuous horizontal casting machine or method.

An extruder comprises a frame 1 that is arranged to travel on a forming platform 3 on wheels 2. The product that is manufactured is shaped by pushing concrete mix through 5 a limited cross section that gives the product its outer shape and forms the cavities called cores in the cross section of the product. The limited cross section is formed by the top surface of the forming platform 3, side walls of the extruder (not numbered) and the wear plate 8 of a top sealing unit 7. Between the top sealing unit 7 and the forming platform 3 and penetrating through the limited cross section are core forming sleeves 6. The core 10 forming sleeves 6 are attached at the end of feed screws 5. The feed screws are connected to a drive mechanism 9 that rotates the screws 5 and provides compacting movement for the screws and the core forming mandrels. A concrete hopper 4 is placed at the opposite end of the feed screws 5 in view of core forming mandrels and over the screws. The apparatus also includes strand guide 10 with guide arms 11 for guiding reinforcement 15 strands.

During the manufacture concrete mix is poured in the hopper 4 and the rotating screws 5 push the mix to the limited cross section around the core forming mandrels. The reaction for of the pushing of concrete mix moves the extruder away from the formed product and an elongated hollow core slab or other extruded product is formed.

2 0 The features and operation of an extruder described above are common to most of the modem extruders. The setup of each machine may vary, but these variations don’t prevent 't q utilizing the invention.

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o The idea of the invention is based on direct, active control of the travelling speed of the o extruder. In one embodiment the active control of the speed is accomplished by an electric ί 25 drive motor thus providing an electric axis for an autoactive extruder. For accomplishing an active control of the speed, means for measuring the speed are needed as well as means lo for propelling the machine in a controlled manner so that the drive of the motor reacts to o the changes in the speed and changes the propelling effect accordingly. One way to implement this is to use a special electric drive motor. Other possibilities can also be 3 0 contemplated, such as hydraulic or pneumatic motor or a cable or bar or a screw drives.

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However, the mechanical simplicity of an electric motor and especially modem methods for controlling electric motors very effectively in a simple manner provide essential benefits.

If the speed of the machine can be kept as constant as possible, the feed and compaction 5 power in the limited cross section through which the concrete mix is pressed and wherein the product is formed, changes as the consistency of the mix changes. If the mix is more fluid, it flows more easily and more mix is fed through the cross section leading rapidly to increased compaction pressure and more compact product. Similarly, if the flow resistance of the mix is increased, less concrete mix flows through the cross section, pressure is 10 relieved and compaction rate of the product decreases. Now, as the compaction rate and pressure in the limited cross section increases, the flow resistance through the cross section increases and the speed of the extmder begins to decrease. Accordingly, the speed measurement indicates change in speed and increases the propulsion power. In a similar manner, when compaction rate decreases, the flow resistance decreases and speed may 15 increase. In this case propulsion power is decreased so that the speed of the extruder is decelerated to a set level. This method also decreases rapid changes in the speed of the machine, i.e. juddering. Juddering has been a problem in concrete extrusion as then the speed of the machine rapidly decreases and afterwards the machine accelerates rapidly or even jumps slightly forward causing an insufficiently compacted area over the cross 2 0 section of the product. Such a area or areas on the length of the product decrease the strength of the product. Since the method according to the invention evens out the changes in the travel resistance of the machine, probability that juddering may cause defects in 't q product quality is decreased or even eliminated.

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o One embodiment for implementation of the invention is depicted in figure 1. The speed o 2 5 control of the extruder is implemented by an auto active electric axle that comprises an g axle and traction wheels 2 on both sides of the extruder. The traction wheels are preferably connected so that same traction force and rotational speed of the wheels 2 is provided on lo both sides of the extruder. A straight axle is a simple way to synchronize the wheels 2.

o Wheels are powered by an electric drive motor 14 that rotates the wheels 2. The speed of 3 0 the extruder is measured from a traction wheel 2 of the machine by speed measurement instrument 12. In this example the current taken by the electric drive motor is also 7 measured by a current measuring instrument 13. The current measurement information and detected velocity are transferred to a summing unit 15, wherein a reference value is calculated n basis of the measured information. From the summing unit 15 the reference value (ref) is transferred to a controller 16 that compares the reference value to a target 5 value (t) and prepares a control signal to the control unit 17 of the electric drive motor 14.

Figure 2 shows a simplified control loop for controlling the speed of an extruder. As in the above example, the speed is measured from a traction wheel 2. The measured value is compared to a set target value, herein 1.8 m/min, in a controller and a control signal is sent to a control unit 17 of an electric drive motor.

10 The measurement, control and calculation can be done by any conventional means used for the purpose. The control loop may be a simple feedback control loop for keeping a set speed or more advanced system including options for using further measurement data, optimizing tools and databases for recommended production values. Any physical or data processing features are preferably integrated to the control system of the extruder.

15 The adjustment and control of speed may be combined with control of other drive variables of the machine, such as electric power of the drive motor, rate of compaction, variation on the rate of compaction (variation in the time axis to illustrate the behavior and performance to be used in optimation), electric power of the top sealing unit, electric power of any other compacting or sealing element, electric power of the drive mechanism 2 0 of a feeding screw, is measured and used for controlling the drive means.

Tt Thus, while there have been shown and described and pointed out fundamental novel ° features of the invention as applied to a preferred embodiment thereof, it will be o understood that various omissions and substitutions and changes in the form and details of o the method and device may be made by those skilled in the art without departing from the g 25 spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same results are within the in scope of the invention. Substitutions of the elements from one described embodiment to co o another are also fully intended and contemplated. It is also to be understood that the drawings are not necessarily drawn to scale but they are merely conceptual in nature. It is 8 the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Reference signs list 5 1. extruder frame 2. wheel 3. forming platform 4. concrete hopper 5. feed screw 10 6. core forming sleeve 7. top sealing unit 8. wear plate 9. drive mechanism 10. strand guide (unit) 15 11. hook arms 12. speed measuring instrument δ ^ 13. current measuring instrument o 99 14. electric drive motor o

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£ 15. summing unit >- 2 0 16. controller m co δ C\l

Claims

Claims Claim 1 Method for controlling the compaction of cast concrete during manufacture by an extruder, 5 characterized of measuring the speed of the extruder during movement and adjusting the speed by an active speed control device.
Claim 2 Method according to claim 1, characterized in that the adjustment of the speed is done by at least one traction wheel (2) driven by drive means (14) that are arranged to propel the 10 extruder on basis of speed measurement so that variations in its travelling speed are reduced.
Claim 3 Method according to claim 1 or 2, characterized in that the drive means are at least one electric motor (14) and the rotation speed and torque of the motor (14) is controlled on 15 basis of measured speed of the extruder in order to provide an auto-active electric axis for the extruder.
Claim 4 Method according to any of the claims 1-3, characterized in that at least one auxiliary ? variable such as electric power of the drive motor (14), rate of compaction, variation on the C\J ^ 2 0 rate of compaction, variation of compaction in the time axis, electric power of a top sealing ° unit (7), electric power of any other compacting or sealing element, electric power of the o drive mechanism (9) of a feeding screw (6), is measured and used for controlling the drive DC means. r-- Claim 5 co o cvj 25 Method according to any of the claims 1-4, characterized in that at least variations in the travelling speed of the extruder during casting of a specific concrete mix composition are measured and analyzed in order to find an optimum set speed for said concrete mix composition. Claim 6 An extruder for producing a concrete product, characterized by means for measuring (12) 5 the speed of the extruder during movement and means for adjusting the speed (13 - 17) by an active speed control device. Claim 7 An extruder according to claim 6, characterized in that the means for adjustment of the speed (13 - 17) are at least one traction wheel (2) driven by drive means (14) that are 10 arranged to propel the extruder and means for measuring the speed of the extruder (12) and controlling the drive means (14) so that variations in its travelling speed are reduced. Claim 8 Extruder according to claim 6 or 7, characterized in that the drive means are at least one electric motor (14) and the rotation speed and torque of the motor (14) is controlled on 15 basis of measured speed of the extruder in order to provide an auto-active electric axis for the extruder. Claim 9 Extruder according to any of the claims 6-8, characterized by means for measuring at ^ least one auxiliary variable (13) such as electric power of the drive motor (14), rate of ° 2 0 compaction, variation on the rate of compaction, variation of compaction in the time axis, o electric power of a top sealing unit (7), electric power of any other compacting or sealing § element, electric power of the drive mechanism (9) of a feeding screw (6). X IX CL LO CO δ C\l Patenttivaatimukset Patenttivaatimus 1 Menetelmä valettavan betonin tiivistymisen ohjaamiseksi ekstmuderilla valmistettaessa, 5 tunnettu ekstruuderin nopeuden mittaamisesta liikkeen aikana ja nopeuden säätämisestä aktiivisella nopeudensäätölaitteella. Patenttivaatimus 2 Patenttivaatimuksen 1 mukainen menetelmä, tunnettu siitä, että nopeuden säätö tehdään vähintään yhdellä käyttöelinten (14) käyttämällä vetopyörällä (2), jotka käyttöelimet on 10 jäij estetty liikuttamaan ekstruuderia nopeuden mittauksen perusteella siten, että sen liikkeen nopeuden muutokset vähenevät. Patenttivaatimus 3 Patenttivaatimuksen 1 tai 2 mukainen menetelmä, tunnettu siitä, että käyttöelimet ovat vähintään yksi sähkömoottori (14) ja moottorin (14) pyörimisnopeutta ja momenttia 15 ohjataan ekstruuderin mitatun nopeuden perusteella automaattisen aktiivisen sähköisen akselin tuottamiseksi ekstruuderille. Patenttivaatimus 4 Jonkin patenttivaatimuksen 1-3 mukainen menetelmä, tunnettu siitä, että vähintään yksi lisämuuttuja, kuten käyttömoottorin (14) sähköteho, tiivistysnopeus, tiivistysnopeuden 2 0 vaihtelu, tiivistysnopeuden vaihtelu aika-akselilla, ylätiivisteyksikön (7) sähköteho, minkä tahansa muun tiivistys- tai riivisteyksikön sähköteho, syöttöruuvin (6) käyttömekanismin (9) sähköteho, mitataan ja sitä käytetään käyttöelimen ohjaamiseen. Patenttivaatimus 5 δ ^ Jonkin patenttivaatimuksen 1-4 mukainen menetelmä, tunnettu siitä, että vähintään o 2 5 ekstruuderin liikkeen nopeuden muutokset tietyn betoniseosyhdisteen valun aikana g mitataan ja analysoidaan ihanteellisen nopeusasetuksen löytämiseksi kyseiselle x betoniseosyhdisteelle. CC CL ^ Patenttivaatimus 6 g Ekstruuderi betonituotteen tuottamiseksi, tunnettu elimistä ekstruuderin nopeuden o 3 0 mittaamiseksi (12) liikkeen aikana ja elimistä nopeuden säätämiseksi (13 -17) aktiivisen nopeudensäätölaitteen avulla. Patenttivaatimus 7 Patenttivaatimuksen 6 mukainen ekstruuderi, tunnettu siitä, että elimet nopeuden säätämiseksi (13-17) ovat vähintään yksi käyttöelinten (14) käyttämä vetopyörä (2), jotka käyttöelimet on sovitettu liikuttamaan ekstruuderiaja elimet ekstruuderin (12) nopeuden mittaamiseksi ja käyttöelimen (14) ohjaamiseksi siten, että sen liikenopeuden vaihtelut 5 pienenevät. Patenttivaatimus 8 Patenttivaatimuksen 6 tai 7 mukainen ekstruuderi, tunnettu siitä, että käyttöelimet ovat vähintään yksi sähkömoottori (14) ja moottorin (14) pyörimisnopeutta ja momenttia ohjataan ekstruuderin mitatun nopeuden perusteella automaattisen aktiivisen sähköisen 10 akselin tuottamiseksi ekstruuderille. Patenttivaatimus 9 Jonkin patenttivaatimuksen 6-8 mukainen ekstruuderi, tunnettu elimistä vähintään yhden lisämuuttujan (13), kuten käyttömoottorin (14) sähköteho, tiivistysnopeus, tiivistysnopeuden vaihtelu, tiivistysnopeuden vaihtelu aika-akselilla, ylätiivisteyksikön (7) 15 sähköteho, minkä tahansa muun tiivistys- tai tiivisteyksikön sähköteho, syöttöruuvin (6) käyttöniekanismin (9) sähköteho, mitataan ja sitä käytetään käyttöelimen ohjaamiseen. 't δ c\j i 1^ o oo o X cc CL 1^ δ oo δ C\l