WO2007009514A1

WO2007009514A1 - Apparatus for producing shaped concrete bodies

Info

Publication number: WO2007009514A1
Application number: PCT/EP2006/003660
Authority: WO
Inventors: Rudolf Braungardt; Holger Stichel
Original assignee: Kobra Formern Gmbh
Priority date: 2005-07-19
Filing date: 2006-04-21
Publication date: 2007-01-25
Also published as: DE102005034153A1; EP1910046A1

Abstract

The invention proposes varying the fundamental frequency of a vibrating apparatus during a vibrating process for an apparatus for producing shaped concrete bodies by compacting a quantity of wet concrete, which is filled into a mould, under the action of the vibrating apparatus.

Description

Apparatus for producing concrete moldings.

The invention relates to a device for the production of concrete moldings by compacting a filled in a mold wet concrete amount.

For the production of concrete moldings by compacting a filled in a mold wet concrete amount molding machines are common, in which a vibrator acting on the concrete amount and this strongly compressed during a short shaking. In particular, devices are used in which a mold with a plurality of mold cavities open at the top and bottom rests on a vibratory support. During the shaking process, the vibrating device causes the substrate to vibrate predominantly vertically, which has been transferred to the amount of concrete in the mold cavities, which is thereby highly compacted. In another embodiment, the vibrator can also be arranged laterally on the mold and stimulate them to vibrate movements, which are transmitted to the concrete amount.

Unwuchttrüttler particular known for the Rütteleinrichtungen. These accelerate a shaft with an imbalance weight at the beginning of a shaking operation to a target speed, which is maintained until the end of the shaking process. It is Z. Example, from US 4,830,597 or DE 91 15 834 U1 known to specify the vibrating frequency adjustable and set two unbalanced weights on separate waves opposite and to change the amplitude of the unbalance movement, the rotational frequency of a wave briefly to the nominal frequency slightly to change and so to adjust the phase position of the opposing unbalanced shafts. (From US Pat. No. 5,527,175 it is known to carry out a plurality of shaking operations one after the other in a ground paver with a vibrator moving over a concrete surface, and before each Rüttelvorgang in a frequency sweep to determine the optimum target frequency for the subsequent shaking of detected natural oscillations.)

Also known z. B. from DD 236 896, in a device for the production of concrete moldings a Rüttelunwucht about a chain and two eccentric unequal sprockets drive, resulting in a shaking movement with superimposition of two frequencies.

Commonly used in the production of concrete moldings is the so-called shock vibration, in which blow bars or impact plates beat periodically with frequencies of typically 50 Hz from below against a vibratory surface on softer the mold rests with the concrete amount. Due to the shock vibration, the shaking motion contains not only the fundamental frequency but also frequency components of higher harmonics of the fundamental frequency.

The present invention has for its object to further improve an apparatus and a method for producing concrete moldings by compacting a moist concrete amount in a mold by the action of a vibrator.

Solutions according to the invention are described in the independent claims. The dependent claims contain advantageous refinements and developments of the invention.

The changeable over the duration of a shaking variable frequency of the vibrator allows surprisingly a significant reduction in the duration of the shaking and / or higher compression of the wet concrete amount against a constant fundamental frequency, such. B. in the typical imbalance. For the course of time with a variable fundamental frequency, it is possible to specify a mean fundamental frequency averaged over the duration of the shaking process, which may in particular be given as a time integral over the variable fundamental frequency divided by the duration of the shaking process. Depending on the nature of the shaking process, the vibrating motion can cause not only the fundamental frequency but also frequency components of higher harmonic frequencies. Of particular advantage is a temporal course of the fundamental frequency, which has at least two temporally spaced relative frequency maxima and a frequency minimum lying between them, wherein advantageously at least one of the relative frequency maxima, preferably both, are above and the relative minimum frequency below the average fundamental frequency.

A relative frequency minimum is to be understood as meaning a frequency value whose temporally adjacent different frequency values are both lower. In a corresponding manner, a relative minimum frequency is understood to be a frequency value to which greater frequency values occur on both sides in time. One of the relative frequency maxima can also represent the absolute maximum frequency over time of the fundamental frequency.

The multiple opposite change of the fundamental frequency between higher and lower frequency values proves to be particularly effective in the compression of the concrete amount. Advantageously, the frequency difference between the relative frequency minimum and the arithmetic mean of the two relative frequency maxima is at least 10%, in particular at least 20%, preferably at least 40% of this mean value. Advantageously, the frequency difference of the relative frequency minimum to each of the two relative frequency maxima is at least 5%, in particular at least 15%, preferably at least 30% of the said mean value. The relative minimum frequency is advantageously at least 10%, preferably at least 20% of the mean fundamental frequency below this. A relative frequency maximum is advantageously at least 20%, in particular at least 40% of the average fundamental frequency above it. The average fundamental frequency is advantageously at least 40 Hz, in particular at least 50 Hz, preferably at least 60 Hz.

In a first embodiment, the vibrator device may contain one or more rotating imbalances, in which, due to the rotating masses to be accelerated or retarded during a change of the fundamental frequency, such a frequency change takes place continuously and the time characteristic of the fundamental frequency has sloping and falling edges. The start-up and the run-out phase at the beginning or end of a shaking operation are advantageously shorter than 10% of the duration of the shaking process and not considered as part of the shaking process with the time-varying fundamental frequency.

In a preferred embodiment, the vibrator device contains actuators without start-up or discharge phase for a shaking process, in particular hydraulic, magnetic or piezoelectric actuators whose excitation fundamental frequency can be changed by the control device abruptly within the range of possible excitation fundamental frequencies to any frequency levels. The excitation via such actuators may already contain higher harmonics of the respective excited fundamental frequency.

Advantageously, at least one frequency change between two is consecutive in the event of a sudden change in the fundamental frequency Basic frequencies at least 10%, preferably at least 20%, in particular at least 40% of the mean fundamental frequency.

In particular, a sudden change in frequency is considered to be a frequency change in which the transition between two fundamental frequencies amounts to less than 0.1%, preferably less than 0.01%, of the duration of the shaking process.

In the case of several incremental changes in the fundamental frequency, the mean time duration between two incremental changes, which corresponds to the residence time at a fundamental frequency, is advantageously at most 1 s, preferably at most 0.2 s, in particular at most 0.1 s. The minimum average residence time is advantageously at least 0.01 s, in particular at least 0.02 s.

The change in the fundamental frequency can in particular with clocked switched actuators, z. B. reversal of the direction of current in magnetic coils, switching valves of a double-acting hydraulic cylinder assembly, etc. advantageously be made by changing the switching cycle times.

During a shaking operation, the control device advantageously sets, in addition to a maximum and a minimum fundamental frequency, at least one further frequency value of the fundamental frequency, which is advantageously at least 20% below the maximum occurring fundamental frequency. Preferably, at least four, in particular at least five different fundamental frequencies are represented in the time course of the fundamental frequency during a shaking process. In particular, the frequency of occurrence of the different fundamental frequencies can be a standard statistical distribution, for example in the manner of white noise sequences. The control device can in Advantageous embodiment of a random number generator, which generates the successive frequencies and / or the time until the next frequency change and thus specifies a time course of the fundamental frequency.

Particularly advantageous is a time characteristic of the fundamental frequency over the duration of a Rüttelvorgangs in which a plurality of relative frequency minima and a plurality of relative frequency maxima occur. As a result, an optimization of the rearrangement and compaction of the body of the concrete amount is achieved alternately and repeatedly for different core sizes and achieved a particularly fast and strong compression of a large core size range containing batch.

Over the duration of a shaking process, an average value of the amount of these frequency differences can then be derived from the chronological progression of the fundamental frequency with a plurality of frequency differences between successive relative frequency maxima and relative frequency minima, which is advantageously at least 10%, in particular at least 20%, in particular at least 40%. the average fundamental frequency is.

The largest relative frequency maximum is advantageously at least 1.5 times, in particular at least 2.5 times, the lowest relative frequency minimum.

In an advantageous development, the control device for different amounts of concrete and / or for different shapes different temporal profiles of the fundamental frequency can be included as a selectable default.

A suitable time curve for the fundamental frequency can be used for an individual concrete quantity on the basis of one or more samples of the mixture, which teilhafterweise make up a maximum of 10% of the batch volume of the mold, determined and stored in the controller as a default. The samples can be taken from a concrete batch itself or in an advantageous development of parameter information on the batch, z. B. grain sizes of sand and / or gravel and their volume fraction, proportion of a cement admixture, water content, etc., are determined separately from the batch based on batch samples composed of reference materials. From the parameter information, a suitable time curve without the use of batch samples can also be determined via a calculation formula and / or assignment tables and stored in the control device as a default or selected from stored profiles. The determination of a suitable time profile for a mixture characterized by parameter data can in particular also be carried out locally away from the molding machine and the determined time profile can be transmitted in digital form by remote data transmission to the control device of the molding machine.

In an advantageous embodiment, it can further be provided that other frequencies are superimposed over at least the predominant part of the duration of the shaking process of the respective fundamental frequency, which are not harmonious to the fundamental frequency, ie represent neither higher harmonics nor subharmonic of the fundamental frequency. When shaking with such a time course on the type of superimposed frequencies is considered as the fundamental frequency of the frequency component of the shaking movement, which currently has the largest proportion of amplitude. The superimposition of non-harmonic frequency components may include in particular the specification of a non-harmonic motion sequence and control of an actuator via a control circuit for maintaining the predetermined sequence of movements and / or the analog control of an actuator without a control loop. The invention is illustrated below with reference to preferred embodiments with reference to the figures still in detail. Showing:

1 shows a frequency characteristic of a typical unbalance shaker with a constant fundamental frequency,

2 shows a principle of a preferred time characteristic of a variable fundamental frequency,

3 shows a noise-like time characteristic of a variable fundamental frequency,

4 shows a time course with a stepwise change in the fundamental frequency,

5 shows a schematic structure of a device,

6 shows a clocked control signal for a plurality of frequency stages,

7 shows a clocked control signal for gradual frequency change,

8 shows a clocked control signal with fast-changing cycle times.

In FIG. 1, the course of the fundamental frequency fG of a typical imbalance shaker in conventional molding machines is sketched over time t as the axis of abscissa. In a start-up phase AP, the rotational frequency of the one or more unbalanced shafts increases rapidly and continuously to a desired value fR, which is maintained for the duration tR of a shaking operation. After completion of the shaking process, the vibrator drive is decelerated in a braking phase EP and the rotational frequency decreases rapidly and continuously. The actual shaking process is the time interval tR with a constant rotational frequency fR of the imbalance shafts. The start-up phase AP and the braking phase EP are as short as possible in the interest of short cycle times of production. In addition to the rotation frequency as the fundamental frequency, the vibration excitation may contain higher frequencies than harmonics of the fundamental frequency.

In contrast, according to the present invention, the fundamental frequency over the duration tR of the shaking operation is varied by an average fundamental frequency, which is defined in particular as a time integral of the frequency response over time divided by the duration tR of the shaking process.

For suitable time courses a variety of variants are conceivable and suitable. A particularly advantageous basic principle is illustrated in FIG. 2, whereby here as in the following possible start-up and braking phases are disregarded before or after the shaking process. To illustrate this basic principle, in FIG. 2, three arbitrarily selected short time intervals t1 <t2 <t3 within the duration tR of the shaking process have a first relative frequency maximum at a fundamental frequency fH1, a second relative frequency maximum at a fundamental frequency fH2, and a first relative time between them Frequency minimum entered at a fundamental frequency fl_1. Irrespective of the rest of the time course of the fundamental frequency before, after or between the registered sections, the latter has such a constellation of frequency values in at least one time segment. The time course of the fundamental frequency can in particular vary between the illustrated hobenen time points have more relative frequency minima and frequency maxima.

The relative frequency maxima can be at the same (fH1 = fH2) or different values of the fundamental frequencies fH1 and fH2. In the example sketched fH2> fH1. The exemplary emphasized frequency values fH1, fl_1, fH2 lie within a frequency band for the fundamental frequency with a lower band limit fU and an upper band limit fθ. The relative frequency maxima or frequency minima of a time characteristic can also lie on the frequency band limits and at the same time form absolute maxima or minima of the time characteristic of the fundamental frequency fG (t). Plotted with is a typical frequency position of a mean fundamental frequency fM, by which the fundamental frequency varies over time. Advantageously, a sequence of two temporally spaced relative frequency maxima and a temporally intermediate relative frequency minimum occur several times within a shaking process.

FIG. 3 outlines an advantageous time profile with fundamental frequency fG (t) varying rapidly and frequently within a frequency band between f0 and fU about a mean fundamental frequency fM. The variation of the fundamental frequency may be performed according to a history fG (t) stored in a controller or recreated in each shaking operation under the influence of a random or pseudo-random generator for which an approximate spectral distribution may be provided.

While in Fig. 3 of a continuous change in the fundamental frequency over time has been assumed, in Fig. 4, a preferred variant is sketched with gradual, erratic change in the fundamental frequency. The transitions between different frequencies are practically delayed. free, in particular with cyclically switchable actuators, such as a hydraulic cylinder assembly, which is preferably bidirectionally operable, with a cycled valve arrangement for acting on one, preferably alternately two fluid chambers of the hydraulic cylinder assembly, or an electromagnet assembly with switchable input voltage or current direction.

Advantageously, the residence time tV at a frequency is at most 1 s, preferably, in particular a maximum of 0.1 s. In extreme cases, the cycle time can also be varied from cycle to cycle of the actuator. The residence time tV at individual frequencies is advantageously at least 10 ms, in particular at least 20 ms. Also marked is a development with a frequency characteristic in which on the one hand a frequency change with a large frequency jump FP of at least 10% of the average fundamental frequency fM is provided, but on the other hand a small quasi-continuous frequency change RF occurs over a small subfrequency band, as a result of which greatly differing Grain size ranges of the mixture for rearrangement are preferably excited, but at the same time within such a grain size range, a partial frequency band is traversed for the most complete possible detection of similar Umordnungssituationen.

With reference to Figure 2, some advantageous relative and absolute parameters of the time course of the fundamental frequency of the vibrator can be illustrated.

The lower limit fU of the frequency band within which the fundamental frequency varies is advantageously at least 20 Hz, in particular at least 25 Hz. The lower limit fU is advantageously below 60 Hz, in particular below 50 Hz, preferably below 40 Hz. The upper limit fθ of the frequency band is advantageously at least 80 Hz, in particular at least 100 Hz. The upper limit fθ can advantageously be less than 200 Hz, in particular less than 150 Hz.

The relative frequency minimum with fl_1 is advantageously 10%, preferably at least 20% of the average fundamental frequency fM below this, fl_1 <0.9 fM or fL1 ≤0.8 fM.

At least one, preferably both of the relative frequency maxima is advantageously at least 10%, preferably at least 20%, in particular at least 40% of the mean fundamental frequency above this, z. B. fH2> 1, 1 fM, preferably fH2> 1, 2 fM, in particular fH2> 1, 4 fM.

The frequency difference fH2-fl_1 between the possibly larger of the two relative frequency maxima and the relative frequency minimum is advantageously at least 10%, in particular at least 20%, preferably at least 30% of the arithmetic mean (fH1 + fH2) / 2 of the two relative frequency maxima.

The average fundamental frequency fM is advantageously at least 40 Hz, in particular at least 50 Hz, preferably at least 60 Hz.

In Fig. 3 is an example of an advantageous time course of the fundamental frequency fG is sketched with continuous frequency variation within a frequency band between fU and fθ, which has a plurality of relative frequency minima and relative frequency maxima. The explained basic sequence of two relative frequency maxima including a relative frequency minimum with the advantageous values or value ratios given for FIG. 2 can be contiguous as a direct temporal sequence of a relative frequency maximum, a relative frequency minimum and a relative frequency maximum, as illustrated in a short period of time by crosses at relative frequency maxima and a relative frequency minimum. However, the basic sequence explained with reference to FIG. 2 can also be given in the course of time of the fundamental frequency, points of time which are further apart from one another and which include further relative or absolute frequency maxima and frequency minima.

A preferred embodiment provides abrupt step-shaped frequency changes over time of the fundamental frequency. An exemplary time course is sketched in FIG. 4. The transitions between the individual frequency stages are so short in time that they are negligible compared to the residence times ZV between successive changes in the fundamental frequency at individual frequency stages. The residence times tV at the individual frequency levels may be uniform or different.

Additionally or alternatively, in the case of a chronological progression with a plurality of successive relative or absolute frequency minima and frequency maxima, advantageously at least one frequency change fS between two successive fundamental frequency values is at least 10%, preferably at least 20%, in particular at least 40% of the mean Fundamental frequency is. An average frequency change averaged over the frequency changes f S during a shaking operation is advantageously at least 10%, in particular at least 20%, preferably at least 40% of the mean fundamental frequency f M.

Advantageously, at least three, in particular at least four, preferably at least five different frequency levels within the Fre- quency band between fU and fθ, wherein at least one frequency value fZ lying between a maximum and a minimum fundamental frequency, typically fθ and fU, is at least 20% above the minimum fundamental frequency, fZ> 1, 2 fU, and at least 20% below the maximum fundamental frequency, fZ <0.8 fθ.

Averaged over a Rüttelvorgang, average residence time tF, d. H. Duration between successive step-shaped frequency changes is advantageously between 0.01 s and 1 s.

The largest relative frequency maximum, typically equal to the upper band limit fθ, is advantageously at least 1.5 times, preferably at least 2 times, especially at least 2.5 times the lowest relative frequency minimum, which is typically equal to the lower band limit fU ,

FIG. 5 schematically shows an arrangement with a shape FE in a molding machine MA. The mold FE is held on a vibrating table RT, above which a vibrating device RV introduces vibrations into the concrete amount in order to strongly compact and consolidate it during a vibrating operation in a short time. A control device SE controls the vibrator during the shaking with a time-varying signal Sl. The vibrator device advantageously contains at least one actuator, which in a particularly advantageous embodiment can be switched between two states in accordance with an upward movement and a downward movement of the vibrating table in time with the control signal. The clock frequency of the control signal determines the fundamental frequency of the vibrator, which varies over the duration of the shaking operation. An example of a control signal with time-variable clock frequency, which is switched over between two signal values O and I, is sketched in FIG. 6 in excerpts. In a first signal section S1, there is a short cycle time corresponding to a high fundamental frequency of the vibrator device. In a second signal section S2, the clock time is much greater corresponding to a lower fundamental frequency and in a third signal section S3, the clock time is shorter again and the fundamental frequency higher. The transition between the different cycle times in the individual signal sections can be abrupt, corresponding to a stepwise change of the fundamental frequency.

In Fig. 7 is in a further signal section SW, a quasi-continuous change in the cycle time, z. To sweep a sub-frequency band, such as RF illustrated in FIG. 4. FIG. 8 shows an embodiment with cycle times which vary greatly between individual clocks, wherein a specific frequency value does not then set with a dwell time.

The control signal is preferably generated according to a predetermined time in the control device. The control device can selectably contain a plurality of predetermined time courses and / or a calculation or assignment rule for determining a time course which is particularly suitable in individual cases as a function of the shape and / or the amount of concrete. A time profile can also be determined externally and entered into the control device as default VZ.

In an especially advantageous embodiment, an actuator can be a hydraulic actuator with two chambers which can be acted upon by pressure in opposite directions via the control signal. The features indicated above and in the claims, as well as the features which can be seen in the figures, can be implemented advantageously both individually and in various combinations. The invention is not limited to the exemplary embodiments described, but can be modified in many ways within the scope of expert knowledge. In particular, the vibrator device can also be operated simultaneously with a plurality of fundamental frequencies.

Claims

Claims:

1. An apparatus for producing concrete form bodies by compacting a filled in a mold wet concrete amount, wherein during a shaking a vibrator with a fundamental frequency to the concrete amount, characterized in that the fundamental frequency of the vibrator over the duration of a shaking operation by means of a control device variably controllable and is varied by averaged over the duration of the shaking average mean square frequency.

2. Apparatus according to claim 1, characterized in that the time characteristic of the fundamental frequency during a shaking operation has at least two temporally spaced relative frequency maxima and a temporally located therebetween relative frequency minimum.

3. Apparatus according to claim 2, characterized in that the frequency difference between the relative frequency minimum and the larger of the two relative frequency maxima is at least 10%, in particular at least 20%, preferably at least 30% of the arithmetic mean of the two frequency maxima.

4. Apparatus according to claim 2 or 3, characterized in that the relative frequency minimum is at least 10%, preferably at least 20% of the average fundamental frequency below this.

5. Device according to one of claims 1 to 4, characterized in that a relative frequency maximum at least 10%, preferably at least 20%, in particular at least 40% of the mean fundamental frequency is above this.

6. Device according to one of claims 1 to 5, characterized in that the average fundamental frequency is at least 40 Hz, in particular at least 50 Hz, preferably at least 60 Hz.

7. Device according to one of claims 1 to 6, characterized in that the fundamental frequency is gradually changed by the control device.

8. The device according to claim 7, characterized in that at least one frequency change between two temporally successive fundamental frequencies at least 10%, preferably at least 20%, in particular at least 40% of the mean fundamental frequency.

9. Apparatus according to claim 7 or 8, characterized in that the averaged over the frequency changes during the period of a shaking medium mean frequency change is at least 10%, in particular at least 20% of the average fundamental frequency.

10.Vorrichtung according to any one of claims 7 to 9, characterized in that the mean time between two step-like changes in the fundamental frequency between 0.01 seconds and 1 second.

11.Vorrichtung according to one of claims 7 to 10, characterized in that the control device adjusts during a shaking in addition to a maximum and a minimum fundamental frequency at least one further frequency value of the fundamental frequency, which is at least 20% above the minimum and at least 20% below the maximum fundamental frequency lies.

12. Device according to one of claims 1 to 11, characterized in that over the duration of a shaking process, the time characteristic of the fundamental frequency has a plurality of relative frequency maxima and relative frequency minima up.

13. The apparatus according to claim 12, characterized in that the mean value of the amount of the frequency difference between temporally successive frequency maxima and frequency minima at least 10%, in particular at least 20%, preferably at least 40% of the mean

Fundamental frequency is.

14. The apparatus of claim 12 or 13, characterized in that the maximum relative frequency maximum is at least 1.5 times, preferably at least 2 times, in particular at least 2.5 times the lowest relative frequency minimum.

15. Device according to one of claims 1 to 14, characterized in that the fundamental frequency at least over the majority of the time duration of the Rüttelvorgangs not harmonic to the fundamental frequency

Frequency components are superimposed.

16. Device according to one of claims 1 to 15, characterized in that the vibrator device contains at least one variable-frequency controllable fluid-actuated actuator.

17. Device according to one of claims 1 to 15, characterized in that the vibrating device contains at least one electromagnet as an actuator.

18. Device according to one of claims 1 to 17, characterized in that the control device includes a random number generator, which serves for specifying a time course for the fundamental frequency and / or for the composi- tion.

19. Device according to one of claims 1 to 17, characterized in that a time characteristic of the fundamental frequency can be stored in the control device.

20. Device according to one of claims 1 to 19, characterized in that a plurality of different time profiles are selected selectable.

21. A process for the production of concrete blocks by compacting a filled in a mold wet concrete amount, wherein during a

Rüttelvorgangs the amount of concrete is varied by means of a vibrator with a shaking movement with a fundamental frequency of the vibrator during the shaking time.

22. The method according to claim 21, characterized in that based on material samples to the concrete amount with a sample volume which makes up a maximum of 10% of the volume of the mold, a suitable time course of the fundamental frequency is determined and stored as a default in the control device.

23. The method according to claim 22, characterized in that the samples are prepared from reference materials according to information about the amount of concrete.

4. The method according to claim 21, characterized in that based on information about the composition of the concrete amount, a time course for the fundamental frequency is determined according to an assignment or calculation rule and stored in the control device.