Patent Application
20090087511
The invention relates generally to masonry production, and more particularly, to apparatus, systems, and processes relating to the shaping of conglomerates, such as concrete conglomerates using harmonic vibration.
For the manufacture of small-format concrete ware in industrial production the devices now mostly used employ the principle of shock vibration for the compacting of the concrete conglomerate. Systems for the generating of vibration are used with such devices that are based on unbalance shafts driven by electric motors as described in detail, for example, in the article “Increasing the Quality of Production by Efficient Compacting” by Berthold Schlecht and Alexander Neubauer appearing in the periodical “Betonwert+Fertigteil-Technik” at pages 44 to 52 of Issue No. 9/2000. On the underside of the table upon which the input form places the concrete conglomerate, but not tightly mounted, there are attached, respectively, two unbalance shafts or two pairs of unbalance shafts so that, in the latter case, the unbalance shafts are put into forced synchronization either mechanically using gears or electronically. As a rule the input form is thus comprised of a so-called pallet—a plank, a plastic slab, or a steel sheet—and a molding box whose side walls define the concrete ware and lie on the pallet. This is primarily due to reasons of production technology, as the removal of the finished concrete ware is done on these pallets, but the process has also been influenced significantly by shock vibration.
Such devices are burdened by disadvantages, however, in that, for the optimal compacting of the concrete as a rule high momentary accelerations are required of as great as 200 m/s2. With the known devices, however, only unbalance forces of a maximum of 200 kN can be provided because, among other things, the bearings of the rotating unbalances would otherwise be exposed to unacceptably high loads along with very short bearing lifetimes. Given the fact that the high accelerations required cannot be provided by means of the harmonic vibration of the table generated by unbalance agitation, they must be produced by another means. This is done with the assistance of so-called shock vibration. In this manner, the high accelerations necessary are generated, briefly each time, by means of so-called concussion hits between the components of the table, pallet, and mold box that are not tightly connected to each other. Furthermore, the generating of the concussion hits occurs by means of knock ridges arranged in a stationary position parallel to the table. The installation of these knock ridges is done purely empirically by matching various mechanical parameters and thus does not always provide optimum adjustment and optimal compacting. The use of a different concrete or a different form thus entails extensive installation work. Further disadvantages of shock vibration are the high emission of noise connected with the concussion hits, the high mechanical load, and high wear on the equipment. The latter also leads to losing the optimal adjustment of the machine and a worsening of the quality of the product.
If one desires to avoid shock vibration one must make up for the absence of the acceleration peaks generated by concussion hits with the concomitant higher forces in harmonic vibration. However, with the known motorized unbalance agitators such higher forces cannot be created. Indeed, use has been made of one or more hydraulically operated servo cylinders instead of motor-driven unbalance agitators so as to be able to generate the higher forces and to make use of the principle of harmonic vibration. There is also a description of the devices based on hydraulic operation for concrete masonry production in the article by Schlecht and Neubauer mentioned above as well as in Application WO 01/47698 A1. The advantages of harmonic vibration are, among other things, that the wear is significantly reduced, there is a reduction in the noise emissions, as the pallet, mold box, and table are tightly connected in this case, the cement usage can be reduced, and the production times may be significantly reduced.
There is also a disadvantage present in the choice of hydraulics as of the operating method, however. First of all, servo hydraulics require that the oil be extremely clean, which can only be achieved in the environment of a concrete plant with high expenditure. Furthermore, the energy requirements of a device based on hydraulics are distinctly higher than those of the conventional shock vibration devices operated by electric motors. Moreover, the production costs of such a servo hydraulic system are distinctly higher than those for a electric motor drive.
In Application WO 01/47698 A1 it is indeed proposed that harmonic vibrations be generated, but no method is referred to for overcoming the known disadvantages of the state of the art as mentioned above.
One aspect of the invention is directed to a device for the compacting of conglomerates, especially of concrete conglomerates for concrete masonry production, utilizing harmonic vibration that does not suffer from the disadvantages of shock vibration and of hydraulic operation, yet still provides sufficiently high accelerations or forces.
A device according to one embodiment of the invention includes a form for the input of the concrete conglomerate, a table with which the form is coupled using mounting components, a vibration generation system attached to the table for the generation of harmonic vibrations and their transfer to the table, a load in the form of a piston to admit the concrete conglomerate with a force, first spring components for the elastic positioning of the table, and second spring components for the elastic positioning of the load.
The device addresses the aforementioned problem of concrete masonry production by employing harmonic vibration. An exemplary vibration generation system includes at least eight rotating shafts in unbalance with rotation axes that are parallel to each other. The unbalance shafts are thus coupled in pairs in their rotational motions and each pair of unbalance shafts has a shared rotation axis that is driven independently of the other pairs. Unlike a conventional device, one balance shaft is thus replaced by a coupled pair of unbalance shafts.
According to one embodiment, the unbalance shafts are generally made shorter and more compact. For example, in order to generate a total force of 600 kN, a force of at least 75 kN must be provided per individual unbalance, that, unlike conventional unbalance shafts, can be reached with a higher unbalance U=mu ru, where the unbalance mass is mu and the unbalance radius is ru. The transfer of a distinctly higher total force is made possible by the fact that eight unbalance shafts are used instead of four in that, as each unbalance shaft is customarily positioned on the table in two roller bearings, the total force can thus be spread out over 16 roller bearings instead of eight.
In order to reduce the wear it is advantageous for the unbalance shafts to provide for an elasticity of EI greater than or equal to 2×105 Nm2, where EI is the elasticity modulus designated for the material used for the unbalance shafts and I is the momentary surface inertia of the unbalance shafts. It is necessary that the unbalance shafts be made of steel for this, with a diameter of at least 80 mm.
The coupling of the rotational motion of two in a pair of connected unbalance shafts can be configured as electronic coupling so that the unbalance shafts are driven in synchronization and the synchronization is provided by an electronic control. The coupling in pairs of two unbalance shafts by means of an elastic coupling is simpler and less expensive, however, and thus preferable. Preferably, it is made as strong as possible due to the torsion from misalignments that can develop from divergences in the momentary local positions of the rotation axes of the two unbalance shafts in relation to each other in the area of the coupling, and it is preferably made as tolerant as possible Preferably, the elastic coupling has a torsion strength of at least 104 Nm/rad and a radial spring strength of 2×107 N/m at most.
The table with form and concrete conglomerate can be put into harmonic vibration with particular effectiveness when the vibrations generated by the unbalance agitators match the natural frequency of the oscillation band on the first spring components that serve for the elastic positioning of the table given that, in such case, their resonance can be used. For this, as a rule, the first spring components are made particularly stiff. This has the disadvantage that, in the creation of resonance, an enormous transfer of vibration to the environment also occurs. The same circumstance also affects the load and the second spring components and the second spring components for the elastic positioning of the load. However, one can obtain good vibration isolation from the environment only with weak first and second spring components. The only useful resonance vibrations are the ones that happen to be the ones sent through the concrete conglomerate by the relative movement between the table and the load. However, a concrete spring with such effect acutely depends on the conglomerate and on the progress of the compacting and therefore the use of resonance is made difficult.
In a preferred configuration, the table and load are thus coupled on three spring components. Advantageously, the third spring component is a mechanical or hydraulic spring with respectively variable spring strengths. This third spring component can then be adjusted to a given operating frequency so that changes in the spring strength of the concrete spring have a distinctly lesser effect on the sum of all springs and can even be offset by variable spring strengths of the third spring component.
In another configuration, the bracing of the form and the table is provided by tension members as mounting components with hydraulic or pneumatic traction. At one end they are attached to the table and at the other end they are connected to the form in a flexible fastened state. As an alternative one end of the tension members can also be attached to the form and at the other end they are connected to the table in a flexible fastened state. In this way, the linkage position of the bracing at the table can be decreased in level. The use of tension members, unlike the conventional use of bracing levers at the level of the form junction, has the advantage that parts that project out far can be avoided, such as those needed conventionally for the mounting mechanism, which are especially prone to being fractured in the high vibration accelerations generally created by the use of harmonic vibrations and resonance.
In a preferred configuration, the tension members are connected to the table with their ends at an angle of more than zero degrees in relation to the perpendicular, preferably at an angle of between ten degrees and thirty degrees. This has the advantage that the mounting contours, that is, the means by which the flexible fastening is created, can be taken out by slackening from the collision space of the form stroke motion and the form can be thus more easily taken out and exchanged.
In a preferred embodiment the mounting components at the table are wedges and at the form are tie rods availed of openings for the passage of the wedges so that, in the fastened state, the wedges enter the openings of the tie rods. To increase and decrease the tension, a hydraulic or pneumatic forward and reverse drive is utilized for the wedges.
In a further configuration, electromagnets are used as the mounting components connected at the table. To this end, the form is made of a material that can be magnetized, such as steel. If a two-part form is used, then not only the mold box but also the pallet between the form box and the table can be made of a material that can be magnetized, such as, for example, steel sheet. If the magnets are turned on when there is an available form, they pull on the form by electromagnetic force and brace it in that manner.
A preferred embodiment of a device for the shaping of conglomerates such as concrete conglomerates for masonry work, includes a form for the input of the concrete conglomerate, a table with which the form is coupled using mounting components, a vibration generation system attached to the table for the generating harmonic vibrations to be transferred to the table, a load in the form of a piston to admit the concrete conglomerate with a force, first spring components for the elastic positioning of the table, and second spring components for the elastic positioning of the load. The vibration generation system preferably includes at least eight rotating unbalance shafts provided with rotational axes parallel to each other. The unbalance shafts are coupled into pairs as to their rotational motion so that each pair of unbalance shafts shares a rotational axis and is driven independently of the other pairs.
The third spring components 7 are designed so that, depending on the concrete conglomerate, the resonance of the vibration system of table 1 and load 4 together can be used as effectively as possible through the entire compacting process, that is, the dependency of the resonance frequency of the compacting state of the concrete conglomerate, which would be very acute without the employment of the third spring components 7, is lessened to the extent possible. The third spring components 7 are situated so that the relative movements occurring between table 1 and load 4 in compacting and unframing are enabled. This can be carried out, for example, with the assistance of hydraulic cylinders. Another possibility is to use the third spring components 7 only part of the time, when table 1 and load 4 are coupled in order to move against each other. Here, steel, rubber, or air springs can be used.
During the vibration process, form 2 is attached to the table by mounting components. In
As an alternative to that the hydraulically driven tie rods can also be arranged with a slight angle of about 10 degrees to 30 degrees in relation to the perpendicular. They no longer would need to be swung out to the side given that, using the diagonal arrangement of the mounting contours, they can be taken out by slackening, depending on the construction, from the collision space of the form stroke motion and the form can be thus more easily taken out and exchanged.
In
With the arrangement and use of unbalance shafts 8 as shown in
In this manner the production of unbalance mass and unbalance radius of 0.7 kgm is able to be achieved so that, with an agitation cycle frequency of Omega=2×pi×60 Hz, individual unbalance forces or agitation force amplitudes of about 100 kN per individual unbalance can be achieved without thus affecting the life time of cylinder roller bearings 17.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20301954.7 | Feb 2003 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP04/00850 | 1/30/2004 | WO | 00 | 6/5/2006 |
