More precisely, the present invention concerns vibration of"green mass"in a moulding process for the creation of mould bodies for the production of electrodes for the melting industry, in particular the aluminium electrolysis industry.

Such electrodes, in particular anodes, are created by the"green mass"being subjected to compaction in a vibration device, which may consist of a moulding box with a base and side walls mounted on a table, plus a plumb that is allowed to slide down between the mould walls (the side walls of the moulding box). There are primarily two types of vibration equipment for moulding anodes available on the market, equipment with plumb vibration and equipment with table vibration. The main difference between them is the location of the vibration unit that generates the dynamic vertical input force for the equipment. For equipment with plumb vibration, the vibration unit is fixed to/integrated in the plumb. For equipment with table vibration, the vibration unit is fixed to/integrated in the table.

NO patent no. 132359 concerns vibration equipment with plumb vibration for the compaction of mould bodies for the production of anode and cathode blocks. The specification states that plumb vibration offers many advantages over table vibration, in particular with regard to simplification of the equipment. By moving the vibration unit to the plumb, the claim was that the vibration principle could be simplified, as the base would be stationary, fixed to the floor. In accordance with the reference, the compression effect is achieved by one or more vibration generators being arranged only on the cover weight or the plumb, the base being stationary and the mould walls being fixed to the base during the creation process. In accordance with the solution stated in the reference, the table is to be the stationary base in order to avoid a coupled mechanical system with several vibrating masses, which is also illustrated in the figure attached to the reference.

The present invention will be described in further detail in the following by means of examples and figures, where: Fig. 1: shows a simplified diagram of improved vibration equipment, Fig. 2: shows a simplified diagram of a first embodiment of vibration equipment in accordance with the present invention, Fig. 3: shows a simplified diagram of a second embodiment of vibration equipment in accordance with the present invention, Fig. 4: shows a simplified diagram of a third embodiment of vibration equipment in accordance with the present invention, Fig. 5: shows a simplified diagram of a fourth embodiment of vibration equipment in accordance with the present invention, Fig. 6: shows a diagram of a mechanical realisation of the principle in Figure 4.

The figure also shows a proposal for how the anode mass can be vibrated with a vacuum, where a vacuum chamber encloses the anode mass and part of the entire plumb.

The mechanical system as stated in NO 132359 has been tested in experiments, but the experiments showed that vibration equipment containing one vibrating mass did not produce the expected result. The reason for this was propagation of dynamic energy to the environment, and the equipment was also unstable. The table was subsequently improved in the experiments and converted into a mass that could be vibrated by placing a spring k1 and a damper d between the table mb and base U, see Fig. 1. In the figure, the anode mass m2 is shown as a complex spring that may also consist of a

spring and damper element k2, d2. It is expedient for the anode mass or spring damper system between the table and floor to be expressed as complex springs since complex springs have a real spring element and a hysteresis damper element. The anode mass may, of course, have other forms of damping than hysteresis damping, such as friction damping, etc. In the same way, different forms of damping may occur in a real damping element such as rubber dampers mounted between the table and the base. In Figure 1, the vibrating plumb is shown as m. The dynamic input force Fdyn_jn against the equipment is a vertical periodic force. In accordance with the above adjustment, the improved equipment will consist of a coupled mechanical system with two vibrating masses. A coupled system with two vibrating masses can also be established by vibration being applied to the table instead of the plumb.

As a consequence of the above improvement, the noise to the environment was considerably reduced. There were many reasons for this: * With 2 vibrating masses and by selecting a frequency range in which the table and the plumb will vibrate in virtual phase opposition (towards 180°), the dynamic gain of the compression force against the anode mass increased since the table also accelerated and contributed to the compression force. This meant that the dynamic input force against the equipment could be reduced to achieve the same dynamic compression against the anode mass. In turn, this led to the dynamically transmitted force against the base U being reduced since the dynamic input force was reduced.

The damper d between the table mb and the base U dissipated dynamic energy.

The base U was protected against shocks from the plumb. A shock contains a range of frequency components. The dynamic energy against the floor could be very high and random if the energy came directly from the plumb. The table was given a protective role so that the floor experienced a continuous sinusoidal force

from the table with the same frequency component as the dynamic input force had, rather than shocks from the plumb.

The equipment was stabilised on account of the damper element d1. Low- frequency unstable fluctuations of the equipment were damped.

In connection with the development of the equipment in accordance with the present invention, it was decided, on the basis of the above knowledge, that the equipment would not comprise a base or foundation (the large passive mass under the equipment).

It was found that optimal equipment should, as far as possible, be able to insulate the dynamic energy itself, so that it is absorbed in the equipment and, as far as possible, in the mass to be compacted/moulded, and so that a minimum quantity of it is emitted to the environment. In the improved equipment, a foundation under the floor on which the vibration equipment may rest has the sole task of damping the rest of the dynamic energy that is emitted from the vibration equipment.

In the aforementioned patent NO 132359, it is also proposed that a"constant compressive force, for example by means of a hydraulic cylinder" (reference number 16 in the figure) be applied to the plumb. The intention was to reduce the weight of the plumb. This is a very unfortunate way of applying external static force to the plumb.

Firstly, the hydraulic cylinder was connected in stationary fashion to the base. Dynamic energy will then be propagated via this connection to the base. Secondly, the hydraulic cylinder contains damping and will directly dissipate dynamic energy that was intended for the anode mass. The dynamic gain towards the anode mass was reduced.

Experiments with a hydraulic cylinder were carried out, but failed for the above reasons.

The present invention concerns further improvements to the prior art by means of a method and equipment for compacting materials, in particular vibration of"green mass" in a moulding process for the creation of mould bodies for the production of electrodes for the melting industry. The equipment comprises two mould parts, at least one of

which has vibration applied to it during the compaction process. Moreover, the mould parts, for example the table and plumb, are mutually physically integrated during vibration by means of a static compressive force, which may consist of at least one spring k3. The vibration equipment may be designed as a closed system in which the vibration energy is emitted to the environment as little as possible. Four embodiments of the equipment, which are closed systems, are shown in Figures 2-6. A fundamental difference between the embodiment shown in Figure 1 and those shown in Figures 2-6 is that the table in the latter is connected to the plumb via one or more springs k3, or an arrangement equivalent to a spring k3.

Although the figures show that the plumb is vibrated, the principles of the present invention can also be implemented by the table being vibrated. The principles of the present invention may also be utilised by horizontal vibration of the mould parts. The mould parts may then be mounted in such a way that they can slide across a mainly horizontal base, for example by the mould parts being supported by a support that is able to slide in a horizontal direction (not shown).

With the present invention, materials can be compacted faster and more precisely with a higher degree of compaction and with less loss of energy to the environment than is possible with prior art equipment. Figure 6 also shows how it is possible to realise such equipment mechanically in such a way as also to achieve vibration with a vacuum, where the vacuum chamber is as small as possible and the gas evacuation time is minimal. These and other advantages can be achieved with the present invention as it is defined in the attached claims 1-18.

The attached Figures 2-5 are simplified diagrams of vibration equipment during vibration when a mass ma is compressed or compacted. Figure 6 is a realisation of the simplified diagram in Figure 4. Figures 2-6 will be explained using the following definitions:

Definitions : U : The base. ma: The mass to be compressed by the vibration equipment. k2 : The spring constant of the mass ma. d2 : The damping of the mass ma. The damping may be in the form of hysteresis, viscous damping, friction, etc. (only one symbol is used for damping in the figures although we may have combinations of different forms of damping). mu : The mass of the plumb or the mass that oscillates between the mass ma and the body with spring constant k3. The vibration unit for plumb vibration is included in this mass. In some setups, there may also be a yoke included as the plumb mass, as shown in Figures 3,4 and 6. As we see in Figure 6, only part of the plumb's total mass is in the vacuum chamber. The yoke and the vibration unit are outside, but are permanently connected with bolts to the part of the plumb that is inside the vacuum chamber. mb : The mass of the table. The mass that oscillates between the mass ma and the body with spring constant k1 or the body with damper element d1. kl : One or more bodies with a total spring constant kl, placed between the table with mass mband the base U. d : One or more bodies with a total damping d1, placed between the table with mass mb and the base U. The damping may be in the form of hysteresis, viscous damping, friction, etc. (only one symbol is used for damping in the figures although we may have combinations of different forms of damping).

k3 : A body with spring constant k3. The plumb must be connected to the table via equipment with properties equivalent to those of a spring k3. The equivalent spring must be progressive in the sense that the static force through it must be independent of how much the mass ma is compressed. With k3 it must be possible to vary the static force from the table to the plumb or keep it constant regardless of the compression of the mass ma. At the same time, the equipment that is to represent k3 must have minimum damping since it takes dynamic energy from the equipment as a whole. One example of such equipment may be air pressure adjustable bellows, as shown in Figure 6, where one set of bellows is placed at each end of the yoke. The bellows"press"the plumb towards the mass ma during vibration. The bellows receive the compressive force from the table mb.

As an exception, the body with spring constant k3 may also have a fixed spring characteristic if the table's"side legs"can be height adjusted during vibration, as shown in Figure 5, so that the static force through k3 is independent of how much the mass ma is compressed. Such height adjustment can be implemented by the side legs being telescopic, for example by using screw jacks or hydraulic/pneumatic cylinders.

Fdyn_in : The mechanical dynamic input force to the vibration equipment. A periodic force with one or more frequency components. The vibration unit fixed to the plumb for plumb vibration generates the dynamic input force. Fdyn in has the same direction as the mass mathat is compressed. In Figure 6, the vibration unit is integrated in the yoke.

The parameters'effect during vibration for plumb vibration: k1 : The vibration equipment was a coupled mechanical system with 2 vibrating masses, an active mass mi and a passive mass mb.

Increase in dynamic gain of dynamic forces against the mass ma.

The compression force against the mass ma increases since the

mass mb also contributes to a great extent to the dynamic compression force.

Reduced noise to the environment since the table and plumb in virtual phase opposition cancel each other out to a great extent against the base. The transmitted dynamic force against the base is therefore less. dl : . Higher stability since d1 filters out low-frequency unwanted fluctuations in the vibration equipment on the table and plumb and thus prevents the equipment from becoming unstable.

Less noise to the environment since di dissipates energy and functions as a buffer against the base.

However, reduced dynamic gain of dynamic forces against the mass ma may occur if the damping is too high or the fundamental frequency of the compression force is too low so that it is in the low- frequency range that d1 has the task to damp. k3 : Introduction of k3 : with static force from the table to the plumb.

Further increase in dynamic gain of dynamic forces against the mass ma on account of a higher compression amplitude of the mass ma and a higher frequency. Since it is possible to increase the static force against the mass ma with k3, the dynamic force against the mass ma will also increase. The vibration unit is also indirectly connected to the table via k3 so that this contributes to increased acceleration of the table and thus also to increased dynamic force.

Another reason for higher dynamic gain is that the static force through k3 leads to the dynamic fluctuation of the mass ma

approaching the total dynamic fluctuation of the table and plumb.

The plumb's dynamics are thus"pressed"further down in the mass ma to be compressed. This leads to a higher compression amplitude of ma. The working frequency of the equipment also increases because the mass ma accelerates the table and plumb to a greater extent because it is in longer contact with the plumb over an oscillation period. The higher dynamic force will contribute the possibility of a higher degree of compaction of the mass ma to be compacted.

Reduced vibration time on account of a higher frequency and higher compression amplitude of ma. This leads to higher capacity.

Measurements show that the time can be reduced from a vibration time of approximately 60 seconds to approximately 20 seconds.

Reduced noise since k3 stores dynamic energy inside the equipment and thus emits less to the environment. Stored dynamic energy in k3 is emitted to the mass ma at the time in the vibration when k3 is extended or ma is compressed. The equipment becomes more of a closed system. If the spring rigidity in k3 is increased, the equipment can store more dynamic energy.

Higher stability since d1 can be increased further without the compression force against the mass ma being reduced. One of the advantages of the present invention is that it is possible to set the vibration frequency of the equipment with just the vibration unit. The working frequency can thus be moved to a greater extent out of the low-frequency range so that it is easier to damp low-frequency signals with d without damping the compression signal that has a higher frequency (easier to introduce a high pass filter). It is therefore easier to increase the damping di without any negative impact on the dynamic gain against the mass to be compressed.

Flexibility. Since the static force against the mass ma can be adjusted via k3, it is possible to adjust the size of the dynamic force against the mass ma. In Figure 6, the air pressure in the bellows can be optimised to determine the size of the force. With the vibration unit, the amplitude [mm] /frequency ratio [Hz] of the dynamic fluctuation of the table and plumb is set. If the equipment is to function more as a beat oscillator, the frequency is reduced with the vibration unit to increase the amplitude [mm] of the dynamic fluctuation of the table and plumb. If the equipment is to function more as a"vibration press", the frequency is increased with the vibration unit so that the amplitude [mm] of the dynamic fluctuation is reduced. Such a setting also reduces the noise to the environment since impacts are reduced if we keep the same dynamic size of the force with the compressed air in the bellows.

The optimal ratio here depends on the mass to be compacted, its dimensions and whether it is vibrated with a vacuum or not.

Maintenance and robustness. The flexibility stated above can lead to a reduction in impacts. This reduces the wear on the equipment and considerably reduces the noise level.

Reduced dynamic energy to the environment: The vibration frequency is adjusted as with the modified equipment towards the frequency at which the dynamic gain against the anode mass is greatest. This is also the frequency at which the table and plumb approach phase opposition. Because the plumb and table are connected to each other via the spring k3, the plumb will contribute to pressing the table up when the table is on its way down towards the floor. Since the transmitted dynamic force against the floor is the sum of the plumb and table forces, where the plumb force acts in the opposite direction to the force from the table, the transmitted dynamic force to the base will be reduced. This results in the vibration equipment emitting less dynamic energy to the environment. In other words, dynamic

energy will be stored in the spring k3 when the table is in the low position and the plumb is in the high position (spring k3 compressed). The spring then emits energy to the anode mass when it is extended (the anode mass is compressed). Dynamic energy is stored to a greater extent inside the system and less is emitted to the environment. Here it is important for the spring k3 to have minimal damping so that the energy that is stored in the spring is used to compress the anode mass and is not converted into other forms of energy such as heat, etc.

Increased dynamic gain against the anode mass: With increased dynamic gain against the anode mass, there is an increased possibility of higher dynamic forces against the anode mass and/or lower dynamic input force (eccentric force). This allows for the product to have a higher density and for higher capacity.

Stability : With stable equipment, there are no random fluctuations of the table and plumb that disturb the steady supply of energy to the mass ma to be compressed. As the equipment in accordance with the present invention has at least one low resonance frequency in addition to the working frequency chosen, it is important to prevent the equipment from oscillating at these frequencies. It is also important to design the equipment so that dynamic gain in these low frequency ranges is minimised. With the present invention, it is possible, with the vibration unit, to increase the working frequency of the equipment.

The damping d1 can thus be increased to minimise low-frequency fluctuations. An upper limit for this damping will be where no significant reduction in dynamic gain against the mass ma is achieved at the working frequency of the equipment.

By regulating the static compressive force from the spring k3, it is possible to adjust the density of the compacted product. The compacting time may also be reduced with an increased static compressive force. This means that the capacity of the equipment can be increased. With the proposed equipment, the compressive force can also be

adjusted during the compaction process itself if this is required. For example, it may be effective to vibrate initially at a relatively high compressive force, which subsequently decreases, and to increase it again towards the end of the vibration process.

Vibration equipment built in accordance with the present invention may comprise means that make it possible to vibrate electrodes so that they have the same density or the same physical dimensions. This can be achieved by the equipment being fitted with measuring equipment that registers how far down the plumb goes during vibration. The quantity of material placed in the mould before vibration is predefined, and it is then simple to establish a value that indicates weight/volume. The vibration may be terminated when a specific level has been reached so that the physical external dimensions are identical.

Moreover, the vibration equipment may have equipment that generates a vacuum in the volume that is delimited by the mould parts (the plumb, the table and the mould walls) containing the mass ma so that any gas can be removed from the moulds (vacuum vibration). This will result in increased density, reduced risk of cracks and vibration at higher temperatures, etc. Figure 6 shows how this can be realised. Some of the complete plumb is inside the vacuum chamber Vr formed by the mould walls Fvl, Fv2 and a vacuum lid Vk. The vacuum lid can be connected via a pipe to equipment that generates a vacuum in the vacuum lid such as a fan or similar (not shown). The rest of the total plumb mass (the yoke/4 and the vibration unit Ve) is outside, but permanently connected with bolts B1, B2 to the part of the plumb Ld that is inside the vacuum chamber Vr. This results in the smallest possible vacuum chamber, and the evacuation time of the gases can be minimised. The bolts must have the smallest possible overall cross-section so that the vacuum has the least possible"suction effect"on the yoke. At the same time, the bolts must be sufficiently dimensioned and located so that the connection is robust and the torque in the yoke is within reasonable limits.

As the mass ma is compacted during vibration, the yoke A will approach the vacuum lid.

There must therefore be a minimum distance to the yoke from the part of the plumb that is inside the vacuum chamber. This distance can be reduced if the vacuum lid also has telescopic properties. The overall height of the vibration equipment can, however, be reduced by integrating the vibration unit in the yoke.