The present invention relates to vibratory conveyors.
Such vibratory conveyors are used in many industries, for all possible materials to the extent that they are at all conveyed by a vibratory conveyor. Thereby, the free-flowing materials are output to a conveying element, usually a conveying trough, which then performs a cyclic forward/upward movement with a corresponding backward movement—the vibration—whereby the individual particles of the material are thrown forward and simultaneously somewhat upward. The conveying element carries out the backward movement before the particles lie on it again so that, upon the next forward/upward movement, the particles can be conveyed one step further. In the case of small displacements, forward conveying can also take place by means of friction differences in the forward and backward movement.
Vibratory conveyors accordingly have a vibrating support arrangement for the interchangeable conveying element lying on it, being designed for example, depending on the material or other criteria, wherein the support arrangement is made to vibrate in the desired way by a drive arrangement.
Vibratory conveyors, in particular, those with a conveying trough, are difficult to design, are largely produced according to empirical findings, and, in trials, are compared to the frequency and throwing angle concerning the material to be conveyed. Some concepts work as desired, others show a poor level of conveying capacity, without being able to see the reasons behind this for the specific case at hand.
A disadvantage of the known vibratory conveyors is the time-delayed controllability of the mass flow output at the end of the conveying element or the conveying trough, which drifts more or less continuously without being regulated, either because of the irregular filling of the conveying element or because of other influences, which is problematic, particularly in the case of gravimetric dosing (if a vibratory conveyor is arranged on a weighing scale), but also in the case of volumetric dosage.
The drive unit 4 has a vibration drive 10, which is designed as an alternating-current-flow coil in the embodiment shown, which forms a periodic magnetic field during operation, thereby acting on a magnet 11, which, in turn, is arranged at the support arrangement 5 and moves this. The leaf springs 12a and 12b form drive levers for the support arrangement 5, are somewhat inclined with regard to the throwing angle and are set into vibrating motion indicated by the double arrows 13a,b by the vibration drive 10 so that the support arrangement 5 carries out an oscillation due to its cyclic parallel shift against a base plate 14 of the drive unit 4 which generates the mass flow m of the conveyed material 9 in the conveying direction x according to the throwing angle given by the direction of the double arrows 13a,b; see the coordinate system 15, whose x-axis points in the conveying direction and whose y-axis points vertically upward. The throwing direction therefore has a component toward the front in the x-direction, and upward in the y-direction.
The drive unit 4 has an operating frequency, which, in the case of a drive unit according to
A vibratory conveyor results with a vibrating motion generating drive unit 4, and a conveying element arranged on the drive unit, wherein the drive unit 4 comprises a support arrangement for the conveying element, which is mounted on the support arrangement 5 via a section (8a) and has a freely extending section 8b.
In diagram 20, curve 21 shows the velocity v in the conveying direction x (
Diagram 25 shows the mass flow m in kg/s in the conveying direction x (coordinate system 15, see
According to the applicant's findings, the behavior of the mass flow over the length of the conveying trough 9 is the reason for the poor controllability of a vibratory conveyor according to
The analysis shows that two reasons for this can be: firstly, due to the vibration movement, the vibratory conveyor 1 tilts around its necessarily elastic supports 3a and 3b, which leads to the fact that the conveying trough does not only perform a translational vibration movement in the sense of arrows 13a and 13b (
Secondly, depending on the formation of the conveying trough 6, its freely extending section 8b tends to oscillate on the plane of
The effect of the vertically oscillating conveying trough 6 has comparable effects as in the case of rotation of the conveying trough: due to the deflection of the conveying trough, the throwing angle is not constant over its length, local material accumulations are formed, which in turn lead to poor controllability of the mass flow. Depending on the formation of the conveying trough, such oscillations can be weakly pronounced and thus less relevant or strongly pronounced and thus highly relevant. The diagrams created for the tilting or rotation of the vibratory conveyor due to the elastic bearing 3a, 3b (
In WO 2017/158496, it has been proposed to avoid a tilting of the vibratory conveyor caused by the vibration movement by means of a suitable formation of the geometry of the drive arrangement (location of the centers of gravity of the components of the vibratory conveyor in conjunction with a guided bearing). In addition, it has been proposed to shift the bearing points of the leaf springs or the vibration-generating levers in such a way that the support arrangement is forced to make a tumbling motion instead of the purely translational vibration movement, which is to compensate the undesirable vertical oscillation of the freely extending section 8b of the conveying trough 6 compared to the support arrangement 5.
The disadvantage of such a vibratory conveyor lies in the fact that the controllability of the mass flow is improved, but it remains unexpectedly difficult. According to the applicant's findings, the corresponding formation of the support arrangement with adjustable bearing points still leads to a deflection of the conveying trough since the tumbling movement results in the rear section 8a being placed obliquely while the front section 8b should pass into a horizontal orientation, wherein this then oscillates with a different flexure depending on the amplitude of the vibration movement. Thus, the throwing angle is not constant over the length and changes depending on the flow rate, which in turn leads to the local material accumulations, which can change with the changed flow rate depending on the operating condition and negatively affect the controllability. In addition, a correct setting in the specific case of a vibratory conveyor running in a line is complex and difficult, for example, also because all operating states and possible conveying troughs must be anticipated and provided during the mechanical calibration of the bearing points.
Accordingly, it is the object of the present invention to create an improved vibratory conveyor with a short regulation time.
This problem is solved by a vibratory conveyor with the distinctive features as set forth herein.
By providing a spring-elastic vibration arrangement acting on the conveying element itself for maintaining a constant throwing angle, a very simple construction is available, which forms a unit with the conveying element and can therefore be easily calibrated for the most diverse conveying elements, even very long or very elastic conveying elements, with different bulk materials. This also applies to conveying troughs, which are not yet in use today, but could be desired by a line operator for the respective line. In addition, a vibration arrangement allows the throwing angle to be maintained over the entire length of the conveying element within a narrow range, which allows a very fast controllability of the mass flow.
Other preferred embodiments have the features of the dependent claims.
The present invention is described in somewhat more detail in the following based on the figures.
The figures show:
Due to the translational vibration movement of the support arrangement 5 (arrows 13a and 13b) the section 8b of the conveying trough 31 moves accordingly along with during operation of the vibratory conveyor 30, whereby the mass 33 opposite the conveying trough 6 and opposite the drive arrangement 4 starts an oscillation shown by the double arrow 36, however, with correct calibration, it does this in such a way that the front section 8b only carries out the translational movement in accordance with the arrow 13c, i.e. a flexure of the conveying trough 31 in the sense of the double arrow 16 (
In this case, the conveying trough 31, the vibration arrangement 32 and the drive arrangement 4 each have a resonance frequency (in the case of the drive arrangement 4 possibly an operating frequency), which are all different from each other. It is often the case that the resonance frequency of the stiffly trained conveying trough 31 is higher than that of the drive arrangement, which is in the range of 60 Hz for many of the vibratory conveyors from prior art. Then, according to the invention, the vibration arrangement 32 shall be interpreted in such a way that its resonance frequency is lower than resonance or operating frequency of the drive arrangement 4. It should be noted, however, that according to the invention now also a soft conveying trough can be used, or an exceptionally long conveying trough, as this would be desired depending on the conception of the line in the specific case per se, but because of the poor controllability—without the exact reasons for this being known—cannot be provided.
On the horizontal axis of both diagrams 40, 41, the ratio
is ablated, i.e. the ratio of the excitation frequency Ω to the resonance frequency ω0 of the spring-mass system (here the conveying trough 6 and the vibration arrangement 32). On the vertical axis, in diagram 40, the ratio
of the resulting amplitude Sr of the spring-ground system to the stimulating amplitude Sa, is ablated, in diagram 41, the phase shift φ between the stimulating oscillation and the thus excited oscillation of the spring-mass system. The phase shift
where D is the attenuation factor and
The support arrangement 5 (
If the conveying trough has a resonance frequency of, for example, 120 Hz, which is therefore higher than the operating frequency of the support arrangement 5 (for example 60 Hz, see above); for the oscillation of the conveying trough 6, the ratio
[do not cross out], see the operating range 45 in diagram 40 (the exact operating point depends on the attenuation of the conveying trough). Via line 46, it can be recognized that the phase of the front section 8b or its front end with relation to the rear end 8a (at the place of connection with the support arrangement 5) is close at φ=0°, see the range 47—the phase of the rear section 8a is, in comparison to the support arrangement 5, at 0° because it is rigidly connected to the support arrangement 5 (a rigid connection results in ω0=∞, i.e.
(In the embodiment shown in accordance with
If the vibration arrangement 32 has a resonance frequency of, for example, 30 Hz, which is thus lower than the operating frequency of the support arrangement 5 (for example 60 Hz, see above), the ratio is
see the operating range 42 in diagram 40 (the exact operating point depends on the attenuation of the conveying trough). Via line 43 it can be recognized that the phase 44 of the pendulum mass 33 with relation to the front end 8b (at the place of connection with the fastening to the trough 35) is close at φ=−180°, see range 44.
In this case, the pendulum mass 33 oscillates almost or in push-pull mode with relation to the front end of the conveying trough 6, with the result that it introduces a transverse force and a flexural momentum into the conveying trough via the spring-elastic tongue 34, which is opposite to its momentary deflection so that this deflection is reduced or disappears with appropriate calibration of the vibration arrangement 33 and the conveying element 6. This in turn means that the throwing angle across the length of the conveying element changes less or not at all, i.e. a quick controllability of the mass flow results.
This results in that a spring-elastic vibration arrangement is provided on the front section (8b) of the conveying element (6), which is arranged and designed in such a way that it oscillates with respect to the oscillation of the drive arrangement with a phase shift counter to the phase shift of the conveying element. Depending on the attenuation of the conveying element or the vibration arrangement, this phase shift is 180° or is close to 180°, but is so large that the controllability of the vibratory conveyor according to the invention is improved compared to an embodiment without a vibration arrangement.
If the conveying element has a lower resonance frequency than the frequency of the support arrangement 6, the operating ranges 42.45 in diagram 40 change. However, the conveying element and the vibration arrangement still oscillate in push-pull mode so that the deflection of the conveying element is reduced or disappears.
Furthermore, this results in that the natural frequencies of the conveying element 6 and the vibration arrangement 32 are different from the operating frequency of the support arrangement 4 and this is higher than the one of the natural frequencies, the other is lower. Being preferred, however, the natural frequency of the conveying element is higher than that of the vibration arrangement 32. A conveying element, in particular, if it is designed as a conveying trough, can generally be designed to be slightly comparably stiff with relation to the vertical direction y merely due to its trough-shaped cross-section, which results in a comparatively high resonance frequency. On the other hand, however, it is also the case that, in the case of longer conveying elements combined with corresponding material, a resonance frequency below the operating frequency may be the case. It should be noted here that with the help of the present invention conveying troughs or conveying elements with a larger length can be considered than was previously the case from the point of view of regulating the conveying quantity.
As shown in
The vibration behavior of the conveying element, for example, a conveying trough 6, is complex, also because the vibration occurs in two directions (x and y, see
A simulation of the applicant led to the following result:
which shows that the arrangement according to the invention can be coordinated in such a way that the influence of the flexural oscillation of the conveying element practically disappears.
The values for the simulated change in the velocity/height of the bulk material are based on the throwing angle over the length of the channel—in the case of the vibration movement (arrows 13a,b in
The control unit 52 detects via the sensor 55 the vertical component of the vibration movement of the support arrangement 5 or the rear end of the conveying trough 6 and via the sensor 56 the vertical component of the vibration movement of the front end of the conveying trough 6. If these components deviate from each other by a specified threshold value stored in the controller 60, the control unit 52 generates a correction signal for the actuating drive 58, which thereby pulls in the leaf spring 59 somewhat (i.e. shortened) or extends (i.e. extended), see the double arrow 62. As explained above, the amplitude of the oscillation of the vibration arrangement 51 changes. The control unit 52 can now process this cycle continuously and thus reduce or prevent a drift in the calibration of vibration arrangement and conveying element 6 due to changing operating conditions. It is also possible that the control unit 52 in this way correctly coordinates a vibratory conveyor 50 that is approximate for a specific conveying task in operation, wherein the control accuracy can be calibrated by means of the specified threshold.
The sensors 55, 56 can be designed as simple accelerometers, such as those available under the designation MPU-6050 by TDK InvenSense. Depending on the construction of the vibratory conveyor 50, other existing data can also be used instead of the data of the rear sensor 55 since the movement of the support arrangement 5 is defined—in any case, however, the vertical movements of the rear section are compared with those of the front section of the conveying element and a deviation is corrected by means of regulating the vibration arrangement 51 until it falls below a specified target value. The person skilled in the art can easily determine such a control cycle for the specific case.
A vibratory conveyor results with a front sensor 56 for the vertical movement of the front section 8b of the conveying element 6 and with a control unit 60, which is designed to detect a deviation of the vertical movement of the front section 8b from the vertical movement of the rear section 8a from the data of the front sensor 56 during operation and to generate a correction signal for an actuator arrangement 58 of the vibration arrangement 51 so that the two vertical movements are mutually similar. Preferably, the vibratory conveyor has a rear sensor for the vertical movement of the rear section 8a of the conveying element. Being furthermore preferred, the front sensor 56, and being particularly preferred, the rear sensor 55 is designed as an accelerometer.
In an exemplary embodiment (not shown in the figures), the vibration arrangement has two vibrating masses, one on each side of the front end of the conveying trough. These can then also be arranged transversely from the conveying trough protruding leaf springs.
Alternatively, it is also according to the invention to hang a vibrating mass on a vertically arranged coil spring, and to arrange a vibration arrangement designed in such a way at the front end of the conveying element. It is also possible to arrange the vibrating mass between two springs. Numerous designs are conceivable for the vibration arrangement according to the invention. Thus, the vibrating mass may also be arranged on a transversely arranged to the conveying element leaf spring or a vertically arranged spiral spring. Likewise, a vertical leaf spring can be used, wherein a correction of the undesirable oscillation of the front end of section 8b would be made by the generated momentum in the conveying trough 6.
Number | Date | Country | Kind |
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00441/18 | Apr 2018 | CH | national |
Filing Document | Filing Date | Country | Kind |
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PCT/IB2019/052268 | 3/20/2019 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2019/193442 | 10/10/2019 | WO | A |
Number | Name | Date | Kind |
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2968424 | Lawson | Jan 1961 | A |
4405043 | Burghart | Sep 1983 | A |
7392897 | Krell | Jul 2008 | B2 |
10961058 | Helfenstein | Mar 2021 | B2 |
Number | Date | Country |
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712253 | Sep 2017 | CH |
102015212538 | Jan 2017 | DE |
1460006 | Sep 2004 | EP |
2426562 | Nov 2006 | GB |
2014201390 | Oct 2014 | JP |
Entry |
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PCT/IB2019/052268 International Search Report, dated Sep. 19, 2019. |
Number | Date | Country | |
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20210016973 A1 | Jan 2021 | US |